JPH08261345A - Relief valve - Google Patents

Abstract

PURPOSE: To perform adjustment of the set oil pressure of a relief valve with high workability and high precision. CONSTITUTION: A relieve valve comprises a casing 2 provided with a pressure oil introduction passage 3 and a pressure oil discharge passage 4 communicated with the pressure oil introduction passage 3; a valve body 6A to open and close a pressure oil introduction passage 3; a valve spring 7 to apply an energizing force in a closing direction on the valve body 6A; and a spring support 8 arranged at the other end of the casing 2 movably forward and backward and support the valve spring 7. In the relief valve, the valve spring 7 comprises a large first coil spring; and a second coil spring 72 arranged coaxially therewith in the first coil spring 71 and having diameter smaller than that of the first coil spring 71 and a low spring constant. The spring support 8 comprises a first screw member 81 screwed in the other end of the casing 2 movably forward and backward and supporting the first coil spring 71: and a second screw member 82 screwed in the central part of the first screw member 81 movably forward and backward and supporting the second coil spring 72. A set oil pressure is finely adjusted by the second screw member 82.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relief valve attached to a hydraulic circuit.

[0002]

2. Description of the Related Art A hydraulic circuit for driving an actuator is used in a rear gate lifter of a truck, a table driving device of a machine tool and the like.

FIG. 4 shows a hydraulic circuit of a table drive device. The hydraulic circuit divides pressure oil generated by a hydraulic pump 11 by the power of a motor 10 by a direction switching valve 12 so that both ends of a cylinder 13 are connected. The piston 14 in the cylinder 13 is driven so that the table 15 connected to the piston 14 is reciprocated.

A relief valve 1 is attached to the hydraulic circuit, and a part of the pressure oil is released to the tank 16 when the piston 14 reaches the stroke end or when the table 15 is overloaded. It plays the role of preventing excessive rise in hydraulic pressure.

As shown in FIG. 5, the relief valve 1 is provided with a pressure oil introduction passage 3 connected to a discharge side circuit pipe and a pressure oil discharge passage 4 communicating with the pressure oil introduction passage 3 at one end of a casing 2. The piston type valve body 6 that opens and closes the pressure oil introduction path 3 is biased by a coil spring 7 that is a valve spring, and the coil spring 7 is received by a screw member that is a spring receiving member that is screwed into the other end of the casing 2. ing. The spring force of the coil spring 7 that biases the valve body 6 is adjusted to a spring force that balances with the set hydraulic pressure by moving the screw member 8 forward and backward. Then, when the hydraulic pressure exceeds the set hydraulic pressure, the valve body 6 is retracted and the pressure oil is released from the pressure oil introduction passage 3 to the pressure oil discharge passage 4.

[0006]

By the way, when a valve spring having a large set hydraulic pressure and a large spring constant is used, particularly when the length of the relief valve is reduced due to the mounting space and the like, Since the spring force changes greatly with a slight advance / retreat, it is extremely difficult to accurately adjust the set hydraulic pressure.

Therefore, an object of the present invention is to propose a relief valve capable of adjusting the set hydraulic pressure with good workability and high accuracy.

[0008]

As shown in FIG. 1, in the first configuration of the present invention, a casing 2 provided with a pressure oil introducing passage 3 and a pressure oil discharging passage 4 communicating with the pressure oil introducing passage 3. A valve body 6A that opens and closes the pressure oil introduction passage 3, a valve spring 7 that applies a biasing force to the valve body 6A in the closing direction, and a valve spring 7 that is provided at the other end of the casing 2 so as to be movable back and forth. In the relief valve having the spring receiver 8 for receiving, the valve spring 7 is composed of a plurality of (two in the illustrated example) valve springs 71 and 72 having different spring constants, and each valve spring 71 and 72 can be independently advanced and retracted. The structure is such that the naive spring receivers 81 and 82 are used (Claim 1).

In the second structure of the present invention, the valve spring 7 is arranged in the first coil spring 71 having a large diameter and in the first coil spring 71 coaxially therewith. A second coil spring 72 having a small diameter and a small spring constant, and the spring receiver 8 is screwed into the other end of the casing 2 such that the spring receiver 8 can be moved back and forth to receive the first coil spring 71.
And a second screw member 82 which is screwed into the central portion of the first screw member 81 so as to be capable of advancing and retracting and receives the second coil spring 72 (claim 2).

[0010]

In the relief valve of the above-mentioned first construction, the spring force of each valve spring 7 having a different spring constant can be adjusted for each spring by advancing and retracting each spring receiver 8 independently. Therefore, the hydraulic pressure can be set with good workability and high accuracy by first performing rough adjustment with a valve spring having a large spring force and then performing fine adjustment with a valve spring having a small spring force.

In the relief valve 1 having the above-mentioned second structure, the second coil spring 72 is coaxially arranged in the first coil spring 71, and the second screw member 82 is connected to the first screw member 81. Since it is arranged coaxially in the center, a compact external dimension can be realized.

[0012]

FIG. 1 shows an embodiment of the present invention. The tubular casing 2 of the relief valve is provided with a screw on the outer circumference of the sleeve 21 at one end thereof so as to be screwed to the pipe of the hydraulic circuit. The tubular sheet 5 is press-fitted into the sleeve 21,
It serves as a pressure oil introduction path 3 for introducing pressure oil from a hydraulic circuit.
Inside the casing 2, a pressure oil discharge passage 4 that communicates with the pressure oil introduction passage 3 and opens to the side surface of the casing 2 is formed.

The seat 5 has a tapered tip portion 51, and a piston type valve body 6A is arranged so as to close the tapered tip portion 51, and the tapered tip portion 51 and the cylinder portion 61 of the valve body 6A. The open ends are in close contact. A guide piston 62 is inserted in the cylinder portion 61. The guide piston 62 has an outer periphery and a cylinder portion 6
It is loosely fitted in the cylinder portion 61 so that the pressure oil flows between the cylinder portion 61 and the cylinder 1.

Inside the casing 2, a first coil spring 71 and a second coil spring 72 are installed as a valve spring 7 for urging the valve body 6A. The first coil spring 71 has a diameter substantially equal to the inner circumference of the casing 2 and is arranged along the inner circumference of the casing 2. The second coil spring 72 has a diameter smaller than that of the first coil spring 71. It has a smaller spring constant and is coaxially inserted into the first coil spring 71. One end of the first coil spring 71 is locked to the outer peripheral step of the cylinder portion 61 of the valve body 6A, and one end of the second coil spring 72 is locked to the bottom step of the cylinder portion 61.

At the other end of the casing 2, there are provided first and second screw members 81 and 82 constituting the spring receiver 8. The first screw member 81 is a thick column having a hollowed central portion and is screwed into the casing 2 so as to be able to move forward and backward, and receives the other end of the first coil spring 71. The second screw member 82 is screwed into the central portion of the first screw member 81 so as to be able to move forward and backward, and the second coil spring 72 is formed at the step portion on the inner side surface thereof.
Is receiving the other end of. A cross-shaped groove for screwing is formed on the outer end surface of each screw member 81, 82.

A nut 9 is screwed onto the outer periphery of the first screw member 81 and is pressed against the end face of the other end of the casing 2 to prevent the first screw member 81 from loosening. ing.

In the relief valve configured as described above, first, the spring force is adjusted to a value close to the set hydraulic pressure by rotating the first screw member 81 and moving it back and forth with the nut 9 loosened. . Next, the second screw member 82 is rotated to move back and forth, and the spring force is finely adjusted to accurately adjust the set hydraulic pressure. After the adjustment is completed, the nut 9 is tightened to prevent the first screw member 81 from loosening.

In the relief valve described above, the pressure oil in the hydraulic circuit is introduced into the pressure oil introducing passage 3 and is filled before and after the pressure oil introducing passage 3 and the guide piston 62 of the valve body cylinder portion 61.

When the pressure oil exceeds the set oil pressure, the valve body 6 is pushed in to open the pressure oil introduction passage 3, and the pressure oil is discharged from the pressure oil discharge passage 4 to a tank (not shown). When the oil pressure decreases, the valve body 6A closes the pressure oil introduction passage 3, and thus the oil pressure is maintained at the set value. In this case, when the valve body 6A is opened and closed, the pressure oil filled behind the guide piston 62 absorbs a sudden change in oil pressure and prevents a chattering phenomenon.

Although the piston type valve element 6A is used as the valve element in the above embodiment, a ball type valve element 6B may be used as shown in FIG. 2 or a poppet as shown in FIG. The valve body 6C of the mold may be used. In these cases, sheet 5
The shape of the tip of the is to correspond to the shape of the valve body. Figure 2
The rest of the structure of the relief valve shown in FIG. 3 is the same as that of the above-described embodiment, and has the same effects.

The present invention can also be applied to a pilot valve of a pilot operated relief valve.

[0022]

As described above, according to the present invention, the valve spring is composed of a plurality of valve springs having different spring constants, and the spring force of each valve spring is adjusted.
Therefore, even if the spring force is large, the set hydraulic pressure can be finely adjusted with good accuracy and good workability. Further, by arranging a plurality of valve springs coaxially and arranging a spring receiver for adjusting the spring force for receiving each valve spring coaxially, the relief valve can be downsized.

[Brief description of drawings]

FIG. 1 is a sectional view of a relief valve of the present invention.

FIG. 2 is a sectional view of another relief valve of the present invention.

FIG. 3 is a sectional view of still another relief valve of the present invention.

FIG. 4 is a diagram showing an example of a hydraulic circuit including a relief valve.

FIG. 5 is a sectional view of a conventional relief valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 relief valve 2 casing 3 pressure oil introduction path 4 pressure oil discharge path 6, 6A, 6B, 6C valve body 7 valve spring 71 first valve spring (first coil spring) 72 second valve spring (second Coil spring) 8 spring bearing 81 first spring bearing (first screw member) 82 second spring bearing (second screw member)

Claims (2)

[Claims] 1. A casing having a pressure oil introduction passage and a pressure oil discharge passage communicating with the pressure oil introduction passage at one end, a valve body for opening and closing the pressure oil introduction passage, and a valve body with a closing direction. In a relief valve including a valve spring that applies a force and a spring receiver that is provided at the other end of the casing so as to be capable of advancing and retracting and receives the valve spring, the valve spring is composed of a plurality of valve springs having different spring constants. A relief valve having a structure in which each spring is independently received by a spring receiver capable of advancing and retracting. 2. A first coil spring having a large diameter, and a second coil spring having a smaller diameter and a smaller spring constant than the first coil spring, wherein the valve spring is arranged coaxially with the first coil spring. A first screw member configured by a coil spring, the spring receiver being screwed into the other end of the casing so as to be capable of advancing and retracting, and receiving the first coil spring; and a central portion of the first screw member. A second screw-in member that can be advanced and retracted to receive the second coil spring.
The relief valve according to claim 1, wherein the relief valve comprises the screw member.