Relief valve with check function

Abstract

To provide a relief valve with a check function that can regulate a relief pressure.SOLUTION: A relief valve with a check function relieves hydraulic fluid from a first port 2 to a second port 3, and comprises: a housing comprising a body 21, and a regulating member 22 provided in the body so as to be capable of being advanced and retreated; a seat member 13 provided in the body, and in which a relief passage 25 leading to both the first port and the second port is formed; a relief valve element 14 for opening and closing the relief passage by being separated from and seated on the seat member, and receiving a pressure in the first port in a direction for opening the relief passage; a first biasing member 15 for biasing the relief valve element against the pressure in the first port, and whose biasing force is regulated when the regulating member is advanced and retreated; a check valve element 16 for opening and closing a check passage 24 leading to both the first port and the second port, and receiving a pressure in the second port in a direction for opening the check passage; and a second biasing member 17 for biasing the check valve element against the pressure in the second port.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a relief valve with a check function for relieving a working fluid from a first port to a second port.

Background Art

[0002] A relief valve with a check function relieves a working oil from a first port to a second port when the pressure of the first port becomes higher than a set pressure (relief function). Further, the relief valve with a check function can supply the working oil from the second port to the first port when the pressure of the second port becomes higher than the pressure of the first port (check function). As such a relief valve with a check function, for example, the relief valve with a check function of Patent Document 1 is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The relief valve with a check function of Patent Document 1 has a first valve body having a check function and a second valve body having a relief function. In the relief valve with a check function, the second valve body is inserted into the first valve body. When the first valve body operates, the first valve body and the second valve body move integrally. Thus, since the first valve body and the second valve body are integrally configured, a mechanism for adjusting the relief pressure from the outside is not provided.

[0005] [[ID=)]] Therefore, an object of the present invention is to provide a relief valve with a check function capable of adjusting the relief pressure from the outside.

Means for Solving the Problems

[0006] The present invention provides a relief valve with a check function for relieving working fluid from a first port to a second port, comprising: a housing having a body and an adjustment member provided on the body so as to be movable back and forth; a seat member provided in the body and having relief passages formed therein that connect to the first port and the second port, respectively; a relief valve body that seats away from the seat member to open and close the relief passage and is subjected to the pressure of the first port in the direction of opening the relief passage; a first biasing member that biases the relief valve body against the pressure of the first port and whose biasing force is adjusted when the adjustment member moves back and forth; a check valve body that opens and closes check passages connected to the first port and the second port, respectively and is subjected to the pressure of the second port in the direction of opening the check passage; and a second biasing member that biases the check valve body against the pressure of the second port.

[0007] According to the present invention, the biasing force of the first biasing member can be adjusted by moving the adjustment member forward and backward relative to the body. This allows the relief pressure to be adjusted from the outside. [Effects of the Invention]

[0008] According to the present invention, the relief pressure can be adjusted from the outside. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view showing a relief valve with a check function according to the first embodiment of the present invention. [Figure 2] Figure 1 is a cross-sectional view showing the relief operation of a relief valve with a check function. [Figure 3] Figure 1 is a cross-sectional view showing the check operation of a relief valve with a check function. [Figure 4] This is a cross-sectional view showing a relief valve with a check function according to a second embodiment of the present invention. [Figure 5] This is a cross-sectional view showing a relief valve with a check function according to the third embodiment of the present invention. [Modes for carrying out the invention]

[0010] Hereinafter, the first to third embodiments of the present invention, specifically the relief valves with check functions (hereinafter simply referred to as "relief valves") 1, 1A, and 1B, will be described with reference to the aforementioned drawings. Note that the concept of direction used in the following description is for convenience of explanation and does not limit the orientation of the invention's configuration to that direction. Furthermore, the relief valves 1, 1A, and 1B described below are merely embodiments of the present invention. Therefore, the present invention is not limited to these embodiments, and additions, deletions, and modifications are possible without departing from the spirit of the invention.

[0011] [First Embodiment] The hydraulic circuit is equipped with a relief valve 1 as shown in Figure 1. When the pressure of the working fluid in the first port 2 exceeds a predetermined pressure (i.e., relief pressure), the relief valve 1 flows working fluid from the first port 2 to the second port 3. Also, when the pressure of the working fluid in the first port 2 is lower than the pressure in the second port 3, the relief valve 1 flows working fluid from the second port 3 to the first port 2. In this embodiment, the first port 2 is, for example, an actuator port, and the second port 3 is a tank port. More specifically, the relief valve 1 comprises a valve block 11, a housing 12, a seat member 13, a relief valve body 14, a first biasing member 15, a check valve body 16, and a second biasing member 17.

[0012] <Valve Block> The valve block 11 is a block body to which the housing 12 is attached. More specifically, the valve block 11 has a valve hole 11a, a first passage 11b, and a second passage 11c. The valve hole 11a is a bottomed hole formed along the axis L1. A first port 2 is formed on the bottom surface defining the valve hole 11a. The first passage 11b is connected to the valve hole 11a via the first port 2. A second port 3 is formed on the inner circumferential surface defining the valve hole 11a. The second passage 11c is connected to the valve hole 11a via the second port 3.

[0013] <Housing> The housing 12 houses a seat member 13, a relief valve body 14, a first biasing member 15, a check valve body 16, and a second biasing member 17. The housing 12 also has a body 21, an adjustment plug 22, and a lock nut 23. More specifically, the housing 12 is formed in a cylindrical shape, for example. The housing 12 has an opening 12a that is inserted into the valve hole 11a toward the first port 2. Therefore, the inside of the housing 12 is connected to the first port 2 through the opening 12a of the housing 12.

[0014] The body 21 has one end, which is on one axial side, inserted into the valve hole 11a toward the first port 2. More specifically, the body 21 is formed in a cylindrical shape. The body 21 is screwed onto the valve block 11. The body 21 has an internal bore consisting of an opening 21a and an internal space 21b. The opening 21a is formed at one end, which is on one axial side of the body 21. The opening 21a is formed to be smaller in diameter than the internal space 21b. A check valve seat 21c is formed in the body 21 so as to surround the opening 21a. A stepped portion 21e is formed in the axial middle portion of the internal space 21b, and the internal space 21b is formed to be smaller in diameter on one axial side than on the other axial side than the stepped portion 21e. Furthermore, a plurality of communication passages 21d are formed on the outer circumferential surface of the body 21 in the portion on one axial side. The plurality of communication passages 21d penetrate the body 21 radially. Furthermore, the multiple communication passages 21d, together with the opening hole 21a and the internal space 21b, form a check passage 24. That is, the check passage 24 is a passage that runs from the multiple communication passages 21da through the internal space 21b to the opening hole 21a. In addition, one end of the body 21 is formed in a tapered shape that narrows in one direction axially in this embodiment. The body 21 is inserted into the valve hole 11a so as to seal around the first port 2 by one end and is screwed into the valve block 11. The opening hole 21a abuts against the first port 2, and the multiple communication passages 21d are positioned to correspond to the second port 3. Therefore, the opening hole 21a is connected to the first port 2, and the multiple communication passages 21d are connected to the second port 3.

[0015] An example of an adjustment member, the adjustment plug 22, is provided in the body 21 so as to be able to move back and forth. More specifically, the adjustment plug 22 is formed in a cylindrical shape with a top. The open end of the adjustment plug 22 is screwed into the body 21. That is, the adjustment plug 22 moves back and forth in the axial direction relative to the body 21 by rotating it around its axis (which coincides with axis L1 in this embodiment). In this embodiment, the adjustment plug 22 is configured to be rotatable using a tool such as a spanner, hex wrench, or screwdriver.

[0016] The lock nut 23 restricts the movement of the adjustment plug 22 relative to the body 21. More specifically, the lock nut 23 is annular in shape and is screwed onto the middle portion of the adjustment plug 22. When tightened, the lock nut 23 abuts against the other end, which is the other axial end of the body 21. This restricts the axial movement of the adjustment plug 22 relative to the body 21. Conversely, when loosened, the lock nut 23 moves away from the other end of the body 21, allowing the axial movement of the adjustment plug 22 relative to the body 21.

[0017] <Sheet material> The seat member 13 is provided inside the housing 12. A relief passage 25 is formed in the seat member 13. The relief passage 25 is connected to the first port 2 and the second port 3, respectively. More specifically, the seat member 13 is formed in a cylindrical shape. More specifically, the middle portion of the seat member 13 has a larger diameter than the portion at one axial end and a smaller diameter than the portion at the other axial end. In the inner hole 13a of the seat member 13, the portion on one axial side forms a passage portion 13b, and the portion on the other axial side forms a valve insertion portion 13c. The passage portion 13b has a smaller diameter than the valve insertion portion 13c. A relief valve seat 13e is formed around the portion of the passage portion 13b that opens to the valve insertion portion 13c. In addition, a plurality of through passages 13f are formed in the middle portion of the seat member 13. The plurality of through passages 13f, together with the inner hole 13a, form the relief passage 25 in the seat member 13. In other words, the relief passage 25 is a passage that continues from the passage portion 13b through the valve insertion portion 13c to a plurality of through passages 13f. Furthermore, a plurality of communication holes 13g are formed on the outer circumferential surface of the axial end portion of the seat member 13. The plurality of communication holes 13g penetrate the axial end portion of the seat member 13 radially. Furthermore, a plurality of communication passages 13h are formed around the inner hole 13a on the other axial end portion of the seat member 13. The communication passages 13h are formed parallel to the axis L1 in the large diameter portion of the seat member 13. The communication passages 13h also constitute a throttling.

[0018] The sheet member 13 configured as described above is disposed in the intermediate portion of the housing 12. More specifically, the sheet member 13 is disposed inside the body 21 on one side in the axial direction from the adjustment plug 22. And the sheet member 13 is fixed inside the housing 12 by screwing the large-diameter portion to the inner peripheral surface of the body 21 and engaging with the stepped portion 21e. Thereby, the inside of the housing 12 is separated by the sheet member 13 into a valve space 12b on one side in the axial direction and a first spring accommodation space 12c on the other side in the axial direction. Also, the sheet member 13 is disposed with the opening on one side in the axial direction facing the first port 2. Thereby, an annular space 12d is formed between the intermediate portion of the sheet member 13 and the body 21 in the valve space 12b. And the through passage 13f is connected to the second port 3 through the annular space 12d. Also, since the opening on one side in the axial direction is disposed facing the first port 2, the passage portion 13b of the relief passage 25 is connected to the first port 2. And the communication passage 13h connects the valve space 12b and the first spring accommodation space 12c.

[0019] <Relief valve body> The relief valve body 14 can be seated on and separated from the sheet member 13. Also, by being seated on and separated from the sheet member 13, the relief passage 25 is opened and closed. Further, the relief valve body 14 receives the pressure of the first port 2 in the direction of opening the relief passage 25 (hereinafter referred to as the "first opening direction"). More specifically, the relief valve body 14 is inserted into the valve insertion portion 13c. And the relief valve body 14 seats the tip-side portion 14a on one side in the axial direction on the relief valve seat 13e. Also, the relief valve body 14 can slide in the axial direction. Therefore, the relief valve body 14 seats on and separates from the relief valve seat 13e, opening and closing the relief passage 25. Also, the relief valve body 14 is configured as follows in the present embodiment.

[0020] That is, the relief valve body 14 is a direct-acting valve body made of a solid member and is formed in a cylindrical shape. The middle portion of the relief valve body 14 is slidably supported by the sheet member 13. Further, in the relief valve body 14, the tip-side portion 14a on one side in the axial direction is formed to have a smaller diameter than the middle portion. The tip-side portion 14a of the relief valve body 14 is formed in a pointed shape. And the tip-side portion 14a of the relief valve body 14 is seated on the relief valve seat 13e so as to pierce the passage portion 13b. Therefore, the tip-side portion 14a of the relief valve body 14 forms a pressure-receiving portion 14c. That is, the relief valve body 14 receives the hydraulic pressure of the passage portion 13b at the pressure-receiving portion 14c. More specifically, the relief valve body 14 receives the hydraulic pressure of the passage portion 13b at the portion corresponding to the passage portion 13b (see the first pressure-receiving area A1 of the pressure-receiving portion 14c in FIG. 1). And since the working fluid of the first port 2 is led to the passage portion 13b, the relief valve body 14 receives the hydraulic pressure of the first port 2 at the pressure-receiving portion 14c of the tip-side portion 14a. The relief valve body 14 receives the load obtained by multiplying the pressure of the first port 2 by the first pressure-receiving area A1 of the pressure-receiving portion 14c from the working fluid in the first opening direction. Therefore, the relief valve body 14 separates from and seats on the sheet member 13 according to the pressure of the first port 2. Further, the relief valve body 14 has a spring receiving portion 14b on the outer peripheral surface of the base end side portion on the other side in the axial direction.

[0021] <First biasing member> The first biasing member 15 biases the relief valve body 14 in a direction to close the relief passage 25 (hereinafter referred to as the "first closing direction") against the pressure of the first port 2. More specifically, the first biasing member 15 is a spring member. In this embodiment, the first biasing member 15 is a compression coil spring. The first biasing member 15 is accommodated in a compressed state in the first spring accommodation space 12c of the housing 12 (that is, inside the adjustment plug 22). More specifically, the first biasing member 15 has one end abutted against the spring receiving portion 14b of the relief valve body 14 and the other end abutted against the ceiling surface of the adjustment plug 22. Thereby, the first biasing member 15 biases the relief valve body 14 in the first closing direction (that is, in one axial direction) against the pressure of the first port 2.

[0022] Furthermore, in the first biasing member 15, the biasing force is adjusted by moving the adjustment plug 22 forward and backward. More specifically, when the lock nut 23 is loosened and the adjustment plug 22 is rotated, the adjustment plug 22 moves forward and backward. This adjusts the amount of compression of the first biasing member 15. The biasing force of the first biasing member 15 is adjusted by the amount of compression of the first biasing member 15.

[0023] <Valve body for checking> The check valve body 16 opens and closes the check passage 24. The check valve body 16 is also subjected to pressure from the second port 3 in the direction that opens the check passage 24 (hereinafter referred to as the "second opening direction"). More specifically, the check valve body 16 is housed in the housing 12, more specifically in the body 21. The check valve body 16 is slidably supported on the seat member 13. More specifically, the check valve body 16 is slidably mounted on the seat member 13. The check valve body 16 seats away from the check valve seat 21c by sliding. The check valve body 16 closes the check passage 24 by seating on the check valve seat 21c. The check valve body 16 also has a connecting passage 16a. The connecting passage 16a guides the working fluid flowing from the first port 2 to the relief passage 25 of the seat member 13 when the check valve body 16 is closing the check passage 24. In this embodiment, the check valve body 16 is formed as follows.

[0024] Specifically, the check valve body 16 is formed in a cylindrical shape. The seat member 13 is slidably inserted into the inner bore of the check valve body 16. The check valve body 16 is housed in the inner space 21b of the body 21. The check valve body 16 also forms an annular valve passage 26 between itself and the body 21. The valve passage 26 is connected to the second port 3 via a plurality of connecting passages 21d. The valve passage 26, together with the opening hole 21a and the plurality of connecting passages 21d, forms a check passage 24. In the check valve body 16, one end, which is the opening end on one axial side, is formed in a tapered shape that narrows as it moves axially in that direction. The check valve body 16 closes the check passage 24 by seating one end on the check valve seat 21c. The check valve body 16 also separates from the check valve seat 21c by sliding axially in the other direction along the seat member 13. This opens the check passage 24. Furthermore, the check valve body 16 is subjected to pressure from the fluid flowing through the check passage 24 at one end. That is, the check valve body 16 is subjected to pressure from the second port 3 in the second opening direction at one end.

[0025] Furthermore, the check valve body 16 has a communication passage 16a, an intermediate section 16b, and a large-diameter section 16c in its internal bore. The communication passage 16a, the intermediate section 16b, and the large-diameter section 16c are arranged in that order from one axial side, and are formed in increasing order of diameter from the communication passage 16a, the intermediate section 16b, and the large-diameter section 16c. The communication passage 16a, which has the smallest diameter of the three, is connected to the first port 2 via an opening hole 21a. One axial end of the seat member 13 is slidably inserted into the intermediate section 16b. The intermediate portion of the seat member 13 is also slidably inserted into the large-diameter section 16c in a sealed state. As a result, the check valve body 16 is stably supported at two points, the intermediate section 16b and the large-diameter section 16c, which are sliding parts. Furthermore, an annular second spring housing space 16d is formed between the large-diameter portion 16c and the axial end portion of the seat member 13, around the intermediate portion of the seat member 13. The second spring housing space 16d is connected to the relief passage 25 via a communication hole 13g. Therefore, working fluid from the first port 2 flows into the second spring housing space 16d via the relief passage 25. As a result, the check valve body 16 is subjected to the pressure from the first port 2 in the direction that closes the check passage 24 (hereinafter referred to as the "second closing direction") on its inner circumferential surface.

[0026] As described above, the check valve body 16 receives the pressure from the second port 3 in the second opening direction at one end and the pressure from the first port 2 in the second closing direction on its inner circumferential surface. The check valve body 16 receives the pressures from each port 3 and 2 in opposing directions at the pressure receiving portion 16e at one end. The second pressure receiving area A2, which is the area of ​​the pressure receiving portion 16e where the pressures from each port 3 and 2 act in opposing directions, corresponds to the area obtained by subtracting the area of ​​the diameter D2 of the opening hole 21a from the area of ​​the hole diameter D1 of the large diameter portion 16c. The check valve body 16 receives a load from the working fluid in the second opening direction, which is obtained by multiplying the second pressure receiving area A2 by the differential pressure Δp obtained by subtracting the pressure of the first port 2 from the pressure of the second port 3.

[0027] <Second biasing member> The second biasing member 17 biases the check valve body 16 in the second closing direction against the pressure of the second port 3. More specifically, the second biasing member 17 is a spring member. In this embodiment, the second biasing member 17 is a compression coil spring. The second biasing member 17 is housed in a compressed state in the second spring housing space 16d within the check valve body 16. More specifically, both ends of the second biasing member 17 are in contact with the seat member 13 and the check valve body 16, respectively. As a result, the second biasing member 17 biases the check valve body 16 in the second closing direction (i.e., axially) against the pressure of the second port 3.

[0028] <Relief valve relief operation> In the relief valve 1, the working fluid introduced to the first port 2 is guided to the passage portion 13b of the relief passage 25 via the opening hole 21a and the connecting passage 16a. When the pressure in the first port 2 exceeds the relief pressure, the relief valve 1 operates as follows: As shown in Figure 2, the relief valve body 14 is lifted against the biasing force of the first biasing member 15, and the relief valve body 14 separates from the relief valve seat 13e. This opens the relief passage 25. As a result, the first port 2 is connected to the second port 3 via the relief passage 25. The working fluid from the first port 2 is then discharged to the second port 3 (see arrow Y1 in Figure 2). When the relief valve body 14 is lifted, the first biasing member 15 is compressed, causing the first spring housing space 12c to contract. As a result, the working fluid is discharged from the first spring housing space 12c to the valve space 12b via the connecting passage 13h. Since the connecting passage 13h constitutes a throttling mechanism, the relief valve body 14 is lifted gradually. Therefore, the relief passage 25 can be opened gradually, which suppresses the occurrence of hunting.

[0029] Furthermore, in the relief valve 1, the relief pressure described above can be adjusted as follows. Specifically, in the relief valve 1, the adjustment plug 22 moves forward and backward by loosening the lock nut 23. In this embodiment, the adjustment plug 22 moves forward and backward by rotating it using a jig. By moving the adjustment plug 22 forward and backward in this way, the amount of compression of the first biasing member 15 can be changed. As a result, the biasing force with which the first biasing member 15 biases the relief valve body 14 changes, and the relief pressure can be adjusted.

[0030] <Relief valve check operation> Furthermore, in the relief valve 1, the working fluid is guided from the second port 3 to the check passage 24, and the working fluid from the first port 2 is guided to the second spring housing space 16d via the relief passage 25. When the pressure at the first port 2 becomes lower than the pressure at the second port 3, the check valve body 16 operates as follows: That is, when the load on the check valve body 16 due to the differential pressure Δp becomes greater than the biasing force of the second biasing member 17, the check valve body 16 is lifted. As a result, the check valve body 16 separates from the check valve seat 21c. This opens the check passage 24. As a result, the second port 3 is connected to the first port 2 via the check passage 24. The working fluid from the second port 3 is then supplied to the first port 2 (see arrow Y2 in Figure 3).

[0031] <Effects of relief valves> In the relief valve 1 of this embodiment, the relief pressure, which is the pressure at which the relief valve body 14 begins to separate from the relief valve seat 13e, can be adjusted from the outside by moving the adjustment plug 22 forward and backward. Furthermore, in the relief valve 1 of this embodiment, the relief passage 25 is closed when the relief valve body 14 seats on the seat member 13 provided in the housing 12. Therefore, the two valve bodies 14 and 16, the relief valve body 14 and the check valve body 16, can each operate independently. That is, since the check valve body 16 can be operated independently, the responsiveness of the check valve body 16 can be improved compared to when the two valve bodies 14 and 16 move in conjunction. To explain in more detail, since the relief valve body 14 and the check valve body 16 operate independently, the weight of the parts that operate during check operation can be reduced. Therefore, the responsiveness of the check valve body 16 can be improved compared to when the two valve bodies 14 and 16 move in conjunction. In addition, in the relief valve 1, the check valve body 16 is slidably supported on the seat member 13. As a result, the seat member 13 functions as a guide for the check valve body 16, so that the increase in the number of parts can be suppressed.

[0032] In the relief valve 1 of this embodiment, the check valve body 16 is slidably supported by the seat member 13 at two sliding portions: an intermediate portion 16b and a large-diameter portion 16c. The second biasing member 17 is housed in a second spring housing space 16d formed between the intermediate portion 16b and the large-diameter portion 16c. Therefore, a compact relief valve 1 can be formed.

[0033] Furthermore, in the relief valve 1 of this embodiment, since the relief valve body 14 is a linear type valve body, the number of parts can be reduced compared to a differential type valve body. Moreover, in the relief valve 1 of this embodiment, the relief valve body 14, the first biasing member 15, the check valve body 16, and the second biasing member 17 are assembled in the housing 12. Therefore, the relief valve 1 can be made into a cartridge. This improves the portability of the relief valve 1 and the ease of assembly to the valve block 11.

[0034] [Second Embodiment] The relief valve 1A of the second embodiment has a similar configuration to the relief valve 1 of the first embodiment. Therefore, the configuration of the relief valve 1A of the second embodiment will mainly be described in terms of the differences from the relief valve 1 of the first embodiment, and identical components will be denoted by the same reference numerals and their description will be omitted. The same applies to the relief valve 1B of the third embodiment.

[0035] The relief valve 1A of the second embodiment shown in Figure 4 comprises a valve block 11A, a housing 12A, a seat member 13, a relief valve body 14, a first biasing member 15, a check valve body 16, and a second biasing member 17. The valve block 11A has a valve hole 11a, a first passage 11b, and a second passage 11c. A check valve seat 11d is formed around the first port 2 in the valve block 11A. The first port 2 and the second port 3 are connected by the valve hole 11a. The valve hole 11a also forms a check passage 24A.

[0036] Housing 12A is formed to be shorter in the axial direction than housing 12 of the first embodiment. More specifically, body 21A is formed to be shorter in the axial direction than body 21 of the first embodiment. Therefore, one end of body 21A is located on the other axial side from one end of body 21 of the first embodiment. Furthermore, one end portion of check valve body 16 protrudes from the opening 21a of body 21A. The check valve body 16 is seated on the check valve seat 11d of valve block 11A. Also, check valve body 16 is positioned with a gap between it and body 21A at the opening 21a. Therefore, the annular space 12d is connected to the second port 3 via the opening 21a.

[0037] In the relief valve 1A configured in this way, when the pressure at the first port 2 exceeds the relief pressure, the relief valve body 14 separates from the relief valve seat 13e, and the relief passage 25 opens. When the relief passage 25 opens, the first port 2 and the second port 3 are connected via the valve space 12b and the opening hole 21a. Then, the working fluid from the first port 2 is discharged to the second port 3. On the other hand, when the pressure at the first port 2 becomes less than the pressure at the second port 3, and the load on the check valve body 16 due to the differential pressure Δp becomes greater than the biasing force of the second biasing member 17, the check valve body 16 separates from the check valve seat 11d, and the check passage 24A opens. As a result, the first port 2 and the second port 3 are connected via the check passage 24A, and the working fluid from the second port 3 is supplied to the first port 2. The relief valve 1A of the second embodiment, configured in this manner, provides the same effects and advantages as the relief valve 1 of the first embodiment.

[0038] [Third Embodiment] The relief valve 1B of the third embodiment shown in Figure 5 comprises a valve block 11, a housing 12, a seat member 13, a relief valve body 14B, a first biasing member 15, a check valve body 16, a second biasing member 17, a rod 18, and a spring receiving member 19. The relief valve body 14B is a differential valve body having a back pressure chamber 27 through which the working fluid flowing through the relief passage 25 is guided. More specifically, the relief valve body 14B is formed in a bottomed cylindrical shape. The relief valve body 14B closes the relief passage 25 by seating its bottom (i.e., the tip portion 14a) on the relief valve seat 13e. The relief valve body 14B also has a through hole 14d formed along its axis (which coincides with the axis L1 in this embodiment). The through hole 14d faces the passage portion 13b of the relief passage 25. The rod 18 is inserted into the inner bore 14e of the relief valve body 14B in a sealed state. The tip of the rod 18 that is inserted into the inner bore 14e is positioned away from the bottom of the relief valve body 14B. As a result, a back pressure chamber 27 is formed in the inner bore 14e of the relief valve body 14. The back pressure chamber 27 is connected to the passage portion 13b of the relief passage 25 via the through hole 14d. Therefore, the pressure from the first port 2 is directed into the back pressure chamber 27. The base end of the rod 18 abuts against the ceiling surface of the adjustment plug 22. This prevents the rod 18 from coming out of the relief valve body 14. The spring receiving member 19 is inserted into the rod 18 and is in contact with the base end of the relief valve body 14B. The spring receiving member 19 receives one end of the first biasing member 15.

[0039] In the relief valve 1B configured in this way, the same relief operation and check operation as in the relief valve 1 of the first embodiment are performed, but the relief operation has the following function. The relief valve body 14B receives a load in the first closing direction from the working fluid guided from the first port 2 to the back pressure chamber 27 via the relief passage 25. Therefore, a portion of the load that the relief valve body 14B receives from the working fluid in the passage portion 13b is canceled. As a result of this cancellation, the load in the opening direction acting on the relief valve body 14B becomes a load obtained by multiplying the pressure at the first port 2 by the pressure at the first port 2 on the third pressure receiving area A3, which is obtained by subtracting the cross-sectional area of ​​the hole diameter D4 of the back pressure chamber 27 from the opening area of ​​the diameter D3 of the opening 13d. Therefore, the load in the opening direction acting on the relief valve body 14B can be kept small, and the seat diameter of the relief valve body 14 can be made larger compared to a direct-acting relief valve body. As a result, the relief valve 1 can handle a larger flow rate than the direct-acting relief valve 1.

[0040] Furthermore, the relief valve 1B of the third embodiment provides the same effects and functions as the relief valve 1 of the first embodiment.

[0041] [Other embodiments] In the relief valves 1, 1A, and 1B of the first to third embodiments, for example, the first port 2 is an actuator port and the second port 3 is a tank port, but the ports do not necessarily have to be in this manner. The check valve body 16 is externally fitted to the seat member 13, but it may also be internally fitted to the seat member 13. Furthermore, in the relief valves 1, 1A, and 1B of the first to third embodiments, each component 13 to 17 is housed in a housing 12 and formed into a cartridge, but it does not necessarily have to be formed into a cartridge. That is, each component 13 to 17 may be assembled to a housing 12 that is assembled to a valve block 11.

[0042] Furthermore, in the relief valves 1, 1A, and 1B of the first to third embodiments, the adjustment plug 22 moves forward and backward relative to the body 21 by rotation, but it may also be configured to move forward and backward by pushing and pulling the adjustment plug 22. Also, the adjustment member is not limited to the adjustment plug 22, but may be an adjustment screw. The adjustment screw can move forward and backward relative to the body 21 by rotation, similar to the adjustment plug 22. The relief pressure is adjusted by the movement of the adjustment screw. [Explanation of Symbols]

[0043] 1,1A,1B Relief valve 2. Port 1 3. Port 2 12,12A Housing 13 Sheet material 14,14B Relief valve body 14c Pressure receiving part 15 First biasing member 16. Valve body for checking 16a Communication path 16d Second spring housing space 17. Second biasing member 21, 21A Body 21d Communication path 22 Adjustment plug (adjustment component) 24,24A Check Passage 25 Relief aisle 27 Back pressure chamber

Claims

1. A relief valve with a check function that relieves hydraulic fluid from a first port to a second port, a housing having a body and an adjustment member provided on the body so as to be able to advance and retreat; a seat member provided in the body, the seat member having relief passages formed therein and connected to the first port and the second port, respectively; a relief valve element that opens and closes the relief passage by being seated on and released from the seat member and receives pressure from the first port in a direction that opens the relief passage; a first biasing member that biases the relief valve body against the pressure of the first port and whose biasing force is adjusted as the adjusting member advances and retreats; a check valve element that opens and closes check passages connected to the first port and the second port, respectively, and receives pressure from the second port in a direction that opens the check passages; a second biasing member that biases the check valve body against the pressure of the second port.

2. 2. The relief valve with check function according to claim 1, wherein the check valve element is slidably supported on the seat member.

3. the check valve element has a communication passage and is fitted onto the seat member; 3. The relief valve with check function according to claim 2, wherein the communication passage guides the working fluid flowing from the first port to the relief passage of the seat member when the check valve element closes the check passage.

4. the check valve element is slidably supported by the seat member at at least two sliding portions spaced apart from each other, 4. The relief valve with check function according to claim 3, wherein the second biasing member is housed between the two sliding portions in the check valve body.

5. 5. The relief valve with check function according to claim 1, wherein the relief valve element has a pressure-receiving portion that receives the pressure of the first port, and the pressure-receiving portion is a direct-acting type valve element made of a solid member.

6. 5. The relief valve with a check function according to claim 1, wherein the relief valve element is a differential type valve element having a back pressure chamber to which the working fluid flowing through the relief passage is guided.

7. 7. The relief valve with check function according to claim 1, wherein the relief valve body, the first biasing member, the check valve body, and the second biasing member are assembled to the housing.

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