JPH109436A - Relief valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a relief valve excellent in an anti-cavitation erosion property in which the liquid contact part where the cavitation is easy to be generated is constituted by a seramic or cemented carbide material, in the relief valve whose operation fluid is a water or a liquid with a small viscosity like water. SOLUTION: A balance piston type relief valve is provided with a main valve part A having a main valve 11 and valve seat 12 and a pilot part B having a poppet valve 31 and valve seat 32 and constituted so that the main valve 11 of the main valve part A is separated from the valve seat 12 and an operation liquid is streamed out from the clearance between the main valve 11 and the valve seat 12 and the pressure of the operation liquid reaches a prescribed certain pressure by that the poppet valve 31 is opened by the pressure of the liquid which is the operation fluid. The squeezed contact liquid parts of the facing part of the main valve 11 and valve seat 12 and the facing part of the poppet valve 31 and the valve seat 32 in which the cavitation is easy to be generated are constituted by the seramic or cemented carbide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relief valve of the balance piston type mainly used for a hydraulic drive device using tap water or fresh water as a working fluid.

[0002]

2. Description of the Related Art Hitherto, as a drive source for driving a high-speed and large-power actuator, a hydraulic drive device mainly using mineral oil as a working fluid has been used. However, the disadvantages of the hydraulic drive device in which the working fluid is mineral oil include a danger of fire due to the burning of the mineral oil, a risk of environmental pollution caused by leakage of the mineral oil, and a disadvantage of the working fluid. There are problems such as the necessity of disposal of mineral oil waste liquid at the time of replacement. In particular, it is clear that there is a great danger in spreading the fire, and there is a demand for a hydraulic drive device using water as a working fluid. To develop this hydraulic drive, it is essential to set the maximum pressure of the hydraulic circuit and to develop a hydraulic relief valve that keeps the circuit pressure constant.

[0003]

When water is used as a working fluid for a balance piston type relief valve, there is a problem of cavitation. Cavitation means that when the pressure difference before and after the throttle is large, a pressure drop occurs according to the flow velocity of the fluid passing through the throttle, and on the low pressure side, the pressure may be lower than the saturated steam pressure of the fluid. Is a phenomenon in which bubbles (cavities) are generated in the air. When the cavitation is generated, not only noise is generated but also a strong impact force is generated, and damage (cavitation erosion) is caused to a liquid contact portion in contact with the working fluid. When using water or a liquid with low viscosity like water as the working fluid, cavitation is likely to occur because the saturated vapor pressure is higher than that of oil, and water or a liquid with low viscosity like water is used as the working fluid. In the relief valve described above, there is a problem that the main valve and the valve seat of the main valve portion where cavitation is liable to occur and the wetted portion of the poppet valve and the valve seat of the pilot portion are damaged, and the life of the relief valve is shortened. Was.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made in consideration of the above problems, and has been made in consideration of the above circumstances. It is an object of the present invention to provide a relief valve in which a liquid part is made of a ceramic or a super alloy and has excellent cavitation erosion resistance.

[0005]

According to a first aspect of the present invention, there is provided an invention comprising a main valve portion having a main valve and a valve seat, and a pilot portion having a poppet valve and a valve seat. When the poppet valve is opened by the pressure of the liquid, the main valve of the main valve portion is separated from the valve seat, the hydraulic fluid flows out from a gap between the main valve and the valve seat, and the pressure of the hydraulic fluid is a predetermined constant. In a relief valve of a balance piston type for increasing pressure, a liquid contact portion where cavitation is likely to occur is made of ceramic or cemented carbide.

According to a second aspect of the present invention, in the relief valve according to the first aspect, cavitation is provided at an opposing portion between the main valve and the valve seat of the main valve portion and at an opposing portion between the poppet valve and the valve seat of the pilot portion. A throttle portion is formed for suppressing the occurrence of pressure. At least one of the main valve and the valve seat of the main valve portion is in contact with the throttle portion, and the pilot portion is at least one of the poppet valve and the valve seat. The liquid part is made of ceramic or cemented carbide.

According to a third aspect of the present invention, in the relief valve according to the first or second aspect, the liquid contact portion is coated with a ceramic or a cemented carbide.

According to a fourth aspect of the present invention, in the relief valve according to the first or second or third aspect, the throttle portion comprises a plurality of stages.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing the overall structure of the relief valve of the present invention. Although water is used as the working fluid in the present embodiment, the working fluid is not limited to water, and may be a liquid having a saturated vapor pressure and a viscosity close to that of water. As shown in FIG. 1, the relief valve includes a main valve portion A and a pilot portion B.

The main valve section A includes a casing 10, a main valve 11, and a valve seat 12. The valve seat 12 is fixed to a hole provided in the casing 10 via an O-ring 14 and a washer 13, and the main valve 11 is supported in a hole provided in the casing 10 by a wear ring (bearing) 15 and moves up and down at a predetermined stroke. It can move.

A coil spring 17 is disposed between the upper part of the main valve 11 and the casing 30 of the pilot section B, and the main valve 11 is attached to the valve seat 12 by the elastic force of the spring 17. It is being rushed. Reference numeral 16 denotes a packing for maintaining airtightness between the inner surface of the casing 10 and the outer peripheral surface of the main valve 11.

The pilot section B includes a casing 30, a poppet valve 31, a valve seat 32, a throttle member 33, a holding member 34, and a holding member 35. The valve seat 32 is fixed by a holding member 34 with a throttle member 33 interposed therebetween. A coiled spring 36 is disposed between the poppet valve 31 and the holding member 35, and the poppet valve 31 is urged toward the valve seat 32 by the elastic force of the spring 36.

The anti-poppet valve 31 of the spring 36
A spring seat 38 is provided at an end on the side of the side. The spring seat 38 rotates a pressure setting handle 37 to advance and retreat in a hole provided in the holding member 35, and the spring 36 applies an elastic force to the poppet valve 31. The power can be adjusted. The poppet valve 31 is supported at one end by a leaf spring 39 fixed to the casing 10.

A plate member 50 is provided on the main valve portion A on the side opposite to the pilot portion B of the casing 10, and a water passage hole 19 penetrating through the plate member 50 and passing through the center of the valve seat 12 is provided. The water passage hole 19 communicates with a water passage hole provided in the multistage throttle portion 18 provided at the center of the main valve 11, and communicates with a secondary pressure chamber 20 formed at the rear end of the main valve 11. I have.

FIG. 2 is a view showing a sectional structure of the main valve 11. A flange 11a and a flange 11b are formed at a front end (lower end in the figure) of the main valve 11 at a predetermined interval in order to form a two-stage throttle, and a multi-stage throttle 1 provided at the center thereof is provided.
Reference numeral 8 is composed of aperture members 18-1, 18-2 and 18-3.
As described later in detail, the outer surfaces of the flanges 11a and 11b and a portion 11c connecting the flanges 11a and 11b are liquid contact portions where cavitation is likely to occur in the working fluid, so that the cavitation erosion is likely to occur. Therefore, this portion is integrally formed of a ceramic material.

A water hole 18 is provided at the center of the throttle member 18-1.
-1a is formed, a water passage hole 18-2a is formed at the center of the throttle member 18-2, and a water passage hole 18-3a is formed at a position off the center of the throttle member 18-3. I have.
The cross-sectional area of each water hole is (cross-sectional area of water hole 18-1a)>
(Cross-sectional area of water passage hole 18-2a)> (Cross-sectional area of water passage hole 18-3a). Aperture member 18-3 and aperture member 18-2
A secondary pressure chamber 29 is provided therebetween.

FIG. 3 is a diagram showing a sectional structure of the poppet valve 31 and the valve seat 32. As will be described later in detail, the outer surfaces of the poppet valve 31 and the valve seat 32 are liquid contact portions where cavitation is likely to occur in the working fluid, and thus are susceptible to cavitation erosion. Therefore, this poppet valve 31
Is also formed of a ceramic material.

In the relief valve having the above structure, the main valve portion A
The water passage hole 19 of the valve seat 12 communicates with high-pressure water such as a hydraulic pump, and the high-pressure water is, as shown in FIG.
8, the water passage holes 18-3a, 2-3 of the throttle member 18-3,
The secondary pressure chamber 2 passes through the secondary pressure chamber 29, the water hole 18-2a of the throttle member 18-2, and the water hole 18-1a of the throttle member 18-1.
0 (see FIG. 1) and further into the water passage hole 32a of the casing 30 of the pilot section B.

Here, the water pressure in the water passage hole 32a is
When the spring force for urging 1 is smaller than the resilience, the water pressure hole 32a of the valve seat 32 is closed by the poppet valve 31. With the same pressure, the main valve 11 is pushed by the elastic force of the spring 17, and the flange 11 a at the tip of the main valve 11 abuts against the valve seat 12 and closes. Therefore, the high-pressure water in the water hole 19 of the valve seat 12 does not flow to the water hole 27.

The water pressure in the water passage hole 19 rises, and the water passage hole 32a
When the water pressure becomes larger than the spring force of the spring 36, the poppet valve 31 is pushed by the water pressure and separates from the valve seat 32. As a result, the high-pressure water flows through the water passage 32a, the water passage 42, the water passage 43, and the water holes 25, 26, 27, and 28 to the water tank.

At this time, the high-pressure working water is supplied to the water passage hole 18-3a of the multistage throttle member 18-1 provided at the center of the main valve 11, the secondary pressure chamber 29, and the multistage throttle members 18-2 and 18-1. The secondary pressure chamber 20 passes through the water holes 18-2a and 18-1a.
However, since the pressure does not drop rapidly but drops stepwise, the occurrence of cavitation is suppressed, and problems such as vibration and impact are not given to the main valve 11. Therefore, the operation of the main valve 11 is stabilized. Also, when the water flows through the water passage hole 32a and flows into the water passage chamber 42, since the pressure is reduced in the water passage hole 32a, the occurrence of cavitation is suppressed, but cavitation is easily generated and cavitation erosion can occur. The sex is great. Therefore, in the present embodiment, the poppet valve 31 is made of a ceramic material.

The pressure of the working fluid (water) rises and the valve seat 32
When the amount of water flowing through the water passage hole 32a increases,
Since the water pressure in the next pressure chamber 20 drops, the water pressure in the water passage hole 19 overcomes the elastic force of the spring 17 and the main valve 11 rises. As a result, the high-pressure water in the water passage hole 19 is supplied to the flanges 11 a and 11 b and the valve seat 1 forming a two-stage throttle at the tip of the main valve 11.
It flows through the gap between the two and further through the water holes 27, 28 to the water tank.

FIG. 4 shows a state where the main valve 11 is separated from the valve seat 12. When the main valve 11 is in contact with the valve seat 12, the lower surface of the flange 11 b contacts the upper surface of the cylindrical projection 12 a of the valve seat 12 to close the water passage chamber 12 b communicating with the water passage hole 19. When the main valve 11 is separated from the valve seat 12, the valve seat 12
A gap a is formed between the lower surface of the flange 11a and the lower surface of the flange 11b.
Between the lower surface of the cylindrical projection 12a and the upper surface of the cylindrical projection 12a. The high-pressure water from the water passage hole 19 is supplied to the water passage chamber 10a surrounded by the throttle gap a, the water passage chamber 12b, the throttle gap b, the outer periphery of the main valve 11 and the cylindrical projection 12a, and the inner surface of the casing 10.
The pressure is reduced step by step and flows to the water passage hole 27.

As described above, the high-pressure water from the water passage hole 19 is gradually reduced in pressure through the throttle gap a, the water passage chamber 12b, the throttle gap b, and the water passage chamber 10a, so that the occurrence of cavitation is suppressed. However, since the high-pressure water is decompressed in this portion, cavitation is likely to occur and cavitation erosion is likely to occur. Therefore, in the present embodiment, the flanges 11a and 11b of the main valve 11 and the portion 11c connecting the flanges 11a and 11b are integrally formed of a ceramic material.

In the above embodiment, the flange 11a, the flange 11b, the connecting portion 11c, and the poppet valve 31 constituting the tip of the main valve 11 are made of ceramic. By forming the portions of the valve material of the main valve portion A and the valve seat 32 of the pilot portion B that are in contact with the working fluid with ceramic, the cavitation erosion resistance can be improved.

Further, in the above-described embodiment, in order to improve the cavitation erosion resistance, the liquid contact portion of the portion where cavitation is likely to occur is made of ceramic, but a cemented carbide may be used instead of ceramic. That is natural. Further, instead of forming the entire liquid contact portion of the portion where cavitation is likely to occur from ceramic or cemented carbide, the surface of the liquid contact portion in contact with the working fluid may be coated with ceramic or cemented carbide.

In the above embodiment, the flange 11a, the flange 11b and the connecting portion 11c constituting the tip of the main valve 11 are made of ceramic. However, the simple main valve 11 having such a structure that cavitation easily occurs. By using only the tip portion of the ceramic as the ceramic, there is an advantage that a complicated portion of another structure can be processed without lowering the processing accuracy.

Further, in the relief valve having the above-described structure, corrosion resistant to the working fluid (here, water) is dealt with by using non-rusting steel for a liquid contacting portion in contact with the working fluid except for a portion where cavitation is likely to occur. It becomes possible.

In the above embodiment, the flange 11a and the flange 11b are formed on the main valve 11 of the main valve portion A and the main valve 11 at the opposite portion of the valve seat 12, so that a two-stage throttle portion is formed. The configuration of the squeezing section is not limited to this.
Needless to say, a multi-stage throttle unit as disclosed in the specification and the drawings of -148038 may be used.

[0030]

As described above, according to the present invention, the following excellent effects can be obtained. (1) According to the first aspect of the present invention, since the liquid-contacting portion at a location where cavitation is likely to occur is made of ceramic or cemented carbide, the relief valve with improved cavitation erosion resistance and long life is provided. it can.

(2) According to the second aspect of the present invention, the throttle portion for suppressing the occurrence of cavitation is provided at the opposed portion between the main valve and the valve seat and at the opposed portion between the poppet valve and the valve seat in the pilot portion. And at least one of the main valve and the valve seat of the main valve portion and the at least one of the poppet valve and the valve seat of the pilot portion are formed of ceramic or cemented carbide. Accordingly, the occurrence of cavitation is suppressed, and even if cavitation occurs, damage due to cavitation erosion is extremely small.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the overall structure of a relief valve according to the present invention.

FIG. 2 is a view showing a sectional structure of a main valve of the relief valve of the present invention.

FIG. 3 is a view showing a cross-sectional structure of a poppet valve and a valve seat of the relief valve of the present invention.

FIG. 4 is a sectional view showing a state in which a main valve of the relief valve of the present invention is separated from a valve seat.

[Explanation of symbols]

 Reference Signs List A Main valve portion B Pilot portion 10 Casing 11 Main valve 12 Valve seat 15 Wear ring 16 Packing 17 Spring 18 Restricted portion 30 Casing 31 Poppet valve 32 Valve seat 33 Restricted member 34 Press member 35 Press member 36 Spring 37 Pressure setting handle 38 Spring Seat 39 leaf spring

Claims (4)

[Claims] A main valve portion having a main valve and a valve seat; and a pilot portion having a poppet valve and a valve seat. When the poppet valve is opened by the pressure of a liquid serving as a working fluid, a main valve portion of the main valve portion is opened. When the valve is separated from the valve seat, the hydraulic fluid flows out of the gap between the main valve and the valve seat, and cavitation occurs in the relief valve of the balance piston type that keeps the pressure of the hydraulic fluid at a predetermined constant pressure. A relief valve characterized in that a liquid contact part at an easy place is made of ceramic or cemented carbide. 2. A throttle portion for suppressing the occurrence of cavitation is formed at a portion of the main valve portion facing the main valve and the valve seat and at a portion of the pilot portion facing the poppet valve and the valve seat. The throttle part liquid-contact part of at least one of the main valve and the valve seat of the valve part and the throttle part liquid-contact part of at least one of the poppet valve and the valve seat of the pilot part are made of ceramic or cemented carbide. Item 2. A relief valve according to Item 1. 3. The relief valve according to claim 1, wherein the liquid contact portion is coated with a ceramic or a cemented carbide. 4. The relief valve according to claim 1, wherein the throttle portion has a plurality of stages.