Work vehicle

Abstract

The present invention comprises: a vehicle body; a traveling device; a support mechanism that is capable of changing the distance between a ground contact surface of the traveling device and the vehicle body; an accessory device; and a coupling mechanism that couples the vehicle body and the accessory device, wherein the coupling mechanism maintains the posture of the accessory device after the support mechanism changes the distance, so that the posture remains the same as before the change.

Description

Work vehicle

[0001] This application claims priority to Japanese Patent Application No. 2024-103504, filed on June 27, 2024, and incorporates by reference all of the contents of said Japanese application.

[0002] A work vehicle suitable for traveling on rough terrain such as mountainous areas is known (see, for example, Patent Document 1). The work vehicle described in Patent Document 1 includes a vehicle body, multiple travel devices, and a support mechanism that supports the multiple travel devices so that they can be raised and lowered individually. The work vehicle can travel while maintaining the vehicle body in a horizontal position by changing the height of the travel devices in accordance with the unevenness of the ground. The work vehicle described in Patent Document 1 also includes a towing support unit to which the tip of a connecting arm extended from a mobile carriage, which is an accessory, is connected. Therefore, the work vehicle can travel while towing the mobile carriage.

[0003] Japanese Patent Application Laid-Open No. 2023-92156

[0004] The work vehicle of the present disclosure comprises a vehicle body, a traveling device, a support mechanism capable of changing the distance between the ground contact surface of the traveling device and the vehicle body, an accessory device, and a connecting mechanism that connects the vehicle body and the accessory device, and the connecting mechanism maintains the attitude of the accessory device after the distance is changed by the support mechanism at the attitude before the change.

[0005] FIG. 1 is a side view of the work vehicle. FIG. 2 is a plan view of the work vehicle shown in FIG. 1. FIG. 3 is an explanatory diagram of the support mechanism at the right front. FIG. 4 is a control block diagram of the work vehicle. FIG. 5 is a front view illustrating the operation of the support mechanism. FIG. 6 is a side view illustrating the operation of the support mechanism. FIG. 7 is a side view showing the coupling mechanism. FIG. 8 is a plan view showing the coupling mechanism. FIG. 9 is a cross-sectional view taken along line A-A in FIG. 2. FIG. 10 is a side view showing a modified coupling mechanism.

[0006] <Problem to be Solved by the Invention> The mobile dolly of Patent Document 1 is simply connected to the towing support part at the tip of the connecting arm, so when it is towed by a work vehicle and travels over uneven ground, it moves up and down to follow the unevenness and is likely to lose its posture. Therefore, when the mobile dolly is loaded with cargo or the like, it is difficult to transport the loaded item stably. The present disclosure aims to provide a work vehicle that can stabilize the posture of an accessory device such as a mobile dolly.

[0007] Effect of the Invention According to the work vehicle of the present disclosure, the attitude of an accessory device such as a mobile carriage can be stabilized.

[0008] <Outline of Embodiments of the Present Disclosure> The following is a list and description of outlines of embodiments of the present disclosure: (1) A work vehicle of this embodiment includes: a vehicle body; a traveling device; a support mechanism that can change the distance between the ground contact surface of the traveling device and the vehicle body; an accessory device; and a coupling mechanism that couples the vehicle body and the accessory device, and the coupling mechanism maintains the attitude of the accessory device after the distance is changed by the support mechanism at the attitude before the change.

[0009] In a work vehicle having the above configuration, the support mechanism changes the distance between the ground contact surface of the traveling device and the vehicle body, thereby maintaining the attitude of the vehicle body. Furthermore, the coupling mechanism that couples the vehicle body and the accessory device maintains the attitude of the accessory device after the distance is changed by the support mechanism at the same attitude as before the change, thereby stabilizing the attitude of the accessory device.

[0010] (2) In the work vehicle of (1) above, the connecting mechanism includes a parallel link mechanism having a pair of upper and lower swing link members that are swingable in the up and down direction.

[0011] According to the above configuration, it is possible to change the vertical position of the accessory device relative to the vehicle body while allowing the attitude of the accessory device to follow the attitude of the vehicle body.

[0012] (3) In the work vehicle of (1) or (2) above, the connecting mechanism includes a fixing member that fixes the swing link member at a predetermined swing position.

[0013] According to the above configuration, the accessory device can be fixed in a state where its vertical position relative to the vehicle body is changed.

[0014] (4) In the work vehicle of any one of (1) to (3) above, the attachment device has a vehicle body connected to the connecting mechanism and a plurality of wheels supported on the vehicle body so as to be movable up and down.

[0015] According to the above configuration, the wheels can be caused to follow the unevenness of the ground and make contact with the ground while maintaining the attitude of the accessory device.

[0016] (5) In the work vehicle of (4) above, the accessory device includes a pair of wheels spaced apart in the left-right direction, a connecting body connecting the pair of wheels, and a support shaft supporting the connecting body between the left-right direction of the pair of wheels so that it can swing up and down relative to the vehicle body.

[0017] According to the above configuration, the pair of wheels can be raised and lowered in opposite directions to each other in accordance with the unevenness of the ground, and can be brought into contact with the ground.

[0018] <Details of Embodiments of the Present Disclosure> Hereinafter, details of embodiments of the present disclosure will be described with reference to the drawings. Note that at least some of the embodiments described below may be combined in any manner.

[0019] [Overall Configuration of Work Vehicle] Figure 1 is a side view of the work vehicle. Figure 2 is a plan view of the work vehicle shown in Figure 1. The work vehicle 10 shown in Figures 1 and 2 is a vehicle that can travel on uneven road surfaces (uneven ground) and slopes.

[0020] In the following description, the direction of the arrow FW shown in the figure is the "front" of the work vehicle 10, which is the straight-ahead direction (direction of travel) of the work vehicle 10. The direction of the arrow BK is the "rear" of the work vehicle 10, which is opposite to the straight-ahead direction. The direction of the arrow RH is the "right" of the work vehicle 10 moving straight, and the direction of the arrow LH is the "left" of the work vehicle 10 moving straight. The direction of the arrow DW is the "down" of the work vehicle 10, which is the road surface side, and the direction of the arrow UP is the "up" of the work vehicle 10, which is the side opposite the road surface.

[0021] The work vehicle 10 has a vehicle body 11, traveling devices 19, support mechanisms 13, a control device 17, a coupling mechanism 60, and an auxiliary device 70. The work vehicle 10 of this embodiment has a plurality of wheels 12, specifically four wheels 12, as the traveling devices 19. The work vehicle 10 has the same number (four) of support mechanisms 13 as the wheels 12. The support mechanisms 13 connect the vehicle body 11 and the wheels 12. The wheels 12 are located at the front and rear of both the left and right sides of the vehicle body 11.

[0022] The vehicle body 11 has a frame 21. The vehicle body 11 has a loading section 22 on top of the frame 21, on which cargo can be loaded. The loading section 22 has a flat loading surface 221 on its upper surface. The loading surface 221 has a substantially rectangular shape in a plan view (see FIG. 2 ). The loading surface 221 is provided so as to extend in the left-right and front-rear directions. The cargo to be loaded is, for example, agricultural equipment, agricultural materials such as fertilizer and chemicals, harvested crops, harvest baskets, or pallets on which these are placed.

[0023] The support mechanisms 13 are located at the left front, right front, left rear, and right rear of the vehicle body 11. The support mechanisms 13 are attached to the vehicle body 11 (part of the frame 21) and support the wheels 12 so that their positions can be changed relative to the vehicle body 11. In particular, the support mechanisms 13 change the distance between the contact surface (the lower surface that contacts the ground) of the wheels 12 and the vehicle body 11. This distance is, for example, the vertical distance between the lower surface of the wheels 12 and the mounting surface 221 of the vehicle body 11 (for example, distances L, L1, and L2 shown in FIGS. 5 and 6 ). The support mechanisms 13 have articulation link mechanisms 30 as operating parts operable to change the positions of the wheels 12. The wheels 12 are attached to the articulation link mechanisms 30. The support mechanisms 13 have actuators 14 that drive the articulation link mechanisms 30.

[0024] The actuator 14 operates the articulating link mechanism 30 to change the attitude of the articulating link mechanism 30. The actuator 14 is a fluid cylinder, and in this embodiment has a first hydraulic cylinder 36 and a second hydraulic cylinder 37. The specific configuration of the support mechanism 13 will be described later. The travel device 19 of the work vehicle 10 has multiple hydraulic motors 15. The hydraulic motors 15 are provided at the ends of the articulating link mechanism 30 together with the wheels 12. The hydraulic motors 15 are travel actuators that rotate and drive the wheels 12.

[0025] The wheels 12 are driven wheels that are rotated by hydraulic motors 15. The rotation of the wheels 12 causes the work vehicle 10 to travel. The travel device of the work vehicle 10 has a plurality of training wheels 16. The training wheels 16 are attached midway along the articulating link mechanism 30. The training wheels 16 are attached to the connecting parts (joint parts) between a first link 31 and a second link 32, which will be described later and which make up the articulating link mechanism 30. The training wheels 16 are driven wheels that can rotate freely.

[0026] The work vehicle 10 has a hydraulic unit (hydraulic pressure supply source) 51, a battery 52, and an engine 53. The hydraulic unit 51 supplies hydraulic oil to the hydraulic motor 15, the first hydraulic cylinder 36, the second hydraulic cylinder 37, and a swing hydraulic cylinder 38 (described later). The hydraulic unit 51 has a hydraulic pump 54 driven by the engine 53, multiple hydraulic control valves 55, and a hydraulic oil tank 56.

[0027] A hydraulic control valve 55 is connected to each of the hydraulic motor 15 and the hydraulic cylinders 36, 37, and 38. The hydraulic control valve 55 is an electromagnetic valve and has the function of supplying, stopping the supply, and adjusting the supply flow rate of hydraulic oil from the hydraulic pump 54. The control device 17 controls the hydraulic control valve 55 to adjust the supply state (supply amount) of hydraulic oil from the hydraulic unit 51. In other words, the control device 17 controls the operation of the hydraulic motor 15 and the hydraulic cylinders 36, 37, and 38.

[0028] The hydraulic unit 51, battery 52, engine 53, and control device 17 are mounted on the vehicle body 11 (frame 21), and in this embodiment (see FIG. 1 ), are located below the loading section 22. The battery 52 supplies power to the control device 17, hydraulic unit 51, and multiple sensors, which will be described later. The work vehicle 10 has an operating handle 18 that is gripped by the worker. The operating handle 18 is attached to the frame 21.

[0029] [Support mechanism 13] The support mechanism 13 supports the wheels 12 so that they can be individually raised and lowered relative to the vehicle body 11. To this end, the support mechanism 13 has a bending link mechanism 30. Figure 3 is an explanatory diagram of the support mechanism 13 at the right front. The bending link mechanism 30 has a first link 31 and a second link 32. Each of the first link 31 and the second link 32 is a linear member.

[0030] A fixed bracket 23 is fixed to a part of the frame 21 of the vehicle body 11. A first end 311 of the first link 31, which faces the frame 21, is supported by the fixed bracket 23 so as to be swingable about a first horizontal axis X1 in the left-right direction. A first end 321 of the second link 32 is supported by a second end 312 of the first link 31 so as to be swingable about a second horizontal axis X2 in the left-right direction. A support bracket 33 is attached to a second end 322, which is the tip side of the second link 32. The wheel 12 is supported by the support bracket 33.

[0031] A set of actuators 14 is provided for one articulating link mechanism 30 having a first link 31 and a second link 32. Each set of actuators 14 has one first hydraulic cylinder 36 and one second hydraulic cylinder 37. The first hydraulic cylinder 36 extends and retracts to swing the first link 31 around the first horizontal axis X1. The first hydraulic cylinder 36 changes the swinging posture of the first link 31 relative to the vehicle body 11. The second hydraulic cylinder 37 extends and retracts to swing the second link 32 around the second horizontal axis X2. The second hydraulic cylinder 37 changes the swinging posture of the second link 32 relative to the first link 31.

[0032] The hydraulic control valve 55 connected to the first hydraulic cylinder 36 and the hydraulic control valve 55 connected to the second hydraulic cylinder 37 are separate valves (see FIG. 4), and the first hydraulic cylinder 36 and the second hydraulic cylinder 37 operate to extend and retract independently. FIG. 4 is a control block diagram of the work vehicle 10. The extension and retraction operations of the first hydraulic cylinder 36 and the second hydraulic cylinder 37 cause the articulating link mechanism 30 to bend and extend.

[0033] 3, for example, when the first hydraulic cylinder 36 extends and retracts while the second hydraulic cylinder 37 is stopped, the first link 31, the second link 32, and the wheel 12 swing together around the first horizontal axis X1 while maintaining a constant relative positional relationship. When the second hydraulic cylinder 37 extends and retracts while the first hydraulic cylinder 36 is stopped, the second link 32 and the wheel 12 swing together around the second horizontal axis X2 while maintaining a constant attitude of the first link 31 relative to the vehicle body 11.

[0034] A support bracket 33 that supports the wheel 12 is attached to the second link 32. The hydraulic motor 15 is mounted on the support bracket 33. The support bracket 33 is attached to the second end 322 of the second link 32 so as to be able to swing about the vertical axis Y in the up-down direction. The support mechanism 13 of the work vehicle 10 has a hydraulic cylinder 38 for swinging (hereinafter referred to as the swing cylinder 38) for changing the rolling direction of the wheel 12. The swing cylinder 38 is attached between a part of the second link 32 and the support bracket 33. When the swing cylinder 38 extends and retracts, the support bracket 33 and the wheel 12 swing about the vertical axis Y. The movement of the swing cylinder 38 changes the traveling direction of the work vehicle 10.

[0035] As described above, the work vehicle 10 of this embodiment has four support mechanisms 13, with each support mechanism 13 provided with a set of actuators 14. The set of actuators 14 provided on one support mechanism 13 and the other set of actuators 14 provided on another support mechanism 13 are separate actuators, and each actuator 14 operates independently. This allows the four wheels 12 to move individually relative to the vehicle body 11. Furthermore, it is possible to vary the positions of the four wheels 12 relative to the vehicle body 11. The support mechanisms 13 allow the distance, particularly the vertical distance, between the contact surface of each wheel 12 and the vehicle body 11 to be changed.

[0036] [Sensor] Figure 4 is a control block diagram of the work vehicle. Figure 4 mainly shows the configuration related to the left front support mechanism 13. Although detailed configurations of the other support mechanisms 13 are omitted in Figure 4, they have the same configuration as the left front support mechanism 13.

[0037] The work vehicle 10 has multiple sensors. A head-side pressure sensor S1 and a rod-side pressure sensor S2 are connected to the second hydraulic cylinder 37. The head-side pressure sensor S1 detects the internal pressure of the head-side oil chamber of the second hydraulic cylinder 37. The rod-side pressure sensor S2 detects the internal pressure of the rod-side oil chamber of the second hydraulic cylinder 37. The control device 17 acquires the detection signals of the sensors S1 and S2.

[0038] A stroke sensor S3 that detects the amount of extension / contraction is provided in each of the first hydraulic cylinder 36 and the second hydraulic cylinder 37. The amount of extension / contraction of each of the first hydraulic cylinder 36 and the second hydraulic cylinder 37 is related to the swing position of each of the first link 31 and the second link 32. Therefore, the detection value of the stroke sensor S3 is correlated with the swing position of each of the first link 31 and the second link 32. The detection value of the stroke sensor S3 uniquely determines the position of the wheel 12 relative to the vehicle body 11. The control device 17 is able to acquire the detection signal of the stroke sensor S3 and detect the position of the wheel 12.

[0039] As described above, the work vehicle 10 has a head-side pressure sensor S1, a rod-side pressure sensor S2, and a stroke sensor S3 as detection devices for detecting the movement of the support mechanism 13 (articulated link mechanism 30). The operation of the actuator 14, which has the first hydraulic cylinder 36 and the second hydraulic cylinder 37, is detected by the stroke sensor S3 (detection device). The control device 17 can obtain the movement of the support mechanism 13 based on the detection signal of the stroke sensor S3.

[0040] The vehicle body 11 is provided with an inclination sensor S4 that detects the inclination state of the vehicle body 11. The inclination sensor S4 is configured using an inertial measurement unit (IMU), which is a well-known configuration. The IMU of this embodiment has a triaxial acceleration sensor and a gyro sensor. The IMU of this embodiment detects changes in the attitude of the vehicle body 11, specifically, tilt in the front-rear and left-right directions. The control device 17 acquires the detection signal of the inclination sensor S4.

[0041] A rotation sensor S5 that detects the rotation speed of the wheel 12 is provided near the wheel 12. The control device 17 acquires a detection signal from the rotation sensor S5. Based on the detection value of the rotation sensor S5, the supply of hydraulic oil to the hydraulic motor 15 is controlled so that the rotation speed of the wheel 12 becomes a target value.

[0042] The vehicle 10 has a pressure sensor S6 that detects the pressure of hydraulic oil supplied to the hydraulic motor 15. The control device 17 acquires the detection signal from the pressure sensor S6. Based on the hydraulic oil pressure detected by the pressure sensor S6, the supply (pressure) of hydraulic oil to the hydraulic motor 15 is controlled so that the drive torque of the wheels 12 becomes a target value. Each of the four swing cylinders 38 is provided with a stroke sensor S7 that can detect the amount of extension and contraction. The control device 17 acquires the detection signal from the stroke sensor S7. This controls the traveling direction of the vehicle 10.

[0043] [Control device 17] The control device 17 has an ECU 171 (Electronic Control Unit) that functions as a main control unit that controls the operation of the work vehicle 10. The ECU 171 has a microcomputer and executes various controls according to a control program. The ECU 171 has a non-volatile memory that stores programs corresponding to the functional units that execute the various controls, and a CPU that executes the programs. The functions (controls) of each functional unit are realized by the CPU executing the programs.

[0044] The ECU 171 has an attitude control unit 172 as one of the functional units. The attitude control unit 172 executes horizontal control and center of gravity position control. The control device 17 (ECU 171) controls the actuator 14 to perform attitude control to maintain the vehicle body 11 in a predetermined attitude while traveling. Note that, in the following, the "predetermined attitude" will be described as an attitude in which the loading section 22 (loading surface 221) of the vehicle body 11 is horizontal (horizontal attitude), but it may also be an attitude other than horizontal.

[0045] (Horizontal Control) When the vehicle 10 is traveling, the posture control unit 172 (ECU 171) performs horizontal control based on the detection signal from the inclination sensor S4. Horizontal control is a control that operates the front, rear, left, and right support mechanisms 13 so that the loading unit 22 (loading surface 221) is in a horizontal position. Based on the detection signal from the inclination sensor S4, the posture control unit 172 determines the tilt angles in the front-rear direction and the left-right direction, with the vehicle body 11 (loading unit 22) in a reference position in which the vehicle body 11 is in a horizontal position. The posture control unit 172 controls the operation of the four first hydraulic cylinders 36 and the four second hydraulic cylinders 37 so that these tilt angles become values ​​corresponding to the horizontal position (i.e., the tilt angles are zero).

[0046] The horizontal control will be further described. The posture control unit 172 calculates the target operation amounts of the four first hydraulic cylinders 36 and the four second hydraulic cylinders 37 required to bring the loading unit 22 to a horizontal position, based on the tilt posture (tilt angle) of the loading unit 22 detected by the tilt sensor S4. The ECU 171 controls the operation of the four first hydraulic cylinders 36 and the four second hydraulic cylinders 37 so that the actual operation amounts detected by the stroke sensor S3 become the target operation amounts.

[0047] (Center of gravity position control) The posture control unit 172 (ECU 171) determines the center of gravity position of the vehicle body 11 based on the detection information of the inclination sensor S4 and the stroke sensor S3, and can perform center of gravity position control to control the operation of the front, rear, left and right support mechanisms 13 so that the center of gravity position is located in the center of multiple (four) wheels 12 in a planar view.

[0048] The center of gravity position control will be further explained. The tilt state of the vehicle body 11 is detected by the output of the tilt sensor S4. The posture control unit 172 determines the tilt angle in the front-to-rear direction and the left-to-right direction from the horizontal posture of the vehicle body 11 based on the detection signal of the tilt sensor S4. The state of the support mechanism 13 (the angle of the first link 31 relative to the vehicle body 11, and the angle of the second link 32 relative to the first link 31) is detected based on the detection results of the extension / contraction amounts of the first hydraulic cylinder 36 and the second hydraulic cylinder 37 detected by the multiple stroke sensors S3.

[0049] As a result, it is possible to obtain by calculation the overall attitude (inclination state) of the vehicle body 11 and the position of the center of gravity of the vehicle body 11 in relation to the ground contact positions of the four wheels 12. The attitude control unit 172 operates the first hydraulic cylinder 36 and the second hydraulic cylinder 37 so that the center of gravity thus obtained becomes the target attitude in which it is located in the center of the multiple (four) wheels 12 in a plan view.

[0050] In this way, center of gravity position control is control that adjusts the pressure (force) supporting the vehicle body 11 so that the center of gravity of the vehicle body 11 converges to the target center of gravity regardless of the unevenness or slope of the road surface. As a variation of center of gravity position control, the attitude control unit 172 does not determine the center of gravity position of the vehicle body 11, but rather determines the ground contact pressure of multiple (four) wheels 12. The ground contact pressure is determined based on detection signals from the pressure sensors S1 and S2. In this case, the attitude control unit 172 (ECU 171) controls the operation of the support mechanism 13 so that the ground contact pressure of the lower wheel 12 and the ground contact pressure of the upper wheel 12 are equal.

[0051] The center of gravity position control makes it possible to generate driving force in all of the wheels 12 in accordance with the unevenness of the road surface. By executing the horizontal control and center of gravity position control, the ECU 171 can operate the support mechanism 13 so that the mounting surface 221 is in a horizontal position and so that all of the wheels 12 generate driving force in accordance with the unevenness of the road surface.

[0052] The attitude control unit 172 (ECU 171) controls the attitude of the vehicle 10 (controls the position of the center of gravity), and the support mechanism 13 operates, allowing the vehicle to travel with all of the four wheels 12 in contact with the road surface (see Figures 5 and 6). In other words, the actuator 14 operates the articulating link mechanism 30, allowing the vehicle to travel with all of the four wheels 12 in contact with the road surface.

[0053] FIG. 5 is a front view illustrating the operation of the support mechanism. FIG. 6 is a side view illustrating the operation of the support mechanism. FIGS. 5(a) and 6(a) show a state in which the four wheels 12 are in contact with the road surface at a certain height. The distance between the ground contact surface of the wheels 12 and the vehicle body 11 (the height of the mounting surface 221) at this time is indicated by the symbol L. From this state, when one of the wheels 12 passes through a depression Q1 in the road surface, as shown in FIGS. 5(b) and 6(b), the attitude control unit 172 (ECU 171) controls the attitude of the support mechanism 13 (the bending link mechanism 30) to increase the distance between the ground contact surface of the wheel 12 and the vehicle body 11 (from distance L to distance L1 (where L1 > L)). In other words, the support mechanism 13 (the bending link mechanism 30) operates to lower the wheel 12 relative to the vehicle body 11. Here, "lowering" includes not only directly downward but also diagonally downward.

[0054] Conversely, as shown in Figures 5(c) and 6(c), when any of the wheels 12 passes over a convex portion Q2 on the road surface, the attitude control unit 172 (ECU 171) controls the attitude so that the support mechanism 13 (bending link mechanism 30) operates to shorten the distance between the ground contact surface of that wheel 12 and the vehicle body 11 (from distance L to distance L2 (where L2 < L)). In other words, the support mechanism 13 (bending link mechanism 30) operates so that the wheel 12 rises relative to the vehicle body 11. The term "rising" as used here includes not only rising directly upward but also rising diagonally upward.

[0055] By the above operation, the loading surface 221 of the loading section 22 in the vehicle body 11 is kept horizontal, and the work vehicle 10 can be traveled with the loading surface 221 kept at a constant height.

[0056] [Coupling mechanism 60] As shown in Figures 1 and 2, the work vehicle 10 is equipped with a coupling mechanism 60. The coupling mechanism 60 is used to couple an accessory device 70 to the rear of the work vehicle 10. The coupling mechanism 60 couples the vehicle body 11 and the accessory device 70. The coupling mechanism 60 in this embodiment includes a mounting frame 61 and a parallel link mechanism 62. The mounting frame 61 is used to attach the parallel link mechanism 62 to the vehicle body 11. The mounting frame 61 is fixed to the frame 21 of the vehicle body 11. The mounting frame 61 is positioned below the loading section 22 and the operating handle 18 of the vehicle body 11.

[0057] As shown in FIG. 2 , the mounting frame 61 includes side frame members 611, a rear frame member 612, and a connecting frame member 613. These are all linear members made of pipe material, plate material, or the like. A pair of left and right side frame members 611 are provided, extending rearward from both the left and right sides of the rear of the frame 21. The rear frame member 612 extends in the left-right direction and connects the rear ends of the pair of side frame members 611. The connecting frame member 613 extends vertically, specifically downward, from approximately the center of the rear frame member 612 in the left-right direction. The mounting frame 61 may be fixed to the frame 21 of the vehicle body 11, or may be detachably attached thereto.

[0058] Fig. 7 is a side view showing the connecting mechanism. Fig. 8 is a plan view showing the connecting mechanism. The parallel link mechanism 62 is attached to the mounting frame 61. The parallel link mechanism 62 is a so-called four-bar link mechanism. The parallel link mechanism 62 has a front link member 621, a swing link member 622, and a rear link member 623. The front link member 621 is substantially formed by the connecting frame member 613 of the mounting frame 61.

[0059] The swing link member 622 is formed linearly from a pipe or plate material. The parallel link mechanism 62 includes a pair of swing link members 622 arranged vertically. The pair of swing link members 622 are parallel to each other. The front ends of the pair of swing link members 622 are swingably connected to the front link member 621. Note that the parallel link mechanism 62 may include three or more swing link members 622, including the pair of swing link members 622, arranged parallel to each other.

[0060] 8, in this embodiment, a pair of swing link members 622 is provided on both the left and right sides of the front link member 621 and the rear link member 623. Therefore, the parallel link mechanism 62 has two pairs of swing link members 622 arranged in the left and right direction.

[0061] The rear end of the swing link member 622 is swingably connected to the rear link member 623. The rear link member 623 is made of a pipe or plate material and is formed in a straight line, extending in the vertical direction. The rear link member 623 and the front link member 621 are arranged in parallel.

[0062] The parallel link mechanism 62 is configured so that the rear part can swing up and down around the fulcrum at the front part fixed to the mounting frame 61. The rear link member 623 moves up and down while maintaining its posture in the front-rear and left-right directions.

[0063] The connecting mechanism 60 includes a connecting member 624 fixed to a rear link member 623. The connecting member 624 extends rearward from the rear link member 623. A connecting shaft 625 is provided at the rear end of the connecting member 624. The connecting shaft 625 has an axis that is oriented in the vertical direction. The connecting member 624 may be fixed to the rear link member 623, or may be configured to be detachable. If the connecting member 624 is detachable, it can be attached according to the type of accessory device 70 to be connected.

[0064] The parallel link mechanism 62 is provided at approximately the center of the mounting frame 61 in the left-right direction, but may be provided on both the left and right sides of the mounting frame 61, or on both the left and right center and the right and left sides.

[0065] [Attachment device 70] As shown in Figures 1 and 2, the attachment device 70 is connected to the connecting mechanism 60. In this embodiment, the attachment device 70 is a trailer (carriage). The trailer 70 travels while being towed by the work vehicle 10. The trailer 70 has a vehicle body 71 and a traveling device 72. The vehicle body 71 has a frame 711 and a loading section 712. The frame 711 is formed by combining linear members into a rectangular shape in top view. A connected member 713 that protrudes forward is provided at the front end of the frame 711, approximately in the center in the left-right direction. The connected member 713 is connected to the connecting member 624 of the parallel link mechanism 62 via a connecting shaft 625 so as to be able to swing freely in the left-right direction.

[0066] The loading section 712 of the vehicle body 71 is disposed on the upper part of the frame 711. The loading section 712 has a loading surface 714 on which cargo can be loaded. The upper surface of the loading surface 714 is formed flat. The loading surface 714 is intended to load, for example, agricultural equipment, agricultural materials such as fertilizer and chemicals, harvested crops, harvest baskets, or pallets on which these are placed. The loading surface 714 is disposed parallel to the loading surface 221 of the vehicle body 11.

[0067] The body 71 of the trailer 70 is connected to the vehicle body 11 via a connecting mechanism 60 including a parallel link mechanism 62. Therefore, the loading surface 714 of the trailer 70 is maintained parallel to the loading surface 221 of the vehicle body 11.

[0068] FIG. 9 is a cross-sectional view taken along line A-A in FIG. 2. As shown in FIGS. 1, 2, and 9, the traveling device 72 has a pair of wheels 721, an axle 722, and a support portion 723. The pair of wheels 721 are arranged on both the left and right sides of the vehicle body 71. The axle 722 extends in the left-right direction and rotatably supports the pair of wheels 721. One wheel 721 is rotatably supported at one end of the axle 722, and the other wheel 721 is rotatably supported at the other end of the axle 722. The axle 722 is arranged below the vehicle body 71 and crosses the vehicle body 71. The axle 722 forms a connecting member that connects the pair of wheels 721.

[0069] The support portion 723 rotatably supports the axle 722. An upper portion of the support portion 723 is attached to the frame 711 of the vehicle body 71. Specifically, a support shaft 715 having an axis in the front-to-rear direction is fixed to the frame 711. An upper portion of the support portion 723 is attached to the support shaft 715 so as to be able to swing up and down. Therefore, the traveling device 72 is configured so that when one wheel 721 rises, the other wheel 721 falls.

[0070] As described above, in the trailer 70 of this embodiment, the pair of wheels 721 are supported so as to be able to move up and down relative to the vehicle body 71. In other words, the trailer 70 is configured so that the distance between the ground contact surface (bottom surface) of the wheels 721 and the vehicle body 71 is changeable. This distance is, for example, the vertical distance between the ground contact surface of the wheels 721 and the mounting surface 714 of the vehicle body 71.

[0071] The vehicle body 71 of the trailer 70 is attached to the vehicle body 11 by a connecting mechanism 60 including a parallel link mechanism 62. Therefore, the vehicle body 71 can move up and down while maintaining its posture relative to the vehicle body 11, particularly its posture in the front-to-rear and left-to-right directions. As described above, the posture of the vehicle body 11 is maintained by the support mechanism 13 changing the distance between the ground contact surfaces of the wheels 12 and the vehicle body 11. Specifically, the loading section 22 (loading surface 221) of the vehicle body 11 is maintained in a horizontal posture. Therefore, the loading section 712 (loading surface 714) of the vehicle body 71 in the trailer 70 is also maintained in a horizontal posture.

[0072] Therefore, the coupling mechanism 60 couples the vehicle body 11 and the vehicle body 71 of the trailer 70 in a manner that causes the attitude of the vehicle body 71 to follow the attitude of the vehicle body 11, and is configured to maintain the attitude of the vehicle body 71 of the trailer 70 before the change, even after the support mechanism 13 changes the distance between the ground contact surface of the wheels 12 and the vehicle body 11. In other words, before the support mechanism 13 changes the distance between the ground contact surface of the wheels 12 and the vehicle body 11, the vehicle body 11 (mounting surface 221) is horizontal and the vehicle body 71 of the trailer 70 is also horizontal, and after the support mechanism 13 changes the distance between the ground contact surface of the wheels 12 and the vehicle body 11, the vehicle body 11 (mounting surface 221) is horizontal and the vehicle body 71 of the trailer 70 is also horizontal.

[0073] On the other hand, the pair of wheels 721 of the traveling device 72 can move up and down relative to the vehicle body 71. Therefore, the wheels 721 can move up and down relative to the vehicle body 71, which is maintained in a horizontal position, following the unevenness of the ground.

[0074] As described above, the body 71 of the trailer 70 is maintained horizontally by following the posture of the main vehicle body 11 of the work vehicle 10, so that the load loaded on the loading section 712 can be transported stably without dropping, and the traveling device 72 of the trailer 70 can follow the unevenness of the ground and keep the wheels 721 in contact with the ground, so that the trailer 70 can travel stably. Furthermore, the trailer 70 can maintain its posture by the connecting mechanism 60 without having to be equipped with a driving unit such as an actuator or motor for maintaining the posture of the body 71. This allows the structure of the trailer 70 to be simplified.

[0075] 1 and 2, the trailer 70 is connected to the vehicle 10 via a connecting shaft 625 so as to be able to swing left and right. This allows the trailer 70 to turn in accordance with the direction of the vehicle 10. In addition, a restricting member 73 is provided between the mounting frame 61 of the connecting mechanism 60 and the body 71 of the trailer 70 to limit the swinging of the trailer 70 around the connecting shaft 625.

[0076] In this embodiment, the restricting member 73 is composed of two ropes. The two ropes are attached in a flexed state between the left and right sides of the rear end of the mounting frame 61 and the left and right sides of the front end of the vehicle body 71 of the trailer 70. As a result, when the trailer 70 swings around the connecting shaft 625, the restricting member 73, which is located on the side opposite the swing direction, is pulled, restricting further swing of the trailer 70. This makes it possible to prevent the trailer 70 from coming into contact with the work vehicle 10 when the work vehicle 10 changes direction. The restricting member 73 may be formed, for example, as a stopper such as a protrusion formed on the connecting member 624 or the connected member 713, which restricts the relative movement of the two.

[0077] [Modification of the Coupling Mechanism 60] Figure 10 is a side view showing a modification of the coupling mechanism. The coupling mechanism 60 can be used to connect various types of equipment, not just trailers, as an accessory device 70. The accessory device 70 shown in Figure 10 is a work device that performs work on the ground, such as a trench cutting device. This trench cutting device 70 does not have wheels that run on the ground, and is fixed at a predetermined height by the coupling mechanism 60.

[0078] The connecting mechanism 60 of this embodiment includes a fixing member 63 that fixes the parallel link mechanism 62 at a predetermined swing position (height). The fixing member 63 is formed linearly and connects the front link member 621 and the rear link member 623 of the parallel link mechanism 62. The fixing member 63 is disposed non-parallel to the swing link member 622. Therefore, the fixing member 63 can limit the swing of the swing link member 622 and fix the parallel link mechanism 62 at the predetermined swing position.

[0079] The fixing member 63 of this modified example is configured by an expandable member, for example, a turnbuckle. The turnbuckle 63 has a body portion 631 with reverse-threaded female threads formed at both ends, and a pair of rod portions 632 with male threads at one end that screw into the female threads of the body portion 631. The other end of each rod portion 632 is swingably connected to the front link member 621 and the rear link member 623. The length of the turnbuckle 63 can be adjusted by rotating the body portion 631, and the swing position of the parallel link mechanism 62 can be adjusted.

[0080] The fixing member 63 is not limited to a turnbuckle, and may be an extendable device such as a hydraulic cylinder. The fixing member 63 may also be a non-extendable member. In this case, the swing position of the parallel link mechanism 62 can be adjusted by replacing multiple types of fixing members 63 with different lengths.

[0081] [Others] The above-described embodiments are illustrative in all respects and are not limiting. The scope of the present disclosure is defined by the claims, not the above-described embodiments, and includes all modifications within the scope equivalent to the configurations described in the claims.

[0082] 10: Work vehicle 11: Vehicle body 13: Support mechanism 19: Traveling device 60: Linking mechanism 62: Parallel link mechanism 622: Swing link member 63: Fixed member 70: Accessory device 71: Vehicle body 715: Support shaft 721: Wheel 722: Axle (connecting body)

Claims

1. A work vehicle comprising: a vehicle body; a traveling device; a support mechanism capable of changing the distance between the ground contact surface of the traveling device and the vehicle body; an accessory device; and a connecting mechanism that connects the vehicle body and the accessory device, wherein the connecting mechanism maintains the attitude of the accessory device after the distance has been changed by the support mechanism in the attitude before the change.

2. A work vehicle as set forth in claim 1, wherein the connecting mechanism includes a parallel link mechanism having a pair of upper and lower swing link members that can swing up and down.

3. A work vehicle according to claim 2, wherein the connecting mechanism includes a fixing member that fixes the swing link member at a predetermined swing position.

4. A work vehicle according to any one of claims 1 to 3, wherein the accessory device has a vehicle body connected to the connecting mechanism and a plurality of wheels supported on the vehicle body so that they can be raised and lowered.

5. A work vehicle as described in claim 4, wherein the accessory device includes a pair of wheels spaced apart in the left-right direction, a connecting body connecting the pair of wheels, and a support shaft supporting the connecting body between the left-right direction of the pair of wheels so that it can swing up and down relative to the vehicle body.

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