阅读说明：本技术 阀和流体压系统 (Valve and fluid pressure system ) 是由 三上晃右 山本良宏 于 2021-03-22 设计创作，主要内容包括：本发明提供一种阀和流体压系统。本发明的阀具备：外壳(201),其具有阀室；以及阀芯(210),其以移动自如的方式收容于阀室(T),在一端侧具有由工作流体的压力产生的力作用的受压面(211),受压面的直径比与阀室相通的高压端口(202)的直径大,该阀芯(210)具备沿着受压面的外周形成的角部(213),角部能够与阀室的高压端口的内壁侧接触。(The invention provides a valve and a fluid pressure system. The valve of the present invention comprises: a housing (201) having a valve chamber; and a valve body (210) which is movably housed in the valve chamber (T), and which has, on one end side, a pressure receiving surface (211) on which a force is applied by the pressure of the working fluid, the pressure receiving surface having a diameter larger than that of a high-pressure port (202) communicating with the valve chamber, wherein the valve body (210) has a corner portion (213) formed along the outer periphery of the pressure receiving surface, the corner portion being capable of coming into contact with the inner wall side of the high-pressure port of the valve chamber.)

1. A valve, wherein,

the valve is provided with:

a housing having a valve chamber having an inner wall and a high pressure port having an opening formed in the inner wall and communicating with the valve chamber; and

a valve body housed in the valve chamber,

The valve core is provided with: a pressure receiving surface formed on one end side of the valve body; and a corner portion formed along an outer periphery of the pressure receiving surface,

a force generated by the pressure of the working fluid acts on the pressure receiving surface,

the pressure receiving surface has a diameter larger than a diameter of the high pressure port,

the corner portion is contactable with the inner wall.

2. A valve, wherein,

the valve is provided with:

a housing having a valve chamber communicating with the high pressure port; and

a valve body housed in the valve chamber,

the valve core is provided with: a pressure receiving surface formed on one end side of the valve body; and a corner portion formed along an outer periphery of the pressure receiving surface,

a force generated by the pressure of the working fluid acts on the pressure receiving surface,

the corner portion is contactable with the housing.

3. A valve, wherein,

the valve is provided with:

a housing having a valve chamber communicating with the high pressure port; and

a valve body housed in the valve chamber,

the spool has a pressure receiving surface formed on one end side of the spool,

the pressure receiving surface opens and closes the high-pressure port,

a force generated by the pressure of the working fluid acts on the pressure receiving surface at the time of opening of the high-pressure port,

the pressure receiving surface has a diameter larger than a diameter of the high pressure port.

4. The valve according to claim 1 or 2,

the high pressure port has a tapered surface formed at an opening of the high pressure port,

the corner portion is formed to contact the tapered surface.

5. The valve according to any one of claims 1 to 3,

the spool has a sliding surface that slides relative to the housing,

the diameter of the pressure receiving surface is smaller than that of the sliding surface.

6. The valve according to claim 5,

the valve element has a step or a tapered surface formed between the pressure receiving surface and the sliding surface.

7. The valve according to claim 5,

the housing has a cylinder formed in the valve chamber,

the sliding surface of the valve body is formed to have substantially the same diameter as that of the cylinder.

8. The valve according to any one of claims 1 to 3,

the valve includes a return spring that urges the valve element in the direction of the high-pressure port.

9. A valve, wherein,

the valve is provided with:

a housing having a valve chamber having an inner wall and a high pressure port having an opening formed in the inner wall and communicating with the valve chamber;

a valve body housed in the valve chamber and movable in the valve chamber; and

A return spring that urges the spool in a direction toward the high-pressure port,

the valve core is provided with: a pressure receiving surface formed on one end side of the valve body; and a corner portion formed along an outer periphery of the pressure receiving surface,

a force generated by the pressure of the working fluid acts on the pressure receiving surface,

the pressure receiving surface has a diameter larger than a diameter of the high pressure port,

the corner portion is capable of contacting the inner wall,

the corner portion is formed to contact a tapered surface formed at the opening of the high-pressure port,

the spool has a sliding surface that slides relative to the housing,

the diameter of the pressure receiving surface is smaller than that of the sliding surface,

the valve element has a step or a tapered surface formed between the pressure receiving surface and the sliding surface,

the sliding surface of the valve body is formed to have a diameter substantially equal to a diameter of a cylinder formed in the valve chamber.

10. A valve, wherein,

the valve is provided with:

a housing having a valve chamber having an inner wall and a high pressure port having an opening formed in the inner wall and communicating with the valve chamber;

a valve body housed in the valve chamber and movable in the valve chamber; and

A return spring that urges the spool in a direction toward the high-pressure port,

the valve core is provided with: a pressure receiving surface formed on one end side of the valve body; and a corner portion formed along an outer periphery of the pressure receiving surface and contactable with the housing,

a force generated by the pressure of the working fluid acts on the pressure receiving surface,

the corner portion is formed to contact a tapered surface formed at the opening of the high-pressure port,

the spool has a sliding surface that slides relative to the housing,

the diameter of the pressure receiving surface is smaller than that of the sliding surface,

the valve element has a step or a tapered surface formed between the pressure receiving surface and the sliding surface,

the sliding surface of the valve body is formed to have a diameter substantially equal to a diameter of a cylinder formed in the valve chamber.

11. A valve, wherein,

the valve is provided with:

a housing having a valve chamber communicating with the high pressure port;

a valve body housed in the valve chamber and movable in the valve chamber; and

a return spring that urges the spool in a direction toward the high-pressure port,

the valve core is provided with: a pressure receiving surface formed on one end side of the valve body and configured to open and close the high-pressure port; and a corner portion formed on the valve element and capable of contacting the housing,

A force generated by the pressure of the working fluid acts on the pressure receiving surface at the time of opening of the high-pressure port,

the pressure receiving surface has a diameter larger than a diameter of the high pressure port,

the corner portion is formed to contact a tapered surface formed at an opening of the high pressure port,

the spool has a sliding surface that slides relative to the housing,

the diameter of the pressure receiving surface is smaller than that of the sliding surface,

the valve element has a step or a tapered surface formed between the pressure receiving surface and the sliding surface,

the sliding surface of the valve body is formed to have a diameter substantially equal to a diameter of a cylinder formed in the valve chamber.

12. A valve, wherein,

the valve is provided with:

a housing having a valve chamber having an inner wall and a high pressure port having an opening formed in the inner wall and communicating with the valve chamber;

a valve body housed in the valve chamber and movable in the valve chamber; and

a return spring that urges the spool in a direction toward the high-pressure port,

the valve core is provided with: an end surface formed on one end side of the valve element; and a corner portion formed along an outer periphery of the end face;

a force generated by the pressure of the working fluid acts on the end face,

The end face has a diameter larger than a diameter of the high pressure port,

the corner portion is capable of contacting the inner wall,

the corner portion is formed to contact a tapered surface formed at the opening of the high-pressure port,

the spool has a sliding surface that slides relative to the housing,

the diameter of the end face is smaller than the diameter of the sliding surface,

the valve element has a step or a tapered surface formed between the end surface and the sliding surface,

the sliding surface of the valve body is formed to have a diameter substantially equal to a diameter of a cylinder formed in the valve chamber.

13. A fluid pressure system in which, in a fluid pressure system,

the fluid pressure system includes:

a fluid pressure pump that generates fluid pressure using a working fluid;

a fluid pressure valve device that switches an output target of the working fluid;

an actuator driven by the working fluid supplied from the fluid pressure valve device; and

a valve having: a housing having a valve chamber having an inner wall and a high pressure port having an opening formed in the inner wall and communicating with the valve chamber; and a valve body housed in the valve chamber,

the valve core is provided with: a pressure receiving surface formed on one end side of the valve body; and a corner portion formed along an outer periphery of the pressure receiving surface,

A force generated by the pressure of the working fluid acts on the pressure receiving surface,

the pressure receiving surface has a diameter larger than a diameter of the high pressure port,

the corner portion is capable of contacting the inner wall,

the valve is used to adjust the pressure of the working fluid.

Technical Field

The present invention relates to a valve and a fluid pressure system with improved override performance.

The present application claims priority based on Japanese application laid-open at 23/4/2020, Japanese application No. 2020-076875, the contents of which are incorporated herein by reference.

Background

There are many construction machines having a hydraulic circuit and driven by hydraulic pressure. A hydraulic circuit is provided with a relief valve that releases pressure when the pressure in a flow path of hydraulic oil exceeds a predetermined value. The relief valve includes a valve element for opening and closing a flow path, and a case for movably housing the valve element. In a conventional relief valve, for example, a valve body is formed in a cylindrical shape, and a closed seat surface is formed on one end side of the valve body.

The corner of the seat surface is tapered. The case side has a tapered surface formed on the valve seat with which the corner of the seat surface comes into contact, and the valve element is in close contact with the valve seat in a state where the valve element is in contact with the valve seat side, thereby blocking the overflow flow path for overflow. The hydraulic oil presses the seat surface of the valve element by the pressure in the flow path. When a pressure equal to or higher than a predetermined value is applied to the valve body, the hydraulic oil pushes the seat surface to move (overshoot) the valve body, thereby opening the relief flow passage, and the hydraulic oil flows into the relief flow passage to release the pressure in the flow passage.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 11-63261

Disclosure of Invention

Problems to be solved by the invention

As shown in fig. 7, in the conventional relief valve 300, a tapered surface 315 is formed at a corner portion 313 of a valve body 310. The conventional relief valve 300 has a pressure receiving surface 311 that receives the fluid force of the hydraulic oil and is formed to have a smaller diameter than the high pressure port 302. The pressure receiving surface 311 of the valve body 310 is inserted into the high-pressure port 302, and the tapered surface 315 of the pressure receiving surface 311 formed at the corner portion 313 is brought into contact with the rear end portion 302A of the high-pressure port 302.

As shown in fig. 8A, when the valve body 310 is compared between before and after movement, the pressure receiving area of the valve body 310 before movement is an area corresponding to the diameter of the high-pressure port 302. As shown in fig. 8B, when the spool 310 moves, the hydraulic oil flows into the valve chamber T from a gap generated between the spool 310 and the high-pressure port. Thus, the pressure receiving area after the movement of the valve body 310 becomes the area of the pressure receiving surface 311 reduced from the diameter of the high pressure port 302. Therefore, the value of the force applied to the valve body 310 obtained by multiplying the area of the high-pressure port by the pressure of the hydraulic oil is the value of the area of the pressure receiving surface 311 by the pressure of the hydraulic oil, and the force applied to the valve body 310 decreases.

In this way, the conventional relief valve has room for improvement because the primary pressure receiving diameter applied to the seat surface decreases as the amount of movement of the valve element increases. If the override characteristic of the relief valve is improved, the work capacity of the construction machine is also improved. The inventors have made extensive studies to improve the override characteristics of a relief valve and to miniaturize the device.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a valve and a fluid pressure system capable of improving the override characteristic and reducing the device configuration.

Means for solving the problems

The valve of a technical scheme of the invention comprises: a housing having a valve chamber having an inner wall and a high pressure port having an opening formed in the inner wall and communicating with the valve chamber; and a valve body housed in the valve chamber, the valve body including: a pressure receiving surface formed on one end side of the valve body; and a corner portion formed along an outer periphery of the pressure receiving surface, on which a force generated by a pressure of a working fluid acts, the pressure receiving surface having a diameter larger than that of the high-pressure port, the corner portion being contactable with the inner wall.

The valve of a technical scheme of the invention comprises: a housing having a valve chamber communicating with the high pressure port; and a valve body housed in the valve chamber, the valve body including: a pressure receiving surface formed on one end side of the valve body; and a corner portion formed along an outer periphery of the pressure receiving surface, on which a force generated by a pressure of the working fluid acts, the corner portion being contactable with the housing.

The valve of a technical scheme of the invention comprises: a housing having a valve chamber communicating with the high pressure port; and a valve body housed in the valve chamber, the valve body having a pressure receiving surface formed on one end side of the valve body, the pressure receiving surface opening and closing the high-pressure port, a force generated by a pressure of a working fluid when the high-pressure port is opened acts on the pressure receiving surface, and a diameter of the pressure receiving surface is larger than a diameter of the high-pressure port.

With this configuration, when the pressure receiving surface of the valve body moves by receiving the fluid force of the working fluid flowing in from the high-pressure port, the fluid force by the working fluid applied to the valve body before and after the movement acts on the area of the pressure receiving surface to be constant, and the override characteristic of the valve body can be improved.

The high-pressure port may have a tapered surface formed at an opening of the high-pressure port, and the corner may be formed to contact the tapered surface.

With this configuration, the corner portion comes into contact with the tapered surface and comes into close contact with the tapered surface in a state where the valve body is pressed toward the high-pressure port, and therefore, the sealing performance of the high-pressure port can be improved.

The valve body may have a sliding surface that slides with respect to the housing, and the pressure receiving surface may have a diameter smaller than that of the sliding surface.

With this configuration, even when the working fluid leaks from between the sliding surface and the housing and the working fluid leaks from the high-pressure port to the low-pressure port, the pressure receiving surface is formed to have a smaller diameter than the sliding surface, and the force applied to the valve element by the pressure of the working fluid is adjusted, thereby preventing the valve element from moving because the pressure of the working fluid is smaller than a predetermined value set in advance.

The valve element may have a step or a tapered surface formed between the pressure receiving surface and the sliding surface.

With this configuration, the valve body can be prevented from moving due to the pressure of the working fluid being a value smaller than a predetermined value set in advance.

The housing may have a cylinder formed in the valve chamber, and the sliding surface of the valve body may be formed to have a diameter substantially equal to a diameter of the cylinder.

With this configuration, the working fluid can be prevented from leaking between the sliding surface and the cylinder according to the properties of the working fluid.

A return spring may be provided to urge the valve body in a direction toward the high-pressure port.

With this configuration, the valve body is pressed toward the high-pressure port by the return spring, and the corner portion is brought into contact with the tapered surface to be in close contact therewith, whereby the sealing performance of the high-pressure port can be improved.

The valve of a technical scheme of the invention comprises: a housing having a valve chamber having an inner wall and a high pressure port having an opening formed in the inner wall and communicating with the valve chamber; a valve body housed in the valve chamber and movable in the valve chamber; and a return spring that urges the valve body in a direction toward the high-pressure port, the valve body including: a pressure receiving surface formed on one end side of the valve body; and a corner portion formed along an outer periphery of the pressure receiving surface, on which a force generated by a pressure of a working fluid acts, the pressure receiving surface having a diameter larger than that of the high-pressure port, the corner portion being capable of contacting the inner wall, the corner portion being formed to contact a tapered surface formed at the opening of the high-pressure port, the valve body having a sliding surface that slides with respect to the housing, the pressure receiving surface having a diameter smaller than that of the sliding surface, the valve body having a step or a tapered surface formed between the pressure receiving surface and the sliding surface, the sliding surface of the valve body being formed to have a diameter substantially equal to a diameter of a cylinder formed in the valve chamber.

The valve of a technical scheme of the invention comprises: a housing having a valve chamber having an inner wall and a high pressure port having an opening formed in the inner wall and communicating with the valve chamber; a valve body housed in the valve chamber and movable in the valve chamber; and a return spring that urges the valve body in a direction toward the high-pressure port, the valve body including: a pressure receiving surface formed on one end side of the valve body; and a corner portion formed along an outer periphery of the pressure receiving surface and capable of contacting the housing, a force generated by a pressure of the working fluid being applied to the pressure receiving surface, the corner portion being formed to contact a tapered surface formed at the opening of the high-pressure port, the valve body having a sliding surface that slides relative to the housing, the pressure receiving surface having a diameter smaller than that of the sliding surface, the valve body having a step or a tapered surface formed between the pressure receiving surface and the sliding surface, the sliding surface of the valve body being formed to have a diameter substantially the same as a diameter of a cylinder formed in the valve chamber.

The valve of a technical scheme of the invention comprises: a housing having a valve chamber communicating with the high pressure port; a valve body housed in the valve chamber and movable in the valve chamber; and a return spring that urges the valve body in a direction toward the high-pressure port, the valve body including: a pressure receiving surface formed on one end side of the valve body and configured to open and close the high-pressure port; and a corner portion that is formed on the valve body and is capable of contacting the housing, and on which a force generated by a pressure of a working fluid acts when the high-pressure port is opened, wherein the pressure receiving surface has a diameter larger than that of the high-pressure port, the corner portion is formed so as to contact a tapered surface formed in an opening of the high-pressure port, the valve body has a sliding surface that slides with respect to the housing, the pressure receiving surface has a diameter smaller than that of the sliding surface, the valve body has a step or a tapered surface formed between the pressure receiving surface and the sliding surface, and the sliding surface of the valve body has a diameter substantially equal to a diameter of a cylinder formed in the valve chamber.

The valve of a technical scheme of the invention comprises: a housing having a valve chamber having an inner wall and a high pressure port having an opening formed in the inner wall and communicating with the valve chamber; a valve body housed in the valve chamber and movable in the valve chamber; and a return spring that urges the valve body in a direction toward the high-pressure port, the valve body including: an end surface formed on one end side of the valve element; and a corner portion formed along an outer periphery of the end face; a force generated by a pressure of a working fluid acts on the end face, a diameter of the end face is larger than a diameter of the high-pressure port, the corner portion is contactable with the inner wall, the corner portion is formed to contact a tapered surface formed at the opening of the high-pressure port, the valve body has a sliding surface that slides with respect to the housing, a diameter of the end face is smaller than a diameter of the sliding surface, the valve body has a step or a tapered surface formed between the end face and the sliding surface, and the sliding surface of the valve body is formed to have a diameter substantially the same as a diameter of a cylinder formed in the valve chamber.

A fluid pressure system according to an aspect of the present invention includes: a fluid pressure pump that generates fluid pressure using a working fluid; a fluid pressure valve device that switches an output target of the working fluid; an actuator driven by the working fluid supplied from the fluid pressure valve device; and a valve having: a housing having a valve chamber having an inner wall and a high pressure port having an opening formed in the inner wall and communicating with the valve chamber; and a valve body housed in the valve chamber, the valve body including: a pressure receiving surface formed on one end side of the valve body; and a corner portion formed along an outer periphery of the pressure receiving surface, on which a force generated by a pressure of the working fluid acts, the pressure receiving surface having a diameter larger than a diameter of the high-pressure port, the corner portion being contactable with the inner wall, the valve being configured to adjust the pressure of the working fluid.

With such a configuration, the override characteristics of the valve of the fluid pressure system can be improved, and the device can be downsized.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, the override characteristics of the valve can be improved, and the device structure can be miniaturized.

Drawings

Fig. 1 is a diagram showing a construction machine according to an embodiment of the present invention.

Fig. 2 is a diagram showing a configuration of a hydraulic system applied to a construction machine according to an embodiment of the present invention.

Fig. 3 is a diagram showing a structure of a relief valve applied to a construction machine according to an embodiment of the present invention.

Fig. 4A is a diagram for explaining the amount of movement of the valve element of the relief valve in the embodiment of the present invention.

Fig. 4B is a diagram for explaining the amount of movement of the valve element of the relief valve in the embodiment of the present invention.

Fig. 5 is a diagram showing a fluid force of the hydraulic oil applied to the valve element of the relief valve in the embodiment of the present invention.

Fig. 6 is a diagram showing a structure of a relief valve according to a modification of the embodiment of the present invention.

Fig. 7 is a diagram showing the structure of a relief valve of a comparative example.

Fig. 8A is a diagram showing an operation of a relief valve of a comparative example.

Fig. 8B is a diagram showing an operation of the relief valve of the comparative example.

Description of the reference numerals

1. A hydraulic system; 100. a construction machine; 101. a revolving body; 102. a traveling body; 103. a cab; 104. a movable arm; 105. a bucket rod; 106. a bucket; 120. an engine; 121. an output shaft; 130. a hydraulic pump; 140. an actuator; 150. a hydraulic valve arrangement; 160. a tank; 200. relief valves (valves); 201. a housing; 202. a high pressure port; 202A, a conical surface; 202B, the rear end; 202C, corner; 203. a cylinder; 203A, leading edge; 205. a low pressure port; 210. a valve core; 211. a pressure receiving surface (end surface); 212. a valve orifice; 213. a corner portion; 216. a step; 217. a sliding surface; 220. a return spring.

Detailed Description

Next, embodiments of the present invention will be described with reference to the drawings.

(construction machine)

As shown in fig. 1, the construction machine 100 is, for example, a hydraulic excavator. The construction machine 100 includes a revolving structure 101 and a traveling structure 102. Revolving unit 101 is rotatably provided on traveling unit 102. The revolving structure 101 is provided with a hydraulic system 1. In the present embodiment, the hydraulic pressure is exemplified as 1 example of the fluid pressure, but the working fluid may be not only the working oil but also another fluid.

Rotator 101 includes: a cab 103 on which an operator can ride; a boom 104 having one end connected to the cab 103 so as to be swingable; an arm 105 having one end connected to the other end (distal end) of the boom 104 on the side opposite to the cab 103 in a swingable manner; and a bucket 106 connected to the other end (tip end) of arm 105 on the side opposite to boom 104 so as to be swingable. In addition, a hydraulic system 1 is provided in the cab 103. The cab 103, the boom 104, the arm 105, and the bucket 106 are driven by hydraulic oil supplied from the hydraulic system 1.

(Hydraulic System)

As shown in fig. 2, the hydraulic system 1 (fluid pressure system) includes: an engine 120 as a driving source; a hydraulic pump 130 (fluid pressure pump) driven by the engine 120; a plurality of actuators 140 that operate each part of the construction machine 100; a hydraulic valve device 150 (fluid pressure valve device) that switches the actions of the plurality of actuators 140; a tank 160 storing working oil; and a relief valve 200 (valve) for pressure adjustment. In the present embodiment, the case where the hydraulic system 1 is applied to a construction machine is exemplified, but the present invention is not limited thereto, and may be applied to other hydraulic devices such as a hydraulic press.

The engine 120 is an internal combustion engine using gasoline fuel or diesel fuel. The engine 120 includes an output shaft 121, and the output shaft 121 is coupled to the hydraulic pump 130. A pipe Q is connected to the hydraulic pump 130. The hydraulic pump 130 is driven by the output shaft 121 to cause the hydraulic oil to flow through the pipe Q, thereby generating a fluid pressure. A hydraulic valve device 150 is connected to the pipe Q.

The hydraulic valve device 150 switches the output target of the working fluid. The hydraulic valve device 150 is connected to a plurality of actuators 140 via a branched pipe Q. The hydraulic valve device 150 is provided in plural, and supplies the hydraulic oil to the plural actuators 140 by switching the hydraulic pressure of the hydraulic oil flowing through the pipe Q by the plural valves. The plurality of actuators 140 drive the cab 103, the boom 104, the arm 105, the bucket 106, and the like. A relief valve 200 is appropriately provided in the hydraulic circuit of the hydraulic system 1, and the relief valve 200 is configured to release the pressure when the pressure in the flow path becomes equal to or higher than a predetermined value set in advance.

As shown in fig. 3, relief valve 200 includes: a housing 201 formed in a cylindrical shape; a valve body 210 housed in the case 201 so as to be movable; and a return spring 220 that urges the spool 210.

The housing 201 is a case fixed to a fixing object such as a construction machine. The housing 201 includes a high-pressure port 202 connected to a high-pressure side of the hydraulic circuit and a low-pressure port 205 connected to a low-pressure side of the hydraulic circuit. The high-pressure port 202 is formed as a circular opening hole formed at one end side of the housing 201. The high pressure port 202 is formed along the axis L of the housing 201. The working oil flows on the inner wall side of the high-pressure port 202.

A tapered surface 202A (valve seat) is formed in the opening at the rear end of the high-pressure port 202, and the diameter of the opening increases to be larger than the diameter of the high-pressure port 202 as the tapered surface 202A (valve seat) extends toward the rear end in cross-sectional view. Among them, the rear end portion of the high-pressure port 202 is an end portion in a direction toward the inside of the housing 201 along the axis L.

The corner 213 is in contact at a position slightly closer to the high-pressure port 202 side than the rear end 202B (end) of the tapered surface 202A. The diameter of the rear end (maximum diameter portion) of the tapered surface 202A is formed slightly larger than the diameter of the corner portion 213 of the spool 210, which will be discussed later. That is, the diameter of the corner portion 213 is formed slightly smaller than the diameter of the rear end 202B of the tapered surface 202A. A low pressure port 205 is formed in communication with the high pressure port 202. The low pressure port 205 is formed in the orthogonal direction of the high pressure port 202. The low pressure port 205 is formed as a circular through hole. The arrangement of the high-pressure port 202 and the low-pressure port 205 is not limited to this, and these members may be arranged in the direction of the axis L.

Inside the housing 201, a cylinder 203 communicating with the high-pressure port 202 is formed along the axis L. The cylinder 203 is formed as a circular hole. A valve body 210 is inserted into the cylinder 203 so as to be slidable in the direction of the axis L. A valve chamber T is formed in a space between the front edge 203A of the cylinder 203 and the rear end of the tapered surface 202A. The high pressure port 202 communicates with the valve chamber T.

The valve body 210 is a piston formed in a cylindrical shape. The valve body 210 opens and closes the high-pressure port 202. For the valve body 210, for example, the rear side of the cylinder 203 is independently formed, and the valve body 210 is inserted from the rear side of the cylinder 203. The valve body 210 may be inserted from the front side of the cylinder 203 by forming a part of the high-pressure port 202 separately.

Wherein the front side of the cylinder 203 represents a portion of the cylinder 203 near the high pressure port, and the rear side of the cylinder 203 represents a portion far from the high pressure port.

The valve body 210 closes the high-pressure port 202, and forms a pressure receiving surface 211 (end surface). The pressure receiving surface 211 has a valve orifice 212 formed as a through hole at the center thereof. A corner 213 is formed around the pressure receiving surface 211. The corner portion 213 is formed along the outer periphery of the pressure receiving surface 211 to have a diameter larger than that of the high-pressure port 202. The pressure receiving surface 211 is configured such that a force generated by the pressure of the static pressure of the hydraulic oil acts on one end side when the high-pressure port 202 is closed, and a force generated by the pressure of the dynamic pressure of the hydraulic oil acts on one end side when the high-pressure port 202 is opened.

The corner 213 is formed such that a side surface thereof is substantially perpendicular to the pressure receiving surface 211 when viewed in cross section of the valve body 210. The corner 213 may be chamfered by R-chamfering or C-chamfering. The pressure receiving surface 211 is formed to have a diameter 2 that is larger than the diameter 3 of the high pressure port 202 and slightly smaller than the diameter at the rear end 202B of the tapered surface 202A. The diameter Φ 1 of the sliding surface 217 on the side surface of the valve body 210, which slides against the cylinder 203, is formed to be substantially the same diameter so as to be slightly smaller than the diameter of the cylinder 203. The sliding surface 217 slides with respect to the cylinder 203.

As shown in fig. 4A and 4B, the following structure is obtained: the opening is closed by bringing the corner portion 213 into contact with the middle of the tapered surface 202A, that is, by bringing the corner portion 213 into contact with the inner wall side of the high-pressure port 202 of the valve chamber T. In this configuration, the opening width communicating with the valve chamber T is smaller in the state where the amount of movement of the valve body 210 is the same than in the case where the corner portion 213 of the relief valve 200 is brought into contact with the vicinity of the rear end 202B of the tapered surface 202A. By configuring the corner portion 213 to be able to contact the vicinity of the rear end 202B of the tapered surface 202A in this manner, the opening width of the relief valve 200 communicating with the valve chamber T can be increased with a small amount of movement of the valve body 210.

Returning to fig. 3, a step 216 is formed on the side surface of the valve body 210 so that the diameter of the sliding surface 217 is reduced. The step 216 may be a tapered surface formed so that the diameter decreases from the sliding surface 217 toward the corner 213. The step 216 may not be formed.

The effect obtained by providing the step 216 is as follows. When the amount of hydraulic oil that has leaked from the sliding surface 217 is large, the flow rate of hydraulic oil that has flowed into the valve orifice 212 increases, and the leaked hydraulic oil is discharged to the low-pressure port 205. The valve body 210 can be prevented from moving when a pressure lower than a preset pressure of the hydraulic oil acts on the valve body 210.

A return spring 220 is provided inside the valve body 210 (on the opposite side of the pressure receiving surface 211). The return spring 220 urges the spool 210 toward the high-pressure port 202. By pressing the valve body 210 toward the high-pressure port 202 by the return spring 220, the corner portion 213 of the valve body 210 is brought into contact with the tapered surface 202A formed in the high-pressure port 202. The return spring 220 has a spring constant set so that the valve body 210 moves when the hydraulic oil reaches a predetermined pressure.

Next, the operation of the relief valve 200 will be described.

When the hydraulic pressure of the hydraulic oil is less than the predetermined value, the pressure receiving surface 211 comes into close contact with the vicinity of the rear end 202B of the tapered surface 202A of the high-pressure port 202. In this state, the spool 210 prevents the working oil from flowing from the high-pressure port 202 into the low-pressure port 205. At this time, a force obtained by multiplying the area of the pressure receiving surface 211 by the pressure of the hydraulic oil acts on the valve body 210 in a direction opposite to the urging direction of the return spring 220.

As shown in fig. 5, when the hydraulic pressure of the hydraulic oil G is equal to or greater than a predetermined value, a force F obtained by multiplying the area of the pressure receiving surface 211 by the pressure of the hydraulic oil G acts on the valve body 210 in a direction opposite to the urging direction of the return spring 220. Then, the return spring 220 contracts, and the spool 210 moves away from the high-pressure port 202 along the axis L (see fig. 3). The working oil G flows into the valve chamber T from a gap generated between the tapered surface 202A and the corner portion 213, and flows into the low-pressure port 205.

At this time, the hydraulic oil G flows so as to have an inertial force, and the streamline direction of the hydraulic oil G that has collided with the pressure receiving surface 211 is bent substantially at right angles toward the corner portion 213 side of the valve body 210, and the hydraulic oil G flows radially with respect to the pressure receiving surface 211. Therefore, the area of the pressure receiving surface 211 becomes the pressure receiving area of the fluid force of the hydraulic oil G acting on the valve body 210. When the valve body 210 moves, a part of the hydraulic oil G accumulated inside the valve body 210 is discharged from the valve orifice 212 (see fig. 3).

If the working oil G continues to flow into the low pressure port 205, the pressure of the working oil decreases to less than a predetermined value. Then, the urging force of the return spring 220 is larger than the fluid force of the hydraulic oil acting on the pressure receiving surface 211, and the valve body 210 is urged by the return spring 220 to move to the original position, and the corner portion 213 comes into contact with the tapered surface 202A. During the movement of the valve body 210, a negative pressure is generated inside the valve body 210, and the hydraulic oil G flows in from the valve orifice 212 (see fig. 3).

According to the relief valve 200, the area of the pressure receiving surface 211 becomes the pressure receiving area of the fluid force of the hydraulic oil acting on the valve element 210, and the pressure receiving area is always kept constant even when the valve element 210 moves, so that the fluid force of the hydraulic oil can be received to a large extent, and the override characteristic of the valve element 210 can be improved. Further, according to the relief valve 200, the structure can be simplified, and the device can be downsized.

[ modified examples ]

As shown in fig. 6, the rear end of the high-pressure port 202 may not be formed with the tapered surface 202A. For example, a corner 202C in a direction perpendicular to the axis L may be formed at the rear end of the high-pressure port 202, and the corner 202C may overlap the pressure receiving surface 211 of the valve body 210 from the corner 213 toward the center by a predetermined width in a region where the pressure receiving surface 211 of the valve body 210 overlaps.

While one embodiment of the present invention has been described above, the present invention is not limited to the above-described one embodiment, and may be modified as appropriate within a range not departing from the gist thereof.