JPS6141470Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a relief valve that operates in the same manner as a differential piston by inserting a sub-piston into a relief piston, and in particular, a relief valve characterized in that the sub-piston is spherical. Regarding.

Conventionally, as this type of relief valve, one shown in FIG. 1, for example, has been proposed.

That is, the stepped bore 2 provided in the housing 1
A piston 3 is slidably provided in the piston 3, a sub-piston 5 is fitted into a piston bore 4 formed on the drain side of the piston 3, and a pressure chamber 6 is formed in the piston bore 4 by insertion of the sub-piston 5.
A communication passage 9 communicates with a high pressure chamber 8 having a hydraulic pressure inflow passage 7, and a spring 10 is brought into contact with the flange 3a of the piston 3 to bias it toward the high pressure chamber 8. A force acting on the hydraulic pressure according to the pressure receiving area difference between the pressure chamber 6 and the pressure chamber 6 pushes the piston 3 to the right, and when this force overcomes the spring 10, the piston 3 moves to the right and generates high pressure. The chamber 8 is communicated with the relief outflow path 11 to release the hydraulic pressure to the drain, thereby maintaining the hydraulic pressure in the high pressure chamber 8 below a predetermined value.

According to the structure in which the sub-piston 5 is provided in addition to the piston 3, the force acting on the piston 3 is obtained according to the difference in pressure receiving area between the high pressure chamber 8 side and the pressure chamber 6 side, and the inflow liquid pressure Even if the pressure is high, there is an advantage that a spring with a small spring load can be used as the spring 10 for setting the relief hydraulic pressure.
Furthermore, since the sub-piston 5, which also has the function of guiding the piston 3 to move in a straight line, does not need to be machined integrally with the housing 1, alignment with the sub-piston 5 is easy when machining the piston bore 4. It also has the advantage that it is not necessary and processing becomes easier.

By the way, since the sub-piston 5 in the above relief valve has a free contact portion with the housing 1, when the piston 3 slides due to hydraulic pressure, if the circumferential area of contact with the piston bore 4 is small, This creates a so-called cantilevered state, and the axial center line of the sub-piston 5 is slightly inclined with respect to the axial center line of the piston 3, causing the inner circumferential surface of the piston bore 4 to be strained, resulting in unstable operation. Ta.

The present invention has been devised by focusing on these conventional problems, and aims to solve the above problems by forming the sub-piston into a spherical shape.

Hereinafter, the present invention will be explained based on the drawings.

FIG. 2 is a sectional view showing an embodiment of the present invention.

First, to explain the configuration, 1 is a housing, 2 is a stepped bore, 3 is a piston, 4 is a bore provided on the drain side of the piston 3, 7 is a hydraulic pressure inflow path, 8 is a high pressure chamber, 9 is a communication path, 10 is a spring, and 11 is a relief outflow path.

To explain in more detail, the stepped bore 2 formed in the housing 1 has a small diameter part and a large diameter part lined up in the axial direction, and the end of the small diameter part has a hydraulic inlet. The road surface 7 is opened, and an annular groove 2a is formed around the shaft, a relief outflow passage 11 is opened in the annular groove 2a, and a liquid communicating with a tank 17 is formed at the end of the large diameter part of the bore. Pressure flow path 18
is opened to form a drain chamber 20. Further, the piston 3 has one end slidably inserted into the small bore diameter part of the stepped bore 2 to define a high pressure chamber 8 into which hydraulic pressure from the hydraulic pressure inflow passage surface 7 is introduced, and furthermore, the piston 3 has one end slidably inserted into the small bore diameter part of the stepped bore 2 to define a high pressure chamber 8 into which the hydraulic pressure from the hydraulic pressure inflow passage surface 7 is introduced. A piston bore 4 is formed inside the piston portion extending into the drain chamber 20.
is open to the drain chamber 20 and connected to the high pressure chamber 8 by a communication passage surface 9 formed in the axial direction inside the piston 3.
is connected to. Further, a flange 3a is integrally formed approximately at the center of the outer circumference of the piston 3, and one end of a spring 10 incorporated in the large diameter portion of the bore comes into contact with the flange 3a, thereby urging the piston 3 toward the high pressure chamber 8 side. However, the relief pressure is determined by the force F of this spring 10.

In addition to this configuration, in the present invention, a cylindrical contact part 12 having a diameter that can be fitted into the piston bore 4 of the piston 3 is provided protrudingly at the end of the stepped bore 2 on the drain side. A spherical sub-piston 14 which is seated in the section 12 and has an outer diameter with a predetermined tolerance with respect to the inner diameter of the piston bore 4 is arranged so that the piston bore 4 of the piston 3 can slide. defined by a sub-piston 14 within;
A pressure chamber 6 communicating with a high pressure chamber 8 is formed through a communication passage 9 .

Here, the pressure receiving area of the piston 3 will be explained as follows.

First, the cross-sectional area of the piston 3 on the high pressure chamber 8 side is A1,
If the cross-sectional area of the pressure chamber 8 in the piston bore 4 is A2, and the cross-sectional area of the communication passage 9 is A3, then the piston 3
The pressure-receiving area on which the hydraulic pressure that pushes the to the right acts is (A1
-A3), and the pressure-receiving area on which the hydraulic pressure that pushes the piston 3 to the left acts is (A2-A3),
The diameter of the piston bore 4 is determined so that the relationship between this pressure receiving area is (A1-A3)>(A2-A3)...(1).

Next, the action will be explained.

When the hydraulic pressure P is applied to the high pressure chamber 8 from the hydraulic inflow path 7, the sub-piston 14 is pressed against the contact portion 12 by the hydraulic pressure flowing into the pressure chamber 6 via the communication path 9.
A force corresponding to the area difference between the high pressure chamber 8 side and the pressure chamber 6 side is applied to the piston 3 in the right direction.

That is, when the force of the spring 10 is F, the following relational expression holds true when the piston 3 is at rest.

P(A1-A3)<P(A2-A3)+F...(2) As is clear from equation (1), when the hydraulic pressure P is low, the force pushing the piston 3 to the left is strong, and the piston 3 is placed in a stopped state.

Subsequently, when the liquid pressure P rises, the pressure receiving area (A1-A3) on the high pressure chamber 8 side is larger than the pressure receiving area (A2 - A3) on the pressure chamber 6 side, so P(A1-A3) - P(A2 -A3)≧F…(3) When the force pushing the piston 3 to the right due to the hydraulic pressure P exceeds the spring force F, the piston 3 moves to the right against the spring 10, and the piston When the left end of 3 reaches the position of the annular groove 2a, the high pressure chamber 8 communicates with the relief outflow path surface 11, the hydraulic pressure is released to the drain, and the hydraulic pressure P reaches the next position (4).
Ensure that the value does not exceed the predetermined value given by the formula.

P=F/(A1-A2) (4) Of course, when the value falls below a predetermined value, the force of the spring 10 causes the piston 3 to return to its original state.

When the piston 3 operates to relieve hydraulic pressure in this way, the spherical sub-piston 14 is in line contact with the piston bore 4 of the piston 3 with its outer circumference, so the piston bore 4 slides. This allows the piston 3 to move smoothly without causing any twisting.

Figure 3 shows another embodiment of the present invention.
This embodiment is characterized in that a restriction 15 is provided in the communication passage 9 of the piston 3, and the other configurations are the same as the embodiment shown in FIG.

When the throttle 15 is provided in this way, the flow of liquid into and out of the pressure chamber 6 is delayed when the piston 3 moves, so the pressure chamber 6 acts as a damper against the piston 3, and is not affected by sudden changes in inflow liquid pressure. However, the movement of the piston 3 is gradual, greatly increasing the stability of the relief operation.

FIG. 4 shows another embodiment of the present invention, which is characterized in that a spring 16 is provided in the piston bore 4 of the piston 3, and the sub-piston 14 is positioned by this spring 16.

In this way, with the spring 16, the sub-piston 14
If the sub-piston 14 is pressed against the abutting portion 12 for positioning, the sub-piston 14 will not move freely when the piston 3 moves, and the sub-piston 14 will always be held at the center position of the piston bore 14, allowing smooth movement of the piston 3. As a result, stable relief operation can be performed, and since the set hydraulic pressure for relief operation is determined by the resultant force (F1 + F2) of springs 10 and 16, a high set pressure can be determined, and it is suitable for high pressure applications. suitable. In each of the above embodiments, when the flow rate is small, the pressure can be maintained constant with a small relief flow rate, so the movement of the piston 3 may be small, and in this case, the cylindrical contact portion 12 Not necessary.

As explained above, according to the present invention, the sub-piston on which the piston bore provided on the drain side of the piston slides has a spherical shape, so even if the piston moves for relief operation,
The piston operates stably and smoothly without twisting between it and the sub-piston, reliably preventing malfunctions that occur during use, and making it possible to obtain a relief valve with excellent reliability and durability. Effects can be obtained.

[Brief explanation of the drawing]

Figure 1 is a sectional view of a conventional relief valve, Figure 2 is a cross-sectional view of a conventional relief valve.
The figure is a sectional view showing one embodiment of the present invention, Nos. 3 and 4.
The figure is a sectional view showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Housing, 2...Stepped bore, 3...Piston, 4...Piston bore, 5...Sub-piston, 6...Pressure chamber, 7...Liquid pressure inflow path, 8...High pressure chamber, 9 ... Communication path, 10, 16 ... Spring, 11 ... Relief outflow path, 12 ... Contact part,
14...Spherical sub-piston, 15...Aperture.

Claims (1)

[Claims for Utility Model Registration] (1) A small diameter bore portion and a large diameter bore portion are formed in the axial direction in the housing, and a hydraulic pressure inflow passage is opened at the end side of the small diameter portion, and the axis of the small diameter bore portion is formed. A stepped bore having a relief outflow passage opened at a circumferential position and a hydraulic pressure outflow passage communicating with the tank at the end of the large diameter part of the bore, and one end of the stepped bore slidably in the small diameter part of the bore. It is inserted to define a high pressure chamber that receives hydraulic pressure supply from the hydraulic pressure inflow path, and the other end extends to the large bore chamber, and the inside of the extended portion communicates with the high pressure chamber via a communication path. and a piston having a piston bore that is open at the shaft end on the large-diameter side of the bore, and further forming the piston bore so that the pressure receiving area at the end of the piston bore is smaller than the pressure receiving area on the high pressure chamber side; a spring for setting a relief pressure that is housed in a large diameter portion of the bore of the attached bore and presses the piston toward the high pressure chamber; A relief valve characterized by comprising a spherical sub-piston that forms a spherical sub-piston. (2) The relief valve according to claim 1, which is a utility model, characterized in that a restriction is provided on the communication passage surface of the piston. (3) The relief valve according to claim 1, wherein the spherical sub-piston is inserted through a spring for positioning the piston bore of the piston.