Work vehicle

Abstract

To appropriately change a tread width to a target value.SOLUTION: A work vehicle includes a traveling vehicle body, a traveling device that supports the traveling vehicle body in a travelable manner, a changing device that is driven by a hydraulic actuator and is capable of changing a tread width of the traveling device, and a control device that performs first changing control of repeating drive control for driving the hydraulic actuator such that the tread width becomes a predetermined target value until the tread width satisfies the predetermined target value. In addition, the control device alternately executes the drive control and the pause control in which the hydraulic actuator is not driven for a predetermined pause time from the start of the first change control until the tread width satisfies a predetermined target value.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a work vehicle such as a tractor. [Background technology]

[0002] The work vehicle disclosed in Patent Document 1 is equipped with a display unit for informing workers of information related to the vehicle, an actuator for changing the tread, a setting operation unit for performing setting operations related to the vehicle, a sensor for detecting the current value of the tread, and a control device that can control the operation of the actuator so that the current value of the tread becomes the set value set by the setting operation unit, and the control device displays the current value and set value of the tread on the display unit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-205440 Summary of the Invention [Problem to be solved by the invention]

[0004] In the work vehicle of Patent Document 1, the tread (tread width) can be changed to a set value by an actuator, and the current value and set value of the tread width can be easily confirmed. In particular, the control device of the work vehicle of Patent Document 1 performs processing to control the actuator so that the tread width falls within a predetermined range from the set value when the tread width is not within the range.

[0005] However, there is room for improvement in the control of the control device when the current value cannot be kept within the above range.

[0006] The present invention has been made to solve the problems of the prior art, and has an object to provide a work vehicle that can appropriately change the tread width to a target value. [Means for solving the problem]

[0007] A work vehicle according to one embodiment of the present invention comprises a traveling body, a traveling device that supports the traveling body so that it can travel, a change device that is driven by a hydraulic actuator and is capable of changing the tread width of the traveling device, and a control device that performs first change control that repeats drive control to drive the hydraulic actuator so that the tread width becomes a predetermined target value until the tread width reaches a predetermined target value. [Effects of the Invention]

[0008] According to the above work vehicle, the tread width can be appropriately changed to the target value. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic side view of a work vehicle. [Figure 2] FIG. 1 is a schematic plan view of a work vehicle. [Figure 3] FIG. 1 is a diagram illustrating a control system for a work vehicle. [Figure 4] 10A and 10B are diagrams illustrating changes in the tread width of a traveling device. [Figure 5] FIG. 2 shows a hydraulic system for a change device. [Figure 6] FIG. 10 is a front view showing the work vehicle performing trench towing. [Figure 7] FIG. 10 is a plan view showing the work vehicle performing trench towing. [Figure 8] FIG. 1 is a diagram showing a work vehicle performing work in a field on which ridges have been formed. [Figure 9] FIG. 4 is a diagram illustrating a target value of the tread width. [Figure 10] FIG. 10 is a diagram illustrating an example of a setting screen. [Figure 11] 4A and 4B are diagrams illustrating the control of the first mode and the second mode by the control device. [Figure 12] FIG. 10 is a diagram illustrating an example of a series of flows of a first change process. [Figure 13] FIG. 10 is a diagram illustrating an example of one drive control. [Figure 14] FIG. 10 is a diagram illustrating another example of one drive control. [Figure 15] 10 is a first map showing the relationship between the amount of temperature rise and the downtime. [Figure 16] 10 is a second map showing the relationship between oil temperature and downtime. [Figure 17] 10 is a third map showing the relationship between the temperature difference and the downtime. [Figure 18] FIG. 2 is a diagram showing an example of a travel route in a farm field. [Figure 19] 10 is a fourth map showing the relationship between the tilt angle and the set number of times. [Figure 20] 10 is a fifth map showing the relationship between the amount of change in tilt angle and the set number of times. [Figure 21] FIG. 10 is a diagram illustrating an example of a flow of determining a termination condition. [Figure 22] FIG. 10 is a diagram illustrating an example of a confirmation screen. [Figure 23] FIG. 10 is a diagram showing a series of flows of a second change process. [Figure 24] FIG. 10 is a diagram showing a series of flows of a third change process. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] FIG. 1 is a schematic side view showing a work vehicle 1. FIG. 2 is a schematic plan view showing the work vehicle 1. FIG. 3 is a diagram showing a control system for the work vehicle 1. As shown in FIGS. 1 and 2, the work vehicle 1 is a vehicle that travels using a traveling device 31. The work vehicle 1 is, for example, a tractor that can be fitted with a working device 100 (implement) on a traveling body 11 (machine body). In the following explanation, the work vehicle 1 will be explained using as an example a tractor that has a driver's seat 12 and is manually operated by an operator seated in the driver's seat 12.

[0012] Although detailed explanation will be omitted, the work vehicle 1 may be operated under automatic driving control without manual operation by an operator, or under remote driving control by manual operation using a remote control device in a remote location. Furthermore, the work vehicle 1 is not limited to a tractor, but may be an agricultural vehicle such as a combine harvester or rice transplanter, or a construction vehicle such as a compact track loader or backhoe.

[0013] In the description of this embodiment, the direction in which an operator seated in the driver's seat 12 of the work vehicle 1 faces (arrow AR1 in FIGS. 1 and 2) is referred to as the forward direction, and the opposite direction (arrow AR2 in FIGS. 1 and 2) is referred to as the rearward direction. The left side of the operator (the near side in FIG. 1, arrow AR3 in FIG. 2) is referred to as the left side, and the right side of the operator (the far side in FIG. 1, arrow AR4 in FIG. 2) is referred to as the right side. In addition, the horizontal direction, which is perpendicular to the fore-and-aft direction, is referred to as the width direction.

[0014] As shown in Figures 1 and 2, the work vehicle 1 is equipped with a traveling body 11. The traveling body 11 supports various devices and equipment that the work vehicle 1 is equipped with. For example, the traveling body 11 is provided with a driver's seat 12 and a protection mechanism 13 for protecting the driver's seat 12. The protection mechanism 13 is, for example, a cabin 13A that surrounds the driver's seat 12. The protection mechanism 13 is not limited to the cabin 13A, and may be a canopy or a rope installed upright behind the driver's seat 12. In addition, a work device 100 that performs work is connected to the traveling body 11.

[0015] The working implement 100 is a device that performs work. In particular, the working implement 100 performs work as the traveling vehicle body 11 travels. The working implement 100 includes a tilling implement that performs tilling work, a tilling implement that performs tilling work, a ridge forming implement that forms ridges, a seeding implement that sows seeds (sowing work), a furrow digging implement that digs furrows, a harvesting implement that harvests crops, a reaping implement that harvests grass and the like, a spreading implement that spreads grass and the like, a grass collecting implement that collects grass and the like, a shaping implement that shapes grass and the like, a fertilizer spreading implement that spreads fertilizer, a pesticide spreading implement that sprays pesticide, a separating implement that separates crops, and the like. In FIGS. 1 and 2, a tilling implement (reversible plow 100A) is shown as an example of the working implement 100. The working implement 100 is connected to the traveling vehicle body 11 via a connecting device 21.

[0016] The work vehicle 1 is equipped with a coupling device 21. The coupling device 21 is a device to which the working implement 100 can be attached and detached. The coupling device 21 is provided at the front and / or rear of the traveling body 11. In the example shown in Figures 1 and 2, the coupling device 21 is provided at the rear of the traveling body 11. Therefore, the work vehicle 1 can couple the working implement 100 to the coupling device 21, and tow the coupled working implement 100 as the traveling body 11 travels.

[0017] The coupling device 21 may be a position changing device 21A that can change the relative position of the working device 100 with respect to the traveling body 11, or a support device that does not change the relative position of the working device 100 and the traveling body 11. An example of the position changing device 21A is a lifting device 21A1 that can change the vertical position of the working device 100 with respect to the traveling body 11. The lifting device 21A1 is configured, for example, by a three-point link mechanism. The support device is configured, for example, by a swing drawbar. Below, an example will be described of a work vehicle 1 that is equipped with a lifting device 21A1 (position changing device 21A) as the coupling device 21.

[0018] 3, the lifting device 21A1 has a lift arm 22, a lower link 23, a top link 24, a lift rod 25, and a lift cylinder 26. The front end of the lift arm 22 is supported at the upper rear part of the traveling vehicle body 11 so as to be swingable upward or downward. The lift cylinder 26 is a hydraulic actuator (hydraulic cylinder) driven by hydraulic oil, and swings (lifts and lowers) the lift arm 22.

[0019] The front end of the lower link 23 is supported on the rear lower part of the vehicle body 11 so as to be able to swing upward or downward. The front end of the top link 24 is supported on the rear part of the vehicle body 11 above the lower link 23 so as to be able to swing upward or downward. A lift rod 25 connects the lift arm 22 and the lower link 23. The rear part of the lower link 23 and the rear part of the top link 24 are formed in a hook shape.

[0020] When the lift cylinder 26 is driven (extends and retracts), the lift arm 22 moves up and down, and the lower link 23 connected to the lift arm 22 via the lift rod 25 also moves up and down. As a result, the working device 100 swings (lifts and lowers) upward or downward with the front part of the lower link 23 as a fulcrum.

[0021] In this embodiment, the working vehicle 1 is a tractor and the working implement 100 is coupled to the coupling device 21, but the working implement 100 is not limited to an implement coupled to the traveling body 11 by the coupling device 21. For example, the working implement 100 may be a front loader attached to the front of the traveling body 11.

[0022] Furthermore, the working device 100 may be any device that is provided on the work vehicle 1 and performs work, and does not have to be detachable from the traveling body 11 like an implement. For example, if the work vehicle 1 is a combine harvester, the working device 100 includes a harvesting device that harvests crops. If the work vehicle 1 is a rice transplanter, the working device 100 includes a planting device that plants seedlings. If the work vehicle 1 is a backhoe or compact track loader, an example of the working device 100 is an attachment.

[0023] The work vehicle 1 is equipped with a traveling device 31. The traveling device 31 is a device that supports the traveling body 11 so that it can travel. The traveling device 31 is driven to provide propulsion force to the traveling body 11. The traveling device 31 has a plurality of wheels 32. The plurality of wheels 32 includes front wheels 32F and rear wheels 32R. The front wheels 32F and rear wheels 32R are each provided as a pair spaced apart in the width direction. Examples of the front wheels 32F and rear wheels 32R include wheeled wheels made up of tires and crawler wheels.

[0024] 2, the traveling device 31 has an axle mechanism 35 that supports each of the multiple wheels 32. The axle mechanism 35 includes an axle 36 that supports the wheels 32. In this embodiment, the traveling device 31 has a first axle mechanism 35F (front axle) that supports the front wheels 32F, and a second axle mechanism 35R (rear axle) that supports the rear wheels 32R.

[0025] Of the pair of front wheels 32F, one (left) front wheel 32F1 (first front wheel) in the width direction is supported by the left axle 36a (first front axle) of the first axle mechanism 35F, and the other (right) front wheel 32F2 (second front wheel) is supported by the right axle 36b (second front axle) of the first axle mechanism 35F.

[0026] Of the pair of rear wheels 32R, one (left) rear wheel 32R1 (first rear wheel) in the width direction is supported by the left axle 36c (first rear axle) of the second axle mechanism 35R, and the other (right) rear wheel 32R2 (second rear wheel) is supported by the right axle 36d (second rear axle) of the second axle mechanism 35R.

[0027] 1 and 2 has four wheels, a pair of front wheels 32F and a pair of rear wheels 32R, but the traveling device 31 may have a pair of wheels 32 spaced apart in the width direction. Therefore, the number of wheels 32 provided on the traveling device 31 may be three, or five or more.

[0028] The work vehicle 1 is equipped with a power unit 41. The power unit 41 is a unit capable of outputting power. The power unit 41 can output power for driving the traveling unit 31, for example. The power unit 41 has a prime mover 42 and a transmission 43. The prime mover 42 is provided at the front of the traveling body 11. In this embodiment, the transmission 43 forms the rear of the traveling body 11.

[0029] The prime mover 42 is configured by, for example, a diesel engine. As another example, the prime mover 42 may be configured by another internal combustion engine such as a gasoline engine, an electric motor, or the like.

[0030] The transmission 43 changes the speed of the power output by the prime mover 42 by switching between gear stages, and is capable of switching the propulsive force of the traveling device 31 and changing the switching state of the traveling device 31 (switching the traveling device 31 to forward or reverse). The transmission 43 is connected to the axle mechanism 35, and drives the multiple wheels 32 via the axle mechanism 35.

[0031] The power unit 41 may be able to output power to other devices or equipment other than the traveling device 31. For example, the power unit 41 may be able to output power for driving the working device 100 in addition to the traveling device 31.

[0032] Specifically, the power unit 41 outputs power to a PTO shaft 44. The transmission 43 transmits the power of the prime mover 42 to the PTO shaft 44. The PTO shaft 44 is an output shaft that is connected to the working device 100 and drives the working device 100. The transmission 43 has a PTO clutch that switches between transmitting and cutting off power to the PTO shaft 44. The PTO clutch is formed, for example, by a hydraulic clutch, and switching on and off the hydraulic clutch switches between transmitting and cutting off power to the PTO shaft 44.

[0033] Furthermore, the power unit 41 outputs power to the hydraulic pump P. The hydraulic pump P is driven by the power output from the prime mover 42, and discharges hydraulic oil drawn from the hydraulic oil tank 58. The hydraulic pump P supplies hydraulic oil to each hydraulic device equipped in the work vehicle 1.

[0034] 3, the work vehicle 1 is equipped with a control device 61. The work vehicle also is equipped with a storage device 62.

[0035] The control device 61 includes one or more processors. The control device 61 is a controller for the work vehicle 1 and performs various controls related to the work vehicle 1. The control device 61 is connected to be able to communicate with each device and apparatus mounted on the work vehicle 1 via an in-vehicle network such as CAN, ISOBUS, LIN, or FlexRay.

[0036] For example, the control device 61 controls one or more control valves 57 provided on the work vehicle 1, and controls the operation of the hydraulic equipment by switching the flow of hydraulic oil discharged by the hydraulic pump P. In this embodiment, the work vehicle 1 is provided with multiple control valves 57. Each control valve 57 is configured by, for example, a solenoid valve, and changes its switching position in response to a control signal output from the control device 61.

[0037] Specifically, the control device 61 controls a control valve 57a (lift control valve) connected to the hydraulic pump P and the lift cylinder 26 to control the operation of the lift cylinder 26. Furthermore, when the work implement 100 has a hydraulic actuator (work actuator) and performs work using the hydraulic actuator, the control device 61 controls the operation of the work implement 100 by controlling a control valve 57b (auxiliary control valve) connected to the hydraulic pump P and the work actuator.

[0038] The control device 61 includes one or more memories, various analog circuits, various digital circuits, etc. The one or more memories store (memorize) software programs and various data to be executed by one or more processors. The control device 61 can read software programs from one or more memories using one or more processors and execute various processes based on the software programs. Note that the control device 61 may also be able to execute various processes based on predetermined logic circuits using one or more processors.

[0039] The processor may be, for example, a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), a field programmable gate array (FPGA), or an application specific integrated circuit (ASIC).

[0040] The control device 61 may execute various processes by having multiple physically separated processors work together, and the configuration is not limited to the configuration described above. In such cases, the multiple processors are mounted on one or more computers that are physically separated from the work vehicle 1, and these processors are connected to each other so that they can communicate with each other via a network such as an in-vehicle network, a LAN, a WAN, or the Internet.

[0041] In addition, the software program may be stored in a storage device 62 (non-volatile memory such as HDD or SSD) communicatively connected to the control device 61, or in an external server device connected via the network, and installed in the memory from there.

[0042] As shown in Fig. 3, the work vehicle 1 is equipped with a display device 63. The display device 63 is composed of a display unit 63a such as a liquid crystal display. The display device 63 is controlled by the control device 61, and displays various information related to the work vehicle 1. The display device 63 is provided near the driver's seat 12.

[0043] As shown in FIG. 3 , the work vehicle 1 is also equipped with an output device 64. The output device 64 is a device that outputs a notification to the worker by outputting sound, light, or the like. Examples of the output device 64 include a speaker that outputs sound, and a lamp that outputs light. The output device 64 outputs a notification by outputting voice from a speaker, a warning sound, or by turning on or blinking a lamp, etc. It is sufficient that the output device 64 is able to output a notification by outputting sound, light, or the like, and the display device 63 may also serve as the output device 64.

[0044] As shown in FIG. 3, the work vehicle 1 is equipped with one or more detection devices 65. The detection devices 65 detect the status of each device and each piece of equipment provided on the work vehicle 1. The detection devices 65 are communicably connected to the control device 61, and output the detected detection results (detection signals) to the control device 61. This allows the control device 61 to obtain the status of each device and each piece of equipment based on the detection signals output from the detection devices 65. Examples of the detection devices 65 include a rotation detection device 65a, a vehicle speed detection device 65b, a height detection device 65c, and an oil temperature detection device 65d.

[0045] The rotation detection device 65a is a sensor that detects the actual rotation speed of the motor 42. The vehicle speed detection device 65b is a sensor that detects the traveling speed (vehicle speed) of the traveling vehicle body 11. The rotation detection device 65a and the vehicle speed detection device 65b are configured by rotation sensors such as rotary encoders.

[0046] The height detection device 65c is a sensor that detects the actual height of the lifting device 21A1. The height detection device 65c is an angle sensor (lift arm sensor) that detects the angle of the lift arm 22, and a cylinder stroke sensor (lift cylinder sensor) that detects the extension (stroke) of the lift cylinder 26.

[0047] Oil temperature detection device 65d is a sensor that detects the temperature t (oil temperature) of hydraulic oil. In this embodiment, the hydraulic oil also serves as the transmission oil of transmission 43, and oil temperature detection device 65d is provided inside transmission 43.

[0048] 1, the work vehicle 1 is equipped with an operating device 66. The operating device 66 has one or more operating tools 67 that accept operations for each device and each piece of equipment provided on the work vehicle 1. Examples of operating tools 67 that the operating device 66 has include an accelerator operating tool 67a, a steering operating tool 67b, a lift operating tool 67c, a PTO operating tool 67d, and a display operating tool 67e.

[0049] Accelerator operation device 67a receives operation of the target rotation speed of prime mover 42. Accelerator operation device 67a includes, for example, an accelerator pedal, an accelerator lever, etc., and detects these operations (operation direction, operation amount, etc.) using a sensor and outputs them as an operation signal to control device 61. Control device 61 controls prime mover 42 so that the actual rotation speed of prime mover 42 becomes the target rotation speed, based on the target rotation speed based on the operation signal from accelerator operation device 67a and the actual rotation speed obtained from the detection result of rotation detection device 65a.

[0050] The steering operation device 67b receives operation of the steering angle and steering direction of the traveling device 31. The steering operation device 67b is, for example, a handle (steering wheel). The handle 67b is connected to a power steering mechanism via a rotary shaft, and the power steering mechanism moves an arm (knuckle arm) that changes the direction of the front wheels 32F. This makes it possible to change the steering direction of the front wheels 32F in response to operation of the handle 67b.

[0051] The lifting operation device 67c receives an operation for setting a target height of the lifting device 21A1. The lifting operation device 67c has, for example, a lifting lever, and detects the operation (direction and amount of operation) of the lifting lever using a sensor, and outputs the operation signal to the control device 61. The lifting operation device 67c may have a lifting switch separate from the lifting lever, and may output an operation signal detected by the lifting switch to the control device 61. Upon receiving the operation signal from the lifting member, the control device 61 controls the lifting control valve 57a based on the target height based on the operation signal and the actual height obtained from the detection result of the height detection device 65c so that the actual height of the lifting device 21A1 becomes the target height.

[0052] The PTO operating device 67d receives an operation to turn on and off the rotation of the PTO shaft 44. The PTO operating device 67d is a push-type or seesaw-type switch, and outputs an operation signal to the control device 61 in response to the operation. When the control device 61 receives an operation signal from the PTO operating device 67d, it controls the turning on and off of the rotation of the PTO shaft 44 based on the operation signal. Specifically, the control device 61 controls the PTO clutch to switch between transmitting and cutting off power to the PTO shaft 44.

[0053] The display operation device 67e accepts operations of the display device 63. The display operation device 67e is a hardware type such as a physical switch, or a software type such as an operable display image displayed on the display unit 63a. In this embodiment, the display device 63 is provided with a physical hardware type switch as the display operation device 67e. Therefore, the display device 63 of this embodiment serves both as an input interface E that accepts input of information by the display operation device 67e accepting operations, and as an output interface that outputs information by displaying a screen on the display unit 63a.

[0054] In this embodiment, a case will be described in which the work vehicle 1 is equipped with an operating device 66, but if the work vehicle 1 can operate under remote driving control or automatic driving control, it does not have to be equipped with an operating device 66. In such cases, the work vehicle 1 may be equipped with an input interface E that accepts input of information and outputs the accepted input information to the control device 61, instead of or in addition to the operating device 66. An example of the input interface E is a communication device that receives information transmitted from outside.

[0055] The communication device is a communication interface and includes a communication circuit. The communication device performs wireless communication with an external server device, a mobile terminal, a remote control device, etc., via, for example, Wi-Fi (Wireless Fidelity, registered trademark) of the IEEE802.11 series of communication standards, a mobile phone communication network, or a data communication network. The communication device wirelessly communicates with the server device, etc., and receives various information, data, signals, etc. The communication device may also serve as an output interface capable of outputting (transmitting) various information, data, signals, etc. to the server device, etc.

[0056] As shown in Fig. 3, the work vehicle 1 is equipped with an attitude detection device 68. The attitude detection device 68 is a device that detects the attitude of the work vehicle 1 (traveling body 11). The attitude detection device 68 is communicably connected to the control device 61, and outputs the detected attitude of the traveling body 11 to the control device 61. Specifically, the attitude detection device 68 detects the three-dimensional inertial motion of the traveling body 11 as the attitude of the traveling body 11.

[0057] The attitude detection device 68 is an inertial measurement unit (IMU) including, for example, an acceleration sensor, a gyro sensor, etc. The attitude detection device 68 detects inclination information (roll angle, pitch angle, and yaw angle) of the traveling vehicle body 11, etc.

[0058] As shown in Fig. 4, the traveling device 31 is capable of changing the tread width W1. Fig. 4 is a diagram illustrating the change in the tread width W1 of the traveling device 31. The tread width W1 is the length from the center of one (left) wheel 32 in the width direction of a pair of wheels 32 to the center of the other (right) wheel 32 in the width direction. At least one of the first axle mechanism 35F and the second axle mechanism 35R is capable of changing the position of the pair of wheels 32 in the width direction. This allows the traveling device 31 to change the tread width W1.

[0059] Specifically, at least one of the first axle mechanism 35F and the second axle mechanism 35R has a sliding mechanism 37 that supports the axle 36 so that it can slide freely in the width direction. In this embodiment, both the first axle mechanism 35F and the second axle mechanism 35R each have a pair of sliding mechanisms 37. The sliding mechanisms 37 are provided on one side and the other side in the width direction of each axle mechanism 35. In the following description, the sliding mechanism 37L on one side in the width direction (left side) may be referred to as the "first sliding mechanism," and the sliding mechanism 37R on the other side in the width direction (right side) may be referred to as the "second sliding mechanism."

[0060] The sliding mechanism 37 slidably supports the base end (the end opposite the wheel 32) of the axle 36. The sliding mechanism 37 has an axle case 37a that supports the axle 36 and a support case 37b that supports the axle case 37a. The axle case 37a rotatably supports the axle 36. The support case 37b supports the axle case 37a so that it can slide in the width direction. Therefore, as the axle case 37a slides in the width direction and its position in the width direction relative to the support case 37b changes, the axle 36 moves in the width direction and the tread width W1 is changed. The base end of the axle 36 is connected to the changing device 35C via a transmission mechanism such as a splined cylindrical shaft with spline grooves formed therein.

[0061] The work vehicle 1 is equipped with a changing device 35C that can be driven to change the tread width W1 of the traveling device 31. Specifically, at least one of the first axle mechanism 35F and the second axle mechanism 35R has an actuator 38 (drive actuator) that changes the tread width W1 by being driven, and constitutes the changing device 35C.

[0062] In this embodiment, the second axle mechanism 35R has a drive actuator 38 and constitutes the changing device 35C. Meanwhile, the first axle mechanism 35F can change the tread width W1 of the front wheels 32F by manually changing the attachment positions of fasteners such as bolts that connect the axle case 37a and the support case 37b. Note that the work vehicle 1 may also be equipped with the first axle mechanism 35F (changing device 35C) that changes the tread width W1 of the front wheels 32F by driving it. Below, the changing device 35C will be described in detail using the second axle mechanism 35R as an example.

[0063] A drive actuator 38 is provided for each sliding mechanism 37. Therefore, in this embodiment, the changing device 35C has a pair of drive actuators 38. When driven, the drive actuators 38 slide the axle case 37a in the width direction, changing the position of the axle case 37a in the width direction relative to the support case 37b. Examples of the drive actuators 38 include a hydraulic actuator 39 (hydraulic cylinder, hydraulic motor, etc.) and an electric actuator (electric cylinder, electric motor, etc.). Below, the changing device 35C will be described using the hydraulic actuator 39 as an example of the drive actuator 38.

[0064] In this embodiment, the hydraulic actuator 39 is a hydraulic cylinder. The hydraulic cylinder connects the axle case 37a and the support case 37b via a bracket or the like, and slides the axle case 37a in the width direction by expanding and contracting.

[0065] The hydraulic cylinder is a double-acting hydraulic cylinder having a first port that supplies hydraulic oil to the cylinder to move the piston rod protruding from the cylinder, and a second port that supplies hydraulic oil to the cylinder to move the piston rod retracting into the cylinder. The hydraulic cylinder expands and contracts by supplying hydraulic oil to either the first port or the second port and discharging hydraulic oil from the other port. In the following description, the hydraulic actuator 39L of the first sliding mechanism 37L may be referred to as the "first hydraulic actuator," and the hydraulic actuator 39R of the second sliding mechanism 37R may be referred to as the "second hydraulic actuator."

[0066] 3, the work vehicle 1 is equipped with a tread detector 65e. The tread detector 65e is a detector 65 that detects length information for detecting the tread width W1. The tread detector 65e is provided in the changing device 35C.

[0067] The tread detecting device 65e is communicably connected to the control device 61 and outputs the detected detection result (detection signal) to the control device 61. As a result, the control device 61 can obtain the tread width W1 based on the detection signal output from the tread detecting device 65e. The tread detecting device 65e includes length detecting devices 65e1 and 65e2 provided in each sliding mechanism 37. Hereinafter, the length detecting device 65e1 provided in the first sliding mechanism 37L may be referred to as the "first length detecting device," and the length detecting device 65e2 provided in the second sliding mechanism 37R may be referred to as the "second length detecting device."

[0068] The length detection devices 65e1 and 65e2 can detect the amount of movement of the wheel 32 in the width direction caused by the drive actuator 38. In this embodiment, the length detection devices 65e1 and 65e2 are sensors that detect the length (separation widths w1 and w2) between the support case 37b and the wheel 32. In this embodiment, the separation widths w1 and w2 are the lengths from the outer ends of the support case 37b in the width direction to the center of the wheel 32 in the width direction.

[0069] For example, the length detection devices 65e1 and 65e2 are sensors (link angle sensors) that detect the angle of the link mechanism that connects the axle case 37a and the support case 37b. The link angle sensors are, for example, potentiometers. The control device 61 obtains (calculates) the separation widths w1 and w2 based on the detection results (link angles) detected by the link angle sensors.

[0070] The length detection devices 65e1 and 65e2 are not limited to link angle sensors, and may be, for example, cylinder stroke sensors that detect the extension (stroke) of the hydraulic actuator 39 (hydraulic cylinder).

[0071] In addition, in the following description, the separation width w1 of the first sliding mechanism 37L detected by the first length detection device 65e1 may be referred to as the "first separation width," and the separation width w2 of the second sliding mechanism 37R detected by the second length detection device 65e2 may be referred to as the "second separation width."

[0072] The control device 61 acquires the separation widths w1 and w2 of each sliding mechanism 37 based on the detection signals from the length detection devices 65e1 and 65e2, and then calculates the actual tread width W1 (actual tread width) based on the separation widths w1 and w2 and predetermined tables, arithmetic formulas, etc. stored in the memory device 62.

[0073] The hydraulic system relating to the change device 35C will be described below. Fig. 5 is a diagram showing the hydraulic system relating to the change device 35C. As shown in Fig. 5, the hydraulic system of the work vehicle 1 has a hydraulic pump P, a discharge oil passage 51, a connecting oil passage 52, a first supply / drain oil passage 53, a second supply / drain oil passage 54, a discharge oil passage 55, a first change control valve 57c, a second change control valve 57d, a first hydraulic actuator 39L, a second hydraulic actuator 39R, and a hydraulic oil tank 58.

[0074] The discharge oil passage 51 is connected to an output port of the hydraulic pump P, and is an oil passage through which the hydraulic oil discharged by the hydraulic pump P flows. In the example shown in Fig. 5, the discharge oil passage 51 is connected to a first change control valve 57c.

[0075] The connecting oil passage 52 is an oil passage that connects the first change control valve 57c and the second change control valve 57d, and allows the hydraulic oil discharged from the first change control valve 57c to flow to the second change control valve 57d.

[0076] The first supply / discharge oil passage 53 is an oil passage that connects the first change control valve 57c and the first hydraulic actuator 39L. The first supply / discharge oil passage 53 includes an oil passage that connects the first change control valve 57c and a first port of the first hydraulic actuator 39L, and an oil passage that connects the first change control valve 57c and a second port of the first hydraulic actuator 39L. The first supply / discharge oil passage 53 allows the flow of hydraulic oil that is supplied from the first change control valve 57c to the first hydraulic actuator 39L and the hydraulic oil that is discharged from the first hydraulic actuator 39L to the first change control valve 57c.

[0077] The second supply / discharge oil passage 54 is an oil passage that connects the second change control valve 57d and the second hydraulic actuator 39R. The second supply / discharge oil passage 54 includes an oil passage that connects the second change control valve 57d and a first port of the second hydraulic actuator 39R, and an oil passage that connects the second change control valve 57d and a second port of the second hydraulic actuator 39R. The second supply / discharge oil passage 54 allows the flow of hydraulic oil that is supplied from the second change control valve 57d to the second hydraulic actuator 39R and the hydraulic oil that is discharged from the second hydraulic actuator 39R to the second change control valve 57d.

[0078] The discharge oil passage 55 is connected to the hydraulic oil tank 58 and is an oil passage that discharges the hydraulic oil to the hydraulic oil tank 58. In the example shown in Fig. 5, the discharge oil passage 55 is connected to the second change control valve 57d.

[0079] First change control valve 57c and second change control valve 57d are switchable between neutral positions 57c1, 57d1, first positions 57c2, 57d2, and second positions 57c3, 57d3, respectively. First change control valve 57c and second change control valve 57d are constituted by, for example, solenoid valves, and are control valves 57 that change their switching positions in response to control signals output from control device 61. First change control valve 57c and second change control valve 57d are normally held in neutral positions 57c1, 57d1 by the elastic force of springs.

[0080] The first change control valve 57c is a control valve 57 that changes the flow rate of hydraulic oil supplied to the first hydraulic actuator 39L and / or the flow rate of hydraulic oil discharged from the first hydraulic actuator 39L, thereby controlling the operation of the first hydraulic actuator 39L. In a neutral position 57c1, the first change control valve 57c stops the supply of hydraulic oil to the first hydraulic actuator 39L and the discharge of hydraulic oil from the first hydraulic actuator 39L. In addition, in the neutral position 57c1, the first change control valve 57c allows the hydraulic oil supplied from the hydraulic pump P to flow into the connecting oil passage 52.

[0081] The first change control valve 57c in the first position 57c2 supplies hydraulic oil supplied from the hydraulic pump P to the first port of the first hydraulic actuator 39L. At this time, the hydraulic oil discharged from the hydraulic pump P is supplied to the first port via the discharge oil passage 51, the first change control valve 57c, and the first supply / discharge oil passage 53. Furthermore, the first change control valve 57c in the first position 57c2 causes hydraulic oil discharged from the second port of the first hydraulic actuator 39L to flow to the connecting oil passage 52. This causes the first hydraulic actuator 39L to extend, and the axle case 37a of the first sliding mechanism 37L moves in a direction (leftward) away from the support case 37b. As a result, the first rear axle 36c moves outward in the width direction (leftward), increasing the first separation width w1 and widening the tread width W1.

[0082] The first change control valve 57c in the second position 57c3 supplies the hydraulic oil supplied from the hydraulic pump P to the second port of the first hydraulic actuator 39L. At this time, the hydraulic oil discharged from the hydraulic pump P is supplied to the second port via the discharge oil passage 51, the first change control valve 57c, and the first supply / discharge oil passage 53. Furthermore, the first change control valve 57c in the second position 57c3 causes the hydraulic oil discharged from the first port of the first hydraulic actuator 39L to flow to the connecting oil passage 52. This causes the first hydraulic actuator 39L to contract, and the axle case 37a of the first sliding mechanism 37L moves in a direction (rightward) approaching the support case 37b. As a result, the first rear axle 36c moves outward in the width direction (rightward), reducing the first separation width w1 and narrowing the tread width W1.

[0083] The second change control valve 57d is a control valve 57 that changes the flow rate of hydraulic oil supplied to the second hydraulic actuator 39R and / or the flow rate of hydraulic oil discharged from the second hydraulic actuator 39R, thereby controlling the operation of the second hydraulic actuator 39R. When the second change control valve 57d is in a neutral position 57d1, it stops the supply of hydraulic oil to the second hydraulic actuator 39R and the discharge of hydraulic oil from the second hydraulic actuator 39R. When the second change control valve 57d is in the neutral position 57d1, it also allows the hydraulic oil supplied from the connection oil passage 52 to flow to the discharge oil passage 55.

[0084] The second change control valve 57d in the first position 57d2 supplies hydraulic oil supplied from the hydraulic pump P to the first port of the second hydraulic actuator 39R. At this time, the hydraulic oil discharged from the hydraulic pump P is supplied to the first port via the discharge oil passage 51, the first change control valve 57c, the connecting oil passage 52, the second change control valve 57d, and the second supply / discharge oil passage 54. Furthermore, the second change control valve 57d in the first position 57d2 causes hydraulic oil discharged from the second port of the second hydraulic actuator 39R to flow to the discharge oil passage 55. This causes the second hydraulic actuator 39R to extend, and the axle case 37a of the second sliding mechanism 37R moves in a direction (rightward) away from the support case 37b. As a result, the second rear axle 36d moves outward in the width direction (to the right), increasing the second separation width w2 and widening the tread width W1.

[0085] The second change control valve 57d in the second position 57d3 supplies hydraulic oil supplied from the hydraulic pump P to the second port of the second hydraulic actuator 39R. At this time, the hydraulic oil discharged from the hydraulic pump P is supplied to the second port via the discharge oil passage 51, the first change control valve 57c, the connecting oil passage 52, the second change control valve 57d, and the second supply / discharge oil passage 54. Also, the second change control valve 57d in the second position 57d3 causes hydraulic oil discharged from the first port of the second hydraulic actuator 39R to flow to the discharge oil passage 55. This causes the second hydraulic actuator 39R to contract, and the axle case 37a of the second sliding mechanism 37R to move in a direction (leftward) approaching the support case 37b. As a result, the second rear axle 36d moves outward in the width direction (leftward), reducing the second separation width w2 and narrowing the tread width W1.

[0086] 5, a relief oil passage 56 is connected between the discharge oil passage 51 and the discharge oil passage 55, and a relief valve 59 is provided in the relief oil passage 56. One end of the relief oil passage 56 is connected to a portion (section) of the discharge oil passage 51 between the hydraulic pump P and the first change control valve 57c. The other end of the relief oil passage 56 is connected to a portion (section) of the discharge oil passage 55 between the second change control valve 57d and the hydraulic oil tank 58. The relief valve 59 causes the hydraulic oil in the discharge oil passage 51 to flow to the discharge oil passage 55 when the pressure in the relief oil passage 56 reaches or exceeds a predetermined pressure (above a set pressure).

[0087] In particular, if an external force acts on the traveling device 31 in the width direction or if there is an obstacle in the width direction of the traveling device 31, when an attempt is made to drive the drive actuator 38 against the external force or obstacle, the pressure in the relief oil passage 56 may exceed the set pressure, causing the relief valve 59 to discharge the hydraulic oil to the discharge oil passage 55.

[0088] For example, when plowing work is performed with the reversible plow 100A coupled to the coupling device 21, the pressure in the relief oil passage 56 may exceed the set pressure. Specifically, when furrow drawing is performed with the reversible plow 100A, the work vehicle 1 travels in a furrow G formed by open-hole plowing or the previous furrow drawing, with the wheels 32 of the traveling device 31 on the furrow G side dropped into the furrow G (see Figures 6 and 7).

[0089] At this time, the traveling body 11 may tilt toward the groove G with respect to the horizontal plane, and the load (external force) acting on the traveling device 31 may increase due to the weight from the traveling body 11. Therefore, in the example shown in Figures 6 and 7, the external force acting toward the inside in the width direction (left direction) on the second front wheel 32F2 and the second rear wheel 32R2 may increase. Also, the external force acting toward the outside in the width direction (left direction) on the first front wheel 32F1 and the first rear wheel 32R1 may increase.

[0090] Furthermore, since the side surfaces of the groove G are located on the outer and inner sides in the width direction of the wheel 32 dropped into the groove G, obstacles are present on both sides in the width direction of the traveling device 31. For this reason, when the outer side in the width direction of the wheel 32 dropped into the groove G comes into contact with the side surfaces of the groove G, the external force on the inner side in the width direction of the wheel 32 may increase. More specifically, in the example shown in Figures 6 and 7, the external force on the inner side in the width direction (to the left) of the second front wheel 32F2 and the second rear wheel 32R2 may increase.

[0091] On the other hand, when the inside of the width direction of the wheel 32 dropped into the groove G comes into contact with the side of the groove G, the external force acting on the outside of the width direction of the wheel 32 may increase. For this reason, in the example shown in Figures 6 and 7, the external force acting on the outside of the width direction (to the right) of the second front wheel 32F2 and the second rear wheel 32R2 may increase.

[0092] Furthermore, as shown in FIG. 7 and other figures, the widthwise center of the reversible plow 100A is offset from the widthwise center of the work vehicle 1. Therefore, as the work vehicle 1 travels, when the bottom of the reversible plow 100A scrapes the soil of the field H, an external force in the widthwise direction may act on the traveling device 31 (see FIG. 7). Furthermore, a reaction force caused by the bottom scraping the soil of the field H by the bottom, i.e., an external force in the opposite direction to the scraping direction of the soil (the direction in which the scraped soil is turned upside down and thrown away), acts on the traveling device 31. For this reason, in the example shown in FIGS. 6 and 7, the external force acting on the inside (leftward) in the widthwise direction on each wheel 32 may increase. Furthermore, the external force acting on the first front wheel 32F1 and the first rear wheel 32R1 toward the outside (leftward) in the widthwise direction may increase.

[0093] Another example of a case where the pressure in the relief oil passage 56 exceeds the set pressure is when the work vehicle 1 is performing work (such as spraying or planting work) in a field H where ridges R are formed. Specifically, when ridges R are formed in the field H, the work vehicle 1 travels by passing each wheel 32 of the traveling device 31 between the ridges R (see FIG. 8).

[0094] Figure 8 shows a case where spraying work is performed in a field H where ridges R have been formed, with the boom sprayer 100B coupled to the coupling device 21. As shown in Figure 8, the sides of the ridges R are located on the outer and inner sides of each wheel 32 in the width direction, so obstacles exist in the width direction of the traveling device 31. For this reason, when the outer side of each wheel 32 in the width direction comes into contact with the side of the ridge R, the external force on the inner side in the width direction applied to the wheel 32 may increase. On the other hand, when the inner side of each wheel 32 in the width direction comes into contact with the side of the ridge R, the external force on the outer side in the width direction applied to the wheel 32 may increase.

[0095] The control device 61 controls the drive actuators 38 (variation control) so that the tread width W1 becomes a predetermined target value W2 (target tread width). The control device 61 performs variation control so that the tread width W1 becomes the target tread width W2 based on the detection results detected by the tread detection device 65e. In this embodiment, the control device 61 controls each hydraulic actuator 39 in variation control so that the first separation width w1 and the second separation width w2 become approximately the same value and the tread width W1 satisfies the target tread width W2.

[0096] In this embodiment, the target tread width W2 is defined as a predetermined range based on a predetermined set value W3. Therefore, the target widths w3 (target separation widths) of the first separation width w1 and the second separation width w2 are also defined as predetermined ranges based on the set value W3.

[0097] Fig. 9 is a diagram illustrating the target value W2 of the tread width W1. As shown in Fig. 9, the target tread width W2 is a range defined by a lower limit target value W21 (lower limit target value) and an upper limit target value W22 (upper limit target value) based on the set value W3. The lower limit target value W21 is the tread width W2 that is smaller than the set value W3 by a predetermined value, and the upper limit target value W22 is the tread width W2 that is larger than the set value W3 by a predetermined value.

[0098] The target separation width w3 is a range defined by a lower limit target width w31 (lower limit target width) corresponding to the lower limit target value W21 and an upper limit target width w32 (upper limit target width) corresponding to the upper limit target value W22.

[0099] The control device 61 acquires the set value W3 based on the information input by the input interface E. As a result, the control device 61 acquires the target separation width w3 based on the set value W3 and a predetermined table, arithmetic expression, etc. stored in the storage device 62. Therefore, it can be said that the control device 61 indirectly acquires the target value W2 by acquiring the target separation width w3. In this embodiment, the display device 63 displays a setting screen D1 on the display unit 63a for accepting input of the set value W3, and the control device 61 acquires the set value W3 input on the setting screen D1.

[0100] Note that if the work vehicle 1 is capable of operating under remote driving control or automatic driving control, the communication device, which is the input interface E, may receive the setting value W3 from an external device (a mobile terminal such as a smartphone or PC operated by a worker or manager, a remote control device, a remote controller, etc.), and the control device 61 may acquire the setting value W3. In the following explanation, an example will be given in which the control device 61 acquires the setting value W3 input on the setting screen D1.

[0101] 10 is a diagram showing an example of the setting screen D1. The setting screen D1 displays a tread width input section 111 and a confirm button 112. The tread width input section 111 is a display image that accepts input of a setting value W3, and accepts input of an arbitrary tread width W1. The tread width input section 111 may accept a specific numerical value of the setting value W3 through operation of a numeric keypad, or may accept the numerical value of the setting value W3 through operation of an enlargement button that operates to gradually increase the tread width W1 and a reduction button that operates to gradually decrease the tread width W1.

[0102] The Confirm button 112 accepts an operation (confirmation operation) to confirm the set value W3 input by the tread width input unit 111. When the Confirm button 112 is operated, the control device 61 acquires the set value W3 input by the tread width input unit 111 and stores it in memory. At this time, if the set value W3 input by the tread width input unit 111 when the Confirm button 112 is operated differs from the set value W3 stored in memory, the control device 61 overwrites the set value W3 stored in memory. This changes the setting of the set value W3. On the other hand, if the set value W3 input by the tread width input unit 111 at the time of the confirmation operation is the same as the set value W3 stored in memory, the control device 61 does not overwrite the set value W3 stored in memory. Therefore, the setting of the set value W3 is not changed.

[0103] The setting screen D1 may display a tread width display section 113 that displays the actual tread width W1, in addition to the tread width input section 111 and the confirm button 112. The setting screen D1 described using FIG. 10 as an example is merely an example, and is not limited to this.

[0104] When the set value W3 is changed, the control device 61 switches to the first mode. In the first mode, the control device 61 performs change control so that the actual tread width W1 satisfies the target tread width W2 corresponding to the changed set value W3. When the actual tread width W1 satisfies the target tread width W2, the control device 61 in the first mode switches to the second mode. In the second mode, the control device 61 performs change control so that the actual tread width W1 maintains the target tread width W2.

[0105] When the actual tread width W1 satisfies the target tread width W2, i.e., when switching to the second mode, the control device 61 in the first mode controls the output device 64 to output a notification that the actual tread width W1 satisfies the target tread width W2. For example, if the output device 64 is a speaker, the speaker outputs a buzzer sound.

[0106] In the variation control, the control device 61 controls each drive actuator 38 so that the first separation width w1 and the second separation width w2 are equal to or greater than the lower limit target width w31 and equal to or less than the upper limit target width w32. Specifically, when the first separation width w1 is smaller than the lower limit target width w31, the control device 61 moves the first variation control valve 57c to the first position 57c2 and extends the first hydraulic actuator 39L, thereby enlarging the first separation width w1 so that the first separation width w1 satisfies the target separation width w3. On the other hand, when the first separation width w1 is larger than the upper limit target width w32, the control device 61 moves the first variation control valve 57c to the second position 57c3 and contracts the first hydraulic actuator 39L, thereby reducing the first separation width w1 so that the first separation width w1 satisfies the target separation width w3.

[0107] Furthermore, when the second separation width w2 is smaller than the lower limit target width w31, the second change control valve 57d is moved to the first position 57c2 and the second hydraulic actuator 39R is extended, thereby enlarging the second separation width w2 so that the second separation width w2 satisfies the target separation width w3. On the other hand, when the second separation width w2 is larger than the upper limit target width w32, the second change control valve 57d is moved to the second position 57c3 and the second hydraulic actuator 39R is contracted, thereby reducing the second separation width w2 so that the second separation width w2 satisfies the target separation width w3.

[0108] As described above, the control device 61 controls the first change control valve 57c and the second change control valve 57d through change control, and extends each hydraulic cylinder, thereby controlling the change device 35C so that the tread width W1 becomes the target tread width W2.

[0109] 11 shows the control of the first mode and the second mode by the control device 61. Hereinafter, the processing of the control device 61 in the first mode and the second mode will be described with reference to FIG.

[0110] First, the control device 61 acquires the target value W2 based on the set value W3 stored in the memory (S1). In this embodiment, the control device 61 acquires the target separation width w3 based on the set value W3.

[0111] When the control device 61 acquires the target value W2 (S1), it determines whether the actual tread width W1 satisfies the target tread width W2 (S2). In this embodiment, the control device 61 determines that the actual tread width W1 satisfies the target tread width W2 when the first separation width w1 satisfies the target separation width w3 and the second separation width w2 satisfies the target separation width w3. Furthermore, the control device 61 determines that the actual tread width W1 does not satisfy the target tread width W2 when the first separation width w1 does not satisfy the target separation width w3 and / or the second separation width w2 does not satisfy the target separation width w3.

[0112] When the control device 61 determines that the actual tread width W1 satisfies the target tread width W2 (S2: Yes), it maintains the first change control valve 57c and the second change control valve 57d in the neutral position 57c1, does not drive each drive actuator 38, and ends the series of processing.

[0113] When the control device 61 determines that the actual tread width W1 does not satisfy the target tread width W2 (S2: No), it checks the current mode to determine whether it is the first mode (S3). When the control device 61 determines that it is the first mode (S3: Yes), it executes a change process related to change control (S4). When the change process is completed, the control device 61 controls the output device 64 to output a notification (S5). At this time, the output device 64 outputs a notification that the actual tread width W1 satisfies the target tread width W2. When the output device 64 outputs the notification (S5), the control device 61 switches from the first mode to the second mode (S6) and ends the series of processes.

[0114] On the other hand, when the control device 61 confirms in step S3 that the current mode is the second mode (S3: No), it executes a change process related to change control (S7). When the control device 61 has finished the change process, it ends the series of processes.

[0115] As described above, when the set value W3 is changed, the control device 61 in the first mode performs change control in the change process, and the actual tread width W1 is changed to the changed target tread width W2. In addition, the control device 61 in the second mode performs change control in the change process, thereby maintaining the actual tread width W1 at the target tread width W2.

[0116] The variation control will be described in detail below. The control device 61 may perform the same variation control in the first mode and the second mode, or may perform different variation controls. For example, the control device 61 performs first variation control as variation control in at least one of the first mode and the second mode.

[0117] The first variation control is a control that repeatedly performs drive control to drive the drive actuator 38 so that the actual tread width W1 becomes the target tread width W2 until the tread width W1 (actual tread width) becomes the target value W2 (target tread width). The control device 61 preferably performs the first variation control as at least the variation control of the second mode. The control device 61 may also perform the first variation control as the variation control of the first mode.

[0118] In the following description, a case where the control device 61 in the second mode performs the first change control as the change control will be described as an example. In such a case, the control device 61 in the second mode executes the first change process that performs the first change control as the change process.

[0119] The control device 61 alternately executes drive control and pause control after starting the first variation control until the actual tread width W1 meets the target tread width W2. In this embodiment, the control device 61 alternately executes drive control and pause control after starting the first variation control until the first separation width w1 meets the target separation width w3 and the second separation width w2 meets the target separation width w3. For this reason, when an external force in the width direction acts on the traveling device 31 or when an obstacle is present in the width direction of the traveling device 31 and the actual tread width W1 cannot be changed to the target tread width W2 in a single drive control, the control device 61 alternates between drive control and pause control.

[0120] FIG. 12 is a diagram illustrating an example of a series of steps in the first change process. In the example of the first change process shown in FIG. 12, the control device 61 starts the first change control (S11) and determines whether a predetermined execution condition is met (S12). The execution condition indicates a condition for whether drive control is performed in the first change control. The execution condition is, for example, that the actual rotation speed of the prime mover 42 is equal to or greater than a predetermined rotation speed (first execution condition) and that the current vehicle speed is equal to or greater than a predetermined speed (second execution condition). The execution condition is pre-stored in the storage device 62. The control device 61 determines whether the execution condition is met based on the actual rotation speed obtained from the detection result of the rotation detection device 65a and the vehicle speed obtained from the detection result of the vehicle speed detection device 65b. Note that the above-described execution conditions are merely examples, and only one of the first execution condition and the second execution condition may be used, and are not limited to the first execution condition and the second execution condition.

[0121] If the control device 61 determines that the execution condition is satisfied (S12: Yes), it executes one drive control (S13). If the control device 61 determines that the execution condition is not satisfied (S12: No) or has executed drive control (S13), it determines whether a predetermined termination condition is satisfied (S14). The termination condition indicates a condition for whether or not to terminate the first variation control. The termination condition is, for example, that the actual tread width W1 satisfies the target tread width W2 (first termination condition) and that the set value W3 has been changed (second termination condition).

[0122] The control device 61 acquires the first separation width w1 and the second separation width w2 based on the detection results of each length detection device 65e1, 65e2, and determines whether the first termination condition is satisfied. Furthermore, when the input interface E receives input of a changed setting value W3 and the setting value W3 stored in memory is changed, the control device 61 determines that the setting value W3 has been changed and that the second termination condition is satisfied. Note that the above-mentioned termination conditions are merely examples and are not limited to the first and second termination conditions.

[0123] If the control device 61 determines that the termination condition is met (S14: Yes), it terminates the first change control (S15) and terminates the first change process. On the other hand, if the control device 61 determines that the termination condition is not met (S14: No), it performs pause control (S16). After performing pause control (S16), the control device 61 returns to the processing of step S12.

[0124] As described above, even if the set value W3 is changed, the control device 61 repeatedly executes drive control and pause control alternately in the first change control until the termination condition is met (at least until the actual tread width W1 meets the target tread width W2).

[0125] Next, the drive control will be described in detail. The drive control is a control for driving the drive actuators 38 so that the actual tread width W1 matches the target tread width W2. In this embodiment, the control device 61 drives the pair of drive actuators 38 through the drive control. At this time, the control device 61 does not drive both of the pair of drive actuators 38 simultaneously. That is, in the drive control, the control device 61 independently controls the drive of the first hydraulic actuator 39L and the drive of the second hydraulic actuator 39R at different timings. That is, in the drive control, the control device 61 changes the control of the first separation width w1 and the second separation width w2 at different timings. Therefore, in the drive control, the control device 61 drives one of the pair of drive actuators 38, stops the drive of the drive actuator 38, and then drives the other drive actuator 38.

[0126] For this reason, the control device 61 does not use drive control to simultaneously move both the first change control valve 57c and the second change control valve 57d from the neutral position 57c1, 57d1 to another position (first position 57c2, 57d2 or second position 57c3, 57d3). In this embodiment, when the control device 61 uses variation control to switch at least one of the first change control valve 57c and the second change control valve 57d from the neutral position 57c1 to another position, the control device 61 maintains the other at the neutral position 57c1.

[0127] Furthermore, the control device 61 does not drive each drive actuator 38 for more than a predetermined set time in one drive control. The set time is defined in advance in the storage device 62. The set time is set to, for example, 5 seconds, and may be editable as needed using information input via the input interface E.

[0128] Hereinafter, one cycle of drive control will be described, taking as an example a case where the control device 61 controls the first hydraulic actuator 39L and then the second hydraulic actuator 39R in drive control.

[0129] Fig. 13 is a diagram illustrating an example of one drive control. As shown in Fig. 13, the control device 61 acquires the first separation width w1 based on the detection result of the first length detection device 65e1 (S21). After acquiring the first separation width w1 (S21), the control device 61 determines whether the first separation width w1 satisfies the target separation width w3 corresponding to the set value W3 stored in the memory (S22).

[0130] If the first separation width w1 does not satisfy the target separation width w3 (S22: No), the control device 61 drives the first hydraulic actuator 39L so that the first separation width w1 satisfies the target separation width w3 (S23). At this time, when the control device 61 drives the first hydraulic actuator 39L, it counts the drive time of the first hydraulic actuator 39L. For example, the control device 61 counts the elapsed time (first elapsed time) during which the first change control valve 57c is moved from the neutral position 57c1 to another position as the drive time of the first hydraulic actuator 39L. The control device 61 continues the processing of steps S21 to S24 until the first separation width w1 satisfies the target separation width w3 (S22: Yes) or until the first elapsed time exceeds a set time (S24: Yes).

[0131] Therefore, if the first separation width w1 does not satisfy the target separation width w3 and the first elapsed time is equal to or less than the set time (S22: No, S24: No), the control device 61 repeats the processing of step S23, moves the first variation control valve 57c from the neutral position 57c1 to the first position 57c2 or the second position 57c3, and drives the first hydraulic actuator 39L. On the other hand, if the first separation width w1 satisfies the target separation width w3 (S22: Yes) or if the first elapsed time exceeds the set time (S24: Yes), the control device 61 returns the first variation control valve 57c to the neutral position 57c1. At this time, the control device 61 resets the first elapsed time to zero.

[0132] If the first separation width w1 satisfies the target separation width w3 (S22: Yes), or if the first elapsed time exceeds the set time (S24: Yes), the control device 61 acquires the second separation width w2 based on the detection result of the second length detection device 65e2 (S25). After acquiring the second separation width w2 (S25), the control device 61 determines whether the second separation width w2 satisfies the target separation width w3 corresponding to the set value W3 stored in the memory (S26).

[0133] If the second separation width w2 does not satisfy the target separation width w3 (S26: No), the control device 61 drives the second hydraulic actuator 39R so that the second separation width w2 satisfies the target separation width w3 (S27). At this time, when the control device 61 drives the second hydraulic actuator 39R, it counts the drive time of the second hydraulic actuator 39R. For example, the control device 61 counts the elapsed time (second elapsed time) during which the second change control valve 57d is moved from the neutral position 57c1 to another position as the drive time of the second hydraulic actuator 39R. The control device 61 continues the processing of steps S25 to S28 until the second separation width w2 satisfies the target separation width w3 (S26: Yes) or until the second elapsed time exceeds a set time (S28: Yes).

[0134] Therefore, if the second separation width w2 does not satisfy the target separation width w3 and the second elapsed time is equal to or less than the set time (S26: No, S28: No), the control device 61 repeats the process of step S27, moves the second change control valve 57d from the neutral position 57c1 to the first position 57c2 or the second position 57c3, and drives the second hydraulic actuator 39R. On the other hand, if the second separation width w2 satisfies the target separation width w3 (S26: Yes) or the second elapsed time exceeds the set time (S28: Yes), the control device 61 returns the second change control valve 57d to the neutral position 57c1 and ends the drive control. At this time, the control device 61 resets the second elapsed time to zero.

[0135] As described above, the control device 61 controls the first hydraulic actuator 39L and then the second hydraulic actuator 39R in the drive control. Therefore, the control device 61 controls both the first hydraulic actuator 39L and the second hydraulic actuator 39R in one drive control. That is, even if both the first separation width w1 and the second separation width w2 do not satisfy the target separation width w3 in one drive control, the required time for one drive control (the sum of the first elapsed time and the second elapsed time) is less than twice the set time.

[0136] In the above example, the control device 61 controls the first hydraulic actuator 39L and then the second hydraulic actuator 39R in drive control, but the control device 61 may control the second hydraulic actuator 39R and then the first hydraulic actuator 39L. Furthermore, the control device 61 only needs to ensure that each drive actuator 38 is not driven for longer than a set time in a single drive control, and may perform drive control such as the modified example shown in FIG.

[0137] 14, the control device 61 continues the processing of steps S21 to S24 until the first elapsed time exceeds the set time (S24: Yes). Specifically, unlike the drive control described using Fig. 13, when the control device 61 determines in step S22 that the first separation width w1 satisfies the target separation width w3 (S22: Yes), the control device 61 proceeds to the processing of step S24.

[0138] Therefore, if the first separation width w1 does not satisfy the target separation width w3 and the first elapsed time is equal to or less than the set time (S22: No, S24: No), the control device 61 continues to control the first hydraulic actuator 39L. On the other hand, if the first elapsed time exceeds the set time (S24: Yes), the control device 61 ends the control of the first hydraulic actuator 39L and returns the first change control valve 57c to the neutral position 57c1.

[0139] 14, the control device 61 continues the processing of steps S25 to S28 until the second elapsed time exceeds the set time (S26: Yes). Specifically, unlike the drive control described using Fig. 13, when the control device 61 determines in step S26 that the second separation width w2 satisfies the target separation width w3 (S26: Yes), the control device 61 proceeds to the processing of step S28.

[0140] Therefore, if the second separation width w2 does not satisfy the target separation width w3 and the second elapsed time is equal to or less than the set time (S26: No, S28: No), the control device 61 continues to control the second hydraulic actuator 39R. On the other hand, if the second elapsed time exceeds the set time (S28: Yes), the control device 61 ends the control of the second hydraulic actuator 39R and returns the first change control valve 57c to the neutral position 57c1.

[0141] In the drive control described above using Figures 13 and 14, the control device 61 has been described as not driving both of the pair of drive actuators 38 simultaneously, but it may also drive both of the pair of drive actuators 38 simultaneously.

[0142] Next, the pause control will be described. The pause control is a control that does not drive the drive actuator 38 for a predetermined pause time T. In the pause control, the control device 61 maintains both the first change control valve 57c and the second change control valve 57d in the neutral position 57c1, and stops the supply of hydraulic oil to each hydraulic cylinder and the discharge of hydraulic oil from each hydraulic cylinder.

[0143] The downtime T is defined (stored) in advance in the storage device 62, and the control device 61 acquires the downtime T stored in the storage device 62. The downtime T is defined, for example, based on the oil temperature t that drives the hydraulic actuator 39. For example, the downtime T is set to, for example, 20 seconds, and may be editable as appropriate using information input via the input interface E.

[0144] It is preferable that the rest time T is defined based on the rising tendency of the oil temperature t when the pressure in the relief oil passage 56 exceeds the set pressure and the relief valve 59 flows the hydraulic oil in the discharge oil passage 51 to the discharge oil passage 55.

[0145] Specifically, the pause time T is defined to be longer when the amount of increase Δt per unit time (amount of temperature increase) of the oil temperature t is a second amount of increase Δt2 that is greater than the first amount of increase Δt1, compared to when the amount of increase Δt per unit time of the oil temperature t is a first amount of increase Δt1. For example, the pause time T is defined to be longer as the amount of temperature increase Δt increases.

[0146] FIG. 15 is a first map M1 (graph) showing the relationship between the temperature rise Δt and the downtime T. In the first map M1 shown in FIG. 15, the horizontal axis represents the temperature rise Δt, and the vertical axis represents the downtime T. In the first map M1 shown in FIG. 15, as the temperature rise Δt increases, the downtime T increases in a downwardly convex curve. The first map M1 is stored in advance in, for example, the storage device 62.

[0147] The control device 61 acquires the current oil temperature t based on the detection result of the oil temperature detection device 65d, and calculates the temperature rise Δt per predetermined unit time (for example, 30 seconds, 60 seconds, etc.). After calculating the temperature rise Δt, the control device 61 acquires the pause time T corresponding to the temperature rise Δt based on the first map M1 stored in the storage device 62.

[0148] Note that the first map M1 shown in FIG. 15 is an example, and the first map M1 may increase in a convex curve as the temperature rise Δt increases, or may increase proportionally in a substantially straight line.

[0149] Furthermore, in the above example, the pause time T is defined based on the rising trend of the oil temperature t, but the pause time T may be defined based on the current oil temperature t. In such a case, the pause time T is defined to be longer when the oil temperature t is a second oil temperature t2 that is higher than the first oil temperature t1 than when the oil temperature t is a first oil temperature t1. For example, the pause time T is defined to be longer as the oil temperature t increases.

[0150] FIG. 16 is a second map M2 (graph) showing the relationship between the oil temperature t and the downtime T. In the second map M2 shown in FIG. 16, the horizontal axis represents the oil temperature t, and the vertical axis represents the downtime T. In the second map M2 shown in FIG. 16, as the oil temperature t increases, the downtime T changes in proportion, drawing a substantially straight line. The second map M2 is stored in advance in, for example, the storage device 62. The control device 61 obtains the current oil temperature t based on the detection result of the oil temperature detection device 65d, and obtains the downtime T corresponding to the oil temperature t from the second map M2.

[0151] In the second map M2, as the oil temperature t increases, the value may increase in an upwardly convex curve or in a downwardly convex curve.

[0152] Alternatively, the pause time T may be defined based on the temperature difference dt (difference) between a predetermined upper limit temperature (a first threshold value described later) and the current oil temperature t. The temperature difference dt is calculated by subtracting the current oil temperature t from the upper limit temperature. In this case, the pause time T is defined to be longer when the temperature difference dt is a second temperature difference dt2 that is smaller than the first temperature difference dt1, compared to when the temperature difference dt is a first temperature difference dt1. For example, the pause time T is defined to be longer as the temperature difference dt becomes smaller.

[0153] FIG. 17 is a third map M3 (graph) showing the relationship between the temperature difference dt and the downtime T. In the third map M3 shown in FIG. 17, the horizontal axis represents the temperature difference dt, and the vertical axis represents the downtime T. In the third map M3 shown in FIG. 17, as the temperature difference dt increases, the downtime T changes in proportion to the increase in the temperature difference dt, drawing a substantially straight line. The third map M3 is pre-stored in, for example, the storage device 62. In this case, the control device 61 obtains the current oil temperature t based on the detection result of the oil temperature detection device 65d, and obtains from the third map M3 the downtime T corresponding to the difference obtained by subtracting the oil temperature t from the upper limit temperature.

[0154] The third map M3 shown in FIG. 17 is an example, and the third map M3 may increase in an upwardly convex curve or in a downwardly convex curve as the temperature difference dt increases.

[0155] In the above description, the first and second termination conditions have been used as examples of termination conditions, but the termination conditions may include other conditions. For example, the control device 61 may terminate the first variation control when a predetermined third termination condition is satisfied in addition to when the first or second termination condition is satisfied.

[0156] The control device 61 ends the first variation control when it executes the drive control a predetermined set number of times N from the start of the first variation control until the tread width W1 (actual tread width) satisfies the target value W2 (target tread width) (third termination condition). Specifically, when the control device 61 starts the first variation control in the first variation process, it counts the number of times the drive control has been executed (number of executions). That is, in the processing of step S13, the control device 61 counts up a counter (execution counter) provided in memory each time it executes one drive control.

[0157] The set number of times N is predefined (stored) in the storage device 62, and the control device 61 acquires the set number of times N stored in the storage device 62. The set number of times N is set to, for example, 60 times, and may be editable as appropriate using information input via the input interface E.

[0158] The set number of times N may also be defined based on a reference traveling speed BV (reference speed) and a reference traveling distance BD (reference distance) of the traveling vehicle body 11. The set number of times N is calculated by dividing a reference time BT (BT = BD / BV) obtained by dividing the reference distance BD by the reference speed BV, and then dividing this by the time TR required for one cycle (one period) of drive control and pause control in the first variation control (N = BT / TR). Taking an example in which the set time for drive control is 5 seconds and the pause time T is 20 seconds, the time TR required for one cycle of drive control and pause control is 30 seconds. Therefore, the set number of times N in this case is set to a value obtained by dividing the reference time BT by the required time TR (30 seconds).

[0159] The reference speed BV is defined, for example, as the vehicle speed when the work vehicle 1 is working. The reference speed BV is the vehicle speed when working at a relatively slow speed (low-speed work). Examples of low-speed work include subsoil breaking work using a subsoiler or combination soiler, and trench digging work using a trenching machine. For example, the vehicle speed during low-speed work is 1.5 to 3 km / h.

[0160] The reference distance BD is defined based on the distance of at least a portion of the travel route L of the work vehicle 1 in a specified field H (reference field BH). The travel route L includes a straight section L1 along which the work vehicle 1 travels straight, and a turning section L2 along which the work vehicle 1 turns.

[0161] FIG. 18 is a diagram showing an example of a travel route L in a field H. The example shown in FIG. 18 shows the travel route L of a work vehicle 1 in a substantially rectangular field H. The straight section L1 is located in a working area e1 of the field H (an area where work is performed inside the headland). The straight section L1 is a route that extends from one end of the working area e1 in the longitudinal direction to the other end. In addition, the turning section L2 is located in the headland area e2 of the field H. The turning section L2 is a route that connects multiple straight sections L1. Therefore, the work vehicle 1 traveling on the travel route L travels back and forth between one end and the other end of the longitudinal direction of the field H.

[0162] The reference distance BD is the distance of a predetermined step on the travel route L. For example, the reference distance BD is the travel distance of the straight section L1 when the work vehicle 1 makes one round trip between one end and the other end in the longitudinal direction of the field H. In this case, the reference distance BD is defined as twice the length BD1 of the longitudinal direction of the working area e1 of the field H (BD = BD1 × 2). Therefore, if the longitudinal length BD1 of the working area e1 is 500 m, the reference distance BD is 1000 m.

[0163] Therefore, if the reference speed BV is 2 km / h and the reference distance BD is 1000 m, the reference time BT obtained by dividing the reference speed BV by the reference distance BD is 1800 seconds, and the set number of times N is calculated as 60 by dividing the reference time BT by the required time TR (30 seconds) for one cycle of drive control and pause control.

[0164] In the above example, the reference speed BV is the vehicle speed during low-speed work, and the set number of times N is defined based on the longitudinal length BD1 of the work area e1 of a specified field H (reference field BH), but the reference speed BV and reference distance BD are not limited to these. For example, if the input interface E can accept input of information related to the longitudinal length BD1 of the field H in which the work vehicle 1 will work, and the reference speed BV, the set number of times N may be defined based on the information accepted as input by the input interface E.

[0165] Furthermore, the set number N may be defined based on, for example, the tilt angle θ of the traveling vehicle body 11 with respect to a horizontal plane. The tilt angle θ is an angle based on at least one of a roll angle and a pitch angle. In this embodiment, the tilt angle θ is the angle of the traveling vehicle body 11 with respect to a horizontal plane, and is the absolute value of the roll angle with the traveling vehicle body 11 in a horizontal position as the reference (zero) (see FIG. 6).

[0166] The set number of times N is defined to be smaller when the tilt angle θ is a second tilt angle θ2 smaller than the first tilt angle θ1 than when the tilt angle θ is a first tilt angle θ1. For example, the set number of times N is defined to decrease as the tilt angle θ decreases. Furthermore, when the tilt angle θ is equal to or greater than a second threshold value θt1, the set number of times N becomes a reference number BN (BN=BT / TR) obtained by dividing the reference time BT by the required time TR for one cycle of the drive control and pause control. Furthermore, the set number of times N may be defined to be smaller than the reference number of times BN when the tilt angle θ is less than the second threshold value θt1, and to decrease as the tilt angle θ decreases.

[0167] FIG. 19 is a fourth map M4 (graph) showing the relationship between the tilt angle θ and the set number of times N. In the fourth map M4 shown in FIG. 19, the horizontal axis represents the tilt angle θ, and the vertical axis represents the set number of times N. In the fourth map M4 shown in FIG. 19, as the tilt angle θ increases, the set number of times N increases in a downwardly convex curve, and then becomes constant (reference number of times BN). The fourth map M4 is stored in advance in, for example, the storage device 62.

[0168] The control device 61 acquires the current tilt angle θ (the absolute value of the roll angle in this embodiment) based on the detection result of the attitude detection device 68. Upon acquiring the tilt angle θ, the control device 61 acquires the set number of times N corresponding to the tilt angle θ based on the fourth map M4 stored in the storage device 62.

[0169] In addition, as the tilt angle θ increases, the fourth map M4 may increase proportionally in a substantially straight line and then become constant (reference number BN), or it may increase in a convex curve and then become constant.

[0170] Furthermore, in the above example, the fourth map M4 is pre-stored in the memory device 62, but the set number of times N may be defined (calculated) by correcting the reference number of times BN with a predetermined correction value based on the inclination angle θ.

[0171] Furthermore, when the set number N is defined based on the inclination angle θ of the traveling vehicle body 11 relative to the horizontal plane, the set number N may be defined based on the amount of change Δθ (inclination angle change amount) of the inclination angle θ per unit time, rather than corresponding to the inclination angle θ itself. The inclination angle change amount Δθ is the absolute value of the amount of change per unit time of an angle based on at least one of the roll angle and the pitch angle.

[0172] The set number N is defined to be smaller when the inclination angle change amount Δθ is the second change amount Δθ2, which is smaller than the first change amount Δθ1, than when the inclination angle change amount Δθ is the first change amount Δθ1. For example, the set number N is defined to decrease as the inclination angle change amount Δθ decreases. Furthermore, the set number N becomes the reference number BN when the inclination angle change amount Δθ is equal to or greater than the third threshold value Δθt1. Furthermore, the set number N may be defined to be smaller than the reference number BN when the inclination angle change amount Δθ is less than the third threshold value Δθt1, and to decrease as the inclination angle change amount Δθ decreases.

[0173] FIG. 20 is a fifth map M5 (graph) showing the relationship between the inclination angle change amount Δθ and the set number of times N. In the fifth map M5 shown in FIG. 20, the horizontal axis represents the inclination angle change amount Δθ, and the vertical axis represents the set number of times N. In the fifth map M5 shown in FIG. 20, as the inclination angle change amount Δθ increases, the set number of times N increases in a downwardly convex curve, and then becomes constant (reference number of times BN). The fifth map M5 is stored in advance in, for example, the storage device 62.

[0174] The control device 61 acquires the current tilt angle θ (the absolute value of the roll angle in this embodiment) based on the detection result of the attitude detection device 68, and calculates the tilt angle change amount Δθ per predetermined unit time (e.g., 30 seconds, 60 seconds, etc.). Upon acquiring the tilt angle change amount Δθ, the control device 61 acquires a set number N corresponding to the tilt angle change amount Δθ based on a fifth map M5 stored in the storage device 62.

[0175] Note that the fifth map M5 shown in FIG. 20 is just an example, and as the inclination angle change amount Δθ increases, the fifth map M5 may increase proportionally in an approximately straight line and then become constant (reference number BN), or may increase in an upward convex curve and then become constant.

[0176] Furthermore, in the above example, the fifth map M5 is pre-stored in the storage device 62, but the set number of times N may be defined (calculated) by correcting the reference number of times BN with a predetermined correction value based on the inclination angle change amount Δθ.

[0177] Furthermore, the set number of times N may be defined based on the working implement 100 attached to the coupling device 21. For example, the set number of times N is defined to be smaller when performing a work (second work) in which the external force is relatively small and the number of obstacles is relatively small, than when performing a work (first work) in which the traveling implement 31 is subjected to a relatively large external force in the width direction or in which an obstacle is present in the width direction of the traveling implement 31. Examples of the first work include work using a reversible plow 100A or a subsoiler, and examples of the second work include work using a tiller or ridge-making device. For example, the set number of times N is stored in the storage device 62 as a table in association with each working implement 100 and the type of work performed by that working implement 100 (type of working implement 100).

[0178] The storage device 62 may store a predetermined correction value corresponding to the task device 100, the task content, etc., and the set number of times N may be defined (calculated) by correcting the reference number of times BN with the correction value. The control device 61 recognizes (identifies) the task device 100 and the task content of the task device 100 based on the information received as input by the input interface E, and obtains the set number of times N corresponding to these.

[0179] For example, if the input interface E is the display device 63, the display device 63 displays a predetermined input screen that accepts input of information (device information) related to the work device 100 attached to the connecting device 21, and the control device 61 recognizes (identifies) the work device 100 and the work content of the work device 100 based on the device information input on the input screen. Also, if the input interface E is a communication device, the communication device may receive the device information input on a predetermined input screen of a mobile terminal or the like carried by the worker, and the control device 61 may acquire the device information. As another example, if the manager has defined in advance on the manager's terminal the work content (work plan) to be performed in the field H, and the work plan includes device information, the communication device may receive the device information, and the control device 61 may acquire the device information.

[0180] In addition, if each work device 100 is equipped with a transmitter (e.g., a beacon) that transmits individual identification information, the control device 61 may identify the work device 100 attached to the connecting device 21 based on the identification information received from the beacon by the input interface E (receiver, beacon scanner), and obtain the device information from a predetermined table stored in the memory device 62.

[0181] When determining whether the termination condition is satisfied in the process of step S14, the control device 61 determines whether the number of executions has reached the set number of times N. Fig. 21 is a diagram illustrating an example of the flow of determining the termination condition.

[0182] 21, the control device 61 first determines whether the first or second termination condition is satisfied (S14a), and if it determines that the first or second termination condition is satisfied (S14a: Yes), the control device 61 proceeds to the processing of step S15 and terminates the first variation control. At this time, the control device 61 resets the execution counter provided in the memory to zero.

[0183] On the other hand, if the control device 61 determines that the first and second termination conditions are not satisfied (S14a: No), it determines whether a third termination condition is satisfied (S14b). For example, the control device 61 acquires the current tilt angle θ based on the detection result of the attitude detection device 68, and acquires the set number of times N corresponding to the current tilt angle θ from the fourth map M4 in the storage device 62. The control device 61 also determines whether the third termination condition is satisfied based on whether an execution counter provided in the memory is equal to or less than the set number of times N.

[0184] If the control device 61 determines that the number of executions is less than the set number of times N and that the third end condition is not satisfied (S14b: No), the control device 61 proceeds to the process of step S16 and performs pause control (S16).

[0185] On the other hand, when the control device 61 determines that the number of executions has reached the set number of times N and that the third end condition is satisfied (S14b: Yes), it controls the output device 64 to output a predetermined notification (S14c). In other words, the output device 64 outputs the predetermined notification when the drive control is executed the set number of times N from the time the control device 61 starts the first variation control (S11) until the tread width W1 meets the target value W2. For example, the control device 61 displays a confirmation screen D2 indicating that the first variation control cannot be continued on the display device 63. At this time, the control device 61 resets an execution counter provided in memory to zero.

[0186] 22 is a diagram showing an example of the confirmation screen D2. In the example shown in FIG. 22, the confirmation screen D2 has a message display section 121, a re-execute button 122, and an end button 123.

[0187] The message display unit 121 displays a message indicating that the first change control cannot be continued. In the example shown in Fig. 22, the message display unit 121 displays the message "The tread width cannot be maintained at the target value." Note that the message display unit 121 is not limited to the example shown in Fig. 22, and may display a message urging the worker to perform maintenance on the work vehicle 1.

[0188] The re-execute button 122 is a button that accepts an operation of whether or not to re-execute the first change control without terminating the first change control. Therefore, after the processing of step S14c, when the re-execute button 122 is operated (S14d: Yes), the control device 61 returns to step S12 and re-executes the first change control. Note that when the re-execute button 122 is operated (S14d: Yes), the control device 61 may return to step S16 and re-execute the first change control.

[0189] The end button 123 is a button that accepts an operation to end the first change control. Therefore, after the processing of step S14c, if the re-execute button 122 is not operated (S14d: No) and the end button 123 is operated (S14e: Yes), the control device 61 proceeds to the processing of step S15 as it considers that the end condition is satisfied and ends the first change control. On the other hand, if the end button 123 is not operated (S14e: No), the control device 61 returns to step S14d.

[0190] In the above example, when the control device 61 determines that the third end condition is satisfied, the control device 61 causes the display device 63 to display the confirmation screen D2, but the control device 61 may also control another output device 64 to output a notification. For example, in addition to or instead of displaying the confirmation screen D2 on the display device 63, the control device 61 may cause a speaker to output a buzzer sound.

[0191] In the above-described embodiment, the control device 61 alternately and repeatedly executes drive control and pause control in the first variation control until a termination condition (first termination condition, second termination condition, or third termination condition) is satisfied. However, the first variation control may be suspended when a predetermined suspension condition is satisfied. The control device 61 determines whether the suspension condition is satisfied in the first variation process, and suspends the first variation control by interrupt processing when the suspension condition is satisfied. Note that when the suspension condition is no longer satisfied, the control device 61 resumes the suspended first variation process. The suspension conditions will be described below using the first to fourth suspension conditions as examples.

[0192] For example, the control device 61 may suspend the first variation control based on the oil temperature t (first suspension condition). The control device 61 suspends the first variation control by interrupt processing when the amount of increase Δt (amount of temperature increase) of the oil temperature t per unit time is equal to or greater than a predetermined fourth threshold. The fourth threshold is defined in advance in the storage device 62. The control device 61 acquires the current oil temperature t based on the detection result of the oil temperature detection device 65d, calculates the amount of temperature increase Δt per predetermined unit time (e.g., 30 seconds, 60 seconds, etc.), and determines whether the amount of temperature increase Δt is equal to or greater than the fourth threshold. Note that the fourth threshold may be editable as appropriate using information input via the input interface E.

[0193] Furthermore, the control device 61 may suspend the first variation control based on at least the oil temperature t based on the first suspension condition, and may suspend the first variation control by interrupt processing when the current oil temperature t is equal to or higher than a predetermined first threshold. Like the fourth threshold, the first threshold may also be defined in advance in the storage device 62 and may be editable as appropriate using information input via the input interface E.

[0194] Furthermore, the control device 61 may suspend the first variation control being executed when the traveling vehicle body 11 is inclined at a predetermined angle or more with respect to the horizontal plane (second suspension condition). The control device 61 suspends the first variation control by interrupt processing when the inclination angle θ is equal to or greater than a fifth threshold value θt2. The fifth threshold value θt2 is defined in advance in the storage device 62. The control device 61 acquires the current inclination angle θ (in this embodiment, the absolute value of the roll angle) based on the detection result of the attitude detection device 68, and determines whether the inclination angle θ is equal to or greater than the fifth threshold value θt2. Note that the fifth threshold value θt2 is preferably greater than the second threshold value θt1. Furthermore, the fifth threshold value θt2 may be editable as appropriate using information input via the input interface E.

[0195] Furthermore, the control device 61 may interrupt the first variation control being executed when the work implement 100 is performing work (third interruption condition). Specifically, the control device 61 interrupts the first variation control being executed when work is being performed in a field H in which furrows G, ridges R, etc. have been formed. Examples of cases in which furrows G and ridges R have been formed in the field H include when plowing work is being performed with the reversible plow 100A coupled to the coupling device 21, or when work has been performed after ridge formation with the ridge-forming device.

[0196] For example, if the work vehicle 1 is equipped with a sensing device that senses the environment around the work vehicle 1, such as a LiDAR (Light Detection And Ranging), the control device 61 determines whether furrows G, ridges R, etc. have been formed in the field H based on the sensing results of the sensing device. Also, if the input interface E receives input of information related to a predefined plan for work in the field H (work plan), the control device 61 determines whether furrows G, ridges R, etc. have been formed in the field H based on the work plan received as input by the input interface E.

[0197] Furthermore, the control device 61 determines whether or not the working implement 100 is performing work based on the status of each device and equipment of the work vehicle 1, the surrounding environment, and the like. For example, when a working implement 100 that switches between a working posture for performing work using the lifting device 21A1 and a non-working posture for not performing work, such as a tilling implement or a plowing implement, is connected to the coupling device 21, the control device 61 can determine whether or not the working implement 100 is performing work based on the detection results of the height detection device 65c and the operation signal of the lifting operation tool 67c. When a working implement 100 that is driven by power output from the PTO shaft 44 or hydraulic oil supplied via the auxiliary control valve 57b, such as a tilling implement or a harvesting implement, is connected to the coupling device 21, the control device 61 can determine whether or not the working implement 100 is performing work based on the operation signal of the operation device 66 (PTO operation tool 67d, etc.) that operates these implements.

[0198] The method for determining whether or not the work device 100 is currently performing work is not limited to the example described above, and the control device 61 may determine whether or not the work device 100 is currently performing work based on other methods. For example, when the storage device 62 stores a field map showing the field H and a work area e1 is defined on the field map, the control device 61 may determine whether or not the work vehicle 1 is currently performing work based on whether or not the work vehicle 1 is located within the work area e1. Specifically, the control device 61 determines that the work device 100 is currently performing work when the work vehicle 1 is located within the work area e1. In such a case, the work vehicle 1 is provided with a positioning device that performs positioning using satellite signals from a satellite positioning system using a GPS antenna, and a sensing device, and the control device 61 acquires the position of the work vehicle 1 based on the detection results of these.

[0199] Furthermore, when the traveling vehicle body 11 performs a turning operation (turning) by the traveling device 31, the control device 61 may suspend the first variation control, instead of the first variation control, until the tread width W1 (actual tread width) meets the target value W2 (target tread width) (fourth suspension condition). For example, the control device 61 determines whether the traveling vehicle body 11 is performing a turning operation based on the steering angle of the traveling device 31. In such a case, the work vehicle 1 is equipped with a steering angle detection device 65f that detects the steering angle of the steering device, and the control device 61 obtains the steering angle of the traveling device 31 based on the detection result of the steering angle detection device 65f. The steering angle detection device 65f is configured by a potentiometer (angle sensor) provided on the steering shaft.

[0200] The method for determining whether the traveling vehicle body 11 is turning is not limited to the example described above, and the control device 61 may use other methods to determine whether work is being performed by the work implement 100. For example, when the storage device 62 stores a field map showing the field H and a headland area e2 is defined in the field map, the control device 61 determines whether the traveling vehicle body 11 is turning based on whether the work vehicle 1 is located within the headland area e2. Specifically, when the work vehicle 1 is located in the headland area e2, the control device 61 determines that the traveling vehicle body 11 is turning.

[0201] Furthermore, if the route (planned travel line) along which the work vehicle 1 will travel is defined in advance on the field map, the control device 61 may determine whether the traveling body 11 is turning based on the position of the work vehicle 1 and the planned travel line. In this case, the control device 61 determines that the traveling body 11 is turning when the work vehicle 1 is located at a turning section L2 of the planned travel line.

[0202] Furthermore, in the case of a tillage implement, plowing implement, or the like, where the working implement 100 that switches between a working posture for working and a non-working posture for not working by the lifting device 21A1 is connected to the coupling device 21, the lifting device 21A1 switches the working implement 100 to the non-working posture when the traveling body 11 performs a swing operation, so the control device 61 may determine whether the traveling body 11 is performing a swing operation based on the detection result of the height detection device 65c and the operation signal of the lifting operation tool 67c. In such a case, the control device 61 determines that the traveling body 11 is performing a swing operation when the lifting device 21A1 is in the non-working posture based on the detection result of the height detection device 65c and the operation signal of the lifting operation tool 67c.

[0203] When the control device 61 suspends the first change control due to the fourth suspension condition, the control device 61 may perform the second change control instead of the first change control. In this case, after suspending the first change process, the control device 61 executes the second change process that performs the second change control as the change process.

[0204] The second variation control is control that continuously drives the drive actuator 38 so that the actual tread width W1 becomes the target tread width W2 until the tread width W1 (actual tread width) satisfies the target value W2 (target tread width). In other words, the second variation control differs from the first variation control in that it repeats the drive control without performing pause control. Also, unlike the first variation control, the second variation control does not include the third termination condition as an termination condition. Also, the second variation control repeats the drive control until the fourth interruption condition is satisfied and the actual tread width W1 becomes the target tread width W2.

[0205] Fig. 23 is a diagram illustrating an example of a series of flows of the second change process. In the example of the second change process shown in Fig. 23, when the control device 61 starts the second change control (S31), it determines whether or not the execution conditions are satisfied (S32). The execution conditions are, for example, the first execution condition and the second execution condition.

[0206] If the control device 61 determines that the execution condition is satisfied (S32: Yes), it executes one drive control (S33). If the control device 61 determines that the execution condition is not satisfied (S32: No) or has executed drive control (S33), it determines whether or not a termination condition is satisfied after the execution of the drive control (S34). The termination condition is a condition other than the third termination condition, such as the first termination condition and the second termination condition.

[0207] If the control device 61 determines that the termination condition is met (S34: Yes), it terminates the second change control (S35) and terminates the second change process. On the other hand, if the control device 61 determines that the termination condition is not met (S34: No), it determines whether the fourth interruption condition is met (S36).

[0208] When the control device 61 determines that the traveling vehicle body 11 is turning by the traveling device 31 and the fourth interruption condition is satisfied (S36: Yes), the control device 61 returns to the processing of step S32. When the control device 61 determines that the traveling vehicle body 11 is not turning by the traveling device 31 and the fourth interruption condition is not satisfied (S36: No), the control device 61 ends the second change control (S37), returns to the interrupted first change process (S38), and ends the second change process. Note that, although an example of the second change process has been described using FIG. 23, the second change process is not limited to this.

[0209] In the above explanation, an example was given in which the control device 61 in the second mode performs first variation control as variation control, but the control device 61 in the first mode may perform third variation control, which is different from the first variation control. In such a case, the control device 61 in the first mode executes a third variation process that performs third variation control as a variation process. The third variation control is a control that executes drive control only once. The third variation control differs from the first variation control and the second variation control in that it does not automatically repeat drive control.

[0210] Fig. 24 is a diagram illustrating an example of a series of flows of the third change process. In the example of the third change process shown in Fig. 24, when the control device 61 starts the third change control (S41), it determines whether or not the execution conditions are satisfied (S42). The execution conditions are, for example, the first execution condition and the second execution condition.

[0211] If the control device 61 determines that the execution condition is satisfied (S42: Yes), it executes one drive control (S43). If the control device 61 determines that the execution condition is not satisfied (S42: No) or has executed drive control (S43), it determines whether or not a first termination condition is satisfied after the execution of the drive control (S44).

[0212] If the control device 61 determines in step S44 that the first termination condition is satisfied (S44: Yes), it terminates the third change control (S45) and terminates the third change process. On the other hand, if the control device 61 determines that the first termination condition is not satisfied (S44: NO), it controls the output device 64 to output a predetermined notification (S46). For example, the control device 61 causes the display device 63 to display a confirmation screen D2.

[0213] If the re-execute button 122 is operated (S47: Yes) after the processing of step S46, the control device 61 returns to step S41 and executes the third change control again. Furthermore, if the re-execute button 122 is not operated (S47: No) and the end button 123 is operated (S48: Yes) after the processing of step S45, the control device 61 ends the third change control (S45) and ends the third change process. On the other hand, if the end button 123 is not operated (S48: No), the control device 61 returns to the processing of step S47. Note that, although an example of the third change process has been described using FIG. 24, the third change process is not limited to this.

[0214] A preferred embodiment of the present invention provides a work vehicle 1 as described in the following items. (Item 1) A work vehicle (1) comprising: a traveling body (11); a traveling device (31) that supports the traveling body (11) so that the traveling body (11) can travel; a change device (35C) that is driven by a hydraulic actuator (39) and that can change the tread width (W1) of the traveling device (31); and a control device (61) that performs first change control that repeats drive control to drive the hydraulic actuator (39) so that the tread width (W1) becomes a predetermined target value (W2) until the tread width (W1) becomes a predetermined target value (W2).

[0215] According to the work vehicle 1 relating to this item 1, the control device 61 repeatedly executes drive control using the first change control, thereby making it possible to appropriately change the tread width W1 to the target value W2 without relying on operation by the operator. (Item 2) The work vehicle 1 described in item 1, wherein the control device 61 alternately executes the drive control and a pause control that does not drive the hydraulic actuator 39 for a predetermined pause time T from the start of the first change control until the tread width W1 meets a predetermined target value W2.

[0216] According to the work vehicle 1 relating to this item 2, even if the tread width W1 does not fluctuate as desired due to factors such as the condition of the ground on which the traveling device 31 is located, an excessive increase in the temperature t of the hydraulic oil caused by the continued application of excessive load to the hydraulic actuator 39 can be suppressed. (Item 3) 3. The work vehicle (1) according to item 2, wherein the rest time (T) is defined based on the temperature (t) of the hydraulic oil that drives the hydraulic actuator (39).

[0217] According to the work vehicle 1 relating to this item 3, an excessive rise in the oil temperature t can be more appropriately suppressed. (Item 4) The work vehicle 1 described in item 3 is defined so that the rest time T is longer when the increase Δt per unit time of the hydraulic oil temperature t is a second increase Δt2 that is greater than the first increase Δt1, compared to when the increase Δt per unit time of the hydraulic oil temperature t is a first increase Δt1.

[0218] According to the work vehicle 1 relating to this item 4, the downtime T is defined in accordance with the rising trend of the hydraulic oil temperature t, and therefore the first variation control can more appropriately prevent the oil temperature t from rising excessively. (Item 5) The work vehicle 1 described in any one of items 2 to 4, wherein the control device 61 terminates the first change control when it has performed the drive control a predetermined set number of times N from the start of the first change control until the tread width W1 satisfies a predetermined target value W2.

[0219] According to the work vehicle 1 relating to this item 5, when the tread width W1 cannot be changed by the change device 35C due to factors such as the condition of the ground on which the traveling device 31 is located, it is possible to avoid continuously performing the first change control, and to suppress an excessive rise in the oil temperature t. (Item 6) The work vehicle 1 described in any one of items 2 to 5 is provided with an output device 64 that outputs a predetermined notification when the drive control is executed a predetermined set number of times N from the time the control device 61 starts the first change control until the tread width W1 meets a predetermined target value W2.

[0220] According to the work vehicle 1 according to this item 6, the worker can know from the notification from the output device 64 that the first variation control has ended. (Item 7) The work vehicle (1) according to item (5) or item (6) citing item (5), wherein the set number of times N is defined based on an inclination angle θ of the traveling body (11) relative to a horizontal plane.

[0221] According to the work vehicle 1 relating to this item 7, the first change control can be appropriately terminated in accordance with the inclination angle θ of the traveling body 11, i.e., the load acting on the traveling device 31 due to the load from the traveling body 11, thereby suppressing an excessive rise in the oil temperature t. (Item 8) The work vehicle 1 described in item 7, wherein the set number of times N is defined to be smaller when the inclination angle θ is a second inclination angle θ2 that is smaller than the first inclination angle θ1 than when the inclination angle θ is a first inclination angle θ1.

[0222] According to the work vehicle 1 related to this item 8, the first variation control can be more appropriately terminated in accordance with the load acting on the traveling gear 31, thereby suppressing an excessive rise in the oil temperature t. Specifically, the load acting on the traveling gear 31 due to the load from the traveling vehicle body 11 may be smaller when the inclination angle θ is small, compared to when the inclination angle θ is large. For this reason, when the load acting on the traveling gear 31 is small, it becomes easier to change the tread width W1, but in cases where the tread width W1 cannot be changed as desired despite the inclination angle θ being relatively small, an excessive rise in the oil temperature t can be suppressed by terminating the first variation control earlier than when the inclination angle θ is relatively large. (Item 9) The work vehicle 1 according to any one of items 2 to 8, wherein the control device 61 suspends the first variation control being executed when the traveling vehicle body 11 is inclined at a predetermined angle or more with respect to a horizontal plane.

[0223] According to the work vehicle 1 relating to this item 9, when the inclination angle θ is large, the load acting on the traveling device 31 due to the load from the traveling body 11 increases compared to when the inclination angle θ is small, and it may become difficult to change the tread width W1. Therefore, when the inclination angle θ is equal to or greater than a predetermined angle, an excessive rise in the oil temperature t caused by forcibly driving the hydraulic actuator 39 can be suppressed. (Item 10) The work vehicle 1 is described in any one of items 2 to 9, and is equipped with a work device 100 that is attached to the traveling body 11 and performs work as the traveling body 11 travels, and the control device 61 interrupts the first change control that is being executed when the work device 100 is performing work.

[0224] According to the work vehicle 1 relating to this item 10, when work is being performed using the work implement 100, the load acting on the traveling gear 31 increases, making it more difficult to change the tread width W1 than when work is not being performed, and therefore it is possible to suppress an excessive rise in oil temperature t that would otherwise occur if the hydraulic actuator 39 were forcibly driven while work was being performed using the work implement 100. (Item 11) The work vehicle 1 described in any one of items 2 to 10, wherein when the traveling body 11 performs a turning operation using the traveling device 31, the control device 61 performs, instead of the first change control, a second change control that continuously drives the hydraulic actuator 39 so that the tread width W1 becomes a predetermined target value W2 until the tread width W1 becomes a predetermined target value W2.

[0225] According to the work vehicle 1 relating to this item 11, when the traveling body 11 performs a turning operation, the condition of the ground on which the traveling device 31 is located is more likely to change than when the traveling body 11 performs a straight-line operation, and the load acting on the traveling device 31 is also more likely to fluctuate relatively easily. Therefore, during the turning operation, the second change control changes the tread width W1 more aggressively than the first change control, and the tread width W1 can be changed appropriately while suppressing an excessive rise in the oil temperature t.

[0226] Although the present invention has been described above, the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0227] 1: Work vehicle 11: Running vehicle (aircraft) 31: Running gear 35C: Change device 39: Hydraulic actuator 61: Control device 64: Output device 100: Work equipment N: Number of times set T: Pause time W1: Tread width W2: Target value t: Hydraulic oil temperature (oil temperature) Δt: Amount of rise Δt1: First rise amount Δt2: Second rise amount θ: Tilt angle θ1: 1st inclination angle θ2: 2nd inclination angle

Claims

1. A running vehicle body, a traveling device that supports the traveling vehicle body so that it can travel; a changing device that is driven by a hydraulic actuator and is capable of changing the tread width of the traveling device; a control device that performs first variation control by repeatedly performing drive control to drive the hydraulic actuator so that the tread width becomes a predetermined target value until the tread width becomes a predetermined target value; A work vehicle equipped with:

2. 2. The work vehicle according to claim 1, wherein the control device alternately executes the drive control and a pause control that does not drive the hydraulic actuator for a predetermined pause time, from when the first variation control is started until the tread width satisfies a predetermined target value.

3. The work vehicle according to claim 2 , wherein the rest time is defined based on the temperature of hydraulic oil that drives the hydraulic actuator.

4. 4. The work vehicle according to claim 3, wherein the rest time is defined to be longer when the amount of increase in temperature of the hydraulic oil per unit time is a second amount of increase that is greater than a first amount of increase, compared to when the amount of increase in temperature of the hydraulic oil per unit time is a first amount of increase.

5. The work vehicle according to any one of claims 2 to 4, wherein the control device terminates the first variation control when the drive control is executed a predetermined set number of times from when the first variation control is started until the tread width satisfies a predetermined target value.

6. The work vehicle according to any one of claims 2 to 4, further comprising an output device that outputs a predetermined notification when the drive control is executed a predetermined number of times from when the control device starts the first variation control until the tread width satisfies a predetermined target value.

7. The work vehicle according to claim 5, wherein the set number of times is defined based on an inclination angle of the traveling vehicle body relative to a horizontal plane.

8. The work vehicle according to claim 7 , wherein the set number of times is defined to be less when the tilt angle is a second tilt angle that is smaller than the first tilt angle than when the tilt angle is a first tilt angle.

9. 5. The work vehicle according to claim 2, wherein the control device suspends the first variation control being executed when the traveling vehicle body is inclined at a predetermined angle or more with respect to a horizontal plane.

10. a working device attached to the traveling vehicle body and performing work as the traveling vehicle body travels; 5. The work vehicle according to claim 2, wherein the control device suspends the first variation control that is being executed when the work device is performing work.

11. The work vehicle according to any one of claims 2 to 4, wherein when the traveling vehicle body performs a turning operation using the traveling device, the control device performs, instead of the first change control, a second change control that continuously drives the hydraulic actuator so that the tread width becomes a predetermined target value until the tread width becomes a predetermined target value.

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