JP7110595B2 - relief valve - Google Patents

Description

The present invention relates to relief valves.

For example, relief valves are used in hydraulic systems of vehicles such as automatic transmissions. In a hydraulic system, when the high-pressure side oil passage such as the oil passage on the pump side reaches a predetermined pressure (relief pressure) or higher, the relief valve releases the operating oil in the high-pressure side oil passage to the low-pressure side oil passage such as the drain side oil passage. Provided for discharge into oil passages.
For example, Cited Document 1 describes a relief valve that includes a valve body, a valve body, and an urging member such as a coil spring that applies a urging force to the valve body, and that is disposed in the path of the oil supply passage. ing.

JP 2011-208651 A

By the way, when increasing the flow rate discharged through the relief valve in the conventional hydraulic system, that is, when increasing the flow rate discharged when the relief pressure is reached, the oil passage from the high-pressure side oil passage to the relief valve is increased. It is necessary to increase the cross-sectional area. Therefore, assuming that the relief pressure is constant before and after the discharge flow rate increases, as the pressure receiving area of the valve body of the relief valve increases, the urging member that resists the pressing force of the valve body due to hydraulic pressure It is necessary to increase the set load of the coil spring. In that case, it becomes difficult to assemble the valve body of the relief valve and the housing parts that accommodate the valve body during manufacturing.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a relief valve that can increase the amount of flow that is discharged when the relief pressure is reached, and that the assembling workability during manufacturing is not deteriorated.

An exemplary first invention of the present application provides a first direction, which is a direction in which a relief hole provided between a high-pressure side channel and a low-pressure side channel is opened, and a direction opposite to the first direction, which is the relief hole. a valve body that opens and closes the relief hole by moving in a second direction that closes the hole; and a biasing member that biases the valve body in the second direction, wherein the valve body comprises a first pressure-receiving surface that receives pressure in the first direction from fluid in the high-pressure-side flow path, and a second pressure-receiving surface that receives pressure in the second direction from fluid in the high-pressure-side flow path. valve.

ADVANTAGE OF THE INVENTION According to this invention, in a relief valve, the flow volume discharged when relief pressure is reached|attained can be increased, and assembly workability|operativity at the time of manufacture can be prevented from worsening.

FIG. 3 is a cross-sectional view of the hydraulic system including the relief valve of the first embodiment when the relief hole is closed; FIG. 4 is a cross-sectional view of the hydraulic system including the relief valve of the first embodiment when the relief hole is open; FIG. 4 is a cross-sectional view of a state in which a separate plate and an upper body portion are not attached at the time of assembly of the relief valve of the first embodiment; FIG. 8 is a cross-sectional view of the hydraulic system including the relief valve of the second embodiment when the relief hole is closed; FIG. 11 is a cross-sectional view of the hydraulic system including the relief valve of the third embodiment when the relief hole is closed; FIG. 6 is a partial enlarged view of FIG. 5 with arrows indicating the flow of hydraulic fluid;

A relief valve 1 according to an embodiment of the present invention will be described below with reference to the drawings.

(1) First Embodiment (1-1) Configuration of Relief Valve of Present Embodiment The configuration of a relief valve 1 of this embodiment will be described below with reference to FIGS. 1 and 2. FIG. FIG. 1 is a cross-sectional view of a hydraulic system including a relief valve 1 of this embodiment when a relief hole VL is closed. FIG. 2 is a cross-sectional view of the hydraulic system including the relief valve 1 of this embodiment when the relief hole VL is open.

As shown in FIGS. 1 and 2, the relief valve 1 of this embodiment is used in a state of being incorporated in a hydraulic system having a laminate structure as a whole. Specifically, the hydraulic system includes an upper main body portion 2, a lower main body portion 3, and a separate plate 4 arranged between the upper main body portion 2 and the lower main body portion 3, which are laminated, and a relief valve 1 is incorporated in the lower body portion 3 .
Each main body is a die-cast member of metal such as aluminum. The separate plate 4 is a flat plate made of a metal material such as iron, and provides a sealing function between adjacent main bodies. The separate plate 4 is provided with communication holes 41 for forming oil passages. In the hydraulic system of this embodiment, the opening area of the communication hole 41 is relatively large in order to increase the flow rate of the fluid discharged through the relief valve 1 .

The upper body portion 2 has a high pressure side oil passage 21 (an example of a high pressure side passage) inside, and an outlet port of the high pressure side oil passage 21 faces the communication hole 41 of the separate plate 4 . The lower body portion 3 includes a low-pressure side oil passage 31 (an example of a low-pressure side passage) inside.

The relief valve 1 has a valve body 5 and a coil spring 6 .
In the following description, along the axis of the valve body 5, which will be described later, the direction toward the upper body portion 2 is the upward direction (the direction indicated by the arrow UP in each figure), and downward along the axis of the valve body 5. Let the direction of the main body part 3 side be the downward direction (the direction indicated by the arrow of LO in each figure). In this embodiment, the downward direction is an example of the first direction, and the upward direction is an example of the second direction.

As shown in FIGS. 1 and 2, the valve body 5 is directed downward, which is the direction to open the relief hole VL provided between the high-pressure side oil passage 21 and the low-pressure side oil passage 31, and closes the relief hole VL. The relief hole VL is opened and closed by sliding (moving) in the upward direction. A coil spring 6 (an example of a biasing member) biases the valve body 5 upward.
As shown in FIG. 1, the high-pressure side oil passage 21 does not communicate with the low-pressure side oil passage 31 when the relief hole VL is closed. On the other hand, as shown in FIG. 2 , when the relief hole VL is open, the high-pressure side oil passage 21 communicates with the low-pressure side oil passage 31 .

As will be described later, the valve body 5 of this embodiment has a forward pressure receiving surface 512 that receives downward pressure from the fluid in the high pressure side oil passage 21 and a reverse pressure receiving surface 512 that receives upward pressure from the fluid in the high pressure side oil passage 21 . It is characterized in that it has a directional pressure receiving surface 522 .

The configuration of the valve body 5 will be described in more detail below.
As shown in FIG. 1 , the valve body 5 has a lower cylindrical portion 51 and an upper cylindrical portion 52 . The lower cylindrical portion 51 is a hollow cylindrical portion that is arranged on one side of the valve body 5 and accommodates the coil spring 6 . The upper cylindrical portion 52 is arranged on the other side of the valve body 5 and is a hollow cylindrical portion. The outer diameter of the upper cylindrical portion 52 is configured to be larger than the outer diameter of the lower cylindrical portion 51 .
The valve body 5 is slidable up and down in a cylindrical cavity provided in the lower body portion 3 . The cavity is defined by a large-diameter sliding surface 32 and a small-diameter sliding surface 33 . The sliding surfaces 32 and 33 are examples of moving surfaces. When the valve body 5 slides up and down, it moves along the sliding surfaces 32 and 33 . At this time, the guide peripheral surface 511 of the lower cylindrical portion 51 of the valve body 5 is guided by the sliding surface 33, and the guide peripheral surface 524 of the upper cylindrical portion 52 of the valve body 5 is guided by the sliding surface 32. .

The upper cylindrical portion 52 of the valve body 5 has a concave cross-sectional shape opening toward the communication hole 41 of the separate plate 4, and defines an inner hole portion 52h for introducing hydraulic oil from the high-pressure side oil passage 21. Prepare. When the relief hole VL is closed, the upper surface 526 of the upper cylindrical portion 52 is in contact with the surface of the separate plate 4 on the lower main body portion 3 side, and the upper end of the inner hole portion 52h faces the communication hole 41. Therefore, the hydraulic fluid in the high-pressure side oil passage 21 flows from the communication hole 41 into the inner hole portion 52h.
In the relief valve 1 of this embodiment, the opening area of the communication hole 41 is increased in order to increase the flow rate discharged through the relief valve 1. be.

The lower cylindrical portion 51 of the valve body 5 has a concave cross-sectional shape opening toward the hole 34 of the lower body portion 3, and the coil spring 6 is accommodated in the inner hole portion. The coil spring 6 is accommodated with a predetermined set load, and the restoring force of the coil spring 6 pushes up the valve body 5 against a downward force acting on a forward pressure receiving surface 512 (to be described later). That is, it acts upward).
The hole 34 is arranged on the side of the low-pressure side oil passage 31 and is provided for discharging the working oil introduced into the valve body 5 through the inner hole portion 52 h of the upper cylindrical portion 52 to the low-pressure side oil passage 31 . As already described, the guide peripheral surface 511 of the lower cylindrical portion 51 slides up and down while being guided by the sliding surface 33. However, since there is a slight gap between the guide peripheral surface 511 and the sliding surface 33, , the working oil that has moved downward from the space S (described later) through the gap is discharged (flowed out) from the hole 34 to the low-pressure side oil passage 31 .

As shown in FIG. 1, in the relief valve 1 of this embodiment, a predetermined space S is provided by partially recessing the outer peripheral surface of the valve body 5 inward from the guide peripheral surfaces 511 and 524 . The space S is, but not limited to, annularly arranged along the circumferential direction of the outer peripheral surface of the valve body 5 .
The valve body 5 has a through hole 523 that guides the working oil in the high-pressure side oil passage 21 of the inner hole portion 52h to the space S. The through hole 523 is a hole that opens in the radial direction of the valve body 5 . The through-holes 523 may guide the high-pressure hydraulic oil in the inner hole portion 52h to the space S, and the number of the through-holes 523 in the radial direction of the valve body 5, the size of the diameter of the through-holes 523, and the cross-sectional shape are not limited. .

In the valve body 5 , the lower cylindrical portion 51 has a forward pressure receiving surface 512 and the upper cylindrical portion 52 has a reverse pressure receiving surface 522 .
The forward pressure receiving surface 512 (an example of a first pressure receiving surface) is a surface that receives pressure in the direction of opening the relief hole VL, that is, in the direction of pushing down the valve body 5 by high-pressure hydraulic oil. The forward pressure receiving surface 512 is a surface facing upward in the space (ie, the inner hole portion 52h, the through hole 523, and the space S) into which high-pressure hydraulic oil is introduced in the valve body 5 .
The reverse pressure receiving surface 522 (an example of a second pressure receiving surface) is a surface that receives pressure in the direction of closing the relief hole VL, that is, in the direction of pushing the valve body 5 upward by high-pressure hydraulic oil. The reverse pressure receiving surface 522 is a surface facing downward in the space in the valve body 5 into which high-pressure hydraulic oil is introduced.

Since the outer diameter of the upper cylindrical portion 52 is larger than the outer diameter of the lower cylindrical portion 51, when the valve body 5 is viewed upward, the outer surface of the upper cylindrical portion 52 has a lower cylindrical shape. A portion that does not overlap with the portion 51 (the outermost portion in the illustrated configuration) is at least part of the reverse pressure receiving surface 522 . As shown in FIG. 1, the outermost portion of the reverse pressure receiving surface 522 in the space S does not face the forward pressure receiving surface 512, so that only a force that substantially pushes the valve body 5 upward is generated. Let
In the relief valve 1 of the present embodiment, the pressure receiving area of the forward pressure receiving surface 512 is larger than the pressure receiving area of the reverse pressure receiving surface 522. It is configured to act downward on the valve body 5 as a whole.

(1-2) Operation of relief valve of this embodiment The operation of the relief valve 1 of this embodiment is as follows.
In the hydraulic system of this embodiment, hydraulic oil in the high-pressure side oil passage 21 is introduced into the relief valve 1 . That is, the hydraulic oil in the high-pressure side oil passage 21 is introduced into the inner hole portion 52h of the upper cylindrical portion 52 of the valve body 5 through the communication hole 41 of the separate plate 4 . Hydraulic oil introduced into the inner hole portion 52h is introduced into the space S through the through hole 523. As shown in FIG. Therefore, the pressure applied to the forward pressure-receiving surface 512 pushes the valve element 5 downward (the force F1 in the direction of opening the relief hole VL), and the pressure applied to the reverse pressure-receiving surface 522 causes the valve element to move downward. A force F2 (a force in a direction to close the relief hole VL) acts to push up the relief hole VL. In the hydraulic system of the present embodiment, in order to increase the flow rate discharged through the relief valve 1, the opening areas of the communication hole 41 and the inner hole portion 52h are relatively wide, compared to the case where the discharge flow rate is small. The downward force F1 due to the pressure applied to the forward pressure receiving surface 512 is increased.
Since the pressure-receiving area of the forward pressure-receiving surface 512 is larger than the pressure-receiving area of the reverse pressure-receiving surface 522, F1>F2 is always established, and the valve body 5 as a whole receives a downward pressing force FT (=F1- F2) is working.

A restoring force FS of the coil spring 6 acts upward on the valve body 5 . Therefore, when the pressure in the high-pressure side oil passage 21 is low, the restoring force FS of the coil spring 6 is greater than the downward force FT due to hydraulic pressure (FS>FT), and the upper surface 526 of the valve body 5 contacts the separate plate 4. 1, and the relief hole VL is closed as shown in FIG.

When the pressure in the high-pressure side oil passage 21 becomes higher than a predetermined relief pressure, the pressing force FT due to hydraulic pressure becomes larger than the restoring force FS of the coil spring 6 (FS<FT), and the upper surface 526 of the valve body 5 separates. It is separated from the plate 4 and the relief hole VL is opened as shown in FIG. As a result, the high-pressure side oil passage 21 and the low-pressure side oil passage 31 communicate with each other, and the working oil in the high-pressure side oil passage 21 is discharged from the low-pressure side oil passage 31 .

As described above, in the operation of the relief valve 1 of the present embodiment, the pressing force FT due to the hydraulic pressure applied to the valve body 5 is the force F1 applied to the forward pressure receiving surface 512 minus the force F2 applied to the reverse pressure receiving surface 522. It has become. Therefore, without changing the relief pressure, the set load of the coil spring 6 can be reduced by the force F2 applied to the reverse pressure receiving surface 522 as compared with the conventional relief valve having only the forward pressure receiving surface. .

(1-3) Assembly Method of Relief Valve of Present Embodiment Next, a method of installing the relief valve 1 to the hydraulic system of the present embodiment will be described with reference to FIG. FIG. 3 is a cross-sectional view of the relief valve 1 of the present embodiment in a state where the separate plate 4 and the upper main body portion 2 are not attached when the relief valve 1 is assembled.

To assemble the relief valve 1, first, the lower body portion 3 is placed on a horizontal surface. Next, with the coil spring 6 set in the inner hole portion of the lower cylindrical portion 51 of the valve body 5, the relief valve 1 is moved by the cavity of the lower main body portion 3 (that is, by the sliding surfaces 32 and 33). defined cavity) with the coil spring 6 on the bottom side. FIG. 3 shows a state in which the relief valve 1 is inserted into the lower body portion 3. As shown in FIG. At this point, the coil spring 6 is in a state of being slightly compressed by the weight of the valve body 5 from its free length.

Next, the separate plate 4 is placed on the lower body portion 3 while aligning the communication hole 41 of the separate plate 4 (not shown in FIG. 3) with the opening of the inner hole portion 52h of the upper cylindrical portion 52 of the valve body 5. do. Further, by arranging the upper body portion 2 on the separate plate 4, the assembly of the relief valve 1 is completed.

When disposing the separate plate 4 on the lower main body portion 3, the separate plate 4 is brought into contact with the upper surface 526 of the valve body 5, and overcomes the elastic force of the coil spring 6 to reach the position shown in FIG. need to be pushed down. Therefore, when the set load of the coil spring 6 is high, it becomes difficult to push down the valve body 5 with the separate plate 4 from the position of the valve body 5 shown in FIG. 3 to the position of the valve body 5 shown in FIG. However, in the relief valve 1 of this embodiment, as described above, the setting load of the coil spring 6 can be reduced, so there is an advantage that the work of pushing down the valve body 5 becomes relatively easy. To lower the set load of the coil spring 6 until the weight of the separate plate 4 pushes the valve body 5 down to the state shown in FIG. If possible, it is more preferable.

As described above, the relief valve 1 of the present embodiment includes the reverse pressure receiving surface 522 that acts in the direction of closing the relief hole VL by the hydraulic oil in the high-pressure side oil passage 21 . Therefore, compared to the case where the reverse pressure receiving surface 522 is not provided, the set load of the coil spring 6 can be reduced. It is possible to prevent deterioration of assembly workability. That is, it is possible to achieve both an increase in the amount of flow discharged when the relief pressure is reached and a reduction in assembly workability during manufacturing.

(2) Second Embodiment Next, a relief valve 1A according to a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a cross-sectional view of the hydraulic system including the relief valve 1A of the second embodiment when the relief hole is closed.
In addition, in FIG. 4, the same components as those mentioned in the first embodiment are denoted by the same reference numerals, and duplicate descriptions will be omitted below.

In the first embodiment, the through hole 523 that penetrates the inner hole portion 52h of the upper cylindrical portion 52 and the space S is provided to guide the high-pressure hydraulic oil in the high-pressure side oil passage 21 to the space S. In the relief valve 1A of this embodiment, the high-pressure working oil is guided from the high-pressure side oil passage 21 to the space S through another oil passage. Therefore, the upper cylindrical portion 52A of the relief valve 1A of this embodiment does not have a through hole between the inner hole portion 52h and the space S.

Referring to FIG. 4, in this embodiment, the upper main body portion 2A, the separate plate 4A, and the lower main body portion 3A are arranged so that an oil passage 35 for guiding hydraulic oil from the high pressure side oil passage 21 to the space S is provided. It is configured.
In the relief valve 1A of this embodiment, hydraulic oil is introduced into the space S from the high-pressure side oil passage 21 through the oil passage 35, and the pressure applied to the reverse pressure receiving surface 522 in the space S causes the valve body 5 to move upward. A pushing force is generated. The effect of the relief valve 1A of this embodiment is the same as that of the relief valve 1 of the first embodiment.

(3) Third Embodiment Next, a relief valve 1B according to a third embodiment of the present invention will be described with reference to FIGS. 5 and 6. FIG. FIG. 5 is a cross-sectional view of the hydraulic system including the relief valve 1B of the present embodiment when the relief hole VL is closed. FIG. 6 is a partially enlarged view of FIG. 5, in which arrows indicate the flow of hydraulic oil in the relief valve 1B of the present embodiment.
In FIGS. 5 and 6, the same components as those mentioned in the first embodiment are denoted by the same reference numerals, and redundant description will be omitted below.

The relief valve 1B of the present embodiment has a basic configuration similar to that of the first embodiment in that a through hole is provided for guiding the high-pressure hydraulic oil in the inner hole portion 52h of the upper cylindrical portion 52B to the space S. Same as relief valve 1. That is, as shown in FIG. 5, the relief valve 1B is provided with a through hole 523B passing through the space S and the inner hole portion 52h of the upper cylindrical portion 52B.
On the other hand, in the relief valve 1B of the present embodiment, unlike the first embodiment, the cross-sectional area of the through-hole 523B (the through-hole 523B is composed of a plurality of through-holes) is determined in consideration of the responsiveness of the relief valve. total cross-sectional area of a plurality of through-holes) is set.

In general, when the relief pressure reaches the relief valve, the relief hole is opened, and it is preferable that the pressure in the high-pressure side oil passage immediately drops to the same pressure as the low-pressure side oil passage. considered to be good. However, if the cross-sectional area of the through hole 523 is too large in the relief valve 1 of the first embodiment, the amount of hydraulic oil flowing into the space S will be reduced to a lower cylindrical shape immediately after the relief hole VL is opened. Since the amount of hydraulic oil that flows out from the small gap between the guide peripheral surface 511 of the portion 51 and the sliding surface 33 is extremely small, the upward force generated on the high pressure opposite direction pressure receiving surface 522 in the space S is exerted by the coil spring 6. The state of assisting the restoring force continues, making it difficult to stably open the relief hole, and the responsiveness deteriorates.
Therefore, in the relief valve 1B of the present embodiment, the amount of hydraulic oil flowing out from the space S through the small gap between the guide peripheral surface 511 of the lower cylindrical portion 51 and the sliding surface 33 is By narrowing the cross-sectional area, the flow rate of hydraulic oil flowing into the space S from the inner hole portion 52h is restricted, and the pressure in the space S is immediately lowered as much as possible, thereby improving the responsiveness immediately after reaching the relief pressure. .

As shown in FIG. 6, in the relief valve 1B of the present embodiment, hydraulic oil in the inner hole portion 52h of the upper cylindrical portion 52B is introduced into the space S through the through hole 523B. Hydraulic oil in the space S passes through a small gap between the guide peripheral surface 511 of the lower cylindrical portion 51 and the sliding surface 33 and is discharged from the hole 34 to the low pressure side oil passage 31 . Therefore, in this embodiment, the cross-sectional area of the through hole 523B is made smaller than the cross-sectional area of the gap between the guide peripheral surface 511 of the lower cylindrical portion 51 and the sliding surface 33 . In other words, the amount of hydraulic fluid that flows into the space S from the through hole 523B per unit time is made smaller than the amount of hydraulic fluid that flows out of the space S per unit time.
As a result, it is possible to prevent the pressure in the space S from being maintained at a high level, and to stably reduce the pressure in the space S after the relief hole is opened. As a result, the relief valve 1B of the present embodiment has good responsiveness immediately after reaching the relief pressure.

Since the amount of hydraulic oil flowing into the space S from the through hole 523B per unit time may be smaller than the amount of hydraulic oil flowing out of the space S per unit time, the outflow destination is the lower cylindrical portion. It is not limited to the gap between the guide peripheral surface 511 of 51 and the sliding surface 33 . For example, a narrow oil passage for discharging hydraulic oil may be provided from the space S to the low-pressure side oil passage 31 .

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited to the above embodiments. Also, the above embodiments can be modified and modified in various ways without departing from the gist of the present invention.

In the above-described embodiment, the case where the space S in which the reverse pressure receiving surface 522 is provided is annularly arranged along the circumferential direction of the outer peripheral surface of the valve body 5 has been described, but this is not the only option. The space S may not be provided at all positions in the circumferential direction of the outer peripheral surface of the valve body 5, and may be provided at a part of the circumferential direction. By arranging the space S in an annular shape along the circumferential direction of the outer peripheral surface, there is an advantage that the pressure receiving area of the opposite direction pressure receiving surface 522 can be increased.

Although it is not essential to provide a through hole in the valve body as shown in the second embodiment (FIG. 4), in the second embodiment, machining of the oil passage 35 may be difficult. In the first embodiment, the processing of providing the through hole 523 in the upper cylindrical portion 52 is relatively easy. Therefore, from the manufacturing point of view, it is advantageous to provide the valve body 5 with a through hole as shown in the first embodiment.

In the relief valves of the first and third embodiments, when through-holes that open in the radial direction of the valve body 5 are provided, the number of through-holes is preferably single. When the amount of hydraulic fluid that flows into the space S per unit time is set to a predetermined amount, a single through-hole allows the cross-sectional area of each through-hole to be larger than a plurality of through-holes. Therefore, processing becomes easy. Further, in the third embodiment, a single through-hole is more advantageous than a plurality of through-holes in stably reducing the pressure in the space S after the relief hole is opened.

In the above-described embodiment, the case where the valve body has a form consisting of two cylindrical portions has been described, but the present invention is not limited to this. The cross-section of the valve body is not limited to a circular shape, and may be oval or honeycomb-shaped, for example.

Reference Signs List 1, 1A, 1B Relief valves 2, 2A Upper body portions 3, 3A Lower body portions 4, 4A Separate plates 41 Communication holes 21 High-pressure side oil passages 31 Low-pressure side oil passages 32, 33 Sliding Moving surface 34 Hole 35 Oil passages 5, 5A, 5B Valve body 51 Lower cylindrical portion 511 Guide peripheral surface 512 Forward pressure receiving surfaces 52, 52A, 52B Upper cylindrical portion 52h Inner hole 522 Reverse pressure receiving surface 523, 523B Through hole 524 Guide peripheral surface 525 Outer peripheral surface 526 Upper surface 6 Coil spring VL Relief hole S Space

Claims (5)

A first direction that is a direction in which a relief hole provided between a high pressure side channel and a low pressure side channel is opened, and a second direction that is a direction opposite to the first direction and is a direction in which the relief hole is closed. a valve body that opens and closes the relief hole by moving to and
a biasing member that biases the valve body in the second direction;
with
The valve body
a first pressure-receiving surface that receives pressure in the first direction by the fluid in the high-pressure channel;
a second pressure-receiving surface that receives pressure in the second direction from the fluid in the high-pressure channel;
with
The valve body
a hollow cylindrical first cylindrical portion disposed on one side of the valve body and containing the biasing member;
a hollow cylindrical second cylindrical portion disposed on the other side of the valve body;
with integrated structure,
The first cylindrical portion has the first pressure receiving surface,
The second cylindrical portion has the second pressure receiving surface,
relief valve. The outer diameter of the second cylindrical portion is larger than the outer diameter of the first cylindrical portion,
When the valve body is viewed in the second direction, a portion of the outer surface of the second cylindrical portion that does not overlap the first cylindrical portion is at least part of the second pressure receiving surface,
A relief valve as claimed in claim 1 . The valve body moves along the moving surface and has a guide peripheral surface guided by the moving surface,
A predetermined space is provided by partially recessing the outer peripheral surface of the valve body from the guide peripheral surface toward the inside,
The valve body has a through hole that guides the fluid in the high pressure side flow path to the space,
A relief valve according to claim 1 or 2 . 4. The relief valve according to claim 3 , wherein the space is annularly arranged along the circumferential direction of the outer peripheral surface of the valve body. 5. The relief valve according to claim 3 , wherein said through - hole is a single hole that opens in the radial direction of said valve body.

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