JPH0868403A - Fluid pressure controller - Google Patents

Abstract

PURPOSE: To certainly stop the operation of a fluid pressure actuator. CONSTITUTION: This fluid pressure controller 30 is included in a counterbalance valve consisting of a sequence valve 31 which prevents fluid from flowing in a supply direction in a first fluid pressure line L1 and allows the fluid to flow in an exhaust direction in the first fluid pressure line L1 when it receives the first pilot pressure from a second fluid pressure line L2, and a first check valve 32 which allows the fluid to flow in a supply direction in a by-pass fluid pressure line L3 and prevents the fluid to flow in the exhaust direction. And, the fluid pressure controller 30 is provided with a second check valve 33 which is attached on a stream side in the exhaust direction lower than the counterbalance valve in the first fluid pressure line L1, allows the fluid to flow in the supply direction in the first fluid pressure line L1, and allows the fluid to flow in the exhaust direction in the first fluid pressure line L1 when it receives second pilot pressure from the second fluid pressure line L2. The second pilot pressure is set smaller than the first pilot pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid pressure control device attached to a fluid pressure circuit for supplying and discharging fluid to and from a fluid pressure actuator.

[0002]

BACKGROUND OF THE INVENTION Fluid such as oil is widely used as a medium for transmitting a force for operating a working device. For example, a boom attached to an aerial work vehicle or a crane vehicle is driven up and down or expanded and contracted by an actuator (hydraulic cylinder) that operates by hydraulic pressure. In the bottom side oil chamber and rod side oil chamber of the hydraulic cylinder (double-acting type), the operating oil is supplied in the supply direction to supply the operating oil to each oil chamber and in the discharging direction to discharge the operating oil from each oil chamber. Are connected to the hydraulic lines. For example, operating oil is supplied to the bottom side oil chamber via a first hydraulic line connected to the bottom side oil chamber, and operated from the rod side oil chamber via a second hydraulic line connected to the rod side oil chamber. When the oil is discharged, the hydraulic cylinder extends and the boom is lifted or extended. On the contrary, if hydraulic oil is supplied to the rod-side oil chamber via the second hydraulic line, and hydraulic oil is discharged from the bottom-side oil chamber via the first hydraulic line, the hydraulic cylinder will contract and the boom will move. Operate laying down or reducing.

A counter balance valve (back pressure holding valve) is attached to the first hydraulic line. The counter balance valve blocks the flow of the hydraulic oil in the first hydraulic line in the supply direction when the spool is in the closed position, while the spool moves to the open position to discharge the hydraulic oil in the first hydraulic line. Flow valve that allows a flow in the direction of flow and a bypass hydraulic line that bypasses this sequence valve and is connected to the first hydraulic line to allow a flow of the hydraulic oil in the supply direction and prevent a flow in the discharge direction. Check valve. The spool of the sequence valve moves to the open position only when it receives the pilot pressure equal to or higher than the predetermined pressure taken out from the second hydraulic line.

With such a counter balance valve, when it is desired to extend the hydraulic cylinder, hydraulic oil can be supplied to the bottom side oil chamber via the bypass hydraulic line and the check valve. On the other hand, when it is desired to reduce the hydraulic cylinder, the hydraulic oil in the second hydraulic line can be discharged through the first hydraulic line while maintaining the hydraulic pressure in the second hydraulic line above a predetermined pressure.

When it is desired to stop the expansion / contraction operation of the hydraulic cylinder on the way in order to keep the boom in a constant undulating or expanding / contracting state, the hydraulic pressure in the second hydraulic line is lower than a predetermined pressure (for example, It is sufficient to prevent discharge of hydraulic oil from the bottom side oil chamber by the closed sequence valve and check valve. As a result, the working oil in the bottom side oil chamber, which has been compressed and has increased in pressure, can support the load of the boom.

[0006]

However, since there is a slight clearance between the spool and the valve body in the sequence valve, even if the spool is completely in the closed position, the hydraulic oil is discharged through this clearance. There is a problem that the hydraulic cylinder leaks in the direction and the hydraulic cylinder gradually shrinks. Also, if dust contained in the hydraulic oil clogs this gap and the movement of the spool becomes poor, the spool will not be completely located in the closed position even if the hydraulic pressure in the second hydraulic line becomes lower than a predetermined pressure, and a large amount will be generated. There is also a possibility that the hydraulic oil of No. 2 will flow in the discharge direction and the hydraulic cylinder will be reduced at a high speed.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a fluid pressure control device capable of reliably stopping the operation of the fluid pressure actuator.

[0008]

In order to achieve the above object, the fluid pressure control device of the present invention prevents the flow of the fluid in the first fluid pressure line in the supply direction, and at the same time, the second fluid pressure line. And a sequence valve that allows the flow of the fluid in the first fluid pressure line in the discharge direction only when receiving the first pilot pressure from the In addition to a counterbalance valve that is composed of a first check valve that blocks the flow to and from, a second check valve is provided. The second check valve is attached downstream of the counterbalance valve in the first fluid pressure line in the discharge direction, allows the flow of the fluid in the first fluid pressure line in the supply direction, and is connected to the second fluid pressure line. The flow of fluid in the first fluid pressure line in the discharge direction is permitted only when the second pilot pressure is received.

[0009]

In such a fluid pressure control device, when the hydraulic oil is supplied to the actuator through the first fluid pressure line, both the second check valve and the first check valve allow the flow of the hydraulic oil. Therefore, the actuator can be operated smoothly. Even if the hydraulic oil leaks from the sequence valve in the discharge direction after the supply of hydraulic oil from the first fluid pressure line is stopped, the leaked hydraulic oil itself causes the poppet of the second check valve to move to the seat of the valve body. Pressed against the surface,
Since the first fluid pressure line is completely closed, there is no hydraulic fluid leakage from the second check valve to the front, and the actuator does not move naturally. Therefore, when the actuator is a hydraulic cylinder for raising and lowering or expanding and contracting the boom, the boom is prevented from naturally falling and contracting.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an aerial work vehicle equipped with a fluid pressure control device according to the present invention. The aerial work vehicle 1 is configured with a truck as a base, and a swivel base 3 which is capable of horizontally swiveling with respect to the vehicle body 2 is attached to a rear portion of the vehicle body 2. A boom 4 is attached to the upper part of the swivel base 3. The boom 4 includes a base boom 4a pivotally attached to the swivel 3 so as to be up and down, an intermediate boom 4b movably inserted in the base boom 4a in the longitudinal direction, and a longitudinal boom in the intermediate boom 4b. The tip boom 4c inserted so as to be movable in any direction is telescopically extendable. The boom 4 has a hydraulic telescopic cylinder (not shown) built therein, and the boom 4 is telescopically driven by the telescopic cylinder. A hydraulic hoisting cylinder 5 is attached between the base boom 4 a and the swivel base 3, and the boom 4 is hoisted and driven by the hoisting cylinder 5.

The hydraulic circuit 20 for controlling the hydraulic pressure supply to the undulating cylinder 5 will be described with reference to FIG. The hydraulic circuit 20 hydraulically connects the first hydraulic line L1 connected to the bottom side oil chamber 5a of the undulating cylinder 5, the second hydraulic line L2 connected to the rod side oil chamber 5b of the undulating cylinder 5, and these hydraulic lines L1 and L2. A pump P or an oil tank T and a switching valve 23 that is selectively connected thereto.

In the hydraulic circuit 20, when the switching valve 23 is switched from the neutral position to connect the first hydraulic line L1 to the hydraulic pump P and the second hydraulic line P2 to the oil tank T, the hydraulic pump P discharges. The working oil flows into the bottom side oil chamber 5a via the first hydraulic line L1 (hereinafter, this flow direction is referred to as a supply direction), and the working oil in the rod side oil chamber 5b is transferred to the second hydraulic line L2.
The oil is discharged to the oil tank T via the oil tank (hereinafter, this flow direction is referred to as a discharge direction), and the undulating cylinder 5 is extended. On the contrary, when the first hydraulic line L1 is connected to the oil tank T and the second hydraulic line P2 is connected to the hydraulic pump P, the hydraulic fluid discharged from the hydraulic pump P is transferred to the rod-side oil via the second hydraulic line L2. While flowing into the chamber 5b, the hydraulic oil in the bottom side oil chamber 5a flows into the first hydraulic line L1.
The oil is discharged to the oil tank T via the, and the undulating cylinder 5 is contracted.

Further, as shown in FIG. 1, the tip boom 4 is
A workbench 6 is attached to the tip of c. The workbench 6 is mounted on the boom 4 by a leveling device (not shown).
It is kept horizontal regardless of the undulations. An operator (not shown) can board the workbench 6, and the operator operates each of the swivel base 3 and the boom 4 through the operation of an operating device (not shown) attached to the workbench 6. You can control and move to any height.

A hydraulic control device 30 according to the present invention is attached to the hydraulic circuit 20 shown in FIG. 2 in order to stop the boom 4 in an arbitrary undulating state. The hydraulic control device 30 includes a counter balance valve and a second balance control valve.
It is composed of a check valve 33.

The counter balance valve comprises a sequence valve 31 and a first check valve 32. The sequence valve 31 is connected to a spool 31a that can move up and down on the first hydraulic line L1, a spring 31b that urges the spool 31a in a downward direction, and a lower side of a valve body (not shown). It is composed of a pilot line 31c. Pilot line 31
c is connected to the second hydraulic line L2, and the spool 31a uses the hydraulic pressure in the second hydraulic line L2 as a pilot pressure.
Lead to the lower side.

In this sequence valve 31, when the pilot pressure is smaller than the urging force of the spring 31b, the spool 31a is located at the lower position and closes the first hydraulic line L1. On the other hand, when the pilot pressure exceeds the urging pressure of the spring 31b, the spool is positioned at the upward movement position, and the flow of the hydraulic oil in the first hydraulic line L1 is blocked, but in the discharge direction. Allow the flow. The spring 31b
The pilot pressure exceeding the urging force of is referred to as the first pilot pressure.

The first check valve 32 is mounted on a bypass hydraulic line L3 that bypasses the sequence valve 31 and is connected to the first hydraulic line L1. The first check valve 32 includes a poppet 32a and a spring (not shown) that biases the poppet 32a in a direction (leftward) in which the poppet 32a is brought into contact with a seat surface of a valve body (not shown). There is. With this first check valve 32,
When the hydraulic oil is about to flow in the bypass hydraulic line L3 in the discharge direction, the hydraulic oil itself will flow into the poppet 32.
Since a is brought into close contact with the sheet surface, this flow is completely blocked. On the other hand, when the hydraulic oil is about to flow in the supply direction in the bypass hydraulic line L3, the poppet 32a is separated from the seat surface by the pressure of the hydraulic oil (pressure exceeding the biasing pressure of the spring). Is acceptable.

The second check valve 33 is attached downstream of the counter balance valve in the first hydraulic line L1 in the discharging direction. The second check valve 33 includes a poppet 33a, a spring (not shown) for urging the poppet 33a in a direction (leftward) for bringing the poppet 33a into contact with a seat surface of a valve body (not shown), and the poppet 33.
It is composed of a piston (not shown) movably arranged on the left side of "a" and a pilot line 33b connected to the left side of the piston in the valve body.
The pilot line 33b is connected to the second hydraulic line L2 and guides the hydraulic pressure in the second hydraulic line L2 to the left side of the piston as pilot pressure.

In the second check valve 33, when the hydraulic oil is going to flow in the first hydraulic line L1 in the supply direction, the pressure of the hydraulic oil exceeds the biasing force of the spring and the spool 33a moves to the right. And allow this flow. If the pilot pressure supplied from the pilot line 33b is smaller than the sum of the biasing pressure of the spring and the pressure of the hydraulic oil when the hydraulic oil is about to flow in the first hydraulic line L1 in the discharge direction, This flow is completely blocked because the hydraulic oil itself brings the poppet 33a into close contact with the seat surface. However, when the pilot pressure in which the pressure of the hydraulic oil exceeds the sum of the biasing pressure of the spring and the pressure of the hydraulic oil acts on the piston, the poppet 32a is pushed to the right by the piston moving to the right and separated from the seat surface. Therefore, this flow is allowed. The pilot pressure that exceeds the sum of the spring bias pressure and the hydraulic oil pressure is referred to as the second pilot pressure. This second pilot pressure is smaller than the first pilot pressure.

Next, the operation of the hydraulic control device 30 thus constructed will be described. When the hydraulic oil from the hydraulic pump P is supplied to the first hydraulic line L1, the pressure of this hydraulic oil causes the poppets 33a and 32a of the second check valve 33 and the first check valve 32 to separate from the seat surface. Since the flow of the hydraulic oil in the first hydraulic line L1 in the supply direction is allowed, the hydraulic oil smoothly flows into the bottom oil chamber 5a through the first hydraulic line L1 and the bypass hydraulic line L3. As a result, the hoisting cylinder 5 extends and discharges the hydraulic oil from the rod-side oil chamber 5b to the tank T via the second hydraulic line L2 (the boom 4 hoists).

When the supply of hydraulic oil to the first hydraulic line L1 is stopped while the undulating cylinder 5 is extended to a certain extent, almost no hydraulic pressure is established in the second hydraulic line L2. 31
a is located in the down position. Therefore, the bottom side oil chamber 5a
Most of the hydraulic oil in the inside is blocked from flowing in the discharge direction by the sequence valve 31, but a part of the hydraulic oil leaks from the gap between the spool 31a and the valve body in the sequence valve 31. However, because the leaked hydraulic oil itself presses the poppet 33a of the second check valve 33 against the seat surface, the flow of the leaked hydraulic oil in the discharge direction is completely prevented by the second check valve 33. Be blocked. Therefore, the undulating cylinder 5 does not naturally contract, and the boom 4 can be maintained in the undulating state at that time.

When the hydraulic oil from the hydraulic pump P is supplied to the second hydraulic line L2 and the hydraulic pressure in the second hydraulic line L2 rises to the second pilot pressure, the second check valve 33 first opens. Further, the second hydraulic line L
When the hydraulic pressure in 2 rises to the first pilot pressure, the sequence valve 31 opens. In this way, the undulating cylinder 5 discharges the hydraulic oil in the bottom side oil chamber 5b to the tank T via the first hydraulic line L1 while the hydraulic pressure in the second hydraulic line L2 is maintained at the same level as the first pilot pressure. While doing so, it smoothly contracts (the boom 4 falls over).

In the above embodiment, the case where the hydraulic cylinder of the hoisting cylinder 5 is mounted is described. However, the fluid pressure control device of the present invention is not limited to this, and it is for a telescopic cylinder for extending and retracting the boom 4. It can also be attached to the hydraulic circuit. Further, the fluid pressure control device of the present invention can be widely applied to a working device for a crane truck instead of the aerial work vehicle shown in the above embodiment.

[0024]

As described above, in the fluid pressure control device of the present invention, the flow in the supply direction of the fluid in the first fluid pressure line is downstream of the counter balance valve in the first fluid pressure line in the discharge direction. With the second
A second check valve that allows the flow of the fluid in the first fluid pressure line in the discharge direction is arranged only when receiving the second pilot pressure taken out from the fluid pressure line. Therefore, if the present fluid pressure control device is used, even if the hydraulic fluid leaks in the discharge direction from the sequence valve after the supply of the hydraulic fluid from the first fluid pressure line to the actuator is stopped, the leaked hydraulic fluid itself Since the poppet of the second check valve is pressed against the seat surface of the valve body, the first fluid pressure line is completely closed. Therefore, it is possible to reliably prevent the natural operation of the actuator due to the hydraulic oil leakage from the second check valve to the front.

[Brief description of drawings]

FIG. 1 is a rear view of an aerial work vehicle equipped with a fluid pressure control device according to the present invention.

FIG. 2 is a hydraulic circuit diagram including the fluid pressure control device.

[Explanation of symbols]

 5 Hydraulic undulating cylinder 30 Fluid pressure control device 31 Sequence valve 32 First check valve 33 Second check valve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B66F 11/04

Claims (1)

[Claims] 1. A fluid pressure circuit connected to a fluid pressure actuator, the fluid pressure circuit having two fluid pressure lines for allowing fluid to flow to the actuator in a supply direction and a discharge direction. The flow of the fluid in the first fluid pressure line in the supply direction is blocked, and the flow of the fluid in the first fluid pressure line in the discharge direction is limited only when the first pilot pressure is received from the second fluid pressure line. A sequence valve that permits and a flow that bypasses the sequence valve and allows the flow of the fluid in the supply direction in the bypass fluid pressure line connected to the first fluid pressure line, and blocks the flow in the discharge direction. Counter balance valve consisting of one check valve, and the counter balance valve in the first fluid pressure line Is attached to the downstream side of the discharge direction, allows the flow of the fluid in the first fluid pressure line in the supply direction, and only when the second pilot pressure is received from the second fluid pressure line. 1. A fluid pressure control device, comprising: a second check valve that allows a fluid in a fluid pressure line to flow in the discharge direction.