Work implement and control method for the work implement

Abstract

To provide a work machine enhancing efficiency while reducing a shock when starting driving a hydraulic actuator.SOLUTION: A work machine comprises a drive unit including a hydraulic actuator operated by hydraulic oil, and a control device for changing a driving speed after the drive unit starts driving. The control device is configured to, when a limit value for limiting operation of the drive unit is equal to or greater than a prescribed threshold, execute first control of changing the driving speed after the drive unit starts driving, according to the control value, and when the limit value is less than the threshold value, in addition to the first control, execute second control of changing a maximum flow rate of the hydraulic oil for operating the hydraulic actuator, according to the limit value.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a work machine such as a tractor and a control method for the work machine.

Background Art

[0002] The lifting device of a work vehicle disclosed in Patent Document 1 is a lifting device of a work vehicle that raises and lowers a work machine connected to a traveling body by the expansion and contraction of a hydraulic cylinder. The lifting device includes a hydraulic cylinder that raises and lowers the work machine by expansion and contraction, a solenoid valve that controls the lifting of the work machine via the hydraulic cylinder, a detection means that detects the lifting height of the work machine, and a control unit that controls the lowering of the work machine by controlling the current supply to the solenoid valve. The control unit increases the current value or duty ratio of the current supplied to the solenoid valve as the difference between the target lifting height and the lifting height of the rotary tilling device becomes larger, and decreases the current value or duty ratio of the current supplied to the solenoid valve as the difference between the lifting height of the rotary tilling device becomes smaller.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the lifting device of the work vehicle of Patent Document 1, the shock during the lifting of the rotary tilling device is reduced to perform smooth lifting work.

[0005] However, if only the control in the lifting device of the work vehicle of Patent Document 1 is used, it may be difficult to achieve both reduction of shock during the lifting of the rotary tilling device and work efficiency.

[0006] The present invention has been made to solve the problems of the prior art, and aims to provide a work machine and a control method for such a work machine that can improve efficiency while reducing the shock when starting the drive of a hydraulic actuator. [Means for solving the problem]

[0007] A work machine according to one aspect of the present invention includes a drive device having a hydraulic actuator that operates with hydraulic fluid, and a control device that changes the drive speed of the drive device after it has started to operate. A first operating tool for operating the aforementioned drive device, The control device is equipped with and restricts the operation of the drive device. The lower the limit value, the more the operation of the drive device by the first operating tool is restricted, and the higher the limit value, the less the operation of the drive device by the first operating tool is restricted. If the aforementioned limit value is greater than or equal to a predetermined threshold, the first control changes the drive speed of the drive device after it starts driving, according to the aforementioned limit value. The limit value increases as the drive speed of the drive device after starting to drive increases, and the limit value decreases as the drive speed of the drive device after starting to drive decreases. The first control is performed, and if the limit value is less than the threshold, the first In addition to the control, a second control changes the maximum flow rate of the hydraulic fluid that operates the hydraulic actuator according to the limit value. The maximum flow rate is increased as the limit value increases, and the maximum flow rate is decreased as the limit value decreases. Perform the second control.

[0008] In the first control, the control device The smaller the deviation between the actual position of the drive member and the target value of the drive member's position, the lower the drive speed. That's fine.

[0010] The aforementioned work machine is ,before The drive device comprises a control valve for controlling a hydraulic actuator, the drive device having a drive member driven by the hydraulic actuator, the first operating tool for manipulating a target value for the position of the drive member, and the control device for controlling the control valve based on a first map showing the relationship between the deviation between the actual position (which is the actual position of the drive member) and the target value, and a target flow rate of the hydraulic fluid that operates the hydraulic actuator, and a second map showing the relationship between a predetermined current value of the control current output to the control valve and the flow rate of the hydraulic fluid from the control valve. Then, the first control and the second control are performed. That's good too.

[0011] In the first control, the control device may output to the control valve a current value lower than the current value obtained based on the second map as the limit value decreases toward the threshold.

[0012] In the first control, the control device may correct the current value obtained based on the second map or the second map by a predetermined correction value based on the limit value, and may decrease the current value as the limit value decreases toward the threshold.

[0013] The second map is defined based on a standard flow rate characteristic that shows the relationship between the current value output to a standard control valve, which is a predetermined control valve, and the flow rate of hydraulic fluid from the standard control valve. The correction value when the limit value is less than or equal to the threshold may be defined by the current value at a predetermined hydraulic fluid flow rate between the flow rate characteristic of an upper limit control valve, which has a higher hydraulic fluid flow rate than the standard flow rate characteristic, and the standard flow rate characteristic.

[0014] In the first control, the control device may count the elapsed time since the first operating tool was operated and the drive device started to operate, and the shorter the elapsed time, the more the target flow rate may be limited.

[0015] The control device may, in the first control, limit the target flow rate based on a third map showing the relationship between the elapsed time and the target flow rate.

[0016] In the first control, the control device may acquire a third map in which the target flow rate for the elapsed time is small as the limit value decreases toward the threshold.

[0017] The drive device is a lifting device capable of raising and lowering the work device, and the control device may acquire different third maps in the first control depending on the content of the work performed by the work device.

[0018] The work machine includes a machine body and a protection mechanism that protects the driver's seat provided on the machine body. The first operating tool includes an internal operating tool provided inside the protection mechanism and an external operating tool provided outside the protection mechanism. In the first control, the control device may obtain a third map different from the case where the external operating tool is operated when the internal operating tool is operated.

[0019] The control device calculates a deviation value of the flow rate characteristic of a high-limit product with a larger flow rate of the hydraulic oil compared to the standard flow rate characteristic indicating the relationship between the current value output to a standard control valve which is a predetermined control valve and the flow rate of the hydraulic oil, corrects the current value output to the control valve using the deviation value, and may output a control current of the corrected current value to the control valve.

[0020] The work machine includes a second operating tool for operating the limit value, and the limit value may be assigned according to the operation amount of the second operating tool.

[0021] The drive device has a drive member driven by driving the hydraulic actuator, and is a lifting device capable of raising and lowering a work device. The hydraulic actuator is a lift cylinder, and the drive member may be a lift arm driven by driving the lift cylinder.

[0022] In response to the operation of the first operating tool, when raising the lift arm, the control device performs the first control, or the first control and the second control. In response to the operation of the first operating tool, when lowering the lift arm, the control device may not perform the first control and the second control.

[0023] In the second control, the control device may increase the maximum flow rate as the limit value increases and decrease the maximum flow rate as the limit value decreases.

[0024] A control method for a working machine according to an aspect of the present invention includes a drive device having a hydraulic actuator operated by hydraulic oil, and a control device for changing a driving speed after the start of driving of the drive device. A first operating tool for operating the aforementioned drive device, It is provided with The lower the limit value that restricts the operation of the drive device, the more the operation of the drive device by the first operating tool is restricted, and the higher the limit value, the less the operation of the drive device by the first operating tool is restricted. A control method for a working machine, when a limit value for restricting the operation of the drive device is equal to or greater than a predetermined threshold value, the control device changes the driving speed after the start of driving of the drive device according to the limit value, which is a first control The limit value increases as the drive speed of the drive device after starting to drive increases, and the limit value decreases as the drive speed of the drive device after starting to drive decreases. A first step of performing a first control, and when the limit value is less than the threshold value, in addition to the first control, the control device changes a maximum flow rate of hydraulic oil for operating the hydraulic actuator according to the limit value, which is a second control A second control that increases the maximum flow rate as the limit value increases and decreases the maximum flow rate as the limit value decreases. A second step of performing the second control, and includes. In the first control of the first step, the driving speed may be lowered as the deviation between the actual position, which is the actual position of the driving member, and the target value of the position of the driving member becomes smaller.

Effect of the Invention

[0025] According to the above working machine and the control method of the working machine, it is possible to improve efficiency while reducing the shock when starting the driving of the hydraulic actuator.

Brief Description of the Drawings

[0026] [Figure 1] It is a side view of a working machine. [Figure 2] It is a diagram showing a control system of a working machine according to the first embodiment. [Figure 3] It is a left rear perspective view showing a lifting device. [Figure 4] It is a left side view showing the lifting operation of the lifting device. [Figure 5] It is a diagram showing an example of a first map. [Figure 6] It is a diagram showing an example of a second map. [Figure 7] It is a diagram showing an example of a second operating tool. [Figure 8] It is a diagram showing a second map when the limit value is 100% and a second map when the limit value is 50%. [Figure 9] It is a diagram showing standard flow rate characteristics and upper limit flow rate characteristics. [Figure 10] This diagram shows the second map when the limit value is 50%, the second map when the limit value is 25%, and the second map when the limit value is 0%. [Figure 11] This diagram shows a series of steps including the processing of the first and second control functions performed by the control device. [Figure 12] This is a diagram showing the control system of the work machine 1 according to the second embodiment. [Figure 13] This figure shows an example of the third map (standard map). [Figure 14] This is a diagram showing an example of the third map (first modified map). [Figure 15] This figure shows an example of the third map (second modified map). [Figure 16] This figure shows an example of standard flow rate characteristics, upper limit flow rate characteristics, and lower limit flow rate characteristics. [Figure 17] This figure shows an example of correcting the discrepancy between the upper and lower flow rate characteristics. [Modes for carrying out the invention]

[0027] One embodiment of the present invention will be described below with reference to the drawings.

[0028] [First Embodiment] First, the work machine 1 will be described using Figures 1 and 2. Figure 1 shows a side view of the work machine 1 according to this embodiment. Figure 2 shows the control system provided by the work machine 1. As shown in Figure 1, the work machine 1 comprises a body 2, a work device 3, a travel device 4, a prime mover 5, a protection mechanism 6, and a drive device 8.

[0029] In this embodiment of the present invention, the direction in which the driver seated in the driver's seat 7 of the work machine 1 faces (direction of arrow A1 in Figure 1) is called the front, and the opposite direction (direction of arrow A2 in Figure 1) is called the rear. The right side of the driver (direction of arrow B2 in Figure 3) is called the right, and the left side of the driver (direction of arrow B1 in Figure 3) is called the left. Furthermore, the horizontal direction (direction of arrow B3 in Figure 3), which is perpendicular to the front-to-back direction of the work machine 1 (direction of arrow A3 in Figure 1), is called the vehicle width direction (or width direction).

[0030] The work device 3 is, for example, an implement, which is connected to the rear of the machine body 2 and can perform various tasks. The type of work device 3 is not particularly limited and may include, for example, a digging device for digging up potatoes and carrots, a fertilizer spreading device (fertilizer application device) for spreading fertilizer and a pesticide spraying device for spraying pesticides, a seeding device for sowing seeds in a field, a harvesting device for harvesting, a mowing device for cutting grass, a spreading device for spreading grass, a grass collecting device for gathering grass, a shaping device for shaping grass, and a ground work device for performing ground work on a field.

[0031] Ground-working equipment includes a rough tillage device (stubble cultivator) for rough tillage, a puddling device (drive harrow) for puddling, and tilling equipment (rotary tiller, subsoiler, plow, cultivator) for tilling. A tilling device (e.g., subsoiler, plow, cultivator) that performs ground-working operations by being towed by the implement 1 is called a towed tilling device. Figure 1 shows an example where a plow is connected to the rear of the machine body 2 as the working device 3.

[0032] The running gear 4 is a device that provides propulsion to the machine body 2. In the example shown in Figure 1, the running gear 4 is a wheeled device having front wheels 4a and rear wheels 4b, but it may also be a crawler-type device.

[0033] The drive unit (lifting device) 8 connects the work device 3 to the machine body 2 and can raise and lower the work device 3 relative to the machine body 2. The lifting device 8 is located at the rear of the machine body 2. The lifting device 8 is composed of, for example, a three-point linkage mechanism. The lifting device 8 is connected to the work device 3. It is detachable. By connecting the work device 3 to the lifting device 8, the machine body 2 can move the work device 3.

[0034] The prime mover 5 is a diesel engine, an electric motor, etc., and in this embodiment, it is composed of a diesel engine. A flywheel housing is provided at the rear of the prime mover 5. The power output by the prime mover 5 is transmitted to the transmission case 9 located at the bottom of the machine body 2.

[0035] As shown in Figure 1, the work machine 1 comprises a driver's seat 7 and an operating device 10 located on the upper part of the machine body 2. The driver's seat 7 is located within a protective mechanism (e.g., a cabin or canopy) 6. The operating device 10 is installed around the driver's seat 7 and includes a section where devices, components, etc. related to the operation of machinery, equipment, tools, components, etc. (e.g., work device 3, travel device 4, prime mover 5, etc.) equipped on the work machine 1 by a worker (operator) seated in the driver's seat 7 are gathered. The operating device 10 includes a steering device consisting of at least a steering wheel.

[0036] As shown in Figure 2, the multiple devices mounted on the work machine 1 are connected by an in-vehicle network N1 such as CAN, ISOBUS, LIN, and FlexRay. The devices connected to the in-vehicle network N1 include the prime mover 5, operating device 10, control device 11, display device 12, starter switch 13, and starter relay 14.

[0037] The display device 12 has a display unit 12a, such as a liquid crystal display, and displays various information about the work machine 1 on the display unit 12a. The display device 12 is installed at any position around the driver's seat 7 (for example, in front, to the side, etc.). In this embodiment, the display device 12 is a monitor (dashboard monitor) installed in the meter panel located in front of the driver's seat 7.

[0038] The display device 12 is operated by a jog dial 41 included in the operating device 10. The jog dial 41 is rotatable. By rotating the jog dial 41, the display device 12 changes the candidate selection item from among the multiple selection items displayed on the display unit 12a. In addition to rotation, the jog dial 41 is also pressable, and the selection item is determined by pressing it.

[0039] The control unit 11 consists of an ECU (Electronic Control Unit) and includes a CPU, volatile memory, non-volatile memory, and other electronic components and electrical circuits. The non-volatile memory of the control unit 11 stores software programs and various data for the CPU to control each part. In other words, the control unit 11 is the controller of the work machine 1.

[0040] The control device 11 performs various controls on the work machine 1. For example, the control device 11 operates the work machine 3, the travel machine 4, the prime mover 5, etc., based on signals (operation signals) input from the operating device 10. As shown in Figure 2, the control device 11 has a storage unit 11a. The storage unit 11a is a non-volatile memory or the like, and is a storage device that stores various kinds of information. For example, the storage unit 11a stores various application software. The storage unit 11a may be a storage device (hard disk drive: HDD, solid state drive: SSD, etc.) located outside the control device 11 and connected to the in-vehicle network N1.

[0041] The starter switch 13 is a switch for starting the engine 5. When the operator inserts the engine key into the key cylinder located around the driver's seat and rotates the engine key, the starter switch 13 outputs an engine start signal (start signal) to the starter relay 14.

[0042] The starter relay 14 is a component that starts the engine 5. When a start signal is input to the starter relay 14, the starter relay 14 starts the engine 5. Note that engine starting, which is one of the engine drive mechanisms, is not limited to a mechanical type (key cylinder type) where the engine key is inserted into the key cylinder to turn on the starter relay 14, but may also be a smart entry type that allows or prohibits engine starting via wireless communication.

[0043] The lifting device 8 will be described in detail below. As shown in Figures 3 and 4, the lifting device 8 is connected to the mission case 9. Figure 3 is a left rear perspective view showing the lifting device 8. Figure 4 is a left side view showing the lifting operation of the lifting device 8. As shown in Figures 3 and 4, the lifting device The assembly 8 includes a lift arm (driver) 21, a top link 22, a lower link 23, a lift rod 24, and a lift cylinder 26 (hydraulic actuator) 26.

[0044] As shown in Figure 3, the lift arm 21 includes a first lift arm 21L and a second lift arm 21R. The first lift arm 21L is positioned on one side (left) in the width direction of the aircraft body. The second lift arm 21R is positioned on the other side (right) in the width direction of the aircraft body. The first lift arm 21L and the second lift arm 21R are pivotably mounted on the aircraft body 2. Specifically, the front ends of the first lift arm 21L and the second lift arm 21R are pivotally supported on the upper part of the mission case 9 and extend toward the rear.

[0045] The top link 22 is positioned between the first lift arm 21L and the second lift arm 21R, with its front end pivotally supported on the upper part of the transmission case 9. The lower link 23 includes the first lower link 23L and the second lower link 23R. The front ends of the first lower link 23L and the second lower link 23R are pivotally supported on the lower part of the transmission case 9. The lift rod 24 includes the first lift rod 24L and the second lift rod 24R. The upper end of the first lift rod 24L is connected to the rear end of the first lift arm 21L, and its lower end is connected to the middle of the first lower link 23L in the longitudinal direction. The upper end of the second lift rod 24R is connected to the rear end of the second lift arm 21R, and its lower end is connected to the middle of the second lower link 23R in the longitudinal direction.

[0046] As shown in Figures 3 and 4, a joint 25 is provided at the rear end of the top link 22 and the rear end of the lower link 23, to which the work device 3 can be connected. By connecting the work device 3 to the rear end of the top link 22 and the rear end of the lower link 23, the work device 3 is connected to the rear of the work machine 1 so as to be able to move up and down. Therefore, the work device 3 is connected to the lift arm 21 via the lift rod 24 and the lower link 23.

[0047] As shown in Figures 3 and 4, the lift cylinder 26 is a hydraulic actuator (hydraulic cylinder) that operates using hydraulic fluid. As shown in Figure 2, the lift cylinder 26 is a single-acting cylinder and has a cylindrical cylinder tube 26a and a piston rod 26b, one end of which is slidably inserted into the cylinder tube 26a. The inside of the cylinder tube 26a is divided into a bottom-side oil chamber and a rod-side oil chamber by a piston housed so as to be movable in the direction along the axis of the cylinder tube 26a (axial direction). Therefore, when hydraulic fluid is supplied to the bottom-side oil chamber, the lift cylinder 26 extends. On the other hand, when hydraulic fluid is discharged from the bottom-side oil chamber, the lift cylinder 26 contracts.

[0048] The lift cylinder 26 includes a first lift cylinder 26L and a second lift cylinder 26R. The first lift cylinder 26L has one end connected to the first lift arm 21L and the other end connected to the lower left of the transmission case 9. The second lift cylinder 26R has one end connected to the second lift arm 21R and the other end connected to the lower right of the transmission case 9. Driven by the lift cylinder 26, the first lift arm 21L and the second lift arm 21R swing in the vertical direction.

[0049] Furthermore, the drive device 8 only needs to include a hydraulic actuator 26 that operates using hydraulic fluid and a drive member 21 that is driven by the hydraulic actuator 26, and is not limited to a lifting device.

[0050] As shown in Figure 2, the work machine 1 is equipped with a hydraulic pump P and a control valve 30. The hydraulic pump P is operated by power generated by the prime mover. The hydraulic pump P discharges hydraulic fluid stored in the hydraulic fluid tank T. The hydraulic pump P is composed of a variable displacement hydraulic pump equipped with a pump capacity control mechanism such as a constant displacement gear pump or a swash plate.

[0051] The control valve 30 controls the hydraulic actuator (lift cylinder) 26. The control valve 30 is excited by a control current output from the control device 11, and its opening degree is changed arbitrarily. This allows the control valve 30 to adjust the hydraulic fluid that operates the lift cylinder 26. The control valve 30 is, for example, a proportional flow control type electromagnetic control valve, and as the current value I of the control current output from the control device 11 increases, the flow rate of hydraulic fluid supplied to the hydraulic actuator 26 increases.

[0052] In this embodiment, the control valve 30 is a first control valve that controls the extension of the lift cylinder 26. It includes a (upward control valve) 30a and a second control valve (downward control valve) 30b that controls the contraction of the lift cylinder 26. The first control valve 30a and the second control valve 30b are connected to both the first lift arm 21L and the second lift arm 21R, and simultaneously extend or contract the first lift arm 21L and the second lift arm 21R.

[0053] The first control valve 30a is provided in the oil passage connecting the hydraulic pump P and the bottom oil chamber, and by changing the degree of opening, the hydraulic fluid discharged by the hydraulic pump P can be supplied to the bottom oil chamber.

[0054] The second control valve 30b is located in the oil passage connecting the bottom oil chamber and the hydraulic oil tank T, and by changing its opening degree, the hydraulic oil from the bottom oil chamber can be discharged into the hydraulic oil tank T.

[0055] Therefore, when the control device 11 outputs a control current to the first control valve 30a and the opening degree of the first control valve 30a is changed, the hydraulic fluid discharged by the hydraulic pump P is supplied to the bottom side oil chamber, and the lift cylinder 26 extends, causing the lift arm 21 to rise. On the other hand, when the control device 11 outputs a control current to the second control valve 30b and the opening degree of the second control valve 30b is changed, the hydraulic fluid in the bottom side oil chamber is discharged to the hydraulic fluid tank T, and the lift cylinder 26 becomes retractable. As a result, the weight of the work device 3 and / or the lift arm 21 causes the lift cylinder 26 to retract, and the lift arm 21 descends.

[0056] Furthermore, the control valve 30 only needs to be able to control the lift cylinder (hydraulic actuator) 26, and the hydraulic system is not limited to the configuration described above. For example, in the example described above, the first control valve 30a and the second control valve 30b are connected to the bottom side oil chamber, but the second control valve 30b may be provided in the oil passage connecting the hydraulic pump P and the rod side oil chamber, and by changing the opening degree, the hydraulic fluid discharged by the hydraulic pump P may be supplied to the rod side oil chamber.

[0057] Furthermore, in the above-described embodiment, the lift cylinder 26 is controlled by changing the opening degrees of the first control valve 30a and the second control valve 30b, but a three-position electromagnetic switching valve that can be switched between a first position that extends the lift cylinder 26, a second position that stops the drive of the lift cylinder 26, and a third position that retracts the lift cylinder 26 may be used as the control valve 30.

[0058] Furthermore, in the above-described embodiment, the first control valve 30a and the second control valve 30b directly adjust the hydraulic fluid that operates the lift cylinder 26. However, the first control valve 30a and the second control valve 30b may also act on a control valve connected to the lift cylinder 26 with pilot oil, and this control valve may adjust the hydraulic fluid that operates the lift cylinder 26. Moreover, the configuration of the hydraulic system is not limited to the above-described configuration.

[0059] The operating device 10 has a first operating tool 42 for operating the drive device (lifting device) 8 (lifting and lowering the work device 3). The first operating tool 42 is an operating device 10 that can operate the target value of the position of the lift arm 21. In response to the operation of the first operating tool 42, the control device 11 controls the control valve 30 so that the deviation ΔD between the actual position, which is the actual position of the lift arm 21, and the target value becomes zero.

[0060] As shown in Figure 2, the work machine 1 is equipped with a detection device 15 for detecting the actual position of the lift arm 21. The detection device 15 is a sensor for calculating the position of the lift cylinder 26. The detection device 15 is connected to the control device 11 and outputs the detected signal (detection signal) to the control device 11.

[0061] In this embodiment, the detection device 15 is a sensor (lift arm sensor) that detects the angle of the lift arm 21, and the control device 11 controls the control valve 30 based on the angle of the lift arm 21 as the position of the lift arm 21. That is, the control device 11 controls the control valve 30 so that the deviation ΔD between the actual position (actual angle of the lift arm 21) and the target value (target angle of the lift arm 21) becomes zero, and operates the lift cylinder 26. The lift arm sensor 15 is, for example, a rotational displacement type variable resistor such as a potentiometer. The lift arm sensor 15 outputs a signal of the detected angle (angle signal) to the control device 11.

[0062] The lift arm sensor 15 only needs to be able to detect the angle of the lift arm 21, and is not limited to this. The detection device 15 only needs to be able to detect parameters for detecting the actual position of the lift arm 21, and may be, for example, a lift cylinder sensor that detects the extension (stroke) of the lift cylinder 26. In such a case, the control device 11 controls the control valve 30 based on the extension amount of the lift cylinder 26 as the position of the lift arm 21. That is, the control device 11 controls the control valve 30 so that the deviation ΔD between the actual position (actual extension amount of the lift cylinder 26) and the target value (target extension amount of the lift cylinder 26) becomes zero, and operates the lift cylinder 26.

[0063] Alternatively, the control device 11 may control the control valve 30 based on the vertical height of a predetermined position (e.g., the rear end) of the lift arm 21. In this case, the control device 11 calculates the vertical height of the rear end of the lift arm 21 based on parameters detected by the detection device 15 (the actual angle of the lift arm 21 and the actual extension amount of the lift cylinder 26) and a predetermined calculation formula. The control device 11 also controls the control valve 30 so that the deviation ΔD between the actual position (e.g., the height of the rear end of the lift arm 21) and the target value (e.g., the target height of the rear end of the lift arm 21) becomes zero, and operates the lift cylinder 26.

[0064] In the following explanation, we will describe an example in which the first operating tool 42 operates the angle of the lift arm 21 as a target value, and the control device 11 controls the control valve 30 so that the deviation ΔD between the actual position (the actual angle of the lift arm 21) and the target value (the target angle of the lift arm 21) becomes zero.

[0065] The first operating device 42 is, for example, a position lever 42a. The position lever 42a is a lever that operates the raising and lowering of the work device 3 and can perform a swinging operation. The position lever 42a is equipped with a potentiometer for detecting the amount of operation of the position lever 42a. The control device 11 can define a target value (target angle) for the lift arm 21 based on the operation signal output from the potentiometer. When the amount of operation of the position lever 42a increases, the control device 11 defines a higher target value in accordance with that amount of operation. On the other hand, when the amount of operation of the position lever 42a decreases, the control device 11 defines a lower target value in accordance with that amount of operation.

[0066] The first operating device 42 is not limited to the position lever 42a, but may also be a lifting operating device 42b that operates the lifting and lowering of the work device 3 separately from the position lever 42a. The lifting operating device 42b may be a push-button switch such as a tactile switch, or a seesaw switch. The lifting operating device 42b is connected to the control device 11 and outputs an operation signal to the control device 11. The control device 11 defines a target value according to the amount of operation of the lifting operating device 42b (for example, operation time or number of operations). In this embodiment, the lifting operating device 42b includes an upward operating device 42b1 that operates the target value of the lift arm 21 to a higher value, and a downward operating device 42b2 that operates the target value of the lift arm 21 to a lower value. That is, when the upward operating device 42b1 is operated, the control device 11 defines a higher target value according to that operation. On the other hand, when the downward operating device 42b2 is operated, the control device 11 defines a lower target value according to that operation.

[0067] As shown in Figure 1, the position lever 42a is located inside the protective mechanism 6, and the lifting / lowering device 42b is located outside the protective mechanism 6 (for example, on the side of the lifting device 8, on the rear fender). In the following description, first operating devices 42 located inside the protective mechanism 6, such as the position lever 42a, are sometimes referred to as "internal operating devices," and first operating devices 42 located outside the protective mechanism 6, such as the lifting / lowering device 42b, are sometimes referred to as "external operating devices."

[0068] Furthermore, although the above example described a case in which the control device 11 defines an arbitrary target value according to the amount of operation of the first operating tool 42, the work machine 1 may also include an upper limit operating tool 43 for operating the upper limit of the position of the lift arm 21 and a lower limit operating tool 44 for operating the lower limit of the position of the lift arm 21, and the first operating tool 42 may include a pump switch 45 for raising or lowering the lift arm 21 to the upper or lower limit of the position of the lift arm 21.

[0069] Furthermore, if the work machine 1 is equipped with an upper limit operating device 43 and a lower limit operating device 44, the control device 11 When controlling the control valve 30 in response to the operation of the position lever 42a or the lifting / lowering device 42b as the first operating tool 42, the lift arm 21 is operated within a range of less than or equal to the upper limit and greater than or equal to the lower limit of the position of the lift arm 21.

[0070] The control device 11 controls the control valve 30 by outputting a control current to the control valve 30 based on the operation signal output from the first operating tool 42. For example, the control device 11 sequentially determines the current value I of the control current to the control valve 30 based on the operation signal, the first map M1, and the second map M2. The first map M1 and the second map M2 are pre-stored in the storage unit 11a.

[0071] When the lift arm 21 is raised, the target value is higher than the actual position, so the deviation ΔD is a positive number. When the lift cylinder 26 is lowered, the target value is lower than the actual position, so the deviation ΔD is a negative number. However, for the sake of explanation, in the following explanation, the deviation ΔD will be described as the absolute value of the difference between the target value and the actual position.

[0072] Furthermore, the first map M1 and the second map M2 may be the same for the case where the lift arm 21 is raised and the case where the lift arm 21 is lowered, or they may be different.

[0073] Figure 5 shows an example of the first map M1. The first map M1 is a map (graph) that shows the relationship between the deviation ΔD between the actual position and the target value and the target flow rate TF of the hydraulic fluid that operates the hydraulic actuator 26. In the graph shown in Figure 5, the horizontal axis shows the deviation ΔD between the actual position and the target value, and the vertical axis shows the target flow rate TF of the hydraulic fluid that operates the hydraulic actuator 26. In the example of the first map M1 shown in Figure 5, as the deviation ΔD between the actual position and the target value increases, the target flow rate TF changes from increasing rapidly to increasing gradually.

[0074] Note that the first map M1 shown in Figure 5 is just one example, and the target flow rate TF may change by gradually increasing and then rapidly increasing as the deviation ΔD between the actual position and the target value increases, or it may increase proportionally and change in a nearly straight line.

[0075] Figure 6 shows an example of the second map M2. The second map M2 is a map (graph) that shows the relationship between the current value I of the control current output to a predetermined control valve 30 (e.g., a standard control valve) and the flow rate (supply amount DF) of the hydraulic fluid from the control valve 30. The standard control valve is the standard control valve 30. In other words, the second map M2 is defined based on the flow rate characteristics SC of the standard control valve in design data or theoretical data. The standard flow rate characteristics SC are the flow rate characteristics of the standard control valve, for example, the flow rate characteristics in design data or theoretical data. Therefore, the standard flow rate characteristics SC are the flow rate characteristics of the standard control valve in design or theoretical data.

[0076] Furthermore, the standard flow rate characteristic SC may be a flow rate characteristic obtained by performing calculations such as averaging or standardizing the measurement data of each flow rate characteristic measured for multiple control valves 30. In other words, the standard flow rate characteristic SC may be a flow rate characteristic based on multiple measured data. Alternatively, the standard flow rate characteristic SC may be the flow rate characteristic shown in the standard product specification data of the control valve 30 provided by the manufacturer or the like.

[0077] In the graph shown in Figure 6, the horizontal axis represents the control current value I, and the vertical axis represents the supply amount DF. In the example of the second map M2 shown in Figure 6, as the control current value I increases, the supply amount DF changes from gradually increasing to rapidly increasing.

[0078] Note that the second map M2 shown in Figure 6 is just an example, and it is sufficient if it is defined based on the flow characteristics in the design data or theoretical data of a predetermined control valve 30.

[0079] Therefore, the control device 11 first calculates the deviation ΔD between the actual position and the target value, and then acquires a first map M1 and a second map M2 according to the direction of movement of the lift arm 21 (up or down). Based on the deviation ΔD and the first map M1, the control device 11 acquires the target flow rate TF. Once the control device 11 acquires the target flow rate TF, it acquires the current value I of the control current based on the target flow rate TF and the second map M2. As a result, the control device 11 controls the control valve 30 by outputting the acquired current value I to the control valve 30.

[0080] Here, the control device 11 gradually decreases the current value I as the deviation ΔD gradually decreases. Also, when the deviation ΔD becomes zero, the control device 11 reduces the control current to the control valve 30. The value I is set to zero. In this way, the control device 11 can drive the lift cylinder 26 by controlling the control valve 30 in response to the operation of the first operating tool 42.

[0081] As shown in Figure 2, the work machine 1 is equipped with a second operating tool 46, and the control device 11 controls the control valve 30 in accordance with the operation of the second operating tool 46, in addition to the operation of the first operating tool 42. The second operating tool 46 is an operating device 10 for operating a limit value V that limits the operation of the drive device (lifting device) 8. In this embodiment, the limit value V is a value that limits the operation of the drive device 8 by the first operating tool 42. The second operating tool 46 is an operating tool that accepts rotational operation, and a limit value V is assigned according to the amount of operation. The second operating tool 46 is assigned a value in the range of 0 to 100% as the limit value V. The control device 11 acquires the operation signal of the second operating tool 46 and acquires the limit value V based on the operation signal. The control device 11 acquires the limit value V based on the acquired operation signal and a predetermined calculation formula or an operation map stored in the storage unit 11a that shows the relationship between the operation signal and the limit value V.

[0082] The control device 11 restricts the operation of the lifting device 8 by the first operating tool 42 as the limit value V decreases, and does not restrict the operation of the lifting device 8 by the first operating tool 42 as the limit value V increases. In other words, when the limit value V is 0%, the control device 11 restricts the operation of the lifting device 8 by the first operating tool 42 the most, and when the limit value V is 100%, it does not restrict the operation of the lifting device 8 by the first operating tool 42.

[0083] The definition of the limit value V is merely an example. The control device 11 may not restrict the operation of the lifting device 8 by the first operating tool 42 when the limit value V is 0%, or it may restrict the operation of the lifting device 8 by the first operating tool 42 to the greatest extent when the limit value V is 100%. Furthermore, the relationship between the magnitude of the limit value V and the degree of restriction on the operation of the lifting device 8 by the first operating tool 42, as well as the range of the limit value V, are not limited to the definition described above.

[0084] As shown in Figure 7, in this embodiment, the second operating tool 46 is a display image displayed on the display unit 12a of the display device 12. In other words, the display device 12 and the jog dial 41 serve as the operating device 10 (second operating tool 46). By operating the jog dial 41, the display device 12 displays an operation screen MD1 on the display unit 12a that displays the second operating tool 46. In the example shown in Figure 7, the second operating tool 46 includes a selection display unit 46a, a gauge image 46b, and an indicator unit 46c.

[0085] The selection display unit 46a is a display image that indicates that the second operating tool 46 can be operated by operating the jog dial 41. The selection display unit 46a changes its display format depending on whether the second operating tool 46 can be operated or not. In this embodiment, the selection display unit 46a is a substantially circular display image. In this embodiment, the thickness of the outer shape and the color are made different when the second operating tool 46 can be operated compared to when it cannot.

[0086] The gauge image 46b is a band-shaped display image that shows the limit value V. The gauge image 46b is displayed as an arc-shaped image surrounding the selection display unit 46a. The gauge image 46b is positioned to form part of a circle (virtual circle O) with the center of the selection display unit 46a as its center. The counterclockwise end of the gauge image 46b indicates that the limit value V is 0%, and the clockwise end indicates that the limit value V is 100%. Near the counterclockwise end of the gauge image 46b, a turtle icon is displayed to indicate that the limit value V is 0%, and near the clockwise end, a rabbit icon is displayed to indicate that the limit value V is 100%.

[0087] The indicator unit 46c is a display image that is rotated in accordance with the operation of the jog dial 41. The indicator unit 46c is, for example, positioned at least near the gauge image 46b and is a display image that indicates the current limit value V. Specifically, in response to the operation of the jog dial 41, the indicator unit 46c moves along the gauge image 46b with the center of the virtual circle O as the axis of rotation. As the limit value V increases, the indicator unit 46c moves the gauge image 46b clockwise, and as the limit value V decreases, it moves the gauge image 46b counterclockwise.

[0088] To explain the operation of the second operating tool 46, when the operator makes the second operating tool 46 operable by operating the jog dial 41, the operator rotates the jog dial 41 clockwise to move the indicator part 46c clockwise and increase the limit value V. Yes, it is possible. On the other hand, while the second operating tool 46 is operational, the operator can move the indicator part 46c counterclockwise by rotating the jog dial 41 counterclockwise, thereby lowering the limit value V. The operator confirms the limit value V by pressing the jog dial 41.

[0089] The operation signal of the second operating tool 46, generated by operating the jog dial 41, is output from the display device 12 to the control device 11.

[0090] Furthermore, in the embodiments described above, the second operating tool 46 is a display image that accepts rotational operation and is operated indirectly by the jog dial 41, but it is sufficient that it can at least operate the limit value V, and its configuration is not limited to the configuration described above. For example, the second operating tool 46 may be a physical dial switch that is operated directly by the operator without going through the jog dial 41.

[0091] Furthermore, the limit value V operated by the second operating tool 46 is stored (retained) in the storage unit 11a. Therefore, even when the starter relay 14 is turned off, the control device 11 can obtain the limit value V stored in the storage unit 11a, and it is not necessary to operate the second operating tool 46 each time the starter relay 14 is turned on (off).

[0092] The control device 11 changes the drive speed (start speed) of the drive device 8 after it has started to drive. Specifically, if the limit value V is greater than or equal to a predetermined threshold, the control device 11 performs a first control to change the drive speed of the lifting device 8 after it has started to drive, according to the limit value V. On the other hand, if the limit value V is less than the threshold, the control device 11 performs a second control in addition to the first control to change the maximum flow rate MF of the hydraulic fluid that operates the hydraulic actuator 26, according to the limit value V. The threshold is a predetermined value, which in this embodiment is 50%. However, the threshold is not limited to 50%; for example, it may be 40% or 60%. Furthermore, the threshold is stored in the memory unit 11a and may be arbitrarily changed by operating the jog dial 41 or the like.

[0093] In this embodiment, the control device 11 performs first control, or first and second control, when raising the lift arm 21 in response to the operation of the first operating tool 42. On the other hand, the control device 11 does not perform first and second control when lowering the lift arm 21 in response to the operation of the first operating tool 42. In other words, when raising the lift arm 21, the control device 11 restricts the operation of the lifting device 8 by the first operating tool 42, and when lowering the lift arm 21, it does not restrict the operation of the lifting device 8 by the first operating tool 42.

[0094] First, the first control will be explained in detail. The control device 11 changes the starting speed of the lifting device (drive device) 8 according to the limit value V, at least within the range where the limit value V is equal to or greater than the threshold value. When the limit value V is less than the threshold value, the control device 11 performs the same first control as when the limit value V is at the threshold value. Furthermore, the control device 11 increases the starting speed of the lifting device 8 as the limit value V increases, and decreases the starting speed of the lifting device 8 as the limit value V decreases.

[0095] In other words, in this embodiment, the control device 11 increases the starting speed as the limit value V increases and decreases the starting speed as the limit value V decreases, within the range where the limit value V is 50% or more and 100% or less, and keeps the starting speed constant when the limit value V is less than 50%.

[0096] Specifically, the control device 11 changes the starting speed of the lifting device 8 by outputting a current value I to the control valve 30 that is lower than the current value I obtained based on the second map M2 as the limit value V decreases toward the threshold. For example, the control device 11 corrects the second map M2 so that the current value I decreases as the limit value V decreases. In other words, when the limit value V is 100%, the control device 11 does not correct the second map M2 in the first control, and when the limit value V is 50% or less, the amount of correction (degree of correction) of the second map M2 by the first control increases.

[0097] The control device 11 acquires a current value I based on the corrected second map M2 and outputs a current value I to the control valve 30 that is lower than the current value I acquired based on the uncorrected second map M2. Figure 8 shows the second map M2 when the limit value V is 100% and the second map M2 when the limit value V is 50%. In Figure 8, the second map M2 when the limit value V is 100% is shown with a solid line, and the second map M2 when the limit value V is 50% is shown with a dashed line. As described above, in the graph shown in Figure 8, the horizontal axis represents the current value I of the control current, and the vertical axis represents the supply amount DF.

[0098] The control device 11 corrects the current value I of the control current of the second map M2 by a predetermined correction value based on the limit value V, and decreases the current value I as the limit value V decreases towards the threshold. On the other hand, as the limit value V increases from the threshold, the control device 11 corrects the current value I so that it approaches the current value I of the control current of the second map M2 before correction.

[0099] Therefore, when the control device 11 corrects the second map M2 with the correction value, the corrected second map M2 is offset in the direction that the current value I becomes zero by a uniform rate according to the correction value, as shown in Figure 8. As the limit value V decreases towards the threshold, the control device 11 offsets the corrected second map M2 in the direction that the current value I becomes zero. In other words, as the limit value V increases from the threshold, the control device 11 brings the corrected second map M2 closer to the standard flow characteristic SC, and as the limit value V decreases from the threshold, it moves the corrected second map M2 further away from the standard flow characteristic SC.

[0100] Therefore, the control valve 30, which receives a control current output from the control device 11, increases its opening degree as the limit value V increases from the threshold, and decreases its opening degree as the limit value V decreases toward the threshold, even if the deviation ΔD is the same. In the following explanation, the current value I obtained based on the corrected second map M2 is called the corrected current value CI.

[0101] The control device 11 acquires a correction map that is pre-stored in the memory unit 11a and shows the relationship between the correction value and the limit value V, and acquires a correction value based on the correction map and the limit value V. In this embodiment, the correction value is a coefficient that is multiplied by the current value I of the control current of the second map M2 before correction. Therefore, the correction value is at its maximum value (1 in this embodiment) when the limit value V is 100%. The correction value also decreases as the limit value V decreases towards the threshold, and is at its minimum value when the limit value V is 50% or less.

[0102] More specifically, the correction value (minimum correction value) when the limit value V is below the threshold is defined by the current value I of the control current at a predetermined supply amount (reference supply amount BF) of the flow characteristics of the upper limit product control valve 30 (upper limit flow characteristics UC), which has a larger supply amount DF than the standard flow characteristics SC, and the standard flow characteristics SC. The reference supply amount BF is the flow rate that is supplied to the control valve 30 and can be supplied by the control valve 30, due to manufacturing errors of equipment constituting the hydraulic system, such as the hydraulic pump P.

[0103] Figure 9 shows the standard flow rate characteristic SC and the upper limit flow rate characteristic UC. In Figure 9, the standard flow rate characteristic SC is shown as a solid line, and the upper limit flow rate characteristic UC is shown as a dashed line. In the graph shown in Figure 9, the horizontal axis represents the control current value I, and the vertical axis represents the supply amount DF.

[0104] The upper limit flow rate characteristic UC is the flow rate characteristic of the upper limit control valve 30, and is, for example, the flow rate characteristic based on design data or theoretical data. In other words, the upper limit flow rate characteristic UC is the design or theoretical flow rate characteristic of the upper limit control valve 30. Alternatively, the upper limit flow rate characteristic UC may be a flow rate characteristic obtained by performing calculations such as averaging or standardizing the measurement data of each flow rate characteristic measured for multiple control valves 30. In other words, the upper limit flow rate characteristic UC may be a flow rate characteristic based on multiple measured data.

[0105] When the supply amount DF is the standard supply amount BF, and the current value I of the control current of the standard flow characteristic SC is taken as the first current value I1, and the current value I of the control current of the upper limit flow characteristic UC is taken as the second current value I2, then the minimum value of the correction value is defined by the ratio of the second current value I2 to the first current value I1. For example, if the first current value I1 is 2500mA and the second current value I2 is 2100mA, the minimum value of the correction value is 0.84. Therefore, when the limit value V is 50% or less, the correction value is 0.84, and the correction current value CI is 0.16% (the ratio of the absolute value ΔI of the difference between the first current value I1 and the second current value I2 to the first current value I1) of the current value I of the control current when the limit value V is 100%.

[0106] Furthermore, in this embodiment, when the limit value V increases from 50% to 100%, the correction value increases within the range of 0.84 or more and 1 or less. For example, the correction value increases proportionally as the limit value V increases from 50% to 100%. Therefore, for example, when the limit value V is 75% In some cases, the correction value will be 0.92.

[0107] Furthermore, the correction value only needs to increase as the limit value V increases from 50% to 100%, and does not need to be proportional.

[0108] Furthermore, in the above-described embodiment, the case in which the control device 11 acquires a correction map pre-stored in the storage unit 11a and acquires a correction value from the correction map was explained as an example. However, the minimum value of the correction value is defined by the ratio of the second current value I2 to the first current value I1, and it is sufficient that the value increases as the limit value V increases from at least 50% to 100%. The control device 11 may be configured to calculate the correction value based on a predetermined calculation formula and perform the first control each time the limit value V is changed.

[0109] Furthermore, although the above-described embodiment explained the case in which the control device 11 corrects the second map M2 with a correction value, the control device 11 may, at least in the first control, output a current value I to the control valve 30 that is lower than the current value I obtained based on the second map M2 as the limit value V decreases toward the threshold, and may be configured to correct the current value I obtained based on the second map M2 with the correction value instead of the second map M2 itself. In such a case, the control device 11 corrects the current value I of the control current obtained based on the second map M2 with a correction value based on the limit value V, and decreases the current value I as the limit value V decreases toward the threshold. On the other hand, as the limit value V increases from the threshold, the control device 11 corrects the current value I so that it approaches the current value I of the control current obtained based on the second map M2.

[0110] In the second control, the control device 11 increases the maximum flow rate MF as the limit value V increases, and decreases the maximum flow rate MF as the limit value V decreases. Here, the maximum flow rate MF is the maximum value of the hydraulic fluid flow that the control valve 30 can supply under the control of the control device 11. In this embodiment, the control device 11 changes the maximum flow rate MF of the hydraulic fluid that operates the hydraulic actuator 26 by correcting the second map M2 according to the limit value V. In other words, when the limit value V is less than the threshold, the second control is performed in addition to the first control, so when the limit value V decreases from above the threshold to below the threshold, the control device 11 further corrects the second map M2 corrected in the first control with a second control different from the first control.

[0111] The control device 11 acquires the limited flow rate CF according to the limit value V and corrects the second map M2 based on the limited flow rate CF. For example, the control device 11 acquires a limit map that is pre-stored in the storage unit 11a and shows the relationship between the limited flow rate CF and the limit value V, and acquires the limited flow rate CF based on the limit map and the limit value V. The limited flow rate CF decreases as the limit value V decreases and is proportional to the limit value V.

[0112] When the limit value V is 0%, the limit flow rate CF, i.e., the minimum value of the limit flow rate CF, is 50% of the maximum flow rate MF in the second map M2 before correction. Also, when the limit value V is 25%, the limit flow rate CF is 75% of the maximum flow rate MF in the second map M2 before correction.

[0113] Therefore, if the maximum flow rate MF of the second map M2 is 100 L / min when the limit value V is 100%, then the limited flow rate CF when the limit value V is 25% will be 75 L / min, and the limited flow rate CF when the limit value V is 0% will be 50 L / min.

[0114] Figure 10 shows the second map M2 when the limit value V is 50%, when the limit value V is 25%, and when the limit value V is 0%. In Figure 10, the second map M2 when the limit value V is 50% is shown as a solid line. The second map M2 when the limit value V is 25% is shown as a dashed line. The second map M2 when the limit value V is 0% is shown as a double dashed line. In the graph shown in Figure 10, the horizontal axis represents the control current value I, and the vertical axis represents the supply amount DF.

[0115] The control device 11 further corrects the second map M2 corrected in the first control to correct a supply amount DF that is higher than the limit flow rate CF to the limit flow rate CF. As a result, as shown in Figure 10, the second map M2 corrected in the first and second controls is corrected to 75 L / min or less when the limit value V is 25%, and to 50 L / min or less when the limit value V is 0%.

[0116] Therefore, if the limit value V is less than 50%, the control device 11 corrects the second map M2 and obtains a current value I for the control current based on the target flow rate TF obtained from the first map M1 and the corrected second map M2. Here, if the maximum flow rate MF (limit flow rate CF) in the corrected second map M2 is less than the target flow rate TF, the control device 11 obtains a current value I where the supply amount DF is the maximum flow rate MF.

[0117] Furthermore, the limited flow rate CF only needs to decrease as the limit value V decreases from at least 50% to 0%, and does not need to be proportional.

[0118] Furthermore, in the second control, the control device 11 may increase the maximum flow rate MF as the limit value V increases and decrease the maximum flow rate MF as the limit value V decreases, and the first map M1 may be corrected instead of the second map M2.

[0119] Furthermore, in the above-described embodiment, the control device 11 was described as acquiring a limit map pre-stored in the storage unit 11a and acquiring the limit flow rate CF from the limit map. However, the limit flow rate CF only needs to be a value that decreases as the limit value V decreases from at least 50% to 0%, and the control device 11 may be configured to calculate the limit flow rate CF based on a predetermined calculation formula each time the limit value V is changed and perform the second control.

[0120] The following describes a series of processes including the first and second control processes performed by the control device 11. Figure 11 is a diagram showing a series of processes including the first and second control processes performed by the control device 11. The series of processes shown in Figure 11 are executed by the CPU based on a software program pre-stored in the storage unit 11a of the control device 11. First, the control device 11 determines whether or not the second operating tool 46 has been operated (S1). The control device 11 acquires the operation signal of the second operating tool 46, and if it determines that the second operating tool 46 has been operated (S1: Yes), it acquires the limit value V based on the operation signal (S2). When the control device 11 acquires the limit value V in S2, it stores the limit value V in the storage unit 11a. On the other hand, if the control device 11 determines that the second operating tool 46 has not been operated (S1: No), it determines whether or not the limit value V is held in the storage unit 11a (S3).

[0121] If the control device 11 determines that a limit value V is stored in the memory unit 11a (S3: Yes), it retrieves the limit value V (S4). In S2 or S4, after retrieving the limit value V, the control device 11 determines whether the limit value V is equal to or greater than the threshold value (S5).

[0122] If the control device 11 determines that the limit value V is greater than or equal to the threshold (S5: Yes), it performs first control based on the acquired limit value V (S6, first step). On the other hand, if the control device 11 determines that the limit value V is less than the threshold (S5: No), it performs first and second control based on the acquired limit value V (S7, second step).

[0123] As described above, the operator can change the drive speed of the lifting device 8 after it starts to drive by operating the limit value V with the second operating tool 46 through the first control. Furthermore, by operating the second operating tool 46 to lower the limit value V below the threshold, the operator can further reduce the drive speed of the lifting device 8 through a second control separate from the first control. Therefore, by operating the second operating tool 46, the work machine 1 can appropriately adjust the balance between suppressing the occurrence of shock after the start of driving and the work efficiency of the lifting device 8.

[0124] A work machine 1 according to one aspect of the present invention comprises a drive device 8 having a hydraulic actuator 26 that operates with hydraulic fluid, and a control device 11 that changes the drive speed of the drive device 8 after it has started to operate. The control device 11 performs a first control to change the drive speed of the drive device 8 after it has started to operate, according to the limit value V, when the limit value V that restricts the operation of the drive device 8 is greater than or equal to a predetermined threshold, and when the limit value V is less than the threshold, in addition to the first control, it performs a second control to change the maximum flow rate MF of the hydraulic fluid that operates the hydraulic actuator 26, according to the limit value V.

[0125] With this configuration, if the limit value V is greater than or equal to the threshold, the drive speed of the drive unit 8 after starting to drive can be changed according to the limit value V. If the limit value V is lower than the threshold, in addition to the first control, the drive speed of the drive unit 8 can be further reduced by a second control separate from the first control. Therefore, the work machine 1 can appropriately adjust the balance between suppressing the occurrence of shock after starting to drive and the work efficiency of the drive unit 8, according to the magnitude of the limit value V.

[0126] Furthermore, in the first control, the control device 11 changes the drive speed of the drive device 8 after the start of driving according to the limit value V, within a range where the limit value V is equal to or greater than the threshold value, and if the limit value V is less than the threshold value, it performs the same first control as when the limit value V is the threshold value.

[0127] With this configuration, the driving speed of the drive unit 8 can be sufficiently changed by the first control when the limit value V is above the threshold, and when the limit value V is below the threshold, the driving speed of the drive unit 8 can be further reduced by the second control.

[0128] Furthermore, in the first control, the control device 11 increases the drive speed of the drive unit 8 after it starts driving as the limit value V increases, and decreases the drive speed of the drive unit 8 after it starts driving as the limit value V decreases.

[0129] This configuration helps to suppress the discrepancy between the drive speed and the magnitude of the limit value V.

[0130] Furthermore, the work machine 1 includes a first operating tool 42 for operating the drive device 8 and a control valve 30 for controlling the hydraulic actuator 26. The drive device 8 has a drive member 21 driven by the hydraulic actuator 26. The first operating tool 42 operates a target value for the position of the drive member 21. The control device 11 controls the control valve 30 based on a first map M1 showing the relationship between the deviation ΔD between the actual position (actual position) of the drive member 21 and the target value, and the target flow rate TF of the hydraulic fluid that operates the hydraulic actuator 26, and a second map M2 showing the relationship between a predetermined current value I of the control current output to the control valve 30 and the flow rate (supply amount) DF of the hydraulic fluid from the control valve 30.

[0131] According to the above configuration, the first control changes the drive speed of the drive unit 8 after it starts to drive, and the second control changes the target flow rate TF, thereby changing the responsiveness (sensitivity) of the drive unit 8 to the operation of the first operating tool 42.

[0132] Furthermore, in the first control, as the limit value V decreases toward the threshold, the control device 11 outputs a current value I to the control valve 30 that is lower than the current value I obtained based on the second map M2.

[0133] With this configuration, the drive speed of the drive unit 8 after it starts driving can be appropriately changed according to the magnitude of the limit value V.

[0134] Furthermore, in the first control, the control device 11 corrects the second map M2 or the current value I obtained based on the second map M2 by a predetermined correction value based on the limit value V, and decreases the current value I as the limit value V decreases towards the threshold.

[0135] With this configuration, the current value I of the control current is corrected by a correction value based on the limit value V, and the drive speed after the start of operation of the drive unit 8 can be changed with a relatively simple process.

[0136] Furthermore, the second map M2 is defined based on a standard flow characteristic SC that shows the relationship between the current value I output to a standard control valve, which is a predetermined control valve 30, and the flow rate DF of the hydraulic fluid from the standard control valve. The correction value when the limit value V is below the threshold is defined by the flow characteristic of the upper limit control valve 30, which has a higher hydraulic fluid flow rate DF than the standard flow characteristic SC, and the current value I at a predetermined hydraulic fluid flow rate BF of the standard flow characteristic SC.

[0137] With this configuration, as the limit value V decreases, the second map M2 is brought substantially closer to the flow characteristics of the upper limit control valve 30. Therefore, by changing the limit value V while also changing the drive speed after the start of operation of the drive unit 8, it is possible to suppress the variation between the upper limit control valve 30 and the standard control valve.

[0138] Furthermore, the work machine 1 is equipped with a second operating tool 46 for manipulating a limit value V, and the limit value V is assigned to the second operating tool 46 according to the amount of manipulation.

[0139] With this configuration, the operator can intuitively and quickly manipulate the limit value V by rotating the dial-shaped second operating tool 46.

[0140] Furthermore, the drive unit 8 is a lifting device capable of raising and lowering the work device 3, and has a drive member 21 driven by the drive of a hydraulic actuator 26. The hydraulic actuator 26 is a lift cylinder 26, and the drive member 21 is a lift arm 21 driven by the drive of the lift cylinder 26.

[0141] This configuration allows for the aforementioned unique effects, and enables the raising and lowering of the work device 3. This allows for an appropriate balance between suppressing the occurrence of shocks after the start of operation and improving work efficiency by raising and lowering the work device 3.

[0142] Furthermore, the control device 11 performs first control, or first and second control, when raising the lift arm 21 in response to the operation of the first operating tool 42, but does not perform first and second control when lowering the lift arm 21 in response to the operation of the first operating tool 42.

[0143] With this configuration, when raising the work device 3, the aforementioned specific effects can be achieved.

[0144] Furthermore, in the second control, the control device 11 increases the maximum flow rate MF as the limit value V increases, and decreases the maximum flow rate MF as the limit value V decreases.

[0145] With this configuration, if the operator wants to increase the drive speed of the drive unit 8 after it starts moving, they can increase the limit value V, and if they want to decrease it, they can decrease the limit value V. Therefore, the operator can operate the limit value V without any discomfort.

[0146] Furthermore, the control method for the work machine 1 includes a drive unit 8 having a hydraulic actuator 26 that operates with hydraulic fluid, and a control device 11 that changes the drive speed of the drive unit 8 after it has started to operate, and includes a first step in which, if a limit value V that restricts the operation of the drive unit 8 is greater than or equal to a predetermined threshold, the control device 11 performs a first control to change the drive speed of the drive unit 8 after it has started to operate according to the limit value V, and a second step in which, if the limit value V is less than the threshold, the control device 11 performs a second control in addition to the first control to change the maximum flow rate MF of the hydraulic fluid that operates the hydraulic actuator 26 according to the limit value V.

[0147] With this configuration, if the limit value V is greater than or equal to the threshold, the drive speed of the drive unit 8 after starting to drive can be changed according to the limit value V. If the limit value V is lower than the threshold, in addition to the first control, the drive speed of the drive unit 8 can be further reduced by a second control separate from the first control. Therefore, the work machine 1 can appropriately adjust the balance between suppressing the occurrence of shock after starting to drive and the work efficiency of the drive unit 8, according to the magnitude of the limit value V. [Second Embodiment] Figure 12 shows another embodiment (second embodiment) of the work implement 1 and the control method for work implement 1. Hereinafter, the work implement 1 and the control method for work implement 1 of the second embodiment will be described, focusing on the configurations that differ from the above-described embodiment (first embodiment). Components common to the first embodiment will be denoted by the same reference numerals, and detailed explanations will be omitted.

[0148] In the second embodiment, the control device 11 performs a first control that differs from the first control in the first embodiment, and changes the drive speed of the drive device 8 after it starts driving, according to the limit value V. In particular, in the first control in the first embodiment, the drive speed of the drive device 8 after it starts driving was changed by correcting the second map M2 or the current value I of the control current according to the limit value V, but the first control in the second embodiment differs from the first control in the first embodiment in that it does not correct the second map M2 and the current value I.

[0149] Specifically, the control device 11 of the second embodiment, as a first control, counts the elapsed time t since the first operating tool 42 was operated and the drive device 8 started to drive, and limits the target flow rate TF the shorter the elapsed time t is.

[0150] Specifically, the control device 11 detects whether the first operating tool 42 is being operated based on the operation signal output from the potentiometer, and can measure, for example, the elapsed time t since the first operating tool 42 was operated by a timing unit (timer) provided in the control device 11. The timing unit measures the elapsed time t since the first operating tool 42 was operated, and if it detects that the first operating tool 42 is not being operated, it resets the measured elapsed time t.

[0151] In the first control, the control device 11 limits the target flow rate TF based on the third map M3. Figure 13 shows an example of the third map M3. In Figure 13, the third map M3 when the limit value V is 100% is shown by a solid line. The third map M3 when the limit value V is 75% is shown by a dashed line. The third map M3 when the limit value V is 50% or less is shown by a double dashed line. As shown in Figure 13, the third map M3 is This is a map (graph) showing the relationship between elapsed time t and the target flow rate TF. In the graph shown in Figure 13, the horizontal axis represents elapsed time t, and the vertical axis represents the target flow rate TF of the hydraulic fluid that operates the hydraulic actuator 26.

[0152] In the following explanation, the target flow rate TF defined in the third map M3 is referred to as the "limiting target flow rate CT". In the example of the third map M3 shown in Figure 13, as the elapsed time t increases, the limiting target flow rate CT changes from gradually increasing to rapidly increasing. The third map M3 is pre-stored in the memory unit 11a. Therefore, the control device 11 obtains the limiting target flow rate CT from the third map M3 according to the elapsed time t, and limits the target flow rate TF by the obtained limiting target flow rate CT.

[0153] Specifically, if the control device 11 finds that the limited target flow rate CT obtained from the third map M3 exceeds the target flow rate TF obtained based on the operating signal of the control device and the first map M1, it limits the target flow rate TF to the limited target flow rate CT and obtains the current value I of the control current based on the limited target flow rate CT and the second map M2. Furthermore, if the elapsed time t exceeds the maximum value tmax1 of the range of elapsed time t defined in the third map M3, the control device 11 performs the first control based on the limited target flow rate CT corresponding to the maximum value tmax1.

[0154] Furthermore, the third map M3 shown in Figure 13 is just one example. In the example shown in Figure 13, the third map M3 includes multiple sections with different slopes. However, at least the third map M3 should change such that the limit target flow rate CT increases as the elapsed time t increases. The third map M3 may increase in a downward-convex curve as the elapsed time t increases, or it may increase proportionally in a roughly straight line.

[0155] In the first control, the control device 11 acquires a third map M3 in which the limit target flow rate CT is small relative to the elapsed time t as the limit value V decreases toward the threshold. In this embodiment, the storage unit 11a stores a third map M3 corresponding to the limit value V, and the control device 11 acquires the third map M3 corresponding to the limit value V from the storage unit 11a according to the limit value V. Furthermore, the multiple third maps M3 are defined by multiplying a predetermined reference map by a value (decrease rate) corresponding to the magnitude of the limit value V. For example, the reduction rate is approximately proportional to the limit value V and is defined to decrease as the limit value V decreases. The reference map is, for example, the third map M3 when the limit value V is 100%.

[0156] Therefore, multiple third maps M3 are defined such that the target flow rate CT per unit of elapsed time t decreases as the limit value V decreases towards the threshold. In other words, the third map M3 with the highest target flow rate CT is the third map M3 when the limit value V is 100%, and the third map M3 with the lowest target flow rate CT is the third map M3 when the limit value V is 50% or less.

[0157] Furthermore, the target flow rate CT in the third map M3 with a predetermined limit value V (first limit value) is greater than the target flow rate CT in the third map M3 with a lower limit value V (second limit value) at any given elapsed time t. In other words, the third map M3 with the first limit value does not intersect with the third map M3 with the second limit value at any given elapsed time t.

[0158] In the example shown in Figure 13, the third map M3 when the limit value V is 75% is defined by multiplying the reference map (the third map M3 when the limit value V is 100%) by a reduction rate of 0.6. Similarly, the third map M3 when the limit value V is 50% or less is defined by multiplying the reference map by a reduction rate of 0.2.

[0159] Furthermore, the rate of decrease only needs to be defined such that it decreases as the limit value V decreases; it does not need to be proportional.

[0160] Furthermore, in the above-described embodiment, the case in which the control device 11 acquires a third map M3 pre-stored in the storage unit 11a according to the limit value V was explained as an example. However, in the first control, the control device 11 only needs to acquire a third map M3 in which the target flow rate TF is small for the elapsed time t as the limit value V decreases toward the threshold. The control device 11 may also be configured to calculate the third map M3 from the reference map based on a predetermined calculation formula each time the limit value V is changed and perform the first control.

[0161] Furthermore, the control device 11 displays different third maps M3 depending on the content of the work performed by the work device 3. It is also possible to obtain the following. In this embodiment, when performing operations (towing operations) in which the lifting device 8 grounds the working device 3 and tows the towing tillage device, such as a towed tillage device such as a subsoiler, plow, and cultivator, it is also possible to obtain the third map M3 shown in Figure 14 (hereinafter referred to as the first modified map M3B for the sake of explanation) instead of the third map M3 shown in Figure 14 (hereinafter referred to as the standard map M3A for the sake of explanation). As shown in Figure 14, the first modified map M3B is a map (graph) that shows the relationship between elapsed time t and the target flow rate TF, similar to the standard map M3A shown in Figure 13. In the graph shown in Figure 14, the horizontal axis shows the elapsed time t, and the vertical axis shows the target flow rate TF of the hydraulic fluid that operates the hydraulic actuator 26.

[0162] In the example shown in Figure 14, the first change map M3B when the limit value V is 100% is shown with a solid line, and the first change map M3B when the limit value V is 75% is shown with a dashed line. Furthermore, in the example shown in Figure 14, the first change map M3B when the limit value V is 50% or less is shown with a double dashed line. In addition, in the example shown in Figure 14, the standard map M3A when the limit value V is 100% is shown with a dashed line for comparison.

[0163] In this embodiment, the control device 11 determines whether the working device 3 is a towed tilling device based on whether the function used when the working device 3 is a towed tilling device is enabled or disabled, and obtains the standard map M3A or the first modified map M3B. Specifically, the control device 11 can switch between the standard mode, which is the position mode, and the draft mode, which is used when the working device 3 is a towed tilling device.

[0164] Position mode is a mode in which the lifting device 8 is operated by the operation of the first operating tool 42 to perform position control. On the other hand, draft mode is a mode in which the lifting device 8 is operated by the operation of the first operating tool 42, and the lifting device 8 is automatically raised and lowered according to the traction load of the work device 3 to perform draft control (draft control) to maintain a predetermined traction load. In other words, draft mode is a mode that is effective when performing work in which a load is generated by the work machine 1 towing the traction tilling device, such as a subsoiler, plow, and cultivator.

[0165] Switching between position mode and draft mode is performed by a mode selector switch 47, which is an operating device 10. The mode selector switch 47 is a push-button switch such as a tactile switch, or a seesaw switch, etc. The mode selector switch 47 is connected to a control device 11 and outputs an operation signal to the control device 11. The control device 11 switches between position mode and draft mode in response to the operation signal, i.e., the operation of the mode selector switch 47.

[0166] The mode switching switch 47 described above is just one example; the control device 11 may switch between position mode and draft mode based on information input to the display device 12.

[0167] As shown in Figures 13 and 14, the first modification map M3B defines a steeper slope of the target flow rate TF with respect to elapsed time t compared to the standard map M3A at the same limit value V. In other words, the target flow rate TF at the same elapsed time t is less restricted when the control device 11 performs the first control in draft mode compared to when the control device 11 performs the first control in position mode. Furthermore, the maximum value tmax2 of the range of elapsed time t defined in the first modification map M3B is defined to be smaller than the maximum value tmax1 of the range of elapsed time t defined in the standard map M3A.

[0168] Furthermore, when the limit value V is the same, the limit target flow rates CT (maximum target flow rates CTmax1, CTmax2) at the maximum values ​​tmax1 and tmax2 within the range of elapsed time t are the same for the first modified map M3B and the standard map M3A. Therefore, when the deviation ΔD between the actual position and the target value is the same at the same elapsed time t, the driving speed of the drive unit 8 after starting to drive can be increased in draft mode compared to position mode.

[0169] In the above-described embodiment, the control device 11 determines that the work performed by the work implement 1 is a towing operation, depending on whether the functions of the work implement 1 are enabled or disabled. However, the display device 12 receives input of the work content, and the control device 11 acquires the work content and determines that it is a towing operation. The configuration may also be such that it determines whether or not, and the method of determination is not limited to the method described above.

[0170] Furthermore, the control device 11 may acquire a different third map M3 when the internal operating device 42a is operated compared to when the external operating device 42b is operated. In this embodiment, when the internal operating device (position lever) 42a is operated, the control device 11 acquires the standard map M3A shown in Figure 13, and when the external operating device (lifting operating device) 42b is operated, it may acquire a third map M3 (hereinafter referred to as the second modified map M3C for the sake of explanation) as shown in Figure 15 instead of the standard map M3A. As shown in Figure 15, the second modified map M3C is a map (graph) that shows the relationship between elapsed time t and the target flow rate TF, similar to the standard map M3A shown in Figure 13. In the graph shown in Figure 15, the horizontal axis shows the elapsed time t, and the vertical axis shows the target flow rate TF of the hydraulic fluid that operates the hydraulic actuator 26.

[0171] In the example shown in Figure 15, the second change map M3C when the limit value V is 100% is shown with a solid line, and the second change map M3C when the limit value V is 75% is shown with a dashed line. Furthermore, in the example shown in Figure 15, the second change map M3C when the limit value V is 50% or less is shown with a double dashed line. In addition, in the example shown in Figure 15, the standard map M3A when the limit value V is 100% is shown with a dashed line for comparison.

[0172] In this embodiment, the control device 11 determines whether the position lever 42a or the lifting / lowering device 42b is being operated based on the operation signal output from the position lever 42a and the operation signal output from the lifting / lowering device 42b.

[0173] As shown in Figures 13 and 15, the second modification map M3C defines a steeper slope for the target flow rate TF with respect to elapsed time t compared to the standard map M3A at the same limit value V. In other words, the target flow rate TF at the same elapsed time t is less restricted when the control device 11 performs the first control in draft mode compared to when the control device 11 performs the first control in position mode.

[0174] Furthermore, the maximum value tmax3 within the elapsed time t range defined in the second modified map M3C is defined to be smaller than the maximum value tmax1 within the elapsed time t range defined in the standard map M3A. In addition, the maximum target flow rates CTmax1 and CTmax3 within the said elapsed time t ranges tmax1 and tmax3 are defined to be smaller in the second modified map M3C compared to the standard map M3A.

[0175] Therefore, if the deviation ΔD between the actual position and the target value is the same over the same elapsed time t, operating with the lifting / lowering device 42b allows for a faster drive speed after the drive unit 8 starts operating compared to using the position lever 42a, while also allowing for finer control.

[0176] According to the first control of the second embodiment, unlike the first control of the first embodiment, the drive speed of the drive device 8 after it has started to drive can be appropriately changed according to the elapsed time t since the drive device 8 started to drive, without correcting the second map M2 or the current value I obtained based on the second map M2. Therefore, even if the control device 11 performs a process to correct the current value I in a process different from the first control or the second control, it can suppress the complexity of the process for calculating the current value I.

[0177] In this embodiment, the control device 11 performs a calibration of the flow rate variation to the lift cylinder 26 caused by the control valve 30, which deviates from the second map M2 (standard flow rate characteristic SC), as a process to correct the current value I. Figure 16 is a diagram showing an example of the standard flow rate characteristic SC, the upper limit flow rate characteristic UC, and the lower limit flow rate characteristic DC (flow rate characteristic of the lower limit control valve 30). Figure 17 is a diagram showing an example in which the deviations of the upper limit flow rate characteristic UC and the lower limit flow rate characteristic DC have been corrected. In Figures 16 and 17, the standard flow rate characteristic SC is shown with a solid line, the upper limit flow rate characteristic UC is shown with a dashed line, and the lower limit flow rate characteristic DC is shown with a double dashed line.

[0178] The control device 11 calculates the deviation value of the flow characteristics of the upper limit control valve 30, corrects the current value I output to the control valve 30 using the deviation value, and outputs the corrected current value I to the control valve 30. In other words, the control device 11 does not calibrate the control valve 30 itself, which shows the flow characteristics UC and UD of the upper limit control valve 30 and lower limit control valve 30 shown in Figure 16, which have deviations from the standard flow characteristics SC. Instead, by adding the deviation value ΔF from the standard flow characteristics SC to the second map M2 or the current value I obtained based on the second map M2, it becomes possible to use it in a manner that approaches the standard flow characteristics SC, as shown in Figure 17. The details of "achievement" are explained below.

[0179] As shown in Figure 12, the work machine 1 is equipped with a calibration mode switch 70, which is operated by the operator to set it to calibration mode. When the operator operates the calibration mode switch 70, it outputs a calibration mode setting instruction to the control device 11. Upon receiving the calibration mode setting instruction, the control device 11 sets it to calibration mode for performing calibration. Calibration mode is a mode other than the normal mode for performing normal operations, etc.

[0180] When in calibration mode, the control device 11 calculates the deviation value ΔF of the flow characteristics of the control valve 30 relative to the standard flow characteristics SC. For example, in calibration mode, the control device 11 corrects the control current to the control valve 30 using the deviation value ΔF and outputs the corrected current value I to the control valve 30.

[0181] For example, the control device 11 calculates a current value I as a deviation value ΔF, which is the difference between the supply amount DF of the control valve 30 when a predetermined calibration current value PI is output to the control valve 30 and the supply amount DF corresponding to the calibration current value PI in the standard flow characteristic SC. The control device 11 adds this deviation value ΔF to the control current supplied to the control valve 30 and outputs a corrected current value I to the control valve 30.

[0182] Furthermore, the control device 11 can perform the above calibration even on control valves 30 that deviate from the standard flow rate characteristics SC, including lower-end control valves 30 with a lower flow rate compared to the standard flow rate characteristics SC. Lower-end control valves 30 are control valves 30 with a lower supply amount DF compared to the standard control valve.

[0183] Specifically, when the control device 11 outputs a predetermined calibration current value PI to the control valve 30 for a predetermined time, it calculates the flow rate value FV of the hydraulic fluid supplied to the lift cylinder 26 using the amount of drive of the lift arm 21 (displacement angle XF) detected by the detection device 15 and the capacity XQ of the hydraulic fluid in the lift cylinder 26. For example, the control device 11 calculates the flow rate value FV of the hydraulic fluid supplied to the lift cylinder 26 by multiplying the displacement angle XF of the lift arm 21 by the unit capacity ΔQ per unit angle of the lift cylinder 26. The storage unit 11a stores the unit capacity ΔQ in advance. That is, by performing this for the control valve 30 for the first lift cylinder 26L and the control valve 30 for the second lift cylinder 26R, the flow rate value FV of the hydraulic fluid in the first lift cylinder 26L and the flow rate value FV of the hydraulic fluid in the second lift cylinder 26R are calculated.

[0184] Alternatively, the control device 11 may calculate the flow rate value FV using the following equation (1), based on the total volume QM of the hydraulic fluid in the lift cylinder 26, the maximum displacement angle XM of the lift arm 21, and the displacement angle XF of the lift arm 21. In this case, the storage unit 11a has previously stored the total volume QM of the hydraulic fluid in the lift cylinder 26. TIFF0007867997000001.tif10154

[0185] If the control device 11 subtracts the standard flow rate value SF, which corresponds to the calibration current value PI in the standard flow characteristic SC, from the flow rate value FV (i.e., the difference between the flow rate value FV and the standard flow rate value SF) is a negative value, it sets the absolute value of the difference between the current value I, which corresponds to the flow rate value FV(FV1) in the standard flow characteristic SC, and the calibration current value PI as the deviation value ΔF(ΔF1). It then adds the deviation value ΔF1 to the current value I of the control current to the control valve 30 to obtain the corrected current value I, and outputs the control current of the corrected current value I to the control valve 30.

[0186] Furthermore, the control device 11 can perform the above calibration even for control valves 30 that deviate from the standard flow rate characteristics SC, or control valves 30 that are at the upper limit and have a higher flow rate than the standard flow rate characteristics SC.

[0187] Specifically, when the control device 11 outputs a control current of calibration current value PI to the control valve 30, it calculates the flow rate value FV (FV2) of the hydraulic fluid supplied to the lift cylinder 26 using the amount of drive (displacement angle) of the lift arm 21 detected by the detection device 15 and the capacity of the hydraulic fluid in the lift cylinder 26. The calculation of the flow rate value FV2 is the same as in the case of the lower limit product control valve 30 described above. Then, the control device 11 calculates the standard flow rate characteristic SC from the flow rate value FV2. If the value obtained by subtracting the standard flow rate value SF corresponding to the calibration current value PI (i.e., the difference between the flow rate value FV and the standard flow rate value SF) is a positive value, the absolute value of the difference between the current value I corresponding to the flow rate value FV in the standard flow characteristic SC and the calibration current value PI is defined as the deviation value ΔF(ΔF2). The current value I obtained by subtracting the deviation value ΔF2 from the current value I of the control current to the control valve 30 is defined as the corrected current value I, and the control current of the corrected current value I is output to the control valve 30.

[0188] The control device 11 calculates the corrected current value I by adding a deviation value ΔF to the current value I of the control current supplied to the control valve 30 if the current value I of the control current supplied to the control valve 30 is greater than or equal to a specified value SV, which represents the current value I corresponding to the minimum flow rate value Fmin of the compensation range in which the supply amount of the control valve 30 is compensated. If the current value I of the control current supplied to the control valve 30 is less than the specified value SV, the control device 11 does not calculate the corrected current value I.

[0189] The control device 11 sets a current value I as the calibration current value PI, which corresponds to any flow rate in the central range located in the middle of the range from the maximum flow rate value LMmax of the lifting device 8 (for example, the maximum flow rate value LMmax of the lift cylinder 26), which is smaller than the maximum supply amount Fmax of the control valve 30, to the minimum flow rate value Fmin for which the supply amount of the control valve 30 is compensated.

[0190] In the first control, the control device 11 counts the elapsed time t from when the first operating tool 42 is operated and the drive device 8 starts driving, and limits the target flow rate TF as the elapsed time t becomes shorter.

[0191] With this configuration, the driving speed of the drive unit 8 after it has started to drive can be appropriately changed according to the elapsed time t since the drive unit 8 started to drive.

[0192] Furthermore, in the first control, the control device 11 limits the target flow rate TF based on a third map M3 that shows the relationship between the elapsed time t and the target flow rate TF.

[0193] With this configuration, the predefined third map M3 allows for the appropriate modification of the drive speed of the drive unit 8 after it starts operating, through a relatively simple process.

[0194] Furthermore, in the first control, the control device 11 acquires a third map M3 in which the target flow rate TF is low relative to the elapsed time t, as the limit value V decreases toward the threshold.

[0195] With this configuration, the drive speed of the drive unit 8 after it starts driving can be appropriately changed according to the magnitude of the limit value V.

[0196] Furthermore, the drive unit 8 is a lifting device that can raise and lower the work device 3, and the control device 11 acquires different third maps M3 in the first control according to the content of the work performed by the work device 3.

[0197] With this configuration, the drive speed of the drive unit 8 after it starts driving can be appropriately changed according to the work being done.

[0198] Furthermore, the work machine 1 comprises a machine body 2 and a protective mechanism 6 that protects the driver's seat provided in the machine body 2. The first operating tool 42 includes an internal operating tool 42a provided inside the protective mechanism 6 and an external operating tool 42b provided outside the protective mechanism 6. In the first control, the control device 11 acquires a third map M3 that is different when the internal operating tool 42a is operated compared to when the external operating tool 42b is operated.

[0199] With this configuration, the drive speed of the drive unit 8 after it starts driving can be appropriately changed depending on whether the operator operates the internal control device 42a or the external control device 42b.

[0200] Furthermore, the control device 11 calculates a deviation value of the flow characteristic of the control valve 30, which is the upper limit product, where the flow rate DF of the hydraulic fluid is greater than that of the standard flow characteristic SC, which shows the relationship between the current value I output to the standard control valve 30 and the flow rate DF of the hydraulic fluid. Using this deviation value, the control device 11 corrects the current value I output to the control valve 30 and outputs the corrected current value I as the control current to the control valve 30.

[0201] This configuration allows for calibration of flow rate variations in the hydraulic actuator 26 caused by a control valve 30 that deviates from the standard flow rate characteristic SC. Therefore, a control valve 30 that deviates from the standard flow rate characteristic SC can be effectively utilized. Furthermore, the operation of the drive unit 8 using a control valve 30 with a deviated flow rate characteristic can be made closer to the operation of other drive units 8 equipped with a control valve 30 that matches the standard flow rate characteristic SC. This reduces variations in the operation of the drive unit 8 even when using a control valve 30 with a deviated flow rate characteristic. Consequently, performance differences between control valve 30 products can be minimized. Therefore, we can provide a stable quality work machine 1.

[0202] Although the present invention has been described above, the embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0203] 1: Work machine 2: Aircraft 3: Work equipment 6: Protection mechanism 8: Drive system (lifting device) 11: Control device 21: Driven component (lift arm) 26: Hydraulic actuator (lift cylinder) 30: Control valve 42: 1st operating tool 42a: Internal operating tool 42b:External control tool 46:Second operating tool BF:Flow rate (standard supply amount) DF:Flow rate (supply amount) I: Current value M1: Map 1 M2: Second map M3: Third Map MF: Maximum flow rate SC: Standard flow characteristics TF: Target flow rate V: Limit value t: elapsed time ΔD: Deviation

Claims

1. A drive device having a hydraulic actuator that operates using hydraulic fluid, A control device for changing the drive speed of the drive device after it has started to drive, A first operating tool for operating the aforementioned drive device, Equipped with, The control device is The lower the limit value that restricts the operation of the drive device, the more the operation of the drive device by the first operating tool is restricted, and the higher the limit value, the less the operation of the drive device by the first operating tool is restricted. If the limit value is greater than or equal to a predetermined threshold, a first control is performed to change the drive speed of the drive device after it starts driving, in accordance with the limit value, wherein the first control is performed to increase the drive speed of the drive device after it starts driving as the limit value increases, and to decrease the drive speed of the drive device after it starts driving as the limit value decreases; if the limit value is less than the threshold, in addition to the first control, a second control is performed to change the maximum flow rate of the hydraulic fluid that operates the hydraulic actuator, in accordance with the limit value, wherein the second control is performed to increase the maximum flow rate as the limit value increases, and to decrease the maximum flow rate as the limit value decreases.

2. The work machine according to claim 1, wherein the control device, in the first control, lowers the drive speed as the deviation between the actual position, which is the actual position of the drive member, and the target value of the position of the drive member becomes smaller.

3. A control valve for controlling the hydraulic actuator, Equipped with, The drive device has a drive member that is driven by the hydraulic actuator, The first operating device manipulates the target value of the position of the drive member, The control device is Based on a first map showing the relationship between the deviation between the actual position of the drive member and the target value, and the target flow rate of the hydraulic fluid that operates the hydraulic actuator, and a second map showing the relationship between the current value of the control current output to the control valve and the flow rate of the hydraulic fluid from the control valve, the control valve is controlled, and the first and second controls are performed. The work machine according to claim 1.

4. The work machine according to claim 3, wherein the control device outputs a current value to the control valve that is lower than the current value obtained based on the second map as the limit value decreases toward the threshold in the first control.

5. The work machine according to claim 4, wherein the control device corrects the current value obtained based on the second map or the second map by a predetermined correction value based on the limit value in the first control, and decreases the current value as the limit value decreases toward the threshold.

6. The second map is defined based on a standard flow rate characteristic that shows the relationship between the current value output to a predetermined control valve, which is a standard control valve, and the flow rate of hydraulic fluid from the standard control valve. The work machine according to claim 5, wherein the correction value when the limit value is less than or equal to the threshold value is defined by the current value at a predetermined hydraulic fluid flow rate between the flow rate characteristics of the upper limit control valve, which has a higher hydraulic fluid flow rate than the standard flow rate characteristics, and the standard flow rate characteristics.

7. The work machine according to claim 3, wherein the control device counts the elapsed time since the first operating tool was operated and the drive device started to drive in the first control, and limits the target flow rate as the elapsed time becomes shorter.

8. The work machine according to claim 7, wherein the control device limits the target flow rate in the first control based on a third map showing the relationship between the elapsed time and the target flow rate.

9. The work machine according to claim 8, wherein the control device, in the first control, acquires a third map in which the target flow rate for the elapsed time is small as the limit value decreases toward the threshold.

10. The aforementioned drive device is a lifting device capable of raising and lowering the work device, The work machine according to claim 9, wherein the control device acquires a different third map in the first control according to the content of the work performed by the work machine.

11. The aircraft and, A protective mechanism for the cockpit provided in the aforementioned aircraft, Equipped with, The first operating tool includes an internal operating tool provided inside the protective mechanism and an external operating tool provided outside the protective mechanism. The work machine according to claim 9, wherein the control device acquires a third map different from the one acquired when the internal operating tool is operated in the first control.

12. The control device calculates a deviation value of the flow rate characteristics of a control valve of the upper limit, which has a higher flow rate of hydraulic fluid than the standard flow rate characteristics that show the relationship between the current value output to a standard control valve, which is a predetermined control valve, and the flow rate of hydraulic fluid, corrects the current value output to the control valve using the deviation value, and outputs the corrected current value as a control current to the control valve, as described in claim 9.

13. The device includes a second operating tool for manipulating the aforementioned limit value, The work machine according to any one of claims 3 to 12, wherein the second operating tool is assigned the limit value according to the amount of operation.

14. The aforementioned drive device has a drive member driven by the hydraulic actuator and is a lifting device capable of raising and lowering the work device. The hydraulic actuator is a lift cylinder, The work machine according to claim 13, wherein the drive member is a lift arm driven by the drive of the lift cylinder.

15. The control device is When raising the lift arm in response to the operation of the first operating tool, the first control, or the first and second control, is performed. The work machine according to claim 14, wherein the first control and the second control are not performed when the lift arm is lowered in response to the operation of the first operating tool.

16. The work machine according to claim 15, wherein the control device increases the maximum flow rate as the limit value increases and decreases the maximum flow rate as the limit value decreases in the second control.

17. A control method for a work machine comprising: a drive device having a hydraulic actuator operated by hydraulic fluid; a control device for changing the drive speed of the drive device after the start of operation; and a first operating tool for operating the drive device, wherein the operation of the drive device by the first operating tool is restricted as the limit value for restricting the operation of the drive device decreases, and the operation of the drive device by the first operating tool is not restricted as the limit value increases, If the limit value restricting the operation of the drive device is greater than or equal to a predetermined threshold, the control device performs a first control in which it changes the drive speed of the drive device after it starts to drive according to the limit value, the first step of which the first control increases the drive speed of the drive device after it starts to drive as the limit value increases, and decreases the drive speed of the drive device after it starts to drive as the limit value decreases. If the limit value is less than the threshold, the control device, in addition to the first control, performs a second control in which it changes the maximum flow rate of the hydraulic fluid that operates the hydraulic actuator according to the limit value, wherein the second control increases the maximum flow rate as the limit value increases and decreases the maximum flow rate as the limit value decreases. A control method for a work machine that includes this.

18. The method for controlling a work machine according to claim 17, wherein in the first control of the first step, the smaller the deviation between the actual position, which is the actual position of the drive member, and the target value of the position of the drive member, the lower the drive speed.

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