JP2008256045A - Relief valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a relief valve capable of optionally setting relief pressure between high relief pressure and low relief pressure. <P>SOLUTION: This relief valve 1a can adjust the relief pressure between the high relief pressure and the low relief pressure by balance of force among a spool 3 pressed by a first pressing member 4, an inner piston 5 arranged inside of the spool 3, and a pushing and pressing portion 8a. The pushing and pressing portion 8a can push-press the first end portion 31 of the spool 3 independently from force applied to the inner piston 5 by pressure of fluid in a first passage 22 connected to a fluid pressure generating source 100 such as a hydraulic pump. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a relief valve.

2. Description of the Related Art Conventionally, an electromagnetic proportional pressure control valve that can adjust the pressure of a fluid in a fluid circuit by changing an input current value is widely known (see Patent Document 1).
JP 2003-185044 A

  There is a relief valve having a configuration in which a pilot pressure is once generated using the electromagnetic proportional pressure control valve as described above, and the relief pressure can be set and changed in two stages of a high pressure value and a low pressure value using this pilot pressure. . The structure of this relief valve is shown in FIGS. The relief valve includes a casing 2, a spool 3, a first biasing member 4, an internal piston 5, a low pressure piston 10, and an electromagnetic proportional pressure control valve 7.

  The casing 2 has a first flow path 22 communicating with a fluid pressure source 100 such as a hydraulic pump, a relief flow path 23, and a second flow path communicating with the first flow path 22 via the electromagnetic proportional pressure control valve 7. And a flow path 24 is formed. In the drawing, the flow paths are indicated by broken lines for convenience.

  The spool 3 is provided with a first internal space 33 that is provided by being recessed from the first end portion 31 on one end side toward the second end portion 32 on the other end side, and the first internal space 33 and the first flow path 22. And a first communication path 34 is formed. The spool 3 opens and closes between the first flow path 22 and the relief flow path 23 by moving in the axial direction.

  The first urging member 4 is provided so as to be able to press the second end 32 of the spool 3 and urges the spool 3 in a direction to close the space between the first flow path 22 and the relief flow path 23.

  The internal piston 5 is arranged in the first internal space 33 on the first end portion 31 side, and on the second end portion 32 side in the axial direction with the first piston portion 51. And a second urging member 53 provided between the first piston portion 51 and the second piston portion 52. Further, in the internal piston 5, a second internal space 55 that communicates with the first internal space 33 through the second communication path 54 provided in the second piston portion 52 and has a smaller diameter than the first internal space 33 is provided. It is formed between the first piston part 51 and the second piston part 52.

  The low pressure piston 10 has the same outer diameter as the spool 3 and faces the first end 31 of the spool 3 and the internal piston 5. The low pressure piston 10 is provided so as to be movable in the axial direction, and the space S10 located on the opposite side of the spool 3 with respect to the low pressure piston 10 is filled with the fluid in the second flow path 24, whereby the spool 3 The first end 31 and the internal piston 5 can be pressed (see arrow A1 in FIG. 7).

  The electromagnetic proportional pressure control valve 7 can depressurize the fluid flowing through the first flow path 22 in accordance with an input command signal and send it to the second flow path 24.

  In this relief valve, the relief pressure can be switched between a high relief pressure and a low relief pressure by controlling a command signal input to the electromagnetic proportional pressure control valve 7.

  First, in a state where a command signal is not input to the electromagnetic proportional pressure control valve 7, the force of the fluid in the first flow path 22 filled in the second internal space 55 pushing the spool 3 through the second piston portion 52 ( 6 (see arrow A2 in FIG. 6) and the biasing force (see arrow A3 in FIG. 6) applied from the first biasing member 4 to the spool 3 are balanced. When the pressure of the fluid in the first flow path 22 increases, the spool 3 moves to the left in the figure against the biasing force A3 of the first biasing member 4. When the pressure of the fluid in the first flow path 22 reaches a predetermined pressure value (high relief pressure), the spool 3 opens between the first flow path 22 and the relief flow path 23 (hereinafter “ This is called a “relief state”), and the fluid is relieved.

  Next, when a command signal is input to the electromagnetic proportional pressure control valve 7 and fluid is sent from the first flow path 22 to the second flow path 24, the pressure of the fluid in the second flow path 24 acts on the low pressure piston 10. . The force acting on the low pressure piston 10 by the pressure of the fluid in the second flow path 24 acts on the internal piston 5 by the force applied to the low pressure piston 10 from the first piston portion 51, that is, the pressure of the fluid in the first flow path 22. When the force is larger than the force to be applied, the low pressure piston 10 presses the first end portion 31 of the spool 3 together with the internal piston 5 as shown by an arrow A1 in FIG. For this reason, the position of the spool 3 is determined by a balance between the force acting on the low pressure piston 10 by the pressure of the fluid in the second flow path 24 and the biasing force of the first biasing member 4. And when the pressure of the fluid of the 1st flow path 22 reaches a predetermined relief pressure, the spool 3 will be in a relief state. Here, since the diameter of the low pressure piston 10 is larger than the diameter of the second internal space 55, the relief pressure in this case is lower than the high relief pressure PH. At this time, the pressure of the fluid in the second flow path 24 is maximum, that is, the same as the pressure of the fluid in the first flow path 22, and the relief pressure becomes the low relief pressure PL.

  However, in this relief valve, the force applied to the low pressure piston 10 from the first piston portion 51, that is, the force acting on the low pressure piston 10 from the internal piston 5 due to the pressure of the fluid in the first flow path 22 is the second flow path. When the pressure acting on the low-pressure piston 10 by the pressure of the fluid 24, that is, when the low-pressure piston 10 is greater than the force A1 pushing the internal piston 5, no command signal is input to the electromagnetic proportional pressure control valve 7 shown in FIG. Similarly to the state, the fluid in the first flow path 22 filled in the second internal space 55 is applied to the spool 3 from the first biasing member 4 with the force A2 pushing the spool 3 through the second piston portion 52. The position of the spool 3 is determined by the balance with the urging force A3. Therefore, until the force acting on the low pressure piston 10 due to the fluid pressure in the second flow path 24 reaches the force acting on the low pressure piston 10 from the internal piston 5 due to the fluid pressure in the first flow path 22, the electromagnetic proportional pressure Even if the command signal input to the control valve 7 changes (see the broken line L3 in FIG. 8), the relief pressure remains constant at the high relief pressure PH (see the solid line L1 in FIG. 8). When the force acting on the low pressure piston 10 due to the fluid pressure in the second flow path 24 reaches the force acting on the low pressure piston 10 from the internal piston 5 due to the fluid pressure in the first flow path 22, the relief pressure becomes low. It changes to the relief pressure PL and becomes constant (see the solid line L2 in FIG. 8). Therefore, it is difficult to arbitrarily set the relief pressure at a value between the high relief pressure and the low relief pressure.

  An object of the present invention is to provide a relief valve that can arbitrarily set a relief pressure between a high relief pressure and a low relief pressure.

  A relief valve according to a first invention includes a casing, a spool, a first urging member, an internal piston, an electromagnetic proportional pressure control valve, and a pressing portion. The casing is formed with a first flow path connected to the fluid pressure generation source, a relief flow path, and a second flow path communicating with the first flow path. In the spool, a first internal space that is provided by being recessed from the first end portion on one end side toward the second end portion on the other end side, and the first internal space communicates with the first internal space and the first flow path. A communication path is formed. The spool opens and closes between the first flow path and the relief flow path. The first urging member is provided so as to be able to press the second end portion of the spool, and urges the spool in a direction to close between the first flow path and the relief flow path. The internal piston has a first piston part, a second piston part, and a second urging member. The first piston portion is disposed on the first end side in the first internal space. The second piston portion is arranged on the second end side along with the first piston portion in the axial direction. The second urging member is provided between the first piston part and the second piston part. In the internal piston, the second internal space communicating with the first internal space via the second communication path provided in the second piston portion and having a smaller diameter than the first internal space is the first piston portion and the second piston. It is formed between the parts. The electromagnetic proportional pressure control valve opens and closes between the first flow path and the second flow path in response to an input command signal, and depressurizes the fluid flowing through the first flow path and sends it to the second flow path. it can. And a press part can press the 1st end part of a spool using the pressure of the fluid of a 2nd flow path independently of the force which acts on an internal piston with the pressure of the fluid of a 1st flow path.

  In this relief valve, the pressing portion uses the pressure of the fluid in the second flow path regardless of the balance between the force due to the pressure of the fluid in the first flow path and the force due to the pressure of the fluid in the second flow path. The first end can be pressed. For this reason, the relief pressure can be arbitrarily set between the high relief pressure and the low relief pressure by adjusting the pressure of the fluid in the second flow path.

  A relief valve according to a second aspect of the present invention is the relief valve according to the first aspect of the present invention, wherein the pressing portion has a third communication path that communicates the space on the first end side of the spool and the second flow path.

  In this relief valve, the fluid in the second flow path is filled into the space on the first end portion side of the spool through the third communication path. The fluid filled in the space on the first end portion side of the spool presses the first end portion of the spool and the internal piston. In this case, the fluid does not press the first end portion and the internal piston integrally as in the conventional low pressure piston 10, but presses the first end portion and the internal piston so that they can move relative to each other. it can. For this reason, a press part can press the 1st end part of a spool independently of the force which acts on an internal piston with the pressure of the fluid of a 1st flow path.

  A relief valve according to a third aspect is the relief valve according to the first aspect, wherein the pressing portion is provided in a cylindrical portion facing the internal piston, and in a tubular space provided on the outer periphery of the cylindrical portion and communicating with the second flow path. And a pressing member which is provided so as to be movable in the axial direction and presses only the first end of the spool by being pressed by the pressure of the fluid in the second flow path.

  In this relief valve, the force due to the pressure of the fluid in the second flow path is transmitted to the first end of the spool via the pressing member. The pressing member can press only the first end of the spool without pressing the internal piston. For this reason, a press part can press the 1st end part of a spool independently of the force which acts on an internal piston with the pressure of the fluid of a 1st flow path.

  A relief valve according to a fourth aspect of the present invention is the relief valve according to the third aspect, wherein the casing has a cylindrical shape having an outer diameter larger than that of the cylindrical portion of the pressing portion and communicates with the second flow path. Yes. The cylindrical portion is a separate body from the casing, and is arranged coaxially in the hole of the casing, thereby constituting the circular tubular space.

  In this relief valve, the cylindrical part of the pressing part is separate from the casing, and is arranged coaxially in the hole of the casing, thereby forming a tubular space in which the pressing member is arranged. For this reason, a press part can be manufactured by making a hole in the casing and disposing the cylindrical part and the press member in the hole. Therefore, this relief valve is easy to manufacture.

  In the relief valve according to the present invention, the pressing portion uses the pressure of the fluid in the second channel regardless of the balance between the force due to the pressure of the fluid in the first channel and the force due to the pressure of the fluid in the second channel. Thus, the first end of the spool can be pressed. For this reason, the relief pressure can be arbitrarily set between the high relief pressure and the low relief pressure by adjusting the pressure of the fluid in the second flow path.

<First Embodiment>
〔Constitution〕
A relief valve 1a according to a first embodiment of the present invention is shown in FIG. The relief valve 1a includes a casing 2, a spool 3, a first biasing member 4, an internal piston 5, an electromagnetic proportional pressure control valve 7, and a pressing portion 8a.

  In the casing 2, a first flow path 22 connected to a fluid pressure generation source 100 such as a hydraulic pump, a relief flow path 23 through which fluid flows out, a second flow path 24 communicating with the first flow path 22, Is formed. A filter 29 is provided in the middle of the first flow path 22. Further, the casing 2 is formed with a spool storage space S1 in which the spool 3 is stored, and a third communication path 81 that connects the spool storage space S1 and the second flow path 24. The casing 2 is divided into a first casing portion 2a in which the spool storage space S1 is formed and a second casing portion 2b in which the third communication path 81 is formed, and the first casing portion 2a and the second casing portion 2b. The joint with the casing portion 2b is sealed by a plurality of seal members 25 such as an O-ring. In the figure, only a part of the seal members 25 are not shown and the others are omitted.

  The spool 3 is disposed in the spool storage space S1 and can move in the axial direction in the spool storage space S1. The spool 3 opens and closes between the first flow path 22 and the relief flow path 23 by moving in the axial direction. Specifically, by moving to the left in the figure and moving to a predetermined relief position, a relief state is established in which the first flow path 22 and the relief flow path 23 are opened. Further, by moving from the relief position to the right side in the figure, the closed state in which the space between the first flow path 22 and the relief flow path 23 is closed is obtained. A first internal space 33 and a first communication path 34 are formed in the spool 3. The first internal space 33 is provided so as to be recessed from the first end portion 31 on one end side toward the second end portion 32 side on the other end side, and has a cylindrical shape corresponding to the shape of the internal piston 5. is doing. The first communication path 34 is formed from the side surface of the spool 3 to the bottom surface of the concave portion constituting the first internal space 33, and communicates the first internal space 33 and the first flow path 22.

  The first urging member 4 is a spring that urges the spool 3 in a direction to close the space between the first flow path 22 and the relief flow path 23. The first biasing member 4 is provided in the spool housing space S <b> 1 of the casing 2 together with the spool 3, one end being fixed to the casing 2, and the other end being fixed to the second end portion 32 of the spool 3. Thereby, the first biasing member 4 can press the second end portion 32 of the spool 3.

  The internal piston 5 is housed in the first internal space 33 of the spool 3 and is movable in the axial direction. The internal piston 5 has a first piston part 51, a second piston part 52, and a second urging member 53.

  The first piston portion 51 is disposed in the first inner space 33 closer to the first end portion 31 than the second piston portion 52. One end of the first piston portion 51 faces the third communication passage 81 and has a tapered shape with a taper formed at the edge thereof. The other end of the first piston portion 51 is provided with a recess 56 that is recessed in the axial direction.

  The second piston part 52 is arranged on the second end part 32 side of the first piston part 51 side by side with the first piston part 51 in the axial direction. A concave portion 57 that is recessed in the axial direction is formed at one end of the second piston portion 52 that faces the first piston portion 51. In addition, the other end of the second piston portion 52 faces the first communication path 34. The concave portion 57 of the second piston portion 52 and the concave portion 56 of the first piston portion 51 constitute a second internal space 55. The second internal space 55 is formed between the first piston portion 51 and the second piston portion 52 and, of course, has a smaller diameter than the first internal space 33. The second piston portion 52 is formed with a second communication passage 54 along the axial direction. The second communication path 54 communicates the second internal space 55 with the space S2 located on the second end 32 side of the spool 3 with respect to the internal piston 5 in the first internal space 33.

  The second urging member 53 is provided between the first piston part 51 and the second piston part 52, and generates a reaction force between the first piston part 51 and the second piston part 52. The second urging member 53 is accommodated in the second internal space.

  The electromagnetic proportional pressure control valve 7 is a ball poppet valve that can adjust the pressure of the fluid by changing the opening of a ball poppet (not shown) according to the solenoid current, and according to an input command signal. Thus, the pressure of the fluid in the second flow path 24 can be adjusted. The electromagnetic proportional pressure control valve 7 controls the opening degree of the ball poppet so that the fluid pressure in the second flow path 24 increases as the current value of the command signal increases (see the broken line L6 in FIG. 3).

  The pressing portion 8a has the above-described third communication passage 81, and the fluid in the second flow path 24 is part of the spool storage space S1 on the first end portion 31 side of the spool 3 through the third communication passage 81. Can be filled. For this reason, the pressing portion 8a uses the pressure of the fluid in the second flow path 24, and independently of the force A4 acting on the internal piston 5 by the pressure of the fluid in the first flow path 22, the first end of the spool 3. The part 31 can be pressed.

[Relief pressure setting]
Next, the setting of the relief pressure by the relief valve 1a will be described.

  First, in a state where no command signal is input to the electromagnetic proportional pressure control valve 7, the same action as that of the conventional relief valve 1a occurs, and the relief pressure becomes a high relief pressure PH (see FIG. 3). The graph of FIG. 3 shows the relationship between the command value to the electromagnetic proportional pressure control valve 7 and the relief pressure, and the relationship between the command value to the electromagnetic proportional pressure control valve 7 and the fluid pressure in the second flow path. Yes. Here, as shown in FIG. 1, the fluid in the first flow path 22 filled in the second internal space 55 pushes the spool 3 via the second piston portion 52, and the first urging member 4 The urging force A3 applied to the spool 3 is balanced. When the pressure of the fluid in the first flow path 22 increases, the spool 3 moves to the left in the figure against the biasing force A3 of the first biasing member 4. Then, when the pressure of the fluid in the first flow path 22 reaches the high relief pressure PH, the spool 3 enters the relief state, and the fluid is relieved. That is, the high relief pressure PH is such that the urging force A3 of the first urging member 4 when the spool 3 is in the relief position and the fluid in the first flow path 22 filled in the second internal space 55 are the second piston. This is the pressure of the fluid in the first flow path 22 when the force A2 pushing the spool 3 through the portion 52 is balanced.

  Next, when a command signal is input to the electromagnetic proportional pressure control valve 7 and fluid is sent from the first flow path 22 to the second flow path 24, the spool storage space passes through the third communication path 81 of the pressing portion 8 a. A portion of S1 located on the first end 31 side with respect to the spool 3 is filled with the fluid in the second flow path 24. This fluid can press the first end 31 of the spool 3 and the internal piston 5 so as to be able to move relative to each other (see arrows A5 and A6 in FIG. 2). For this reason, as shown in FIG. 2, the pressing portion 8 a uses the pressure of the fluid in the second flow path 24 and is independent of the force A4 acting on the internal piston 5 by the pressure of the fluid in the first flow path 22. The first end 31 of the spool 3 can be pressed. Then, the force A6 acting on the first end portion 31 of the spool 3 by the pressure of the fluid in the second flow path 24, and the fluid in the first flow path 22 filled in the second internal space 55 enter the second piston section 52. Thus, the resultant force with the force A2 pushing the spool 3 via the first biasing member 4 and the biasing force A3 applied to the spool 3 are balanced. The force A6 acting on the first end portion 31 of the spool 3 by the pressure of the fluid in the second flow path 24 can be changed by changing the command signal to the electromagnetic proportional pressure control valve 7, thereby The relief pressure can be arbitrarily set as indicated by a solid line L4. When the pressure of the fluid in the second flow path 24 becomes maximum, that is, when the pressure of the fluid in the second flow path 24 becomes the same as the pressure of the fluid in the first flow path 22, the relief valve 1a Is the lowest relief pressure (low relief pressure PL) (see solid line L5 in FIG. 3).

〔Characteristic〕
In the relief valve 1a, the relief pressure is increased by a balance of forces between the spool 3 biased by the first biasing member 4, the internal piston 5 provided inside the spool 3, and the pressing portion 8a. It can be adjusted between pressure and low relief pressure. Here, the pressing portion 8a can press the first end 31 of the spool 3 independently of the force acting on the internal piston 5 by the pressure of the fluid in the first flow path 22, and the pressing force is electromagnetic It can be arbitrarily set by adjusting the pressure of the fluid in the second flow path 24 by the proportional pressure control valve 7. For this reason, the relief pressure can be arbitrarily set between the high relief pressure PH and the low relief pressure PL by changing the command signal to the electromagnetic proportional pressure control valve 7 as described above.

Second Embodiment
A relief valve 1b according to a second embodiment of the present invention is shown in FIG. In this relief valve 1b, it replaces with the press part 8a of the relief valve 1a concerning 1st Embodiment, and the press part 8b is provided. The pressing portion 8 b includes a cylindrical portion 82 and a pressing member 83.

  The cylindrical portion 82 is a portion formed at the center portion of the second casing portion 2b by forming a circular hole 28 therein. The cylindrical portion 82 faces the internal piston 5, and a circular tubular space S <b> 3 constituted by the circular tubular hole 28 is formed on the outer periphery thereof. The tubular space S3 communicates with the second flow path 24. Further, the outer diameter of the cylindrical portion 82 is substantially the same as the inner diameter of the first inner space 33 and the outer diameter of the inner piston 5.

  The pressing member 83 is provided so as to be movable in the axial direction in the tubular space S3. The second flow path 24 communicates with the space on the opposite side of the spool 3 from the pressing member 83 in the tubular space S3. The pressing member 83 is pressed in the direction toward the spool 3 by the pressure of the fluid in the second flow path 24 by filling the space with the fluid from the second flow path 24 (see arrow A7 in the figure). . The pressing member 83 has a tubular shape having an inner diameter and an outer diameter substantially similar to the first end portion 31 of the spool 3, and the first end of the spool 3 is caused by the pressure of the fluid in the second flow path 24. Only the part 31 can be pressed.

  As described in the first embodiment, since the end of the first piston portion 51 has a tapered shape, the inner diameter of the pressing member 83 is the inner diameter of the first end 31 of the spool 3, that is, Even if it is slightly smaller than the diameter of the first internal space 33, it is possible to press only the first end portion 31 of the spool 3 without contacting the first piston portion 51.

  About another structure and the setting of relief pressure, it is the same as that of the relief valve 1a concerning 1st Embodiment.

  Even with the relief valve 1b as described above, the same effects as those of the relief valve 1a according to the first embodiment can be obtained.

<Third Embodiment>
A relief valve 1c according to a third embodiment of the present invention is shown in FIG. In the relief valve 1c, a pressing portion 8c is provided instead of the pressing portion 8a of the relief valve 1a according to the first embodiment. The casing 2 is formed with a hole 27 having a cylindrical shape and communicating with the second flow path 24. The hole 27 is substantially the same as the outer diameter of the first end portion 31 of the spool 3 and has a diameter larger than the outer diameter of a cylindrical portion 84 of the pressing portion 8c described later. The pressing portion 8 c has a cylindrical portion 84 and a pressing member 85.

  The cylindrical portion 84 is separate from the casing 2, and has an outer diameter that is smaller than the hole of the casing 2 and smaller than the outer diameter of the internal piston 5. The cylindrical portion 84 is disposed coaxially with the central axis of the hole 27 inside the hole 27 of the casing 2. Thereby, between the outer peripheral surface of the cylindrical part 84 and the inner peripheral surface of the hole 27, the space S4 similar to the circular tubular space S3 of the relief valve 1b according to the second embodiment is configured. Since the outer diameter of the cylindrical portion 84 and the diameter of the hole 27 are determined by the lower limit value of the pressure to be adjusted, the lower limit value of the pressure to be adjusted can be set by adjusting these diameters.

  The pressing member 85 is the same as the pressing member 83 of the relief valve 1b according to the second embodiment.

  About another structure and the setting of relief pressure, it is the same as that of the relief valve 1a concerning 1st Embodiment.

  The relief valve 1c can achieve the same effects as the relief valve 1a according to the above embodiment. In the relief valve 1c, the cylindrical portion 27 is formed in the casing 2, and the cylindrical portion 84 and the pressing member 85 are disposed in the hole 27, whereby the pressing portion 8c can be easily manufactured.

  The present invention can arbitrarily set the relief pressure between a high relief pressure and a low relief pressure, and is useful as a relief valve.

Sectional drawing which shows the structure of the relief valve concerning 1st Embodiment. Sectional drawing which shows the structure of the relief valve concerning 1st Embodiment. The figure which shows the relationship between the command value and relief pressure to an electromagnetic proportional pressure control valve. Sectional drawing which shows the structure of the relief valve concerning 2nd Embodiment. Sectional drawing which shows the structure of the relief valve concerning 3rd Embodiment. Sectional drawing which shows the structure of the conventional relief valve. Sectional drawing which shows the structure of the conventional relief valve. The figure which shows the relationship between the command value to the electromagnetic proportional pressure control valve in a conventional relief valve, and relief pressure.

Explanation of symbols

1a-1c Relief valve 2 Casing 3 Spool 4 First urging member 5 Internal piston 7 Electromagnetic proportional pressure control valve 8a-8c Pressing portion 22 First flow path 23 Relief flow path 24 Second flow path 33 First internal space 34 First 1 communication path 51 1st piston part 52 2nd piston part 53 2nd biasing member 55 2nd internal space 81 3rd communication path 82, 84 Cylindrical part 83,85 Pressing member

Claims (4)

A casing formed with a first flow path connected to the fluid pressure generating source, a relief flow path, and a second flow path communicating with the first flow path;
A first internal passage that is provided by being recessed from the first end portion on one end side toward the second end portion on the other end side, and communicates the first internal space and the first flow path. A spool that opens and closes between the first flow path and the relief flow path;
A first urging member that is provided so as to be able to press the second end of the spool and urges the spool in a direction to close the space between the first flow path and the relief flow path;
A first piston portion disposed on the first end portion side in the first internal space; a second piston portion disposed on the second end portion side by side in the axial direction with the first piston portion; A second biasing member provided between the first piston part and the second piston part, and communicates with the first internal space via a second communication path provided in the second piston part. And an internal piston in which a second internal space having a smaller diameter than the first internal space is formed between the first piston portion and the second piston portion;
Electromagnetic proportionality that opens and closes between the first flow path and the second flow path in accordance with an input command signal and depressurizes the fluid flowing through the first flow path and sends it to the second flow path. A pressure control valve;
A pressing part capable of pressing the first end of the spool using the pressure of the fluid in the second flow path independently of the force acting on the internal piston by the pressure of the fluid in the first flow path;
Relief valve equipped with. The pressing portion includes a third communication path that communicates the space on the first end side of the spool and the second flow path.
The relief valve according to claim 1. The pressing portion is provided so as to be movable in the axial direction in a cylindrical portion facing the internal piston, and in a cylindrical space provided on an outer periphery of the cylindrical portion and communicating with the second flow path. A pressing member that presses only the first end of the spool by being pressed by the pressure of the fluid,
The relief valve according to claim 1. The casing has a cylindrical shape having an outer diameter larger than that of the cylindrical portion, and a hole communicating with the second flow path is formed.
The cylindrical portion is separate from the casing, and is arranged coaxially in the hole of the casing to constitute the circular space.
The relief valve according to claim 3.

Images