JPH08210538A - Relief valve - Google Patents

Abstract

PURPOSE: To provide a highly precise relief valve while reducing a ratio of modification such as replacement of parts and partial intercontact correction after assembly. CONSTITUTION: A poppet 7a is directly fitted in a valve body 7A slidably, while a spring 7e projectingly energizing the poppet 7a and a plug 18 receiving the spring 7e are installed in the valve body 7A removably. When an oil pressure working on the inside of a poppet seat 7d restricting a projecting shift of the poppet 7a becomes the predetermined value or more, the poppet 7a is retracted against energizing force of the spring 7e so as to accomplish a condition for relief operation, while a shim 19 altering the installation length of the spring 7e is removably arranged between the poppet 7a and the plug 18 in the inside of the valve body 7A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a relief valve, and more particularly to a technique for achieving both simplification of structure and improvement of accuracy.

[0002]

2. Description of the Related Art For example, Japanese Patent Application No. 6-349 filed earlier
No. 50 proposes a relief valve having a structure incorporated in a valve casing in a hydraulic pressure grading mechanism.

[0003]

The above relief valve includes a valve body (reference numeral 7A) and a poppet guide (reference numeral 7).
c) and a poppet seat (reference numeral 7d) are installed in a valve casing (reference numeral 16) in a state of being fitted relative to each other, and a relief operation is performed by sliding movement of a spring-biased poppet (reference numeral 7a). Is configured. That is,
A portion for interior of the poppet is constituted by three parts, and the valve body and the poppet guide, and the poppet guide and the poppet seat are respectively fitted. Therefore, in order to provide a reliable, reliable, and highly accurate relief valve, it is necessary to ensure the roundness, cylindricity, concentricity, etc. of the poppet and each part around the poppet. It is difficult to ensure the accuracy with the above structure that straddles a large number of parts, and the rework rate after assembly such as part replacement or partial hit correction tends to be high. An object of the present invention is to realize a highly precise relief valve by reassembling the structure while keeping the repair rate low.

[0004]

To achieve the above object, the present invention is directed to a spring in which a poppet is slidably fitted directly in a valve body and biases the poppet so as to project, and a spring opposite to the poppet side of the spring. A lid member for receiving the side end is detachably attached to the valve body, and a cylindrical poppet seat for restricting the poppet protruding movement is provided. As the hydraulic pressure acting on the poppet seat reaches a predetermined value or more, The poppet is configured to move in and out against the biasing force of the spring to perform a relief operation, and a shim that changes the mounting length of the spring can be attached / detached between the poppet and the lid member inside the valve body. It is characterized by being equipped with a relief valve.

[0005]

In the structure of claim 1, the conventional two parts, the valve body and the poppet guide, can be constituted by one part only of the valve body, and the number of constituent parts is reduced by one.
Therefore, the total error due to the accumulation of the assembly error and the product error can be reduced, and the accuracy can be improved. In the conventional structure, the spring inside the valve body is inserted and removed from the poppet guide side.To remove the spring for cleaning and inspection after mounting it on the valve casing, remove the valve body from the valve casing. Although it was necessary to perform a troublesome operation of taking out the spring from the fitting portion with the poppet guide, in the structure of the present application, it suffices to remove the lid member mounted on the opposite side of the valve body from the poppet guide side, This makes it possible to save the trouble of attaching and detaching the valve casing and the trouble of having to operate the spring, the catch piece, etc. together when the valve casing is reset.

Further, since the spring mounting portion can be exposed only by attaching / detaching the lid member from the outside of the valve casing, the spring pressure, that is, the relief pressure can be easily adjusted by changing the shim or by increasing / decreasing the shim. Easy to reset the relief pressure. On the other hand, when the shim adjustment type is used in the conventional structure, the screw operation structure is adopted because the valve casing, which is cumbersome to disassemble, is not attached and removed each time, and the screw operation structure is adopted. There is a disadvantage that it is difficult to reset the pressure state.

[0007]

As a result, it is possible to provide a relief valve capable of simultaneously achieving the effects of reducing the number of parts by providing the valve body with the function of the conventional poppet guide and simplifying the relief pressure adjusting operation by the shim adjusting structure. I was able to.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an operating circuit structure of a hydraulic motor 1 for driving a crawler traveling device of a small backhoe in the forward and reverse directions. The hydraulic motor 1 and the three-position switching type control valve 2 are connected by a pair of oil supply and drain passages 3 and 4, and hydraulic oil from a hydraulic pump (not shown) is supplied to the hydraulic motor 1 by a switching operation of the control valve 2. The hydraulic motor 1 can be rotated in the forward and reverse directions by supplying and discharging. When the hydraulic motor 1 is loaded with a load more than the set value, it has a function of avoiding the pair of oil supply / discharge passages 3 and 4 from being drained by short-circuiting, and a function of mitigating a start shock or a reverse shock of the hydraulic motor 1. A hydraulic pressure grading mechanism A is provided.

FIG. 2 shows a hydraulic pressure grading mechanism A, which comprises a pair of relief valves 7 and 8 for discharging oil when the hydraulic pressure in the oil supply and discharge passages 3 and 4 exceeds a predetermined value, and a pair of winding springs 12 and 12. A pair of oil chambers 10 and 11 is urged by a piston 9 biased to a predetermined position.
Of the cushion portion 15 that is urged to return to a predetermined volume, and the connection oil passages 13 and 1 that communicate the pressure supply side oil passages 5 and 6 and the oil chambers 10 and 11 of the relief valves 7 and 8, respectively.
4 and 4 are internally mounted in the valve casing 16.

The structure of the relief valves 7 and 8 will be described. A valve body 7A (8) screwed to the valve casing 16 is provided.
A), poppet 7a (8a), valve body 7A (8
The oil supply / discharge passage 3 includes a poppet sheet 7d (8d) fitted and attached to A), a plug (corresponding to a lid member) 18, and the like.
The hydraulic oil supplied from the supply / drain port P3 connected to the valve body passes through the insides of the poppet seat 7d and the poppet 7a into the internal space of the valve body 7A, and the communication hole S formed in the valve body 7A causes the cushion portion to pass through. It is configured to be supplied to one of the oil chambers 15 of 15.

Spring 7e (8e) for setting relief pressure
Is mounted between a flange 20 externally fitted to the end of the poppet 7a and a shim 19 externally fitted to the inner end of the plug 18, and the shim 19 is replaced by detaching the screwed plug 18.
Alternatively, the relief pressure can be changed by increasing or decreasing the shim 19. When the pressure of the hydraulic oil from the supply / discharge port P3 exceeds the relief pressure, the poppet 7a moves to the plug 18 side,
A short circuit hole 17 formed at the inner end of the valve body 7A,
Also, the supply / discharge port P4 is short-circuited to the other supply / discharge oil passage 4.

In the state shown in FIG. 1, the control valve 2 is moved to the neutral position N.
The hydraulic motor 1 is operated in the stopped state. When the control valve 2 is operated to the right rotation position R, for example, from this state, hydraulic oil is supplied from the control valve 2 to the hydraulic motor 1 through the oil passage 3 and the hydraulic motor 1 starts rotating to the right. In this case, the working oil is supplied to the hydraulic motor 1 and at the same time, the working oil from the control valve 2 is also supplied to the one oil chamber 10 of the cushion portion 15 via the supply / discharge oil passage 3 and the connection oil passage 13. Then, the piston 9 moves leftward on the paper surface and compresses the spring 12 of the oil chamber 11 on the opposite side. Therefore, when the hydraulic motor 1 starts to rotate, the hydraulic oil for the hydraulic motor 1 is temporarily used for compression of the spring 12 of the cushion portion 15 by the pushing movement of the piston 9 to suppress a rapid increase in pressure. As a result, the hydraulic motor 1 starts rotating smoothly with less shock.

In the configuration shown in FIG. 1, when the control valve 2 is operated to the right rotation position R and the hydraulic motor 1 is rotating to the right, the control valve 2 is rotated from the right rotation position R to the left. When suddenly operated to the position L, the hydraulic motor 1 and the cushion portion 1
5, the hydraulic oil is discharged from one of the oil chambers 10, and the hydraulic oil is supplied to the oil passage 4 and the other oil chamber 11 on the opposite side, so that the hydraulic motor 1 starts to rotate to the left. Even at this time, the expansion of the other oil chamber 11 suppresses a rapid increase in pressure, and the hydraulic motor 1 starts rotating to the left with less shock from the state of rotating to the right. This state also occurs when the control valve 2 is suddenly operated from the left rotation position L to the right rotation position R.

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration shown in the attached drawings.

[Brief description of drawings]

FIG. 1 Operating circuit diagram of hydraulic motor

FIG. 2 is a sectional view of a grading mechanism showing the structure of a relief valve.

[Explanation of symbols]

 7A Valve body 7a Poppet 7d Poppet seat 7e Spring 18 Lid member 19 Shim

Claims (1)

[Claims] 1. A poppet (7a) is slidably fitted directly into a valve body (7A), and the poppet (7a) is slidably fitted therein.
A spring (7e) for biasing a) to project, and the spring (7e)
In the valve body (7A), a lid member (18) that receives an end portion of the poppet (7a) opposite to the side of the poppet (7a) is detachably mounted, and a cylindrical poppet sheet () that restricts the protruding movement of the poppet (7a). 7d) is provided, and this poppet sheet (7
As the hydraulic pressure acting in d) becomes a predetermined value or more, the poppet (7a) resists the biasing force of the spring (7e).
Of the shim (1) for changing the mounting length of the spring (7e) while being configured to move in and out for relief operation.
A relief valve in which 9) is detachably mounted between the poppet (7a) and the lid member (18) in the valve body (7A).