Work vehicle

Abstract

To provide a working vehicle supporting wheels for traveling by a plurality of stretching mechanisms which can change a travel direction of a machine body while suppressing possibility of turning.SOLUTION: A working vehicle includes: stretching mechanisms 4 which are mounted on a plurality of places of a machine body 1 and extending from the machine body 1; stretching actuators 18 and 23 which enable stretching operation of the stretching mechanisms 4; wheels 5 for traveling supported on extension ends of the stretching mechanisms 4 so as to be capable of changing its direction around vertical shaft cores P4 in a vertical direction; driving actuators capable of rotationally driving the wheels 5; and steering actuators capable of changing the wheels 5 around the vertical shaft cores 4.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a work vehicle suitable for traveling on uneven work ground. [Background technology]

[0002] An example of the above-mentioned work vehicle is disclosed in Patent Document 1. In Patent Document 1, the bending / extending mechanism is attached to multiple points on the body and extended from the body, and wheels for running are supported on the extended ends of the bending / extending mechanism. The machine is configured to run while bending and extending the bending / extending mechanism using a bending / extending actuator depending on the work site.

[0003] In Patent Document 1, the base of the bending and stretching mechanism is attached to the aircraft body so that its orientation can be changed left and right, and the direction of travel of the aircraft is changed by changing the orientation of the entire bending and stretching mechanism left and right relative to the aircraft body. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-1443 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the work vehicle of Patent Document 1, for example, when the traveling direction of the vehicle body is changed to the right, when the bending and extending mechanism is turned to the right, the wheel supported on the extended end of the bending and extending mechanism moves to the right relative to the vehicle body. This causes the center of gravity of the vehicle body to be located to the left of the wheel, which may cause the work vehicle to tip over, for example, on a slope.

[0006] The present invention aims to configure a work vehicle whose running wheels are supported by multiple bending and extending mechanisms so that the direction of travel of the body can be changed while reducing the possibility of tipping over. [Means for solving the problem]

[0007] The work vehicle of the present invention includes a body, a bending / extending mechanism attached to a plurality of locations on the body and extended from the body, a bending / extending actuator capable of bending and extending the bending / extending mechanism, a wheel for traveling that is located at an extended end of the bending / extending mechanism and supported on the extended end of the bending / extending mechanism so as to be capable of changing its direction about a vertical axis along a vertical direction, and a drive actuator that is capable of rotating and driving the wheel, and the bending / extending mechanism is attached to the body so as to be unable to change its direction left and right and to be able to swing back and forth about a first left and right axis along a left and right direction, and a first link that extends downward from the body. and a second link attached to the lower part of the first link so as to be unable to change its direction to the left or right and so as to be able to swing up and down about a second left-right axis along the left-right direction, and extending from the lower part of the first link in a direction away from the aircraft body along the front-rear direction, the wheel is supported on the extending end of the second link so as to be able to change its direction to the left or right about the vertical axis, and is provided along the second link, and a steering actuator is provided which can change the direction of the wheel about the vertical axis, and which is attached to the extending end of the second link so as to be able to change its direction to the left or right about the vertical axis. a wheel support member for supporting the wheel, the drive actuator being a motor attached to the wheel support member and capable of rotating the wheel, the steering actuator being a telescopic cylinder attached across the wheel support member and the second link so as to follow the second link and capable of changing the orientation of the wheel support member to the left or right by extending and contracting, the telescopic cylinder overlapping the second link in a side view.

[0008] According to the present invention, the bending / extending mechanism is attached to multiple points on the body and extended from the body, and wheels for running are supported on the extended ends of the bending / extending mechanism, and the bending / extending mechanism can be bent and extended by a bending / extending actuator according to the work site, and the wheels can be rotated and driven by a drive actuator, allowing running.

[0009] According to the present invention, the wheels are supported on the extending end of the bending / extending mechanism so that their orientation can be changed around the vertical axis along the vertical direction, and the orientation of the wheels can be changed by the steering actuator. The direction of travel of the vehicle can be changed by changing the orientation of the wheels relative to the articulation mechanism using the steering actuator, and there is no need to change the orientation of the entire articulation mechanism relative to the vehicle. Since there is no need to change the orientation of the entire bending and extending mechanism relative to the machine body, the wheels do not move to the right or left relative to the machine body when changing the machine body's direction of travel, reducing the possibility of the work vehicle tipping over.

[0010] When the entire articulation mechanism is turned relative to the machine body, the wheels skid across the work area, resulting in a large lateral load being placed on the articulation mechanism. According to the present invention, since there is no need to change the orientation of the entire bending and extension mechanism relative to the aircraft body, large lateral loads are not placed on the bending and extension mechanism when changing the direction of travel of the aircraft, which is advantageous in terms of the durability of the bending and extension mechanism.

[0011]

[0012] According to the present invention, the bending and stretching mechanism has a first link and a second link. The first link is attached to the body so as to be swingable back and forth about a first left-right axis along the left-right direction, and its orientation cannot be changed left-right. The second link is attached to a lower part of the first link so as to be swingable up and down about a second left-right axis along the left-right direction, and its orientation cannot be changed left-right. By using such a first link and second link, it is possible to obtain a bending and stretching mechanism that is bendable but cannot change its direction to the left or right.

[0013]

[0014] According to the present invention, the motor that drives the wheels is attached to the wheel support member that supports the wheels, so even if the wheel support member is turned left or right, there is no change in the positional relationship of the wheels and motor to the wheel support member, which is advantageous in terms of simplifying the wheel drive structure by the motor.

[0015] According to the present invention, the telescopic cylinder is attached across the wheel support member and the second link, and the orientation of the wheel support member is changed to the left or right by the telescopic cylinder performing telescopic operation. In this case, since the telescopic cylinder is provided along the second link, the telescopic cylinder can be arranged compactly. 。

[0016] In the present invention, it is preferable that the wheels are supported on one of the left and right portions of the wheel support member, and the motor and the telescopic cylinder are attached to the other left and right portions of the wheel support member.

[0017] According to the present invention, the wheel, motor, and telescopic cylinder are provided on opposite sides of the wheel support member and are provided on the wheel support member with little interference with each other, which is advantageous in terms of simplifying the support structure for the wheel, motor, and telescopic cylinder.

[0018] In the present invention, it is preferable that the bending and extending mechanisms are attached to the right and left parts of the body, the wheels are supported on parts of the wheel support members opposite the left and right center of the body, and the motor and the telescopic cylinder are attached to parts of the wheel support members on the left and right center side of the body.

[0019] According to the present invention, when the folding / extending mechanism is attached to the right and left parts of the body, the motor and the telescopic cylinder are attached to the wheel support members at the center of the left and right sides of the body, which is advantageous in terms of protecting the motor and the telescopic cylinder.

[0020] In the present invention, it is preferable that an auxiliary wheel is provided that is supported at a connection portion between the first link and the second link so as to be freely rotatable about a third left-right axis along the left-right direction.

[0021] In the bending / extending mechanism, when the first link and the second link are bent / extended by the bending / extending actuator, there is a possibility that the connection portion between the first link and the second link may come into contact with the work surface. According to the present invention, the auxiliary wheels are supported at the connection portion between the first link and the second link. Therefore, even if the connection portion between the first link and the second link approaches the work site, the auxiliary wheels touch the work site, thereby preventing damage to the connection portion between the first link and the second link due to contact with the work site.

[0022] According to the present invention, the auxiliary wheels are supported freely rotatable around the third left-right axis along the left-right direction. Therefore, even if the auxiliary wheels touch the work ground while the work vehicle is traveling, the auxiliary wheels rotate in the direction of travel of the work vehicle and the travel of the work vehicle is not impeded by the auxiliary wheels. According to the present invention, the auxiliary wheels are supported so as to be freely rotatable, and no structure for driving the auxiliary wheels to rotate is provided, which is advantageous in terms of simplifying the structure. In the present invention, it is preferable that the bending and stretching mechanisms are attached to the right and left parts of the body, and the auxiliary wheels are supported on parts opposite the left and right center of the body at the connection part between the first link and the second link. In the present invention, it is preferable that a wheel support member is provided, which is attached to the extended end of the second link so that its direction can be changed left and right around the vertical axis, and which supports the wheel, the wheel being supported on a portion of the wheel support member opposite the left and right center of the body, and the auxiliary wheel is provided on the opposite side of the left and right center of the body from the wheel in a plan view. In the present invention, it is preferable that the bending and extension mechanisms are attached to the right and left parts of the body, and are provided between the right bending and extension mechanisms and the left bending and extension mechanisms in a planar view, and are equipped with a frame on which luggage, etc. can be carried. [Brief description of the drawings]

[0023] [Figure 1] FIG. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] FIG. 13 is a left side view of the vicinity of the right front bending / extending mechanism. [Diagram 5] FIG. 13 is a cross-sectional plan view of the area around the right front bending and extending mechanism. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Figures 1 to 5 show remote-controlled and autonomous work vehicles, and in Figures 1 to 5, F indicates the forward direction, B indicates the backward direction, U indicates the upward direction, D indicates the downward direction, R indicates the right direction, and L indicates the left direction.

[0025] (Overall configuration of the work vehicle) As shown in Figures 1, 2 and 3, hydraulic equipment 2 and control equipment 3 are mounted on a machine body 1, four bending and extension mechanisms 4 are attached to the right front, left front, right rear and left rear of the machine body 1 and extend from the machine body 1, and right front, left front, right rear and left rear running wheels 5 are supported on the extended ends of the bending and extension mechanisms 4 to form the entire work vehicle.

[0026] (Aircraft configuration) 1, 2 and 3, left and right frames 6 extending along the front-rear direction and front and rear frames 7 extending along the left-right direction are connected to form a frame body having a rectangular shape in a plan view, and front and rear frames 8 extending along the left-right direction are connected across the frames 6. Left and right frames 9 having a channel shape (having a U-shaped cross section) in a side view are connected across the frames 8, and front and rear frames 10 extending along the left-right direction are connected across the frames 9.

[0027] The left and right frame-shaped members 11 are connected to the right and left parts of the frame 8. The frame-shaped member 11 has an upper part 11a and a lower part 11b formed in a channel shape in a plan view, a front part 11c connected across the front parts of the upper part 11a and the lower part 11b, a rear part 11d connected across the rear parts of the upper part 11a and the lower part 11b, and an intermediate part 11e connected across the front-to-rear intermediate parts of the upper part 11a and the lower part 11b.

[0028] Five flat plate-like frames 12 are connected across the upper portions 11a of the left and right frame-shaped members 11. Left and right frames 13 extending along the front-rear direction are connected to the frame 10, and extend forward from the front frame 7 and rearward from the rear frame 7. A plurality of frames 14 extending along the left-right direction are connected across the frames 13.

[0029] As described above, the machine body 1 has the frames 6 to 10, the frame-shaped member 11, the frames 12, 13, 14, and the like. The hydraulic equipment 2 is supported by frames 9 and 10, and the control equipment 3 is supported by frames 6 and 7, with the hydraulic equipment 2 and the control equipment 3 being surrounded by the frames 6 to 10, a frame-shaped member 11, and frames 12, 13, and 14. Luggage and the like can be loaded onto the frame 12 and the frames 13 and 14.

[0030] (Configuration of bending and extension mechanism) As shown in FIGS. 1, 2 and 3, the bending / stretching mechanism 4 has a first link 21 and a second link 22, and the first link 21 and the second link 22 are configured as described below.

[0031] As shown in Figures 1, 2, and 3, in the aircraft 1, a channel-shaped support bracket 15 is connected to four connecting portions of the frames 6 and 7, namely the front right, front left, rear right, and rear left, and the support bracket 15 is surrounded by a frame-shaped member 11.

[0032] 1, 3, 4, and 5, the first link 21 is configured in a flat plate shape and two first links 21 are provided. An upper portion of the first link 21 is attached to the support bracket 15 (aircraft body 1) around an axis P1 (corresponding to a first left-right axis) along the left-right direction so as to be swingable back and forth, and the first link 21 extends downward from the support bracket 15 (aircraft body 1). As a result, the first link 21 can swing back and forth around the axis P1, but cannot change its orientation left and right.

[0033] 4 and 5, the second link 22 has a flat first portion 22a, two second portions 22b formed by bending a round bar into a crank shape, and a boss portion 22c (corresponding to an extended end portion). The front portion of the first portion 22a and the front portion of the second portion 22b are connected, and the boss portion 22c is connected to the front portions of the first portion 22a and the second portion 22b in an up-down direction.

[0034] In the right front and left front bending and extending mechanisms 4, the rear of the second link 22 is attached to the lower part of the first link 21 so as to be able to swing up and down around an axis P2 (corresponding to the second left-right axis) along the left-right direction, and the second link 22 extends from the lower part of the first link 21 forward in the fore-and-aft direction, that is, in the direction away from the body 1.

[0035] In the right rear and left rear bending and extending mechanisms 4, the front part of the second link 22 is attached to the lower part of the first link 21 so as to be able to swing up and down around an axis P2 (corresponding to the second left-right axis) along the left-right direction, and the second link 22 extends from the lower part of the first link 21 toward the rear, which is the direction away from the aircraft body 1, along the fore-and-aft direction. As a result, the second link 22 is capable of swinging up and down about the axis P2, but is unable to change its orientation left and right.

[0036] An auxiliary wheel 27 is supported freely rotatably around an axis P3 (corresponding to a third left-right axis) that is concentric with the axis P2 and extends in the left-right direction on the right lateral side of the connection between the right front and right rear first links 21 and second links 22.

[0037] An auxiliary wheel 27 is supported on the left lateral side at the connection between the left front and left rear first links 21 and second links 22 so as to be freely rotatable around an axis P3 (corresponding to a third left-right axis) that is concentric with the axis P2 and extends in the left-right direction.

[0038] (Configuration of bending and stretching mechanism) As shown in Figures 1 and 4, the linkage link 16 is attached to the support bracket 15 so as to be swingable around an axis P5 along the left-right direction, and the linkage link 17 is attached to the upper part of the first link 21 so as to be swingable around an axis P6 along the left-right direction, and the extended ends of the linkage links 16 and 17 are connected.

[0039] A double-acting hydraulic cylinder 18 (corresponding to a bending / extending actuator) is connected between the extending ends of the connecting links 16, 17 and the lower part of the first link 21. When the hydraulic cylinder 18 is operated to extend or retract, the first link 21 is operated to swing back and forth around the axis P1 relative to the support bracket 15 (aircraft body 1).

[0040] As shown in Figures 1, 3, 4, and 5, link 19 is attached to the lower part of first link 21 so as to be swingable around axis P7 along the left-right direction, and link 20 is attached to second link 22 so as to be swingable around axis P8 along the left-right direction, and the extended ends of link 19, 20 are connected.

[0041] A double-acting hydraulic cylinder 23 (corresponding to a bending / extending actuator) is connected between the extending ends of the connecting links 19, 20 and the upper part of the first link 21. When the hydraulic cylinder 23 is operated to extend or retract, the second link 22 is operated to swing up and down around the axis P2 relative to the first link 21.

[0042] Based on a command from the control device 3, hydraulic oil is supplied to and discharged from the hydraulic device 2 to the hydraulic cylinders 18, 23, thereby expanding and contracting the hydraulic cylinders 18, 23. The hydraulic cylinders 18, 23 swing the first link 21 back and forth and swing the second link 22 up and down, thereby bending and extending the bending and extending mechanism 4.

[0043] By independently bending and extending each of the bending and extending mechanisms 4, the attitude of the machine body 1 can be set as desired in accordance with the unevenness and slope of the work ground. Even if the connection portion between the first link 21 and the second link 22 approaches the work ground by bending and extending the bending and extending mechanisms 4, the auxiliary wheels 27 touch the work ground, thereby preventing the connection portion between the first link 21 and the second link 22 from contacting the work ground.

[0044] (Wheel support and drive configuration) As shown in Figures 2 to 5, four wheel support members 24 are provided, and the wheel support members 24 are attached to the boss portion 22c of the second link 22 so that their orientation can be changed left and right around an axis P4 (corresponding to the vertical axis) along the vertical direction.

[0045] The wheels 5 are rotatably supported on the right lateral side portions (corresponding to the left or right side portions of the wheel support members 24) of the right front and right rear wheel support members 24 (corresponding to the portion of the wheel support member 24 opposite the left or right center A1 of the fuselage 1).

[0046] The wheels 5 are rotatably supported on the left lateral side portions (corresponding to the left or right side portions of the wheel support members 24) of the left front and left rear wheel support members 24 (corresponding to the portion of the wheel support member 24 opposite the left or right center A1 of the fuselage 1). As a result, the wheel 5 is supported on the extending end of the bending and stretching mechanism 4 (second link 22) so as to be able to change its direction left and right around an axis P4 along the up-down direction.

[0047] A hydraulic motor 25 (corresponding to a drive actuator and motor) is attached to the left lateral side portion (corresponding to the other left or right side portion of the wheel support member 24) of the right front and right rear wheel support members 24 (corresponding to the portion of the wheel support member 24 on the left or right center A1 side of the aircraft body 1).

[0048] A hydraulic motor 25 (corresponding to a drive actuator and motor) is attached to the right lateral side portion (corresponding to the other left or right side portion of the wheel support member 24) of the left front and left rear wheel support members 24 (corresponding to the portion of the wheel support member 24 on the left or right center A1 side of the aircraft body 1).

[0049] Based on commands from the control device 3, hydraulic oil is supplied and discharged from the hydraulic equipment 2 to the hydraulic motors 25, and the hydraulic motors 25 drive the wheels 5 independently in forward and reverse directions, causing the work vehicle to move forward, backward, and stop.

[0050] (Wheel steering configuration) As shown in Figures 2 to 5, a bracket 24a is provided on the left lateral side of the right front and right rear wheel support member 24, and a bracket 22d is provided on the left lateral side of the right front and right rear second link 22 (first portion 22a).

[0051] A bracket 24a is provided on the right lateral side of the left front and left rear wheel support members 24, and a bracket 22d is provided on the right lateral side of the left front and left rear second links 22 (first portions 22a).

[0052] A double-acting hydraulic cylinder 26 (corresponding to a steering actuator and a telescopic cylinder) is attached across the bracket 24a of the wheel support member 24 and the bracket 22d of the second link 22, and the hydraulic cylinder 26 is attached across the wheel support member 24 and the second link 22 so as to run along the second link 22 (first portion 22a).

[0053] As a result, the right front and right rear hydraulic cylinders 26 are arranged on the left lateral side portions (corresponding to the other left or right side portions of the wheel support member 24) of the right front and right rear second links 22 (first portions 22a) (corresponding to the portion of the wheel support member 24 on the left or right center A1 side of the aircraft 1).

[0054] The left front and left rear hydraulic cylinders 26 are arranged on the right lateral side (corresponding to the other left or right side part of the wheel support member 24) of the left front and left rear second links 22 (first part 22a) (corresponding to the part of the wheel support member 24 on the left or right center A1 side of the aircraft 1).

[0055] Based on the command of the control device 3, hydraulic oil is supplied and discharged from the hydraulic equipment 2 to the hydraulic cylinder 26, and the hydraulic cylinder 26 is extended and retracted, whereby the four sets of wheel support members 24, wheels 5 and hydraulic motors 25 are each independently operated to change direction left and right around the axis P4.

[0056] As described above (Wheel support and drive configuration), in addition to the wheels 5 being independently driven in forward and reverse directions, the wheels 5 can also be independently turned left and right, allowing the work vehicle to turn right and left while moving forward and backward, and make swivel turns to the right and left.

[0057] (First Alternative Embodiment of the Invention) Instead of four bending / extending mechanisms 4 and wheels 5, six bending / extending mechanisms 4 and wheels 5 may be provided, or eight bending / extending mechanisms 4 and wheels 5 may be provided. According to this configuration, in addition to attaching the bending / extending mechanism 4 to the right front, left front, right rear, and left rear parts of the body 1, the bending / extending mechanism 4 can be configured to be attached to the middle part of the front to rear of the body 1 and extend outward to the right and left.

[0058] (Second Alternative Embodiment of the Invention) In the bending / extending mechanism 4, instead of the hydraulic cylinders 18 and 23, an electric cylinder (not shown) or an electric motor (not shown) may be used as a bending / extending actuator.

[0059] In place of the hydraulic motor 25, an electric motor (not shown) may be used as a drive actuator for the wheel 5.

[0060] In the wheels 5, instead of the hydraulic cylinder 26, an electric cylinder (not shown) or an electric motor (not shown) may be used as a steering actuator.

[0061] (Third Alternative Embodiment of the Invention) In the right front or right rear second link 22 , the wheel 5 may be supported on the left lateral side of the wheel support member 24 , and the hydraulic motor 25 and the hydraulic cylinder 26 may be attached to the right lateral side of the wheel support member 24 .

[0062] (Fourth Alternative Embodiment of the Invention) In the left front or left rear second link 22 , the wheel 5 may be supported on the right lateral side of the wheel support member 24 , and the hydraulic motor 25 and the hydraulic cylinder 26 may be attached to the left lateral side of the wheel support member 24 .

[0063] (Fifth Alternative Embodiment of the Invention) At the connection portion between the first link 21 and the second link 22, an auxiliary wheel 27 may be supported to be freely rotatable about an axis P3 that is aligned in the left-right direction at a position different from the axis P2. At the connection portion between the right front or right rear first link 21 and the second link 22, an auxiliary wheel 27 may be supported on the left lateral side. At the connection portion between the left front or left rear first link 21 and the second link 22, an auxiliary wheel 27 may be supported on the right lateral side. [Industrial Applicability]

[0064] The present invention can be applied to work vehicles that are suitable for traveling on uneven work ground, and can also be applied to work vehicles on which a worker can ride. [Explanation of symbols]

[0065] 1 Aircraft 4 Bending and stretching mechanism 5 wheels 13 Frame 14 Frame 18 Hydraulic cylinder (bending / extending actuator) 21 First link 22 Second Link 22c Boss portion (extending end portion) 23 Hydraulic cylinder (bending / extending actuator) 24 Wheel support member 25 Hydraulic motor (drive actuator, motor) 26 Hydraulic cylinders (steering actuators, telescopic cylinders) 27 Auxiliary wheels A1 left and right center P1 axis (first left and right axis) P2 axis (second left and right axis) P3 axis (3rd left and right axis) P4 shaft core (upper and lower shaft core)

Claims

1. The aircraft and A bending and stretching mechanism attached to a plurality of locations on the airframe and extended from the airframe; A bending / extending actuator capable of bending and extending the bending / extending mechanism; A wheel for running is located at an extension end of the bending and stretching mechanism and is supported on the extension end of the bending and stretching mechanism so as to be changeable in direction around a vertical axis along a vertical direction; a drive actuator capable of rotating the wheel; the bending and stretching mechanism has a first link attached to the body and extending downward from the body so as to be unable to change its orientation left and right and swingable forward and backward around a first left and right axis along the left and right direction, and a second link attached to a lower part of the first link and extending from the lower part of the first link in a direction away from the body along the front and back direction so as to be unable to change its orientation left and right and swingable up and down around a second left and right axis along the left and right direction, The wheel is supported on an extended end of the second link so as to be able to change its direction left and right about the vertical axis, and a steering actuator is provided along the second link, and the steering actuator is capable of changing the direction of the wheel about the vertical axis; a wheel support member is provided which is attached to an extending end of the second link so as to be capable of changing its orientation left and right around the vertical axis and which supports the wheel; the drive actuator is a motor attached to the wheel support member and capable of rotating the wheel, the steering actuator is a telescopic cylinder that is attached between the wheel support member and the second link so as to be aligned with the second link and that is capable of changing the direction of the wheel support member to the left or right by telescopic actuation, The telescopic cylinder overlaps with the second link in a side view of the work vehicle.

2. The wheel is supported on one of the left and right portions of the wheel support member, 2. The work vehicle according to claim 1, wherein the motor and the telescopic cylinder are attached to the other of the left and right portions of the wheel support member.

3. The bending and stretching mechanism is attached to the right and left parts of the body, The wheels are supported on the wheel support members at portions opposite to the left-right center of the vehicle body, 3. The work vehicle according to claim 2, wherein the motor and the telescopic cylinder are attached to a portion of the wheel support member that is on a lateral center side of the vehicle body.

4. A work vehicle as claimed in any one of claims 1 to 3, further comprising an auxiliary wheel supported at a connection portion between the first link and the second link so as to be freely rotatable about a third left-right axis along the left-right direction.

5. The bending and stretching mechanism is attached to the right and left parts of the body, 5. The work vehicle according to claim 4, wherein the auxiliary wheel is supported on a portion of the connection portion between the first link and the second link opposite a lateral center of the vehicle body.

6. a wheel support member is provided which is attached to an extending end of the second link so as to be capable of changing its orientation left and right around the vertical axis and which supports the wheel; The wheels are supported on the wheel support members at portions opposite to the left-right center of the vehicle body, The work vehicle according to claim 5 , wherein the auxiliary wheel is provided on the opposite side of the left-right center of the vehicle body from the wheel in a plan view.

7. The bending and stretching mechanism is attached to the right and left parts of the body, A work vehicle as described in any one of claims 1 to 6, comprising a frame that is provided between the right bending / extending mechanism and the left bending / extending mechanism in a plan view and is capable of carrying cargo.

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