JPH10278602A - Running transmission structure for working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make shifting run smoothly and quickly regardless of the condition of the ground while enabling various work requiring different vehicle speed to be performed without trouble. SOLUTION: A running main speed change unit MA is composed of a main transmission 10 capable of making quadruple speed change by shift gears 11 and 12 and a low speed transmission unit LD capable of making double speed change by the shift gear 31 of an auxiliary transmission 30 which is provided with an overdrive unit OD capable of being geared and ungeared freely by a shift gear 32. When a vehicle is in operation, gear shift can be changed on the low speed side by replacing shift gears 11, 12 and 31 with the overdrive unit OD ungeared. When the vehicle is to be moved, the gear shift can be changed on the high speed side by replacing shift gears 11 and 12. A gear shift restraining device is provided so that the overdrive unit OD shift gear 32 can be geared only when the main transmission 10 and the low speed transmission unit LD are in neutral position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission structure for driving a working vehicle such as an agricultural tractor.

[0002]

2. Description of the Related Art For example, in an agricultural tractor, it has been possible to travel at high speed by shifting the traveling main transmission to a high speed side.
It was for work done at high speed, such as plowing with a plow.

[0003]

Conventionally, when traveling, even when shifting to the highest speed, the vehicle can travel only at a low speed. For this reason, even if the road surface conditions, such as a pavement road, are good, it may take time because the vehicle does not come out at a speed. SUMMARY OF THE INVENTION An object of the present invention is to provide a traveling power transmission structure that can perform a task that requires both low-speed traveling and high-speed traveling without any trouble, and that can quickly travel at a speed according to ground conditions when moving.

[0004]

The constitution, operation and effect of the invention according to claim 1 are as follows.

[Structure] A traveling main transmission unit which can be shifted by a shift lever and an overdrive unit which can be turned on and off by an operating tool different from the shift lever are provided, and the traveling main transmission unit is in a neutral state. When the overdrive section is in the off state, the overdrive section is allowed to be switched from off to on, and when the traveling main transmission section is in the transmission state, the overdrive section is switched from off to on. A transmission structure for traveling of a work vehicle provided with a shift check device that disables the operation.

[Operation] When performing the work, the overdrive section is turned off so that the high speed transmission is controlled so that the main transmission section for traveling is shifted at a low speed so that the work requiring low speed traveling or high speed traveling is performed. The traveling speed according to the required work can be obtained. Then, when traveling, the speed of the main transmission portion for traveling is changed on the high-speed side in which the overdrive portion is engaged so that high-speed transmission is performed, so that a traveling speed higher than that at the time of work can be obtained. . In addition, on uneven terrain, a low-speed side moving speed can be obtained by shifting the traveling main transmission to a lower speed side.
A high-speed moving speed can be obtained by shifting the traveling main transmission unit to a high-speed side. During this traveling traveling, the overdrive section cannot be switched on due to the shift restraint device unless the traveling main transmission section is in the neutral state. When the overdrive section is switched on, the traveling main transmission section is not activated. Is already in the transmission state and can run while avoiding the occurrence of troubles such as sudden start or engine stop.

[Effect] At the time of work, the overdrive section is turned off, and the main speed change section for running is shifted to an appropriate speed state, so that a running speed corresponding to the work can be obtained, and work requiring low speed running can be performed at high speed. Work requiring traveling can be performed as desired. In addition, when moving, the overdrive section is engaged to achieve a higher running speed than during work, and sudden start and engine stop are avoided by the action of the variable speed check device, and furthermore, in the case of uneven terrain However, even in the case of leveling, the traveling speed of the corresponding speed can be displayed and the vehicle can travel smoothly and quickly, and the time required for traveling can be shortened and work can be performed efficiently.

The structure, operation and effect of the invention according to claim 2 are as follows.

In the configuration according to the first aspect of the present invention, the traveling speed can be changed by the shift operation of the traveling main transmission portion by the shift lever regardless of whether the overdrive portion is in the on state or the off state. It is configured to do so.

[Operation] The on / off operation of the overdrive portion is performed by a dedicated operating tool, and the speed change operation when the overdrive is turned on and the speed change operation when the overdrive is turned off can be performed with the same speed change lever. Is what you do.

[Effect] In contrast to a configuration in which a shift operation is performed by a dedicated shift lever during work traveling and a shift operation is performed by a dedicated shift lever during traveling traveling, a shift operation during work traveling is also performed during shifting. For the operation, the same shift lever can be handled, and the shift operation can be performed so that an operation error hardly occurs.

The structure, operation and effect of the invention according to claim 3 are as follows.

In the structure according to the second aspect of the present invention, it is possible to freely switch between an operation state in which the shift range of the traveling main transmission portion is limited to a part on the low speed side and an operation release state in which the shift range restriction is released. Equipped with simple gearshift limiting means,
When the overdrive section is operated to enter, the shift limiting means is automatically in the operating state, and when the overdrive section is operated to be turned off, the shift limiting means is automatically in the released state. It is configured to be switched.

[Operation] When the overdrive section is turned off or on, the shift operation of the traveling main transmission section can be performed in the same transmission range, so that the transmission range of the traveling main transmission section is widened. If the traveling speed during work can be changed over a wide range from low speed to high speed, the traveling speed during movement can also be changed over a wide range. In this case, the entire shifting range during the movement is located on the higher speed side than during the work, so that if the main transmission unit for traveling is shifted to the higher speed side during the movement, the traveling speed becomes too high. That is, a problem such as an engine stop occurring due to a speed increase operation to an unnecessary high speed is likely to occur. However, when the overdrive portion is turned on, the shift limiting means is automatically switched to the operating state, and the main traveling speed change portion can shift only in a portion of the shift range on the low speed side. Things. That is, at the time of work, the traveling main transmission portion is shifted over the entire shifting range so that the traveling speed can be changed over a wide range from low speed to high speed. Can be changed while preventing the occurrence.

[Effect] The speed change range of the traveling main transmission portion is widened so that various operations can be performed from a very low traveling speed to a high traveling speed. In addition, the traveling main transmission portion can be shifted while the traveling speed does not become too high, so that traveling can be performed while smoothly shifting without engine stop or the like.

The structure, operation and effect of the invention according to claim 4 are as follows.

[Structure] In the structure of the invention according to any one of claims 1 to 3, a traveling auxiliary transmission having the overdrive portion and a low-speed transmission portion transmitting at a lower speed than the overdrive portion is driven. The main drive unit is connected in series, and the main transmission unit for traveling is constituted by the low speed transmission unit of the auxiliary transmission unit for traveling and the main transmission unit for traveling, and the overdrive unit is included. In such a case, the low-speed transmission unit is configured to be maintained at the cutting position.

[Operation] The traveling sub-transmission and the traveling main transmission are connected in series, and the shift range in which the traveling main transmission can be shifted and the transmission range of the low-speed transmission portion of the traveling sub-transmission are described. The shift range necessary for changing the traveling speed over the desired range is obtained by the combination of In addition, by connecting an overdrive portion that can only turn on and off the overdrive and the main driving device in series, and appropriately setting the shift range in which the main driving device can change the speed, as a whole, It is also possible to achieve the required shift range. However, in this case, it is necessary to provide the traveling main transmission with the same transmission range as the overall required transmission range, so that the traveling main transmission becomes complicated and large in size, and the entire device becomes large. On the other hand, a predetermined shift range is produced by a combination of the shift range of the main traveling transmission and the shift range of the low-speed transmission portion of the auxiliary sub-transmission, so that the traveling main transmission is relatively structured. The running speed can be changed over a desired shift range while being simple and compact.

When the overdrive portion is engaged, the low-speed transmission portion is maintained in the off position, and the transmission is performed while preventing the both from entering into a state in which the auxiliary transmission is damaged.

[Effect] The entire transmission can be relatively simple in structure and small in size. In addition, the overdrive section and the low-speed transmission section are both inserted into each other, so that the sub-transmission is not damaged, so that the transmission is highly reliable.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a pair of left and right front wheels 1, 1 and rear wheels 2, 2 which are freely drivable are configured to run on their own, and the front wheels 1 are steered. A lift arm 5 for connecting various working devices such as a rotary tilling device (not shown) to a rear part of a self-propelled body having a driving unit having a steering handle 3, a driver's seat 4, and the like, and a working device connected thereto. And a power take-out shaft 6 for transmitting power to the agricultural tractor.

A differential mechanism 8 for rear wheels is provided at the rear of a gear transmission case 7 forming a self-propelled body. As shown in FIG. 2, the rotational output of the engine E is transmitted to the main clutch C1 via a main clutch C1. C1 is transmitted to the input shaft 9 of the transmission case 7, which is also used as the output shaft, and the rotating power of the input shaft 9 is transmitted to the input shaft 13 of the traveling transmission M.
The input gear 8a of the rear wheel differential mechanism 8 is formed as an integral part at the rear end of the output shaft 34 of the traveling transmission M, and the rotational output of the traveling transmission M is transmitted to the rear wheel differential mechanism 8 The traveling of the self-propelled body is made possible by the configuration of transmitting the vehicle.

The traveling transmission M is provided with the input shaft 13.
The transmission main transmission 10 having a first shift gear 11, a second shift gear 12, and the like as an input shaft, and a transmission clutch C
2, an input shaft 23 is connected in series, and has a first shift gear 21 and a second shift gear 22. A forward / reverse switching device 20, and an input shaft 33 is connected in series to an output shaft 24 of the forward / reverse switching device 20. And the first shift gear 31, the second shift gear 32, the output shaft 3
4 and a super reduction gear 40 having one shift gear 41 and the like.

The traveling main transmission 10 is provided with the input shaft 13.
Input shaft gears 15a to 15 which are rotatably supported integrally with each other
5d, four output gears 16a to 16d which are rotatably supported by the output shaft 14 in a state of being respectively meshed with the four input shaft gears 15a to 15d, and the four output shaft gears 16a to 16d. The first shift gear 11, the output shaft 14 of which supports the output shaft 14 so as to be integrally rotatable between the first output shaft gear 16a and the second output shaft gear 16b, and the fourth one of the four output shaft gears 16a to 16d. The output shaft 14 includes the second shift gear 12 and the like, which are supported so as to be integrally rotatable between the third output shaft gear 16c and the fourth output shaft gear 16d.
The shift gear 11 is connected to the first output gear 16a and the second output gear 1
6b, and the second shift gear 12 is switched to the third output gear 16c and the fourth output gear 16d, so that the first to fourth speeds can be switched. It is configured in.

That is, the first shift gear 11 is connected to the output shaft 1
When the one side surface of the first output shaft gear 16a meshes with the side output gear portion by sliding operation with respect to the shift gear support portion of No. 4, the first speed is established, and the rotating power of the input shaft 13 is changed to the first input shaft. The speed is reduced by the gear 15 a and the first output shaft gear 16 a and transmitted to the first shift gear 11.
Is transmitted to the output shaft 14. First shift gear 11
When one side of the second input shaft gear 16b meshes with the output gear portion of the second output shaft gear 16b, the second speed is established, and the rotational power of the input shaft 13 is reduced by the second input shaft gear 15b and the second output shaft gear 16b. Then, the power is transmitted to the first shift gear 11, and the rotating power of the first shift gear 11 is transmitted to the output shaft 14. When the second shift gear 12 is slid with respect to the shift gear supporting portion of the output shaft 14 and one side surface of the third output shaft gear 16c meshes with the side output gear portion, the third speed is established and the input shaft 13 The rotating power is reduced by the third input shaft gear 15c and the third output shaft gear 16c and transmitted to the second shift gear 12, and the rotating power of the second shift gear 12 is transmitted to the output shaft 14.
When the second shift gear 12 meshes with the output gear portion on one side of the fourth output shaft gear 16d, the fourth speed is established, and the rotating power of the input shaft 13 is changed to the fourth input shaft gear 15d and the fourth output shaft gear. 16d and transmitted to the second shift gear 12, and the rotational power of the second shift gear 12 is transmitted to the output shaft 14.

The forward / reverse switching device 20 includes the input shaft 23
Input shaft gears 25a to 2 rotatably supported by each other
5c, the second of the three input shaft gears 25a to 25
An intermediate gear 26 supported by a boss of the input shaft gear 25b so as to be relatively rotatable, a reverse rotation gear 27 meshing with the third input shaft gear 25c among the three input shaft gears 25a to 25c, and the three input shafts The first shift gear 21 and the second input shaft gear, the boss portion of the second input shaft gear 25b being rotatably supported integrally between the first input shaft gear 25a and the intermediate gear 26 among the gears 25a to 25c. The second shift gear 22, the input shaft 23 of which is integrally rotatably supported between the second input gear 25b and the third input shaft gear 25c, and the first input shaft gear 25a, the intermediate gear 26, and the reverse rotation gear 27 mesh with each other. The first shift gear 21 includes three output shaft gears 28a to 28c and the like, which are rotatably supported integrally on the output shaft 24.
To the first input shaft gear 25a and the intermediate gear 26, and the second shift gear 22 to the second input shaft gear 25b and the third input shaft gear 25c.
It is configured so that it can be switched between two high speed stages on the forward side and one reverse stage.

That is, the second shift gear 22 is connected to the input shaft 2
3, one side surface of the second input shaft gear 25b meshes with the side input gear portion by sliding operation with respect to the shift gear support portion, and the first shift gear 21 is moved with respect to the boss portion of the second input shaft gear 25b. When one side surface of the first input shaft gear 25a meshes with the flank input gear portion by sliding operation, the forward speed is reduced, and the rotating power of the input shaft 23 is reduced by the second shift gear 22 and the second input shaft gear 25b. To the first shift gear 21 via
The rotational power of the first shift gear 21 is applied to the first input shaft gear 25.
a and the transmission is transmitted to the output shaft 24 by the first output shaft gear 28a. When the second shift gear 22 meshes with the input gear of one side of the second input shaft gear 25b and the first shift gear 21 meshes with the input gear of one side of the intermediate gear 27, the forward gear High speed, input shaft 2
3 is the second shift gear 22 and the second input shaft gear 25
b to the first shift gear 21, and the rotational power of the first shift gear 21 is transmitted to the intermediate gear 26 and the second output shaft gear 2.
8b and transmitted to the output shaft 24. Second
When one side surface of the shift gear 22 meshes with the input gear portion on one side of the third input shaft gear 25c, the shift gear 22 becomes the reverse side, and the input shaft 2
The rotation power of the second shift gear 22, which rotates integrally with the third gear 3, is a third input shaft gear 25c, a reverse rotation gear 27, and a third output shaft gear 28c.
And the speed is changed and transmitted to the output shaft 24.

As shown in FIG. 3, the traveling auxiliary transmission 30 includes three gears 35, 36, 37 that the input shaft 33 supports so as to be relatively rotatable, and these three gears 35, 36, 37.
The first shift gear 3 whose input shaft 33 is supported so as to be integrally rotatable between a low-speed gear 35 and a high-speed gear 36 of the first 37
1. The second shift gear 32, which supports the input shaft 33 so as to be rotatable integrally with the high-speed gear 36 of the three gears 35, 36, 37 and the overdrive gear 37, and a large mesh with the low-speed gear 35. A first output shaft gear 38 rotatably supported by the output shaft 34 with a radial gear portion 38a at one end and a small-diameter gear portion 38b meshing with the high-speed gear 36 at the other end; A second output shaft gear 39 rotatably supported integrally with the output shaft 34 while meshing with the drive gear 37;
The first shift gear 31 is switched to a low-speed gear 35 and a high-speed gear 36, and the second shift gear 31
The shift gear 32 is engaged and disengaged with the overdrive gear 37, and the shift gear 41 is engaged and disengaged with the first output shaft gear 38, so that the overdrive speed, the first speed and the second speed lower than this speed are achieved. The configuration is such that the gear can be switched to a total of three gear stages, including the second gear.

That is, the first shift gear 31 is connected to the input shaft 3
Transmission gear 3 as a shift gear support that rotates integrally with the transmission gear 3
1a to be engaged with the passive gear 35a on one side of the low-speed gear 35, and the shift gear 41a.
The first output shaft gear 3 is slidably operated on a transmission gear 41a as a shift gear support portion which rotates integrally with the output shaft 34.
8 is engaged with the gear portion 38c on one end side, the first speed is established, and the rotating power of the first shift gear 31 rotating integrally with the input shaft 33 is reduced to the low speed gear 35 and the large-diameter gear portion of the first output shaft gear 38. The transmission is transmitted to the shift gear 41 by the gear 38a, and the rotational power of the shift gear 41 is transmitted to the output shaft 34. In this case, since the transmission ratio between the low-speed gear 35 and the large-diameter gear portion 38a is set for reduction, the input shaft 3
The rotation power of No. 3 is decelerated and transmitted to the output shaft 34. The first shift gear 31 is connected to a passive gear portion 36 a on one side of the high-speed gear 36.
When the shift gear 41 is meshed with the first output shaft gear 38, the second speed is established, and the rotating power of the first shift gear 31 rotating integrally with the input shaft 33 is changed to the high speed gear 36 and the first output shaft. The transmission is transmitted to the shift gear 41 by the small-diameter gear portion 38b of the gear 38.
Is transmitted to the output shaft 34. In this case, since the transmission ratio between the high-speed gear 36 and the small-diameter gear portion 38b is set to about 1, the rotation speed of the output shaft 34 is reduced to the input shaft 33.
And becomes higher than the rotation speed of the first speed. When the second shift gear 32 engages with the passive gear portion 37a of the overdrive gear 37 by sliding operation on the transmission gear 32a as a shift gear supporting portion that rotates integrally with the input shaft 33, the second shift gear 32 rotates integrally with the input shaft 33. The rotational power of the two-shift gear 32 is shifted by the overdrive gear 37 and the second output shaft gear 39 and transmitted to the output shaft 34. In this case, the overdrive gear 3
7 and the second output shaft gear 39 to the transmission gear 36
The transmission ratio between the input shaft 33 and the small-diameter gear portion 38b is set to be higher than the transmission ratio, so that the rotational power of the input shaft 33 is increased and transmitted to the output shaft 34, and the rotation of the output shaft 34 The speed is higher than the rotation speed in the case of the second speed. The transmission ratio between the overdrive gear 37 and the second output shaft gear 39 is preferably set to 2-3.

That is, the low-speed gear 35, the first shift gear 3
1, high speed gear 36, first output shaft gear 38, shift gear 4
1 constitutes a low-speed transmission portion LD of the subtransmission 30, and the second shift gear 32, the overdrive gear 37, and the second output shaft gear 39 each constitute an overdrive portion OD of the subtransmission 30. . The overdrive portion OD includes a shaft portion of the input shaft 33 on which the rear wheel differential mechanism 8 is located, compared to a shaft portion including the low speed transmission portion LD,
The output shaft 34 is provided so as to extend from a shaft portion on which the rear wheel differential mechanism 8 is located to a shaft portion including the low-speed transmission portion LD.

The first shift gear 31 of the first shift gear 31 and the second shift gear 32 is a low-speed shift gear 31, the second shift gear 32 is an overdrive shift gear 32, and the low-speed shift gear 31 is By engaging the shift gear 41 with the first output shaft gear 38 at 35, the low-speed transmission portion LD enters the low-speed side and the subtransmission 30 enters the first speed. By meshing the low-speed shift gear 31 with the high-speed gear 36 and the shift gear 41 with the first output shaft gear 38, the low-speed transmission unit LD enters the high-speed side engagement state, and the subtransmission 30 sets the output speed to the first speed. This is the second speed, which is higher than the second speed. By meshing the overdrive shift gear 32 with the overdrive gear 37, the overdrive section LD is brought into the engaged state, and the subtransmission 30 changes the overdrive speed so that the output speed is higher than the first speed and the second speed. Become a step.

As is clearly shown in FIG.
Is an input gear 42 meshing with the first output shaft gear 38,
A small-diameter gear 4 that supports the input gear 42 at one end so as to rotate integrally with the other end of a transmission shaft 43 that supports the input gear 42 at the other end.
4. The output shaft 3 meshes with the small-diameter gear 44.
4 includes an output gear 45 rotatably supported by the output gear 45, the shift gear 41, and the like.
4, the one side surface of the output gear 45 is engaged with the side gear portion 45a by sliding operation with respect to the transmission gear 41a, or the engagement is released, thereby switching between the on state and the off state. It is configured as follows. That is, when the shift gear 41 meshes with the output gear 45,
In this state, the rotational power of the first output shaft gear 38 is reduced by the input gear 42, the small diameter gear 44, and the output gear 45 and transmitted to the shift gear 41, and the rotational power of the shift gear 41 is transmitted to the output shaft 34. Output gear 4 of shift gear 41
When the meshing of the gear 5 is released, the cutting state is established.

The traveling main transmission unit MA is constituted by the traveling main transmission 10 and the low speed transmission unit LD of the traveling auxiliary transmission 30. The traveling main transmission unit MA is clearly shown in FIG. As described above, the shift operation is performed by the shift lever 50 among the shift lever 50, the overdrive operating tool 51, and the deceleration lever 52 located on the left lateral side of the driver's seat 4, and the overdrive section OD is operated by the overdrive operating tool 51. The super speed reducer 40 is operated by the speed reduction lever 52, and the forward / reverse switching device 20 includes a forward / reverse lever 49 located on the side of the handle post as shown in FIG.
It is configured to be operated by a high / low speed switch 48 located on the operation panel. The high / low speed switch 48 may be implemented by being attached to the grip of the forward / reverse lever 49. The operation structure is configured as follows.

As shown in FIG. 9, the shifter 5 which slides the overdrive shift gear 32 of the subtransmission 30 is operated.
7 is penetrated through the transmission case 7, and the overdrive operating tool 51 is attached to an end of the rotation support shaft 57 a protruding outside from the mission case 7.
Are connected to be rotatable integrally. That is, the overdrive operating tool 51 is moved around the axis of the rotation support shaft 57a in the lateral direction of the vehicle body in the second direction of the lever guide 56 shown in FIG.
By swinging along the guide groove 56b, the shifter 57 can swing around the axis of the rotation support shaft 57a, and the overdrive shift gear 32 can slide. Then, when the overdrive operating tool 51 is turned to the cutting position OFF located at one end of the second guide groove 56b, the overdrive shift gear 32 is brought into the meshing release position where it is disengaged from the passive gear portion 37a of the overdrive gear 37, Insert the overdrive operating tool 51 into the second guide groove 56.
b, the overdrive shift gear 32 is turned on.
At the position where it meshes with the passive gear portion 37a.

As shown in FIG. 9, a rotation shaft 58a of a shifter 58 for slidingly operating the shift gear 41 of the reduction gear 40.
Is connected through a link rod 58c to a swing link 58b integrally rotatably connected to an end of the rotary support shaft 58a protruding from the mission case 7 to the outside. The base end of the reduction lever 52 is rotatably connected to the lateral side wall of the transmission case 7. That is, the shifter 58 is rotated by swinging the reduction lever 52 in the vehicle longitudinal direction around the pivot shaft 52a of the transmission case 7 along the third guide groove 56c of the lever guide 56 shown in FIG. The shift gear 4 can be swung around the axis of the support shaft 58a.
1 can be slid. Then, the deceleration lever 52 is moved to the first cutting position OFF1 located at one end of the third guide groove 56c.
, The shift gear 41 is disengaged from the gear portion 45a of the output gear 45, and the gear portion 3 of the first output shaft gear 38
8c, and the deceleration lever 52 is moved to the second cutting position O located in the middle of the third guide groove 56c.
When the FF 2 is operated, the shift gear 41 is also moved from the gear portion 45 a of the output gear 45 to the gear portion 3 of the first output shaft gear 38.
8c, the shift gear 41 is disengaged from the gear portion 38c of the first output shaft gear 38 when the speed reduction lever 52 is operated to the ON position ON at the other end of the third guide groove 56c. Gear portion 45a of output gear 45
It becomes the deceleration entering position that meshes with.

The forward / reverse lever 49 is supported by a handle post so as to be swingable in the longitudinal direction of the vehicle body, and is linked to a shifter that slides the second shift gear 22 of the forward / reverse switching device 20. That is, the swinging operation of the forward / reverse lever 49 switches the forward / backward switching device 20 between the forward side and the reverse side.

As shown in FIG. 2, the first transmission
A plurality of hydraulic pistons P having a shifter for sliding operation of the shift gear 11 provided inside the gear transmission case 7
1 to P3 and P5, the shifter for sliding the second shift gear 11 of the main transmission 10 is slidably connected to the first hydraulic piston P1.
And a shifter for sliding the low-speed shift gear 31 of the auxiliary transmission 30 is connected to the second hydraulic piston P2 of the plurality of hydraulic pistons P1 to P3, P5.
5, a shifter for sliding operation of the first shift gear 21 of the forward / reverse switching device 20 is connected to the third hydraulic piston P3 among the plurality of hydraulic pistons P1 to P3, P5.
Among them are connected to the fifth hydraulic piston P5. FIG.
, Two first solenoid valves V1 and V1 connected to the first hydraulic piston P1, and two second solenoid valves V2 and V2 connected to the second hydraulic piston P2.
V2, two third solenoid valves V3 and V3 connected to the third hydraulic piston P3, and the fifth hydraulic piston P5.
The pump port of each electromagnetic valve connected to one fifth electromagnetic valve V5 connected to the first filter F1, an oil supply passage 1 having an oil supply section 100 to the power steering device, and the like.
01 is connected to the discharge side of the hydraulic pump PM, and the suction side of the hydraulic pump PM is connected to the second filter F2.
The gear transmission case 7 is connected to an oil outlet of the gear transmission case 7 by a suction oil passage 102 having the same.

That is, the hydraulic pump PM is driven by the engine E, and the lubrication stored in the gear transmission case 7 for lubrication of the main traveling transmission 10, the forward / reverse switching device 20, the auxiliary transmission 30, and the like. The oil is taken out through the second filter F2 so that the oil can be removed even if dust such as iron powder is mixed therein.
On the downstream side of M, the fluid passes through the first filter F1 again and is supplied to each of the electromagnetic valves V1 to V3 and V5 as clean working oil subjected to dust removal processing. The two first solenoid valves V1 and V1 control the supply of hydraulic oil to the first hydraulic piston P1 to drive and stop the first hydraulic piston P1, and the first hydraulic piston P1 causes the main transmission 10 to operate. Is operated to change the first shift gear 11. The two second solenoid valves V2 and V2 control the supply of hydraulic oil to the second hydraulic piston P2 to drive and stop the second hydraulic piston P2. 2 shift gear 12
Change the operation. Two third solenoid valves V3, V3
Controls the supply of hydraulic oil to the third hydraulic piston P3 to drive and stop the third hydraulic piston P3, and the third hydraulic piston P3 switches the low-speed shift gear 31 of the auxiliary transmission 30. The fifth solenoid valve V5 controls the supply of hydraulic oil to the fifth hydraulic piston P5 to drive and stop the fifth hydraulic piston P5. The fifth hydraulic piston P5 controls the first shift gear 21 of the forward / reverse switching device 20. Change the operation.

The transmission clutch C2 is constituted by a hydraulic clutch which is operated to be turned on and off by a fourth hydraulic piston P4 incorporated in the clutch body, and a pilot control valve 55a for the fourth hydraulic piston P4, a plurality of check valves for detection. A control hydraulic circuit 55 including a control hydraulic circuit 55b and the like is connected to the oil supply passage 101 and is linked to the plurality of hydraulic pistons P1 to P3, P5 and the forward / reverse lever 49 so that the hydraulic pistons P1 to P3, P5 Is driven or the forward / reverse lever 49 is operated, this is detected by the check valve 55b, and at least one of the shift gears 11, 12, 21, 22, 31 is changed. The clutch C2 for shifting is automatically turned off, and the hydraulic pistons P1 to P3, 5. When the forward / reverse lever 49 stops, this is detected by the check valve 55b, and it is determined that the shifting operation of the shift gears 11, 12, 21, 22, 31 has been completed, and the shift clutch C2 is automatically engaged. It is configured to return to. That is, the main transmission 10, the forward / reverse switching device 20, and the auxiliary transmission 30
When the gearshift operation is performed, the gearshift clutch C2 is disengaged to disengage the interlocking of the main transmission 10 with the wheels 1, 2 or the interlocking of the forward / reverse switching device 10 and the subtransmission 30 with the engine E. The shifting of the shift gears 11, 12, 21, 22, 31 can be carried out smoothly, and when the shifting operation of the main transmission 10, the forward / reverse switching device 20 and the auxiliary transmission 30 is completed, the transmission clutch C2 is returned to enable the transmission from the engine E to the wheels 1 and 2.

The first electromagnetic valve V1, the second electromagnetic valve V2, the third electromagnetic valve V3, and the fifth electromagnetic valve V5 are each connected to a lead wire 1 having a connector 103.
04 is linked to the shift control mechanism 53,
An operation position sensor 54 for operating the shift control mechanism 53 on the shift lever 50 and the overdrive operating tool 5
The detection switch 69 acting on the switch 1 and the high / low speed switch 48 are linked to each other. The operation position sensor 54 is a potentiometer that is rotated by the operation force of the shift lever 50, and the shift lever 50 measures the parking position P, the neutral position N, the first speed position D1 to the eighth speed position D8 shown in FIG. Which of the ten operation positions has been operated is detected, and the detection result is output to the transmission control mechanism 53 as an electric signal. The detection switch 69 turns the overdrive operating tool 51 into the ON position.
When the overdrive lever 51 is pressed by the lever 51, and when the overdrive lever 51 is operated to the cutting position OFF, the press operation by the lever 51 is released, so that the overdrive lever 51 enters. It is configured to detect which one of the position ON and the cut position OFF has been operated, and output the detection result to the transmission control mechanism 53 as an electric signal. Transmission control mechanism 53
Is constituted by a microcomputer. When the shift lever 50, the overdrive operating tool 51, and the high / low speed switch 48 are operated, the operation position sensor 54 and the detection switch 69 are operated.
And the high-low speed switch 48 and the electromagnetic valves V1 to V3, V5 based on the shift control program preset and input in the storage unit of the shift control mechanism 53.
The hydraulic pistons P1, P
2, P3 and P5 are automatically operated as follows.

That is, when the high / low speed switch 48 is switched to the high speed side, the fifth hydraulic piston P5 is moved to the first shift gear 21a based on the information from the switch 48.
Is operated so as to be in a high-speed position at which it meshes with the intermediate gear 26, and when the high / low speed switch 48 is operated to switch to the low speed side, the fifth shift piston P5 moves the first shift gear 21a to the 1 input shaft gear 2
An operation is performed so that the low-speed position meshes with 5a.

When the shift lever 50 is operated to the parking position P or the neutral position N, the shift control mechanism 53 automatically enters the transmission stop control mode based on information from the potentiometer 54. That is, the first hydraulic piston P1, the second hydraulic piston P2 and the third hydraulic piston P2 are prioritized over the information from the detection switch 69 and based on the information from the potentiometer 54.
In the control mode for operating the hydraulic piston P3, the first
The hydraulic piston P1 is operated so that the first shift gear 11 is at a neutral position where the first shift gear 11 does not mesh with the first output shaft gear 16a or the second output shaft gear 16b, and the second hydraulic gear P2 is moved by the second shift gear 12 to the third output gear. The third hydraulic piston P3 is operated to a neutral position in which the low-speed shift gear 31 does not mesh with the low-speed gear 35 or the high-speed gear 36 so that the third hydraulic piston P3 is operated so as not to mesh with the shaft gear 16c or the fourth output shaft gear 16d. Operate to become.

When the overdrive operating tool 51 is in the cutting position OF
When operated to F, the transmission control mechanism 53 automatically enters the low-speed transmission control mode based on information from the detection switch 69. That is, the control mode is such that the three hydraulic pistons P1, P2, and P3 are switched based on the information from the potentiometer 54. When the shift lever 50 is operated to the first speed position D1,
Operating the first hydraulic piston P1 so that the first shift gear 11 is in the first speed position where the first shift gear 11 meshes with the first output shaft gear 16a;
The second hydraulic piston P3 is operated such that the second shift gear 12 is at a neutral position where the second shift gear 12 does not mesh with the third output shaft gear 16c or the fourth output shaft gear 16d, and the third hydraulic piston P3 is operated.
Is operated so that the low-speed shift gear 31 is at a low-speed position where the low-speed shift gear 31 meshes with the low-speed gear 35. When the shift lever 50 is operated to the second speed position D2, the first hydraulic piston P1 is operated so as to be in the second speed position where the first shift gear 11 meshes with the second output shaft gear 16b, and the second hydraulic piston P2 is operated. The second shift gear 12 is operated so as to be in the neutral position where it does not mesh with the third output shaft gear 16c or the fourth output shaft gear 16d, and the third hydraulic piston P3 is moved to the low speed position where the low speed shift gear 31 meshes with the low speed gear 35. Operate to become.
When the shift lever 50 is operated to the third speed position D3, the first
The hydraulic piston P1 is operated so that the first shift gear 11 is at a neutral position where the first shift gear 11 does not mesh with the first output shaft gear 16a or the second output shaft gear 16b, and the second hydraulic gear P2 is moved by the second shift gear 12 to the third output gear. 3 meshing with the shaft gear 16c
The third hydraulic piston P3 is operated so as to be at the low speed position where the low speed shift gear 31 is engaged with the low speed gear 35. Shift lever 50 in fourth speed position D
4, the first hydraulic piston P1 is moved from the first shift gear 11 to the first output shaft gear 16a.
6b, the second hydraulic piston P2 is operated so as to be in the fourth speed position where the second shift gear 12 meshes with the fourth output shaft gear 16d, and the third hydraulic piston P3 is operated at a low speed. The shift gear 31 is operated so as to be at a low speed position where the low speed gear 35 meshes with the low speed gear 35. When the shift lever 50 is operated to the fifth speed position D5, the first hydraulic piston P1 moves the first shift gear 11 to the first output shaft gear 16
a so that the second hydraulic piston P2 is shifted to the third output shaft gear 16 by the second shift piston 12.
The third hydraulic piston P3 is operated so as to be in the high-speed position where the low-speed shift gear 31 is engaged with the high-speed gear 36 so as to be in the neutral position where the low-speed shift gear 31 does not mesh with the fourth output shaft gear 16d. When the shift lever 50 is operated to the sixth speed position D6, the first hydraulic piston P1 is moved to the first shift gear 1 position.
1 is operated so as to be in the second speed position meshing with the second output shaft gear 16b, and the second hydraulic piston P2 is moved to the second shift gear 1
2 is operated so as to be in a neutral position where it does not mesh with the third output shaft gear 16c and the fourth output shaft gear 16d, and the third hydraulic piston P3 is brought into a high speed position where the low speed shift gear 31 meshes with the high speed gear 36. To operate. Shift lever 5
When 0 is operated to the seventh speed position D7, the first hydraulic piston P1 is operated so that the first shift gear 11 is at a neutral position where the first shift gear 11 does not mesh with either the first output shaft gear 16a or the second output shaft gear 16b. Then, the second hydraulic piston P2 is operated so as to be in the third speed position where the second shift gear 12 meshes with the third output shaft gear 16c, and the third hydraulic piston P3 is shifted to the high speed position where the low speed shift gear 31 meshes with the high speed gear 36. Operate as follows. When the shift lever 50 is operated to the eighth speed position D8, the first hydraulic piston P1 is moved to a neutral position where the first shift gear 11 does not mesh with either the first output shaft gear 16a or the second output shaft gear 16b. The second hydraulic piston P2 is operated so as to be in the fourth speed position where the second shift gear 12 meshes with the fourth output shaft gear 16d, and the third hydraulic piston P3 is operated in the high speed position where the low speed shift gear 31 meshes with the high speed gear 36. Operate to become.

The overdrive operating tool 51 is in the ON position.
Is operated, the shift control mechanism 53 operates the detection switch 6
9 automatically enters the overdrive control mode. That is, the hydraulic pistons P1, P2 and P
The third hydraulic piston P3 of the three is a potentiometer 5
4, the shift gear 31 for low speed is maintained so as to be in the neutral position where it does not mesh with the low speed gear 35 and the high speed gear 36, and the shift gear 31 for the hydraulic pistons P1, P2 and P3 is not operated. The control mode is such that only the first hydraulic piston P1 and the second hydraulic piston P2 are switched based on the information from the potentiometer 54.
Then, when the shift lever 50 is operated to the first speed position D1, the first shift piston 11 moves the first hydraulic piston P1 to the first shift position.
The first hydraulic gear P is operated so as to be in the first speed position meshing with the output shaft gear 16a.
The third hydraulic piston P3 is operated to a neutral position where the low-speed shift gear 31 does not mesh with the low-speed gear 35 or the high-speed gear 36 so that the neutral position does not mesh with the output shaft gear 16c and the fourth output shaft gear 16d. Perform maintenance operation so that When the shift lever 50 is operated to the second speed position D2, the first hydraulic piston P1
The second hydraulic gear P is operated so as to be in the second gear position so as to mesh with the output shaft gear 16b.
The third hydraulic piston P3 is operated to a neutral position where the low-speed shift gear 31 does not mesh with the low-speed gear 35 or the high-speed gear 36 so that the neutral position does not mesh with the output shaft gear 16c and the fourth output shaft gear 16d. Perform maintenance operation so that When the shift lever 50 is operated to the third speed position D3, the first shift piston 11 moves the first hydraulic piston P1 to the first gear position.
Operate so that the output shaft gear 16a and the second output shaft gear 16b do not mesh with the neutral position, and move the second hydraulic piston P2 to the third speed position where the second shift gear 12 meshes with the third output shaft gear 16c. To maintain the third hydraulic piston P3 at a neutral position where the low-speed shift gear 31 does not mesh with the low-speed gear 35 or the high-speed gear 36. When the shift lever 50 is operated to the fourth speed position D4, the first shift piston 11 moves the first hydraulic piston P1 to the first gear position.
The second hydraulic piston P2 is operated so as to be in the fourth speed position where the second shift gear 12 meshes with the fourth output shaft gear 16d so that the neutral position does not mesh with the output shaft gear 16a and the second output shaft gear 16b. To maintain the third hydraulic piston P3 at a neutral position where the low-speed shift gear 31 does not mesh with the low-speed gear 35 or the high-speed gear 36.

As shown in FIG. 9, the transmission gear 7 is swingably supported by a transmission case 7 via a rotary support shaft 59a and is slidably operated by the third hydraulic piston P3 to slide the low speed shift gear 31. The shifter 59 to be operated is provided with the first restraining arm 61 so as to swing integrally with the shifter 59 by integral formation, and the second restraining arm 62 is mounted to the shifter 57 that slides the shift gear 32 for overdrive. By being provided so as to swing integrally with the shifter 57 by integral formation, the second restraint arm 62 is provided with a restraint pin 64 whose tip side slidably enters a pin hole 63 provided in the first restraint arm 61. A shift operation is performed in which both the low-speed shift gear 31 and the overdrive shift gear 32 are engaged. It has configured transmission restraining device 60 to odd.

That is, as shown in FIG. 10A, when the shifter 59 is in the operating position where the low-speed shift gear 31 is engaged with the high-speed gear 36, the two control arms 61,
Reference numeral 62 denotes a positional relationship in which the restraining pin 64 enters one end of the arc-shaped first pin hole 63a centered on the axis of the rotation support shaft 59a of the pin hole 63, as shown in FIG. When the shifter 59 is in the operating position where the low-speed shift gear 31 is engaged with the low-speed gear 35, the two control arms 61 and 62 are connected to the other end of the first pin hole portion 63a of the pin hole 63 by the control pin 64. In any case, the first restraining arm 61 is connected to the restraining pin 6.
The stopper 4 acts as a stopper to receive and support the shifter 57. That is, the shift gear 32 for overdrive is received and supported so as not to swing to the side meshing with the overdrive gear 37. On the other hand, as shown in FIG. 10B, when the shifter 59 is in the operation position where the low-speed shift gear 31 does not mesh with the low-speed gear 35 or the high-speed gear 36, the two restraint arms 61 and 62 are pin holes. 63, a second pin hole portion 6 extending from a middle portion of the first pin hole portion 63a in a direction intersecting the first pin hole portion 63a.
The position is such that the traction pin 64 can move inside the inside 3b, and the first traction arm 61 releases the stopper action on the traction pin 64 to allow the shifter 57 to swing. As shown in FIG.
Is in the operating position for engaging the overdrive shift gear 32 with the overdrive gear 37, the two restraint arms 61, 62 are engaged in the second pin hole portion 6 of the pin hole 63.
It becomes a positional relationship in which the restraining pin 64 enters the end of 3b,
The traction pin 64 acts as a stopper on the first traction arm 61 to receive and support the shifter 59. That is, the low-speed shift gear 31 is received and supported so as not to swing to the operation position where it engages with the low-speed gear 35 or the operation position where it engages with the high-speed gear 36. In contrast, FIG.
As shown in (a) to (c), when the shifter 57 is in the operation position for disengaging the overdrive shift gear 32 from the overdrive gear 37, both the restraint arms 61 and 62 are connected to the first pin of the pin hole 63. The positional relationship is such that the traction pin 64 can move inside the hole portion 63 a, and the traction pin 64 releases the stopper action on the first traction arm 61 to allow the shifter 59 to swing.

Thus, when the low-speed shift gear 31 is at the neutral position where it does not mesh with either the low-speed gear 35 or the high-speed gear 36, the shift check device 60 releases the overdrive shift gear 32 from meshing with the overdrive gear 37. When the low-speed shift gear 31 is in the position meshed with the low-speed gear 35 or the high-speed gear 36, the shift check device 60 sets the overdrive shift gear 32 to the overdrive gear. It is not possible to switch from the disengaged position to the engaged position for 37. Further, when the overdrive shift gear 32 is at the disengaged position disengaged from the overdrive gear 37, the transmission check device 60 causes the low-speed shift gear 31 to mesh with the low-speed gear 35 and the high-speed gear 36 from the disengaged position. Position is allowed, but when the overdrive shift gear 32 is in the position meshed with the overdrive gear 37,
The low-speed shift gear 31 is a low-speed gear 3
5 and the high-speed gear 36 cannot be switched from the disengaged position to the engaged position.

Further, the shift control mechanism 53 is provided only when the shift lever 50 is operated to the parking position P or the neutral position N and both the first shift gear 11 and the second shift gear 12 of the main transmission 10 are operated to the neutral position. By operating the low-speed shift gear 31 of the auxiliary transmission 30 to the neutral position, the traveling main transmission unit MA makes the first shift gear 11
When both the shift gear 12 and the low-speed shift gear 31 are in the neutral state where they are in the neutral position, the transmission check device 60 allows the overdrive portion OD to be switched from the off-going to the on-going, and the traveling main transmission portion. When the MA is in the transmission state in which one of the first shift gear 11 and the second shift gear 12 and the low-speed shift gear 31 are in the meshing position, the transmission restraint device 60 turns off the overdrive portion OD. Is disabled.

As shown in FIG. 5, a stopper 66 for the shift lever 50 is mounted on the back side of the lever guide 56. When the electromagnetic solenoid 67 attached to the base end side of the stopper 66 and the lever guide 56 is turned on and off, the stopper 66 is swung around the axis of the pivot shaft 68 by the driving force of the electromagnetic solenoid 67, Action part 66a on the tip side of 66
Enters the moving path of the shift lever 50 and the shift lever 5
0, which can be received and supported so as not to be operated at a speed higher than the fourth speed position D4, and the action portion 66a is retracted from the moving path of the shift lever 50 to the lateral outside thereof to release the stopper action on the shift lever 50. The operation is switched to the operation release state.

As shown in FIG. 11, the electromagnetic solenoid 6
7 is linked to the speed change control mechanism 53, and the speed change control mechanism 53 is based on information from the detection switch 69 and a control program preset and input to a storage unit of the speed change control mechanism 53. By automatically switching the electromagnetic solenoid 67, the stopper 66
Is switched between the operation state and the operation release state. That is, when the overdrive operating tool 51 is operated to enter the ON position, the transmission control mechanism 53 determines that the overdrive unit OD has been operated to enter based on the information from the detection switch 69, and based on the determination result, By automatically operating the electromagnetic solenoid 67 to the stopper operation side, the stopper 66 is switched to the operation state. Then, the overdrive operating tool 51
Is operated to the cutting position OFF, the transmission control mechanism 53
Determines that the overdrive section OD has been turned off based on the information from the detection switch 69, and automatically operates the electromagnetic solenoid 67 to the stopper releasing side based on the result of this determination, thereby causing the stopper 66 to operate as described above. Switch to the release state.

Thus, when the overdrive portion OD is turned off, the stopper 66 is automatically switched to the operation release state by the shift control mechanism 53 so that the shift lever 50 can be operated to the eighth speed position D8. By widening the operation range of the speed change lever 50, the main speed change section MA for traveling can be adjusted to the number of shift speeds of the main speed change device 10 and the sub speed change device 3
The speed change lever 50 allows the speed change operation to be performed over the entire eight steps determined by the combination with the number of speed steps of the low speed transmission portion LD being zero. That is, the shift range in which the shift operation can be performed by the shift lever 50 of the traveling main transmission unit MA is set to the eight stages originally provided in the traveling main transmission unit MA. When the overdrive section OD is operated, the stopper 66 is automatically switched to the operating state by the shift control mechanism 53, and the shift lever 50 is turned on.
The operating range of the transmission lever 50 is reduced so that the vehicle can only be operated up to the fourth speed position D4.
The transmission lever 5 is provided only in four low-speed stages of the eight stages determined by the combination with the number of low-speed transmission units LD.
0 disables the shifting operation. That is, the shift range in which the shift operation can be performed by the shift lever 50 of the traveling main transmission unit MA is limited to a part on the lower speed side of the shift range originally provided in the traveling main transmission unit MA.

That is, when performing work traveling, the deceleration lever 52 is operated to the first cutting position OFF1 and the
The transmission by the low-speed transmission unit LD is enabled while the value is set to 0, or the transmission by the low-speed transmission unit LD is enabled while the super reduction gear 40 is turned on by operating the deceleration lever 52 to the ON position. At the same time, the overdrive operating tool 51 is turned to the cut position OFF, and the overdrive section OD is turned to the cut position. Then, the stopper 66 is released from the operation for automatic operation of the shift control mechanism 53, and the shift lever 50 can be operated to the eighth speed position D8.
Can be shifted over the entire shift range from the first gear to the eighth gear, which is inherently provided.

That is, as shown in FIG. 12, when the shift lever 50 is operated to the first speed position D1, the main transmission 10
Both the transmission and the auxiliary transmission 30 are at the first speed, and the traveling transmission M is at the first speed on the low speed side where the low speed transmission portion LD is engaged. When the shift lever 50 is operated to the second speed position D2, the main transmission 10 is shifted to the sub-transmission 30 in the second speed.
Becomes the first speed, and the traveling transmission M becomes the second speed on the lower speed side. When the shift lever 50 is operated to the third speed position D3, the main transmission 10 is shifted to the third speed and the auxiliary transmission 30 is shifted to the first speed, and the traveling transmission M is shifted to the third speed on the low speed side. Be faster. When the shift lever 50 is operated to the fourth speed position D4, the main transmission 10 is in the fourth speed and the auxiliary transmission 30 is in the first speed, and the traveling transmission M is in the low speed fourth speed. Be faster. Shift lever 50 to fifth speed position D
When the speed is changed to 5, the main transmission 10 is shifted to the first speed and the auxiliary transmission 30 is shifted to the second speed, and the traveling transmission M is shifted to the lower fifth speed. When the shift lever 50 is operated to the sixth speed position D6, the main transmission 10 is shifted to the second speed and the auxiliary transmission 30 is shifted to the second speed, and the traveling transmission M is shifted to the low-speed sixth speed. Be faster. Shift lever 50
When the gearbox is operated to the speed position D7, the main transmission 10 is set to the third speed and the auxiliary transmission 30 is set to the second speed, and the traveling transmission M is set to the lower seventh speed. When the shift lever 50 is operated to the eighth speed position D8, the main transmission 10 is in the fourth speed and the auxiliary transmission 30 is in the second speed, and the traveling transmission M is in the low-speed eighth position. Be faster.

When traveling, the deceleration lever 52
To the second cutting position OFF2 to move the overdrive portion O
D and the overdrive operating tool 51 is turned on to turn the overdrive section OD on.
Operate at the entrance. At this time, the operation of the overdrive unit OD is performed only when the shift lever 50 is operated to the parking position P or the neutral position N and the traveling main transmission unit MA is in the neutral state by the operation of the shift check device 60. Becomes possible. Then, the stopper 66 is activated for the automatic operation of the transmission control mechanism 53, so that the transmission lever 50 can be operated only up to the fourth speed position D4. The gear can be shifted in the range from the first gear to the fourth gear in the gear range from the first gear to the eighth gear.

That is, as shown in FIG. 12, when the shift lever 50 is operated to the first speed position D1, the main transmission 10
At the first speed, the overdrive portion OD of the subtransmission 30 is turned on, and the traveling transmission M is at the first overdrive speed. When the shift lever 50 is operated to the second speed position D2, the overdrive portion OD of the subtransmission 30 is turned on at the second speed, and the traveling transmission M is in the second overdrive position. Be faster. When the shift lever 50 is operated to the third speed position D3, the main transmission 10 is shifted to the third speed and the overdrive portion O of the subtransmission 30 is operated.
D enters, and the transmission M for traveling becomes the third speed of overdrive. When the shift lever 50 is operated to the fourth speed position D4, the main transmission 10 enters the fourth drive speed, the overdrive portion OD of the subtransmission 30 is engaged, and the traveling transmission M becomes the fourth overdrive. Be faster. The gear positions (first to eighth speeds) of the traveling transmission M shown in FIG.
The figure shows a speed state obtained only by a combination of the shift speed of the main transmission 10 and the shift speed of the auxiliary transmission, in which the switching between the forward / reverse switching device 20 and the super-reduction device 40 is excluded from the calculation.

In performing the work, the overdrive operating tool 51 is turned to the cutting position OFF, and the auxiliary transmission 30 is turned on.
Turn off the overdrive part OD. When the deceleration lever 52 is operated to enter the ON position, the super reduction gear 40
Shift gear 41 meshes with the output gear 45, and the super reduction gear 40 is turned on, and the front and rear wheels 1 and 2 are driven at a lower speed than the drive speed when the auxiliary transmission 30 is set to the first speed or the second speed. Can be driven.

The shift lever 50 is mounted on the basis of the mounting structure shown in FIGS. That is, the lever support 7 rotatably supports the boss 50a of the transmission lever 50 with the pair of tongues 71a, 71a via the pivot pin 70.
1 is connected to a connecting portion 71b of the lever support 71 located below the tongue piece portion 71a so as to be integrally rotatable with a locking pin 72, and the connecting shaft 73 is connected to a bracket body 74a. A mounting bracket 74 rotatably supported by the first tongue piece 74b;
The transmission lever 50 is supported on the rear wheel fender 75 by connecting the rear wheel fender 75 to the rear wheel fender 75 via a connection bolt 76 that fixes the rear wheel 4a to the inner surface of the vehicle body of the rear wheel fender 75. The lever is a cross-swingable lever that swings in the vehicle longitudinal direction around the axis Y of the pivot pin 70 in the vehicle lateral direction, and swings along the first guide groove 56a that is bent as shown in FIG. It can be operated dynamically. One end of a helical spring 77 externally fitted to the boss portion 50a of the shift lever 50 is received and supported by the lever support 71, and the other end of the helical spring 77 is brought into contact with the base end of the shift lever 50. The spring 77 urges the shift lever 50 to swing against one inner wall surface of the first guide groove 56a.

The main body of the potentiometer 54 is fixed to a support plate 78 extending from the second tongue piece 74c of the mounting bracket 74, and the rotary operation shaft 54a of the potentiometer 54 is rotated integrally with one end of the connecting shaft 73. Shift lever 5 that can be freely connected and swingably operated around axis X
With the configuration in which the shift lever 50 rotates together with 0, the potentiometer 54 detects which of the parking position P, the neutral position N, and the first to eighth speed positions D1 to D8 has been operated. It is possible to do.

A positioning plate 81 comprising the upper edge of the main body 74a of the mounting bracket 74, a positioning member 83 pivotally connected to the free end side of the lever support 71 by a connecting pin 82, and a positioning member 83 The positioning body 83 and the tongue piece 71a of the lever support 71 are urged so as to urge the positioning roller 84 positioned inside the positioning body 83 against the uneven portion 81a of the positioning plate 81. A positioning mechanism 85 for positioning the transmission lever 50 at each of the operation positions P, N, D1 to D8 by a positioning spring 85 attached over the
Is configured. That is, when the shift lever 50 is swung along the first guide groove 56a, the lever support 7
1 swings around the axis X together with the speed change lever 50 to move the positioning body 83 along the uneven portion 81 a of the positioning plate 81. When the shift lever 50 is moved to each operation position P,
When operated to N, D1 to D8, the positioning roller 84 enters the recessed portion corresponding to the operation position P, N, D1 to D8 of the shift lever 50 in the uneven portion 81a due to the positioning spring 85, and the shift lever is moved. 50 is positioned at its operation position P, N, D1 to D8.

A brake cable 92 is connected to a free end side of a swing link 91 which is supported by a main body 74a of the mounting bracket 74 via a pivot pin 90 so as to be vertically swingable. The lever support 71 is provided with a link operation cam 93 composed of a roller that freely rolls into the long hole 91a of the swing link 91, and the shift lever 50 is operated between the neutral position N and the eighth speed position D8. In this case, the link operation cam 93 is moved by the swing link 9 because of the distance from the axis X of the long hole portion into which the link operation cam 93 is inserted.
1 is pushed up to the brake release position against the tension of the brake cable 92 and is maintained.
Is operated to the parking position P, the link operation cam 93 releases the push-up action on the swing link 91 because of the distance from the axis X of the long hole portion in which the link operation cam 93 enters in this case. Then, the swing link 91 is configured to be lowered to the brake-engaged position by the tension of the brake cable 92.

As shown in FIG. 8, the brake cable 92 is connected to an operation arm 94 of the parking brake device B. In the parking brake device B, as shown in FIG. 3, the output shaft 34 is connected to the second output shaft gear 39 and the rear wheel differential mechanism 8.
A transmission gear 95 for transmitting power to a front-wheel differential mechanism (not shown) in conjunction with a third output shaft gear G that is supported so as to be rotatable integrally with the transmission wheel, and the transmission case 7 slides. A brake pin 96 movably supported, and a brake spring 9 for slidably biasing the brake pin 96 such that a distal end working portion 96a of the brake pin 96 enters between teeth of the gear 95.
7 and the like. That is, the brake cable 9
2 is pulled by the swing link 91 to swing the operation arm 94 to the cutting position OFF, and the rotation support shaft 94a of the operation arm 94 is integrally rotatably connected to the inner end of the transmission case. The operation claw 98 is pressed against the flange 96a of the brake pin 96 to slide the brake pin 96 to the brake release position against the brake spring 97. Then, since the distal end working portion 96a of the brake pin 96 comes off from between the teeth of the gear 95 and releases the braking on the gear 95, the brake device B is turned off to release the braking on the front and rear wheels 1 and 2. When the brake cable 92 is loosened by the swing link 91 and the operation arm 94 is turned on by the operation force of the brake spring 97, the operation claw 98 releases the pressing action on the flange 96a, and the brake pin is released. 96
Is slid to the brake position by the brake spring 97. Then, since the distal end working portion 96b of the brake pin 96 enters between the teeth of the gear 95 to lock the gear 95 so as not to rotate, the brake device B is engaged to apply a brake to the front and rear wheels 1 and 2.

That is, when the shift lever 50 is operated to the neutral position N and the traveling position of the first speed position D1 to the eighth speed position D8, the swing link 91 is pushed up by the link operation cam 93, and the brake cable 92 is pulled. By operating and operating the operation arm 94 to the brake release position OFF, the parking brake device B is automatically switched off. When the shift lever 50 is moved to the parking position P, the swing link 91 is lowered to release the push-up by the link operation cam 93, and the brake cable 92 is loosened to operate the operation arm 94 to the brake-engaged position ON. Then, the parking brake device B is automatically turned on.

[Another Embodiment] By adopting the following control mode switching means in place of the stopper 66, the speed change range of the main traveling speed change section MA is restricted or the restriction is released. It may be configured and implemented. That is, when the overdrive unit OD is operated to be turned off, the control mode for automatically operating the control valves V1 to V3 based on the information from the potentiometer 54 by the transmission control mechanism 53 is changed to the main transmission unit for traveling. Each of the control valves V1 to V is controlled so that MA switches from the first speed to the eighth speed on the low speed side.
3 is automatically switched to a low-speed control mode in which the automatic transmission 3 is operated based on the information from the detection switch 69, and when the overdrive section OD is operated to enter, the transmission control mechanism 53 Potentiometer 54
The control mode in which the control valves V1 to V3 are automatically operated based on the information from the control valves V1 to V3 is set such that the traveling main transmission unit MA switches from the first speed to the fourth speed of the overdrive.
The control mode switching means for automatically performing the switching operation based on the information from the detection switch 69 is adopted for the overdrive control mode for automatically operating the control unit 3. Therefore, the control mode switching means and the stopper 66 are collectively referred to as a shift limiting means.

[Brief description of the drawings]

Fig. 1 Side view of the whole agricultural tractor

FIG. 2 is a schematic view of a traveling transmission device.

FIG. 3 is a sectional view of a traveling auxiliary transmission.

FIG. 4 is a plan view of an operation unit.

FIG. 5 is an explanatory diagram of an operation position of a shift lever.

FIG. 6 is a side view of the transmission lever mounting structure.

FIG. 7 is a sectional view of a transmission lever mounting structure.

FIG. 8 is a sectional view of a parking brake device.

FIG. 9 is a side view of the speed reduction lever and the speed change check device.

FIG. 10 is an explanatory view showing the operation of the transmission check device.

FIG. 11 is a hydraulic circuit and a block diagram of a shift operation.

FIG. 12 is an explanatory diagram of a speed state of the traveling transmission.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Main transmission device for traveling 30 Sub transmission device for traveling 50 Transmission gear lever 51 Operating tool 60 Transmission control device 66 Transmission limiting means OD Overdrive section LD Low-speed transmission section MA Main transmission section for traveling

Claims (4)

[Claims] 1. A traveling main transmission unit which can be shifted by a transmission lever, and an overdrive unit which can be turned on and off by an operating tool different from the transmission lever, and wherein the traveling main transmission unit is in a neutral state. In some cases, the overdrive section is allowed to be operated to switch from off to on, and when the traveling main transmission section is in the transmission state, the overdrive section is operated to be switched from off to on. A transmission structure for traveling of a work vehicle provided with a variable speed check device that disables the vehicle. 2. The vehicle according to claim 1, wherein the traveling speed is changed by a shift operation of the traveling main transmission unit by the transmission lever in a state where the overdrive unit is in an on state or an off state. The transmission structure for traveling of the described working vehicle. 3. A shift limiting means which is switchable between an operation state in which the shift range of the traveling main transmission portion is limited to a part on a low speed side and an operation release state in which the shift range limit is released, and When the drive unit is operated to enter, the shift limiting unit is automatically switched to the operating state, and when the overdrive unit is operated to be switched off, the shift limiting unit is automatically switched to the released state. The traveling transmission structure for a working vehicle according to claim 2, wherein the transmission structure is configured to be driven. 4. A traveling auxiliary transmission including the overdrive portion and a low-speed transmission portion transmitting at a lower speed than the overdrive portion is connected in series to a traveling main transmission, and The low speed transmission unit and the traveling main transmission constitute the traveling main transmission unit, and when the overdrive unit is turned on, the low speed transmission unit is maintained to be turned off. Claims 1 to
4. The traveling transmission structure for a working vehicle according to any one of the above items 3.