JPS5824672B2 - pressure control valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a balanced piston type pressure control valve that regulates the upper limit of pressure on the inlet side of a meter-in flow rate control valve.

2. Description of the Related Art Conventionally, a pressure control valve shown in FIG. 1 is known as a pressure control valve used when meter-in control of an actuator such as a cylinder is performed using a flow control valve.

In Fig. 1, 1 is a differential cylinder as a controlled actuator, 2 is a single coil type electromagnetic system with 4 points 2
Position switching valve, 3 is oil tank, 4 is variable flow rate control valve, 5
is a relief valve, 6 is a constant volume pump, and 7 is an oil tank.

In the system shown in FIG. 1, during the speed control of the actuator cylinder, the IJ pressure is always the constant circuit maximum pressure regardless of the magnitude of the load pressure of the actuator 1;
Since the surplus flow is returned to the tank 8 at a higher pressure than the relief valve 5, circuit efficiency is poor and energy loss is large, causing an increase in tank oil temperature.

Further, even if the flow rate control valve is equipped with pressure compensation, the pressure difference between the inlet and the outlet is affected by the load pressure, and the controlled flow rate also fluctuates to some extent due to fluctuations in the pressure difference.

The purpose of this invention is to perform meter-in control of an actuator such as a cylinder with a flow control valve, without losing the relief function that allows the maximum pressure of the circuit to be freely set from the outside. IJ on the inlet side of the flow control valve depending on the actuator load pressure on the side
- Variably control the flow pressure to a pressure value lower than the maximum pressure setting value of the circuit, and keep the pressure difference between the inlet and outlet of the flow control valve as high as possible beyond the pressure difference necessary for stable operation of the flow control valve. When the pressure is kept at a nearly constant set pressure value, and when the load pressure is high or when the outlet side of the flow control valve is closed by a switching valve, etc., use the normal balance piston type IJ IJ-
To provide a pressure control valve which performs a relief operation in the same way as a pressure control valve and allows the maximum circuit pressure to be freely set by a bundle.

That is, the pressure control valve of the present invention is a pressure control valve that controls the inlet side pressure of a flow control valve that meters-in controls the flow of pressure oil to an actuator such as a cylinder, and includes a pilot poppet that can adjust the pressure for setting the maximum circuit pressure. A part of the inlet pressure is transferred to the tank so that the inlet pressure does not exceed the maximum pressure setting value of the circuit. The balance piston type pressure control valve is characterized by releasing a part of the pilot pressure to the tank in accordance with the load pressure on the outlet side of the flow control valve, thereby controlling the pressure in the flow rate control valve according to the load pressure. Another pilot valve is provided for controlling the pilot pressure to a pressure value below the upper limit, and this other pilot valve receives the pilot pressure on one end face, receives the load pressure on the other end face, and receives the load pressure on the other end face. a slidable spool pressed from the side by an adjustable spring, the spool being moved against the spring force of the spring and the load pressure by the pilot pressure acting on the one end face; Accordingly, the present invention further includes a throttle control section for opening a pilot chamber of the pilot poppet valve communicating with the back of the main valve piston to a tank.

In this way, in the pressure control valve of the present invention, the IJ of the circuit
+)-F pressure is controlled according to the load pressure of the actuator below the maximum pressure setting value of the circuit, and the pressure difference between the inlet and outlet of the flow control valve is always maintained at a substantially constant value determined by the spring force of the spring. It is possible to do so.

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 2, the same reference numerals as in FIG. 1 are shown.

9 is a balanced piston type relief valve that is not much different from a normal one, and its inlet port 35 is connected to the inlet side of the flow control valve 4, and is used for flow control to meter-in control the flow of pressure oil from the pump 6 to the cylinder 1. Controls the pressure on the inlet side of the valve 4.

This balanced piston type relief valve 9 is equipped with a pilot poppet valve 34 for setting the circuit maximum pressure, which is regulated by an adjustment bundle 23, and this poppet valve 34 sets the upper limit of the pilot pressure in the valve chamber 10 at the back of the main valve piston 15. is regulated.

16 is a small throttle hole 2 that communicates the inlet port 35 and the valve chamber 10, 17 is a passage that communicates the valve chamber 10 with the pilot chamber 38 on the valve seat side of the poppet valve 34, and 28 is the poppet valve 34.
29 is a passage bored in the main valve 15 to communicate the main valve spring chamber 37 with the tank chamber 30.

The pressure setting of a normal balanced piston type IJ valve is done only by the pilot poppet valve 34,
The pressure control valve of the present invention controls the pilot pressure in the valve chamber 10 of the balance piston type relief valve 9 to be below its upper limit in order to keep the difference between the inlet side pressure and the outlet side pressure of the flow rate control valve 4 constant. Another pilot valve 11
This is provided.

That is, the pilot valve 11 is comprised of a spool 13 and a spring 14 that are slidably disposed within its main body 12, and the spool 13 receives the pilot pressure of the pilot chamber 38 through a passage 18 on one side 19 thereof. At the same time, the load pressure of the cylinder 1 is guided to the other end surface 20 through a conduit 21 and a port 22, and the spring 14 is applied to the other end surface 20 to provide elastic pressure so as to be adjustable by an adjustment screw 31. has been done.

Reference numeral 33 denotes a valve chamber in which one end surface 19 of the spool 13 is located, and as mentioned above, the passage 18 connects the pilot chamber 38.
26 is another valve chamber that communicates with the spring chamber 36, that is, the low pressure side that communicates with the tank 8, by a passage 2γ. The portion 25 and the tapered portion at one end of the spool 13 form a throttle control portion that opens the valve chamber 33 into the valve chamber 26 as the spool 13 moves against the spring 14.

Note that 32 is a plug that closes the end of the valve chamber 33.

In the pressure control valve according to the present invention shown in FIG. 2, the setting of the circuit maximum pressure, that is, the setting of the IJ-F pressure, is performed by regulating the pressure of the poppet valve 34 by the bundle 23, as in the usual case.

When the circuit pressure P2 led to the inlet port 35 is less than the maximum pressure setting value P1m, the valve chamber 1 on the back of the main valve piston
0 pressure, that is, the pilot pressure acting on the pilot poppet valve 34, matches the circuit pressure P2, and the pressure in the pyloft chamber 38 is equal to the pressure in the poppet valve 3 set by the handle 23.
The poppet valve 34 remains closed unless the set pressure of 4 is exceeded.

In this state, the pilot pressure P1 in the pilot chamber 38 is acting on one end surface 19 of the spool 13, and the load pressure P3 and the spring force of the spring 14 are acting on the other end surface 20.

Therefore, if the pilot pressure P1 increases, the spool 13 moves to the right in the figure to open the throttle control section, and conversely, if the load pressure P3 increases, it moves to the left in the figure to close the throttle control section. try

Control of the pilot pressure by this spool 13 is performed by setting the pressure receiving areas of both end faces of the spool to be equal A, and assuming that the pilot pressure is Pl and the load pressure is P3, P is P3+F/A
・・・・・・・・・・・・(1) (However, F:
The spring force of the spring 14) is performed so that the following relationship is satisfied.

When the pilot pressure rises and the left side of equation (1) becomes smaller than the right side, the flow flowing out from the throttle control section to the tank increases due to the operation of the spool 13, and this causes the pressure in the valve chamber 10 at the back of the main valve piston to decrease. As a result, the main valve piston 15 moves against the main valve spring, and the port 35
and 30 to increase the relief flow rate.

While the spool 13 is operating, the pressure oil flow is at port 3.
5° → Small hole 16 → Valve chamber 10 → Passage 17 → Pilot chamber 3
8 → passage 18 → valve chamber 33 → throttle control section → valve chamber 26 → passage 21 → spring chamber 36 → passage 28 → main valve spring chamber 37 → passage 2
9 → port 30 → flow to tank 8, and according to the differential pressure generated before and after the small hole 16, the main valve pi.

A relief action by the stone 15 is performed.

This IJ IJ-f operation is performed in a circuit pressure range lower than the circuit maximum pressure setting value P1m, and in this case, the differential pressure before and after the small hole 16 is ΔP2, and the pilot pressure inside the valve chamber 10 is
If =P3+F/A, then the person at flow control valve 4.

The circuit pressure P2 at the mouth is P2-P3+F/A+ΔP2...
...(2).

If the minimum differential pressure before and after the flow control valve 4 required for stable operation is ΔP, then ΔP>F/A+ΔP2 ・・・・・・・・・・・・・・・
・(3) The spring force F of the spring 14 is adjusted so that ・is satisfied.
may be set using the adjustment screw 31.

Normally, ΔP2 has only a very small fluctuation, so the relief pressure (circuit pressure) P2 is approximately equal to the sum of the load pressure P3 and the constant value F/A, and the pressure difference ΔP before and after the flow control valve 4
is maintained at a substantially constant value that is greater than the value necessary for stable operation and changes only by the amount of variation in ΔP2.

In this case, if Pl exceeds the maximum pressure setting value P1m set in the pilot poppet 34, the poppet 34 opens like a normal relief valve, and the pressure oil in the valve chamber 10 flows from the spring chamber 36 to the passage 28 and the main valve spring chamber. 27 and passage 29 to the tank chamber 30, whereby the main valve is connected to port 3.
It goes without saying that the opening between the tank chamber 5 and the tank chamber 30 should be further widened.

Furthermore, when the cylinder 1 reaches its stroke end, there is no flow in the flow rate control valve 4, so the differential pressure before and after it becomes zero and becomes P2-P3, and the spool 13
The end face 19 is moved by the spring force until it comes into contact with the plug 32, and the communication between the valve chambers 33 and 26 is cut off. Therefore, the circuit pressure P2 is set in the poppet valve 34 as in a normal balance piston type relief valve. IJ to maximum pressure IJ
- It will be controlled.

When using the pressure control valve of the present invention that operates in this way, the differential pressure before and after the flow control valve 4 is controlled to be almost constant, so if a pressure compensating type is used as the flow control valve 4, the control accuracy can be improved. is significantly improved, and even in the case of a simple throttle valve type, flow rate control close to that of a pressure compensation type can be performed.

As described above, in the pressure control valve of the present invention, the pilot pressure of the relief valve is always controlled to a value obtained by adding a constant value to the load pressure of the actuator. Therefore, the excess flow rate can be returned to the tank at a lower pressure than the IJ valve, and it is possible to improve circuit efficiency and reduce energy loss.

Furthermore, since the pressure difference between the inlet and the outlet of the flow control valve is approximately constant, it is possible to significantly improve the control accuracy of the pressure compensation type flow control valve.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram showing a conventional example, and FIG. 2 is a cross-sectional configuration explanatory diagram showing an embodiment of the present invention. 1...Cylinder, 4...Flow control valve,
9...Balance piston type relief valve, 11.
...Pilot valve, 13...Spool,
14... Spring, 34... Pilot poppet valve.

Claims (1)

[Claims] 1 A pressure control valve that controls the inlet side pressure of a flow rate control valve that meters-in controls the flow of pressure oil to an actuator such as a cylinder, and is equipped with a pilot poppet valve that can adjust the pressure for setting the maximum pressure in the circuit. A balanced piston type pressure control valve that releases a portion of the inlet side pressure to a tank so as to regulate the upper limit of the pilot pressure on the back of the main valve piston so that the inlet side pressure does not exceed the circuit maximum pressure setting value. , another pi tant valve that controls the pilot pressure to a pressure value below the upper limit according to the load pressure by releasing a part of the pilot pressure to the tank according to the load pressure on the outlet side of the flow rate control valve. The other pilot valve has one end face receiving the pilot pressure, the other end face receiving the load pressure, and a slidable spool pressed by an adjustable spring from the other end face. The pilot chamber of the pilot poppet valve communicates with the back of the main valve piston as the spool moves against the spring force of the spring and the load pressure due to the pilot pressure acting on the one end surface. A pressure control valve characterized in that it is equipped with a throttle control section that opens the flow to a tank.