TYING TOOL

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims priority from Japanese Patent Application No. 2024-232115 filed on December 27, 2024. The entire content of the priority application is incorporated herein by reference.

TECHNICAL FIELD

[0002] The art disclosed herein relates to a tying tool.

BACKGROUND ART

[0003]Japanese Patent Application Publication No. H10-046821 describes a tying tool configured to tie a tying target with a wire. The tying tool includes: a tying mechanism configured to perform a tying operation including: a feeding motion in which the tying mechanism feeds the wire; and a twisting motion in which the tying mechanism twists the wire; a feeding motor configured to cause the tying mechanism to perform the feeding motion; a twisting motor configured to cause the tying mechanism to perform the twisting motion; and a control unit configured to control the feeding motor and the twisting motor. The control unit is configured to, after the control unit has driven the twisting motor to cause the tying mechanism to start the twisting motion, stop the twisting motor to cause the tying mechanism to stop the twisting motion when a twisting stop condition is satisfied.

SUMMARY

[0004] A state of a twisting motor changes during the course of using a tying tool. For example, parts constituting the twisting motor thermally expands or thermally contracts. Further, the parts constituting the twisting motor are worn. Viscosity of lubricant added to the twisting motor changes by temperature and/or changes over time. A state of the tying mechanism also changes in the same manner. Twisting torque at completion of the twisting motion (hereafter, termed ‘twisting completion torque’) may vary depending on such change of the state of the twisting motor and/or the tying mechanism. The present teachings provide an art configured to allow suppression of variation in twisting completion torque that is caused by changes in the state of a twisting motor and/or a tying mechanism.

[0005] A tying tool may be configured to tie a tying target using a wire. The tying tool may comprise: a tying mechanism configured to perform tying operation including: a feeding motion in which the tying mechanism feeds the wire; and a twisting motion in which the tying mechanism twists the wire; a feeding motor configured to cause the tying mechanism to perform the feeding motion; a twisting motor configured to cause the tying mechanism to perform the twisting motion; a detector configured to detect state information representing a state of at least one of the tying mechanism, the feeding motor, and the twisting motor; and a control unit configured to control the feeding motor and the twisting motor. The control unit may be configured to, after the control unit has driven the twisting motor to cause the tying mechanism to start the twisting motion, stop the twisting motor to cause the tying mechanism to stop the twisting motion when a twisting stop condition is satisfied. The control unit may be configured to, when the twisting motion is to be performed, set the twisting stop condition for the twisting motion based on the state information detected by the detector before performing the twisting motion.

BRIEF DESCRIPTION OF DRAWINGS

[0006]FIG. 1 illustrates a rebar tying tool 2 according to a first embodiment from a rear upper left side.

[0007]FIG. 2 illustrates the rebar tying tool 2 according to the first embodiment from a front lower left side with a cover member 16 opened.

[0008]FIG. 3 illustrates a perspective view of a reel 18 configured to be attached to the rebar tying tool 2 according to the first embodiment.

[0009]FIG. 4 illustrates a cross-sectional view of a reel holder 12 and its surroundings in the rebar tying tool 2 according to the first embodiment.

[0010]FIG. 5 illustrates an internal structure of the rebar tying tool 2 according to the first embodiment.

[0011]FIG. 6 illustrates a feeding mechanism 24 in the rebar tying tool 2 according to the first embodiment from a front upper left side.

[0012]FIG. 7 illustrates a cross-sectional view of a guide mechanism 26 and its surroundings in the rebar tying tool 2 according to the first embodiment.

[0013]FIG. 8 illustrates a cutting mechanism 28 of the rebar tying tool 2 according to the first embodiment from the front upper left side in a state where a shear member 64 is positioned at a location not having moved beyond a wire hole 74.

[0014]FIG. 9 illustrates the cutting mechanism 28 of the rebar tying tool 2 according to the first embodiment from the front upper left side in a state where the shear member 64 is positioned at a location having moved beyond the wire hole 74.

[0015]FIG. 10 illustrates a twisting mechanism 30 being at an initial position in the rebar tying tool 2 according to the first embodiment from the front upper left side.

[0016]FIG. 11 illustrates a cross-sectional perspective view of the twisting mechanism 30 being at the initial position in the rebar tying tool 2 according to the first embodiment.

[0017]FIG. 12 illustrates a rotation regulating unit 86 and its surroundings in the rebar tying tool 2 according to the first embodiment from the front upper left side.

[0018]FIG. 13 illustrates a cross-sectional view of a grasping unit 88 and its surroundings in the rebar tying tool 2 according to the first embodiment.

[0019]FIG. 14 illustrates the cutting mechanism 28, the twisting mechanism 30, and their surroundings from a front upper right side when the rebar tying tool 2 according to the first embodiment executes the feeding motion.

[0020]FIG. 15 illustrates the cutting mechanism 28, the twisting mechanism 30, and their surroundings from the front upper right side when the rebar tying tool 2 according to the first embodiment executes a tip grasping motion.

[0021]FIG. 16 illustrates the cutting mechanism 28, the twisting mechanism 30, and their surroundings from the front upper right side when the rebar tying tool 2 according to the first embodiment executes a retracting motion.

[0022]FIG. 17 illustrates the cutting mechanism 28, the twisting mechanism 30, and their surroundings from the front upper right side when the rebar tying tool 2 according to the first embodiment executes a cutting motion.

[0023]FIG. 18 illustrates the cutting mechanism 28, the twisting mechanism 30, and their surroundings from the front upper right side when the rebar tying tool 2 according to the first embodiment executes a twisting motion.

[0024]FIG. 19 illustrates the rotation regulating unit 86 and its surroundings in the rebar tying tool 2 according to the first embodiment from a front lower left side.

[0025]FIG. 20 illustrates a block diagram showing a schematic electrical configuration of the rebar tying tool 2 according to the first embodiment.

[0026]FIG. 21 illustrates a flow chart of a main process executed by a control circuit 230 of the rebar tying tool 2 according to the first embodiment.

[0027]FIG. 22 schematically illustrates a wire type table stored by the control circuit 230 in the rebar tying tool 2 according to the first embodiment.

[0028]FIG. 23 illustrates a flow chart of an initialization process executed by the control circuit 230 of the rebar tying tool 2 according to the first embodiment.

[0029]FIG. 24 illustrates a flow chart of a returning-to-initial position process executed by the control circuit 230 of the rebar tying tool 2 according to the first embodiment.

[0030]FIG. 25 illustrates a flow chart of a cutting attempt process executed by the control circuit 230 of the rebar tying tool 2 according to the first embodiment.

[0031]FIG. 26 illustrates a graph indicating change over time of a twisting motor current value I while the control circuit 230 of the rebar tying tool 2 according to the first embodiment is executing the cutting attempt process.

[0032]FIG. 27 illustrates a graph indicating change over time of the twisting motor current value I while the control circuit 230 of the rebar tying tool 2 according to the first embodiment is executing the cutting attempt process.

[0033]FIG. 28 illustrates a flow chart of a small-amount feeding process executed by the control circuit 230 of the rebar tying tool 2 according to the first embodiment.

[0034]FIG. 29 illustrates a flow chart of a tying process executed by the control circuit 230 of the rebar tying tool 2 according to the first embodiment.

[0035]FIG. 30 illustrates a flow chart of a feeding process executed by the control circuit 230 of the rebar tying tool 2 according to the first embodiment.

[0036]FIG. 31 illustrates a flow chart of a tip grasping process executed by the control circuit 230 of the rebar tying tool 2 according to the first embodiment.

[0037]FIG. 32 illustrates a flow chart of a retracting process executed by the control circuit 230 of the rebar tying tool 2 according to the first embodiment.

[0038]FIG. 33 illustrates a flow chart of a cutting and twisting process executed by the control circuit 230 of the rebar tying tool 2 according to the first embodiment.

[0039]FIG. 34 illustrates a graph indicating change over time of the twisting motor current value I while the control circuit 230 of the rebar tying tool 2 according to the first embodiment is executing the tip grasping process.

[0040]FIG. 35 illustrates change over time of the twisting motor current value I while the control circuit 230 of the rebar tying tool 2 according to the first embodiment is executing the cutting and twisting process.

[0041]FIG. 36 illustrates a flow chart of a feeding process executed by the control circuit 230 of a rebar tying tool 2 of the second embodiment.

[0042]FIG. 37 illustrates a flow chart of the tip grasping process executed by the control circuit 230 of the rebar tying tool 2 of the second embodiment.

[0043]FIG. 38 illustrates a flow chart of the cutting and twisting process executed by the control circuit 230 of a rebar tying tool 2 of the third embodiment.

DETAILED DESCRIPTION

[0044] Representative, non-limiting examples of the present disclosure will now be described in further detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the disclosure. Furthermore, each of the additional features and teachings disclosed below may be utilized separately or in conjunction with other features and teachings to provide improved tying tools, as well as methods for using and manufacturing the same.

[0045] Moreover, combinations of features and steps disclosed in the following detailed description may not be necessary to practice the disclosure in the broadest sense, and are instead taught merely to particularly describe representative examples of the disclosure. Furthermore, various features of the above-described and below-described representative examples, as well as the various independent and dependent claims, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.

[0046] All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter.

[0047] In one aspect of the present teachings, a tying tool may be configured to tie a tying target using a wire. The tying tool may comprise: a tying mechanism configured to perform a tying operation including: a feeding motion in which the tying mechanism feeds the wire; and a twisting motion in which the tying mechanism twists the wire; a feeding motor configured to cause the tying mechanism to perform the feeding motion; a twisting motor configured to cause the tying mechanism to perform the twisting motion; a detector configured to detect state information representing a state of at least one of the tying mechanism, the feeding motor, and the twisting motor; and a control unit configured to control the feeding motor and the twisting motor. The control unit may be configured to, after the control unit has driven the twisting motor to cause the tying mechanism to start the twisting motion, stop the twisting motor to cause the tying mechanism to stop the twisting motion when a twisting stop condition is satisfied. The control unit may be configured to, when the twisting motion is to be performed, set the twisting stop condition for the twisting motion based on the state information detected by the detector before performing the twisting motion.

[0048] According to the above configuration, when the twisting motion is executed, the twisting stop condition for such twisting motion is set based on the state(s) of the feeding motor, the twisting motor and/or the tying mechanism before execution of such twisting motion. This can suppress variation in the twisting completion torque that is caused by the changes in the state of the twisting motor and/or the tying mechanism.

[0049] In one aspect of the present teachings, the control unit may be configured to reset the twisting stop condition each time the tying operation is to be performed.

[0050] According to the above configuration, when the state of the twisting motor and/or the tying mechanism (e.g., temperature of the twisting motor) changes while the tying operation is repeated, the twisting stop condition continues to be updated to follow the change in the state of the twisting motor and/or the tying mechanism. This can further suppress variation in twisting completion torque that is caused by the change in the state of the twisting motor and/or the tying mechanism.

[0051] In one aspect of the present teachings, the control unit may be configured to set the twisting stop condition for the twisting motion based on the state information detected by the detector during a period from when the tying operation is started until the twisting motion is started.

[0052] According to the above configuration, the twisting stop condition for the twisting motion is set based on the state(s) of the feeding motor, the twisting motor, and/or the tying mechanism immediately before such twisting motion is started (i.e., latest state(s) of the feeding motor, twisting motor, and/or the tying mechanism). This can further suppress the variation in the twisting completion torque that is caused by change in the state of the twisting motor and/or the tying mechanism.

[0053] In one aspect of the present teachings, the control unit may be configured to set the twisting stop condition for a next twisting motion based on the state information detected by the detector during a period from when the twisting motion is stopped until the tying operation is finished.

[0054] According to the above configuration, the twisting stop condition for the next twisting motion to be performed next is set based on the state(s) of the feeding motor, the twisting motor, and/or the tying mechanism immediately after stopping the twisting motion. Due to this, the state(s) immediately after stopping the twisting motion of the feeding motor, the twisting motor and/or the tying mechanism can be feedbacked on the next twisting motion.

[0055] In one aspect of the present teachings, the control unit may be configured to set the twisting stop condition based on the state information detected by the detector during a period in which the twisting motor is driven to cause the tying mechanism to perform a motion other than the twisting motion.

[0056] During a course of using the tying tool, behavior of the twisting motor and/or the tying mechanism may change, for example, due to a change in viscosity of the lubricant. This may become a reason why the twisting completion torque varies. According to the above configuration, the twisting stop condition is set based on the states of the feeding motor, the twisting motor and/or the tying mechanism that are detected during a period while the twisting motor is running. Due to this, the twisting stop condition can be set by taking into account the change(s) in the behavior of the twisting motor and/or the tying mechanism. This can suppress the variation in the twisting completion torque that is caused by the change(s) in the behavior of the twisting motor and/or the tying mechanism.

[0057] In one aspect of the present teachings, the tying mechanism may include a twisting mechanism configured to perform the twisting motion. The control unit may be configured to set the twisting stop condition based on the state information detected by the detector during a period in which the twisting mechanism does not hold the wire.

[0058] When the twisting mechanism is holding the wire, a load applied on the twisting mechanism and the twisting motor (i.e., states of the twisting motor and the tying mechanism) depends on characteristics of the wire (e.g., strength, hardness). Accordingly, if the twisting stop condition is set based on the state(s) of the feeding motor, the twisting motor and/or the tying mechanism, the wire characteristics that are detected during the period while the twisting mechanism is holding the wire may be reflected on the twisting stop condition. This may not be proper depending on the situation. According to the above configuration, the twisting stop condition is set based on the state(s) of the feeding motor, the twisting motor and/or the tying mechanism that are detected during the period while the twisting mechanism is not holding the wire. Due to this, the wire characteristics can be suppressed from being reflected on the twisting stop condition.

[0059] In one aspect of the present teachings, the detector may detect a current flowing through a detection-target motor which is one of the feeding motor and the twisting motor as the state information. The twisting stop condition may include a current difference value being greater than or equal to a predetermined difference threshold, wherein the current difference value represents a difference between a current value flowing through the twisting motor while the twisting motion is ongoing and a reference value. The control unit may be configured to, when the twisting motion is to be performed, set the reference value for the twisting motion based on the current value detected by the detector before performing the twisting motion.

[0060] During a course of using the tying tool, a loss amount of the twisting motor and/or the tying mechanism may change due to the change in the viscosity of lubricant. This may become a reason why the twisting completion torque varies. Also, the current value flowing through the detection target motor may increase or decrease in response to the increase or decrease in the loss amount of the twisting motor and/or the tying mechanism. In this case, from the magnitude of the current flowing through the detection target motor during its operation of the detection target motor, the magnitude of the loss amount in the twisting motor and/or the tying mechanism can be estimated. According to the above configuration, the twisting stop condition is set based on the current value flowing through the detection target motor. Due to this, the twisting stop condition can be set taking into account the magnitude of the loss amount in the twisting motor and/or the tying mechanism. This can suppress variation in the twisting completion torque that is caused by the change(s) in the loss amount of the twisting motor and/or the tying mechanism.

[0061] In one aspect of the present teachings, the detector may detect a current flowing through a detection-target motor which is one of the feeding motor and the twisting motor as the state information. The twisting stop condition may include a current value flowing through the twisting motor while the twisting motion is ongoing being greater than or equal to a current threshold which is set based on a reference value. The control unit may be configured to, when the twisting motion is to be performed, set the reference value for the twisting motion based on the current value detected by the detector before performing the twisting motion. The current threshold may be set to a larger value as the reference value is greater.

[0062] During a course of using the tying tool, a loss amount of the twisting motor and/or the tying mechanism may change due to the change in the viscosity of lubricant. This may become a reason why the twisting completion torque varies. Also, the current value flowing through the detection target motor may increase or decrease during operation of the detection target motor in response to the increase or decrease in the loss amount of the twisting motor and/or the tying mechanism. In this case, from the magnitude of the current flowing through the detection target motor during its operation of the detection target motor, the magnitude of the loss amount in the twisting motor and/or the tying mechanism can be estimated. According to the above configuration, the twisting stop condition is set based on the current value flowing through the detection target motor. Due to this, the twisting stop condition can be set taking into account the magnitude of the loss amount in the twisting motor and/or the tying mechanism. This can suppress variation in the twisting completion torque that is caused by the change(s) in the loss amount of the twisting motor and/or the tying mechanism.

[0063] In one aspect of the present teachings, the control unit may be configured to set, as the reference value, a minimum value of the current flowing through the detection-target motor during a period in which the detection-target motor is driven to cause the tying mechanism to perform an operation other than the twisting motion, wherein a start-up time of the detection-target motor is excluded from the period.

[0064] If the loss amount in the twisting motor and/or the tying mechanism is greater than normal, there is a concern that the twisting completion torque will be smaller than normal. According to the above configuration, since the current value flowing through the detection target motor during its operation of the detection target motor becomes larger when the loss amount in the twisting motor and/or the tying mechanism is greater than normal, the reference value for the twisting stop condition is set to a larger value than normal. Therefore, the twisting stop condition is not satisfied until the current value flowing through the twisting motor becomes larger than normal. Consequently, when the loss amount in the twisting motor and/or the tying mechanism is larger than normal, the twisting motion continues until the current flowing through the twisting motor becomes a value larger than normal. This can suppress the twisting completion torque from becoming smaller than normal, by which the twisting completion torque becomes its normal value. Conversely, if the loss amount in the twisting motor and/or the tying mechanism is smaller than normal, there is a concern that the twisting completion torque may become larger than normal. According to the above configuration, since the current flowing through the detection target motor during its operation of the detection target motor becomes smaller when the loss amount in the twisting motor and/or the tying mechanism is smaller than normal, the reference value for the twisting stop condition is set to a smaller value than normal. Consequently, the twisting stop condition is satisfied even when the current flowing through the twisting motor is smaller than normal. As a result, when the loss amount in the twisting motor and/or the tying mechanism is smaller than normal, the twisting motion stops when the current flowing through the twisting motor is smaller than normal. This can suppress the twisting completion torque from becoming larger than normal, allowing the twisting completion torque to be its normal value. According to the above configuration, it is possible to suppress variation in the twisting completion torque that is caused by changes in the amount of loss in the twisting motor and/or the tying mechanism.

(First Embodiment)

[0065]As illustrated in FIG. 1, a rebar tying tool 2 ties plural rebars R with a wire W. The diameter of the wire W used in the rebar tying tool 2 is for example within a range of 0.5 mm to 2.5 mm, and is selected according to the diameter of the rebars R to be tied. For example, when the rebars R with a small diameter of 16 mm or less (e.g., diameter 16 mm) are to be tied, the wire with a diameter of 1.6 mm or less (e.g., 0.8 mm), while when the rebars R with a large diameter of greater than 16 mm (e.g., diameter 25 mm or 32 mm) are to be tied, the wire W with a diameter of 1.6 mm or more (e.g., 2.0 mm) is used.

[0066]The rebar tying tool 2 comprises a body 4, a grip 6, a battery receptacle part 10, and a reel holder 12. The grip 6 is a member for an operator to grasp. The grip 6 is disposed at a lower portion of the rear side of the body 4. The grip 6 is configured integrally with the body 4. A trigger 8 is attached to an upper portion of the front side of the grip 6. The grip 6 houses a trigger switch 9 (see FIG. 5) configured to detect whether the trigger 8 is pushed in or not, therein. The battery receptacle part 10 is disposed below the grip 6. The battery receptacle part 10 is configured integrally with the grip 6. The battery receptacle part 10 is configured to have a battery pack B detachably attached thereto. The battery pack B is for example a lithium-ion battery. The reel holder 12 is disposed at a lower portion of the front side of the body 4. The reel holder 12 is disposed frontward of the grip 6. In the present embodiment, the longitudinal direction of a twisting mechanism 30 (see FIGS. 5, 10) to be described later will be termed a front-rear direction, a direction perpendicular to the front-rear direction will be termed an up-down direction, and a direction perpendicular to the front-rear and up-down directions will be termed a left-right direction.

[0067] The upper surface of the body 4 comprises a power switch 4a configured for switching on/off power of the rebar tying tool 2, a setting switch 4b configured for changing various settings such as tying force of the rebar tying tool 2, and a display unit 4c configured to display information regarding current settings of the rebar tying tool 2.

[0068]As illustrated in FIG. 2, the reel holder 12 comprises a holder housing 14 and a cover member 16. The holder housing 14 is attached to the lower portion of the front side of the body 4 and to the front portion of the battery receptacle part 10. The cover member 16 is attached to the holder housing 14 such that the cover member 16 is pivotable about a pivot axis 14a at the upper portion of the holder housing 14. An accommodating space 12a is defined by the holder housing 14 and the cover member 16. The reel 18 is disposed in the accommodating space 12a. The holder housing 14 comprises a plurality of ribs 15 protruding from the inner wall of the holder housing 14 below the reel 18. The plurality of ribs 15 extends in the left-right direction. The plurality of ribs 15 contacts the wire W when the rebar tying tool 2 is retracting the wire W into the reel 18. Due to this, the wire W can be suppressed from directly contacting the inner wall of the holder housing 14, by which wear of the inner wall of the holder housing 14 can be suppressed.

[0069]As illustrated in FIG. 3, the reel 18 comprises a bobbin 200 and the wire W wound on the bobbin 200. The bobbin 200 comprises a bobbin body 202 around which the wire W is wound, a left flange 204 extending radially outward from the left end of the bobbin body 202, a right flange 206 extending radially outward from the right end of the bobbin body 202, a recess 208 recessed leftward from the right surface of the bobbin body 202, and a protrusion 210 protruding rightward from the bottom of the recess 208.

[0070]As illustrated in FIG. 4, the reel 18 is installed in the reel holder 12 with the reel 18 receiving a support tube 212 arranged inside the holder housing 14 in its recess 208. The reel 18 is rotatably supported by the support tube 212.

[0071] There are various types of the wire W used for the rebar tying tool 2. The types of the wire W can be distinguished from each other in, for example, the diameter of the wire W, the material of the wire W, presence/absence of coating material coating the wire W, presence/absence of surface treatment on the wire W and/or contents of the surface treatment.

[0072] The rebar tying tool 2 further comprises a wire type detector unit 214 configured to detect the type of the wire W wound on the bobbin 200. The wire type detector unit 214 is arranged inside the support tube 212. The left surface of the support tube 212 comprises an opening 216 configured to receive the protrusion 210 of the bobbin 200 into the inside of the support tube 212.

[0073]The wire type detector unit 214 comprises a movable member 218, a wire type detection magnet 220, a biasing member 222, and a sensor board 224. The wire type detection magnet 220 is fixed to the movable member 218. The movable member 218 is configured to slide in the left-right direction inside a guide space 225 defined within the support tube 212. The movable member 218 is biased leftward by the biasing member 222. When the reel 18 is not installed onto the support tube 212, the movable member 218 is retained at the left end of the guide space 225 by the biasing force of the biasing member 222. When the reel 18 is installed on the support tube 212, the protrusion 210 of the bobbin 200 contacts the left surface of the movable member 218 to press the movable member 218 rightward against the biasing force of the biasing member 222. Due to this, the position of the wire type detection magnet 220 fixed to the movable member 218 in the left-right direction changes. The sensor board 224 comprises three Hall sensors 226a, 226b, and 226c that are aligned in the left-right direction. The Hall sensors 226a, 226b, and 226c each detect magnetic intensity from the wire type detection magnet 220, output an H signal when the detected magnetic intensity is high, and output an L signal when the detected magnetic intensity is low. Combination of output signals (termed also a signal pattern) from the Hall sensors 226a, 226b, and 226c differs according to the position of the wire type detection magnet 220. Although not illustrated, the length of the protrusion 210 of the bobbin 200 differs according to the type of the wire W wound on the bobbin 200. Due to this, a pressing degree of the movable member 218 when the reel 18 is installed on the support tube 212, that is, the position of the wire type detection magnet 220 differs according to the type of the wire W wound on the bobbin 200. Also, the output signals from the Hall sensors 226a, 226b, and 226c of the sensor board 224 differ according to the position of the wire type detection magnet 220. Accordingly, in the present embodiment, the type of the wire W wound on the bobbin 200 can be determined from the signal pattern outputted from the sensor board 224 (see FIG. 22).

[0074]As illustrated in FIG. 5, the rebar tying tool 2 comprises a control board 20. The control board 20 is accommodated in the battery receptacle part 10. The control board 20 controls operation of the rebar tying tool 2.

[0075]The rebar tying tool 2 comprises a feeding mechanism 24, a guide mechanism 26, a cutting mechanism 28 (see FIG. 7), the twisting mechanism 30, a feeding motor 32, and a twisting motor 76. In the present embodiment, the feeding mechanism 24, the guide mechanism 26, the cutting mechanism 28, and the twisting mechanism 30 will be collectively termed “tying mechanism 100”. The feeding mechanism 24 is accommodated in a front lower portion of the body 4. The feeding mechanism 24 feeds the wire W to the guide mechanism 26 and retracts the wire W from the guide mechanism 26. The guide mechanism 26 is arranged at a front portion of the body 4. The guide mechanism 26 guides the wire W fed from the feeding mechanism 24 around the rebars R in a circular ring shape. The cutting mechanism 28 is accommodated in the lower portion of the body 4. The cutting mechanism 28 cuts the wire W in a state of being wound around the rebars R. The twisting mechanism 30 is accommodated in the body 4. The twisting mechanism 30 twists the wire W around the rebars R. The feeding motor 32 is a motor configured to operate the feeding mechanism 24. The twisting motor 76 is a motor configured to operate the cutting mechanism 28 and the twisting mechanism 30. Each of the feeding motor 32 and the twisting motor 76 is connected to the control board 20 via wiring(s) that are not shown. Each of the feeding motor 32 and the twisting motor 76 is driven by electric power supplied from the battery pack B. Actuation of each of the feeding motor 32 and the twisting motor 76 is controlled by the control board 20.

(Configuration of Feeding Motor 32)

[0076] As illustrated in FIG. 6, the feeding motor 32 is a brushless motor comprising a stator 32b comprising teeth (not shown) on which a coil 32a is wound, a rotor (not shown) disposed inside the stator 32b, and an output shaft (not shown) fixed to the rotor. The rotor comprises permanent magnets including magnetic polars circumferentially arranged. A rotation detecting board 33 with a plurality of Hall sensors (not shown) mounted thereon is fixed to the stator 32b. The rotation detecting board 33 detects rotation of the feeding motor 32 (specifically, rotation of the rotor) by the plurality of Hall sensors detecting magnetic force from the rotor.

(Configuration of Feeding Mechanism 24)

[0077] The feeding mechanism 24 comprises a reduction drive part 34 and a feeding part 36. The output shaft of the feeding motor 32 is coupled to the reduction drive part 34. The reduction drive part 34 uses, for example a planetary gear mechanism to reduce rotation of the feeding motor 32 and transmit the same to a drive gear 42 of the feeding part 36.

[0078]The feeding part 36 comprises a base member 38, a guide member 40, the drive gear 42, a first gear 44, a second gear 46, a gear support member 48, and a biasing member 52. The guide member 40 is fixed to the base member 38. The guide member 40 has a guide hole 40a configured to allow the wire W pass therethrough. The guide hole 40a has a tapered shape with a wider lower end and a shallower upper end.

[0079]The drive gear 42 is coupled to the reduction drive part 34. The first gear 44 is rotatably supported by the base member 38. The first gear 44 meshes with the drive gear 42. The first gear 44 is caused to rotate by rotation of the drive gear 42. The first gear 44 has a groove 44a. The groove 44a is defined on the outer circumferential surface of the first gear 44 in a direction extending along the rotation direction of the first gear 44. The second gear 46 meshes with the first gear 44. The second gear 46 is rotatably supported by a support part 48b of the gear support member 48. The second gear 46 has a groove 46a. The groove 46a is defined on the outer circumferential surface of the second gear 46 in a direction along the rotation direction of the second gear 46. The gear support member 48 is supported by the base member 38 such that the gear support member 48 can swing about a swing axis 48a. The gear support member 48 comprises the support part 48b extending upward from the swing axis 48a and an operation part 48c extending downward from the swing axis 48a. The biasing member 52 biases the operation part 48c rearward. Due to this, the support part 48b supporting the second gear 46 is biased frontward (i.e., direction approaching the first gear 44), by which the second gear 46 is pressed against the first gear 44. As a result of this, the wire W is sandwiched between the groove 44a of the first gear 44 and the groove 46a of the second gear 46. When the operation part 48c is pushed in against the biasing force of the biasing member 52, the second gear 46 separates from the first gear 44. Due to this, when the reel 18 is to be replaced, the wire W can be easily passed between the groove 44a of the first gear 44 and the groove 46a of the second gear 46.

[0080] The wire W moves by the feeding motor 32 rotating under a state where the wire W is sandwiched between the groove 44a of the first gear 44 and the groove 46a of the second gear 46. In the present embodiment, when the feeding motor 32 rotates in the forward direction, the drive gear 42 rotates in a direction D1 shown in FIG. 6, by which the wire W is fed toward the guide mechanism 26. When the feeding motor 32 rotates in the reverse direction, the drive gear 42 rotates in a direction D2 shown in FIG. 6, by which the wire W retracts from the guide mechanism 26.

(Configuration of Guide Mechanism 26)

[0081] As illustrated in FIG. 7, the guide mechanism 26 comprises a wire guide 56, an upper guide arm 58, and a lower guide arm 60. The wire W having been fed by the feeding mechanism 24 passes inside the wire guide 56.

[0082]The upper guide arm 58 is disposed at a front upper portion of the body 4. The upper guide arm 58 defines an upper guide path 58a. The wire W having passed inside the wire guide 56 passes in the upper guide path 58a. A first guide pin 61 and a second guide pin 62 are arranged in the upper guide path 58a. When the wire W passes through the upper guide path 58a while in contact with the first guide pin 61 and the second guide pin 62, a downward curl is imparted to the wire W.

[0083] The lower guide arm 60 is disposed at a front lower portion of the body 4. The lower guide arm 60 is fabricated by three flat metal plates being welded to each other. Due to this, as compared to when the lower guide arm 60 is fabricated by one metal plate being bent, the lower guide arm 60 can be easily fabricated. The lower guide arm 60 defines a lower guide path 60a. The wire W having passed inside the upper guide path 58a passes in the lower guide path 60a. In FIG. 7, a part of the wire W that is hidden by the lower guide arm 60 and the twisting mechanism 30 is shown in a broken line.

(Configuration of Cutting Mechanism 28)

[0084]As illustrated in FIG. 8, the cutting mechanism 28 comprises a shear member 64, a guide member 66, an operation member 68, and a biasing member 70. The shear member 64 has a circular column shape extending in the front-rear direction. The guide member 66 comprises a guide path 72 configured to receive the shear member 64 such that the shear member 64 can slide in the front-rear direction. The guide path 72 extends in the front-rear direction. Also, the guide member 66 comprises a wire hole 74 configured to allow the wire W pass therethrough. The wire hole 74 opens on the guide path 72 and extends in a direction crossing the guide path 72 (i.e., up-down direction). As illustrated in FIG. 7, the wire hole 74 is arranged above an exit of the wire guide 56 of the guide mechanism 26. Due to this, the wire W having passed through the wire guide 56 passes the wire hole 74, prior to reaching the upper guide path 58a.

[0085]As illustrated in FIG. 8, the operation member 68 is fixed to the rear end of the shear member 64. The biasing member 70 biases the operation member 68 rearward relative to the guide member 66. Normally, the operation member 68 is retained in the position shown in FIG. 8 due to the biasing force of the biasing member 70. At this occasion, the shear member 64 is located in a position where the shear member 64 does not close the wire hole 74 in the guide path 72. When force pushing the operation member 68 frontward is applied on the operation member 68 from the state shown in FIG. 8 and that force exceeds the biasing force of the biasing member 70, the operation member 68 moves frontward. When this happens, the shear member 64 moves frontward along the guide path 72. As illustrated in FIG. 9, when the shear member 64 moves frontward so that the shear member 64 closes the wire hole 74, the wire W passing through the wire hole 74 is sheared at an upper end position 74a of the wire hole 74. Accordingly, in the present embodiment, the upper end position 74a of the wire hole 74 will also be termed “cutting position 74a”.

(Configuration of Twisting Motor 76)

[0086]As illustrated in FIG. 10, the twisting motor 76 is a brushless motor comprising a stator 76b comprising teeth (not shown) on which a coil 76a is wound, a rotor 76c disposed inside the stator 76b, and an output shaft (not shown) fixed to the rotor 76c. The rotor 76c comprises permanent magnets including magnetic polars circumferentially arranged. A rotation detecting board 78 with a plurality of Hall sensors (not shown) mounted thereon is fixed to the stator 76b. The rotation detecting board 78 detects rotation of the twisting motor 76 (specifically, rotation of the rotor 76c) by the plurality of Hall sensors detecting magnetic force from the rotor 76c. In the present embodiment, the same parts are used in the twisting motor 76 and the feeding motor 32 (see FIG. 6).

(Configuration of Twisting Mechanism 30)

[0087] The twisting mechanism 30 comprises a reduction drive unit 82, a sleeve unit 84, a rotation regulating unit 86, and a grasping unit 88. The output shaft of the twisting motor 76 is coupled to the reduction drive unit 82. The reduction drive unit 82 uses a planetary gear mechanism to reduce the rotation of the twisting motor 76 and transmits the same to a screw shaft 92 (see FIG. 11) of the sleeve unit 84.

[0088]As illustrated in FIG. 11, the sleeve unit 84 comprises the screw shaft 92, an inner sleeve 94, an outer sleeve 96, and a push member 98. The screw shaft 92 extends along a center axis CX extending in the front-rear direction. The screw shaft 92 rotates about the center axis CX along with the rotation of the twisting motor 76. A ball groove 102 is defined on the outer circumferential surface of the screw shaft 92. The ball groove 102 extends helically in the front-rear direction. A ball 104 is movably held in the ball groove 102.

[0089]The inner sleeve 94 comprises a circular cylinder part 106 and a flange part 108. The circular cylinder part 106 extends along the center axis CX. The circular cylinder part 106 has the screw shaft 92 inserted therethrough. The circular cylinder part 106 has a ball holding hole 110 extending through the circular cylinder part 106 in a thickness direction. The ball holding hole 110 holds the ball 104 rotatably within the ball groove 102. The flange part 108 protrudes outward in the radial direction of the circular cylinder part 106 from the rear end of the circular cylinder part 106.

[0090]The outer sleeve 96 extends along the center axis CX. The outer sleeve 96 has the circular cylinder part 106 of the inner sleeve 94 inserted therethrough. The outer sleeve 96 is fixed to the circular cylinder part 106 of the inner sleeve 94 by pin(s) that are not shown. Due to this, the outer sleeve 96 moves with the inner sleeve 94 in the front-rear direction, and rotates with the inner sleeve 94. The rear end of the outer sleeve 96 contacts the front surface of the flange part 108 of the inner sleeve 94. The outer sleeve 96 contacts the ball 104 from outside in the radial direction of the center axis CX, by which the outer sleeve 96 suppresses the ball 104 from slipping out of the ball groove 102 and the ball holding hole 110.

[0091]The outer sleeve 96 comprises a small diameter part 112 and a large diameter part 114 arranged rearward of the small diameter part 112. The small diameter part 112 is inserted in a ring sleeve 116 fixed to the body 4. The ring sleeve 116 receives the outer sleeve 96 such that the outer sleeve 96 can rotate about the center axis CX.

[0092]The push member 98 is arranged at a step between the large diameter part 114 and the small diameter part 112. The push member 98 has a substantially plate shape. The push member 98 is sandwiched between the step between the large diameter part 114 and the small diameter part 112 and a C ring 118 attached to the small diameter part 112 in the front-rear direction. Due to this, the push member 98 is immovable relative to the outer sleeve 96 in the front-rear direction. When the outer sleeve 96 moves relative to the body 4 in the front-rear direction, the push member 98 moves along with the outer sleeve 96 in the front-rear direction. Also, the push member 98 is immovable relative to the body 4. Due to this, even when the outer sleeve 96 rotates relative to the body 4, the push member 98 will not rotate about the center axis CX.

[0093] When the push member 98 is to move frontward with the outer sleeve 96, the push member 98 contacts the operation member 68 of the cutting mechanism 28 shown in FIG. 8 and pushes the operation member 68 frontward against the biasing force of the biasing member 70. Due to this, the cutting motion by the cutting mechanism 28 is executed.

[0094]As illustrated in FIG. 12, eight fins 120 are disposed on the outer circumferential surface of the large diameter part 114. Each of the eight fins 120 protrudes outward in the radial direction from the outer circumferential surface of the large diameter part 114. The eight fins 120 are arranged at 45-degree intervals from each other around the outer circumferential surface of the large diameter part 114. The eight fins 120 comprise seven short fins 122 and one long fin 124. The length in the front-rear direction of the long fin 124 is longer than the length in the front-rear direction of each of the short fins 122. In the front-rear direction, the position of the rear end of the long fin 124 is the same as the positions of the rear ends of the short fins 122. On the other hand, in the front-rear direction, the front end of the long fin 124 is located frontward of the front ends of the short fins 122. The eight fins 120 permit or prohibit rotation of the outer sleeve 96 by cooperating with the rotation regulating unit 86.

[0095]The rotation regulating unit 86 comprises a left stopper 126L and a right stopper 126R. The left stopper 126L comprises a base member 128L, a swing member 130L, and a torsion spring 132L. Screw holes 128a are defined on the base member 128L. Screws 128b (see FIG. 1) inserted through through holes (not shown) defined on the housing (see FIG. 1) are screwed in the screw holes 128a. Due to this, the base member 128L is fixed to the housing. The swing member 130L is supported by the base member 128L via a swing shaft 134L extending in the front-rear direction such that the swing member 130L can swing. The swing member 130L comprises a restricting piece 136L extending in the front-rear direction. The restricting piece 136L is disposed upward of the swing shaft 134L and rightward of the base member 128L. The torsion spring 132L biases the restricting piece 136L in a direction of separating away from the base member 128L (i.e., rightward). The right stopper 126R comprises a base member 128R, a swing member 130R, and a torsion spring 132R. The base member 128R is fixed to the housing in the same manner as the base member 128L. The swing member 130R is supported by the base member 128R via a swing shaft 134R extending in the front-rear direction such that the swing member 130R can swing. The swing member 130R comprises a restricting piece 136R extending in the front-rear direction. The restricting piece 136R is disposed upward of the swing shaft 134R and leftward of the base member 128R. The torsion spring 132R biases the restricting piece 136R in a direction of separating away from the base member 128R (i.e., leftward).

[0096]When the screw shaft 92 (see FIG. 11) rotates in a right-hand thread direction D3, one of the fins 120 contacts the upper surface of the restricting piece 136R, by which the outer sleeve 96 is prohibited from rotating. At this occasion, the inner sleeve 94 and the outer sleeve 96 move frontward due to the ball 104 (see FIG. 11) moving within the ball groove 102 (see FIG. 11) along with the rotation of the screw shaft 92. Contrary to this, when the screw shaft 92 rotates in a left-hand thread direction D4, one of the fins 120 contacts the restricting piece 136R but pushes in the restricting piece 136R rightward. At this occasion, the rotation of the outer sleeve 96 is not prohibited, by which the inner sleeve 94 and the outer sleeve 96 rotate along with the screw shaft 92 in the left-hand thread direction D4.

[0097] When the screw shaft 92 (see FIG. 11) rotates in the right-hand thread direction D3, one of the fins 120 contacts the restricting piece 136L but pushes in the restricting piece 136L leftward. At this occasion, the rotation of the outer sleeve 96 is not prohibited, by which the inner sleeve 94 and the outer sleeve 96 rotate along with the screw shaft 92 in the right-hand thread direction D3. Contrary to this, when the screw shaft 92 rotates in the left-hand thread direction D4, one of the fins 120 contacts the upper surface of the restricting piece 136L, by which the outer sleeve 96 is prohibited from rotating. At this occasion, the inner sleeve 94 and the outer sleeve 96 move rearward due to the ball 104 (see FIG. 11) moving within the ball groove 102 (see FIG. 11) along with the rotation of the screw shaft 92.

[0098]As illustrated in FIG. 10, the grasping unit 88 protrudes frontward (toward the rebars R) from the front portion of the sleeve unit 84. The grasping unit 88 extends along the center axis CX. The grasping unit 88 comprises a clamp shaft 152, a right clamp member 154, and a left clamp member 156.

[0099]As illustrated in FIG. 11, the clamp shaft 152 is inserted in the inner sleeve 94 and the outer sleeve 96. The clamp shaft 152 is disposed on the center axis CX. A hollow part 152a configured to receive the screw shaft 92 rotatably about the center axis CX is defined at the rear end of the clamp shaft 152. The clamp shaft 152 is configured rotatable relative to the screw shaft 92 about the center axis CX and also immovable in the front-rear direction.

[0100]The clamp shaft 152 comprises a plate part 158, a fitting hole 160, and an accommodating hole 162. The plate part 158 is located at a front portion of the clamp shaft 152. The plate part 158 has a substantially plate shape extending along the up-down direction and the front-rear direction. The fitting hole 160 extends through the plate part 158 in its thickness direction (i.e., left-right direction). The fitting hole 160 fits with the pin 164. The accommodating hole 162 is disposed rearward of the plate part 158. The accommodating hole 162 extends through the clamp shaft 152 in the left-right direction, and thus extends in the front-rear direction.

[0101] As illustrated in FIG. 13, the right clamp member 154 is attached to the clamp shaft 152 in a manner where the right clamp member 154 extends in the accommodating hole 162 (see FIG. 11) of the clamp shaft 152 from right to left. The left clamp member 156 is attached to the clamp shaft 152 in a manner where the left clamp member 156 extends in the accommodating hole 162 from left to right.

[0102]The right clamp member 154 comprises a base part 166, a pin retaining part 168, and a clamp piece 170. The base part 166 has a substantially plate shape extending along the front-rear direction and the left-right direction. Cam holes 166a, 166b are defined on the base part 166. Each of the cam holes 166a, 166b extends frontward from the rear end thereof, bends to extend in a right-front direction, further bends to extend frontward, bends to extend in the right-front direction, and further bends to extend frontward. The pin retaining part 168 is disposed near a right-front end of the base part 166. The pin retaining part 168 is arranged on the upper surface of the base part 166. The pin retaining part 168 retains the pin 164 such that the pin 164 can slide. The clamp piece 170 extends frontward from the right-front end of the base part 166.

[0103]The left clamp member 156 comprises a base part 178 and a clamp piece 180. The base part 178 has a substantially plate shape extending along the front-rear direction and the left-right direction. Cam holes 178a, 178b are defined on the base part 178. Each of the cam holes 178a, 178b extends frontward from the rear end thereof, bends to extend in a left-front direction, and further bends to extend frontward. The clamp piece 180 extends frontward from a left-front end of the base part 178.

[0104]The base part 166 of the right clamp member 154 and the base part 178 of the left clamp member 156 are plugged in the accommodating hole 162 (see FIG. 11) of the clamp shaft 152. In this state, an engagement pin 182a is arranged in the cam holes 166a, 178a. The engagement pin 182a is fixed to the outer sleeve 96, and also configured movable in the cam holes 166a, 178a in the front-rear direction. An engagement pin 182b is arranged in the cam holes 166b, 178b. The engagement pin 182b is fixed to the outer sleeve 96, and also configured movable in the cam holes 166b, 178b in the front-rear direction. The grasping unit 88 is coupled, via the engagement pins 182a, 182b, to the outer sleeve 96 such that the grasping unit 88 cannot rotate about the center axis CX relative to the outer sleeve 96 and also coupled to the outer sleeve 96 such that the grasping unit 88 can move relative to the outer sleeve 96 in the front-rear direction.

[0105]When the twisting mechanism 30 is in the initial position, the right clamp member 154 is located furthest to the right from the clamp shaft 152. In this case, a right wire path 184 where the wire W can pass is formed between the clamp piece 170 of the right clamp member 154 and the plate part 158 of the clamp shaft 152. When the outer sleeve 96 moves frontward from this state, the engagement pins 182a, 182b move frontward along the cam holes 166a, 166b. Due to this, the right clamp member 154 moves leftward, and the right wire path 184 starts to be closed. The grasping unit 88 grasps the wire W passing in the right wire path 184 by closing the right wire path 184 (see FIGS. 17, 18).

[0106] Also, when the twisting mechanism 30 is in the initial position, the left clamp member 156 is located furthest to the left from the clamp shaft 152. In this case, a left wire path 186 where the wire W can pass is formed between the clamp piece 180 of the left clamp member 156 and the plate part 158 of the clamp shaft 152. When the outer sleeve 96 moves frontward from this state, the engagement pins 182a, 182b move frontward along the cam hole 178a and the cam hole 178b. Due to this, the left clamp member 156 moves rightward and the left wire path 186 starts to be closed. The grasping unit 88 grasps the wire W passing in the left wire path 186 by closing the left wire path 186 (see FIGS. 15 to 18).

(Mechanical Operation of Rebar Tying Tool 2 During Tying Operation)

[0107]Next, with reference to FIGS. 14 to 18, mechanical operation of the rebar tying tool 2 during a tying operation of the rebar tying tool 2 tying the rebars R with the wire W will be described. In the tying operation, the rebar tying tool 2 sequentially executes a feeding motion, a tip grasping motion, a retracting motion, a cutting motion, a twisting motion, and a returning-to-initial position motion. Here, the position of the twisting mechanism 30 when the rebar tying tool 2 starts the tying operation will be termed “initial position”. When the twisting mechanism 30 is in the initial position, the long fin 124 is in contact with the upper surface of the restricting piece 136L of the left stopper 126L. The push member 98 is separated from the operation member 68 of the cutting mechanism 28 (see FIG. 8). As illustrated in FIG. 13, the engagement pin 182a is located at the rear portion of each of the cam holes 166a, 178a, the engagement pin 182b is located at the rear portion of each of the cam holes 166b, 178b.

(Feeding Motion)

[0108] When the feeding motor 32 rotates in the forward direction from the state where the twisting mechanism 30 is in the initial position, the feeding mechanism 24 feeds the wire W wound on the reel 18. In this case, the tip of the wire W sequentially passes in the wire guide 56 of the guide mechanism 26, the wire hole 74 of the cutting mechanism 28, the right wire path 184 of the twisting mechanism 30, the upper guide path 58a of the guide mechanism 26, the lower guide path 60a of the guide mechanism 26, and the left wire path 186 of the twisting mechanism 30. Due to this, as illustrated in FIG. 14, the wire W is wrapped around the rebars R in a circular ring shape.

(Tip Grasping Motion)

[0109] When the twisting motor 76 rotates in the forward direction from this state, the screw shaft 92 rotates in the right-hand thread direction D3. Due to this, the outer sleeve 96 rotates in the right-hand thread direction D3 and then one of the short fins 122 contacts the upper surface of the restricting piece 136R (see FIG. 12) of the right stopper 126R, by the outer sleeve 96 is prohibited from rotating in the right-hand thread direction D3. In this case, the outer sleeve 96 moves frontward relative to the grasping unit 88 with the inner sleeve 94. Due to the outer sleeve 96 moving frontward, the engagement pin 182a moves to the middle portion in the cam holes 166a, 178a, while the engagement pin 182b moves to the middle portion in the cam holes 166b, 178b. At this occasion, because shapes of the cam holes 166a, 166b and the cam holes 178a, 178b are different from each other, the left wire path 186 closes before the right wire path 184 closes. Due to this, as illustrated in FIG. 15, while the left wire path 186 is fully closed, the right wire path 184 is not fully closed. Due to this, the grasping unit 88 grasps a portion of the wire W that is in the left wire path 186 (i.e., near the tip of the wire W). Here, in the state shown in FIG. 15, although the wire W is regulated from diverting from the right wire path 184, the wire W is permitted to move in the right wire path 184.

(Retracting Motion)

[0110] When the twisting motor 76 stops and the feeding motor 32 rotates in the reverse direction from this state, the feeding part 36 retracts the wire W around the rebars R. Because the grasping unit 88 is grasping the vicinity of the tip of the wire W, the diameter of the wire W around the rebars R starts to shrink by the wire W being retracted. Due to this, as illustrated in FIG. 16, the wire W is closely attached on the rebars R.

(Cutting Motion)

[0111] When the twisting motor 76 rotates in the forward direction again from this state, the outer sleeve 96 advances such that the push member 98 (see FIG. 10) pushes in the operation member 68 frontward, by which the shear member 64 advances frontward to the position closing the wire hole 74. Due to this, as illustrated in FIG. 17, the wire W is cut at the cutting position 74a. Also, due to the advancing of the outer sleeve 96, the engagement pin 182a moves to the front portion in the cam holes 166a, 178a, while the engagement pin 182b moves to the front portion in the cam holes 166b, 178b. Due to this, both the left wire path 186 and the right wire path 184 are fully closed. Due to this, the grasping unit 88 grasps a portion of the wire W that is in the left wire path 186 and a portion of the wire W that is in the right wire path 184. In other words, the grasping unit 88 grasps the wire W at two points, i.e., near the tip of the wire W and near the rear end of the wire W.

(Twisting Motion)

[0112] When the outer sleeve 96 further advances due to the forward rotation of the twisting motor 76 from this state, the rear ends of the fins 120 (see FIG. 12) move to a position frontward of the front end of the restricting piece 136R (see FIG. 12), as a result of which the fins 120 are not in contact with the restricting piece 136R anymore. Due to this, the outer sleeve 96 is permitted to rotate in the right-hand thread direction D3. Thereafter, the outer sleeve 96 rotates in the right-hand thread direction D3 due to the forward rotation of the twisting motor 76. The grasping unit 88, that is coupled to the outer sleeve 96 such that the grasping unit 88 cannot rotate relative to the outer sleeve 96, also rotates in the right-hand thread direction D3. Due to this, as illustrated in FIG. 18, the wire W being grasped by the grasping unit 88 starts to be twisted.

(Returning-to-Initial Position Motion)

[0113] Thereafter, the twisting motor 76 rotates in the reverse direction, by which the screw shaft 92 rotates in the left-hand thread direction D4. Due to this, the outer sleeve 96 rotates in the left-hand thread direction D4, and then one of the short fins 122 (see FIG. 12) or the long fin 124 (see FIG. 12) contacts the upper surface of the restricting piece 136L of the left stopper 126L (see FIG. 12), by which the outer sleeve 96 is prohibited from rotating in the left-hand thread direction D4. In this case, the outer sleeve 96 retracts with the inner sleeve 94 relative to the grasping unit 88. Due to the outer sleeve 96 retracting, the engagement pin 182a moves rearward in the cam holes 166a, 178a, while the engagement pin 182b moves rearward in the cam holes 166b, 178b. Due to this, the right wire path 184 and the left wire path 186 are opened, by which the wire W being grasped by the grasping unit 88 is detached from the grasping unit 88. If one of the short fins 122 was in contact with the restricting piece 136L, when the outer sleeve 96 retracts, the front ends of the short fins 122 move to a spot rearward of the rear end of the restricting piece 136L. Due to this, that short fin 122 is not in contact with the restricting piece 136L anymore, the outer sleeve 96 again rotates in the left-hand thread direction D4. Thereafter, when the long fin 124 contacts the upper surface of the restricting piece 136L, the outer sleeve 96 is prohibited again from rotating. Due to this, the twisting mechanism 30 returns to the initial position (see FIG. 10). On the other hand, if the long fin 124 was in contact with the restricting piece 136L, after the outer sleeve 96 has started to retract, the contact between the long fin 124 and the restricting piece 136L is not released, and the twisting mechanism 30 returns to the initial position.

[0114] As illustrated in FIG. 19, the twisting mechanism 30 further comprises an initial position detecting magnet 140a, a tip grasping position detecting magnet 140b, and a twisting start detecting magnet 140c. The initial position detecting magnet 140a and the tip grasping position detecting magnet 140b are attached to the left surface of the push member 98. The twisting start detecting magnet 140c is attached to the lower surface of the swing member 130L of the left stopper 126L.

[0115] As illustrated in FIG. 20, the rebar tying tool 2 further comprises an initial position detecting sensor 142a configured to detect magnetic intensity from the initial position detecting magnet 140a, a tip grasping position detecting sensor 142b configured to detect magnetic intensity from the tip grasping position detecting magnet 140b, and a twisting start detecting sensor 142c configured to detect magnetic intensity from the twisting start detecting magnet 140c. Although not illustrated, the position of each sensor 142a, 142b, and 142c is fixed relative to the body 4.

[0116] The initial position detecting sensor 142a is arranged so as to face the initial position detecting magnet 140a (see FIG. 19) when the twisting mechanism 30 is in the initial position (see FIG. 10). Due to this, the magnetism from the initial position detecting magnet 140a detected by the initial position detecting sensor 142a is the most intense when the twisting mechanism 30 is in the initial position. Accordingly, the initial position detecting sensor 142a detects whether the twisting mechanism 30 is in the initial position or not by detecting whether the magnetism from the initial position detecting magnet 140a is intense or not. Likewise, the tip grasping position detecting sensor 142b is arranged so as to face the tip grasping position detecting magnet 140b (see FIG. 19) when, during the tying operation, the twisting mechanism 30 is in a tip grasping position (see FIG. 15) where the twisting mechanism 30 grasps the vicinity of the tip of the wire W. The magnetism from the tip grasping position detecting magnet 140b detected by the tip grasping position detecting sensor 142b is the most intense when the twisting mechanism 30 is in the tip grasping position. Accordingly, the tip grasping position detecting sensor 142b detects whether the twisting mechanism 30 is in the tip grasping position or not by detecting whether the magnetism from the tip grasping position detecting magnet 140b is intense or not. Likewise, the twisting start detecting sensor 142c is disposed below the swing member 130L (see FIG. 19). Because the swing member 130L does not swing from when the twisting mechanism 30 moves from the initial position until when the twisting mechanism 30 starts the twisting motion, the twisting start detecting sensor 142c faces the twisting start detecting magnet 140c (see FIG. 19) disposed on the lower surface of the swing member 130L. When the twisting mechanism 30 starts the twisting motion, because the restricting piece 136L of the swing member 130L is pushed in leftward by one of the fins 120 (see FIG. 12), the twisting start detecting sensor 142c and the twisting start detecting magnet 140c do not face anymore. At this occasion, the magnetic intensity detected by the twisting start detecting sensor 142c changes. Accordingly, the twisting start detecting sensor 142c detects whether the twisting mechanism 30 has started the twisting motion or not by detecting whether the magnetic intensity has changed or not.

(Configuration of Control Board 20)

[0117] As illustrated in FIG. 20, the control board 20 comprises a control circuit 230, a power circuit 232, a motor current detecting circuit 234, and a battery voltage detecting circuit 236.

[0118] The control circuit 230 comprises a processor and a memory composed of a ROM, a RAM, etc. The ROM has program(s) configured to control the rebar tying tool 2 stored therein. The RAM has respective signals inputted to the control board 20 and/or various data generated in the course of the processor executing processes, temporarily stored therein. The processor is configured to control the rebar tying tool 2 by executing a process based on the information stored in the memory.

[0119] The power circuit 232 adjusts electric power supplied from the battery pack B to be at a predetermined voltage, and supplies the same to each component in the rebar tying tool 2 (e.g., the feeding motor 32, the twisting motor 76).

[0120] The motor current detecting circuit 234 detects current flowing through the feeding motor 32 and current flowing through the twisting motor 76. The motor current detecting circuit 234 is a circuit which measures a current value through the feeding motor 32 and a current value through the twisting motor 76.

[0121] The battery voltage detecting circuit 236 detects the voltage of the battery pack B (i.e., battery remaining level). The battery voltage detecting circuit 236 may be a circuit which measures a voltage value of the battery pack B and/or may be a circuit which obtains a voltage value measured by voltage measurement instrument (not shown), which the battery pack B includes, through communication with the battery pack B.

(Main Process: FIG. 21)

[0122] The control circuit 230 repeatedly executes a main process when power of the rebar tying tool 2 is ON.

[0123] In S2, the control circuit 230 executes a wire type determination process. The wire type determination process comprises the control circuit 230 determining the type of the wire W based on a signal pattern outputted by the sensor board 224 of the wire type detector unit 214. The control circuit 230 has a wire type table shown in FIG. 22 stored therein. The wire type table has relation(s) between the signal pattern and the type of the wire W defined therein. Accordingly, the control circuit 230 refers to the wire type table to determine the type of the wire W. In the present embodiment, the type of the wire W is determined by distinction between three types: annealed wire (i.e., the wire W subjected to an annealing treatment and having iron as its main component); polycoated wire (i.e., annealed wire coated with a polyester resin); and stainless-steel wire (i.e., the wire W having stainless steel as its main component). Also, in the present embodiment, the above three types of the wire W are classified into high-strength wire W and low-strength wire W. For example, wires are classified based on the relative magnitude of their maximum tensile load of each wire. Alternatively, wires are classified based on the relative magnitude of their yield point load of each wire. According to this, the annealed wire is classified as low-strength wire W, the polycoated wire is classified as low-strength wire W, and the stainless steel wire is classified as high-strength wire W. The maximum tensile load and yield point load of the stainless steel wire are 115% or more of the maximum tensile load and yield point load of the annealed wire and the polycoated wire, respectively. Furthermore, in the present embodiment, the above three types of wire W are classified into high-hardness wire W, medium-hardness wire W, and low-hardness wire W. For example, they are classified based on the relative magnitude of their Vickers hardness values of the wires. Accordingly, the annealed wire is classified as medium-hardness wire W, the polycoated wire is classified as low-hardness wire W, and the stainless steel wire is classified as high-hardness wire W. The hardness (i.e., Vickers hardness) of the stainless steel wire is 115% or more of the hardness (i.e., Vickers hardness) of the polycoated wire. After S2 shown in FIG. 21, the process proceeds to S4.

[0124] In S4, the control circuit 230 determines whether the type of the wire W was determined or not in the wire type determination process executed in S2. For example, when the reel 18 is not installed in the reel holder 12, it is determined that the type of the wire W is not determined (i.e., NO) in the wire type determination process. If the type of the wire W is determined (in case of YES), the process proceeds to S6.

[0125] In S6, the control circuit 230 determines whether the battery voltage detected by the battery voltage detecting circuit 236 is less than or equal to a specific first voltage threshold V1 or not. Here, the control circuit 230 determines whether the battery voltage has lowered or not. When the battery voltage lowers, the feeding motor 32 or the twisting motor 76 cannot be driven at a desired output, and thus an initialization process may end incompletely. When the battery voltage exceeds the first voltage threshold V1 (in case of NO), the process proceeds to S8.

[0126] In S8, the control circuit 230 executes the initialization process as a preparatory process for the tying operation. Although details are to be described below, by executing the initialization process, the tip position of the wire W is aligned with a predetermined position (specifically, cutting position 74a shown in FIG. 7), and also the twisting mechanism 30 is set to the initial position. After S8, the process proceeds to S10.

[0127] In S10, the control circuit 230 determines whether the battery voltage has become equal to or less than a specific second voltage threshold V2 while the initialization process is ongoing or not. When either the feeding motor 32 or the twisting motor 76 is driven during the initialization process, the battery voltage temporarily decreases due to the internal resistance of the driven motor. Therefore, in S10, the control circuit 230 determines whether the battery voltage has lowered or not by taking into account the decrease in battery voltage caused by the motor's internal resistance. If the battery voltage is equal to or less than the second voltage threshold V2 (in case of YES), the process proceeds to S12.

[0128] In S12, the control circuit 230 sets a low voltage flag indicating that the battery voltage has lowered. The low voltage flag is deleted if an error process (process of S30) to be described below is executed. After S12, the process proceeds to S14.

[0129]In S14, the control circuit 230 determines whether or not the trigger 8 is pushed in and thus the trigger switch 9 is turned on. When the trigger 8 is not pushed in and thus the trigger switch 9 is off (in case of NO), the process repeats S14. If the trigger switch 9 is turned on (in case of YES), the process proceeds to S16.

[0130] In S16, the control circuit 230 executes the wire type determination process. The wire type determination process is the same as the one described in S2. After S16, the process proceeds to S18.

[0131] In S18, the control circuit 230 determines whether or not the type of the wire W has been determined in the wire type determination process executed in S16. For example, if the reel 18 is not installed in the reel holder 12, it is determined that the type of the wire W is not determined in the wire type determination process (i.e., NO). If the type of the wire W is determined (in case of YES), the process proceeds to S20.

[0132] In S20, the control circuit 230 determines whether or not the low voltage flag is set. If the low voltage flag is not set (in case of NO), the process proceeds to S22.

[0133] In S22, the control circuit 230 determines whether the battery voltage is equal to or less than the first voltage threshold V1 or not. The first voltage threshold V1 is the same as the one described in S6. In S22, the control circuit 230 determines whether the battery voltage has lowered or not. When the battery voltage exceeds the first voltage threshold V1 (in case of NO), the process proceeds to S24.

[0134] In S24, the control circuit 230 executes the tying process for causing the rebar tying tool 2 to execute the tying operation. Although details will be described later, by executing the tying process, the rebar tying tool 2 ties the rebars R with the wire W. After S24, the process proceeds to S26.

[0135] In S26, the control circuit 230 determines whether or not the battery voltage has become equal to or less than the second voltage threshold V2 while the tying process is ongoing. The second voltage threshold V2 is the same as the one described in S10. When either the feeding motor 32 or the twisting motor 76 is driven during the tying process, the battery voltage temporarily decreases due to the internal resistance of the driven motor. Therefore, in S26, the control circuit 230 determines whether the battery voltage has lowered or not by taking into account the decrease in battery voltage caused by the motor's internal resistance. If the battery voltage is equal to or less than the second voltage threshold V2 (in case of YES), the process proceeds to S28.

[0136] In S28, the control circuit 230 sets the low voltage flag except when the low voltage flag has already been set. The low voltage flag is deleted when the error process (process of S30) to be described below is executed. After S28, the process returns to S14.

[0137] If the type of the wire W is not determined (in case of NO) in S4, if the battery voltage is equal to or less than the first voltage threshold V1 (in case of YES) in S6, if the type of the wire W is not determined (in case of NO) in S18, if the low voltage flag has been set (in case of YES) in S20, or if the battery voltage is equal to or less than the first voltage threshold V1 (in case of YES) in S22, the process proceeds to S30. In S30, the control circuit 230 executes the error process. In the error process, the control circuit 230 causes the display unit 4c to display the content of the error (e.g., the type of the wire W having not been determined, and the lowered battery voltage). Also, the control circuit 230 prohibits the feeding motor 32 and the twisting motor 76 from being driven. The error process is continued, for example, until the power of the rebar tying tool 2 is turned off.

(Parameter Change Related to Main Process)

[0138] The control circuit 230 changes the first voltage threshold V1 and the second voltage threshold V2 according to the type of the wire W determined in the wire type determination process. Specifically, the control circuit 230 makes the voltage thresholds V1, V2 set for the stainless-steel wire (i.e., high-strength wire W) higher than the voltage thresholds V1, V2 set for the annealed wire and the polycoated wire (i.e., low-strength wire W). When feeding (or twisting) the high-strength wire W, higher output is required as compared to when feeding (or twisting) the low-strength wire W. Due to this, when the high-strength wire W is used, the voltage thresholds V1, V2 are made higher, and the error process caused by the decrease in the battery voltage is executed earlier. Due to this, the rebar tying tool 2 can be suppressed from the feeding motion (or the twisting motion) ending incompletely. On the other hand, when the low-strength wire W is used, the voltage thresholds V1, V2 are made lower, and the battery voltage is consumed as much as possible. Due to this, replace frequency of the battery pack B can be decreased.

(Initialization Process: FIG. 23)

[0139] The initialization process is executed in S8 of the main process (see FIG. 21).

[0140] In S50, the control circuit 230 executes a returning-to-initial position process for the twisting mechanism 30 to return to the initial position, except when the twisting mechanism 30 is already in the initial position.

(Returning-to-Initial Position Process: FIG. 24)

[0141] When the returning-to-initial position process is started, the process proceeds to S52.

[0142] In S52, the control circuit 230 drives the twisting motor 76 such that the twisting motor 76 rotates in the reverse direction. Due to this, the twisting mechanism 30 moves toward the initial position. Specifically, the screw shaft 92 rotates in the left-hand thread direction D4, by which the outer sleeve 96 retracts. When the control circuit 230 drives the twisting motor 76, the control circuit 230 executes control of adjusting the voltage value applied on the twisting motor 76 to a specific target voltage value (also termed constant-voltage control). Also, the control circuit 230 keeps driving the twisting motor 76 driven in S52 until the control circuit 230 stops the same in S56. After S52, the process proceeds to S54.

[0143] In S54, the control circuit 230 determines whether or not the twisting mechanism 30 has reached the initial position based on the detection result of the initial position detecting sensor 142a. If the twisting mechanism 30 has not reached the initial position (in case of NO), the process repeats S54. While S54 is repeated, the twisting mechanism 30 is moving toward the initial position. If the twisting mechanism 30 reaches the initial position (in case of YES), the process proceeds to S56.

[0144] In S56, the control circuit 230 stops the twisting motor 76. After S56, the returning-to-initial position process ends. When the returning-to-initial position process ends, the process proceeds to S60 shown in FIG. 23. In S60, the control circuit 230 executes a cutting attempt process for attempting to cut the wire W.

(Cutting Attempt Process: FIG. 25)

[0145] When the cutting attempt process is started, the process proceeds to S62.

[0146] In S62, the control circuit 230 drives the twisting motor 76 such that the twisting motor 76 rotates in the forward direction. Due to this, the screw shaft 92 rotates in the right-hand thread direction D3, by which the outer sleeve 96 advances, and the cutting mechanism 28 starts the cutting motion. That is, the shear member 64 moves frontward along the guide path 72. When the control circuit 230 drives the twisting motor 76, the control circuit 230 executes control of adjusting the voltage value applied on the twisting motor 76 to a specific target voltage value (also termed constant-voltage control). Also, the control circuit 230 keeps driving the twisting motor 76 driven in S62 until the control circuit 230 stops the same in S76. After S62, the process proceeds to S64.

[0147]In S64, the control circuit 230 determines whether or not an elapsed time since when the twisting motor 76 was activated in S62 (i.e., running time of the twisting motor 76) has exceeded a first predetermined time T₁. If the running time of the twisting motor 76 is equal to or less than the first predetermined time T₁ (in case of NO), the process repeats S64. The first predetermined time T₁ is a waiting period until a start-up current flowing through the twisting motor 76 exceeds its peak. If the running time of the twisting motor 76 exceeds the first predetermined time T₁ (in case of YES), the process proceeds to S66.

[0148]In S66, the control circuit 230 calculates a current threshold I_th to be used in a later process based on the current value flowing through the twisting motor 76. For example, the control circuit 230 calculates a value obtained by adding a predetermined value to the average value of the current flowing through the twisting motor 76 during the period in which S66 and S68 are repeatedly executed, as the current threshold I_th. After S66, the process proceeds to S68.

[0149]In S68, the control circuit 230 determines whether or not the running time of the twisting motor 76 has exceeded a second predetermined time T₂ which is longer than the first predetermined time T₁. If the running time of the twisting motor 76 is equal to or less than the second predetermined time T₂ (in case of NO), the process returns to S66. If the running time of the twisting motor 76 exceeds the second predetermined time T₂ (in case of YES), the process proceeds to S70.

[0150]In S70, the control circuit 230 determines whether or not a state where the current value flowing through the twisting motor 76 (i.e., the twisting motor current value I) exceeds the current threshold I_th calculated in S66 continues over a predetermined time. When the cutting mechanism 28 cuts the wire W, a load applied on the twisting motor 76 via the cutting mechanism 28 increases. In this case, because the control circuit 230 is executing the constant-voltage control on the twisting motor 76, the twisting motor current value I increases due to the increase in the load applied on the twisting motor 76. Due to this, as illustrated in FIG. 26, after the twisting motor current value I exceeds the peak of the start-up current, the twisting motor current value I increases again. Based on this, if the state where the twisting motor current value I exceeds the current threshold I_th continues over the predetermined time in S70 (in case of YES), it can be presumed that the cutting mechanism 28 has cut the wire W. Contrary to this, when the cutting mechanism 28 does not cut the wire W, a large load is not applied on the twisting motor 76. Due to this, as illustrated in FIG. 27, after the twisting motor current value I exceeds the peak of the start-up current, the twisting motor current value I does not increase anymore. Based on this, if the state where the twisting motor current value I exceeds the current threshold I_th does not continue over the predetermined time in S70 (in case of NO), it can be presumed that the cutting mechanism 28 has not cut the wire W. Accordingly, in S70 shown in FIG. 25, the control circuit 230 can be regarded as determining whether the cutting mechanism 28 has cut the wire W. If the state where the twisting motor current value I exceeds the current threshold I_th continues over the predetermined time (in case of YES), the process proceeds to S72.

[0151] In S72, the control circuit 230 sets a cut-complete flag indicating that the cutting mechanism 28 has cut the wire W. The cut-complete flag is deleted for example when the initialization process (see FIG. 23) ends. After S72, the process proceeds to S74.

[0152] If the state where the twisting motor current value I exceeds the current threshold I_th does not continue over the predetermined time in S70 (in case of NO) or after S72, the process proceeds to S74. In S74, the control circuit 230 determines whether or not the shear member 64 has moved beyond the cutting position 74a (see FIG. 7). At this occasion, the control circuit 230 determines whether or not the twisting mechanism 30 has started the twisting motion based on the detection result of the twisting start detecting sensor 142c. This is because the shear member 64 is at the position beyond the cutting position 74a (see FIG. 17) when the twisting mechanism 30 is starting the twisting motion. If the shear member 64 has not moved beyond the cutting position 74a (in case of NO), the process returns to S70. Due to this, S70, S72, and S74 are repeated. During the repeated processes, the shear member 64 is advancing along the guide path 72. Due to this, the shear member 64 eventually moves beyond the cutting position 74a. If the shear member 64 has moved beyond the cutting position 74a (in case of YES), the process proceeds to S76.

[0153] In S76, the control circuit 230 stops the twisting motor 76. After S76, the process proceeds to S78.

[0154] In S78, the control circuit 230 drives the twisting motor 76 such that the twisting motor 76 rotates in the reverse direction. Due to this, the twisting mechanism 30 moves toward the initial position. Specifically, the screw shaft 92 rotates in the left-hand thread direction D4, by which the outer sleeve 96 retracts. When the control circuit 230 drives the twisting motor 76, the control circuit 230 executes control of adjusting the voltage value applied on the twisting motor 76 to a specific target voltage value (also termed constant-voltage control). Also, the control circuit 230 keeps driving the twisting motor 76 driven in S78 until the control circuit 230 stops the same in S82. After S78, the process proceeds to S80.

[0155] In S80, the control circuit 230 determines whether or not the twisting mechanism 30 has reached the initial position based on the detection result of the initial position detecting sensor 142a. If the twisting mechanism 30 has not reached the initial position (in case of NO), the process repeats S80. While S80 is repeated, the twisting mechanism 30 moves toward the initial position. If the twisting mechanism 30 reaches the initial position (in case of YES), the process proceeds to S82.

[0156] In S82, the control circuit 230 stops the twisting motor 76. After S82, the cutting attempt process ends. When the cutting attempt process ends, the process proceeds to S90 shown in FIG. 23.

[0157] In S90, the control circuit 230 counts the number of times the cutting attempt process is executed (i.e., number of times of cutting attempts) while the initialization process is ongoing. After S90, the process proceeds to S92.

[0158] In S92, the control circuit 230 determines whether the cut-complete flag has been set. If the cut-complete flag is not set (in case of NO), the process proceeds to S94.

[0159]In S94, the control circuit 230 determines whether or not the number of times of cutting attempts is equal to or more than an upper limit number of times of attempts (e.g., 10 times). If the number of times of cutting attempts is less than the upper limit number of times of attempts (in case of NO), the process proceeds to S100. In S100, the control circuit 230 executes a small-amount feeding process for feeding a small amount of the wire W.

(Small-Amount Feeding Process: FIG. 28)

[0160] When the small-amount feeding process is started, the process proceeds to S102.

[0161] In S102, the control circuit 230 drives the feeding motor 32 such that the feeding motor 32 rotates in the forward direction. Due to this, the feeding mechanism 24 starts the feeding motion. When the control circuit 230 drives the feeding motor 32, the control circuit 230 executes control of adjusting the voltage value applied on the feeding motor 32 to a specific target voltage value (also termed constant-voltage control). Also, the control circuit 230 keeps driving the feeding motor 32 driven in S102 until the control circuit 230 stops the same in S106. After S102, the process proceeds to S104.

[0162] In S104, the control circuit 230 determines whether or not the number of times the feeding motor 32 rotated (which may hereinbelow be termed “rotation number”) since when the feeding motor 32 was activated has become equal to or more than a first target number of times the feeding motor 32 rotated (which may hereinbelow be termed “first target rotation number”) based on the detection result of the rotation detecting board 33. The feeding amount of the wire W by the small-amount feeding process is proportional to the rotation number of the feeding motor 32. The first target rotation number used in S104 is set such that the feeding amount of the wire W by the small-amount feeding process is small. The small amount herein mentioned means, for example, a feeding amount that is smaller than a distance between the position intermediate between the first gear 44 and the second gear 46 (see FIG. 6) and the cutting position 74a (see FIG. 7). If the rotation number of the feeding motor 32 is less than the first target rotation number (in case of NO), the process repeats S104. While S104 is repeated, the feeding motion by the feeding mechanism 24 is continued, by which the wire W keeps being fed. If the rotation number of the feeding motor 32 becomes equal to or more than the first target rotation number (in case of YES), the process proceeds to S106.

[0163] In S106, the control circuit 230 stops the feeding motor 32. After S106, the small-amount feeding process ends. When the small-amount feeding process ends, the process returns to S60 shown in FIG. 23.

[0164] Normally, the cutting mechanism 28 cuts the wire W by repeating the cutting attempt process and the small-amount feeding process, by which the tip position of the wire W is aligned with the cutting position 74a (see FIG. 7). Also, since the cut-complete flag is set when the cutting mechanism 28 has cut the wire W, YES is determined in the following S92, and the initialization process ends.

[0165] However, there may be a case in which the number of times of cutting attempts keeps increasing without the wire W being cut. For example, this may happen when the wire W is not properly set in the feeding mechanism 24. In this case, the number of times of cutting attempts is determined as being equal to or more than the upper limit number of times of attempts (YES) in S94, and the process proceeds to S96. In S96, the control circuit 230 executes the error process. In the error process, the control circuit 230 causes the display unit 4c to display the content of the error (e.g., improper setting of the wire W in the feeding mechanism 24). Also, the control circuit 230 prohibits the feeding motor 32 and the twisting motor 76 from being driven. The error process is continued, for example, until the power of the rebar tying tool 2 is turned off.

(Parameter Changes Related to Small-Amount Feeding Process)

[0166] The control circuit 230 changes the target voltage value for the constant-voltage control in the small-amount feeding process (see FIG. 28) according to the type of the wire W determined in the wire type determination process of the main process (see FIG. 21). Specifically, the control circuit 230 makes the target voltage value set for the annealed wire (i.e., medium-hardness wire W) lower than the target voltage value set for the stainless-steel wire (i.e., high-hardness wire W). Also, the target voltage value set for the polycoated wire (i.e., low-hardness wire W) is made lower than the target voltage value set for the annealed wire (i.e., medium-hardness wire W). As the hardness of the wire W is lower, the wire W is more easily damaged while the wire W is being fed by the feeding mechanism 24. The polycoated wire (i.e., wire W with coating material) risks having its coating material peeled off. Due to this, when the low-hardness wire W is used, the target voltage value is lowered to prevent damage on the surface of wire W. When the wire W with coating material is used, the target voltage value is lowered and the rotation speed of the feeding motor 32 is decreased to suppress the coating material from peeling off. On the other hand, when the high-hardness wire W is used, the target voltage value is increased to raise the rotation speed of the feeding motor 32 to feed the wire W quickly.

[0167] Also, the control circuit 230 changes the first target rotation number at the small-amount feeding process according to the type of the wire W. Specifically, the control circuit 230 makes the first target rotation number set for the polycoated wire (i.e., the wire W with coating material) greater than the first target rotation number set for the annealed wire and the stainless-steel wire (i.e., the wire W without coating material). Since the wire W with coating material tends to slip easier than the wire W without coating material, the feeding amount of the wire W with coating material by the feeding mechanism 24 may result in being smaller than a desired amount. Due to this, when the wire W with coating material is used, the feeding amount is adjusted to achieve the desired amount by increasing the first target rotation number.

(Tying Process: FIG. 29)

[0168] The tying process is executed in S24 of the main process (see FIG. 21).

[0169] The tying process comprises the control circuit 230 sequentially executing the feeding process, the tip grasping process, the retracting process, the cutting and twisting process, and the returning-to-initial position process. The feeding process is a process of causing the rebar tying tool 2 to execute the feeding motion by rotating the feeding motor 32 in the forward direction. The tip grasping process is a process of causing the rebar tying tool 2 to execute the tip grasping motion by rotating the twisting motor 76 in the forward direction. The retracting process is a process of causing the rebar tying tool 2 to execute the retracting motion by rotating the feeding motor 32 in the reverse direction. The cutting and twisting process is a process of causing the rebar tying tool 2 to execute the cutting motion and the twisting motion by rotating the twisting motor 76 in the forward direction. The returning-to-initial position process is a process of causing the rebar tying tool 2 to execute the returning-to-initial position motion by rotating the twisting motor 76 in the reverse direction.

(Feeding Process: FIG. 30)

[0170] In S122, the control circuit 230 drives the feeding motor 32 such that the feeding motor 32 rotates in the forward direction. Due to this, the feeding mechanism 24 starts the feeding motion. When the control circuit 230 drives the feeding motor 32, the control circuit 230 executes the control of adjusting the voltage value applied on the feeding motor 32 to a specific target voltage value (also termed constant-voltage control). Also, the control circuit 230 keeps driving the feeding motor 32 driven in S122 until the control circuit 230 stops the same in S126. After S122, the process proceeds to S124.

[0171] In S124, the control circuit 230 determines whether or not the rotation number of the feeding motor 32 since when the feeding motor 32 was activated has become equal to or more than a second target number of times the feeding motor 32 rotated (hereinbelow termed “second target rotation number”) based on the detection result of the rotation detecting board 33. The feeding amount of the wire W by the feeding process is proportional to the rotation number of the feeding motor 32. The second target rotation number used in S124 is set, for example, such that the feeding amount of the wire W by the feeding process is approximately 320 mm. If the rotation number of the feeding motor 32 is less than the second target rotation number (in case of NO), the process repeats S124. While S124 is repeated, the feeding motion by the feeding mechanism 24 is continued, by which the wire W is gradually wound around the rebars R in a circular ring shape. If the rotation number of the feeding motor 32 becomes equal to or more than the second target rotation number (in case of YES), the process proceeds to S126.

[0172] In S126, the control circuit 230 stops the feeding motor 32. After S126, the feeding process ends.

(Parameter Changes Related to Feeding Process)

[0173] The control circuit 230 changes the target voltage value for the constant-voltage control in the feeding process according to the type of the wire W determined in the wire type determination process of the main process (see FIG. 21). Specifically, the control circuit 230 makes the target voltage value set for the annealed wire (i.e., the medium-hardness wire W) lower than the target voltage value set for the stainless-steel wire (i.e., the high-hardness wire W). Also, the target voltage value set for the polycoated wire (i.e., the low-hardness wire W) is made lower than the target voltage value set for the annealed wire (i.e., the medium-hardness wire W). As the hardness of the wire W is lower, the wire W is more easily damaged while the wire W is being fed by the feeding mechanism 24. The polycoated wire (i.e., wire W with coating material) risks having its coating material peeled off. Due to this, when the low-hardness wire W is used, the target voltage value is lowered to prevent damage on the surface of wire W. When the wire W with coating material is used, the target voltage value is lowered to reduce the rotation speed of the feeding motor 32 to suppress the coating material from peeling off. On the other hand, when the high-hardness wire W is used, the target voltage value is increased to raise the rotation speed of the feeding motor 32 to feed the wire W quickly.

[0174] Also, the control circuit 230 changes the second target rotation number at the feeding process according to the type of the wire W. Specifically, the control circuit 230 makes the second target rotation number set for the polycoated wire (i.e., the wire W with coating material) greater than the second target rotation number set for the annealed wire and the stainless-steel wire (i.e., the wire W without coating material). Since the wire W with coating material tends to slip easier than the wire W without coating material, the feeding amount of the wire W with coating material by the feeding mechanism 24 may result in being smaller than a desired amount. Due to this, when the wire W with coating material is used, the feeding amount is adjusted to achieve the desired amount by increasing the second target rotation number.

(Tip Grasping Process: FIG. 31)

[0175] In S132, the control circuit 230 drives the twisting motor 76 such that the twisting motor 76 rotates in the forward direction. Due to this, the screw shaft 92 rotates in the right-hand thread direction D3 from the state where the twisting mechanism 30 is in the initial position, by which the outer sleeve 96 advances. When the control circuit 230 drives the twisting motor 76, the control circuit 230 executes control of adjusting the voltage value applied on the twisting motor 76 to a specific target voltage value (also termed constant-voltage control). Also, the control circuit 230 keeps driving the twisting motor 76 driven in S132 until the control circuit 230 stops the same in S144. After S132, the process proceeds to S134.

[0176]In S134, the control circuit 230 determines whether or not an elapsed time since when the twisting motor 76 was activated in S132 (i.e., running time of the twisting motor 76) has exceeded a current mask time T_m. If the running time of the twisting motor 76 is equal to or less than the current mask time T_m (in case of NO), the process repeats S134. The current mask time T_m is a standby time until the start-up current flowing through the twisting motor 76 exceeds its peak. If the running time of the twisting motor 76 exceeds the current mask time T_m (in case of YES), that is, if the start-up current flowing through the twisting motor 76 exceeds its peak, the process proceeds to S136.

[0177]In S136, the control circuit 230 sets a reference value I_r used in a later process. For example, the control circuit 230 sets the twisting motor current value I when the running time of the twisting motor 76 exceeds the current mask time T_m as the reference value I_r. After S136, the process proceeds to S138.

[0178]In S138, the control circuit 230 determines whether or not the current twisting motor current value I is smaller than the set reference value I_r. If the current twisting motor current value I is smaller than the reference value I_r (in case of YES), the process proceeds to S140.

[0179]In S140, the control circuit 230 sets the current twisting motor current value I as a new reference value I_r. That is, the control circuit 230 updates the reference value I_r. The control circuit 230 refers to the updated reference value I_r in the following processes.

[0180] If the current twisting motor current value I is equal to or more than the reference value I_r in S138 (in case of NO), or after S140, the process proceeds to S142. In S142, the control circuit 230 determines whether or not the twisting mechanism 30 has reached the tip grasping position based on the detection result of the tip grasping position detecting sensor 142b. If the twisting mechanism 30 has not reached the tip grasping position (in case of NO), the process returns to S138. If the twisting mechanism 30 has reached the tip grasping position (in case of YES), the process proceeds to S144.

[0181] In S144, the control circuit 230 stops the twisting motor 76. After S144, the tip grasping process ends.

(RETRACTING PROCESS: FIG. 32)

[0182] In S152, the control circuit 230 drives the feeding motor 32 such that the feeding motor 32 rotates in the reverse direction. Due to this, the feeding mechanism 24 starts the retracting motion. When the control circuit 230 drives the feeding motor 32, the control circuit 230 executes control of causing the current value flowing through the feeding motor 32 to follow a specific target current value (also termed constant-current control). Also, the control circuit 230 keeps driving the feeding motor 32 driven in S152 until the control circuit 230 stops the same in S158. After S152, the process proceeds to S154.

[0183] In S154, the control circuit 230 determines whether or not the rotation number of the feeding motor 32 since when the feeding motor 32 was activated has become equal to or more than an upper limit number of times the feeding motor 32 rotated (hereinbelow termed “upper limit rotation number”) based on the detection result of the rotation detecting board 33. If the rotation number of the feeding motor 32 is less than the upper limit rotation number (in case of NO), the process proceeds to S156.

[0184] In S156, the control circuit 230 determines whether or not the rotation speed of the feeding motor 32 has become equal to or more than a retract termination speed based on the detection result of the rotation detecting board 33. When the wire W is closely attached to the rebars R due to the retraction of the wire W, the feeding mechanism 24 cannot retract the wire W any further. In this case, a load applied through the feeding mechanism 24 on the feeding motor 32 increases. Because, in the retracting process, the control circuit 230 executes the constant-current control, the rotation speed of the feeding motor 32 gradually decreases as a load applied on the feeding motor 32 increases. Accordingly, in S156, the control circuit 230 can be regarded as determining whether or not the wire W has been closely attached to the rebars R. If the rotation speed of the feeding motor 32 exceeds the retract termination speed (in case of NO), that is, if the wire W is not closely attached to the rebars R, the process returns to S154.

[0185] If the rotation number of the feeding motor 32 is equal to or more than the upper limit rotation number in S154 (in case of YES), the process proceeds to S158. Alternatively, if the rotation speed of the feeding motor 32 is equal to or less than the retract termination speed in S156 (in case of YES), that is, if the wire W is closely attached to the rebars R, the process proceeds to S158. In S158, the control circuit 230 stops the feeding motor 32. After S158, the retracting process ends.

(Parameter Change Related to Retracting Process)

[0186] The control circuit 230 changes the target current value for constant-current control in the retracting process (i.e., torque of the feeding motor 32) and the retract termination speed according to the type of the wire W determined in the wire type determination process of the main process (see FIG. 21). Specifically, the control circuit 230 makes the target current value set for the polycoated wire (i.e., the wire W with coating material) lower than the target current value set for the annealed wire and the stainless-steel wire (i.e., the wire W without coating material). Also, the control circuit 230 makes the retract termination speed set for the polycoated wire (i.e., the wire W with coating material) higher than the retract termination speed set for the annealed wire and the stainless-steel wire (i.e., the wire W without coating material). Since the wire W with coating material tends to slip easier than the wire W without coating material, if the torque of the feeding motor 32 is excessively high, slippage may occur between the feeding mechanism 24 and the wire W, as a result of which it may take a long time for the rotation speed of the feeding motor 32 to become equal to or less than the retract termination speed. As such, it may take long time to complete the retracting process. Due to this, when the wire W with coating material is used, the target current value is lowered to suppress slippage between the feeding mechanism 24 and the wire W. Also, the retract termination speed is increased, the feeding motor 32 is stopped earlier. Due to this, the retracting process can be completed quickly.

(Cutting and Twisting Process: FIG. 33)

[0187] In S172, the control circuit 230 drives the twisting motor 76 such that the twisting motor 76 rotates in the forward direction. Due to this, the screw shaft 92 rotates in the right-hand thread direction D3 such that the outer sleeve 96 advances from the state where the twisting mechanism 30 is in the tip grasping position. When the control circuit 230 drives the twisting motor 76, the control circuit 230 executes control of adjusting the voltage value applied on the twisting motor 76 to a specific target voltage value (also termed constant-voltage control). Also, the control circuit 230 keeps driving the twisting motor 76 driven in S172 until the control circuit 230 stops the same in S190. After S172, the process proceeds to S174.

[0188] In S174, the control circuit 230 determines whether or not the twisting mechanism 30 has started the twisting motion based on the detection result of the twisting start detecting sensor 142c. If the twisting mechanism 30 has not started the twisting motion (in case of NO), the process repeats S174. While S174 is repeated, the twisting mechanism 30 gradually moves toward the position at which the twisting mechanism 30 starts the twisting motion. If the twisting mechanism 30 starts the twisting motion (in case of YES), the process proceeds to S176.

[0189] In S176, the control circuit 230 starts counting the number of times the twisting motor 76 rotated (hereinbelow termed “rotation number”) based on the detection result of the rotation detecting board 78. Due to this, the rotation number of the twisting motor 76 since the twisting mechanism 30 started the twisting motion is counted. After S176, the process proceeds to S178.

[0190] In S178, the control circuit 230 determines whether or not the rotation number of the twisting motor 76 since the twisting mechanism 30 started the twisting motion has become equal to or more than a lower limit number of times the twisting motor 76 rotated (hereinbelow termed “lower limit rotation number”). If the rotation number of the twisting motor 76 is less than the lower limit rotation number (in case of NO), the process repeats S176. By S176 being repeated, the twisting mechanism 30 continues the twisting motion to a degree that is minimally required. If the rotation number of the twisting motor 76 is equal to or more than the lower limit rotation number (in case of YES), the process proceeds to S180.

[0191]In S180, the control circuit 230 calculates a current difference value ΔI used in a later process. The control circuit 230 calculates a value obtained by subtracting the reference value I_r set in the tip grasping process (see FIG. 31) from the current twisting motor current value I as the current difference value ΔI. After S180, the process proceeds to S182.

[0192]In S182, the control circuit 230 determines whether the current difference value ΔI calculated in S180 is equal to or more than a first difference threshold I_d1 or not. The first difference threshold I_d1 is set according to a setting value of tying force that is set in advance by a user. At the setting value for tying force is higher, the first difference threshold I_d1 is set to a greater value. As the setting value for tying force is lower, the first difference threshold I_d1 is set to a smaller value. Since, as the twisting mechanism 30 twists the wire W, twisting torque of the wire W increases, load applied through the twisting mechanism 30 on the twisting motor 76 increases. In this case, because the control circuit 230 executes the constant-voltage control on the twisting motor 76, as the load on the twisting motor 76 increases, the twisting motor current value I, i.e., the current difference value ΔI increases. If the current difference value ΔI increases and thus the current difference value ΔI becomes equal to or more than the first difference threshold I_d1, YES is determined in S182 and the process proceeds to S190. In S190, the control circuit 230 stops the twisting motor 76. Due to this, when the twisting torque of the wire W has increased to some extent, the twisting motion ends. Also, the first difference threshold I_d1 is set such that the twisting torque when the current difference value ΔI reaches the first difference threshold I_d1 (i.e., when the twisting motion ends) is of a desired magnitude according to the setting value of tying force. Due to this, the twisting torque of the wire W when the twisting motion ends (i.e., twisting completion torque) is adjusted to a desired magnitude according to the tying force setting value. In S182, the control circuit 230 can be regarded as determining whether the twisting torque of the wire W has become of the desired magnitude or not.

[0193] If the current difference value ΔI is less than the first difference threshold I_d1 in S182 (in case of NO), the process proceeds to S184. In S184, the control circuit 230 determines whether the current difference value ΔI calculated in S180 is equal to or more than a second difference threshold I_d2 that is smaller than the first difference threshold I_d1. Similar to the first difference threshold I_d1, the second difference threshold I_d2 is set according to the tying force setting value that is set in advance by the user. The second difference threshold I_d2 is set such that the twisting torque when the current difference value ΔI reaches the second difference threshold I_d2 is not of the desired magnitude but is of a certain degree of magnitude.

[0194] If the current difference value ΔI is equal to or more than the second difference threshold I_d2 in S184 (in case of YES), the process proceeds to S186. In S186, the control circuit 230 monitors a time rate of change dI/dt of the twisting motor current value I, and determines whether or not the time rate of change dI/dt has changed from positive to negative. When the twisting mechanism 30 continues twisting the wire W, the wire W may become on the verge of being twisted off. Immediately before the wire W is twisted off, tension of the wire W lowers, by which the load applied on the twisting motor 76 lowers. In this case, since the control circuit 230 executes the constant-voltage control on the twisting motor 76, due to the decrease in the load applied on the twisting motor 76, the twisting motor current value I, that is, the current difference value ΔI decreases. When the current difference value ΔI decreases, because the time rate of change dI/dt changes from positive to negative, YES is determined in S186 and the process proceeds to S190. In S190, the control circuit 230 stops the twisting motor 76. Due to this, because the twisting motion ends immediately before the wire W is twisted off, the wire W can be suppressed from being twisted off. In S184, the control circuit 230 can be regarded as determining whether the wire W is on the verge of being twisted off or not.

[0195] If the current difference value ΔI is less than the second difference threshold I_d2 in S184 (in case of NO), or if the time rate of change dI/dt has not changed from positive to negative in S186 (in case of NO), the process proceeds to S188. In S188, the control circuit 230 determines whether or not the rotation number of the twisting motor 76 since the twisting mechanism 30 started the twisting motion has become equal to or more than the upper limit rotation number. If the rotation number of the twisting motor 76 is less than the upper limit rotation number (in case of NO), the process returns to S180. If the rotation number of the twisting motor 76 is equal to or more than the upper limit rotation number (in case of YES), the process proceeds to S190. In S190, the control circuit 230 stops the twisting motor 76. Due to this, the twisting motion ends.

[0196] After S190, the cutting and twisting process ends.

(Parameter Changes Related to Cutting and Twisting Process)

[0197]The control circuit 230 changes the first difference threshold I_d1 and the second difference threshold I_d2 according to the type of the wire W determined in the wire type determination process of the main process (see FIG. 21). Specifically, the control circuit 230 makes the difference thresholds I_d1, I_d2 set for the stainless-steel wire (i.e., high-strength wire W) higher than the difference thresholds I_d1, I_d2 set for the annealed wire and the polycoated wire (i.e., low-strength wires W). When a high-strength wire W is twisted, high output is required for the twisting motor 76. However, if the twisting motor 76 is caused to exert high output also when twisting a low-strength wire W, the wire W may be twisted off. Accordingly, when a high-strength wire W is used, the difference thresholds I_d1, I_d2 are made higher, and the twisting motor 76 is caused to exert high output. Contrary to this, when a low-strength wire W is used, the difference thresholds I_d1, I_d2 are made lower, and the twisting motor 76 is not caused to exert high output. Due to this, the wire W can be suppressed from being twisted off.

(Returning-To-Initial Position Process)

[0198] In the returning-to-initial position process, the control circuit 230 drives the twisting motor 76 such that the twisting motor 76 rotates in the reverse direction, and causes the twisting mechanism 30 to return to the initial position. Here, because the returning-to-initial position process in the tying process is the same as the returning-to-initial position process (see FIG. 24) that is aforementioned as a part of the initialization process (see FIG. 23), FIG. 24 should be referred to for details thereof.

(Advantages of Tying Process)

[0199] As illustrated in FIGS. 34, 35, the twisting motor current value I when the same process is executed may vary according to the temperature of an environment in which the rebar tying tool 2 is used. This is because the viscosity of lubricant added to the twisting mechanism 30 and the twisting motor 76 may change depending on the temperature of the environment in which the rebar tying tool 2 is used, for example, by which the loss amount in the twisting mechanism 30 and the twisting motor 76 changes. For example, in a low-temperature (-20°C) environment, as compared to a room temperature (e.g., 27°C) environment, the loss amount in the twisting mechanism 30 and the twisting motor 76 is greater and the twisting motor current value I is greater. Due to this, if the twisting motion is stopped in response to the twisting motor current value I becoming greater after starting the twisting motion, the twisting completion torque may become smaller in the low-temperature environment, as compared to that in the room-temperature environment.

[0200]Thus, in the tying process of the present embodiment, the reference value I_r is set as an index representing the magnitude of the loss amount in the twisting mechanism 30 and the twisting motor 76, and this reference value I_r is reflected in the condition for stopping the twisting motion (i.e., the twisting stop condition). The twisting stop condition herein mentioned is the determination condition in S182 shown in FIG. 33.

[0201]As illustrated in FIG. 34, the reference value I_r is a minimum value of the twisting motor current value I in a period in the tip grasping process (see FIG. 31) from when the twisting motor 76 is activated after the current mask time T_m has elapsed (i.e., period after exceeding the peak of the start-up current of the twisting motor 76). The reference value I_r in the low-temperature environment is a greater value than the reference value I_r in the room-temperature environment. This is because in the low-temperature environment, the loss amount in the twisting mechanism 30 and the twisting motor 76 is greater than that in the room-temperature environment.

[0202] As illustrated in FIG. 35, in the present embodiment, when, after starting the twisting motion, the difference ΔI between the twisting motor current value I and the reference value I_r becomes the first difference threshold I_d1, the twisting stop condition is satisfied. Thereafter, the twisting motor 76 stops, and the twisting motion stops. Due to this, in the low-temperature environment, the twisting motion is continued until the twisting motor current value I becomes an excessively large value as compared to that in the room-temperature environment. As a result of this, the increase in the loss amount in the low-temperature environment is cancelled out, by which the twisting completion torque becomes of the same magnitude as in the room-temperature environment. Due to this, the twisting completion torque can be suppressed from varying depending on the temperature of the environment in which the rebar tying tool 2 is used. In other words, the twisting completion torque can be suppressed from varying depending on the change(s) in the loss amount in the twisting mechanism 30 and the twisting motor 76.

[0203] Also in the present embodiment, as another twisting stop condition, there is a determination condition of S184 shown in FIG. 33. This twisting stop condition is set also based on the reference value I_r.

(Second Embodiment)

[0204]The rebar tying tool 2 of the present embodiment differs from the rebar tying tool 2 of the first embodiment in that the control circuit 230 sets the reference value I_r based on a feeding motor current value I’, instead of setting the reference value I_r based on the twisting motor current value I. Specifically, the rebar tying tool 2 of the present embodiment differs from the rebar tying tool 2 of the first embodiment in that the control circuit 230 executes the feeding process shown in FIG. 36 instead of the feeding process shown in FIG. 30, and executes the tip grasping process shown in FIG. 37 instead of the tip grasping process shown in FIG. 31. Hereafter, these differences will be described.

[0205] (Feeding Process: FIG. 36)

[0206] In S202, the control circuit 230 drives the feeding motor 32 such that the feeding motor 32 rotates in the forward direction. Due to this, the feeding mechanism 24 starts the feeding motion. When the control circuit 230 drives the feeding motor 32, the control circuit 230 executes the control of adjusting the voltage value applied on the feeding motor 32 to a specific target voltage value (also termed constant-voltage control). Also, the control circuit 230 keeps driving the feeding motor 32 driven in S202 until the control circuit 230 stops the same in S214. After S202, the process proceeds to S204.

[0207]In S204, the control circuit 230 determines whether or not an elapsed time since when the feeding motor 32 was activated in S202 (i.e., running time of the feeding motor 32) has exceeded a current mask time T_m’. If the running time of the feeding motor 32 is equal to or less than the current mask time T_m’ (in case of NO), the process repeats S204. The current mask time T_m’ is a standby time until the start-up current flowing through the feeding motor 32 exceeds its peak. If the running time of the feeding motor 32 exceeds the current mask time T_m’ (in case of YES), that is, if the start-up current flowing through the feeding motor 32 exceeds its peak, the process proceeds to S206.

[0208]In S206, the control circuit 230 sets a reference value I_r to be used in the cutting and twisting process (see FIG. 33). For example, the control circuit 230 sets the feeding motor current value I’ when the running time of the feeding motor 32 exceeds the current mask time T_m’ as the reference value I_r. After S206, the process proceeds to S208.

[0209]In S208, the control circuit 230 determines whether the current feeding motor current value I’ is smaller than the set reference value I_r or not. If the current feeding motor current value I’ is smaller than the reference value I_r (in case of YES), the process proceeds to S210.

[0210]In S210, the control circuit 230 sets the current feeding motor current value I’ as a new reference value I_r. That is, the control circuit 230 updates the reference value I_r. The control circuit 230 refers to the updated reference value I_r in a later process.

[0211] If the current feeding motor current value I’ is equal to or more than the reference value I_r in S208 (in case of NO), or after S210, the process proceeds to S212. In S212, the control circuit 230 determines whether or not the rotation number of the feeding motor 32 since when the feeding motor 32 was activated has become equal to or more than the second target rotation number based on the detection result of the rotation detecting board 33 (the same as S124 shown in FIG. 30). If the rotation number of the feeding motor 32 is less than the second target rotation number (in case of NO), the process returns to S208. If the rotation number of the feeding motor 32 becomes equal to or more than the second target rotation number (in case of YES), the process proceeds to S214.

[0212] In S214, the control circuit 230 stops the feeding motor 32. After S214, the feeding process shown in FIG. 36 ends.

(Tip Grasping Process: FIG. 37)

[0213] In S222, the control circuit 230 drives the twisting motor 76 such that the twisting motor 76 rotates in the forward direction. Due to this, from the state where the twisting mechanism 30 is in the initial position, the screw shaft 92 rotates in the right-hand thread direction D3 and the outer sleeve 96 advance. When the control circuit 230 drives the twisting motor 76, the control circuit 230 executes control of adjusting the voltage value applied on the twisting motor 76 to a specific target voltage value (also termed constant-voltage control). Also, the control circuit 230 keeps driving the twisting motor 76 driven in S222 until the control circuit 230 stops the same in S226. After S222, the process proceeds to S224.

[0214] In S224, the control circuit 230 determines whether or not the twisting mechanism 30 has reached the tip grasping position based on the detection result of the tip grasping position detecting sensor 142b. If the twisting mechanism 30 has not reached the tip grasping position (in case of NO), the process repeats S224. If the twisting mechanism 30 has reached the tip grasping position (in case of YES), the process proceeds to S226.

[0215] In S226, the control circuit 230 stops the twisting motor 76. After S226, the tip grasping process shown in FIG. 37 ends.

[0216]The load required for moving the twisting mechanism 30 (see FIG. 10) and the load required for moving the feeding mechanism 24 (see FIG. 6) are different from each other, and thus, as in the first embodiment, there will be a difference between the reference value I_r set based on the twisting motor current value I as in the first embodiment and the reference value I_r set based on the feeding motor current value I’ as in the present embodiment. This difference may be reflected on the current difference value ΔI calculated in S180 of the cutting and twisting process shown in FIG. 33. Accordingly, in order to offset this difference, the control circuit 230 of the present embodiment may add a predetermined correction value to the current difference value ΔI calculated in S180 of the cutting and twisting process. For example, if the load required for moving the feeding mechanism 24 is considered small as compared to the load required for moving the twisting mechanism 30, the feeding motor current value I’ can be considered to be small as compared to the twisting motor current value I. In this case, as compared to the current difference value ΔI based on the twisting motor current value I, the current difference value ΔI based on the feeding motor current value I’ is considered to be greater. Accordingly, a negative correction value may be added to the current difference value ΔI of the present embodiment (i.e., the current difference value ΔI based on the feeding motor current value I’) in order to offset the difference from the current difference value ΔI of the first embodiment (i.e., the current difference value ΔI based on the twisting motor current value I). Contrary to this, if the load required for moving the feeding mechanism 24 is considered greater as compared to the load required for moving the twisting mechanism 30, a positive correction value may be added to the current difference value ΔI of the present embodiment. Alternatively, the control circuit 230 may correct the reference value I_r, and/or may correct the difference thresholds I_d1, I_d2 used in S182, S184 of the cutting and twisting process, instead of correcting the current difference value ΔI.

(Third Embodiment)

[0217]The rebar tying tool 2 of the present embodiment differs from the rebar tying tool 2 of the first embodiment in that the control circuit 230 monitors the twisting motor current value I instead of monitoring the current difference value ΔI obtained by subtracting the reference value I_r from the twisting motor current value I, in order to stop the twisting motion. Specifically, the rebar tying tool 2 of the present embodiment differs from the rebar tying tool 2 of the first embodiment in that the control circuit 230 executes, instead of the cutting and twisting process shown in FIG. 33, the cutting and twisting process shown in FIG. 38. Here, in the cutting and twisting process shown in FIG. 38, S180, S182, and S184 in the cutting and twisting process shown in FIG. 33 are replaced with S280, S282, and S284. The other processes of the cutting and twisting process shown in FIG. 38 are the same as those of the cutting and twisting process shown in FIG. 33, and thus same reference numerals will be given and descriptions thereof may be omitted.

(Cutting and Twisting Process: FIG. 38)

[0218] If the rotation number of the twisting motor 76 is equal to or more than the lower limit rotation number in S178 (in case of YES) or if the rotation number of the twisting motor 76 is less than the upper limit rotation number in S188 (in case of NO), the process proceeds to S280.

[0219]In S280, the control circuit 230 sets a first current threshold I_c1 and a second current threshold I_c2 to be used in a later process based on the reference value I_r set in the tip grasping process (see FIG. 31) and the tying force setting value set in advance by the user. The second current threshold I_c2 is set to a value smaller than the first current threshold I_c1. For example, each of the first current threshold I_c1 and the second current threshold I_c2 may be set to a value obtained by adding a correction value according to the tying force setting value to the reference value I_r. This correction value may be set to a greater value for a greater tying force setting value. Alternatively, each of the first current threshold I_c1 and the second current threshold I_c2 may be a value obtained by adding a correction value according to the tying force setting value to a value which discretely increases or decreases in response to the increase and decrease of the reference value I_r. Each of the first current threshold I_c1 and the second current threshold I_c2 that are set as such is set to a greater value for a greater reference value I_r if the tying force setting value is under the same condition(s). After S280, the process proceeds to S282.

[0220]In S282, the control circuit 230 determines whether the current twisting motor current value I is equal to or more than the first current threshold I_c1 set in S280. Since, as the twisting mechanism 30 twists the wire W, twisting torque of the wire W increases, load applied through the twisting mechanism 30 on the twisting motor 76 increases. In this case, because the control circuit 230 executes the constant-voltage control on the twisting motor 76, as the load on the twisting motor 76 increases, the twisting motor current value I increases. As a result, when the twisting motor current value I becomes equal to or more than the first current threshold I_c1, YES is determined in S282 and the process proceeds to S190. In S190, the control circuit 230 stops the twisting motor 76. Due to this, the twisting torque of the wire W has increased to some extent, the twisting motion ends. Due to this, the twisting torque of the wire W when the twisting motion ends (i.e., the twisting completion torque) is adjusted to have a desired magnitude according to the tying force setting value. In S282, the control circuit 230 can be regarded as determining whether or not the twisting torque of the wire W has become of a desired magnitude.

[0221]If the twisting motor current value I is less than the first current threshold I_c1 in S282 (in case of NO), the process proceeds to S284. In S284, the control circuit 230 determines whether the current twisting motor current value I is equal to or more than the second current threshold I_c2 set in S280. If the twisting motor current value I is equal to or more than the second current threshold I_c2 (in case of YES), the process proceeds to S186. If the twisting motor current value I is less than the second current threshold I_c2 (in case of NO), the process proceeds to S188.

[0222]In the present embodiment also, as described in the second embodiment, the control circuit 230 may set the reference value I_r based on the feeding motor current value I’, instead of setting the reference value I_r based on the twisting motor current value I.

(Modifications)

[0223] The rebar tying tool 2 may be used as a tying tool configured to tie a tying target (e.g., metal pipes other than the rebars R).

[0224](See FIG. 31) The control circuit 230 may not newly set the reference value I_r each time the control circuit 230 executes the tip grasping process. For example, the control circuit 230 may set the reference value I_r (S136, S138, and S140) only in the tip grasping process executed for the first time since power on of the rebar tying tool 2.

[0225] (See FIGS. 23 to 25) The control circuit 230 may set the twisting motor current value I detected while the returning-to-initial position process (i.e., S50) in the initialization process is ongoing as the reference value I_r, instead of setting the twisting motor current value I detected while the tip grasping process is ongoing (i.e., during the period from when the tying operation is started until the twisting motion is started) as the reference value I_r. Alternatively, the control circuit 230 may set the twisting motor current value I detected in the period when S66 and S68 in the cutting attempt process are repeated as the reference value I_r. Alternatively, the control circuit 230 may drive the twisting motor 76 extra between S74 and S76 in the cutting attempt process, and set the twisting motor current value I detected in such time window as the reference value I_r. Alternatively, the control circuit 230 may set the twisting motor current value I detected during a period in the cutting attempt process when S80 is repeated (i.e., period while the twisting mechanism 30 is moving toward the initial position) as the reference value Ir.

[0226](See FIG. 29) The control circuit 230 may set the twisting motor current value I detected while the returning-to-initial position process of the tying process is ongoing (i.e., period from when the twisting motion stops until the tying operation ends) as the reference value I_r, instead of setting the twisting motor current value I detected while the tip grasping process is ongoing (i.e., period from when the tying operation is started until the twisting motion is started) as the reference value I_r.

[0227](See FIG. 33) The control circuit 230 may set the twisting motor current value I detected while S174 is repeated in the cutting and twisting process (i.e., period while the twisting mechanism 30 is in contact with the wire W) as the reference value I_r, instead of setting the twisting motor current value I detected while the tip grasping process is ongoing (i.e., period while the twisting mechanism 30 is not holding the wire W) as the reference value I_r.

[0228](See FIG. 33) The control circuit 230 may set or change the twisting stop condition based on the state of the twisting motor 76 other than the current value flowing through the twisting motor 76. For example, the rebar tying tool 2 may further comprise a temperature sensor configured to detect the temperature of the twisting motor 76. The control circuit 230 may set or change the twisting stop condition based on the temperature detected by the temperature sensor. For example, the control circuit 230 may change the first difference threshold I_d1 and the second difference threshold I_d2 according to the temperature of the twisting motor 76. Also, the temperature of the twisting motor 76 referred to by the control circuit 230 in this case may not be limited to the temperature detected during a period while the twisting motor 76 is running, but may be the temperature detected in a period while the twisting motor 76 is stopped. In yet another example, the temperature sensor may not be installed in the twisting motor 76 but in a mechanical component to which lubricant is applied. Due to this, the temperature sensor may detect the temperature of the lubricant.

[0229] (See FIG. 33) The control circuit 230 may change the determination condition of S188 based on the reference value I_r. For example, the upper limit rotation number used in S188 is increased if the reference value I_r is high, and the upper limit rotation number may be decreased if the reference value I_r is low.

[0230] (See FIG. 22) The wire type detector unit 214 may be configured to detect the wire W of another type than the three types described in the embodiments (e.g., wire W plated with zinc).

[0231] The control circuit 230 may classify the wire W based on characteristics (e.g., friction coefficient) other than strength, hardness, and presence/absence of coating material).

[0232] (See FIG. 21) The control circuit 230 may change the voltage thresholds V1, V2 based on characteristics other than strength (e.g., hardness). For example, the voltage thresholds V1, V2 set for the high-hardness wire W may be set higher than the voltage thresholds V1, V2 set for the low-hardness wire W.

[0233] (See FIGS. 28, 30) The control circuit 230 may change the target voltage value of the feeding motor 32 in the small-amount feeding process and the feeding process according to characteristics other than hardness (e.g., strength). For example, the target voltage value set for low-strength wire W may be set lower than the target rotation speed set for high-strength wire W.

[0234] (See FIG. 28) The control circuit 230 may change the first target rotation number in the small-amount feeding process according to characteristics other than presence/absence of coating material (e.g., friction coefficient of the wire W). For example, the first target rotation number set for the wire W with a low friction coefficient may be made more than the first target rotation number set for the wire W with a high friction coefficient.

[0235] (See FIG. 30) The control circuit 230 may change the second target rotation number in the feeding process according to characteristics other than presence/absence of coating material (e.g., friction coefficient of the wire W). For example, the second target rotation number set for the wire with a low friction coefficient may be made more than the second target rotation number set for the wire with a high friction coefficient.

[0236] (See FIG. 23) The control circuit 230 may execute the small-amount feeding process after starting the initialization process and before executing the cutting attempt process.

[0237] (See FIG. 28) The feeding amount of the wire W in the small-amount feeding process may not be small. That is, the feeding amount may be greater than the distance between the position intermediate between the first gear 44 and the second gear 46 (see FIG. 6) and the cutting position 74a (see FIG. 7).

[0238](See FIG. 25) The control circuit 230 may determine that the cutting mechanism 28 has cut the wire W (i.e., YES) when the current value flowing through the twisting motor 76 (i.e., the twisting motor current value I) exceeds the current threshold I_th in S70 of the cutting attempt process.

[0239](See FIG. 25) The control circuit 230 may determine whether the cutting mechanism 28 has cut the wire W or not, without referring to the twisting motor current value I in S70 of the cutting attempt process. For example, the rebar tying tool 2 may comprise a cut-end detection sensor (e.g., image sensor) configured to detect a cut end that is generated when the wire W is cut by the cutting mechanism 28. The control circuit 230 may determine whether the cutting mechanism 28 has cut the wire W based on the detection result of the cut-end detection sensor.

[0240] (See FIG. 25) The control circuit 230 may switch the rotation direction of the twisting motor 76 from forward rotation to reverse rotation without based on the detection result of the twisting start detecting sensor 142c in S74, S76, and S78 of the cutting attempt process. For example, the control circuit 230 may switch the rotation direction of the twisting motor 76 from forward rotation to reverse rotation when the rotation number of the twisting motor 76 since when the twisting motor 76 was activated in S62 exceeds a predetermined number of times in S62.

(Features of Embodiments)

[0241] In one or more embodiments, the rebar tying tool 2 (example of a tying tool) is configured to tie the rebars R (example of a tying target) using the wire W. The rebar tying tool 2 comprises: the tying mechanism 100 configured to perform tying operation including: the feeding motion in which the tying mechanism 100 feeds the wire W; and the twisting motion in which the tying mechanism 100 twists the wire W; the feeding motor 32 configured to cause the tying mechanism 100 to perform the feeding motion; the twisting motor 76 configured to cause the tying mechanism 100 to perform the twisting motion; the control board 20 (example of a detector) configured to detect the twisting motor current value I (or the feeding motor current value I’) (example of state information) representing a state of at least one of the tying mechanism 100, the feeding motor 32, and the twisting motor 76; and the control circuit 230 (example of a control unit) configured to control the feeding motor 32 and the twisting motor 76. The control circuit 230 is configured to, after the control circuit 230 has driven the twisting motor 76 to cause the tying mechanism 100 to start the twisting motion, stop the twisting motor 76 to cause the tying mechanism 100 to stop the twisting motion when the twisting stop condition (i.e., determination condition of S182, determination condition of S184) is satisfied. The control circuit 230 is configured to, when the twisting motion is to be performed, set the twisting stop condition for the twisting motion based on the twisting motor current value I (or the feeding motor current value I’) detected by the control board 20 before performing the twisting motion.

[0242]According to the above configuration, when the twisting motion is executed, the twisting stop condition for such twisting motion is set based on the state(s) of the feeding motor 32, the twisting motor 76, and/or the tying mechanism 100 before execution of such twisting motion. This can suppress variation in the twisting completion torque that is caused by the change in the state of the twisting motor 76 and/or the tying mechanism 100.

[0243] In one or more embodiments, the control circuit 230 is configured to reset the twisting stop condition each time the tying operation is to be performed.

[0244]According to the above configuration, when the state of the twisting motor 76 and/or the tying mechanism 100 (e.g., temperature of the twisting motor 76) changes while the tying operation is repeated, the twisting stop condition continues to be updated to follow the change in the state of the twisting motor 76 and/or the tying mechanism 100. This can further suppress variation in twisting completion torque that is caused by the change in the state of the twisting motor 76 and/or the tying mechanism 100.

[0245] In one or more embodiments, the control circuit 230 is configured to set the twisting stop condition for the twisting motion based on the twisting motor current value I (or the feeding motor current value I’) detected by the control board 20 while the tip grasping process is ongoing (or while the feeding process is ongoing) (example of during a period from when the tying operation is started until the twisting motion is started).

[0246] According to the above configuration, the twisting stop condition for the twisting motion is set based on the state(s) of the feeding motor 32, the twisting motor 76, and/or the tying mechanism 100 immediately before such twisting motion is started (i.e., latest state(s) of the feeding motor 32, twisting motor 76, and/or the tying mechanism 100). This can further suppress the variation in the twisting completion torque that is caused by change in the state of the twisting motor 76 and/or the tying mechanism 100.

[0247] In one or more embodiments, the control circuit 230 is configured to set the twisting stop condition for a next twisting motion based on the twisting motor current value I detected by the control board 20 while the returning-to-initial position process is ongoing (example of during a period from when the twisting motion is stopped until the tying operation is finished).

[0248]According to the above configuration, the twisting stop condition for the next twisting motion to be performed next is set based on the state(s) of the feeding motor 32, the twisting motor 76, and/or the tying mechanism 100 immediately after stopping the twisting motion. Due to this, the state(s) immediately after stopping the twisting motion of the feeding motor 32, the twisting motor 76 and/or the tying mechanism 100 can be feedbacked on the next twisting motion.

[0249] In one or more embodiments, the control circuit 230 is configured to set the twisting stop condition based on the twisting motor current value I (or the feeding motor current value I’) detected by the control board 20 during a period in which the twisting motor 76 is driven to cause the tying mechanism 100 to perform the tip grasping motion (or while the feeding motion is ongoing) (example of a motion other than the twisting motion).

[0250]During a course of using the rebar tying tool 2, behavior of the twisting motor 76 and/or the tying mechanism 100 may change, for example, due to a change in viscosity of the lubricant. This may become a reason why the twisting completion torque varies. According to the above configuration, the twisting stop condition can be set based on the state(s) of the feeding motor 32, the twisting motor 76, and/or the tying mechanism 100 that are detected by the control board 20 during a period while the twisting motor 76 is running. Due to this, the twisting stop condition can be set by taking into account the change(s) in the behavior of the twisting motor 76 and/or the tying mechanism 100. This can suppress the variation in the twisting completion torque that is caused by the change(s) in the behavior of the twisting motor 76 and/or the tying mechanism 100.

[0251] In one or more embodiments, the tying mechanism 100 includes the twisting mechanism 30 configured to perform the twisting motion. The control circuit 230 is configured to set the twisting stop condition based on the twisting motor current value I (or the feeding motor current value I’) detected by the control board 20 while the tip grasping process is ongoing (example of during a period in which the twisting mechanism does not hold the wire).

[0252]When the twisting mechanism 30 is holding the wire W, a load applied on the twisting mechanism 30 and the twisting motor 76 (i.e., states of the twisting motor 76 and the tying mechanism 100) depends on characteristics of the wire W (e.g., strength, hardness). Accordingly, if the twisting stop condition is set based on the state(s) of the feeding motor 32, the twisting motor 76 and/or the tying mechanism 100 that are detected during the period while the twisting mechanism 30 is holding the wire W, the wire W’s characteristics may be reflected on the twisting stop condition. This may not be proper depending on the situation. According to the above configuration, the twisting stop condition is set based on the state(s) of the feeding motor 32, the twisting motor76, and/or the tying mechanism 100 that are detected during the period while the twisting mechanism 30 is not holding the wire W. Due to this, the wire W’s characteristics can be suppressed from being reflected on the twisting stop condition.

[0253]In one or more embodiments, the control board 20 detects the twisting motor current value I (or the feeding motor current value I’) flowing through the twisting motor 76 (or the feeding motor 32) (example of a detection-target motor) as the state information. The twisting stop condition includes the current difference value ΔI being greater than or equal to the first difference threshold Id1 (or the second difference threshold Id2), wherein the current difference value ΔI represents a difference between the twisting motor current value I while the twisting motion is ongoing and a specific reference value I_r. The control circuit 230 is configured to, when the twisting motion is to be performed, set the reference value I_r for the twisting motion based on the twisting motor current value I (or the feeding motor current value I’) detected by the control board 20 before performing the twisting motion.

[0254]During a course of using the rebar tying tool 2, a loss amount of the twisting motor 76 and/or the tying mechanism 100 may change due to the change in the viscosity of lubricant. This may become a reason why the twisting completion torque varies. Also, the twisting motor current value I (or the feeding motor current value I’) during operation of the twisting motor 76 (or the feeding motor 32) may increase or decrease in response to the increase or decrease in the loss amount of the twisting motor 76 and/or the tying mechanism 100. In this case, from the magnitude of the twisting motor current value I (or the feeding motor current value I’) during its operation of the twisting motor 76 (or the feeding motor 32), the magnitude of the loss amount in the twisting motor 76 and/or the tying mechanism 100 can be estimated. According to the above configuration, the twisting stop condition is set based on the twisting motor current value I (or the feeding motor current value I’). Due to this, the twisting stop condition can be set taking into account the magnitude of the loss amount in the twisting motor 76 and/or the tying mechanism 100. This can suppress variation in the twisting completion torque that is caused by the change in the loss amount of the twisting motor 76 and/or the tying mechanism 100.

[0255]In one or more embodiments, the control board 20 detects the twisting motor current value I (or the feeding motor current value I’) flowing through the twisting motor 76 (or the feeding motor 32) (example of a detection-target motor) as the state information. The twisting stop condition includes the twisting motor current value I while the twisting motion is ongoing being greater than or equal to the first current threshold Ic1 (or the second current threshold Ic2) which is set based on the specific reference value I_r. The control circuit 230 is configured to, when the twisting motion is to be performed, set the reference value I_r for the twisting motion based on the twisting motor current value I (or the feeding motor current value I’) detected by the control board 20 before performing the twisting motion. The first current threshold Ic1 (or the second current threshold Ic2) is set to a larger value as the reference value I_r is greater.

[0256]During a course of using the rebar tying tool 2, a loss amount of the twisting motor 76 and/or the tying mechanism 100 may change due to the change in the viscosity of lubricant. This may become a reason why the twisting completion torque varies. Also, the twisting motor current value I (or the feeding motor current value I’) during its operation of the twisting motor 76 (or the feeding motor 32) in response to the increase or decrease in the loss amount of the twisting motor 76 and/or the tying mechanism 100. In this case, from the magnitude of the twisting motor current value I (or the feeding motor current value I’) during its operation of the twisting motor 76 (or the feeding motor 32), the magnitude of the loss amount in the twisting motor 76 and/or the tying mechanism 100 can be estimated. According to the above configuration, the twisting stop condition is set based on the twisting motor current value I (or the feeding motor current value I’). Due to this, the twisting stop condition can be set taking into account the magnitude of the loss amount in the twisting motor 76 and/or the tying mechanism 100. This can suppress variation in the twisting completion torque that is caused by the change in the loss amount of the twisting motor 76 and/or the tying mechanism 100.

[0257]In one or more embodiments, the control circuit 230 is configured to set, as the reference value I_r, a minimum value of the twisting motor current value I (or the feeding motor current value I’) during the period in the tip grasping process from when the twisting motor 76 is activated after the current mask time Tm has elapsed (or the period in the feeding process from when the feeding motor 32 is activated after the current mask time Tm’ has elapsed) (example of a period in which the detection-target motor is driven to cause the tying mechanism to perform an operation other than the twisting motion, wherein a start-up time of the detection-target motor is excluded from the period).

[0258]If the loss amount in the twisting motor 76 and/or the tying mechanism 100 is greater than normal, there is a concern that the twisting completion torque will be smaller than normal. According to the above configuration, since the twisting motor current value I (or the feeding motor current value I’) during its operation of the twisting motor 76 (or the feeding motor 32) becomes larger when the loss amount in the twisting motor 76 and/or the tying mechanism 100 is greater than normal, the reference value I_r for the twisting stop condition is set to a larger value than normal. Therefore, the twisting stop condition is not satisfied until the twisting motor current value I becomes larger than normal. Consequently, when the loss amount in the twisting motor 76 and/or the tying mechanism 100 is larger than normal, the twisting motion continues until the twisting motor current value I becomes a value larger than normal. This can suppress the twisting completion torque from becoming smaller than normal, by which the twisting completion torque becomes its normal value. Conversely, if the loss amount in the twisting motor 76 and/or the tying mechanism 100 is smaller than normal, there is a concern that the twisting completion torque may become larger than normal. According to the above configuration, since the twisting motor current value I (or the feeding motor current value I’) during its operation of the twisting motor 76 (or the feeding motor 32) becomes smaller when the loss amount in the twisting motor 76 and/or the tying mechanism 100 is smaller than normal, the reference value I_r for the twisting stop condition is set to a smaller value than normal. Consequently, the twisting stop condition is satisfied even when the twisting motor current value I is smaller than normal. As a result, when the loss amount in the twisting motor 76 and/or the tying mechanism 100 is smaller than normal, the twisting motion stops when the twisting motor current value I is smaller than normal. This can suppress the twisting completion torque from becoming larger than normal, allowing the twisting completion torque to be its normal value. According to the above configuration, it is possible to suppress variation in the twisting completion torque that is caused by changes in the amount of loss in the twisting motor 76 and/or the tying mechanism 100.