JP6770928B2 - Transmission for work vehicles and work vehicles equipped with this - Google Patents

Description

In the present invention, the upper transmission shaft and the lower transmission shaft arranged adjacent to each other on the same axis in the front and rear, and the transmission state from the upper transmission shaft to the lower transmission shaft are displayed inside the transmission case. The present invention relates to a transmission for a work vehicle equipped with a transmission switching device for switching, and a work vehicle equipped with the transmission.

In the above-mentioned transmission for a work vehicle, the transmission switching device has a reduction mechanism for decelerating the power from the upper transmission shaft, and the power from the upper transmission shaft directly transmits the transmission state to the lower transmission shaft. It is equipped with a switching mechanism that switches between a speed state and a deceleration state that is transmitted via a deceleration mechanism, and the deceleration mechanism is integrated with the deceleration shaft arranged parallel to the upper transmission shaft and the lower transmission shaft, and the upper transmission shaft. The first reduction gear arranged on the shaft of the transmission shaft on the good side in the rotating state, the second reduction gear and the third reduction gear arranged on the shaft of the reduction shaft in the state of being integrally rotated with the reduction shaft, and the poor It has a fourth reduction gear arranged on the shaft of the lower transmission shaft in a state of rotating relative to the side transmission shaft, and the switching mechanism is on the axis of the upper transmission shaft in a state of being integrally rotated with the upper transmission shaft. The first meshed rotating body arranged in the above and the second meshed rotating body arranged on the shaft of the lower transmission shaft so as to rotate relative to the lower transmission shaft in a state of being integrally rotated with the fourth reduction gear. , Lower side transmission so that it rotates integrally with the lower side transmission shaft in a state where movement in the axial direction is allowed between the constant velocity position that meshes with the first meshed rotating body and the deceleration position that meshes with the second meshed rotating body. Some are configured to have a meshing rotating body arranged on the shaft of the shaft (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2001-105912 (paragraph number 0028, FIGS. 3-4)

In the configuration described in Patent Document 1, the switching mechanism includes a first meshed rotating body arranged on the shaft of the upper transmission shaft, a second meshed rotating body arranged on the shaft of the lower transmission shaft, and a second meshed rotating body. The meshing rotating body is dispersedly assembled on the upper transmission shaft and the lower transmission shaft. Therefore, the meshing rotating body assembled on the lower transmission shaft has a constant velocity position where it meshes with the first meshed rotating body assembled on the upper transmission shaft, and the second meshed rotating body assembled on the lower transmission shaft. When confirming the operation of whether or not the vehicle moves normally over the deceleration position where the first meshed rotating body is assembled, the upper transmission shaft to which the first meshed rotating body is assembled and the second meshed rotating body and the meshing rotating body are used. It is necessary to assemble the assembled lower transmission shafts so that they are located adjacent to each other in the front-rear direction on the same axis. Then, if a problem occurs in this operation check, it is necessary to release the assembly of the upper transmission shaft and the lower transmission shaft in order to make fine adjustments to the meshing rotating body or the first meshed rotating body. .. As a result, there is room for improvement in facilitating assembly including confirmation of operation of the switching mechanism.

That is, it is desired that the assembly including the operation check of the switching mechanism can be easily performed.

As a means to solve the above problems
The transmission for a work vehicle according to the present invention includes an upper transmission shaft and a lower transmission shaft arranged adjacent to each other on the same axis in the front-rear direction, and from the upper transmission shaft to the lower transmission. Equipped with a transmission switching device that switches the transmission state to the shaft
The transmission switching device includes a deceleration mechanism for decelerating the power from the upper transmission shaft, a constant velocity state in which the power from the upper transmission shaft is directly transmitted to the lower transmission shaft, and the deceleration mechanism. Equipped with a switching mechanism to switch to the deceleration state transmitted via
The deceleration mechanism includes a deceleration shaft arranged in parallel with the upper transmission shaft and the lower transmission shaft, and the upper transmission shaft in a state where movement in the axial direction with respect to the upper transmission shaft is permitted. A first reduction gear arranged on the shaft of the upper transmission shaft so as to rotate integrally, and a second reduction gear and a third reduction gear arranged on the shaft of the reduction shaft while rotating integrally with the reduction shaft. It has a gear and a fourth reduction gear arranged on the shaft of the lower transmission shaft in a state of rotating relative to the lower transmission shaft.
The switching mechanism is arranged on the axis of the upper transmission shaft so as to rotate integrally with the upper transmission shaft in a state where movement in the axial direction with respect to the upper transmission shaft is permitted. The rotating body, the second meshed rotating body arranged on the shaft of the lower transmission shaft so as to rotate relative to the lower transmission shaft in a state of being integrally rotated with the fourth reduction gear, and the first covering. The lower side transmission shaft so as to rotate integrally with the lower side transmission shaft in a state where movement in the axial direction is allowed between the constant velocity position that meshes with the meshing rotating body and the deceleration position that meshes with the second meshed rotating body. It has a meshing rotating body arranged on the shaft of the above, and is assembled to the lower transmission shaft together with the first reduction gear and the fourth reduction gear .
The transmission case has a structure in which an upper case having the upper transmission shaft and a lower case having the lower transmission shaft are connected to each other.
The upper case is provided with a vertical first support wall at an end on the side of the lower case, and the first support wall is in a state where the upper case and the lower case are connected to each other. It is arranged at a position where it enters the inside of the lower case, and the first support wall supports the upper transmission shaft in a penetrating state .

According to this means, by assembling the switching mechanism together with the first reduction gear and the fourth reduction gear to the lower transmission shaft, the meshing rotating body has a constant velocity position where it meshes with the first meshed rotating body and the second meshed rotating body. It is possible to confirm the operation of whether or not the vehicle moves normally over the deceleration position where it meshes with. Then, if a problem occurs in this operation check, the problem can be solved by making fine adjustments to the meshing rotating body or the first meshed rotating body assembled to the lower transmission shaft. As a result, assembly including confirmation of operation of the switching mechanism can be facilitated.

As one of the means for making the present invention more suitable,
The transmission case, in the arrangement position of the transmission switching device is configured to split structure which is divided into said downstream side case with the downstream side transmission shaft and the upstream side case with the upstream side transmission shaft,
In the deceleration mechanism and the switching mechanism, the first reduction gear and the first meshed rotating body are arranged on the axis of the upper transmission shaft in association with the connection between the upper case and the lower case. The deceleration is performed so that the first reduction gear and the first meshed rotating body are removed from the shaft of the upper transmission shaft as the connection between the upper case and the lower case is released. The entire mechanism and the entire switching mechanism are assembled to the lower case together with the lower transmission shaft.

According to this means, when assembling the transmission switching device to the transmission case, the deceleration mechanism and the switching mechanism can be assembled to the lower case together with the lower transmission shaft from the split end side of the lower case with the upper case. it can. Then, after this assembly, the reduction mechanism and switching are performed by connecting the upper case and the lower case so that the first reduction gear and the first meshed rotating body are arranged on the axis of the upper transmission shaft. The mechanism can be assembled to the transmission case so as to extend over the upper transmission shaft and the lower transmission shaft. That is, the transmission switching device can be easily assembled inside the transmission case so as to cover the upper transmission shaft and the lower transmission shaft.

When removing the transmission switching device from the transmission case, the first reduction gear and the first meshed gear are engaged by releasing the connection between the upper case and the lower case and separating the upper case and the lower case. The rotating body can be removed from the shaft of the upper transmission shaft, and the entire reduction mechanism and the entire switching mechanism can be left in the lower case together with the lower transmission shaft and the like. Then, the deceleration mechanism and the switching mechanism remaining in the lower case can be removed from the lower case together with the lower transmission shaft and the like from the split end side of the lower case with the upper case. That is, the transmission switching device can be easily removed from the transmission case, which facilitates maintenance of the transmission switching device and the like.

As one of the means for making the present invention more suitable,
The first reduction gear and the first meshed rotating body are integrally formed.

According to this means, as compared with the case where the first reduction gear and the first meshed rotating body are individually formed independently, it is possible to simplify the configuration by reducing the number of parts.

As one of the means for making the present invention more suitable,
The speed reduction mechanism is a creep speed change mechanism that reduces the power from the upper transmission shaft at an ultra-low speed.

According to this means, it is possible to reduce the output rotation speed of the work vehicle transmission to an ultra-low speed, and at the same time, it is possible to easily attach / detach the creep transmission to / from the transmission case.

As a means to solve the above problems
The work vehicle according to the present invention includes the work vehicle transmission.

According to this means, by providing the above-mentioned transmission for a work vehicle, it is possible to provide a work vehicle that can be easily assembled including checking the operation of the switching mechanism.

It is a left side view of a tractor. It is the schematic of the transmission for a work vehicle which shows the transmission system of a tractor. It is a cross-sectional plan view of the transmission for a work vehicle which shows the transmission system of a tractor. It is a cross-sectional plan view of the main part which shows the structure of the 1st transmission mechanism in a main transmission. It is a cross-sectional plan view of the main part which shows the structure of the 2nd transmission mechanism of a main transmission and a creep transmission. It is a vertical sectional left side view of the main part which shows the structure of the 1st transmission shaft side in the auxiliary transmission. It is a vertical sectional left side view of the main part which shows the structure of the 2nd transmission shaft side in the auxiliary transmission. It is a vertical sectional front view of a transmission for a work vehicle which shows arrangement of a transmission shaft. It is a vertical sectional front view of a transmission for a work vehicle which shows the shape of a valve unit mounting part and a storage chamber. It is a perspective view of the valve unit mounting part in the transmission for a work vehicle. 9 is a cross-sectional view of XII-XII in FIG. 9 (longitudinal left side view of a valve unit mounting portion). It is a right side view of a valve unit. It is a vertical cross-sectional left side view of the main part which shows the state which divided the transmission case provided with the creep transmission of a reference form into front and back at the place where the creep transmission is arranged. It is a vertical cross-sectional left side view of the main part which shows the state which divided the transmission case into front and back at the place where a creep transmission is arranged.

Hereinafter, as an example of a mode for carrying out the present invention, an embodiment in which the transmission for a work vehicle according to the present invention is applied to a tractor as an example of a work vehicle will be described with reference to the drawings.
The direction indicated by the arrow of reference numeral F shown in FIGS. 1 and 11 is the front side of the tractor, and the direction indicated by the arrow of reference numeral U is the upper side of the tractor.

As shown in FIG. 1, the tractors exemplified in the present embodiment include a driving unit 1 arranged in the front half of the vehicle body, a boarding-type driving unit 2 arranged in the latter half of the vehicle body, and a transmission for a work vehicle (hereinafter,). (Called a transmission) 3, a fuel tank 4 arranged adjacent to the left side of the transmission 3, left and right front wheels 5 arranged to be driveable and steerable to the left and right of the prime mover 1, and driveable to the left and right of the transmission 3. The left and right rear wheels 6 are arranged, and a link mechanism 7 for connecting a working device attached to the rear end of the transmission 3 so as to be able to move up and down is provided.

The driving unit 1 includes a front frame 8 arranged on the front side of the vehicle body, an engine 9 supported on the rear side of the front frame 8, a swing-opening / closing bonnet 10 covering the engine 9 and the like. I have. The engine 9 has an output shaft 9A (see FIG. 2) that projects rearward toward the rear transmission 3.

The driver unit 2 includes a cabin 11 that is vibration-proof supported by the transmission 3, a steering wheel 12 for steering wheel that is arranged on the inner front side of the cabin 11, and a driver's seat that is arranged on the inner rear side of the cabin 11. It is equipped with 13.

As shown in FIGS. 1 to 3, the transmission 3 includes a transmission case (hereinafter referred to as a T / M case) 14 that also serves as a rear frame of a vehicle body and an oil tank, and an input shaft 15 into which power from an engine 9 is input. First output shaft 16 for front wheels that outputs power for front wheel drive, left and right second output shafts 17 for rear wheels that output power for rear wheel drive, PTO shaft 18 that outputs power for work, input The traveling transmission system 19 that transmits the power input to the shaft 15 to the first output shaft 16 and the left and right second output shafts 17, and the work transmission system 20 that transmits the power input to the input shaft 15 to the PTO shaft 18. And so on. The axes of the first output shaft 16 and the PTO shaft 18 are set in the front-rear direction of the vehicle body. The left and right second output shafts 17 have their axial center directions set to the left and right directions of the vehicle body.

The T / M case 14 is bolted to the rear ends of the first case 21, bolted to the rear end of the engine 9, the second case 22 bolted to the rear end of the first case 21, and the second case 22. The third case 23, the fourth case 24 bolted to the rear end of the third case 23, the fifth case 25 bolted to the lower end of the second case 22, and the left and right left and right ends of the fourth case 24. The left and right sixth cases 26, which are connected by bolts, are provided. That is, the T / M case 14 is configured in a 7-divided structure that can be divided into 7 cases 21 to 26. The second case 22 has a front cover 27 bolted to the inner flange 22A thereof, a first support wall 28 bolted to the rear end of the second case 22, and the like. In the second case 22, a partition wall 22B that divides the internal space into a front space and a rear space is integrally formed. The third case 23 has a second support wall 29 and the like bolted to the connecting portion 23A inside the case 23. At the rear end of the third case 23, a partition wall 23B that partitions the internal space and the internal space of the fourth case 24 is integrally formed. The fourth case 24 includes a rear cover 30 and the like that are bolted to the rear end.

As shown in FIGS. 2 to 9, the traveling transmission system 19 is an electro-hydraulic control type forward / backward switching device 31 that switches the power input to the input shaft 15 between the power for forward traveling and the power for reverse traveling. An electro-hydraulic control type main transmission 32 that shifts the running power from the advance switching device 31 to eight stages, a creep transmission 33 that shifts the traveling power from the main transmission 32 to two stages, and a creep transmission. The auxiliary transmission 34 that shifts the driving power from 33 to three stages, the distribution shaft 35 that distributes the traveling power from the auxiliary transmission 34 back and forth, and the front wheels that distribute the traveling power distributed by the distribution shaft 35. A reduction gear set 36 that decelerates for driving, an electro-hydraulic control type drive switching unit 37 that switches the transmission state from the reduction gear set 36 to the first output shaft 16, and a distribution shaft that allows differential between the left and right rear wheels 6. Left and right planetary gear type deceleration that decelerates the running power from the rear wheel differential device 38 that distributes the running power from 35 to the left and right rear wheels 6 and the running power from the rear wheel differential device 38 for rear wheel drive. The device 39 and the left and right side brakes 40 that act on the left and right differential shafts 38A of the rear wheel differential device 38 are provided.

The rear wheel differential device 38 includes a hydraulic differential switching mechanism 38B that switches its operating state between a differential allowable state and a differential stop state. The left and right planetary gear type speed reducers 39 transmit the power after deceleration by them to the left and right rear wheels 6 via the left and right second output shafts 17.

As shown in FIG. 1, the power for driving the front wheels from the first output shaft 16 is externally transmitted while allowing the differential between the external transmission shaft 41 that rotates integrally with the first output shaft 16 and the left and right front wheels 5. The power for driving the front wheels from the shaft 41 is transmitted to the left and right front wheels 5 via a front wheel differential device (not shown) that distributes the power for driving the front wheels to the left and right front wheels 5. The front wheel differential device includes a hydraulic differential switching mechanism that switches the operating state between the differential allowable state and the differential stop state.

As shown in FIGS. 2 to 3 and 8, the work transmission system 20 has a work power transmission upper relay shaft 42 arranged on the same axis as the input shaft 15 in a state of being integrally rotated with the input shaft 15. It is provided with a lower side relay shaft 43, a working power switching device 44 for switching a transmission state from the lower side relay shaft 43 to the PTO shaft 18, and the like.

As shown in FIGS. 2 to 3 and 9, the forward / backward switching device 31 inputs the forward multi-plate clutch 45, the reverse multi-plate clutch 46, and the input shaft 15 arranged on the input shaft 15. The reverse rotation shaft 47 arranged in parallel with the shaft 15, the forward output gear 48 that outputs the power transmitted via the forward multi-plate clutch 45 as the forward power, and the reverse multi-plate clutch 46 transmit the power. It includes a reverse gear set 49 that transmits the generated power to the reverse rotation shaft 47, a reverse rotation output gear 50 that outputs the reverse rotation power of the reverse rotation shaft 47 as reverse rotation power, and the like. That is, the forward / reverse forward switching device 31 employs a multi-plate clutch type transmission switching device in which the transmission state is switched by the intermittent operation of the two multi-plate clutches 45 and 46 for the front wheel and the reverse movement.

In the forward / backward switching device 31, the front end side of the input shaft 15 and the front end portion of the reverse rotation shaft 47 are supported by the front cover 27, and the rear end portion of the input shaft 15 and the rear end portion of the reverse rotation shaft 47 are second. By being supported by the partition wall 22B of the case 22, it is arranged in the front space inside the second case 22.

As shown in FIGS. 2 to 5 and 8 to 9, the main transmission 32 has a first transmission shaft 51 for input, a second transmission shaft 52 for relay, a third transmission shaft 53 for output, and a first transmission. Eight-speed transmission including a first transmission mechanism 54 that shifts the power input to the shaft 51 in four stages, and a second transmission mechanism 55 that shifts the power after shifting by the first transmission mechanism 54 in two stages of high and low. It is composed of expressions. The first transmission mechanism 54 interrupts transmission to four sets of transmission gear sets 56 to 59 and corresponding transmission gear sets 56 to 59 that transmit from the first transmission shaft 51 to the second transmission shaft 52 at different gear ratios. It has four gear shifting multi-plate clutches 60 to 63, and the like. The second transmission mechanism 55 interrupts the power from the two sets of reduction gear sets 64 and 65 and the corresponding reduction gear sets 64 and 65 that are transmitted from the second transmission shaft 52 to the third transmission shaft 53 at different gear ratios. It has two deceleration multi-plate clutches 66, 67, and the like. That is, the main transmission 32 includes a multi-plate clutch type transmission switching device whose transmission state is switched by intermittent operation of four transmission multi-plate clutches 60 to 63 and two reduction multi-plate clutches 66 and 67. It has been adopted.

In the main transmission 32, the front end portions of the transmission shafts 51 to 53 are supported by the partition wall 22B of the second case 22, and the rear end portions of the transmission shafts 51 to 53 are supported by the first support wall 28. Therefore, it is arranged in the rear space inside the second case 22.

In the main transmission 32, the three transmission shafts 51 to 53 are arranged in parallel with their axial center directions set in the front-rear direction of the vehicle body. The second transmission shaft 52 employs a tubular shaft that is externally fitted to the upper relay shaft 42 of the work transmission system 20 so as to be relatively rotatable. The third transmission shaft 53 is arranged adjacent to the front and rear on the same axis as the first transmission shaft 68 for input in the auxiliary transmission 34.

As shown in FIGS. 2 to 3 and 5, in the creep transmission 33, the third transmission shaft 53 of the main transmission 32 serves as a transmission shaft on the upper side with respect to the creep transmission 33, and the first transmission of the auxiliary transmission 34 The shaft 68 is arranged between the third transmission shaft 53 of the main transmission 32 and the first transmission shaft 68 of the auxiliary transmission 34 so that the shaft 68 serves as the lower transmission shaft with respect to the creep transmission 33.

The creep transmission 33 is a reduction mechanism 69 that reduces the power from the third transmission shaft 53 of the main transmission 32, and the third transmission shaft 53 of the main transmission 32 to the first transmission shaft 68 of the auxiliary transmission 34. A synchromesh type switching mechanism 70 that switches the transmission state between the constant velocity state in which the power from the third transmission shaft 53 is directly transmitted to the first transmission shaft 68 and the deceleration state in which the power is transmitted via the reduction mechanism 69, etc. Have. That is, the creep transmission 33 employs a synchromesh type transmission switching device in which the transmission state is switched by the switching operation of the synchromesh type switching mechanism 70.

The reduction mechanism 69 employs a creep transmission mechanism that reduces the power from the third transmission shaft 53 of the main transmission 32 to an ultra-low speed via two sets of reduction gear sets 71, 72 having a large gear ratio. There is.

As shown in FIGS. 2 to 3 and 6 to 7, the auxiliary transmission 34 has a first transmission shaft 68, a second transmission shaft 73 arranged in parallel with the first transmission shaft 68, and different gear ratios. Three sets of transmission gear sets 74 to 76 that are transmitted from one transmission shaft 68 to the second transmission shaft 73, and a synchromesh type first switching mechanism that intermittently transmits transmission from the first transmission shaft 68 to the reduction gear set 72 for high speed. 77, Synchromesh type second switching mechanism 78 that interrupts the transmission from the medium speed and low speed gear sets 75 and 76 to the second gear 73, and the gear transmitted to the second gear 73. It has an output gear set 79, etc. that outputs the rear power to the distribution shaft 35. That is, the auxiliary transmission 34 employs a synchromesh type transmission switching device in which the transmission state is switched by the switching operation of the two synchromesh type switching mechanisms 70.

In the auxiliary transmission 34, the front end of the first transmission shaft 68 and the front end of the second transmission shaft 73 are supported by the second support wall 29, and the rear end of the first transmission shaft 68 and the second transmission shaft 73 The rear end portion is supported by the partition wall 23B of the third case 23, so that the rear end portion is arranged in the internal space of the third case 23.

As shown in FIGS. 2 and 8 to 9, the drive switching unit 37 includes a front wheel transmission shaft 80 arranged directly above the first output shaft 16 and parallel to the first output shaft 16, and a first front wheel drive shaft. It has a drive switching device 81, a second drive switching device 82 for accelerating the front wheels, and the like. In the drive switching unit 37, the front end of the front wheel transmission shaft 80 is supported by the partition wall 22B of the second case 22, the rear end of the front wheel transmission shaft 80 is supported by the first support wall 28, and the first output. Since the shaft 16 is supported by the fifth case 25, it is arranged over the rear side space inside the second case 22 and the internal space of the fifth case 25.

The first drive switching device 81 is a reduction gear set 83 that decelerates the power for front wheel drive from the reduction gear set 36 for constant speed drive, and a multi-speed transmission for intermittent transmission to the reduction gear set 83. It has a plate clutch 84, and the like. The reduction gear set 83 decelerates the power for driving the front wheels so that the left and right front wheels 5 are driven at the same peripheral speed as the left and right rear wheels 6, and transmits the power for driving the front wheels from the front wheel transmission shaft 80 to the first output shaft 16. The multi-plate clutch 84 for constant velocity transmission has a transmission state in which the left and right front wheels 5 are driven at the same peripheral speed as the left and right rear wheels 6, and a cutoff state in which the left and right front wheels 5 are driven by the propulsive force of the left and right rear wheels 6. It switches to. That is, the first drive switching device 81 employs a multi-plate clutch type transmission switching device in which the transmission state is switched by the intermittent operation of the multi-plate clutch 84 for constant velocity transmission.

The second drive switching device 82 increases the speed of the front wheel drive power from the reduction gear set 36 for the speed-up drive, and the speed-up transmission for interrupting the transmission to the speed-up gear set 85. It has a multi-plate clutch 86, etc. for The speed-increasing gear set 85 speeds up the power for driving the front wheels so that the left and right front wheels 5 are driven at a peripheral speed that is about twice that of the left and right rear wheels 6, and the front wheel transmission shaft 80 to the first output shaft Tell 16. The multi-plate clutch 84 for speed-up transmission is driven by a transmission state in which the left and right front wheels 5 are driven at a peripheral speed approximately twice that of the left and right rear wheels 6, and the left and right front wheels 5 are driven by the propulsive force of the left and right rear wheels 6. It switches to the shutoff state. That is, the second drive switching device 82 employs a multi-plate clutch type transmission switching device in which the transmission state is switched by the intermittent operation of the multi-plate clutch 84 for speed-increasing transmission.

In the drive switching unit 37, in the multi-plate clutch 84 for constant velocity transmission and the multi-plate clutch 86 for speed-increasing transmission, the multi-plate clutch 84 for constant velocity transmission is supported on the front side of the front wheel transmission shaft 80. Further, the multi-plate clutch 86 for speed-increasing transmission is arranged side by side on the front wheel transmission shaft 80 in a state of being supported on the rear side of the front wheel transmission shaft 80.

As shown in FIGS. 2 to 3, the work power switching device 44 transmits the power transmitted via the hydraulic PTO clutch 87 and the PTO clutch 87 that interrupt and interrupt the work power from the lower relay shaft 43. It has a constant mesh type first speed change mechanism 88 that shifts gears, a constant mesh type second speed change mechanism 89 that shifts the power after shifting by the first speed change mechanism 88 to two high and low speeds, and the like. A multi-plate clutch is used for the PTO clutch 87. That is, in the work power switching device 44, the transmission state is switched by the intermittent operation of the multi-plate clutch (PTO clutch) 87 for work and the switching operation of the two constant mesh type transmission mechanisms 88 and 89. A clutch-type, constant-mesh type transmission switching device is used. The working power switching device 44 is arranged in the internal space of the fourth case 24 by being supported by the rear cover 30 or the like.

With the above configuration, the transmission 3 has, as a plurality of transmission switching devices configured in a multi-plate clutch type, forward / backward switching devices 31 and 4 having two multi-plate clutches 45 and 46 for front wheels and reverse. A main transmission 32 having a multi-plate clutch 60 to 63 for shifting and two multi-plate clutches 66 and 67 for deceleration, a first drive switching device 81 having a multi-plate clutch 84 for constant speed transmission, and a speed increasing transmission The second drive switching device 82 having the multi-plate clutch 84 and the working power switching device 44 having the multi-plate clutch 87 for work are provided.

As shown in FIGS. 2 to 5 and 8, in the main transmission 32, the four transmission multi-plate clutches 60 to 63 are superior in the transmission direction among the three transmission shafts 51 to 53 arranged in parallel. They are arranged side by side in the front-rear direction on the axis of the first transmission shaft 51 arranged on the side. As a result, the first transmission shaft 51 functions as a transmission shaft that supports the four transmission multi-plate clutches 60 to 63. The two deceleration multi-plate clutches 66 and 67 are arranged in the front-rear direction on the axis of the third transmission shaft 53 arranged on the lower side in the transmission direction among the three transmission shafts 51 to 53 arranged in parallel. Have been placed. As a result, the third transmission shaft 53 functions as a reduction shaft that supports the two reduction multi-plate clutches 66 and 67. In the main transmission 32, the four speed change multi-plate clutches 60 to 63 and the two reduction multi-plate clutches 66 and 67 are arranged in parallel so as to be adjacent to each other in the radial direction. ..

That is, in the main transmission 32, the four speed change multi-plate clutches 60 to 63 and the two deceleration multi-plate clutches 66 and 67 are arranged at the same positions in the front-rear direction of the vehicle body. As a result, for example, as compared with the case where the four gear shifting multi-plate clutches 60 to 63 and the two deceleration multi-plate clutches 66 and 67 are misaligned at different positions in the front-rear direction of the vehicle body. Therefore, the front-rear length of the main transmission 32 can be shortened, and the front-rear length of the transmission 3 provided with the main transmission 32 can be shortened. As a result, it is possible to prevent an increase in the size of the tractor, which increases the overall length of the tractor due to the increase in the front-rear length of the transmission 3.

As shown in FIGS. 2 and 8, in the main transmission 32, the second transmission shaft 52 of the three transmission shafts 51 to 53 arranged in parallel is the first transmission shaft (transmission shaft) as an intermediate shaft. It is arranged between 51 and the third transmission shaft (deceleration shaft) 53.

As a result, the four sets of transmission gear sets 56 to 59 transmitted from the first transmission shaft 51 to the second transmission shaft 52 are the first transmission gears 56A to 59A arranged on the shaft of the first transmission shaft 51, respectively. , The second transmission gears 56B to 59B arranged on the axis of the second transmission shaft 52 can be configured. Further, the two sets of reduction gear sets 64 and 65 transmitted from the second transmission shaft 52 to the third transmission shaft 53 are the first reduction gears 64A and 65A arranged on the shaft of the second transmission shaft 52, respectively. It can be configured by the second reduction gears 64B and 65B arranged on the shaft of the third transmission shaft 53.

That is, each of the four sets of transmission gear sets 56 to 59 and the two sets of reduction gear sets 64 and 65 can be configured with the minimum number of gears (two). As a result, the main transmission 32 can be made compact and the configuration can be simplified by reducing the number of parts.

Further, in the main transmission 32, the second transmission gear 56B of the second gear set 57 of the four sets of transmission gear sets 56 to 59 is used for high speed of the two sets of reduction gear sets 64 and 65. Also serves as the first reduction gear 65A of the reduction gear set 65. As a result, the main transmission 32 can be further made compact and the configuration can be simplified by reducing the number of parts.

As shown in FIG. 8, in the main transmission 32, the three transmission shafts 51 to 53 arranged in parallel are abbreviated with the second transmission shaft (intermediate shaft) 52 as the upper apex in the front-rear direction view of the vehicle body. They are arranged to form an isosceles triangle.

As a result, in the main transmission 32, the four transmission multi-plate clutches 60 to 63 or the two deceleration multi-plate clutches 66 and 67 are arranged on the shaft to make the first transmission shaft 51 heavier. The third transmission shaft 53 and the third transmission shaft 53 are arranged side by side in the lower part of the main transmission 32. Further, the second transmission shaft 52, which is lightened by not arranging the multi-plate clutches 60 to 63 for shifting and the multi-plate clutches 66 and 67 for deceleration on the shaft, is intermediate between the first transmission shaft 51 and the third transmission shaft 53. And, it will be arranged at a position above the first transmission shaft 51 and the third transmission shaft 53.

That is, the main transmission 32 can be arranged in the internal space of the second case 22 in a state where the center of gravity is low and the left-right balance is improved. As a result, the stability of the tractor including the transmission 3 including the main transmission 32 can be improved.

As shown in FIG. 8, in the main transmission 32, the three transmission shafts 51 to 53 arranged in parallel include the gear shifting multi-plate clutches 60 to 63 and the deceleration multi-plate clutches 66 and 67. The second transmission shaft (intermediate shaft) 52, which is not arranged on the shaft, is a pair of upper and lower spaces 90 having a substantially triangular shape formed between the multi-plate clutches 60 to 63 for shifting and the multi-plate clutches 66 and 67 for deceleration. It enters the upper space 90 of 91.

As a result, the vertical length of the main transmission 32 can be shortened, and the vertical length of the transmission 3 provided with the main transmission 32 can be shortened. As a result, the height position of the driving unit 2 arranged above the transmission 3 can be lowered, and the vehicle height of the tractor can be lowered.

Further, as described above, since the second transmission shaft 52 is a tubular shaft that is externally fitted to the upper relay shaft 42 of the work transmission system 20 so as to be relatively rotatable, the upper relay shaft 42 is also used for shifting. It enters the upper space 90 formed between the plate clutches 60 to 63 and the reduction multi-plate clutches 66 and 67. As a result, the good side relay shaft 42 can be arranged in the internal space of the second case 22 without securing a dedicated arrangement space for passing the good side relay shaft 42.

As shown in FIG. 8, of the three transmission shafts 51 to 53, the axes of the first transmission shaft 51 and the second transmission shaft 52 are at least the front wheel transmission shaft 80 and the first output shaft 16. They are distributed to the left and right so as to have a substantially symmetrical positional relationship with respect to the line connecting one of the axial centers and the axial center of the second transmission axis 52.

As shown in FIG. 8, in the drive switching unit 37, the multi-plate clutch 84 for constant speed transmission and the multi-plate clutch 86 for speed-increasing transmission are on the upper side of the multi-plate clutches 60 to 63 for shifting and for deceleration. It is arranged below the main transmission 32 in a state of entering the lower space 91 formed between the multi-plate clutches 66 and 67.

As a result, the vertical length of the second case 22 in which the main transmission 32 and the drive switching unit 37 are arranged in the internal space can be shortened, and the vertical length of the transmission 3 provided with them can be shortened. it can. As a result, the height position of the driving unit 2 arranged above the T / M case 14 can be lowered, and the vehicle height of the tractor can be lowered.

Further, the multi-plate clutch 84 for constant speed transmission and the multi-plate clutch 86 for speed-increasing transmission are arranged below the main transmission 32, so that the multi-plate clutches 84 and 86 of the main transmission 32 Compared with the case where the transmission is arranged above, the center of gravity of the transmission 3 including the main transmission 32 and the drive switching unit 37 can be lowered. As a result, the stability of the tractor provided with the transmission 3 can be improved.

As shown in FIGS. 2 to 5 and 8, among the above-mentioned five transmission switching devices 31, 32, 44, 81, 82, the forward / backward switching device 31 and the main transmission 32 provided in the traveling transmission system 19 , The first drive switching device 81 and the second drive switching device 82 are arranged in the internal space of the second case 22 as a transmission switching device for traveling. The work power switching device 44 provided in the work transmission system 20 is arranged in the internal space of the fourth case 24 as a transmission switching device for work.

That is, in this transmission 3, the transmission switching devices 31, 32, 81, 82 for traveling having the multi-plate clutches 45, 46, 60 to 63, 66, 67, 84, 86 that are intermittently operated by electro-hydraulic control. Are collectively arranged in the internal space of the second case 22, so that the hydraulic operation system for each of the transmission switching devices 31, 32, 81, 82 for traveling can be easily configured in the state of being gathered in the second case 22. can do.

The forward / backward switching device 31, the main transmission 32, the first drive switching device 81, and the second drive switching device 82 provided as the transmission switching device for traveling are the multi-plate clutch 45 provided in all of them. The radial sizes of 46, 60 to 63, 66, 67, 84, 86 are set to the same size.

As a result, the clutch plates (drive plate and driven plate) 92, pressure plate 93, piston 94, etc. used for each of the multi-plate clutches 45, 46, 60 to 63, 66, 67, 84, 86 can be used. The radial size of the clutch can be a common component common to all multi-plate clutches 45, 46, 60 to 63, 66, 67, 84, 86. As a result, it is possible to facilitate parts management.

Further, in controlling the intermittent operation of each multi-plate clutch 45, 46, 60 to 63, 66, 67, 84, 86 by electro-hydraulic control, since the piston 94 and the like are common parts, each multi-plate clutch By making the initial pressures for 45,46,60 to 63,66,67,84,86 the same, the timing of clutch meet in each multi-plate clutch 45,46,60 to 63,66,67,84,86 can be adjusted. Can be the same. As a result, it becomes easy to create each control program necessary for properly controlling the intermittent operation of each of the multi-plate clutches 45, 46, 60 to 63, 66, 67, 84, 86 by electro-hydraulic control.

In the traveling transmission system 19, the low-speed deceleration multi-plate clutch 66 provided in the second transmission mechanism 55 of the main transmission 32 is after deceleration by the low-speed reduction gear set 64 in the main transmission 32 and Since the power for traveling with a large torque before being branched into the front wheel drive and the rear wheel drive is interrupted, the forward / reverse switching device 31, the main transmission 32, the first drive switching device 81, and the second drive switching are performed. The load conditions are stricter than those of the other multi-plate clutches 45, 46, 60 to 63, 67, 84, 86 provided in each of the devices 82.

The forward / backward switching device 31, the main transmission 32, the first drive switching device 81, and the second drive switching device 82 are all of the multi-plate clutches 45, 46, 60 to 63, 66, 67, The radial sizes of 84 and 86 are set to the same size with a large size suitable for the low-speed deceleration multi-plate clutch 66 on the low speed side where the load condition is the most severe.

As a result, the other multi-plate clutches 45, 46, 60 to 63, 67, 84, 86, which have more margin in terms of load conditions than the low-speed deceleration multi-plate clutch 66, are equipped with the clutch plate 92. The number of sheets can be reduced, and the length in the axial direction (front-rear direction of the vehicle body) can be shortened. Then, a forward / backward switching device 31, a main transmission 32, a first drive switching device 81, having a multi-plate clutch 45, 46, 60 to 63, 67, 84, 86 capable of shortening the length in the axial direction. In the second drive switching device 82, the length of the second drive switching device 82 in the front-rear direction of the vehicle body can be shortened, and the front-rear length of the transmission 3 provided with them can be shortened. As a result, it is possible to prevent an increase in the size of the tractor, which increases the overall length of the tractor due to the increase in the front-rear length of the transmission 3.

Further, in the above configuration, the radial sizes of the multi-plate clutches 45, 46, 60 to 63, 66, 67, 84, 86 are increased, so that the multi-plate clutches 60 to 63 for shifting and the multi-plate clutches for deceleration are increased. The pair of upper and lower spaces 90 and 91 having a substantially triangular shape formed between the plate clutches 66 and 67 also become large. As a result, as described above, the second transmission shaft 52 and the upper relay shaft 42 that enter the upper space 90 can be made to enter the upper space 90 deeper. Further, as described above, the upper side of the multi-plate clutch 84 for constant velocity transmission and the multi-plate clutch 86 for speed-increasing transmission that enter the lower space 91 can be made deeper into the lower space 91. ..

As a result, the radial sizes of the multi-plate clutches 45, 46, 60 to 63, 66, 67, 84, 86 are large enough to be suitable for the low-speed deceleration multi-plate clutch 66 where the load conditions are the most severe. Even though the sizes are set to the same size, it is possible to suppress the occurrence of a problem that the vertical length of the transmission 3 provided with them becomes long.

By the way, in the main transmission 32, the low-speed deceleration multi-plate clutch 66 and the high-speed deceleration multi-plate clutch 67 have torque after deceleration by the low-speed reduction gear set 64 or the high-speed reduction gear set 65. Since the power for traveling with a large amount is interrupted, the load condition becomes stricter than that of the multi-plate clutches 60 to 63 for shifting, which interrupts the power for traveling with a small torque before deceleration. Therefore, when the radial sizes of the multi-plate clutches 60 to 63, 66, 67 provided in the main transmission 32 are set to the same size as described above, each of the deceleration multi-plate clutches 66 has its own size. The number of clutch plates 92 to be equipped is larger than that of the multi-plate clutches 60 to 63 for shifting, and the length in the axial direction (front-rear direction of the vehicle body) is longer.

In consideration of this point, in the main transmission 32, four gear shifting multi-plate clutches 60 to 63 having a shorter length in the axial direction are adjacent to each other on the axis of the first transmission shaft 51 in the front-rear direction. Have been placed. Further, two deceleration multi-plate clutches 66 and 67 having a long length in the axial direction are arranged adjacent to each other on the axis of the third transmission shaft 53 in the front-rear direction.

As a result, for example, two of the four gear shifting multi-plate clutches 60 to 63 whose length in the axial direction is shortened are arranged adjacent to each other on the axis of the first transmission shaft 51 in the front-rear direction. Compared with the case where the remaining two are arranged adjacent to each other on the axis of the third transmission shaft 53 in the front-rear direction together with the two deceleration multi-plate clutches 66 and 67 having a longer length in the axial direction. , The front-rear length of the main transmission 32 can be shortened. As a result, the front-rear length of the transmission 3 provided with the main transmission 32 can be shortened, and in the tractor equipped with the transmission 3, it is possible to prevent the tractor having a long overall length from becoming large.

As shown in FIGS. 4 to 5, in each of the multi-plate clutches 45, 46, 60 to 63, 66, 67, 84, 86 whose diameters have been increased as described above, the piston 94 has a large diameter as a whole. Only the pressing portion 94A that presses the clutch plate 92 is formed in a stepped shape with an enlarged diameter.

This makes it possible to prevent a decrease in the responsiveness of the piston 94 caused by an increase in the volume of the piston 94 when the entire diameter of the piston 94 is increased. Further, it is possible to prevent the centrifugal force generated at the time of rotation of the piston 94 from becoming large due to the increase in the volume of the piston 94, whereby a return that requires a spring force to overcome the centrifugal force is required. As the spring 95, a spring with a small diameter having a weak spring force can be adopted.

As shown in FIGS. 2 to 5, in the forward / backward switching device 31, the forward / backward multi-plate clutch 45 and the reverse multi-plate clutch 46 share a single clutch housing 96. In the main transmission 32, the first-speed multi-plate clutch 60 and the second-speed multi-plate clutch 61, which are adjacent to the front and rear of the four speed change multi-plate clutches 60 to 63, share a single clutch housing 97. Further, the three-speed multi-plate clutch 62 and the four-speed multi-plate clutch 63 adjacent to each other in the front and rear share a single clutch housing 98. Two deceleration multi-plate clutches 66 and 67 adjacent to each other in the front and rear share a single clutch housing 99.

As a result, the front and rear multi-plate clutches 45, 46, 60 to 63, 66, 67 share the clutch housings 97 to 99 to make the forward / backward switching device 31 and the main transmission 32 compact in the front-rear direction. In addition, it is possible to improve the assembling property by reducing the number of parts.

In the forward / backward switching device 31, the main transmission 32, the first drive switching device 81, and the second drive switching device 82, the clutch housings 96 to 99 and the clutch hubs 100 to 103 are each added with a clutch plate 92. Has a length that allows.

As a result, each of the forward / backward switching device 31, the main transmission 32, the first drive switching device 81, and the second drive switching device 82 provided in the transmission 3 can be changed, for example, without causing the transmission 3 to become large in size. By adding a clutch plate 92, it is possible to easily cope with other tractors whose load conditions become severe due to the installation of the engine 9 having a large horsepower. That is, the transmission 3 can be made highly versatile so that it can be used for other tractors having different specifications.

As shown in FIG. 2, in the drive switching unit 37, the first drive switching device 81 is the first reduction gear 83A of the reduction gear set 83 arranged on the front wheel transmission shaft 80, and the constant speed transmission. The multi-plate clutch 84, etc. are unitized with the front wheel transmission shaft 80. In the second drive switching device 82, the first speed-up gear 85A of the speed-up gear set 85 arranged on the front wheel transmission shaft 80, the multi-plate clutch 84 for speed-up transmission, and the like are unitized. ing.

That is, in the drive switching unit 37, the first drive switching device 81 and the second drive switching device 82 accelerate with the second reduction gear 83B of the reduction gear set 83 arranged on the axis of the first output shaft 16. It is individually unitized except for the second speed-increasing gear 85B of the gear set 85.

As a result, in the drive switching unit 37, the speed increasing gear set 85 can be arranged between the first drive switching device 81 and the second drive switching device 82, and the first drive switching device 81 and the second drive can be arranged. It is not necessary to arrange the speed increasing gear set 85 behind the second drive switching device 82 as in the case where the switching device 82 is integrally unitized.

As a result, the separation distance between the speed-increasing gear set 85 and the reduction gear set 83 arranged on the front side of the vehicle body of the first drive switching device 81 can be shortened, and the second reduction gear of the reduction gear set 83 can be shortened. The front-rear length of the first output shaft 16 in which the 83B and the second speed-up gear 85B of the speed-up gear set 85 are arranged on the shaft, and the front-rear length of the fifth case 25 supporting the first output shaft 16. Can be shortened. As a result, it is possible to reduce the weight of the transmission 3 provided with them.

As shown in FIG. 2, the drive switching unit 37 is provided with the second drive switching device 82 unitized as described above so as to be detachably attached to the front wheel transmission shaft 80.

As a result, the drive switching unit 37 is provided with only the first drive switching device 81 by performing a simple operation of attaching and detaching the unitized second drive switching device 82 to and from the front wheel transmission shaft 80. By providing a standard specification that can switch between a drive state and a four-wheel drive state, and a first drive switching device 81 and a second drive switching device 82, it is possible to switch between a two-wheel drive state, a four-wheel drive state, and a front wheel speed-up state. The specifications can be easily changed to the possible front wheel speed-up specifications. As a result, the versatility of the transmission 3 can be increased.

As shown in FIG. 2, the first output shaft 16 is arranged on the shaft in a state where the second reduction gear 83B and the second speed increase gear 85B are integrally rotated, so that the second drive switching device 82 is arranged. It is configured to be usable in each of the standard specification (not installed specification) that is not installed and the front wheel speed-up specification (installed specification) in which the second drive switching device 82 is installed.

As a result, when the specification of the drive switching unit 37 is changed between the standard specification and the front wheel speed-up specification, it is not necessary to replace the first output shaft 16 according to the specification change. As a result, it is possible to easily change the specifications of the drive switching unit 37.

Although not shown, this tractor is a forward / backward switching command and a shifting command based on operations of a forward / backward switching lever, a main shifting lever, a front wheel drive selection switch, a diff lock pedal, etc. provided in the driving unit 2. It is equipped with an electronic control unit that outputs various control commands such as front wheel drive switching commands.

As shown in FIGS. 2 to 3 and 8, in this tractor, the forward / backward switching device 31, the main transmission 32, the drive switching unit 37, the rear wheel differential device 38, the front wheel differential device, and the like are included. It is a hydraulic device that is electro-hydraulic controlled by the control operation of the electronic control unit. Among these hydraulic devices, a forward / backward switching device 31, a main transmission 32, a drive switching unit 37, a rear wheel differential device 38, and the like are provided inside the T / M case 14.

As shown in FIGS. 2 to 3 and 9, the transmission 3 has a pump unit 104 that pumps oil stored inside the T / M case 14 toward each hydraulic device such as a forward / backward switching device 31 and a pump unit 104. A valve unit 105 that controls the flow of oil to each hydraulic device such as the forward / backward switching device 31 is provided.

When the pump unit 104 and the valve unit 105 are arranged at the upper end of the T / M case 14, there is a risk that the pump unit 104 and the valve unit 105 will come into contact with the cabin 11 vibration-proof supported by the transmission 3 due to vibration during traveling. Therefore, in order to avoid this contact, it is arranged on the right side of the T / M case 14. Since the right side portion of the T / M case 14 is a lateral portion that is open to the outside where the fuel tank 4 is not adjacent to the fuel tank 4, maintenance of the pump unit 104 and the valve unit 105 can be easily performed.

As shown in FIGS. 2 to 3 and 9 to 10, the T / M case 14 has a pump unit mounting portion 106 to which the pump unit 104 is mounted from the right outside thereof and a valve unit 105 from the right outside of the T / M case 14. Has a valve unit mounting portion 107 to which the The pump unit mounting portion 106 bulges outward from the right side of the third case 23 in the T / M case 14. The valve unit mounting portion 107 is formed on the right side portion of the second case 22 in the T / M case 14.

As shown in FIGS. 2 to 3, the pump unit 104 includes a dual first hydraulic pump 104A attached to the front end of the pump unit mounting portion 106 and a second hydraulic pump 104A attached to the rear end of the pump unit mounting portion 106. It has a hydraulic pump 104B. The first hydraulic pump 104A and the second hydraulic pump 104B are driven by the power transmitted from the work transmission system 20 via the gear set 108 for driving the pump. The gear set 108 for driving the pump includes a first gear 108A that also serves as a coupling for interlocking and connecting the upper relay shaft 42 and the lower relay shaft 43 of the work transmission system 20, a second gear 108B for relay, and an output. It has a third gear 108C, etc. for use.

As shown in FIGS. 3, 9, and 11-12, the valve unit 105 includes a base plate 110 attached to the valve unit mounting portion 107, and a first valve block 111 and a second valve block 112 having a plurality of solenoid valves. , Etc.

The first valve block 111 is a plurality of electromagnetic valves, such as a forward electromagnetic on / off valve 113 that switches the oil flow to the forward multi-plate clutch 45, and a reverse electromagnetic on / off valve that switches the oil flow to the reverse multi-plate clutch 46. Valve 114, Electromagnetic on / off valve 115 for 1st speed to switch oil flow to multi-plate clutch 60 for 1st speed, Electromagnetic on / off valve 116 for 2nd speed to switch oil flow to multi-plate clutch 61 for 2nd speed Electromagnetic on / off valve 117 for 3rd speed to switch oil flow to multi-plate clutch 62, electromagnetic on / off valve 118 for 4th speed to switch oil flow to multi-plate clutch 63 for 4th speed, multi-plate clutch 84 for constant speed transmission Difference between the electromagnetic on / off valve 119 for constant velocity transmission, the electromagnetic on / off valve 120 for acceleration transmission that switches the oil flow to the multi-plate clutch 86 for acceleration transmission, and the differential device 38 for the rear wheels. It has an electromagnetic on / off valve 121 for rear wheel differential that switches the oil flow to the dynamic switching mechanism 38B, and an electromagnetic on / off valve 122 for front wheel differential that switches the oil flow to the differential switching mechanism of the front wheel differential device. are doing.

The second valve block 112 is a plurality of electromagnetic valves, such as a forward / backward electromagnetic proportional valve 123 that continuously controls the flow of oil to the forward multi-plate clutch 45 and the reverse multi-plate clutch 46, and two deceleration multi-plates. Low-speed electromagnetic proportional valve 124 that continuously controls the flow of oil to the low-speed deceleration multi-plate clutch 66 of the clutches 66 and 67, and the high-speed side of the two deceleration multi-plate clutches 66 and 67. It has an electromagnetic proportional valve 125 for high speed that continuously controls the flow of oil with respect to the deceleration multi-plate clutch 67.

Although not shown, the base plate 110, the first valve block 111, and the second valve block 112 include a plurality of electro-hydraulic controls such as a forward / backward switching device 31, a main transmission 32, and a drive switching unit 37. An internal oil passage is formed.

As shown in FIGS. 9 to 11, the valve unit mounting portion 107 is formed with a recess 107A that partitions the storage chamber 126 for the first valve block from the base plate 110. The first valve block 111 is assembled to the storage chamber forming surface 110A that forms the storage chamber 126 with the recess 107A of the valve unit mounting portion 107 in the base plate 110. The second valve block 112 is assembled to the outer surface 110B of the base plate 110 opposite to the storage chamber forming surface 110A.

As a result, when the valve unit 105 is attached to the valve unit mounting portion 107 of the T / M case 14, the first valve block 111 having 10 electromagnetic on / off valves 113 to 122 is replaced with the T / M case 14. On the right side, it is configured to be stored in a storage chamber 126 formed separately from the internal space of the T / M case 14. Further, the second valve block 112 having the three electromagnetic proportional valves 123 to 125 is configured to be arranged at a position laterally outside the storage chamber 126 on the right side of the T / M case 14.

With the above configuration, iron powder and the like contained in the oil stored inside the T / M case 14 are excited by the electromagnetic on / off valves 113 to 122 and the electromagnetic proportional valves 123 to 125 to the valve unit 105. It is possible to prevent it from being sucked toward. As a result, iron powder and the like contained in the oil inside the T / M case 14 enter the inside of the valve unit 105 due to the suction, and each electromagnetic on / off valve 113 to 122 and each electromagnetic proportional valve It is possible to avoid the possibility of biting into any of 123 to 125.

Further, as in the case where the first valve block 111 is arranged in the internal space of the T / M case 14, an opening for allowing the first valve block 111 to enter the internal space of the T / M case 14 is provided in the valve unit mounting portion 107. Since it is not necessary to form the T / M case 14, it is possible to prevent a decrease in strength in the T / M case 14 due to the formation of the opening.

Then, the first valve block 111 having electromagnetic on / off valves 113 to 122 having a high risk of oil leakage is housed in the storage chamber 126, and the second valve block 112 having electromagnetic proportional valves 123 to 125 having a low risk of oil leakage. Is arranged outside the T / M case 14, so that the recess 107A for the storage chamber formed in the T / M case 14 can be narrowed while preventing the oil from leaking to the outside, and the T / M can be narrowed. The internal space of the case 14 can be widened. As a result, it becomes easy to arrange and assemble the traveling transmission system 19 and the work transmission system 20 arranged in the internal space of the T / M case 14.

When the valve unit 105 is attached to the valve unit mounting portion 107 of the T / M case 14, at least the upper end portion of the first valve block 111 is on the oil level of the oil stored inside the T / M case 14. The mounting height position is set so that it is located higher than the height position.

As shown in FIGS. 3 and 9 to 11, the valve unit mounting portion 107 applies excess oil from the first valve block 111 to the T / M case 14 at a position above the vehicle body of the first valve block 111 in the recess 107A. Seven return oil passages 107B are formed to return to the inside of the.

As a result, the oil leaked from the electromagnetic on / off valves 113 to 122 of the first valve block 111 can be stored as lubricating oil up to a position above the vehicle body of the first valve block 111 in the storage chamber 126. When the oil level of the lubricating oil reaches the return oil passage forming portion of the storage chamber 126, the lubricating oil that has reached the return oil passage forming portion is used as surplus oil from each return oil passage 107B to the T / M case 14. Can be returned to the inside of. Further, due to a large tilt of the tractor or the like, the oil stored inside the T / M case 14 flows into the storage chamber 126 from each return oil passage 107B together with the iron powder contained in the oil. It is possible to make it difficult for defects to occur.

As shown in FIGS. 9 to 11, in the valve unit mounting portion 107, seven return oil passages 107B are formed in two upper and lower stages. As a result, as compared with the case where all the return oil passages 107B are formed at the same height position, the oil stored inside the T / M case 14, together with the iron powder and the like contained in this oil, are each. It is possible to prevent a problem of flowing from the return oil passage 107B into the storage chamber 126.

In the upper and lower two-stage return oil passages 107B, three return oil passages 107B are formed in the upper stage and four return oil passages 107B are formed in the lower stage, so that the opening area by the upper return oil passage 107B is returned to the lower stage. It is formed so as to be smaller than the opening area of the oil passage 107B.

This is because when the return oil passage 107B is formed in two upper and lower stages, most of the excess oil returns from the lower return oil passage 107B to the inside of the T / M case 14, and the upper return oil passage The 107B is considered to be used as an auxiliary when the amount of oil leaking from each electromagnetic on / off valve 113 to 122 is large, and thus the return oil passage 107B in the upper stage which is used as an auxiliary is used. It is possible to prevent a decrease in strength in the T / M case 14 due to an unnecessarily wide opening area.

As shown in FIGS. 3, 9, and 11, each return oil passage 107B is provided with an oil filter 127. As a result, even if the oil stored inside the T / M case 14 flows into the storage chamber 126 from each return oil passage 107B, iron powder and the like contained in this oil will flow into the storage chamber 126. It can be prevented from flowing in. Further, as described above, when the seven return oil passages 107B are formed in two upper and lower stages, and the oil filter 127 provided in the lower return oil passage 107B is clogged, the oil filter 127 is clogged. The excess oil in the storage chamber 126 can be returned to the inside of the T / M case 14 from the upper return oil passage 107B.

As shown in FIGS. 9 to 11, in the valve unit mounting portion 107, the recess 107A is a T / M case 14 via a lower recessed portion 107a in which the first valve block 111 is housed and each return oil passage 107B. It has an upper recessed portion 107b that communicates with the inside of the. The upper recessed portion 107b is formed to have a recessed depth shallower than that of the lower recessed portion 107a and narrower than that of the lower recessed portion 107a.

As a result, for example, as compared with the case where the upper recessed portion 107b in which the first valve block 111 is not housed is formed so as to have the same recessing depth and the same width as the lower recessed portion 107a, T / The internal space of the M case 14 can be widened. As a result, it becomes easy to arrange and assemble the traveling transmission system 19 and the work transmission system 20 arranged in the internal space of the T / M case 14.

Although not shown, the input shaft 15 of the transmission 3 is supported by a forward oil passage extending from the front portion of the input shaft 15 supported by the front cover 27 and the forward multi-plate clutch 45, and the front cover 27. A reverse oil passage extending from the front portion of the input shaft 15 and the reverse multi-plate clutch 46 is formed. The front wheel transmission shaft 80 of the drive switching unit 37 has a constant velocity oil passage extending from the rear end portion of the front wheel transmission shaft 80 supported by the first support wall 28 and the multi-plate clutch 84 for constant velocity transmission. , A speed-increasing oil passage extending between the rear end of the front wheel transmission shaft 80 supported by the first support wall 28 and the multi-plate clutch 84 for speed-up transmission is formed.

As shown in FIGS. 4 to 5 and 8 to 11, in the main transmission 32, the three transmission shafts 51 to 53 have the first transmission shaft (transmission shaft) at the lower end of the second transmission shaft (intermediate shaft) 52. The upper end of the 51 and the upper end of the third transmission shaft (deceleration shaft) 53 are located above the vehicle body, and the upper end of the first transmission shaft 51 is located below the upper end of the third transmission shaft 53. It is arranged like this. The first transmission shaft 51 includes a first-speed oil passage 51A extending from the front end of the first transmission shaft 51 supported by the partition wall 22B of the second case 22 and the first-speed multi-plate clutch 60, and the partition wall of the second case 22. The front end of the first transmission shaft 51 supported by 22B, the second speed oil passage 51B extending over the second speed multi-plate clutch 61, and the front end of the first transmission shaft 51 supported by the partition wall 22B of the second case 22. For 4th speed including the 3rd speed oil passage 51C extending over the 3rd speed multi-plate clutch 62 and the front end of the 1st transmission shaft 51 supported by the partition wall 22B of the 2nd case 22 and the 4th speed multi-plate clutch 63. An oil passage 51D, etc. are formed. The third transmission shaft (reduction shaft) 53 includes a low-speed oil passage 53A extending from the front end of the third transmission shaft 53 supported by the partition wall 22B of the second case 22 and the low-speed deceleration multi-plate clutch 66. , A high-speed oil passage 53B extending between the front end of the third transmission shaft 53 supported by the partition wall 22B of the second case 22 and the high-speed deceleration multi-plate clutch 67 is formed.

The valve unit mounting portion 107 is formed at a predetermined position in the vehicle body front-rear direction in which the partition wall 22B is formed in the second case 22 of the T / M case 14. The partition wall 22B has an internal oil passage 22C for 1st speed and a valve unit 105 extending from a connection port 105A for 1st speed formed in the valve unit 105 and an oil passage 51A for 1st speed formed in the 1st transmission shaft 51. The internal oil passage 22D for the second speed extending between the formed connection port 105B for the second speed and the oil passage 51B for the second speed formed on the first transmission shaft 51, and the connection port for the third speed formed in the valve unit 105. The internal oil passage 22E for the third speed extending between the 105C and the oil passage 51C for the third speed formed on the first transmission shaft 51, the connection port 105D for the fourth speed formed on the valve unit 105, and the first transmission shaft 51. Low speed over the 4th speed internal oil passage 22F, the low speed connection port 105E formed on the valve unit 105, and the low speed oil passage 53A formed on the 3rd transmission shaft 53. The internal oil passage 22G for high speed and the internal oil passage 22H for high speed extending between the connection port 105F for high speed formed in the valve unit 105 and the high speed oil passage 53B formed in the third transmission shaft 53 are formed. Has been done.

As a result, hydraulic pressure is applied to the inside of the T / M case 14 in forming each of the six main shifting hydraulic paths extending from the valve unit 105 and the multi-plate clutches 60 to 63, 66, 67 of the main transmission 32. There is no need to assemble the pipe. Further, the internal oil passages 22C to 22H of the partition wall 22B extending between the valve unit 105 and the first transmission shaft 51 or the third transmission shaft 53 can be formed in the shortest length with a simple linear shape. As a result, the work man-hours required to form each hydraulic path for the main shift can be reduced.

Further, since each of the internal oil passages 22C to 22H of the partition wall 22B is formed in a simple linear shape and has the shortest length, the main shift over the valve unit 105 and the multi-plate clutches 60 to 63, 66, 67 of the main transmission 32. Each of the six hydraulic paths for the system can be formed in the shortest shape with a simple shape. As a result, the responsiveness of each of the multi-plate clutches 60 to 63, 66, 67 in the main transmission 32 is improved.

As shown in FIGS. 3 and 9, the valve unit mounting portion 107 has four transmission multi-plate clutches 60 to 63 rather than the third transmission shaft 53 supporting the two reduction multi-plate clutches 66 and 67. It is arranged near the first transmission shaft 51 that supports.

As a result, the number of long internal oil passages 22G and 22H formed in the partition wall 22B is increased as compared with the case where the valve unit mounting portion 107 is arranged closer to the third transmission shaft 53 than to the first transmission shaft 51. Can be reduced. As a result, it is possible to prevent the strength of the partition wall 22B from being lowered due to an increase in the number of long internal oil passages 22G and 22H formed in the partition wall 22B.

As shown in FIGS. 2 to 3, 5 and 14, in the creep transmission 33, the reduction gear 69 is parallel to the third transmission shaft 53 of the main transmission 32 and the first transmission shaft 68 of the auxiliary transmission 34. A first arranged on the axis of the third transmission shaft 53 so as to rotate integrally with the third transmission shaft 53 in a state where movement in the axial direction with respect to the arranged reduction shaft 130 and the third transmission shaft 53 is permitted. The first reduction gear 71A, the second reduction gear 71B and the third reduction gear 72A arranged on the reduction shaft 130 in a state of being integrally rotated with the reduction shaft 130, and the first reduction gear 71A in a state of being relative to the first transmission shaft 68. It has a fourth reduction gear 72B, etc. arranged on the speed change shaft 68. Then, among the two sets of reduction gear sets 71 and 72 described above, the first reduction gear 71A and the second reduction gear 71B reduce and transmit from the third transmission shaft 53 to the reduction shaft 130 at a larger gear ratio on the upper side in the transmission direction. The reduction gear set 71 of the above is configured. Further, among the two sets of reduction gear sets 71 and 72 described above, the third reduction gear 72A and the fourth reduction gear 72B reduce and transmit from the reduction shaft 130 to the first transmission shaft 68 at a larger gear ratio on the lower side in the transmission direction. The reduction gear set 72 of the above is configured.

The switching mechanism 70 is arranged on the axis of the third transmission shaft 53 so as to rotate integrally with the third transmission shaft 53 in a state where the movement in the axial direction with respect to the third transmission shaft 53 is allowed. The second meshed rotating body 132 arranged on the axis of the first speed change shaft 68 so as to rotate relative to the first speed change shaft 68 in a state of being integrally rotated with the rotating body 131 and the fourth reduction gear 72B, and the first The first shift so as to rotate integrally with the first shift shaft 68 in a state where movement in the axial direction is allowed between the constant velocity position that meshes with the meshed rotating body 131 and the deceleration position that meshes with the second meshed rotating body 132. It has a meshing rotating body 133, etc. arranged on the shaft of the shaft 68, and is assembled to the first speed change shaft 68 together with the first reduction gear 71A and the fourth reduction gear 72B (see FIG. 14).

By assembling the switching mechanism 70 together with the first reduction gear and the fourth reduction gear to the first transmission shaft 68 in this way, the meshing rotating body 133 meshes with the first meshed rotating body 131 at a constant velocity position and a second covering. It is possible to confirm the operation of whether or not the meshing rotating body 132 and the deceleration position where the meshing rotating body 132 meshes with each other and move normally without difficulty. If a problem occurs in this operation check, the problem can be solved by making fine adjustments of the rotating bodies 131 to 133 assembled to the first speed change shaft 68. As a result, the assembly including the operation check of the switching mechanism 70 can be facilitated.

As shown in FIGS. 2 to 3, 5 and 14, the T / M case 14 has a second case 22 and a first case 22 on the upper side in the transmission direction provided with the third transmission shaft 53 at the location where the creep transmission 33 is arranged. The division positions of the second case 22 and the third case 23 are set so as to be divided into the third case 23 on the lower side in the transmission direction provided with the transmission shaft 68. In the speed reduction mechanism 69 and the switching mechanism 70, the first reduction gear 71A and the first meshed rotating body 131 are arranged on the axis of the third transmission shaft 53 as the second case 22 and the third case 23 are connected. Then, when the connection between the second case 22 and the third case 23 is released, the reduction mechanism is removed so that the first reduction gear 71A and the first meshed rotating body 131 are removed from the third transmission shaft 53. The entire 69 and the entire switching mechanism 70 are assembled in the third case 23 together with the first transmission shaft 68.

As a result, when the creep transmission 33 is assembled to the T / M case 14, the reduction mechanism 69 and the switching mechanism 70 are moved from the split end side of the third case 23 with the second case 22 together with the first transmission shaft 68 and the like. It can be assembled to the third case 23. Then, after this assembly, the second case 22 and the third case 23 are connected so that the first reduction gear 71A and the first meshed rotating body 131 are arranged on the axis of the third transmission shaft 53. , The deceleration mechanism 69 and the switching mechanism 70 can be assembled to the T / M case 14 in a state of extending over the third transmission shaft 53 and the first transmission shaft 68. That is, the creep transmission 33 can be easily assembled inside the T / M case 14 so as to cover the third transmission shaft 53 and the first transmission shaft 68.

Further, when the creep transmission 33 is removed from the T / M case 14, the connection between the second case 22 and the third case 23 is released to separate the second case 22 and the third case 23. The 1 reduction gear 71A and the 1st meshed rotating body 131 can be removed from the axis of the 3rd transmission shaft 53, and the entire reduction mechanism 69 and the entire switching mechanism 70 can be removed together with the 1st transmission shaft 68 and the like. It can be left in the case 23. Then, the speed reduction mechanism 69 and the switching mechanism 70 remaining in the third case 23 can be removed from the third case 23 together with the first speed change shaft 68 and the like from the split end side of the third case 23 with the second case 22. .. That is, the creep transmission 33 can be easily removed from the T / M case 14, which facilitates maintenance of the creep transmission 33 and the like.

As shown in FIG. 14, in the creep transmission 33, the first reduction gear 71A of the reduction mechanism 69 and the first meshed rotating body 131 of the switching mechanism 70 are integrally formed. As a result, as compared with the case where the first reduction gear 71A and the first meshed rotating body 131 are individually formed independently, it is possible to simplify the configuration by reducing the number of parts.

As shown in FIGS. 2, 5, and 14, in the creep transmission 33, the front end of the reduction shaft 130 is supported by the first support wall 28, and the rear end thereof is the front end of the distribution shaft 35. It is supported. The first reduction gear 71A is spline-fitted to the rear portion of the third transmission shaft 53 in a state of being integrally formed with the first meshed rotating body 131. The second reduction gear 71B is spline-fitted to the front end side of the reduction shaft 130. The third reduction gear 72A is integrally formed at the rear end of the reduction shaft 130. The first meshed rotating body 131 is spline-fitted to the rear end portion of the third transmission shaft 53 while being supported by the rotating body 135 spline-fitted to the front end portion of the first transmission shaft 68 so as to be relatively rotatable. ing. The second meshed rotating body 132 is engaged and connected to the fourth reduction gear 72B so as to rotate integrally with the fourth reduction gear 72B. The meshing rotating body 133 is spline-fitted to the outer peripheral portion of the rotating body 135. That is, in the creep transmission 33, the reduction shaft 130, the second reduction gear 71B, and the third reduction gear 72A are detachably provided in the third case 23 in a state of being unitized as the first unit 33A. .. Further, the first reduction gear 71A, the fourth reduction gear 72B, the first meshed rotating body 131, the second meshed rotating body 132, the meshing rotating body 133, the rotating body 135, and the like are unitized as the second unit 33B. It is detachably provided in the third case 23 in a state.

FIG. 13 shows a reference form of the creep transmission 33 having a configuration different from that of the creep transmission 33 described above with respect to the first reduction gear 71A of the reduction mechanism 69 and the first meshed rotating body 131 of the switching mechanism 70. ..

In the creep transmission 33 shown in FIG. 13, the first reduction gear 71A of the reduction mechanism 69 and the first meshed rotating body 131 of the switching mechanism 70 are individually formed independently. In the reduction mechanism 69, only the first reduction gear 71A is assembled to the second case 22 together with the third transmission shaft 53, and substantially the entire reduction mechanism 69 excluding the first reduction gear 71A is the first transmission shaft. It is assembled to the third case 23 together with 68 and the switching mechanism 70.

As a result, when the creep transmission 33 is assembled to the T / M case 14, the first reduction gear 71A of the reduction mechanism 69 is moved from the split end side of the second case 22 with the third case 23 to the third transmission shaft 53. It can be assembled to the second case 22 together with the above. Further, substantially the entire reduction mechanism 69 excluding the first reduction gear 71A and the switching mechanism 70 are moved from the split end side of the third case 23 with the second case 22 to the third case 23 together with the first speed change shaft 68 and the like. Can be assembled. Then, the first meshed rotating body 131 assembled to the third case 23 is arranged on the axis of the third transmission shaft 53 assembled to the second case 22, and the second meshed rotating body 131 is assembled to the third case 23. By connecting the second case 22 and the third case 23 so that the reduction gear 71B meshes with the first reduction gear 71A assembled to the second case 22, the creep transmission 33 is combined with the third transmission shaft 53. It can be assembled to the T / M case 14 in a state of extending over the first shift shaft 68.

When removing the creep transmission 33 from the T / M case 14, creep is performed by disconnecting the second case 22 and the third case 23 and separating the second case 22 and the third case 23. The transmission 33 is divided into a first reduction gear 71A assembled in the second case 22 and substantially the entire reduction mechanism 69 and a switching mechanism 70 assembled in the third case 23 except for the first reduction gear 71A. be able to. Then, by this division, the first reduction gear 71A can be removed from the second case 22 together with the third transmission shaft 53 and the like from the divided end side of the second case 22 with the third case 23. Further, substantially the entire reduction mechanism 69 excluding the first reduction gear 71A and the switching mechanism 70 are moved from the split end side of the third case 23 with the second case 22 from the third case 23 together with the first speed change shaft 68 and the like. Can be removed.

In the creep transmission 33 shown in FIG. 13, similarly to the creep transmission 33 described above, the reduction shaft 130, the second reduction gear 71B, and the third reduction gear 72A are unitized as the first unit 33A. It is detachably provided in the third case 23 (see FIGS. 2 and 7). On the other hand, in the creep transmission 33, the first reduction gear 71A is spline-fitted to the rear portion of the third transmission shaft 53 and is prevented from coming off by the retaining ring 134. Therefore, unlike the creep transmission 33 described above, except for the first reduction gear 71A, the fourth reduction gear 72B, the first meshed rotating body 131, the second meshed rotating body 132, the meshed rotating body 133, and the rotating body 135 and the like are detachably provided in the third case 23 in a state of being unitized as the second unit 33B.

As shown in FIGS. 2 to 3 and 6 to 7, in the main transmission 32 and the auxiliary transmission 34, the main transmission 32 is arranged on the upper side in the transmission direction inside the T / M case 14, and the auxiliary transmission 34 is arranged on the lower side in the transmission direction. The T / M case 14 is divided into a second case 22 on the upper side in the transmission direction provided with the main transmission 32 and a third case 23 on the lower side in the transmission direction with the auxiliary transmission 34. An opening 136 is formed at the front end of the third case 23, which is the split end of the 23 with the second case 22. In the auxiliary transmission 34, the output gear set 79 described above is interchangeably arranged at the frontmost position of the auxiliary transmission 34 near the opening 136 of the third case 23.

As a result, in this tractor, by replacing the output gear set 79 with another output gear set 79 having a different gear ratio, the maximum vehicle speed of the tractor can be easily set to a vehicle speed suitable for the work mode performed by the user. can do. Then, the output gear set 79 is easily replaced from the opening 136 of the third case 23 that is exposed when the T / M case 14 is divided into the second case 22 and the third case 23 for the replacement. be able to. That is, the maximum vehicle speed of the tractor can be easily set and changed to a vehicle speed suitable for the work mode or the like performed by the user by a simple replacement work of the output gear set 79 performed from the opening 136 of the third case 23.

By the way, as described above, the T / M case 14 is configured to be divided into a second case 22 on the upper side in the transmission direction and a third case 23 on the lower side in the transmission direction at the location where the creep transmission 33 is arranged. Has been done. The creep transmission 33 is assembled at a position on the opening side inside the third case 23, which is a portion adjacent to the output gear set 79 across the second support wall 29. The creep transmission 33 is detachably provided in the third case 23 in a state in which substantially the entire or the entire creep transmission 33 is unitized into the first unit 33A and the second unit 33B.

As a result, when replacing the output gear set 79, first, the connection between the second case 22 and the third case 23 in the T / M case 14 is released to separate the second case 22 and the third case 23. .. Next, the first unit 33A and the second unit 33B of the creep transmission 33 arranged on the opening side of the third case 23 are removed from the opening 136 of the third case 23 exposed by this separation, and then the second unit 33B is removed. By removing the 2 support wall 29, it is possible to replace the output gear set 79 from the opening 136 of the third case 23. Then, by exchanging the output gear set 79 from the opening 136 of the third case 23, the maximum vehicle speed of the tractor can be easily set and changed to a vehicle speed suitable for the work mode or the like performed by the user.

That is, although the creep transmission 33 is arranged at the divided portion between the second case 22 and the third case 23 in the T / M case 14, the output gear set 79 is replaced from the opening 136 of the third case 23. The maximum vehicle speed of the tractor can be easily changed to a vehicle speed suitable for the work mode performed by the user.

In the present invention, the upper transmission shaft and the lower transmission shaft arranged adjacent to each other on the same axis in the front and rear, and the transmission state from the upper transmission shaft to the lower transmission shaft are displayed inside the transmission case. It can be applied to a transmission for a work vehicle equipped with a transmission switching device for switching, and a work vehicle such as a tractor, a mowing machine, a combine, a rice transplanter, a transportation work vehicle, etc. equipped with the transmission for the work vehicle.

3 Transmission for work vehicle 14 Transmission case 22 Upper side case 23 Lower side case 33 Transmission switching device 53 Upper side transmission shaft 68 Lower side transmission shaft 69 Deceleration mechanism 70 Switching mechanism 71A 1st reduction gear 71B 2nd reduction gear 72A 3rd reduction Gear 72B 4th reduction gear 130 Reduction shaft 131 1st meshed rotating body 132 2nd meshed rotating body 133 meshing rotating body

Claims (5)

Inside the transmission case, a transmission switching device that switches between the upper transmission shaft and the lower transmission shaft arranged adjacent to each other on the same axis in the front-rear direction and the transmission state from the upper transmission shaft to the lower transmission shaft. With and
The transmission switching device includes a deceleration mechanism for decelerating the power from the upper transmission shaft, a constant velocity state in which the power from the upper transmission shaft is directly transmitted to the lower transmission shaft, and the deceleration mechanism. Equipped with a switching mechanism to switch to the deceleration state transmitted via
The deceleration mechanism includes a deceleration shaft arranged in parallel with the upper transmission shaft and the lower transmission shaft, and the upper transmission shaft in a state where movement in the axial direction with respect to the upper transmission shaft is permitted. A first reduction gear arranged on the shaft of the upper transmission shaft so as to rotate integrally, and a second reduction gear and a third reduction gear arranged on the shaft of the reduction shaft while rotating integrally with the reduction shaft. It has a gear and a fourth reduction gear arranged on the shaft of the lower transmission shaft in a state of rotating relative to the lower transmission shaft.
The switching mechanism is arranged on the axis of the upper transmission shaft so as to rotate integrally with the upper transmission shaft in a state where movement in the axial direction with respect to the upper transmission shaft is permitted. The rotating body, the second meshed rotating body arranged on the shaft of the lower transmission shaft so as to rotate relative to the lower transmission shaft in a state of being integrally rotated with the fourth reduction gear, and the first covering. The lower side transmission shaft so as to rotate integrally with the lower side transmission shaft in a state where movement in the axial direction is allowed between the constant velocity position that meshes with the meshing rotating body and the deceleration position that meshes with the second meshed rotating body. It has a meshing rotating body arranged on the shaft of the above, and is assembled to the lower transmission shaft together with the first reduction gear and the fourth reduction gear .
The transmission case has a structure in which an upper case having the upper transmission shaft and a lower case having the lower transmission shaft are connected to each other.
The upper case is provided with a vertically oriented first support wall at an end on the side of the lower case, and the first support wall is in a state where the upper case and the lower case are connected to each other. A transmission for a work vehicle, which is arranged at a position where it enters the inside of the lower case, and the first support wall supports the upper transmission shaft in a penetrating state . The transmission case, in the arrangement position of the transmission switching device is configured to split structure which is divided into said downstream side case with the downstream side transmission shaft and the upstream side case with the upstream side transmission shaft,
In the deceleration mechanism and the switching mechanism, the first reduction gear and the first meshed rotating body are arranged on the axis of the upper transmission shaft in association with the connection between the upper case and the lower case. The deceleration is performed so that the first reduction gear and the first meshed rotating body are removed from the shaft of the upper transmission shaft as the connection between the upper case and the lower case is released. The work vehicle transmission according to claim 1, wherein the entire mechanism and the entire switching mechanism are assembled to the lower case together with the lower transmission shaft. The transmission for a work vehicle according to claim 1 or 2, wherein the first reduction gear and the first meshed rotating body are integrally formed. The transmission for a work vehicle according to any one of claims 1 to 3, wherein the speed reduction mechanism is a creep speed change mechanism that reduces power from the upper transmission shaft to an ultra-low speed. A work vehicle provided with the work vehicle transmission according to any one of claims 1 to 4.

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