Work machine

Abstract

To provide a work machine capable of reducing a difference in timing between an opening of a meter-out portion of a control valve and an opening of a load holding valve.SOLUTION: A work machine includes a control valve 17 that controls a flow of pressurized oil to a boom cylinder 7, a load holding valve 19 provided between a port 18A of the boom cylinder 7 and the control valve 17, solenoid valves 25A and 25B that generate pilot pressure to operate the control valve 17, a solenoid valve 27 that generates pilot pressure to operate the load holding valve 19, and a controller 21. The controller 21 performs control of the control valve 17 via the solenoid valve 25B to supply pressurized oil to a port 18B of the boom cylinder 7 and discharge pressurized oil from the port 18A, changes a control command output to the solenoid valve 27 to learn a control command when the load holding valve 19 begins to open, and corrects a control table using the learned control command.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a work machine such as a hydraulic excavator. [Background technology]

[0002] A work machine such as a hydraulic excavator is equipped with a hydraulic pump, a hydraulic actuator that drives a work device having multiple joints, and a directional control valve that controls the flow direction and flow rate of pressure oil to the hydraulic actuator. The directional control valve controls the supply and discharge direction of pressure oil, the flow rate of pressure oil supplied from the hydraulic pump to the hydraulic actuator, and the flow rate of pressure oil discharged from the hydraulic actuator to an oil tank based on commands from a controller. In addition to the directional control valve, the work machine is also equipped with various other control valves. To control the opening amount of these control valves, a control table is prepared that shows the relationship between the current value output from the controller and the opening amount of the control valve. To control the capacity of the hydraulic pump, a control table is prepared that shows the relationship between the current command value output from the controller and the pump capacity.

[0003] Here, regulators that vary the displacement of hydraulic pumps are not necessarily uniform in shape due to manufacturing variations and deterioration over time. Therefore, the relationship between the current command value and the pump displacement in the control table is not necessarily the same even for regulators with the same specifications, and deviations may occur over time. A technique for correcting the control table is known to eliminate deviations (errors) in the relationship between the current command value and the pump displacement in the control table. The controller measures the hydraulic pump's discharge pressure while changing the current command value output to the regulator, obtains calibration data consisting of combinations of the current command value and the hydraulic pump's discharge pressure, and corrects the control table based on the obtained calibration data to eliminate errors in the control table (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6966830 Summary of the Invention [Problem to be solved by the invention]

[0005] One of the control valves mentioned above is a solenoid valve that generates pilot pressure to operate a load holding valve that holds the load of a hydraulic actuator, and this solenoid valve is controlled by a controller in response to an operation command from an operating device.

[0006] When the operating device is not being operated, the controller does not operate the solenoid valve and closes the load holding valve, thereby preventing the hydraulic actuator from being driven by the weight of the working device. When the operating device is operated, the controller uses a control table that shows the relationship between operation commands and control commands to obtain a control command corresponding to the operation command and outputs the obtained control command to the solenoid valve. The solenoid valve generates pilot pressure corresponding to the control command and outputs it to the load holding valve, switching the load holding valve from a closed state to an open state. This allows the hydraulic actuator to be driven by operating the operating device.

[0007] In order to eliminate the discrepancy in the relationship between the control command (current command value) and the pilot pressure in the control table, it is conceivable to apply the technology of Patent Document 1. However, errors in the control table may be influenced not only by manufacturing variations in the solenoid valve, but also by manufacturing variations in the load holding valve (i.e., a discrepancy in the relationship between the pilot pressure of the solenoid valve and the opening amount of the load holding valve). When manufacturing variations in the load holding valve affect the errors in the control table, it is not possible to fully eliminate the discrepancy in the timing between the meter-out opening of the control valve and the opening of the load holding valve, and it is not possible to fully reduce the discrepancy in the timing between the meter-out opening of the control valve and the opening of the load holding valve.

[0008] The present invention has been made in consideration of the above circumstances, and its object is to provide a work machine that can reduce the difference in timing between the opening of the meter-out of the control valve and the opening of the load holding valve. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides a hydraulic system including a vehicle body, a working device connected to the vehicle body, at least one hydraulic actuator that drives the working device, a prime mover mounted on the vehicle body, a hydraulic pump driven by the prime mover, a control valve that controls the hydraulic pump to supply pressure oil to one of a first port and a second port of the hydraulic actuator and to discharge pressure oil from the other port, a load holding valve that is provided between the first port of the hydraulic actuator and the control valve and that can be switched between an open state and a closed state, an operating device that outputs an operation command that instructs the operation of the hydraulic actuator, a first solenoid valve that generates a pilot pressure that operates the control valve, a second solenoid valve that generates a pilot pressure that operates the load holding valve, and a control valve that controls the first solenoid valve and the second solenoid valve in response to the operation command from the operating device. and a controller that controls a solenoid valve, wherein the controller uses a control table to obtain a control command corresponding to the operation command and outputs the obtained control command to the second solenoid valve to switch the load holding valve from the closed state to the open state. In a working machine, a posture sensor is provided that detects the posture of the working device, and the controller controls the control valve via the first solenoid valve to open a meter-in side that supplies pressure oil from the hydraulic pump to the second port of the hydraulic actuator and open a meter-out side that discharges pressure oil from the first port, while changing the control command output to the second solenoid valve, learns the control command when the posture of the working device detected by the posture sensor begins to change as a control command when the load holding valve begins to open, and corrects the control table using the learned control command. [Effects of the Invention]

[0010] According to the present invention, it is possible to reduce the difference in timing between the opening of the meter-out valve of the control valve and the opening of the load holding valve. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a side view showing the structure of a work machine according to an embodiment of the present invention. [Figure 2A]FIG. 2 is a diagram illustrating a part of the configuration of a drive device according to an embodiment of the present invention. [Figure 2B] 2B is a diagram showing a part of the configuration of a drive device according to one embodiment of the present invention, together with details of the solenoid valve unit shown in FIG. 2A. FIG. [Figure 3] 4 is a flowchart showing correction control of a control table of a controller according to an embodiment of the present invention. [Figure 4] 5 is a time chart showing changes over time in a boom angle, a control command for lowering a boom, and a control command for disabling a function in one embodiment of the present invention. [Figure 5] FIG. 10 is a diagram illustrating a control table for function deactivation in one embodiment of the present invention. [Figure 6] 6 is a time chart showing a change over time in a control command for function release and an opening amount of a load holding valve in one embodiment of the present invention and a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment of the present invention will be described with reference to the drawings.

[0013] FIG. 1 is a side view showing the structure of a work machine according to this embodiment.

[0014] The work machine of this embodiment is a hydraulic excavator, and includes a travelable running body 1 and a rotating body 2 rotatably provided above the running body 1, with the running body 1 and the rotating body 2 constituting a vehicle body. The running body 1 travels by the rotation of left and right traveling motors (not shown). The rotating body 2 rotates by the rotation of a swing motor (not shown).

[0015] A working device 3 is connected to the revolving structure 2. The working device 3 includes a boom 4 connected to the revolving structure 2 so as to be rotatable in the vertical direction, an arm 5 connected to the boom 4 so as to be rotatable in the vertical direction, and a bucket 6 (work implement) connected to the arm 5 so as to be rotatable in the vertical direction. The boom 4 rotates relative to the revolving structure 2 as a result of the extension and contraction of a boom cylinder 7. The arm 5 rotates relative to the boom 4 as a result of the extension and contraction of an arm cylinder 8. The bucket 6 rotates relative to the arm 5 as a result of the extension and contraction of a bucket cylinder 9. An attitude sensor 10 is attached to the working device 3 to detect the rotation angle (boom angle) of the boom 4 relative to the revolving structure 2 as the attitude of the working device 3. The attitude sensor 10 is configured, for example, by an inertial measurement unit.

[0016] The revolving body 2 includes a cab 11 in which the operator sits, and a machinery room 12 that houses equipment (more specifically, a prime mover, hydraulic pump, control valves, etc., which will be described later). A driver's seat (not shown) in which the operator sits is provided inside the cab 11. Left and right travel operation devices (not shown) are provided in front of the driver's seat, which the driver operates in the forward and backward directions with his or her hands or feet to command the operation of the left and right travel motors, respectively.

[0017] To the right of the driver's seat is provided an operation control device 13 (see FIG. 2B described later) that the driver operates left and right by hand to command the operation of the bucket cylinder 9 and also operates back and forth by hand to command the operation of the boom cylinder 7. To the left of the driver's seat is provided an operation control device (not shown) that the driver operates left and right by hand to command the operation of the swing motor and also operates back and forth by hand to command the operation of the arm cylinder 8.

[0018] The work machine of this embodiment is equipped with a drive unit that drives multiple hydraulic actuators (more specifically, the travel motor, swing motor, boom cylinder 7, arm cylinder 8, and bucket cylinder 9 described above). Fig. 2A is a diagram showing part of the configuration of the drive unit of this embodiment, and Fig. 2B is a diagram showing part of the configuration of the drive unit of this embodiment together with details of the solenoid valve unit shown in Fig. 2A. Of the configuration related to the drive of the multiple hydraulic actuators, Figs. 2A and 2B only show the configuration related to the drive of the boom cylinder 7. Note that the configuration related to the drive of the other hydraulic actuators is substantially the same as the configuration related to the drive of the boom cylinder 7.

[0019] The drive device of this embodiment includes a prime mover 14 (more specifically, an engine or an electric motor), a hydraulic pump 15 and a pilot pump 16 driven by the prime mover 14, a control valve 17 that controls the flow (more specifically, the direction and flow rate) of pressurized oil from the hydraulic pump 15 to the boom cylinder 7, a load holding valve 19 provided between a port 18A (first port) on the bottom side of the boom cylinder 7 and the control valve 17, a solenoid valve unit 20, and a controller 21.

[0020] Load holding valve 19 is provided in the oil passage between bottom port 18A of boom cylinder 7 and control valve 17, and is composed of check valve 22 with a backflow prevention function and release valve 23 that releases the backflow prevention function of check valve 22. The backflow prevention function of check valve 22 allows the flow of pressure oil from control valve 17 to bottom port 18A of boom cylinder 7, but blocks the flow of pressure oil from bottom port 18A of boom cylinder 7 to control valve 17. Release valve 23 switches check valve 22 from a closed state to an open state in response to the pilot pressure described below, and controls the opening amount to release the backflow prevention function. In other words, it allows the flow of pressure oil from bottom port 18A of boom cylinder 7 to control valve 17.

[0021] The solenoid valve unit 20 includes a solenoid valve 25A (first solenoid valve) that uses the discharge pressure of the pilot pump 16 as its source pressure, generates a pilot pressure that operates the control valve 17, and outputs it to a pressure receiving portion 24A of the control valve 17, a solenoid valve 25B (first solenoid valve) that uses the discharge pressure of the pilot pump 16 as its source pressure, generates a pilot pressure that operates the control valve 17, and outputs it to a pressure receiving portion 24B of the control valve 17, and a solenoid valve 27 (second solenoid valve) that uses the discharge pressure of the pilot pump 16 as its source pressure, generates a pilot pressure that operates the load holding valve 19, and outputs it to the load holding valve 19 (more specifically, the pressure receiving portion 26 of the release valve 23).

[0022] Controller 21 has a processor that executes control according to a program and a memory that stores programs and data. The controller has a function of controlling solenoid valves 25A, 25B, and 27 in response to operation commands from work operation device 13. Work operation device 13 has a lever that can be operated by the driver, and a potentiometer that outputs a first operation command corresponding to the amount of operation of the rear side of the lever or a second operation command corresponding to the amount of operation of the front side of the lever.

[0023] When a first operation command is input from work operation device 13, controller 21 uses a boom-raising control table showing the relationship between the first operation command (current value) and a boom-raising control command (current value) to obtain a boom-raising control command corresponding to the first operation command, and outputs the obtained boom-raising control command to solenoid valve 25A. Solenoid valve 25A generates a pilot pressure corresponding to the boom-raising control command and outputs it to pressure-receiving section 24A of control valve 17. As a result, control valve 17 is switched to the left-side switching position in the figure, controlling the opening amount of the meter-in side that supplies pressure oil from hydraulic pump 15 to bottom-side port 18A of boom cylinder 7, and also controlling the opening amount of the meter-out side that discharges pressure oil from rod-side port 18B (second port) of boom cylinder 7 to the oil tank. At this time, load holding valve 19 allows pressure oil to flow from control valve 17 to bottom-side port 18A of boom cylinder 7. As a result, boom cylinder 7 extends, and boom 4 rises.

[0024] When a second operation command is input from work operation device 13, controller 21 uses a boom-lowering control table that indicates the relationship between the second operation command (current value) and a boom-lowering control command (current value) to obtain a boom-lowering control command that corresponds to the second operation command, and outputs the obtained boom-lowering control command to solenoid valve 25B. Solenoid valve 25B generates a pilot pressure that corresponds to the boom-lowering control command and outputs it to pressure-receiving section 24B of control valve 17. As a result, control valve 17 is switched to the right-hand switching position in the figure, and controls the amount of opening on the meter-in side that supplies pressure oil from hydraulic pump 15 to port 18B on the rod side of boom cylinder 7, and also controls the amount of opening on the meter-out side that discharges pressure oil from port 18A on the bottom side of boom cylinder 7 to the oil tank.

[0025] At this time, controller 21 acquires a function release control command corresponding to the second operation command using a function release control table (see FIG. 5 described later) that indicates the relationship between the second operation command (current value) and a function release control command (current value), and outputs the acquired function release control command to solenoid valve 27. Solenoid valve 27 generates pilot pressure corresponding to the function release control command and outputs it to load retention valve 19 (more specifically, pressure receiving portion 26 of release valve 23). As a result, load retention valve 19 controls the opening amount of check valve 22, and allows pressure oil to flow from bottom-side port 18A of boom cylinder 7 to control valve 17. As a result, boom cylinder 7 retracts and contracts, and boom 4 lowers.

[0026] A feature of this embodiment is that the controller 21 has a function of learning the control command when the load holding valve 19 (more specifically, the check valve 22) begins to open, and correcting the control table for function release based on the learned control command. Details of this function will be explained using Figs. 3 and 4. Fig. 3 is a flowchart showing the correction control of the control table of the controller in this embodiment. Fig. 4 is a time chart showing the time-dependent changes in the boom angle, the control command for boom lowering, and the control command for function release in this embodiment. The control shown in Fig. 3 is started in response to a command from, for example, a terminal in the operator's cab 11 or an external terminal.

[0027] First, in step S1 of Fig. 3, the controller 21 determines whether the working implement 3 is in a learning attitude (more specifically, an attitude in which the working implement 3 is not in contact with the ground and pressure is not building up on the bottom side of the boom cylinder 7) based on the boom angle detected by the attitude sensor 10. If the working implement 3 is in the learning attitude, the process proceeds to step S2.

[0028] In step S2, the controller 21 stores the boom angle detected by the attitude sensor 10 as an initial value A0 (see FIG. 4), and then proceeds to step S3.

[0029] In step S3, controller 21 outputs a predetermined value (see FIG. 4) to solenoid valve 25B as a control command for lowering the boom. As a result, control valve 17 is switched by the pilot pressure generated by solenoid valve 25B, and the meter-in side opening that supplies pressure oil from hydraulic pump 15 to port 18B on the rod side of boom cylinder 7 is controlled to a predetermined value, and the meter-out side opening that discharges pressure oil from port 18A on the bottom side of boom cylinder 7 to the oil tank is controlled to a predetermined value.

[0030] Furthermore, controller 21 outputs a first value (for example, a predetermined value ΔB as shown in FIG. 4) to solenoid valve 25B as a control command B for disabling the function. Thereafter, the process proceeds to step S4, where controller 21 determines whether the attitude of boom 4 of working implement 3 has started to change based on whether the amount of change in the boom angle detected by attitude sensor 10 (the difference from initial value A0) is equal to or greater than a predetermined threshold value ΔA (see FIG. 4). For example, as shown in FIG. 4, if the amount of change in the boom angle detected by attitude sensor 10 is less than threshold value ΔA, the process proceeds to step S5.

[0031] In step S5, controller 21 sets a second value (see FIG. 4) obtained by adding a predetermined value ΔB to the first value as control command B for function release. Then, proceeding to step S3, controller 21 outputs the predetermined value to solenoid valve 25B as a control command for boom lowering, and outputs the second value to solenoid valve 25B as control command B for function release. Then, proceeding to step S4, controller 21 determines whether the attitude of boom 4 of working implement 3 has started to change based on whether the amount of change in the boom angle detected by attitude sensor 10 is equal to or greater than threshold value ΔA. For example, as shown in FIG. 4, if the amount of change in the boom angle detected by attitude sensor 10 is less than threshold value ΔA, proceeding to step S5.

[0032] In step S5, controller 21 sets a third value (see FIG. 4) obtained by adding a predetermined value ΔB to the second value as control command B for function release. Then, proceeding to step S3, controller 21 outputs the predetermined value to solenoid valve 25B as a control command for boom lowering, and also outputs the third value to solenoid valve 25B as control command B for function release. Then, proceeding to step S4, controller 21 determines whether the attitude of boom 4 of working implement 3 has started to change based on whether the amount of change in the boom angle detected by attitude sensor 10 is equal to or greater than threshold value ΔA. For example, as shown in FIG. 4, if the amount of change in the boom angle detected by attitude sensor 10 is equal to or greater than threshold value ΔA, proceeding to step S6.

[0033] In step S6, the controller 21 learns the control command B (i.e., the third value) when the attitude of the boom 4 of the work implement 3 begins to change as the control command B1 when the load holding valve 19 begins to open. Then, the process proceeds to step S7.

[0034] In step S7, the controller 21 corrects the control table for function deactivation based on the learned control command B1. The correction method will be described.

[0035] 5, in the control table before correction, when the second operation command is between 0 and C1, the control command for function release is 0, when the second operation command increases from C1 to C2, the control command for function release increases from 0 to Bmax (maximum value) in proportion to the second operation command, and when the second operation command is between C2 and Cmax (maximum value), the control command for function release is Bmax. The second operation command C1 corresponds to the control command D for boom lowering when the meter-in and meter-out of the control valve 17 begin to open.

[0036] The controller 21 corrects the control table, for example, as shown in Fig. 5. In detail, the control command for releasing the function corresponding to the second operation command C1 is corrected from a value close to 0 to the control command B1 learned as described above. Accordingly, when the second operation command increases from C1 to C2, the control command for releasing the function is corrected so as to increase from B1 to Bmax (maximum value) in proportion to the second operation command.

[0037] Next, the effects of this embodiment will be explained in comparison with a comparative example (where the control table for function release is not corrected). Fig. 6 is a time chart showing the change over time in the control command for function release and the opening amount of the load holding valve in this embodiment and the comparative example.

[0038] At time t, controller 21 acquires control command D for boom lowering that corresponds to second operation command C1 from work operation device 13, and outputs the acquired control command D for boom lowering to solenoid valve 25B. As a result, control valve 17 is switched by the pilot pressure generated by solenoid valve 25B, and the meter-in side that supplies pressure oil from hydraulic pump 15 to port 18B on the rod side of boom cylinder 7 begins to open, and the meter-out side that discharges pressure oil from port 18A on the bottom side of boom cylinder 7 to the oil tank begins to open.

[0039] In the comparative example, the controller 21 does not correct the control table for function release. Therefore, at time t, the controller 21 acquires a value close to 0 as a control command for function release corresponding to the second operation command C1 from the work operating device 13, and outputs the acquired control command for function release to the solenoid valve 27. If there is a deviation in the relationship between the control command of the controller 21 and the pilot pressure of the solenoid valve 27 due to manufacturing variations in the solenoid valve 27, a delay Δt1 in the timing of opening of the load retention valve 19 will occur. Furthermore, if there is a deviation in the relationship between the pilot pressure of the solenoid valve 27 and the opening amount of the load retention valve 19 due to manufacturing variations in the load retention valve 19, a delay Δt2 in the timing of opening of the load retention valve 19 will occur.

[0040] In this embodiment, the controller 21 learns the control command B1 when the load retention valve 19 begins to open, and corrects the control table for function release based on the learned control command B1. Therefore, at time t, the controller 21 acquires the control command B1 for function release that corresponds to the second operation command C1 from the work operation device 13, and outputs the acquired control command B1 for function release to the solenoid valve 27. This eliminates the delays Δt1 and Δt2 in the timing of the opening of the load retention valve 19 described above. Therefore, the difference in timing between the opening of the meter-out of the control valve 17 and the opening of the load retention valve 19 can be reduced.

[0041] Note that, in the above embodiment, the load holding valve 19 is provided between the bottom-side port 18A of the boom cylinder 7 and the control valve 17, but this is not limiting. The load holding valve 19 may also be provided between the rod-side port of the arm cylinder 8 and the control valve. In this modified example, a posture sensor that detects the rotation angle (arm angle) of the arm 5 relative to the boom 4 is attached to the work implement 3. The controller 21 controls the control valve via the solenoid valve to open the meter-in side that supplies pressure oil from the hydraulic pump to the bottom-side port of the arm cylinder 8 and open the meter-out side that discharges pressure oil from the rod-side port, while changing the control command output to the solenoid valve 27, and learns the control command when the arm angle detected by the posture sensor starts to change as the control command when the load holding valve 19 starts to open, and corrects the control table using the learned control command.

[0042] Although the above description has been given taking a shovel as an example of an object to which the present invention is applied, the present invention is not limited to this and may be applied to other work machines. [Explanation of symbols]

[0043] 1. Running body 2 Rotating body 3 Work equipment 4. Boom 5 Arm 7 Boom cylinder 8 Arm Cylinder 10. Attitude Sensor 13 Work operating device 14 Prime Mover 15 Hydraulic pump 17 Control valve 18A port (1st port) 18B port (second port) 19 Load holding valve 21 Controller 25A, 25B Solenoid valve (first solenoid valve) 27 Solenoid valve (second solenoid valve)

Claims

1. The car body and a working device connected to the vehicle body; at least one hydraulic actuator that drives the working device; a prime mover mounted on the vehicle body; a hydraulic pump driven by the prime mover; a control valve that controls the hydraulic pump to supply pressure oil to one of a first port and a second port of the hydraulic actuator and to discharge pressure oil from the other port; a load holding valve that is provided between the first port of the hydraulic actuator and the control valve and that can be switched between an open state and a closed state; an operating device that outputs an operation command that instructs an operation of the hydraulic actuator; a first solenoid valve that generates a pilot pressure for operating the control valve; a second solenoid valve that generates a pilot pressure for operating the load holding valve; a controller that controls the first solenoid valve and the second solenoid valve in response to the operation command from the operation device, the controller uses a control table to obtain a control command corresponding to the operation command, and outputs the obtained control command to the second solenoid valve to switch the load holding valve from the closed state to the open state, in a working machine, a posture sensor for detecting the posture of the working device; The controller controlling the control valve via the first solenoid valve to open a meter-in side that supplies pressure oil from the hydraulic pump to the second port of the hydraulic actuator and to open a meter-out side that discharges pressure oil from the first port, while changing a control command to be output to the second solenoid valve; a control command when the attitude of the working device detected by the attitude sensor starts to change is learned as a control command when the load holding valve starts to open; A work machine characterized in that the control table is corrected using learned control commands.

2. 2. The work machine according to claim 1, The working device has a boom rotatably connected to the vehicle body, the at least one hydraulic actuator includes a boom cylinder that rotates the boom relative to the vehicle body; The work machine is characterized in that the load holding valve is provided between the first port of the boom cylinder and the control valve.

3. 2. The work machine according to claim 1, the working device includes a boom rotatably connected to the vehicle body and an arm rotatably connected to the boom, the at least one hydraulic actuator includes a boom cylinder that rotates the boom relative to the vehicle body, and an arm cylinder that rotates the arm relative to the boom, The work machine according to claim 1, wherein the load holding valve is provided between the first port of the arm cylinder and the control valve.

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