JPH08258584A - Hydraulic clutch operating structure - Google Patents

Abstract

PURPOSE: To prevent the different state of transmission torque of hydraulic clutches by setting in such a way that the operating pressure corresponding to the operating position of a human-initiated operating means at the time of operating from the transmission cutoff side of the hydraulic clutches to the transmission side is on the higher side than the operating pressure corresponding to the operating position of the human-initiated operating means at the time of operating conversely. CONSTITUTION: On the basis of the detected value of a position sensor 68, a control valve 35 is operated so as to obtain operating pressure corresponding to the operating position of a human-initiated operating means 52. At this time, it is so set that the operating pressure corresponding to the operating position of the human-initiated operating means 52 at the time of operating from the transmission cutoff side of hydraulic clutches 5, 6 to the transmission side is on the higher side than the operating pressure corresponding to the operating position of the human-initiated operating means 52 at the time of operating from the transmission side of the hydraulic clutches 5, 6 to the transmission cutoff side. This can prevent the different state of the transmission torque of the hydraulic clutches 5, 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operating structure for a wet multi-plate hydraulic clutch used for traveling or for transmitting power to a working device.

[0002]

2. Description of the Related Art In a wet multi-plate hydraulic clutch used for running a work vehicle, for example, a control valve capable of changing and adjusting the operating pressure of the hydraulic clutch and an artificial operating tool (clutch pedal, etc.) are mechanically provided. In some cases, the control valve is operated in association with the operation of a manual operation tool to change and adjust the operating pressure of the hydraulic clutch. Thus, the hydraulic clutch is operated to the transmission side and the transmission interruption side by operating the manual operation tool, and the hydraulic clutch can be brought into the half-clutch state by operating the manual operation tool to the intermediate position. .

[0003]

The wet multi-plate hydraulic clutch as described above is generally changed from the transmission disengaged state to the transmission state due to the fact that the static friction coefficient of the friction plate is larger than the dynamic friction coefficient and the conditions such as lubricating oil. It has a characteristic that it is difficult to switch, and conversely, once it is in the transmission state, it is difficult to switch from the transmission state to the transmission cutoff state (characteristic that it is difficult to connect and difficult to cut).

As a result, there is a difference in the transmission torque of the hydraulic clutch between the case where the manual operation tool is operated from the transmission interruption side to the transmission side and the case where the manual operation tool is operated from the transmission side to the transmission interruption side. is there. In other words, even if the manipulator is operated to the same operating position, if the transmission shut-off side is operated to the above-mentioned operating position, the transmission torque of the hydraulic clutch is relatively small, and conversely the manipulator is moved from the transmission side. When the hydraulic clutch is operated to the above-described operation position, the transmission torque of the hydraulic clutch is relatively large, and the operator who operates the manual operation tool may feel uncomfortable. It is an object of the present invention to prevent a state in which the transmission torque of the hydraulic clutch is different due to the difference in the operating direction of the manual operation tool in the operation structure of the hydraulic clutch.

[0005]

The feature of the present invention resides in that the hydraulic clutch operating structure as described above is constructed as follows. [1] Equipped with a wet multi-plate hydraulic clutch, a control valve capable of changing and adjusting the operating pressure of the hydraulic clutch, an artificial operation tool that is operated artificially, and a position sensor that detects the operation position of the artificial operation tool. , Equipped with a control means for operating the control valve so that the operating pressure corresponds to the operating position of the manual operation tool based on the detected value of the position sensor, and the manual operation tool moves from the transmission side of the hydraulic clutch to the transmission cutoff side. The operating pressure corresponding to the operating position of the manual operating tool when the manual operating tool is operated from the transmission disengagement side of the hydraulic clutch to the transmission side is higher than the operating pressure corresponding to the operating position of the manual operating tool when operated. It is set to be on the high voltage side.

[2] In the configuration of the above item [1], as the transmission arranged on the lower side of the hydraulic clutch is operated to shift to a higher speed side, the manual operation tool moves from the transmission side of the hydraulic clutch to the transmission cutoff side. It is set so that the difference between the operating pressures when it is operated and when it is operated from the transmission cutoff side to the transmission side is large.

[0007]

[Action]

[I] When configured as in the preceding paragraph [1], as shown in, for example, the solid line A1 and the alternate long and short dash line A2 in FIG. 4, the manual operation tool 52 is provided between the transmission cutoff side (step position) and the transmission side (return position). When operated, the operating pressure P of the hydraulic clutches 5 and 6 is set to a value corresponding to the operating position of the manual operating tool 52 by the control valve based on the detection of the operating position of the manual operating tool 52 by the position sensor. Is adjusted to. In this case, when configured as in the previous section [1], when the manual operation tool 52 is operated from the transmission side (return position) to the transmission cutoff side (stepping position) as shown by the solid line A1 and the alternate long and short dash line A2 in FIG. Operating pressure P corresponding to the operating position of the artificial operating tool 52 (dotted line A
Compared to 2), the manual operation tool 52 has a transmission blocking side (stepping position)
Manipulation tool 5 when it is operated from the power transmission side (return position)
The operating pressure P (solid line A1) corresponding to the operation position 2 is on the high pressure side.

As a result, in the hydraulic clutch in which it is difficult to switch from the transmission cut-off state to the transmission state, the operating pressure corresponding to the operation position of the manual operation tool is set higher, and the hydraulic clutch transmission is changed in place of the operation position of the manual operation tool. The state in which the switching to the state is delayed is reduced. Conversely, in a hydraulic clutch that is difficult to switch from the power transmission state to the power transmission disengagement state, the operating pressure corresponding to the operation position of the manual operation tool is set to a low level, and the hydraulic clutch transmission is switched to the power transmission disengagement state regardless of the operation position of the manual operation tool. The state of delayed switching is reduced. Therefore, there is a difference in the transmission torque of the hydraulic clutch between the case where the manual operation tool is operated from the transmission interruption side to a certain operation position and the case where the manual operation tool is operated from the transmission side to the aforementioned operation position. Can be reduced.

[II] When configured as in the above item [2],
As in the case of the configuration of the above [1], the "action" described in the above [I] is provided, and in addition to this, the following "action" is provided. In general, a transmission may be arranged on the lower side of the hydraulic clutch so that the power from the hydraulic clutch is transmitted to the traveling wheels and the working device via the transmission. In this case, the larger the gear shift operation on the lower hand side is, the larger load is applied to the hydraulic clutch. Therefore, as the gear shift operation is performed on the higher speed side, the hydraulic clutch is in the transmission disengaged state. The characteristic that it is difficult to switch to the power transmission state and that it is difficult to switch from the power transmission state to the power transmission cutoff state (characteristic that it is difficult to connect and hard to cut) becomes strong.

Therefore, if the configuration as in the above item [2] is adopted,
As the lower gearbox is operated to shift to the higher speed side,
The difference in the operating pressure P in the above item [1] (the difference between the solid line A1 and the alternate long and short dash line A2 shown in FIG. 4) is set to a large value. As a result, even if the transmission on the lower side is operated to shift to the high speed side and a large load is applied to the hydraulic clutch, the manual operation tool is operated from the transmission cutoff side to a certain operating position as described in [I] above. It is possible to reduce the state that the transmission torque of the hydraulic clutch is different between the case and the case where the manual operation tool is operated from the transmission side to the above-mentioned operation position.

[0011]

According to the present invention, in the operation structure of the wet multi-plate hydraulic clutch, the transmission torque of the hydraulic clutch is different even at the same operating position of the manual operating tool due to the difference in the operating direction of the manual operating tool. It was possible to reduce the number of states to say, and it was possible to suppress the operator's discomfort and improve the operational feeling of the hydraulic clutch.

According to the second aspect, similar to the case of the first aspect, the above-mentioned "effect of the invention" is provided. According to the second aspect of the present invention, regardless of the gear position of the transmission on the lower side of the hydraulic clutch,
It was possible to reduce the situation where the transmission torque of the hydraulic clutch was different even at the same operating position of the human operating tool, and it was possible to suppress the operator's discomfort and further improve the operational feeling of the hydraulic clutch.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. (1) FIG. 1 shows the inside of a mission case 8 of a four-wheel drive agricultural tractor, in which power from an engine 1 is transmitted to a PTO via a transmission shaft 2 and a hydraulic multi-plate PTO clutch 3.
It is transmitted to the shaft 4. The power from the engine 1 is applied to the forward clutch 5 (corresponding to a hydraulic clutch) or the reverse clutch 6
(Corresponding to hydraulic clutch), cylindrical shaft 7, main transmission 10
(Corresponding to a transmission device), the first auxiliary transmission device 11 (corresponding to a transmission device), the second auxiliary transmission device 12 (corresponding to a transmission device), and the rear wheel differential device 13 are transmitted to the left and right rear wheels 14. It The power branched from immediately before the rear wheel differential device 13 is transmitted through the transmission shaft 15, the hydraulic clutch type front wheel transmission device 16, the front wheel transmission shaft 17, and the front wheel differential device 18 to the left and right front wheels 19.
Is transmitted to

The forward clutch 5 and the reverse clutch 6 are wet multi-plate hydraulics in which a friction plate (not shown) and a piston (not shown) are combined, and are operated to the transmission side by supplying hydraulic oil. , Is urged toward the transmission cutoff side by a spring (not shown). When the forward clutch 5 is operated to the transmission side, the power of the engine 1 is transferred from the forward clutch 5 to the cylindrical shaft 7
It flows directly to and the aircraft advances. When the reverse clutch 6 is operated to the transmission side, the power of the engine 1 is transmitted to the cylindrical shaft 7 in the reverse rotation state via the reverse clutch 6 and the transmission shaft 20, and the machine body moves backward.

The main transmission 10 comprises four hydraulic multi-plate type first speed clutches 21, second speed clutches 22 and third speed clutches 23.
And a four-speed clutch 24 are arranged in parallel in a hydraulic clutch type so that four speeds can be obtained. By operating one of the first-fourth clutches 21-24 to the transmission side, The power from the cylindrical shaft 7 on the first side is subjected to a speed change operation in four stages and transmitted to the transmission shaft 25 on the lower side.

The first auxiliary transmission 11 is also of a hydraulic clutch type in which two hydraulic multi-plate low speed clutches 26 and a high speed clutch 27 are arranged in parallel, and one of the low speed and high speed clutches 26, 27 is used. By operating to the transmission side, the power from the transmission shaft 25 on the main transmission device 10 side is shifted in two stages and transmitted to the second auxiliary transmission device 12 on the lower side. The second sub-transmission device 12 is of a synchromesh type in which the shift member 53 is slid and operated, and is capable of shifting in two stages, and is mechanically shifted by a shift lever 28 described later.

(2) Next, forward and reverse clutches 5, 6,
The hydraulic circuit for the main transmission 10 and the like will be described. FIG.
As shown in FIG. 3, an electromagnetic proportional valve 35 (corresponding to a control valve) for the forward and reverse clutches 5, 6 and pilot operated switching valves 36a, 37a are provided in an oil passage 30 from the pump 29.
Pilot operated switching valves 31a, 32a, 33a for the first to fourth speed clutches 21 to 24 of the main transmission 10.
34a, the low speed and high speed clutch 2 of the first auxiliary transmission device 11
Electromagnetic proportional valves 38 and 39 for 6 and 27 are connected in parallel.

An oil passage 40 branched from the oil passage 30 is provided with a hydraulic clutch 4 for differential lock operation in the front wheel differential device 18.
1, a pilot operated switching valve 42a, a hydraulic clutch 43 for differential lock operation in the rear wheel differential device 13
To the pilot operated switching valve 44a, the standard clutch 45 and the speed increasing clutch 46 of the front wheel transmission 16 (see FIG. 1).
(See the reference), pilot operated switching valves 47a, 48
a is connected in parallel. Each switching valve 31a-34
a, 36a, 37a, 42a, 44a, 47a, 48a
Is urged by a spring toward the oil discharge side (transmission cutoff side), and is operated to the supply side (transmission side) by supplying pilot hydraulic oil as described later.

A pilot oil passage 50 is branched from the oil passage 30 via a pressure reducing valve 49, and the pilot oil passage 50 is connected to the switching valves 31a to 34a, 36a, 37a, 42a, 44a ,.
47a, 48a are connected to the operation parts, and the operation parts have electromagnetically operated valves 31b, 32b, 33b, 34b, 36b,
37b, 42b, 44b, 47b, 48b are connected. Each solenoid operated valve 31b-34b, 36b, 37b,
42b, 44b, 47b, and 48b are urged toward the oil discharge side (transmission cutoff side) by springs, and when these are electrically operated to the supply side, the pilot operating oil causes the switching valves 31a to 34b.
a, 36a, 37a, 42a, 44a, 47a, 48a
Are supplied to the operation unit of the above, and these are operated to the supply side (transmission side).

(3) Next, the forward and reverse clutches 5,
6. The configuration of the operation unit of the main transmission 10 and the like will be described. As shown in FIGS. 2 and 3, at the base of the steering handle 58 for the front wheels 19, a forward / backward lever 59 for transmitting an electric forward signal and a backward signal is provided, and the forward / backward lever 59 is provided around the horizontal axis of the control portion of the aircraft. A gear shift lever 28 is supported so as to be swingable. Shift member 5 of second auxiliary transmission device 12 (see FIG. 1)
A shift fork 54 that slides 3 is mechanically interlocked with a shift lever 28 by a linkage mechanism 55, and the shift lever 28 is operated to three positions of a neutral stop position N, a low speed position L, and a high speed position H. The second auxiliary transmission device 12 is operated to change gears. A pair of limit switches 9 for detecting that the speed change lever 28 is operated to the low speed position L and the high speed position H is provided.

A lock pin 56, which is vertically movable, is provided on a lateral side portion of the speed change lever 28, and an operation button 57 for vertically moving the lock pin 56 is provided at an upper portion of the speed change lever 28. The lock pin 56 is a spring (not shown)
Is urged to move to a fixed position above the paper surface (the operation button 57 is also urged to the protruding side on the left side of the paper surface), and the lock pin 56 is engaged with the fixed guide plate 60. Causes the gear shift lever 28 to move to the neutral stop position N,
It is held at each of the low speed position L and the high speed position H. When the operation button 57 is pushed, the lock pin 56 is moved to the holding release position below the paper surface, and the gear shift lever 28 can be operated to the neutral stop position N, the low speed position L and the high speed position H.

A shift-up button 61 and a shift-down button 62 are vertically arranged on the left lateral side of the shift lever 28, and when the shift-up button 61 and the shift-down button 62 are pressed once as described later, one shift is performed. Up signal and shift down signal are transmitted,
The shift operation of the main and first auxiliary transmissions 10 and 11 shown in FIG. 1 is performed.

As shown in FIG. 2, a 7-segment gear shift display portion 64 for displaying the gear shift positions (1st to 8th gears) of the main and first auxiliary transmissions 10, 11 and a forward / reverse clutch by a forward / reverse lever 59. A forward lamp 65 and a backward lamp 66, which indicate which one of 5 and 6 is operated on the transmission side,
A neutral stop lamp 67 indicating that the shift lever 28 is operated to the neutral stop position N is provided in the control section.
As shown in FIG. 3, a pressure sensor 74 is provided to detect whether or not the operating pressures of the forward and reverse clutches 5 and 6 have reached a predetermined pressure in a transmission state. The lamps 65 and 66 are turned on.

(4) Next, the shift operation by the forward / backward lever 59, the shift lever 28, the shift up button 61 and the shift down button 62 will be described. When the forward / backward lever 59 shown in FIG. 2 is operated to the forward drive position F, an operation current is supplied to the electromagnetic operation valve 36b shown in FIG.
6a is operated to the supply side, the forward clutch 5 is operated to the transmission side, and the forward lamp 65 is turned on. On the contrary, when the forward / reverse lever 59 is operated to the reverse position R, the operation current is supplied to the electromagnetic operation valve 37b shown in FIG. 3, the switching valve 37a is operated to the supply side, and the reverse clutch 6 is moved to the transmission side. When operated, the reverse lamp 66 is turned on and the buzzer 71 shown in FIG. 2 operates intermittently.

As shown in FIG. 1, the main transmission 10 is capable of shifting in four stages and the first sub-transmission 11 is capable of shifting in two stages. Gear shifting is possible. In this case, the first auxiliary transmission 1
In the state in which the first low speed clutch 26 is operated to the transmission side, the first to fourth speed clutches 21 to 24 of the main transmission device 10 correspond to the shift positions of the first to fourth speeds, and the first auxiliary transmission device. In the state where the high speed clutch 27 of No. 11 is operated to the transmission side, the first speed to fourth speed clutches 21 to 2 of the main transmission 10 are
4 corresponds to the shift positions of the 5th speed to the 8th speed.

As shown in FIG. 3, the first speed of the main transmission 10 is increased.
Each of the fourth speed clutches 21 to 24 and the low speed and high speed clutches 26 and 27 of the first auxiliary transmission 11 is provided with a pressure sensor 74 for detecting whether or not the operating pressures thereof have reached a predetermined pressure in a transmission state. The current shift positions (1st speed to 8th speed) of the main and first auxiliary transmissions 10 and 11 are detected by the detection of each pressure sensor 74, and the detected shift positions are displayed on the shift display portion 64. .

When the shift-up button 61 of the shift lever 28 is pressed once while the shift lever 28 shown in FIG. 2 is being operated to the low speed position L or the high speed position H,
The main and first auxiliary transmissions 10, 11 are shifted to a shift position one speed higher than the current shift position, the shift position after the shift is displayed on the shift display portion 64, and the buzzer 71 is operated only once. The operator is informed of the end of the gear shift operation by operating. On the contrary, when the shift down button 62 is pushed once, the main and first auxiliary transmissions 10 and 11 are shifted to a shift position one speed lower than the current shift position, and the shift position after the shift is changed. Displayed on the display unit 64, the buzzer 71 operates only once to notify the operator of the end of the gear shift operation.

Next, for example, the forward / reverse lever 59 is operated to the forward position F (the forward clutch 5 is operated to the transmission side and the reverse clutch 6 is operated to the transmission interruption side), and the speed change lever 28 is moved to the low speed position. In the state of operating to L (the state in which the speed change lever 28 is held at the low speed position L by the operation button 57 and the lock pin 56), the operation button 5
When 7 is pushed and the lock pin 56 is removed downward from the guide plate 60, the switching valve 36a is operated toward the oil drain side by the electromagnetic operation valve 36b shown in FIG.
Is automatically operated to the transmission blocking side.

As a result, the speed change lever 28 is operated from the low speed position L to the neutral stop position N or the high speed position H while the operation button 57 is being pressed, and the operation button 57 is returned to the lock pin 56 to operate the speed change lever 28. Is held at the neutral stop position N or the high speed position H. In this case, when the operation button 57 is returned to the neutral stop position N, the switching valve 36a is operated to the supply side by the electromagnetic operation valve 36b,
The forward clutch 5 is immediately and automatically operated to the transmission side by the solenoid proportional valve 35. Operation button 5 at high speed position H
When 7 is returned, the solenoid operated valve 36b causes the switching valve 3
6a is operated to the supply side, and the forward clutch 5 is gradually and automatically operated to the transmission side by the solenoid proportional valve 35. With the forward / reverse lever 59 operated to the reverse position R (the reverse clutch 6 is operated to the transmission side, the forward clutch 5
When the operation button 57 of the speed change lever 28 is pressed and returned as described above, the reverse clutch 6 is automatically operated to the transmission interruption side and the transmission side.

(5) Next, the operation of the forward and reverse clutches 5, 6 by the clutch pedal 52 to the transmission side and the transmission interruption side will be described. As shown in FIGS. 2 and 3, a clutch pedal 5 for operating the forward and reverse clutches 5, 6.
2 (corresponding to an artificial operation tool) is provided, and the clutch pedal 5
A potentiometer 68 (corresponding to a position sensor) for detecting the second operation position is provided. Switching valves 36a, 37
An on-off valve 5 that can drain pilot hydraulic oil from the operating part of a.
1 (a spring (not shown) urges it toward the closing side), and when the clutch pedal 52 is stepped on a little before the limit, the opening / closing valve 51 is mechanically operated to the opening side by the clutch pedal 52. It

As a result, as shown by the solid line A1 in FIG.
In the state where the clutch pedal 52 is operated to the depressing position where it has been depressed to the limit, the clutch pedal 52 mechanically operates the open / close valve 51 to the open side, and the switching valves 36a and 37a.
Is operated to the oil drain side, and the forward clutch 5 (or the reverse clutch 6) is operated to the transmission cutoff side. When the clutch pedal 52 is operated to the return position (transmission side) in this state, as shown by the solid line A1 in FIG.
Based on the detection of the operation position of the clutch pedal 52 by the electromagnetic proportional valve 35, the operating pressure P of the forward clutch 5 (or the reverse clutch 6) is changed and adjusted by the electromagnetic proportional valve 35 to a value corresponding to the operation position of the clutch pedal 52. To go. The operating pressure P increases as the clutch pedal 52 is moved to the return position, and the forward clutch 5 (or the reverse clutch 6) is operated to the transmission side, and the clutch pedal 52 is operated to the intermediate position. Forward clutch 5
(Or the reverse clutch 6) is in a half-clutch state (the above corresponds to the control means).

On the contrary, as shown by the one-dot chain line A2 in FIG. 4, when the clutch pedal 52 is operated to the return position and the forward clutch 5 (or the reverse clutch 6) is operated to the transmission side, the clutch pedal 52 is operated. When is operated to the stepping position (transmission shutoff side), the forward proportional clutch 5 (or the reverse clutch 6) is actuated by the solenoid proportional valve 35 based on the detection of the operating position of the clutch pedal 52 by the potentiometer 68 as described above. The pressure P is changed and adjusted so as to have a value corresponding to the operation position of the clutch pedal 52. The operating pressure P decreases as the clutch pedal 52 is operated to the stepped position, and the forward clutch 5 (or the reverse clutch 6) is operated to the transmission cutoff side, and the clutch pedal 52 is moved to the intermediate position. When operated, the forward clutch 5 (or the reverse clutch 6) is in a half-clutch state (the above corresponds to the control means).

In this case, the solid line A1 and the alternate long and short dash line A in FIG.
As shown in 2, the operating pressure P (one-dot chain line A2) corresponding to the operating position of the clutch pedal 52 when the clutch pedal 52 is operated from the return position (transmission side) to the stepping position (transmission cutoff side), The operating pressure P (solid line A) corresponding to the operating position of the clutch pedal 52 when the clutch pedal 52 is operated from the stepped position (transmission cut-off side) to the return position (transmission side).
1) is set on the high voltage side.

As shown in the above paragraph (1) and FIG. 1, the main transmission 10 capable of shifting to four speeds and the first transmission capable of shifting to two high and low speeds.
With the second auxiliary transmissions 11 and 12, the traveling system can perform a total of 16 speeds, and the pressure sensor 74 and the limit switch 9 shown in FIGS. The position (lowest speed) to the 16th speed position (highest speed) can be recognized. by this,
The operating speed P (solid line A) when the clutch pedal 52 is operated from the stepped position (transmission cut-off side) to the return position (transmission side) as the shift position of the current traveling system is set to the higher speed side.
1) is changed to the high pressure side, or the operating pressure P (dashed line A2) when the clutch pedal 52 is operated from the return position (transmission side) to the stepped position (transmission cutoff side) is changed to the low pressure side. The setting is changed so that the difference in the operating pressure P (the difference between the solid line A1 and the alternate long and short dash line A2 shown in FIG. 4) is set to be large.

It should be noted that reference numerals are given in the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a transmission system in a mission case.

FIG. 2 is a diagram showing a linked state of a shift lever and a second auxiliary transmission device, a shift display portion, and a linked state of each portion.

FIG. 3 is a hydraulic circuit diagram of a main transmission, a first sub transmission, and the like.

FIG. 4 is a diagram showing a relationship between an operating position of a clutch pedal and an operating pressure of a forward clutch (reverse clutch).

[Explanation of symbols]

 5, 6 Hydraulic clutch 10, 11, 12 Transmission 35 Control valve 52 Manual operation tool 68 Position sensor P Hydraulic clutch operating pressure

Claims (2)

[Claims] 1. A wet multi-plate hydraulic clutch (5), (6)
A control valve (35) capable of changing and adjusting the operating pressure (P) of the hydraulic clutches (5), (6), an artificial operation tool (52) that is artificially operated, and the artificial operation tool (52). Position sensor (68) for detecting the operation position of (1), and an operating pressure (P) corresponding to the operation position of the manual operation tool (52) is obtained based on the detection value of the position sensor (68). Is provided with a control means for operating the control valve (35), and the artificial operation tool (52) is a hydraulic clutch (5), (6).
The operating pressure (P) corresponding to the operating position of the manual operating tool (52) when the manual operating tool (52) is operated from the power transmission side to the power transmission disconnecting side of the hydraulic clutch (5),
The operating pressure (P) corresponding to the operation position of the manual operation tool (52) when operated from the transmission cutoff side of (6) to the transmission side.
However, the operating structure of the hydraulic clutch is set to be on the high pressure side. 2. Transmissions (10), (11), (12) arranged on the lower side of the hydraulic clutches (5), (6).
When the gear shift operation is performed to a higher speed side, the human-operated operation tool (52) is operated from the transmission side of the hydraulic clutches (5) and (6) to the transmission cutoff side, and from the transmission cutoff side to the transmission side. The operating structure of the hydraulic clutch according to claim 1, wherein the difference in the operating pressure (P) at the time of being set is set to be large.