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EP-4379150-B1 - WORK MACHINE

EP4379150B1EP 4379150 B1EP4379150 B1EP 4379150B1EP-4379150-B1

Inventors

  • IGARASHI TERUKI
  • TANAKA HIROAKI
  • FUKUCHI RYOHEI
  • SUZUKI YUSUKE

Dates

Publication Date
20260506
Application Date
20230330

Claims (9)

  1. A work machine (1) comprising; a hydraulic pump (201, 202) that delivers a hydraulic operating fluid; a hydraulic cylinder (5, 6, 7) driven by the hydraulic operating fluid delivered from the hydraulic pump (201, 202); a driving target member (8, 9, 10) driven by the hydraulic cylinder (5, 6, 7); a flow control valve (D1 - D6) that controls a flow rate of the hydraulic operating fluid supplied from the hydraulic pump (201, 202) to the hydraulic cylinder (5, 6, 7); a solenoid valve (55a, 55b, 56a, 56b, 57a, 57b, 58a, 58b, 59a, 59b) that generates an operation pressure for operating the flow control valve (D1 - D6); a controller (40) that controls the solenoid valve (55a, 55b, 56a, 56b, 57a, 57b, 58a, 58b, 59a, 59b) ; and a pressure sensor (201b, 202b, 203b) that senses a pressure of the hydraulic cylinder (5, 6, 7), wherein an opening characteristic table (T, Ti, To) that defines a relation between the operation pressure and opening area of the flow control valve (D1 - D6) is stored in the controller (40), and the controller (40) is configured to execute learning processing of changing in a stepwise manner the operation pressure generated by the solenoid valve (55a, 55b, 56a, 56b, 57a, 57b, 58a, 58b, 59a, 59b) and storing the operation pressure when the pressure of the hydraulic cylinder (5, 6, 7) sensed by the pressure sensor (201b, 202b, 203b) or a time change rate of the pressure of the hydraulic cylinder (5, 6, 7) has become a reference value set in advance, calculate a differential pressure across the flow control valve (D1 - D6), compute a target opening area of the flow control valve (D1 - D6) on the basis of the differential pressure across the flow control valve (D1 - D6) calculated and a target flow rate of the hydraulic operating fluid that passes through the flow control valve (D1 - D6), compute a target value of the operation pressure generated by the solenoid valve (55a, 55b, 56a, 56b, 57a, 57b, 58a, 58b, 59a, 59b) , on the basis of the opening characteristic table (T, Ti, To), the target opening area computed, and a learning result operation pressure that is the operation pressure stored in the learning processing, and control the solenoid valve (55a, 55b, 56a, 56b, 57a, 57b, 58a, 58b, 59a, 59b) on the basis of the target value of the operation pressure computed.
  2. The work machine (1) according to claim 1, wherein the controller (40) is configured to correct the opening characteristic table (T, Ti, To) on the basis of the learning result operation pressure, and refer to the opening characteristic table (T, Ti, To) corrected and compute the target value of the operation pressure on the basis of the target opening area.
  3. The work machine (1) according to claim 1, wherein the controller (40) is configured to refer to the opening characteristic table (T, Ti, To) and compute the target value of the operation pressure on the basis of the target opening area, correct the target value of the operation pressure on the basis of the learning result operation pressure, and control the solenoid valve (55a, 55b, 56a, 56b, 57a, 57b, 58a, 58b, 59a, 59b) on the basis of the target value of the operation pressure corrected.
  4. The work machine (1) according to claim 1, wherein the controller (40) is configured to store, as the learning result operation pressure, the operation pressure when a pressure of an outlet side of the hydraulic cylinder (5, 6, 7) has become equal to or lower than a pressure threshold as the reference value in a process of raising in the stepwise manner the operation pressure generated by the solenoid valve (55a, 55b, 56a, 56b, 57a, 57b, 58a, 58b, 59a, 59b) , in the learning processing, calculate a differential pressure across a meter-out passage part of the flow control valve (D1 - D6), compute a target opening area of the meter-out passage part of the flow control valve (D1 - D6) on the basis of the differential pressure across the meter-out passage part calculated and a target flow rate of the hydraulic operating fluid that passes through the meter-out passage part, and compute the target value of the operation pressure generated by the solenoid valve (55a, 55b, 56a, 56b, 57a, 57b, 58a, 58b, 59a, 59b) , on the basis of the opening characteristic table (T, Ti, To), the target opening area computed, and the learning result operation pressure.
  5. The work machine (1) according to claim 1, wherein the controller (40) is configured to store, as the learning result operation pressure, the operation pressure when an increase rate of pressure of an inlet side of the hydraulic cylinder (5, 6, 7) has become equal to or higher than an increase rate threshold as the reference value in a process of raising in the stepwise manner the operation pressure generated by the solenoid valve (55a, 55b, 56a, 56b, 57a, 57b, 58a, 58b, 59a, 59b) , in the learning processing, calculate a differential pressure across a meter-in passage part of the flow control valve (D1 - D6), compute a target opening area of the meter-in passage part of the flow control valve (D1 - D6) on the basis of the differential pressure across the meter-in passage part calculated and a target flow rate of the hydraulic operating fluid that passes through the meter-in passage part, and compute the target value of the operation pressure generated by the solenoid valve (55a, 55b, 56a, 56b, 57a, 57b, 58a, 58b, 59a, 59b) , on the basis of the opening characteristic table (T, Ti, To), the target opening area computed, and the learning result operation pressure.
  6. The work machine (1) according to claim 4, wherein the work machine (1) includes a first flow control valve (D1) and a second flow control valve (D2) as the flow control valve (D1 - D6), the first flow control valve (D1) and the second flow control valve (D2) are configured to cause the hydraulic operating fluid discharged from the hydraulic cylinder (5, 6, 7) to pass through the first flow control valve (D1) and the second flow control valve (D2), and the controller (40) is configured to raise in a stepwise manner the operation pressure generated by the solenoid valve (55a, 55b) corresponding to the second flow control valve (D2), in a state in which the first flow control valve (D1) is opened in the learning processing, and store, as the learning result operation pressure, the operation pressure when the pressure of the outlet side of the hydraulic cylinder (5, 6, 7) has become equal to or lower than the pressure threshold in the process of raising in the stepwise manner the operation pressure generated by the solenoid valve (55a, 55b).
  7. The work machine (1) according to claim 1, comprising: a plurality of the hydraulic pumps (201, 202); a plurality of the hydraulic cylinders (5, 6, 7); a plurality of the flow control valves (D1 - D6) corresponding to each of the plurality of the hydraulic cylinders (5, 6, 7); and a plurality of the solenoid valves (55a, 55b, 56a, 56b, 57a, 57b, 58a, 58b, 59a, 59b) capable of individually controlling each of the plurality of the flow control valves (D1 - D6), wherein each of the plurality of the hydraulic pumps (201, 202) is allowed to individually connect to, on a one-to-one basis, a respective one of the plurality of the flow control valves (D1 - D6) corresponding to each of the plurality of the hydraulic cylinders (5, 6, 7), and the controller (40) is configured to change synchronously and in a stepwise manner a plurality of the operation pressures generated by each of the plurality of the solenoid valves (55a, 55b, 56a, 56b, 57a, 57b, 58a, 58b, 59a, 59b) and input pressures of the plurality of the hydraulic cylinders (5, 6, 7) sensed by the pressure sensor (201b, 202b, 203b), and store the operation pressure when each of the pressures of the plurality of the hydraulic cylinders (5, 6, 7) or time change rates of the pressures of the plurality of the hydraulic cylinders (5, 6, 7) has become the reference value set with regard to a respective one of the plurality of the solenoid valves (55a, 55b, 56a, 56b, 57a, 57b, 58a, 58b, 59a, 59b) , as the learning result operation pressure of the respective one of the plurality of the solenoid valves (55a, 55b, 56a, 56b, 57a, 57b, 58a, 58b, 59a, 59b) .
  8. The work machine (1) according to claim 1, comprising: a posture sensor (30-33, 50) that senses a posture of a work device (1A) to which a plurality of the driving target members (8, 9, 10) are joined, wherein the controller (40) is configured to determine whether or not the posture of the work device (1A) sensed by the posture sensor (30-33, 50) is a learning start posture defined in advance, and employ at least a state in which the posture of the work device (1A) is the learning start posture as one of conditions for starting the learning processing.
  9. The work machine (1) according to claim 1, comprising: a temperature sensor (19) that senses temperature of the hydraulic operating fluid, wherein the controller (40) is configured to determine whether or not the temperature of the hydraulic operating fluid sensed by the temperature sensor (19) is equal to or higher than a temperature threshold set in advance, and employ at least a state in which the temperature of the hydraulic operating fluid is equal to or higher than the temperature threshold as one of conditions for starting the learning processing.

Description

Technical Field The present invention relates to a work machine. Background Art In recent years, demands for semi-automatic operation, automatic operation, remote operation, and so forth have been increasing with regard to work machines such as hydraulic excavators, and advancement toward electronic control of the work machines has been made. As a technique that allows the electronic control of the work machine, there is a technique in which hydraulic actuators are controlled with use of solenoid valves. For example, a method in which control valves for controlling hydraulic actuators such as hydraulic cylinders and hydraulic motors are operated by a pilot pressure (operation pressure) generated by a solenoid valve has been known. Here, a technique in which, in electronic control of a work machine, the individual difference of the work machine is considered and data used for control is calibrated to improve the excavation accuracy has been known (refer to Patent Document 1). In Patent Document 1, an invention intended to improve the excavation accuracy in semi-automatic operation is disclosed. A work machine described in Patent Document 1 includes a controller that stores data that defines the relation between a pilot pressure and the operating velocity of a cylinder. The controller repeats processing of temporarily lowering the current value of a current output to a solenoid valve (solenoid proportional control valve) and thereafter outputting a current with a current value larger than that before the lowering to the solenoid valve, to thereby raise in a stepwise manner the current value of the current output to the solenoid valve. The controller calibrates the relation between the pilot pressure and the operating velocity of the cylinder in the above-described data on the basis of the operating velocity of the cylinder when the current value has risen in the stepwise manner. Prior Art Document Patent Document Patent Document 1: PCT Patent Publication No. WO2018/087831 Summary of the Invention Problem to be Solved by the Invention However, in the case of employing an open center system as the hydraulic system applied to the work machine, the operating velocity of the cylinder with respect to the current value of the current output to the solenoid valve changes depending on the hydraulic load. Therefore, even when the operating velocity of the hydraulic cylinder in a specific hydraulic load condition (for example, in-air operation) is learned, there is a possibility that the operating velocity of the hydraulic cylinder deviates from the operating velocity at the time of the learning in an actual hydraulic load condition (for example, excavation or pressing of a ground surface). In this case, improvement in the excavation accuracy cannot be expected. The present invention intends to provide a work machine capable of performing work with high accuracy with suppression of variation in operation of a hydraulic cylinder attributable to the individual difference of the work machine, irrespective of the configuration of a hydraulic system. Means for Solving the Problem A work machine according to one aspect of the present invention includes a hydraulic pump that delivers a hydraulic operating fluid, a hydraulic cylinder driven by the hydraulic operating fluid delivered from the hydraulic pump, a driving target member driven by the hydraulic cylinder, a flow control valve that controls the flow rate of the hydraulic operating fluid supplied from the hydraulic pump to the hydraulic cylinder, a solenoid valve that generates an operation pressure for operating the flow control valve, a controller that controls the solenoid valve, and a pressure sensor that senses a pressure of the hydraulic cylinder. An opening characteristic table that defines a relation between the operation pressure and the opening area of the flow control valve is stored in the controller. The controller is configured to execute learning processing of changing in a stepwise manner the operation pressure generated by the solenoid valve and storing the operation pressure when the pressure of the hydraulic cylinder sensed by the pressure sensor or the time change rate of the pressure of the hydraulic cylinder has become a reference value set in advance. The controller is configured to calculate the differential pressure across the flow control valve and compute a target opening area of the flow control valve on the basis of the calculated differential pressure across the flow control valve and a target flow rate of the hydraulic operating fluid that passes through the flow control valve. The controller is configured to compute a target value of the operation pressure generated by the solenoid valve, on the basis of the opening characteristic table, the target opening area computed, and a learning result operation pressure that is the operation pressure stored in the learning processing, and control the solenoid valve on the basis of the computed targ