Method for controlling work machine, program for controlling work machine, system for controlling work machine, and work machine

Abstract

To provide a method for controlling work machine, a program for controlling work machine, a system for controlling work machine, and a work machine which exhibit high operability while mitigating shocks generated at the stroke end of a hydraulic cylinder during an operation of the work machine.SOLUTION: This method for controlling the work machine executes, in a one-direction operation in which a stroke of a hydraulic cylinder changes to one side, first control for setting an opening amount of a spool of a direction switching valve of the hydraulic cylinder to an area set in accordance with an operation amount of a lever operation until position information of the stroke reaches a first position, executes second control for reducing the opening amount by a prescribed method until the position information goes beyond the first position to reach a second position before a stroke end, and executes the first control until the position information goes beyond the second position to reach the stroke end.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a control method for a work machine, a control program for a work machine, a control system for a work machine, and a work machine. [Background technology]

[0002] As a related technique, a hydraulic excavator is known that controls the opening area of ​​a supply passage of a control valve for supplying hydraulic oil to a hydraulic cylinder so as to be smaller as the piston of the hydraulic cylinder that drives an attachment approaches the stroke end (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-169796 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a work machine including a hydraulic excavator according to the related art, when the operating lever is fully tilted to perform a dumping operation to extend the arm portion of the work machine having an attachment at the tip forward, the opening area of ​​the supply passage of the control valve becomes smaller as the piston of the hydraulic cylinder for the arm approaches the stroke end, and the shock caused by the dumping operation of the arm is reduced. On the other hand, there are work machines that have an operating characteristic in which the amount of operation of the operating lever is increased according to the load on the work machine. In such a work machine, depending on the load on the work machine, the hydraulic cylinder for the arm may not reach the stroke end position, and the arm may not be extended to the maximum extension position. A similar problem may also occur with the hydraulic cylinder for the boom.

[0005] Furthermore, in recent years, as fuel economy in work machines has progressed and the opening area of ​​the supply passage of the control valve has been reduced, the flow rate of hydraulic oil required by the hydraulic cylinder has decreased, and some work machines therefore implement control to reduce the flow rate of the pump. In these work machines, the above-mentioned problem can occur more noticeably.

[0006] The present invention has been made in consideration of the problems with the conventional technology described above, and an object of the present invention is to provide a control method for a work machine, a control program for a work machine, a control system for a work machine, and a work machine which provide good operability while mitigating impacts at the stroke ends of hydraulic cylinders that occur while the work machine is in operation. [Means for solving the problem]

[0007] A control method for a work machine according to one aspect of the present invention is a control method for a work machine that changes the stroke of a hydraulic cylinder by controlling an opening amount of a spool of a directional control valve through which hydraulic oil discharged from a hydraulic pump flows, the control method comprising: detecting position information related to the change in stroke of the hydraulic cylinder; executing a first control in a one-way operation in which the stroke of the hydraulic cylinder changes to one side, setting the opening amount to an area set in accordance with an amount of lever operation until the position information reaches a first position; if the one-way operation is greater than a specified amount of operation, executing a second control in which the opening amount is reduced in a predetermined manner until the position information passes beyond the first position and reaches the second position just before the stroke end; and executing the first control in the one-way operation until the position information passes beyond the second position and reaches the stroke end.

[0008] A work machine control program according to one aspect of the present invention causes one or more arithmetic devices to execute the work machine control method.

[0009] A work machine control system according to one embodiment of the present invention is a work machine control system including a control unit that changes the stroke of a hydraulic cylinder by controlling the opening amount of a spool of a directional control valve through which hydraulic oil discharged from a hydraulic pump flows, and a sensor that detects position information related to the change in the stroke of the hydraulic cylinder, wherein the control unit executes a first control to set the opening amount to an area set in accordance with the amount of lever operation until the position information reaches a first position, and if the one-way operation is greater than a specified amount of operation, executes a second control to reduce the opening amount in a predetermined manner until the position information passes beyond the first position and reaches the second position just before the stroke end, and executes the first control until the position information passes beyond the second position and reaches the stroke end, in the one-way operation.

[0010] A work machine according to one aspect of the present invention includes a work machine control system and a work implement operated by the hydraulic cylinder.

[0011] A control method for a work machine according to one embodiment of the present invention is a control method for a work machine that changes the stroke of a hydraulic cylinder, the control method for a work machine including: detecting position information related to the change in the stroke of the hydraulic cylinder; in a one-way operation in which the stroke of the hydraulic cylinder changes to one side, executing a first control that sets a stroke speed to a set value in accordance with the amount of operation of an operating lever until the position information reaches a first position; in the one-way operation, executing a second control that reduces the stroke speed in a predetermined manner until the position information passes beyond the first position and reaches the second position just before the stroke end; and in the one-way operation, executing the first control until the position information passes beyond the second position and reaches the stroke end. Effect of the Invention

[0012] According to the present invention, it is possible to provide a control method for a work machine, a control program for a work machine, a control system for a work machine, and a construction machine which provide good operability while mitigating the impact at the stroke end of a hydraulic cylinder that occurs during operation of the work machine. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a left side view of a hydraulic excavator according to a first embodiment of the present invention. [Diagram 2] 1 is a schematic diagram of a control system for a hydraulic excavator according to a first embodiment of the present invention. [Diagram 3] 4 is an example of a first control map of the hydraulic excavator according to the first embodiment of the present invention. [Figure 4] 4 is an example of a second control map of the hydraulic excavator according to the first embodiment of the present invention. [Diagram 5] 5 is another example of the second control map of the hydraulic excavator according to the first embodiment of the present invention. [Figure 6] 5 is an example of a third control map of the hydraulic excavator according to the first embodiment of the present invention. [Figure 7] 3 is an example of a set pressure map for the hydraulic excavator according to the first embodiment of the present invention. [Figure 8] 4 is a graph showing the relationship between the operation amount and the hydraulic pump flow rate of the hydraulic excavator according to the first embodiment of the present invention. [Figure 9] FIG. 1 is a flowchart of a control flow of a control device for a hydraulic excavator according to a first embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] A first embodiment of the present invention will be described in detail below with reference to the accompanying drawings, taking a hydraulic excavator 100 as a representative example of a work machine according to the present invention. Note that the direction in which the work machine 400 is attached to the upper rotating body 300 is the front, and the opposite direction is the rear.

[0015] As shown in FIG. 1, the hydraulic excavator 100 is configured to include a self-propelled lower traveling body 200, an upper rotating body 300 rotatably supported on the lower traveling body 200, and a work machine 400 supported in front of the upper rotating body 300 so as to be freely rotatable up and down, and further includes a control system 500 as shown in FIG. 3.

[0016] The lower running body 200 has a center frame (not shown) and side frames 210 that are paired symmetrically with the center frame and extend in the fore-and-aft direction, and drive wheels 211 driven by a traveling motor 213 are mounted at the rear ends of the left and right side frames 210, and a number of idler wheels 212 are arranged facing forward, and tracks 214 are wound around the drive wheels 212 and the idler wheels 213.

[0017] The upper rotating body 300 is arranged from the front to the rear end of the aircraft and is composed of a driver's section 310 which has a boarding gate on one side of the front of the aircraft, a machinery room 320 which is formed from the other side of the aircraft to the rear of the aircraft and is configured below the driver's section 310, and a swing post 330 which is supported on a protruding part at the front end of the aircraft so as to be freely rotatable left and right, and which supports a work machine 400 so as to be freely rotatable up and down.

[0018] The work machine 400 comprises a boom 410 supported on a swing post 330 so as to be rotatable up and down, an arm 420 attached to the tip of the boom 410 so as to be rotatable up and down, a bucket 430 attached to the tip of the arm 420 so as to be rotatable, and a swing cylinder (not shown) for moving the swing post 330 is disposed on the right side of the frame of the upper rotating body 300. A potentiometer 610 for measuring the rotation angle of the boom 410 is attached to the left side of the base end of the boom 410, and a potentiometer 620 for measuring the rotation angle of the arm 410 is attached to the left side of the tip of the boom 410.

[0019] The boom cylinder 440 is installed in front of and below the boom 410. When hydraulic oil is supplied from the control valve to the rod-side oil chamber of the boom cylinder 440, the boom cylinder 440 contracts, so the boom 410 descends. If hydraulic oil continues to be supplied, the boom cylinder 440 contracts to the stroke end in the direction in which the rod is contracted. If hydraulic oil is supplied from the control valve to the bottom-side oil chamber of the boom cylinder 440, the boom cylinder 440 extends, so the boom 410 rises. If hydraulic oil continues to be supplied, the boom cylinder 440 extends to the stroke end in the direction in which the rod is extended. Here, the potentiometer 610 measures the rotation angle of the boom 410, but it can be said that it measures the rod position of the boom cylinder 440 corresponding to the rotation angle of the boom 410. In other words, the potentiometer 610 detects position information related to the change in the stroke of the boom cylinder 440.

[0020] The arm cylinder 450 is installed above the boom 410. When hydraulic oil is supplied from the control valve to the rod side oil chamber of the arm cylinder 450, the arm cylinder 450 contracts, causing the arm 420 to perform a dumping motion in which it rotates forward. If hydraulic oil continues to be supplied, the arm cylinder 450 is contracted to the stroke end in the direction in which the rod is contracted. If hydraulic oil is supplied from the control valve to the bottom side oil chamber of the arm cylinder 450, the arm cylinder 450 extends, causing the arm 420 to perform a crowding motion in which it rotates backward. If hydraulic oil continues to be supplied, the arm cylinder 450 extends to the stroke end in the direction in which the rod is extended. Here, the potentiometer 620 measures the rotation angle of the arm 420, but it can be said that it measures the rod position of the arm cylinder 450 corresponding to the rotation angle of the arm 420. In other words, the potentiometer 620 detects position information related to the change in the stroke of the arm cylinder 450.

[0021] The bucket cylinder 470 is disposed in front (above) of the arm 420, and is connected to the arm 420 and the bucket 430 via the bucket link 460. When hydraulic oil is supplied from the control valve to the rod side oil chamber of the bucket cylinder 470, the bucket cylinder 470 contracts, causing the bucket 430 to perform a dumping motion by rotating forward, and as hydraulic oil continues to be supplied, the bucket cylinder 470 is contracted to the stroke end in the direction in which the rod is contracted. When hydraulic oil is supplied from the control valve to the bottom side oil chamber of the bucket cylinder 470, the bucket cylinder 470 extends, causing the bucket 430 to perform a crowding motion by rotating backward, and as hydraulic oil continues to be supplied, the bucket cylinder 470 extends to the stroke end in the direction in which the rod is extended.

[0022] The engine room 320 is equipped with multiple devices, such as an engine (not shown), a variable displacement pump 511 that is driven by the engine and pumps hydraulic oil to multiple actuators that move the hydraulic excavator 100, such as the boom cylinder 440 and the arm cylinder 450, a control valve 514 which is an assembly of directional control valves that control the corresponding actuators, and a pilot pump 512 which generates a control signal pressure (pilot pressure) input to the control valve 514 and a primary pressure of the pilot pressure input to a regulator 511a which controls the flow rate of the variable displacement pump 511.

[0023] The driver's area 310 is formed by a seat 311, a floor material 313 extending forward from the lower front surface of a seat mount 312 below the seat 311, an operating device 314, and a display device 315 arranged to the right front of the seat 311.

[0024] The operating device 314 is arranged in a row on the left and right in front of the seat 311 and includes left and right travel levers 314a protruding from the floor material 313, left and right operating levers 314b1, 314b2 erected in console boxes arranged on the left and right of the seat 311, and a cut-off lever 314c extending forward from the left console box and disabling all actuators of the hydraulic excavator 100 by rotating the console rearward together with the console.

[0025] Next, the control system 500 of the hydraulic excavator 100 will be described with reference to FIG.

[0026] The control system 500 is comprised of at least a hydraulic circuit 510, a control device 520, an operating device 314, and potentiometers 610 and 620.

[0027] The operating device 314 outputs the operating direction and operating amount of each operating lever as an operating signal to the control device 520, and the control device 520 outputs an electrical signal to the solenoid proportional valve 517, and the solenoid proportional valve 517 outputs pilot pressure to the input port of the control valve 514 to operate each actuator.

[0028] In hydraulic circuit 510, high-pressure hydraulic oil piping extending from variable displacement pump 511 is represented by a solid line, and low-pressure hydraulic oil (pilot pressure) piping extending from pilot pump 512 is represented by a dotted line.

[0029] The hydraulic circuit 510 includes a center bypass flow path 513 extending from a variable displacement pump 511 that controls the discharge flow rate by inputting the pilot pressure reduced by an electromagnetic proportional valve 518 to a regulator 511a, and a control valve 514 that is composed of a directional control valve that controls each actuator connected to each oil passage extending from the center bypass flow path 513. The hydraulic circuit 510 is a so-called closed center circuit in which no flow path is formed connecting the center bypass flow path 513 to the tank 515 regardless of the sliding position of the spool of the directional control valve, but is not limited to this.

[0030] The control valve 514 comprises a directional control valve 514a which controls the boom cylinder 440, a directional control valve 514b which controls the arm cylinder 450, and a plurality of other directional control valves which respectively control a plurality of other actuators, for example, the left and right traveling motors 211, the bucket cylinder 470, a swing motor (not shown), etc., and descriptions of the plurality of other actuators and the plurality of other directional control valves are omitted in the hydraulic circuit 510. Also, pilot pressure is input to a pilot pressure input port of the directional control valve constituting the control valve 514 from an electromagnetic proportional valve 517 in accordance with conditions set according to the amount of operation of the operating device 314.

[0031] Pilot pressure output from solenoid proportional valves 517a1, 514a2 according to set conditions depending on the direction and amount of operation (tilt amount) of right operating lever 314b2 is input to pilot pressure input ports 514a1, 514a2 of directional control valve 514a, causing the spool of directional control valve 514a to slide and oil according to the opening amount of the corresponding spool flow to the rod side oil chamber or bottom side oil chamber of boom cylinder 440, changing the stroke of boom cylinder 440, and the speed of the changing stroke corresponds to the opening amount of the spool.

[0032] Pilot pressure output from solenoid proportional valve 517b1 according to preset conditions that correspond to the direction of operation and amount of operation (tilt amount) of left operating lever 314b1 is input to pilot pressure input port 514b1 of directional control valve 514b, causing the spool of directional control valve 514b to slide, and oil according to the opening amount of the corresponding spool flows to the rod side oil chamber or bottom side oil chamber of arm cylinder 450, changing the stroke of arm cylinder 450, and the speed of the changing stroke corresponds to the opening amount of the spool.

[0033] The above-mentioned set conditions are set by a map of the opening amount of the spool of the directional control valve stored in a storage unit 522 of the control device 520, which will be described later, and a plurality of maps are switched as necessary.

[0034] The pressure in the hydraulic circuit 510 is detected by a pressure sensor 519 , and the detection result is transmitted to a control device 520 .

[0035] According to the detection result of the pressure sensor 519, the control device 520 controls the discharge flow rate of the variable displacement pump 511 so as not to exceed a preset pressure that is arbitrarily set, in order to prevent damage to the hydraulic equipment.

[0036] The control device 520 is an ECU (electronic control unit) and is composed of at least an input buffer that converts the signal level of a digital input signal, an AD converter that performs digital conversion of an analog input signal, a calculation unit 521 consisting of a microcomputer that calculates control amounts from various input signals, an output driver that converts the output signal of the microcomputer into a drive signal form that drives an actuator, a communication driver, a communication receiver, etc.

[0037] Signals input to control device 520 are represented by dashed dotted lines with arrows pointing to control device 520, and signals output from control device 520 are represented by dashed dotted lines with arrows pointing to the equipment to which the signal is input.

[0038] The calculation unit 521 includes a storage unit 522 , a spool opening amount determination unit 523 , and a pump flow rate calculation unit 524 .

[0039] The memory unit 522 has the above-mentioned spool opening map and a set pressure map for determining the pump flow rate.

[0040] The spool opening map includes a first control map that determines the opening of the spool of the directional control valve of the corresponding operating device 314 in accordance with the amount of operation of the operating device 314, a second control map that determines the opening of the spool in response to a change in extension of the stroke of the hydraulic cylinder, and a third control map that determines the opening of the spool in response to a change in contraction of the stroke of the hydraulic cylinder. In other words, the second and third control maps are control maps related to an operation (extension or contraction) that changes the stroke of the hydraulic cylinder to one side.

[0041] FIG. 3 is an example of the first control map, which shows the opening amount of the spool of the directional control valve 514 in response to the inclination (operation amount) of the operating lever 314b2 tilted forward. A spool opening amount determination unit 523 calculates a control value for the solenoid proportional valve 517b2 in accordance with the first control map, and the control device 520 executes the first control for the hydraulic excavator 100, which sends a control command to the solenoid proportional valve 517b2.

[0042] By executing the first control, the opening amount of the spool increases according to the amount of operation, the flow rate of hydraulic oil flowing to the bottom side oil chamber of the arm cylinder 450 increases, and the extension speed (stroke speed) of the arm cylinder 450 increases.

[0043] 4 is an example of the second control map, which shows the stroke position of the arm cylinder 450 and the opening amount of the spool of the directional control valve 514 when the operating lever 314b2 is tilted forward (operation amount 100%). In this embodiment, the stroke position uses the value detected by the potentiometer 620, and the spool opening amount decision unit 523 calculates the control value for the solenoid proportional valve 517b2 in accordance with the second control map.

[0044] In FIG. 4, from stroke positions 0 (the position where the arm cylinder 450 is most retracted) to S1, the opening amount (100%) of the spool of the directional control valve 514 is determined by the tilt amount (operation amount 100%) of the operating lever 314b2, regardless of the stroke position.

[0045] FIG. 5 is another example of the second control map, which shows the stroke position of the arm cylinder 450 and the opening amount of the spool of the directional control valve 514 when the operating lever 314b2 is tilted 90% forward (operation amount 90%). From a stroke position of 0 (position where the arm cylinder 450 is most retracted) to S1, the opening amount of the spool of the directional control valve 514 (90%) is determined by the tilt amount of the operating lever 314b2 (operation amount 90%) regardless of the stroke position.

[0046] That is, in the second control map, when the stroke position is 0 to S1, the spool opening determination unit 523 calculates a control value for the electromagnetic proportional valve 517b2 in accordance with the first control map, and the control device 520 executes the first control on the hydraulic excavator 100. That is, the stroke speed of the arm cylinder 450 is controlled by the first control.

[0047] In FIG. 4, when the stroke position exceeds S1, the opening amount of the spool of the directional control valve 514 drops from 100% (90% in FIG. 3) to 80%, and the opening amount is maintained at 80% until S2, and when S2 is exceeded, the opening amount of the spool of the directional control valve 514 drops from 80% to 20%, and the opening amount is maintained at 20% until S21, which is just before the stroke end SE (the position where the arm cylinder 450 is most extended).

[0048] That is, until the stroke position exceeds S1 and reaches almost the stroke end SE, the spool opening determination unit 523 calculates a control value for the solenoid proportional valve 517b2 in accordance with the second control map that reduces the opening of the spool (in this embodiment, the opening is reduced stepwise), and the control device 520 executes the second control on the hydraulic excavator 100. That is, the stroke speed of the arm cylinder 450 is controlled by the second control.

[0049] Furthermore, when S21 is exceeded, the spool opening amount corresponding to the operation amount increases to 100% in FIG. 4, and to 90% in FIG. 5, and is maintained until the stroke end SE.

[0050] That is, in the second control map, until the stroke position exceeds S21 and reaches the stroke end SE, the spool opening determination unit 523 calculates a control value for the solenoid proportional valve 517b2 in accordance with the first control map, and the control device 520 executes the first control on the hydraulic excavator 100. That is, the stroke speed of the arm cylinder 450 is controlled by the first control.

[0051] 6 is an example of the third map, which shows the stroke position of the arm cylinder 450 and the opening amount of the spool of the directional control valve 514 when the operating lever 314b2 is tilted rearward (operation amount 100%). In this embodiment, the stroke position uses the value detected by the potentiometer 620, and the spool opening amount decision unit 523 calculates the control value for the solenoid proportional valve 517b1 according to the second control map.

[0052] In FIG. 6, from stroke positions 0 (the position where the arm cylinder 450 is fully extended) to S1, the opening amount (100%) of the spool of the directional control valve 514 is determined by the tilt amount (operation amount 100%) of the operating lever 314b2, regardless of the stroke position.

[0053] That is, in the third control map, when the stroke position is 0 to s1, the spool opening determination unit 523 calculates a control value for the electromagnetic proportional valve 517b1 in accordance with the first control map, and the control device 520 executes the first control on the hydraulic excavator 100. That is, the stroke speed of the arm cylinder 450 is controlled by the first control.

[0054] In FIG. 6, when the stroke position exceeds s1, the opening amount of the spool of the directional control valve 514 drops from 100% to 80%, and maintains the opening amount at 80% until s2, and when s2 is exceeded, the opening amount of the spool of the directional control valve 514 drops from 80% to 20%, and maintains the opening amount at 20% until s21, which is just before the stroke end se (the position where the arm cylinder 450 is most retracted).

[0055] That is, until the stroke position exceeds s1 and reaches almost the stroke end se, the spool opening determination unit 523 calculates a control value for the solenoid proportional valve 517b2 in accordance with the third control map that reduces the opening of the spool (in this embodiment, the opening is reduced stepwise), and the control device 520 executes the second control on the hydraulic excavator 100. That is, the stroke speed of the arm cylinder 450 is controlled by the second control.

[0056] Furthermore, when s21 is exceeded, in FIG. 6, the spool opening amount corresponding to the operation amount increases to 100% and is maintained until the stroke end se.

[0057] That is, in the third control map, until the stroke position exceeds s21 and reaches the stroke end se, the spool opening determination unit 523 calculates a control value for the electromagnetic proportional valve 517b1 in accordance with the first control map, and the control device 520 executes the first control on the hydraulic excavator 100. That is, the stroke speed of the arm cylinder 450 is controlled by the first control.

[0058] In summary, the control according to the present invention, whether it is the second control map (when hydraulic oil is supplied to the bottom side oil chamber of the hydraulic cylinder) or the third control map (when hydraulic oil is supplied to the rod side oil chamber of the hydraulic cylinder), when the stroke of the hydraulic cylinder changes toward the stroke end, supplies hydraulic oil to the hydraulic cylinder by the first control, which increases the flow rate of hydraulic oil supplied to the hydraulic cylinder to a flow rate corresponding to the operation amount (sets the stroke speed according to the operation amount) until a position a certain distance away from the stroke end, thereby enabling the work equipment to move in accordance with the operation amount, and once that position is exceeded, the second control reduces the flow rate of hydraulic oil supplied to the hydraulic cylinder (reduces the stroke speed) to mitigate the impact on the work equipment associated with the stroke end, and by executing the first control, which increases the flow rate of hydraulic oil supplied to the hydraulic cylinder just before the stroke end to a flow rate corresponding to the operation amount (sets the stroke speed according to the operation amount), the work equipment can be reliably made to move as intended by the operator. Furthermore, when the operating amount is small, the impact on the work machine associated with the stroke end is small, so the control of the present invention is executed when the magnitude of the operating amount is exceeded. For example, in this embodiment, the control is executed when the operating amount is greater than 80%, but the value of the operating amount can be determined arbitrarily.

[0059] Next, FIG. 7 is an example of a set pressure map, in which the maximum set pressure of the hydraulic pump 511 is determined based on the amount of operation of the operation device 314.

[0060] A pump flow rate calculation unit 524 calculates the flow rate of the hydraulic pump 511 so that the pressure detected by the pressure sensor 519 does not exceed the set pressure map, and outputs a control command for the solenoid proportional valve 518 from the control device 520 to control the flow rate of the hydraulic pump 511. As a result, as shown in Fig. 8, the flow rate of the hydraulic pump 511 is controlled in accordance with the operation amount.

[0061] The above-described control of the hydraulic pump not only improves fuel efficiency but also enables the amount of operation of the operating lever to be increased in accordance with the load on the work equipment, thereby improving operability; in particular, executing control according to the second control map or the third control map on the shovel 100 that performs such control can contribute to achieving both good operability and the mitigation of shocks at the stroke end of the hydraulic cylinder that occur during work.

[0062] The control flow will be described with reference to Fig. 9. Fig. 9 is a flowchart relating to a control method.

[0063] The left operating lever 314b is tilted forward to perform the dump operation of the arm 420 (S1).

[0064] If the amount of operation of the left operating lever 314b1 is greater than 80% (S2: YES), the control device 520 supplies hydraulic oil to the bottom-side oil chamber of the arm cylinder 450 based on the third control map, and dumps the arm 420 to the maximum extension position (S3).

[0065] When the amount of operation of the left operating lever 314b1 is 80% or less (S3: NO), the control device 520 supplies hydraulic oil to the bottom side oil chamber of the arm cylinder 450 based on the first control map, and dumps the arm 420 to the maximum extension position (S4).

[0066] The flowchart shown in FIG. 9 is merely an example, and processes may be added or omitted as appropriate, processes may be repeatedly executed, and the order of processes may be changed as appropriate.

[0067] Next, a modification of the first embodiment of the present invention will be described.

[0068] In the first embodiment, the second control reduces the spool opening amount in two stages, but it may also be reduced in two or more stages, or in one stage. Furthermore, it may be reduced linearly with respect to the stroke position.

[0069] In addition to the pump flow rate control in the first embodiment, pump flow rate control in which the pump flow rate is controlled in response to a manipulated variable, such as positive control or negative control, may be used.

[0070] In the first embodiment, a potentiometer is used as the sensor that detects position information related to changes in the stroke of the hydraulic cylinder, but it may also be a stroke sensor that directly detects the stroke of the hydraulic cylinder, or an acceleration sensor may be used to detect the attitude of the work machine.

[0071] The invention according to the embodiment of the present invention can be specified as follows.

[0072] <Appendix 1> A control method for a work machine that changes the stroke of a hydraulic cylinder by controlling an opening amount of a spool of a directional control valve through which hydraulic oil discharged from a hydraulic pump flows, the control method for a work machine comprising: detecting position information related to a change in the stroke of the hydraulic cylinder; executing a first control for setting the opening amount to an area set in accordance with an amount of lever operation until the position information reaches a first position in one-way operation, if the amount of operation is greater than a specified amount in the one-way operation, executing a second control for reducing the opening amount in a predetermined manner until the position information passes beyond the first position and reaches the second position just before the stroke end; and executing the first control until the position information passes beyond the second position and reaches the stroke end in the one-way operation.

[0073] <Appendix 2> A control method for a work machine according to appendix 1, wherein the opening amount during the first control is larger than the opening amount during the second control.

[0074] <Appendix 3> A control method for a work machine as described in appendix 1 or appendix 2, wherein the predetermined method reduces the opening amount in a stepwise manner.

[0075] <Appendix 4> A control method for a work machine as described in any one of appendices 1 to 3, in which the flow rate of the hydraulic pump is controlled in accordance with an operation amount.

[0076] <Appendix 5> A method for controlling a construction machine as described in any one of Appendices 1 to 4, in which an upper limit of a maximum set pressure of the hydraulic pump is controlled in accordance with the operation amount, and a flow rate of the hydraulic pump is controlled so that the pressure of the hydraulic pump does not exceed the maximum set pressure.

[0077] <Appendix 6> A work machine control program for causing one or more arithmetic devices to execute the work machine control method described in any one of Appendices 1 to 5.

[0078] <Appendix 7> A control system for a work machine comprising: a control unit that changes a stroke of a hydraulic cylinder by controlling an opening amount of a spool of a directional control valve through which hydraulic oil discharged from a hydraulic pump flows; and a sensor that detects position information related to a change in the stroke of the hydraulic cylinder, wherein the control unit executes a first control to set the opening amount to an area set in accordance with an amount of lever operation until the position information reaches a first position in a one-way operation in which the stroke of the hydraulic cylinder changes to one side; and, if the one-way operation is greater than a prescribed amount of operation, executes a second control to reduce the opening amount in a predetermined manner until the position information passes beyond the first position and reaches the second position just before the stroke end; and executes the first control in the one-way operation in which the position information passes beyond the second position and reaches the stroke end.

[0079] <Appendix 8> A work machine comprising the work machine control system according to appendix 7 and a work implement operated by the hydraulic cylinder.

[0080] <Appendix 9> A control method for a work machine that changes the stroke of a hydraulic cylinder, the control method comprising: detecting position information related to a change in the stroke of the hydraulic cylinder; executing a first control that sets a stroke speed to a set value according to an operation amount of an operating lever until the position information reaches a first position, in one-way operation, executing a second control that reduces the stroke speed in a predetermined manner until the position information passes beyond the first position and reaches the second position just before the stroke end, in the one-way operation; and executing the first control until the position information passes beyond the second position and reaches the stroke end, in the one-way operation.

[0081] The various configurations described in the first embodiment and the modifications thereof described above can be adopted in appropriate combination.

[0082] In the above, a hydraulic excavator has been used as an example of a work machine, but the work machine is not limited to a hydraulic excavator and may be not only a compact track loader, a wheel loader, or other construction machine, but also a tractor or other work machine. Furthermore, although an engine has been used as the prime mover in the above description, an electric motor may also be used.

[0083] Although the embodiment of the present invention has been described above, the scope of the present invention is not limited to this, and the invention can be expanded or modified without departing from the spirit of the invention. [Industrial Applicability]

[0084] The present invention relates to a work machine control method, a work machine control program, a work machine control system, and a work machine, and has industrial applicability. [Explanation of symbols]

[0085] 100 Hydraulic excavator (working machine) 450 Arm cylinder (hydraulic cylinder) 514b Directional switching valve 520 Control device (control unit) 522 Memory unit 523 Spool opening amount determination unit 620 Potentiometer (sensor)

Claims

1. A control method for a work machine that changes the stroke of a hydraulic cylinder by controlling an opening amount of a spool of a directional control valve through which hydraulic oil discharged from a hydraulic pump flows, the control method comprising: detecting position information related to a change in the stroke of the hydraulic cylinder; executing a first control in one-way operation in which the stroke of the hydraulic cylinder changes to one side, for setting the opening amount to an area set in accordance with an amount of operation of a lever until the position information reaches a first position; if the one-way operation is greater than a specified amount of operation, executing a second control in which the opening amount is reduced in a predetermined manner until the position information passes beyond the first position and reaches the second position just before the stroke end; and executing the first control in the one-way operation until the position information passes beyond the second position and reaches the stroke end.

2. 2. A method for controlling a work machine according to claim 1, wherein the amount of opening during said first control is greater than the amount of opening during said second control.

3. 3. A method according to claim 2, wherein said predetermined method reduces the opening amount in stages.

4. 4. A method for controlling a work machine according to claim 1, wherein a flow rate of the hydraulic pump is controlled in accordance with an operation amount.

5. 4. A control method for a working machine according to any one of claims 1 to 3, wherein an upper limit of a maximum set pressure of the hydraulic pump is controlled in accordance with the operation amount, and a flow rate of the hydraulic pump is controlled so that the pressure of the hydraulic pump does not exceed the maximum set pressure.

6. A construction machine control program for causing one or more arithmetic devices to execute the construction machine control method according to any one of claims 1 to 3.

7. A control system for a work machine comprising: a control unit that changes the stroke of a hydraulic cylinder by controlling an opening amount of a spool of a directional control valve through which hydraulic oil discharged from a hydraulic pump flows; and a sensor that detects position information related to the change in the stroke of the hydraulic cylinder, wherein the control unit executes a first control in one-way operation in which the stroke of the hydraulic cylinder changes to one side, to set the opening amount to an area set in accordance with an amount of lever operation until the position information reaches a first position, and if the one-way operation is greater than a specified amount of operation, executes a second control to reduce the opening amount in a predetermined manner until the position information passes beyond the first position and reaches the second position just before the stroke end, and executes the first control in the one-way operation until the position information passes beyond the second position and reaches the stroke end.

8. A work machine comprising: a control system for the work machine; and a work implement operated by the hydraulic cylinder.

9. A control method for a work machine that changes the stroke of a hydraulic cylinder, the control method comprising: detecting position information related to a change in the stroke of the hydraulic cylinder; executing a first control in one-way operation in which the stroke of the hydraulic cylinder changes to one side, which sets a stroke speed to a set value in accordance with an operation amount of an operating lever until the position information reaches a first position; executing a second control in the one-way operation in which the stroke speed is reduced in a predetermined manner until the position information passes beyond the first position and reaches a second position just before a stroke end; and executing the first control in the one-way operation in which the stroke speed is passed beyond the second position and reaches the stroke end.

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