Working machine

Abstract

To provide a working machine that can travel in a travel state of being suited for a condition of a travelling field.SOLUTION: A working machine includes: a holding frame 25 connected to a vehicle body frame 15 via a fulcrum shaft 28 having a fulcrum axis extending in a vehicle body lateral width direction and supported to the vehicle body frame 15 so as to be vertically swingable about the fulcrum axis as a swing axis; wheels 2, 3 fitted to the vehicle body frame 15 while being held to the holding frame 25 so as to be vertically swingable; and a fulcrum shaft change mechanism for changing the position of the fulcrum shaft 28.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a working machine.

Background Art

[0002] As shown in Patent Document 1, there is a working machine (tractor) in which a vehicle body is supported by front wheels and rear wheels.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventionally, when the traveling ground is uneven, the vehicle body attitude with respect to the ground is likely to change when the wheels enter the concave portion of the traveling ground or when the wheels climb over the convex portion of the traveling ground. When the traveling ground is inclined, the vehicle body inclines along the traveling ground and is likely to slip depending on the inclination angle. If the vehicle body attitude with respect to the ground changes or the vehicle body slips, the work finish deteriorates, for example, the working depth changes.

[0005] The present invention provides a working machine capable of traveling in a traveling state adapted to the conditions of the traveling ground.

Means for Solving the Problems

[0006] The working machine according to the present invention is connected to a vehicle body frame via a fulcrum shaft having a fulcrum axis extending in the vehicle body width direction, and is supported by the vehicle body frame in a state where it can swing up and down with the fulcrum axis as a swing axis, a holding frame, a wheel held by the holding frame and attached to the vehicle body frame in a state where it can swing up and down, and a fulcrum axis changing mechanism for changing the position of the fulcrum axis.

[0007] According to this configuration, since the wheels move up and down relative to the vehicle body frame with the fulcrum axis as the swing fulcrum due to the vertical swing of the holding frame, for example, when the wheel enters the concave portion, the holding frame swings downward and the wheel descends relative to the vehicle body frame, and changes in the posture of the vehicle body due to the concave portion can be prevented or suppressed. When the wheel rides over the convex portion, the holding frame swings upward and the wheel ascends relative to the vehicle body frame, and changes in the posture of the vehicle body due to the convex portion can be prevented or suppressed. In the case of an inclined ground, the swing angle of the holding frame relative to the vehicle body frame is set corresponding to the inclination angle of the traveling ground, and the vertical position of the wheel relative to the vehicle body frame is set so that the vehicle body can be maintained in a horizontal or nearly horizontal posture regardless of the inclination of the traveling ground. By changing the position of the fulcrum axis relative to the vehicle body frame, the connection position of the holding frame in the vehicle body frame changes. Thus, the position setting of the wheel relative to the vehicle body frame can be made appropriate so that the wheels can be properly moved up and down by the swing of the holding frame. That is, it is possible to travel in a traveling state adapted to the situation of the traveling ground.

[0008] In the present invention, it is preferable that the fulcrum axis changing mechanism changes the position of the fulcrum axis to an arbitrary position relative to the vehicle body frame.

[0009] According to this configuration, since the connection position of the holding frame in the vehicle body frame can be adjusted to an arbitrary position corresponding to the situation of the traveling ground, it is possible to travel in a traveling state adapted to the situation of the traveling ground.

[0010] In the present invention, it is preferable that the fulcrum axis changing mechanism changes the position of the fulcrum axis stepwise in the front-rear direction relative to the vehicle body frame.

[0011] According to this configuration, since the connection position of the holding frame in the vehicle body frame can be adjusted stepwise in the front-rear direction according to the situation of the driving ground, it is possible to drive in a driving state adapted to the situation of the driving ground.

[0012] In the present invention, it is preferable to include an actuator that changes the position of the fulcrum shaft and an artificial operation device that designates the position of the fulcrum shaft, and the fulcrum shaft changing mechanism changes the position of the fulcrum shaft with the actuator in response to the position designated by the artificial operation device.

[0013] According to this configuration, by designating the position of the fulcrum shaft with an artificial operation device, the position of the fulcrum shaft is changed by the actuator to a position corresponding to the designated position, and the connection position of the holding frame in the vehicle body frame is changed. Therefore, the connection position of the holding frame in the vehicle body frame can be adjusted by artificial adjustment.

[0014] In the present invention, it is preferable to include an actuator that changes the position of the fulcrum shaft and a first detection device that detects the operation of a steering operation tool that performs a steering operation of the vehicle body, and the fulcrum shaft changing mechanism changes the position of the fulcrum shaft with the actuator in response to the detection result detected by the first detection device.

[0015] According to this configuration, when the steering operation tool is operated to perform the steering operation of the vehicle body, the operation of the steering operation tool is detected by the first detection device, and the position of the fulcrum shaft is changed by the actuator in response to this detection result, and the connection position of the fulcrum shaft to the vehicle body frame is changed. That is, simply by operating the steering operation tool, the connection position of the holding frame in the vehicle body frame is automatically adjusted to the connection position corresponding to the traveling direction of the vehicle body, and the vehicle body can be made to travel in a traveling state adapted to the traveling direction in which the vehicle body is to travel. For example, when the vehicle body is steered in a straight-ahead direction, the connection position of the holding frame in the vehicle body frame is automatically adjusted to a position corresponding to straight-ahead travel, and the vehicle body can travel in a traveling state adapted to straight-ahead travel. When the vehicle body is steered in a turning direction, the connection position of the holding frame in the vehicle body frame is automatically adjusted to a position corresponding to turning travel, and the vehicle body can travel in a traveling state adapted to turning travel.

[0016] In the present invention, it is preferable to include an actuator that changes the position of the fulcrum shaft and a second detection device that detects the state of the traveling surface in front of the vehicle body, and the fulcrum shaft change mechanism changes the position of the fulcrum shaft with the actuator in response to the traveling surface state detected by the second detection device.

[0017] According to this configuration, the state of the traveling surface in front of the vehicle body is detected by the second detection device, and the position of the fulcrum shaft is changed by the actuator in response to the detected traveling surface state, and the connection position of the holding frame in the vehicle body frame is changed. That is, the connection position of the holding frame in the vehicle body frame is automatically adjusted to the connection position corresponding to the traveling surface state, and the vehicle body can travel in a traveling state adapted to the traveling surface state. For example, when there is a recess in the traveling ground, the connection position of the holding frame in the vehicle body frame is automatically adjusted to the connection position corresponding to the recess, and the vehicle body can travel while preventing or suppressing the change in the posture of the vehicle body due to the recess. When there is a protrusion on the traveling ground, the connection position of the holding frame in the vehicle body frame is automatically adjusted to the connection position corresponding to the protrusion, and the vehicle body can travel while preventing or suppressing the change in the posture of the vehicle body due to the protrusion.

[0018] In the present invention, it is preferable to include an actuator that changes the position of the fulcrum shaft, and a third detection device that detects the work content, and the fulcrum shaft change mechanism changes the position of the fulcrum shaft with the actuator in accordance with the work content detected by the third detection device.

[0019] According to this configuration, the work content is detected by the third detection device, the position of the fulcrum shaft is changed by the actuator in accordance with the detected work content, and the connection position of the holding frame in the vehicle body frame is changed. That is, the connection position of the holding frame in the vehicle body frame is automatically adjusted to the connection position corresponding to the work content, and the vehicle can travel in a running state adapted to the work content.

[0020] In the present invention, it is preferable to include a transmission wheel body on the fulcrum shaft side provided on the fulcrum shaft and to which power from a power source is transmitted, a transmission wheel body on the wheel side provided on the holding frame and to which power is transmitted to the wheel, and an endless rotating transmission body wound around the transmission wheel body on the fulcrum shaft side and the transmission wheel body on the wheel side.

[0021] According to this configuration, since the power from the power source is transmitted to the wheel by the transmission wheel body on the fulcrum shaft side, the transmission wheel body on the wheel side, and the endless rotating transmission body wound around the transmission wheel body on the fulcrum shaft side and the transmission wheel body on the wheel side, the power transmission system can be made lighter and more compact compared to the case where the power is transmitted by a linkage rod.

[0022] In the present invention, it is preferable to include a tension operation member that performs a tension operation on the endless rotating transmission body, and a biasing mechanism that presses and biases the tension operation member against the endless rotating transmission body.

[0023] According to this configuration, the tension operation member is pressed and biased against the endless rotating transmission body by the biasing mechanism, and loosening due to elongation of the endless rotating transmission body is prevented, so that power can be firmly transmitted to the wheel regardless of elongation of the endless rotating transmission body.

Brief Description of the Drawings

[0024]

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Mode for Carrying Out the Invention

[0025] Hereinafter, an embodiment which is an example of the present invention will be described with reference to the drawings. In the following description, regarding the vehicle body of a tractor (an example of a "working machine"), the direction of arrow F shown in FIGS. 1, 2, etc. is the "front direction of the vehicle body", the direction of arrow B is the "rear direction of the vehicle body", the direction of arrow U is the "upper direction of the vehicle body", the direction of arrow D is the "lower direction of the vehicle body", the direction of arrow L is the "left direction of the vehicle body", and the direction of arrow R is the "right direction of the vehicle body". The left - right direction of the vehicle body corresponds to the vehicle body width direction.

[0026] 〔Regarding the whole tractor〕 As shown in FIGS. 1 and 2, the tractor includes a vehicle body 4 supported by a pair of left and right steerable and drivable front wheels 1, a pair of left and right drivable rear wheels 2, and a pair of left and right drivable middle wheels 3. The front wheels 1, rear wheels 2, and middle wheels 3 are tire wheels. A prime mover 5 is formed at the front part of the vehicle body 4. The prime mover 5 is provided with an engine 6, an engine bonnet 7 covering the engine 6, etc. A fuel tank 8 for the engine is provided on the right side of the engine bonnet 7. At the rear part of the vehicle body 4, a riding-type control unit 9 is formed where the driver rides and controls the vehicle body. The control unit 9 is formed in a state where the periphery is open, that is, in a state without a so-called cabin. As shown in FIGS. 1 and 2, the control unit 9 is provided with a control seat 10, a steering wheel 11 for steering the front wheels 1, a step 12 which is a floor part located in front of and below the control seat 10, a roll-over protective structure (ROPS) 13, etc. Rear wheel fenders 14 covering the rear wheels 2 are provided on both outer sides of the control unit 9. The ROPS 13 stands upright upward from the vehicle body frame 15 behind the control seat 10. At the rear part of the vehicle body frame 15, a connecting device 16 is provided for connectably coupling various working devices such as a rotary tilling device (not shown).

[0027] 〔Regarding the vehicle body frame〕 As shown in FIGS. 1 and 6, etc., the vehicle body frame 15 is composed of an engine 6, a transmission device 17 extending rearward from the rear part of the engine 6, and a front frame 18 extending forward from the lower part of the engine 6. The transmission device 17 includes a transmission case 19. Inside the transmission case 19, a traveling transmission (not shown) to which the driving force from the engine 6 as a driving source (power source) is input via a main clutch (not shown), a rear-wheel differential mechanism 20 (see FIG. 6) to which the output of the traveling transmission is input, and a working transmission (not shown) to which the driving force from the engine 6 is input are provided. As shown in FIGS. 5 and 9, a power take-off shaft 21 for taking out the power from the working transmission and transmitting it to a working device connected thereto is provided at the rear part of the transmission case 19. As shown in FIGS. 6 and 7, etc., the transmission case 19 is configured to be dividable into a front case part 19a connected to the engine 6, a middle case part 19b extending rearward from the rear part of the front case part 19a, and a rear case part 19c extending rearward from the rear part of the middle case part 19b.

[0028] 〔Regarding the connecting device〕 As shown in FIGS. 2 and 9, etc., the connecting device 16 includes a lower link 16a swingably connected to both lateral sides at the rear part of the transmission case 19, a top link 16b swingably connected to the transmission case 19 above the lower link 16a, and a lift arm 16c swingably connected to both lateral sides at the upper part of the transmission case 19. The lift arm 16c and the lower link 16a are connected by a lift rod 16e. In this embodiment, the right lift rod 16e is a hydraulic cylinder for rolling.

[0029] In the connecting device 16, the left and right lower links 16a and the top link 16b are connected to the working device, so that the working device is connected to the vehicle body 4 in a towable manner. The left and right lift arms 16c are swung up and down by the extension and contraction of the hydraulic cylinder 16d, and the lower link 16a is swung up and down by the lift arm 16c via the lift rod 16e, so that the lifting operation of the working device is performed. The right lower link 16a is swung by the extension and contraction of the hydraulic cylinder for rolling, so that the rolling operation of the working device is performed.

[0030] 〔Regarding the front wheels〕 As shown in FIGS. 5 and 6, front axle cases 23 having front axles 1a are provided at both ends of a front wheel drive case 22 extending in the vehicle body width direction below the front frame 18. The front wheels 1 are held by the front axles 1a. The front wheel drive case 22 is connected to the front frame 18 so as to be swingable up and down with a rolling axis X in the vehicle body longitudinal direction located at the center of the front wheel drive case 22 in the vehicle body width direction as a swing fulcrum. The left and right front wheels 1 are held by the vehicle body frame 15 via the front axle case 23 and the front wheel drive case 22. Rolling of the vehicle body frame 15 around the rolling axis X of the left and right front wheels 1 is enabled.

[0031] The front axle case 23 is connected to the front wheel drive case 22 so as to be swingable with a steering axis in the vehicle body vertical direction as a swing fulcrum. The left and right front wheels 1 are steered by the rotation operation of the steering wheel 11 and the swing operation of the front axle case 23 around the steering axis with respect to the front wheel drive case 22.

[0032] As shown in FIG. 5, a rotating shaft 24 extends forward from the transmission device 17 and is connected to the front wheel drive case 22. The power input from the engine 6, which is the drive source, to the traveling transmission of the transmission device 17 is input into a front wheel differential mechanism (not shown) provided inside the front wheel drive case 22 via the rotating shaft 24, and is transmitted from the front wheel differential mechanism to the left and right front axles 1a to drive the left and right front wheels 1.

[0033] [Regarding the middle wheels and the rear wheels] The left and right middle wheels 3 are configured to be supported by the vehicle body frame 15 based on the same support structure and driven based on the same drive structure. The left and right rear wheels 2 are configured to be supported by the vehicle body frame 15 based on the same support structure and driven based on the same drive structure. In the following, when explaining the support structure of the left and right middle wheels 3, the drive structure of the left and right middle wheels 3, the support structure of the left and right rear wheels 2, the drive structure of the left and right rear wheels 2, etc., the left and right front wheels 1 will be simply referred to as the front wheels 1, the left and right middle wheels 3 will be simply referred to as the middle wheels 3, and the left and right rear wheels 2 will be simply referred to as the rear wheels 2 for explanation.

[0034] As shown in FIGS. 1 and 2, the middle wheel 3 is positioned between the front wheel 1 and the rear wheel 2, and the front wheel 1, the middle wheel 3, and the rear wheel 2 are configured to be aligned in the longitudinal direction of the vehicle body. The middle wheel 3 is configured to be located within the width of the front wheel 1 and within the width of the rear wheel 2 in the region between the front wheel 1 and the rear wheel 2. In this embodiment, the middle wheel 3 is located within the width of the front wheel 1 and within the width of the rear wheel 2, but it is not limited thereto, and the middle wheel 3 may protrude laterally outside or laterally inside the vehicle body with respect to both the front wheel 1 and the rear wheel 2, or either one of them. The outer diameter of the middle wheel 3 is set to be smaller than the outer diameter of the rear wheel 2. The outer diameter of the middle wheel 3 is set to be smaller than the outer diameter of the front wheel 1. The outer diameter of the rear wheel 2 is set to be larger than the outer diameter of the middle wheel 3 and larger than the outer diameter of the front wheel 1. The outer diameters of the front wheel 1, the middle wheel 3, and the rear wheel 2 include the rubber lug portions formed on the outer peripheral portions of the tires.

[0035] As shown in FIGS. 1, 2, 4, 5, etc., a holding frame 25 is provided on the lateral outside of the vehicle body frame 15, and the middle wheel 3 and the rear wheel 2 are held by the vehicle body frame 15 via the holding frame 25.

[0036] Specifically, as shown in FIGS. 3 and 5, a middle axle 3a is provided in a middle wheel holding portion 25a located at the front portion of the holding frame 25. The middle axle 3a is provided in the middle wheel holding portion 25a by attaching a middle axle case 26 having the middle axle 3a to the middle wheel holding portion 25a. The middle wheel 3 is rotatably and drivably held in the middle wheel holding portion 25a by being held by the middle axle 3a.

[0037] As shown in FIGS. 3 and 5, a rear axle 2a is provided in a wheel holding portion 25b located at the rear portion of the holding frame 25. The rear axle 2a is provided in the wheel holding portion 25b by attaching a rear axle case 27 having the rear axle 2a to the wheel holding portion 25b. The rear wheel 2 is rotatably and drivably held in the wheel holding portion 25b by being held by the rear axle 2a.

[0038] As shown in FIGS. 3 and 5, a fulcrum shaft 28 extending in the vehicle body width direction is attached to an intermediate portion 25c located between the middle wheel holding portion 25a and the wheel holding portion 25b of the holding frame 25. The fulcrum shaft 28 is connected to the vehicle body frame 15. The holding frame 25 is held by the vehicle body frame 15 via the fulcrum shaft 28.

[0039] As shown in FIG. 5, the fulcrum shaft 28 that connects the holding frame 25 holding the left middle wheel 3 and the left rear wheel 2 to the vehicle body frame 15 and the fulcrum shaft 28 that connects the holding frame 25 holding the right middle wheel 3 and the right rear wheel 2 to the vehicle body frame 15 are constituted by the same fulcrum shaft.

[0040] As shown in FIGS. 3 and 7, the holding frame 25 is formed such that in a side view of the vehicle body, the position of a wheel side portion 25d extending from the intermediate portion 25c to the side where the wheel holding portion 25b is located is higher than the position of a middle wheel side portion 25e extending from the intermediate portion 25c to the side where the middle wheel holding portion 25a is located, and the wheel side portion 25d is in an inclined posture where it is located higher as it is farther from the intermediate portion 25c. In the present embodiment, the middle wheel side portion 25e is a front side portion extending forward from the intermediate portion 25c, and the wheel side portion 25d is a rear side portion extending rearward and upward from the intermediate portion 25c.

[0041] As shown in FIGS. 2 and 3, the holding frame 25 is arranged so as to pass below the rear wheel fender 14 in the front-rear direction in a state of overlapping the rear wheel fender 14 in plan view. The holding frame 25 is shown by a broken line in FIG. 2. As can be understood from the description of FIG. 2 and the descriptions of FIGS. 1 and 3, the portion near the tip of the holding frame 25 does not overlap with the rear wheel fender 14, and other portions (rear-side portions) excluding the portion near the tip of the holding frame 25 overlap with the rear wheel fender 14 up to the rear end. The portion near the tip of the holding frame 25 overlaps with the step 12 of the operation unit 9.

[0042] As shown in FIG. 3, the holding frame 25 is arranged so as to pass below the operation unit 9 in the front-rear direction in a side view of the vehicle body. The holding frame 25 is shown by a solid line in FIG. 3. As can be understood from the description of FIG. 3, in a side view of the vehicle body, the front end of the holding frame 25 is located below the steering wheel 11, and the rear end of the holding frame 25 is located below the driver's seat 10 of the operation unit 9. The left and right holding frames 25 are shown by broken lines in FIG. 2. As can be understood from the description of FIG. 2, in plan view, the steering wheel 11 and the driver's seat 10 are located between the left and right holding frames 25.

[0043] As shown in FIGS. 3 and 5, the holding frame 25 is arranged such that the center C1 of the holding frame 25 in the front-rear direction is located on the rear side of the center C2 of the vehicle body frame 15 in the front-rear direction. In the present embodiment, as shown in FIG. 3, the front end of the holding frame 25 is located on the rear side of the center C2 of the vehicle body frame 15 in the front-rear direction. However, the present invention is not limited to this, and the front end of the holding frame 25 may be located on the front side of the center C2 of the vehicle body frame 15 in the front-rear direction.

[0044] As shown in FIGS. 2 and 5, the holding frame 25 is arranged so as to pass through the space between the rear wheel 2 and the transmission case 19 and the space between the middle wheel 3 and the vehicle body frame 15 in the front-rear direction. As shown in FIGS. 5 and 6, in plan view, the holding frame 25 is located between the middle axle case 26 and the transmission case 19 and between the rear axle case 27 and the transmission case 19.

[0045] As shown in FIGS. 2 and 5, the holding frame 25 is arranged to be located inside the vehicle body width direction with respect to the middle wheel 3 and the rear wheel 2. As shown in FIGS. 5 and 6, the middle axle 3a and the rear axle 2a are configured to be located outside the vehicle body width direction with respect to the holding frame 25. The middle wheel 3 and the rear wheel 2 can be detached from the holding frame 25 from the outside of the vehicle body width direction.

[0046] 〔Regarding the drive of the middle wheel and the rear wheel〕 Power from the engine as a drive source or power source is input to the transmission device 17, and is transmitted from the transmission device 17 to the middle wheel 3 and the rear wheel 2 so that the middle wheel 3 and the rear wheel 2 are driven. As shown in FIG. 6, the transmission device 17 has a middle wheel power transmission mechanism 41 that transmits power to the middle wheel 3 and a wheel power transmission mechanism 51 that transmits power to the rear wheel 2. The middle wheel power transmission mechanism 41 and the wheel power transmission mechanism 51 that transmit power to the rear wheel 2 are provided inside the holding frame 25.

[0047] Specifically, as shown in FIG. 6, an upper transmission device 30 is provided across the lateral side portion of the transmission device 17 and the fulcrum shaft 28, a first lower transmission device 40 is provided across the fulcrum shaft 28 and the middle axle 3a, and a second lower transmission device 50 is provided across the fulcrum shaft 28 and the rear axle 2a.

[0048] As shown in FIGS. 6 and 9, the auxiliary transmission device 30 includes a transmission case 31 that is located across the lateral side of the transmission case 19 and the fulcrum shaft 28 inside the holding frame 25. Inside the transmission case 31, there are provided a transmission member 33 provided on the output shaft 32 of the transmission device 17, an input portion 34 (see FIG. 10) rotatably provided on the fulcrum shaft 28, and an interlocking member 35 that interlocks the transmission member 33 and the input portion 34.

[0049] In the present embodiment, as shown in FIGS. 6 and 9, the output shaft 32 is the output shaft of the rear wheel differential mechanism 20, the transmission member 33 and the input portion 34 are chain sprockets, and the interlocking member 35 is an endless rotating chain. A tensioning operation member 36 is provided outside each of the portion of the endless rotating chain from the transmission member 33 to the input portion 34 and the portion of the endless rotating chain from the input portion 34 to the transmission member 33. The tensioning operation member 36 is swingably held by the transmission case 31 and is pressed against the endless rotating chain by a spring 37 to tension the endless rotating chain. In the present embodiment, the spring 37 is provided, but as the tensioning operation member 36, a bent round bar or a resin tensioner or the like having an elasticity to press the endless rotating chain may be adopted, and the spring 37 may not be provided.

[0050] In the auxiliary transmission device 30, the power of the transmission device 17 transmitted to the transmission member 33 is transmitted from the transmission member 33 to the input portion 34 by the interlocking member 35. In the present embodiment, the endless rotating chain constituting the interlocking member 35 is maintained in a tensioned state necessary for power transmission by the tensioning operation member 36.

[0051] As shown in FIGS. 6 and 8, the first auxiliary transmission device 40 includes the holding frame 25 and the middle axle case 26, and the power from the transmission device 17 transmitted to the input portion 34 by the auxiliary transmission device 30 is transmitted to the middle wheels 3 by the holding frame 25 and the middle axle case 26.

[0052] Specifically, as shown in FIGS. 6 and 8, the first auxiliary transmission device 40 is provided with an intermediate wheel power transmission mechanism 41 provided across the holding frame 25 and the intermediate axle case 26.

[0053] As shown in FIGS. 6 and 8, the intermediate wheel power transmission mechanism 41 is provided across the inside of the holding frame 25 and the inside of the intermediate axle case 26. The intermediate wheel power transmission mechanism 41 includes a first transmission wheel body 42 on the fulcrum shaft side rotatably provided on the fulcrum shaft 28, a transmission wheel body 44 on the intermediate wheel side provided on the input shaft 43 of the intermediate axle case 26, an endless rotating transmission body 45 wound around the first transmission wheel body 42 on the fulcrum shaft side and the transmission wheel body 44 on the intermediate wheel side, and an intermediate wheel gear transmission part 46 provided across the input shaft 43 of the intermediate axle case 26 and the intermediate axle 3a.

[0054] As shown in FIG. 8, tension operation members 49 are provided outside each of the portion of the endless rotating transmission body 45 from the first transmission wheel body 42 to the transmission wheel body 44 and the portion of the endless rotating transmission body 45 from the transmission wheel body 44 to the first transmission wheel body 42. The tension operation member 49 is swingably held by the holding frame 25 and is pressed and biased against the endless rotating transmission body 45 by a biasing mechanism 49a to perform a tension operation on the endless rotating transmission body 45. In the present embodiment, the first transmission wheel body 42 on the fulcrum shaft side and the transmission wheel body 44 on the intermediate wheel side are chain sprockets, and the endless rotating transmission body 45 is an endless rotating chain. The biasing mechanism 49a is a spring. In the present embodiment, although the biasing mechanism 49a is provided, as the tension operation member 49, a bent round bar material or a resin tensioner or the like having an elasticity to press the endless rotating chain may be adopted, and the biasing mechanism 49a may not be provided.

[0055] As shown in FIG. 10, the cylindrical bosses 47 for attaching the first transmission wheel body 42 and the input portion 34 to the fulcrum shaft 28 are constituted by the same cylindrical boss, and the first transmission wheel body 42 and the input portion 34 are connected by the cylindrical boss 47. An intermediate cylinder 48 is interposed between the cylindrical boss 47 and the fulcrum shaft 28. The intermediate cylinder 48 is fixed to the annular connecting member 62 and positions the cylindrical boss 47 with respect to the fulcrum shaft 28. The fixing of the intermediate cylinder 48 to the annular connecting member 62 is performed by welding.

[0056] As shown in FIG. 6, the middle gear transmission portion 46 includes an input shaft gear 46a held by the input shaft 43 of the middle axle case 26 and a middle axle gear 46b held by the middle axle 3a. The input shaft gear 46a and the middle axle gear 46b are meshed with each other. In the middle gear transmission portion 46, the rotational direction of the power from the input portion 34 transmitted to the input shaft 43 is changed to the reverse rotational direction by the input shaft gear 46a and the middle axle gear 46b and output to the middle axle 3a. The gear diameter of the middle axle gear 46b is set larger than the gear diameter of the input shaft gear 46a.

[0057] In the first low-speed transmission device 40, the power from the transmission device 17 transmitted to the input portion 34 is transmitted to the middle axle 3a by the middle wheel power transmission mechanism 41. In the middle wheel power transmission mechanism 41, the power from the input portion 34 transmitted to the first transmission wheel body 42 is transmitted to the middle axle 3a by the endless rotating transmission body 45, the transmission wheel body 44, and the middle gear transmission portion 46. The rotational direction of the power from the input portion 34 transmitted to the input shaft 43 of the middle axle case 26 is changed to the power in the reverse rotational direction by the middle gear transmission portion 46 and transmitted to the middle axle 3a. The endless rotating transmission body 45 is maintained in a tension state necessary for power transmission by the tension operation member 49.

[0058] As shown in FIGS. 6 and 8, in the second low-speed transmission device 50, the holding frame 25 and the rear axle case 27 are provided, and the power from the transmission device 17 transmitted to the input portion 34 by the high-speed transmission device 30 is transmitted to the rear wheels 2 by the holding frame 25 and the rear axle case 27.

[0059] Specifically, as shown in FIGS. 6 and 8, the second auxiliary transmission device 50 is provided with a wheel power transmission mechanism 51 provided across the holding frame 25 and the rear axle case 27.

[0060] As shown in FIGS. 6 and 8, the wheel power transmission mechanism 51 is provided across the inside of the holding frame 25 and the inside of the rear axle case 27. The wheel power transmission mechanism 51 includes a second transmission wheel body 52 on the fulcrum shaft side rotatably provided on the fulcrum shaft 28, a transmission wheel body 54 on the wheel side provided on the input shaft 53 of the rear axle case 27, an endless rotating transmission body 55 wound around the second transmission wheel body 52 on the fulcrum shaft side and the transmission wheel body 54 on the wheel side, and a wheel gear transmission portion 56 provided across the input shaft 53 of the rear axle case 27 and the rear axle 2a.

[0061] As shown in FIG. 8, tension operation members 59 are provided outside each of the portion of the endless rotating transmission body 55 from the second transmission wheel body 52 to the transmission wheel body 54 and the portion of the endless rotating transmission body 55 from the transmission wheel body 54 to the second transmission wheel body 52. The tension operation member 59 is swingably held by the holding frame 25 and is pressed and biased against the endless rotating transmission body 55 by a biasing mechanism 59a to perform a tension operation on the endless rotating transmission body 55. In the present embodiment, the second transmission wheel body 52 on the fulcrum shaft side and the transmission wheel body 54 on the wheel side are chain sprockets, and the endless rotating transmission body 55 is an endless rotating chain. The biasing mechanism 59a is a spring. In the present embodiment, although the biasing mechanism 59a is provided, as the tension operation member 59, a bent round bar material or a resin tensioner or the like having an elasticity to press the endless rotating chain may be adopted, and the biasing mechanism 59a may not be provided.

[0062] As shown in FIG. 10, a cylinder boss 47 for attaching the second transmission wheel body 52 and the input portion 34 to the fulcrum shaft 28 is constituted by the same cylinder boss, and the second transmission wheel body 52 and the input portion 34 are connected by the cylinder boss 47.

[0063] As shown in Fig. 6, the wheel gear transmission part 56 includes an input shaft gear 56a held by the input shaft 53 of the rear axle case 27 and a rear axle gear 56b held by the rear axle 2a. The input shaft gear 56a and the rear axle gear 56b are meshed with each other. In the wheel gear transmission part 56, the rotational direction of the power from the input part 34 transmitted to the input shaft 53 is changed to the reverse rotational direction by the input shaft gear 56a and the rear axle gear 56b and output to the rear axle 2a. The gear diameter of the rear axle gear 56b is set larger than the gear diameter of the input shaft gear 56a.

[0064] In the second secondary transmission device 50, the power from the transmission device 17 transmitted to the input part 34 is transmitted to the rear axle 2a by the wheel power transmission mechanism 51. In the wheel power transmission mechanism 51, the power from the input part 34 transmitted to the second transmission wheel body 52 is transmitted to the rear axle 2a by the endless rotating transmission body 55, the transmission wheel body 54, and the wheel gear transmission part 56. The rotational direction of the power from the input part 34 transmitted to the input shaft 53 of the rear axle case 27 is changed to the power in the reverse rotational direction by the wheel gear transmission part 56 and transmitted to the rear axle 2a. The endless rotating transmission body 55 is maintained in the tension state necessary for power transmission by the tension operation member 59.

[0065] As shown in Fig. 6, brakes 60 are provided on the left and right output shafts 32 of the transmission device 17 inside the transmission case 19. The output shaft 32 is the output shaft of the rear wheel differential mechanism 20. In this embodiment, the left and right brakes 60 are multi-plate friction brakes. The left and right brakes 60 are configured to brake the output shaft 32. When the output shaft 32 is braked, the transmission member 33 is braked. When the transmission member 33 is braked, the braking force applied to the transmission member 33 is transmitted to the middle axle 3a via the primary transmission device 30 and the middle wheel power transmission mechanism 41. Further, the braking force applied to the transmission member 33 is transmitted to the rear axle 2a via the primary transmission device 30 and the wheel power transmission mechanism 51. When the transmission member 33 is braked by the brake 60, the middle wheel 3 and the rear wheel 2 are braked. By simply operating the brake 60 to engage, the middle wheel 3 and the rear wheel 2 can be braked.

[0066] As shown in FIGS. 7 and 10, in the middle portion 25c of the holding frame 25, an annular connecting member 62 connected to the outer wall portion 25f of the holding frame 25 via a lid member 61 described later is connected to an intermediate cylinder 48 rotatably fitted onto a fulcrum shaft 28, and a connecting portion 25g provided on the inner wall portion 25r of the holding frame 25 is rotatably connected to an end portion 31a held by the fulcrum shaft 28 in the transmission case 31. The middle portion 25c of the holding frame 25 is rotatably connected to the fulcrum shaft 28 via the lid member 61, the annular connecting member 62, the intermediate cylinder 48, and the transmission case 31. That is, the holding frame 25 is held by the vehicle body frame 15 in a state where it can swing up and down with the fulcrum axis Y of the fulcrum shaft 28 extending in the vehicle body width direction of the fulcrum shaft 28 as a swing fulcrum.

[0067] As shown in FIGS. 3, 13, and 14, a hydraulic cylinder 63 is connected to the rear portion of the holding frame 25, and the holding frame 25 can be swung by the hydraulic cylinder 63 as an actuator.

[0068] Specifically, as shown in FIGS. 13 and 14, in the present embodiment, the hydraulic cylinder 63 is a double-rod cylinder in which the cylinder rod 63a protrudes from both end portions of the cylinder tube 63b. A bifurcated connecting member 64 provided at the lower portion of the cylinder rod 63a and a cylinder connecting member 65 provided at the rear portion of the holding frame 25 are connected via a connecting pin 66. The cylinder rod 63a and the holding frame 25 are interlocked via the connecting member 64, the connecting pin 66, and the cylinder connecting member 65. A tube guard 67 provided on the cylinder tube 63b is connected to a support shaft 68 provided on the roll bar 13. The roll bar 13 is provided with support column portions 13a fixed to both lateral side portions of the vehicle body frame 15 and an upper roll bar portion 13b connected to the left and right support column portions 13a so as to be capable of switching between an upright posture and a fallen posture. The support shaft 68 is provided on the support column portion 13a. The cylinder tube 63b is supported by the support column portion 13a via the tube guard 67 and the support shaft 68.

[0069] As shown in Fig. 2, the portion of the cylinder rod 63a protruding upward from the cylinder tube 63b passes through the opening provided in the rear wheel fender 14 and protrudes upward from the rear wheel fender 14. As shown in Fig. 13, the portion of the cylinder rod 63a protruding upward from the cylinder tube 63b and the potentiometer 69 held by the support portion 13a of the roll bar 13 are connected via a link mechanism 70. The potentiometer 69 enables the detection of the lifting and lowering stroke of the cylinder rod 63a as the rocking stroke of the holding frame 25.

[0070] The hydraulic cylinder 63 swings the holding frame 25 with respect to the vehicle body frame 15 in a direction in which the wheel side portion 25d of the holding frame 25 descends and the middle wheel side portion 25e ascends by pushing down the cylinder connecting member 65 by the downwardly operating cylinder rod 63a. The hydraulic cylinder 63 swings the holding frame 25 with respect to the vehicle body frame 15 in a direction in which the wheel side portion 25d ascends and the middle wheel side portion 25e descends by pulling up the cylinder connecting member 65 by the upwardly operating cylinder rod 63a.

[0071] As shown in Figs. 3 and 7, a first positioning portion 71 is provided at the upper part of the middle wheel side portion 25e of the holding frame 25, and a second positioning portion 72 is provided at the upper part of the wheel side portion 25d of the holding frame 25. When the wheel side portion 25d of the holding frame 25 descends, the middle wheel side portion 25e ascends and the first positioning portion 71 abuts against the first stopper 73 (see Figs. 3 and 8) provided on the vehicle body frame 15, thereby setting the lower limit of the descent of the wheel side portion 25d and the upper limit of the ascent of the middle wheel side portion 25e. When the middle wheel side portion 25e of the holding frame 25 descends, the wheel side portion 25d ascends and the second positioning portion 72 abuts against the second stopper 74 (see Figs. 3 and 8) provided on the vehicle body frame 15, thereby setting the lower limit of the descent of the middle wheel side portion 25e and the upper limit of the ascent of the wheel side portion 25d. The first positioning portion 71, the second positioning portion 72, the first stopper 73, and the second stopper 74 set the swingable swing stroke of the holding frame 25.

[0072] As shown in FIG. 15, an operating device 76 is linked to the operation valves 75 of the hydraulic cylinder 63 that swings the left holding frame 25 and the hydraulic cylinder 63 that swings the right holding frame 25, respectively. The operating device 76 is configured to switch the operation valves 75 of the left and right hydraulic cylinders 63 by manual operation. In this embodiment, the operating tool of the operating device 76 is an operation switch (not shown). In addition to the operation switch, an operation lever can be adopted. Also, a remote operation device capable of wireless remote operation of the operation valve 75 can be adopted.

[0073] By switching the operation valve 75 to switch the hydraulic cylinder 63 to operate on the ascending side and the descending side of the cylinder rod 63a, the holding frame 25 is changed in posture to the first posture S1 shown in FIGS. 1 and 3 and the second posture S2 shown in FIG. 4 by the hydraulic cylinder 63.

[0074] As shown in FIGS. 1 and 3, when the holding frame 25 is changed in posture to the first posture S1, the middle wheel 3 is positioned on the ground G by the descent of the middle wheel side portion 25e of the holding frame 25. That is, the middle wheel 3 and the rear wheel 2 are brought into a grounded state by the holding frame 25. When the middle wheel 3 and the rear wheel 2 are brought into a grounded state, all of the front wheel 1, the middle wheel 3, and the rear wheel 2 are in contact with the ground. That is, the vehicle body travels on six wheels.

[0075] As shown in FIG. 4, when the holding frame 25 is changed in posture to the second posture S2, the middle wheel 3 rises and separates from the ground G by the ascent of the middle wheel side portion 25e of the holding frame 25. The middle wheel 3 is made non-grounded by the holding frame 25, and the rear wheel 2 is made grounded. When the middle wheel 3 is non-grounded and the rear wheel 2 is grounded, only the front wheel 1 and the rear wheel 2 of the front wheel 1, the middle wheel 3, and the rear wheel 2 are in contact with the ground. That is, the vehicle body travels on four wheels.

[0076] When operating and traveling, by changing the posture of the holding frame 25 to the first posture S1, the vehicle body 4 is supported by the grounding of all of the front wheels 1, the middle wheels 3, and the rear wheels 2. Therefore, it is possible to travel in a state where it is less likely to slip than when the posture of the holding frame 25 is changed to the second posture S2 and the middle wheels 3 are not grounded, and it is easy to travel straight ahead.

[0077] When turning, by changing the posture of the holding frame 25 to the second posture S2, the vehicle body 4 is supported by the grounding of only the front wheels 1 and the rear wheels 2 among the front wheels 1, the middle wheels 3, and the rear wheels 2. Therefore, it is possible to turn in a state where the turning resistance applied is smaller than when the posture of the holding frame 25 is changed to the first posture S1 and the middle wheels 3 are grounded.

[0078] When the middle wheels 3 are changed from the grounded state to the non-grounded state, the wheel-side portion 25d of the holding frame 25 is swing-operated downward by the hydraulic cylinder 63. Therefore, with the ground contact point of the rear wheels 2 as the reaction point, the fulcrum shaft 28 is pushed up, and the rear portion of the vehicle body frame 15 is pushed up with the front axle 1a as the swing fulcrum. In addition to this, the middle-wheel side portion 25e of the holding frame 25 is lifted by the hydraulic cylinder 63 with the fulcrum axis Y of the fulcrum shaft 28 as the swing fulcrum, and the middle wheels 3 are lifted. Since the vehicle body frame 15 is pushed up and the middle wheels 3 are lifted by the swing of the holding frame 25, the middle wheels 3 can be efficiently lifted from the ground.

[0079] By rocking the holding frame 25 from the first posture S1 further in the direction in which the middle wheel side portion 25e descends, with the contact point of the middle wheel 3 as the reaction point, the fulcrum shaft 28 is pushed up and the rear wheel 2 rises and separates from the ground G. That is, among the front wheel 1, the middle wheel 3, and the rear wheel 2, a state where only the front wheel 1 and the middle wheel 3 are in contact with the ground can be exhibited. The holding frame 25 can be rocked within a rocking range that extends over a rocking posture of the rear wheel floating in which the middle wheel 3 descends and contacts the ground and the rear wheel 2 separates from the ground G, and a rocking posture of the middle wheel floating in which the rear wheel 2 descends and contacts the ground and the middle wheel 3 separates from the ground G. By rocking the holding frame 25 to a rocking posture between the rocking posture of the rear wheel floating and the rocking posture of the middle wheel floating, the middle wheel 3 and the rear wheel 2 contact the ground.

[0080] As shown in FIG. 15, an accumulator 78 is connected to a hydraulic circuit 77 that connects an operation valve 75 and a hydraulic cylinder 63. In the present embodiment, the accumulator 78 is connected to a hydraulic circuit portion 77a of the hydraulic circuit 77 where the hydraulic cylinder 63 is operated on the descending side of the cylinder rod 63a. When pulsation or impact pressure acts on the hydraulic cylinder 63 due to the ground reaction force applied to the rear wheel 2 or the like, it is alleviated by the accumulator 78. The running vibration can be alleviated by the accumulator 78. In the present embodiment, the accumulator 78 is connected only to the hydraulic circuit portion 77a on the side of lowering the rear wheel 2 with respect to the vehicle body frame 15, but in addition to the hydraulic circuit portion 77a, the accumulator 78 may also be connected to a hydraulic circuit portion 77b on the side of raising the rear wheel 2 with respect to the vehicle body frame 15.

[0081] The connection of the fulcrum shaft 28 to the vehicle body frame 15 is performed based on a connecting device 80 shown in FIGS. 5 and 11.

[0082] As shown in FIGS. 5 and 11, the connecting device 80 is provided with a pair of left and right connecting frames 81 extending in the longitudinal direction of the vehicle body. A fulcrum shaft 28 is inserted and fixed to fulcrum shaft holding portions 82 formed at intermediate portions in the longitudinal direction of the vehicle body of the left and right connecting frames 81, respectively. In the present embodiment, the fixing of the fulcrum shaft 28 to the fulcrum shaft holding portion 82 is performed by welding. Connecting portions 83 are provided before and after the left and right connecting frames 81, respectively. The front connecting portion 83 is connected to a front holding portion 84 provided at the lower portion of the transmission case 19, and the rear connecting portion 83 is connected to a rear holding portion 85 provided at the lower portion of the transmission case 19, whereby the left and right connecting frames 81 are configured to be connected to the transmission case 19. The fulcrum shaft 28 is connected to the transmission case 19 of the vehicle body frame 15 via the left and right connecting frames 81.

[0083] As shown in FIG. 11, the connecting device 80 is provided with a fulcrum shaft changing mechanism 86 capable of changing the connecting position of the fulcrum shaft 28 in the vehicle body frame 15.

[0084] As shown in FIG. 11, the fulcrum shaft changing mechanism 86 includes a connecting bolt 87 for detachably connecting the front connecting portion 83 of the left and right connecting frames 81 to the front holding portion 84, bolt mounting holes 84a provided at a plurality of locations in the longitudinal direction of the vehicle body of the front holding portion 84, a connecting bolt 87 for detachably connecting the rear connecting portion 83 of the left and right connecting frames 81 to the rear holding portion 85, and bolt mounting holes 85a provided at a plurality of locations in the longitudinal direction of the vehicle body of the rear holding portion 85.

[0085] In the fulcrum shaft changing mechanism 86, the connection bolts 87 of the previous connecting portion 83 are replaced with the bolt mounting holes 84a at a plurality of locations on the front holding portion 84, and the connection bolts 87 of the subsequent connecting portion 83 are replaced with the bolt mounting holes 85a at a plurality of locations on the rear holding portion 85, whereby the connection position of the fulcrum shaft 28 on the vehicle body frame 15 is changed in the vehicle body longitudinal direction. In the present embodiment, as connection positions where the fulcrum shaft 28 can be connected, a first connection position P1, a second connection position P2, and a third connection position P3 that are arranged at intervals in the vehicle body longitudinal direction as shown in FIGS. 5 and 7 are set, and the connection position of the fulcrum shaft 28 is configured to be changeable stepwise at three locations in the vehicle body longitudinal direction. The first connection position P1 is the foremost connection position among the three connection positions. The third connection position P3 is the rearmost connection position among the three connection positions. The second connection position P2 is a connection position between the first connection position P1 and the third connection position P3.

[0086] For example, when towing a working device or during turning travel, by connecting the fulcrum shaft 28 to the vehicle body frame 15 at the third connection position P3, the ground reaction forces of the middle wheels 3 and the rear wheels 2 can be applied to the vehicle body frame 15 at a position rearward of when connected at the first connection position P1 or the second connection position P2.

[0087] For example, in the case of uneven ground, by connecting the fulcrum shaft 28 to the vehicle body frame 15 at the second connection position P2, the ground reaction forces of the middle wheels 3 and the rear wheels 2 can be applied to the vehicle body frame 15 at a position rearward of when connected at the first connection position P1 and forward of when connected at the third connection position P3.

[0088] For example, in the case of land leveling, by connecting the fulcrum shaft 28 to the vehicle body frame 15 at the first connection position P1, the ground reaction forces of the middle wheels 3 and the rear wheels 2 can be applied to the vehicle body frame 15 at a position forward of when connected at the second connection position P2 or the third connection position P3.

[0089] In this embodiment, a plurality of bolt mounting holes 84a at multiple locations on the front holding part 84 are arranged in the front-rear direction at the same interval as the interval between two connecting bolts 87 at two locations on the previous connecting part 83, and a plurality of bolt mounting holes 85a at multiple locations on the rear holding part 85 are arranged in the front-rear direction at the same interval as the interval between two connecting bolts 87 at two locations on the rear connecting part 83. Regardless of whether the first connection position P1, the second connection position P2, or the third connection position P3 is adopted as the connection position of the fulcrum shaft 28, two bolt mounting holes 84a out of the plurality of bolt mounting holes 84a at the front holding part 84 are adopted, and two bolt mounting holes 85a out of the plurality of bolt mounting holes 85a at the rear holding part 85 are adopted. When changing the connection position between the first connection position P1 and the second connection position P2, and when changing the connection position between the second connection position P2 and the third connection position P3, that is, when changing the connection position by one step in the front-rear direction, one of the two bolt mounting holes 84a, 85a is used as a common bolt mounting hole. In this embodiment, two bolt mounting holes 84a, 85a and two connecting bolts 87 are adopted, but one or three or more bolt mounting holes and one or three or more connecting bolts 87 may be adopted.

[0090] As shown in FIG. 7, fulcrum shaft mounting holes 88 are opened at three locations in the front-rear direction on the outer wall part 25f of the holding frame 25. When changing the connection position of the fulcrum shaft 28 on the vehicle body frame 15, the fulcrum shaft 28 is attached to the holding frame 25 through the fulcrum shaft mounting hole 88 corresponding to the connection position of the fulcrum shaft 28 on the vehicle body frame 15 among the three fulcrum shaft mounting holes 88. Thus, regardless of the change in the connection position of the fulcrum shaft 28 on the vehicle body frame 15, the front-rear positions of the middle wheel 3 and the rear wheel 2 with respect to the vehicle body 4 can be kept unchanged.

[0091] That is, when connecting the fulcrum shaft 28 at the first connection position P1, the fulcrum shaft 28 is attached to the holding frame 25 at the foremost fulcrum shaft mounting hole 88 among the three fulcrum shaft mounting holes 88. In this case, as shown in FIG. 8, the fulcrum shaft 28 is inserted through the foremost fulcrum shaft insertion hole 89 among the three fulcrum shaft insertion holes 89 opened in the inner wall portion 25r of the holding frame 25. When the fulcrum shaft 28 is attached at the foremost fulcrum shaft mounting hole 88 in this way, by attaching the first lid member 61a among the three types of lid members 61 shown in FIG. 16 to the surface side of the outer wall portion 25f, the fulcrum shaft mounting hole 88 without the fulcrum shaft 28 can be closed by the first lid member 61a. Also, as shown in FIG. 9, among the three output shaft insertion holes 90 opened in the transmission case 31 of the upper transmission device 30, the foremost output shaft insertion hole 90 is made to allow the output shaft 32 to pass through, enabling the change of the attachment position of the fulcrum shaft 28 in the holding frame 25.

[0092] When connecting the fulcrum shaft 28 at the second connection position P2, the fulcrum shaft 28 is attached to the holding frame 25 at the second fulcrum shaft mounting hole 88 from the front among the three fulcrum shaft mounting holes 88. In this case, the fulcrum shaft 28 is inserted through the second fulcrum shaft insertion hole 89 from the front among the three fulcrum shaft insertion holes 89. When the fulcrum shaft 28 is attached at the second fulcrum shaft mounting hole 88 in this way, by attaching the second lid member 61b among the three types of lid members 61 to the surface side of the outer wall portion 25f, the fulcrum shaft mounting hole 88 without the fulcrum shaft 28 can be closed by the second lid member 61b. Also, among the three output shaft insertion holes 90, the second output shaft insertion hole 90 from the front is made to allow the output shaft 32 to pass through, enabling the change of the attachment position of the fulcrum shaft 28 in the holding frame 25.

[0093] When connecting the fulcrum shaft 28 at the third connection position P3, among the three fulcrum shaft mounting holes 88, the fulcrum shaft 28 is attached to the holding frame 25 at the rearmost fulcrum shaft mounting hole 88. In this case, among the three fulcrum shaft insertion holes 89, the rearmost fulcrum shaft insertion hole 89 is configured such that the fulcrum shaft 28 passes through it. When the fulcrum shaft 28 is attached at the rearmost fulcrum shaft mounting hole 88 in this way, by attaching the third cover member 61c among the three types of cover members 61 to the surface side of the outer wall portion 25f, the fulcrum shaft mounting hole 88 without the fulcrum shaft 28 can be closed by the third cover member 61c. Further, among the three output shaft insertion holes 90, the rearmost output shaft insertion hole 90 is configured such that the output shaft 32 passes through it, enabling the change of the attachment position of the fulcrum shaft 28 in the holding frame 25.

[0094] As shown in FIG. 16, in each of the three types of cover members 61, there are formed a fulcrum shaft hole A1 into which the end portion of the fulcrum shaft 28 fits, a plurality of first bolt mounting holes A2 for attaching connection bolts for connecting the cover member 61 to the outer wall portion 25f, and a plurality of bolt mounting holes A3 for attaching connection bolts for connecting the annular connection member 62 (see FIG. 10).

[0095] In the present embodiment, a fulcrum shaft changing mechanism 86 is adopted in which the connection position of the fulcrum shaft 28 in the vehicle body frame 15 is changed stepwise in three positions in the vehicle body longitudinal direction, but it is not limited to this. For example, it is possible to adopt a fulcrum shaft changing mechanism in which the connection position of the fulcrum shaft 28 is changed stepwise in two positions or four or more positions in the vehicle body longitudinal direction. Further, a guide member for slidably holding the connection frame 81 is provided, and a fixing mechanism for fixing the connection frame 81 at an arbitrary position of the guide member is provided, and it is possible to adopt a fulcrum shaft changing mechanism in which the connection position of the fulcrum shaft 28 can be changed steplessly to an arbitrary position in the vehicle body longitudinal direction. It is possible to adopt a fulcrum shaft changing mechanism in which the connection position of the fulcrum shaft 28 can be changed in the vehicle body vertical direction. Further, it is possible to adopt a fulcrum shaft changing mechanism in which the connection position of the fulcrum shaft 28 can be changed in both the vehicle body longitudinal direction and the vehicle body vertical direction.

[0096] 〔Regarding the cover〕 As shown in FIGS. 1 and 2, the control unit 9 is provided with a step 12 as a floor portion located in front of and below the driver's seat 10, and entrance / exit openings 9a located above the step 12 on both lateral sides of the control unit 9. The middle wheels 3 are configured to be located laterally outside the step 12. As shown in FIGS. 1, 2, and 3, a cover 91 located beside the step 12 is provided inside the vehicle body width direction from the middle wheels 3. The cover 91 is attached to the outer surface side of a support member 92 erected at the lateral end of the step 12. The size of the cover 91 in the side view of the vehicle body is set to cover the lower part of the entrance / exit opening 9a from the lateral outside. Even if soil or the like is splashed by the middle wheels 3 and heads toward the control unit 9, it hits the cover 91, and thus the cover 91 prevents soil or the like from entering the control unit 9. In the present embodiment, the cover 91 is made of metal.

[0097] As shown in FIG. 1, the position of the upper end 91t of the cover 91 is configured to be higher than the position of the upper end 3t of the middle wheels 3. Even if soil or the like splashed by the middle wheels 3 is at a position higher than the upper end 3t of the middle wheels 3, it hits the cover 91.

[0098] As shown in FIG. 1, the position of the upper end 91t of the cover 91 is configured to be lower than the position of the upper end 2t of the rear wheels 2. The position of the upper end 91t of the cover 91 is configured to be higher than the position of the upper end 1t of the front wheels 1.

[0099] As shown in FIGS. 1, 2, and 3, a rear wheel fender 14 covering the rear wheels 2 is provided laterally outside the control unit 9. As shown in FIGS. 1 and 2, the rear wheel fender 14 is attached to the vehicle body frame 15 by a wall plate 9b extending from the inner edge of the rear wheel fender 14 in the vehicle body width direction toward the vehicle body frame 15. The wall plate 9b forms the lateral wall of the control unit 9.

[0100] As shown in FIGS. 2 and 3, an end portion 91r on the side where the rear wheel fender 14 of the cover 91 is located is configured to be positioned opposite to an end portion (the end portion facing the boarding and alighting opening 9a) on the side where the middle wheel 3 of the rear wheel fender 14 is located. More specifically, the end portion 91r of the cover 91 faces the end portion facing the boarding and alighting opening 9a of the rear wheel fender 14 from the front. Even if soil or the like splashed by the middle wheel 3 goes from the cover 91 toward the rear wheel fender 14, it is difficult to get into the control unit 9 from the end portion 91r of the cover 91.

[0101] As shown in FIGS. 1, 2, and 3, the engine bonnet 7 of the power unit 5 is provided at the front portion of the vehicle body 4 on the side opposite to the side where the rear wheel 2 is located with respect to the middle axle 3a of the middle wheel 3. In a side view of the vehicle body, the cover 91 is located across a position facing the end portion 7t on the side where the middle wheel 3 of the engine bonnet 7 is located and a position facing the end portion on the side where the middle wheel 3 of the rear wheel fender 14 is located. More specifically, the end portion 91f on the side where the engine bonnet 7 of the cover 91 is located faces the end portion 7t on the side where the middle wheel 3 of the engine bonnet 7 is located from below. The end portion 91r on the side where the rear wheel fender 14 of the cover 91 is located faces the end portion on the side where the middle wheel 3 of the rear wheel fender 14 is located from the front (the side opposite to the side where the rear wheel 2 is located). Even if soil or the like splashed by the middle wheel 3 goes from the cover 91 toward the power unit 5, it is difficult to get into the control unit 9 from the end portion 91f of the cover 91. Even if soil or the like splashed by the middle wheel 3 goes from the cover 91 toward the rear wheel fender 14, it is difficult to get into the control unit 9 from the end portion 91r of the cover 91.

[0102] 〔Regarding the boarding and alighting step〕 The rocking wheel is provided with a boarding and alighting step 93. Specifically, the middle wheel 3 that rocks is provided with the boarding and alighting step 93. More specifically, as shown in FIGS. 1 and 12, the boarding and alighting step 93 is provided at a portion of the lateral outer side of the middle wheel 3 that is located closer to the axle center side than the outer peripheral edge of the middle wheel 3. In the present embodiment, the boarding and alighting step 93 is attached to the rim 3b of the middle wheel 3. The boarding and alighting step 93 is provided with a mounting seat portion 93a (see FIG. 17), and the connection is performed by tightening and connecting the mounting seat portion 93a to the rim 3b. The connection of the mounting seat portion 93a to the rim 3b is performed by engaging a connection bolt mounted in a mounting hole 93d provided in the mounting seat portion 93a with the rim 3b. It is possible to board the control unit 9 and get off from the control unit 9 using the boarding and alighting step 93.

[0103] That is, when boarding the control unit 9, as shown in FIG. 12, place one foot on the boarding and alighting step 93. Using the boarding and alighting step 93 as a step, step onto the middle wheel 3, place the foot from the middle wheel 3 on the cover 91, and step over the cover 91 to enter the step 12 of the control unit 9. When getting off from the control unit 9, place one foot on the cover 91 from the step 12 of the control unit 9 and step onto the middle wheel 3. Place one foot from the middle wheel 3 on the boarding and alighting step 93 and get off onto the ground from the boarding and alighting step 93. By using the boarding and alighting step 93 in this way, it is easier to step onto the middle wheel 3 and board the control unit 9 than directly stepping onto the middle wheel 3 from the ground. It is easier to get off onto the ground and get off from the control unit 9 than directly getting off from the middle wheel 3 to the ground. Since the position of the upper end 91t of the cover 91 is lower than the position of the upper end 2t of the rear wheel 2, it is easier to step onto the cover 91 from the middle wheel 3. It is preferable for the operator to use the boarding and alighting step 93 when all six wheels are in contact with the ground (when the middle wheel 3 provided with the boarding and alighting step 93 is in contact with the ground).

[0104] As shown in FIGS. 1, 2, and 12, a handrail 94 is provided on the rear wheel fender 14. When getting on and off the vehicle with respect to the control unit 9, the body can be stabilized by holding the handrail 94 with one hand and the steering wheel 11 with the other hand.

[0105] As shown in FIGS. 1, 12, and 17, the boarding / alighting step 93 is configured such that its shape in the direction of view along the axle center 3c of the middle wheel 3 is circular. No matter what rotational position the middle wheel 3 stops at, it is easy to step on the boarding / alighting step 93 due to its circular shape.

[0106] As shown in FIGS. 12 and 17, the boarding / alighting step 93 is provided with a plurality of rod-shaped members 93b in the direction along the axle center 3c of the middle wheel 3 arranged in the circumferential direction of the boarding / alighting step 93. The plurality of rod-shaped members 93b are arranged in the circumferential direction of the boarding / alighting step 93 with adjacent rod-shaped members 93b spaced apart. The ends of the plurality of rod-shaped members 93b on the side opposite to the middle wheel side are connected by an annular connecting member 93c. Water, soil, etc. attached to the boarding / alighting step 93 easily fall out between the rod-shaped members 93b. As shown in FIG. 12, the connecting member 93c is configured not to protrude outward from the total width of the tire. Specifically, in the tire width direction, the position of the outer end of the connecting member 93c and the position of the outer end of the tire are the same. However, since the outer end of the rim 3b enters inside the outer end of the tire, the length of the boarding / alighting step 93 in the direction along the axle center 3c of the middle wheel 3 is relatively long, making it easy to step on the boarding / alighting step 93.

[0107] 〔Regarding the fuel tank〕 As shown in FIGS. 1 and 2, the engine bonnet 7 of the driving part 5 is provided at the front part of the vehicle body 4 on the side opposite to the side where the rear wheel 2 is located with respect to the middle axle 3a of the middle wheel 3. A fuel tank 8 for the engine is provided laterally outside the engine bonnet 7. In the present embodiment, the fuel tank 8 is provided laterally outside the right side of the engine bonnet 7. The fuel tank 8 is provided at a position higher than the upper end 91t of the cover 91. The fuel tank 8 is placed on a mounting table 95 and fixed to the mounting table 95 by a fixing band. The mounting table 95 is supported by front and rear columns 97 erected from a support frame 96 of the engine bonnet 7. As shown in FIG. 2, the fuel tank 8 and the holding frame 25 do not overlap in plan view. As shown in FIG. 1, the fuel tank 8 is located at a position higher than the upper end 1t of the front wheel 1 and higher than the upper end 3t of the middle wheel 3. The fuel tank 8 and the middle wheel 3 overlap in plan view. The fuel tank 8 and the boarding / alighting step 93 provided on the middle wheel 3 are located close to each other, and it is easy to refuel the fuel tank 8 by stepping on the boarding / alighting step 93.

[0108] Since the fuel tank 8 is located at a position higher than the upper end 91t of the cover 91 at a position on the side opposite to the side where the rear wheel 2 is located with respect to the middle axle 3a, it is difficult for dirt splashed by the middle wheel 3 to hit the fuel tank 8.

[0109] It is possible to adopt, instead of the fuel tank 8, a fuel tank integrally formed with the cover 91 by making the cover 91 of resin, or a fuel tank integrally formed with the rear wheel fender 14 by making the rear wheel fender 14 of resin.

[0110] 〔Alternative Embodiment〕 (1) FIG. 18 is a side view showing an alternative embodiment of an interlocking mechanism 98 for interlocking the hydraulic cylinder 63 and the holding frame 25. The interlocking mechanism 98 of the alternative embodiment has an interlocking accommodation part 99, and allows the holding frame 25 to swing up and down within a set range in the stopped state of the hydraulic cylinder 63 by the interlocking accommodation part 99.

[0111] Specifically, as shown in FIG. 18, the interlocking release portion 99 is configured such that the pin hole 100 of the bifurcated connecting member 64 provided on the cylinder rod 63a is formed as a long hole, and the connecting pin 66 is slidably engaged with the pin hole 100.

[0112] In the interlocking release portion 99, when the connecting pin 66 slides along the pin hole 100 with respect to the connecting member 64, the vertical swing of the holding frame 25 in the stopped state of the hydraulic cylinder 63 is allowed. The slidable stroke of the connecting pin 66 is set according to the length of the pin hole 100, and the set range in which the vertical swing of the holding frame 25 is allowed is set by this slide stroke.

[0113] (2) FIG. 19 is a side view showing another embodiment of the swing range setting structure for setting the swing range of the holding frame 25. In the swing range setting structure of the other embodiment, a stopper 101 fixed to the end portion of the fulcrum shaft 28 by a connecting bolt and fixed to the vehicle body frame 15 via the fulcrum shaft 28, and positioning projections 102 provided at two upper and lower positions of the lid member 61 are provided. The swingable range of the holding frame 25 is set by the stopper 101 and the positioning projections 102 at two upper and lower positions.

[0114] That is, in the swing range setting structure of another embodiment, when the wheel side portion 25d of the holding frame 25 descends, the lower positioning projection 102 of the two positioning projections 102 hits the stopper 101 to set the lower limit of the descent of the wheel side portion 25d and the upper limit of the ascent of the middle wheel side portion 25e. When the middle wheel side portion 25e of the holding frame 25 descends, the upper positioning projection 102 hits the stopper 101 to set the lower limit of the descent of the middle wheel side portion 25e and the upper limit of the ascent of the wheel side portion 25d.

[0115] (3) FIG. 20 is a side view showing still another embodiment of a swing range setting structure for setting the swing range of the holding frame 25. In the swing range setting structure of still another embodiment, a stopper 103 fixed to the end of the fulcrum shaft 28 by a connecting bolt and fixed to the vehicle body frame 15 via the fulcrum shaft 28, and a positioning projection 104 provided at one location on the lid member 61 are provided. An arc-shaped long hole 103a is opened in the stopper 103, and the positioning projection 104 is engaged with the long hole 103a. The swingable swing range of the holding frame 25 is set by the stopper 103 and the positioning projection 104.

[0116] That is, in the swing range setting structure of still another embodiment, when the wheel side portion 25d of the holding frame 25 descends, the positioning projection 104 rises inside the long hole 103a and hits the stopper 103 at the upper end of the long hole 103a, setting the lower limit of the descent of the wheel side portion 25d and the upper limit of the ascent of the middle wheel side portion 25e. When the middle wheel side portion 25e of the holding frame 25 descends, the positioning projection 104 descends inside the long hole 103a and hits the stopper 103 at the lower end of the long hole 103a, setting the lower limit of the descent of the middle wheel side portion 25e and the upper limit of the ascent of the wheel side portion 25d.

[0117] (4) FIG. 21 is a plan view showing a fuel tank installation structure of another embodiment. In the fuel installation structure of another embodiment, the fuel tank 8 is provided at a position higher than the upper end 91t of the cover 91 and inside the vehicle body width direction from the cover 91 on the right side and laterally outside of the engine bonnet 7.

[0118] (5) FIG. 22 is a plan view showing a fulcrum shaft changing mechanism 105 of another embodiment. In the fulcrum axis changing mechanism 105 of another embodiment, a front guide member 106 that slidably holds the left and right connection frames 81 on the front side of the vehicle body with respect to the fulcrum axis 28, a rear guide member 107 that slidably holds the left and right connection frames 81 on the rear side of the vehicle body with respect to the fulcrum axis 28, and a position changing cylinder 108 connected to the central portion of the fulcrum axis 28 in the vehicle body width direction are provided. The left and right front guide members 106 and the left and right rear guide members 107 are fixed to the lower portion of the vehicle body frame 15. In the present embodiment, the position changing cylinder 108 is a hydraulic cylinder.

[0119] In the fulcrum axis changing mechanism 105 of another embodiment, the fulcrum axis 28 is guided by the front guide member 106 and the rear guide member 107 by the expansion and contraction of the position changing cylinder 108 as an actuator and is moved in the vehicle body front-rear direction. The connection position of the fulcrum axis 28 on the vehicle body frame 15 is steplessly changed to an arbitrary position in the vehicle body front-rear direction by the position changing cylinder 108.

[0120] As shown in FIG. 23, a control device 110 is linked to an operation valve 109 of the position changing cylinder 108. A first detection device 111, a second detection device 112, a third detection device 113, and an artificial operation device 114 are linked to the control device 110. The control device 110 is constituted by a microcomputer.

[0121] The artificial operation device 114 has an operation part 114a that can be artificially operated, and is configured such that the connection position where the fulcrum axis 28 should be positioned is specified by the operation of the operation part 114a. The control device 110 controls the operation valve 109 in response to the specification by the artificial operation device 114 to expand and contract the position changing cylinder 108, and changes the connection position of the fulcrum axis 28 on the vehicle body frame 15 to the specified connection position by the position changing cylinder 108. The connection position of the fulcrum axis 28 on the vehicle body frame 15 can be adjusted by the artificial operation device 114 to a desired connection position.

[0122] In the manual operation device 114 of the present embodiment, the operation unit 114a is a dial, and the connection position of the fulcrum shaft 28 is specified by rotating the dial. As the manual operation device 114, in addition to the one operated by a dial, it may be one operated by a touch panel.

[0123] The first detection device 111 is configured to detect the operation of the steering operation tool 115 that performs the steering operation of the vehicle body 4. The control device 110 controls the operation valve 109 based on the detection result by the first detection device 111 to expand and contract the position change cylinder 108, and changes the connection position of the fulcrum shaft 28 on the vehicle body frame 15 to a connection position corresponding to the detection result by the first detection device 111 by the position change cylinder 108. For example, when the front wheel 1 is steered by a set angle or more from the straight-ahead direction to the left or right, the connection position of the fulcrum shaft 28 in this case is located behind the connection position of the fulcrum shaft 28 when the front wheel 1 is steered in the straight-ahead direction or in a steering state with an angle less than the set angle, and the connection position is changed.

[0124] In the present embodiment, the steering operation tool 115 is the steering wheel 11, and the first detection device 111 is a rotary potentiometer linked to the steering wheel 11. As the steering operation tool 115, in addition to the steering wheel 11, a steering lever or the like can be adopted. As the first detection device 111, in addition to a rotary potentiometer, a detection switch can be adopted.

[0125] The second detection device 112 is configured to detect the running surface state in front of the vehicle body 4. The control device 110 controls the operation valve 109 based on the detection result by the second detection device 112 to expand and contract the position change cylinder 108, and changes the connection position of the fulcrum shaft 28 on the vehicle body frame 15 to a connection position corresponding to the detection result by the second detection device 112 by the position change cylinder 108. For example, when the unevenness of the running surface is severe, the connection position of the fulcrum shaft 28 in this case is located behind the connection position of the fulcrum shaft 28 when the unevenness of the running surface is not so severe, and the connection position is changed.

[0126] In this embodiment, the second detection device 112 is a camera. As the second detection device 112, in addition to a camera, a ground sensor can be adopted. Further, based on the running surface state detected in the previous running and stored in the control device 110 and the position information of the vehicle body 4, a detection device that detects the stored running surface state as the running surface state at the running time point may be adopted as the second detection device 112.

[0127] The third detection device 113 is configured to detect the work content. The control device 110 controls the operation valve 109 based on the detection result by the third detection device 113 to expand and contract the position change cylinder 108, and changes the connection position of the fulcrum shaft 28 in the vehicle body frame 15 to the connection position corresponding to the detection result by the third detection device 113 by the position change cylinder 108. For example, in the case of a work content with a large towing load, the connection position of the fulcrum shaft 28 in this case is changed so as to be located on the rear side of the connection position of the fulcrum shaft 28 when the towing load is not so large.

[0128] In this embodiment, the third detection device 113 is configured to detect the work content by detecting, by contact or the like, a detected portion formed on a work device connected to the connection device 16, so as to detect what kind of work device the work device is, such as a rotary tiller, a roll roller, a chemical sprayer, or the like.

[0129] (6) In the above-described embodiment, the drive source is the engine 6, but the drive source is not limited to the engine 6, and an electric motor or a combination of an engine and an electric motor may be adopted.

[0130] (7) In the above-described embodiment, an example in which the middle wheel 3 is provided is shown, but it is possible to implement without the middle wheel 3. That is, in the case where the rear wheel 2 is located on the lateral outside of the step 12, the traveling device is configured by the front wheel 1 and the rear wheel 2 without the middle wheel 3.

[0131] (8) In the above-described embodiment, an example in which only one middle wheel 3 is provided has been shown, but two or more middle wheels 3 may be provided.

[0132] (9) In the above-described embodiment, an example in which both the front wheel 1 and the rear wheel 2 are drive wheels, and the outer diameter of the middle wheel 3 is smaller than the outer diameter of either the front wheel 1 or the rear wheel 2 has been shown, but it is not limited to this. Only one of the front wheel 1 and the rear wheel 2 may be a drive wheel. In the case where only one of the front wheel 1 and the rear wheel 2 is a drive wheel, the outer diameter of the middle wheel 3 may be smaller than the outer diameter of the drive wheel among the front wheel 1 and the rear wheel 2.

[0133] (10) In the above-described embodiment, an example in which the middle wheel 3 and the rear wheel 2 (drive wheel) are held by the holding frame 25 and supported by the vehicle body frame 15 via the holding frame 25 has been shown, but it may be the case where the holding frame 25 is not provided and the middle wheel 3 and the rear wheel 2 are directly supported by the vehicle body frame 15. Also, it may be the case where the middle wheel 3 is held by the holding frame 25 and the rear wheel 2 (drive wheel) is not held by the holding frame 25. In the case where the middle wheel 3 is held by the holding frame 25 and the rear wheel 2 (drive wheel) is not held by the holding frame 25, a fulcrum shaft 28 may be provided at an intermediate portion between the middle wheel holding portion 25a of the holding frame 25 and a wheel holding portion located outside the holding frame 25. This fulcrum shaft 28 is provided on the holding frame 25.

[0134] (11) In the above-described embodiment, an example in which the holding frame 25 is supported by the vehicle body frame 15 at the intermediate portion 25c has been shown, but the holding frame 25 may be swingably supported by the vehicle body frame 15 at any location.

[0135] (12) In the above-described embodiment, an example in which the fulcrum axis Y is located between the wheel holding portion 25b and the middle wheel holding portion 25a has been shown, but it may be located at any part of the holding frame 25.

[0136] (13) In the above-described embodiment, an example in which the holding frame 25 is supported by the vehicle body frame 15 so as to be swingable about the fulcrum axis Y has been shown. However, the holding frame 25 may be supported by the vehicle body frame 15 so as not to be swingable.

[0137] (14) In the above-described embodiment, an example in which the fulcrum shaft 28 is provided has been shown. However, as a structure for swingably connecting the holding frame 25 to the vehicle body frame 15, any connection structure such as a link mechanism in addition to the fulcrum shaft may be adopted.

[0138] (15) In the above-described embodiment, an example in which the fulcrum shaft 28 is provided in the intermediate portion 25c has been shown. However, it may be provided at any portion of the holding frame 25.

[0139] (16) In the above-described embodiment, the hydraulic cylinder 63 as an actuator for swing-operating the holding frame 25 is provided. However, it may be a structure without an actuator.

[0140] (17) In the above-described embodiment, a hydraulic cylinder is adopted as an actuator for swing-operating the holding frame 25. However, not limited to the hydraulic cylinder, an electric motor, a hydraulic motor, etc. can be adopted.

[0141] (18) In the above-described embodiment, the accumulator 78 is provided. However, it may be a structure without an accumulator.

[0142] (19) In the above-described embodiment, an example in which the holding frame 25 passes below the rear wheel fender 14 in a state of overlapping with the rear wheel fender 14 in a plan view has been shown. However, the holding frame 25 may be provided in any arrangement.

[0143] (20) In the above-described embodiment, an example in which the holding frame 25 passes through the space between the rear wheel 2 and the transmission case 19 in the front-rear direction has been shown. However, the holding frame 25 may be provided in any arrangement.

[0144] (21) In the above-described embodiment, an example in which the rear axle 2a is located laterally outside the vehicle body with respect to the holding frame 25 has been shown. However, the present invention is not limited to this, and it may be located in any arrangement with respect to the holding frame 25, such as laterally inside the vehicle body with respect to the holding frame 25.

[0145] (22) In the above-described embodiment, an example in which the center C1 of the holding frame 25 is located rearward of the center C2 of the vehicle body frame 15 has been shown. However, the present invention is not limited to this. The center C1 and the center C2 may be located at the same position in the longitudinal direction of the vehicle body, or the center C1 may be located forward of the center C2.

[0146] (23) In the above-described embodiment, an example in which the middle-wheel power transmission mechanism 41 and the wheel power transmission mechanism 51 are provided in the holding frame 25 has been shown. However, the middle-wheel power transmission mechanism 41 and the wheel power transmission mechanism 51 may not be provided in the holding frame 25.

[0147] (24) In the above-described embodiment, an example in which the middle-wheel power transmission mechanism and the wheel power transmission mechanism are provided inside the holding frame 25 has been shown. However, the present invention is not limited to this, and they may be provided outside the holding frame.

[0148] (25) In the above-described embodiment, an example in which the input unit 34 is provided has been shown. However, the input unit 34 may not be provided, and the driving force from the transmission device 17 may be individually transmitted to the middle-wheel power transmission mechanism 41 and the wheel power transmission mechanism 51.

[0149] (26) In the above-described embodiment, an example in which the middle-wheel power transmission mechanism 41 and the wheel power transmission mechanism 51 include an endless rotating chain has been shown. However, the present invention is not limited to this, and they may include a rotating transmission shaft.

[0150] (27) In the present embodiment, an example in which the first transmission wheel body 42 on the fulcrum shaft side, the second transmission wheel body 52, the transmission wheel bodies 44 and 54 on the wheel side, and the endless rotating transmission bodies 45 and 55 are provided has been shown. However, these may not be adopted.

[0151] (28) In this embodiment, an example in which the stretching operation members 49 and 59 and the biasing mechanisms 49a and 59a are provided has been shown, but they may not be provided.

[0152] (29) In the above-described embodiment, an example in which the transmission member 33 capable of performing a braking operation is provided has been shown, but the transmission member 33 may not be provided.

[0153] (30) In the above-described embodiment, an example in which the middle-wheel gear transmission part 46 and the wheel gear transmission part 56 are provided has been shown, but the middle-wheel gear transmission part 46 and the wheel gear transmission part 56 may not be provided. Further, when the middle-wheel gear transmission part 46 and the wheel gear transmission part 56 are provided, the middle-wheel gear transmission part 46 and the wheel gear transmission part 56 may output without changing the rotation direction from the input part 34 to the reverse direction.

[0154] (31) In the above-described embodiment, an example in which the rear wheel 2 is held by the wheel holding part 25b has been shown, but instead of the rear wheel 2, the front wheel 1 may be held.

[0155] (32) In the above-described embodiment, an example in which the position of the wheel-side part 25d is higher than the position of the middle-wheel-side part 25e and the wheel-side part 25d is in an inclined posture has been shown, but the shape of the holding frame 25 may be any shape.

[0156] (33) In the above-described embodiment, an example in which the position of the upper end 91t of the cover 91 is higher than the position of the upper end 3t of the middle wheel 3 has been shown, but it is not limited to this. The position of the upper end 91t of the cover 91 and the position of the upper end 3t of the middle wheel 3 may be the same in the vertical direction. Further, the position of the upper end 91t of the cover 91 may be lower than the position of the upper end 3t of the middle wheel 3.

[0157] (34) In the above-described embodiment, an example where the position of the upper end 91t of the cover 91 is lower than the position of the upper end 2t of the rear wheel 2 has been shown, but it is not limited to this. The position of the upper end 91t of the cover 91 and the position of the upper end 2t of the rear wheel 2 may be the same in the vertical direction. Also, depending on the size of the outer diameter of the rear wheel 2, the position of the upper end 91t of the cover 91 may be higher than the position of the upper end 2t of the rear wheel 2.

[0158] (35) In the above-described embodiment, an example where the end portion 91r of the cover 91 is located at a position facing the rear wheel fender 14 has been shown, but the end portion 91r of the cover 91 may not face the rear wheel fender 14.

[0159] (36) An example where the cover 91 is located across the position facing the end portion 7t of the engine bonnet 7 and the position facing the end portion of the rear wheel fender 14 has been shown, but it may not have this configuration.

[0160] (37) In the above-described embodiment, an example where the boarding / alighting step 93 is provided has been shown, but the boarding / alighting step 93 may not be provided.

[0161] (38) In the above-described embodiment, an example where the boarding / alighting step 93 is circular has been shown, but it may not be circular. For example, it may have any shape such as a rod shape extending outward from the center of the axle.

[0162] (39) In the above-described embodiment, an example where the rod-shaped members 93b arranged at intervals in the circumferential direction of the boarding / alighting step 93 are provided has been shown, but it may not have this rod-shaped member. That is, it may be circular without holes around the boarding / alighting step 93.

[0163] (40) In the above-described embodiment, an example where the fuel tank 8 is provided on the right outer side of the engine bonnet 7 has been shown, but it may be provided on the left outer side of the engine bonnet 7. The fuel tank 8 may be provided on both outer sides of the engine bonnet 7.

[0164] (41) In the above-described embodiment, an example in which an actuator for changing the position of the fulcrum shaft 28 is provided has been shown, but it may not be provided with an actuator.

[0165] (42) In the above-described embodiment, an example in which the position-changing cylinder 108 is adopted as the actuator has been shown. However, not limited to this, an electric motor, a hydraulic motor, or the like may be adopted.

[0166] (43) In the above-described embodiment, an example in which the first detection device 111, the second detection device 112, the third detection device 113, and the manual operation device 114 are provided has been shown. However, only one of these, or only two of these, or only three of these may be provided.

[0167] (44) In the above-described embodiment, the steering wheel 11 is adopted as the steering operation tool, but various operation tools with different forms such as a steering lever can be adopted.

[0168] (45) In the above-described embodiment, an example in which a connecting device is provided has been shown, but it may not be provided with a connecting device.

Industrial Applicability

[0169] The present invention can be applied not only to tractors but also to various working machines such as rice transplanters and chemical sprayers.

Explanation of Signs

[0170] 2 Rear wheels (wheels) 3 Middle wheels (wheels) 4 Vehicle body 6 Engine (power source) 11 Steering wheel (steering operation tool) 15 Vehicle body frame 25 Holding frame 28 Fulcrum shaft 42 First transmission wheel body (transmission wheel body) 44 Transmission wheel body 45 endless rotating transmission member 49 tensioning operation member 49a biasing mechanism 52 second transmission wheel body (transmission wheel body) 54 transmission wheel body 55 endless rotating transmission member 59 tensioning operation member 59a biasing mechanism 86 fulcrum axis changing mechanism 105 fulcrum axis changing mechanism 108 position changing cylinder (actuator) 111 first detection device 112 second detection device 113 third detection device 114 manual operation device Y fulcrum axis

Claims

1. A holding frame that is connected to a vehicle body frame via a fulcrum shaft having a fulcrum axis extending in the vehicle body width direction, and is supported by the vehicle body frame in a state where it can swing up and down with the fulcrum axis as a swing axis; A wheel that is held by the holding frame and is attached to the vehicle body frame in a state where it can swing up and down; A fulcrum axis changing mechanism for changing the position of the fulcrum axis, and a working machine provided with the same.

2. The working machine according to claim 1, wherein the fulcrum axis changing mechanism changes the position of the fulcrum axis to an arbitrary position with respect to the vehicle body frame.

3. The working machine according to claim 1, wherein the fulcrum axis changing mechanism changes the position of the fulcrum axis stepwise in the front-rear direction with respect to the vehicle body frame.

4. An actuator for changing the position of the fulcrum axis; An artificial operation device for designating the position of the fulcrum axis, and The working machine according to claim 1 or 2, wherein the fulcrum axis changing mechanism changes the position of the fulcrum axis with the actuator in response to the position designated by the artificial operation device.

5. An actuator for changing the position of the fulcrum axis; A first detection device for detecting the operation of a steering operation tool for performing a steering operation of the vehicle body, and The working machine according to claim 1 or 2, wherein the fulcrum axis changing mechanism changes the position of the fulcrum axis with the actuator in response to the detection result detected by the first detection device.

6. An actuator for changing the position of the fulcrum axis; A second detection device for detecting the running surface state in front of the vehicle body, and The working machine according to claim 1 or 2, wherein the fulcrum axis changing mechanism changes the position of the fulcrum axis with the actuator in response to the running surface state detected by the second detection device.

7. An actuator for changing the position of the fulcrum axis; A third detection device for detecting the work content, and The working machine according to claim 1 or 2, wherein the fulcrum axis changing mechanism changes the position of the fulcrum axis with the actuator in response to the work content detected by the third detection device.

8. A transmission wheel body on the fulcrum axis side provided on the fulcrum axis and to which power from a power source is transmitted; A transmission wheel body on the wheel side provided on the holding frame and transmitting power to the wheel; The working machine according to claim 1, further comprising an endless rotating transmission body wound around the transmission wheel body on the fulcrum axis side and the transmission wheel body on the wheel side.

9. A tensioning operation member for tensioning the endless rotating transmission body The working machine according to claim 8, further comprising a biasing mechanism that biases and presses the stretching operation member against the endless rotating transmission body.

Images