Working machinery and methods

Abstract

To improve the operability of the work machinery. [Solution] The work machine equipped with a work implement includes a hydraulic pump for discharging hydraulic fluid, a hydraulic cylinder for operating the work implement, a meter-in passage connecting the hydraulic pump and the rod chamber of the hydraulic cylinder, a meter-out passage connecting the cap chamber of the hydraulic cylinder and a tank, a meter-in control valve for controlling the flow rate of hydraulic fluid supplied from the hydraulic pump to the rod chamber of the hydraulic cylinder, a meter-out control valve for controlling the flow rate of hydraulic fluid discharged from the cap chamber of the hydraulic cylinder to the tank, a regeneration passage connecting the meter-out passage between the meter-out control valve and the tank and the meter-in passage between the meter-in control valve and the rod chamber, and a controller. The controller calculates the external force acting on the hydraulic cylinder and, upon receiving an operation signal to operate the work implement so that the hydraulic cylinder retracts, controls at least one of the meter-in control valve and the hydraulic pump based on the calculated external force.

Description

Technical Field

[0001] The present disclosure relates to a work machine and a method.

Background Art

[0002] In the technical field related to work machines, a boom lowering regeneration circuit of a hydraulic excavator as disclosed in Patent Document 1 is known.

Prior Art Documents

Patent Documents

[0007] According to this disclosure, the operability of the work machine will be improved. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a side view showing a work machine according to an embodiment. [Figure 2] Figure 2 is a schematic diagram showing the control system of a work machine according to an embodiment. [Figure 3] Figure 3 is a block diagram of the controller according to the embodiment. [Figure 4] Figure 4 is a schematic diagram showing the hydraulic system in a regenerated state according to the embodiment. [Figure 5] Figure 5 is a schematic diagram showing a hydraulic system in a pump-assisted state according to an embodiment. [Figure 6] Figure 6 is a diagram illustrating the method for calculating the regeneration factor according to the embodiment. [Figure 7] Figure 7 is a diagram illustrating the method for calculating the target meter-out opening area according to the embodiment. [Figure 8]Figure 8 is a diagram illustrating the method for calculating the target pump flow rate and the target meter-in opening area according to the embodiment. [Figure 9] Figure 9 shows an example of a monitor according to the embodiment. [Figure 10] Figure 10 shows an example of a monitor according to an embodiment. [Figure 11] Figure 11 is a timing chart showing the control method of the hydraulic system according to the embodiment. [Figure 12] Figure 12 is a flowchart showing a control method for a hydraulic system according to an embodiment. [Modes for carrying out the invention]

[0009] [Working machinery] Figure 1 is a side view showing a work machine 1 according to an embodiment. The work machine 1 operates at a work site. In this embodiment, the work machine 1 is a hydraulic excavator. The work machine 1 comprises a traveling body 2, a rotating body 3, a work machine 4, a hydraulic cylinder 5, a controller 6, a work machine operating device 7, and a monitor 50.

[0010] The running body 2 supports the rotating body 3. The running body 2 has a pair of tracks 2A. The working machine 1 moves as the tracks 2A rotate.

[0011] The slewing body 3 is positioned above the traveling body 2. The slewing body 3 is supported so as to be rotatable relative to the traveling body 2. The slewing body 3 has a cab. The operator of the work machine 1 is seated in the cab. The work machine operating device 7 and the monitor 50 are located in the cab. The work machine operating device 7 outputs operating signals for operating the work machine 4. The work machine operating device 7 is, for example, a lever that can be operated by the operator. The monitor 50 includes a display device and an input device. The display device of the monitor 50 provides display data to the operator. The input device of the monitor 50 is configured to be operable by the operator. The input device of the monitor 50 generates input data when operated by the operator. The traveling body 2 and the slewing body 3 constitute the body of the work machine 1.

[0012] The working machine 4 is rotatably connected to the revolving body 3. The working machine 4 includes a boom 8, an arm 9, and a bucket 10. The boom 8 is rotatably connected to the front part of the revolving body 3. The arm 9 is rotatably connected to the tip of the boom 8. The bucket 10 is rotatably connected to the tip of the arm 9.

[0013] The hydraulic cylinder 5 operates the working machine 4. The hydraulic cylinder 5 is driven by hydraulic oil. The hydraulic cylinder 5 includes a boom cylinder 11, an arm cylinder 12, and a bucket cylinder 13.

[0014] The boom cylinder 11 operates the boom 8. The operation of the boom 8 includes a raising operation and a lowering operation. When the boom cylinder 11 extends, the boom 8 performs a raising operation. When the boom cylinder 11 contracts, the boom 8 performs a lowering operation.

[0015] The arm cylinder 12 operates the arm 9. The operation of the arm 9 includes an excavation operation and a dumping operation. When the arm cylinder 12 extends, the arm 9 performs an excavation operation. When the arm cylinder 12 contracts, the arm 9 performs a dumping operation.

[0016] The bucket cylinder 13 operates the bucket 10. The operation of the bucket 10 includes an excavation operation and a dumping operation. When the bucket cylinder 13 extends, the bucket 10 performs an excavation operation. When the bucket cylinder 13 contracts, the bucket 10 performs a dumping operation.

[0017] [Control System] Figure 2 is a schematic diagram showing the control system 14 of the work machine 1 according to the embodiment. As shown in Figure 2, the control system 14 includes a controller 6, a work machine operating device 7, a power source 15, and a hydraulic system 16. Figure 2 shows the hydraulic system 16 for driving the boom cylinder 11. The power source 15 is, for example, a diesel engine. The power source 15 may also be an electric motor. The controller 6 receives operation signals from the work machine operating device 7. The controller 6 is configured to control the power source 15 and the hydraulic system 16.

[0018] The boom cylinder 11 includes a cylinder tube 111, a piston 112 that is movable inside the cylinder tube 111, and a rod 113 connected to the piston 112. The internal space of the cylinder tube 111 is divided by the piston 112 into a rod chamber 11A and a cap chamber 11B. The rod 113 is positioned in the rod chamber 11A. The boom cylinder 11 extends when hydraulic fluid is supplied to the cap chamber 11B and discharged from the rod chamber 11A. The boom cylinder 11 retracts when hydraulic fluid is supplied to the rod chamber 11A and discharged from the cap chamber 11B. In this embodiment, the pressure-receiving area of ​​the piston 112 facing the rod chamber 11A is smaller than the pressure-receiving area of ​​the piston 112 facing the cap chamber 11B.

[0019] The hydraulic system 16 includes a hydraulic pump 17, a tank 18, a pump passage 19, a rod-side passage 20, a rod-side control valve 21, a cap-side passage 22, a cap-side control valve 23, a solenoid proportional valve 70, a drain passage 25, a regeneration passage 26, a check valve 27, a rod-side pressure sensor 28, and a cap-side pressure sensor 29.

[0020] The hydraulic pump 17 is driven by power transmitted from the power source 15. The hydraulic pump 17 discharges hydraulic fluid. The hydraulic pump 17 is a variable displacement hydraulic pump in which the discharge volume changes, for example, by controlling the tilt angle of the swash plate. The discharge volume of the hydraulic pump 17 is controlled by the controller 6. The pump passage 19 is connected to the discharge port of the hydraulic pump 17. The hydraulic pump 17 draws in hydraulic fluid contained in the tank 18 and discharges it into the pump passage 19.

[0021] The rod-side control valve 21 is configured to control the flow rate of hydraulic fluid supplied to the rod chamber 11A of the boom cylinder 11 or the flow rate of hydraulic fluid discharged from the rod chamber 11A. In this embodiment, the rod-side control valve 21 is a hydraulic pilot-operated control valve having a spool. The displacement of the spool of the rod-side control valve 21 is controlled by the pilot pressure acting on the pilot oil chamber. The spool of the rod-side control valve 21 is movable between a neutral position N1, a raised position U1, and a lowered position D1. The rod-side control valve 21 has a meter-in opening 30 and a meter-out opening 31. The opening area of ​​the meter-in opening 30 and the meter-out opening 31 changes as the displacement of the spool of the rod-side control valve 21 is controlled. When the spool of the rod-side control valve 21 is in the lowered position D1, the rod-side control valve 21 functions as a meter-in control valve that controls the flow rate of hydraulic fluid supplied from the hydraulic pump 17 to the rod chamber 11A of the boom cylinder 11. Figure 2 shows the state in which the spool of the rod-side control valve 21 is positioned in the neutral position N1.

[0022] The rod-side control valve 21 has a pump port P1, a first rod port P2, a second rod port P3, and a drain port P4. The pump port P1 is connected to the hydraulic pump 17 via a pump passage 19. The first rod port P2 and the second rod port P3 are each connected to the rod chamber 11A of the boom cylinder 11 via a rod-side passage 20. The drain port P4 is connected to the tank 18 via a drain passage 25.

[0023] The cap-side control valve 23 is configured to control the flow rate of hydraulic fluid supplied to the cap chamber 11B of the boom cylinder 11 or the flow rate of hydraulic fluid discharged from the cap chamber 11B. In this embodiment, the cap-side control valve 23 is a pressure-pilot-operated control valve having a spool. The displacement of the spool of the cap-side control valve 23 is controlled by the pilot pressure acting on the pilot oil chamber. The spool of the cap-side control valve 23 is movable between a neutral position N2, a raised position U2, and a lowered position D2. The cap-side control valve 23 has a meter-in opening 32 and a meter-out opening 33. By controlling the displacement of the spool of the cap-side control valve 23, the opening areas of the meter-in opening 32 and the meter-out opening 33 change. When the spool of the cap-side control valve 23 is in the lowered position D2, the cap-side control valve 23 functions as a meter-out control valve that controls the flow rate of hydraulic fluid discharged from the cap chamber 11B of the boom cylinder 11 to the tank 18. Figure 2 shows the state in which the spool of the cap-side control valve 23 is positioned in the neutral position N2.

[0024] The cap-side control valve 23 has a pump port P5, a first cap port P6, a second cap port P7, a regeneration port P8, and a drain port P9. The pump port P5 is connected to the hydraulic pump 17 via a pump passage 19. The first cap port P6 and the second cap port P7 are each connected to the cap chamber 11B of the boom cylinder 11 via a cap-side passage 22. The regeneration port P8 is connected to a regeneration passage 26. The drain port P9 is connected to the tank 18 via a drain passage 25.

[0025] The electromagnetic proportional valve 70 supplies hydraulic fluid discharged from the pilot hydraulic pump 71 to the pilot oil chamber of the rod-side control valve 21 and the pilot oil chamber of the cap-side control valve 23. Based on command signals from the controller 6, the electromagnetic proportional valve 70 generates pilot pressure to control the spool displacement of the rod-side control valve 21 and the spool displacement of the cap-side control valve 23, respectively. That is, the controller 6 can control the rod-side control valve 21 and the cap-side control valve 23 by controlling the pilot pressure generated by the electromagnetic proportional valve 70. The electromagnetic proportional valve 70 includes 70CC and 70CD for controlling the rod-side control valve 21. The electromagnetic proportional valve 70 includes 70RC and 70RD for controlling the cap-side control valve 23.

[0026] The regeneration channel 26 connects the regeneration port P8 of the cap-side control valve 23 to the rod-side channel 20. A check valve 27 is positioned in the regeneration channel 26. The check valve 27 prevents the flow of hydraulic fluid from the rod-side channel 20 to the regeneration port P8 of the cap-side control valve 23.

[0027] If the controller 6 does not receive an operation signal from the work equipment operating device 7, the spool of the rod-side control valve 21 is positioned in the neutral position N1, and the spool of the cap-side control valve 23 is positioned in the neutral position N2. When the spool of the rod-side control valve 21 is positioned in the neutral position N1 and the spool of the cap-side control valve 23 is positioned in the neutral position N2, no hydraulic fluid flows through the rod-side control valve 21 and the cap-side control valve 23. When the spool of the rod-side control valve 21 is positioned in the neutral position N1 and the spool of the cap-side control valve 23 is positioned in the neutral position N2, no hydraulic fluid is supplied to the boom cylinder 11, no hydraulic fluid is discharged from the boom cylinder 11, and the boom cylinder 11 does not drive.

[0028] When the controller 6 receives an operation signal from the work equipment operating device 7 to raise the boom 8, it controls the rod-side control valve 21 so that the spool of the rod-side control valve 21 is positioned in the raised position U1, and controls the cap-side control valve 23 so that the spool of the cap-side control valve 23 is positioned in the raised position U2. When the spool of the rod-side control valve 21 is positioned in the raised position U1 and the spool of the cap-side control valve 23 is positioned in the raised position U2, hydraulic fluid is supplied to the cap chamber 11B via the cap-side control valve 23 and hydraulic fluid is discharged from the rod chamber 11A. When the spool of the rod-side control valve 21 is positioned in the raised position U1 and the spool of the cap-side control valve 23 is positioned in the raised position U2, the boom cylinder 11 extends and the boom 8 is raised.

[0029] When the controller 6 receives an operation signal from the work equipment operating device 7 to lower the boom 8, it controls the cap-side control valve 23 so that the spool of the cap-side control valve 23 is positioned in the lowered position D2. When the spool of the cap-side control valve 23 is positioned in the lowered position D2, hydraulic fluid is discharged from the cap chamber 11B via the cap-side control valve 23. A portion of the hydraulic fluid discharged from the cap chamber 11B is supplied to the rod chamber 11A via the regeneration passage 26, and the remaining hydraulic fluid is discharged to the tank 18. When the spool of the cap-side control valve 23 is positioned in the lowered position D2, the boom cylinder 11 retracts, and the boom 8 moves downward.

[0030] Furthermore, when the controller 6 receives an operation signal from the work equipment operating device 7 to lower the boom 8, it controls the rod-side control valve 21 so that the spool of the rod-side control valve 21 is positioned at the lowered position D1, and controls the cap-side control valve 23 so that the spool of the cap-side control valve 23 is positioned at the lowered position D2, based on the external force acting on the boom cylinder 11, which will be described later. When the spool of the rod-side control valve 21 is positioned at the lowered position D1 and the spool of the cap-side control valve 23 is positioned at the lowered position D2, hydraulic fluid is supplied to the rod chamber 11A on the rod side via the rod-side control valve 21 and hydraulic fluid is discharged from the cap chamber 11B. When the spool of the cap-side control valve 23 is positioned at the lowered position D2 and the spool of the rod-side control valve 21 is positioned at the lowered position D1, the boom cylinder 11 retracts and the boom 8 lowers.

[0031] The rod-side pressure sensor 28 is located in the rod-side flow path 20. The rod-side pressure sensor 28 detects the pressure of the hydraulic fluid flowing through the rod-side flow path 20. When the boom cylinder 11 retracts, the rod-side pressure sensor 28 detects the meter-in pressure, which indicates the pressure of the hydraulic fluid supplied to the rod chamber 11A.

[0032] The cap-side pressure sensor 29 is located in the cap-side flow path 22. The cap-side pressure sensor 29 detects the pressure of the hydraulic fluid flowing through the cap-side flow path 22. When the boom cylinder 11 retracts, the cap-side pressure sensor 29 detects the meter-out pressure, which indicates the pressure of the hydraulic fluid discharged from the cap chamber 11B.

[0033] [controller] Figure 3 is a block diagram of a controller 6 according to an embodiment. The controller 6 includes a processor 34, a storage device 35, and an input / output interface 36.

[0034] The processor 34 includes a CPU (Central Processing Unit). The storage device 35 includes a recording medium on which computer programs and data are recorded in a readable format by the processor 34. The storage device 35 includes system memory such as RAM (Random Access Memory) or ROM (Read Only Memory) and auxiliary storage memory such as semiconductor memory. The controller 6 is connected to the hydraulic pump 17, the work equipment operating device 7, the rod-side pressure sensor 28, the cap-side pressure sensor 29, the electromagnetic proportional valve 70, and the monitor 50 via an input / output interface 36.

[0035] The processor 34 includes an estimation unit 37, a determination unit 38, an arithmetic unit 39, and a control unit 40. The storage device 35 includes a storage unit 41.

[0036] The estimation unit 37 calculates the external force acting on the boom cylinder 11. The external force acting on the boom cylinder 11 refers to the force acting on the rod 113 of the boom cylinder 11 from outside the boom cylinder 11. In this embodiment, when the estimation unit 37 receives an operation signal from the work machine operating device 7 that operates the boom cylinder 11 to retract at least, it calculates the external force acting on the rod 113, with the direction of extension of the boom cylinder 11 being the positive direction. That is, if the direction of the external force acting on the rod 113 is in the direction that extends the boom cylinder 11, the calculated value of the external force will be a positive value. On the other hand, if the direction of the external force acting on the rod 113 is in the direction that retracts the boom cylinder 11, the calculated value of the external force will be a negative value. In the following description, the external force acting on the boom cylinder 11 calculated by the estimation unit 37 will be appropriately referred to as the estimated external force Fe.

[0037] The estimation unit 37 calculates the estimated external force Fe based on the meter-in pressure Pi, which indicates the pressure of the hydraulic fluid supplied to the rod chamber 11A of the boom cylinder 11; the meter-out pressure Po, which indicates the pressure of the hydraulic fluid discharged from the cap chamber 11B; the rod-side pressure-receiving area Ar, which is the pressure-receiving area of ​​the piston 112 facing the rod chamber 11A; and the cap-side pressure-receiving area Ac, which is the pressure-receiving area of ​​the piston 112 facing the cap chamber 11B. The meter-in pressure Pi is detected by the rod-side pressure sensor 28. The meter-out pressure Po is detected by the cap-side pressure sensor 29. The rod-side pressure-receiving area Ar and the cap-side pressure-receiving area Ac are known data derived from the design data or specifications data of the boom cylinder 11. The estimated external force Fe is calculated based on the following equation (1).

[0038] Fe = Pi × Ar - Po × Ac …(1)

[0039] The estimated external force Fe when the boom cylinder 11 retracts correlates, for example, with the magnitude of the resistance force (load) that the work machine 4 receives from the outside. When the load on the boom 8 is small during the operation of the work machine 4, the resistance force received by the boom cylinder 11 is small, and therefore the estimated external force Fe is also small. When the load on the boom 8 is large, the resistance force received by the boom cylinder 11 is large, and therefore the estimated external force Fe is also large. An example of the operation of the work machine 4 where the load on the boom 8 is small is when the boom 8 moves downward while the work machine 4 is away from the work object. An example of the operation of the work machine 4 where the load on the boom 8 is large is when the boom 8 moves downward so that the bucket 10 is pressed against the ground while the bucket 10 is in contact with the ground. When the boom 8 moves downward so that the bucket 10 is pressed against the ground while the bucket 10 is in contact with the ground, the ground is compacted by the bucket 10, or at least a part of the body of the work machine 1 is lifted off the ground.

[0040] In the following description, the lowering motion of the boom 8 while the work machine 4 is away from the work object will be referred to as "air operation" as appropriate, and the lowering motion of the boom 8 while the bucket 10 is in contact with the ground and the bucket 10 is pressed against the ground will be referred to as "heavy load operation" as appropriate.

[0041] The determination unit 38 determines the state of the hydraulic system 16 based on the estimated external force Fe calculated by the estimation unit 37. The determination unit 38 calculates the regeneration factor Rf based on the estimated external force Fe and the operation signal from the work equipment operating device 7. The calculation unit 39 calculates the target meter-out opening area based on the operation signal from the work equipment operating device 7 and the operating mode. The calculation unit 39 calculates the target meter-in opening area and the target pump flow rate Qp based on the operation signal from the work equipment operating device 7, the operating mode, and the regeneration factor Rf calculated by the determination unit. The control unit 40 controls the cap-side control valve 23 (meter-out control valve) based on the target meter-out opening area calculated by the calculation unit 39. The control unit 40 controls the rod-side control valve 21 (meter-in control valve) based on the target meter-in opening area calculated by the calculation unit 39. The control unit 40 controls the hydraulic pump 17 based on the target pump flow rate Qp calculated by the calculation unit 39.

[0042] [Hydraulic system status] In this embodiment, the determination unit 38 changes the state of the hydraulic system 16 to at least a regeneration state, a pump support state, and a normal state. The regeneration state refers to a state in which hydraulic fluid discharged from the cap chamber 11B passes through the regeneration passage 26 and is supplied to the rod chamber 11A. In the regeneration state, no hydraulic fluid is supplied from the hydraulic pump 17 to the boom cylinder 11. The pump support state refers to a state in which hydraulic fluid discharged from the cap chamber 11B passes through the regeneration passage 26 and is supplied to the rod chamber 11A, and hydraulic fluid discharged from the hydraulic pump 17 is also supplied to the rod chamber 11A. The normal state refers to a state in which hydraulic fluid discharged from the hydraulic pump 17 is supplied to the rod chamber 11A based on an operation signal generated by the operation of the work equipment operating device 7. An operation signal from the work equipment operating device 7 that is operated to retract the boom cylinder 11 is transmitted from the work equipment operating device 7 to the controller 6.

[0043] <Playback status> Figure 4 is a schematic diagram showing the hydraulic system 16 in a regenerated state according to the embodiment. As shown in Figure 4, the spool of the rod-side control valve 21 is positioned in the neutral position N1, and the spool of the cap-side control valve 23 is positioned in the lowered position D2. The cap-side passage 22 is connected to the drain passage 25 via the meter-out opening 33 of the cap-side control valve 23. In this case, the cap-side passage 22 and the drain passage 25 may be considered as a single meter-out passage. The meter-out passage connects the cap chamber 11B of the boom cylinder 11 to the tank 18. The regeneration passage 26 connects the meter-out opening 33 of the cap-side control valve 23 to the rod chamber 11A. One end of the regeneration passage 26 is connected to the meter-out passage between the meter-out opening 33 of the cap-side control valve 23 and the tank 18. The other end of the regeneration passage 26 is connected to the rod-side passage 20.

[0044] The regeneration state is a state in which hydraulic fluid discharged from the cap chamber 11B passes through the regeneration passage 26 and is supplied to the rod chamber 11A, and hydraulic fluid is not supplied to the rod chamber 11A from the hydraulic pump 17. As shown in Figure 4, the meter-in opening 30 of the rod-side control valve 21 is closed. After the hydraulic fluid that has flowed through the cap-side passage 22 flows from the first cap port P6 to the meter-out opening 33, some of the hydraulic fluid flows out from the regeneration port P8 and flows through the regeneration passage 26. In the regeneration state, the meter-out pressure is higher than the meter-in pressure, so the check valve 27 does not block the flow of hydraulic fluid. After passing through the check valve 27, the hydraulic fluid flows into the rod-side passage 20 and is supplied to the rod chamber 11A. That is, some of the hydraulic fluid discharged from the cap chamber 11B is supplied to the rod chamber 11A, and the remaining hydraulic fluid is discharged to the tank 18. For example, if the size of the rod-side pressure-receiving area Ar in the rod chamber 11A is 50% of the size of the cap-side pressure-receiving area Ac in the cap chamber 11B, then 50% of the hydraulic fluid that flows out of the cap chamber 11B will be supplied to the rod chamber 11A.

[0045] If the decision unit 38 has just received an operation signal from the work equipment operating device 7 to lower the boom 8, it determines the state of the hydraulic system 16 to the regenerated state. The control unit 40 controls at least one of the rod-side control valve 21 and the hydraulic pump 17 so that the state of the hydraulic system 16 becomes the regenerated state.

[0046] The determination unit 38 determines that the estimated external force Fe calculated by the estimation unit 37 is smaller than the first threshold Ha, and sets the state of the hydraulic system 16 to the regeneration state. If the estimated external force Fe is smaller than the first threshold Ha, the control unit 40 controls at least one of the rod-side control valve 21 and the hydraulic pump 17 so that the state of the hydraulic system 16 is the regeneration state. The first threshold Ha is a predetermined value and is stored in the storage unit 41.

[0047] In other words, if the controller 6 determines that the estimated external force Fe is lower than the first threshold Ha, it controls the hydraulic pump 17, the rod-side control valve 21, and the cap-side control valve 23 so that the hydraulic fluid discharged from the cap chamber 11B and passing through the regeneration channel 26 is supplied to the rod chamber 11A, and a regeneration state is reached in which no hydraulic fluid is supplied to the rod chamber 11A from the hydraulic pump 17.

[0048] <Pump support status> Figure 5 is a schematic diagram showing the hydraulic system 16 in the pump support state according to the embodiment. As shown in Figure 5, the spool of the rod-side control valve 21 is positioned in the lowered position D1, and the spool of the cap-side control valve 23 is positioned in the lowered position D2. The rod-side passage 20 is connected to the pump passage 19 via the meter-in opening 30 of the rod-side control valve 21. At this time, the pump passage 19 and the rod-side passage 20 may be considered as a single meter-in passage. The meter-in passage connects the hydraulic pump 17 and the rod chamber 11A of the boom cylinder 11. The cap-side passage 22 is connected to the drain passage 25 via the meter-out opening 33 of the cap-side control valve 23. At this time, the cap-side passage 22 and the drain passage 25 may be considered as a single meter-out passage. The meter-out passage connects the cap chamber 11B of the boom cylinder 11 and the tank 18. The regeneration passage 26 connects the meter-out opening 33 of the cap-side control valve 23 and the rod chamber 11A. One end of the regeneration channel 26 is connected to the meter-out channel between the meter-out opening 33 of the cap-side control valve 23 and the tank 18. The other end of the regeneration channel 26 is connected to the meter-in channel between the meter-in opening 30 of the rod-side control valve 21 and the rod chamber 11A.

[0049] The pump support state is a state in which the hydraulic fluid discharged from the cap chamber 11B passes through the regeneration passage 26 and is supplied to the rod chamber 11A, and the hydraulic fluid discharged from the hydraulic pump 17 is also supplied to the rod chamber 11A. As shown in Figure 5, the meter-in opening 30 of the rod-side control valve 21 is open. The hydraulic fluid discharged from the hydraulic pump 17 flows through the pump passage 19 and then flows into the meter-in opening 30 of the rod-side control valve 21 via the pump port P1. The hydraulic fluid that has flowed through the meter-in opening 30 flows out from the first rod port P2, flows through the rod-side passage 20, and is supplied to the rod chamber 11A.

[0050] In the pump-assisted state, if the meter-out pressure is higher than the meter-in pressure, the check valve 27 does not block the flow of hydraulic fluid. The hydraulic fluid that passes through the check valve 27 flows into the rod-side passage 20 and is then supplied to the rod chamber 11A. That is, a portion of the hydraulic fluid discharged from the cap chamber 11B and the hydraulic fluid discharged from the hydraulic pump 17 are supplied to the rod chamber 11A. On the other hand, in the pump-assisted state, if the meter-in pressure is higher than the meter-out pressure, the check valve 27 blocks the flow of hydraulic fluid. That is, the hydraulic fluid that flows out from the regeneration port P8 does not flow into the rod-side passage 20. Therefore, the hydraulic fluid discharged from the cap chamber 11B flows from the first cap port P6 into the meter-out opening 33, then flows out from the drain port P9 and is discharged into the tank 18.

[0051] When the determination unit 38 receives an operation signal from the work machine operation device 7, if it determines that the estimated external force Fe calculated by the estimation unit 37 is equal to or greater than the first threshold Ha, it determines the state of the hydraulic system 16 to the pump support state. If the estimated external force Fe is equal to or greater than the first threshold Ha, the control unit 40 controls at least one of the rod-side control valve 21 and the hydraulic pump 17 so that the state of the hydraulic system 16 becomes the pump support state.

[0052] In other words, when the controller 6 determines that the estimated external force Fe is greater than or equal to the first threshold Ha, it controls the hydraulic pump 17, the rod-side control valve 21, and the cap-side control valve 23 so that both the hydraulic fluid discharged from the cap chamber 11B and passing through the regeneration channel 26, and the hydraulic fluid discharged from the hydraulic pump 17 are supplied to the rod chamber 11A.

[0053] <Normal state> In the normal state, the hydraulic fluid is supplied from the hydraulic pump 17 to the rod chamber 11A at the same flow rate as the target supply flow rate determined based on the operation signal from the work equipment operating device 7. In the normal state, the arrangement of the spools of the rod-side control valve 21 and the cap-side control valve 23 is the same as in Figure 5.

[0054] Under normal conditions, if the meter-out pressure is higher than the meter-in pressure, the check valve 27 does not block the flow of hydraulic fluid. The hydraulic fluid that passes through the check valve 27 flows into the rod-side passage 20 and is then supplied to the rod chamber 11A. That is, a portion of the hydraulic fluid discharged from the cap chamber 11B and the hydraulic fluid discharged from the hydraulic pump 17 are supplied to the rod chamber 11A. On the other hand, under normal conditions, if the meter-in pressure is higher than the meter-out pressure, the check valve 27 blocks the flow of hydraulic fluid. That is, the hydraulic fluid that flows out from the regeneration port P8 does not flow into the rod-side passage 20. Therefore, the hydraulic fluid discharged from the cap chamber 11B flows from the first cap port P6 into the meter-out opening 33, then flows out from the drain port P9 and is discharged into the tank 18.

[0055] When the determination unit 38 receives an operation signal from the work machine operation device 7, if it determines that the estimated external force Fe calculated by the estimation unit 37 is greater than or equal to the second threshold Hb, which is greater than the first threshold Ha, it determines the state of the hydraulic system 16 to be the normal state. If the estimated external force Fe is greater than or equal to the second threshold Hb, the control unit 40 controls the hydraulic pump 17, the rod-side control valve 21, and the cap-side control valve 23 so that the state of the hydraulic system 16 is the normal state. If the estimated external force Fe is greater than or equal to the second threshold Hb, the control unit 40 controls at least one of the rod-side control valve 21 and the hydraulic pump 17 so that hydraulic fluid is supplied from the hydraulic pump 17 to the rod chamber 11A. The second threshold Hb is a predetermined value and is stored in the storage unit 41.

[0056] In other words, if the controller 6 determines that the estimated external force Fe is greater than or equal to the second threshold Hb, which is greater than the first threshold Ha, it controls the hydraulic pump 17, the rod-side control valve 21, and the cap-side control valve 23 so that the same flow rate of hydraulic fluid as the target supply flow rate determined based on the operation signal from the work equipment operating device 7 is supplied from the hydraulic pump 17 to the rod chamber 11A.

[0057] <Control for each state> The control unit 40 controls at least one of the rod-side control valve 21 and the hydraulic pump 17 so as not to supply hydraulic fluid from the hydraulic pump 17 to the rod chamber 11A when the estimated external force Fe is less than the first threshold Ha.

[0058] When the estimated external force Fe is greater than or equal to the second threshold Hb, the control unit 40 calculates the target supply flow rate of hydraulic fluid supplied from the hydraulic pump 17 to the rod chamber 11A based on the operation signal from the work machine operating device 7, and controls at least one of the rod-side control valve 21 and the hydraulic pump 17 based on the target supply flow rate.

[0059] The control unit 40 calculates a regeneration factor Rf, which is the ratio of hydraulic fluid supplied to the rod chamber 11A through the regeneration channel 26, according to the calculated estimated external force Fe, when the estimated external force Fe is greater than or equal to a first threshold Ha and less than a second threshold Hb. The controller 6 calculates a target supply flow rate of hydraulic fluid supplied to the rod chamber 11A from the hydraulic pump 17 based on the operation signal from the work equipment operating device 7 and the regeneration factor, and controls at least one of the rod-side control valve 21 and the hydraulic pump 17 based on the target supply flow rate. In the pump boost state, the controller 6 controls at least one of the rod-side control valve 21 and the hydraulic pump 17 so that both the hydraulic fluid that has passed through the regeneration channel 26 and the hydraulic fluid discharged from the hydraulic pump 17 are supplied to the rod chamber 11A.

[0060] When the supply flow rate from the hydraulic pump 17 to the rod chamber 11A increases, the control unit 40 limits the rate of change of the supply flow rate over time so as not to exceed a specified first rate of change. When the supply flow rate of the hydraulic fluid supplied from the hydraulic pump 17 to the rod chamber 11A decreases, the control unit 40 limits the rate of change of the supply flow rate over time so as not to fall below a specified second rate of change. The first and second rates of change may be predetermined values. The first and second rates of change may be stored in advance in the storage unit 41.

[0061] In other words, when the supply flow rate from the hydraulic pump 17 to the rod chamber 11A increases, the control unit 40 controls at least one of the rod-side control valve 21 and the hydraulic pump 17 so that the supply flow rate does not increase rapidly. When the supply flow rate from the hydraulic pump 17 to the rod chamber 11A decreases, the control unit 40 controls at least one of the rod-side control valve 21 and the hydraulic pump 17 so that the supply flow rate does not decrease rapidly.

[0062] The operator can change the first rate of change and the second rate of change by operating the input device of the monitor 50. The calculation unit 39 can change the first rate of change and the second rate of change, respectively, based on the input data from the monitor 50 for changing the first rate of change and the second rate of change.

[0063] <Calculation of the regeneration factor> Figure 6 is a diagram illustrating the method for calculating the regeneration factor according to the embodiment. The determination unit 38 calculates the regeneration factor Rf. The regeneration factor Rf refers to the ratio of the hydraulic fluid that flows into the rod chamber 11A to the hydraulic fluid that passes through the regeneration channel 26 and is supplied to the rod chamber 11A. In the embodiment, a regeneration factor Rf of 1 means that all of the hydraulic fluid flowing into the rod chamber 11A is supplied from the regeneration channel 26. A regeneration factor Rf of 1 means that the state of the hydraulic system 16 is a regeneration state. In the embodiment, a regeneration factor Rf of 0 means that all of the hydraulic fluid flowing into the rod chamber 11A is supplied from the hydraulic pump 17. A regeneration factor Rf of 0 means that the state of the hydraulic system 16 is a normal state. In the embodiment, a regeneration factor Rf greater than 0 and less than 1 means that the hydraulic fluid supplied to the rod chamber 11A is supplied from the regeneration channel 26 and also from the hydraulic pump 17. A regeneration factor Rf greater than 0 and less than 1 means that the state of the hydraulic system 16 is a pump support state.

[0064] If the estimated external force Fe is less than the first threshold Ha, the regeneration factor Rf is 1, and the hydraulic system 16 is in a regenerated state. If the estimated external force Fe is greater than or equal to the first threshold Ha and less than the second threshold Hb, the regeneration factor Rf is greater than 0 and less than 1, and the hydraulic system 16 is in a pump support state. If the estimated external force Fe is greater than or equal to the second threshold Hb, the regeneration factor Rf is 0, and the hydraulic system 16 is in a normal state.

[0065] As shown in Figure 6, the determination unit 38 calculates the regeneration factor Rf based on the operation signal from the work machine operating device 7, the estimated external force Fe calculated by the estimation unit 37, the first correlation data, and the second correlation data.

[0066] The determination unit 38 receives an operation signal from the work implement operating device 7 and determines whether the work implement operating device 7 is being operated repeatedly based on the operation signal (step SA1).

[0067] A repetitive operation refers to an operation in which the hydraulic cylinder 5 is operated so that it repeatedly contracts and extends. Another example of a repetitive operation is an operation in which the work implement 4 is operated so that it vibrates up and down. Examples of repetitive operations include boom compaction, in which the bucket 10 is continuously pressed against the construction surface to compact it, and bucket shaking.

[0068] The determination unit 38 calculates the repetition factor Fr by band-pass filtering the operation signal from the work implement operating device 7 and then low-pass filtering the absolute value of the band-pass filtered operation signal. The repetition factor Fr is a value that indicates the degree of periodic fluctuation of the operation signal. If the repetition factor Fr is greater than a predetermined value, it is determined that the work implement operating device 7 is being operated repeatedly.

[0069] Next, the determination unit 38 sets the parameters of the second correlation data based on the repeated operation factor Fr (step SA2).

[0070] The parameters of the second correlation data set in step SA2 include at least one of the first threshold Ha and the second threshold Hb in step SA2 in Figure 6. For example, when the repetition factor Fr is greater than a predetermined value, i.e., when repeated operation is performed, if the first threshold Ha and the second threshold Hb are set to low values ​​so that the estimated external force Fe is always greater than or equal to the second threshold Hb, the regeneration factor Rf calculated in step SA2 is fixed to 0. When the regeneration factor Rf is fixed to 0, the state of the hydraulic system 16 is fixed to the normal state. That is, when repeated operation is performed, the same flow rate of hydraulic fluid as the target supply flow rate determined based on the operation signal is supplied from the hydraulic pump 17 to the rod chamber 11A. This improves operability, for example, during boom compaction operation.

[0071] The memory unit 41 pre-stores first correlation data showing the relationship between the repeated operation factor Fr and the parameters. The first correlation data includes table data for converting the repeated operation factor Fr into parameters. The determination unit 38 sets the parameters based on the first correlation data.

[0072] In this embodiment, the parameters include a parameter V1 (first parameter) used during normal operation and a parameter V2 (second parameter) used during repeated operation. Each of the parameter V1 for normal operation and the parameter V2 for repeated operation can be changed based on input data (first parameter and second parameter) from the monitor 50 (input device). That is, the first correlation data can be changed based on input data generated by the operation of the monitor 50. For example, the rate of change of the parameter with respect to the repeat operation factor Fr (the slope of the graph of the first correlation data shown in Figure 6) is changed based on the input data from the monitor 50.

[0073] The memory unit 41 pre-stores second correlation data showing the relationship between the estimated external force Fe and the regeneration factor Rf. The second correlation data includes table data for converting the estimated external force Fe to the regeneration factor Rf. The determination unit 38 calculates the regeneration factor Rf based on the second correlation data (step SA3).

[0074] The second correlation data can be modified based on input data (first and second parameters) from the monitor 50 (input device). For example, based on the input data from the monitor 50, the rate of change of the regeneration factor Rf with respect to the estimated external force Fe (the slope of the graph of the second correlation data shown in Figure 6) is changed. When the second correlation data is changed, the storage unit 41 stores the modified second correlation data.

[0075] (If the estimated external force cannot be calculated) As shown in equation (1), the meter-in pressure Pi detected by the rod-side pressure sensor 28 and the meter-out pressure Po detected by the cap-side pressure sensor 29 are used in calculating the estimated external force Fd. If at least one of the rod-side pressure sensor 28 and the cap-side pressure sensor 29 is abnormal, the estimation unit 37 may not be able to obtain the meter-in pressure Pi and the meter-out pressure Po. That is, if at least one of the rod-side pressure sensor 28 and the cap-side pressure sensor 29 is abnormal, the estimation unit 37 may not be able to calculate the estimated external force Fd. If it is determined that the estimated external force Fd cannot be calculated, the determination unit 38 determines the regeneration factor Rf to be 0. That is, if it is determined that the estimated external force Fd cannot be calculated, the control unit 40 controls at least one of the rod-side control valve 21 and the hydraulic pump 17 so that the same flow rate of hydraulic fluid as the target supply flow rate determined based on the operation signal generated from the work machine operating device 7 is supplied from the hydraulic pump 17 to the rod chamber 11A. If it is determined that the estimated external force Fd cannot be calculated, the state of the hydraulic system 16 is fixed to the normal state.

[0076] [Calculation processing by the calculation unit] Figure 7 is a diagram illustrating the method for calculating the target meter-out opening area according to the embodiment. Figure 8 is a diagram illustrating the method for calculating the target pump flow rate Qp and the target meter-in opening area according to the embodiment.

[0077] <Calculation of target meter-out opening area> The memory unit 41 has pre-stored third correlation data for calculating the target cylinder speed. The third correlation data shows the relationship between the operation signal indicating the amount of operation of the work equipment operating device 7 and the target cylinder speed, which is the target value of the boom cylinder 11.

[0078] The third correlation data represents the correlation between the operation signal indicating the amount of operation of the work machine operating device 7 and the cylinder speed of the boom cylinder 11 when the boom 8 is lowering and only the hydraulic fluid discharged from the cap chamber 11B and passed through the regeneration channel 26 is supplied to the rod chamber 11A. The third correlation data includes table data for converting the operation signal into a target cylinder speed. The storage unit 41 stores multiple sets of third correlation data for the work machine 1 according to its operating mode. The operating mode is set so that, for example, the responsiveness to the operation signal, the amount of work performed by the work machine 1, and the fuel efficiency can be changed according to the application.

[0079] As shown in Figure 7, the calculation unit 39 selects a third correlation data depending on the operating mode. Based on the selected third correlation data, the calculation unit 39 calculates the target cylinder speed from the operation signal (step SB1).

[0080] Next, the calculation unit 39 calculates the static target actuator meter-out flow rate Qsao, which is the target flow rate of the hydraulic fluid discharged from the cap chamber 11B, based on the target cylinder speed calculated in step SB1 and the cap-side pressure-receiving area Ac (step SB2).

[0081] Furthermore, the calculation unit 39 calculates the static target valve meter-out flow rate Qsbo, which is the target flow rate of the hydraulic fluid passing through the meter-out opening 33 of the cap-side control valve 23, based on the static target actuator meter-out flow rate Qsao calculated in step SB2 (step SB3). In this embodiment, the static target valve meter-out flow rate Qsbo is the same value as the static target actuator meter-out flow rate Qsao. That is, [Qsbo = Qsao].

[0082] As shown in the graph of step SB6 in Figure 7, the static target valve meter-out flow rate Qsbo includes a rise period in which it rises from zero at a rate of increase corresponding to the manipulated amount of the operating signal.

[0083] The calculation unit 39 selects a rate of change according to the operating mode (step SB4). The rate of change is pre-stored in the storage unit 41.

[0084] The calculation unit 39 receives an operation signal from the work implement operating device 7 and determines, based on the operation signal, whether or not the work implement operating device 7 is being operated repeatedly.

[0085] The calculation unit 39 calculates the repetition factor Fr by band-pass filtering the operation signal from the work implement operating device 7 and then low-pass filtering the absolute value of the band-pass filtered operation signal. The repetition factor Fr is a value that indicates the degree of periodic fluctuation of the operation signal. If the repetition factor Fr is greater than a predetermined value, it is determined that the work implement operating device 7 is being operated repeatedly.

[0086] Next, the calculation unit 39 adjusts the rate of change calculated in step SB4 based on the repeated operation factor Fr (step SB5).

[0087] The calculation unit 39 calculates the target meter-out flow rate Qo (step SB6) by changing the rate of increase during the rise period and the rate of decrease during the fall period of the static target valve meter-out flow rate Qsbo based on the rate of change adjusted in step SB5. For example, the adjusted rate of change is smaller than the rate of increase during the rise period of the static target valve meter-out flow rate Qsbo. That is, the calculation unit 39 calculates the target meter-out flow rate Qo such that it is smaller than the rate of change during the rise period of the static target valve meter-out flow rate Qsbo.

[0088] The calculation unit 39 calculates the target meter-out opening area based on the target meter-out flow rate Qo calculated in step SB6 (step SB7). In this embodiment, the calculation unit 39 calculates the target meter-out opening area from the target meter-out flow rate Qo calculated in step SB6, based on a fifth correlation data showing the relationship between the target meter-out flow rate Qo and the target meter-out opening area. The fifth correlation data is, for example, data obtained from the correlation between the opening area of ​​the meter-out opening 31, which has been measured in advance, and the flow rate of the hydraulic fluid discharged from the cap chamber 11B, when the boom 8 is lowering and only the hydraulic fluid that has been discharged from the cap chamber 11B of the boom cylinder 11 and passed through the regeneration channel 26 is supplied to the rod chamber 11A. The fifth correlation data is stored in advance in the storage unit 41.

[0089] The calculation unit 39 may calculate the differential pressure across the target meter-out opening based on the operation signal from the work machine operating device 7, and then calculate the target meter-out opening area based on the calculated differential pressure across the target meter-out opening, the target meter-out flow rate Qo calculated in step SB6, and a calculation formula (for example, Bernoulli's equation).

[0090] Furthermore, the calculation unit 39 may calculate the target meter-out opening area based on the sixth correlation data, which shows the relationship between the operation signal and the target meter-out opening area and is pre-stored in the storage unit 41, and the operation signal from the work equipment operating device 7. The calculation unit 39 may also change the relationship between the operation signal from the work equipment operating device 7 and the meter-out opening area based on the input data received from the input device of the monitor 50.

[0091] <Target pump flow rate and target meter-in opening area calculation target flow rate> The memory unit 41 pre-stores fourth correlation data for calculating the target cylinder speed. The fourth correlation data shows the relationship between the operation signal indicating the amount of operation of the work implement operating device 7 and the target cylinder speed, which is the target value of the boom cylinder 11. The fourth correlation data represents the correlation between the operation signal indicating the amount of operation of the work implement operating device 7 and the cylinder speed of the boom cylinder 11 when the boom 8 is lowered and only the hydraulic fluid discharged from the hydraulic pump 17 is supplied to the rod chamber 11A. The fourth correlation data includes table data for converting the operation signal to the target cylinder speed. Similar to the third correlation data, the memory unit 41 stores multiple sets of fourth correlation data according to the operating mode of the work machine 1.

[0092] As shown in Figure 8, the calculation unit 39 selects a fourth correlation data depending on the operating mode. Based on the selected fourth correlation data, the calculation unit 39 calculates the target cylinder speed from the operation signal (step SC1).

[0093] Next, the calculation unit 39 calculates the static target actuator meter-in flow rate Qsai, which is the target flow rate of the hydraulic fluid supplied to the rod chamber 11A, based on the target cylinder speed calculated in step SC1 and the rod-side pressure-receiving area Ar (step SC2).

[0094] Furthermore, the calculation unit 39 calculates the static target valve meter-in flow rate Qsbi, which is the target flow rate of the hydraulic fluid flowing into the meter-in opening 30 of the rod-side control valve 21, based on the static target actuator meter-in flow rate Qsai and the regeneration factor Rf calculated in step SC2 (step SC3). In this embodiment, the static target valve meter-in flow rate Qsbi is calculated based on the following equation (2).

[0095] Qsbi = (1 - Rf) × Qsai …(2)

[0096] As shown in the graphs for steps SC6 and SC9 in Figure 8, the static target valve meter-in flow rate Qsbi includes a rise period in which it rises from zero at a rate of increase corresponding to the manipulated amount of the operating signal.

[0097] The calculation unit 39 selects a rate of change according to the operating mode (step SC4). The rate of change is pre-stored in the storage unit 41.

[0098] The calculation unit 39 receives an operation signal from the work implement operating device 7 and determines, based on the operation signal, whether or not the work implement operating device 7 is being operated repeatedly.

[0099] The calculation unit 39 calculates the repetition factor Fr by band-pass filtering the operation signal from the work implement operating device 7 and then low-pass filtering the absolute value of the band-pass filtered operation signal. The repetition factor Fr is a value that indicates the degree of periodic fluctuation of the operation signal. If the repetition factor Fr is greater than a predetermined value, it is determined that the work implement operating device 7 is being operated repeatedly.

[0100] Next, the calculation unit 39 adjusts the rate of change calculated in step SC4 based on the repeated operation factor Fr (step SC5).

[0101] The calculation unit 39 calculates the target pump flow rate Qp (step SC6) by changing the rate of increase during the rise period and the rate of decrease during the fall period of the static target valve meter-in flow rate Qsbi based on the rate of change adjusted in step SC5. For example, the adjusted rate of change is smaller than the rate of increase during the rise period of the static target valve meter-in flow rate Qsbi. That is, the calculation unit 39 calculates the target pump flow rate Qp such that it is smaller than the rate of change during the rise period of the static target valve meter-in flow rate Qsbi.

[0102] Furthermore, the calculation unit 39 selects a rate of change according to the operating mode (step SC7). The rate of change is pre-stored in the storage unit 41.

[0103] The calculation unit 39 receives an operation signal from the work implement operating device 7 and determines, based on the operation signal, whether or not the work implement operating device 7 is being operated repeatedly.

[0104] The calculation unit 39 calculates the repetition factor Fr by band-pass filtering the operation signal from the work implement operating device 7 and then low-pass filtering the absolute value of the band-pass filtered operation signal. The repetition factor Fr is a value that indicates the degree of periodic fluctuation of the operation signal. If the repetition factor Fr is greater than a predetermined value, it is determined that the work implement operating device 7 is being operated repeatedly.

[0105] Next, the calculation unit 39 adjusts the rate of change calculated in step SC7 based on the repeated operation factor Fr (step SC8).

[0106] The calculation unit 39 calculates the target meter-in flow rate Qi by changing the rate of increase during the rise period and the rate of decrease during the fall period of the static target valve meter-in flow rate Qsbi based on the rate of change adjusted in step SC8 (step SC9). For example, the adjusted rate of change is smaller than the rate of increase during the rise period of the static target valve meter-in flow rate Qsbi. That is, the calculation unit 39 calculates the target meter-in flow rate Qi such that it is smaller than the rate of change during the rise period of the static target valve meter-in flow rate Qsbi. When the target meter-in flow rate Qi (target supply flow rate) increases, the calculation unit 39 limits the rate of change of the target meter-in flow rate Qi over time so as not to exceed the rate of change during the rise period (first rate of change) of the static target valve meter-in flow rate Qsbi. Also, the adjusted rate of change is smaller than the rate of decrease during the fall period of the static target valve meter-in flow rate Qsbi. That is, the calculation unit 39 calculates the target meter-in flow rate Qi such that it is smaller than the rate of change during the fall period of the static target valve meter-in flow rate Qsbi. The calculation unit 39 limits the rate of change of the target meter-in flow rate Qi over time to not fall below the rate of change (second rate of change) during the decline of the static target valve meter-in flow rate Qsbi when the target meter-in flow rate (target supply flow rate) decreases.

[0107] The calculation unit 39 calculates the target meter-in opening area based on the target meter-in flow rate Qi calculated in step SC9 (step SC10). In this embodiment, the calculation unit 39 calculates the target meter-in opening area based on the differential pressure before and after the meter-in opening, the target meter-in flow rate Qi, and a calculation formula. The calculation formula is, for example, Bernoulli's equation. The calculation unit 39 may also calculate the target meter-in opening area by multiplying the target meter-in flow rate Qi by a predetermined positive proportionality constant. Furthermore, if a seventh correlation data showing the relationship between the target meter-in flow rate Qi and the target meter-in opening area is predetermined, the calculation unit 39 may calculate the target meter-in opening area by inputting the target meter-in flow rate Qi into the seventh correlation data.

[0108] [Monitor] Figures 9 and 10 show examples of the monitor 50 according to the embodiment. The operator can change the setting value of the work machine 1 by operating the monitor 50, which is an input device. The input / output interface 36 receives input data generated when the monitor 50 is operated. As shown in Figures 7 and 8, the calculation unit 39 can change the setting value of the work machine 1 based on the input data (mode setting) generated when the monitor 50 is operated. By operating the monitor 50, the operator can, for example, change the first parameter V1 shown in Figure 6 or change the second parameter V2. By operating the monitor 50, the operator can, for example, change the third correlation data shown in step SB1 in Figure 7 or change the rate of change shown in step SB6. By operating the monitor 50, the operator can, for example, change the fourth correlation data shown in step SC1 in Figure 8, change the rate of change shown in step SC6, or change the rate of change shown in step SC9. In addition, the calculation unit 39 can change the first threshold Ha and the second threshold Hb based on the input data generated when the monitor 50 is operated.

[0109] Figure 9 shows the display screen of the monitor 50 for changing the rate of change shown in step SB6 of Figure 7 and steps SC6 and SC9 of Figure 8. As described above, the rate of change shown in step SB6 of Figure 7 represents the rate of change over time of the target meter-out flow rate Qo. That is, the rate of change shown in step SB6 of Figure 7 affects the rate of change over time of the target meter-out opening. The rate of change shown in step SB6 of Figure 7 affects the responsiveness of the cylinder speed to the amount of operation of the work implement operating device 7 in the regeneration state. Also, as described above, the rates of change shown in steps SC6 and SC9 of Figure 8 represent the rate of change over time of the flow rate of the hydraulic fluid supplied from the hydraulic pump 17 to the rod chamber 11A. The rates of change shown in steps SC6 and SC9 of Figure 8 affect the responsiveness of the cylinder speed to the amount of operation of the work implement operating device 7 in the pump support state. When the operator wants to change the responsiveness of the cylinder speed, they move the slider 51 displayed on the display screen of the monitor 50 left or right. Moving the slider 51 to the right increases the responsiveness of the cylinder speed to the amount of operation of the work implement operating device 7. As the slider 51 is moved to the left, the responsiveness of the cylinder speed to the amount of operation of the work implement operating device 7 decreases. The calculation unit 39 can change each of the change rates shown in step SB6 in Figure 7, and steps SC6 and SC9 in Figure 8, based on the input data from the monitor 50.

[0110] The calculation unit 39 can change the relationship between the operation signal and the target cylinder speed of the boom cylinder 11 for both the regeneration state, where the estimated external force Fe is lower than the first threshold Ha, and the normal state, where the estimated external force Fe is equal to or greater than the second threshold Hb.

[0111] Figure 10 shows the display screen of the monitor 50 for changing the maximum cylinder speed of the hydraulic cylinder 5. The calculation unit 39 can change the maximum cylinder speed of at least the boom cylinder 11 based on the input data from the monitor 50. The calculation unit 39 can change the maximum target cylinder speed in step SB1 of Figure 7 by changing the third correlation data shown in step SB1 of Figure 7 based on the input data from the monitor 50. As the maximum target cylinder speed in step SB1 of Figure 7 is changed, the maximum value of the target meter-out flow rate Qo is changed, which in turn changes the maximum meter-out opening area of ​​the cap-side control valve 23, and thus changes the maximum cylinder speed of the boom cylinder 11 in the regeneration state. In addition, the calculation unit 39 can change the maximum target cylinder speed in step SC1 of Figure 8 by changing the fourth correlation data shown in step SC1 of Figure 8 based on the input data from the monitor 50. As the maximum value of the target cylinder speed in step SC1 in Figure 8 is changed, the maximum values ​​of the target meter-in flow rate Qi and the target pump flow rate Qp are changed, which in turn changes the maximum value of the meter-in opening area of ​​the rod-side control valve 21 and the discharge flow rate of the hydraulic pump 17, thereby changing the maximum value of the boom cylinder 11 in its normal state.

[0112] In the example shown in Figure 10, the monitor 50 displays a slider 52 for changing the "all axes" setting, which indicates the maximum cylinder speed of all hydraulic cylinders 5 that operate the work machine 4. The monitor 50 also displays sliders 52 for changing the maximum cylinder speed of the boom cylinder 11 when raising the boom 8 (boom raising), and sliders 52 for changing the maximum cylinder speed of the boom cylinder 11 when lowering the boom 8 (boom lowering). The monitor 50 also displays sliders 52 for changing the maximum cylinder speed of the arm cylinder 12 when excavating the arm 9, and sliders 52 for changing the maximum cylinder speed of the arm cylinder 12 when dumping the arm 9 (arm dump).

[0113] The monitor 50 also displays sliders 52 for changing the maximum cylinder speed of the bucket cylinder 13 when the bucket 10 is performing an excavation operation (bucket excavation), and sliders 52 for changing the maximum cylinder speed of the bucket cylinder 13 when the bucket 10 is performing a dumping operation (bucket dumping). The monitor 50 also displays a slider 52 for changing the maximum rotation speed of the rotation motor when the slewing body 3 is performing a rotation operation.

[0114] The calculation unit 39 can change the maximum cylinder speed of the boom cylinder 11 when lowering the boom 8, based on the input data from the monitor 50. The calculation unit 39 can change the maximum cylinder speed of the boom cylinder 11 for both the regeneration state, where the estimated external force Fe is lower than the first threshold Ha, and the pump support state, where the estimated external force Fe is greater than or equal to the first threshold Ha.

[0115] [Control Method] Figure 11 is a timing chart showing the control method of the hydraulic system 16 according to the embodiment.

[0116] In Figure 11, time point t1 is a time point after time point 0, time point t2 is a time point after time point t1, time point t3 is a time point after time point t2, time point t4 is a time point after time point t3, time point t5 is a time point after time point t4, and time point t6 is a time point after time point t5.

[0117] In Figure 11, line La indicates the amount of operation of the work machine operating device 7. Line Lb indicates the target actuator meter-out flow rate corresponding to the amount of operation. Line Lc indicates the static target valve meter-out flow rate Qsbo. Line Ld indicates the target valve meter-out opening. Line Le indicates the meter-out pressure Po detected by the cap-side pressure sensor 29. Line Lf indicates the meter-in pressure Pi detected by the rod-side pressure sensor 28. Line Lg indicates the estimated external force Fe calculated by the estimation unit 37. Line Lh indicates the regeneration factor Rf, which is the ratio of the hydraulic fluid flowing into the rod chamber 11A to the hydraulic fluid that passes through the regeneration channel 26 and is supplied to the rod chamber 11A. A regeneration factor Rf of 1 means that all of the hydraulic fluid flowing into the rod chamber 11A is supplied from the regeneration channel 26. A regeneration factor Rf of 0 means that all of the hydraulic fluid flowing into the rod chamber 11A is supplied from the hydraulic pump 17. Line Li indicates the target actuator meter-in flow rate corresponding to the amount of operation of the work equipment operating device 7. Line Lj indicates the static target valve meter-in flow rate Qsbi. Line Lk indicates the target pump flow rate Qp, which is the target flow rate of the hydraulic fluid discharged from the hydraulic pump 17. Line Lm indicates the actual flow rate of the hydraulic fluid flowing into the boom cylinder 11 and is proportional to the cylinder speed.

[0118] As shown in Figure 11, the operation of the work equipment operating device 7 is started so that the boom cylinder 11 retracts at time t1. The estimation unit 37 calculates the estimated external force Fe. Between time t1 and time t2, the estimated external force Fe is lower than the first threshold Ha, so the hydraulic system 16 is in a regenerated state.

[0119] When the estimated external force Fe reaches the first threshold Ha at time t2, the hydraulic system 16 changes from a regeneration state to a pump support state. When the estimated external force Fe becomes greater than or equal to the first threshold Ha, the control unit 40 controls at least one of the rod-side control valve 21 and the hydraulic pump 17 such that the flow rate of hydraulic fluid supplied from the hydraulic pump 17 to the rod chamber 11A increases at a specified rate as the estimated external force Fe increases.

[0120] When the estimated external force Fe reaches the second threshold Hb at time t3, the hydraulic system 16 changes from the pump assist state to the normal state.

[0121] The calculation unit 39 can change the rate of change of the hydraulic fluid flow rate supplied from the hydraulic pump 17 to the rod chamber 11A based on the input data from the monitor 50, for example, between time point t2 and time point t4. For example, the calculation unit 39 can adjust the rate of change of the flow rate so that the rate of increase of the hydraulic fluid flow rate supplied from the hydraulic pump 17 to the rod chamber 11A is large between time point t2 and time point t4. As a result, the flow rate of hydraulic fluid supplied from the hydraulic pump 17 to the rod chamber 11A increases in addition to the hydraulic fluid supplied from the regeneration channel 26 to the rod chamber 11A, so the cylinder speed of the boom cylinder 11 increases. That is, the acceleration when the boom cylinder 11 retracts can be increased.

[0122] Furthermore, the calculation unit 39 can change the rate of change of the hydraulic fluid flow rate supplied from the hydraulic pump 17 to the rod chamber 11A, not only between time points t2 and t4, but also when the hydraulic system 16 changes from a normal state to a regenerated state after time point t4, based on the input data from the monitor 50. For example, the calculation unit 39 can adjust the rate of change of the flow rate so that the rate of decrease of the hydraulic fluid flow rate supplied from the hydraulic pump 17 to the rod chamber 11A becomes larger in the time after time point t4 (the absolute value of the rate of decrease becomes smaller, i.e., the gradient becomes gentler). As a result, the flow rate of hydraulic fluid supplied from the hydraulic pump 17 to the rod chamber 11A decreases gradually, suppressing abrupt changes in the cylinder speed of the boom cylinder 11 in the pump support state. In other words, the speed when the boom cylinder 11 retracts can be increased seamlessly.

[0123] Furthermore, the calculation unit 39 can change the first threshold Ha and the second threshold Hb based on the input data from the monitor 50. For example, by setting the first threshold Ha to a low value, hydraulic fluid is supplied to the rod chamber 11A from the hydraulic pump 17 earlier while hydraulic fluid is being supplied to the rod chamber 11A from the regeneration channel 26, so the cylinder speed increases earlier when the boom cylinder 11 retracts. In other words, after the operation of the work machine operating device 7 is started, the transition from the regeneration state to the pump support state is made earlier, improving the responsiveness of the boom cylinder 11. On the other hand, by setting the first threshold Ha to a high value, the regeneration state is maintained for a longer period of time, meaning that the timing of the start of the supply of hydraulic fluid from the hydraulic pump 17 to the rod chamber 11A is delayed, improving the fuel efficiency of the work machine 1. By setting the second threshold Hb to a low value, the transition from the pump support state to the normal state is made earlier, improving the responsiveness of the boom cylinder 11. On the other hand, by setting the second threshold Hb to a high value, the pump support state is maintained for a longer period of time, improving the fuel efficiency of the work machine 1.

[0124] Figure 12 is a flowchart showing the control method for the hydraulic system 16 according to the embodiment.

[0125] The estimation unit 37 starts calculating the estimated external force Fe (step S1). When the system receives an operation signal from the work equipment operating device 7 to lower the boom 8, the determination unit 38 determines the state of the hydraulic system 16 to the regenerated state. The control unit 40 controls at least one of the rod-side control valve 21 and the hydraulic pump 17 so that the hydraulic system 16 is in the regenerated state.

[0126] When the operation of the work machine operating device 7 is started, the estimated external force Fe changes. The determination unit 38 determines whether the estimated external force Fe is equal to or greater than the first threshold Ha (step S2).

[0127] In step S2, if it is determined that the estimated external force Fe is not greater than or equal to the first threshold Ha (step S2: No), the regeneration state of the hydraulic system 16 is maintained (step S3).

[0128] In step S2, if it is determined that the estimated external force Fe is greater than or equal to the first threshold Ha (step S2: Yes), the determination unit 38 decides to transition the hydraulic system 16 from the regeneration state to the pump support state. The control unit 40 controls at least one of the rod-side control valve 21 and the hydraulic pump 17 so that the hydraulic system 16 enters the pump support state (step S4).

[0129] The determination unit 38 determines whether the estimated external force Fe is equal to or greater than the second threshold Hb (step S5).

[0130] In step S5, if it is determined that the estimated external force Fe is not greater than or equal to the second threshold Hb (step S5: No), the pump support state of the hydraulic system 16 is maintained.

[0131] In step S5, if it is determined that the estimated external force Fe is greater than or equal to the second threshold Hb (step S5: Yes), the determination unit 38 decides to transition the hydraulic system 16 from the pump support state to the normal state (step S6). The control unit 40 controls at least one of the rod-side control valve 21 and the hydraulic pump 17 so that the hydraulic system 16 returns to the normal state (step S7).

[0132] [effect] As described above, in this embodiment, the controller 6 calculates an estimated external force Fe acting on the rod 113 with the direction in which the boom cylinder 11 extends being the positive direction. When it receives an operation signal to operate the work machine 4 so that the boom cylinder 11 retracts, it controls at least one of the rod-side control valve 21 and the hydraulic pump 17 based on the calculated estimated external force Fe to control the flow rate of hydraulic fluid supplied to the rod chamber 11A. If the calculated estimated external force Fe is smaller than the first threshold Ha, the controller 6 controls the hydraulic system 16 to enter a regeneration state. In this embodiment, if the calculated estimated external force Fe is smaller than the first threshold, the controller 6 controls at least one of the rod-side control valve 21 and the hydraulic pump 17 so that hydraulic fluid is not supplied from the hydraulic pump 17 to the rod chamber 11A. As a result, only the hydraulic fluid that has been discharged from the cap chamber 11B and passed through the regeneration passage 26 is supplied to the rod chamber 11A, improving the energy efficiency of the work machine 1 and improving the operability of the work machine 1. Furthermore, based on the operation signal indicating the amount of operation of the work implement operating device 7, the opening area of ​​the meter-out opening of the cap-side control valve 23 is controlled, thereby controlling the pressure and flow rate of the hydraulic fluid discharged from the cap chamber 11B. This allows the amount of operation of the work implement operating device 7 to be adjusted in accordance with the operation signal. This enables operability that matches the operator's intentions.

[0133] When the calculated estimated external force Fe exceeds the first threshold Ha, the controller 6 transitions the hydraulic system 16 from the regeneration state to the pump support state. In the pump support state, both the hydraulic fluid that has passed through the regeneration passage 26 and the hydraulic fluid discharged from the hydraulic pump 17 are supplied to the rod chamber 11A. Furthermore, the flow rate of the hydraulic fluid supplied from the hydraulic pump 17 to the rod chamber 11A increases or decreases according to the estimated external force Fe and the rate of change set by the operator, thereby suppressing abrupt changes in the cylinder speed of the boom cylinder 11 in the pump support state. As a result, the speed at which the boom cylinder 11 retracts can be changed seamlessly, improving the operability of the work machine 1.

[0134] If the calculated estimated external force Fe exceeds the second threshold Hb, the controller 6 transitions the hydraulic system 16 from the pump support state to the normal state. In the normal state, only the hydraulic fluid discharged from the hydraulic pump 17 is supplied to the rod chamber 11A. Furthermore, since the hydraulic fluid is supplied from the hydraulic pump 17 to the rod chamber 11A at the same flow rate as the target supply flow rate determined based on the operation signal from the work equipment operating device 7, the amount of operation of the work equipment operating device 7 can be adjusted in accordance with the operation signal. This enables operability that matches the operator's intentions.

[0135] In this embodiment, the maximum cylinder speed or cylinder acceleration of the boom cylinder 11 can be changed based on input data from the monitor 50. The operator can operate the monitor 50 to improve the operating speed and responsiveness of the boom cylinder 11, or to improve the fuel efficiency of the work machine 1. This allows the operator to change the characteristics of the work machine 1 to prioritize energy efficiency or operability according to their preference.

[0136] [Other embodiments] The estimation unit 37 in the above-described embodiment calculates the estimated external force Fe based on the meter-in pressure Pi detected by the rod-side pressure sensor 28 and the meter-out pressure Po detected by the cap-side pressure sensor 29, but is not limited to this. For example, in the working machine 1 according to another embodiment, a strain gauge may be attached to the connection between the boom 8 and the slewing body 3, and the estimation unit 37 may calculate the estimated external force Fe based on the measured value of the strain gauge.

[0137] The controller 6 according to the above embodiment may consist of a single controller, or the configuration of controller 6 may be divided into multiple controllers, and the multiple controllers may function by cooperating with each other. For example, some of the controllers constituting the input / output interface 36 may be mounted on the work machine 1, while the other controllers constituting the processor 34 and storage device 35 may be provided outside the work machine 1. For example, if the work machine 1 according to another embodiment is remotely operated, the components other than the control unit 40 may be provided in the remote controller.

[0138] In other embodiments, the work machine 1 may be controlled by a remote control system located at a remote location, and the input / output interface 36 may receive operation signals from the remote control system. In this case, the controller 6 may calculate the regeneration factor Rf, the target meter-out opening area, the target meter-in opening area, and the target pump flow rate Qp based on the operation signals received from the remote control system. The control unit 40 may control the rod-side control valve 21, the cap-side control valve 23, and the hydraulic pump 17 based on the operation signals received from the remote control system.

[0139] In other embodiments, the work machine 1 may be operated autonomously. For example, the work machine 1 may be equipped with a measuring device for receiving measurement data regarding the position, orientation, and surrounding terrain of the work machine 1, and the control unit 40 may generate operation signals to operate the work machine 4 based on the measurement data and pre-stored design data.

[0140] The work machine 1 according to other embodiments is not limited to a hydraulic excavator, but may be other work machines having work equipment such as a wheel loader. [Explanation of Symbols]

[0141] 1...Work machine, 2...Traction unit, 2A...Track, 3...Slewing unit, 4...Work machine, 5...Hydraulic cylinder, 6...Controller, 7...Work machine operating device, 8...Boom, 9...Arm, 10...Bucket, 11...Boom cylinder, 11A...Rod chamber, 11B...Cap chamber, 12...Arm cylinder, 13...Bucket cylinder, 14...Control system, 15...Power source, 16...Hydraulic system, 17...Hydraulic pump, 18...Tank, 19...Pump passage, 20...Rod side passage (meter-in passage), 21...Rod side control valve (meter-in control valve), 22...Cap side passage (meter-out passage), 23...Cap side control valve (meter-out control valve), 25...Drain passage, 26...Regeneration passage, 27...Check valve, 28...Rod side pressure sensor S, 29...Cap side pressure sensor, 30...Meter-in opening, 31...Meter-out opening, 32...Meter-in opening, 33...Meter-out opening, 34...Processor, 35...Storage device, 36...Input / output interface, 37...Estimation unit, 38...Determination unit, 39...Calculation unit, 40...Control unit, 41...Storage unit, 50...Monitor, 51...Slider, 52...Slider, 70...Solenoid proportional valve, 71...Pilot hydraulic pump, 111...Cylinder tube, 112...Piston, 113...Rod, P1...Pump port, P2...First rod port, P3...Second rod port, P4...Drain port, P5...Pump port, P6...First cap port, P7...Second cap port, P8...Regeneration port, P9...Drain port.

Claims

1. A work machine equipped with a work implement, A hydraulic pump that discharges hydraulic fluid, A hydraulic cylinder for operating the aforementioned work machine, A meter-in passage connecting the hydraulic pump and the rod chamber of the hydraulic cylinder, A meter-out passage connecting the cap chamber and tank of the hydraulic cylinder, A meter-in control valve controls the flow rate of hydraulic fluid supplied from the hydraulic pump to the rod chamber of the hydraulic cylinder, A meter-out control valve controls the flow rate of hydraulic fluid discharged from the cap chamber of the hydraulic cylinder to the tank, A regeneration channel connecting the meter-out flow path between the meter-out control valve and the tank, and the meter-in flow path between the meter-in control valve and the rod chamber, Equipped with a controller, The aforementioned controller, The external force acting on the hydraulic cylinder is calculated, When an operation signal is received to operate the work machine so that the hydraulic cylinder retracts, at least one of the meter-in control valve and the hydraulic pump is controlled based on the calculated external force. Agricultural machinery.

2. A first pressure sensor for detecting the pressure in the rod chamber, It includes a second pressure sensor for detecting the pressure in the cap chamber, The aforementioned controller, The external force is calculated based on the pressure detected by the first pressure sensor, the pressure detected by the second pressure sensor, the pressure-receiving area of ​​the piston facing the rod chamber, and the pressure-receiving area of ​​the piston facing the cap chamber. The work machine according to claim 1.

3. The aforementioned controller, The external force is calculated with the direction in which the hydraulic cylinder extends as the positive direction. When the external force is less than a first threshold, the meter-in control valve and the hydraulic pump are controlled so as not to supply the hydraulic fluid from the hydraulic pump to the rod chamber. The work machine according to claim 1.

4. It is equipped with an input device configured to be operable by an operator, The aforementioned controller, Based on the input data received from the input device, the first threshold is changed. The work machine according to claim 3.

5. The aforementioned controller, Based on the aforementioned operation signal, the meter-out control valve is controlled. The work machine according to claim 1.

6. It is equipped with an input device configured to be operable by an operator, The aforementioned controller, Based on the input data received from the input device, the relationship between the operation signal and the opening area of ​​the meter-out control valve is changed. The working machine according to claim 5.

7. The aforementioned controller, The external force is calculated with the direction in which the hydraulic cylinder extends as the positive direction. If the external force is greater than or equal to the second threshold, the target supply flow rate of the hydraulic fluid supplied from the hydraulic pump to the rod chamber is calculated based on the operation signal. Based on the target supply flow rate, control at least one of the meter-in control valve and the hydraulic pump. The work machine according to claim 1.

8. It is equipped with an input device configured to be operable by an operator, The aforementioned controller, Based on the input data received from the input device, the second threshold is changed. The work machine according to claim 7.

9. It is equipped with an input device configured to be operable by an operator, The aforementioned controller, Based on the input data received from the input device, the relationship between the operation signal and the target supply flow rate is changed. The work machine according to claim 7.

10. The aforementioned controller, The external force is calculated with the direction in which the hydraulic cylinder extends as the positive direction. If the external force is greater than or equal to a first threshold and less than a second threshold, the ratio of the hydraulic fluid supplied to the rod chamber through the regeneration channel is calculated according to the calculated external force. Based on the aforementioned operation signal and the aforementioned ratio, the target supply flow rate of the hydraulic fluid supplied from the hydraulic pump to the rod chamber is calculated. Based on the target supply flow rate, control at least one of the meter-in control valve and the hydraulic pump. The work machine according to claim 1.

11. The aforementioned controller, The meter-in control valve and the hydraulic pump are controlled so that both the hydraulic fluid that has passed through the regeneration channel and the hydraulic fluid discharged from the hydraulic pump are supplied to the rod chamber. The work machine according to claim 10.

12. The aforementioned controller, When the target supply flow rate increases, the rate of change of the target supply flow rate over time is limited so as not to exceed a specified first rate of change. If the target supply flow rate decreases, the rate of change of the target supply flow rate over time shall be limited so as not to fall below a specified second rate of change. The work machine according to claim 10.

13. It is equipped with an input device configured to be operable by an operator, The aforementioned controller, Based on the input data received from the input device, the first rate of change and the second rate of change are changed. The working machine according to claim 12.

14. The aforementioned controller, When an operation signal is received to operate the hydraulic cylinder so that it repeatedly contracts and extends, The first threshold, the second threshold, the first rate of change, the second rate of change, and the relationship between the operation signal and the target supply flow rate are changed. The working machine according to claim 12.

15. The aforementioned controller, If it is determined that the external force cannot be calculated, the target supply flow rate of the hydraulic fluid supplied from the hydraulic pump to the rod chamber is calculated based on the operation signal, and at least one of the meter-in control valve and the hydraulic pump is controlled based on the target supply flow rate. The work machine according to claim 1.

16. Work equipment and A hydraulic pump that discharges hydraulic fluid, A hydraulic cylinder for operating the aforementioned work machine, A meter-in passage connecting the hydraulic pump and the rod chamber of the hydraulic cylinder, A meter-out passage connecting the cap chamber and tank of the hydraulic cylinder, A meter-in control valve controls the flow rate of hydraulic fluid supplied from the hydraulic pump to the rod chamber of the hydraulic cylinder, A meter-out control valve controls the flow rate of hydraulic fluid discharged from the cap chamber of the hydraulic cylinder to the tank, A regeneration channel connecting the meter-out flow path between the meter-out control valve and the tank, and the meter-in flow path between the meter-in control valve and the rod chamber, A method for controlling a work machine comprising a controller, The aforementioned controller, The external force acting on the hydraulic cylinder is calculated, When an operation signal is received to operate the work machine so that the hydraulic cylinder retracts, at least one of the meter-in control valve and the hydraulic pump is controlled based on the calculated external force. method.

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