Operating vehicles and their control methods

Abstract

A work vehicle includes: a power source; a travel device having a clutch between the power source and a transmission capable of adjusting engagement, and traveling based on power transmitted from the power source; a work machine; a drive device that actuates the work machine based on power transmitted from the power source; and a control device that outputs control commands for controlling the engagement of the clutch based on the state of the work machine.

Description

Technical Field

[0001] This disclosure relates to operating vehicles and methods for controlling operating vehicles. Background Technology

[0002] In the technical field of work vehicles, wheeled loaders that automatically excavate objects, such as those disclosed in Patent Document 1, are known.

[0003] Patent Document 1: International Publication No. 2015 / 004809 Summary of the Invention

[0004] When a wheel loader is excavating an object, it moves towards the object and inserts at least a portion of the machine into it. Due to the forward movement of the wheel loader, for example, the machine may be pressed forcefully against the object, potentially causing the wheel loader to malfunction. If this malfunction occurs, the wheel loader's operational efficiency will decrease.

[0005] The purpose of this disclosure is to enable working vehicles to detach from a state of immobility during the excavation of an object.

[0006] According to this disclosure, a work vehicle is provided, comprising: a power source; a travel device having a clutch between the power source and a transmission capable of adjusting engagement, and traveling based on power transmitted from the power source; a work machine; a drive device that drives the work machine based on power transmitted from the power source; and a control device that outputs control commands for controlling the engagement of the clutch based on the state of the work machine.

[0007] According to this disclosure, it is possible to detach the working vehicle from a state of immobility during the excavation of an object. Attached Figure Description

[0008] Figure 1 This is a side view showing the work vehicle involved in the implementation method.

[0009] Figure 2 This is a diagram showing the machine and drive device involved in the implementation method.

[0010] Figure 3 This is a structural diagram showing the work vehicle involved in the implementation method.

[0011] Figure 4 This is a functional block diagram illustrating the control system of the work vehicle involved in the implementation method.

[0012] Figure 5 This is a block diagram illustrating the control device of the work vehicle involved in the implementation method.

[0013] Figure 6This is a diagram used to illustrate the excavation operation of the work vehicle involved in the implementation method.

[0014] Figure 7 This is a timing diagram illustrating the control method for the work vehicle involved in the implementation method.

[0015] Figure 8 This is a flowchart illustrating the control method for the work vehicle involved in the implementation method.

[0016] Figure 9 This is a flowchart illustrating the control method for the work vehicle involved in the implementation method.

[0017] Figure 10 This is a flowchart illustrating the control method for the work vehicle involved in the implementation method.

[0018] Figure 11 This is a diagram used to illustrate the automatic bucket collection cycle table involved in the implementation method. Detailed Implementation

[0019] The embodiments of this disclosure will now be described with reference to the accompanying drawings, but this disclosure is not limited to these embodiments. The constituent elements of the embodiments described below can be appropriately combined. Furthermore, there are cases where some constituent elements are not used.

[0020] In this implementation, a local coordinate system is established for the work vehicle 1, and the positional relationships of each part are explained with reference to this local coordinate system. In the local coordinate system, the direction extending left-right (vehicle width direction) from the perspective of the operator riding in the work vehicle 1 is defined as the X-axis, the direction extending forward-backward along the work vehicle 1 is defined as the Y-axis, and the direction extending up-down along the work vehicle 1 is defined as the Z-axis. The +X direction is to the right, and the -X direction is to the left. The +Y direction is forward, and the -Y direction is backward. The +Z direction is upward, and the -Z direction is downward.

[0021] [Wheel Loader]

[0022] Figure 1 This is a side view showing the work vehicle 1 according to the embodiment. In the embodiment, the work vehicle 1 is a wheel loader. In the embodiment, the work vehicle 1 may be referred to as wheel loader 1.

[0023] like Figure 1 As shown, the wheel loader 1 includes: a body 2, an articulated mechanism 3, a cab 4, a running gear 5, a work machine 6, and a drive unit 7. The wheel loader 1 travels on the work site via the running gear 5. The wheel loader 1 uses the work machine 6 to perform tasks on the work site.

[0024] The vehicle body 2 supports the work machine 6. The vehicle body 2 includes a front part 2F and a rear part 2R. The front part 2F is positioned forward of the rear part 2R. The front part 2F and the rear part 2R are connected by a hinge mechanism 3. The hinge mechanism 3 includes a hinge cylinder 8. The hinge cylinder 8 is a hydraulic cylinder. The hinge cylinder 8 connects the front part 2F and the rear part 2R. By extending and retracting the hinge cylinder 8, the front part 2F bends to the left or right relative to the rear part 2R. By bending the front part 2F relative to the rear part 2R, the travel direction of the wheel loader 1 can be adjusted.

[0025] The cockpit 4 is supported on the vehicle body 2. In this embodiment, the cockpit 4 is located on the upper part of the rear 2R of the vehicle body. Inside the cockpit 4 is a driver's seat 9 and a control lever 10. The operator sits in the driver's seat 9. The control lever 10 is operated by the operator. The control lever 10 is located near the driver's seat 9.

[0026] The traveling device 5 travels on the ground GR at the work site. The traveling device 5 supports the vehicle body 2. The traveling device 5 includes wheels 28. The wheels 28 include: a front wheel 28F mounted on the front 2F of the vehicle body, and a rear wheel 28R mounted on the rear 2R of the vehicle body. The wheels 28 are in contact with the ground GR. The wheel loader 1 travels by rotating the wheels 28.

[0027] In this embodiment, the X-axis is parallel to the rotation axis CXf of the front wheel 28F. The Z-axis is orthogonal to the contact surface of the front wheel 28F at the ground contact point GR. When the wheel loader 1 is traveling in a straight line, the rotation axis CXf of the front wheel 28F is parallel to the rotation axis CXr of the rear wheel 28R.

[0028] The work machine 6 is used to perform operations. The operations performed by the work machine 6 can include excavation, loading, transportation, and snow removal. In one embodiment, the work machine 6 excavates the object ET. The object ET can be a hill situated on the ground GR.

[0029] Figure 2 This diagram illustrates the work machine 6 and drive device 7 according to the embodiment. Figure 1 and Figure 2 As shown, the work machine 6 is connected to the front 2F of the vehicle body. The work machine 6 includes a boom 12 and a bucket 13. Furthermore, the work machine 6 includes a crank 14 and a bucket connecting rod 15. A drive unit 7 is used to operate the work machine 6. The drive unit 7 includes a boom cylinder 18 and a bucket cylinder 19. The boom cylinder 18 is a hydraulic cylinder. The bucket cylinder 19 is a hydraulic cylinder.

[0030] The base of the boom 12 is rotatably connected to the front part 2F of the vehicle body. The boom 12 rotates about the rotation axis AXa relative to the front part 2F of the vehicle body. A bracket 16 is fixed to the middle part of the boom 12.

[0031] Bucket 13 is a working component used for digging up an object ET. Bucket 13 is used to hold the excavated object. Bucket 13 has a bottom plate portion 13B. The front end of the bottom plate portion 13B is provided with a cutting edge 13T. The cutting edge 13T extends in the left-right direction. In addition, bucket 13 has an opening portion 13M.

[0032] The base end of the bucket 13 is rotatably connected to the front end of the boom 12. The bucket 13 rotates relative to the boom 12 about the rotation axis AXb. The bucket 13 is positioned in front of the front wheel 28F. A bracket 17 is fixed to a portion of the bucket 13.

[0033] The middle part of the crank 14 is rotatably connected to the support 16 of the boom 12. The crank 14 rotates about the rotation axis AXc relative to the support 16 of the boom 12.

[0034] The base end of the bucket connecting rod 15 is rotatably connected to the lower end of the crank 14. The bucket connecting rod 15 rotates relative to the crank 14 about the rotation axis AXd. The front end of the bucket connecting rod 15 is rotatably connected to the bracket 17 of the bucket 13. The bucket connecting rod 15 rotates relative to the bracket 17 of the bucket 13 about the rotation axis AXe. The crank 14 is connected to the bucket 13 via the bucket connecting rod 15.

[0035] Boom cylinder 18 is used to move boom 12. The base end of boom cylinder 18 is connected to the front part 2F of the vehicle body. The base end of boom cylinder 18 rotates relative to the front part 2F of the vehicle body about the rotation axis AXf. Boom 12 is fixed to bracket 11. The front end of boom cylinder 18 is connected to bracket 11 of boom 12. Boom 12 rotates relative to boom cylinder 18 about the rotation axis AXg.

[0036] Bucket cylinder 19 is used to actuate bucket 13. The base end of bucket cylinder 19 is connected to the front part 2F of the vehicle body. The front end of bucket cylinder 19 is connected to the upper end of crank 14. Crank 14 rotates relative to bucket cylinder 19 about the rotation axis AXh.

[0037] [The operation of the work machine]

[0038] The excavator 6 is a frontloading type excavator with the bucket 13 opening 13M facing forward during excavation operations. The boom 12 is raised or lowered by the extension and retraction of the boom cylinder 18. The bucket 13 is retracted or tipped by the extension and retraction of the bucket cylinder 19. The excavated material scooped up by the blade tip 13T enters the inside of the bucket 13 through the opening 13M.

[0039] The lifting motion of boom 12 refers to the movement of boom 12 around the rotation axis AXa, causing the front end of boom 12 to move away from the ground GR. The lowering motion of boom 12 refers to the movement of boom 12 around the rotation axis AXa, causing the front end of boom 12 to move closer to the ground GR.

[0040] If boom cylinder 18 extends, boom 12 will rise. If boom cylinder 18 retracts, boom 12 will lower.

[0041] The bucket retraction action of the bucket 13 refers to the action of rotating the bucket 13 around the rotation axis AXb, so that the opening 13M of the bucket 13 faces upward and the cutting edge 13T moves away from the ground GR. The bucket tipping action of the bucket 13 refers to the action of rotating the bucket 13 around the rotation axis AXb, so that the opening 13M of the bucket 13 faces downward and the cutting edge 13T moves closer to the ground GR.

[0042] If the bucket cylinder 19 extends, the crank 14 rotates such that its upper end moves forward and its lower end moves backward. If the lower end of the crank 14 moves backward, the bucket 13 retracts backward via the bucket connecting rod 15, thus performing a bucket retraction action. If the bucket cylinder 19 shortens, the crank 14 rotates such that its upper end moves backward and its lower end moves forward. If the lower end of the crank 14 moves forward, the bucket 13 is pushed forward by the bucket connecting rod 15, thus performing a bucket tipping action.

[0043] By retracting the bucket 13, the excavated material is scooped up by the bucket 13 and held in the bucket 13. By tipping the bucket 13, the excavated material held in the bucket 13 is discharged from the bucket 13.

[0044] [Structure of the work vehicle]

[0045] Figure 3 This is a structural diagram showing the wheeled loader 1 according to the implementation method. For example... Figure 3 As shown, the wheel loader 1 includes: a power source 20, a power take-off (PTO) device 21, a travel device 5, a drive device 7, an operating lever 10, and a control device 50.

[0046] The power source 20 is, for example, a diesel engine. The power source 20 is used to generate power.

[0047] The power output device 21 is connected to the power source 20. The power output device 21 distributes power from the power source 20 to the driving unit 5 and the drive unit 7. At least a portion of the power generated by the power source 20 is transmitted to the driving unit 5 via the power output device 21. At least a portion of the power generated by the power source 20 is transmitted to the drive unit 7 via the power output device 21.

[0048] The drive unit 7 operates the work machine 6 based on power transmitted from the power source 20 via the power output device 21. The drive unit 7 includes: a hydraulic pump 22, a boom control valve 23, a bucket control valve 24, a boom cylinder 18, and a bucket cylinder 19.

[0049] Hydraulic pump 22 is connected to power take-off unit 21. Hydraulic pump 22 discharges hydraulic oil based on power transmitted from power source 20. At least a portion of the hydraulic oil discharged from hydraulic pump 22 is supplied to boom cylinder 18 via boom control valve 23. At least a portion of the hydraulic oil discharged from hydraulic pump 22 is supplied to bucket cylinder 19 via bucket control valve 24.

[0050] The boom control valve 23 controls the direction and flow rate of the hydraulic oil supplied from the hydraulic pump 22 to the boom cylinder 18. By controlling the direction of the hydraulic oil supplied to the boom cylinder 18, the boom cylinder 18 extends and retracts, causing the boom 12 to rise or fall. By controlling the flow rate of the hydraulic oil supplied to the boom cylinder 18, the boom cylinder speed, which represents the extension and retraction speed of the boom cylinder 18, is controlled, thereby controlling the operating speed of the boom 12. The operating speed of the boom 12 includes: the angular velocity of the boom 12 about the rotation axis AXa when the boom 12 is rising, and the angular velocity of the boom 12 about the rotation axis AXa when the boom 12 is falling.

[0051] The bucket control valve 24 controls the direction and flow rate of the hydraulic oil supplied from the hydraulic pump 22 to the bucket cylinder 19. By controlling the direction of the hydraulic oil supplied to the bucket cylinder 19, the bucket cylinder 19 extends and retracts, and the bucket 13 retracts or tilts. By controlling the flow rate of the hydraulic oil supplied to the bucket cylinder 19, the bucket cylinder speed, which represents the extension and retraction speed of the bucket cylinder 19, is controlled, thereby controlling the operating speed of the bucket 13. The operating speed of the bucket 13 includes: the angular velocity of the bucket 13 centered on the rotation axis AXb when the bucket 13 retracts, and the angular velocity of the bucket 13 centered on the rotation axis AXb when the bucket 13 tilts.

[0052] The driving device 5 is driven by power transmitted from the power source 20 via the power output device 21. The driving device 5 includes a clutch 25, a torque converter 26, a transmission 27, and wheels 28. Power generated by the power source 20 is transmitted to the wheels 28 via the clutch 25, torque converter 26, and transmission 27. The power generated by the power source 20 is transmitted to the wheels 28, causing the wheels 28 to rotate, thereby driving the driving device 5.

[0053] Clutch 25 is disposed between power source 20 and transmission 27. Clutch 25 is connected to power take-off unit 21. In one embodiment, clutch 25 is disposed between power take-off unit 21 and torque converter 26. Clutch 25 is a wet multi-plate hydraulic clutch capable of adjusting the engagement degree between the input shaft side and the output shaft side. Clutch 25 includes input-side components and output-side components.

[0054] The engagement degree of clutch 25 varies depending on the clutch pressure applied to clutch 25. Clutch pressure refers to the pressure of the hydraulic oil applied to the input and output components of clutch 25. By changing the engagement degree of clutch 25, the power transmitted from power take-off unit 21 to torque converter 26 changes.

[0055] The engagement degree of clutch 25 can be adjusted between 0% and 100%. At the minimum clutch pressure, the engagement degree is 0%. The higher the clutch pressure, the greater the engagement degree. At the maximum clutch pressure, the engagement degree is 100%. A 0% engagement degree indicates a disengaged state where the input and output components are not engaged, and the power transmitted from the power take-off device 21 to the driving device 5 is not transmitted to the torque converter 26. A 100% engagement degree indicates a fully engaged state where the input and output components are engaged, and all the power transmitted from the power take-off device 21 to the driving device 5 is transmitted to the torque converter 26. A partial engagement state where the engagement degree is greater than 0% and less than 100% indicates a partially engaged state where the input and output components slide relative to each other, allowing some of the power from the power take-off device 21 to be transmitted to the torque converter 26. By adjusting the engagement degree of the clutch 25, the power transmission rate from the power output device 21 to the hydraulic torque converter 26 can be adjusted.

[0056] The torque converter 26 is positioned between the clutch 25 and the transmission 27.

[0057] The transmission 27 has multiple speed clutches and multiple reversing clutches. By selectively engaging or disengaging each of the multiple speed clutches, the gears of the transmission 27 can be changed. By selectively engaging or disengaging the multiple reversing clutches, the forward or reverse movement of the driving device 5 can be switched.

[0058] The control lever 10 includes a boom control lever 29, a bucket control lever 30, and a gear shift lever 31. The operator operates the boom control lever 29 to move the boom 12. The operator operates the bucket control lever 30 to move the bucket 13. The operator operates the gear shift lever 31 to change the gear position of the transmission 27.

[0059] If the boom operating lever 29 is operated, a boom operation signal is sent from the boom operating lever 29 to the control device 50. Based on the boom operation signal from the boom operating lever 29, the control device 50 controls the boom control valve 23. By controlling the boom control valve 23, the boom cylinder 18 extends or retracts, thereby actuating the boom 12. If the bucket operating lever 30 is operated, a bucket operation signal is sent from the bucket operating lever 30 to the control device 50. Based on the bucket operation signal from the bucket operating lever 30, the control device 50 controls the bucket control valve 24. By controlling the bucket control valve 24, the bucket cylinder 19 extends or retracts, thereby actuating the bucket 13.

[0060] If the gear lever 31 is operated, a gear position operation signal is sent from the gear lever 31 to the control device 50. The control device 50 changes the gear position of the transmission 27 based on the gear position operation signal from the gear lever 31.

[0061] The boom operating lever 29 is equipped with a forced downshift switch 32. The forced downshift switch 32 is used to downshift the gear of the transmission 27 when the gear lever 31 is not operated. A lower gear refers to a gear with a larger gear ratio.

[0062] If the operator operates the forced downshift switch 32, a forced downshift operation signal is output from the forced downshift switch 32 to the control device 50. Based on the forced downshift operation signal from the forced downshift switch 32, the control device 50 changes the gear of the transmission 27 at the moment the forced downshift operation signal is received to a lower gear. For example, if the gear is in second gear at the moment the forced downshift operation signal is received, the control device 50 changes the gear of the transmission 27 from second gear to a first gear, which is lower than second gear.

[0063] In addition, the wheel loader 1 has: boom angle sensor 33, bucket angle sensor 34, pressure sensor 35 and vehicle speed sensor 36.

[0064] The boom angle sensor 33 is used to detect the boom angle α, which represents the angle of the boom 12. The boom angle sensor 33 is used to detect the boom angle α relative to the vehicle body 2 in a local coordinate system. As an example of the boom angle sensor 33, a potentiometer disposed at the connection between the front part 2F of the vehicle body and the boom 12 can be shown. Figure 2As shown, the boom angle α is the angle between lines L1 and L2, where line L1 connects the rotation axes AXa and AXb, and line L2 passes through the rotation axis AXa and is parallel to the line connecting the rotation axes CXf and CXr. In this embodiment, when the boom 12 is tilted relative to line L2 toward the ground GR side, the boom angle α is negative. As the boom 12 rises, the boom angle α increases. The detection data from the boom angle sensor 33 is output to the control device 50. The control device 50 can calculate the boom angular velocity αv, representing the angular velocity of the boom 12 centered on the rotation axis AXa, based on the detection data from the boom angle sensor 33. That is, the boom angle sensor 33 can function as an angular velocity sensor for detecting the boom angular velocity αv. Furthermore, the boom angle sensor 33 can also be a stroke sensor for detecting the stroke of the boom cylinder 18.

[0065] The bucket angle sensor 34 is used to detect the bucket angle β, which represents the angle of the bucket 13. The bucket angle sensor 34 is also used to detect the crank angle, which represents the angle of the crank 14 relative to the boom 12 in the local coordinate system. As an example of the bucket angle sensor 34, a potentiometer disposed at the connection between the boom 12 and the crank 14 can be shown. The bucket angle sensor 34 is used to detect the angle between the boom 12 and the crank 14, i.e., the crank angle. The crank angle corresponds one-to-one with the bucket angle β. By detecting the crank angle, the bucket angle β can be detected. Figure 2 As shown, the bucket angle β is the angle between lines L3 and L4, where line L3 passes through the rotation axis AXb and is parallel to the bottom surface 132 of the bucket 13, and line L4 passes through the rotation axis AXb and is parallel to line L2. In this embodiment, the bucket angle β is negative when line L3 is tilted relative to line L4 toward the ground GR. The bucket angle β increases when the bucket 13 retracts. The detection data from the bucket angle sensor 34 is output to the control device 50. The control device 50 can calculate the bucket angular velocity βv, representing the angular velocity of the bucket 13 centered on the rotation axis AXb, based on the detection data from the bucket angle sensor 34. That is, the bucket angle sensor 34 can function as an angular velocity sensor for detecting the bucket angular velocity βv. Furthermore, the bucket angle sensor 34 can also be a stroke sensor for detecting the stroke of the bucket cylinder 19.

[0066] Pressure sensor 35 is used to detect the pressure of the hydraulic oil in boom cylinder 18. The pressure of the hydraulic oil in boom cylinder 18 includes the cylinder bottom pressure Pb of boom cylinder 18. The detection data of pressure sensor 35 is output to control device 50.

[0067] The vehicle speed sensor 36 is used to detect the vehicle speed Vc, which represents the travel speed of the driving device 5. The detection data of the vehicle speed sensor 36 is output to the control device 50.

[0068] In addition, the wheel loader 1 is equipped with an interface device 37. The interface device 37 is located inside the cab 4.

[0069] The interface device 37 includes an automatic digging start switch 38, a sound output unit 39, and a display unit 40. The sound output unit 39 outputs, for example, a warning sound. The display unit 40 is used to display display data related to the status or control of the working machine 6.

[0070] [Control System]

[0071] Figure 4 This is a functional block diagram showing the control system 60 of the wheel loader 1 according to the embodiment. The control system 60 includes: a control device 50, a control lever 10, a travel device 5, a drive device 7, a boom angle sensor 33, a bucket angle sensor 34, a pressure sensor 35, a vehicle speed sensor 36, and an interface device 37.

[0072] The control unit 50 includes a computer system. The control unit 50 outputs control commands for controlling the wheel loader 1.

[0073] Figure 5 This is a block diagram illustrating the control device 50 of the wheel loader 1 according to the embodiment. (As shown) Figure 5 As shown, the control device 50 includes a processor 51, main memory 52, a memory 53, and an interface 54. The processor 51 executes a computer program to process the actions of the workstation 6. Examples of the processor 51 include a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). Examples of the main memory 52 include non-volatile memory or volatile memory. Examples of non-volatile memory include ROM (Read Only Memory). Examples of volatile memory include RAM (Random Access Memory). The memory 53 is a non-transitory tangible storage medium. Examples of memory 53 include magnetic disks, magneto-optical disks, and semiconductor memory. The memory 53 can be an internal medium directly connected to the bus of the control device 50, or an external medium connected to the control device 50 via the interface 54 or a communication line. The memory 53 stores the computer program used to control the workstation 6.

[0074] like Figure 4 As shown, the control device 50 communicates with the operating lever 10, the travel device 5, the drive device 7, the boom angle sensor 33, the bucket angle sensor 34, the pressure sensor 35, the vehicle speed sensor 36, and the interface device 37.

[0075] The control device 50 outputs control commands to the clutch 25 for controlling the clutch 25. Based on the state of the machine 6, the control device 50 outputs control commands for controlling the engagement degree of the clutch 25. The state of the machine 6 includes the operating speed of the machine 6. The operating speed of the machine 6 includes the bucket angular velocity βv, which represents the angular velocity of the bucket 13. The bucket angular velocity βv is detected by the bucket angle sensor 34. In this embodiment, the control device 50 outputs control commands for controlling the engagement degree of the clutch 25 based on the detection data from the bucket angle sensor 34.

[0076] In this embodiment, the control command output from the control device 50 to control the engagement degree of the clutch 25 can be referred to as a clutch command.

[0077] The control device 50 outputs control commands to the transmission 27 for controlling the transmission 27. The control device 50 outputs control commands for changing the gear position of the transmission 27. The control device 50 outputs control commands to make the driving device 5 move forward or backward.

[0078] In this embodiment, the control command output from the control device 50 for changing the gear position of the transmission 27 can be called a gear shift command. Furthermore, the control command output from the control device 50 for moving the driving device 5 forward can be called a forward command.

[0079] The control device 50 outputs control commands for controlling the work machine 6 to at least one of the boom control valve 23 and the bucket control valve 24. The control device 50 outputs control commands to the boom control valve 23 to cause the boom 12 to rise or fall at a predetermined boom angular velocity αv. The control device 50 outputs control commands to the bucket control valve 24 to cause the bucket 13 to retract or tip at a predetermined bucket angular velocity βv.

[0080] The control device 50 controls the sound output unit 39 and the display unit 40 of the interface device 37 respectively.

[0081] [Automatic Excavation Control]

[0082] In this embodiment, the wheel loader 1 uses the work machine 6 to perform excavation work on the object ET in either manual or automatic digging mode. In manual operation, the operator operates at least one of the boom control lever 29 and the bucket control lever 30 to move the work machine 6. In automatic digging mode, the work machine 6 operates based on control commands output from the control device 50, rather than based on the operation of the boom control lever 29 and the bucket control lever 30. The automatic digging mode reduces the operator's workload during digging operations.

[0083] In automatic excavation mode, the control device 50 performs automatic excavation control on the work machine 6. The control commands output from the control device 50 in automatic excavation control include: an automatic lifting command to cause the boom 12 to lift and lower, and an automatic bucket retraction command to cause the bucket 13 to retract.

[0084] In the implementation, the lifting action of the boom 12 based on the automatic lifting command can be referred to as the automatic lifting action, and the bucket 13 based on the automatic bucket folding command can be referred to as the automatic bucket folding action.

[0085] Figure 6 This is a diagram illustrating the digging operation of the wheeled loader 1 according to the embodiment. (See diagram below.) Figure 6 As shown in (A), during excavation operations, the wheel loader 1 moves towards the object ET. As the wheel loader 1 moves forward, the attitude of the work machine 6 is adjusted so that the object ET can be excavated using the bucket 13. In this embodiment, the attitude of the work machine 6 is adjusted such that the cutting edge 13T of the bucket 13 approaches or contacts the ground GR. By moving the wheel loader 1 forward with the cutting edge 13T approaching or contacting the ground GR, the cutting edge 13T of the bucket 13 is inserted into the lower end of the object ET.

[0086] When automatic digging control is initiated, the operator operates the automatic digging start switch 38 on the interface device 37. If the operator operates the automatic digging start switch 38, an automatic digging start signal is sent from the automatic digging start switch 38 to the control device 50. After receiving the automatic digging start signal from the automatic digging start switch 38, the control device 50 initiates automatic digging control. The control device 50 displays a flag indicating that automatic digging control is in progress on the display unit 40.

[0087] like Figure 6 As shown in (B), in automatic excavation control, after the cutting edge 13T of the bucket 13 is inserted into the object ET, the control device 50 causes the bucket 13 to retract. Thus, the object ET is excavated by the bucket 13. The bucket 13 scoops up the excavated material. The excavated material is held in the bucket 13.

[0088] In automatic excavation control, when the bucket 13, which is inserted into the object ET, performs an automatic bucket retraction action, the control device 50 starts the automatic bucket retraction action based on the vehicle speed Vc of the travel device 5 and the cylinder bottom pressure Pb of the boom cylinder 18. Furthermore, the control device 50 terminates the automatic bucket retraction action based on the vehicle speed Vc of the travel device 5 and the increase in cylinder bottom pressure Pb since the start of the automatic bucket retraction action. That is, in automatic excavation control, the control device 50 starts the automatic bucket retraction action based on the detection data from the speed sensor 36 and the pressure sensor 35. The control device 50 terminates the automatic bucket retraction action based on the detection data from the speed sensor 36 and the increase in the pressure sensor 35 since the start of the automatic bucket retraction action.

[0089] Furthermore, if the operator operates the forced downshift switch 32 in the automatic digging control, the control device 50 will shift the gear of the transmission 27 to a lower gear. Because the transmission 27 is shifted to a lower gear, the traction force of the wheel loader 1 increases. Due to the increased traction force of the wheel loader 1, the digging efficiency of the wheel loader 1 is improved.

[0090] As described above, in automatic excavation control, the wheel loader 1 moves towards the object ET and inserts its bucket 13 into the object. Due to the forward movement of the wheel loader 1, for example, the bucket 13 is pressed forcefully against the object ET, which may cause the wheel loader 1 to malfunction. That is, if the bucket 13 is pressed forcefully against the object ET, the work machine 6 or the travel device 5 may malfunction. Malfunctions of the work machine 6 in automatic excavation control include the bucket 13 failing to automatically retract. Malfunctions of the travel device 5 in automatic excavation control include the forward wheels 28 failing to rotate. If the wheel loader 1 malfunctions, its operating efficiency will decrease.

[0091] In this implementation, during automatic excavation control, the control device 50 outputs control commands to control the engagement degree of the clutch 25 based on the state of the excavator 6. The state of the excavator 6 includes its operating speed. The operating speed of the excavator 6 includes the bucket angular velocity βv. The bucket angular velocity βv is detected by the bucket angle sensor 34. Based on the detection data from the bucket angle sensor 34, if the control device 50 determines that the bucket 13 and wheels 28 cannot operate, it outputs control commands to reduce the engagement degree of the clutch 25.

[0092] When the wheel loader 1 moves toward the object ET to excavate it, the engagement of the clutch 25 is set to a high value (e.g., 100%). If the clutch 25 is kept at a high engagement value when the bucket 13 is pressed hard against the object ET and the bucket 13 and wheels 28 cannot move, the bucket 13 will remain pressed hard against the object ET.

[0093] In this implementation, when the wheel loader 1 cannot operate in the automatic excavation control, the engagement degree of the clutch 25 is reduced. Because the engagement degree of the clutch 25 is reduced, the power transmitted from the power take-off unit 21 to the wheels 28 is reduced. Consequently, the force exerted by the workpiece 6 on the object ET is reduced. Furthermore, because the power transmitted from the power take-off unit 21 to the wheels 28 is reduced, the traction force of the wheel loader 1 is reduced.

[0094] The power output device 21 distributes power from the power source 20 to the travel unit 5 and the drive unit 7. Because the engagement of the clutch 25 decreases, the power distributed to the travel unit 5 decreases, while the power distributed to the drive unit 7 increases. That is, the power required to automatically retract the bucket 13 increases. Since the force of the bucket 13 pressing against the object ET decreases, the increased power enables the bucket 13 to automatically retract.

[0095] Figure 7 This is a timing diagram illustrating the control method of the wheel loader 1 according to the implementation method.

[0096] Figure 7 The first graph shown in (A) illustrates the relationship between the time [sec.] from the start of automatic excavation control and the vehicle speed Vc [km / h] of the driving device 5. The vehicle speed Vc is detected by the vehicle speed sensor 36.

[0097] Figure 7 The second graph shown in (B) illustrates the relationship between the time [sec.] from the start of automatic digging control and the command value [%] of the automatic lifting command output from control device 50. A state where the automatic lifting command command value is 0 [%] indicates that the boom control valve 23, used to lift the boom 12, is fully closed. If the command value of the automatic lifting command increases from 0 [%], the opening of the boom control valve 23 also increases. A state where the automatic lifting command command value is 100 [%] indicates that the boom control valve 23, used to lift the boom 12, is fully open. A state where the automatic lifting command command value is 0 [%] includes a state where the automatic lifting command is not output from control device 50. A state where the automatic lifting command command value is greater than 0 [%] includes a state where the automatic lifting command is output from control device 50.

[0098] Figure 7 The third graph shown in (C) illustrates the relationship between the time [sec.] from the start of automatic excavation control and the boom angle α [deg]. The boom angle α is detected by the boom angle sensor 33.

[0099] Figure 7 The fourth graph shown in (D) illustrates the relationship between the time [sec.] from the start of automatic digging control and the bottom pressure Pb [MPa] of the boom cylinder 18. The bottom pressure Pb is detected by pressure sensor 35.

[0100] Figure 7 The fifth graph (E) shows the relationship between the time [sec.] from the start of automatic digging control and the command value [%] of the automatic bucket retraction command output from control device 50. A state where the automatic bucket retraction command value is 0 [%] indicates that the bucket control valve 24, which causes the bucket 13 to retract, is fully closed. If the command value of the automatic bucket retraction command increases from 0 [%], the opening of the bucket control valve 24 also increases. A state where the automatic bucket retraction command value is 100 [%] indicates that the bucket control valve 24, which causes the bucket 13 to retract, is fully open. A state where the automatic bucket retraction command value is 0 [%] includes a state where the automatic bucket retraction command is not output from control device 50. A state where the automatic bucket retraction command value is greater than 0 [%] includes a state where the automatic bucket retraction command is output from control device 50.

[0101] Figure 7 The sixth graph shown in (F) illustrates the relationship between the time [sec.] from the start of automatic digging control and the bucket angle β. The bucket angle β is detected by the bucket angle sensor 34.

[0102] Figure 7 The seventh graph shown in (G) illustrates the relationship between the time [sec.] from the start of automatic digging control and the bucket angular velocity βv. The bucket angular velocity βv is detected by the bucket angle sensor 34.

[0103] Figure 7The eighth graph (H) shows the relationship between the time [sec.] from the start of automatic excavation control and the command value [%] of the clutch command output from control device 50 to control the engagement degree of clutch 25. A clutch command value of 0% indicates that the clutch 25 is 0% engaged, i.e., clutch 25 is disengaged. If the clutch command value increases from 0%, the engagement degree of clutch 25 also increases. A clutch command value greater than 0% and less than 100% indicates that the clutch 25 is partially engaged, with the engagement degree greater than 0% and less than 100%. A clutch command value of 100% indicates that the clutch 25 is fully engaged, with the engagement degree of clutch 25 at 100%.

[0104] If the operator activates the automatic digging start switch 38, automatic digging control will begin at time t0. For example... Figure 6 As shown in (A), the attitude of the work machine 6 is adjusted such that the bucket 13 is close to or in contact with the ground GR. The wheel loader 1 moves toward the object ET at a vehicle speed Vo.

[0105] At time t1, bucket 13 is inserted into object ET. If bucket 13 is inserted into object ET, the vehicle speed Vc decreases and the cylinder bottom pressure Pb increases.

[0106] At time t2, following time t1, the automatic lifting action begins. At time t2, when the preset automatic lifting start conditions are met, the control device 50 outputs an automatic lifting command to cause the boom 12 to perform the automatic lifting action. The automatic lifting start conditions include: the vehicle speed Vc is less than a preset vehicle speed judgment value d, and the cylinder bottom pressure Pb is greater than a preset pressure judgment value b. As an example, the vehicle speed judgment value d is 3 [km / h], and the pressure judgment value b is 5 [MPa]. The wheels 28 are loaded due to the lifting action of the boom 12, preventing wheel slippage.

[0107] Furthermore, in the implementation, at time t3 after time t2, the command value of the automatic rise / fall command is reduced.

[0108] At time t4, following time t3, the automatic bucket retraction action begins. At time t4, when the preset automatic bucket retraction start conditions are met, the control device 50 outputs an automatic bucket retraction command to cause the bucket 13 to automatically retract. The automatic bucket retraction start conditions include: the vehicle speed Vc is less than a preset vehicle speed judgment value k, and the cylinder bottom pressure Pb is greater than a preset pressure judgment value j. As an example, the vehicle speed judgment value k is 1.45 [km / h], and the pressure judgment value j is 16 [MPa].

[0109] In this embodiment, after the automatic lifting action ends, the control device 50 begins the automatic bucket-retracting action. After stopping the output of the automatic lifting command, the control device 50 begins outputting the automatic bucket-retracting command.

[0110] The automatic bucket retraction action of bucket 13 increases both the bucket angle β and the bucket angular velocity βv. Furthermore, the automatic bucket retraction action of bucket 13 increases the cylinder bottom pressure Pb. During the automatic bucket retraction action, the vehicle speed Vc decreases. The automatic bucket retraction action of bucket 13 excavates a portion of the object ET, creating space in front of the wheels 28. Consequently, the vehicle speed Vc increases.

[0111] At time t5, after time t4, the automatic bucket retraction action ends. Control device 50 stops outputting the automatic bucket retraction command at time t5 when the preset automatic bucket retraction end conditions are met. The automatic bucket retraction end conditions include: the vehicle speed Vc is greater than a preset vehicle speed judgment value n, and the increase in cylinder bottom pressure Pb from time t4 when the automatic bucket retraction action begins is greater than a preset pressure judgment value m. As an example, the vehicle speed judgment value n is 1.3 [km / h], and the pressure judgment value m is 3 [MPa].

[0112] In this embodiment, after the automatic bucket-collecting action ends, the control device 50 begins the automatic lifting action. After stopping the output of the automatic bucket-collecting command, the control device 50 begins outputting the automatic lifting command.

[0113] At time t6, after time t5, the automatic bucket retraction start condition is met again. At time t6, when the automatic bucket retraction start condition is met, control device 50 stops outputting automatic lifting commands and starts outputting automatic lifting commands.

[0114] While outputting a forward command to move the traveling device 5 forward, the control device 50 also outputs automatic lifting and automatic bucket retraction commands by repeatedly performing automatic lifting and automatic bucket retraction actions.

[0115] Due to the forward movement of the wheel loader 1, for example, if the bucket 13 is forcefully pressed against the object ET, the wheel loader 1 may become unable to operate. That is, if the bucket 13 is forcefully pressed against the object ET, the bucket 13 may not be able to automatically retract, or the travel device 5 may not be able to move forward. For example, in Figure 7 During the period from time t6 to time t7, as shown, the bucket 13 became inoperable and the bucket angular velocity βv decreased, while the vehicle speed Vc approached 0. Furthermore, not only did the bucket 13 become inoperable, but the boom 12 also became inoperable, the boom angle α remained unchanged, and the cylinder bottom pressure Pb reached the relief pressure Pr.

[0116] In this implementation, when the bucket angular velocity βv is less than a preset speed judgment value s for a specified time ts or more, and the clutch control start condition is met, the control device 50 outputs a clutch command to reduce the engagement degree of the clutch 25. As an example, the speed judgment value s is 4 [deg / sec.], and the specified time ts is 0.5 [sec.].

[0117] exist Figure 7 In the example shown, clutch control to reduce the engagement degree of clutch 25 begins at time t7, after time t6. Control device 50 outputs a clutch command to reduce the engagement degree of clutch 25 at time t7 when the clutch control start condition is met.

[0118] In this implementation, the engagement degree of clutch 25 gradually decreases from time t7 to time t8, which follows time t7. As an example, the rate of decrease u of engagement degree per unit time is 0.18% per sec. Furthermore, the engagement degree of clutch 25 is controlled to be no lower than a preset minimum limit value w. As an example, the minimum limit value w is 1%.

[0119] By gradually reducing the engagement of clutch 25, the power distributed to drive unit 7 increases, and bucket 13 begins to move. Figure 7 In the example shown, at time t9 after time t8, bucket 13 begins to move, and the bucket angular velocity βv gradually increases. Bucket 13 is able to disengage from its inoperable state. Furthermore, the automatic bucket retraction action of bucket 13 causes a portion of the object ET to be excavated, creating space in front of wheel 28. As a result, the travel device 5 also begins to move, and the vehicle speed Vc begins to increase.

[0120] When the clutch control termination condition is met, the control device 50 outputs a clutch command, increasing the engagement degree of the clutch 25. The clutch control termination condition can be that a predetermined time has elapsed since the start of clutch control at time t7. Alternatively, the clutch control termination condition can be that the bucket angular velocity βv has been greater than a preset speed judgment value y for a predetermined time ty or more. As an example, the speed judgment value y is 1 [deg / sec.], and the predetermined time ty is 0.5 [sec.]. Furthermore, the clutch control termination condition can also be that the bucket angular velocity βv has increased to a value greater than 0 [deg / sec.]. Figure 7 In the example shown, clutch control ends at time t10, a predetermined time elapsed from time t7. Time t10 is after time t9. At time t10, the bucket angular velocity βv is greater than the speed judgment value s.

[0121] In this implementation, the engagement degree of clutch 25 gradually increases from time t10 to time t11 after time t10. As an example, the rate of increase v of the engagement degree per unit time is 0.18 [% / sec.]. Furthermore, the engagement degree of clutch 25 is controlled to not exceed a preset maximum limit value z. As an example, the maximum limit value z is the engagement degree of clutch 25 before the engagement degree decreases (the engagement degree at time t7).

[0122] [Control methods for work vehicles]

[0123] Figure 8 , Figure 9 ,and Figure 10 These are flowcharts illustrating the control method of the wheel loader 1 according to the implementation method.

[0124] In this implementation, the control device 50 defines multiple stages representing the state of automatic excavation control. As stages, the control device 50 defines stages 0 to 7.

[0125] Phase 0 represents the standby and end states of automatic digging control. Phase 1 represents the judgment state of the start condition of automatic digging control. Phase 2 represents the execution state of automatic lifting action. Phase 3 represents the state of waiting for the start of automatic lifting action. Phase 4 represents the execution state of automatic lifting action. Phase 5 represents the execution state of automatic bucket retraction action. Phase 6 represents the judgment state of the end condition of automatic bucket retraction and the judgment state of the start condition of clutch control. Phase 7 represents the execution state of automatic lifting action.

[0126] The control device 50 determines whether the wheel loader 1 is in automatic excavation control (step S1).

[0127] In step S1, if it is determined that the system is not in automatic digging control (step S1: No), the control device 50 determines whether the automatic digging mode has been activated. That is, the control device 50 determines whether the automatic digging mode is valid (step S2).

[0128] When the control device 50 receives an automatic digging start signal from the automatic digging start switch 38, it determines that the automatic digging mode has been activated.

[0129] In step S2, if it is determined that the automatic digging mode has been turned on (step S2: Yes), the control device 50 causes the display unit 40 of the interface device 37 to display a flag indicating that the automatic digging mode has been turned on (step S3).

[0130] After the display unit 40 displays the mark, the control device 50 determines whether the insertion conditions of the wheel loader 1 with the object ET are met (step S4).

[0131] The insertion condition refers to the condition where the wheel loader 1 moves forward and the bucket 13 approaches or contacts the ground GR. For example... Figure 6 As shown in (A), when automatic excavation control is executed, the attitude of the work machine 6 is adjusted such that the cutting edge 13T of the bucket 13 approaches or contacts the ground GR. The wheel loader 1 moves toward the object ET in the state after the attitude of the work machine 6 has been adjusted.

[0132] When the control device 50 has issued a forward command to the travel device 5, it can determine that the wheel loader 1 is moving forward. When the detection value of the boom angle sensor 33 is less than a preset angle judgment value 'a', the control device 50 can determine that the bucket 13 is approaching or contacting the ground GR. As an example, the angle judgment value 'a' is -30 degrees. Therefore, the control device 50 can determine whether the insertion conditions of the wheel loader 1 are met.

[0133] In step S4, if the insertion condition is determined to be met (step S4: yes), the control device 50 determines whether the forced downshift condition is met (step S5).

[0134] Forced downshifting conditions refer to the conditions where the transmission 27 is set to automatic transmission mode and the control device 50 is input with a forced downshifting command, or the transmission 27 is in first gear and the forced downshifting switch 32 is activated.

[0135] In step S5, if the forced downshift condition is met (step S5: Yes), the control device 50 changes the state of automatic digging control to stage 1 in order to start automatic digging control (step S6).

[0136] The control device 50 determines whether the termination condition of the automatic excavation control is met (step S7).

[0137] In the implementation, the termination condition of automatic digging control includes at least one of the following conditions: the automatic digging mode is turned off; a control command different from the forward command is output to the transmission 27; a predetermined time (e.g., 0.5 sec.) has elapsed after the bucket 13 reaches the bucket retraction limit position; the boom angle α is a predetermined angle (e.g., 0 degrees) or greater; the work machine 6 is locked; a malfunction occurs in the control system 60 associated with the work machine 6; the amount of operation of the boom control lever 29 for lowering the boom 12 is greater than a predetermined amount; and the amount of operation of the bucket control lever 30 for tipping the bucket 13 is greater than a predetermined amount.

[0138] The bucket retraction limit refers to the position where, within the extension range of the bucket cylinder 19, the bucket cylinder 19 extends to its limit, making it impossible for the bucket 13 to retract further. The bucket retraction limit is detected by the bucket angle sensor 34.

[0139] In step S7, if the termination condition of automatic excavation control is not met (step S7: No), the control device 50 determines whether the state of automatic excavation control is stage 1 (step S8).

[0140] In step S8, if the state of automatic excavation control is determined to be stage 1 (step S8: yes), the control device 50 determines whether the automatic lifting start condition is met (step S9).

[0141] The automatic lifting start condition is the condition for the automatic lifting action of the boom 12 to begin. In the implementation, the automatic lifting start condition is that the speed Vc of the travel device 5 is less than the preset speed judgment value d for a specified time tb or more, the cylinder bottom pressure Pb of the boom cylinder 18 is greater than the preset pressure judgment value b for a specified time ta or more, and the boom angle α is less than the preset angle judgment value c.

[0142] As an example, the vehicle speed judgment value d is 3 [km / h], the pressure judgment value b is 5 [MPa], the angle judgment value c is -10 [deg], the specified time ta is 0.1 [sec.], and the specified time tb is 0.1 [sec.].

[0143] In step S9, if the automatic lifting start condition is met (step S9: Yes), the control device 50 changes the automatic digging control state to stage 2 (step S10) in order to start the automatic lifting action.

[0144] The control device 50 determines whether the automatic excavation control is in stage 2 (step S11).

[0145] In step S11, if the automatic excavation control is determined to be in stage 2 (step S11: yes), the control device 50 determines whether the automatic lifting end condition is met (step S12).

[0146] The automatic lifting termination condition is the condition under which the automatic lifting action of boom 12 ends. In the implementation, the automatic lifting termination condition is that the increase in boom angle α, calculated from the moment boom 12 begins the automatic lifting action, is greater than a preset angle judgment value f, or the state where the cylinder bottom pressure Pb is greater than a preset pressure judgment value g has lasted for a specified time tc or more.

[0147] As an example, the angle judgment value f is 2 [deg], the pressure judgment value g is 30 [MPa], and the specified time tc is 0.1 [sec.].

[0148] In step S12, if the automatic lifting end condition is met (step S12: yes), the control device 50 changes the automatic digging control state to stage 3 (step S13) in order to wait for the start of the automatic lifting action.

[0149] The control device 50 initializes the clutch control counter tm of the clutch 25 (step S14). That is, the control device 50 sets the counter tm to 0.

[0150] The control device 50 determines whether the automatic excavation control is in stage 3 (step S15).

[0151] In step S15, if the state of automatic excavation control is determined to be stage 3 (step S15: Yes), the control device 50 sets the instruction value of automatic bucket collection instruction to 0 [%] and the instruction value of automatic lifting instruction to 0 [%] (step S16).

[0152] Figure 11 This is a diagram illustrating the automatic bucket-collecting cycle table involved in the implementation method. Automatic bucket-collecting commands are output based on the automatic bucket-collecting cycle table. The automatic bucket-collecting cycle table begins upon entering stage 3. (As shown...) Figure 11 As shown, the automatic bucket retraction cycle table includes: an ON time Δt1 for opening the bucket control valve 24 to initiate the bucket retraction action of the bucket 13, and an OFF time Δt2 for closing the bucket control valve 24. In the automatic bucket retraction cycle table, the ON time Δt1 and OFF time Δt2 are each set with multiple values ​​based on a predetermined number of automatic bucket retraction actions. The automatic bucket retraction cycle table is pre-stored in the control device 50.

[0153] In the implementation, the ON time Δt1 is repeated at least four times and the OFF time Δt2 is repeated four times. Furthermore, Figure 11The diagram schematically represents two ON times Δt1 and one OFF time Δt2. The first ON time Δt1 is set to 0 [sec.]. The second OFF time Δt2 is set to 0.4 [sec.]. The second ON time Δt1 is set to 0.6 [sec.]. The second OFF time Δt2 is set to 0.3 [sec.]. The third ON time Δt1 is set to 0.6 [sec.]. The third OFF time Δt2 is set to 0.3 [sec.]. The fourth ON time Δt1 is set to 0.6 [sec.]. The fourth OFF time Δt2 is set to 0.2 [sec.]. Furthermore, from the fifth time onwards, the ON time Δt1 is set to 0.6 [sec.], and the OFF time Δt2 from the fifth time onwards is set to 0.2 [sec.].

[0154] The control device 50 determines whether an OFF time Δt2 has elapsed since the automatic lifting end condition was met (step S17).

[0155] In this implementation, the control device 50 does not start the automatic bucket-collecting action until the OFF time Δt2 has elapsed after the previous automatic bucket-collecting end condition of the driven boom 12 is met.

[0156] In step S17, if it is determined that the OFF time Δt2 has elapsed (step S17: Yes), the control device 50 changes the state of automatic excavation control to stage 4 in order to perform automatic lifting action (step S18).

[0157] The control device 50 determines whether the automatic excavation control is in stage 4 (step S19).

[0158] In step S19, when the automatic excavation control is determined to be in stage 4 (step S19: yes), the control device 50 determines whether the boom angle α is less than the preset angle judgment value r (step S20).

[0159] As an example, the angle judgment value r is -33 [deg].

[0160] In step S20, if it is determined that the boom angle α is less than the angle judgment value r (step S20: Yes), the control device 50 sets the command value of the automatic bucket retraction command to 0 and sets the command value of the automatic lifting command to a command value q that is greater than 0 (step S21).

[0161] As an example, the instruction value q is 80%.

[0162] Next, the control device 50 determines whether the automatic bucket collection start condition is met (step S22).

[0163] The automatic bucket retraction start condition is the condition under which the automatic bucket retraction action of bucket 13 begins. The automatic bucket retraction start condition is the same as the automatic lifting end condition. In the implementation embodiment, the automatic bucket retraction start condition is that the vehicle speed Vc is less than the preset vehicle speed judgment value k for a specified time td or more, and the cylinder bottom pressure Pb is greater than the preset pressure judgment value j for a specified time te or more.

[0164] As an example, the vehicle speed judgment value k is 1.45 [km / h], the pressure judgment value j is 16 [MPa], the specified time td is 0.1 [sec.], and the specified time te is 0.1 [sec.].

[0165] In step S22, if the automatic bucket-collecting start condition is met (step S22: Yes), the control device 50 changes the automatic digging control state to stage 5 in order to execute the automatic bucket-collecting action (step S23).

[0166] The control device 50 determines whether the automatic excavation control is in stage 5 (step S24).

[0167] In step S24, if the state of automatic excavation control is determined to be stage 5 (step S24: Yes), the control device 50 sets the command value of the automatic lifting command to 0 and sets the command value of the automatic bucket retraction command to a command value p greater than 0 (step S25).

[0168] As an example, the instruction value p is 80 [%. By outputting the automatic bucket retraction instruction, bucket 13 begins the automatic bucket retraction action.

[0169] The control device 50 determines whether the ON time Δt1 has elapsed since the automatic hopper collection start condition was met (step S26).

[0170] In step S26, if it is determined that the ON time Δt1 has elapsed (step S26: Yes), the control device 50 changes the state of the automatic digging control to stage 6 (step S27) in order to determine the end condition of the automatic bucket collection and the start condition of the clutch control.

[0171] The control device 50 determines whether the automatic excavation control is in stage 6 (step S28).

[0172] In step S28, if the automatic excavation control is determined to be in stage 6 (step S28: Yes), the control device 50 determines whether the clutch control start condition is met (step S29).

[0173] The clutch control start condition is the condition that causes the engagement degree of clutch 25 to begin to decrease. In this embodiment, the clutch control start condition is the condition that the state of the bucket angular velocity βv being less than a preset speed judgment value s has lasted for a specified time ts or more.

[0174] As an example, the speed judgment value s is 4 [deg / sec.], and the specified time ts is 0.5 [sec.].

[0175] In step S29, if the clutch control start condition is determined to be met (step S29: Yes), the control device 50 sets the clutch control counter tm of the clutch 25 to a predetermined value tn (step S30).

[0176] As an example, the value tn is specified as 50.

[0177] The control device 50 determines whether the automatic bucket collection end condition is met (step S31).

[0178] The automatic bucket retraction termination condition is the condition for ending the automatic bucket retraction action. In the implementation, the automatic bucket retraction termination condition is that the cylinder bottom pressure Pb is greater than the pressure judgment value j and the increase in cylinder bottom pressure Pb from the moment the automatic bucket retraction action starts from bucket 13 is greater than the preset pressure judgment value m, or the vehicle speed Vc is greater than the vehicle speed judgment value n for a specified time tf or more.

[0179] As an example, the vehicle speed judgment value n is 1.3 [km / h], the pressure judgment value m is 3 [MPa], and the specified time tf is 0.1 [sec.].

[0180] In step S31, if the automatic bucket-closing end condition is met (step S31: Yes), the control device 50 sets the command value of the automatic bucket-closing command to 0 [%). Furthermore, the control device 50 increments the current number of automatic bucket-closing actions by 1 (step S32).

[0181] Since the automatic bucket retraction command is set to 0%, the action of bucket cylinder 19 stops, and the automatic bucket retraction action of bucket 13 ends.

[0182] In order to wait for the start of the automatic lifting action, the control device 50 changes the state of the automatic excavation control to stage 3 (step S33).

[0183] The control device 50 determines whether the automatic excavation control is in stage 7 (step S34).

[0184] In step S34, if the automatic excavation control is determined to be in stage 7 (step S34: Yes), the control device 50 determines whether the boom angle α is less than the angle judgment value r (step S35).

[0185] In step S35, if it is determined that the boom angle α is less than the angle judgment value r (step S35: Yes), the control device 50 sets the command value of the automatic lifting command to the command value x (step S36).

[0186] As an example, the instruction value x is 80 [%.

[0187] The control device 50 determines whether to continue clutch control of the clutch 25 (step S37).

[0188] In this implementation, the control device 50 determines to continue clutch control if the counter tm is greater than 0.

[0189] In step S37, if it is determined that control of the clutch 25 should continue (step S37: Yes), the control device 50 reduces the clutch command value by a reduction rate u [% / sec] (step S38). The reduction rate u represents the rate of reduction of the engagement degree of the clutch 25 per unit time. As an example, the reduction rate u is 0.18 [% / sec]. Furthermore, the clutch command (engagement degree of the clutch 25) is controlled to be no lower than a preset minimum limit value w. As an example, the minimum limit value w is 1 [%].

[0190] The control device 50 decrements the counter tm by 1 (step S39).

[0191] The control device 50 determines whether the automatic excavation control is in stage 0 (step S40).

[0192] In step S40, if it is determined that the state of the automatic excavation control is not stage 0 (step S40: No), the control device 50 sets the boom command to the sum of the current lever command and the current automatic lifting command (step S41).

[0193] In addition, the control device 50 sets the bucket command to the sum of the current lever command and the current automatic bucket retraction command (step S42).

[0194] The lever command is a control command obtained from the operation amount of the boom control lever 29 or the bucket control lever 30, used to determine the opening degree of the boom control valve 23 or the bucket control valve 24. When none of the levers (29, 30) are operated, the lever command is 0.

[0195] The control device 50 determines whether the conditions for completing the automatic excavation control are met (step S43).

[0196] The completion condition for automatic digging control is that the digging performed by the automatic digging control has been completed. In this implementation, the completion condition for automatic digging control is that a predetermined time tg has elapsed after the bucket 13 reaches the bucket retraction limit position during automatic digging control. As an example, the predetermined time tg is 0.5 [sec.].

[0197] In step S43, if the conditions for the completion of automatic digging control are met (step S43: Yes), the control device 50 outputs a completion sound from the sound output unit 39 of the interface device 37 indicating that the digging performed by the automatic digging control has been completed (step S44).

[0198] By outputting sound from the sound output unit 39, the operator of the wheel loader 1 can know that the digging controlled by the automatic digging has been completed.

[0199] In order to initiate the automatic lifting action after detecting the bucket limit position, the control device 50 changes the state of the automatic digging control to stage 7 (step S45).

[0200] The control device 50 determines whether to end the automatic excavation control (step S46).

[0201] For example, if the operator of the wheel loader 1 deactivates the automatic digging mode, operates the boom control lever 29 to lower the boom 12, or operates the bucket control lever 30 to tip the bucket 13, the operator's operation takes priority, and the automatic digging control performed by the control device 50 ends.

[0202] In step S46, if it is determined that the automatic digging control should not be terminated (step S46: No), the control device 50 returns to "start" and executes the processing from step S1 onwards.

[0203] In step S46, if it is determined that the automatic digging control has ended (step S46: Yes), the control device 50 ends the automatic digging control and the sound output unit 39 of the interface device 37 outputs an incomplete sound indicating that the automatic digging control has ended in an incomplete state (step S47).

[0204] By outputting an incomplete tone from the sound output unit 39, the operator of the wheel loader 1 can be informed that the automatic digging control has ended midway.

[0205] The completion tone output in step S44 is different from the incomplete tone output in step S47. Therefore, the operator can distinguish whether the digging controlled by the automatic digging system is complete or has ended in an incomplete state. After step S47, the control device 50 returns to "Start" and executes the processing from step S1 onwards.

[0206] In step S1, if it is determined that the device is in automatic excavation control (step S1: Yes), the control device 50 performs the processing from step S7 onwards.

[0207] In step S2, if it is determined that the automatic digging mode is turned off (step S2: no), the control device 50 removes the flag indicating that the automatic digging mode is turned on from the display unit 40 of the interface device 37 (step S48).

[0208] After performing step S48, the control device 50 changes the state of automatic digging control to stage 0 (step S49) in order to end automatic digging control.

[0209] After completing step S49, the control device 50 executes the processing from step S34 onwards.

[0210] In step S4, if the insertion condition is not met (step S4: No), the control device 50 does not perform automatic digging control, but performs the processing from step S34 onwards.

[0211] In step S5, if the forced downshift condition is not met (step S5: No), the control device 50 does not perform automatic digging control, but performs the processing from step S34 onwards.

[0212] In step S7, if the termination condition of automatic digging control is met (step S7: yes), the control device 50 does not execute automatic digging control, but executes the processing from step S34 onwards.

[0213] In step S8, if it is determined that the state of automatic excavation control is not stage 1 (step S8: no), the control device 50 performs the processing from step S11 onwards.

[0214] In step S9, if the automatic lifting start condition is not met (step S9: No), the control device 50 does not start the automatic lifting action, but executes the processing from step S34 onwards.

[0215] In step S11, if it is determined that the state of automatic excavation control is not stage 2 (step S11: no), the control device 50 performs the processing from step S15 onwards.

[0216] In step S12, if the automatic lifting end condition is not met (step S12: No), the control device 50 does not end the automatic lifting action, but judges whether the neutral state of the boom operating lever 29 has lasted for a specified time th (step S50).

[0217] As an example, the time th is specified as 0.1 [sec.].

[0218] In step S50, if it is determined that the neutral state of the boom operating lever 29 has lasted for a predetermined time th (step S50: Yes), the control device 50 sets the command value of the automatic lifting command to the command value h (step S51).

[0219] As an example, the instruction value h is 80 [%.

[0220] In step S50, if it is determined that the neutral state of the boom operating lever 29 has not lasted for a predetermined time th (step S50: No), it indicates that the operator of the wheel loader 1 has operated the boom operating lever 29. In order to prioritize the operator's operation, the control device 50 sets the automatic lifting command to 0 [%] (step S52).

[0221] After executing step S51 or step S52, the control device 50 executes the processing from step S34 onwards.

[0222] In step S15, if it is determined that the state of automatic excavation control is not stage 3 (step S15: no), the control device 50 performs the processing from step S19 onwards.

[0223] In step S17, if it is determined that the OFF time Δt2 has not elapsed (step S17: No), the control device 50 executes the processing from step S19 onwards.

[0224] In step S19, if it is determined that the state of automatic excavation control is not stage 4 (step S19: no), the control device 50 performs the processing from step S24 onwards.

[0225] In step S20, if the boom angle α is determined to be greater than or equal to the angle judgment value r (step S20: No), the control device 50 executes the processing from step S24 onwards.

[0226] In step S22, if it is determined that the automatic bucket start condition is not met (step S22: No), the control device 50 executes the processing from step S24 onwards.

[0227] In step S24, if it is determined that the state of automatic excavation control is not stage 5 (step S24: no), the control device 50 performs the processing from step S28 onwards.

[0228] In step S26, if it is determined that the ON time Δt1 has not elapsed (step S26: No), the control device 50 executes the processing from step S28 onwards.

[0229] In step S28, if it is determined that the state of automatic excavation control is not stage 6 (step S28: No), the control device 50 performs the processing from step S34 onwards.

[0230] In step S29, if it is determined that the clutch control condition is not met (step S29: yes), the control device 50 does not execute the processing of step S30, but executes the processing from step S31 onwards.

[0231] In step S34, if it is determined that the state of automatic excavation control is not stage 7 (step S34: No), the control device 50 performs the processing from step S37 onwards.

[0232] In step S35, if the boom angle α is determined to be greater than or equal to the angle judgment value r (step S35: No), the control device 50 executes the processing from step S37 onwards.

[0233] In step S37, if it is determined that clutch control of clutch 25 will not continue (step S37: No), the control device 50 increases the clutch command value by an increase rate v [% / sec] (step S53). The increase rate v represents the rate of increase of the engagement degree of clutch 25 per unit time. As an example, the increase rate v is 0.18 [% / sec.]. Furthermore, the clutch command value (clutch 25 engagement degree) is controlled to not exceed a preset maximum limit value z. As an example, the maximum limit value z is the engagement degree of clutch 25 before it decreases. After performing the processing in step S53, the control device 50 performs the processing from step S40 onwards.

[0234] In step S40, if the state of the automatic excavation control is determined to be stage 0 (step S40: yes), the control device 50 executes the processing from step S46 onwards.

[0235] In step S43, if it is determined that the completion condition of automatic excavation control is not met (step S43: No), the control device 50 executes the processing from step S46 onwards.

[0236] [Effect]

[0237] As described above, in this embodiment, the engagement degree of the clutch 25 is controlled based on the state of the work machine 6. Increasing the engagement degree of the clutch 25 increases the traction force (grip force of the wheels 28 on the ground GR) of the wheel loader 1. This allows the wheel loader 1 to excavate the object ET. In cases where the work machine 6 and wheels 28 are pressed forcefully against the object ET due to the forward movement of the wheel loader 1, causing the wheel loader 1 to become immobile, the engagement degree of the clutch 25 is reduced to disengage the wheel loader 1 from the state of tense traction. This allows the bucket 13 to retract. In this way, by reducing the engagement degree of the clutch 25, the wheel loader 1 can be disengaged from a state of immobility during the excavation of the object ET.

[0238] In this embodiment, the control device 50 controls the engagement degree of the clutch 25 based on the operating speed of the loader 6. If the loader 6 and its wheels 28 are pressed forcefully against the object ET due to the forward movement of the wheel loader 1, the loader 6 becomes inoperable. Based on the operating speed of the loader 6, when it is determined that the loader 6 is inoperable, the loader 6 can be disengaged from the inoperable state by reducing the engagement degree of the clutch 25.

[0239] When the clutch control start condition is met, the control device 50 outputs a clutch command to reduce the engagement degree of the clutch 25. In this embodiment, the clutch control start condition is that the operating speed of the machine 6 is less than the speed judgment value s for a predetermined time ts or more. By defining the clutch control start condition, the control device 50 can appropriately reduce the engagement degree of the clutch 25.

[0240] The power generated by the power source 20 is distributed to the travel unit 5 and the drive unit 7 by the power output device 21. When the wheel loader 1 becomes inoperable, reducing the engagement of the clutch 25 increases the power distributed to the drive unit 7 used to drive the work machine 6. As a result, the work machine 6 and the wheels 28 can disengage from the inoperable state.

[0241] During excavation, the bucket 13 of the excavator 6 is inserted into the object ET. The control device 50 can appropriately control the engagement of the clutch 25 based on the bucket angular velocity βv to make the inoperable bucket 13 operable.

[0242] When the automatic bucket retraction start condition, defined by the travel device 5's speed Vc and the cylinder bottom pressure Pb of the boom cylinder 18, is met, the control device 50 initiates the bucket retraction operation of the bucket 13. Furthermore, when the automatic bucket retraction end condition, defined by the travel device 5's speed Vs and the increase in cylinder bottom pressure Pb calculated from the start of the bucket retraction operation, is met, the control device 50 terminates the bucket retraction operation of the bucket 13. Thus, the bucket retraction operation of the bucket 13 begins and ends at appropriate times.

[0243] [Other Implementation Methods]

[0244] In the above embodiment, the control device 50 controls the engagement degree of the clutch 25 based on the bucket angular velocity βv as the operating speed of the machine 6. The control device 50 may also use the boom angular velocity αv as the operating speed of the machine 6, thereby controlling the engagement degree of the clutch 25. The control device 50 may also reduce the engagement degree of the clutch 25 if it is determined that the boom 12 cannot operate based on the boom angular velocity αv.

[0245] In the above-described embodiment, as the state of the work machine 6, the control device 50 controls the engagement degree of the clutch 25 based on the operating speed of the work machine 6, including at least one of the bucket angular velocity βv and the boom angular velocity αv. The control device 50 may also use the pressure of the hydraulic oil in the boom cylinder 18 as the state of the work machine 6 to control the engagement degree of the clutch 25. As described above, if the boom 12 cannot operate, a situation arises where the cylinder bottom pressure Pb of the boom cylinder 18 reaches the safety pressure Pr. The control device 50 can reduce the engagement degree of the clutch 25 if it determines that the pressure of the hydraulic oil in the boom cylinder 18 has reached the safety pressure. Furthermore, the control device 50 can reduce the engagement degree of the clutch 25 if it determines that the pressure of the hydraulic oil in the bucket cylinder 19 has reached the safety pressure.

[0246] In the above-described embodiments, the automatic digging start switch 38 and the forced downshift switch 32 can also be used simultaneously. By using both the automatic digging start switch 38 and the forced downshift switch 32, the gear of the transmission 27 is changed to a lower gear when the automatic digging mode is started, thus enabling easy and efficient digging operations.

[0247] Symbol Explanation

[0248] 1…Wheel loader (operating vehicle); 2…Body; 2F…Front of body; 2R…Rear of body; 3…Articulation mechanism; 4…Cockpit; 5…Travel system; 6…Working machine; 7…Drive unit; 8…Articulated cylinder; 9…Driver's seat; 10…Operating lever; 11…Bracket; 12…Boom; 13…Bucket; 13B…Floor plate; 13M…Opening; 13T…Cutting edge; 14…Crank; 15…Bucket connection 16…Lever; 17…Boom cylinder; 18…Boom cylinder; 19…Bucket cylinder; 20…Power source; 21…Power take-off device; 22…Hydraulic pump; 23…Boom control valve; 24…Bucket control valve; 25…Clutch; 26…Torque converter; 27…Transmission; 28…Wheel; 28F…Front wheel; 28R…Rear wheel; 29…Boom control lever; 30…Bucket control lever; 31…Gear shift lever; 32…Forced… Downshift switch; 33… Boom angle sensor; 34… Bucket angle sensor; 35… Pressure sensor; 36… Vehicle speed sensor; 37… Interface device; 38… Automatic digging start switch; 39… Sound output unit; 40… Display unit; 50… Control device; 51… Processor; 52… Main memory; 53… Memory; 54… Interface; 60… Control system; 132… Bottom surface; AXa… Rotating shaft; AXb… Rotating shaft; AXc… Rotating shaft; AXd… Rotating shaft; AXe… Rotating shaft; AXf… Rotating shaft; AXg… Rotating shaft; AXh… Rotating shaft; CXf… Rotating shaft; CXr… Rotating shaft; ET… Object; GR… Ground; L1… Line; L2… Line; L3… Line; L4… Line; Pb… Cylinder bottom pressure; Vc… Vehicle speed; α… Boom angle; αv… Boom angular velocity; β… Bucket angle; βv… Bucket angular velocity.

Claims

1. A working vehicle, characterized in that, have: Power source; A driving device having an adjustable engagement clutch between the power source and the transmission, and driving based on power transmitted from the power source; Work machine; A drive unit that moves the machine based on power transmitted from the power source; as well as The control device, based on the state of the working machine, outputs control commands to control the engagement degree of the clutch. The state of the working machine includes its operating speed. When the clutch control initiation condition is met—that the operating speed of the machine has been less than the speed judgment value for a specified period of time—the control device outputs the control command to reduce the engagement degree.

2. The working vehicle according to claim 1, characterized in that, have: A power take-off device that distributes power from the power source to the travel device and the drive device. The power allocated to the drive unit increases based on the reduction in engagement.

3. The operating vehicle according to claim 1 or 2, characterized in that, The work machine includes a boom and a bucket. The operating speed of the machine includes the angular velocity of the bucket.

4. The operating vehicle according to claim 3, characterized in that, The drive unit includes a boom cylinder for moving the boom and a bucket cylinder for moving the bucket. The control device initiates the bucket retraction action based on the travel speed of the travel device and the pressure of the hydraulic oil in the boom cylinder; and terminates the bucket retraction action based on the travel speed of the travel device and the increase in pressure calculated from the start of the bucket retraction action.

5. A control method for a work vehicle, characterized in that, include: Output control commands to engage the clutch so that power generated by the power source in the work vehicle equipped with the work machine is transmitted to the driving device having the clutch, which is configured between the power source and the transmission and is capable of adjusting the degree of engagement. as well as Based on the state of the machine, a control command is output to reduce the engagement degree of the clutch. The state of the working machine includes its operating speed. When the clutch control initiation condition is met—that the operating speed of the machine has been less than the speed judgment value for a specified period of time—the control command is output to reduce the engagement degree.

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