JP2000273915A - Hydraulic system of working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic system of a working vehicle capable of preventing the leakage of accumulated oil and extending an operable time after an engine is cut off. SOLUTION: Hydraulic oil from a main hydraulic pump is supplied to both right and left traveling motors 3L and 3R and a working actuator, the hydraulic oil from a sub-hydraulic pump is supplied to the working actuator, and a selector valve 11 is operated when both right and left traveling motors 3L and 3R are driven, the hydraulic oil from the sub-hydraulic pump is supplied to the working actuator, and a hydraulic system of a working vehicle is so constituted that signal hydraulic oil for switching the selector valve 11 is returned to an oil tank when both right and left traveling motors 3L and 3R are in an undriven state. In that case, it is equipped with a pilot control valve of the working actuator, an unload valve used for supplying hydraulic oil to the pilot control valve in a connectable manner and an accumulating section provided to an upstream side of the unload valve, the accumulating section prevents the backflow to the upstream side, and the signal hydraulic oil of the selector valve 11 is supplied from the upstream side of the accumulating section.

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 working vehicle such as a backhoe, there is one shown in FIGS. In this hydraulic system, a plurality of hydraulic pumps P1, P2, and P3 are driven by an engine, and hydraulic 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 swing motor 7 ,
The power is supplied to actuators such as 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.

[0004] The pressure oil flowing through the signal oil passage 120 for switching the switching diversion valve 11 is returned to the oil tank 115 via the tank circuit 110 when the left and right traveling motors are not driven. In addition, control valves C4, C5, C8, C
Reference numeral 9 denotes a hydraulic pilot switching type using a pilot operation valve 19, and pressure oil from a pilot pressure oil hydraulic pump P 4 is supplied to the pilot operation valve 19 via an unload valve 18.
Supplied to

[0005]

In a working vehicle such as a backhoe, at the time of maintenance or the like, in order to release the pressure in the hose, the engine is stopped with the front of the boom or the like kept up, and then the engine is stopped. Then, 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. 4 and 5, the unload valve 18 is operated so that the pilot operation valve 19 can be operated even after the engine is turned off and the hydraulic pump is stopped.
An accumulator ACC for accumulating the pilot pressure is provided between the hydraulic pressure pump P4 and the pilot pressure oil hydraulic pump P4, and a check valve 130 is provided upstream of the accumulator ACC to constitute an accumulator 140. However, the signal oil passage 20 for switching the switching branch valve 11 is taken from the unload valve 18. Since the unload valve 19 is connected to the accumulator ACC, the oil accumulated in the accumulator ACC leaked from the signal oil passage 20 when the engine 13 was stopped.

Therefore, the pressure accumulation time by the accumulator ACC is short, and the operable time of the pilot control valve 19 is short (about 16 seconds). 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 hydraulic oil from a main hydraulic pump to a left and right traveling motor and a work actuator, and to supply hydraulic oil from a sub hydraulic pump. Is supplied to the working actuator, and the switching valve is operated when the left and right traveling motors are driven, so that the hydraulic oil from the sub hydraulic pump is supplied to the working actuator, and a signal for switching the switching valve is provided. A hydraulic system for a working vehicle configured to return pressure oil to an oil tank when the left and right traveling motors are not driven, the pilot operation valve of the working actuator, and supply of the pressure oil to the pilot operation valve. And a pressure accumulator provided upstream of the unload valve. The pressure accumulator prevents backflow to the upstream side, and is upstream of the pressure accumulator. It is that it is configured to supply a signal pressure oil of the switching valve from.

According to this structure, the pressure accumulating portion is prevented from flowing backward to the upstream side and supplies the signal pressure oil of the switching valve from the upstream side, so that the pressure oil accumulated in the pressure accumulating portion is prevented from leaking. Thus, the operation time of the pilot operation valve after the engine is stopped can be lengthened. And it is preferable that the accumulator has an accumulator provided on the upstream side of the unload valve and a check valve provided on the upstream side of the accumulator. , The signal pressure oil of the switching valve may be supplied.

In view of the above technical means, the switching valve is not limited to the one described above, and the signal pressure oil for switching leaks to the tank when the switching valve is not operated. If so, the above technical means are effective. Therefore, in view of this, as a second technical means of the present invention, a pilot operation valve of a working actuator,
A hydraulic system for a work vehicle, comprising: an unload valve for connecting and disconnecting the supply of pressure oil to the pilot operation valve; and a pressure accumulator provided upstream of the unload valve. And a switching valve configured to return the signal pressure oil to the tank so that the signal pressure oil is supplied from the upstream side of the pressure accumulating unit.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In the backhoe hydraulic system shown schematically in FIG. 1 and divided into left and right parts in FIGS. 2 and 3, four hydraulic pumps P1, P2, P
3 and P4 to supply the hydraulic oil of the dual variable displacement main hydraulic pumps P1 and P2 to the traveling motors 3L and 3R of the crawler type left and right traveling device via the control valves C1 and C2, Boom cylinder 4, bucket cylinder 5, arm cylinder 6, service actuator (attachment) via control valves C3, C10, C4, C5, C6
10 to the first working actuator.

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.

Further, the hydraulic oil from the third sub-hydraulic pump P3 is supplied to the turning motor 7,
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.

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, and the main hydraulic pump P1 Is supplied to the suction side of the control valve C1 to which the pressurized oil is supplied, so that the traveling motor 3R can be driven, and the divided other flow passes through the oil passage 25 via the control valves C5, C6, and C10. 6. It can be supplied to the service actuator 10 and the like. The control valves C3, C4, C5, C7 and the switching diverting valve 11 are of a hydraulic pilot switching type, and the hydraulic oil from the pilot pressure hydraulic pump P4 is composed of an accumulator ACC and a check valve 130 provided upstream thereof. Accumulator 14
0, a swash plate angle changing travel speed switching valve 17, an unload valve 18, and a control valve C via a pilot operation valve 19.
3, C4, C5, and C7, and are also supplied to the switching diversion valve 11 via the signal oil passage 20.

The signal oil passage 20 of the switching flow dividing valve 11 is connected to the upstream side of the check valve 130, that is, between the pressure accumulating section 140 and the pilot pressure hydraulic pump P4, from which pressure oil is supplied. Signal oil passage 20 of switching diversion valve 11
Is connected to a pilot pressure control oil passage 21. The pilot pressure control oil passage 21 includes 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 running motors 3L and 3R, and control valves C1 to C from the oil passage 20.
6, a second control oil passage 21B that drains oil through C10.

Next, the operation of the hydraulic system will be described. Left and right running motor 3 without operating control valves C1, C2
In the non-driven state of L and 3R, the oil of the main hydraulic pump P1 can be supplied to the boom cylinder 4 and the bucket cylinder 5, and the oil of the main hydraulic pump P2 is supplied to the arm cylinder 6
And the service actuator 10, and the oil of the sub-hydraulic pump P 3 can be supplied to the swing 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 is supplied to the left and right traveling motors 3L and 3R.
The pilot pressure control oil passage 21 is blocked by the switching of the control valves C1 and C2, the pilot pressure rises, and the switching flow dividing valve 11 is operated to change from the distribution position to the distribution flow supply position. , Sub hydraulic pump P3
Can be supplied to the boom cylinder 4, the bucket cylinder 5, the arm cylinder 6, and the service actuator 10.

When the engine 13 is turned off while the front is raised, the pressure oil accumulated in the accumulator ACC can be supplied to the pilot operation valve 19 through the unload valve 18 which is in a flowing state. Therefore, even after the engine 13 is stopped, the front can be lowered by operating the pilot operation valve 19, and the pressure in the hose can be released. Here, since the signal oil passage 20 of the switching flow dividing valve 11 is connected to the upstream side of the check valve 130 of the pressure accumulating unit 140, the pressure stored in the accumulator ACC may not leak from the signal oil passage 20 after the engine is stopped. Absent. Therefore, in the present embodiment, the time for which the accumulator ACC holds the pressure is about 4 minutes, which is longer than the conventional case.

[0018]

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 a detailed explanatory view showing a right half of a conventional hydraulic system.

FIG. 5 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 130 Check valve 140 Accumulator ACC accumulator

Continued on the front page F-term (reference) 2D003 AA01 AB01 AB03 CA05 CA06 DA03 3H089 AA60 AA72 AA73 AA74 BB30 CC01 CC09 CC11 DA03 DA04 DA06 DB07 DB33 DB46 DB48 EE01 FF05 GG02 JJ02

Claims (3)

[Claims] 1. A pressure valve from a main hydraulic pump is supplied to a left and right traveling motor and a work actuator, and a pressure oil from a sub hydraulic pump is supplied to a work actuator. Is operated to supply the pressure oil from the sub-hydraulic pump to the working actuator, and the signal pressure oil for switching the switching valve returns to the oil tank when the left and right traveling motors are not driven. A hydraulic system for a working vehicle, comprising: a pilot-operated valve of the working actuator; an unload valve for disconnecting / connecting supply of pressure oil to the pilot-operated valve; and a pressure accumulator provided upstream of the unload valve. And the pressure accumulator is configured to prevent backflow to the upstream side and to supply signal pressure oil for the switching valve from the upstream side of the pressure accumulator. And the hydraulic system of the working vehicle. 2. The pressure accumulating section has an accumulator provided upstream of an unload valve and a check valve provided upstream of the accumulator, and a signal of the switching valve is provided from upstream of the check valve. 2. The apparatus according to claim 1, wherein the apparatus is configured to supply pressurized oil.
The working vehicle hydraulic system as described. 3. A work comprising: 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 pressure accumulator provided upstream of the unload valve. A hydraulic system for a vehicle, comprising: a switching valve configured to return a signal pressure oil for switching to a tank when the vehicle is not operating, wherein the signal pressure oil is supplied from an upstream side of the pressure accumulating unit. A hydraulic system for a work vehicle, wherein the hydraulic system is used.