JP2572159Y2 - Traveling system hydraulic control device for work vehicle - Google Patents

Description

[Detailed description of the invention]

[0001]

INVENTION The present invention relates, in a working vehicle such as a tractor, in conjunction with the shift operation of the travel gear device, to automatically intermittently controlling the travel hydraulic clutch via a hydraulic clutch control valve The present invention relates to a traveling system hydraulic control device for a working vehicle.

[0002]

2. Description of the Related Art There is conventionally known a work vehicle such as a tractor that performs a so-called non-clutch shift by automatically connecting and disconnecting a traveling hydraulic clutch in conjunction with a shift operation of a traveling transmission. Then, as shown in FIG. 6, a shift control valve A that is switched in conjunction with the operation of the shift lever of the tractor and is held at each switching position via the positioning plate B, and each of the shift control valves A A group of hydraulic actuators C, D, and E for mechanically shifting the speed of the traveling transmission of the work vehicle in accordance with the switching position;
A hydraulic clutch control valve G for intermittently controlling the traveling hydraulic clutch F of the work vehicle in conjunction with the switching operation of the work vehicle, and a hydraulic clutch control valve G provided on the lower side of the hydraulic path of the hydraulic clutch control valve G, and partially provided within the circuit with a predetermined pressure or more. that a <br/> pilot pressure relief valve H in order to release the pressure when a pressure is applied has been proposed by the present applicant.

[0003]

In the prior art, the tractor can be moved at a low speed even at a very low torque due to the reduction ratio.
Even when the hydraulic oil is at a low pressure while the hydraulic clutch control valve G is operating, the torque can be sufficiently transmitted.
However, the hydraulic clutch control valve G is provided, on the lower side of the hydraulic path, with a pilot pressure relief valve H that only releases the pressure when the circuit internal pressure partially becomes higher than a predetermined pressure during manual switching. Therefore, when the hydraulic oil is in a low pressure state, it is possible to shift at a high speed. During the shift, the hydraulic oil having a pressure enough to press the synchro is supplied via the hydraulic clutch control valve G, and the traveling hydraulic pressure is There has been a problem in that the clutch F can be engaged and disengaged, thereby causing a gear noise during shifting.

Accordingly, the present invention allows the hydraulic oil to flow through the hydraulic clutch circuit only when the hydraulic oil of the hydraulic clutch control valve G rises to the set pressure, thereby ensuring that the traveling hydraulic clutch F is always intermittently operated. It is another object of the present invention to provide a traveling-system hydraulic control device for a working vehicle, which does not cause gear noise during shifting.

[0005]

Means for Solving the Problems The present invention to achieve the above object, a shift control valve that will be switching operations in conjunction with the operation of the shift lever, pressure in accordance with the switch position of the shift control valve
A group of hydraulic actuators that are supplied with oil and operate ;
Running mechanically controlled by hydraulic actuators
The traveling system hydraulic control device for a working vehicle, comprising: a row transmission, and a hydraulic clutch control valve for intermittently controlling a traveling hydraulic clutch in conjunction with a switching operation of a transmission control valve.
Branch from the hydraulic path that supplies hydraulic oil to the control valve
Is set in the hydraulic path for supplying pressure oil to the switch control valve.
Supply only the pressure oil that has reached the pressure to the hydraulic clutch control valve
A pressure compensating valve is provided for switching operation of the shift control valve.
The hydraulic clutch control valve is switched in conjunction with it,
The traveling hydraulic clutch is disconnected once, and the traveling hydraulic
When the clutch is engaged, the traveling transmission is
Pressure at which gear shifting operation is not properly performed mechanically by the tutor
Under pressure, the pressure compensating valve becomes a hydraulic clutch control valve.
Do not supply pressurized oil to the
It is characterized in that the clutch is not substantially connected .

[0006]

With the above arrangement, the traveling system hydraulic control device of the present invention operates the hydraulic clutch control valve only when the shift control valve is switched and when the hydraulic oil rises to the set pressure by the pressure compensating valve. Oil will be supplied,
The traveling hydraulic clutch is always operated at a pressure equal to or higher than a predetermined pressure, so that the clutch is reliably disconnected and no gear noise occurs .

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be specifically described below with reference to the accompanying drawings. FIG. 2 shows a schematic configuration of a tractor as a working vehicle to which one embodiment is applied. In the tractor 1, a main shift lever 3, an auxiliary shift lever 4, and a shuttle shift lever 5 are provided beside a driver's seat 2. Each is arranged.

Here, the driving system of the tractor 1 will be schematically described with reference to FIG.
The transmission 8 connected via the second transmission includes a second main transmission mechanism 9, a first main transmission mechanism 10, a traveling hydraulic clutch 11, a forward / reverse switching mechanism 12, a first auxiliary transmission mechanism 13, and a second auxiliary transmission mechanism. By being transmitted to the rear wheel 16 of the tractor 1 via the differential device 14 and the differential device 15, a traveling drive system that rotationally drives the drive wheels is configured. Also , the first PT
O transmission mechanism 17, second PTO transmission mechanism 18, transmission shaft 1
9. By transmitting the power to the PTO shaft 21 via the third PTO transmission mechanism 20, a PTO shaft drive system that rotationally drives the PTO shaft 21 serving as a power source of a work machine or the like is configured.

The first main transmission mechanism 10 switches from a neutral gear to a first gear or a second gear, and includes a first hydraulic cylinder 22 as a hydraulic actuator.
The speed change operation is performed. Further, the second main transmission mechanism 9 is provided between the neutral speed and the third speed or the fourth speed.
The gear is switched to the speed position, and the speed is changed by a second hydraulic cylinder 23 as a hydraulic actuator. The first auxiliary transmission mechanism 13 switches the output rotation of the forward / reverse switching mechanism 12 between high and low, ie, H and L, and is operated by a third hydraulic cylinder 24 as a hydraulic actuator. ing. And
The operation of the first hydraulic cylinder 22, the second hydraulic cylinder 23, and the third hydraulic cylinder 24 is controlled in accordance with the switching position of a later-described shift control valve that is switched by the main shift lever 3. .

The forward / reverse switching mechanism 12 transmits the output rotation of the traveling hydraulic clutch 11 to the first auxiliary transmission mechanism 13 as it is or in reverse, and transmits the output rotation to the shift rail 25 that is interlocked with the shuttle transmission lever 5. The switching operation is performed via the. Further, the second auxiliary transmission mechanism 14
Is for switching the output rotation of the first sub-transmission mechanism 13 between high and low two stages of H and L stages, and the speed is changed via a shift rail 26 interlocked with the sub-transmission lever 4.

FIG. 1 shows a hydraulic circuit of a traveling-system hydraulic control device for controlling the on / off control of the traveling hydraulic clutch 11 and the operation of the first to third hydraulic cylinders 22 to 24. This hydraulic circuit is used in common with the hydraulic control device 27 for the power steering device and the hydraulic control device 28 for the quick turn device provided in the tractor 1. A shunt valve 30 for supplying pressure oil, and a shunt valve 3
And a shift control valve 31 and a hydraulic clutch control valve 32 to which the pressure oil is supplied via the control valves 0 and 0, respectively. The first hydraulic cylinder 22, the second hydraulic cylinder 23, and the third hydraulic cylinder 24 are connected to the shift control valve 31, respectively, and the traveling hydraulic clutch 11 is connected to the hydraulic clutch control valve 32.

The flow dividing valve 30 includes two pressure control valves 30a and 30b connected in parallel to the oil pump 29.
And a switching valve 30c connected to the downstream side of one of the pressure control valves 30a. The switching valve 30c is connected to the shift control valve 31, the hydraulic clutch control valve 32 and the quick turn valve via an oil passage L1. Each is connected to a device hydraulic control device 28. The other pressure control valve 30b is connected to the hydraulic control device 2 for the power steering device via the oil passage L2.
7 is connected.

The switching valve 30c is a spring return type electromagnetic switching type. In the spring return state, the oil passage L1 communicates with the drain side, and the oil passage L2 and the pressure control valve 30a are cut off. At the time of energization, the communication between the oil passage L1 and the drain side is cut off, and the oil passages L1 and L2 are connected to the oil pump 29 via the pressure control valve 30a.
The pressure control valve 30a prevents the pressure oil in the oil passage L1 from flowing back toward the oil passage L2 when the switching valve 30c is energized.

Microswitches 33 and 34 for controlling the energization of the switching valve 30c are provided in contact with the shift rails 25 and 26 to detect the movement of the shift rails 25 and 26, respectively. At the time of shifting operation of the shift lever 4, the micro switch 33 or the micro switch 34 having a normally closed contact is turned off and the switching valve 30c is returned to the spring, thereby connecting the oil path L1 to the drain side. I have.

The shift control valve 31 is of a rotary switching type in which N (neutral) and F1 to F8 switching positions are continuous, and is switched by the main shift lever 3.
Further, it is held at each switching position via a positioning plate 41. The first hydraulic cylinder 22, the second hydraulic cylinder 23, and the third hydraulic cylinder 24 are controlled to expand and contract, respectively, according to the switching positions of the shift control valve 31. For example, at the N position, the first main transmission mechanism 10 and the second main transmission mechanism 9 are both shifted to the neutral stage by controlling both the first hydraulic cylinder 22 and the second hydraulic cylinder 23 to the neutral intermediate extension position. Is done. Also,
In each of the switching positions of N, F1, F2, F3, and F4, the third hydraulic cylinder 24 reaches the contraction limit, and the first subtransmission mechanism 13 is in the low-speed L stage. In each of the switching positions of F5, F6, F7, and F8, The third hydraulic cylinder 24 reaches the extension limit, and the first subtransmission mechanism 13 enters the high speed H stage. And F1, F2, F
While the second main transmission mechanism 9 is in the neutral N stage at the switching position between F5 and F6, the first hydraulic cylinder 22 is controlled to expand and contract, and the first main transmission mechanism 10 is in the first speed at the switching position between F1 and F5. The shift operation is performed to the second speed at the switching position between F2 and F6. At the switching position of F3, F4, F7, F8, the first main transmission mechanism 10 is in the neutral N-stage, while the second hydraulic cylinder 23 is controlled to expand and contract. The shift operation is performed to the third speed at the switching position of F7 and to the fourth speed at the switching positions of F4 and F8.

A pressure compensating valve 42 for compensating the pressure of the pressure oil is provided on the upstream side of the oil passage L1 for supplying the pressure oil to the hydraulic clutch control valve 32.
Only the pressure oil that has reached the pressure set by 2 is supplied to the hydraulic clutch control valve 32.

The hydraulic clutch control valve 32 includes a shift control valve 3
1 is a two-position switching valve provided with a spool 32a which is pushed and operated by a positioning plate 41 interlocked with a pilot pressure of a pilot oil passage L4 communicating with the oil passage L1 through an orifice 35 at one end of the spool 32a. Act through the pilot piston 32b. When the spool 32a is pushed against the pilot pressure, the hydraulic clutch control valve 32 connects the oil passage L5 to the traveling hydraulic clutch 11 to the drain side, and the spool 32a is turned off by the pilot pressure. In other words,
A predetermined pressure oil from the oil passage L1 that has passed through the pressure compensating valve 42 is supplied to the traveling hydraulic clutch 11 via the oil passage L5. The traveling hydraulic clutch 11 disconnects the traveling drive system of the tractor 1 when the oil passage L5 is connected to the drain side, and is supplied with pressure oil when the oil passage L5 and the oil passage L1 are connected. It operates to connect the traveling drive system.

A boost control valve 36 is connected between an oil passage L5 to the traveling hydraulic clutch 11 and the third hydraulic cylinder 24 via an oil passage L6. The pressure control valve 36 performs drain control so as to gradually increase the pressure of the pressure oil supplied to the traveling hydraulic clutch 11. The pressure of the oil passage L5 is set to a pressure lower than the pressure set by the pressure control valve 30 a. A spring return type internal pilot pressure control valve 36a for draining oil, and an orifice 36b
And an accumulator 36c connected to the third hydraulic cylinder 24 to supply a pressure against the pilot pressure to the pressure control valve 36a.
d.

Further, a pilot pressure relief valve 37 for preventing a set pilot pressure from rising is connected to the pilot oil passage L4. Further, pilot pressure drain control valves 38, 39, and 40 corresponding to the first hydraulic cylinder 22, the second hydraulic cylinder 23, and the third hydraulic cylinder 24 are connected to the pilot oil passage L4.

The pilot pressure drain control valves 38, 3
9 and 40 are spring-return type 2 in which the spool is pushed and operated.
A position switching valve that connects the pilot oil passage L4 to the drain side to reduce the pilot pressure when the spool is in the pushing operation state, and holds the pilot pressure by blocking the drain state of the pilot oil passage L4 in the spring return state. It has become.
The pilot pressure drain control valve 38 is linked to the first hydraulic cylinder 22 so as to return to a spring only at its neutral intermediate extension position, the extension limit and the contraction limit, and is installed such that the spool is pushed during the operation. Have been. Similarly, the pilot pressure drain control valve 39 is installed so that the spring returns only at the neutral intermediate extension position of the second hydraulic cylinder 23, the extension limit and the contraction limit, and the spool is pushed during the operation. . Further, the pilot pressure drain control valve 40 is installed so as to return to a spring only at its contraction limit and extension limit in conjunction with the third hydraulic cylinder 24, and to operate the spool during its operation.

Next, the operation of the hydraulic control system for a traveling vehicle of a working vehicle according to an embodiment having the above-described structure will be described. First, when the sub-shift lever 4 or the shuttle shift lever 5 is not operated, the microswitch 3
Reference numerals 3 and 34 are ON, and the switching valve 30c of the flow dividing valve 30 is switched to connect the oil passage L1 to the pressure control valve 30a. For this reason, pressure oil at the pressure set by the pressure control valve 30 a is directly supplied to the shift control valve 31, and pressure oil at a predetermined pressure is supplied to the hydraulic clutch control valve 32 via the pressure compensation valve 42. Further, pressure oil is supplied to the pilot oil passage L4 via the orifice 35.

In such a state, when the main shift lever 3 is switched to the N position, that is, when the shift control valve 31 is switched to the N position, the third hydraulic cylinder 24 reaches the contraction limit and the first sub-transmission mechanism 13 operates. The low-speed L stage is set, and the first hydraulic cylinder 22 and the second hydraulic cylinder 23 are both controlled to the neutral intermediate extension position, so that the first main transmission mechanism 10 and the second main transmission mechanism 9 are both neutral N. It is a step. At this time, since the spool 32 a of the hydraulic clutch control valve 32 is pushed by the positioning plate 41, the hydraulic clutch control valve 32 uses the hydraulic oil of the predetermined pressure set by the pressure compensating valve 42 to drive the traveling hydraulic clutch 11. Is switched to a position where the oil passage L5 is connected to the drain side, and the traveling hydraulic clutch 11 disconnects the traveling drive system of the tractor 1.

Next, when the shift control valve 31 is switched to the F1 position by the main shift lever 3, the shift control valve 31 is held at the switch position, the first hydraulic cylinder 22 is extended, and the first main shift mechanism 10 is moved. The shift operation is performed to the first speed. At this time, the positioning plate 41 faces the spool 32a of the hydraulic clutch control valve 32. But the first
When the hydraulic cylinder 22 is performing the extension operation and the shift operation to the first speed is not completed, the pilot pressure drain control valve 38 is operated to push the spool and the pilot oil passage L
4 is connected to the drain side, and the pilot pressure is reduced. Therefore, the hydraulic clutch control valve 32 is
a is in the switching state with the full stroke, and the disconnected state of the traveling hydraulic clutch 11 is reliably maintained.

When the first hydraulic cylinder 22 reaches the extension limit and the shifting operation to the first speed is completed, the pilot pressure drain control valve 38 returns to the spring state to prevent the drain state of the pilot oil passage L4, so that the hydraulic pressure is reduced. The clutch control valve 32 is switched by the pilot piston 32b receiving the pilot pressure in the pilot oil passage L4 to push the spool 32a, and the spool 32a is fitted into the hole of the positioning plate 41. In this manner, the oil passage L1 and the oil passage L5 to the traveling hydraulic clutch 11 are connected, and the traveling hydraulic clutch 11 automatically receives the supply of the predetermined pressure oil and automatically connects the traveling drive system. At this time, since the pilot piston 32b acts as a resistance to the movement of the spool 32a due to the pilot pressure, the spool 32a moves slowly and switches the hydraulic clutch control valve 32.

Subsequently, when the shift control valve 31 is switched from the F1 position to the F2 position by the main shift lever 3, the spool 32a of the hydraulic clutch control valve 32 initially resists the pilot pressure at the spool operating portion of the positioning plate 41. The push operation is performed, and the hydraulic clutch control valve 3
2 switches to connect the oil passage L5 to the traveling hydraulic clutch 11 to the drain side, and thus the traveling hydraulic clutch 1
1 automatically disconnects the traveling drive system of the tractor 1. At this time, since the pilot pressure relief valve 37 prevents the pilot pressure in the pilot oil passage L4 from rising, the operation of the spool 32a pushed and pushed against the pilot pressure is smooth and the response is high. Good. Therefore, the hydraulic clutch control valve 32 switches with good responsiveness, and the traveling hydraulic clutch 11 is quickly disconnected. Therefore, the first main transmission mechanism 10 smoothly moves to the second main transmission mechanism 10 by the contraction of the first hydraulic cylinder 22.
The shift operation is performed to the first gear.

When the first hydraulic cylinder 22 is in the contracting operation and the shifting operation to the second speed is not completed, the pilot pressure drain control valve 38 is connected to the pilot oil passage L4 as described above. Since the pilot pressure is released, the hydraulic clutch control valve 32 is in the switching state in which the spool 32a has full stroke, and the disconnected state of the traveling hydraulic clutch 11 is reliably maintained. And the first hydraulic cylinder 2
When 2 reaches the contraction limit and the shift operation to the second speed is completed, the pilot pressure drain control valve 38 prevents the drain state of the pilot oil passage L4 as described above, and the hydraulic clutch control valve 32 By switching, the traveling hydraulic clutch 11 automatically connects the traveling drive system.

When the shift control valve 31 is switched to the F2 position to the F8 position by the main shift lever 3, the hydraulic clutch control valve 32 operates the traveling hydraulic clutch 11 at the beginning of the shift operation as described above. In order to disengage the clutch, it is smoothly switched with good responsiveness, and during the shifting operation, the switching state is reliably maintained, and when the shifting operation is completed, the switching is performed to connect the traveling hydraulic clutch 11.

On the other hand, when the shuttle shift lever 5 is switched, the shift rail 25 moves and the micro switch 3 is moved.
3 is turned off, the switching valve 30c of the flow dividing valve 30 is de-energized, and the oil path L1 is connected to the drain side by spring return. Therefore, even when the shift control valve 31 is at an arbitrary switching position, the hydraulic oil in the oil passage L5 is drained and the traveling hydraulic clutch 11 is automatically disengaged. , The operation is smoothly switched to the forward gear or the reverse gear. When this switching operation is completed, the micro switch 33 is turned on, the switching valve 30c is switched by energization, and the oil passage L1 is connected to the pressure control valve 30a side. Then, the pressure oil from the pressure control valve 30a is supplied to the oil passage L1,
Pressure compensation valve 42, hydraulic clutch control valve 32, oil passage L
The driving hydraulic clutch 11 is supplied to the driving hydraulic clutch 11 via the control unit 5 and thus the driving hydraulic clutch 11 is automatically connected. It should be noted that also in the case of the switching operation of the auxiliary transmission lever 4, the switching valve 30c
Are similarly switched, the intermittent control of the traveling hydraulic clutch 11 is automatically performed.

When, for example, the first sub-transmission mechanism 13 is switched from the L-stage to the H-stage by switching the sub-transmission lever 4, the shift rail 26 moves and the micro switch 34 is turned off by the movement, and the switching valve is switched. When the switching operation of the switch 30c is performed, the hydraulic clutch 11 for traveling is automatically intermittently controlled. At the same time, the third hydraulic cylinder 24 contracts, and the pilot pressure drain control valve 40 is switched. By switching the pilot pressure drain control valve 40, the oil passage 6
The pressure oil is supplied to the pressure increasing control valve 36 via the control valve to be in an operating state, the pressure of the pressure oil supplied to the traveling hydraulic clutch 11 is gradually increased, and the operation of the traveling hydraulic clutch 11 is performed more reliably. become.

Since the pressure control valve 30a is provided in the oil passage L1 in the flow dividing valve 30, the pressure oil flows backward from the oil passage L1 to the oil passage L2 even when the hydraulic control device 28 for the quick turn device operates. Never do. Accordingly, it is possible to prevent the pressure of the hydraulic oil in the oil passage L1, the pilot oil passage L4, and the oil passage L5 from decreasing, and the first hydraulic cylinder 22, the second hydraulic cylinder 23, the third hydraulic cylinder 24, the pressure compensating valve 42, the hydraulic clutch The control valve 32, the traveling hydraulic clutch 11 and the like can be reliably operated to maintain a stable traveling state.

FIGS. 4 and 5 show another embodiment having a configuration replacing the boosting control valve 36 in the above embodiment. In this embodiment, there is provided a pressure control valve 43, and an oil path switching valve 45 connected to the oil passage L1 and the pressure control valve 43, for controlling the pressure oil to the traveling hydraulic clutch 11 in conjunction with the shift operation. ing. The pressure control valve 43 includes a pressure control valve 43a having a spring in a valve body 43c.
, A plunger 43b, and a small-diameter orifice 44 formed in the piston to be switched by a pilot piston.
a and an orifice switching valve 44 comprising a large-diameter orifice 44b. Further, in the valve body 43c, a boosting characteristic switching piston 47 fitted to the relief valve type piston, a piston operating port 48 to which the pressure oil is supplied in conjunction with the auxiliary speed change, a return spring 49, a piston A hole 50 for introducing pressure oil into the orifice formed in
A concave portion 51 formed at the tip of the plunger is provided.

The oil passage switching valve 45 includes a pilot piston 4
5a and 45b, and the pilot piston 45a has
A return spring 45c is provided. The pilot piston 45a has pilot pressure drain control valves 38, 3
A check valve 46 is installed in the oil suction line on the oil passages 9 and 40.
And the drain line L8 is connected. Further, a pilot line connected from the oil passage L1 via the orifice 35 is connected to the pilot piston 45b. Further, a pressure control valve 43 a of the pressure control valve 43 is connected to the oil passage switching valve 45. An oil passage L7 connected to the oil passage of the third hydraulic cylinder 24 is connected to a pilot piston that switches between the small-diameter orifice 44a and the large-diameter orifice 44b.

In the second embodiment having such a configuration, the pressure-increase characteristic switching piston 47 of the pressure-increase control valve 43 is
Normally, it is retracted by the return spring 49, the large-diameter orifice 44b is closed by the piston, and the small-diameter orifice 44a is in the operating state. When the first sub-transmission mechanism 13 is switched by operating the sub-transmission lever 4, pressure oil is supplied to the piston operation port 48 in conjunction with this operation, and the pressure-increase characteristic switching piston 47 is pushed up against the return spring 49. Can be The pressure oil flowing into the port from the traveling hydraulic clutch 11 pushes up the piston and the plunger and flows from the hole 50 to the tank. At this time, the small diameter orifice 4
The pressure oil flows from 4a and slowly operates the plunger 43b, and the pressure of the port on the traveling hydraulic clutch 11 side also changes accordingly.

When the plunger 43b operates up to the stroke end, the pressure in the left and right chambers of the piston becomes equal, the piston is closed by the spring force of the pressure control valve 43a, and the pressure in the port on the traveling hydraulic clutch 11 side becomes
The pressure rises to the pressure set by the pressure control valve 43a.
In this manner, the pressure-increase characteristic of the pressure oil can be changed in conjunction with the speed change operation, so that the on-off operation of the traveling hydraulic clutch 11 can be smoothly performed with a good feeling, similarly to the first embodiment. , And surely. In addition, a concave portion is formed at the distal end portion of the plunger, and the distal end portion of the boosting characteristic switching piston is movable in the concave portion.

[0035]

As described above, according to the working vehicle hydraulic control system for a working vehicle of the present invention, the operation of the shift lever is interlocked with the operation of the shift lever.
The shift control valve that is operated to switch and the switching positions of the shift control valve
A group of hydraulic actuators that operate by being supplied with pressure oil according to the position
Mechanically shifts the traveling transmission by the
And mechanically shifting the transmission
The shifting clutch operation required for
Hydraulic clutch that can be switched in conjunction with the control valve switching operation
Intermittently controlled automatically via control valve, comfortable
A simple non-clutch shift can be realized. Also book
The present invention relates to a traveling system hydraulic control device for a work vehicle,
Hydraulic clutch control valve for intermittently controlling the traveling hydraulic clutch
A pressure compensating valve in the pressure oil supply path of
Traveling transmission becomes hydraulic actuator by compensation valve
Therefore, under the pressure where the gears are not properly shifted mechanically, the hydraulic pressure
Do not supply hydraulic fluid to the clutch control valve, and
So that the traveling hydraulic clutch is not substantially connected.
In this case, the gear noise of the traveling transmission is prevented.
And ensure that subsequent transmission gearing is not damaged.
Naturally, it can be prevented.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of a traveling vehicle hydraulic control device of a work vehicle according to the present invention.

FIG. 2 is a schematic configuration diagram of a tractor to which one embodiment is applied.

FIG. 3 is a schematic configuration diagram of a tractor drive system to which an embodiment is applied;

FIG. 4 is a sectional view showing an internal structure of a valve case according to another embodiment of the present invention.

FIG. 5 is a hydraulic circuit diagram in another embodiment.

FIG. 6 is a hydraulic circuit diagram of a traveling system hydraulic control device of a conventional working vehicle.

[Explanation of symbols]

 Reference Signs List 1 tractor 3 main transmission lever 8 traveling transmission 11 traveling hydraulic clutch 22 first hydraulic cylinder 23 second hydraulic cylinder 24 third hydraulic cylinder 31 shift control valve 31a shaft 32 hydraulic clutch control valve 32a spool 32b pilot piston 32c spring 37 Pilot pressure relief valve 38 Pilot pressure drain control valve 39 Pilot pressure drain control valve 40 Pilot pressure drain control valve 41 Positioning plate 42 Pressure compensation valve

Claims (1)

(57) [Scope of request for utility model registration] 1. A shift lever (3) in conjunction with the operation switch operated Ru shift control valve (31), the shift control valve (31)
A group of hydraulic actuators that operate is supplied with pressurized oil in response to the switching position of the (22) (23) (24), hydraulic
Mechanical by actuators (22) (23) (24)
Traveling transmission device (8), which is subjected to a shifting operation, and a traveling hydraulic clutch in conjunction with a switching operation of a transmission control valve (31).
In a traveling vehicle hydraulic pressure control device including a hydraulic clutch control valve (32 ) for intermittently controlling (11) , a hydraulic path (L) for supplying pressure oil to the shift control valve (31)
Branching from 1), pressurized oil is supplied to the hydraulic clutch control valve (32).
In the supply hydraulic path, the pressure oil that has reached the set pressure
Pressure compensation valve for supplying pressure to the hydraulic clutch control valve (32)
And a hydraulic clutch in conjunction with the switching operation of the shift control valve (31).
The switch control valve (32) is switched so that the running oil
The pressure clutch (11) is disconnected once, and the traveling hydraulic pressure is again applied.
When the clutch (11) is engaged, the traveling transmission
(8) is a hydraulic actuator (22) (23) (24)
Under pressure where the gears are not mechanically shifted properly
The pressure compensating valve (42) is a hydraulic clutch control valve (3).
2) Do not supply pressurized oil to, and in that case, run
The traveling system hydraulic control device for a working vehicle, wherein the hydraulic clutch (11) is not substantially connected .