JPH0381032B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a pressure control valve used for pressure control in a hydraulic circuit, and more specifically to an electromagnetic control valve with extremely excellent pressure override characteristics, simple structure, and low cost. Regarding control valves.

Conventional configurations and their problems As is well known, in various hydraulic circuits, the pressure control valves used to obtain the desired hydraulic pressure are generally of the following types: direct acting type, differential type, and pressure balanced type. It is used. Among these, pressure-balanced valves have the best pressure override characteristics, but have the drawbacks of being complicated and expensive in structure, and being greatly affected by dirt in the oil. Furthermore, although the direct-acting valves mentioned above have a simple structure, they have extremely poor pressure override characteristics, and because they receive hydraulic pressure directly through the valve opening area, large springs and solenoid forces are required to obtain high pressure and large flow rates. becomes. Furthermore, differential valves have a relatively simple structure, are resistant to dirt, and can obtain relatively high pressures and large flow rates, but they have the disadvantage of poor pressure override characteristics. FIG. 1 schematically shows the structure of a conventional differential valve, and the reason for the poor pressure override characteristics will be explained with reference to this diagram. 1st
In the figure, a valve body a is provided with a pressure oil inlet b and a pressure oil outlet c communicating with a tank chamber c', and is configured to open and close a passage between the pressure oil inlet b and the pressure oil outlet c within the valve body a. The hydraulic pressure is controlled by the biasing force of a spring g of a movably held valve d. When the pressure oil is flowing through the pressure oil inlet b and the pressure oil outlet c, the force that the valve d receives in the direction shown by the arrow e is the force A due to the oil pressure on the pressure oil inlet b side, and The force received in the direction of the arrow f, which is opposite to the above, is the force B due to the hydraulic pressure applied to the back of the valve d from the spring chamber h side where the spring g is arranged (the valve d is connected to the pressure oil outlet c by the small hole k). Because they are connected, the pressure in the spring chamber h and the pressure oil outlet c are the same) and the fluid force m
and spring force D. The diameter of the thick part of valve d is D ₁
The diameter of the thin part is D ₂ The diameter where the tank chamber c pressure acts on valve d is D ₃ The hydraulic pressure on the pressure oil inlet b side and the spring chamber h and tank chamber c sides are P ₁ and P ₂ respectively, and the deflection of spring g Let L be the spring constant and K be the spring constant, then the force A due to the hydraulic pressure on the pressure oil inlet b side, the force B due to the hydraulic pressure received from the spring chamber h side, the fluid force m, and the spring force D are as shown below.

A = π/4 (D ² ₁ - D ² ₂ ) x P ₁ B = π/4 (D ² ₁ - D ² ₃ ) x P ₂ m = F D = K x L () Hydraulic pressure is determined by screw j A desired value is set by changing the force of spring g. Here, when pressure oil inlet b and pressure oil outlet c are not communicating (when valve d is closed, pressure oil is not flowing), the force applied to valve d is the force applied in the e direction: A... ...() Force applied in the f direction: B+D ...() Here, when the oil pressure _P1 at the pressure oil inlet b exceeds a certain set value, the valve d moves in the e direction so that the pressure oil is discharged from the pressure oil outlet c. Moving.

That is, the balance equation of valve d just before pressure oil starts flowing is A=B+D...(), and the balance equation of valve d when pressure oil starts flowing is A=B+D+m...(). In other words, the pressure when valve d starts to open from the closed state and the pressure after it starts to open are:
This results in a difference in control pressure due to the flow force m. Conventional differential pressure control valves weigh 5 to 10 kg/
cm ² difference, which was a major cause of deterioration of the override characteristics of conventional differential pressure control valves.

Here, pressure oil leaks and flows into the spring chamber h from the valve d, but is returned to the pressure oil outlet c side through the pore K in the valve d.

Furthermore, when valve d opens a little and pressure oil flows from pressure oil inlet b to pressure oil outlet c, the flow velocity of pressure oil increases, and force is applied in the direction of closing valve d.
The pressure distribution in the vicinity became unstable, and there was a possibility that valve d would repeatedly open and close in a short period of time (chattering), making hydraulic control impossible.

OBJECTS OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional drawbacks, and to provide a pressure control valve that is simple in structure, has good pressure override characteristics, and does not cause valve chattering.

Structure of the Invention In order to achieve this object, the present invention provides a valve body having a pressure oil inlet and a pressure oil discharge port, and a valve that opens and closes a passage between the pressure oil inlet and the pressure oil discharge port within the valve body. , a solenoid connected to one side of the valve, a spring disposed on the opposite side of the valve, a spring chamber housing the spring, and communication between the pressure oil outlet and the spring chamber within the valve body. and a throttle valve which is provided in the bypass pipe and can be adjusted from the outside to open at a constant pressure depending on the pressure applied to the pressure oil inlet, When the valve is open, the overlap between the valve and the valve body is larger, so that the amount of pressure oil leaking from the pressure oil inlet to the spring chamber is reduced.

Description of examples An embodiment of the present invention will be described below.

As an embodiment of the present invention is schematically shown in FIG. 2, 1 is a valve body having a pressure oil inlet 2 and a pressure oil outlet 3; A valve 4 movably held to open and close a passageway to and from the
There is. Here, valve 4 is a spool valve, and valve 4
When the valve 4 is fully closed, a part of the valve 4 protrudes into the pressure oil inlet 2, and the overlap distance with the valve body 1 toward the spring chamber 5 side is small. When the valve 4 is opened, the valve 4 moves and the overlap with the valve body 1 is small. The lap charge is set to increase.

Behind the valve 4, there is a spring 6 connected to the valve 4 in a spring chamber 5, which can be adjusted with a screw 7. A bypass pipe line 10 having a throttle valve 9 is installed between the tank chamber 8 that connects the spring chamber 5 to the pressure oil outlet 3, and the pressure oil flows into the spring chamber 5 as leakage oil from the clearance part of the valve 4. , this pressure oil flows out to the tank chamber 8 through the bypass pipe line 10,
The throttle valve 9 creates a hydraulic pressure difference between the spring chamber 5 and the tank chamber 8. 11 is a solenoid,
Reference numeral 12 denotes a plunger, which is disposed on the side facing the spring 6, and whose operating pressure can be set by the electromagnetic force of the spring b and the solenoid 11.

Now, when the operating pressure is set to a desired value, the following relational expressions () and () are established. When valve 4 is fully closed, the balance of forces in valve 4 when it tries to open due to hydraulic pressure _P1 is A'+F+G=D'+E......() However, A'=π/4(D ' ₁ −D' ₂ )×P ₁ D'=K×L E=π/4D' ₁ ² ×P ₃ F=π/4D' ₃ ² ×P ₂ ...(') (G is the electromagnetic Here, D' ₁ is the diameter of the larger side of the valve 4, D' ₂ is the diameter of the smaller side of the valve 4, and D' ₃ is the diameter at which the pressure in the tank chamber 8 acts on the valve 4.

Here, P ₃ is the hydraulic pressure in the spring chamber 5, P ₂ is the hydraulic pressure in the tank chamber 8, and when the valve 4 is closed, the overlap between the valve body 1 and the valve 4 toward the spring chamber 5 side is small. Therefore, a relatively large amount of oil leaks to the spring chamber side, and by appropriately adjusting the throttle valve 9, a pressure _P3 is generated in the spring chamber 5. Here, P ₃ > P ₂ . That is, E is the force pushing the valve 4 in the closing direction due to the pressure _P3 in the spring chamber 5, and F
is the force that pushes the valve 4 in the opening direction due to the pressure P ₂ in the tank chamber 8.

Also, when valve 4 is slightly opened and pressure oil starts flowing, the balance of valve 4 is A'+F+G=D'+m+E'...() where m=F is the flow force of pressure oil.

Here, the amount of wrap between the valves 4 and 1 toward the spring chamber 5 increases due to the movement of the valve 4, and the leakage of pressure oil toward the spring chamber 5 decreases. The difference between pressures P ₃ and P ₂ almost disappears.

( _P2P3 ) _.

That is, E'=π/4D ² ₁ ×P ₂ ...('), mE-E' ...() is established, and the fluid force m is canceled out.

For example, in Figure 3, the set pressure is 10, 20, 30Kg/
This figure shows the flow rate and pressure characteristics of the above pressure control valve when expressed as cm ² . A is 10Kg/cm ² sets,
B indicates 20 Kg/cm ² set, C indicates 30 Kg/cm ² set, and the difference between the set pressure and the pressure at the beginning of opening was extremely small, both being 1 to 2 Kg/cm ² or less.

Furthermore, when the bypass pipe line 10 is throttled by the throttle valve 9, the spring chamber 5 also has the function of a dubbing chamber, and the valve 4
It has the function of suppressing vibrations even if it is subjected to the force of rapidly repeating opening and closing due to hydraulic fluid flow force.

Effects of the Invention As is clear from the above description, according to the present invention, the amount of oil leaking from the valve from the spring chamber to the tank chamber can be changed by changing the lap distance between the valve and the valve body when the valve is opened and closed. A bypass pipe is provided to allow this flow to be made variable, and a throttle valve is set therein.The throttle valve forms a hydraulic pressure difference between the spring chamber and the tank chamber, and the throttle valve is adjusted to the desired value. By adjusting the value, the pressure between the spring chamber and the tank chamber can be freely adjusted, and the tank chamber pressure can be set higher when the valve is closed than when the valve is open, which reduces the fluid flow force. Since it is possible to compensate for the force caused by the pressure and the force caused by the resistance of the pipeline on the tank chamber side, extremely good pressure override characteristics can be obtained. Since the spring chamber can be used as a damping chamber by the throttle valve, chattering of the valve can be prevented.

In addition, since it can be used as a structure for a differential pressure control valve, it is small, lightweight, and inexpensive, and is resistant to dust and highly reliable. Furthermore, when combined with a solenoid, it has the advantage of being usable as an electromagnetically controlled pressure control valve that can be remotely operated, making it extremely useful for use in various hydraulic circuits. In addition, the amount of pressure oil leaking from the pressure oil inlet to the spring chamber is configured so that the overlap between the valve and the valve body is larger when the valve is open than when the valve is closed, so that the amount of pressure oil leaking from the pressure oil inlet to the spring chamber is larger when the valve is closed. With the throttle valve, the spring chamber pressure can be set higher when the valve is closed than when the valve is open, and the force on the valve due to the pressure oil flow force when the valve is open can be canceled out, improving the pressure override characteristics. Further, since leakage of pressure oil can be adjusted only by changing the overlap dimension between the valve and the valve body without providing an orifice or the like, an inexpensive pressure control valve can be provided without the need for special processing.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a conventional differential pressure control valve, Fig. 2 is a sectional view of an electromagnetically controlled pressure control valve according to an embodiment of the present invention, and Fig. 3 is a pressure override characteristic of the same pressure control valve. It is a diagram. 1... Valve body, 2... Pressure oil inlet, 3... Pressure oil outlet, 4... Valve, 5... Spring chamber, 6... Spring, 8...
... Tank chamber, 9 ... Throttle valve, 10 ... Bypass pipe line.

Claims (1)

[Claims] 1. A valve body having a pressure oil inlet and a pressure oil outlet, a valve that opens and closes a passage between the pressure oil inlet and the pressure oil outlet in this valve body, and a solenoid connected to one side of this valve. , a spring disposed on opposite sides of the valve, a spring chamber housing the spring, a bypass conduit communicating the pressure oil outlet and the spring chamber within the valve body, and provided in the bypass passage, A throttle valve is provided that can be adjusted from the outside to open at a constant pressure depending on the pressure applied to the pressure oil inlet, and the valve and the valve body are closer together when the valve is open than when the valve is closed. A pressure control valve configured to reduce the amount of pressure oil leaking from the pressure oil inlet to the spring chamber by increasing the wrap distance.