Caterpillar SARL

Problem: In a hydraulic control system including a prime motor, a plurality of variable-capacity hydraulic pumps driven by the prime motor, and a plurality of hydraulic actuators driving the hydraulic pumps as a hydraulic source, merging of the discharged oil of the hydraulic pump is reduced to reduce the decrease in efficiency and operability caused by the merging. Solution: A controller is provided to control the pump capacity of the hydraulic pumps and the rotational speed of the prime motor, and the controller is provided with a reference pump flow rate setting unit that sets a reference pump flow rate, a target pump flow rate setting unit that sets a target pump flow rate of each hydraulic pump for each hydraulic pump according to operation of a manipulator, and a pump flow rate control unit that, when the target pump flow rate of any hydraulic pumps exceeds the reference pump flow rate, maximizes the pump capacity of the hydraulic pump, and increases the rotational speed of the prime motor, thereby increasing the pump flow rate to be greater than the reference pump flow rate.

Problem: In a case where the hydraulic actuator A supplied with hydraulic oil only from the first hydraulic pump and the hydraulic actuator B supplied with hydraulic oil from the first and second hydraulic pumps are operated simultaneously, even if the required flow rate for the first hydraulic pump of the hydraulic actuators A and B exceeds the first hydraulic pump maximum discharge flow rate, the hydraulic actuators A and B can be driven at the operation speed corresponding to the operation amount of the operation means. Solution: A target flow rate correction means is provided for setting the bucket cylinder required flow rate as a target flow rate from the hydraulic pump to the bucket cylinder, a flow rate obtained by subtracting the bucket cylinder required flow rate from the pump maximum discharge flow rate as a target flow rate from the hydraulic pump to the boom cylinder, and setting a flow rate obtained by subtracting the target flow rate from the hydraulic pump to the boom cylinder from the bucket cylinder total required flow rate as a target flow rate from the hydraulic pump to the boom cylinder.

The present disclosure is generally directed towards a machine requiring separate control of a swing function, travel function and implements. The machine comprises a swing-travel hydraulic system for controlling swing and travel motor arrangements in closed loop circuits with a swing-travel pump arrangement. The machine may further comprise a separate implement hydraulic system operating an implement motor arrangement in an open loop circuit.

Problem to Be Solved: To investigate an opening area control of a flow control valve disposed on upstream side of the stick's direction change-over valve when using the flow control valve as a valve for restricting the supply flow rate to stick cylinder during interlocking operation of the swiveling motor and stick cylinder. Solution: A configuration is provided to control the opening area of the stick's first flow control valve based on a target supply flow rate to the stick cylinder, target differential pressure between first hydraulic pump A and supply pressure to the stick cylinder, and opening area of supply valve passage to the stick's direction change-over valve and also control that the differential pressure is set larger as operating amount of swiveling manipulator increases during interlocking operation of the swiveling motor and stick cylinder and the opening area of stick's first flow control valve is made smaller as the differential pressure increases.

Problem: Calibration to make the correspondence relationship between the operation amount of the operator and the supply flow rate to the hydraulic actuator be a preset setting relationship is made easy. Solution: The control valve that controls the supply flow rate to the hydraulic actuator is configured with a spool valve, a pressure compensation valve that maintains a front and rear differential pressure of the spool valve to be constant, and electromagnetic proportional valves that output pilot pressure to the spool valve, and a measured data that actually measures the correspondence between the output pilot pressure from the electromagnetic proportional valves and the supply flow from the control valve before the control valve is installed in the working machine is configured to calibrate the corresponding data of the operation amount of the operator and the output current value to the electromagnetic proportional valves.

Problem to be solved: To provide a hydraulic circuit for a construction machine capable of supplying hydraulic oil to a closed circuit without a charge pump. Means for solving the problem: The open circuit of the hydraulic circuit includes a hydraulic pump, a hydraulic actuator operated by hydraulic oil discharged from the hydraulic pump, a directional switching valve for switching a flow direction of the hydraulic oil from the hydraulic pump to the hydraulic actuator, a return line connecting the directional switching valve and a hydraulic oil tank, and a return check valve provided in the return line. The closed circuit of the hydraulic circuit includes a bidirectional hydraulic pump having a first port and a second port, a hydraulic motor operated by hydraulic oil discharged from the bidirectional hydraulic pump, a first line connecting the first port of the bidirectional hydraulic pump and the hydraulic motor, and a second line connecting the second port of the bidirectional hydraulic pump and the hydraulic motor. Between the open circuit and the closed circuit, a charge line connecting the return line and the first line via a first check valve and connecting the return line and the second line via a second check valve is provided.

Problems: Provided is a drive control device for a fluid pressure cylinder that has good operability for expanding and contracting the fluid pressure cylinder in the vicinity of a stroke end. Solutions: A drive control device includes an expansion and contraction unit configured to expand and contract a fluid pressure cylinder in response to an operation of an operating body; a position detection unit configured to detect an expansion and contraction position of the fluid pressure cylinder; a speed detection unit configured to detect an expansion and contraction speed of the fluid pressure cylinder; a limiting unit configured to limit, according to the expansion and contraction position of the fluid pressure cylinder within a predetermined range from a stroke end and the expansion and contraction speed in a stroke end direction, the expansion and contraction speed of the fluid pressure cylinder in the stroke end direction by the expansion and contraction unit; and a stopping unit configured to stop expansion and contraction of the fluid pressure cylinder at a predetermined position by reducing an amount of a working fluid supplied to the fluid pressure cylinder as a distance of the fluid pressure cylinder from the predetermined position in the vicinity of the stroke end is shorter.

PURPOSE: To control crane operation in safety and high working efficiency by limiting upper limit value of swing angle speed automatically, corresponding to a working radius calculated from the length and angle of a boom and a load factor of a crane. CONSTITUTION: A working radius R is searched from a boom angle beta and a boom length L detected with detectors 1, 2, with a computing element 3, and an allowable maximum swing angle speed omegamax is computed by a first function generating means 7. Meanwhile, from a cane load W detected with a detector 4, working radius R, and boom length L, a rated value Wa with a computing element 5, moreover a load factor P with a dividing apparatus 6 are searched, and a decreasing factor of swing angle speed K is calculated with a second function generating means 8. omegamax.K is searched with a multiplicator 9, and output as a control signal which sets it as the upper limit value of swing angle speed, to a swing driving mechanism A. Hereby, the swing angle speed corresponding to various working radii and load factors are obtained. The maximum swing angle speed is limited according to the working condition, and controlling of crane operation can be performed in safety and high working efficiency.

A method of operating a work vehicle is provided. The work vehicle comprises a swing apparatus rotatable about a swing axis. The swing apparatus comprises an arm arrangement comprising a boom and a stick, a boom actuator for controlling the boom, and at least one boom head pressure sensor for generating boom head pressure data indicative of a boom head pressure of the boom actuator. The method comprises, by a control system, determining a maximum allowable swing speed of the swing apparatus rotating about the swing axis, to account for the moment of inertia of the swing apparatus, based on boom head pressure data and a map linking boom head pressure data with the maximum allowable swing speed. The method further comprises limiting a maximum operational swing speed of the swing apparatus to the maximum allowable swing speed.

Problem: In a hydraulic system in which a manual line relief valve that adjusts the relief setting pressure is arranged in the line relief oil path formed by branching from the actuator line from the control valve to the hydraulic actuator, the relief setting pressure adjustment operation of the line relief valve can be performed independently with good accuracy. Solution: A controller 20 for controlling a perform of a relief setting pressure adjustment operation of a line relief valve 25 is provided with a pump flow control means that controls the pump flow rate during the relief setting pressure adjustment operation, an instruction command output means 54 that instructs a perform of the relief setting pressure adjustment operation by a manual operation, and a notification command output means 55 that notifies that the pump pressure detected by a pressure sensor 31 during the relief setting pressure adjustment operation is within a predetermined range of the target relief setting pressure.