JP2000273899A - Hydraulic system of work vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a leakage of accumulated oil and prolong the time while operation is possible after an engine is stopped. SOLUTION: This hydraulic system of a work vehicle is constituted in such a way that pressure oil from a main hydraulic pump P1 is supplied to right and left running motors 3R and 3L and a work actuator, a selector valve 11 is operated when the left and right running motors 3L, 3R are driven to supply pressure oil from a subhydraulic pump P3 to the work actuator, and signal pressure oil for switching the selector valve 11 returns into an oil tank when the left and right running motors 3L, 3R are not driven. A pilot-operated valve of the work actuator and an unload valve connecting and disconnecting the supply of pressure oil to the pilot-operated valve are provided, and signal pressure oil for the selector valve 11 is supplied from the upstream side of the unload valve. A pressure accumulation part is provided between the unload valve and the pilot-operated valve, and a check valve is provided on the upstream side of the pressure accumulation part so that pressure oil in the pressure accumulation part does not flow as signal pressure oil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hydraulic system for a working vehicle such as a backhoe.

[0002]

2. Description of the Related Art As a hydraulic system for a work vehicle such as a backhoe, there is one shown in FIGS. In this hydraulic system, a plurality of hydraulic pumps P1, P2, P3, and P4 are driven by an engine, and pressure oil of the hydraulic pumps is supplied to left and right traveling motors 3L and 3R, a boom cylinder 4, a bucket cylinder 5, an arm cylinder 6, and a turning cylinder. The motor is supplied to actuators such as the motor 7, the swing cylinder 8 and the dozer cylinder 9, and is supplied to an external detachable service actuator (attachment) 10 such as a breaker via a service port 14.

The main hydraulic pumps P1 and P2 use variable displacement pumps, and the hydraulic pumps support each other, so that the bias in the hydraulic pressure and the oil amount can be eliminated and the proper hydraulic pressure can always be maintained. The hydraulic pressure from the first main hydraulic pump P1 is supplied to the right traveling motor 3R, the boom cylinder 4, and the bucket cylinder 5, and the hydraulic oil from the second main hydraulic pump P2 is supplied to the left traveling motor 3L, the arm cylinder 6, and the service actuator 10. Supply and supply the hydraulic oil from the third sub-hydraulic pump P3 to the swing motor 7, the swing cylinder 8 and the dozer cylinder 9 to bend even if a front operation (boom, bucket, arm, etc.) is performed during traveling. A switching diversion valve (switching valve) 11 is provided so that the vehicle can travel straight without traveling, and hydraulic oil from the sub hydraulic pump 3 is supplied to the boom cylinder 4 and the bucket. Linda 5, and supplies it to the arm cylinder 6 and the service actuator 10.

The pressure oil flowing through the signal oil passage 20 for switching the switching diversion valve 11 returns to the oil tank 115 via the tank circuit 110 when the left and right traveling motors are not driven. Further, control valves C4, C5, C8, C9 of a working actuator such as a boom.
Is a hydraulic pilot switching type using a pilot operation valve 19, and pressure oil from a pilot pressure oil hydraulic pump P4 is supplied to the pilot operation valve 19 via an unload valve 18.

[0005]

In a work vehicle such as a backhoe, at the time of maintenance or the like, in order to release the pressure in the hydraulic hose, the engine is stopped while the front of the boom or the like is kept raised. Thereafter, the front is operated and lowered by the pilot operation valve 19. Further, depending on the way of storing the work vehicle, there is a case where it is desired to turn off the engine while the front is raised and then install the front.

Conventionally, as shown in FIGS. 5 and 6, the unload valve 18 and the pilot pressure oil are controlled so that the pilot operation valve 19 can be operated even after the engine 13 is turned off and the hydraulic pump P4 is stopped. Between the hydraulic pump P4 for
An accumulator (accumulator) ACC for accumulating pilot pressure is provided, and a check valve 130 is provided upstream of the accumulator (ACC). However, conventionally, a signal oil passage 20 for switching the switching diversion valve 11 is provided between the unload valve 18 and the accumulator ACC. Unload valve 1
9 was connected to the accumulator ACC, and when the engine 13 was stopped, the pressure oil accumulated in the accumulator ACC leaked from the signal oil passage 20.

Therefore, the pressure accumulation time by the accumulator ACC after the engine is stopped is short, and the pilot operation valve 1
Nine operable times were short (about 16 seconds). Further, after the engine is stopped, if power is not supplied to the unload valve 19, the pilot operation cannot be performed at all. In this case, the key must be returned to, for example, the ACC position to supply electricity to the unload valve 18, which is complicated. The present invention has been made in view of such circumstances, and has as its object to prevent leakage of accumulated oil and extend the operable time after the engine is stopped.

[0008]

A first technical means for solving the problems in the present invention is to supply pressure oil from a main hydraulic pump to a left and right traveling motor and a work actuator, and the left and right traveling motors are driven. When the switching valve is operated, the hydraulic oil from the sub hydraulic pump is supplied to the working actuator, and the signal pressure oil for switching the switching valve is supplied to the oil tank when the left and right traveling motors are not driven. A hydraulic system for a working vehicle configured to return to the working operation, wherein a pilot operated valve of the working actuator;
An unload valve that disconnects and connects the supply of pressure oil to the pilot operation valve, and a hydraulic system of a work vehicle configured to supply signal pressure oil of the switching valve from an upstream side of the unload valve. A pressure accumulator is provided between the unload valve and the pilot operation valve, and a check valve is provided upstream of the accumulator to prevent the pressure oil of the accumulator from flowing as the signal pressure oil. .

With this configuration, the pilot can be operated even after the engine is stopped by the pressure stored in the pressure accumulating section provided between the unload valve and the pilot operation valve. A check valve is provided to prevent the pressure oil in the pressure accumulator from leaking as signal pressure oil. This prevents the pressure oil in the pressure accumulator from leaking as signal pressure oil, allowing pilot operation after the engine is stopped. Time can be lengthened. Further, in a hydraulic system in which a pressure accumulator is provided between a hydraulic pump and a pilot operation valve in order to enable a pilot operation after the engine is stopped, the unload valve supplies pressure oil when a solenoid is excited. It is preferable that the solenoid valve of the unload valve be provided with an exciting means for exciting the solenoid of the unload valve for a predetermined time after the engine is stopped.

In this case, it is convenient to excite the unload valve after stopping the engine without having to return the engine key to the ACC position again. Further, the unload valve comprises an electromagnetic valve that supplies pressure oil to the pilot operation valve when the solenoid is excited, and the pressure oil of the pressure accumulating section returns to the oil tank when the unload valve is not excited. It is preferable to configure as follows. In this case, after the engine stops, while the unload valve is in the excited state, the pressure of the pressure accumulator is maintained, but when the unload valve is de-energized, the pressure oil in the pressure accumulator returns to the oil tank and the pilot operation is performed. Becomes impossible, and the pilot operation in the unloaded state is prevented.

Further, it is preferable that the check valve is disposed between a signal oil passage through which the signal pressure oil flows and the unload valve, and the check valve is provided inside the unload valve. To prevent the pressure oil of the pressure accumulator from flowing as the signal pressure oil when the unload valve is excited, and the pressure of the pressure accumulator when the unload valve is de-energized. The oil may be configured to return to the oil tank. Further, in view of the above technical means, the switching valve is not limited to the above-mentioned usage, and the above-described switching valve is not limited to the above as long as the signal pressure oil for switching leaks to the tank when the switching valve is not operated. Technical measures are effective.

Accordingly, in view of this, as a second technical means of the present invention, a pilot operation valve of a working actuator, an unload valve for disconnecting / connecting the supply of pressure oil to the pilot operation valve, and A switching valve configured to return the signal pressure oil for switching to the tank during non-operation, and to supply the signal pressure oil of the switching valve from the upstream side of the unload valve. In the hydraulic system, a pressure accumulator is provided between the unload valve and the pilot operation valve, and a check valve is provided upstream of the pressure accumulator so that the pressure oil of the pressure accumulator does not flow as the signal pressure oil. You can be.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. In the first embodiment of the backhoe hydraulic system schematically shown in FIG. 1 and divided into left and right parts in FIGS. 2 and 3, respectively, four hydraulic pumps P1, P2, P3 and P4 are driven by the engine 13 to The hydraulic oil of the main hydraulic pumps P1, P2 of the continuous variable displacement type is supplied to the control valves C1, C2.
The traveling motor 3 of the crawler type left and right traveling device via 2
L, 3R and control valves C3, C10, C
4, C5, and C6, and are supplied to first working actuators such as a boom cylinder 4, a bucket cylinder 5, an arm cylinder 6, and a service actuator (attachment) 10.

The service actuator 10 is a breaker, an auger, a cutter, or the like, and has various hydraulic capacities. The service actuator 10 is detachably connected to the service port 14 of the backhoe. The main hydraulic pump P1, the control valve C1,
A first hydraulic circuit is formed by the traveling motor 3R, the control valves C3 and C4, the boom cylinder 4, the bucket cylinder 5, and the like. The main hydraulic pump P2, the control valve C2, the traveling motor 3L, the control valves C5 and C6, the arm The second hydraulic circuit is formed by the cylinder 6, the service actuator 10, and the like, and the boom cylinder 4, the bucket cylinder 5, the arm cylinder 6, the service actuator 10, and the like are the first type work actuator.

The hydraulic oil from the third sub-hydraulic pump P3 is supplied to the swing motor 7, via the control valves C7, C8 and C9.
It can be supplied to the second-type working actuators such as the swing cylinder 8 and the dozer cylinder 9 and can also be supplied to the switching diverting valve (switching valve) 11, which forms a third hydraulic circuit. Switching diversion valve 1
Reference numeral 1 denotes a two-position switching type between a distribution position and a branch supply position, and when operated to the branch supply position, communicates with the two oil passages 24 and 25 to equally divide the pressure oil of the sub-hydraulic pump P3 into an oil passage 2.
4 and 25 can be supplied.

Then, the divided stream of the pressure oil of the sub hydraulic pump P3 can be supplied to the boom cylinder 4 and the bucket cylinder 5 through the oil passage 24 and the control valves C3 and C4. , Through the oil passage 25, the control valve C5,
Supply to the arm cylinder 6, the service actuator 10 and the like via C6 and C10 is enabled. The control valve C3,
C4, C5, C7 and the switching flow dividing valve 11 are of a hydraulic pilot switching type, and a pilot pressure hydraulic pump P4
From the control valves C3 and C3 through the check valve 130 and the unload valve 18 and through the pilot operation valve 19.
4, C5 and C7, and also to the switching diversion valve 11 via the signal oil passage 20.

Unload valve 18 and pilot operation valve 19
A pressure accumulator (accumulator) ACC for accumulating the pilot operation pressure is provided between the pressure accumulator and the accumulator ACC. The signal oil passage 20 of the switching branch valve 11 is located upstream of the check valve 130, that is, between the check valve 130 and the hydraulic pump P4.
, From which signal pressure oil is supplied. The pilot pressure control oil passage 2 is provided in the signal oil passage 20 of the switching branch valve 11.
1 is connected. This pilot pressure control oil passage 21
A first control oil passage 21A that drains oil from the signal oil passage 20 through the control valves C1 and C2 of the left and right traveling motors 3L and 3R;
There is a second control oil passage 21B that drains oil from the oil passage 20 through the control valves C1 to C6 and C10.

Exciting means 35 is connected to the solenoid of the unload valve 18 which is an electromagnetic valve, and the excited state of the solenoid of the unload valve 18 is maintained by the exciting means 35 for a predetermined time even after the engine is stopped. . The exciting unit 35 may employ a suitable circuit such as a charging circuit capable of discharging for a predetermined time even after the engine is stopped, a control device for supplying electricity from the battery of the vehicle until a certain time after the engine is stopped by the timer unit, or the like. . Next, the operation of the hydraulic system will be described.

When the left and right traveling motors 3L, 3R are not driven without operating the control valves C1, C2, the main hydraulic pump P
1 can be supplied to the boom cylinder 4 and the bucket cylinder 5, the oil of the main hydraulic pump P2 can be supplied to the arm cylinder 6 and the service actuator 10, and the oil of the sub hydraulic pump P3 is the turning motor 7, the swing cylinder. 8 and the dozer cylinder 9. When the control valves C1 and C2 are operated for straight traveling,
The oil of the main hydraulic pumps P1 and P2
L, 3R to drive the control valves C1, C2
, The pilot pressure control oil passage 21 is blocked and the pilot pressure rises, and the switching diversion valve 11 is actuated to change the distribution position from the distribution position to the diversion supply position. 5. Arm cylinder 6 and service actuator 10
Can be supplied.

Even when the engine 13 is turned off, the pilot operation can be performed by the pressurized oil stored in the accumulator ACC. Therefore, even if the engine 13 is stopped while the front is raised, the pilot operation valve 19
, The front can be lowered, and the pressure in the hose can be released. Here, for a predetermined time after the engine 13 is stopped, the unload valve 18 is excited by the exciting means 35, and is maintained at a position where the flow between the check valve 130 and the pilot operation valve 19 is established.

Therefore, the pressure of the accumulator ACC is prevented from leaking to the signal oil passage 20 by the check valve 130, and the pilot operation can be performed for a relatively long time even after the engine is stopped. Further, by appropriately changing the setting of the time during which the exciting means 35 supplies electricity to the unload valve 18, the time during which the pilot can be operated after the engine is stopped can be set arbitrarily. on the other hand,
After a lapse of a predetermined time, the solenoid of the unload valve 18 is demagnetized to return the accumulator ACC and the return oil passage 3 to the tank.
When 0 is in the circulation state (the state shown in FIGS. 2 and 3), the pressure stored in the accumulator ACC is discharged to the oil tank 115 through the return oil passage 30, and the pilot operation cannot be performed. Thus, in the present embodiment, the pilot operation in the unload state of the unload valve 18 is prevented.

The second embodiment shown in FIG. 4 differs from the first embodiment in that the check valve 130 is provided in the unload valve. However, the point provided upstream of the accumulator ACC (between the accumulator ACC and the signal oil passage 20) is the same as in the first embodiment, and the operation is common. That is, the engine 1
For a predetermined time after the stop, the unloading valve 18 is excited by the exciting means 35 and is held at a position where the side where the check valve 130 is provided is connected to the pilot operation valve 19.

Therefore, the pressure of the accumulator ACC is prevented from leaking to the signal oil passage 20 by the check valve 130, and the pilot operation can be performed for a relatively long time even after the engine is stopped. On the other hand, when a predetermined time has elapsed and the solenoid of the unload valve 18 has been demagnetized and the accumulator ACC and the return oil passage 30 to the tank are in a flow state (the state shown in FIG. 4), the pressure stored in the accumulator ACC becomes The oil is discharged to the oil tank 115 through the return oil passage 30, and the pilot operation cannot be performed.

[0024]

As described above, according to the present invention, it is possible to prevent the accumulated oil from leaking and extend the operable time after stopping the engine.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing a hydraulic system for a work vehicle according to the present invention.

FIG. 2 is a detailed explanatory diagram showing a right half of the hydraulic system.

FIG. 3 is a detailed explanatory diagram showing a left half of the hydraulic system.

FIG. 4 is an explanatory view of a main part of a second embodiment of the present invention.

FIG. 5 is a detailed explanatory diagram showing a right half of a conventional hydraulic system.

FIG. 6 is a detailed explanatory view showing a left half of a conventional hydraulic system.

[Explanation of symbols]

 3 Traveling Motor 4 Boom Cylinder 5 Bucket Cylinder 6 Arm Cylinder 7 Swing Motor 8 Swing Cylinder 9 Dozer Cylinder 10 Service Actuator 11 Switching Dividing Valve (Switching Valve) 18 Unload Valve 19 Pilot Operating Valve 20 Signal Oil Path 21 Pilot Pressure Control Oil Path 30 Return oil path 30 35 Exciting means 115 Oil tank 130 Check valve ACC Accumulator (accumulator) P1 Main hydraulic pump P2 Main hydraulic pump P3 Sub hydraulic pump P4 Hydraulic pump for pilot pressure

Claims (6)

[Claims] 1. A pressure oil from a main hydraulic pump is supplied to a left and right traveling motor and a work actuator, and when the left and right traveling motor is driven, a switching valve is operated to supply pressure oil from a sub hydraulic pump to the work actuator. A hydraulic fluid for a working vehicle, wherein the hydraulic fluid is supplied to a working actuator, and signal pressure oil for switching the switching valve is returned to an oil tank when the left and right traveling motors are not driven. A pilot-operated valve, and an unload valve that disconnects and connects the supply of pressure oil to the pilot-operated valve, and is configured to supply signal pressure oil for the switching valve from the upstream side of the unload valve. In the vehicle hydraulic system, a pressure accumulator is provided between the unload valve and the pilot operation valve so that the pressure oil of the pressure accumulator does not flow as the signal pressure oil. A hydraulic system for a work vehicle, wherein a check valve is provided upstream of the pressure accumulating unit. 2. An unloading valve comprising an electromagnetic valve for supplying pressure oil to the pilot operation valve when a solenoid is excited, and an excitation for energizing the solenoid of the unloading valve for a predetermined time after the engine is stopped. 2. The hydraulic system for a work vehicle according to claim 1, further comprising means. 3. The unload valve comprises an electromagnetic valve that supplies pressure oil to the pilot operation valve when a solenoid is excited, and the pressure oil of the pressure accumulating unit is oil when the unload valve is de-energized. The hydraulic system for a work vehicle according to claim 1, wherein the hydraulic system is configured to return to the tank. 4. The work vehicle according to claim 1, wherein the check valve is disposed between a signal oil passage through which the signal pressure oil flows and the unload valve. Hydraulic system. 5. The unload valve comprises an electromagnetic valve that supplies pressure oil to the pilot operation valve when a solenoid is excited, and the check valve is disposed inside the unload valve, When the valve is energized, the pressure oil of the accumulator is prevented from flowing as the signal pressure oil, and when the unload valve is de-energized, the pressure oil of the accumulator returns to the oil tank. The hydraulic system for a work vehicle according to any one of claims 1 to 3, wherein the hydraulic system is configured. 6. A pilot operation valve of a working actuator, an unload valve for connecting / disconnecting supply of pressure oil to the pilot operation valve, and a signal pressure oil for switching when the valve is not operated returns to the tank. And a switching valve, the hydraulic pressure system of a work vehicle configured to supply the signal pressure oil of the switching valve from the upstream side of the unload valve, between the unload valve and the pilot operation valve A hydraulic system for a work vehicle, comprising: a pressure accumulating section; and a check valve provided upstream of the pressure accumulating section so that pressure oil of the pressure accumulating section does not flow as the signal pressure oil.