Work vehicle

Abstract

Provided is a work vehicle capable of ensuring a large steering angle for wheels. The work vehicle (1) comprises a vehicle body (2), wheels (30) disposed on the sides of the vehicle body (2), and a drive unit (40) for driving the wheels (30). At least a portion of the drive unit (40) is located at a position on the outside facing a tread section (30a) of the wheels (30) and overlapping the wheels (30) in the width direction of the vehicle body (2).

Description

Work vehicles

[0001] The present invention relates to a work vehicle for performing work such as agricultural work.

[0002] A known work vehicle is disclosed in Patent Document 1. The work vehicle disclosed in Patent Document 1 includes a vehicle body, wheels (front wheels and rear wheels) arranged on the sides of the vehicle body, and a drive unit for driving the wheels. The drive unit of this work vehicle includes an electric motor that drives the wheels (front wheels), and a transmission mechanism that is housed in a front axle case and transmits power from the electric motor to the wheels (front wheels).

[0003] Japanese Patent Publication No. 2012-56542

[0004] In the above-described work vehicle, the electric motor that constitutes the drive unit and the transmission mechanism housed in the front axle case are located on the inside (vehicle body side) of the wheels, which makes it difficult to steer the wheels at a large angle to the inside.

[0005] The present invention has been made in consideration of the above problems, and has an object to provide a work vehicle that can ensure a large steering angle for the wheels.

[0006] A work vehicle according to one embodiment of the present invention comprises a vehicle body, wheels arranged on the sides of the vehicle body, and a drive unit for driving the wheels, with at least a portion of the drive unit being located on the outside opposite the tread portion of the wheels and overlapping with the wheels in the width direction of the vehicle body.

[0007] The drive unit has a steering mechanism that changes the direction of the wheels, a drive device that generates power, and a transmission mechanism that transmits the power generated by the drive device to the wheels, and at least a portion of the drive unit that is located in a position overlapping with the wheels may be the steering mechanism.

[0008] The drive unit has a steering mechanism that changes the direction of the wheels, a drive device that generates power, and a transmission mechanism that transmits the power generated from the drive device to the wheels, and at least a portion of the drive unit that is located in a position overlapping with the wheels may be the drive device.

[0009] The drive unit has a steering mechanism that changes the direction of the wheels, a drive device that generates power, and a transmission mechanism that transmits the power generated by the drive device to the wheels, and at least a portion of the drive unit that is located in a position overlapping with the wheels may be the transmission mechanism.

[0010] The steering mechanism may have a rotating body that rotates about an axis in the vertical direction when the wheels are steered, and the axis of the rotating body may be located above the wheels.

[0011] The transmission mechanism may have a first transmission shaft that is disposed above the wheel and extends in a vertical direction.

[0012] The transmission mechanism may have a second transmission shaft that rotates upon receiving power transmitted from the first transmission shaft, and the second transmission shaft may be disposed inside the wheel and extend in the vertical direction.

[0013] The work vehicle may be equipped with a height change mechanism that changes the height of the vehicle body from the ground, and the first transmission shaft or the second transmission shaft may be extendable and retractable in accordance with the change in height of the vehicle body by the height change mechanism.

[0014] The first transmission shaft has an upper shaft to which power from the drive unit is transmitted and a lower shaft that transmits the power transmitted to the upper shaft to the second transmission shaft, and the axis of the upper shaft and the axis of the lower shaft are arranged on the same straight line, and the distance between the upper end of the upper shaft and the lower end of the lower shaft may change as the height of the vehicle body is changed by the height change mechanism.

[0015] The first transmission shaft may have a cylindrical intermediate shaft having an upper portion into which the upper shaft is inserted and a lower portion into which the lower shaft is inserted, a first spline formed on an outer surface of the upper shaft, the lower shaft being cylindrical and having a second spline formed on an inner surface, the intermediate shaft having an internal spline formed on the inner surface and an external spline formed on the outer surface, the first spline meshing with the internal spline and the second spline meshing with the external spline.

[0016] The steering mechanism may have a cylinder with a rod that extends and retracts in a direction perpendicular to the axis, the rotating body having a first connection part to which the rod is connected and a second connection part to which the wheel is connected, and the cylinder may rotate the rotating body around the axis by extending and retracting the rod, thereby rotating the wheel around the axis.

[0017] The wheels may include a left front wheel, a right front wheel, a left rear wheel, and a right rear wheel, and the drive units may include a first drive unit for driving the left front wheel, a second drive unit for driving the right front wheel, a third drive unit for driving the left rear wheel, and a fourth drive unit for driving the right rear wheel, wherein the first drive unit includes a portion arranged around the left front wheel, the second drive unit includes a portion arranged around the right front wheel, the third drive unit includes a portion arranged around the left rear wheel, and the fourth drive unit includes a portion arranged around the right rear wheel.

[0018] The work vehicle may include a frame structure that supports the vehicle body, and the drive unit may be attached to the frame structure.

[0019] The frame structure may have a side frame arranged on the side of the vehicle body and an upper frame arranged above the vehicle body, and the drive unit may have a drive device that generates power to drive the wheels, and the drive device may be attached to the side frame.

[0020] The frame structure may have a side frame arranged on the side of the vehicle body and an upper frame arranged above the vehicle body, and the drive unit may have a drive device that generates power to drive the wheels, and the drive device may be attached to the upper frame.

[0021] According to the work vehicle of the present invention, a large steering angle of the wheels can be ensured.

[0022] 1 is a perspective view showing an embodiment of a work vehicle; FIG. 2 is a left side view showing an embodiment of a work vehicle; FIG. 3 is a right side view showing an embodiment of a work vehicle; FIG. 4 is a front view showing an embodiment of a work vehicle; FIG. 5 is a rear view showing an embodiment of a work vehicle; FIG. 6 is a plan view showing an embodiment of a work vehicle; FIG. 7 is a block diagram showing an example of the overall configuration of a work vehicle; FIG. 8 is a perspective view of a frame structure; FIG. 9 is an exploded perspective view of side frames (left frame, right frame); FIG. 10 is a perspective view showing an upper frame (lateral frame) and a side frame separately; FIG. 11 is a view of a first drive unit (not including a steering mechanism) from the rear left; FIG. 12 is a view of a first drive unit (not including a steering mechanism) from the front right; FIG. 13 is a view of a third drive unit from the rear right; FIG. 14 is a view of a third drive unit from the upper left; FIG. 15 is a view of a first drive unit (including a steering mechanism) from the rear right; FIG. 16 is a view of a first drive unit (including a steering mechanism) from the rear; FIG. 17 is a view of a first drive unit (not including a steering mechanism) from the rear; FIG. 18 is a plan view showing a steering mechanism (left steering mechanism) and wheels (left front wheel). 1 is a plan view showing a state in which the rod of the cylinder of the steering mechanism (left steering mechanism) is extended. FIG. 2 is a plan view showing a state in which the rod of the cylinder of the steering mechanism (left steering mechanism) is retracted. FIG. 3 is a plan view showing a change in the position of the left front wheel when the left front wheel is rotated inward. FIG. 4 is a perspective view showing another embodiment of the work vehicle. FIG. 5 is a left side view showing another embodiment of the work vehicle. FIG. 6 is a schematic front view showing the first drive unit with the first transmission shaft retracted. FIG. 7 is a view of the first drive unit with the first transmission shaft retracted, viewed from the right rear. FIG. 8 is a view of the first drive unit with the first transmission shaft extended, viewed from the left front. FIG. 9 is a front view of the first drive unit with the first transmission shaft extended. FIG. 10 is a view of the third drive unit with the lower transmission shaft extended, viewed from the left front. FIG. 11 is a view of the third drive unit with the lower transmission shaft extended, viewed from the right rear. 1 is a front view showing that at least a portion of a first drive unit is in an outer overlap position, FIG. 2 is a plan view showing that at least a portion of a third drive unit is in an outer overlap position, and FIG. 3 is a schematic plan view showing a work vehicle in a state where the rods of the left cylinder and the right cylinder are retracted.1 is a plan view showing a work vehicle in a state in which the rods of the left cylinder and the right cylinder are extended. FIG. 2 is a schematic plan view showing a work vehicle equipped with a distance change mechanism including a first change mechanism, a second change mechanism, a third change mechanism, and a fourth change mechanism. FIG. 3 is a schematic rear view illustrating a configuration for individually operating the left change mechanism and the right change mechanism. FIG. 4 is a flowchart showing an example (first example) of the operation of the distance change mechanism. FIG. 5 is a schematic plan view showing an example (first example) of the operation of the distance change mechanism. FIG. 6 is a schematic plan view showing an example (first example) of the operation of the distance change mechanism. FIG. 7 is a schematic plan view showing an example (first example) of the operation of the distance change mechanism. FIG. 8 is a flowchart showing a modified example of the first example. FIG. 9 is a flowchart showing another example (second example) of the operation of the distance change mechanism. FIG. 10 is a schematic plan view showing another example (second example) of the operation of the distance change mechanism. FIG. 11 is a schematic plan view showing another example (second example) of the operation of the distance change mechanism. FIG. 12 is a schematic plan view showing another example (second example) of the operation of the distance change mechanism. 1 is a front view showing another embodiment of the work vehicle with the vehicle body raised. FIG. 2 is a view showing a first correspondence table. FIG. 3 is a view showing a second correspondence table. FIG. 4 is a front view showing the work vehicle with the vehicle body height set to a first crop-compatible height. FIG. 5 is a front view showing the work vehicle with the vehicle body height set to a second crop-compatible height. FIG. 6 is a flowchart showing an example (first example) of the operation of the height change mechanism. FIG. 7 is a flowchart showing a modified example of the first example. FIG. 8 is a flowchart showing an example (second example) of the operation of the height change mechanism. FIG. 9 is a flowchart showing a modified example of the second example. FIG. 10 is a schematic side view illustrating an example (first example) of the operation of the height change mechanism. FIG. 11 is a schematic side view illustrating an example (first example) of the operation of the height change mechanism. FIG. 12 is a schematic front view illustrating an example (second example) of the operation of the height change mechanism. FIG. 13 is a schematic side view showing a work vehicle equipped with a position change mechanism, with the power unit (battery) in a rear position. FIG. 14 is a schematic side view showing a work vehicle equipped with a position change mechanism, with the power unit (battery) in an optimal position between the front position and the rear position.1 is a schematic side view showing a work vehicle equipped with a position change mechanism, showing a state in which the power unit (battery) is in a front position. FIG. 2 is a schematic perspective view showing a modified example of the position change mechanism, showing a state in which the storage frame and the power unit (battery) are in a rear position. FIG. 3 is a schematic perspective view showing a modified example of the position change mechanism, showing a state in which the storage frame and the power unit (battery) have been moved forward. FIG. 4 is a flowchart showing an example of the control operation of the position change control unit of the first embodiment. FIG. 5 is a graph showing an example of a change in slip ratio measured by a slip ratio measurement device. FIG. 6 is a flowchart showing an example of the control operation of the position change control unit of the second embodiment. FIG. 7 is a schematic side view illustrating an example of the operation of the position change mechanism. FIG. 8 is a graph showing an example of a change in torque measured by a torque measurement device. FIG. 9 is a schematic side view illustrating an example of the operation of the position change mechanism. FIG. 10 is a flowchart showing another example of the control operation of the position change control unit of the second embodiment. FIG. 11 is a left side view showing yet another embodiment of the work vehicle. FIG. 12 is a front view showing a method of attaching the support frame to the vehicle body from above. FIG. 13 is a left side view showing a method of attaching the support frame to the vehicle body from above. FIG. 14 is a front view showing a work vehicle of an embodiment not equipped with a height change mechanism. Fig. 10 is a left side view of a work vehicle equipped with a support frame of another embodiment. Fig. 11 is a front view of a work vehicle equipped with a support frame of another embodiment. Fig. 12 is a plan view showing the support frame etc. of another embodiment. Fig. 13 is a left side view illustrating a method of attaching the support frame of another embodiment to the vehicle body from the rear. Fig. 14 is a front view illustrating a method of attaching the support frame of another embodiment to the vehicle body from above. Fig. 15 is a front view showing a work vehicle of an embodiment in which the support frame is located below the side frames.

[0023] A preferred embodiment of a work vehicle 1 according to the present invention will now be described. Figures 1 to 7 are diagrams showing one embodiment of the work vehicle 1. Figure 1 is a perspective view of the work vehicle 1. Figure 2 is a left side view of the work vehicle 1. Figure 3 is a right side view of the work vehicle 1. Figure 4 is a front view of the work vehicle 1. Figure 5 is a rear view of the work vehicle 1. Figure 6 is a plan view of the work vehicle 1. Figure 7 is a block diagram showing the overall configuration of the work vehicle 1.

[0024] In the following description, the direction indicated by arrow X1 in the drawings is referred to as the forward direction, the direction indicated by arrow X2 as the backward direction, the direction indicated by arrow Y1 as the left direction, the direction indicated by arrow Y2 as the right direction, the direction indicated by arrow Z1 as the upward direction, and the direction indicated by arrow Z2 as the downward direction. In addition, the direction indicated by arrow X3 is referred to as the forward / backward direction, the direction indicated by arrow Y3 as the left / right direction, and the direction indicated by arrow Z3 as the up / down direction.

[0025] Examples of work performed by the work vehicle 1 include, but are not limited to, agricultural work, industrial (civil engineering, construction, etc.) work, and transportation work. In a preferred embodiment of the present invention, the work performed by the work vehicle 1 is agricultural work (farm work). Below, an example will be described in which the work performed by the work vehicle 1 is farm work. In this case, the work vehicle 1 is an agricultural work vehicle.

[0026] As shown in Figures 1 to 6, the work vehicle 1 includes a vehicle body 2 and a traveling device 3 that supports the vehicle body 2 so that it can travel. In this embodiment, the vehicle body 2 is formed in a substantially rectangular parallelepiped shape with an internal space. However, the shape of the vehicle body 2 is not limited to a substantially rectangular parallelepiped shape. Various devices and equipment are housed in the internal space of the vehicle body 2. Therefore, in the following description, the vehicle body 2 may be referred to as the "storage frame 2." In this embodiment, the storage frame 2 is the entire vehicle body 2. In other words, the storage frame 2 constitutes the vehicle body 2.

[0027] 2 and 3, a power unit 4 for driving the traveling device 3 is mounted (housed) in the interior space of the vehicle body 2. The power unit 4 generates power for driving the traveling device 3, and the power is supplied to the traveling device 3. As shown in FIG. 7, the power unit 4 includes a motor 5 and a battery 7. In the present embodiment, the vehicle body 2 mounts (houses) a battery 7, which will be described later, as the power unit 4.

[0028] The motor 5 is a traveling system motor that generates power to drive the traveling device 3. The motor 5 is an electric motor that is driven by electricity. An inverter 23 (see FIG. 7) is connected to the motor 5. The inverter 23 controls the rotation of the motor 5 based on a control signal from a control device 15, which will be described later. The battery 7 stores the power supplied to the motor 5. However, the power device 4 may include an engine instead of the motor 5. The power device 4 may also include a fuel cell.

[0029] As shown in FIG. 7 , the work vehicle 1 is equipped with a motor 5, which is a traveling motor, and a motor 6, which is a working motor. The working motor generates power to drive devices and mechanisms other than the traveling device 3. The motor 6 is an electric motor that is driven by power supplied from a battery 7. The rotation of the motor 6 can be controlled by an inverter 23. Hereinafter, the motor 5 may be referred to as the "traveling motor 5," and the motor 6 may be referred to as the "working motor 6."

[0030] The traveling motor 5 and the working motor 6 can be driven independently of each other. The working motor 6 is a motor for driving a hydraulic pump that operates a hydraulic cylinder, which will be described later. The working motor 6 also drives the external output shaft 8.

[0031] As described above, the battery 7, which is part of the power unit 4, is housed in the vehicle body 2 (see FIGS. 2 and 3). Although not shown, the vehicle body 2 also houses a cooling system (radiator, fan, water pump, compressor, etc.) that cools the power unit 4 (motor 5, motor 6, battery 7, etc.), and a hydraulic system (control valves, etc.) that actuates hydraulic cylinders (cylinder 62, left cylinder 81L, right cylinder 81R, lift cylinder 91, cylinder 113), etc., which will be described later, based on control signals from the control device 15.

[0032] As shown in Figure 2, the external output shaft 8 protrudes rearward from the rear of the vehicle body 2. The external output shaft 8 is an output shaft for extracting the power of the work motor 6 to the outside of the vehicle body 2. The power extracted from the external output shaft 8 is input to a work implement 200 for performing work. This drives the work implement 200 to perform work.

[0033] Examples of the working device 200 include, but are not limited to, devices that perform agricultural work (farm work), devices that perform civil engineering work, devices that perform construction work, devices that perform transportation work, etc. In the embodiment described below, the working device 200 is a device that performs farm work.

[0034] Examples of the working device 200 for performing agricultural work include a spraying device for spreading fertilizer, chemicals, and other spray materials, a sowing device for sowing seeds, a tilling device for tilling the soil, a tilling device (plow) for tilling the soil, a weeding device for weeding, and a soil-piling device for piling up soil. However, the type of working device 200 is not particularly limited as long as it is a device for performing agricultural work. Furthermore, if the working device 200 is an electrically powered working device, it may be driven by power extracted from the battery 7 via a power line to the outside of the vehicle body 2, instead of being driven by power extracted from the external output shaft 8.

[0035] The vehicle body 2 is capable of traveling by being driven by the traveling devices 3. As shown in Figures 4, 5, etc., the traveling devices 3 include a left traveling device 3L provided on the left side of the vehicle body 2 and a right traveling device 3R provided on the right side of the vehicle body 2. The vehicle body 2 is located between the left traveling device 3L and the right traveling device 3R. As shown in Figure 2, the left traveling device 3L includes a left front wheel 3LF and a left rear wheel 3LB. As shown in Figure 3, the right traveling device 3R includes a right front wheel 3RF and a right rear wheel 3RB.

[0036] Hereinafter, for convenience of explanation, the left front wheel 3LF, the right front wheel 3RF, the left rear wheel 3LB, and the right rear wheel 3RB may be collectively referred to as "wheels 30." Furthermore, the left front wheel 3LF and the right front wheel 3RF may be collectively referred to as "front wheels 30F," and the left rear wheel 3LB and the right rear wheel 3RB may be collectively referred to as "rear wheels 30B."

[0037] The wheels 30 (left front wheel 3LF, right front wheel 3RF, left rear wheel 3LB, right rear wheel 3RB) are arranged on the sides of the vehicle body 2. The left front wheel 3LF and the left rear wheel 3LB are arranged on the left side of the vehicle body 2. The right front wheel 3RF and the right rear wheel 3RB are arranged on the right side of the vehicle body 2. In the case of the work vehicle 1 of this embodiment, the size (diameter and width) of the rear wheels (left rear wheel 3LB, right rear wheel 3RB) is larger than the size (diameter and width) of the front wheels (left front wheel 3LF, right front wheel 3RF). However, the size of the front wheels (left front wheel 3LF, right front wheel 3RF) and the size of the rear wheels (left rear wheel 3LB, right rear wheel 3RB) may be the same, or the size of the front wheels may be larger than the size of the rear wheels.

[0038] In this embodiment, the traveling device 3 is a wheel-type traveling device in which the front wheels (left front wheel 3LF, right front wheel 3RF) and rear wheels (left rear wheel 3LB, right rear wheel 3RB) are all tires. However, the traveling device 3 may be a crawler-type traveling device in which the left traveling device 3L and the right traveling device 3R are crawlers, or the traveling device 3 may be a traveling device in which one of the front wheels or the rear wheels is a wheel and the other is a crawler.

[0039] 1 to 3, the work vehicle 1 is equipped with a fender 55L that covers the upper and front of the left rear wheel 3LB, and a fender 55R that covers the upper and front of the right rear wheel 3LR. The fender 55L is attached to a first connector 19L3 (see FIG. 8) of the frame structure 18, which will be described later. The fender 55R is attached to a first connector 21R3 (see FIG. 8) of the frame structure 18, which will be described later. Although not shown, the work vehicle 1 may also be equipped with fenders that cover the front wheels (left front wheel 3LF, right front wheel 3RF).

[0040] As shown in Figure 7, the work vehicle 1 is equipped with a transmission 9. The transmission 9 is capable of switching the propulsion force of the traveling device 3 by changing gears. The transmission 9 is also capable of switching between forward and reverse travel of the traveling device 3. The transmission 9 may be equipped with a speed change clutch that can switch between a four-wheel drive state (4WD) in which all four wheels (left front wheel 3LF, right front wheel 3RF, left rear wheel 3LB, right rear wheel 3RB) are driven, and a two-wheel drive state (2WD) in which only the rear wheels (left rear wheel 3LB, right rear wheel 3RB) or only the front wheels (left front wheel 3LF, right front wheel 3RF) are driven.

[0041] As shown in Figures 2, 3, 5, and 6, the work vehicle 1 is equipped with a mounting unit 10 to which a work device 200 for performing the work described above is attached. The work device 200 is detachably attached to the mounting unit 10. The mounting unit 10 is provided at the rear of the vehicle body 2. Figure 5 is a view of the mounting unit 10 as seen from behind.

[0042] The mounting part 10 is composed of a three-point link mechanism. Specifically, as shown in FIG. 5, the mounting part 10 has a lift arm 10a, a lower link 10b, a top link 10c, a lift rod 10d, and a lift cylinder 10e. The front end of the lift arm 10a is supported on the upper rear part of the vehicle body 2 so that it can swing upward or downward. The lift arm 10a swings (lifts and lowers) by driving the lift cylinder 10e. The lift cylinder 10e is composed of a hydraulic cylinder. The lift cylinder 10e is connected to a hydraulic pump (not shown) via a control valve (not shown).

[0043] The hydraulic pump is driven by the work system motor 6. The control valve is an electromagnetic valve or the like whose flow path is controlled to open or close by the control device 15. The flow of hydraulic oil discharged from the hydraulic pump is controlled by the control valve, thereby allowing the lift cylinder 10e to extend or retract.

[0044] The front end of the lower link 10b is supported on the rear lower part of the vehicle body 2 so as to be able to swing upward or downward. The front end of the top link 10c is supported on the rear part of the vehicle body 2 above the lower link 10b so as to be able to swing upward or downward. A lift rod 10d connects the lift arm 10a to the lower link 10b. A working device 200 is connected to the rear part of the lower link 10b and the rear part of the top link 10c. When the lift cylinder 10e is driven (extends and retracts), the lift arm 10a rises and falls, and the lower link 10b, which is connected to the lift arm 10a via the lift rod 10d, rises and falls. As a result, the working device 200 swings upward or downward (lifts and falls) around the front part of the lower link 10b as a fulcrum.

[0045] The work implement 200 attached to the attachment unit 10 is towed and moved by the work vehicle 1 as the work vehicle 1 travels. Note that instead of the work implement 200, a cart or the like for transporting agricultural produce or the like may be attached to the attachment unit 10. The attachment unit 10 may also be provided in a part other than the rear of the vehicle body 2 (for example, the front or side). Instead of being attached to the attachment unit 10, the work implement 200 may be placed on top of the work vehicle 1 (see Figure 75, etc.). In this case, the work implement 200 moves while being placed on top of the work vehicle 1 as the work vehicle 1 travels.

[0046] 7, the work vehicle 1 is equipped with a positioning device 11. The positioning device 11 can detect the position of the vehicle body 2 (positioning information including latitude and longitude) using a satellite positioning system (positioning satellite) such as D-GPS, GPS, GLONASS, Beidou, Galileo, or Michibiki. That is, the positioning device 11 receives satellite signals (position of the positioning satellite, transmission time, correction information, etc.) transmitted from the positioning satellites, and detects the position of the vehicle body 2 (for example, latitude and longitude) based on the satellite signals.

[0047] The positioning device 11 has a receiving device 12 and an inertial measurement unit (IMU) 13. The receiving device 12 has an antenna and the like and is a device that receives satellite signals transmitted from positioning satellites, and is attached to the vehicle body 2. The inertial measurement unit 13 has an acceleration sensor that detects acceleration, a gyro sensor that detects angular velocity, and the like. The inertial measurement unit 13 is attached to the vehicle body 2. The inertial measurement unit 13 can detect the roll angle, pitch angle, yaw angle, etc. of the vehicle body 2. Note that the yaw angle may be detected by installing multiple positioning devices 11.

[0048] As shown in FIG. 7 , the work vehicle 1 is equipped with a communication device 14. The communication device 14 includes a communication circuit for communicating via an on-board network and a wireless communication circuit for wireless communication. The wireless communication circuit can directly or indirectly communicate wirelessly with an external device using communication standards such as IEEE 802.11 series Wi-Fi (Wireless Fidelity, registered trademark), BLE (Bluetooth (registered trademark) Low Energy), LPWA (Low Power Wide Area), and LPWAN (Low-Power Wide-Area Network). As another example, the communication device 14 may be provided with a communication circuit capable of wirelessly communicating with an external device via, for example, a mobile phone communication network or a data communication network. Examples of external devices include a personal computer, a smartphone, a tablet computer, a PDA, or a server. Examples of external devices include an operation device 101, which will be described later.

[0049] As shown in Fig. 7, the work vehicle 1 is equipped with a control device 15. The control device 15 is a device that performs various controls of the work vehicle 1. The control device 15 is equipped with a calculation unit (CPU, etc.) and a storage unit (RAM, ROM, etc.). The storage unit may include an external memory provided outside the control device 15. The control device 15 is connected to the various devices and mechanisms shown in Fig. 7 via an in-vehicle LAN (on-board network) such as a CAN (Controller Area Network) or a communication line.

[0050] The control device 15 controls the operation of various devices and mechanisms communicably connected to the control device 15 by having the calculation unit execute various control programs stored in the memory unit. The functions of each control unit of the control device 15 (autonomous driving control unit 15A, distance change control unit 15B, height change control unit 15C, position change control unit 15D) described below are realized by having the calculation unit execute predetermined control programs stored in the memory unit.

[0051] As shown in Fig. 7, the control device 15 includes an automatic driving control unit 15A. The automatic driving control unit 15A controls the automatic driving of the work vehicle 1. The automatic driving control unit 15A is capable of executing line-type automatic driving control and autonomous-type automatic driving control. In line-type automatic driving control, the automatic driving control unit 15A controls the operation of the steering mechanism 60, transmission 9, motor 5, etc., which will be described later, so that the work vehicle 1 (vehicle body 2) moves along a predetermined planned driving line.

[0052] In autonomous automatic driving control, the automatic driving control unit 15A sets the direction of travel (steering direction) and vehicle speed (vehicle speed) of the vehicle body 2 based on the results of sensing (detecting objects) around the work vehicle 1 (vehicle body 2) using the positioning device 11, etc., and controls the operation of the steering mechanism 60, transmission 9, motor 5, etc. so that the set steering and vehicle speed are achieved. Note that it may be possible to switch between line-type automatic driving control and autonomous automatic driving control using a switch, etc. Furthermore, the automatic driving control unit 15A may be configured to be able to execute either line-type automatic driving control or autonomous automatic driving control. Note that the configuration of the automatic driving control unit 15A is not limited to the configuration described above.

[0053] The work vehicle 1 can perform automatic driving (unmanned driving) without an operator on board because the control device 15 includes the automatic driving control unit 15A. Therefore, the work vehicle 1 in the illustrated embodiment does not have a driver's seat where an operator sits. However, the work vehicle 1 may also be a vehicle that performs automatic driving with an operator on board. Alternatively, the work vehicle 1 may be a vehicle that is driven and driven by an operator on board. When the work vehicle 1 is a vehicle in which an operator rides, a driver's seat is provided in the vehicle body 2.

[0054] As shown in FIG. 7 , the work vehicle 1 is equipped with a lighting device 16. The lighting device 16 is provided on the vehicle body 2. The lighting device 16 includes at least a headlight that illuminates the area ahead of the vehicle body 2. In addition to the headlight, the lighting device 16 may also include a plurality of work lights that illuminate the area around the vehicle body 2. The work lights can, for example, illuminate the sides (left and right) of the vehicle body 2 or the area behind the vehicle body 2. The lighting device 16 may also include status indicator lights, left and right lights, brake lights, etc.

[0055] As shown in Fig. 7, the work vehicle 1 is equipped with an alarm device 17. The alarm device 17 uses sound, light, etc. to alert people around the vehicle body 2 of danger (such as the approach of the vehicle body 2). The alarm device 17 is composed of a speaker, a warning light, etc.

[0056] As shown in Figure 1 and other figures, the work vehicle 1 is equipped with a frame structure 18 that is arranged around the vehicle body 2 and attached to the vehicle body 2. As shown in Figure 8 and other figures, the frame structure 18 includes a left frame 18L, a right frame 18R, and a lateral frame 18M. As shown in Figures 1 and 4 and other figures, the left frame 18L is provided on the left side of the vehicle body 2. The left frame 18L extends in the up-down direction along the vehicle body 2. The left frame 18L also extends in the front-rear direction along the vehicle body 2. The right frame 18R is provided on the right side of the vehicle body 2. The right frame 18R extends in the up-down direction along the vehicle body 2. The right frame 18R also extends in the front-rear direction along the vehicle body 2.

[0057] The left frame 18L connects the left front wheel 3LF and the left rear wheel 3LB. The right frame 18R connects the right front wheel 3RF and the right rear wheel 3RB. The left frame 18L and the right frame 18R are frames disposed on the sides of the vehicle body 2. For this reason, the left frame 18L and the right frame 18R may be collectively referred to as the "side frame 18LR."

[0058] The horizontal frame 18M connects the left frame 18L and the right frame 18R. More specifically, the horizontal frame 18M connects the upper part of the left frame 18L and the upper part of the right frame 18R. The horizontal frame 18M is also a frame that is disposed above the vehicle body. For this reason, the horizontal frame 18M may be referred to as the "upper frame 18M."

[0059] 4, the vehicle body 2 is disposed between the left frame 18L and the right frame 18R in a front view. In other words, the vehicle body 2 is disposed in a position sandwiched between the left frame 18L and the right frame 18R. The vehicle body 2 is also disposed below the lateral frame 18M. Therefore, the vehicle body 2 is disposed in a position surrounded by the left frame 18L, the right frame 18R, and the lateral frame 18M in a front view.

[0060] As shown in FIG. 9 and other figures, the left frame 18L is composed of a first left frame 19L and a second left frame 20L. The first left frame 19L is composed of a first front support pillar 19L1, a first rear support pillar 19L2, and a first connector 19L3. The first front support pillar 19L1 and the first rear support pillar 19L2 are spaced apart in the front-to-rear direction and extend parallel to each other in the up-to-down direction. As shown in FIGS. 1 and 4, the first front support pillar 19L1 is located on the left side of the front of the vehicle body 2. As shown in FIG. 5, the first rear support pillar 19L2 is located on the left side of the rear of the vehicle body 2. The first front support pillar 19L1 and the first rear support pillar 19L2 are formed in a cylindrical (rectangular) shape.

[0061] As shown in FIG. 9 , the first connector 19L3 connects the first front support 19L1 and the first rear support 19L2. The first connector 19L3 is composed of frame members 19AL, 19BL, 19CL, 19DL, and 19EL. The frame member 19AL extends in the front-to-rear direction and connects the upper portion of the first front support 19L1 to the upper portion of the first rear support 19L2. The frame member 19BL extends in the front-to-rear direction to the left of the frame member 19AL. The frame member 19CL connects the front portion of the frame member 19AL to the front portion of the frame member 19BL. The frame member 19DL connects the rear portion of the frame member 19AL to the rear portion of the frame member 19BL. The frame member 19EL connects a midpoint in the front-rear direction of the frame member 19AL and a midpoint in the front-rear direction of the frame member 19BL.

[0062] As shown in FIG. 9 , the second left frame 20L is composed of a second front support 20L1, a second rear support 20L2, and a second connector 20L3. The second front support 20L1 and the second rear support 20L2 are spaced apart in the front-to-rear direction and extend parallel to each other in the up-down direction. The second connector 20L3 connects the second front support 20L1 and the second rear support 20L2. The second connector 20L3 is composed of frame members 20FL, 20GL, 20HL, and 20IL. The frame member 20FL extends in the front-to-rear direction and connects the upper portion of the second front support 20L1 to the upper portion of the second rear support 20L2. The frame member 20GL extends rightward from the front portion of the right surface of the frame member 20FL. The frame member 20HL extends rightward from the rear portion of the right surface of the frame member 20FL. The frame member 20IL extends rightward from the middle portion of the right surface of the frame member 20FL in the front-to-rear direction.

[0063] As shown by the downward arrow in Figure 9, the second front support 20L1 is inserted from above into the cylindrical first front support 19L1. The second rear support 20L2 is inserted from above into the cylindrical first rear support 19L2. This combines the first left frame 19L and the second left frame 20L (see Figure 10). The second front support 20L1 can move up and down along the first front support 19L1. The second rear support 20L2 can move up and down along the first rear support 19L2. This allows the second left frame 20L to move up and down relative to the first left frame 19L.

[0064] As shown in FIG. 9 , the right frame 18R is composed of a first right frame 21R and a second right frame 22R. The first right frame 21R is composed of a first front support pillar 21R1, a first rear support pillar 21R2, and a first connector 21R3. The first front support pillar 21R1 and the first rear support pillar 21R2 are spaced apart in the front-to-rear direction and extend parallel to each other in the up-down direction. As shown in FIGS. 1 and 4 , the first front support pillar 21R1 is located on the right side of the front portion of the vehicle body 2. As shown in FIG. 5 , the first rear support pillar 21R2 is located on the right side of the rear portion of the vehicle body 2. The first front support pillar 21R1 and the first rear support pillar 21R2 are formed in a cylindrical (rectangular) shape.

[0065] The first connector 21R3 connects the first front support 21R1 and the first rear support 21R2. The first connector 21R3 is composed of frame members 21AR, 21BR, 21CR, 21DR, and 21ER. The frame member 21AR extends in the front-to-rear direction and connects the upper part of the first front support 21R1 to the upper part of the first rear support 21R2. The frame member 21BR extends in the front-to-rear direction to the right of the frame member 21AR. The frame member 21CR connects the front part of the frame member 21AR to the front part of the frame member 21BR. The frame member 21DR connects the rear part of the frame member 21AR to the rear part of the frame member 21BR. The frame member 21ER connects the midpoint of the frame member 21AR to the midpoint of the frame member 21BR in the front-to-rear direction.

[0066] The second right frame 22R is composed of a second front support 22R1, a second rear support 22R2, and a second connector 22R3. The second front support 22R1 and the second rear support 22R2 are spaced apart in the front-to-rear direction and extend parallel to each other in the up-down direction. The second connector 22R3 connects the second front support 22R1 and the second rear support 22R2. The second connector 22R3 is composed of frame members 22FR, 22GR, 22HR, and 22IR. The frame member 22FR extends in the front-to-rear direction and connects the upper part of the second front support 22R1 to the upper part of the second rear support 22R2. The frame member 22GR extends leftward from the front portion of the left surface of the frame member 22FR. The frame member 22HR extends leftward from the rear portion of the left surface of the frame member 22FR. The frame member 22IR extends leftward from a midpoint in the front-to-rear direction of the left surface of the frame member 22FR.

[0067] As shown by the downward arrow in Figure 9, the second front support 22R1 is inserted from above into the cylindrical first front support 21R1. The second rear support 22R2 is inserted from above into the cylindrical first rear support 21R2. This combines the first right frame 21R and the second right frame 22R (see Figure 10). The second front support 22R1 can move up and down along the first front support 21R1. The second rear support 22R2 can move up and down along the first rear support 21R2. This allows the second right frame 22R to move up and down relative to the first right frame 21R.

[0068] As shown in Figure 10, the horizontal frame 18M is composed of frame members 18MA, 18MB, 18MC, 18MD, and 18ME. The frame member 18MA is located on the left side of the horizontal frame 18M and extends in the front-to-rear direction. The frame member 18MB is located on the right side of the horizontal frame 18M and extends in the front-to-rear direction. The frame members 18MA and 18MB are arranged parallel to each other with a gap in the left-to-right direction.

[0069] Frame members 18MC, 18MD, and 18ME extend parallel to one another in the left-right direction. Frame member 18MC connects the front of frame member 18MA to the front of frame member 18MB. Frame member 18MD connects the rear of frame member 18MA to the rear of frame member 18MB. Frame member 18ME connects the midpoint of frame member 18MA in the front-to-rear direction to the midpoint of frame member 18MB in the front-to-rear direction.

[0070] The frame members 18MC, 18MD, and 18ME are formed in a cylindrical (rectangular) shape. As shown by the arrows in Figure 10, the frame member 20GL is inserted into the frame member 18MC from the left, and the frame member 22GR is inserted from the right. The frame member 20HL is inserted into the frame member 18MD from the left, and the frame member 22HR is inserted from the right. The frame member 20IL is inserted into the frame member 18ME from the left, and the frame member 22IR is inserted from the right. This combines the horizontal frame 18M, the second left frame 20L, and the second right frame 22R (see Figure 10).

[0071] The frame member 20GL inserted into the frame member 18MC from the left can move left and right along the frame member 18MC. The frame member 20HL inserted into the frame member 18MD from the left can move left and right along the frame member 18MD. The frame member 20IL inserted into the frame member 18ME from the left can move left and right along the frame member 18ME. This allows the left frame 18L to move left and right relative to the horizontal frame 18M, to the left of the horizontal frame 18M.

[0072] The frame member 22GR inserted into the frame member 18MC from the right can move left and right along the frame member 18MC. The frame member 22HR inserted into the frame member 18MD from the right can move left and right along the frame member 18MD. The frame member 22IR inserted into the frame member 18ME from the right can move left and right along the frame member 18ME. This allows the right frame 18R to move left and right relative to the horizontal frame 18M, to the right of the horizontal frame 18M.

[0073] As described above, the second left frame 20L can move up and down relative to the first left frame 19L. The second right frame 22R can move up and down relative to the first right frame 21R. Therefore, the horizontal frame 18M (movable frame 32, described later) combined with the second left frame 20L and the second right frame 22R can move up and down relative to the first left frame 19L and the first right frame 21R (fixed frame 31, described later).

[0074] As shown in Figures 1, 4, and 5, the vehicle body 2 is fixed to the lower part of the horizontal frame 18M. Specifically, the vehicle body 2 is fixed to the lower part of the frame members 18MA and 18MB. This allows the vehicle body 2 to move integrally with the horizontal frame 18M. Therefore, when the horizontal frame 18M moves up and down relative to the first left frame 19L and the first right frame 21R, the vehicle body 2 moves up and down together with the horizontal frame 18M.

[0075] The frame structure 18 has a fixed frame 31 to which the traveling device 3 is attached, and a movable frame 32 attached to the vehicle body 2. Of the frame structure 18, the second left frame 20L, the second right frame 22R, and the horizontal frame 18M are movable frames 32 that are vertically movable. The first left frame 19L and the first right frame 21R are fixed frames 31 that do not move vertically. The vehicle body 2 moves vertically together with the movable frame 32 relative to the fixed frame 31, i.e., rises and falls.

[0076] A height change mechanism 90, which will be described later, changes the height of the vehicle body 2 from the ground by raising and lowering the movable frame 32 relative to the fixed frame 31. The traveling devices 3 are attached to the fixed frames. More specifically, the left traveling device 3L is attached to the first left frame 19L. The right traveling device 3R is attached to the first right frame 21R. When the movable frame 32 is raised and lowered relative to the fixed frame 31, the vehicle body 2 is raised and lowered relative to the traveling devices 3.

[0077] As described above, the left frame 18L and the right frame 18R can move left and right relative to the lateral frame 18M. Because the vehicle body 2 is fixed to the lateral frame 18M, the left frame 18L and the right frame 18R can move left and right relative to the vehicle body 2. Specifically, the left frame 18L can move in a direction away from the vehicle body 2 (leftward) and a direction toward the vehicle body 2 (rightward). The right frame 18R can move in a direction away from the vehicle body 2 (rightward) and a direction toward the vehicle body 2 (leftward).

[0078] Because the left traveling unit 3L is attached to the left frame 18L (first left frame 19L), the left traveling unit 3L can move left and right as the left frame 18L moves left and right. Because the right traveling unit 3R is attached to the right frame 18R (first right frame 21R), the right traveling unit 3R can move left and right as the right frame 18R moves left and right.

[0079] 7, the work vehicle 1 is equipped with a drive unit 40 for driving the wheels (left front wheel 3LF, right front wheel 3RF, left rear wheel 3LB, and right rear wheel 3RB). The drive unit 40 has a drive device 45 that generates power, a transmission mechanism 50 that transmits the power generated by the drive device 45 to the wheels 30, and a steering mechanism 60 that changes the direction of the wheels (left front wheel 3LF, right front wheel 3RF).

[0080] 2 and 3, the drive unit 40 includes a first drive unit 41 for driving the left front wheel 3LF, a second drive unit 42 for driving the right front wheel 3RF, a third drive unit 43 for driving the left rear wheel 3LB, and a fourth drive unit 44 for driving the right rear wheel 3RB. The first drive unit 41, the second drive unit 42, the third drive unit 43, and the fourth drive unit 44 each have a drive device 45 and a transmission mechanism 50, which will be described later. The first drive unit 41 and the second drive unit 42 each have a steering mechanism 60, which will be described later. Each drive unit is attached to the frame structure 18.

[0081] 2 and 3, the first drive unit 41 includes a portion disposed around the left front wheel 3LF, the second drive unit 42 includes a portion disposed around the right front wheel 3RF, the third drive unit 43 includes a portion disposed around the left rear wheel 3LB, and the fourth drive unit 44 includes a portion disposed around the right rear wheel 3RB.

[0082] Specifically, the first drive unit 41 includes a portion disposed on the left side of the vehicle body 2 around the left front wheel 3LF (see FIG. 2). The second drive unit 42 includes a portion disposed on the right side of the vehicle body 2 around the right front wheel 3RF (see FIG. 3). The third drive unit 43 includes a portion disposed on the left side of the vehicle body 2 around the left rear wheel 3LB (see FIG. 2). The fourth drive unit 44 includes a portion disposed on the right side of the vehicle body 2 around the right rear wheel 3RB (see FIG. 3).

[0083] In this embodiment, the drive device 45 is a motor. More specifically, the drive device 45 is the traveling motor 5 described above. In other words, the motor that constitutes the drive device 45 is the same as the motor included in the power unit 4 described above. As will be described below, the motors 5 that constitute the drive device 45 of the drive unit 40 include a motor 5LF, a motor 5RF, a motor 5LB, and a motor 5RB.

[0084] First, the configuration of the first drive unit 41 will be described. As shown in Figures 2, 11, and 12, the first drive unit 41 has a motor 5LF and a transmission mechanism 50LF that transmits the power of the motor 5LF to the left front wheel 3LF. When the first drive unit 41 drives the motor 5LF, the power of the motor 5LF is transmitted to the left front wheel 3LF via the transmission mechanism 50LF.

[0085] As shown in Figure 2, the motor 5LF is disposed above the left front wheel 3LF. The motor 5LF is disposed forward of the central axis (rotation axis) of the left front wheel 3LF. The motor 5LF is attached to a side frame 18LR (see Figure 8) of the frame structure 18. Specifically, the motor 5LF is attached to the first left frame 19L, which is the left side frame 18LR, via a motor bracket (not shown). The output shaft of the motor 5LF extends in the left-right direction.

[0086] 11 and 12 , the transmission mechanism 50LF is composed of a plurality of transmission shafts and a plurality of gears. The plurality of transmission shafts includes a first transmission shaft 501, a second transmission shaft 502, a third transmission shaft 503, and a fourth transmission shaft 504. The plurality of gears includes a first gear 505, a second gear 506, a third gear 507, a fourth gear 508, a fifth gear 509, a sixth gear 510, a seventh gear 511, an eighth gear 512, a ninth gear 513, and a tenth gear 514.

[0087] As described above, the transmission mechanism 50LF has a first transmission shaft 501 and a second transmission shaft 502. The first transmission shaft 501 is disposed above the left front wheel 3LF and extends in the vertical direction. The second transmission shaft 502 rotates upon receiving power transmitted from the first transmission shaft 501. The second transmission shaft 502 is disposed inward (to the right) of the left front wheel 3LF and extends in the vertical direction. A first gear 505 is attached to the lower part of the first transmission shaft 501. A second gear 506 is attached to the upper part of the second transmission shaft 502. The first gear 505 and the second transmission shaft 502 are in mesh with each other. A third gear 507 is attached to the upper part of the first transmission shaft 501. The third gear 507 is a bevel gear and is in mesh with a fourth gear 508, which is also a bevel gear.

[0088] The fourth gear 508 is attached to the left portion of the third transmission shaft 503 extending in the left-right direction. A fifth gear 509 is attached to the right portion of the third transmission shaft 503. The fifth gear 509 meshes with a sixth gear 510. The fifth gear 509 and the sixth gear 510 each consist of a pair of gears arranged parallel to each other. The sixth gear 510 is attached to the fourth transmission shaft 504 extending in the left-right direction. A seventh gear 511 is attached to the left portion of the fourth transmission shaft 504. The seventh gear 511 meshes with an eighth gear 512. The eighth gear 512 is attached to the output shaft 5LFa of the motor 5LF.

[0089] A ninth gear 513 is attached to the lower part of the second transmission shaft 502. The ninth gear 513 is a bevel gear and meshes with a tenth gear 514, which is also a bevel gear. The tenth gear 514 is attached to a rotation shaft 3LFa (the central axis of the left front wheel 3LF) that extends inward (to the right) from the center of the left front wheel 3LF.

[0090] When the output shaft 5LFa of the motor 5LF rotates, the eighth gear 512 rotates, and the seventh gear 511 meshing with the eighth gear 512 rotates. When the seventh gear 511 rotates, the sixth gear 510 rotates together with the fourth transmission shaft 504. When the sixth gear 510 rotates, the fifth gear 509 meshing with the sixth gear 510 rotates. When the fifth gear 509 rotates, the fourth gear 508 rotates together with the third transmission shaft 503. When the fourth gear 508 rotates, the third gear 507 meshing with the fourth gear 508 rotates. When the third gear 507 rotates, the first gear 505 rotates together with the first transmission shaft 501.

[0091] When the first gear 505 rotates, the second gear 506, which meshes with the first gear 505, rotates. When the second gear 506 rotates, the ninth gear 513 rotates together with the second transmission shaft 502. When the ninth gear 513 rotates, the tenth gear 514, which meshes with the ninth gear 513, rotates. When the tenth gear 514 rotates, the left front wheel 3LF rotates together with the rotation shaft 3LFa. In this way, the left front wheel 3LF can be rotated by driving the motor 5LF.

[0092] Next, the configuration of the second drive unit 42 that rotates the right front wheel 3RF will be described. As shown in Figure 3, the second drive unit 42 has a motor 5RF and a transmission mechanism 50RF that transmits the power of the motor 5RF to the right front wheel 3RF. When the second drive unit 42 drives the motor 5RF, the power of the motor 5RF is transmitted to the right front wheel 3RF via the transmission mechanism 50RF.

[0093] The motor 5RF is disposed above the right front wheel 3RF. The motor 5RF is disposed forward of the central axis (rotation axis) of the right front wheel 3RF. The motor 5RF is attached to a side frame 18LR (see FIG. 8) of the frame structure 18. Specifically, the motor 5RF is attached to the first right frame 21R, which is the right side frame 18LR, via a motor bracket (not shown). By driving the motor 5RF, the right front wheel 3RF can be rotated.

[0094] The configuration of the transmission mechanism 50RF is the same as that of the transmission mechanism 50LF, except that it is arranged symmetrically with respect to the center of the width (left-right) of the vehicle body 2, so a description thereof will be omitted.

[0095] Next, the configuration of the third drive unit 43 that rotates the left rear wheel 3LB will be described. As shown in Figures 2, 13, and 14, the third drive unit 43 has a motor 5LB and a transmission mechanism 50LB that transmits the power of the motor 5LB to the left rear wheel 3LB. When the third drive unit 43 drives the motor 5LB, the power of the motor 5LB is transmitted to the left rear wheel 3LB via the transmission mechanism 50LB.

[0096] As shown in Figure 2, the motor 5LB is located above and in front of the left rear wheel 3LB. The motor 5LB is attached to a side frame 18LR (see Figure 8) of the frame structure 18. Specifically, the motor 5LB is attached to the first left frame 19L, which is the left side frame 18LR, via a motor bracket (not shown).

[0097] 13 and 14 , the transmission mechanism 50LB is composed of a plurality of transmission shafts and a plurality of gears. The plurality of transmission shafts includes a lower transmission shaft 520, an intermediate transmission shaft 521, and an upper transmission shaft 522. The plurality of gears includes an eleventh gear 523, a twelfth gear 524, a thirteenth gear 525, a fourteenth gear 526, a fifteenth gear 527, a sixteenth gear 528, a seventeenth gear 529, and an eighteenth gear 530.

[0098] As described above, the transmission mechanism 50LB has a lower transmission shaft 520, an intermediate transmission shaft 521, and an upper transmission shaft 522. The upper transmission shaft 522 is disposed rearward of the output shaft 5LBa of the motor 5LB and extends in the left-right direction parallel to the output shaft 5LBa. The upper transmission shaft 522 transmits power from the output shaft 5LBa of the motor 5LB to the intermediate transmission shaft 521. The intermediate transmission shaft 521 is disposed rearward of the upper transmission shaft 522 and extends in the left-right direction parallel to the upper transmission shaft 522. The intermediate transmission shaft 521 transmits power transmitted from the upper transmission shaft 522 to the lower transmission shaft 520. The lower transmission shaft 520 is disposed inward (to the right) of the left rear wheel 3LB and extends forward and upward.

[0099] The output shaft 5LBa of the motor 5LB extends in the left-right direction. An eleventh gear 523 is attached to the output shaft 5LBa of the motor 5LB. A twelfth gear 524 is attached to the right portion of the upper transmission shaft 522. The eleventh gear 523 and the twelfth gear 524 mesh with each other. A thirteenth gear 525 is attached to the left portion of the upper transmission shaft 522. A fourteenth gear 526 is attached to the left portion of the intermediate transmission shaft 521. The thirteenth gear 525 and the fourteenth gear 526 each consist of a pair of gears arranged parallel to each other. The thirteenth gear 525 and the fourteenth gear 526 mesh with each other.

[0100] A fifteenth gear 527 is attached to the right portion of the intermediate transmission shaft 521. The fifteenth gear 527 is a bevel gear and meshes with a sixteenth gear 528, which is also a bevel gear. The sixteenth gear 528 is attached to the upper portion of the lower transmission shaft 520. A seventeenth gear 529 is attached to the lower portion of the lower transmission shaft 520. The seventeenth gear 529 is a bevel gear and meshes with an eighteenth gear 530, which is also a bevel gear. The eighteenth gear 530 is attached to a rotation shaft 3LBa that extends inward (to the right) from the center of the left rear wheel 3LB.

[0101] When the output shaft 5LBa of the motor 5LB rotates, the 11th gear 523 rotates, and the 12th gear 524 meshing with the 11th gear 523 rotates. When the 12th gear 524 rotates, the 13th gear 525 rotates together with the upper transmission shaft 522. When the 13th gear 525 rotates, the 14th gear 526 meshing with the 13th gear 525 rotates. When the 14th gear 526 rotates, the 15th gear 527 rotates together with the intermediate transmission shaft 521. When the 15th gear 527 rotates, the 16th gear 528 meshing with the 15th gear 527 rotates. When the 16th gear 528 rotates, the 17th gear 529 rotates together with the lower transmission shaft 520. When the 17th gear 529 rotates, the 18th gear 530 meshing with the 17th gear 529 rotates. When the eighteenth gear 530 rotates, the left rear wheel 3LB rotates together with the rotary shaft 3LBa. In this manner, the left rear wheel 3LB can be rotated by driving the motor 5LB.

[0102] Next, the configuration of the fourth drive unit 44 that rotates the right rear wheel 3RB will be described. As shown in Figure 3, the fourth drive unit 44 has a motor 5RB and a transmission mechanism 50RB that transmits the power of the motor 5RB to the right rear wheel 3RB. When the fourth drive unit 44 drives the motor 5RB, the power of the motor 5RB is transmitted to the right rear wheel 3RB via the transmission mechanism 50RB.

[0103] The motor 5RB is disposed above and in front of the right rear wheel 3RB. The motor 5RB is attached to a side frame 18LR (see FIG. 8) of the frame structure 18. Specifically, the motor 5RB is attached to the first right frame 21R, which is the right side frame 18LR, via a motor bracket (not shown).

[0104] The configuration of the transmission mechanism 50RB is the same as that of the transmission mechanism 50LB, except that it is arranged symmetrically with respect to the center of the width (left-right) of the vehicle body 2, so a description thereof will be omitted.

[0105] The third drive unit 43 and the fourth drive unit 44 are provided with brake devices 51 (see FIGS. 13 and 14). The brake devices 51 are, for example, disc brakes. By activating the brake device 51 of the third drive unit 43, it is possible to stop the rotation of the left rear wheel 3LB. By activating the brake device 51 of the fourth drive unit 44, it is possible to stop the rotation of the right rear wheel 3RB. The activation of the brake devices 51 can be controlled by the control device 15.

[0106] As shown in Fig. 7, the drive unit 40 has a steering mechanism 60 that changes the direction of the wheels 30. In the present embodiment, the steering mechanism 60 is a mechanism that changes the direction of the front wheels (left front wheel 3LF and right front wheel 3RF) among the wheels 30. As shown in Figs. 2 and 3, the steering mechanism 60 includes a left steering mechanism 60L that changes the direction of the left front wheel 3LF and a right steering mechanism 60R that changes the direction of the right front wheel 3RF.

[0107] As shown in Fig. 2, the first drive unit 41 is equipped with a left steering mechanism 60L. As shown in Fig. 3, the second drive unit 42 is equipped with a right steering mechanism 60R. The configurations of the left steering mechanism 60L and the right steering mechanism 60R are the same except that they are symmetrical across the center in the width direction (left-right direction) of the vehicle body 2. Therefore, hereinafter, as the configuration of the steering mechanism 60, the configuration of the left steering mechanism 60L will be described, and a description of the configuration of the right steering mechanism 60R will be omitted.

[0108] As shown in FIGS. 2 , 15 , and 16 , the steering mechanism 60 (left steering mechanism 60L) has a rotating body 61 that rotates about an axis AX1 in the vertical direction when steering the wheel (left front wheel 3LF). The axis AX1 of the rotating body 61 is located above the wheel (left front wheel 3LF). The axis AX1 of the rotating body 61 is located in a position that overlaps with the wheel (left front wheel 3LF) in a plan view (see FIG. 18 ). The rotating body 61 has a first portion 611, a second portion 612, a third portion 613, and a fourth portion 614. The first portion 611, the second portion 612, the third portion 613, and the fourth portion 614 are integrated to form a single rotating body 61.

[0109] The first portion 611 is formed in a cylindrical shape with its central axis facing up and down. The central axis of the first portion 611 (the central axis of the cylinder) coincides with the axis AX1 described above. Therefore, the central axis of the first portion 611 is located above the left front wheel 3LF. When the left front wheel 3LF is steered, the rotating body 61 rotates around the axis of the central axis of the first portion 611 (i.e., around the axis AX1). The first transmission shaft 501 is inserted through the first portion 611. An upper portion of the first transmission shaft 501 protrudes upward from the first portion 611. A protrusion 611a protruding in the radial direction of the first portion 611 (horizontal direction away from the central axis of the first portion 611) is provided on the outer circumferential surface of the first portion 611.

[0110] The second part 612 is formed in a cylindrical shape with its central axis facing the vertical direction. The second part 612 is disposed inward (to the right) of the wheel (left front wheel 3LF). The second part 612 accommodates the second transmission shaft 502 (see FIGS. 11 and 17).

[0111] The third part 613 connects the lower end of the first part 611 and the upper end of the second part 612. The third part 613 is located higher than the left front wheel 3LF. The third part 613 is formed in a generally elliptical shape in a plan view. The third part 613 functions as a gear box that houses the first gear 505 and the second gear 506 (see FIGS. 11 and 17 ).

[0112] The fourth part 614 is connected to the lower end of the second part 612. The fourth part 614 has a cylindrical part 614a connected to the lower end of the second part 612 and a conical part 614b provided at the lower end of the cylindrical part 614a. The fourth part 614 is disposed inward (to the right) of the left front wheel 3LF. The fourth part 614 functions as a gear box that houses the ninth gear 513 and the tenth gear 514 (see FIGS. 12 and 17).

[0113] The conical portion 614b of the fourth portion 614 is connected to the left front wheel 3LF. As a result, when the rotating body 61 rotates about the axis AX1, causing the fourth portion 614 to rotate about the axis AX1, the left front wheel 3LF also rotates about the axis AX1. In other words, as the rotating body 61 rotates about the axis AX1, the left front wheel 3LF also rotates about the axis AX1. Note that the fourth portion 614 does not rotate together with the rotation of the left front wheel 3LF (rotation about the rotation axis 3LFa) when the work vehicle 1 is traveling.

[0114] 15, 16, and 18, the steering mechanism 60 has a cylinder 62 with a rod 62a that extends and retracts in a direction perpendicular to the axis AX1 (the front-rear direction). The cylinder 62 is made up of a hydraulic cylinder. The rotating body 61 has a first connection part 61a to which the rod 62a is connected and a second connection part 61b to which the wheel (left front wheel 3LF) is connected.

[0115] The first connecting portion 61a is composed of the protrusion 611a described above. A shaft 61c passes through the protrusion 611a constituting the first connecting portion 61a in the vertical direction. A tip member 62b attached to the tip of a rod 62a is fitted into the upper part of the shaft 61c. The tip member 62b can rotate around the central axis of the shaft 61c.

[0116] The second connection part 61b is composed of the above-mentioned fourth part 614. The second connection part 61b is connected to the inside (right side) of the wheel (left front wheel 3LF) at the bottom of the rotating body 61. The second connection part 61b is connected via a bearing or the like so as not to rotate together with the wheel (left front wheel 3LF) when traveling.

[0117] The cylinder 62 rotates the rotor 61 around the axis AX1 by extending and retracting the rod 62a, thereby rotating the left front wheel 3LF around the axis AX1. First, we will describe what happens when the rod 62a extends. As shown in FIG. 19 , when the rod 62a extends (see arrow R1), the first part 611 rotates around the axis AX1 together with the protrusion 611a (see arrow R2). When the first part 611 rotates around the axis AX1, the second part 612, the third part 613, and the fourth part 614, which are integrated with the first part 611, also rotate around the axis AX1. When the fourth part 614 rotates around the axis AX1, the left front wheel 3LF, which is connected to the fourth part 614, also rotates around the axis AX1 (see arrow R3). As a result, the orientation of the left front wheel 3LF changes so that the front part faces outward (to the right).

[0118] Next, we will explain what happens when the rod 62a is retracted. As shown in FIG. 20 , when the rod 62a is retracted (see arrow R4), the first part 611 rotates around the axis AX1 together with the protrusion 611a (see arrow R5). The rotation direction at this time is opposite to that when the rod 62a is extended. When the first part 611 rotates around the axis AX1, the second part, the third part 613, and the fourth part 614, which are integrated with the first part 611, also rotate around the axis AX1. When the fourth part 614 rotates around the axis AX1, the left front wheel 3LF, which is connected to the fourth part 614, also rotates around the axis AX1 (see arrow R6). As a result, the left front wheel 3LF changes orientation so that its front portion faces inward (leftward).

[0119] As described above, the left steering mechanism 60L can rotate the left front wheel 3LF about the axis AX1 by driving the cylinder 62 to extend and retract the rod 62a. Similarly, the right steering mechanism 60R can rotate the right front wheel 3RF about the axis AX1 by driving the cylinder 62 to extend and retract the rod 62a. In this way, the traveling direction of the work vehicle 1 can be changed by driving the steering mechanism 60 to change the orientation of the left front wheel 3LF and the right front wheel 3RF.

[0120] As is clear from the above explanation, the axis AX1, which is the rotation axis of the wheels (left front wheel 3LF, right front wheel 3RF), becomes the steering axis when the wheels (left front wheel 3LF, right front wheel 3RF) are steered. Here, as described above, the axis AX1, which is the steering axis, is located above the wheels (front wheels). This prevents the wheels (front wheels) from intruding into the vehicle body 2 when steering, compared to when the steering axis is located inside the wheels. This point will be explained below with reference to FIG. 21.

[0121] FIG. 21 is a plan view showing the change in position of the left front wheel 3LF when the left front wheel 3LF is rotated inward as indicated by arrow R7 (when the left front wheel 3LF is steered leftward). The position of the left front wheel 3LF before rotation (before steering) is shown by a solid line, and the position of the left front wheel 3LF after rotation (after steering) is shown by a virtual line. As shown in FIG. 21 , because the steering axis (axis AX1) of the left front wheel 3LF is located above the left front wheel 3LF, the amount (length) of the left front wheel 3LF intruding into the vehicle body 2 after steering is reduced compared to when the steering axis is located inward of the left front wheel 3LF (for example, when the steering axis is located at AX2). Therefore, interference between the wheels (front wheels) and the vehicle body 2 is prevented during steering, allowing for a larger steering angle.

[0122] As another embodiment of the drive unit 45, the motor of the drive unit 45 may be an in-wheel motor. In this case, all of the left front wheel 3LF, the right front wheel 3RF, the left rear wheel 3LB, and the right rear wheel 3RB may be driven by the in-wheel motor, or only some of the wheels (for example, the left front wheel 3LF and the right front wheel 3RF, or the left rear wheel 3LB and the right rear wheel 3RB) may be driven by the in-wheel motor.

[0123] 22 and 23 are diagrams showing another embodiment of the work vehicle 1. The work vehicle 1 according to this embodiment differs from the work vehicle 1 of the above-described embodiment (see FIGS. 1 to 6, etc.) in part of the configuration (arrangement) of the drive unit 40 for driving the wheels 30. The drive unit 40 of the work vehicle 1 according to this embodiment will be described below.

[0124] The drive unit 40 includes a first drive unit 41 for driving the left front wheel 3LF, a second drive unit 42 for driving the right front wheel 3RF, a third drive unit 43 for driving the left rear wheel 3LB, and a fourth drive unit 44 for driving the right rear wheel 3RB. Each drive unit is attached to the frame structure 18.

[0125] First, the configuration of the first drive unit 41 will be described. The first drive unit 41 has a motor 5LF and a transmission mechanism 50LF that transmits the power of the motor 5LF to the left front wheel 3LF. The motor 5LF is disposed above the vehicle body 2. The motor 5LF is attached to an upper frame 18M of the frame structure 18. The motor 5LF is attached to the upper frame 18M via a motor bracket (not shown). The output shaft of the motor 5LF extends to the left.

[0126] 24 and 25 , the transmission mechanism 50LF is composed of a plurality of transmission shafts and a plurality of gears. The plurality of transmission shafts includes a first transmission shaft 501, a second transmission shaft 502, and a third transmission shaft 503. The plurality of gears includes a first gear 505, a second gear 506, a third gear 507, a fourth gear 508, a fifth gear 509, a sixth gear 510, a ninth gear 513, and a tenth gear 514.

[0127] As described above, the transmission mechanism 50LF has the first transmission shaft 501, the second transmission shaft 502, and the third transmission shaft 503. The first transmission shaft 501 is disposed above the left front wheel 3LF and extends in the vertical direction. The second transmission shaft 502 is disposed inward (to the right) of the left front wheel 3LF and extends in the vertical direction. The third transmission shaft 503 is disposed above the first transmission shaft 501 and the second transmission shaft 502 and extends in the left-right direction.

[0128] The first transmission shaft 501, the second transmission shaft 502, and the third transmission shaft 503 are attached to the frame structure 18 via bearings or the like. The upper part of the first transmission shaft 501 is attached to the movable frame 32 (the second left frame 20L or the horizontal frame 18M). The second transmission shaft 502 is attached to the fixed frame 31. The third transmission shaft 503 is attached to the movable frame 32 (the second left frame 20L or the horizontal frame 18M).

[0129] The third transmission shaft 503 rotates upon receiving rotational power from the motor 5LF. The first transmission shaft 501 rotates upon receiving power transmitted from the third transmission shaft 503. The second transmission shaft 502 rotates upon receiving power transmitted from the first transmission shaft 501.

[0130] A first gear 505 is attached to the bottom of the first transmission shaft 501. A second gear 506 is attached to the top of the second transmission shaft 502. The first gear 505 and the second gear 506 mesh with each other. A third gear 507 is attached to the top of the first transmission shaft 501. The third gear 507 is a bevel gear, and meshes with a fourth gear 508, which is also a bevel gear.

[0131] The fourth gear 508 is attached to the left portion of the third transmission shaft 503. A fifth gear 509 is attached to the right portion of the third transmission shaft 503. The fifth gear 509 meshes with a sixth gear 510. The fifth gear 509 and the sixth gear 510 each consist of a pair of gears arranged parallel to each other. The sixth gear 510 is attached to the output shaft 5LFa of the motor 5LF.

[0132] A ninth gear 513 is attached to the lower part of the second transmission shaft 502. The ninth gear 513 is a bevel gear and meshes with a tenth gear 514, which is also a bevel gear. The tenth gear 514 is attached to a rotation shaft 3LFa (the central axis of the left front wheel 3LF) that extends inward (to the right) from the center of the left front wheel 3LF.

[0133] As described above, the first drive unit 41 of this alternative embodiment differs from the first drive unit 41 of the above-described embodiment (see Figures 11, 12, and 17) in that it does not have the fourth transmission shaft 504, the seventh gear 511, or the eighth gear 512, and the sixth gear 510 is attached to the output shaft 5LFa of the motor 5LF.

[0134] When the output shaft 5LFa of the motor 5LF rotates, the sixth gear 510 rotates, and the fifth gear 509 meshing with the sixth gear 510 rotates. When the fifth gear 509 rotates, the fourth gear 508 rotates together with the third transmission shaft 503. When the fourth gear 508 rotates, the third gear 507 meshing with the fourth gear 508 rotates. When the third gear 507 rotates, the first gear 505 rotates together with the first transmission shaft 501. When the first gear 505 rotates, the second gear 506 meshing with the first gear 505 rotates. When the second gear 506 rotates, the ninth gear 513 rotates together with the second transmission shaft 502. When the ninth gear 513 rotates, the tenth gear 514 meshing with the ninth gear 513 rotates. When the tenth gear 514 rotates, the left front wheel 3LF rotates together with the rotation shaft 3LFa. In this way, the left front wheel 3LF can be rotated by driving the motor 5LF.

[0135] The first transmission shaft 501 is extendable in the vertical direction. More specifically, the first transmission shaft 501 is extendable in accordance with a change in the height of the vehicle body 2 by a height change mechanism 90, which will be described later. The height change mechanism 90 is a mechanism that can change the height of the vehicle body 2 from the ground. The specific configuration of the height change mechanism 90 will be described in detail later, but here, the structure that allows the first transmission shaft 501 to extend and contract will be described.

[0136] As shown in Figures 26 and 27, the first transmission shaft 501 has an upper shaft 501a and a lower shaft 501b. Power from the motor 5LF is transmitted to the upper shaft 501a. The lower shaft 501b transmits the power transmitted to the upper shaft 501a to the second transmission shaft 502. The upper shaft 501a is formed in a cylindrical or columnar shape. The lower shaft 501b is formed in a cylindrical shape. The axis of the upper shaft 501a and the axis of the lower shaft 501b are arranged on the same straight line extending in the vertical direction. As the height of the vehicle body 2 is changed by the height change mechanism 90, the distance between the upper end of the upper shaft 501a and the lower end of the lower shaft 501b of the first transmission shaft 501 changes. In other words, the upper shaft 501a rises relative to the lower shaft 501b. This changes the vertical length of the first transmission shaft 501.

[0137] The first transmission shaft 501 has an intermediate shaft 501c. The axis of the intermediate shaft 501c is arranged on the same line as the axis of the upper shaft 501a and the axis of the lower shaft 501b. The intermediate shaft 501c is formed in a cylindrical shape. The intermediate shaft 501c has an upper portion 501c1 into which the upper shaft 501a is inserted and a lower portion 501c2 into which the lower shaft 501b is inserted.

[0138] First splines are formed on the outer surface of the upper shaft 501a. The first splines have convex ridges formed at equal intervals in the circumferential direction on the outer surface of the upper shaft 501a and extending in the vertical direction. Second splines are formed on the inner surface of the lower shaft 501b. The second splines have concave grooves formed at equal intervals in the circumferential direction on the inner surface of the lower shaft 501b and extending in the vertical direction.

[0139] An internal spline is formed on the inner surface of the intermediate shaft 501c. The internal spline has recessed grooves formed at equal intervals in the circumferential direction on the inner surface of the intermediate shaft 501c and extending in the vertical direction. An external spline is formed on the outer surface of the intermediate shaft 501c. The external spline has ridges formed at equal intervals in the circumferential direction on the outer surface of the intermediate shaft 501c and extending in the vertical direction.

[0140] The first spline meshes with the internal spline. More specifically, the convex ridges of the first spline mesh with the concave grooves of the internal spline. The second spline meshes with the external spline. More specifically, the concave grooves of the second spline mesh with the convex ridges of the external spline. As a result, the rotation of the upper shaft 501a is transmitted to the intermediate shaft 501c, and the rotation of the intermediate shaft 501c is transmitted to the lower shaft 501b. Therefore, the upper shaft 501a, the intermediate shaft 501c, and the lower shaft 501b of the first transmission shaft 501 rotate integrally around the axis.

[0141] Furthermore, because the ridges of the first spline and the grooves of the inner spline both extend in the vertical direction, the upper shaft 501a can move up and down along the axis of the intermediate shaft 501c. Because the grooves of the second spline and the ridges of the outer spline both extend in the vertical direction, the intermediate shaft 501c can move up and down along the axis of the lower shaft 501b. This vertical movement allows the first transmission shaft 501 to expand and contract. Figures 26 and 27 show the first transmission shaft 501 in an expanded state. Figures 24 and 25 show the first transmission shaft 501 in a contracted state.

[0142] The first transmission shaft 501 extends and retracts by driving the lifting cylinder 91 (see Figures 22, 30, etc.) of the height changing mechanism 90. The first transmission shaft 501 extends and retracts in accordance with the extension and retraction of the rod 91a of the lifting cylinder 91. When the rod 91a of the lifting cylinder 91 is extended and retracted to raise and lower the car body 2 together with the frame structure 18, the first transmission shaft 501 extends and retracts.

[0143] 30 and 31, when the rod 91a of the lift cylinder 91 is extended to lift the vehicle body 2, the first transmission shaft 501 is extended. As shown in Figures 22 and 23, when the rod 91a of the lift cylinder 91 is retracted to lower the vehicle body 2, the first transmission shaft 501 is retracted.

[0144] The movable parts (upper shaft 501a, intermediate shaft 501c) of the first transmission shaft 501 when it extends and retracts are attached to the movable frame 32 (the second left frame 20L or the second right frame 22R) via a bearing device (not shown). This allows the upper shaft 501a and intermediate shaft 501c to extend and retract when the movable frame 32 moves up and down together with the vehicle body 2.

[0145] In the above description, the first transmission shaft 501 is configured to be extendable in the vertical direction, but the second transmission shaft 502 may be configured to be extendable in the vertical direction instead of the first transmission shaft 501. In this case, the second transmission shaft 502 may be configured to have the upper shaft, lower shaft, and intermediate shaft described above.

[0146] In the above description, the first transmission shaft 501 includes the upper shaft 501a, the lower shaft 501b, and the intermediate shaft 501c. However, the intermediate shaft 501c may be omitted. In this case, the upper shaft 501a and the lower shaft 501b may be connected by a spline without using an intermediate shaft. That is, an external spline may be formed on the outer peripheral surface of the upper shaft 501a, and an internal spline may be formed on the inner peripheral surface of the lower shaft 501b, and these external spline and internal spline may be engaged with each other.

[0147] Next, the configuration of the second drive unit 42 that rotates the right front wheel 3RF will be described. As shown in Figure 22 etc., the second drive unit 42 has a motor 5RF and a transmission mechanism 50RF that transmits the power of the motor 5RF to the right front wheel 3RF. The motor 5RF is disposed above the vehicle body 2. The motor 5RF is attached to an upper frame 18M of the frame structure 18.

[0148] The motor 5RF is attached to the upper frame 18M via a motor bracket (not shown). The output shaft of the motor 5RF extends to the right. The configuration of the transmission mechanism 50RF is the same as that of the transmission mechanism 50LF, except that it is disposed symmetrically with respect to the center of the vehicle body 2 in the width direction (left-right direction), and therefore a description thereof will be omitted. The first transmission shaft 501 of the transmission mechanism 50RF is extendable and retractable in accordance with changes in the height of the vehicle body 2 by the height change mechanism 90.

[0149] Next, the configuration of the third drive unit 43 that rotates the left rear wheel 3LB will be described. As shown in Figure 22 and other figures, the third drive unit 43 has a motor 5LB and a transmission mechanism 50LB that transmits the power of the motor 5LB to the left rear wheel 3LB. The motor 5LB is attached to the upper frame 18M of the frame structure 18. The motor 5LB is attached to the upper frame 18M via a motor bracket (not shown). The output shaft of the motor 5RB extends to the left.

[0150] As shown in Figures 28 and 29, the transmission mechanism 50LB includes a lower transmission shaft 520, an upper transmission shaft 522, a first transmission gear 541, a second transmission gear 542, a third transmission gear 543, a fourth transmission gear 544, a fifth transmission gear 545, and a sixth transmission gear 546.

[0151] As described above, the transmission mechanism 50LB has a lower transmission shaft 520 and an upper transmission shaft 522. The upper transmission shaft 522 is disposed behind the output shaft 5LBa of the motor 5LB and extends in the left-right direction parallel to the output shaft 5LBa. The upper transmission shaft 522 receives power from the output shaft 5LBa of the motor 5LB and transmits it to the lower transmission shaft 520. The lower transmission shaft 520 extends in the up-down direction.

[0152] The output shaft 5LBa of the motor 5LB extends in the left-right direction. A first transmission gear 541 is attached to the output shaft 5LBa. A second transmission gear 542 is attached to the left portion of the upper transmission shaft 522. The first transmission gear 541 and the second transmission gear 542 are in mesh with each other. Each of the first transmission gear 541 and the second transmission gear 542 is composed of a pair of gears arranged parallel to each other.

[0153] A third transmission gear 543 is attached to the right portion of the upper transmission shaft 522. The third transmission gear 543 is a bevel gear and meshes with a fourth transmission gear 544, which is also a bevel gear. The fourth transmission gear 544 is attached to the upper portion of the lower transmission shaft 520. A fifth transmission gear 545 is attached to the lower portion of the lower transmission shaft 520. The fifth transmission gear 545 is a bevel gear and meshes with a sixth transmission gear 546, which is also a bevel gear. The sixth transmission gear 546 is attached to a rotation shaft 3LBa that extends inward (to the right) from the center of the left rear wheel 3LB.

[0154] When the output shaft 5LBa of the motor 5LB rotates, the first transmission gear 541 rotates, and the second transmission gear 542 meshing with the first transmission gear 541 rotates. When the second transmission gear 542 rotates, the third transmission gear 543 rotates together with the upper transmission shaft 522. When the third transmission gear 543 rotates, the fourth transmission gear 544 meshing with the third transmission gear 543 rotates. When the fourth transmission gear 544 rotates, the fifth transmission gear 545 rotates together with the lower transmission shaft 520. When the fifth transmission gear 545 rotates, the sixth transmission gear 546 meshing with the fifth transmission gear 545 rotates. When the sixth transmission gear 546 rotates, the left rear wheel 3LB rotates together with the rotation shaft 3LBa. In this way, the left rear wheel 3LB can be rotated by driving the motor 5LB.

[0155] Next, the configuration of the fourth drive unit 44 that rotates the right rear wheel 3RB will be described. As shown in FIG. 22 and other figures, the fourth drive unit 44 includes a motor 5RB and a transmission mechanism 50RB that transmits the power of the motor 5RB to the right rear wheel 3RB. The motor 5RB is attached to the upper frame 18M of the frame structure 18. The configuration of the transmission mechanism 50RB is the same as the configuration of the transmission mechanism 50LB except that it is disposed symmetrically with respect to the center of the vehicle body 2 in the width direction (left-right direction), and therefore a description thereof will be omitted. The transmission mechanism 50RB can rotate the right rear wheel 3RB by driving the motor 5RB.

[0156] The third drive unit 43 and the fourth drive unit 44 are provided with a brake device 51. The operation of the brake device 51 can be controlled by the control device 15.

[0157] The lower transmission shafts 520 of the third drive unit 43 and the fourth drive unit 44 are extendable and retractable in accordance with the change in height of the vehicle body 2 by the height change mechanism 90. Figures 28 and 29 show the lower transmission shaft 520 in an extended state. The extension and retraction structure of the lower transmission shaft 520 is the same as the extension and retraction structure of the first transmission shaft 501 described above. In other words, the lower transmission shaft 520 has an upper shaft 520a, a lower shaft 520b, and an intermediate shaft 520c that have the same configurations as the upper shaft 501a, the lower shaft 501b, and the intermediate shaft 501c of the first transmission shaft 501 described above.

[0158] In the lower transmission shaft 520, the rotation of the upper shaft 520a is transmitted to the intermediate shaft 520c, and the rotation of the intermediate shaft 520c is transmitted to the lower shaft 520b. As a result, in the first transmission shaft 501, the upper shaft 520a, the intermediate shaft 520c, and the lower shaft 520b rotate integrally around their respective axes. The upper shaft 520a can move up and down along the axis of the intermediate shaft 520c, and the intermediate shaft 520c can move up and down along the axis of the lower shaft 520b. This movement allows the lower transmission shaft 520 to extend and retract in the up and down direction.

[0159] The lower transmission shaft 520 extends and retracts by driving the lifting cylinder 91 of the height changing mechanism 90. The lower transmission shaft 520 extends and retracts in accordance with the extension and retraction of the rod 91 a of the lifting cylinder 91. When the rod 91 a of the lifting cylinder 91 is extended and retracted to raise and lower the vehicle body 2 together with the frame structure 18, the lower transmission shaft 520 extends and retracts.

[0160] When the rod 91a of the lift cylinder 91 is extended to raise the vehicle body 2, the lower transmission shaft 520 is extended (see FIGS. 30 and 31). When the rod 91a of the lift cylinder 91 is retracted to lower the vehicle body 2 (see FIGS. 22 and 23), the lower transmission shaft 520 is retracted.

[0161] The movable parts (upper shaft 520a, intermediate shaft 520c) of the lower transmission shaft 520 when it extends and retracts are attached to the movable frame 32 (the second left frame 20L or the second right frame 22R) via a bearing device (not shown). This allows the upper shaft 520a and intermediate shaft 520c to extend and retract when the movable frame 32 moves up and down together with the vehicle body 2.

[0162] As described above, the drive unit 40 of the work vehicle 1 according to another embodiment can extend and retract the first transmission shaft 501 of the first drive unit 41 and the second drive unit 42 and the lower transmission shaft 520 of the third drive unit 43 and the fourth drive unit 44 by driving the lifting cylinder 91 of the height changing mechanism 90. This allows the vehicle body 2 to be raised and lowered while maintaining power transmission from the motor 5 disposed above the vehicle body 2 to the wheels 30.

[0163] 16, 17, 32, and 33, at least a portion of the drive unit 40 is located on the outside facing the tread portion 30a of the wheel 30, and is positioned so as to overlap the wheel 30 in the width direction (left-right direction) of the vehicle body 2. The tread portion 30a is the portion of the wheel 30 that comes into contact with the ground.

[0164] Hereinafter, for convenience of explanation, "an outer position facing the tread portion 30a of the wheel 30 and overlapping with the wheel 30 in the width direction of the vehicle body 2" will be referred to as "outer overlap position." Also, "an outer position facing the tread portion 30a of the wheel 30" may be referred to as "the periphery of the wheel 30."

[0165] The position (angle) of the wheel 30 that serves as the reference when determining whether at least a portion of the drive unit 40 is in the outer overlap position is the position (angle) of the wheel 30 when the work vehicle 1 is moving straight forward or backward. In other words, the position (angle) of the wheel 30 that serves as the reference when determining whether at least a portion of the drive unit 40 is in the outer overlap position is the position (angle) of the wheel 30 when it is not being steered left or right.

[0166] The "at least a part of the drive unit 40" in the outer overlap position is, for example, the drive device 45. In this case, the entire drive device 45 may be in the outer overlap position, or only a part of the drive device 45 may be in the outer overlap position. In other words, it is sufficient that at least a part of the drive device 45 is in the outer overlap position.

[0167] 16, 17, and 32, in the case of the first drive unit 41, a portion of the motor 5LF, which is the drive device 45, is in the outer overlap position OP1. A portion of the motor 5LF is located above the tread portion 30a facing the tread portion 30a of the left front wheel 3LF. Although not illustrated, in the case of the second drive unit 42, similar to the case of the first drive unit 41, a portion of the motor 5RF, which is the drive device 45, is in the outer overlap position. A portion of the motor 5RF is located above the tread portion 30a facing the tread portion 30a of the right front wheel 3RF.

[0168] As shown in Figure 33, in the case of the third drive unit 43, a portion of the motor 5LB, which is the drive device 45, is in the outer overlap position OP1. A portion of the motor 5LB is located above and in front of the tread portion 30a facing the tread portion 30a of the left rear wheel 3LB. Although not illustrated, in the case of the fourth drive unit 44, as in the case of the third drive unit 43, a portion of the motor 5RB, which is the drive device 45, is in the outer overlap position. A portion of the motor 5RB is located above and in front of the tread portion 30a facing the tread portion 30a of the right rear wheel 3RB.

[0169] The "at least a part of the drive unit 40" in the outer overlap position may be, for example, the transmission mechanism 50. In this case, the entire transmission mechanism 50 may be in the outer overlap position, or only a part of the transmission mechanism 50 may be in the outer overlap position. In other words, it is sufficient that at least a part of the transmission mechanism 50 is in the outer overlap position.

[0170] 16, 17, and 32, in the case of the first drive unit 41, a portion of the transmission mechanism 50LF is in the outer overlap position OP1. Specifically, of the transmission mechanism 50LF, the first transmission shaft 501, the third transmission shaft 503, the first gear 505, the second gear 506, the third gear 507, and the fourth gear 508 are partially or entirely in the outer overlap position OP1. Furthermore, although not illustrated, in the case of the second drive unit 42, as in the case of the first drive unit 41, the first transmission shaft 501, the third transmission shaft 503, the first gear 505, the second gear 506, the third gear 507, and the fourth gear 508 are partially or entirely in the outer overlap position.

[0171] 33 , in the case of the third drive unit 43, a portion of the transmission mechanism 50LB is in the outer overlap position. Specifically, of the transmission mechanism 50LB, the intermediate transmission shaft 521, the upper transmission shaft 522, the eleventh gear 523, the twelfth gear 524, the thirteenth gear 525, and the fourteenth gear 526 are in the outer overlap position OP1 in part or in whole. Also, although not illustrated, in the case of the fourth drive unit 44, as in the case of the third drive unit 43, the intermediate transmission shaft 521, the upper transmission shaft 522, the eleventh gear 523, the twelfth gear 524, the thirteenth gear 525, and the fourteenth gear 526 are in the outer overlap position in part or in whole of the transmission mechanism 50RB.

[0172] "At least a part of the drive unit 40" in the outer overlap position may be, for example, the steering mechanism 60. In this case, the entire steering mechanism 60 may be in the outer overlap position, or only a part of the steering mechanism 60 may be in the outer overlap position. In other words, it is sufficient that at least a part of the steering mechanism 60 is in the outer overlap position.

[0173] 16, in the case of the first drive unit 41, a portion of the left steering mechanism 60L is in the outer overlap position OP1. Specifically, in the left steering mechanism 60L, a portion of the rotating body 61 and a portion of the cylinder 62 are in the outer overlap position OP1. Furthermore, although not illustrated, in the case of the second drive unit 42, a portion of the rotating body 61 and a portion of the cylinder 62 are in the outer overlap position OP1 in the right steering mechanism 60R.

[0174] The "at least a part of the drive unit 40" in the outer overlapping position is at least one of the drive device 45, the transmission mechanism 50, and the steering mechanism 60. In other words, the "at least a part of the drive unit 40" in the outer overlapping position may be one, two, or three of the drive device 45, the transmission mechanism 50, and the steering mechanism 60.

[0175] For example, the drive unit 45, the transmission mechanism 50, and the steering mechanism 60 may all be configured so that at least a portion thereof is in the outer overlapping position. In the embodiments shown in Figures 1 to 6, 15, 16, etc., a portion of the drive unit 45, a portion of the transmission mechanism 50, and a portion of the steering mechanism 60 are in the outer overlapping position.

[0176] In another embodiment shown in Figures 22 to 25, at least a portion of the drive units 40 (first drive unit 41, second drive unit 42) is in the outer overlapping position, but "at least a portion of the drive units 40" in the outer overlapping position is two of the drive device 45, the transmission mechanism 50, and the steering mechanism 60. Specifically, in this embodiment, a portion of the transmission mechanism 50 and a portion of the steering mechanism 60 are in the outer overlapping position, and the drive device 45 is not in the outer overlapping position. That is, as shown in Figure 22 and other figures, the motors 5LF, 5RF, 5LB, and 5RB that make up the drive device 45 are located above the vehicle body 2 on the inside of the wheels 30, and therefore are not in the outer overlapping position.

[0177] 32, by having at least a portion of drive unit 40 at outer overlap position OP1, it is possible to ensure a steering area for the wheels (left front wheel 3LF, right front wheel 3RF) that is longer by the width OW1 where drive unit 40 overlaps with outer overlap position OP1, compared to a conventional case in which drive unit 40 is located inside (toward vehicle body 2) of wheels 30. This allows for a larger steering angle for the wheels (left front wheel 3LF, right front wheel 3RF).

[0178] As shown in FIG. 7 , the work vehicle 1 is equipped with a first detection device 70. The first detection device 70 detects the situation around the vehicle body 2. Hereinafter, the first detection device 70 may be referred to as the "situation detection device." The first detection device 70 detects road information, which is information about roads on which the traveling devices 3 can travel, as the situation around the vehicle body 2. More specifically, the first detection device 70 detects road information, which is values ​​related to roads on which the traveling devices 3 can travel. The first detection device 70 detects, for example, the width of the traveling path as road information. The width of the traveling path detected by the first detection device 70 is the width of an object that the work vehicle 1 is attempting to straddle between the left traveling device 3L and the right traveling device 3R. The first detection device 70 detects, for example, the width of a ridge on the ground or the width of an obstacle on the ground that obstructs travel, as the width of the traveling path.

[0179] Furthermore, the first detection device 70 detects, for example, the height of the road as road information. The height of the road detected by the first detection device 70 is the height of an object that the work vehicle 1 is attempting to straddle between the left traveling device 3L and the right traveling device 3R. The first detection device 70 detects, for example, the height of ridges on the ground, the height of obstacles on the ground that obstruct traveling, etc. as the height of the road.

[0180] Examples of obstacles that impede travel include grooves or holes formed in the ground, crops planted on the ground, and obstacles on the ground (e.g., stones or artificial installations). Typically, the first detection device 70 can detect the height of the crops planted on the ground as the height of the obstacle. The height of the crops detected by the first detection device 70 is the height from the ground where the wheels 30 of the traveling device 3 touch the ground to the top of the crops. For example, if the crops are planted in ridges, the wheels 30 of the traveling device 3 will touch the ground between the ridges rather than on the ridges, and the height of the crops detected by the first detection device 70 will be "the height of the crops themselves + the height of the ridges."

[0181] 7, the first detection device 70 includes a camera (image capture device) 71, a sensor 72, and a calculation unit 73. In the present embodiment, the first detection device 70 includes both the camera 71 and the sensor 72, but may include only one of them.

[0182] The camera 71 is composed of a CCD camera equipped with a CCD (Charge Coupled Devices) image sensor, a CMOS camera equipped with a CMOS (Complementary Metal Oxide Semiconductor) image sensor, or the like. The camera 71 is mounted on the vehicle body 2 and captures images of the surroundings of the vehicle body 2. The camera 71 may be capable of capturing images in at least one direction among the front, rear, left, and right of the vehicle body 2, including at least the traveling direction of the vehicle body 2. Preferably, the camera 71 is positioned so as to capture images in the front, rear, and sides (left and right) of the vehicle body 2. The camera 71 may also be positioned so as to capture images in directions other than the front, rear, and sides (left and right) of the vehicle body 2 (for example, the right front, left front, front-downward, rear-downward, etc.).

[0183] The camera 71 captures images of the surroundings of the vehicle body 2 and generates an image signal. The calculation unit 73 is composed of a computer or the like including a signal processing circuit that processes the generated image signal. The signal processing circuit detects the state of the object (presence or absence of the object, the position of the object, the type of the object, the size of the object, etc.) based on the image signal output from the camera 71. The object includes the aforementioned ridges, obstacles, etc.

[0184] The sensor 72 is an optical sensor, such as a LiDAR (Light Detection and Ranging) sensor. The LiDAR (laser sensor) emits pulsed measurement light (laser light) millions of times per second from a light source such as a laser diode. The measurement light is reflected by a rotating mirror to scan horizontally or vertically, projecting it onto a predetermined detection range (sensing range). The LiDAR then receives the measurement light reflected by an object with a light-receiving element. The signal processing circuit of the calculation unit 73 detects the state of the object (presence / absence of the object, its position, type, size, etc.) based on the light-receiving signal output from the LiDAR's light-receiving element. Examples of objects include the aforementioned ridges and obstacles. The signal processing circuit also detects the distance to the object based on the time between the LiDAR emitting the measurement light and receiving the reflected light (the TOF (Time of Flight) method). Note that the LiDAR distance detection method may be a method other than the TOF method.

[0185] The sensor 72 may be an acoustic sensor. Preferably, the sensor 72 includes both an optical sensor and an acoustic sensor, but it may also include either one. The acoustic sensor may be, for example, an airborne ultrasonic sensor such as a sonar. The airborne ultrasonic sensor transmits measurement waves (ultrasound waves) within a predetermined detection range using a transmitter, and receives the reflected waves from an object using a receiver. The signal processing circuit detects the state of the object (presence or absence of the object, its position, type, size, etc.) based on the signal output from the receiver. Objects include the aforementioned ridges and obstacles. The signal processing circuit also detects the distance to the object based on the time between the transmission of the measurement wave by the airborne ultrasonic sensor and the reception of the reflected wave (the TOF (Time of Flight) method). Note that the distance detection method using the acoustic sensor may be a method other than the TOF method.

[0186] The sensor 72 described above is mounted on the vehicle body 2 and detects objects around the vehicle body 2. The sensor 72 only needs to be able to detect objects in at least one direction, including the traveling direction of the vehicle body 2, among the front, rear, left, and right of the vehicle body 2. Preferably, the sensor 72 is arranged to detect objects in the front, rear, and sides (left and right) of the vehicle body 2. The sensor 72 may also be arranged to detect objects in directions other than the front, rear, and sides (left and right) of the vehicle body 2 (for example, in the front right, front left, front-downward, rear-downward, etc.).

[0187] The first detection device 70 may detect the inclination of the ground in the lateral direction as the condition around the vehicle body 2. In this case, the first detection device 70 can detect the height of the ground on which the left traveling device 3L is traveling and the height of the ground on which the right traveling device 3R is traveling as the condition around the vehicle body 2. In this case, for example, an inclination sensor that detects the inclination of the vehicle body 2 in the lateral direction can be used as the first detection device 70. Also, a camera 71 may be used as the first detection device 70, and the calculation unit 73 may detect the inclination of the ground in the lateral direction based on an image captured by the camera 71.

[0188] As shown in Fig. 7, the work vehicle 1 is equipped with a second detection device 75. The second detection device 75 detects the distance between the left traveling device 3L and the right traveling device 3R. Hereinafter, the second detection device 75 may be referred to as the "distance detection device." As the second detection device (distance detection device) 75, for example, the optical sensor or sonic sensor described above can be used.

[0189] The distance between the left traveling unit 3L and the right traveling unit 3R detected by the second detection device 75 is the distance between the inner surface of the left traveling unit 3L and the inner surface of the right traveling unit 3R. Specifically, it is the smaller of the distance between the inner surface of the left front wheel 3LF and the inner surface of the right front wheel 3RF, and the distance between the inner surface of the left rear wheel 3LB and the inner surface of the right rear wheel 3RB.

[0190] 6, if the distance DB between the inner surface of the left rear wheel 3LB and the inner surface of the right rear wheel 3RB is smaller than the distance DF between the inner surface of the left front wheel 3LF and the inner surface of the right front wheel 3RF (DB<DF), the second detection device 75 detects the distance DB between the inner surface of the left rear wheel 3LB and the inner surface of the right rear wheel 3RB as the distance between the left traveling device 3L and the right traveling device 3R. If the distance DF between the inner surface of the left front wheel 3LF and the inner surface of the right front wheel 3RF and the distance DB between the inner surface of the left rear wheel 3LB and the inner surface of the right rear wheel 3RB are the same (DB=DF), the second detection device 75 detects either the distance DF or the distance DB as the distance between the left traveling device 3L and the right traveling device 3R. If the distance DF between the inner surface of the left front wheel 3LF and the inner surface of the right front wheel 3RF is smaller than the distance DB between the inner surface of the left rear wheel 3LB and the inner surface of the right rear wheel 3RB (DB > DF), the second detection device 75 detects the distance DF between the inner surface of the left front wheel 3LF and the inner surface of the right front wheel 3RF as the distance between the left running device 3L and the right running device 3R.

[0191] As shown in FIG. 7 , the work vehicle 1 is equipped with a third detection device 77. The third detection device 77 detects the height of the vehicle body 2 from the ground. Hereinafter, the third detection device 77 may be referred to as the "height detection device." For example, the optical sensor or sonic sensor described above may be used as the third detection device 77. The height of the vehicle body 2 detected by the third detection device 77 is the distance between the ground and the underside of the vehicle body 2. In detail, the height of the vehicle body 2 detected by the third detection device 77 is the distance between the ground and the lowest part (bottom) of the vehicle body 2 (see height HA in FIGS. 2 and 4 as an example).

[0192] As shown in Fig. 7, the work vehicle 1 is equipped with a distance change mechanism 80. The distance change mechanism 80 changes the distance between the left traveling device 3L and the right traveling device 3R. As shown in Figs. 6 and 34, the distance change mechanism 80 includes a left change mechanism 80L that changes the left-right position of the left traveling device 3L, and a right change mechanism 80R that changes the left-right position of the right traveling device 3R. Note that Fig. 34 is a simplified view of Fig. 6.

[0193] As shown in Figures 6 and 34, the left changing mechanism 80L has a left cylinder 81L that moves the left traveling device 3L left or right. The left cylinder 81L moves the left front wheel 3LF and the left rear wheel 3LB left or right. The left front wheel 3LF and the left rear wheel 3LB are connected by a left connector 82L. As a result, the left cylinder 81L can move the left connector 82L left or right, thereby moving the left front wheel 3LF and the left rear wheel 3LB together left or right.

[0194] As shown in Figures 6 and 34, the right change mechanism 80R has a right cylinder 81R that moves the right traveling device 3R left or right. The right cylinder 81R moves the right front wheel 3RF and the right rear wheel 3RB left or right. The right front wheel 3RF and the right rear wheel 3RB are connected by a right connector 82R. As a result, the right cylinder 81R can move the right connector 82R left or right, thereby moving the right front wheel 3RF and the right rear wheel 3RB together left or right.

[0195] The lower end of the left connector 82L is located higher than the lower end of the left traveling unit 3L. The lower end of the right connector 82R is located higher than the lower end of the right traveling unit 3R. Therefore, the left connector 82L and the right connector 82R do not come into contact with the ground like the left traveling unit 3L and the right traveling unit 3R. The left connector 82L and the right connector 82R are positioned at a predetermined height so as not to come into contact with ridges, crops, etc.

[0196] In this embodiment, the left coupling part 82L is the left frame 18L of the frame structure 18. The right coupling part 82R is the right frame 18R of the frame structure 18. The left front wheel 3LF is rotatably attached to the first left frame 19L (see FIG. 9 ) of the left frame 18L via the above-mentioned first drive unit 41 and the like. The left rear wheel 3LB is rotatably attached to the first left frame 19L of the left frame 18L via the above-mentioned third drive unit 43 and the like during traveling.

[0197] The right front wheel 3RF is rotatably attached to the first right frame 21R of the right frame 18R (see FIG. 9) via the above-mentioned second drive unit 42, etc. The right rear wheel 3RB is rotatably attached to the first right frame 21R of the right frame 18R via the above-mentioned fourth drive unit 44, etc. during traveling.

[0198] This allows the left front wheel 3LF and the left rear wheel 3LB (i.e., the left traveling device 3L) to move left and right together with the left frame 18L. Also, the right front wheel 3RF and the right rear wheel 3RB (i.e., the right traveling device 3R) to move left and right together with the right frame 18R.

[0199] The right cylinder 81R and the left cylinder 81L are hydraulic cylinders that are operated (extended and retracted) by hydraulic oil supplied from a hydraulic pump driven by the working motor 6 described above.

[0200] As shown in Figures 6 and 34, the left cylinder 81L has a cylinder tube 81La attached to the vehicle body 2 and a rod 81Lb that protrudes from the cylinder tube 81La and extends to the left. A left coupling 82L is connected to the tip of the rod 81Lb of the left cylinder 81L. When the rod 81Lb of the left cylinder 81L extends to the left, the left coupling 82L moves to the left, and the left front wheel 3LF and the left rear wheel 3LB move together to the left. When the rod 81Lb of the left cylinder 81L contracts to the right, the left coupling 82L moves to the right, and the left front wheel 3LF and the left rear wheel 3LB move together to the right.

[0201] As shown in Figures 6 and 34, the right cylinder 81R has a cylinder tube 81Ra attached to the vehicle body 2 and a rod 81Rb that protrudes from the cylinder tube 81Ra and extends to the right. A right coupling 82R is connected to the tip of the rod 81Rb of the right cylinder 81R. When the rod 81Rb of the right cylinder 81R extends to the right, the right coupling 82R moves to the right, and the right front wheel 3RF and the right rear wheel 3RB move together to the right. When the rod 81Rb of the right cylinder 81R contracts to the left, the right coupling 82R moves to the left, and the right front wheel 3RF and the right rear wheel 3RB move together to the left.

[0202] As described above, the left front wheel 3LF and the left rear wheel 3LB (i.e., the left traveling device 3L) can be changed in lateral position by operating (extending and retracting) the left cylinder 81L. Also, the right front wheel 3RF and the right rear wheel 3RB (i.e., the right traveling device 3R) can be changed in lateral position by operating (extending and retracting) the right cylinder 81R. Therefore, the distance between the left traveling device 3L and the right traveling device 3R can be changed by operating one or both of the left cylinder 81L and the right cylinder 81R.

[0203] When changing the distance between the left traveling device 3L and the right traveling device 3R, it is preferable to move (extend or shorten) the rods of the left cylinder 81L and the right cylinder 81R the same distance in opposite directions. However, when changing the distance between the left traveling device 3L and the right traveling device 3R, it is also possible to move the rods of the left cylinder 81L and the right cylinder 81R by different distances in opposite directions, or to move the rods of the left cylinder 81L and the right cylinder 81R by different distances in the same direction.

[0204] 6 and 34 show a state in which the rods of the left cylinder 81L and the right cylinder 81R are retracted. In this state, the distance DB (see FIG. 6) between the left traveling unit 3L and the right traveling unit 3R is short. By extending the rods of the left cylinder 81L and the right cylinder 81R from this state (see arrows YL and YR in FIG. 35), the left traveling unit 3L (left front wheel 3LF, left rear wheel 3LB) and the right traveling unit 3R (right front wheel 3RF, right rear wheel 3RB) move in opposite directions (see arrows in FIG. 34). This allows the distance DB (see FIG. 6) between the left traveling unit 3L and the right traveling unit 3R to be increased, as shown in FIG. 35.

[0205] FIG. 36 shows a modified example of the distance change mechanism 80. As shown in FIG. 36 , the distance change mechanism 80 may include a first change mechanism 801 that changes the left-right position of the left front wheel 3LF, a second change mechanism 802 that changes the left-right position of the left rear wheel 3LB, a third change mechanism 803 that changes the right-left position of the right front wheel 3RF, and a fourth change mechanism 804 that changes the right-left position of the right rear wheel 3RB. In this case, the left change mechanism 80L includes the first change mechanism 801 and the second change mechanism 802. The right change mechanism 80R includes the third change mechanism 803 and the fourth change mechanism 804.

[0206] In this case, the left cylinder 81L includes a left front cylinder 81LF that moves the left front wheel 3LF left or right and a left rear cylinder 81LB that moves the left rear wheel 3LB left or right. The right cylinder 81R includes a right front cylinder 81RF that moves the right front wheel 3RF left or right and a right rear cylinder 81RB that moves the right rear wheel 3RB left or right.

[0207] In this case, there is no left connecting portion 82L connecting the left front wheel 3LF and the left rear wheel 3LB, and the left front wheel 3LF and the left rear wheel 3LB are not connected. The left frame 18L is divided into two, front and rear, with the left front wheel 3LF attached to the front left frame 18LF and the left rear wheel 3LB attached to the rear left frame 18LB. This allows the left front wheel 3LF and the left rear wheel 3LB to move left and right independently of each other.

[0208] Furthermore, there is no right coupling portion 82R connecting the right front wheel 3RF and the right rear wheel 3RB, and the right front wheel 3RF and the right rear wheel 3RB are not connected. The right frame 18R is divided into two, front and rear, with the right front wheel 3RF attached to the front right frame 18RF and the right rear wheel 3RB attached to the rear right frame 18RB. This allows the right front wheel 3RF and the right rear wheel 3RB to move left and right independently of each other.

[0209] The first changing mechanism 801, the second changing mechanism 802, the third changing mechanism 803, and the fourth changing mechanism 804 can be driven independently. Specifically, the left front cylinder 81LF, the left rear cylinder 81LB, the right front cylinder 81RF, and the right rear cylinder 81RB can be operated independently. This allows the left and right positions of the left front wheel 3LF, the left and right rear wheel 3LB, the right front wheel 3RF, and the right rear wheel 3RB to be changed independently.

[0210] The arrows in Figure 36 indicate the state in which the left and right positions of the left front wheel 3LF, the left and right positions of the left rear wheel 3LB, the right front wheel 3RF, and the right rear wheel 3RB are each changed independently by extending the rods of the left front cylinder 81LF, the left rear cylinder 81LB, the right front cylinder 81RF, and the right rear cylinder 81RB.

[0211] The operation of the distance change mechanism 80 is controlled by the control device 15. As shown in FIG. 7 , the control device 15 includes a distance change control unit 15B. The distance change mechanism 80 changes the distance between the left traveling device 3L and the right traveling device 3R so that the distance between the left traveling device 3L and the right traveling device 3R corresponds to the detection result of the first detection device 70. In this embodiment, the distance change control unit 15B operates the distance change mechanism 80 based on the detection results of the first detection device 70 and the second detection device 75 to change the distance between the left traveling device 3L and the right traveling device 3R.

[0212] The distance change operation by the distance change mechanism 80 is performed by the distance change control unit 15B controlling the distance change mechanism 80. An example of the operation of the distance change mechanism 80 will be described below, and the operation of the distance change mechanism 80 in the following description is performed by the distance change control unit 15B controlling the distance change mechanism 80 based on the detection results of the first detection device 70 and / or the second detection device 75. In other words, the operation of the distance change mechanism 80 described below is controlled by the distance change control unit 15B.

[0213] For example, when the first detection device 70 detects the width of the traveling path, the distance change mechanism 80 changes the distance between the left traveling device 3L and the right traveling device 3R so that the distance between them corresponds to the width of the traveling path. More specifically, when the first detection device 70 detects the width of the traveling path, the distance change mechanism 80 changes the distance between the left traveling device 3L and the right traveling device 3R so that the distance between them is the width of the traveling path or wider than the width of the traveling path (i.e., equal to or greater than the width of the traveling path).

[0214] As a specific example, when the first detection device 70 detects the width of a ridge path, the distance change mechanism 80 changes the distance between the left traveling device 3L and the right traveling device 3R so that the distance between them corresponds to the width of the ridge. More specifically, while the vehicle body 2 is traveling, the distance change mechanism 80 changes the distance between the left traveling device 3L and the right traveling device 3R so that the traveling device 3 can straddle the detected ridge. In other words, the distance change mechanism 80 changes the distance between the left traveling device 3L and the right traveling device 3R so that the distance between them is the same as or wider than the width of the ridge (i.e., greater than or equal to the width of the ridge).

[0215] Furthermore, when the first detection device 70 detects the width of an obstacle, the distance change mechanism 80 changes the distance between the left traveling device 3L and the right traveling device 3R so that the traveling device 3 can straddle the detected obstacle while the vehicle body 2 is traveling. In other words, the distance change mechanism 80 changes the distance between the left traveling device 3L and the right traveling device 3R so that the distance between the left traveling device 3L and the right traveling device 3R is the same as or wider than the width of the obstacle (i.e., so that it is equal to or greater than the width of the obstacle).

[0216] The distance change mechanism 80 can individually operate the left change mechanism 80L and the right change mechanism 80R based on the detection results of the first detection device 70. In the present embodiment, the distance change mechanism 80 can individually operate the left change mechanism 80L and the right change mechanism 80R based on the detection results of the first detection device 70 and the detection results of the second detection device 75. As a result, the distance change mechanism 80 can operate only the left change mechanism 80L, can operate only the right change mechanism 80R, or can operate both the left change mechanism 80L and the right change mechanism 80R.

[0217] As described above, the distance change mechanism 80 can individually operate the left change mechanism 80L and the right change mechanism 80R based on the detection results of the first detection device 70. Therefore, the distance change mechanism 80 can move the lower of the left traveling device 3L and the right traveling device 3R away from the widthwise center of the vehicle body 2 based on the lateral inclination of the ground detected by the first detection device 70. Figure 37 schematically shows the operation of this distance change mechanism 80. For example, if the first detection device 70 detects that the right side of the ground GR is inclined lower than the left side, the distance change mechanism 80 moves the lower of the left traveling device 3L and the right traveling device 3R away from the widthwise center of the vehicle body 2. This allows the vehicle body 2 to be stabilized on an inclined surface.

[0218] The distance change mechanism 80 changes the distance between the left traveling device 3L and the right traveling device 3R by operating both or one of the left change mechanism 80L and the right change mechanism 80R of the distance change mechanism 80. When the left change mechanism 80L is operated, the rod of the left cylinder 81L extends or retracts, changing the left-right position of the left traveling device 3L. When the right change mechanism 80R is operated, the rod of the right cylinder 81R extends or retracts, changing the left-right position of the right traveling device 3R. By changing the left-right positions of both or one of the left traveling devices 3L and the right traveling device 3R, the distance between the left traveling device 3L and the right traveling device 3R is changed. Preferably, the distance change control unit 15B changes the left-right positions of both the left traveling device 3L and the right traveling device 3R by the same distance in opposite directions.

[0219] The second detection device 75 can detect the distance between the left traveling device 3L and the right traveling device 3R by detecting the amount of extension and contraction of each of the left change mechanism 80L and the right change mechanism 80R. Specifically, the second detection device 75 can detect the distance between the left traveling device 3L and the right traveling device 3R by detecting the amount of extension and contraction of the rod of the left cylinder 81L of the left change mechanism 80L and the amount of extension and contraction of the rod of the right cylinder 81R of the right change mechanism 80R.

[0220] In this case, information such as the relationship between the extension and contraction amount of the rod of the left cylinder 81L and the position of the left traveling unit 3L, the relationship between the extension and contraction amount of the rod of the right cylinder 81R and the position of the right traveling unit 3R, and the relationship between "the positions of the left traveling unit 3L and the right traveling unit 3R" and "the distance between the left traveling unit 3L and the right traveling unit 3R" is stored in advance in the memory unit of the control unit 15. The second detection device 75 detects the extension and contraction amount of the rods of the left cylinder 81L and the right cylinder 81R, and detects the distance between the left traveling unit 3L and the right traveling unit 3R based on the detection result and the information stored in the memory unit.

[0221] Figure 38 is a flowchart showing one example (first example) of the operation of the distance change mechanism 80 controlled by the distance change control unit 15B. Below, an example of the operation of the distance change mechanism 80 controlled by the distance change control unit 15B will be described with reference to Figure 38. Note that here, an example will be described in which the "road information" of the "conditions around the vehicle body 2" detected by the first detection device 70 is the "width of a ridge on the ground," and a ridge UN whose width is detected is located ahead in the direction of travel of the vehicle body 2 of the work vehicle 1 (see Figure 39).

[0222] In this case, the first detection device 70 detects the width W1 of the ridge UN located ahead in the traveling direction (S1) as road information about the conditions around the vehicle body 2. The detected width W1 of the ridge UN may be the width of the base (lower end) of the ridge UN, the width of the top surface (upper end) of the ridge UN, or the width at the height between the lower end and the upper end of the ridge UN.

[0223] When detecting the width W1 of the ridge UN, if the first detection device 70 is a camera, the camera 71 captures an image of the ridge UN in front of the vehicle body 2 and generates an image signal. The calculation unit 73 detects the width W1 of the ridge UN based on the generated image signal. Meanwhile, the second detection device 75 detects the distance D1 between the left traveling unit 3L and the right traveling unit 3R (S2). In the example shown in Figure 39, the distance DB between the left rear wheel 3LB and the right rear wheel 3RB is smaller than the distance DF between the left front wheel 3LF and the right front wheel 3RF, so the distance DB is detected as the distance D1 (the same applies to the following examples). The width W1 and the distance D1 are detected before the vehicle body 2 reaches the ridge UN. The detection of the width W1 or the distance D1 may occur first, or they may occur simultaneously.

[0224] The distance change control unit 15B compares the ridge width W1 detected by the first detection device 70 with the distance D1 detected by the second detection device 75 (S3). Based on the comparison result, the distance change control unit 15B operates the distance change mechanism 80 to change the distance D1 so that the distance D1 corresponds to the ridge width W1. The change of the distance D1 by the distance change mechanism 80 is performed while the vehicle body 2 is traveling until it reaches above the ridge UN ahead in the traveling direction or before it begins traveling.

[0225] If the comparison result is D1<W1 (S4, No), the distance change mechanism 80 changes the distance D1 so that D1≧W1 (S5). Specifically, the distance D1 is increased by extending the rods of the left cylinder 81L and the right cylinder 81R (see FIG. 40). If the comparison result is D1≧W1 (S4, Yes), the distance change mechanism 80 does not change the distance D1 (S6). The work vehicle 1 travels toward and reaches the ridge UN with the distance D1 changed (S5) or not changed (S6) (S7).

[0226] As a result of the control operation described above, whether the width W1 of the ridge UN is greater than or less than the distance D1 between the left traveling unit 3L and the right traveling unit 3R, when the work vehicle 1 reaches the ridge UN, D1 ≥ W1 holds. Therefore, the work vehicle 1 can travel across the ridge UN using the left traveling unit 3L and the right traveling unit 3R to perform work (see Figure 41).

[0227] 42 is a flowchart showing a modification of Example 1. In this modification, the first step (S1) to the third step (S3) of the operation of distance change mechanism 80 are the same as the operation of Example 1, but the fourth step (S4) and onwards are different from Example 1.

[0228] In the fourth step (S4), the distance change control unit 15B determines whether the ridge width W1 is the same as the distance D1 between the left traveling unit 3L and the right traveling unit 3R (S4). If D1 = W1 (S4, Yes), the distance change mechanism 80 does not change the distance D1 (S5). If D1 = W1 is not true (S4, No), the distance change mechanism 80 determines whether D1 < W1 (S6). If D1 < W1 (S6, Yes), the distance change mechanism 80 changes (extends) the distance D1 so that D1 = W1 (S7). Specifically, the distance D1 is extended by extending the rods of the left cylinder 81L and the right cylinder 81R. If D1 > W1 (S6, No), the distance change mechanism 80 changes (shortens) the distance D1 so that D1 = W1 (S8). Specifically, the distance D1 is shortened by shortening the rods of the left cylinder 81L and the right cylinder 81R. The work vehicle 1 travels towards the ridge UN and reaches the ridge UN (S9) with the distance D1 changed (extended or shortened) (S7, S8) or not (S5).

[0229] Through the control operation described above, whether the width W1 of the ridge UN is greater or smaller than the distance D1 between the left traveling unit 3L and the right traveling unit 3R, when the work vehicle 1 reaches the ridge UN, D1 = W1. Therefore, the work vehicle 1 can travel across the ridge UN with the left traveling unit 3L and the right traveling unit 3R and perform work, with the distance D1 set to an appropriate length that is neither too narrow nor too wide compared to the ridge width W1.

[0230] When a work implement is mounted on the mounting portion 10 and the wheels 30 and the work implement overlap in the fore-and-aft direction, the shortest value of the distance D1 between the left traveling unit 3L and the right traveling unit 3R is set to be wider than the width of the work implement. This makes it possible to prevent interference between the wheels 30 and the work implement when the distance D1 is changed.

[0231] Figure 43 is a flowchart showing another example (second example) of the operation of the distance change mechanism 80 controlled by the distance change control unit 15B. Hereinafter, with reference to Figure 43, another example (second example) of the operation of the distance change mechanism 80 controlled by the distance change control unit 15B will be described. Note that here, an example will be described in which the "road information" of the "circumstances around the vehicle body 2" detected by the first detection device 70 is the "width of a ridge on the ground," and a ridge (second ridge UN2) whose width is detected is present to the side (left or right) of the vehicle body 2 of the work vehicle 1 (see Figure 44).

[0232] In this case, while the vehicle body 2 is traveling along the first ridge UN1 (straddling the first ridge UN1), the first detection device 70 detects the width W2 of the second ridge UN2 adjacent to the first ridge UN1 (S1). The second ridge UN2 is the next ridge on which work will be performed after work on the first ridge UN1. Detection of the second ridge UN2 is possible by installing the first detection device 70 at a higher position than the second ridge UN2. If the first detection device 70 is a camera, the camera 71 captures an image of the second ridge UN2 on the side of the vehicle body 2 and generates an image signal. The calculation unit 73 detects the width W2 of the second ridge UN2 based on the generated image signal. Meanwhile, the second detection device 75 detects the distance D1 between the left traveling unit 3L and the right traveling unit 3R (S2). The width W2 and the distance D1 are detected before the vehicle body 2 reaches the second ridge UN2. The width W2 and the distance D1 may be detected either first or at the same time.

[0233] The distance change control unit 15B compares the ridge width W2 detected by the first detection device 70 with the distance D1 detected by the second detection device 75 (S3). Based on the comparison result, the distance change control unit 15B operates the distance change mechanism 80 to change the distance D1 so that the distance D1 corresponds to the ridge width W2.

[0234] If the comparison result is D1<W2 (S4, No), the distance change mechanism 80 changes the distance D1 so that D1≧W2 (S5). Specifically, the distance D1 is increased by extending the rods of the left cylinder 81L and the right cylinder 81R. If the comparison result is D1≧W1 (S4, Yes), the distance change mechanism 80 does not change the distance D1 (S6). The distance change mechanism 80 changes the distance D1 while the vehicle body 2 is turning (see arrow TN1 in FIG. 45 ) to end its travel along the first ridge and transition to traveling along the second ridge UN2. However, the distance change mechanism 80 may change the distance D1 while traveling straight before or after turning, rather than while turning. The work vehicle 1 travels towards the second ridge UN2 with the distance D1 changed (S5) or not changed (S6) and reaches the second ridge UN2 (S7).

[0235] As a result of the control operation described above, whether the width W2 of the second ridge UN2 is greater than or less than the distance D1 between the left traveling unit 3L and the right traveling unit 3R, when the work vehicle 1 reaches the second ridge UN2, D1 ≥ W2 holds. Therefore, the work vehicle 1 can travel across the second ridge UN2 using the left traveling unit 3L and the right traveling unit 3R to perform work (see Figure 46).

[0236] 47 is a flowchart showing a modification of Example 2. In this modification, the first step (S1) to the third step (S3) of the operation of distance change mechanism 80 are the same as the operation of Example 2, but the fourth step (S4) and onwards are different from Example 2.

[0237] In the fourth step (S4), the distance change control unit 15B determines whether the ridge width W2 is the same as the distance D1 between the left traveling unit 3L and the right traveling unit 3R (S4). If D1 = W2 (S4, Yes), the distance change mechanism 80 does not change the distance D1 (S5). If D1 = W2 is not true (S4, No), the distance change mechanism 80 determines whether D1 < W2 (S6). If D1 < W2 (S6, Yes), the distance change mechanism 80 changes (extends) the distance D1 so that D1 = W2 (S7). Specifically, the distance D1 is extended by extending the rods of the left cylinder 81L and the right cylinder 81R. If D1 > W2 (S6, No), the distance change mechanism 80 changes (shortens) the distance D1 so that D1 = W2 (S8). Specifically, the distance D1 is shortened by shortening the rods of the left cylinder 81L and the right cylinder 81R. The work vehicle 1 travels toward the ridge UN and reaches the second ridge UN2 (S9) with the distance D1 changed (extended or shortened) (S7, S8) or not (S5).

[0238] Through the control operation described above, whether the width W2 of the second ridge UN2 is greater or smaller than the distance D1 between the left traveling unit 3L and the right traveling unit 3R, when the work vehicle 1 reaches the second ridge UN2, D1 = W2. Therefore, the work vehicle 1 can travel across the second ridge UN2 with the left traveling unit 3L and the right traveling unit 3R and perform work, with the distance D1 set to an appropriate length that is neither too narrow nor too wide compared to the width W2 of the second ridge.

[0239] The operations of the first example (including modified examples) and the second example (including modified examples) described above can be combined and implemented. In this case, when the vehicle body 2 travels along the first ridge UN1 of the crop, the control operations shown in FIG. 38 or 42 are executed, as in the first example. Specifically, until the vehicle body 2 reaches the crop, the first detection device 70 detects the width W1 of the first ridge ahead in the traveling direction of the vehicle body 2, and the second detection device 75 detects the distance D1 between the left traveling unit 3L and the right traveling unit 3R. Next, the distance change control unit 15B compares the width W1 with the distance D1, and based on the comparison result, the distance change mechanism 80 is operated to change the distance D1 so that D1≧W1 or D1=W1.

[0240] Next, as in the second example, when the vehicle body 2 is traveling along the first ridge UN1, the control operation shown in Figure 43 or 47 is executed. Specifically, the first detection device 70 detects the width W2 of the second ridge UN2 adjacent to the first ridge UN1, and the second detection device 75 detects the distance D1 between the left traveling unit 3L and the right traveling unit 3R. Next, the distance change control unit 15B compares the width W2 with the distance D1, and based on the comparison result, the distance change mechanism 80 is operated to change the distance D1 so that D1 ≥ W2 or D1 = W2.

[0241] If there are three or more crop ridges, the operation performed when the vehicle body 2 is traveling along the second ridge UN2 can be repeated. That is, the width of the third ridge adjacent to the second ridge is detected, the width of the third ridge is compared with the distance D1 between the left traveling unit 3L and the right traveling unit 3R, and the distance change mechanism 80 is operated based on the comparison result to change the distance D1.

[0242] In the control operations of the first example (including modified examples) and the second example (including modified examples) described above, the first detection device 70 may detect either the distance between the passages between the furrows (passage pitch) and / or the width of the passages between the furrows, in addition to or instead of the ridge width. In this case, the distance change control unit 15B operates the distance change mechanism 80 to change the distance D1 so that the left traveling unit 3L or the right traveling unit 3R can travel across the furrows, taking into account the distance between the passages between the furrows (passage pitch) and / or the width of the passages between the furrows.

[0243] As described above, distance D1 can be changed in accordance with the width of the ridge by operating distance change mechanism 80 to change distance D1 based on the detection results of first detection device 70 and second detection device 75. Therefore, even if the width of the ridge is wider than the expected width (standard width), the work vehicle 1 can reliably travel across the ridge with left traveling device 3L and right traveling device 3R.

[0244] In the above example (see Figures 38 to 45), the vehicle body 2 can travel so that the center of the vehicle body 2 in the width direction (left and right direction) coincides with the center of the ridge in the width direction, under control of the automatic driving control unit 15A. As a result, when the distance change mechanism 80 changes the distance D1 so that D1 ≥ W1 (or D1 = W1) or D1 ≥ W2 (or D1 = W2), the work vehicle 1 can reliably travel across the ridge with the left traveling unit 3L and the right traveling unit 3R.

[0245] The distance change control unit 15B drives the distance change mechanism 80 to change the distance D1 between the left traveling device 3L and the right traveling device 3R, and this change may be made before the work vehicle 1 starts work, or may be made while the work vehicle 1 is working. If the distance D1 is changed while the work vehicle 1 is working, the distance D1 can be changed (fine-tuned) appropriately in accordance with the work situation.

[0246] As shown in Figure 7, the work vehicle 1 is equipped with a height change mechanism 90. The height change mechanism 90 changes the height of the vehicle body 2 from the ground. The height change mechanism 90 raises and lowers the vehicle body 2, which is an accommodation frame 2 that accommodates the battery 7. The height change mechanism 90 raises and lowers the vehicle body 2 at a position between the left traveling unit 3L and the right traveling unit 3R in the width direction (left-right direction) of the vehicle body 2. The height change mechanism 90 changes the height of the vehicle body 2 from the ground by raising and lowering a frame structure 18 attached to the vehicle body 2.

[0247] As shown in Figures 1 to 3, the height change mechanism 90 has a lifting cylinder 91. The lifting cylinder 91 raises and lowers the movable frame 32 (second left frame 20L, second right frame 22R, and lateral frame 18M) of the frame structure 18. The vehicle body 2 is raised and lowered by raising and lowering the movable frame 32. Therefore, the vehicle body 2 can be raised and lowered by driving the lifting cylinder 91.

[0248] The lift cylinder 91 is composed of a hydraulic cylinder. The lift cylinder 91 has a rod 91a that extends and retracts in the vertical direction and a cylinder tube 91b to which hydraulic oil is supplied to drive the rod 91a (see Figures 1, 30, etc.). The tip of the rod 91a is connected to the frame structure 18. The lift cylinder 91 includes a left lift cylinder 91L and a right lift cylinder 91R. The left lift cylinder 91L is disposed on the left side of the vehicle body 2. The right lift cylinder 91R is disposed on the right side of the vehicle body 2.

[0249] 1 and 2, the rod 91La of the left lifting cylinder 91L is connected to the second left frame 20L of the frame structure 18. More specifically, the rod 91La of the left lifting cylinder 91L is connected to a left plate 99L fixed to the second left frame 20L. This allows the left lifting cylinder 91L to lift and lower the second left frame 20L, which is a movable frame of the left frame 18L, by extension and contraction of the rod 91La.

[0250] 1 and 3, the rod 91Ra of the right lift cylinder 91R is connected to the second right frame 22R of the frame structure 18. More specifically, the rod 91Ra of the right lift cylinder 91R is connected to a right plate 99R fixed to the second right frame 22R. This allows the right lift cylinder 91R to lift and lower the second right frame 22R, which is a movable frame of the right frame 18R, by extension and contraction of the rod 91Ra.

[0251] The cylinder tube 91Lb of the left lift cylinder 91L is attached to a bracket (not shown) fixed to the first left frame 19L. The cylinder tube 91Rb of the right lift cylinder 91R is attached to a bracket (not shown) fixed to the first right frame 21R. As shown in FIGS. 2 and 3 , the lower ends (lower ends of the cylinder tubes 91Lb, 91Rb) of the lift cylinders (left lift cylinder 91L, right lift cylinder 91R) are located at the same or approximately the same height from the ground as the vehicle body 2 when the vehicle body 2 is at a height (a first height described below) between the left traveling unit 3L and the right traveling unit 3R.

[0252] However, the lower ends of the lifting cylinders (left lifting cylinder 91L, right lifting cylinder 91R) do not have to be positioned at the same or approximately the same height from the ground as the vehicle body 2 when it is at a height between the left running device 3L and the right running device 3R (the first height described later).

[0253] In this embodiment, the lower ends (lower ends of the cylinder tubes 91Lb, 91Rb) of the lifting cylinders (left lifting cylinder 91L, right lifting cylinder 91R) are located at a height slightly higher than the height HA of the vehicle body 2 from the ground when the vehicle body 2 is at a height located between the left running device 3L and the right running device 3R (see Figure 2).

[0254] When the rod 91La of the left lift cylinder 91L extends and retracts, the second left frame 20L rises and lowers. When the rod 91Ra of the right lift cylinder 91R extends and retracts, the second right frame 22R rises and lowers. This allows the frame structure 18 to rise and lower as the rods 91a of the lift cylinders 91 (left lift cylinder 91L, right lift cylinder 91R) extend and retract. Because the vehicle body 2 is attached to the frame structure 18, the vehicle body 2 can be raised and lowered as the rods 91a of the lift cylinders 91 extend and retract. By raising and lowering the vehicle body 2, the height of the vehicle body 2 from the ground can be changed.

[0255] 48, 49, and 50 show a state in which the rod 91a of the lifting cylinder 91 is extended to raise the vehicle body 2. As the vehicle body 2 rises, the mounting part 10 provided on the vehicle body 2 also rises. Therefore, by raising the vehicle body 2, the working device mounted on the mounting part 10 can also be raised.

[0256] The operation of the height change mechanism 90 is controlled by the control device 15. As shown in Fig. 7 , the control device 15 includes a height change control unit 15C. The height change control unit 15C transmits a control signal to the height change mechanism 90 by causing the calculation unit of the control device 15 to execute a program stored in the storage unit. The height change mechanism 90 is driven based on the control signal transmitted from the height change control unit 15C. In other words, the height change mechanism 90 changes the height of the vehicle body 2 by being driven based on the control of the control device 15.

[0257] The height change mechanism 90 can change the height of the car body 2 to any height within a preset height range. Specifically, the height change mechanism 90 can change the height of the car body 2 to any height between a first height HA (see FIGS. 2 and 4 ) and a second height HB (see FIGS. 49 and 50 ) that is higher than the first height HA. In other words, the preset height range is the range between the first height HA and the second height HB. In this embodiment, the height of the car body 2 when the rod of the lift cylinder 91 is at its shortest is the first height HA, and the height of the car body 2 when the rod of the lift cylinder 91 is at its longest is the second height HB.

[0258] The first height HA is the lowest height (lower limit height) of the height of the vehicle body 2 that can be changed by the height change mechanism 90. The second height HB is the highest height (upper limit height) of the height of the vehicle body 2 that can be changed by the height change mechanism 90. The height change mechanism 90 can change the height of the vehicle body 2 to the first height HA, which is the lower limit height, the second height HB, which is the upper limit height, or any height (intermediate height) between the upper limit height and the lower limit height.

[0259] The height change mechanism 90 can change the height of the vehicle body 2, for example, in accordance with the work performed by the working device. Specifically, the height change mechanism 90 can change the height of the vehicle body 2 in accordance with the work performed by the working device attached to the mounting unit 10. By changing the height of the vehicle body 2, the height of the working device attached to the mounting unit 10 is also changed.

[0260] As shown in Fig. 7 , the work vehicle 1 is equipped with a recognition device 100 that recognizes the work device attached to the mounting unit 10. The recognition device 100 recognizes the type of work device attached to the mounting unit 10. For example, the recognition device 100 receives an identification signal transmitted from the work device when the work device is attached to the mounting unit 10, and recognizes the work device attached to the mounting unit 10 based on the identification signal. The recognition device 100 may also be a camera that captures an image of the work device attached to the mounting unit 10. In this case, the recognition device 100 recognizes the work device attached to the mounting unit 10 based on an image of the work device captured by the camera.

[0261] The height change mechanism 90 can change the height of the vehicle body 2 in accordance with the work device recognized by the recognition device 100. In other words, the height change mechanism 90 can change the height of the vehicle body 2 in accordance with the work device attached to the mounting unit 10. For example, the work vehicle 1 sets the height of the vehicle body 2 to a first working height when the work device attached to the mounting unit 10 is a first work device, and sets the height of the vehicle body 2 to a second working height when the work device attached to the mounting unit 10 is a second work device.

[0262] The memory unit of the control device 15 stores a first correspondence table TB1 (see FIG. 51 ) that associates the type of work implement with the height of the vehicle body 2. The number of combinations of the type of work implement and the height of the vehicle body 2 included in the first correspondence table TB1 is not particularly limited, and can be any number equal to or greater than two.

[0263] When the working device recognized by the recognition device 100 is the first working device, the height change control unit 15C reads out the height of the vehicle body 2 corresponding to the first working device from the first correspondence table TB1 (first working height), and sends a control signal to drive the lifting cylinder 91 of the height change mechanism 90 so that the height of the vehicle body 2 becomes the read height (first working height). When the working device recognized by the recognition device 100 is the second working device, the height change control unit 15C reads out the height of the vehicle body 2 corresponding to the second working device from the first correspondence table TB1, and sends a control signal to drive the lifting cylinder 91 of the height change mechanism 90 so that the height of the vehicle body 2 becomes the read height (second working height).

[0264] The first working height and the second working height are either the first height (lower limit height), the second height (upper limit height), or any height (intermediate height) between the upper limit height and the lower limit height. The first working height and the second working height are usually different heights, but may be the same height.

[0265] The first working height is set to a height suitable for the first working implement to perform work. The first working height is a height suitable for a working implement (e.g., a tillage implement) whose working position is located below the vehicle body 2. If the first working implement is a tillage implement that tills a field, the first working height is set to a height suitable for the tillage implement (first working implement) to perform work (tilling).

[0266] If the first working implement is a working implement such as a tilling implement whose working position is located below the vehicle body 2, lowering the height of the vehicle body 2 (setting it to the first working height) also lowers the height of the working implement, making it possible to carry out work (tilling work, etc.) smoothly.

[0267] Furthermore, when the first working implement is a towed implement attached to the attachment portion 10 of the vehicle body 2, such as a tillage implement, the work performed by the working implement is often work on the ground (ground work) and is heavy-load work. Therefore, when the first working implement is a towed implement, the height of the vehicle body 2 can be lowered (as the first working height) to lower the center of gravity of the work vehicle 1, allowing the vehicle body 2 to perform work in a stable state.

[0268] The second working height is set to a height suitable for the second working device to perform its work. The second working height is a height suitable for a working device (e.g., a spraying device) whose working position is located above the vehicle body 2, for example. If the second working device is a spraying device that sprays a chemical solution, the second working height is set to a height suitable for the spraying device (second working device) to perform its work (spraying the chemical solution). In this case, the second working height is set to a height higher than the first working height.

[0269] If the second work device is a work device such as a spraying device whose working position is located above the vehicle body 2, the work (spraying work, etc.) can be carried out smoothly by increasing the height of the vehicle body 2 (setting it to the second working height).

[0270] As described above, by providing the height change mechanism 90, the work vehicle 1 can change the height of the vehicle body 2 to match multiple types of work implements that each have different working heights. Therefore, work can be performed using multiple types of work implements that each have different working heights on a single work vehicle.

[0271] The height change mechanism 90 can change the height of the vehicle body 2 in response to a height specification made by an operation device 101 (see FIG. 7 ). The operation device 101 is a device that can perform an operation to specify the height of the vehicle body 2. The operation device 101 is a device (external device) that is located outside the work vehicle 1, and is configured to be able to communicate with the control device 15 wirelessly or via a wire. The operation device 101 is, for example, a portable device such as a remote control device, a tablet, a smartphone, or a PDA.

[0272] The operation device 101 is equipped with an input unit for inputting the desired height of the vehicle body 2. The input unit is, for example, a push button, a rotary dial, a touch panel, etc. When the operator inputs the desired height from the input unit of the operation device 101, the input specified height is sent to the control device 15. The control device 15 sends a control signal to drive the lifting cylinder 91 of the height change mechanism 90 so that the height of the vehicle body 2 becomes the specified height. As a result, the height of the vehicle body 2 is changed to the height specified by the operation device 101.

[0273] The height change mechanism 90 can change the height of the vehicle body 2 in accordance with the height of crops planted on the ground on which the work vehicle 1 travels. For example, when the crop planted on the ground is a first crop, the height change mechanism 90 sets the height of the vehicle body 2 to a first height (lower limit height) or higher. The memory unit of the control device 15 stores the height of the vehicle body 2 corresponding to the first crop (hereinafter referred to as the "first crop corresponding height"). The first crop corresponding height is the height of the vehicle body 2 set in accordance with the first crop, and is a height equal to or higher than the first height (lower limit height).

[0274] The area where the first crop is planted may include weeds that are shorter than the first crop (weeds that are shorter than the first height HA). Even in this case, the height changing mechanism 90 keeps the height of the vehicle body 2 at or above the first height (lower limit height) regardless of the presence of short weeds.

[0275] The fact that the crop planted on the ground is the first crop can be detected by the above-described first detection device 70. A second correspondence table TB2 (see FIG. 52 ) that associates the type of crop with the height of the vehicle body 2 is stored in the memory unit of the control device 15. The number of combinations of the type of crop and the height of the vehicle body 2 included in the second correspondence table TB2 is not particularly limited and can be any number equal to or greater than two.

[0276] The height of the vehicle body 2 associated with the first crop stored in the second correspondence table TB2 is the first crop-associated height. In the second correspondence table TB2, the first crop-associated height is set to be equal to or greater than the height of the first crop. The height change mechanism 90 can change the height of the vehicle body 2 by determining that the first crop-associated height is equal to or greater than the height of the first crop or greater than the height of the first crop.

[0277] When the crop recognized by the first detection device 70 is the first crop, the height change control unit 15C reads the height of the vehicle body 2 corresponding to the first crop (first crop-corresponding height) from the second correspondence table TB2 and sends a control signal to drive the lifting cylinder 91 of the height change mechanism 90 so that the height of the vehicle body 2 becomes the read height (first crop-corresponding height). This changes the height of the vehicle body 2 to the first crop-corresponding height. As a result, the height of the vehicle body 2 becomes equal to or greater than the height of the first crop SM1 (see FIG. 53 ). Therefore, when the left traveling unit 3L and the right traveling unit 3R travel across the first crop SM1, it is possible to prevent the lower part of the vehicle body 2 from contacting the first crop SM1. In the example shown in FIG. 53 , the first crop-corresponding height HC1 of the vehicle body 2 is higher than the height HS1 of the first crop SM1. However, it may be the same height as the height HS1 of the first crop SM1.

[0278] When a second crop that is taller than the first crop is planted on the ground, the height change mechanism 90 sets the height of the vehicle body 2 to a height higher than the height corresponding to the first crop and equal to or lower than a second height (upper limit height). The height of the vehicle body 2 corresponding to the second crop (hereinafter referred to as the "height corresponding to the second crop") is stored in the memory unit of the control device 15. The height corresponding to the second crop is a height of the vehicle body 2 set for the second crop, and is higher than the height corresponding to the first crop and equal to or lower than the second height (upper limit height).

[0279] In the second correspondence table TB2 described above, the second crop corresponding height is set to be equal to or greater than the height of the second crop. The height changing mechanism 90 can change the height of the vehicle body 2 by determining that the second crop corresponding height is equal to or greater than the height of the second crop.

[0280] The first detection device 70 can detect that the crop planted on the ground is the second crop. When the crop detected by the first detection device 70 is the second crop, the height change control unit 15C reads the height of the vehicle body 2 corresponding to the second crop (the height corresponding to the second crop) from the second correspondence table TB2 and sends a control signal to drive the lifting cylinder 91 of the height change mechanism 90 so that the height of the vehicle body 2 becomes the read height (the height corresponding to the second crop). This changes the height of the vehicle body 2 to the height corresponding to the second crop. As a result, the height of the vehicle body 2 becomes equal to or greater than the height of the second crop SM2 (see FIG. 54 ). Therefore, when the left traveling unit 3L and the right traveling unit 3R travel across the second crop SM2, it is possible to avoid the lower part of the vehicle body 2 coming into contact with the second crop SM2. In the example shown in Figure 54, the second crop corresponding height HC2 of the vehicle body 2 is higher than the height HS2 of the second crop SM2, but it may also be the same height as the height HS2 of the second crop SM2.

[0281] The height change mechanism 90 can change the height of the vehicle body 2 in the vertical direction between a height at which the vehicle body 2 overlaps with the wheels 30 and a height at which the vehicle body 2 is higher than the wheels 30. In this embodiment, the height at which the vehicle body 2 overlaps with the wheels 30 is the first height (lower limit height) described above (see FIG. 4), but may be a height higher than the first height. In this embodiment, the height at which the vehicle body 2 is higher than the wheels 30 is the second height (upper limit height) described above (see FIG. 50), but may be a height lower than the second height.

[0282] The height change mechanism 90 can change the height of the vehicle body 2 in the vertical direction between a height at which the vehicle body 2 overlaps with the traveling unit 3 and a height at which the vehicle body 2 is higher than the traveling unit 3. The height at which the vehicle body 2 overlaps with the traveling unit 3 is a height at which the vehicle body 2 is sandwiched between the left traveling unit 3L and the right traveling unit 3R (see FIG. 4). The height at which the vehicle body 2 is higher than the traveling unit 3 is a height at which the vehicle body 2 is positioned higher than the left traveling unit 3L and the right traveling unit 3R (see FIG. 50).

[0283] In the example shown in FIG. 4 , the height at which the vehicle body 2 overlaps with the traveling device 3 is the same as the height at which the vehicle body 2 overlaps with the wheels 30 described above. That is, in the case of this embodiment, the height at which the vehicle body 2 overlaps with the traveling device 3 is the first height (lower limit height) described above. However, the height at which the vehicle body 2 overlaps with the traveling device 3 may also be a height at which the vehicle body 2 is above the wheels 30 (i.e., a height at which the vehicle body 2 overlaps with a part of the traveling device 3 other than the wheels 30). That is, it may be a height higher than the first height. Furthermore, in the example shown in FIG. 50 , the height at which the vehicle body 2 is above the traveling device 3 is the second height (upper limit height), but it may also be a height lower than the second height.

[0284] As described above, the vehicle body 2 is disposed between the left traveling unit 3L and the right traveling unit 3R. The height change mechanism 90 raises and lowers the vehicle body 2 between the left traveling unit 3L and the right traveling unit 3R to change the height of the vehicle body 2. In other words, the vehicle body 2 moves up and down through the space formed between the left traveling unit 3L and the right traveling unit 3R.

[0285] Figures 55 to 58 are flowcharts showing an example of the operation of the height change mechanism 90 controlled by the height change control unit 15C. Two examples (first example and second example) of the operation of the height change mechanism 90 controlled by the height change control unit 15C and their modified examples will be described below with reference to Figures 55 to 58. First, the first example of the operation of the height change mechanism 90 will be described with reference to Figure 55.

[0286] The first example is a case where the "circumstances around the vehicle body 2" detected by the first detection device 70 is the "height of crops in front of the vehicle body 2." In this case, the first detection device 70 detects the height H1 of the crops SM in front of the vehicle body 2 in the traveling direction (S1) (see FIG. 59 ). At this time, if the first detection device 70 is a camera 71, the camera 71 captures an image of the crops SM in front of the vehicle body 2 and generates an image signal. The calculation unit 73 detects the height H1 of the crops SM based on the generated image signal. The calculation unit 73 can detect the height H1 of the crops SM by, for example, measuring (estimating) the distance (length) from the ground to the top of the crop based on an image of the crop.

[0287] Meanwhile, the third detection device 77 detects the height H2 of the vehicle body 2 from the ground (S2). The heights H1 and H2 are detected before the vehicle body 2 reaches the crop. The detection of height H1 or height H2 may occur first, or may occur simultaneously. The height change control unit 15C compares the crop height H1 detected by the first detection device 70 with the height H2 of the vehicle body 2 detected by the third detection device 77 (S3).

[0288] Based on the comparison result, the height change control unit 15C operates the height change mechanism 90 to change the height H2 so that the height H2 of the vehicle body 2 is equal to or greater than the height H1 of the crop. If the comparison result is H2H1) (S5). Specifically, the height H2 is changed by extending the rod 91a of the lifting cylinder 91, thereby increasing the height of the vehicle body 2 (see FIG. 60). The height change mechanism 90 changes the height H2 while the vehicle body 2 is traveling until it reaches above the crop SM ahead in the traveling direction or before it travels. If the comparison result is H2≧H1 (Yes in S4), the height change mechanism 90 does not change the height H2 (S6). The work vehicle 1 travels toward the crops with the height H2 changed (S5) or not (S6), until the vehicle body 2 reaches above the crop SM (S7).<h1>

[0289] Due to the control operation described above, even if height H1 of the crop SM is higher than height H2 of the vehicle body 2, H2 ≥ H1 holds when the vehicle body 2 of the work vehicle 1 reaches above the crop SM. Therefore, the work vehicle 1 can perform work on the crop SM while avoiding contact of the vehicle body 2 with the crop SM.

[0290] 56 is a flowchart showing a modification of Example 1. In this modification, the first step (S1) to the third step (S3) of the operation of the height changing mechanism 90 are the same as those in Example 1, but the fourth step (S4) and onwards are different from Example 1.

[0291] In a fourth step (S4), the height change control unit 15C determines whether the height H1 of the crop is the same as the height H2 of the vehicle body 2 (S4). If H1=H2 (S4, Yes), the height change mechanism 90 does not change the height H2 (S5). If H1=H2 is not the case (S4, No), it determines whether H2

[0292] ​If H2H1 (S6, No), the height change mechanism 90 changes (decreases) the height H2 so that H1=H2 (S8). Specifically, the height H2 is changed by shortening the rod 91a of the lifting cylinder 91, thereby decreasing the height of the vehicle body 2. The work vehicle 1 travels toward the crops with the height H2 changed (increased or decreased) (S7, S8) or not (S5), until the vehicle body 2 reaches above the crops SM (S9).<h1>

[0293] Through the control operation described above, whether the crop height H1 is higher or lower than the height H2 of the vehicle body 2, when the vehicle body 2 of the work vehicle 1 reaches above the crops, H1 = H2. Therefore, the work vehicle 1 can perform work while traveling with the height H2 of the vehicle body 2 set to an appropriate height that is neither too high nor too low compared to the crop height H1. This allows work on the crops to be carried out smoothly.

[0294] Next, a second example of the control operation by the height change control unit 15C will be described with reference to Figure 57. The second example is an example in which the "circumstances around the vehicle body 2" detected by the first detection device 70 is the "height of the crops on the side of the vehicle body 2." In other words, this is an example in which there is a crop SM2 whose height is detected on the side (left or right) of the vehicle body 2 of the work vehicle 1 (see Figure 61). The crop SM is planted in multiple rows, and Figure 61 shows a first row RT1 and a second row RT2.

[0295] In this case, while the vehicle body 2 is traveling along the first row RT1 of the crop SM1, the first detection device 70 detects the height H3 of the crop SM2 in the second row RT2 adjacent to the first row RT1 (S1). The second row RT2 is the row on which work will be performed next after work on the first row RT1. Detection of the height H3 of the crop SM2 in the second row RT2 is possible by installing the first detection device 70 at a higher position than the crop SM2 in the second row RT2. If the first detection device 70 is a camera 71, the camera 71 captures an image of the crop SM2 in the second row RT2 located to the side of the vehicle body 2 and generates an image signal. The calculation unit 73 detects the height H3 of the crop SM2 in the second row RT2 based on the generated image signal. The calculation unit 73 detects the height H3 of the crop SM2 in the second row RT2 in the same manner as the method for detecting the height H1 of the crop SM described above.

[0296] Meanwhile, the third detection device 77 detects the height H2 of the vehicle body 2 from the ground (S2). The height H2 is detected before the vehicle body 2 reaches the second row RT2. The height change control unit 15C compares the height H3 of the crops SM2 in the second row RT2 detected by the first detection device 70 with the height H2 of the vehicle body 2 detected by the third detection device 77 (S3). Based on the comparison result, the height change control unit 15C operates the height change mechanism 90 to change the height H2 so that the height H2 of the vehicle body 2 is equal to or greater than the height H3 of the crops SM2.

[0297] If the comparison result is H2<H3 (S4, No), the distance change mechanism 80 changes the height H2 so that H2≧H3 (H2=H3 or H2>H3) (S5). Specifically, the height H2 is changed by extending the rod 91a of the lifting cylinder 91. The height change mechanism 90 changes the height H2 while the vehicle body 2 is turning to end its travel along the first row RT1 and transition to travel along the second row RT2. However, the height change mechanism 90 may change the height H2 while traveling straight before or after the turn, rather than while turning. If the comparison result is H2≧H3 (S4, Yes), the height change mechanism 90 does not change the height H2 (S6). The work vehicle 1 travels toward the crop with the height H2 changed (S5) or not changed (S6), and the vehicle body 2 reaches above the crop SM2 (S7).

[0298] Due to the control operation described above, even if height H3 of the crop SM2 is higher than height H2 of the vehicle body 2, H2≧H3 holds when the vehicle body 2 of the work vehicle 1 reaches above the crop SM2. Therefore, the work vehicle 1 can perform work on the crop SM2 while avoiding contact of the vehicle body 2 with the crop SM2.

[0299] 58 is a flowchart showing a modification of Example 2. In this modification, the first step (S1) to the third step (S3) of the operation of the height changing mechanism 90 are the same as the operation of Example 2, but the fourth step (S4) and onwards are different from Example 2.

[0300] In a fourth step (S4), the height change control unit 15C determines whether the height H3 of the crop SM2 is the same as the height H2 of the vehicle body 2 (S4). If H2 = H3 (S4, Yes), the height change mechanism 90 does not change the height H2 (S5). If H2 = H3 is not true (S4, No), the height change mechanism 90 determines whether H2 < H3 (S6). If H2 < H3 (S6, Yes), the height change mechanism 90 changes (increases) the height H2 so that H2 = H3 (S7). Specifically, the height change mechanism 90 extends the rod 91a of the lifting cylinder 91 to change the height H2 and increase the height of the vehicle body 2. If H2 > H3 (S6, No), the height change mechanism 90 changes (decreases) the height H2 so that H2 = H3 (S8). Specifically, the height change mechanism 90 shortens the rod 91a of the lifting cylinder 91 to change the height H2 and decrease the height of the vehicle body 2. The work vehicle 1 travels toward the crops with the height H2 changed (increased or decreased) (S7, S8) or not (S5), and the vehicle body 2 reaches above the crops SM2 (S9).

[0301] Through the control operation described above, whether the height H3 of the crop SM2 is higher or lower than the height H2 of the vehicle body 2, when the vehicle body 2 of the work vehicle 1 reaches above the crop SM2, H2 = H3. Therefore, the work vehicle 1 can perform work while traveling with the height H2 of the vehicle body 2 set to an appropriate height that is neither too high nor too low relative to the height H3 of the crop SM2. This allows work on the crop SM2 to be carried out smoothly.

[0302] As described above, the height H2 can be changed in accordance with the height of the crops SM by operating the height change mechanism 90 to change the height H2 of the vehicle body 2 based on the detection results of the first detection device 70 and the third detection device 77. Therefore, even if the height of the crops SM is high, the work vehicle 1 can travel without the vehicle body 2 coming into contact with the crops when traveling across the crops SM with the left traveling unit 3L and the right traveling unit 3R (see FIG. 54 ).

[0303] Furthermore, when the height of the vehicle body 2 is changed to be the same as the height of the crops SM (see Figures 56 and 58), work can be performed while traveling with the height H2 of the vehicle body 2 set to an appropriate height relative to the height H1 or H3 of the crops. This allows work on the crops to be performed smoothly while avoiding the vehicle body 2 from coming into contact with the crops.

[0304] The operations of the first example (including modified examples) and the second example (including modified examples) described above can be combined and implemented. In this case, when the vehicle body 2 travels along the first row RT1 of crops, the control operations shown in FIG. 55 (or FIG. 56) are executed, as in the first example. Specifically, until the vehicle body 2 reaches the crops, the first detection device 70 detects the height H1 of the crops in the first row RT1 ahead in the direction of travel of the vehicle body 2, and the third detection device 77 detects the height H2 of the vehicle body 2 from the ground. Next, the height change control unit 15C compares the height H1 with the height H2, and based on the comparison result, operates the height change mechanism 90 to change the height H2 so that the height H2 is equal to or greater than the height H1 of the crops (or the same as the height H1). The work vehicle 1 then travels along the first row RT1.

[0305] Next, as the vehicle body 2 travels along the first row RT1, the operation shown in Figure 57 (or Figure 58) is performed, as in the second example. Specifically, the first detection device 70 detects the height H3 of the crops SM in the second row RT2 adjacent to the first row RT1, and the third detection device 77 detects the height H2 of the vehicle body 2 from the ground. Next, the height change control unit 15C compares the height H3 with the height H2, and based on the comparison result, the height change mechanism 90 is operated to change the height H2 so that the height H2 is equal to or greater than the height H3 (or equal to the height H3). Thereafter, the work vehicle 1 travels along the second row RT2.

[0306] If there are three or more rows of crops, the above-described operation can be repeated. That is, while the vehicle body 2 is traveling along the second row, the height of the crops SM in the third row adjacent to the second row is detected, the detected height is compared with the height H2 of the vehicle body 2 from the ground, and the height changing mechanism 90 is operated based on the comparison result to change the height H2.

[0307] The change in height of the vehicle body 2 performed by the height change control unit 15C driving the height change mechanism 90 can be performed before the work vehicle 1 starts work, or can be performed while the work vehicle 1 is working. By changing the height of the vehicle body 2 while the work vehicle 1 is working, the height of the vehicle body 2 can be appropriately changed (fine-tuned) in accordance with the work situation.

[0308] As shown in Figure 7, the work vehicle 1 is equipped with a position change mechanism 110. The position change mechanism 110 changes the position of the power unit 4. In the present embodiment, the position change mechanism 110 changes the position of the power unit 4 relative to the vehicle body 2. More specifically, the position change mechanism 110 changes the position of the battery 7 relative to the vehicle body 2. However, the position change mechanism 110 may change the position of a power unit 4 other than the battery 7, rather than the position of the battery 7. Examples of the power unit 4 other than the battery 7 that is moved by the position change mechanism 110 include the motor 5, and an engine or fuel cell that replaces the motor 5.

[0309] In the following description, the position change mechanism 110 will be described as a mechanism that changes the position of the battery 7 relative to the vehicle body 2. The position change mechanism 110 changes the front-rear position or left-right position of the battery 7 relative to the vehicle body 2. In this embodiment, the position change mechanism 110 changes the front-rear position of the battery 7 relative to the vehicle body 2.

[0310] In this embodiment, the positional relationship between the vehicle body 2 and the traveling device 3 (the positional relationship in the direction of movement of the power unit 4) is constant (does not change). Therefore, it can also be said that the position changing mechanism 110 is a mechanism that changes the position of the power unit 4 relative to the traveling device 3.

[0311] As described above, the battery 7, which is part of the power unit 4, is housed in the housing frame 2 that constitutes the vehicle body 2. The position change mechanism 110 changes the position of the battery 7 (power unit) within the housing frame 2. In other words, the position change mechanism 110 changes the position of the battery 7 (power unit) within the vehicle body 2.

[0312] As shown in Figure 62, the position changing mechanism 110 includes a guide rail 111, a slide member 112, and a cylinder 113. Note that in Figure 62, the work vehicle 1 is shown in a simplified form to make it easier to understand the position changing mechanism 110.

[0313] The guide rails 111 are fixed to the storage frame (vehicle body) 2 and extend in the front-rear direction. The slide members 112 are disposed on the guide rails 111 and are movable in the front-rear direction along the guide rails 111. The battery 7 is fixed to the slide members 112. The battery 7 is movable in the front-rear direction along the guide rails 111 in conjunction with the movement of the slide members 112.

[0314] The cylinder 113 is composed of a hydraulic cylinder. The cylinder 113 has an extendable rod 113a and a cylinder tube 113b. The cylinder tube 113b is fixed to the storage frame 2. The tip of the rod 113a is attached to the battery 7 or the slide member 112. The slide member 112 moves back and forth along the guide rail 111 as the rod 113a extends and retracts. As a result, the battery 7 also moves back and forth along the guide rail 111 (see Figures 62, 63, and 64).

[0315] Note that instead of being configured to change the position of the battery 7 (power unit) within the storage frame 2, the position change mechanism 110 may be configured to change the position of the battery 7 (power unit) together with the storage frame 2. In this case, the guide rails 111 may be fixed to the frame structure 18 (see FIG. 8 ), and the storage frame 2 that stores the battery 7 may be attached to the slide member 112.

[0316] 65, guide rails 111 are fixed to frame members 18MA and 18MB of a horizontal frame 18M of the frame structure 18, and the storage frame 2 is attached to a slide member 112 that is movable along the guide rails 111. A cylinder tube 113b of the cylinder 113 is fixed to the horizontal frame 18M.

[0317] As a result, when the rod 113a of the cylinder 113 extends or retracts, the storage frame 2 moves in the front-to-rear direction together with the slide member 112 along the guide rail 111, and the battery 7 stored in the storage frame 2 also moves in the front-to-rear direction along the guide rail 111 (see Figures 65 and 66). When the storage frame 2 moves in the front-to-rear direction in this way, the position of the storage frame 2 in the front-to-rear direction relative to the traveling device 3 changes.

[0318] In the above-described embodiment, the storage frame 2 constitutes the entire vehicle body 2, but the storage frame 2 may also constitute a part of the vehicle body 2. Therefore, the configuration in which the position of the power unit 4 is changed together with the storage frame 2 may be a configuration in which the position of the power unit 4 is changed together with the storage frame, which is the entire vehicle body 2, or a configuration in which the position of the power unit 4 is changed together with the storage frame, which is a part of the vehicle body 2. In either configuration, the positions of the storage frame 2 and the power unit 4 relative to the traveling unit 3 are changed.

[0319] In the case of a configuration in which the position of the power unit 4 is changed together with the storage frame that is part of the vehicle body 2 (i.e., when the storage frame is part of the vehicle body 2), the position changing mechanism 110 moves the storage frame that is part of the vehicle body 2 relative to the vehicle body 2. In this case, it is sufficient that the storage frame is capable of storing at least the power unit 4 (battery 7, etc.).

[0320] The operation of the position change mechanism 110 is controlled by the control device 15. As shown in FIG. 7 , the control device 15 includes a position change control unit 15D. Two embodiments of the position change control unit 15D will be described below. The following two embodiments are examples in which the power unit 4 is a battery 7, but the power unit 4 is not limited to a battery 7 and may be a motor, an engine, a fuel cell, or the like. Therefore, in the descriptions of the following two embodiments, the battery 7 can be read as the power unit 4.

[0321] First, the position change control unit 15D of the first embodiment will be described. The position change control unit 15D of the first embodiment operates the position change mechanism 110 to change the position of the power unit 4 based on the slip ratio of the wheels 30 when the work vehicle 1 is traveling.

[0322] In the first embodiment, the work vehicle 1 is equipped with a slip ratio measurement device 120 that measures the slip ratio of the wheels 30 while the vehicle is traveling (see FIG. 7). The slip ratio measurement device 120 calculates the slip ratio as follows: "Slip ratio = (Vb - Vw) / Vb (where Vb is the vehicle speed, and Vw is the wheel speed (circumferential speed of the wheels))" (1).

[0323] Specifically, the slip ratio measuring device 120 calculates the slip ratio of the rear wheels by the formula "slip ratio = (Vb - Vr) / Vb (where Vb is the vehicle speed, Vr is the rear wheel speed (circumferential speed of the rear wheels))" (2), and calculates the slip ratio of the front wheels by the formula "slip ratio = (Vb - Vf) / Vb (where Vb is the vehicle speed, Vf is the front wheel speed (circumferential speed of the front wheels))" (3).

[0324] When the drive wheels of the work vehicle 1 are rear wheels, the slip ratio measurement device 120 calculates the slip ratio using the above formula (2). When the drive wheels of the work vehicle 1 are front wheels, the slip ratio measurement device 120 calculates the slip ratio using the above formula (3).

[0325] The position change control unit 15D operates the position change mechanism 110 to change the position of the battery 7 based on the slip ratio of the wheels 30 when the work vehicle 1 is traveling, measured by the slip ratio measurement device 120. Specifically, the position change control unit 15D operates the cylinder 113 of the position change mechanism 110 to extend or shorten the rod 113a, thereby changing the position of the battery 7.

[0326] 67 is a flowchart showing an example of the control operation of the position change control unit 15D of the first embodiment. Hereinafter, an example of the control operation by the position change control unit 15D of the first embodiment will be described with reference to FIG.

[0327] First, while the work vehicle 1 is traveling, the position change control unit 15D drives the position change mechanism 110 to move the battery 7 (see FIGS. 62 to 64), and measures the change in slip ratio associated with the movement of the battery 7 using the slip ratio measurement device 120 (S1). The graph in Fig. 68 shows an example of the change in slip ratio measured by the slip ratio measurement device 120. The horizontal axis of the graph in Fig. 68 represents the fore-and-aft position of the battery 7 (position in the fore-and-aft direction), with the left side of the horizontal axis representing the front and the right side representing the rear.

[0328] Next, the position change control unit 15D calculates the position of the battery 7 where the slip ratio measured by the slip ratio measurement device 120 is lowest as the optimal position (S2). In the graph of FIG. 68, the slip ratio is lowest at point A. Therefore, the position change control unit 15D calculates the front-to-rear position of the battery 7 corresponding to point A as the optimal position of the battery 7. The optimal position of the battery 7 is the position where the center of gravity of the vehicle body 2 is optimal (optimum center of gravity position). Next, the position change control unit 15D operates the position change mechanism 110 based on the calculation result of the optimal position, and moves the battery 7 to the optimal position (see FIG. 63) (S3). Thereafter, the work vehicle 1 travels with the battery 7 moved to the optimal position (S4).

[0329] This allows the work vehicle 1 to travel stably with less wheel slippage. Furthermore, it is possible to improve working horsepower when performing work with a work implement attached to the attachment unit 10. When a work implement is attached to or detached from the attachment unit 10 provided at the rear of the vehicle body 2, the center of gravity of the work vehicle 1 changes, and therefore the weight balance changes. At this time, the weight balance can be optimized by driving the position change mechanism 110 with the position change control unit 15D to move the battery 7. For example, when a work implement is attached to the attachment unit 10 provided at the rear of the vehicle body 2, the weight balance of the work vehicle 1 can be optimized and working horsepower can be improved by moving the battery 7 forward.

[0330] The position change control unit 15D may calculate the position of the center of gravity of the vehicle body 2 based on the longitudinal position of the battery 7, and perform control operations using the longitudinal position of the center of gravity of the vehicle body 2 instead of the longitudinal position of the battery 7. In this case, the horizontal axis of the graph in Figure 68 represents the longitudinal position of the center of gravity of the vehicle body 2. In this case, the control operations can be performed by replacing the "longitudinal position of the battery 7" in the above explanation with "longitudinal position of the center of gravity of the vehicle body 2."

[0331] Next, a description will be given of a position change control unit 15D according to the second embodiment. The position change control unit 15D according to the second embodiment operates the position change mechanism 110 to change the position of the battery 7 based on the torque of the wheels 30 when the work vehicle 1 is traveling.

[0332] In the second embodiment, the work vehicle 1 is equipped with a torque measuring device 121 that measures the torque of the wheels 30 while traveling (see FIG. 7). The torque measuring device 121 measures the torque of the front wheels 30F and the torque of the rear wheels 30B. The torque measuring device 121 measures, for example, the rotational torque of the motor 5 that drives the wheels 30 (front wheels 30F, rear wheels 30B). The torque measuring device 121 calculates the measured rotational torque of the motor 5 as the torque of the wheels 30 (front wheels 30F, rear wheels 30B).

[0333] As described above, the motor 5 includes a motor 5LF that drives the left front wheel 3LF, a motor 5RF that drives the right front wheel 3RF, a motor 5LB that drives the left rear wheel 3LB, and a motor 5RB that drives the right rear wheel 3RB. When the torque measuring device 121 measures the rotational torque of the motor 5 that drives the wheels 30, the torque measuring device 121 measures the rotational torque of each of the four motors (motor 5LF, motor 5RF, motor 5LB, and motor 5RB). The torque measuring device 121 then calculates the average value or total value of the rotational torques of motor 5LF and motor 5RF as the torque of the front wheel 30F. The torque measuring device 121 also calculates the average value or total value of the rotational torques of motor 5LB and motor 5RB as the torque of the rear wheel 30B.

[0334] The position change control unit 15D operates the position change mechanism 110 to change the position of the battery 7 based on the torque of the wheels 30 when the work vehicle 1 is traveling, measured by the torque measurement device 121. Specifically, the position change control unit 15D operates the cylinder 113 of the position change mechanism 110 to extend or shorten the rod 113a, thereby changing the position of the battery 7. In more detail, the position change control unit 15D moves the battery 7 forward when the torque of the rear wheels 30B falls below a predetermined value, and moves the battery 7 rearward when the torque of the front wheels 30F falls below a predetermined value.

[0335] Figure 69 is a flowchart showing an example of the control operation of the position change control unit 15D of the second embodiment. An example of the control operation by the position change control unit 15D of the second embodiment will be described below with reference to Figure 69. Here, an example will be described in which the rear wheels of the work vehicle 1 become stuck in mud or mire while traveling. Note that being stuck refers to the wheels becoming stuck in mud or mire and the work vehicle being unable to move.

[0336] While the work vehicle 1 is traveling, the torque of the rear wheels 30B is measured by the torque measuring device 121 (S1). The position change control unit 15D determines whether the torque of the rear wheels 30B measured by the torque measuring device 121 has fallen below a predetermined value (S2). If it is determined that the torque of the rear wheels 30B has fallen below the predetermined value (S2, Yes), the position change mechanism 110 is activated to move the battery 7 forward (S3) (see FIG. 72).

[0337] When the torque of the rear wheel 30B falls below a predetermined value, this means that the rear wheel 30B has become stuck in the groove MZ1, for example, and the work vehicle 1 has become stuck (see Figure 70). The graph in Figure 71 shows an example of changes in torque measured by the torque measuring device 121. In the graph in Figure 71, the torque of the rear wheel suddenly drops from time B, and from time C onwards the torque of the rear wheel 30B remains approximately constant at a low value. This shows that from time C onwards the rear wheel 30B is spinning, i.e. the work vehicle 1 is stuck.

[0338] When the position change mechanism 110 is operated to move the battery 7 forward (S3), the center of gravity of the work vehicle 1 moves forward. This allows the work vehicle 1 to escape from the stuck state (state in which the rear wheels 30B are spinning freely), and allows it to continue traveling (forward) (S5) (see arrow X10 in Figure 72).

[0339] If the position change control unit 15D determines that the torque of the rear wheels 30B is not below a predetermined value (S2, No), it does not operate the position change mechanism 110 and does not move the battery 7 (S4). If the torque of the rear wheels 30B is not below a predetermined value, the work vehicle 1 is not stuck (the rear wheels are not spinning freely), so the work vehicle 1 can continue traveling (forward) without operating the position change mechanism 110 (moving the battery 7) to move the center of gravity (S5).

[0340] Figure 73 is a flowchart showing an example of the control operation of the position change control unit 15D when the front wheels get stuck in mud or mire while the work vehicle 1 is traveling. That is, Figure 69 shows a case where the work vehicle 1 gets stuck due to the rear wheels spinning freely, and Figure 73 shows a case where the work vehicle 1 gets stuck due to the front wheels spinning freely.

[0341] While the work vehicle 1 is traveling, the torque of the front wheels is measured by the torque measuring device 121 (S1). The position change control unit 15D determines whether the torque of the front wheels measured by the torque measuring device 121 has fallen below a predetermined value (S2). If the torque of the front wheels has fallen below the predetermined value, this indicates that the work vehicle 1 has become stuck, for example, due to the front wheels getting stuck in a ditch. If it is determined that the torque of the front wheels has fallen below the predetermined value (S2, Yes), the position change mechanism 110 is activated to move the battery 7 rearward (S3).

[0342] When the position change mechanism 110 is operated to move the battery 7 rearward (S3), the center of gravity of the work vehicle 1 moves rearward. This allows the work vehicle 1 to escape from the stuck state (state in which the front wheels are spinning) and continue traveling (S5).

[0343] If the position change control unit 15D determines that the torque of the front wheels is not below a predetermined value (S2, No), it does not operate the position change mechanism 110 and does not move the battery 7 (S4). If the torque of the front wheels is not below a predetermined value, the work vehicle 1 is not stuck (the front wheels are not spinning freely), so the work vehicle 1 can continue traveling without operating the position change mechanism 110 (moving the battery 7) to move the center of gravity (S5).

[0344] If the work vehicle 1 becomes stuck while traveling unmanned and performing work, there is a risk that work will be halted for an extended period of time. However, as described above, the position change control unit 15D can operate the position change mechanism 110 to move the battery 7 forward or backward when the torque of the wheels (front wheels or rear wheels) falls below a predetermined value, causing the wheels (front wheels or rear wheels) to spin freely, thereby resolving the stuck state of the work vehicle 1 and preventing work from being halted for an extended period of time.

[0345] As described above, the weight balance of the work vehicle 1 can be adjusted by driving the position change mechanism 110 with the position change control unit 15D to change the position of the power unit 4. This makes it possible to adjust the weight balance of the work vehicle 1 without using a weight (counterweight) for adjusting the weight balance of the work vehicle 1. Therefore, a work vehicle 1 equipped with the position change mechanism 110 does not need to be equipped with a weight for adjusting the weight balance of the work vehicle 1. However, the work vehicle 1 may be equipped with a weight. In this case, the weight can be made smaller.

[0346] Examples of situations in which the position change control unit 15D drives the position change mechanism 110 to change the position of the power unit 4 and adjust the weight balance of the work vehicle 1 include when the work vehicle 1 gets stuck because a wheel (front or rear wheel) gets stuck in a groove, as described above, when a work implement is attached or detached, and when the soil on which the work vehicle 1 is traveling changes. For example, if the work vehicle 1 travels on a paved public road and then enters a field, the soil on which it travels changes. In this case, by changing the position of the power unit 4 and adjusting the weight balance of the work vehicle 1, it becomes possible to continue stable traveling even if the soil on which it travels changes.

[0347] Furthermore, the control operation by the position change control unit 15D described above is such that the position change mechanism 110 changes the front-to-rear position of the power unit 4 (battery 7) relative to the vehicle body 2. However, the control operation by the position change control unit 15D may also be such that the position change mechanism 110 changes the left-to-right position of the power unit 4 (battery 7) relative to the vehicle body 2.

[0348] When the position change mechanism 110 is configured to change the left-right position of the power unit 4 (battery 7) relative to the vehicle body 2, the guide rail 111 is arranged to extend in the left-right direction, and the extension direction of the rod 113a of the cylinder 113 is set to the left-right direction, thereby making the slide member 112 movable in the left-right direction.

[0349] According to a configuration in which the position change mechanism 110 changes the left-right position of the power unit 4 (battery 7) relative to the vehicle body 2, when the left and right heights of the vehicle body 2 differ, for example, on a slope, the vehicle body 2 can be stabilized by changing the left-right position of the power unit 4 relative to the vehicle body 2.

[0350] 74 and 75 show yet another embodiment of the work vehicle 1. The work vehicle 1 comprises a vehicle body 2, a traveling device 3 that supports the vehicle body 2 so that it can travel, and a work implement 200 for performing work. The configurations of the vehicle body 2 and the traveling device 3 are as described above. As also described above, the work implement 200 is an implement that performs various tasks such as agricultural work.

[0351] 75, the devices 201 included in the working device 200 are arranged on opposite sides of the vehicle body 2. Hereinafter, the device 201 arranged on one side of the vehicle body 2 will be referred to as a first device 201A, and the device 201 arranged on the other side of the vehicle body 2 will be referred to as a second device 201B.

[0352] In this embodiment, the devices 201 included in the working device 200 are arranged on opposite sides Y1 and Y2 of the vehicle body 2. Specifically, the first device 201A is arranged on the left side Y1, and the second device 201B is arranged on the right side Y2. However, the devices 201 included in the working device 200 may also be arranged on opposite sides in front and rear of the vehicle body 2. In this case, the first device 201A is arranged on the front, and the second device 201B is arranged on the rear.

[0353] Furthermore, the devices 201 included in the working device 200 may be arranged on opposite sides of the vehicle body 2, on the left and right, and in front and rear. In this case, the devices 201 may include a first device, a second device, a third device, and a fourth device. For example, the first device is arranged on the left, the second device is arranged on the right, the third device is arranged in front, and the fourth device is arranged in the rear.

[0354] The device (first device 201A) and the device (second device 201B) arranged on one side facing each other across the vehicle body 2 may have the same function or different functions. For example, if the first device 201A and the second device 201B are both tanks that store liquid, the first device 201A and the second device 201B are devices that have the same function (the function of storing liquid). For example, if the first device 201A is a tank that stores liquid and the second device 201B is a battery that stores power, the first device 201A and the second device 201B are devices that have different functions (the function of storing liquid and the function of storing power).

[0355] In the present embodiment, the working device 200 is a device that performs agricultural work (agricultural work device). Specifically, the working device 200 is a spraying device that sprays a spray liquid such as a chemical solution or liquid fertilizer. However, the working device 200 is not limited to a spraying device. The working device 200 may be an agricultural work device that performs work other than spraying in a field, or may be a device that performs work other than agricultural work. Hereinafter, the working device 200 will be described as a spraying device and will be referred to as the "spraying device 200."

[0356] In this embodiment, the equipment 201 included in the spraying device 200 is a tank 202 that stores the spray liquid of the spraying device 200. The tank 202 includes a first tank 202A arranged on one side (left side) of the vehicle body 2 and a second tank 202B arranged on the other side (right side) of the vehicle body 2. In other words, the first equipment 201A is the first tank 202A, and the second equipment 201B is the second tank 202B.

[0357] The spraying device 200 has a pump 204 and a boom 205. The pump 204 can be driven by an operating motor 6 mounted on the vehicle body 2. The pump 204 and the boom 205, and the pump 204 and the tank 202 are each connected by a pipe, hose, or other tube (not shown) through which the spray liquid can flow. Although not shown, the spraying device 200 can also be appropriately equipped with other components necessary for spraying the spray liquid.

[0358] The pump 204 sends the spray liquid stored in the first tank 202A and the second tank 202B to the boom 205. The boom 205 includes a left boom 205L and a right boom 205R. The left boom 205L extends further to the left than the vehicle body 2. The right boom 205R extends further to the right than the vehicle body 2. The boom 205 (left boom 205L and right boom 205R) extends in the left-right direction behind the upper part of the vehicle body 2. The positions (orientations) of the left boom 205L and the right boom 205R may be changeable between a spraying position extending horizontally (left-right direction) and a storage position extending upward.

[0359] The left boom 205L and the right boom 205R have a plurality of nozzles (not shown) arranged along their length. The spray liquid stored in the first tank 202A and the second tank 202B is sent to the left boom 205L and the right boom 205R by driving the pump 204, and is sprayed downward from the nozzles of the left boom 205L and the right boom 205R.

[0360] As shown in Figures 74 and 75, the work vehicle 1 is equipped with a frame structure 18. As described above, the frame structure 18 includes the left frame 18L, the right frame 18R, and the lateral frame 18M (see Figure 8, etc.). The equipment 201 includes a first equipment 201A arranged to the left of the left frame 18L and a second equipment 201B arranged to the right of the right frame 18R. In the case of this embodiment, a first tank 202A is arranged to the left of the left frame 18L as the first equipment 201A. A second tank 202B is arranged to the right of the right frame 18R as the second equipment 201B.

[0361] The work vehicle 1 is equipped with a support frame 210 that supports the equipment 201 and is detachable from the vehicle body 2. The support frame 210 is disposed above the equipment 201. The support frame 210 extends in the left-right direction so as to straddle the first equipment 201A and the second equipment 201B. The first equipment 201A is attached to the lower left of the support frame 210. The second equipment 201B is attached to the lower right of the support frame 210. In other words, the support frame 210 extends in the left-right direction so as to connect the upper part of the first equipment 201A and the upper part of the second equipment 201B. In this way, the support frame 210 supports the equipment 201 (the first equipment 201A and the second equipment 201B) from above.

[0362] As shown in Figure 75, the distance (left-right distance) between the first device 201A and the second device 201B attached to the support frame 210 is longer than the width (left-right length) of the vehicle body 2. In addition, the distance between the first device 201A and the second device 201B attached to the support frame 210 is longer than the width (left-right length) of the frame structure 18. As a result, a space SP1 (see Figure 76) is formed between the first device 201A and the second device 201B, into which the vehicle body 2 and the frame structure 18 can enter. As shown in Figure 75, when the spraying device 200 is attached to the vehicle body 2, the vehicle body 2 and the frame structure 18 can enter this space SP1.

[0363] As shown in Figures 74 and 75, the support frame 210 includes a first support frame 211 and a second support frame 212. The first support frame 211 and the second support frame 212 are arranged parallel to each other with a gap in the front-to-rear direction. The first support frame 211 is attached so as to connect the upper front portion of the first device 201A to the upper front portion of the second device 201B. The second support frame 212 is attached so as to connect the upper rear portion of the first device 201A to the upper rear portion of the second device 201B.

[0364] The support frame 210 may include one or three or more frames, instead of two frames, the first support frame 211 and the second support frame 212. The specific shape of the support frame 210 is not particularly limited as long as it can support the first device 201A and the second device 201B from above.

[0365] As shown in Figure 74, a pump 204 is attached to the support frame 210. More specifically, the pump 204 is attached to a support member 215 that extends rearward from the second support frame 212. The pump 204 attached to the support member 215 is located at the rear of the upper part of the vehicle body 2. However, the pump 204 may also be attached to another location on the work vehicle 1, such as the mounting portion 10 (see Figure 74).

[0366] The support frame 210 is attached to the vehicle body 2 from above. Specifically, as shown in Figures 76 and 77 , the support frame 210 is attached to the vehicle body 2 by driving the lifting cylinder 91 of the height changing mechanism 90 to raise the vehicle body 2 together with the movable frame 32 (see arrow U1). More specifically, the support frame 210 is attached to the vehicle body 2 via the frame structure 18 by being placed above the frame structure 18.

[0367] When attaching the support frame 210 to the vehicle body 2, first, with the vehicle body 2 in a low position (for example, the first height (lower limit height)), the support frame 210 is positioned above the vehicle body 2 (see FIGS. 76 and 77). At this time, the first device 201A and the second device 201B are positioned so that they overlap the vehicle body 2 in the front-rear direction, and the vehicle body 2 is positioned between the first device 201A and the second device 201B in the left-right direction. Next, the height change mechanism 90 is driven to raise the vehicle body 2 to a higher position (for example, the second height (upper limit height)) (see arrow U1 in FIGS. 76 and 77).

[0368] As a result, the vehicle body 2 is sandwiched between the first equipment 201A and the second equipment 201B, and the support frame 210 is placed on top of the frame structure 18 (movable frame 32), and the support frame 210 is attached to the vehicle body 2 (see Figures 74 and 75).

[0369] The work vehicle 1 in the embodiment shown in Figures 74 to 77 is configured to include a height change mechanism 90, but instead of this configuration, it may be configured without including a height change mechanism 90. Figure 78 shows an embodiment in which the work vehicle 1 is configured without a height change mechanism 90 (lifting cylinder 91, etc.). The work vehicle 1 in this embodiment is configured so that the body 2 is positioned higher than the traveling devices 3 by the frame structure 18, and a first device 201A and a second device 201B are positioned on either side of the body 2.

[0370] In the work vehicle 1 of this embodiment, the vehicle body 2 is always in a high position (above the traveling gear 3). Therefore, the equipment 201 can be arranged (mounted) on the opposing left and right sides (or front and rear) of the vehicle body 2 without having to move the vehicle body 2 upward. In the case of the work vehicle 1 of this embodiment, the support frame 210 can be mounted on the vehicle body 2 by lifting the support frame 210 above the vehicle body 2 and then lowering it.

[0371] 79 and 80 show a work vehicle 1 equipped with a support frame 210 of another embodiment. The support frame 210 of this embodiment is disposed below the equipment 201. The support frame 210 extends in the left-right direction so as to straddle the first equipment 201A and the second equipment 201B. The first equipment 201A is attached to the upper left part of the support frame 210. The second equipment 201B is attached to the upper right part of the support frame 210. In other words, the support frame 210 is attached so as to connect the lower part of the first equipment 201A and the lower part of the second equipment 201B. In this way, the support frame 210 supports the equipment 201 (the first equipment 201A and the second equipment 201B) from below.

[0372] 80 , the distance (left-right distance) between the first device 201A and the second device 201B attached to the support frame 210 is longer than the width (left-right length) of the vehicle body 2. In addition, the distance between the first device 201A and the second device 201B attached to the support frame 210 is longer than the width of the frame structure 18. As a result, a space SP2 is formed between the first device 201A and the second device 201B, into which the vehicle body 2 and the frame structure 18 can enter. When the spraying device 200 is attached to the vehicle body 2, the vehicle body 2 and the frame structure 18 can enter this space SP2.

[0373] As shown in Fig. 81 , the support frame 210 includes a first support frame 211, a second support frame 212, and a third support frame 213. The first support frame 211 and the second support frame 212 are arranged parallel to each other with a gap in the left-right direction and extend in the front-rear direction. The first support frame 211 supports the lower part of the first device 201A. The second support frame 212 supports the lower part of the second device 201B.

[0374] The third support frame 213 connects the rear of the first support frame 211 and the rear of the second support frame 212. The front of the first support frame 211 and the front of the second support frame 212 are not connected. When the support frame 210 is attached to the vehicle body 2, the vehicle body 2 is located in a space SP3 surrounded by the first support frame 211, the second support frame 212, and the third support frame 213.

[0375] 79 and 81 , a pump 204 is attached to the support frame 210. More specifically, the pump 204 is attached to the third support frame 213. The pump 204 attached to the third support frame 213 is located at the rear of the lower part of the vehicle body 2. The boom 205 is disposed behind the third support frame 213. The boom 205 extends in the left-right direction behind the lower part of the vehicle body 2.

[0376] The support frame 210 is attached to the vehicle body 2 from the rear. When attaching the support frame 210 to the vehicle body 2, first, the height change mechanism 90 is driven to raise the vehicle body 2 to a high position (for example, the second height (upper limit height)). Next, with the vehicle body 2 in the high position, the support frame 210 is positioned behind the vehicle body 2 (see FIG. 82 ). At this time, the first device 201A and the second device 201B are positioned so that they overlap the vehicle body 2 in the vertical direction, and the vehicle body 2 is positioned between the first device 201A and the second device 201B in the horizontal direction.

[0377] Next, the support frame 210 is moved forward (see arrow AF1 in FIG. 82 ). At this time, the vehicle body 2 is sandwiched between the first support frame 211 and the second support frame 212. The first support frame 211 is placed on the left frame 18L, and the second support frame 212 is placed on the right frame 18R (see FIG. 80 ). As a result, the vehicle body 2 is sandwiched between the first device 201A and the second device 201B, and the support frame 210 is placed on the top of the side frames 18LR (left frame 18L, right frame 18R) of the frame structure 18, and the support frame 210 is attached to the vehicle body 2 (see FIG. 80 ). With the support frame 210 attached to the vehicle body 2, the first support frame 211 is located to the left of the vehicle body 2, the second support frame 212 is located to the right of the vehicle body 2, and the third support frame 213 is located at the rear of the vehicle body 2.

[0378] The support frame 210 may be attached to the vehicle body 2 from the front. In this case, the third support frame 213 connects the front portion of the first support frame 211 to the rear portion of the second support frame 212, but does not connect the rear portion of the first support frame 211 to the rear portion of the second support frame 212. In this case, when the support frame 210 is attached to the vehicle body 2, the first support frame 211 is located to the left of the vehicle body 2, the second support frame 212 is located to the right of the vehicle body 2, and the third support frame 213 is located in front of the vehicle body 2.

[0379] Alternatively, the support frame 210 may be attached to the vehicle body 2 from above. In this case, the support frame 210 is attached to the vehicle body 2 by raising the vehicle body 2 using the height change mechanism 90 described above. When attaching the support frame 210 to the vehicle body 2, first, the vehicle body 2 is in a low position (e.g., the first height), and the support frame 210 is positioned above the vehicle body 2 (see FIG. 83 ). At this time, the first device 201A and the second device 201B are positioned so that they overlap the vehicle body 2 in the front-rear direction, and the vehicle body 2 is positioned between the first device 201A and the second device 201B in the left-right direction. Next, the height change mechanism 90 is driven to raise the vehicle body 2 to a higher position (e.g., the second height) (see arrow U2 in FIG. 83 ). As a result, the vehicle body 2 is sandwiched between the first equipment 201A and the second equipment 201B, and the support frame 210 is placed on the top of the side frame 18LR (left frame 18L, right frame 18R) of the frame structure 18, and the support frame 210 is attached to the vehicle body 2 (see Figure 80).

[0380] 80, the support frame 210 is configured to rest on the upper part of the side frame 18LR when attached to the vehicle body 2. However, in the present invention, instead of this configuration, the support frame 210 may be configured to be located below the side frame 18LR when attached to the vehicle body 2 (see FIG. 84).

[0381] 84 , the support frame 210 is located below the side frame 18LR. The first support frame 211 and the second support frame 212 sandwich the fixed frame 31 from the left and right. The support frame 210 is attached to the frame structure 18 by sandwiching the fixed frame 31 from the left and right between the first support frame 211 and the second support frame 212. The inner surface (right surface) of the first support frame 211 abuts against the outer surface (left surface) of the first left frame 19L, and the inner surface (left surface) of the second support frame 212 abuts against the outer surface (right surface) of the first right frame 21R.

[0382] The support frame 210 can be attached to the frame structure 18, for example, by engaging locking devices provided on the inner surfaces of the first support frame 211 and the second support frame 212 with locking devices provided on the outer surfaces of the first left frame 19L and the first right frame 21R.

[0383] In the above-described embodiment, the equipment 201 included in the working device 200 is the tank 202, but the equipment 201 included in the working device 200 may be a battery. In this case, the battery includes a first battery arranged on one side (left) of the vehicle body 2 and a second battery arranged on the other side (right) of the vehicle body 2. In other words, the first equipment 201A is the first battery, and the second equipment 201B is the second battery. The first battery is arranged on one side (left or front) of the vehicle body 2. The second battery is arranged on the other side (right or rear) of the vehicle body 2.

[0384] The work vehicle 1 according to the present invention has been described above, but the work vehicle 1 does not necessarily have to include all of the above-described components. A portion of the above-described components may be selected and included as appropriate depending on the application of the work vehicle 1, etc. For example, the control device 15 may include only one or two of the distance change control unit 15B, height change control unit 15C, and position change control unit 15D. In this case, the work vehicle 1 may include only one or two of the distance change mechanism 80, height change mechanism 90, and position change mechanism 110 that correspond to the control units.

[0385] The main characteristic features and effects of the work vehicle 1 described above are as follows.

[0386] (Item A1) A work vehicle 1 comprising a vehicle body 2, left and right running devices 3 that support the vehicle body 2 so that it can run, a first detection device 70 that detects the situation around the vehicle body 2, and a distance change mechanism 80 that changes the distance between the left and right running devices 3L, 3R, wherein the distance change mechanism 80 changes the distance so that the distance corresponds to the detection result of the first detection device 70.

[0387] According to this work vehicle 1, the distance between the left and right traveling units 3L, 3R can be adjusted in accordance with the surrounding conditions. More specifically, the distance between the left and right traveling units 3L, 3R can be adjusted by the distance change mechanism 80 so as to correspond to the detection results of the surrounding conditions of the vehicle body 2 detected by the first detection device 70. This makes it possible to avoid travel being obstructed by objects with a width greater than the distance between the left and right traveling units.

[0388] (Item A2) The first detection device 70 detects road information, which is a value related to the road on which the traveling device 3 can travel, as the conditions around the vehicle body 2, and the distance change mechanism 80 is a work vehicle 1 described in Item A1, in which the distance changes so that the distance corresponds to the road information.

[0389] According to this work vehicle 1, the distance between the left and right traveling units 3L, 3R can be adjusted to correspond to road information, which is a value relating to the road on which the traveling units 3 can travel.

[0390] (Item A3) The work vehicle 1 is described in Item A2, in which the first detection device 70 detects the width of the roadway as the road information, and the distance change mechanism 80 changes the distance so that the distance corresponds to the width of the roadway.

[0391] According to this work vehicle 1, the distance between the left and right traveling devices 3L, 3R can be adjusted to correspond to the width of the travel path.

[0392] (Item A4) The work vehicle 1 is described in Item A3, in which the first detection device 70 detects the width of a ridge on the ground as the width of the travel path, and the distance change mechanism 80 changes the distance so that it corresponds to the width of the ridge.

[0393] With this work vehicle 1, the distance between the left and right traveling devices 3L, 3R can be adjusted to correspond to the width of the ridges, so that the work vehicle 1 can travel across the ridges even when the ridges are wide.

[0394] (Item A5) This is a work vehicle 1 described in Item A4, in which the first detection device 70 detects the width of the ridge UN ahead of the vehicle body 2 in the traveling direction, and the distance change mechanism 80 changes the distance during or before the vehicle body 2 reaches above the ridge UN ahead in the traveling direction.

[0395] With this work vehicle 1, it is possible to prevent the left and right traveling devices 3L, 3R from coming into contact with the ridges ahead of the vehicle body 2 in the traveling direction.

[0396] (Item A6) The work vehicle 1 described in Item A4 is one in which the first detection device 70 detects the width of the second ridge UN2 adjacent to the first ridge UN1 when the vehicle body 2 is traveling along the first ridge UN1, and the distance change mechanism 80 changes the distance while the vehicle body 2 turns to end traveling along the first ridge UN1 and transition to traveling along the second ridge UN2.

[0397] According to this work vehicle 1, when the vehicle body 2 moves from the first ridge to the second ridge, it is possible to avoid the left and right traveling devices 3L, 3R coming into contact with the second ridge.

[0398] (Item A7) The first detection device 70 detects the width of an obstacle on the ground that obstructs travel as the width of the travel path, and the distance change mechanism 80 changes the distance so that the travel device 3 can cross the detected obstacle when the vehicle body 2 is traveling.This is a work vehicle 1 described in Item A3.

[0399] According to this work vehicle 1, when the vehicle body 2 travels toward an obstacle on the ground, the left and right traveling devices 3L, 3R can avoid contact with the obstacle.

[0400] (Item A8) The work vehicle 1 is described in any of items A1 to A7, wherein the traveling device 3 includes a left traveling device 3L provided on the left side of the vehicle body 2 and a right traveling device 3R provided on the right side of the vehicle body 2, the distance change mechanism 80 includes a left change mechanism 80L that changes the left-right position of the left traveling device 3L and a right change mechanism 80R that changes the left-right position of the right traveling device 3R, and the distance change mechanism 80 individually operates the left change mechanism 80L and the right change mechanism 80R based on the detection result of the first detection device 70.

[0401] With this work vehicle 1, the left change mechanism 80L and the right change mechanism 80R can be operated individually based on the detection results of the first detection device 70, so that the left and right positions of the left change mechanism 80L and the right change mechanism 80R can be individually set to optimal positions depending on the left and right positional relationship between the vehicle body 2 and obstacles, etc.

[0402] (Item A9) This is a work vehicle 1 described in Item A8, in which the first detection device 70 detects the left-right inclination of the ground as the condition around the vehicle body 2, and the distance change mechanism 80 moves the lower of the left running device 3L and the right running device 3R away from the widthwise center of the vehicle body 2 based on the detected inclination.

[0403] According to this work vehicle 1, the work vehicle 1 can be stabilized on an inclined surface that is inclined in the left-right direction.

[0404] (Item A10) The traveling device includes a left traveling device 3L provided on the left side of the vehicle body 2 and a right traveling device 3R provided on the right side of the vehicle body 2, the left traveling device 3L having a left front wheel 3LF and a left rear wheel 3LB, the right traveling device 3R having a right front wheel 3RF and a right rear wheel 3RB, and the distance change mechanism 80 includes a first change mechanism 801 that changes the left-right position of the left front wheel 3LF and a second change mechanism 802 that changes the left-right position of the left rear wheel 3LB. The work vehicle 1 includes a distance change mechanism 802 that changes the left-right position of the right front wheel 3RF, a third change mechanism 803 that changes the left-right position of the right rear wheel 3RB, and a fourth change mechanism 804 that changes the left-right position of the right rear wheel 3RB, wherein the distance change mechanism 80 individually operates the first change mechanism 801, the second change mechanism 802, the third change mechanism 803, and the fourth change mechanism 804 based on the detection result of the first detection device 70.

[0405] According to this work vehicle 1, by individually operating the first change mechanism 801, the second change mechanism 802, the third change mechanism 803, and the fourth change mechanism 804, the left and right positions of the left front wheel 3LF, the left rear wheel 3LB, the right front wheel 3RF, and the right rear wheel 3RB can each be individually adjusted to the optimal position.

[0406] (Item A11) The work vehicle 1 according to any one of items A1 to A10, further comprising a second detection device 75 that detects the distance between the left and right traveling devices 3L, 3R.

[0407] With this work vehicle 1, the distance between the left and right traveling units 3L, 3R can be adjusted by the distance change mechanism 80 based on the detection results of the conditions around the vehicle body 2 detected by the first detection device 70 and the distance between the left and right traveling units 3L, 3R detected by the second detection device 75.

[0408] (Item A12) The running device 3 includes a left running device 3L provided on the left side of the vehicle body 2 and a right running device 3R provided on the right side of the vehicle body 2, the distance change mechanism 80 includes a left change mechanism 80L that changes the left-right position of the left running device 3L and a right change mechanism 80R that changes the left-right position of the right running device 3R, and the second detection device 75 is a work vehicle 1 described in Item A11 that detects the distance between the left and right running devices 3L, 3R by detecting the amount of extension and contraction of each of the left change mechanism 80L and the right change mechanism 80R.

[0409] According to this work vehicle 1, the second detection device 75 detects the distance between the left and right traveling units 3L, 3R by detecting the amount of extension and contraction of each of the left change mechanism 80L and the right change mechanism 80R, so that the distance between the left and right traveling units 3L, 3R can be detected accurately and easily.

[0410] (Item A13) The first detection device 70 detects the width of a ridge on the ground as the surrounding conditions of the vehicle body 2, and the distance change mechanism 80 changes the distance so that it corresponds to the width of the ridge based on the width of the ridge and the distance between the left and right running devices 3L, 3R.This is a work vehicle 1 described in Item A11.

[0411] With this work vehicle 1, the distance between the left and right traveling units 3L, 3R can be adjusted to correspond to the width of the ridge based on the width of the ridge and the distance between the left and right traveling units 3L, 3R. Therefore, even if the ridge is wide, the work vehicle 1 can travel across the ridge.

[0412] (Item A14) The first detection device 70 is a work vehicle 1 described in any of items A1 to A13, which has a camera 71 mounted on the vehicle body 2 and capable of photographing ridges ahead of the vehicle body 2 as the vehicle body 2 travels, and a calculation unit 73 that calculates the width of the ridge based on the image captured by the camera 71.

[0413] With this work vehicle 1, the width of the ridge ahead of which the vehicle body 2 is traveling can be reliably calculated based on the image captured by the camera 71.

[0414] (Item A15) The first detection device 70 is a work vehicle 1 described in any of items A1 to A13, which has a sensor 72 mounted on the vehicle body 2 and capable of detecting ridges ahead of the vehicle body 2 as it travels, and a calculation unit 73 that calculates the width of the ridges based on the detection data of the sensor 72.

[0415] According to this work vehicle 1, the width of the ridge ahead of which the vehicle body 2 is traveling can be reliably calculated based on the detection data from the sensor 72.

[0416] (Item B1) A work vehicle 1 comprising a vehicle body 2, a running device 3 that supports the vehicle body 2 so that it can run, and a height change mechanism 90 that changes the height of the vehicle body 2 from the ground, wherein the height change mechanism 90 can arbitrarily change the height of the vehicle body 2 between a first height HA and a second height HB that is higher than the first height HA.

[0417] According to this work vehicle 1, the height of the vehicle body can be changed according to various situations. Therefore, for example, the height of the vehicle body can be changed to a height suitable for the work to be performed by the work vehicle.

[0418] (Item B2) A work vehicle 1 described in Item B1 is provided with an attachment section 10 provided on the vehicle body 2 to which a work device 200 can be attached and detached, and the height change mechanism 90 changes the height of the vehicle body 2 in accordance with the work performed by the work device 200.

[0419] According to this work vehicle 1, the height of the vehicle body 2 can be changed in accordance with the work being performed by the work device 200, so that the work device 200 can be set to the optimum height for the work, allowing the work to be performed smoothly.

[0420] (Item B3) The work vehicle 1 is described in Item B2 and is equipped with a recognition device 100 that recognizes the work device 200 attached to the attachment portion 10, and the height change mechanism 90 changes the height of the vehicle body 2 in accordance with the work device 200 recognized by the recognition device 100.

[0421] According to this work vehicle 1, the height of the vehicle body 2 can be changed in accordance with the work device 200 recognized by the recognition device 100, so the height of the vehicle body 2 can be changed to reliably correspond to the work device 200 attached to the attachment section 10.

[0422] (Item B4) The work vehicle 1 is described in Item B1 and is equipped with an operating device 101 for performing an operation to specify the height of the vehicle body 2, and the height change mechanism 90 changes the height of the vehicle body 2 in response to the height specified by the operating device 101.

[0423] According to this work vehicle 1, the worker can change the height of the vehicle body 2 by specifying the height of the vehicle body 2 using the operation device 101.

[0424] (Item B5) The height change mechanism 90 is the work vehicle 1 described in Item B2, which sets the height of the vehicle body 2 to a first working height when the work device 200 attached to the attachment unit 10 is a first working device, and sets the height of the vehicle body 2 to a second working height when the work device 200 attached to the attachment unit 10 is a second working device different from the first working device.

[0425] According to this work vehicle 1, the height change mechanism 90 can adjust the height of the first working device and the second working device to a height suitable for each work.

[0426] (Item B6) The height change mechanism 90 is a work vehicle 1 described in Item B1 that sets the height of the vehicle body 2 to be equal to or greater than the first height HA when the crop SM planted in the ground is the first crop SM1.

[0427] This work vehicle 1 is capable of traveling across the first crop SM1 while avoiding the vehicle body 2 coming into contact with the first crop SM1 planted on the ground.

[0428] (Item B7) The height change mechanism 90 is a work vehicle 1 described in Item B6 that, when the crop SM planted in the ground is a second crop SM2 that is taller than the first crop SM1, changes the height of the vehicle body 2 to a height that is higher than the height of the vehicle body 2 set corresponding to the first crop SM1 and is equal to or lower than the second height HB.

[0429] With this work vehicle 1, when the crop SM planted on the ground becomes the second crop SM2, which is higher than the first crop SM1, the height of the vehicle body 2 becomes higher than the height of the vehicle body 2 set corresponding to the first crop SM1 and lower than the second height HB, so that the vehicle body 2 can travel across the second crop SM2 while avoiding contact with the second crop SM2.

[0430] (Item B8) The height change mechanism 90 is a work vehicle 1 described in Item B7 that makes the height of the vehicle body 2 set corresponding to the first crop SM1 higher than the first crop SM1, and makes the height of the vehicle body 2 set corresponding to the second crop SM2 higher than the second crop SM2.

[0431] With this work vehicle 1, when a first crop SM1 and a second crop SM2 are planted at different heights on the ground, the vehicle body 2 can travel across the first crop SM1 and the second crop SM2 while avoiding contact with the first crop SM1 and the second crop SM2.

[0432] (Item B9) A work vehicle 1 described in any of Items B1 to B8, wherein the running gear 3 includes wheels 30, and the height change mechanism 90 is capable of changing the height of the vehicle body 2 in the vertical direction between the first height HA where the vehicle body 2 overlaps with the wheels 30, and the second height HB where the vehicle body 2 is higher than the wheels 30.

[0433] This work vehicle 1 can travel over crops, obstacles, etc. that are about the same height as the wheels 30, avoiding contact with such crops, obstacles, etc.

[0434] (Item B10) The height change mechanism 90 is a work vehicle 1 described in any of Items B1 to B9, which is capable of changing the height of the vehicle body 2 in the vertical position between the first height HA where the vehicle body 2 overlaps with the running device 3, and the second height HB where the vehicle body 2 is higher than the running device 3.

[0435] This work vehicle 1 can travel over crops, obstacles, etc. that are about the same height as the traveling device 3, while avoiding contact with such crops, obstacles, etc.

[0436] (Item B11) The work vehicle 1 is described in any one of items B1 to B10, in which the traveling device 3 includes a left traveling device 3L provided on the left side of the vehicle body 2 and a right traveling device 3R provided on the right side of the vehicle body 2, the vehicle body 2 is disposed between the left traveling device 3L and the right traveling device 3R, and the height change mechanism 90 raises and lowers the vehicle body 2 between the left traveling device 3L and the right traveling device 3R to change the height of the vehicle body 2.

[0437] According to this work vehicle 1, by making the vehicle body 2 higher than the height of crops, obstacles, etc., it is possible to straddle crops, obstacles, etc. between the left traveling device 3L and the right traveling device 3R.

[0438] (Item B12) A work vehicle 1 according to any one of items B1 to B11, comprising a frame structure 18 arranged around the vehicle body 2 and attached to the vehicle body 2, the frame structure 18 including a left frame 18L provided on the left side of the vehicle body 2 and extending in the vertical direction, a right frame 18R provided on the right side of the vehicle body 2 and extending in the vertical direction, and a lateral frame 18M connecting an upper part of the left frame 18L to an upper part of the right frame 18R, the vehicle body 2 being arranged in a position surrounded by the left frame 18L, the right frame 18R, and the lateral frame 18M in a front view, and the height change mechanism 90 changing the height of the vehicle body 2 from the ground by raising and lowering the frame structure 18.

[0439] According to this work vehicle 1, the vehicle body 2 is positioned in a position surrounded by the left frame 18L, the right frame 18R, and the lateral frame 18M, so that the vehicle body 2 can be protected from external forces. In addition, because the height of the vehicle body 2 from the ground can be changed by raising and lowering the frame structure 18, the load on the vehicle body 2 can be reduced compared to when the vehicle body 2 is raised and lowered directly.

[0440] (Item B13) The height change mechanism 90 has a rod 91a that extends and retracts in the vertical direction and a lifting cylinder 91 that raises and lowers the frame structure 18, and the lower end of the lifting cylinder 91 is a work vehicle 1 described in Item B12 that is located at the same or approximately the same height from the ground as the vehicle body 2 at the first height HA.

[0441] According to this work vehicle 1, when the vehicle body 2 is lowered to the lowest position, the amount by which the upper part of the lifting cylinder 91 protrudes upward from the vehicle body 2 can be kept to a minimum.

[0442] (Item B14) A work vehicle 1 described in items B1 to B13, which is equipped with a situation detection device (first detection device) 70 that detects the situation around the vehicle body 2, a height detection device (third detection device) 77 that detects the height of the vehicle body 2 from the ground, and a control device 15 that operates the height change mechanism 90 based on the detection results of the situation detection device 70 and the height detection device 77 to change the height of the vehicle body 2.

[0443] According to this work vehicle 1, the height of the vehicle body 2 can be changed based on the detection results of the situation detection device 70 and the height detection device 77, so that the height of the vehicle body 2 can be reliably set to the optimum height depending on the surrounding conditions.

[0444] (Item B15) The situation detection device 70 detects the height of any obstacles on the ground that hinder travel as a condition surrounding the vehicle body 2, and the control device 15 compares the height of the obstacles detected by the situation detection device 70 with the height of the vehicle body 2 detected by the height detection device 77, and operates the height change mechanism 90 to change the height of the vehicle body 2 so that the height of the vehicle body 2 is equal to or greater than the height of the obstacles.This is the work vehicle 1 described in Item B14.

[0445] According to this work vehicle 1, the height of the vehicle body 2 can be set to a height that will not come into contact with obstacles, so that the vehicle body 2 can be reliably prevented from coming into contact with obstacles.

[0446] (Item B16) The work vehicle 1 according to item B15, wherein the situation detection device 70 detects the height of crops SM planted on the ground as the height of the obstruction.

[0447] According to this work vehicle 1, the height of the vehicle body 2 can be set to a height that will not come into contact with the crops SM, so that the vehicle body 2 can be reliably prevented from coming into contact with the crops SM.

[0448] (Item B17) The situation detection device 70 detects the height of the crops SM ahead of the vehicle body 2 in the direction of travel, and the control device 15 operates the height change mechanism 90 to change the height of the vehicle body 2 while the vehicle body 2 is traveling until it reaches the crops SM ahead in the direction of travel, as described in Item B16.

[0449] With this work vehicle 1, it is possible to prevent the left and right traveling devices 3L, 3R from coming into contact with the crops SM that are ahead of the vehicle body 2 in the traveling direction.

[0450] (Item B18) This is a work vehicle 1 described in Item B16, in which the situation detection device 70 detects the height of the crops SM in a second row RT2 adjacent to the first row RT1 of crops SM when the vehicle body 2 is traveling along the first row RT1 of the crops SM, and the control device 15 operates the height change mechanism 90 to change the height of the vehicle body 2 while the vehicle body 2 is turning to end its travel along the first row RT1 and transition to travel along the second row RT2.

[0451] With this work vehicle 1, when the vehicle body 2 moves from the first row RT1 to the second row RT2 and travels, it is possible to avoid the left and right traveling devices 3L, 3R coming into contact with the crops SM in the second row RT2.

[0452] (Item C1) A work vehicle 1 comprising a vehicle body 2, a running device 3 that supports the vehicle body 2 so that it can run, and a height change mechanism 90 that changes the height of the vehicle body 2 from the ground, wherein the running device 3 includes a left running device 3L provided on the left side of the vehicle body 2 and a right running device 3R provided on the right side of the vehicle body 2, the vehicle body 2 is located between the left running device 3L and the right running device 3R, and the height change mechanism 90 raises and lowers the vehicle body 2 at a position between the left running device 3L and the right running device 3R in the width direction of the vehicle body 2.

[0453] According to this work vehicle 1, by raising and lowering the vehicle body 2 between the left and right traveling devices 3L, 3R, it is possible to travel reliably across crops and the like between the left and right traveling devices 3L, 3R.

[0454] (Item C2) The work vehicle 1 according to Item C1 is provided with a power unit 4 that generates power to drive the traveling device 3, and the vehicle body 2 is a housing frame 2 that houses the power unit 4.

[0455] According to this work vehicle 1 , the height changing mechanism 90 allows the storage frame 2 that stores the power unit 4 to be raised and lowered.

[0456] (Item C3) The power unit 4 includes a motor 5 and a battery 7 that stores the power supplied to the motor 5, and the height change mechanism 90 is a work vehicle 1 described in Item C2 that raises and lowers the storage frame 2 in which the battery 7 is stored.

[0457] According to this work vehicle 1 , the height changing mechanism 90 allows the storage frame 2 that stores the battery 7 to be raised and lowered.

[0458] (Item C4) The work vehicle 1 is described in any of Items C1 to C3, and is provided with a frame structure 18 arranged around the vehicle body 2, the left traveling device 3L including a left front wheel 3LF and a left rear wheel 3LB, the right traveling device 3R including a right front wheel 3RF and a right rear wheel 3RB, and the frame structure 18 having a left frame 18L connecting the left front wheel 3LF and the left rear wheel 3LB, and a right frame 18R connecting the right front wheel 3RF and the right rear wheel 3RB.

[0459] According to this work vehicle 1, the frame structure 18 can connect the left front wheel 3LF and left rear wheel 3LB of the left running device 3L, and the right front wheel 3RF and right rear wheel 3RB of the right running device 3R around (outside) the vehicle body 2.

[0460] (Item C5) The frame structure 18 is a work vehicle 1 described in Item C4, which has a fixed frame 31 to which the traveling device 3 is attached and a movable frame 32 attached to the vehicle body 2, and the height change mechanism 90 raises and lowers the movable frame 32 relative to the fixed frame 31.

[0461] According to this work vehicle 1 , the vehicle body 2 can be raised and lowered relative to the traveling device 3 by raising and lowering the movable frame 32 relative to the fixed frame 31 .

[0462] (Item C6) The work vehicle 1 is described in any one of Items C1 to C5, wherein the height change mechanism 90 is capable of changing the height of the vehicle body 2 to any height within a preset height range.

[0463] According to this work vehicle 1, the height of the vehicle body 2 can be changed to an optimum height by the height change mechanism 90.

[0464] (Item C7) The work vehicle 1 is described in any one of Items C1 to C6, in which the height change mechanism 90 is capable of changing the height of the vehicle body 2 to a height sandwiched between the left traveling device 3L and the right traveling device 3R.

[0465] With this work vehicle 1, the height of the vehicle body 2 can be changed to a height sandwiched between the left running device 3L and the right running device 3R, so that the height of the vehicle body 2 can be lowered to lower the vehicle height (height of the work vehicle 1).

[0466] (Item C8) The work vehicle 1 is described in any one of Items C1 to C7, in which the height change mechanism 90 is capable of changing the height of the vehicle body 2 to a height higher than the left traveling device 3L and the right traveling device 3R.

[0467] With this work vehicle 1, the height of the vehicle body 2 can be changed to a height higher than the left running device 3L and the right running device 3R, making it possible to travel across crops SM and the like that are at the same height as the left running device 3L and the right running device 3R.

[0468] (Item C9) The work vehicle 1 according to item C4 or C5, wherein the vehicle body 2 is disposed at a position sandwiched between the left frame 18L and the right frame 18R.

[0469] According to this work vehicle 1, the left and right sides of the vehicle body 2 can be protected by the left frame 18L and the right frame 18R.

[0470] (Item C10) The work vehicle 1 is described in any one of Items C4, C5, and C9, wherein the frame structure 18 includes a horizontal frame 18M that connects the left frame 18L and the right frame 18R.

[0471] According to this work vehicle 1, a highly rigid frame structure 18 can be obtained in which the left frame 18L, the right frame 18R, and the lateral frame 18M are integrated.

[0472] (Item C11) The horizontal frame 18M connects the upper part of the left frame 18L and the upper part of the right frame 18R, and the vehicle body 2 is a work vehicle 1 described in Item C10, which is positioned in a position surrounded by the left frame 18L, the right frame 18R, and the horizontal frame 18M when viewed from the front.

[0473] According to this work vehicle 1, the left, right and upper sides of the vehicle body 2 can be protected by the left frame 18L, the right frame 18R and the lateral frame 18M.

[0474] (Item C12) The height change mechanism 90 has a lifting cylinder 91 that raises and lowers the movable frame 32, the left frame 18L and the right frame 18R each have the fixed frame 31 and the movable frame 32, and the lifting cylinder 91 includes a left lifting cylinder 91L that raises and lowers the movable frame 32 of the left frame 18L and a right lifting cylinder 91R that raises and lowers the movable frame 32 of the right frame 18R, which is the work vehicle 1 described in Item C5.

[0475] According to this work vehicle 1, the movable frame 32 of the left frame 18L and the movable frame 32 of the right frame 18R can be raised and lowered individually by the lifting cylinders 91, respectively.

[0476] (Item D1) A work vehicle 1 comprising a vehicle body 2, a traveling device 3 that supports the vehicle body 2 so that it can travel, a power unit 4 for driving the traveling device 3, and a position change mechanism 110 that changes the position of the power unit 4.

[0477] With this work vehicle 1, the weight balance of the work vehicle 1 can be adjusted without the need for weights, and the center of gravity of the work vehicle 1 can be changed depending on the situation. This allows the work vehicle 1 to travel and work stably in accordance with the surrounding conditions. Furthermore, because the center of gravity is changed by changing the fore-and-aft position of the existing power unit 4 of the work vehicle 1, there is no need to separately mount other heavy objects (such as liquids) on the vehicle body 2 for the purpose of changing the center of gravity, and the vehicle body can be prevented from becoming heavy.

[0478] (Item D2) The work vehicle 1 is described in Item D1, wherein the position changing mechanism 110 changes the position of the power unit 4 in the front-to-rear direction.

[0479] According to this work vehicle 1, the weight balance of the work vehicle 1 in the longitudinal direction can be adjusted without the need for weights, and the position of the center of gravity of the work vehicle 1 in the longitudinal direction can be changed depending on the situation.

[0480] (Item D3) The power unit 4 has a motor 5 and a battery 7 that stores the power supplied to the motor 5, and the position change mechanism 110 is a work vehicle 1 described in item D1 or item D2 that changes the position of the battery 7.

[0481] According to this work vehicle 1, the weight balance of the work vehicle 1 can be easily adjusted by changing the position of the battery 7, which is a heavy object.

[0482] (Item D4) A work vehicle 1 according to any one of items D1 to D3, which is provided with a storage frame 2 that stores the power unit 4, and the position change mechanism 110 changes the position of the power unit 4 within the storage frame 2.

[0483] According to this work vehicle 1, by changing the position of the power unit 4 within the storage frame 2, the position of the center of gravity of the work vehicle 1 can be changed depending on the situation.

[0484] (Item D5) A work vehicle 1 according to any one of items D1 to D3, which is provided with a storage frame 2 that stores the power unit 4, and the position change mechanism 110 changes the position of the power unit 4 together with the storage frame 2.

[0485] According to this work vehicle 1, by changing the position of the power unit 4 together with the storage frame 2, the position of the center of gravity of the work vehicle 1 can be changed depending on the situation.

[0486] (Item D6) A work vehicle 1 described in any of Items D1 to D5, which is equipped with a slip ratio measuring device 120 that measures the slip ratio of the wheels 30 of the traveling device 3 while traveling, and a control device 15 that operates the position changing mechanism 110 based on the slip ratio measured by the slip ratio measuring device 120 to change the position of the power unit 4.

[0487] According to this work vehicle 1, by changing the position of the power unit 4 based on the slip ratio measured by the slip ratio measurement device 120, the work vehicle 1 can travel stably in a state where wheel slip is unlikely to occur.

[0488] (Item D7) The control device 15 is a work vehicle 1 described in Item D6, which calculates the position of the power unit 4 where the slip ratio is lowest as the optimal position, and operates the position change mechanism 110 based on this calculation result to move the power unit 4 to the optimal position.

[0489] According to this work vehicle 1, by moving the power unit 4 to the optimum position where the slip ratio is lowest, the work vehicle 1 can travel stably in a state where wheel slip is unlikely to occur.

[0490] (Item D8) The traveling device 3 is a work vehicle 1 described in Item D6 that has front wheels 30F provided at the front of the vehicle body 2 and rear wheels 30B provided at the rear of the vehicle body 2, and the slip ratio measuring device 120 calculates the slip ratio using the following formula (1): "Slip ratio = (Vb - Vw) / Vb (where Vb: vehicle speed, Vw: wheel speed)" ... (1).

[0491] According to this work vehicle 1, the slip ratio can be accurately calculated based on the vehicle body speed Vb and the wheel speed Vw.

[0492] (Item D9) A work vehicle 1 described in any of Items D1 to D5, which is equipped with a torque measuring device 121 that measures the torque of the wheels 30 of the traveling device 3 while traveling, and a control device 15 that operates the position change mechanism 110 based on the torque measured by the torque measuring device 121 to change the position of the power unit 4.

[0493] According to this work vehicle 1, when the work vehicle 1 becomes stuck and the wheels spin and torque decreases, the position of the power unit 4 is changed to change the position of the center of gravity of the vehicle, thereby enabling the work vehicle 1 to escape from the stuck state.

[0494] (Item D10) The work vehicle 1 is described in Item D9, in which the traveling device 3 has front wheels 30F provided at the front of the vehicle body 2 and rear wheels 30B provided at the rear of the vehicle body 2, the torque measuring device 121 measures the torque of the front wheels 30F and the torque of the rear wheels 30B, respectively, and the control device 15 moves the power unit 4 forward when the torque of the rear wheels 30B falls below a predetermined value, and moves the power unit 4 backward when the torque of the front wheels 30F falls below the predetermined value.

[0495] With this work vehicle 1, in both cases where the front wheels spin freely and where the rear wheels spin freely, the work vehicle 1 can escape from a stuck state by changing the position of the power unit 4 and shifting the vehicle's center of gravity forward or backward.

[0496] (Item D11) A work vehicle 1 described in any of items D1 to D10 that does not include a weight for adjusting the weight balance of the work vehicle 1, and the position change mechanism 110 adjusts the weight balance of the work vehicle 1 without using the weight by changing the position of the power unit 4.

[0497] According to this work vehicle 1, the work vehicle 1 can be made lighter by not providing weights, and the power unit 4 can function as a substitute for weights, allowing the weight balance of the work vehicle 1 to be adjusted.

[0498] (Item E1) A work vehicle 1 comprising a vehicle body 2, a traveling device 3 that supports the vehicle body 2 so that it can travel, and a work device 200 for performing work, in which equipment 201 included in the work device 200 is arranged on one side and the other side facing each other across the vehicle body 2.

[0499] According to this work vehicle 1, the center of gravity of the work vehicle 1 can be lowered compared to when the equipment 201 included in the work device 200 is mounted on the vehicle body 2, thereby improving the stability of the work vehicle 1.

[0500] (Item E2) The work vehicle 1 is described in Item E1, in which the equipment 201 is arranged on the left and right sides of the vehicle body 2, facing each other.

[0501] According to this work vehicle 1, the position of the center of gravity of the work vehicle 1 can be lowered while optimizing the left and right weight balance of the work implement 200.

[0502] (Item E3) The work vehicle 1 is described in Item E1, in which the equipment 201 is arranged on opposite sides of the vehicle body 2, in front and behind.

[0503] According to this work vehicle 1, the center of gravity of the work vehicle 1 can be lowered while optimizing the weight balance between the front and rear of the work implement 200.

[0504] (Item E4) Work vehicle 1 according to any one of items E1 to E3, wherein device 201A arranged on one side and device 201B arranged on the other side are devices having the same function.

[0505] According to this work vehicle 1, multiple devices having the same function can be allocated and arranged on either side of the vehicle body 2. This prevents the center of gravity of the work vehicle 1 from becoming higher due to multiple devices having the same function being arranged on the vehicle body 2. Furthermore, the weight balance between the left and right sides of the work vehicle 1 can be optimized.

[0506] (Item E5) The work vehicle 1 is described in any one of items E1 to E3, wherein the device 201A arranged on one side and the device 201B arranged on the other side are devices having different functions.

[0507] According to this work vehicle 1, multiple devices with different functions can be allocated and arranged on either side of the vehicle body 2. This prevents the center of gravity of the work vehicle 1 from becoming higher due to multiple devices with different functions being arranged on the vehicle body 2. Furthermore, the weight balance between the left and right sides of the work vehicle 1 can be optimized.

[0508] (Item E6) The work vehicle 1 is described in any of items E1 to E5, in which the work device 200 is a spray device that sprays spray liquid, the equipment 201 is a tank 202 that stores the spray liquid, and the tank 202 includes a first tank 202A arranged on one side of the vehicle body 2 and a second tank 202B arranged on the other side of the vehicle body 2.

[0509] According to this work vehicle 1, the multiple tanks (first tank 202A and second tank 202B) can be allocated and arranged on either side of the vehicle body 2. Therefore, it is possible to prevent the center of gravity of the work vehicle 1 from becoming higher due to the multiple tanks being arranged on the vehicle body 2. In addition, the left and right weight balance of the work vehicle 1 can be optimized.

[0510] (Item E7) The work device 200 is a work vehicle 1 described in any one of items E1 to E6, which includes a battery 7 as the equipment, and the battery 7 includes a first battery arranged on one side of the vehicle body 2 and a second battery arranged on the other side of the vehicle body.

[0511] With this work vehicle 1, multiple batteries (first battery and second battery) can be allocated and arranged on either side of the vehicle body 2. This prevents the center of gravity of the work vehicle 1 from being raised due to multiple batteries being arranged on the vehicle body 2. Furthermore, the left and right weight balance of the work vehicle 1 can be optimized.

[0512] (Item E8) A work vehicle 1 according to any one of items E1 to E7, comprising a support frame 210 that supports the equipment and is detachable from the vehicle body 2, the support frame 210 being positioned above the equipment.

[0513] According to this work vehicle 1, the equipment can be attached to and detached from the vehicle body 2 together with the support frame 210 as needed. Furthermore, because the support frame 210 is disposed above the equipment, by placing the support frame 210 above the vehicle body 2, it is possible to place the equipment on either side of the vehicle body 2.

[0514] (Item E9) A work vehicle 1 according to any one of items E1 to E7, comprising a support frame 210 that supports the equipment and is detachable from the vehicle body 2, the support frame 210 being positioned below the equipment.

[0515] According to this work vehicle 1, the equipment can be attached to and detached from the vehicle body 2 together with the support frame 210 as needed. Furthermore, because the support frame 210 is disposed below the equipment, the equipment can be reliably supported by the support frame 210.

[0516] (Item E10) A work vehicle 1 described in Item E2, which is provided with a frame structure 18 arranged around the vehicle body 2 and attached to the vehicle body 2, the frame structure 18 including a left frame 18L arranged on the left side of the vehicle body 2 and extending in the vertical direction, a right frame 18R arranged on the right side of the vehicle body 2 and extending in the vertical direction, and a horizontal frame 18M connecting the left frame 18L and the right frame 18R, and the equipment including a first equipment 201A arranged on the left side of the left frame 18L and a second equipment 201B arranged on the right side of the right frame 18R.

[0517] With this work vehicle 1, the vehicle body 2 can be protected by the frame structure 18, and the first equipment 201A can be placed on the left side of the vehicle body 2 and the second equipment 201B can be placed on the right side of the vehicle body 2 without being obstructed by the frame structure 18.

[0518] (Item E11) The work vehicle 1 is described in item E8, wherein the support frame 210 is attached to the vehicle body 2 from above.

[0519] According to this work vehicle 1, when it is not possible to secure a large space around the vehicle body 2, the equipment can be attached to the vehicle body 2 from above together with the support frame 210.

[0520] (Item E12) The work vehicle 1 according to item E9, wherein the support frame 210 is attached to the vehicle body 2 from the front or rear.

[0521] According to this work vehicle 1, when it is not possible to secure a large space on the sides or above the vehicle body 2, the equipment can be attached to the vehicle body 2 together with the support frame 210 from the front or rear.

[0522] (Item E13) The work vehicle 1 according to any one of items E1 to E11, further comprising a height change mechanism 90 that changes the height of the vehicle body 2 from the ground.

[0523] According to this work vehicle 1, by changing the height of the vehicle body 2 using the height changing mechanism 90, it becomes possible to easily attach equipment together with the support frame 210 to the vehicle body 2 from above.

[0524] (Item F1) A work vehicle 1 comprising a vehicle body 2, wheels 30 arranged on the sides of the vehicle body 2, and a drive unit 40 for driving the wheels 30, wherein at least a portion of the drive unit 40 is positioned on the outside opposite the tread portion 30a of the wheels 30 and overlaps with the wheels 30 in the width direction of the vehicle body 2.

[0525] With this work vehicle 1, a wheel steering area can be secured that is longer by the width OW1 where the width OW2 of the drive unit 40 in the left-right direction overlaps with the outer overlap position OP1, compared to when the drive unit 40 is located inside (towards the vehicle body 2) of the wheel 30. This allows a larger steering angle of the wheel 30 to be secured.

[0526] (Item F2) The drive unit 40 has a steering mechanism 60 that changes the direction of the wheels 30, a drive device 45 that generates power, and a transmission mechanism 50 that transmits the power generated by the drive device 45 to the wheels 30, and at least a portion of the drive unit 40 that is located in a position overlapping with the wheels 30 is the steering mechanism 60, which is the work vehicle 1 described in Item F1.

[0527] With this work vehicle 1, a wheel steering area can be secured that is longer by the width of the steering mechanism 60 in the left-right direction that overlaps with the outer overlap position OP1 than when the steering mechanism 60 is located inside (towards the vehicle body 2) of the wheel 30. This allows a larger steering angle for the wheel 30 to be secured.

[0528] (Item F3) The drive unit 40 has a steering mechanism 60 that changes the direction of the wheels 30, a drive device 45 that generates power, and a transmission mechanism 50 that transmits the power generated from the drive device 45 to the wheels, and at least a portion of the drive unit 40 that is located in a position overlapping with the wheels 30 is the drive device 45, which is the work vehicle 1 described in Item F1.

[0529] With this work vehicle 1, a wheel steering area can be secured that is longer by the width of the drive unit 45 in the left-right direction that overlaps with the outer overlap position OP1 than when the drive unit 45 is located inside (towards the vehicle body 2) of the wheel 30. This allows a larger steering angle for the wheel 30 to be secured.

[0530] (Item F4) The drive unit 40 has a steering mechanism 60 that changes the direction of the wheels 30, a drive device 45 that generates power, and a transmission mechanism 50 that transmits the power generated by the drive device 45 to the wheels 30, and at least a portion of the drive unit 40 that is located in a position overlapping with the wheels 30 is the transmission mechanism 50, which is the work vehicle 1 described in Item F1.

[0531] With this work vehicle 1, a region for steering the wheels can be secured that is longer by the width of the transmission mechanism 50 in the left-right direction that overlaps with the outer overlap position OP1 than when the transmission mechanism 50 is located inside (towards the vehicle body 2) of the wheels 30. This allows a larger steering angle for the wheels 30 to be secured.

[0532] (Item F5) The steering mechanism 60 is a work vehicle 1 described in Item F2, which has a rotating body 61 that rotates around an axis in the vertical direction when the wheel 30 is steered, and the axis AX1 of the rotating body 61 is located above the wheel 30.

[0533] According to this work vehicle 1, a larger steering angle of the wheel 30 can be ensured compared to when the axis AX1 of the rotating body 61 is located inside the wheel 30 (towards the vehicle body 2).

[0534] (Item F6) The work vehicle 1 is described in item F4, wherein the transmission mechanism 50 has a first transmission shaft 501 that is disposed above the wheels 30 and extends in the vertical direction.

[0535] According to this work vehicle 1, the first transmission shaft 501 extends vertically above the wheel 30, thereby preventing the transmission mechanism 50 from protruding too far inward of the wheel 30 (towards the vehicle body 2) and interfering with the movement of the wheel when steering.

[0536] (Item F7) The transmission mechanism 50 has a second transmission shaft 502 that rotates upon receiving power transmitted from the first transmission shaft 501, and the second transmission shaft 502 is a work vehicle 1 described in Item F6, which is positioned inside the wheels 30 and extends in the vertical direction.

[0537] According to this work vehicle 1, the second transmission shaft 502 is positioned inside the wheels 30 and extends in the vertical direction, making it possible to easily and reliably transmit power from the second transmission shaft 502 to the wheels 30.

[0538] (Item F8) A work vehicle 1 described in Item F7 is provided with a height change mechanism 90 that changes the height of the vehicle body 2 from the ground, and the first transmission shaft 501 or the second transmission shaft 502 is extendable and retractable in accordance with the change in height of the vehicle body 2 by the height change mechanism 90.

[0539] According to this work vehicle 1, even when the height of the vehicle body 2 is changed by the height changing mechanism 90, power can be transmitted reliably by the transmission mechanism 50.

[0540] (Item F9) The first transmission shaft 501 has an upper shaft 501a to which power from the drive unit 45 is transmitted, and a lower shaft 501b that transmits the power transmitted to the upper shaft 501a to the second transmission shaft 502, and the axis of the upper shaft 501a and the axis of the lower shaft 501b are arranged on the same straight line, and the distance between the upper end of the upper shaft 501a and the lower end of the lower shaft 501b changes as the height of the vehicle body 2 is changed by the height change mechanism 90.This is the work vehicle 1 described in Item F8.

[0541] According to this work vehicle 1, when the height of the vehicle body 2 is changed by the height change mechanism 90, the first transmission shaft 501 can be extended or retracted by changing the distance between the upper end of the upper shaft 501a and the lower end of the lower shaft 501b.

[0542] (Item F10) The first transmission shaft 501 has a cylindrical intermediate shaft 501c having an upper portion 501c1 into which the upper shaft 501a is inserted and a lower portion 501c2 into which the lower shaft 501b is inserted, a first spline is formed on the outer surface of the upper shaft 501a, the lower shaft 501b is cylindrical and has a second spline formed on its inner surface, the intermediate shaft 501c has an internal spline formed on its inner surface and an external spline formed on its outer surface, the first spline meshes with the internal spline, and the second spline meshes with the external spline, in the work vehicle 1 described in Item F9.

[0543] According to this work vehicle 1, when the height of the vehicle body 2 is changed by the height change mechanism 90, the first transmission shaft 501 can be extended and retracted while maintaining power transmission between the upper shaft 501a, the intermediate shaft 501c, and the lower shaft 501b.

[0544] (Item F11) The steering mechanism 60 has a cylinder 113 with a rod 113a that extends and retracts in a direction perpendicular to the axis, the rotating body 61 has a first connection part 61a to which the rod 113a is connected and a second connection part 61b that is connected to the wheel 30, and the cylinder 113 rotates the rotating body 61 around the axis by extending and retracting the rod 113a, thereby rotating the wheel 30 around the axis, which is the work vehicle 1 described in item F5.

[0545] According to this work vehicle 1, the steering mechanism 60 can be arranged compactly around the wheels 30, and the wheels 30 can be reliably steered by the extension and contraction of the rod 113a.

[0546] (Item F12) The work vehicle 1 is described in any one of items F1 to F11, wherein the wheels 30 include a left front wheel 3LF, a right front wheel 3RF, a left rear wheel 3LB, and a right rear wheel 3RB, and the drive unit 40 includes a first drive unit 41 for driving the left front wheel 3LF, a second drive unit 42 for driving the right front wheel 3RF, a third drive unit 43 for driving the left rear wheel 3LB, and a fourth drive unit 44 for driving the right rear wheel 3RB, and the first drive unit 41 includes a portion arranged around the left front wheel 3LF, the second drive unit 42 includes a portion arranged around the right front wheel 3RF, the third drive unit 43 includes a portion arranged around the left rear wheel 3LB, and the fourth drive unit 44 includes a portion arranged around the right rear wheel 3RB.

[0547] According to this work vehicle 1, the left front wheel 3LF, the right front wheel 3RF, the left rear wheel 3LB, and the right rear wheel 3RB can be driven independently by different drive units (first drive unit 41, second drive unit 42, third drive unit 43, and fourth drive unit 44). Furthermore, because the first drive unit 41, second drive unit 42, third drive unit 43, and fourth drive unit 44 can be disposed near the periphery of each wheel, a large steering angle can be ensured for each wheel.

[0548] (Item F13) The work vehicle 1 according to any one of items F1 to F12, further comprising a frame structure 18 that supports the vehicle body 2, and the drive unit 40 is attached to the frame structure 18.

[0549] According to this work vehicle 1, by attaching the drive unit 40 to the frame structure 18 rather than to the vehicle body 2, it becomes easy to position at least a portion of the drive unit 40 at an outer position opposite the tread portion 30a of the wheel 30 and overlapping with the wheel 30 in the width direction of the vehicle body 2.

[0550] (Item F14) The frame structure 18 has a side frame 18LR arranged on the side of the vehicle body 2 and an upper frame 18M arranged above the vehicle body 2, and the drive unit 40 has a drive device 45 that generates power to drive the wheels 30, and the drive device 45 is attached to the side frame 18LR, which is a work vehicle 1 described in item F13.

[0551] With this work vehicle 1, the drive unit 45 that generates the power to drive the wheels 30 can be positioned on the side of the vehicle body 2, making it easy to position the drive unit 45 at an outer position opposite the tread portion 30a of the wheels 30 and overlapping with the wheels 30 in the width direction of the vehicle body 2.

[0552] (Item F15) The frame structure 18 has a side frame 18LR arranged on the side of the vehicle body 2 and an upper frame 18M arranged above the vehicle body 2, and the drive unit 40 has a drive device 45 that generates power to drive the wheels 30, and the drive device 45 is attached to the upper frame 18M, which is a work vehicle 1 described in item F13.

[0553] According to this work vehicle 1, the drive unit 45 that generates the power to drive the wheels 30 can be positioned above the vehicle body 2, so that when the vehicle body 2 is raised or lowered, the drive unit 45 can be raised or lowered together with the vehicle body 2.

[0554] Although the embodiments of the present invention have been described above, the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. 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.

[0555] REFERENCE SIGNS LIST 1 Work vehicle 2 Vehicle body 3 Traveling device 3L Left traveling device 3LB Left rear wheel 3LF Left front wheel 3R Right traveling device 3RB Right rear wheel 3RF Right front wheel 18 Frame structure 18LR Side frame 18M Upper frame 30 Wheel 30a Tread portion 40 Drive unit 41 First drive unit 42 Second drive unit 43 Third drive unit 44 Fourth drive unit 45 Drive unit 50 Transmission mechanism 60 Steering mechanism 61 Rotating body 61a First connection portion 61b Second connection portion 90 Height change mechanism 113a Rod 113 Cylinder 501 First transmission shaft 501a Upper shaft 501b Lower shaft 501c1 Upper portion 501c2 Lower portion 502 Second transmission shaft AX1 Axial center

Claims

1. A work vehicle comprising: a vehicle body; wheels arranged on the sides of the vehicle body; and a drive unit for driving the wheels, wherein at least a part of the drive unit is positioned on the outside facing the tread portion of the wheels and in a position overlapping with the wheels in the width direction of the vehicle body.

2. A work vehicle as described in claim 1, wherein the drive unit has a steering mechanism that changes the direction of the wheels, a drive device that generates power, and a transmission mechanism that transmits the power generated by the drive device to the wheels, and at least a portion of the drive unit that is positioned overlapping with the wheels is the steering mechanism.

3. A work vehicle as described in claim 1, wherein the drive unit has a steering mechanism that changes the direction of the wheels, a drive device that generates power, and a transmission mechanism that transmits the power generated from the drive device to the wheels, and at least a portion of the drive unit that is positioned overlapping with the wheels is the drive device.

4. A work vehicle as described in claim 1, wherein the drive unit has a steering mechanism that changes the direction of the wheels, a drive device that generates power, and a transmission mechanism that transmits the power generated by the drive device to the wheels, and at least a portion of the drive unit that is positioned overlapping with the wheels is the transmission mechanism.

5. A work vehicle as described in claim 2, wherein the steering mechanism has a rotating body that rotates about a vertical axis when the wheels are steered, and the axis of the rotating body is located above the wheels.

6. A work vehicle according to claim 4, wherein the transmission mechanism has a first transmission shaft that is disposed above the wheels and extends in the vertical direction.

7. A work vehicle as described in claim 6, wherein the transmission mechanism has a second transmission shaft that rotates by receiving power transmitted from the first transmission shaft, and the second transmission shaft is disposed inward of the wheels and extends in a vertical direction.

8. A work vehicle as described in claim 7, further comprising a height change mechanism for changing the height of the vehicle body from the ground, wherein the first transmission shaft or the second transmission shaft is extendable and retractable in accordance with changes in the height of the vehicle body caused by the height change mechanism.

9. A work vehicle as described in claim 8, wherein the first transmission shaft has an upper shaft to which power from the drive unit is transmitted and a lower shaft which transmits the power transmitted to the upper shaft to the second transmission shaft, the axis of the upper shaft and the axis of the lower shaft are arranged on the same straight line, and the distance between the upper end of the upper shaft and the lower end of the lower shaft changes as the height of the vehicle body is changed by the height change mechanism.

10. A work vehicle as described in claim 9, wherein the first transmission shaft has a cylindrical intermediate shaft having an upper part into which the upper shaft is inserted and a lower part into which the lower shaft is inserted, a first spline is formed on the outer surface of the upper shaft, the lower shaft is cylindrical and has a second spline formed on its inner surface, the intermediate shaft has an internal spline formed on its inner surface and an external spline formed on its outer surface, the first spline meshes with the internal spline, and the second spline meshes with the external spline.

11. A work vehicle as described in claim 5, wherein the steering mechanism includes a cylinder with a rod that expands and contracts in a direction perpendicular to the axis, the rotating body includes a first connection part to which the rod is connected and a second connection part to which the wheel is connected, and the cylinder rotates the rotating body about the axis by expanding and contracting the rod, thereby rotating the wheel about the axis.

12. A work vehicle as described in claim 1, wherein the wheels include a left front wheel, a right front wheel, a left rear wheel, and a right rear wheel; the drive units include a first drive unit for driving the left front wheel, a second drive unit for driving the right front wheel, a third drive unit for driving the left rear wheel, and a fourth drive unit for driving the right rear wheel; the first drive unit includes a portion arranged around the left front wheel, the second drive unit includes a portion arranged around the right front wheel, the third drive unit includes a portion arranged around the left rear wheel, and the fourth drive unit includes a portion arranged around the right rear wheel.

13. A work vehicle according to claim 1, further comprising a frame structure supporting said vehicle body, said drive unit being attached to said frame structure.

14. A work vehicle as described in claim 13, wherein the frame structure has a side frame arranged on the side of the vehicle body and an upper frame arranged above the vehicle body, the drive unit has a drive device that generates power to drive the wheels, and the drive device is attached to the side frame.

15. A work vehicle as described in claim 13, wherein the frame structure has a side frame arranged on the side of the vehicle body and an upper frame arranged above the vehicle body, the drive unit has a drive device that generates power to drive the wheels, and the drive device is attached to the upper frame.

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