Working vehicle

Abstract

To provide a working vehicle capable of traveling at the same maximum traveling speed as in the case of wheels even when the maximum traveling speed is regulated or a crawler traveling device is mounted in place of the wheels.SOLUTION: A first transmission part 40 and a second transmission part 50 are provided in a transmission device 16 for changing the speed of power of a prime mover 12 and transmitting it to an axle 2a. When a first transmission wheel body 44 is attached to a first transmission shaft 42, and a second transmission wheel body 45 is attached to a second transmission shaft 43, the first transmission part 40 is brought into a speed-reducing transmission state in which speed-reducing transmission is performed from the first transmission shaft 42 to the second transmission shaft 43. When the second transmission wheel body 45 is attached to the first transmission shaft 42, and the first transmission wheel body 44 is attached to the second transmission shaft 43, the first transmission part is brought into a speed-increasing transmission state in which speed-increasing transmission is performed from the first transmission shaft 42 to the second transmission shaft 43. The drive speed of the axle 2a when the first transmission part 40 is set to the speed-increasing transmission state, and the second transmission part 50 is set to the highest speed transmission state is higher than the drive speed of the axle 2a when the first transmission part 40 is set to the speed-reducing transmission state, and the second transmission part 50 is set to the highest speed transmission state.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] As shown in Patent Document 1, there are Tracks (crawler running devices) equipped with a drive wheel (sprocket) attached to an axle (rear axle), a front guide wheel (front tension wheel), a rear guide wheel (rear roller), a ground contact roller, and a crawler belt. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-81144 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for a work vehicle that can travel not only by wheels but also by tracks (crawler travelling devices). In tracks that are configured with drive wheels attached to axles, the outer diameter of the drive wheels is generally smaller than the outer diameter of the wheels, so when tracks are attached, even if the axles are driven at the same drive speed as when wheels are attached, the vehicle's traveling speed will be slower than when wheels are attached.As a result, in the case of a work vehicle that has a specified maximum travelling speed, when wheels are attached, the vehicle can travel at the specified maximum speed, but when tracks are attached, it can only travel at a speed slower than the specified maximum speed.

[0005] To provide a work vehicle that can travel at the same maximum traveling speed as when wheels are attached or at a maximum traveling speed that is not significantly different from that when wheels are attached, even when a maximum traveling speed is regulated and tracks are attached instead of wheels. [Means for solving the problem]

[0006] The work vehicle according to the present invention comprises: The vehicle is provided with a prime mover, a transmission device that receives power from the prime mover, changes the speed of the input power, and outputs the power, and an axle that is driven by the power from the transmission device, and the transmission device is provided with a first transmission unit and a second transmission unit that are connected in series in a power transmission system that transmits the power from the prime mover to the axle, and the first transmission unit has first and second transmission rings that can be attached to a first transmission shaft located on the upstream side in the power transmission direction and a second transmission shaft located on the downstream side in the power transmission direction, and the first transmission rings are attached to the first transmission shaft and the second transmission rings are attached to the second transmission shaft, so that the power of the first transmission shaft is reduced in speed by the first and second transmission rings and transmitted to the second transmission shaft. and is configured to be switched to a speed-up transmission state such that the power of the first transmission shaft is increased in speed by the first transmission ring and the second transmission ring and is transmitted to the second transmission shaft by attaching the first transmission ring to the second transmission shaft, and is switched to a speed-up transmission state such that the power of the first transmission shaft is increased in speed by the first transmission ring and the second transmission ring and is transmitted to the second transmission shaft, and the transmission device is configured such that the drive speed of the axle in a first maximum speed transmission state in which the first transmission unit is switched to the speed-up transmission state and the second transmission unit is changed to the maximum speed transmission state is higher than the drive speed of the axle in a second maximum speed transmission state in which the first transmission unit is switched to the speed-down transmission state and the second transmission unit is changed to the maximum speed transmission state.

[0007] With this configuration, the speed difference between the axle drive speed in the first highest speed transmission state and the axle drive speed in the second highest speed transmission state is appropriately set in consideration of the difference in diameter between the wheel and the drive wheel of the track (crawler traveling device), and the transmission is switched to the first high-speed transmission state when the wheel is attached, and switched to the second high-speed transmission state when the track is attached, so that the peripheral speed of the wheel when the axle is driven at maximum speed with the wheel attached and the peripheral speed of the drive wheel when the track is attached and the axle is driven at maximum speed become the same or nearly the same. In other words, the traveling speed of the vehicle body when the wheel is driven at maximum speed and the traveling speed of the vehicle body when the track is driven at maximum speed can be made the same or nearly the same, so even if a maximum traveling speed is specified, even if tracks are attached instead of wheels, the vehicle can travel at the same maximum traveling speed as when wheels are attached or at a maximum traveling speed that is not significantly different.

[0008] In the present invention, The first transmission section includes a first transmission case that houses the first transmission wheel and the second transmission wheel, and it is preferable that the first transmission case and a second transmission case provided in the second transmission section are formed separately.

[0009] According to this configuration, by opening only the first transmission case of the first and second transmission cases, the first transmission wheel and the second transmission wheel can be replaced with the first transmission shaft and the second transmission shaft, making it easy to switch the first transmission section between a speed-down transmission state and a speed-up transmission state.

[0010] In the present invention, Preferably, the first transmission ring is a first gear, the second transmission ring is a second gear that engages with the first gear, and the outer diameter of the second gear is larger than the outer diameter of the first gear.

[0011] According to this configuration, the power of the first transmission shaft is transmitted to the second transmission shaft by the engagement between the first gear and the second gear, so that power can be transmitted from the first transmission shaft to the second transmission shaft without transmission loss regardless of whether the first gear or the second gear is replaced with the first transmission shaft or the second transmission shaft.

[0012] In the present invention, It is preferable that the first transmission wheel is a first belt pulley, the second transmission wheel is a second belt pulley connected to the first belt pulley by an endless belt, and the outer diameter of the second belt pulley is larger than the outer diameter of the first belt pulley.

[0013] According to this configuration, the power of the first transmission shaft is transmitted to the second transmission shaft by the first belt pulley, the endless belt, and the second belt pulley, so that power can be transmitted from the first transmission shaft to the second transmission shaft at low cost. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a side view of a multipurpose vehicle with front and rear wheels attached, viewed from the left side. [Figure 2] FIG. 1 is a side view of a multipurpose vehicle with Tracks (crawler traveling devices) attached, viewed from the left side. [Figure 3] FIG. 2 is a block diagram showing the drive structure of the front and rear axles. [Figure 4] FIG. 2 is a plan view showing the on-board charger and the charging port. [Figure 5] FIG. 2 is an explanatory diagram showing a charging procedure. [Figure 6] FIG. 2 is an explanatory diagram showing a charging procedure. [Figure 7] Schematic diagram of the drive structure of the wheels and tracks. [Figure 8] FIG. 4 is a cross-sectional view showing the first transmission portion in a speed reduction transmission state. [Figure 9] FIG. 4 is a cross-sectional view showing the first transmission portion in a speed-up transmission state. [Figure 10] FIG. 10 is a schematic diagram of a drive structure for wheels and tracks in another embodiment. [Figure 11] FIG. 10 is a schematic diagram of a drive structure for wheels and tracks in another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings. In the following explanation, with respect to the body of a multipurpose vehicle (an example of a "work vehicle"), the direction of arrow F shown in Figures 1 and 2 will be referred to as the "forward direction of the body," the direction of arrow B shown in Figures 1 and 2 will be referred to as the "rearward direction of the body," the direction of arrow U shown in Figures 1 and 2 will be referred to as the "upward direction of the body," the direction of arrow D shown in Figures 1 and 2 will be referred to as the "downward direction of the body," the direction toward the front of the paper in Figures 1 and 2 will be referred to as the "leftward direction of the body," and the direction toward the back of the paper in Figures 1 and 2 will be referred to as the "rightward direction of the body."

[0016] [Overall configuration of multipurpose vehicle] The utility vehicle shown in FIG. 1 is used for a variety of purposes, including transporting luggage and recreation. The utility vehicle includes a body 3 supported by a pair of left and right front wheels 1 that can be driven and steered, and a pair of left and right rear wheels 2 that can be driven. The body 3 includes a body frame 4 located at the bottom of the body 3 and extending in the longitudinal direction of the body 3, and a front lid 5 located at the front of the body 3. A front axle 1a that supports the front wheels 1 is drivably mounted in a front-wheel drive case 1b and is held to the body frame 4 via the front-wheel drive case 1b. A rear axle 2a that supports the rear wheels 2 is mounted in a transmission 16 and is held to the body frame 4 via the transmission 16. A driver's section 6, where a driver sits, is provided at the front of the body 3. The driver's section 6 includes a driver's seat 7, a steering wheel 8 that steers the front wheels 1, a dashboard 9, and a roof protector 10 that covers the passenger compartment. A loading platform 11 is supported on the body frame 4 behind the driver's section 6.

[0017] [Front and rear axle drive configuration] As shown in FIG. 1, an electric motor 12 as a prime mover, a continuously variable transmission 15, and a transmission 16 are provided below a loading platform 11.

[0018] As shown in FIG. 2, an electric motor 12 is connected to an inverter 13, and the inverter 13 is connected to a battery 14. The inverter 13 and the battery 14 are mounted on a vehicle body 3. An output portion (not shown) of the electric motor 12 is connected to an input portion (not shown) of a continuously variable transmission 15, and an output portion (not shown) of the continuously variable transmission 15 is connected to an input portion (not shown) of a transmission 16. A rear wheel differential mechanism 17 is provided in the transmission 16, and the rear wheel differential mechanism 17 is connected to the left and right rear axles 2a. A front wheel output shaft 18 is provided in the front portion of the transmission 16, and the front wheel output shaft 18 is connected to an input shaft 19a of a front wheel differential mechanism 19 (see FIG. 1) via a rotating shaft 18a (see FIG. 1). The front wheel differential mechanism 19 is connected to the left and right front axles 1a. The front wheel differential mechanism 19 is housed in a front wheel drive case 1b. In this embodiment, the continuously variable transmission 15 is a belt-type continuously variable transmission, but it may be a transmission such as a hydrostatic continuously variable transmission.

[0019] DC power output from battery 14 is introduced into inverter 13 and converted into AC power, and the AC power output from inverter 13 is introduced into electric motor 12 to drive electric motor 12. Power output from electric motor 12 is input into continuously variable transmission 15 and changed in speed, and power output from continuously variable transmission 15 is input into transmission 16 and converted into rear wheel drive force and front wheel drive force. The rear wheel drive force is transmitted to rear wheel differential mechanism 17 and from rear wheel differential mechanism 17 to the left and right rear axles 2a. Front wheel drive force is transmitted from front wheel output shaft 18 via rotating shaft 18a to front wheel differential mechanism 19 and from front wheel differential mechanism 19 to the left and right front axles 1a.

[0020] [Battery charging configuration] 1, a front panel section 20 constituting the front part of the vehicle body 3 includes a front lid 5 located at the upper part of the front panel section 20, a dash panel 21 separating the space inside the front lid 5 from the driver's section 6, and front side panels 22 located on the left and right sides of the front panel section 20. The front lid 5 is configured to be able to swing open and close up and down around a fulcrum axis P (see FIG. 1) located at the rear of the front lid 5 and extending in the vehicle width direction.

[0021] As shown in FIGS. 1 and 4 , an on-vehicle charger 25 capable of charging the battery 14 is provided in the space inside the front lid 5. The on-vehicle charger 25 is provided with a current-carrying cable 26 extending from the rear of the on-vehicle charger 25. The current-carrying cable 26 is flexible and can be bent. A power-receiving connector 27 is connected to the end of the current-carrying cable 26 opposite the on-vehicle charger side. The power-receiving connector 27 is connected to the on-vehicle charger 25 via the current-carrying cable 26 and can conduct electricity to the on-vehicle charger 25. In this embodiment, the current-carrying cable 26 is inseparably connected to the on-vehicle charger 25.

[0022] 1 and 4, charging port 28 is provided in left side portion 21a of the left side of the vehicle body and in right side portion 21b of the right side of the vehicle body. Left side portion 21a corresponds to the left side of dash panel 21, and right side portion 21b corresponds to the right side of dash panel 21.

[0023] The charging port portions 28 of the left and right lateral portions 21a, 21b are configured so that a power receiving connector 27 can be attached to the charging port portion 28 from inside the vehicle body, and the power receiving connector 27 can be removed from the charging port portion 28 to inside the vehicle body. When the power receiving connector 27 is attached to the charging port portions 28 of the left and right lateral portions 21a, 21b, a charging cable 29 can be connected to the power receiving connector 27 from the lateral outer side of the vehicle body, and the charging cable 29 can be removed from the power receiving connector 27 to the lateral outer side of the vehicle body. The charging cable 29 is connected to the power receiving connector 27 by connecting a power supply connector 30 (see FIG. 4) connected to the end of the charging cable 29 to the power receiving connector 27. The charging port portions 28 of the left and right lateral portions 21a, 21b are configured so that they can be opened and closed using removable caps 32 (see FIG. 4).

[0024] Charging port 28 on left side portion 21a and right side portion 21b is located at a position higher than the upper end 1t of front wheel 1. This makes it easier to prevent charging port 28 from becoming wet even when traveling through marshes or puddles.

[0025] Charging port units 28 in left lateral portion 21a and right lateral portion 21b are provided in locations above front wheels 1. Charging port units 28 are located near driver's section 6, making it easy to check the location of charging port units 28 on vehicle body 3 from driver's section 6. In this embodiment, charging port units 28 in left lateral portion 21a and right lateral portion 21b are provided in area A above front wheels 1 that corresponds to the diameter of front wheels 1, but charging port units 28 can also be provided in locations slightly offset in the front or rear of area A.

[0026] 4, distance L1 from cable connection point 25a, where current-carrying cable 26 of on-board charger 25 is connected, to charging port 28 in left side section 21a is set to be equal to distance L2 from cable connection point 25a to charging port 28 in right side section 21b. Whether power-receiving connector 27 is attached to charging port 28 in left side section 21a or right side section 21b, the length of current-carrying cable 26 can be set to a length that does not allow it to slacken too much.

[0027] The battery 14 can be charged in the following manner. 5 , when the vehicle is parked with a charging stand 35 (an example of a power source) located on the left side of the vehicle body 3, the front lid 5 is opened, the power receiving connector 27 is attached to the charging port 28 in the left side section 21a, and the cap 32 for the charging port 28 is removed to open the charging port 28. If the power receiving connector 27 was attached to the charging port 28 in the right side section 21b when it was stored, the power receiving connector 27 is transferred from the charging port 28 in the right side section 21b to the charging port 28 in the left side section 21a. The power supply connector 30 of the charging cable 29 is connected to the power receiving connector 27 attached to the charging port 28 in the left side section 21a, and the end of the charging cable 29 opposite to the charging port 28 is connected to the connector 35a of the charging stand 35, and power is supplied from the charging stand 35 to the on-board charger 25 via the charging cable 29 and the current-carrying cable 26.

[0028] 6 , when the vehicle is parked with the charging stand 35 located on the right side of the vehicle body 3, the front lid 5 is opened, the power receiving connector 27 is attached to the charging port 28 in the right side section 21b, and the cap 32 for the charging port 28 is removed to open the charging port 28. If the power receiving connector 27 was attached to the charging port 28 in the left side section 21a when it was stored, the power receiving connector 27 is transferred from the charging port 28 in the left side section 21a to the charging port 28 in the right side section 21b. The power supply connector 30 of the charging cable 29 is connected to the power receiving connector 27 attached to the charging port 28 in the right side section 21b, and the end of the charging cable 29 opposite to the charging port 28 is connected to the connector 35a of the charging stand 35, and power is supplied from the charging stand 35 to the on-board charger 25 via the charging cable 29 and the current-carrying cable 26.

[0029] The multipurpose vehicle shown in FIG. 2 is the multipurpose vehicle shown in FIG. 1, except that Tracks (crawler traveling devices) 60 are attached to the front axle 1a and rear axle 2a instead of the front wheels 1 and rear wheels 2.

[0030] [Tracks (crawler running device)] As shown in FIG. 2 , the tracks 60 of the front axle 1 a and the rear axle 2 a each include a drive wheel 61, a front guide wheel 62 located in front of and below the drive wheel 61, a rear guide wheel 63 located behind and below the drive wheel 61, a plurality of ground-contact wheels 64 located in a line in the front-to-rear direction between the front guide wheel 62 and the rear guide wheel 63, and a crawler belt 65. The crawler belt 65 is wound around the drive wheel 61, the front guide wheel 62, the ground-contact wheels 64, and the rear guide wheel 63. In this embodiment, the crawler belt 65 is made of rubber. The front guide wheel 62, the ground-contact wheels 64, and the rear guide wheel 63 are rotatably supported on a track frame 66. The rear guide wheel 63 is configured as a tension wheel. The drive wheel 61 is rotatably supported on the upper part of a support rod 67 extending upward from two positions, front and rear, of the track frame 66, and is attached to the front axle 1 a or the rear axle 2 a so as to be integrally rotatable and detachable. The truck frame 66 is supported on the front axle 1 a or the rear axle 2 a via a support rod 67 and a drive wheel 61 .

[0031] The Tracks 60 can be attached to and detached from the front axle 1 a and the rear axle 2 a by attaching and detaching the drive wheels 61 to and from the front axle 1 a and the rear axle 2 a. In the Tracks 60, the drive wheels 61 are driven by the front axle 1 a or the rear axle 2 a, and the crawler belts 65 are driven by the drive wheels 61.

[0032] [Wheels and Tracks Drive Structure] 7, in the continuously variable transmission 15, the power of the electric motor 12 is input to the input shaft 15a, and the input power is converted into power whose rotational speed is continuously variable and output from the output shaft 15b. In this embodiment, the continuously variable transmission 15 is composed of an input split pulley 15c whose belt winding diameter can be changed, an output split pulley 15d whose belt winding diameter can also be changed, an endless belt 15e, etc. The continuously variable transmission 15 is a belt-type continuously variable transmission.

[0033] As shown in Fig. 7, the transmission 16 has a power transmission system in which power from the electric motor 12 is input through the continuously variable transmission 15, and the input power is transmitted to the front axle 1a and the rear axle 2a after being speed-shifted. The transmission 16 is provided with a first transmission unit 40 and a second transmission unit 50. The first transmission unit 40 and the second transmission unit 50 are arranged to be connected in series in the power transmission system. In this embodiment, the first transmission unit 40 and the second transmission unit 50 are connected in an arrangement in which the first transmission unit 40 is located upstream of the second transmission unit 50 in the power transmission direction, but this is not limiting, and the first transmission unit 40 may be connected in an arrangement in which the first transmission unit 40 is located downstream of the second transmission unit 50 in the power transmission direction.

[0034] 7 and 8, the transmission case of the transmission 16 is made up of a first transmission case 41 and a second transmission case 52. The first transmission section 40 is provided with the first transmission case 41. The first transmission case 41 houses a first transmission shaft 42, a second transmission shaft 43, a first transmission wheel 44, and a second transmission wheel 45.

[0035] The first transmission shaft 42 and the second transmission shaft 43 are arranged in parallel. The first transmission shaft 42 is connected to the output shaft 15b of the continuously variable transmission device 15, and the second transmission shaft 43 is connected to the input shaft 51 of the second transmission unit 50. The first transmission shaft 42 is located upstream of the second transmission shaft 43 in the transmission direction, and the second transmission shaft 43 is located downstream of the first transmission shaft 42 in the transmission direction.

[0036] The first transmission ring 44 and the second transmission ring 45 are configured to be detachable from the first transmission shaft 42 and the second transmission shaft 43, respectively. More specifically, as shown in Fig. 8, the first transmission ring 44 and the second transmission ring 45 have spline holes 44a and 45a, respectively, and can be inserted into and removed from the spline shaft portions of the first transmission shaft 42 and the second transmission shaft 43 by removing detachable retaining rings 46 from the first transmission shaft 42 and the second transmission shaft 43, respectively. The first transmission ring 44 and the second transmission ring 45 are connected to the first transmission shaft 42 and the second transmission shaft 43, respectively, by spline engagement so as to be integrally rotatable. The first transmission ring 44 and the second transmission ring 45 are configured to be detachable and interlockingly connected by engagement. The outer diameter of the second transmission wheel 45 is set to be larger than the outer diameter of the first transmission wheel 44. In this embodiment, the first transmission wheel 44 is a first gear, and the second transmission wheel 45 is a second gear. The first gear and the second gear are engageable and disengageable, and the outer diameter of the second gear is set to be larger than the outer diameter of the first gear.

[0037] In the first transmission section 40, as shown in Fig. 8, the first transmission wheel 44 is attached to the first transmission shaft 42, and the second transmission wheel 45 is attached to the second transmission shaft 43, thereby establishing a speed-reduction transmission state in which the power of the first transmission shaft 42 is reduced by the first transmission wheel 44 and the second transmission wheel 45 and transmitted to the second transmission shaft 43. In the first transmission section 40, as shown in Fig. 9, the second transmission wheel 45 is attached to the first transmission shaft 42, and the first transmission wheel 44 is attached to the second transmission shaft 43, thereby establishing an speed-up transmission state in which the power of the first transmission shaft 42 is increased by the second transmission wheel 45 and the first transmission wheel 44 and transmitted to the second transmission shaft 43. The first transmission section 40 can be switched between a speed-down transmission state and a speed-up transmission state by switching the first transmission wheel 44 between the first transmission shaft 42 and the second transmission shaft 43, and by switching the second transmission wheel 45 between the first transmission shaft 42 and the second transmission shaft 43.

[0038] As shown in FIG. 8 and other figures, the first transmission case 41 and the second transmission case 52 of the first transmission unit 40 are formed as separate cases, and the first transmission case 41 is configured to be detachably attached to the second transmission case 52. In this embodiment, the first transmission case 41 is detachably attached to a lateral portion of the second transmission case 52. The first transmission case 41 is detachably attached to the second transmission case 52 using connecting bolts.

[0039] By removing the first transmission case 41 from the second transmission case 52 and opening it, the first transmission shaft 42 of the first transmission wheel 44 can be replaced with the second transmission shaft 43, and the second transmission shaft 45 can be replaced with the first transmission shaft 42 and the second transmission shaft 43. The first transmission case 41 can be closed by attaching it to the second transmission case 52.

[0040] As shown in Fig. 7, the second transmission section 50 is provided with a second transmission case 52. The second transmission case 52 houses a transmission mechanism 53. As shown in Fig. 7, the transmission mechanism 53 is provided with an input shaft 51 connected to the second transmission shaft 43 of the first transmission section 40, an output shaft 54 ​​arranged parallel to the input shaft 51, and a gear-type transmission section 55 provided between the input shaft 51 and the output shaft 54. The gear-type transmission section 55 is provided with a first shift gear 56 and a second shift gear 57 that can be shifted.

[0041] In the second transmission unit 50, by appropriately shifting the first shift gear 56 and the second shift gear 57, the second transmission unit 50 changes speed among a first forward speed forward transmission state in which the power transmitted from the first transmission unit 40 to the input shaft 51 is changed by the gear-type transmission unit 55 to forward power of the first forward speed and output from the output shaft 54, a second forward speed forward transmission state in which the power transmitted from the first transmission unit 40 to the input shaft 51 is changed by the gear-type transmission unit 55 to forward power of the second forward speed which is faster than the forward power of the first forward speed and output from the output shaft 54, and a reverse speed forward transmission state in which the power transmitted from the first transmission unit 40 to the input shaft 51 is changed by the gear-type transmission unit 55 to reverse power and output from the output shaft 54. The second forward speed forward transmission state of the second transmission unit 50 is the highest forward speed forward transmission state.

[0042] 7, the output from the output shaft 54 ​​of the second transmission unit 50 is transmitted to an intermediate shaft 59 connected to the output shaft 54 ​​via a gear mechanism 58, to the rear wheel differential mechanism 17 connected to the intermediate shaft 59 via a transmission gear 59a, and from the rear wheel differential mechanism 17 to the left and right rear axles 2a. The power transmitted from the output shaft 54 ​​of the second transmission unit 50 to the intermediate shaft 59 is transmitted to a front wheel output shaft 18 (see FIG. 2) protruding forward from the second transmission case 52, and is transmitted from the front wheel output shaft 18 to the front wheel differential mechanism 19 (see FIG. 1) via a rotary shaft 18a (see FIG. 1), and from the front wheel differential mechanism 19 to the left and right front axles 1a.

[0043] The transmission 16 is shifted to a first high-speed transmission state by switching the first transmission unit 40 to an increasing speed transmission state and the second transmission unit 50 to a forward transmission state of second forward speed, which is the highest speed transmission state, and is shifted to a second high-speed transmission state by switching the first transmission unit 40 to a decreasing speed transmission state and the second transmission unit 50 to a forward transmission state of second forward speed, which is the highest speed transmission state. The transmission 16 is configured so that a drive speed V1 of the front axle 1 a and rear axle 2 a when shifted to the first high-speed transmission state is faster than a drive speed V2 of the front axle 1 a and rear axle 2 a when shifted to the second high-speed transmission state.

[0044] When Tracks 60 are attached to the front axle 1 a and the rear axle 2 a, by shifting the transmission 16 to the first high-speed transmission state, the vehicle body 3 travels forward at the maximum traveling speed corresponding to the drive speed V1 of the front axle 1 a and the rear axle 2 a. When the front wheels 1 and the rear wheels 2 are attached, by shifting the transmission 16 to the second high-speed transmission state, the vehicle body 3 travels forward at the maximum traveling speed corresponding to the drive speed V2 of the front axle 1 a and the rear axle 2 a. Since the outer diameter of the drive wheels 61 of the Tracks 60 is smaller than the outer diameter of the front wheels 1 and rear wheels 2, when running on the Tracks 60, the front axles 1a and rear axles 2a can only be driven at the same maximum speed as when running on the front wheels 1 and rear wheels 2, and the vehicle can only run at a maximum running speed that is slower than the maximum running speed when running on the front wheels 1 and rear wheels 2. Therefore, the transmission 16 is configured so that the speed difference between the drive speed V1 and the drive speed V2 is the set speed difference V, which is set so that the maximum running speed when running on the Tracks 60 and the maximum running speed when running on the front wheels 1 and rear wheels 2 are the same or almost the same.

[0045] When front wheels 1 and rear wheels 2 are attached, the transmission 16 is shifted to the second high-speed transmission state to drive the front wheels 1 and rear wheels 2, and when Tracks 60 are attached instead of the front wheels 1 and rear wheels 2, the transmission 16 is shifted to the first high-speed transmission state to drive the Tracks 60, so that even when traveling with Tracks 60, the vehicle can travel at the same or nearly the same maximum traveling speed as when traveling with front wheels 1 and rear wheels 2.

[0046] Even if the maximum possible traveling speed is specified as the maximum traveling speed when the front wheels 1 and rear wheels 2 are attached and the transmission 16 is shifted to the second high-speed transmission state, even if Tracks 60 is attached, it is possible to travel at the same or nearly the same maximum traveling speed as the specified maximum traveling speed by shifting the transmission 16 to the first high-speed transmission state.

[0047] [Another embodiment] (1) Figures 10 and 11 are schematic diagrams of a drive structure for wheels and tracks according to another embodiment. In the drive structure according to the another embodiment, the first transmission wheel 44 of the first transmission unit 40 is a first belt pulley, the second transmission wheel 45 of the first transmission unit 40 is a second belt pulley, and the first transmission unit 40 is provided with an endless belt 47 wound around the first transmission wheel 44 and the second transmission wheel 45 to link the first transmission wheel 44 and the second transmission wheel 45. The outer diameter of the second belt pulley is set larger than the outer diameter of the first belt pulley.

[0048] In the first transmission section 40, as shown in FIG. 10, a first transmission wheel 44 is attached to the first transmission shaft 42, and a second transmission wheel 45 is attached to the second transmission shaft 43, and an endless belt 47 is wound around the first transmission wheel 44 and the second transmission wheel 45, thereby establishing a speed reduction transmission state in which the power of the first transmission shaft 42 is reduced by the first transmission wheel 44, the endless belt 47, and the second transmission wheel 45 and transmitted to the second transmission shaft 43. In the first transmission section 40, as shown in FIG. 11, a second transmission wheel 45 is attached to the first transmission shaft 42, and a first transmission wheel 44 is attached to the second transmission shaft 43, and an endless belt 47 is wound around the first transmission wheel 44 and the second transmission wheel 45, thereby establishing an increased speed transmission state in which the power of the first transmission shaft 42 is increased in speed by the second transmission wheel 45, the endless belt 47, and the first transmission wheel 44 and transmitted to the second transmission shaft 43.

[0049] The first transmission case 41 of the first transmission section 40 has a fixed case section 41a attached to the electric motor 12 and the second transmission case 52, and an openable / closable case section 41b that can be detached from the fixed case section 41a. By removing the openable / closable case section 41b from the fixed case section 41a and opening it, the first transmission wheel 44 and the second transmission wheel 45 can be replaced with the first transmission shaft 42 and the second transmission shaft 43.

[0050] (2) In the above embodiment, the electric motor 12 is provided as the prime mover. However, the prime mover may be an engine or a combination of an engine and an electric motor.

[0051] (3) In the above embodiment, the first transmission unit 40 is located upstream of the second transmission unit 50 in the transmission direction and is connected to the second transmission unit 50, but it may also be connected to the second transmission unit 50 downstream of the second transmission unit 50 in the transmission direction.

[0052] (4) In the above embodiment, the second transmission unit 50 is capable of shifting between two forward speed states, i.e., forward first speed and forward second speed, but is not limited to this and may be capable of shifting between three or more forward speed states.

[0053] (5) In the above-described embodiment, the first transmission case 41 and the second transmission case 52 are formed separately. However, the first transmission case 41 and the second transmission case 52 may be formed integrally, and the transmission case may be provided with an operating opening for replacing the first transmission wheel 44 and the second transmission wheel 45 with the first transmission shaft 42 and the second transmission shaft 43. [Industrial Applicability]

[0054] The present invention can be applied to various types of work vehicles such as tractors and rice transplanters in addition to multipurpose vehicles. [Explanation of symbols]

[0055] 1a Front axle (axle) 2a Rear axle (axle) 12 Electric motor (prime mover) 16 Transmission 40 First gear shift section 41 First Mission Case 42 First transmission shaft 43 Second transmission shaft 44 First transmission wheel 45 Second transmission wheel 50 Second gear shift section 52 Second Mission Case 47 endless belt

Claims

1. The prime mover and a transmission that receives power from the prime mover, changes the speed of the input power, and outputs the power; an axle driven by power from the transmission; the transmission device is provided with a first transmission unit and a second transmission unit connected in series in a power transmission system that transmits power from the prime mover to the axle, the first speed-changing unit has a first transmission wheel and a second transmission wheel that are switchably attached to a first transmission shaft located on the upstream side in the power transmission direction and a second transmission shaft located on the downstream side in the power transmission direction, and is configured so that when the first transmission wheel is attached to the first transmission shaft and the second transmission wheel is attached to the second transmission shaft, a speed-reduction transmission state is switched to so that the power of the first transmission shaft is reduced by the first transmission wheel and the second transmission wheel and is transmitted to the second transmission shaft, and when the first transmission wheel is attached to the second transmission shaft and the second transmission wheel is attached to the first transmission shaft, a speed-up transmission state is switched to so that the power of the first transmission shaft is increased by the first transmission wheel and the second transmission wheel and is transmitted to the second transmission shaft, The transmission device is configured so that the drive speed of the axle in a first maximum speed transmission state in which the first transmission unit is switched to the speed-increasing transmission state and the second transmission unit is changed to the maximum speed transmission state is faster than the drive speed of the axle in a second maximum speed transmission state in which the first transmission unit is switched to the speed-decreasing transmission state and the second transmission unit is changed to the maximum speed transmission state.

2. the first transmission portion includes a first transmission case that houses the first transmission wheel and the second transmission wheel, The work vehicle according to claim 1 , wherein the first transmission case and the second transmission case of the second transmission portion are formed separately.

3. the first transmission wheel is a first gear; the second transmission wheel is a second gear that engages with the first gear, 3. A work vehicle according to claim 1, wherein the outer diameter of the second gear is larger than the outer diameter of the first gear.

4. the first transmission wheel is a first belt pulley, the second transmission wheel is a second belt pulley connected to the first belt pulley by an endless belt, 3. A work vehicle according to claim 1, wherein the outer diameter of the second belt pulley is larger than the outer diameter of the first belt pulley.

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