JP2002054603A - Accumulator charge circuit for running damper system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a problem of a fall of a hoist by return of part of pressure holding oil in a hoist cylinder from a pressure reducing valve of an accumulator charge circuit to a tank in a hoist holding state of the hoist cylinder when a damper system is not operating. SOLUTION: This circuit is provided with a multi-control valve 3, a damper oil passage 21 communicated with the bottom side 15 of the hoist cylinder 8, an accumulator 20 provided in the damper oil passage 21, a running damper changing valve 22 to communicate or shield the accumulator side of the damper oil passage 21 with/from the bottom side 15 of the hoist cylinder 8, and a charge circuit 41 to accumulate specified pressure oil in the accumulator 20 through the pressure reducing valve 42. A charge line 43 of the charge circuit 41 is connected to the upstream side of a bucket control valve 7 of the multi-control valve 3, thereby a fall of the hoist can be prevented by return of a part of oil from the pressure reducing valve 42 in the accumulator charge circuit 41 to the tank in a hoist holding state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an accumulator charge circuit in a traveling damper system for a wheel loader.

[0002]

2. Description of the Related Art Conventionally, a wheel loader has been provided with a traveling damper system for absorbing pressure fluctuations generated on the bottom side of a hoist cylinder when traveling while holding a load with a hoist.

In this traveling damper system, an accumulator is provided in an oil passage communicating with the bottom side of the hoist cylinder,
When the load reaches a predetermined traveling speed or higher while holding the load, the accumulator communicates with the bottom side of the hoist cylinder to absorb pressure pulsation with damper oil stored in the accumulator. Have been. In this case, if the pressure of the accumulator is low when the hoist cylinder is communicated with the accumulator, the hoist cylinder will drop, so the pressure in the accumulator will be close to the bottom pressure of the hoist cylinder when the load is held. Is set.

[0004] In the charge circuit for accumulating pressure in the accumulator, a charge line is connected to an oil passage communicating with the bottom side of the hoist cylinder. The charge circuit is provided with a pressure reducing valve, and reduces the pressure on the hoist cylinder bottom side to a predetermined pressure and stores the pressure in the accumulator.

A hydraulic circuit as shown in FIG. 3 is sometimes used as such a charge circuit. The hydraulic circuit includes a damper oil passage 101 connected to the hoist cylinder bottom side 105, an accumulator 102, and a traveling damper switching valve 103 for communicating or closing the damper oil passage 101.
Are provided. In the case of this hydraulic circuit, a special valve (a self-closing valve that closes with a metal touch) with extremely low leakage is used as the pressure reducing valve 104 when accumulating the pressure in the accumulator 102.

The traveling damper switching valve 103 is operated by a switching valve 106 for communicating or shutting off the hoist cylinder bottom side 105 and the accumulator 102, and a pilot oil from a pilot pump 107 for operating the switching valve 106. A switching assist valve 108 is provided. During operation of the hoist cylinder, when the pressure on the hoist cylinder bottom side 105 increases while the switching valve 106 is closed, the pressure is accumulated in the accumulator 102 from the oil passage 101 via the pressure reducing valve 104. This circuit is an accumulator charge circuit.

During traveling, the switching assist valve 10
8, the switching valve 106 is switched, the hoist cylinder bottom side 105 communicates with the accumulator 102, the hoist cylinder rod side 110 communicates with the tank 111, and the traveling damper system using the accumulator 102 functions.

[0008]

In the case of the accumulator charge circuit of the traveling damper system, since the oil for the damper is accumulated in the accumulator 102 from an oil passage connected to the hoist cylinder bottom side 105, the accumulator 102 is not operated. If the pressure on the bottom side 105 of the hoist cylinder is higher than the set pressure of the pressure reducing valve 104 while holding the load,
In some cases, some oil may be returned to 1 and the hoist may descend naturally.

Therefore, even when the hoist cylinder bottom side 105 communicates with the accumulator 102 to perform the damper function while the load is being held, if the pressure in the oil passage 101 becomes equal to or higher than the set pressure of the pressure reducing valve 104, Part of the oil passes through the pressure reducing valve 104 and returns to the tank 111,
A smooth operation may be hindered by a decrease in the amount of oil in the oil passage 101.

[0010] This means that when a normal pressure reducing valve is used as the pressure reducing valve 104, the hoist descending amount becomes large. In FIG. 3 described above, a self-closing valve with a very small leakage amount is used as a countermeasure. In some cases, a hunting phenomenon occurs and a sound is emitted.

In the charge circuit, the traveling damper switching valve 103 for communicating or shutting off the hoist cylinder bottom 105 and the accumulator 102 is a normal switching valve. Causes a leak even in the closed state.

[0012]

In order to solve the above-mentioned problems, the present invention provides a bucket control valve for operating a bucket cylinder using oil supplied from a hydraulic pump, and a hoist using oil supplied from the hydraulic pump. A multi-control valve in which a hoist control valve for operating a cylinder is arranged in series from the upstream side, a damper oil passage communicating with a bottom side of the hoist cylinder, an accumulator provided in the damper oil passage, and the damper oil passage A travel damper switching valve that connects or disconnects the accumulator side and the bottom side of the hoist cylinder, and a charge circuit that stores a predetermined pressure oil in the accumulator via a pressure reducing valve. The multi-control valve is connected to the upstream side of the bucket control valve. By connecting the charge line of the charge circuit upstream of the bucket control valve in this manner, the oil flows from the charge line to the accumulator side only when the hydraulic pressure of the multi-control valve increases due to the operation of the hoist or the bucket. In this state, the oil amount in the damper oil passage does not fluctuate.

Further, a bucket control valve for operating a bucket cylinder with oil supplied from a hydraulic pump and a hoist control valve for operating a hoist cylinder with oil supplied from the hydraulic pump are arranged in series from the upstream side. A multi-control valve, a damper oil passage communicating with the bottom side of the hoist cylinder, an accumulator provided in the damper oil passage, and a travel damper switch for communicating or blocking the accumulator side of the damper oil passage and the bottom side of the hoist cylinder. A valve, and a charge circuit for storing a predetermined pressure oil in the accumulator via a pressure reducing valve, wherein a charge line of the charge circuit is provided downstream of the bucket control valve of the multi-control valve and upstream of the hoist control valve. Side. In this case, even if the bucket operation is performed while the hoist is held, it is possible to prevent the oil amount in the damper oil passage from fluctuating.

Further, a bucket control valve for operating a bucket cylinder with oil supplied from a hydraulic pump,
A multi-control valve in which a hoist control valve for operating a hoist cylinder with oil supplied from a hydraulic pump is arranged in series from the upstream side; a damper oil passage communicating with the bottom side of the hoist cylinder; and a damper oil passage provided in the damper oil passage. An accumulator, a traveling damper switching valve that connects or disconnects the accumulator and the bottom side of the hoist cylinder through the damper oil passage, and a charge circuit that accumulates the pressure in the accumulator via a pressure reducing valve that reduces the pressure to a predetermined oil pressure. If a load check valve is provided in the hoist control valve and a charge line of a charge circuit is connected downstream of the load check valve, a charge line can be easily provided by using a connection portion provided in the load check valve. be able to.

A travel damper switching valve is provided with a logic valve for communicating or shutting off the damper oil passage with a pilot pressure on the bottom side of the hoist cylinder and the accumulator side, and releasing the pilot pressure on the shutoff side of the logic valve in accordance with the running speed. Thus, a travel damper system including a travel damper switching valve that is switched by the hydraulic pressure on the hoist cylinder bottom side and the accumulator side can be configured by using a switching valve that switches the damper oil passage to a communicating state.

Further, if the damper oil passage shut-off side of the logic valve is constituted by a pilot check valve, oil leaking when the damper oil passage is shut off can be suppressed.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a hydraulic circuit diagram of an accumulator charge circuit showing an embodiment of the present invention. In this figure, three types of accumulator charging circuits are shown in the same drawing, and the positions, positions, and positions are different embodiments, and a charging circuit is connected to any of the positions.

As shown, an oil passage 2 from a hydraulic pump 1 is connected to a P port 4 of a multi-control valve 3. In the multi-control valve 3, a bucket control valve 7 for operating a bucket cylinder 6 from the upstream side of the supply oil passage 5 and a hoist control valve 9 for operating a hoist cylinder 8 are arranged in series.
The bucket control valve 7 is connected to oil passages 12 and 13 that communicate with a rod side 10 and a bottom side 11 of a bucket cylinder 6 that operates the bucket. The hoist control valve 9 has a rod side 14 of the hoist cylinder 8.
And oil passages 16 and 17 communicating with the bottom side 15 are connected.

The control valves 7 and 9 are provided with load check valves 18 and 19, respectively. The control valve 7 or 9 is operated while the bucket cylinder 6 or the hoist cylinder 8 is maintained at a high pressure, and the oil passage is controlled. 12,1
It is configured to hold the high-pressure oil on both cylinders 6, 8 when 3, 16, 17 are communicated.

On the other hand, the bottom side 15 of the hoist cylinder 8
Is connected to a damper oil passage 21. The damper oil passage 21 is connected to an accumulator 20 that absorbs a pulsation caused by a pressure fluctuation on the bottom side 15 when the vehicle travels while holding a load with the hoist cylinder 8. The damper oil passage 21 communicates with the oil passage 17. This damper oil passage 21
Is provided with a traveling damper switching valve 22 that connects or disconnects the accumulator 20 side and the hoist cylinder bottom side 15. The traveling damper switching valve 22 divides the damper oil passage 21 into oil passages 23 and 24 between the hoist cylinder bottom 15 and the accumulator 20.

The travel damper switching valve 22 has a shut-off side 26 for shutting off the oil passage 23 and the oil passage 24 by the pressure in the oil passages 23 and 24, and an oil passage 23 and the oil passage 24. A logic valve 25 having a communication side 27 for communication is provided. In this embodiment, since the damper oil passage shutoff side 26 of the logic valve 25 is constituted by a pilot check valve, the damper oil passage 21 can be stably shut off when switched to the shutoff side 26. Further, the logic valve 25 includes a hoist cylinder bottom side 15.
And a high-pressure selector 30 for guiding the pressure of the accumulator 20 from the pilot circuits 28 and 29 are provided. A pilot circuit 32 is guided from the high-pressure selector 30 to the shut-off side 26 of the logic valve 25 via an electrically controlled switching valve 31. The pilot circuits 3 are also connected to the communication side 27 of the logic valve 25 from the oil passages 23 and 24.
3 is led.

The switching valve 31 has a communicating side 34 for guiding the pilot circuit 32 from the high-pressure selector 30 to the shut-off side of the logic valve 25 and a relief side 35 for releasing the shut-off pilot pressure of the pilot circuit 32 to the tank 36. It is configured to be switchable. The switching valve 31 is electrically switched in accordance with the traveling speed.
When the running speed reaches a predetermined speed, the mode is switched to the relief side 35. When the switching valve 31 is switched to the relief side 35,
The shut-off pilot pressure of the logic valve 25 is released from the pilot circuit 32 to the tank 36, and the logic valve 25 is switched to the communication side 27 by the communication pilot pressure from the pilot circuit 33 of the logic valve 25.

The rod side 14 of the hoist cylinder 8
Is provided with a rod-side traveling damper switching valve 37. The rod-side traveling damper switching valve 37 is also a switching valve that is switched by an electric signal, and can switch the oil passage 38 between a shut-off side 39 and a relief side 40 to the tank 36.

On the other hand, a charge circuit 41 for accumulating oil is provided in the oil passage 24 connected to the accumulator 20. The charge circuit 41 is provided with a pressure reducing valve 42 for reducing the pressure to a predetermined oil pressure. This pressure reducing valve 4
2 is adjusted to a set pressure close to the bottom pressure when the load is held by the hoist cylinder 8. A check valve 44 holds the pressure on the accumulator 20 side.

The inlet PC of the charge line 43 of the charge circuit 41 is connected to a position close to the P port 4 on the upstream side of the bucket control valve 7 of the multi-control valve 3.

FIG. 2 is a hydraulic circuit diagram showing an operation state of the accumulator charge circuit shown in FIG. According to the accumulator charge circuit configured to accumulate the pressure in the accumulator 20 from the position as described above, when the pressure in the supply oil passage 5 of the multi-control valve 3 is increased by operating the hoist cylinder 8 or the bucket cylinder 6. Then, the oil flows to the charge line 43 of the charge circuit 41, and the accumulator 2 is operated until the pressure reaches the set pressure of the pressure reducing valve 42.
The pressure is accumulated to zero.

Therefore, even if the holding pressure on the hoist cylinder bottom 15 increases when the traveling damper is not operated, the pressure does not act on the pressure reducing valve 42 of the charge circuit 41. Absent.

When the vehicle travels with the load held by the hoist cylinder 8, the switching valve 31 is moved to the communication side 34.
From the closed side 26 to the communicating side 27, and the hoist cylinder bottom 15 and the accumulator 20 are in communication with each other. At this time, the rod-side traveling damper switching valve 37 is also switched from the shut-off side 39 to the relief side 40 by an electric signal,
The rod side 14 becomes the tank pressure. This state is a running damper system operating state.

By the way, when the inlet PC of the charge line 43 is connected to the above-described position, the pressure on the P port 4 side increases due to the operation of the bucket cylinder 6 during traveling because the inlet PC of the charge line 43 is upstream of the bucket control valve 7. ,
When the pressure exceeds the set pressure of the pressure reducing valve 42 provided in the charge circuit 41 and becomes higher than the accumulator pressure, it flows to the accumulator 20 through the check valve 44. In this case, the oil supplied by the hydraulic pump 1 flows into the oil passage 24, causing a change in the oil amount in the damper oil passage 21.

Therefore, as shown in the figure, the inlet PC of the charge line 43 of the charge circuit 41 is connected to the downstream side of the bucket control valve 7 of the multi-control valve 3 and the upstream side of the hoist control valve 9.
If connected to this position, since it is on the downstream side of the bucket cylinder 6, the hoist cylinder 8 is operated without being affected by the operation of the bucket cylinder 6, and only when the pressure in the supply oil passage 5 is increased. Then, oil flows to the charge line 43 of the charge circuit 41 and is accumulated in the accumulator 20 until the pressure reaches the set pressure of the pressure reducing valve 42.

Therefore, even if the vehicle travels with the load held by the hoist cylinder 8, there is no change in the oil amount in the damper oil passage 21, so that the hoist cylinder 8 does not drop during traveling. .

When the charging line 43 of the charging circuit 41 is connected downstream of the bucket control valve 7 of the multi-control valve 3 and upstream of the hoist control valve 9 as described above, the control valve for the hoist is used. The inlet PC of the charge line 43 may be connected to a position on the downstream side of the load check valve 19 provided in the fuel cell 9.

In this case, the charge line 43 can be easily connected using a connection port (not shown) generally provided on the downstream side of the load check valve 19. Even when the hoist cylinder 8 is operated, the pressure is accumulated in the accumulator 20 via the charge circuit 41 only by the charge line 43 connected in this manner.

Therefore, even if the vehicle travels while holding the load with the hoist cylinder 8, the amount of oil in the damper oil passage 21 does not change, so that the hoist cylinder 8 does not drop.

The above-described embodiment is an embodiment, and various changes can be made without departing from the gist of the present invention, and the present invention is not limited to the above-described embodiment.

[0036]

The present invention is embodied in the form described above and has the following effects.

Since the charge line of the charge circuit is connected to the upstream side of the hoist control valve, even if the hoist is in the holding state, the holding pressure on the bottom side of the hoist cylinder is affected by the charge line and the work is smooth. There is nothing to hinder. Further, since the charge line of the charge circuit is connected to the upstream side of the hoist control valve, there is no need to specialize the pressure reducing valve of the charge line.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of an accumulator charge circuit showing an embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram showing an operation state of the accumulator charge circuit shown in FIG.

FIG. 3 is a hydraulic circuit diagram showing an example of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Hydraulic pump 2 ... Oil passage 3 ... Multi control valve 4 ... P port 5 ... Supply oil passage 6 ... Bucket cylinder 7 ... Bucket control valve 8 ... Hoist cylinder 9 ... Hoist control valve 10 ... Rod side 11 ... Bottom side 12, 13 ... oil passage 14 ... rod side 15 ... bottom side 16, 17 ... oil passage 18, 19 ... load check valve 20 ... accumulator 21 ... damper oil passage 22 ... traveling damper switching valve 23, 24 ... oil passage 25 ... logic Valve 26 Shut-off side 27 Communication side 28, 29 Pilot oil path 30 High-pressure selection part 31 Switching valve 32, 33 Pilot oil path 34 Communication side 35 Relief side 36 Tank 37 Switching valve 38 Oil Road 39 ... cut-off side 40 ... relief side 41 ... charge circuit 42 ... pressure reducing valve 43 ... charge line 44 ... check valve

Continued on front page F-term (reference) 2D003 AA01 AB03 AB07 AC01 BA01 BB03 CA02 CA09 DA03 3H089 BB05 BB16 CC01 CC11 DA02 DB05 DB44 DB47 DB48 DB49 DB50 DB55 DB68 DC02 GG02 JJ01

Claims (5)

[Claims] 1. A bucket control valve for operating a bucket cylinder with oil supplied from a hydraulic pump and a hoist control valve for operating a hoist cylinder with oil supplied from the hydraulic pump are arranged in series from the upstream side. A multi-control valve, a damper oil passage communicating with the bottom side of the hoist cylinder, an accumulator provided in the damper oil passage, and a travel damper switch for communicating or blocking the accumulator side of the damper oil passage and the bottom side of the hoist cylinder. A travel damper system comprising: a valve; and a charge circuit for storing a predetermined pressure oil in the accumulator via a pressure reducing valve, wherein a charge line of the charge circuit is connected to an upstream side of a bucket control valve of the multi-control valve. Accumulator charge circuit. 2. A bucket control valve for operating a bucket cylinder with oil supplied from a hydraulic pump and a hoist control valve for operating a hoist cylinder with oil supplied from the hydraulic pump are arranged in series from the upstream side. A multi-control valve, a damper oil passage communicating with the bottom side of the hoist cylinder, an accumulator provided in the damper oil passage, and a travel damper switch for communicating or blocking communication between the accumulator side of the damper oil passage and the bottom side of the hoist cylinder. A valve, and a charge circuit for storing a predetermined pressure oil in the accumulator via a pressure reducing valve, wherein a charge line of the charge circuit is provided downstream of the bucket control valve of the multi-control valve and upstream of the hoist control valve. The accumulator charge circuit of the traveling damper system connected to the side. 3. A multi-unit in which a bucket control valve for operating a bucket cylinder with oil supplied from a hydraulic pump and a hoist control valve for operating a hoist cylinder with oil supplied from a hydraulic pump are arranged in series from the upstream side. A control valve, a damper oil passage communicating with the bottom side of the hoist cylinder, an accumulator provided in the damper oil passage, and a travel damper switching valve that communicates or shuts off the accumulator and the bottom side of the hoist cylinder with the damper oil passage. A charge circuit that accumulates the pressure in the accumulator via a pressure reducing valve that reduces the pressure to a predetermined oil pressure, a load check valve is provided in the hoist control valve, and a charge line of the charge circuit is provided downstream of the load check valve. The accumulator charge circuit of the connected traveling damper system. 4. A travel damper switching valve comprising: a logic valve for communicating or shutting off a damper oil passage by a pilot pressure on the bottom side of the hoist cylinder and an accumulator side; and releasing a pilot pressure on the shutoff side of the logic valve in accordance with the running speed. The accumulator charge circuit of the traveling damper system according to any one of claims 1 to 3, wherein the switching valve is configured to switch the damper oil passage to a communication state. 5. The pilot check valve according to claim 4, wherein the damper oil passage cutoff side of the logic valve is constituted by a pilot check valve.
An accumulator charge circuit for the traveling damper system according to any one of the preceding claims.