SHEET CONVEYANCE DEVICE AND IMAGE FORMING APPARATUS INCORPORATING THE SHEET CONVEYANCE DEVICE

TECHNICAL FIELD

[0001]Embodiments of the present disclosure relate to a sheet conveyance device and an image forming apparatus incorporating the sheet conveyance device.

BACKGROUND ART

[0002]Sheet conveyance devices are known that include a conveyance roller pair that conveys a sheet, and a rotator having a contact part to which the leading end of the sheet contacts. For such a rotary member included in a sheet conveyance device, the leading end of the sheet contacts the contact part of the rotator at a position upstream from the conveyance roller pair in the sheet conveyance direction and the rotary member rotates while correcting the skew of the sheet.

[0003]In a sheet conveyance device described in PTL1, the leading end of a sheet contacts the contact part of the rotator so that the sheet is bent to correct the skew of the sheet, and the rotator rotates as the contact part is pressed due to the stiffness of the sheet, so that the leading end of the sheet reaches the conveyance roller pair.

CITATION LIST

Patent Literature

[PTL 1]

SUMMARY OF INVENTION

Technical Problem

[0005]However, if a sheet having relatively large stiffness such as a thick paper is conveyed, the leading end of the sheet applies a relatively large pressing force to the contact part and reaches the conveyance roller pair without being sufficiently bent, which is likely to result in insufficient correction of the skew of the sheet.

Solution to Problem

[0006]In order to address the above-described inconvenience, embodiments of the present disclosure described herein provide a novel sheet conveyance device includes a conveyance roller pair, a conveyance member, a rotator, and a driver. The conveyance roller pair conveys a sheet in a sheet conveyance direction. The conveyance member is disposed upstream from the conveyance roller pair in the sheet conveyance direction and conveys the sheet to the conveyance roller pair at a given conveyance speed. The rotator is coaxial with one of the conveyance roller pair and has a contact part to which a leading end of the sheet is contactable to correct skew of the sheet. The driver rotates the rotator to cause the contact part to move at a moving speed slower than the given conveyance speed of the conveyance member while the leading end contacts the contact part and moves to the conveyance roller pair.

[0007]Further, embodiments of the present disclosure described herein provide an image forming apparatus including the above-described sheet conveyance device and an image forming device to form an image on the sheet conveyed from the sheet conveyance device.

Advantageous Effects of Invention

[0008]According to one aspect of the present disclosure, a preferable skew correction can be performed on a sheet having a relatively large stiffness.

BRIEF DESCRIPTION OF DRAWINGS

[0009]A more complete appreciation of embodiments of the present disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings.

[0010]FIG. 1 is a diagram illustrating a schematic configuration of a copier according to an embodiment of the present disclosure.

[0011]FIG. 2 is a perspective view of a sheet conveyance device and a registration roller pair, viewed from one axial end (i.e., the front side of the copier of FIG. 1).

[0012]FIG. 3 is a perspective view of the sheet conveyance device and the registration roller pair, viewed from the other axial end (i.e., the rear side of the copier of FIG. 1).

[0013]FIG. 4 is an A-A cross-sectional view of the sheet conveyance device of FIG. 3.

[0014]FIG. 5A is a cross-sectional view of a shutter shaft, viewed from the other axial end.

[0015]FIG. 5B is a B-B cross-sectional view of the shutter shaft of FIG. 5A.

[0016]FIGS. 6A and 6B are diagrams each illustrating a shutter in a case where each pin insertion hole is a through hole that penetrates the shutter shaft, according to an embodiment of the present disclosure.

[0017]FIGS. 7A, 7B, 7C, 7D, 7E, 7F, and 7G are diagrams illustrating a sheet skew correction operation performed by a shutter, according to an embodiment of the present disclosure.

[0018]FIG. 8A is a graph illustrating a change in the angular velocity of the shutter in the sheet skew correction operation.

[0019]FIG. 8B is a graph illustrating a change in a radius of the rotary cam at a contact position at which the rotary cam and a cam follower contact in the sheet skew correction operation.

[0020]FIG. 9 is a perspective view of a shutter having a planner contact area, according to an embodiment of the present disclosure.

[0021]FIGS. 10A and 10B are diagrams each illustrating states where a punched hole of a sheet passes a contact area, according to an embodiment of the present disclosure.

[0022]FIGS. 11A and 11B are diagrams illustrating the contact area of the shutter according to a modification of an embodiment of the present disclosure.

[0023]FIG. 12 is a schematic perspective view of a sheet conveyance device according to Modification 1 of an embodiment of the present disclosure.

[0024]FIG. 13 is a schematic perspective view of a sheet conveyance device according to Modification 2 of an embodiment of the present disclosure.

[0025]FIG. 14 is a graph indicating the relation between the rotation angle of the shutter and the rotational speed of the shutter in Modification 2.

[0026]FIGS. 15A, 15B, 15C, 15D, 15E, and 15F are schematic diagrams illustrating operations of a shutter according to Modification 3 of an embodiment of the present disclosure.

[0027]The accompanying drawings are intended to depict embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views.

DESCRIPTION OF EMBODIMENTS

[0028]In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result.

[0029]It will be understood that if an element or layer is referred to as being “on,” “against,” “connected to” or “coupled to” another element or layer, then it can be directly on, against, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, if an element is referred to as being “directly on,” “directly connected to” or “directly coupled to” another element or layer, then there are no intervening elements or layers present. As used herein, the term “connected/coupled” includes both direct connections and connections in which there are one or more intermediate connecting elements. Like numbers refer to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

[0030]Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements describes as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, term such as “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors herein interpreted accordingly.

[0031]Referring now to the drawings, embodiments of the present disclosure are described below.

[0032]As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0033]A description is now given of a copier as an image forming apparatus that executes an electrophotographic image forming process for forming images by electrophotography, according to an embodiment of the present disclosure.

[0034]The copier serving as an image forming apparatus is referred to as a copier 1.

[0035]FIG. 1 is a diagram illustrating a schematic configuration of the copier 1 according to an embodiment of the present disclosure.

[0036]The copier 1 includes, for example, a printer device 6, a sheet feeding device 7 disposed below the printer device 6, and an image reading device 4 disposed above the printer device 6. As illustrated in FIG. 1, the printer device 6 includes, for example, a process unit 2 and a transfer unit 10. The process unit 2 serves as a process cartridge including a photoconductor 11 serving as a drum-shaped latent image bearer, a charging unit, a developing unit, and a cleaning unit as a single unit. The transfer unit 10 includes a transfer roller 10a serving as a transfer member.

[0037]The charging unit uniformly charges the photoconductor 11. The developing unit develops an electrostatic latent image formed on the surface of the photoconductor 11 into a visible toner image by supplying toner onto the electrostatic latent image. The cleaning unit cleans the photoconductor 11 by removing, for example, residual toner remaining on the surface of the photoconductor 11 after the transfer of the toner image.

[0038]The printer device 6 further includes an optical writing unit 15, a toner bottle 3, a waste toner bottle 12, and a fixing unit 20. The optical writing unit 15 serves as a latent image former is disposed at the left of the process unit 2 in FIG. 1.

[0039]The toner bottle 3 is disposed above the optical writing unit 15 in FIG. 1. The toner bottle 3 accommodates toner (fresh toner) to be supplied to the developing unit included in the process unit 2. The waste toner bottle 12 is disposed below the optical writing unit 15 in FIG. 1. The waste toner bottle 12 stores toner collected by a collecting member included in the process unit 2. The fixing unit 20 is disposed above a transfer nip region formed by the photoconductor 11 and the transfer roller 10a disposed facing each other. The sheet feeding device 7 includes, for example, sheet trays 14a and 14b respectively accommodating stacked sheets P, sheet feed roller pairs 8a and 8b, and sheet conveyance roller pairs 16a and 16b.

[0040]In image information executed by the printer device 6, the optical writing unit 15 emits light to the surface of the photoconductor 11 uniformly charged by the charging unit, based on the image information (image data) of an original document read by the image scanner 4 or image information input via an external device. This results in the formation of an electrostatic latent image on the surface of the photoconductor 11. This electrostatic latent image is developed with toner applied by the developing unit into a visible toner image.

[0041]On the other hand, in the sheet feeding device 7, a pickup roller feeds the sheets P one by one from a selected sheet tray 14 (i.e., the sheet tray 14a or the sheet tray 14b). Then, a sheet P fed from the sheet tray 14 is conveyed by the sheet feed roller 8 (i.e., the sheet feed roller 8a or the sheet feed roller 8b) and the sheet conveyance roller pair 16 (i.e., the sheet conveyance roller pair 16a or the sheet conveyance roller pair 16b) toward a registration roller pair 9 serving as a conveyance roller pair. Then, the skew of the sheet P is corrected by shutters 50 (see FIG. 2) each serving as a rotator, and the sheet P is conveyed to the transfer nip region. Details of the shutters 50 are described below.

[0042]In the transfer nip region, a transfer bias is applied to the transfer roller 10a to electrostatically transfer the toner image on the photoconductor 11 onto the sheet P. After the toner image is transferred onto the sheet P, the sheet P is conveyed to the fixing unit 20. In the fixing unit 20, the toner image is fixed to the sheet P by application of heat and pressure. The sheet P having the fixed toner image is ejected by a sheet ejection roller pair 13 to be stacked on a sheet ejection tray 5 disposed below the image reading device 4.

[0043]FIG. 2 is a perspective view of a sheet conveyance device 100 and the registration roller pair 9, viewed from the first axial end of the registration roller pair 9 (i.e., the front side of the copier 1 of FIG. 1).

[0044]FIG. 3 is a perspective view of the sheet conveyance device 100 and the registration roller pair 9, viewed from the second axial end of the registration roller pair 9 that is an opposite axial end of the first axial end (i.e., the rear side of the copier 1 of FIG. 1).

[0045]A first conveyance guide 19a and a second conveyance guide 19b are disposed between the sheet conveyance roller pair 16a and the registration roller pair 9. The second conveyance guide 19b is disposed close to a driven roller 9b of the registration roller pair 9 and has a curved shape such that the center of the second conveyance guide 19b in the sheet conveyance direction is located farther away from the sheet conveyance passage than both ends of the second conveyance guide 19b in the sheet conveyance direction. As a result, a space in which a sheet is bent when the shutters 50 correct the skew of the sheet is provided between the sheet conveyance roller pair 16a and the registration roller pair 9. In addition, the sheet conveyance roller pair 16a conveys the sheet slightly toward the second conveyance guide 19b so that the sheet is bent toward the second conveyance guide 19b.

[0046]In the present embodiment, the sheet conveyance roller pair 16a is employed but the configuration is not limited to the above-described configuration. For example, a registration roller pair may be disposed downstream from the sheet feed roller pair 8a in the sheet conveyance direction. In addition, the sheet feeding method may be a friction pad method. Further, the driven roller may not be disposed.

[0047]The registration roller pair 9 includes three drive rollers 9a arranged at given intervals in the axial direction, and three driven rollers 9b disposed facing the respective drive rollers 9a. The three drive rollers 9a are mounted on a drive shaft 91a so as to rotate with the drive shaft 91a.

[0048]On the other hand, the three driven rollers 9b are supported to be rotatable relative to a shutter shaft 91b serving as a rotary shaft. The respective driven rollers 9b are pressed toward the corresponding drive rollers 9a by respective pressure mechanisms 80.

[0049]The drive shaft 91a and the shutter shaft 91b are rotatably supported by the housing of the copier 1 via bearings 93.

[0050]A drive gear 62 that meshes with a motor gear 61a of a conveyance motor 61 serving as a drive source is mounted on the drive shaft 91a at the other end so that the drive gear 62 rotates together with the drive shaft 91a. As a result, the respective drive rollers 9a rotate due to the driving force of the conveyance motor 61. An input gear 63 that meshes with a tooth-missing gear 64 mounted on the other end of the shutter shaft 91b is mounted on the drive shaft 91a so that the input gear 63 rotates together with the drive shaft 91a.

[0051]The three pressure mechanisms 80 provided corresponding to the respective driven rollers 9b include pressure brackets 82, pressure springs 81, and paper dust removers 83 that remove paper dust attached to the surfaces of the driven rollers 9b.

[0052]The pressure brackets 82 are attached to respective bracket attachment portions 91c (also see FIG. 5B) disposed at both ends of the driven rollers 9b. The pressure brackets 82 are biased by the respective pressure springs 81 toward the respective drive rollers 9a. As a result, the driven rollers 9b are pressed to the respective drive rollers 9a by the respective pressure brackets 82 to form respective conveyance nip regions and be preferably rotated together with the respective drive rollers 9a.

[0053]The four shutters 50 each serving as a rotator are mounted on the shutter shaft 91b so that the shutters 50 are rotated with the shutter shaft 91b as a single unit. The shutters 50 are alternately arranged with the driven rollers 9b in the axial direction. To be more specific, each of the driven rollers 9b is disposed between the adjacent shutters 50 in the axial direction.

[0054]As illustrated in FIG. 3, each of the shutters 50 has three contact parts 51 and three contact areas 52 in the rotational direction. The leading end of a sheet P contacts the contact parts 51. The sheet P contacts the contact areas 52 after the leading end of the sheet P passes through the registration roller pair 9. The contact areas 52 have respective sloped faces 52a on both sides and the sloped faces 52a decrease in height toward respective ends in the axial direction.

[0055]A sheet detector 40 that detects the leading and trailing ends of the sheet in the sheet conveyance direction is disposed at one end of the shutter shaft 91b. The sheet detector 40 includes a transmission-type optical sensor 42 and a feeler 41. The feeler 41 is mounted on the one end of the shutter shaft 91b so that the feeler 41 is rotated together with the shutter shaft 91b.

[0056]The feeler 41 is provided with three shields 41a in the rotational direction. As described below, as the leading end of a sheet enters the conveyance nip region of the registration roller pair 9, any one of the shields 41a of the feeler 41 enters between a light receiving element and a light emitting element of the transmission-type optical sensor 42 to block light emitted from the light emitting element. As a result, the light receiving element no longer detects light from the light emitting element, and the entry of the leading end of the sheet into the conveyance nip region is detected.

[0057]Based on the detection result of the leading end of the sheet by the sheet detector 40, the writing timing of the optical writing unit 15 is controlled, and the toner image on the photoconductor 11 enters the transfer nip region when the sheet enters the transfer nip region. The timing at which the sheet detector 40 detects the leading end of the sheet (i.e., the timing at which the shield 41a of the feeler 41 blocks the light from the light emitting element) is not limited to the above-described timing, and may be appropriately set based on, for example, the sheet conveyance speed and the distances from the registration roller pair 9 to the transfer nip region.

[0058]On the other hand, when the trailing end of the sheet passes through the shutters 50, the shields 41a of the feeler 41 pass through between the light receiving element and the light emitting element of the transmission-type optical sensor 42. As a result, the light receiving element receives light emitted from the light emitting element, and the sheet detector 40 detects the trailing end of the sheet. Based on the detection timing of the sheet detector 40 that detects the trailing end of the sheet, the length of the sheet in the sheet conveyance direction can be detected.

[0059]A rotation mechanism 70 that rotates the shutters 50 is mounted on the other end of the shutter shaft 91b. The rotation mechanism 70 includes a rotary cam 71, a cam follower 74, an arm 72, and a cam spring 73. The rotary cam 71 is disposed to the tooth-missing gear 64 in a single mold. The arm 72 is rotatably supported by the housing of the copier 1 and supports the cam follower 74. The cam spring 73 serves as a biasing force applier that biases the arm 72.

[0060]In the present embodiment, the cam follower 74, the arm 72, and the cam spring 73 are included in a presser.

[0061]FIG. 4 is an A-A cross-sectional view of the sheet conveyance device 100 of FIG. 3.

[0062]As illustrated in FIG. 4, one end of the pressure spring 81 of the pressure mechanism 80 is attached to a spring holder 82a of the pressure bracket 82 and a member of the housing of the copier 1 in a compressed manner. The paper dust removers 83 include a resin sheet made of, for example, polyethylene terephthalate (PET). The paper dust removers 83 are attached to sheet attachment parts 82b of the pressure brackets 82 by, for example, a double-sided tape so that the leading ends of the paper dust removers 83 contact the surfaces of the respective driven rollers 9b.

[0063]Removal of paper dust on the driven rollers 9b by the paper dust removers 83 can prevent the paper dust from transferring from the driven rollers 9b to the sheet P. The surface of the sheet P that the driven rollers 9b contact is the surface onto which the toner image is transferred at the transfer nip region. By removing paper dust on the driven rollers 9b with the paper dust removers 83 to prevent the transfer of paper dust from the driven rollers 9b to the sheet P, the toner image to be transferred onto the sheet P can be prevented from being disturbed by paper dust.

[0064]FIG. 5A is a cross-sectional view of the shutter shaft 91b, viewed from the other axial end. FIG. 5B is a B-B cross-sectional view of the shutter shaft 91b of FIG. 5A.

[0065]As illustrated in FIG. 5A, grooves 64c having a recessed shape are disposed at three positions in the circumferential direction of the tooth-missing gear 64. Teeth 64a are formed at the distal ends of the extensions 64b extending from one circumferential end of the grooves 64c toward the other circumferential end. As a result, a gap is formed inside the extensions 64b having the teeth 64a formed at the distal ends of the extensions 64b. The extensions 64b can be bent in the normal direction.

[0066]By making the extensions 64b bendable in the normal direction, the impact generated when the teeth 64a of the tooth-missing gear 64 meshes with the input gear 63 (see FIGS. 2 and 3) of the drive shaft 91a can be absorbed by the bending of the extensions 64b. As a result, vibration and noise can be reduced.

[0067]As illustrated in FIG. 5B, both ends of the shutter shaft 91b are formed in a D-cut shape, and the feeler 41 is attached to a D-shaped portion 191a at one end (i.e., a right end in FIG. 5B) of the shutter shaft 91b. A resin member having the tooth-missing gear 64 and a rotary cam 71 is attached to a D-shaped portion 191b at the other end of the shutter shaft 91b. The four shutters 50 are attached to respective pins 94 on the shutter shaft 91b.

[0068]The shutter shaft 91b has four pin insertion holes 191d into which the pins 94 are inserted. The pin insertion holes 191d are located at the same positions as the cutout portions (i.e., the plane portions) of the D-shaped portions 191a and 191b in the rotational direction of the shutter shaft 91b, and are disposed up to the axial center of the shutter shaft 91b. Further, communication holes 191e having a diameter smaller than the diameter of the pin insertion holes 191d are formed in the shutter shaft 91b. The communication holes 191e communicate with the respective four pin insertion holes 191d. These communication holes 191e are provided for blowing off chips and machining oil by air when the pin insertion holes 191d are formed by machining, and may not be provided. The pins 94 serving as engaging pins inserted into the respective pin insertion holes 191d are fitted into respective grooves 151. By so doing, the shutters 50 are assembled to the shutter shaft 91b so as to rotate together with the shutter shaft 91b.

[0069]FIGS. 6A and 6B are diagrams illustrating a shutter 50 in a case where each pin insertion hole 191d is a through hole that penetrates the shutter shaft 91b.

[0070]As illustrated in FIG. 6B, in the configuration in which the pin insertion holes 191d are through holes that pass through the shutter shaft 91b and the pins 94 pass through the respective pin insertion holes 191d, any of the pins 94 is likely to come off the corresponding pin insertion hole 191d from the opposite side to the insertion side of the pin 94. Further, in the configuration in which each of the pins 94 is inserted through the corresponding pin insertion hole 191d, two grooves 151 of the corresponding shutter 50 that the pin 94 engages are disposed at an interval of 180 degrees in the rotational direction, as illustrated in FIG. 6A. As a result, the shutter 50 is likely to be erroneously assembled to the shutter shaft 91b while the shutter 50 is shifted by substantially 180 degrees in phase from the position illustrated in FIG. 6A.

[0071]By contrast, in the present embodiment, the pin insertion holes 191d have a depth up to the axial center of the shutter shaft 91b. For this reason, different from the configuration illustrated in FIGS. 6A and 6B, the pin 94 does not come off from the corresponding pin insertion hole 191d from the opposite side to the insertion side of the pin 94. Further, the groove 151 of the shutter 50 that the pin 94 engages is disposed at one position in the rotational direction, so that an assembly error does not occur. As a result, in comparison with the configuration in which the pin insertion holes 191d are through holes, the configuration according to the present embodiment can enhance the assembly performance.

[0072]The pin insertion holes 191d are located at the same positions as the cutout portions (i.e., the plane portions) of the D-shaped portions 191a and 191b in the rotational direction. Inserting the pin 94 into the corresponding pin insertion hole 191d causes the center of gravity of the shutter shaft 91b to offset to the insertion side of the pin 94. On the other hand, the center of gravity of the D-shaped portions 191a and 191b is offset to the opposite side of the cutout portions. By locating the pin insertion holes 191d at the same positions as the cutout portions of the D-shaped portions 191a and 191b in the rotational direction, the offset of the center of gravity of the D-shaped portions 191a and 191b and the offset of the center of gravity due to the pins 94 can be made in opposite directions to each other. As a result, the offset of the center of gravity due to the pins 94 can be cancelled by the offset of the center of gravity of the D-shaped portions 191a and 191b, and the offset of the center of gravity of the shutter shaft 91b can be minimized. As a result, the shutter shaft 91b can be smoothly rotated.

[0073]FIGS. 7A, 7B, 7C, 7D, 7E, 7F, and 7G are diagrams illustrating a sheet skew correction operation performed by the shutters 50.

[0074]FIG. 8A is a graph illustrating a change in the angular velocity of the shutters 50 in the sheet skew correction operation.

[0075]FIG. 8B is a graph illustrating a change in the radius of the rotary cam 71 at the contact position at which the rotary cam 71 contacts the cam follower 74 in the sheet skew correction operation.

[0076]Reference sign “a” in FIGS. 8A and 8B indicates a point in time at which the leading end of a sheet contacts the contact part 51 of the shutter 50, which corresponds to the position illustrated in FIG. 7A. Reference sign “b” in FIGS. 8A and 8B indicates a point in time in which the tooth-missing gear 64 is drivingly coupled to the input gear 63, which corresponds to the position illustrated in FIG. 7B. Further, reference sign “c” in FIGS. 8A and 8B indicates a point in time at which the drive coupling of the tooth-missing gear 64 and the input gear 63 is released, which corresponds to the position illustrated in FIG. 7C. Reference sign “d” in FIGS. 8A and 8B indicates a point in time at which the leading end of the sheet reaches the nip region of the registration roller pair 9, which corresponds to the position illustrated in FIG. 7D. Reference sign “e” in FIGS. 8A and 8B indicates a point of time at which the leading end of the sheet separates from the contact part 51 of the shutter 50, which corresponds to the position illustrated in FIG. 7F. Reference sign “f” in FIGS. 8A and 8B indicates a point of time at which the contact area 52 of the shutter 50 contact the trailing end of the sheet, which corresponds to the position illustrated in FIG. 7G. Further, reference sign “g” in FIGS. 8A and 8B indicates a point of time at which the following contact part 51 is located at the standby position.

[0077]As illustrated in FIGS. 7A to 7G, the rotary cam 71 has three cam portions 71a. The cam follower 74 is mounted on one end (i.e., one end of the driven roller 9b) of the arm 72. A support shaft 72a is mounted on the opposite end of the arm 72 that is opposite to the one end of the arm 72. The support shaft 72a is rotatably supported by the housing of the copier 1. The arm 72 rotates around the support shaft 72a as a fulcrum. The arm 72 is biased by the cam spring 73 in a rotational direction (i.e., the clockwise direction in FIGS. 7A to 7G).

[0078]As illustrated in FIG. 7A, when one of the three contact parts 51 of the shutter 50 is located at the standby position where the leading end of the sheet conveyed to the shutter 50 waits for the contact part 51 of the shutter 50, the cam follower 74 is positioned at a recessed portion between the cam portions 71a of the rotary cam 71.

[0079]When the cam follower 74 is located at the recessed portion of the rotary cam 71, the rotary cam 71 is to be rotated against the biasing force of the cam spring 73 no matter when the rotary cam 71 is rotated in the clockwise direction or the counterclockwise direction in FIG. 7A. As a result, when the cam follower 74 is located at the recessed portion between the cam portions 71a of the rotary cam 71, one of the contact parts 51 of the shutter 50 remains at the standby position due to the biasing force of the cam spring 73.

[0080]When the leading end of the sheet P conveyed by the conveyance roller pair on the upstream side in the sheet conveyance direction (i.e., the sheet conveyance roller pair 16a) contacts the contact part 51 located at the standby position (i.e., the point “a” in FIGS. 8A and 8B), the shutter 50 rotates in the counterclockwise in FIG. 7A against the biasing force of the cam spring 73 due to the stiffness of the sheet (i.e., the period A in FIGS. 8A and 8B). Then, as illustrated in FIG. 7B, the teeth 64a of the tooth-missing gear 64 mesh with the input gear 63 to drivingly be coupled to the input gear 63 (i.e., the point “b” in FIGS. 8A and 8B). As a result, the driving force of the conveyance motor 61 (see FIG. 2) is transmitted from the input gear 63, and the shutters 50 are driven to rotate in the counterclockwise direction in FIG. 7B (i.e., the period B in FIGS. 8A and 8B).

[0081]In the present embodiment, the outer diameter of the tooth-missing gear 64 is greater than the outer diameter of the input gear 63. Due to such a configuration, when the tooth-missing gear 64 is drivingly coupled to the input gear 63, the shutter 50 is driven at a rotation speed lower than the rotation speed of the registration roller pair 9 according to the reduction ratio between the tooth-missing gear 64 and the input gear 63. The registration roller pair 9 is driven at the rotation speed as the rotation speed of the sheet conveyance roller pair 16a. For this reason, the contact parts 51 of each of the shutter 50 move toward the conveyance nip region of the registration roller pair 9 at a speed slower than the conveyance speed of the sheet. As a result, as illustrated in FIG. 7C, the sheet is bent due to the speed difference between the sheet conveyance speed and the moving speed of each of the contact parts 51 to correct the skew of the sheet.

[0082]As illustrated in FIG. 7C, when the cam follower 74 passes the top of the cam portion 71a of the rotary cam 71 and the biasing force of the cam spring 73 applied in the direction in which the shutter 50 is rotated in the clockwise direction in FIG. 7C is switched to the direction in which the shutters 50 are rotated in the counterclockwise direction in the drawing, the drive coupling of the tooth-missing gear 64 and the input gear 63 is released (i.e., the point “c” in FIGS. 8A and 8B).

[0083]When the drive coupling between the tooth-missing gear 64 and the input gear 63 is released, the shutter 50 receives the force applied by the cam spring 73 for rotating the shutter 50 in the counterclockwise direction in FIG. 7C and the force applied by the leading end of the sheet pressing the contact parts 51. At this time, the force applied by the leading end of the sheet pressing the contact part 51 is greater than the force applied by the cam spring 73. Due to such a configuration, the contact parts 51 move at substantially the sheet conveyance speed (i.e., the periods C and D in FIGS. 8A and 8B).

[0084]As the leading end of the sheet presses the contact part 51 to cause the contact part 51 to separate from the leading end of the sheet (i.e., the point “e” in FIGS. 8A and 8B), the shutter 50 rotates with the biasing force of the cam spring 73 (i.e., the period E in FIGS. 8A and 8B). Then, as illustrated in FIG. 7G, when the contact area 52 of the following contact part 51 contacts the trailing end of the sheet being conveyed by the registration roller pair 9, the shutter 50 stops the rotation (i.e., the point “f” in FIGS. 8A and 8B). When the trailing end of the sheet passes through the contact area 52, the shutter 50 rotates with the biasing force of the cam spring 73 again (i.e., the period F in FIGS. 8A and 8B), and the following contact part 51 is located at the standby position (i.e., the point “g” in FIGS. 8A and 8B).

[0085]As described above, in the present embodiment, the shutters 50 are disposed to correct the skew of the sheet by the shutters 50. As a result, the configuration according to the present embodiment is more advantageous in the following point than the configuration in which the registration roller pair 9 is temporarily stopped so that the leading end of the sheet contacts the conveyance nip region of the registration roller pair 9 to correct the skew of the sheet. In other words, when the registration roller pair 9 corrects the skew of the sheet, a certain nip width is needed to stop the leading end of a stiff sheet such as thick paper with reliability in the conveyance nip region. As a result, the diameters of both rollers of the registration roller pair 9 need to be increased, which is likely to increase the size of the apparatus such as the copier 1. By contrast, when the skew of the sheet is corrected by the shutters 50, the conveyance nip width of the registration roller pair 9 can be reduced, and the diameters of both rollers of the registration roller pair 9 are prevented from being increased, preventing an increase in the size of the apparatus.

[0086]Further, when the skew of the sheet is corrected by the shutters 50, and the skew correction can be performed without temporarily stopping the sheet, the interval between adjacent sheets in the sheet conveyance direction can be reduced when compared with a configuration in which the registration roller pair 9 corrects the skew of the sheet. Accordingly, the productivity can be enhanced. Further, an electromagnetic clutch, for example, for temporarily stopping the registration roller pair 9 can be obviated.

[0087]For example, it is also conceivable to employ the configuration in which the shutter 50 is rotated with the stiffness of the sheet in the period in which the skew correction of the sheet is performed by bending the sheet from when the leading end of the sheet contacts the contact part 51 until the cam follower 74 climbs over the top of the cam portion 71a and the biasing direction of the cam spring 73 changes. In such a configuration, a sheet having relatively large stiffness such as a thick paper has a relatively large force to press the contact part 51, and cannot sufficiently reduce the moving speed of the leading end of the sheet with the shutter 50. As a result, such a sheet having relatively large stiffness like a thick paper is not likely to correct the skew of the sheet as desired. In order to address this inconvenience, an increase in the biasing force of the cam spring 73 may be conceived to increase the rotational load of the shutter 50. However, a sheet having relatively small stiffness such as a thin paper cannot rotate the shutter 50 with the stiffness of the sheet, and is likely to cause a paper jam with a sheet having bellows.

[0088]By contrast, in the present embodiment, the shutters 50 are driven to rotate so that the contact parts 51 rotate at the moving speed slower than the sheet conveyance speed of the sheet in the period in which the cam follower 74 climbs over the top of the cam portion 71a and the biasing direction of the cam spring 73 changes (i.e., the period B in FIG. 8). As a result, regardless of the stiffness of a sheet, the moving speed of the leading end of the sheet can be made constant while the shutters 50 are driven and rotated. Further, regardless of the stiffness of a sheet, the sheet can be bent according to the speed difference between the moving speed of the leading end of the sheet and the sheet conveyance speed of the sheet conveyance roller pair 16a. As a result, regardless of the stiffness of a sheet, a good skew correction can be performed on a sheet.

[0089]FIG. 9 is a perspective view of the shutter 50 having a planner contact area 52.

[0090]Then, as illustrated in FIG. 7G, the contact area 52 of the shutter 50 contacts the trailing end of the sheet being conveyed by the registration roller pair 9. At this time, if the sheet has a punched hole on the trailing end, the contact area 52 falls into the punched hole of the sheet.

[0091]At this time, when the contact area 52 is planar as illustrated in FIG. 9, both ends of the contact area 52 in the axial direction are caught by the edge of the punched hole of the sheet, which is likely to tear the sheet or cause a paper jam.

[0092]FIGS. 10A and 10B are diagrams illustrating respective states where punched holes of the sheet P passes the contact area 52.

[0093]By contrast, in the present embodiment, as illustrated in FIG. 3, the contact area 52 of the shutter 50 includes the sloped face 52a that decreases in height toward both axial ends. As a result, as illustrated in FIGS. 10A and 10B, even if the contact area 52 falls into the punched hole(s) Pa of the sheet, both axial ends of the contact area 52 can be prevented from falling into the punched hole Pa. Accordingly, both axial ends of the contact area 52 can be prevented from being caught by the edge of the punched hole Pa. Further, before the axial center of the contact area 52 comes into contact with the edge of the punched hole Pa, the sloped faces 52a of the contact area 52 climb over the sheet face, which reduces the chance that the axial center of the contact area 52 falls into the punched hole(s) Pa. Accordingly, the axial center of the contact area 52 can be prevented from being caught by the edge of the punched hole Pa.

[0094]FIGS. 11A and 11B are diagrams illustrating the contact area 52 of the shutter 50 according to a modification of an embodiment of the present disclosure.

[0095]Further, the distal end of the contact area 52 may have a curved face as illustrated in FIG. 11a or the contact area 52 may be curved in the axial direction as illustrated in FIG. 11B. These configurations illustrated in FIGS. 11A and 11B can prevent the contact area 52 from being caught by the edge of the punched hole Pa.

[0096]A description is now given of a schematic configuration of modifications of the above-described embodiments.

Modification 1

[0097]FIG. 12 is a schematic perspective view of a sheet conveyance device 100A according to Modification 1 of the above-described embodiments of the present disclosure.

[0098]In the sheet conveyance device 100A according to Modification 1, the input gear 65 that transmits the driving force of the conveyance motor 61 to the tooth-missing gear 64 is mounted on a member other than the drive shaft 91a. In Modification 1, the input gear 65 is a two-step gear and includes a first gear portion 65a and a second gear portion 65b. The first gear portion 65a is meshed with the motor gear 61a of the conveyance motor 61. The second gear portion 65b is meshed with the tooth-missing gear 64. The first gear portion 65a of the input gear 65 has a diameter greater than the diameter of the motor gear 61a. The second gear portion 65b of the input gear 65 has a diameter smaller than the diameter of the tooth-missing gear 64. The input gear 65 transmits the driving force to the tooth-missing gear 64 in a two-step reduction.

[0099]Since the gap between the drive shaft 91a and the shutter shaft 91b of the registration roller pair 9 is relatively narrow, it is likely that a sufficient reduction gear ratio cannot be obtained between the input gear 63 mounted on the drive shaft 91a and the tooth-missing gear 64 mounted on the shutter shaft 91b. As a result, the moving speed of the contact part 51 cannot be sufficiently reduced with respect to the sheet conveying speed, and the sheet may be insufficiently bent, resulting in insufficient skew correction.

[0100]By contrast, in Modification 1, a large reduction ratio can be easily obtained. As a result, the moving speed of the contact part 51 can be sufficiently reduced with respect to the sheet conveyance speed, and the sheet can be sufficiently bent, and sufficient skew correction can be performed.

Modification 2

[0101]FIG. 13 is a schematic perspective view of a sheet conveyance device 100B according to Modification 2 of the above-described embodiments of the present disclosure.

[0102]In Modification 2, the sheet conveyance device 100B includes a shutter motor 67 that drives and rotates the shutters 50, separate from the conveyance motor 61. Due to such a configuration, a controller 68 serving as a controller performs drive control to rotate the shutters 50. In Modification 2, the sheet conveyance device 100B does not include the rotation mechanism 70 and the gear to be meshed with the input gear 65 is changed from the tooth-missing gear 64 to a shutter gear 66 having the teeth formed on the entire circumference.

[0103]FIG. 14 is a graph illustrating the relation between the rotation angle of the shutter 50 and the rotational speed of the shutter 50 in Modification 2.

[0104]Reference sign “al” in FIG. 14 indicates a point in time at which the leading end of a sheet contacts the contact part 51. Reference sign “b1” in FIG. 14 indicates a point in time at which the rotational speed of the shutter motor 67 is changed. Further, reference sign “c1” in FIG. 14 indicates a point in time at which the leading end of the sheet reaches the registration roller pair 9. Reference sign “d1” in FIG. 14 indicates a point in time at which the contact part 51 is retracted from the sheet conveyance passage. Reference sign “e1” in FIG. 14 indicates a point in time at which the contact area 52 contacts the trailing end of the sheet. Reference sign “f1” in FIG. 14 indicates a point in time at which the following contact part 51 comes to the standby position.

[0105]The controller 68 starts driving the shutter motor 67 before the leading end of the sheet contacts the contact part 51. Then, the controller 68 controls the rotation speed of the shutter motor 67 so that the shutter 50 is driven and rotated at the rotational speed at which the moving speed of the contact part 51 is equal to or smaller than the sheet conveyance speed.

[0106]When the leading end of the sheet conveyed by the sheet conveyance roller pair 16a contacts the contact part 51 that moves at a moving speed slower than the sheet conveyance speed (i.e., the period al in FIG. 14), and the sheet is bent to correct the skew of the sheet (i.e., the period A1 in FIG. 14).

[0107]After a specified period of time has elapsed from the start of driving the shutter motor 67 (i.e., the timing b1 in FIG. 14), the controller 68 increases the rotation speed of the shutter motor 67 to drive and rotate the shutter 50 so that the moving speed of the contact part 51 is equal to or greater than the sheet conveyance speed (i.e., the periods B1 and C1 in FIG. 14). Then, the rotation speed of the shutter motor 67 is increased slightly before the leading end of the sheet reaches the conveyance nip region of the registration roller pair 9 (i.e., the timing c1 in FIG. 14). By so doing, the moving speed of the contact part 51 can be equal to or greater than the sheet conveyance speed before the leading end of the sheet reaches the registration roller pair 9. This action is taken to avoid the following situation. If the moving speed of the contact part 51 is slower than the sheet conveyance speed even after the leading end of the sheet reaches the registration roller pair 9, the leading end of the sheet is deformed into the shape of bellows, which is likely to cause a paper jam.

[0108]When the contact part 51 retracts from the sheet conveyance passage to a position at which the leading end of the sheet does not contact the contact part 51 (i.e., the timing d1 in FIG. 14), the controller 68 decreases the rotation speed of the shutter motor 67. As a result, the rotational speed of the shutter 50 decreases (i.e., the period D1 in FIG. 14). For example, when the sheet detector 40 detects the leading end of the sheet, the controller 68 starts timer measurement. When the timer reaches a specified time, the controller 68 determines that the contact part 51 has retracted from the sheet conveyance passage and decreases the rotation speed of the shutter motor 67.

[0109]Then, the shutter motor 67 is temporarily stopped at a timing when the contact area 52 comes into contact with the trailing end of the sheet (i.e., the timing e1 in FIG. 14). After the trailing end of the sheet passes the contact area 52, the controller 68 starts driving the shutter motor 67 again to locate the following contact part 51 at the standby position (i.e., the period E1 in FIG. 14).

[0110]The rotation control of the shutters 50 is not limited to this rotation control in FIG. 14. For example, after the leading end of the sheet contacts the contact part 51 to bend the sheet and the skew is corrected, the controller 68 may start driving the shutter motor 67 to drive and rotate the shutter 50 so that the moving speed of the contact part 51 is changed to be equal to or greater than the sheet conveyance speed. Further, the controller 68 may control the driving of the shutter motor 67 so that the contact area 52 does not contact the trailing end of the sheet. For example, the driving of the shutter motor 67 is temporarily stopped at a timing before the contact area 52 reaches the position at which the contact area 52 contacts the trailing end of the sheet. By so doing, the contact area 52 may not contact the trailing end of the sheet. Further, the controller 68 may rotate the shutter 50 at a constant low speed after the contact part 51 is retracted from the sheet conveyance passage and control the contact part 51 to come to the standby position when the trailing end of the sheet passes the standby position. By so doing, the contact area 52 does not contact the trailing end of the sheet.

[0111]Since the configuration according to Modification 2 does not use the tooth-missing gear 64, vibration or noise is not generated at the time of drive coupling of the tooth-missing gear 64.

Modification 3

[0112]FIGS. 15A, 15B, 15C, 15D, 15E, and 15F are schematic diagrams illustrating operations of the shutter 50 according to Modification 3 of the above-described embodiments of the present disclosure.

[0113]As illustrated in FIGS. 15A to 15F, the configuration according to Modification 3 includes the rotation mechanism including a second input gear 77 and a second tooth-missing gear 78. The rotation mechanism causes the shutters 50 to rotate such that the contact part 51 is located at the standby position, after the drive coupling of the tooth-missing gear 64 is released.

[0114]In Modification 3, the shutter 50 has one contact part 51, and the tooth-missing gear 64 includes a spring attachment member 64d. One end of the tension spring 79 that positions the contact part 51 at the standby position illustrated in FIG. 15A is attached to the spring attachment member 64d. The other end of the tension spring 79 is attached to the housing of the apparatus.

[0115]As illustrated in FIG. 15A, when the contact part 51 is located at the standby position, the distance between the spring attachment member 64d of the tooth-missing gear 64 and the spring attachment member of the housing of the apparatus is the shortest.

[0116]As a result, the biasing force of the tension spring 79 is applied in the reverse direction that is opposite to the rotational direction whenever the tooth-missing gear 64 is rotated from the standby position in the clockwise direction or the counterclockwise direction in FIG. 15A. Accordingly, the application of the biasing force of the tension spring 79 can locate the contact part 51 at the standby position.

[0117]The second input gear 77 is mounted on the drive shaft 91a and the second tooth-missing gear 78 is mounted on the shutter shaft 91b. The diameter of the second tooth-missing gear 78 is equal to or larger than the diameter of the second input gear 77, and the speed is constant or increased.

[0118]It is preferable to set the number of teeth of the second input gear 77 to be an integer multiple including the same number of teeth of the input gear 63. By setting the number of teeth of the second input gear 77 to be an integer multiple including the same number of teeth of the input gear 63, the phase of the teeth of the second input gear 77 when the drive coupling of the tooth-missing gear 64 is released is determined to be one type. This makes the movement of the second tooth-missing gear 78 in drive coupling the same as the movement of the tooth-missing gear 64 in drive coupling. As a result, the rotation of the shutter 50 is stabilized. The module of the input gear 63 and the module of the second input gear 77 may be different from each other.

[0119]As in the above-described embodiment, when the leading end of the sheet reaches the contact part 51 to rotate the shutter 50 by a given angle due to the stiffness of the sheet, the tooth-missing gear 64 is drivingly coupled to the input gear 63, as illustrated in FIG. 15B. Then, as in the above-described embodiment, the shutter 50 is driven and rotated so that the contact part 51 moves at a movement speed slower than the sheet conveyance speed. By so doing, the sheet is bent to perform skew correction on the sheet.

[0120]Then, before the leading end of the sheet reaches the conveyance nip region of the registration roller pair 9, the drive coupling of the tooth-missing gear 64 is released, and the second tooth-missing gear 78 is drivingly coupled to the second input gear 77 (see FIG. 15C). In the period after the drive coupling of the tooth-missing gear 64 is released and before the second tooth-missing gear 78 is drivingly coupled, the shutter 50 is rotated in the counterclockwise direction in FIG. 15C due to the inertial force and the stiffness of the sheet.

[0121]As described above, the diameter of the second tooth-missing gear 78 is equal to or greater than the diameter of the second input gear 77. As a result, when the second tooth-missing gear 78 is drivingly coupled to the second input gear 77, the shutter 50 is driven and rotated so that the contact part 51 moves at a moving speed equal to or greater than the sheet conveyance speed (i.e., the sheet conveyance speed of the registration roller pair 9) (see FIG. 15D).

[0122]Then, as illustrated in FIG. 15E, the drive coupling of the second tooth-missing gear 78 is released at the timing slightly before the contact area 52 contacts the trailing end of the sheet. After the drive connection of the second tooth-missing gear 78 is released, the shutter 50 is rotated by the biasing force of the tension spring 79, and the contact area 52 contacts the trailing end of the sheet. Then, when the trailing end of the sheet passes through the contact area 52, the shutter 50 is rotated by the biasing force of the tension spring 79 as illustrated in FIG. 15F, and the contact parts 51 is located at the standby position again.

[0123]The configuration according to the present embodiment illustrated in, for example, FIGS. 2 and 3 has a space to obtain the range of rotation of the arm 72. However, the configuration according to Modification 3 does not need to have such a space, which facilitates a reduction in the size of the apparatus. On the other hand, since the configuration according to the present embodiment does not include the second tooth-missing gear 78, vibration or noise is not generated at the time of drive coupling of the second tooth-missing gear 78.

[0124]The above-described embodiments are illustrative and do not limit the present disclosure. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the present disclosure.

[0125]The above-described embodiments are limited examples, and the present disclosure includes, for example, the following aspects having advantageous effects.

Aspect 1

[0126]In Aspect 1, a sheet conveyance device (for example, the sheet conveyance device 100) includes a conveyance roller pair (for example, the registration roller pair 9), a rotator (for example, the shutters 50), a driver (for example, the input gear 63, the tooth-missing gear 64). The conveyance roller pair conveys a sheet (for example, the sheet P). The rotator has a contact part (for example, the contact part 51) to which a leading end of the sheet contacts. The rotator corrects skew of the sheet while the rotator rotates with the contact part being in contact with the leading end of the sheet. The driver rotates to rotate the rotator for a given time to cause the contact part to move at a moving speed slower than a sheet conveyance speed of a conveyance member (for example, the sheet conveyance roller pair 16a) disposed upstream from the conveyance roller pair in a sheet conveyance direction in a period from when the leading end of the sheet contacts the contact part to when the leading end of the sheet reaches the conveyance roller pair.

[0127]According to this configuration, as described in the embodiments above, the driver causes the contact part to move at a moving speed slower than the sheet conveyance speed in a given period of time from when the leading end of a sheet contacts the contact part to when the leading end of the sheet reaches the conveyance roller pair. Thus, the sheet can be bent by a certain amount regardless of the stiffness of the sheet. Accordingly, a preferable skew correction can be performed on a sheet having a relatively large stiffness.

Aspect 2

[0128]In Aspect 2, the sheet conveyance device according to Aspect 1 further includes a drive source (for example, the conveyance motor 61). The driver includes a tooth-missing gear (for example, the tooth-missing gear 64) and an input gear (for example, the input gear 63). The tooth-missing gear is rotated with the rotator (for example, the shutter 50). The input gear transmits a driving force of the drive source to the tooth-missing gear.

[0129]According to this configuration, as described in the embodiments above, as the contact part (for example, the contact parts 51) is pushed by the sheet to rotate the rotator by a given angle, the contact part is meshed with the input gear such as the input gear 63, so that the contact part such as the contact part 51 can drive and rotate the rotator that moves at a moving speed slower than the sheet conveyance speed. After the above-described given time has elapsed, the drive coupling of the tooth-missing gear 64 and the input gear 63 is released, and the contact part 51 can be moved at the same speed as the conveyance speed of the sheet.

Aspect 3

[0130]In Aspect 3, in the sheet conveyance device according to Aspect 2, the driver (for example, the input gear 63, the tooth-missing gear 64) is a conveyance motor (for example, the conveyance motor 61) to rotate the conveyance roller pair (for example, the registration roller pair 9).

[0131]According to this configuration, as described in the embodiments above, a single motor can drive the rotator such as the shutters 50 and the conveyance roller pair such as the registration roller pair 9, so that a reduction in cost and weight of the apparatus and energy saving can be facilitated.

Aspect 4

[0132]In Aspect 4, in the sheet conveyance device according to Aspect 3, the input gear (for example, the input gear 63) is disposed on a shaft (for example, the shutter shaft 91b) of a drive roller (for example, the drive shaft 91a) of the conveyance roller pair (for example, the registration roller pair 9).

[0133]According to this configuration, as described in the embodiments above, the conveyance motor (for example, the conveyance motor 61) can drive the rotator such as the shutters 50 and the conveyance roller pair such as the registration roller pair 9.

Aspect 5

[0134]In Aspect 5, the sheet conveyance device according to any one of Aspects 2 to 4 further includes a presser (for example, the cam follower 74, the arm 72, the cam spring 73) and a rotation mechanism (for example, the rotation mechanism 70). The presser presses the rotator (for example, the shutter 50). The rotation mechanism causes the presser to rotate the rotator after the tooth-missing gear (for example, the tooth-missing gear 64) and the input gear (for example, the input gear 63) are disengaged from each other.

[0135]According to this configuration, as described in the embodiments above, after the drive coupling of the tooth-missing gear 64 is released, the rotator is rotated by the pressing force of the rotation mechanism, so that the contact part 51 is located at the standby position at which the leading end of the sheet contacts the contact part 51.

Aspect 6

[0136]In Aspect 6, the sheet conveyance device according to any one of Aspects 2 to 4 further includes another tooth-missing gear (for example, the second tooth-missing gear 78) and another input gear (for example, the second input gear 77). Said another input gear transmits a driving force of the drive source (for example, the conveyance motor 61) to said another tooth-missing gear. Said another tooth-missing gear meshes with said another input gear to rotate the rotator (for example, the shutter 50) to make a moving speed of the contact part (for example, the contact part 51) be faster than a conveyance speed of the sheet, after the tooth-missing gear and the input gear are disengaged from each other.

[0137]According to this configuration, as described with reference to FIG. 15, after the drive coupling of the tooth-missing gear such as the tooth-missing gear 64 is released, the rotator such as the shutters 50 is rotated by said another tooth-missing gear such as the second tooth-missing gear 78, so that the contact part such as the contact part 51 is located at the standby position at which the leading end of the sheet contacts the contact part such as the contact part 51.

Aspect 7

[0138]In Aspect 7, in the sheet conveyance device according to Aspect 6, said another input gear (for example, the second input gear 77) has a number of teeth to be an integer multiple including a same number of teeth of the input gear (for example, the input gear 63).

[0139]According to this configuration, as described in the embodiments above, the movement of the second tooth-missing gear 78 when the second tooth-missing gear 78 is drivingly coupled is the same movement as the tooth-missing gear 64, so that the rotational motion of the rotator such as the shutter 50 can be stabilized.

Aspect 8

[0140]In Aspect 8, the sheet conveyance device according to any one of Aspects 2 to 7 further includes a rotary shaft (for example, the shutter shaft 91b) to which the rotator (for example, the shutter 50) and the tooth-missing gear (for example, the tooth-missing gear 64) are attached. The rotary shaft includes a pin (for example, the pin 94) to be engaged with the rotator. The rotary shaft has a D-shaped portion (for example, the D-shaped portions 191a, 191b) and a pin insertion hole (for example, the pin insertion hole 191d) into which the pin is inserted. The pin insertion hole is extended to a center of the rotary shaft. The pin insertion hole is disposed at a position substantially same as a position of a plane portion of the D-shaped portion in a rotational direction of the rotary shaft.

[0141]As a result, as described in the embodiments above, the offset of the center of gravity due to the pin such as the pins 94 can be cancelled by the offset of the center of gravity of the D-shaped portion such as the D-shaped portions 191a and 191b, and the offset of the center of gravity of the rotary shaft such as the shutter shaft 91b can be minimized. Accordingly, the rotary shaft can be smoothly rotated as much as possible.

Aspect 9

[0142]In Aspect 9, in the sheet conveyance device according to Aspect 1, the driver (for example, the input gear 63, the tooth-missing gear 64) includes a drive source (for example, the shutter motor 67), a drive train (for example, the input gear 65, the shutter gear 66), and a controller (for example, the controller 68). The drive train transmits a driving force of the drive source. The controller is to control a rotation speed of the drive source. The controller is to cause the drive source to rotate the rotator (for example, the shutter 50) for a given period of time to move the contact part (for example, the contact part 51) of the rotator at a speed slower than a speed of conveyance of the sheet (for example, the sheet P).

[0143]According to this configuration, as described in Modification 2, vibration or noise can be reduced when compared with a configuration in which a tooth-missing gear is used for a certain period of time to move the contact part 51 at a moving speed slower than the sheet conveyance speed.

Aspect 10

[0144]In Aspect 10, in the sheet conveyance device according to Aspect 9, the controller (for example, the controller 68) is to rotate the rotator for a given period of time to cause the contact part to move at the speed slower than the speed of conveyance of the sheet, and causes the drive source such as the shutter motor 67 to move the contact part such as the contact part 51 of the rotator at a speed equal to or faster than the speed of conveyance of the sheet in response to rotation of the rotator.

[0145]According to this configuration, as described in Modification 2, the leading end of the sheet is prevented from being deformed in a shape of bellows.

Aspect 11

[0146]In Aspect 11, in the sheet conveyance device according to any one of Aspects 1 to 10, the rotator has a contact area (for example, the contact area 52) with a contact face (for example, the contact face 52a) that contacts a downstream side of a front face of the sheet (for example, the sheet P) conveyed by the conveyance roller pair (for example, the registration roller pair 9) in a sheet conveyance direction, and the contact face of the contact area is a slope inclined to separate from the front face of the sheet, toward an end from a center in a width direction of the sheet.

[0147]According to this configuration, as illustrated in FIGS. 10A and 10B, the leading end of the contact area such as the contact area 52 is prevented from being caught by the punched hole formed in the downstream side of the sheet in the sheet conveyance direction.

Aspect 12

[0148]In Aspect 12, an image forming apparatus (for example, the copier 1) includes the sheet conveyance device (for example, the sheet conveyance device 100) according to any one of Aspects 1 to 11, and an image forming device (for example, the printer device 6) to form an image on the sheet (for example, the sheet P conveyed from the sheet conveyance device. The configuration can provide an image forming apparatus with high productivity to prevent an image from being formed in a tilted manner with respect to the sheet.

[0149]The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the present invention.

Aspect 13

[0150]In Aspect 13, a sheet conveyance device (for example, the sheet conveyance device 100) includes a conveyance roller pair (for example, the registration roller pair 9), a conveyance member (for example, the sheet conveyance roller pair 16a), a rotator (for example, the shutters 50), and a driver (for example, the input gear 63, the tooth-missing gear 64). The conveyance roller pair conveys a sheet (for example, the sheet P) in a sheet conveyance direction. The conveyance member is disposed upstream from the conveyance roller pair in the sheet conveyance direction and conveys the sheet to the conveyance roller pair at a given conveyance speed. The rotator is coaxial with one of the conveyance roller pair and has a contact part to which a leading end of the sheet is contactable to correct skew of the sheet. The driver rotates the rotator to cause the contact part (for example, the contact part 51) to move at a moving speed slower than the given conveyance speed of the conveyance member while the leading end contacts the contact part and moves to the conveyance roller pair.

Aspect 14

[0151]In Aspect 14, in the sheet conveyance device according to Aspect 13, the driver includes a drive source (for example, the conveyance motor 61), a tooth-missing gear (for example, the tooth-missing gear 64), and an input gear (for example, the input gear 63). The drive source generates a driving force to rotate another of the conveyance roller pair (for example, the registration roller pair 9). The tooth-missing gear is coaxial with the rotator (for example, the shutter 50) and rotatable with the rotator. The input gear on said another of the conveyance roller pair engages with the tooth-missing gear to transmit the driving force of the drive source the tooth-missing gear.

Aspect 15

[0152]In Aspect 15, in the sheet conveyance device according to Aspect 14, the drive source includes a conveyance motor (for example, the conveyance motor 61).

Aspect 16

[0153]In Aspect 16, in the sheet conveyance device according to Aspect 15, wherein said another of the conveyance roller pair (for example, the registration roller pair 9) includes a shaft (for example, the shutter shaft (for example, the shutter shaft 91b), a drive roller (for example, the drive shaft 91a) on the shaft driven by the drive source, and the input gear (for example, the input gear 63) on the shaft driven by the drive source.

Aspect 17

[0154]In Aspect 17, the sheet conveyance device according to any one of Aspects 14 to 16 further includes a presser (for example, the cam follower 74, the arm 72, the cam spring 73) and a rotation mechanism (for example, the rotation mechanism 70). The presser presses the rotator (for example, the shutter 50). The rotation mechanism causes the presser to rotate the rotator in response to a disengagement of the tooth-missing gear (for example, the tooth-missing gear 64) from the input gear (for example, the input gear 63).

Aspect 18

[0155]In Aspect 18, the sheet conveyance device according to any one of Aspects 14 to 16 further includes another tooth-missing gear (for example, the second tooth-missing gear 78) and another input gear (for example, the second input gear 77). Said another tooth-missing gear is coaxial with the rotator (for example, the shutter 50) and the tooth-missing gear (for example, the tooth-missing gear 64). Said another input gear on said another of the conveyance roller pair (for example, the registration roller pair 9) engages with said another tooth-missing gear to transmit the driving force of the drive source (for example, the conveyance motor 61) to said another tooth-missing gear. Said another tooth-missing gear engages with said another input gear to cause the contact part (for example, the contact part 51) of the rotator to move at another moving speed faster than the given conveyance speed of the conveyance member (for example, the sheet conveyance roller pair 16a) in response to a disengagement of the tooth-missing gear (for example, the tooth-missing gear 64) from the input gear (for example, the input gear 63).

Aspect 19

[0156]In Aspect 19, the sheet conveyance device according to Aspect 18, said another input gear (for example, the second input gear 77) has a number of teeth that is an integer multiple of a number of teeth of the input gear including a number same as the number of teeth of the input gear (for example, the input gear 63).

Aspect 20

[0157]In Aspect 20, the sheet conveyance device according to any one of Aspects 14 to 19, said one of the conveyance roller pair (for example, the registration roller pair 9) includes a rotary shaft (for example, the shutter shaft 91b) attached with the rotator and the tooth-missing gear (for example, the tooth-missing gear 64) and including a pin (for example, the pin 94) engaged with the rotator (for example, the shutter 50). The rotary shaft has a D-shaped portion (for example, the D-shaped portions 191a, 191b) having a planer portion at given position in a rotation direction of the rotary shaft, and a pin insertion hole (for example, the pin insertion hole 191d) into which the pin is inserted. The pin insertion hole is extended to a center of the rotary shaft and is disposed at a position substantially same as the position of the plane portion of the D-shaped portion in the rotational direction of the rotary shaft.

Aspect 21

[0158]In Aspect 21, the sheet conveyance device according to Aspect 13, the driver (for example, the input gear 63, the tooth-missing gear 64) includes a drive source (for example, the shutter motor 67) to generate a driving force to rotate another of the conveyance roller pair (for example, the registration roller pair 9), a drive train (for example, the input gear 65, the shutter gear 66) to transmit the driving force of the drive source to the rotator (for example, the shutter 50), and a controller (for example, the controller 68) to control a number of rotations of the drive source per a given period of time, and cause the drive source to rotate the rotator for the given period of time to cause the contact part (for example, the contact part 51) to move at the moving speed slower than the given conveyance speed of the conveyance member (for example, the sheet conveyance roller pair 16a).

Aspect 22

[0159]In Aspect 22, in the sheet conveyance device according to Aspect 21, the controller (for example, the controller 68) is to rotate the rotator (for example, the shutter 50) for the given period of time to cause the contact part (for example, the contact part 51) to move at the moving speed slower than the conveyance speed, and cause the drive source (for example, the shutter motor 67) to move the contact part of the rotator at another moving speed equal to or faster than the conveyance speed after an elapse of the given period time.

Aspect 23

[0160]In Aspect 23, in the sheet conveyance device according to any one of Aspects 13 to 22, said one of the conveyance roller pair (for example, the registration roller pair 9) includes a rotary shaft (for example, the motor shaft 91b) attached with the rotator (for example, the shutter 50), the rotator has a contact area (for example, the contact area 52) on a contact face (for example, the contact face 52a) contactable the sheet conveyed by the conveyance roller pair in the conveyance direction, and the contact face of the contact area has a slope inclined in an axial direction of the rotary shaft.

Aspect 24

[0161]In Aspect 24, in the sheet conveyance device according to any one of Aspects 13 to 23, an outer diameter of the tooth-missing gear (for example, the tooth-missing gear 64) is larger than an outer diameter of the input gear (for example, the input gear 63).

Aspect 25

[0162]In Aspect 25, an image forming apparatus (for example, the copier 1) includes the sheet conveyance device (for example, the sheet conveyance device 100) according to any one of Aspects 13 to 24, and an image forming device (for example, the printer device 6) to form an image on the sheet conveyed from the sheet conveyance device.

[0163]The functionality of the elements disclosed herein may be implemented using circuitry or processing circuitry which includes general purpose processors, special purpose processors, integrated circuits, application specific integrated circuits (ASICs), digital signal processors (DSPs), field programmable gate arrays (FPGAs), conventional circuitry and/or combinations thereof which are configured or programmed to perform the disclosed functionality.

[0164]Processors are considered processing circuitry or circuitry as they include transistors and other circuitry therein. In the disclosure, the circuitry, units, or means are hardware that carry out or are programmed to perform the recited functionality. The hardware may be any hardware disclosed herein or otherwise known which is programmed or configured to carry out the recited functionality. When the hardware is a processor which may be considered a type of circuitry, the circuitry, means, or units are a combination of hardware and software, the software being used to configure the hardware and/or processor.

[0165]This patent application is based on and claims priority to Japanese Patent Application No. 2022-191040, filed on Nov. 30, 2022, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.

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