JP2002295702A - Spring balance type valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent the occurrence of abnormal sound caused by the vibration of a valve element in opening a valve. SOLUTION: In a spring balance type valve, a helical compression spring 20 is stored in a spring storing chamber 34 of a spring storing member 19, and the valve element 18 is pressed onto a valve seat 13 by a snapping force of the spring. At least an opening side part of the spring storing chamber is provided with a spring holding member 40. The spring holding member 40 is made of a material with an elastic coefficient lower than that of a material constituting the spring storing member 19 and the helical compression spring 20, and the spring 20 is held in a contact state of the inner peripheral surface of the spring holding member 40 with the spring 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spring balanced valve suitable for a relief valve for a hydraulic circuit or the like.

[0002]

2. Description of the Related Art Generally, in a spring balanced valve such as a balance piston type relief valve, a valve element (for example, a pilot valve element in a relief valve) is pressed against a valve seat by the resilient force of a compression coil spring. When the pressure of the working fluid to be introduced is equal to or higher than a predetermined value, the valve body opens (ie, opens) from the valve seat against the elastic force of the compression coil spring. It is configured as follows. Here, the compression coil spring is housed in, for example, a spring housing chamber opened to the valve seat side, and each member is arranged such that the valve body is interposed between the compression coil spring and the valve seat. I have.

[0003]

In the above-described spring balanced valve, when the valve body is opened away from the valve seat, the holding state of the valve body becomes unstable. Under the pressure of the fluid, it is likely to vibrate in such a manner as to oscillate in a radial direction (a direction orthogonal to the axial direction), and there is an inconvenience that abnormal noise is generated due to the vibration.

Japanese Patent Application Laid-Open No. 11-159648 discloses that a piston opposed to a pilot valve element is mounted in a valve hole in which the valve seat is formed so as to be movable in an axial direction, and a primary pressure is kept constant. At the time above, in the balanced piston type relief valve configured so that the piston pushes the valve body back to the valve opening side against the elastic force of the compression coil spring by the pressure, the piston, the valve body and the In order to prevent the valve element from swinging around the contact point of
There is disclosed a piston in which the shape of the end face is devised so that the valve body is pressed against the inner peripheral surface side of the valve hole. However, even with such a means, the movement of the valve body can be restricted. Since only a very small portion at the tip is used and the force for pressing the valve body against the inner peripheral side of the valve hole is small, it is difficult to sufficiently prevent the generation of abnormal noise due to the vibration of the valve body.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a spring-balanced valve that can effectively suppress generation of abnormal noise due to vibration of a valve body when the valve is opened.

[0006]

According to the present invention, the vibration of the valve element is made such that the valve element rocks while being accompanied by a radial swing (oscillation due to elastic deformation) of a compression coil spring supporting the valve body. . Therefore, by suppressing the swing of the compression coil spring, it is possible to effectively regulate the swing of the valve body supported by the compression coil spring. However, as means for suppressing such a radial oscillation of the compression coil spring, for example, the inner diameter of the entire spring accommodating chamber is made equal to or smaller than the outer diameter of the compression coil spring to restrain the compression coil spring. With such a structure, it is practically difficult to incorporate the compression coil spring into the spring accommodating chamber, and if it is possible to assemble the compression coil spring, the compression coil spring is locked in the spring accommodating chamber, and the smooth expansion and contraction thereof occurs. Deformation is hindered, which may cause malfunction.

SUMMARY OF THE INVENTION The present invention has been made in view of the foregoing, and has a valve seat member having a working fluid flow passage, a valve seat formed at an open end thereof, and a movable member for moving the valve seat in the opening and closing direction. A valve body provided so as to be able to be provided, a spring housing member provided behind the valve body, and having a spring housing chamber opened toward the valve seat side; A compression coil spring which is housed in a deformed state and presses the valve body toward the closed position by its resilient force, and when the pressure of the working fluid is equal to or higher than a predetermined value, the valve body is pressed by the compression coil. In a spring-balanced valve configured to open against a spring force of a spring, at least an opening side portion in the spring housing chamber is more elastic than a material forming the spring housing member and a material forming a compression coil spring. Low coefficient material It consists, in close contact with the radially outer side on the outer peripheral surface of the compression coil spring in which the spring holding member for holding the compression coil spring is provided.

According to this structure, the compression coil spring is held in a state in which the spring holding member provided in the spring accommodating chamber and the compression coil spring are in close contact with each other, so that the compression coil spring swings in the radial direction. Consequently, the radial movement of the valve element supported by the spring is effectively restricted, and the generation of abnormal noise due to the vibration of the valve element is suppressed.

Here, instead of providing the spring holding member, a small-diameter portion having an inner diameter smaller than the outer diameter of the compression coil spring can be formed integrally with the spring housing member at the same location as the location where the spring holding member is provided. However, since the spring accommodating member is a pressure vessel, and the constituent material thereof is required to have a certain level of rigidity and strength, the small diameter portion is formed integrally with the spring accommodating member. It is extremely difficult to insert a compression coil spring whose outer diameter is larger than its inner diameter inside the inside of the coil. Must match, not realistic.
Even if the dimensional accuracy can be controlled and assembled, even if the outer surface of the compression coil spring is in close contact with the inner surface of the small-diameter portion, the compression coil spring can slide extremely large from the inner peripheral surface of the small-diameter portion at the contact portion. As a result, the spring will not be able to extend and contract smoothly.

On the other hand, according to the present invention, the spring holding member is provided with another spring holding member made of a material having a lower elastic coefficient (that is, rich in elasticity) than the constituent materials of the spring housing member and the compression coil spring. Therefore, even if the inner diameter of the spring holding member is slightly smaller than the inner diameter of the spring accommodating chamber, it is possible to insert a large-diameter compression coil spring inside the spring holding member by utilizing the elastic deformation of the member. In the state after the insertion, even if the outer peripheral surface of the compression coil spring is pressed against the inner peripheral surface of the spring holding member, the spring holding member follows the axial displacement caused by the expansion and contraction of the compression coil spring. When the member is appropriately elastically deformed, a smooth expansion and contraction operation of the compression coil spring can be guaranteed.

That is, according to the present invention, the valve opening caused by the radial swing of the compression coil spring can be achieved without inconvenience during assembly and while ensuring the smooth expansion and contraction of the compression coil spring. It is possible to effectively suppress the vibration of the valve element at the time.

Here, the spring holding member may be of any shape and structure as long as it can support the compression coil spring from the outside in close contact with it.
It is preferable to have a cylindrical holding portion having an inner diameter equal to or smaller than the outer diameter of the compression coil spring, and the cylindrical holding portion is provided at least at an opening side portion in the spring accommodating chamber. . According to this configuration, the spring can be held in a more stable state from the outside in the radial direction by bringing the compression coil spring into close contact with the inner circumferential surface of the cylindrical holding portion over the entire circumference. In addition, it is easy to assemble the spring holding member into the spring accommodating chamber.

Although the specific material of each member is not limited,
It is preferable that the spring holding member is rich in elasticity enough to secure the smooth movement of the compression coil spring by the elastic deformation as described above, and has strength enough to withstand the pressure of the working fluid. Specifically, it is preferable that the spring housing member and the compression coil spring are made of a metal material, and the spring holding member is made of a synthetic resin material.

The spring holding member may be provided, for example, over the entire area of the spring accommodating chamber in the axial direction. However, if the spring holding member is provided at least on the opening side portion of the spring accommodating member, the spring holding member extends in the radial direction of the compression coil spring. Swing can be effectively suppressed. Therefore, if this spring holding member is provided only on the opening side portion of the spring accommodating member, the spring holding member can be downsized while a sufficient noise prevention effect is maintained.

In this case, if the spring holding member is formed with a contact portion that comes into contact with the open end face of the spring housing member from the valve seat side, the spring holding member can be used during use of the valve. It is possible to reliably prevent the inconvenience of accidentally moving to the back of the spring storage chamber.

Although the specific application of the spring balanced valve according to the present invention is not limited, it is particularly suitable for a balance piston type relief valve in which the valve element is a pilot valve element and is opened by the primary pressure of the working fluid. It is.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the drawings.

The valve shown in the figure is a balance piston type relief valve, which comprises main body members 10 and 12 constituting a valve main body, and the valve main body includes an anti-cavitation valve 14, a pressure regulating valve body 15, a piston 16 and a pilot valve. Valve element 18,
Plug (spring housing member) 19 and compression coil spring 20
Is incorporated.

The main body member 10 is on the front end side (the left side in FIG. 1).
Small diameter portion 10a and large diameter portion 1 on the rear end side (right side in FIG. 1)
The main body member 12 also has a cylindrical shape integrally having a small-diameter portion 12a on the front end side and a large-diameter portion 12b on the rear end side. The large diameter portion 1 of the main body member 10
0b is screwed into a female screw formed on the inner peripheral surface of the main member 12 and a male screw formed on the outer peripheral surface of the small diameter portion 12a of the main body member 12, and a seal member 22 is inserted between the large diameter portion 10b and the small diameter portion 12a. Is interposed. A male screw is also formed on the outer peripheral surface of the small-diameter portion 10a of the main body member 10, and this male screw is screwed into a screw hole of the directional control valve 50 shown by a two-dot chain line in FIG. .

From the small-diameter portion 12a of the main body member 12, a seat portion (valve seat member) 12s having a smaller diameter than the small-diameter portion 12a extends toward the front end side, and a small-diameter valve hole is provided on the central axis of the seat portion 12s. (Working fluid flow passage) 12c is formed. As shown in FIG. 2, the rear end (right end in FIG. 2) of the valve hole 12c is beveled in a tapered shape at its peripheral edge, whereby a valve seat 13 is formed. Also, the seat 12
A communication port 12d is formed in the vicinity of the boundary between the s and the small diameter portion 12a so as to radially communicate the inside and the outside of the main body member 12.

The anti-cavitation valve 14 has a cylindrical shape having a small diameter portion 14a on the front end side and a large diameter portion 14b on the rear end side, and a primary flow path 35 of the working fluid is provided inside the small diameter portion 14a. On the other hand, a secondary flow path 36 for the working fluid is formed between the main body member 10 and the inner peripheral surface.

The rear end of the large-diameter portion 14b is
The large diameter portion 1 is fitted to the outside of the large diameter portion 1s so as to be relatively movable in the axial direction with respect to the sheet portion 12s.
A seal member 24 is interposed between 4b and the sheet portion 12s. A flow port 14c for a working fluid that penetrates the large diameter portion 14b from the front side in the radial direction is formed. Further, the front end face of the small diameter portion 14a is formed in a tapered shape, and serves as a seal surface 14f that partitions a pump port (primary port) P and a tank port (secondary port) in the directional control valve 50. .

The pressure regulating valve element 15 has a cylindrical shape and is accommodated in the large diameter portion 14b of the anticavitation valve 14 at a position forward of the seat portion 12s so as to be movable in the axial direction. Pressure valve body 15 and seat 12
s, a back pressure chamber 26 is formed. A seal member 23 is interposed between the outer peripheral surface of the pressure regulating valve body 15 and the inner peripheral surface of the large diameter portion 14b.

A tapered surface 15d is formed on the outer peripheral portion of the front end of the pressure regulating valve body 15, while a portion of the large diameter portion 14b on the front side of the flow port 14c has a smaller inner diameter than a rear portion thereof. A valve seat 14d is formed by the step, and the flow opening 14c is closed by the pressure regulating valve body 15 with the tapered surface 15d of the pressure regulating valve body 15 abutting against the valve seat 14d from behind. The flow port 14c is opened when the tapered surface 15d moves rearward from the valve seat 14d.

The piston 16 includes a main body cylindrical portion 16a, a flange portion 16b, and a poppet pressing shaft portion 1 in that order from the front end side.
A pressure receiving chamber 16d that opens forward is formed on the central axis of the main body cylindrical portion 16a, and the pressure receiving chamber 16d and the outer back pressure chamber 26 are located at the back of the pressure receiving chamber 16d.
And a squeezing hole 16e communicating with.

The front portion of the pressure regulating valve element 15 has a smaller inner diameter than the rear portion, and the front portion thereof has the piston 16
Of the main body cylindrical portion 16a is inserted with almost no gap,
An adjusting spring 28 made of a compression coil spring is interposed between the step portion 15a formed at the boundary between the inner surface of the front portion and the inner surface of the rear portion and the flange portion 16b of the piston 16. On the other hand, the poppet pressing shaft portion 16c is
s is fitted in the valve hole 12c, and an axial working fluid flow passage is secured between the inner peripheral surface of the valve hole 12c and the outer peripheral surface of the poppet pressing shaft 16c.

The pilot valve element 18 integrally has a substantially mushroom-shaped poppet 18a whose diameter decreases toward the front and a shaft 18b extending rearward from the center of the poppet 18a. Has a shape capable of contacting the valve seat 13 of the seat portion 12s.

The plug 19 is connected to the large diameter portion 12 of the main body member 12.
b is inserted from the rear end opening and fixed. Specifically, a male screw formed on the outer peripheral surface of the middle portion of the plug 19 is screwed to a female screw formed on the inner peripheral surface of the rear end opening of the large diameter portion 12b, and the nut 3 screwed to the male screw.
2, the insertion depth position of the plug 19 is fixed. Depending on the insertion depth, a pilot spring 20
The resilience of is adjustable. A seal member 30 is interposed between the outer peripheral surface of the front part of the plug 19 and the inner peripheral surface of the small diameter portion 12a of the main body member.

The plug 19 has a spring accommodating chamber 34 opening forward, and a valve chamber is formed by the spring accommodating chamber 34 and the inner space of the main body member 12. The pilot spring 20 is housed. When the pilot spring 20 is fitted on the outside of the shaft portion 18b of the pilot valve body 18, the rear end face of the poppet portion 18a of the valve body 18 and the rear end face (rear end face) of the spring housing chamber 34 are connected. The pilot valve element 18 is urged forward by its resilient force,
When the conical surface of the poppet portion 18a is pressed against the valve seat 13, the valve-closed state is maintained.

Basically, the inner diameter of the spring accommodating chamber 34 is set larger than the outer diameter of the pilot spring 20.
The inner diameter of only the rear end portion 34a of the spring accommodating chamber 34 is set substantially equal to the outer diameter of the pilot spring 20, and the rear end of the pilot spring 20 is fitted and fixed in the rear end portion 34a.

Further, as a feature of this valve, a spring holding member 40 as shown in FIG. 2 is provided at the front end side of the plug 19.

The spring holding member 40 is provided in the spring accommodating chamber 34.
Cylindrical holding portion 41 inserted inside the front end opening side portion of
And a flange (abutting portion) 42 protruding radially outward from the front end of the cylindrical holding portion 41. The flange 42 contacts the front end face of the plug 19 from the front side to the depth. The cylindrical holding portion 41 is inserted into the spring accommodating chamber 34.
The flange 42 is for preventing the spring holding member 40 from accidentally entering the interior of the spring accommodating chamber 34 during use of the valve, and the prevention effect is not limited to the flange 42,
For example, it can also be obtained by providing a contact portion only in a part of the circumferential direction.

The material forming the spring holding member 40 is as follows:
Any material may be used as long as it has a lower elastic coefficient than the constituent material of the plug 19 and the constituent material of the pilot spring 20 as the spring accommodating member, and has such a rigidity as not to cause significant deformation or breakage due to the pressure of the working fluid. Is good. More specifically, the plug 19 is preferably made of a metal material such as stainless steel, the pilot spring 20 is preferably made of a metal material such as spring steel, and the plug 19 is preferably made of a synthetic resin. As the synthetic resin, a relatively hard resin (for example, a fluorine resin) is more preferable. Further, other than such a synthetic resin, a hard rubber or the like can be applied as long as sufficient durability can be ensured.

The cylindrical holding portion 41 of the spring holding member 40
Is set to be equal to or smaller than the outer diameter of the pilot spring 20. Therefore, the spring is accommodated in the spring accommodating chamber 34 with the outer peripheral surface of the pilot spring 20 in contact with the inner peripheral surface of the cylindrical holding portion 41.

The outer diameter of the cylindrical holding part 41 is
4 may be substantially equal to the inner diameter of the cylindrical holding portion 41.
Is slightly larger than the inner diameter of the spring housing chamber 34,
The spring holding member 40 can be easily fixed to the plug 19 by press-fitting the cylindrical holding portion 41 into the inside of the spring accommodating chamber 34.

The axial length of the cylindrical holding portion 41 can be set as appropriate, but at least in the region where the lateral deformation of the compression coil spring can be restricted at least at the front end opening side of the spring accommodating chamber 34. Only needs to be present.

Next, the operation of this valve will be described.

First, in use, the front-side small-diameter portion 10a of the main body member 10 has the directional control valve 50 with the seal member 38 interposed therebetween.
Is screwed into the screw hole and fixed.

On the other hand, in the direction switching valve 50, a pump port P and a tank port T which intersect each other are formed, and the primary side passage 35 inside the anti-cavitation valve 14 is inserted by the insertion of the front small diameter portion 10a. The secondary passage 36 communicates with the tank port T while communicating with the pump port P.

When the working fluid is introduced into the tank port P in this state, the pressure is reduced by the anti-cavitation valve 14.
Acting forward on a step 14e at the boundary between the small diameter portion 14a and the large diameter portion 14b.
Is seated on a tapered valve seat 52 formed at the intersection of the ports P and T to define the ports P and T.

Here, when the introduction pressure (primary pressure) of the working fluid into the primary side passage 35 is equal to or lower than a predetermined pressure, the resilient force of the pilot spring 20 causes the pilot valve element 18 to operate.
Of the poppet 18a is pressed against the valve seat 13, and the front end of the poppet 18a pushes the poppet pressing shaft 16c of the piston 16 to the front side.
8, the valve body 15 is transmitted to the pressure regulating valve body 15 through the valve closing position, that is, its tapered surface 15d.
Is held at a position where it is pressed forward against the valve seat 14 d of the anti-cavitation valve 14. Accordingly, in this state, the communication port 14c is closed, and the connection between the primary passage 35 and the secondary passage 36 is shut off.

When the primary pressure becomes lower than the secondary pressure due to the occurrence of cavitation, the secondary pressure acts on the outer surface of the step portion 14e of the cavitation valve 14 in the reverse direction. As a result, the anti-cavitation valve 14 is retracted, the sealing surface 14f is separated from the valve seat 52, and the ports P and T are directly communicated with each other.
Cavitation is prevented from continuing.

On the other hand, when the primary pressure exceeds a certain pressure, the following relief operation is performed. That is, the poppet pressing shaft portion 16c of the piston 16 receiving the primary pressure
Pushes back the pilot valve element 18 against the resilient force of the pilot spring 20, whereby the poppet portion 18a of the pilot valve element 18 is separated from the valve seat 13 (opening of the pilot valve element 18). . Thereby, the back pressure chamber 26
The working fluid inside flows out into the valve chamber in the main body member 12 through the flow path between the valve hole 12c and the poppet pressing shaft portion 16c, and is discharged to the secondary side passage 36 through the communication port 12d.

Due to this outflow, the pressure in the back pressure chamber 26 decreases and the differential pressure from the primary pressure further increases, so that the pressure regulating valve body 15 receiving the primary pressure on the front end face is moved to the back pressure chamber 2.
Then, the tapered surface 15d moves away from the valve seat 14d (the valve opening of the pressure regulating valve element 15). With this valve opening, the working fluid in the primary passage 35 is released directly from the communication port 14c to the secondary passage 36, thereby preventing an excessive rise in the primary pressure.

At the time of this valve opening, the pilot valve element 1
The poppet portion 18a of FIG. 8 is separated from the valve seat 13 and is in an unstable state without being restrained by the valve seat 13 (FIG. 2).
Two-dot chain line). Here, conventionally, since there was no spring holding member 40 and there was a gap between the pilot spring 20 and the inner surface of the spring accommodating chamber 34, the swing of the pilot spring 20 in the radial direction allowed by the gap was allowed. The pilot valve element 18 is likely to vibrate while swaying in the radial direction with the movement, and there is a possibility that remarkable noise may occur due to the vibration. However, in the illustrated valve, the front end opening side of the spring accommodating chamber 34 is provided. Spring holding member 40 and pilot spring 2
Since the spring 20 is held in a state in which the pilot valve 20 is in close contact with the pilot spring 20, the pivoting of the pilot spring 20 in the radial direction and the radial movement of the pilot valve element 18 supported by the spring 20 are effectively performed. The noise can be restricted, and generation of abnormal noise due to the vibration of the valve body can be suppressed.

Further, since the spring holding member 40 is a separate member from the plug 19, which is a spring accommodating member, a material (generally, a metal material) having sufficient strength is used for the plug 19 and the pilot spring 20. However, since the spring holding member 40 is made of a material having a lower elastic coefficient (for example, a synthetic resin), even if the inner diameter of the spring holding member 40 is slightly smaller than the inner diameter of the spring accommodating chamber 34, the elastic deformation of the member is reduced. It is possible to insert the large-diameter pilot spring 20 into the inside thereof by utilizing the above, and the dimensional accuracy can be easily managed. Even in the state after the insertion, the spring holding member 40 appropriately elastically deforms following the axial displacement due to the expansion and contraction of the pilot spring 20, so that the smooth expansion and contraction operation of the pilot spring 20 can be guaranteed.
Therefore, the dimensional control of the spring holding member 40 becomes very easy.

The specific shape and structure of the spring holding member are not limited to those shown in the drawings, but may be any as long as the compression coil spring can be supported from the outside and the deflection of the spring can be regulated. For example, a plurality of strip-shaped elastic pieces are intermittently arranged in the circumferential direction and fixed, for example, by bonding to the inner peripheral surface on the opening side of the spring accommodating chamber. (Pilot spring 20 in the example shown)
May be brought into contact with each other.

On the other hand, the specific shape of the valve body is not limited to the poppet shape as shown in the figure, but is also applicable to a valve in which a valve body made of a hard sphere is fitted into the front end opening of a compression coil spring.

The present invention is not limited to the above-described balance piston type relief valve, but can be applied to other spring balanced type valves such as a pressure reducing valve and a check valve.

[0050]

As described above, the present invention relates to a spring-balanced valve in which a valve body is pressed against a valve seat by the resilient force of a compression coil spring housed in a spring housing chamber of a spring housing member. A spring holding member having a lower elastic modulus than the spring housing member and the compression coil spring is provided at least on the opening side of the spring holding member. The spring is held in a state where the inner peripheral surface of the spring holding member and the compression coil spring are in contact with each other. With this configuration, it is possible to effectively suppress the generation of abnormal noise caused by the vibration of the valve element when the valve is opened, while ensuring the smooth expansion and contraction operation of the compression coil spring.

[Brief description of the drawings]

FIG. 1 is a sectional front view of a balance piston type relief valve according to an embodiment of the present invention.

FIG. 2 is a sectional front view showing a main part of the relief valve.

[Explanation of symbols]

 10, 12 Body member 12s Seat portion (valve seat member) 13 Valve seat 18 Pilot valve body 19 Plug (spring housing member) 20 Pilot spring (compression coil spring) 34 Spring housing chamber 35 Primary side passage 36 Secondary side passage 40 Spring holding member 41 Cylindrical holding part 42 Flange (contact part)

Claims (6)

[Claims] A valve seat member having a working fluid flow passage, a valve seat formed at an open end thereof, a valve body provided so as to be movable in a direction to open and close the valve seat, A spring accommodating member provided behind the valve body and having a spring accommodating chamber that opens toward the valve seat side; and the spring accommodating member accommodates the spring accommodating member in a compression deformed state. A compression coil spring that presses the valve body toward the closed position, wherein when the pressure of the working fluid is equal to or higher than a predetermined value, the valve body is opened against the elastic force of the compression coil spring by the pressure. In the spring-balanced valve described above, at least an opening side portion in the spring housing chamber is made of a material having a lower elastic coefficient than a material forming the spring housing member and a material forming the compression coil spring, and an outer periphery of the compression coil spring. Its diameter on the surface A spring balanced type valve provided with a spring holding member that holds the compression coil spring in close contact from the outside. 2. The spring balanced valve according to claim 1, wherein
The spring housing member has a cylindrical holding portion having an inner diameter equal to or smaller than the outer diameter of the compression coil spring, and the cylindrical holding portion is provided at least on an opening side portion in the spring housing chamber. A spring balanced valve. 3. The spring-balanced valve according to claim 1, wherein said spring accommodating member is made of a metal material, and said spring holding member is made of a synthetic resin material. valve. 4. The spring-balanced valve according to claim 1, wherein the spring holding member is provided only on an opening-side portion of the spring accommodating chamber. . 5. The valve according to claim 4, wherein:
A spring-balanced valve, wherein a contact portion is formed on the spring holding member so as to come into contact with the open end surface of the spring housing member from the valve seat side. 6. The spring-balanced valve according to claim 1, wherein the spring-balanced valve is a balance piston type relief valve, and the valve body is opened by a primary pressure of the working fluid. A spring-balanced valve characterized in that it is a pilot valve element to be driven.