JPH051702A - Pressure control valve - Google Patents

Abstract

PURPOSE:To simplify and miniaturize the structure of a hydraulic system circuit and to prevent the system from hunting by providing functions of a relief valve and an unloading valve. CONSTITUTION:A seat valve 3 is provided with an extremely small quantity of flow passage 37 for hunting prevention and a large quantity of flow passage 38 for unloading. The seat valve 3 is risen as a first poppet 18, thereby discharged flow from a hydraulic pump 100 being discharged via the large quantity of flow passage 38 to a tank T for effecting unloading. When the maximum load pressure of a circuit reaches a predetermined value, a second poppet 26 rises, thereby oil in a sub-control chamber 27 being relieved to the tank T through a third fluid chamber 22, third oil passage 29, second fluid chamber 17, first oil passage 19, third line 32 and second line 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure control valve, and more particularly to a pressure control valve which has the functions of a relief valve and an unload valve and is suitable for use in a hydraulic system of a construction machine.

[0002]

2. Description of the Related Art Various pressure control valves are used in hydraulic systems of hydraulic machines such as hydraulic excavators for circuit protection and other purposes. FIG. 4 is a circuit diagram showing an example of a conventional hydraulic system, which is a variable displacement hydraulic pump 100.
On the discharge side of, the direction switching valves 101A and 101B of the type that is center-blocked at the time of neutral are connected to an actuator that drives a load. In addition, the variable displacement hydraulic pump 1
The tilting angle control valve 103
Is connected to the pilot portions of the tilt angle control valve 103 facing each other, and the signal pressure P _L corresponding to the maximum load pressure detected by the directional control valves 101A and 101B and derived by the signal line 104, The discharge pressure P _{S of the} variable displacement hydraulic pump 100 is introduced.

The tilt angle control valve 103 is provided with a spring 105, and the tilt angle control valve 103 causes the discharge pressure P _{S of the} variable displacement hydraulic pump 100 to exceed the maximum load pressure of a plurality of actuators. The pump tilting is adjusted so that the spring 105 is kept high by a predetermined value.

The signal line 104 has a relief valve 106 and an unload valve 107 for limiting the maximum load pressure.
Is provided, the relief valve 106, the unload valve 107,
The direction switching valves 101A and 101B and the variable displacement hydraulic pump 100 are connected to the tank T by pipelines.

Further, the unload valve 107 has a spring 10
8 is provided, and the unload differential pressure ΔP = P _S −P _L is set by this spring 108.

In this system, the directional control valve 101A,
An unload valve 107 is provided for the purpose of preventing the minimum tilt discharge amount at that time from reaching the relief pressure and reducing energy loss when P _L = 0 when 101B is neutral. Further, in this system, as described above, the pump displacement is adjusted so as to maintain the discharge pressure P _S higher than the maximum load pressure P _L of the plurality of actuators by a predetermined value. Since the unloading valve 107 is set to have the unloading differential pressure ΔP = P _S −P _L , the system is likely to cause hunting. In order to prevent this, Japanese Patent Application No. 1-263683
There is an example in which the spool of the unload valve 107 is provided with a metering unit to bleed off the main circuit flow rate for a minute flow rate, as disclosed in Japanese Patent No.

[0007]

In the above-mentioned prior art, the unload valve 107 and the relief valve 106 must be separately provided, and the overall structure is complicated and large, and accordingly, the manufacturing cost increases. is there. As an integrated unload valve and relief valve, Japanese Patent Application No. 63-24
Although there are those disclosed in Japanese Patent Application No. 3466 and Japanese Patent Application No. 1-338167, these conventional techniques have the problem of hunting in the above-mentioned system.

The present invention has been made in view of the above-mentioned circumstances in the prior art, and an object thereof is to provide the functions of a relief valve and an unload valve, to make the hydraulic system circuit structure small and simple, and , To provide a pressure control valve capable of preventing system hunting.

[0009]

In order to achieve this object, the present invention forms a first control chamber on the back side of a seat valve, the inlet side of the seat valve and the first control chamber. A variable throttle portion that changes the opening degree according to the displacement of the seat valve is formed in the seat valve, and the seat valve inlet side and the outlet side are provided on the seat valve seat side when the seat valve is slightly lifted. A minute flow rate passage for communication is formed, a first cylinder chamber is provided at an axial center position of the seat valve, a first piston is housed in the first cylinder chamber, and one end side of the first piston is provided. The seat valve inlet pressure is introduced into the first fluid chamber formed in the first cylinder chamber, and the second fluid chamber is provided above the first control chamber, and the second fluid chamber and the first fluid chamber are provided. A first poppet that communicates with or cuts off from the control chamber and that interlocks with the first piston. And a first spring that biases the first poppet in the second fluid chamber, a third fluid chamber above the second fluid chamber, and the second fluid chamber and the second fluid chamber. A second cylinder chamber that connects the two fluid chambers is provided between the three fluid chambers, the second cylinder chamber accommodates a second piston that interlocks with the first poppet, and the second fluid chamber is connected to the third fluid chamber. A second spring for accommodating the second poppet, forming a sub-control chamber between the second poppet and the second piston, and providing a second spring for biasing the second poppet in the third fluid chamber A connection flow path that connects the second fluid chamber and the third fluid chamber to the seat valve outlet conduit is provided, and a load pressure signal is guided to the sub-control chamber.

[0010]

Since the present invention has the above-mentioned configuration, in the steady state, the discharge pressure of the pump is guided from the inlet side of the seat valve to the first control chamber through the throttle, and the seat valve is in the seat state. .

When the signal pressure of the load introduced into the sub control chamber rises and reaches a predetermined value, the second poppet moves under the second spring force and moves upward, and the sub control chamber moves to the third position. Leading to the fluid chamber.

Therefore, the oil in the sub-control chamber is guided to the outlet pipe line of the seat valve by the connecting flow passage through the second cylinder chamber and the third fluid chamber, and the maximum load pressure is adjusted to a predetermined set value. .

[0013] Hydraulic systems in unloaded state or operating conditions, the pump discharge pressure P _S is increased, the differential pressure P _S -P _L between the maximum load pressure P _L, i.e., the pressure and the secondary control of the first fluid chamber When the force due to the pressure difference in the chamber reaches a predetermined set value of the first spring, the first piston and the first poppet move upward, and the first control chamber communicates with the second fluid chamber.

Therefore, the oil in the first control chamber is guided to the outlet pipe line of the seat valve by the connection passage, the seat valve moves upward and is opened, and the minute flow rate of the discharge amount of the pump is a minute flow rate. It flows out to the tank through the passage. Further, when P _S −P _L becomes large, the first piston and the first piston
Poppet moves further up. As a result, the surplus flow rate of the pump discharge amount is discharged to the tank through the large opening.

[0015]

Embodiments of the pressure control valve of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the construction of an embodiment of the present invention, FIG. 2 is a circuit diagram of a hydraulic system to which the embodiment shown in FIG. 1 is applied, and FIG. 3 shows an operating state of the hydraulic system shown in FIG. It is an explanatory view shown.

In the pressure control valve 33 shown in FIG. 1, a fluid passage 35 is provided at one end of a tubular valve body 1, and the fluid passage 3 is provided.
5, a fluid passage 9 and a main fluid chamber 6 continuous with the fluid passage 9 are provided. It is arranged so as to face the fluid passage 35 of the valve body 1, forms an inner wall end of the fluid passage 35 and the main seat portion 5,
A seat valve 3 which is slidable in a main cylinder chamber 2 formed in a valve body 1 is provided. A first cylinder chamber 10 having a sectional area of a1 is formed in the seat valve 3 at the axial center position, and a first piston 11 is slidably accommodated in the first cylinder chamber 10. . A first fluid chamber 12 is provided between the facing end surfaces of the first piston 11 and the first cylinder chamber 10, and an oil passage hole that connects the first fluid chamber 12 and the main fluid chamber 6 to the seat valve 3 is provided. 13 is formed.

In the valve body 1, a first control chamber 4 is provided above the seat valve 3 and a thin groove-like oil passage 14 is formed in the axial direction of the seat valve 3. Groove 14 and first
The inner wall cutout portion of the control chamber 4 forms a variable throttle portion 39 that communicates the first control chamber 4 and the main fluid chamber 6 with each other as the seat valve 3 moves. Furthermore, at the one end of the seat valve 3, the main fluid chamber 6 and the fluid passage 35 are
A minute flow rate passage channel 37 communicating with each other and a large flow rate passage channel 38 continuous with the minute flow rate passage channel 37 are formed.

In the upper part of the first control chamber 4, the valve body 1
A sub-housing 16 is arranged inside, and a second cylinder member 20 is fitted on the upper part of the sub-housing 15. A second fluid chamber 17 is formed in the sub-housing 16, and a second cylinder chamber 23 having a sectional area of a2 is formed at the axial center position of the second cylinder member 20. Between the sub housing 16 and the end surface of the seat valve 3,
A main valve spring 15 is provided, and a first poppet 18 is provided through an opening 16a formed in the center of the sub housing 16.
Is connected to the end of the first piston 11. A second piston 24 is fixed to the first poppet 18, and the second piston 24 is slidably inserted into the second cylinder chamber 23. A first spring 25 is provided between the end faces of the cylinder member 20. A first oil passage 19 is formed in the sub-housing 16 in the vicinity of the opening 16a, and the first oil passage 19 is connected to the second pipe 8 or the tank by the third pipe 32. It is connected.

In the valve body 1, a third fluid chamber 22 is provided above the second cylinder member 20, and the second cylinder member 20 has a third fluid chamber 22 and a second fluid chamber 22. A third oil passage 29 for communicating 17 is formed. In the third fluid chamber 22, a second hopet 26 is provided at the position of the second cylinder chamber 23, and the third fluid chamber 22 is provided.
Plug 2 to valve body 1 so as to close the opening above
1 is screwed together. An adjuster 31 is screwed onto the plug 21 with a nut, and a second spring 30 is provided between the end surface of the adjuster 31 and the second poppet 26. The initial deflection of the second spring 30 is the adjuster 3
It can be adjusted by 1. A sub-control chamber 27 is provided between the end faces of the second poppet 26 and the second piston 24.
A second oil passage 28 communicating with the sub-control chamber 27 is formed on the outer peripheral surface of the valve body 1, and the second oil passage 28 is connected to the signal line 104. There is.

The pressure control valve 33 thus constructed is arranged in the hydraulic system as shown in FIG. That is, the fluid passage 9 is located on the discharge side of the variable displacement hydraulic pump 100.
Fluid path 3 of the pressure control valve 33, which is connected via the conduit 7 of
5 and the first oil passage 19 are connected to the tank T by the second pipeline 8 and the third pipeline 32, respectively. The configuration of the other parts in the circuit of the hydraulic system to which the above embodiment is applied is the same as the circuit of the conventional hydraulic system shown in FIG. 4 already described.

Next, the operation of the embodiment configured as described above will be described.

Discharge pressure P of the variable displacement hydraulic pump 100
_S is introduced into the first fluid chamber 12 from the first conduit 7 through the fluid passage 9, the main fluid chamber 6, and the oil passage hole 13. In addition, from the signal line 104 via the second oil passage 28,
The maximum load pressure is introduced into the sub control chamber 27 as the signal pressure P _L. The tilt control of the variable displacement hydraulic pump 100 is performed so that the differential pressure P _S −P _L between the discharge pressure P _S and the signal pressure P _L of the variable displacement hydraulic pump 100 maintains a predetermined value.
When the value of P _S −P _L is small, the discharge pressure P _S passes through the first pipe line 7, the fluid line 9, the main fluid chamber 6, the oil passage 14 and the variable throttle unit 39 and the pressure control valve 33. First control room 4
Will be introduced to. In this state, the seat valve 3 has the main fluid chamber 6
Due to the area difference between the pressure receiving area Aa inside and the pressure receiving area Ab inside the first control chamber 4 and the spring force of the main valve spring 15, the fluid passage 35
The main sheet portion 5 is pressed to the side and is in the sheet state. Therefore, the first pipe line 7 and the second pipe line 8 are cut off, and the seat valve 3 is closed.

When P _S -P _L rises, that is, from the resultant force of the pressure introduced into the sub control chamber 27 via the signal line 104 and the second oil passage 28 and the spring force of the first spring 25. However, when the discharge pressure P _S introduced into the first fluid chamber 12 increases, the first poppet 18 moves upward in FIG. 1 (at the time of unloading valve cracking differential pressure in FIG. 3). When the first poppet 18 moves upward in this way, the second fluid chamber 17 and the first control chamber 4 communicate with each other, and the oil in the main fluid chamber 6 allows the oil passage groove 14, the variable throttle portion 39, and the It flows out to the second pipeline 8 via the first control chamber 4, the second fluid chamber 17, the first oil passage 19, and the third pipeline 32. At this time, the variable diaphragm unit 3
A pressure drop is caused by passing through 9, so that the fluid pressure of the oil in the first control chamber 4 is reduced. Therefore, the seat valve 3 moves upward in FIG. 1 to be in the open state, the first pipe line 7 and the second pipe line 8 communicate with each other through the minute flow passage 37, and the variable displacement hydraulic pump. The surplus of the discharge amount of 100 flows into the tank T.

Here, the variable displacement hydraulic pump 100 is
The tilt angle control valve 103 controls to hold the differential pressure P _S -P _L between the discharge pressure P _S and the signal pressure P _L at the pump tilt control target differential pressure shown in FIG. At this time, the excess amount of the pump discharge flow rate due to the control error caused by the control accuracy or the delay of the signal line will flow out from the seat valve 3 to the tank T as described above, so that the hunting of the system can be prevented and the system can be stabilized. Pump control can be realized. On the other hand, when the direction switching valves 101A and 101B are in the neutral state, the signal pressure P _L becomes the pressure of the tank T, the variable displacement hydraulic pump 100 moves in the minimum tilting direction, and the minimum discharge amount is obtained. P _S −P _L rises, and the first poppet 18 moves further upward in FIG. 1 (at the second unload valve differential pressure setting in FIG. 3). The fluid pressure of the oil in the first control chamber 4 is reduced, and the variable throttle unit 39 regulates the pressure in the first control chamber 4, so that the seat valve 3 further moves upward in FIG. 1.
As a result, the first pipe line 7 and the second pipe line 8 communicate with each other through the large flow passage passage 38, and the discharge flow rate of the variable displacement hydraulic pump 100 flows into the tank T and is unloaded. be able to.

When the maximum load pressure of the circuit rises and reaches a predetermined value, the second signal pressure P _L introduced into the sub control chamber 27 through the signal line 104 and the second oil passage 28 is increased. The force that pushes up the poppet 26 becomes greater than the spring force of the second spring 30, and the second poppet 26 moves upward in FIG. When the second poppet 26 moves upward, the oil in the sub-control chamber 27 is transferred to the third fluid chamber 22 and the third oil passage 2
9, the second fluid chamber 17, the first oil passage 19 and the third conduit 32, and flows out to the second conduit 8. In this way, the maximum load pressure of the circuit is adjusted to a predetermined set value.

As described above, in the above embodiment, the pressure control valve 33 is provided with the relief valve function part and the unload valve function part in the integrated cartridge type, and the unload valve function part further includes an excessive small amount of the pump discharge flow rate. Since the flow rate is made to flow into the tank T, stable pump control can be performed without causing hatching, and the circuit configuration of the hydraulic system to which this embodiment is applied can be downsized and the manufacturing cost can be reduced. Can be realized.

[0028]

As described above, according to the present invention, one seat valve having the variable throttle portion and the minute flow passage is formed, and simple structural parts are added to the seat valve.
It is possible to have both functions of a relief valve and an unload valve, and when applied to a hydraulic system, hunting does not occur, stable pump control can be performed, and the entire circuit can be downsized. The manufacturing cost can be reduced as compared with that.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the configuration of an embodiment of a pressure control valve of the present invention.

FIG. 2 is a circuit diagram of a hydraulic system to which the embodiment shown in FIG. 1 is applied.

FIG. 3 is an explanatory diagram showing an operating state of the hydraulic system shown in FIG.

FIG. 4 is a circuit diagram of a conventional hydraulic system.

[Explanation of symbols]

1 valve body 2 Main cylinder chamber 3 seat valve 4 First control room 5 Main seat section 7 First pipeline 8 second pipeline 9 fluid path 10 First cylinder chamber 12 First fluid chamber 13 oil holes 14 oil passage 16 sub housing 17 Second fluid chamber 18 First Poppet 22 Third fluid chamber 23 Second cylinder chamber 24 Second piston 25 first spring 26 Second Poppet 29 Third oil passage 30 Second spring 32 Third conduit 33 Pressure control valve 104 signal line

Claims (2)

[Claims] 1. A first control chamber is formed on the back side of a seat valve, and the inlet side of the seat valve and the first control chamber are connected to each other, and the opening degree is changed according to the displacement of the seat valve. A variable flow restrictor is formed in the seat valve, and a minute flow passage that connects the seat valve inlet side and the outlet side is formed on the seat valve seat side when the seat valve is slightly lifted, and a shaft of the seat valve is formed. The first cylinder chamber is provided at the center position, the first piston is housed in the first cylinder chamber, and the seat is provided in the first fluid chamber formed in the first cylinder chamber on one end side of the first piston. A valve inlet pressure is introduced, a second fluid chamber is provided above the first control chamber, and the second fluid chamber and the first control chamber are communicated or cut off, and interlocked with the first piston. The first poppet and the first spring for urging the first poppet. In the fluid chamber, a third fluid chamber is provided above the second fluid chamber, and a second cylinder chamber is provided between the second fluid chamber and the third fluid chamber to communicate them with each other. A second piston that is interlocked with the first poppet is stored in the second cylinder chamber, a second poppet is stored in the third fluid chamber, and the second poppet and the second poppet are stored in the second fluid chamber. A sub control chamber is formed between the pistons, a second spring for urging the second poppet is provided in the third fluid chamber, and the second fluid chamber and the third fluid chamber are connected to the seat valve. A pressure control valve characterized in that a connection flow path communicating with an outlet pipe line is provided so that a pressure signal of a load is guided to the sub control chamber. 2. The pressure control valve according to claim 1, wherein the pressure control valve is formed as an integral cartridge type as a whole.