Relief valve
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-02-10
- Publication Date
- 2026-08-13
Smart Images
Figure JP2025004385_13082026_PF_FP_ABST
Abstract
Description
Relief valve
[0001] The present disclosure relates to a relief valve.
[0002] For example, the pressure reducing valve of Patent Document 1 has a relief valve. The pressure reducing valve is provided in the middle of a fluid circuit connecting the hydrogen tank and the fuel cell of a fuel cell vehicle. The pressure reducing valve reduces high-pressure hydrogen gas and sends the reduced-pressure hydrogen gas to the fuel cell. When the pressure at the output port of the pressure reducing valve exceeds a predetermined pressure, the relief valve opens. That is, the piston moves in the valve-opening direction against the elastic force of the spring due to the pressure at the output port, and the valve body of the piston separates from the valve seat. Hydrogen gas passes between the valve seat and the valve body and is discharged to the outside.
[0003] Japanese Patent Application Laid-Open No. 2019-185584
[0004] The relief valve of Patent Document 1 has the following concerns. That is, when the pressure at the output port of the pressure reducing valve is below a predetermined pressure, the piston is pressed in the valve-closing direction by the elastic force of the spring, and the valve body maintains a state of being pressed against the valve seat. The spring load is set to a magnitude necessary to keep the relief valve closed against high-pressure hydrogen gas. Therefore, depending on the usage situation of the pressure reducing valve, a large spring load is applied to the valve body, and the valve body may be damaged.
[0005] The relief valve according to one aspect of the present disclosure includes a housing, a piston, a biasing member, and a guide passage. The housing is a cylindrical body having a circular cross-sectional shape. The housing includes a peripheral wall having an output port for gas, a first end wall provided at a first end of the peripheral wall and having an input port for gas and a valve seat surrounding the input port, and a second end wall provided at a second end of the peripheral wall. The piston is axially slidably accommodated inside the housing. The piston has a valve body configured to open and close the input port by axially contacting or separating from the valve seat. The biasing member is disposed between the piston and the second end wall. The biasing member is configured to constantly bias the piston in the valve-closing direction. The guide passage is configured to guide the gas flowing into the input port so as to reduce the force in the valve-opening direction acting on the piston.
[0006] Figure 1 is a front view of a valve device in which a relief valve according to the first embodiment is provided. Figure 2 is a cross-sectional view of the relief valve of Figure 1, cut in the axial direction. Figure 3 is a cross-sectional view of the relief valve according to the second embodiment, cut in the axial direction. Figure 4 is a cross-sectional view of the relief valve according to the third embodiment, cut in the axial direction.
[0007] <First Embodiment> The relief valve 1 according to the first embodiment will now be described. As shown in Figure 1, the relief valve 1 is installed, for example, in the valve device 2 of a hydrogen vehicle. A hydrogen vehicle is a vehicle that uses hydrogen as energy, and is either a hydrogen engine vehicle or a hydrogen fuel cell vehicle. The valve device 2 is installed in the middle of the piping that connects the gas tank 3 in which hydrogen gas is stored and the consuming equipment 4 that consumes hydrogen. The consuming equipment 4 is either a hydrogen engine or a hydrogen fuel cell.
[0008] The valve device 2 includes a relief valve 1, a body 5, and a pressure reducing valve 6. The body 5 is a cylindrical body having a rectangular or circular cross-sectional shape and has a primary port 5A and a secondary port 5B. The primary port 5A is the inlet for hydrogen gas. The primary port 5A extends axially from the body 5 and opens at the first end of the body 5. The secondary port 5B is the outlet for hydrogen gas and opens at a suitable location on the body 5.
[0009] The pressure reducing valve 6 is built into the body 5 near the second end. The second end is the end of the body 5 opposite to the first end. The pressure reducing valve 6 is connected to the primary port 5A and the secondary port 5B. The primary port 5A and the secondary port 5B are gas passages through which hydrogen gas flows. The pressure reducing valve 6 reduces the pressure of the hydrogen gas supplied from the gas tank 3 via the primary port 5A to below the set pressure. The pressure reducing valve 6 supplies the reduced pressure hydrogen gas to the consumer device 4 via the secondary port 5B.
[0010] The primary pressure is the pressure of the hydrogen gas supplied through the primary port 5A. If the consuming device 4 is a hydrogen engine or a hydrogen fuel cell, the primary pressure is high, for example, around 70.0 MPa. The secondary pressure is the pressure reduced by the pressure reducing valve 6, i.e., the pressure of the hydrogen gas supplied to the consuming device 4. The secondary pressure is set appropriately according to the specifications of the consuming device 4.
[0011] The relief valve 1 is attached to the side wall of the body 5. The side wall has a relief valve mounting portion 5C. The relief valve mounting portion 5C is a cylindrical body with a circular cross-sectional shape and protrudes radially outward from the outer circumferential surface of the body 5. The relief valve 1 is a cylindrical body with a circular cross-sectional shape. The first end of the relief valve 1 is screwed into the relief valve mounting portion 5C. The second end of the relief valve 1 is exposed to the outside of the relief valve mounting portion 5C. The second end is the end of the relief valve 1 opposite to the first end.
[0012] The relief valve 1 is connected to the secondary port 5B via a communication passage 5D. The communication passage 5D is a gas flow path provided inside the body 5. Secondary pressure is applied to the relief valve 1 via the communication passage 5D. When the secondary pressure reaches an excessive pressure exceeding the set pressure set for the relief valve 1, the relief valve 1 automatically releases the secondary pressure to the outside. The outside is, for example, the atmosphere. In other words, the relief valve 1 suppresses the rise in secondary pressure by releasing a portion of the hydrogen gas flowing inside the secondary port 5B to the outside. The secondary pressure is kept below the set pressure of the relief valve 1.
[0013] <Configuration of Relief Valve 1> Next, the configuration of the relief valve 1 will be described. As shown in Figure 2, the relief valve 1 has a housing 11, a piston 12, a pressure regulating member 13, and a compression coil spring 14.
[0014] The housing 11 is a cylindrical metal body with a circular cross-sectional shape and has an input port 11A, an output port 11B, and a valve seat 11C. The input port 11A is provided on the first end wall of the housing 11. The first end wall is a wall that closes the first end of the housing 11 and has a circular cross-sectional shape. The input port 11A penetrates the first end wall in the axial direction of the housing 11. The output port 11B is provided on the peripheral wall of the housing 11, near the first end wall. The output port 11B penetrates the peripheral wall of the housing 11 in the radial direction. The valve seat 11C is provided on the inner surface of the first end wall of the housing 11. The valve seat 11C is a cylindrical body with a circular cross-sectional shape and surrounds the input port 11A. The inner diameter of the valve seat 11C is the same as the inner diameter of the input port 11A. The inner circumferential surface of the valve seat 11C is flush with the inner circumferential surface of the input port 11A.
[0015] The second end of the housing 11 is open to the outside. The second end is the end opposite to the first end of the housing 11. The inner circumferential surface of the housing 11 has a female threaded portion 11D. The female threaded portion 11D is provided on the inner circumferential surface of the housing 11 in a predetermined region in the axial direction of the housing 11. The female threaded portion 11D is located near the second end of the housing 11. The first and second ends of the housing 11 are also the first and second ends of the circumferential wall of the housing 11.
[0016] The piston 12 is housed inside the housing 11. The piston 12 is a cylindrical metal body with a circular cross-section. The first end of the piston 12 is closed by an end wall. The second end of the piston 12 is open to the outside. The second end is the end of the piston 12 opposite to the first end. The outer diameter of the piston 12 is about the same as, or slightly smaller than, the inner diameter of the part of the housing 11 closest to the first end. The outer circumferential surface of the piston 12 is axially slidable relative to the inner circumferential surface of the housing 11.
[0017] The piston 12 has a valve body 12A. The valve body 12A is a plate-shaped body with a circular cross-section and is fitted onto the first end of the piston 12. The valve body 12A is made of, for example, resin or rubber. The outer diameter of the valve body 12A is larger than the outer diameter of the valve seat 11C. The valve body 12A is arranged coaxially with the valve seat 11C. The valve body 12A can contact and separate from the valve seat 11C in the axial direction of the housing 11. That is, the valve body 12 opens and closes the input port 11A by contacting or separating from the seat 11C in the axial direction.
[0018] The piston 12 has a fitting projection 12B. The fitting projection 12B is a cylindrical body with a circular cross-sectional shape and is provided on the inner surface of the end wall of the piston 12. The fitting projection 12B is arranged coaxially with the valve body 11C. The tip of the fitting projection 12B does not protrude axially from the second end of the piston 12, but is located inside the piston 12. The tip is the end of the fitting shaft portion 12B opposite to the end wall of the piston 12.
[0019] The fitting projection 12B has a first sealing member 12C. The first sealing member 12C is a rubber annular body, for example, a packing having a Y-shaped cross-section. The first sealing member 12C is fitted into a groove provided on the outer circumferential surface of the fitting projection 12B. The groove has a rectangular cross-section and is provided around the entire circumference of the outer circumferential surface of the fitting projection 12B.
[0020] The piston 12 has a through hole 12D. The through hole 12D penetrates the piston 12, more specifically the valve body 12A and the fitting projection 12B in the axial direction. The through hole 12D is coaxially positioned with the valve body 12A and the fitting projection 12B. The through hole 12D is a gas passage through which hydrogen gas flows.
[0021] The area S1 of the tip surface of the fitting projection 12B is smaller than the area S2 of the portion of the piston 12 that is exposed to the inside of the valve seat 11C. The tip surface of the fitting projection 12B is the end surface of the fitting projection 12B on the side opposite to the valve body 12A. The area S2 of the portion of the piston 12 that is exposed to the inside of the valve seat 11C is basically the same as the cross-sectional area of the internal space of the valve seat 12 when the valve seat 11C is cut by a plane perpendicular to the axial direction of the piston 12.
[0022] The pressure regulating member 13 is a cylindrical metal body with a circular cross-sectional shape. The first end of the pressure regulating member 13 is open to the outside. The second end of the pressure regulating member 13 is closed by an end wall. The second end is the end of the pressure regulating member 13 opposite to the first end.
[0023] The pressure regulating member 13 has a male threaded portion 13A. The male threaded portion 13A is provided on the outer circumferential surface of the first end of the pressure regulating member 13. The male threaded portion 13A is screwed into the female threaded portion 11D of the housing 11. By rotating the pressure regulating member 13, it is possible to move the pressure regulating member 13 forward and backward in the axial direction of the housing 11. The pressure regulating member 13 also serves as a second end wall that closes the second end of the housing 11.
[0024] The second end of the pressure regulating member 13 is exposed to the outside of the housing 11. A lock nut 15 is screwed onto the second end of the pressure regulating member 13 that is exposed to the outside of the housing 11. The lock nut 15 prevents the pressure regulating member 13 from loosening, for example. The axial position of the pressure regulating member 13 is maintained by the lock nut 15.
[0025] The pressure regulating member 13 has a second sealing member 13B. The second sealing member 13B is a rubber annular body, for example, an O-ring with a circular cross-sectional shape. The second sealing member 13B is fitted into a groove provided on the outer circumferential surface of the fitting projection 12B. The groove has a rectangular cross-sectional shape and is provided around the entire circumference of the outer circumferential surface of the fitting projection 12B. In the axial direction of the pressure regulating member 13, the second sealing member 13B is positioned closer to the second end of the pressure regulating member 13 than the male threaded portion 13A. The second sealing member 13B ensures airtightness between the outer circumferential surface of the pressure regulating member 13 and the inner circumferential surface of the housing 11.
[0026] The pressure regulating member 13 has a support shaft portion 13C. The support shaft portion 13C is a columnar body having a circular cross-sectional shape and is provided on the inner surface of the end wall of the pressure regulating member 13. The support shaft portion 13C is arranged coaxially with the fitting projection 12B. The tip of the support shaft portion 13C protrudes axially from the first end of the pressure regulating member 13 and is located inside the piston 12. The tip is the end of the support shaft portion 13C opposite to the end wall of the pressure regulating member 13.
[0027] The support shaft portion 13C has a fitting recess 13D. The fitting recess 13D is a recess with a circular cross-sectional shape and opens to the tip surface of the support shaft portion 13C. The fitting recess 13D is arranged coaxially with the fitting projection 12B of the piston 12. The tip of the fitting projection 12B is fitted into the fitting recess 13D. The outer circumferential surface of the fitting projection 12B is slidable in the axial direction relative to the inner circumferential surface of the fitting recess 13D. The first sealing member 12C ensures airtightness between the outer circumferential surface of the fitting projection 12B and the inner circumferential surface of the fitting recess 13D. When the relief valve 1 is closed, an axial gap is formed between the tip surface of the fitting projection 12B and the inner end surface of the fitting recess 13D. Also, when the relief valve 1 is closed, an axial gap is formed between the tip surface of the support shaft portion 13C and the inner surface of the end wall of the piston 12.
[0028] The pressure regulating member 13 has a ventilation hole 13E. The ventilation hole 13E extends in a direction intersecting the axial direction of the pressure regulating member 13. The space between the inner circumferential surface of the pressure regulating member 13 and the outer circumferential surface of the support shaft portion 13C is in communication with the outside of the housing 11 via the ventilation hole 13E. The outside is, for example, the atmosphere.
[0029] The compression coil spring 14 is interposed between the piston 12 and the pressure regulating member 13. The first end of the compression coil spring 14 is positioned in the space between the inner circumferential surface of the piston 12 and the outer circumferential surface of the support shaft portion 13C. The second end of the compression coil spring 14 is positioned in the space between the inner circumferential surface of the pressure regulating member 13 and the outer circumferential surface of the support shaft portion 13C. The second end is the end of the compression coil spring 14 opposite to the first end.
[0030] The compression coil spring 14 is interposed in an axially compressed state between the inner surface of the end wall of the piston 12 and the inner surface of the end wall of the pressure regulating member 13. The inner surface of the end wall of the piston 12 functions as a first spring seat on which the first end of the compression coil spring 14 sits. The inner surface of the end wall of the pressure regulating member 13 functions as a first spring seat on which the second end of the compression coil spring 14 sits.
[0031] The compression coil spring 14 is a biasing member that constantly biases the piston 12 in the valve closing direction, which is from the second end to the first end of the housing 11. When the pressure of the hydrogen gas flowing into the input port 11A is less than or equal to the set pressure of the relief valve 1, that is, less than or equal to the spring load of the compression coil spring 14, the elastic force of the compression coil spring 14 maintains the valve body 12A pressed axially against the valve seat 11C.
[0032] Incidentally, the axial distance between the pressure regulating member 13 and the piston 12 can be changed by rotating the pressure regulating member 13 in a tightening or loosening direction relative to the housing 11. The axial distance is the axial distance between the inner surface of the end wall of the piston 12 and the inner surface of the end wall of the pressure regulating member 13. The shorter the axial distance, the more the compression coil spring 14 is compressed, and the greater the spring load F0 of the compression coil spring 14. In other words, the pressure at which the valve body 12A opens can be changed by rotating the pressure regulating member 13 in a tightening or loosening direction relative to the housing 11.
[0033] When the relief valve 1 is closed, three chambers are separated inside the relief valve 1 while maintaining airtightness. The three chambers include the first chamber C1, the second chamber C2, and the third chamber C3.
[0034] The first chamber C1 is a chamber into which hydrogen gas flows through the input port 11A. The first chamber C1 is a space that includes the internal space of the valve seat 11C, the internal space of the through hole 12D, and the gap between the tip surface of the fitting projection 12B and the inner end surface of the fitting recess 13D. The first chamber C1 is a space defined by the inner circumferential surface of the valve seat 11C, the inner circumferential surface of the through hole 12D, the tip surface of the fitting projection 12B, the inner circumferential surface of the fitting recess 13D, and the inner end surface of the fitting recess 13D.
[0035] The second chamber C2 is the space between the first end wall of the housing 11 and the piston 12, and is provided corresponding to the output port 11B. The second chamber C2 is a space defined by the inner circumferential surface of the housing 11, the outer circumferential surface of the valve seat 11C, the inner surface of the first end wall of the housing 11, and the outer surface of the end wall of the piston 12. The second chamber C2 communicates with the outside of the housing 11 via the output port 11B. The output port 11B communicates with the outside of the body 5, for example, via a through hole provided in the circumferential wall of the relief valve mounting portion 5C. The through hole penetrates the circumferential wall of the relief valve mounting portion 5C in the radial direction.
[0036] The third chamber C3 is a chamber that houses the compression coil spring 14. The third chamber C3 is the space between the pressure regulating member 13 and the piston 12. The third chamber C3 includes a first space and a second space. The first space is defined by the inner circumferential surface of the piston 12, the inner surface of the end wall of the piston 12, and the outer circumferential surface of the support shaft portion 13C. The second space is defined by the inner circumferential surface of the pressure regulating member 13, the inner surface of the end wall of the pressure regulating member 13, and the outer circumferential surface of the support shaft portion 13C.
[0037] <Operation of Relief Valve 1> Next, the operation of relief valve 1 will be explained. When the pressure of the hydrogen gas flowing into the input port 11A is less than or equal to the set pressure of relief valve 1, relief valve 1 is kept closed. That is, the valve body 12A is maintained in the closed position by the elastic force of the compression coil spring 14. The closed position is the position of the valve body 12A that contacts the valve seat 11C in the axial direction. The pressure of the hydrogen gas flowing into the input port 11A is basically equal to the secondary pressure.
[0038] When the pressure of the hydrogen gas flowing into the input port 11A exceeds the set pressure of the relief valve 1, the relief valve 1 opens. That is, the piston 12 moves in the valve opening direction against the elastic force of the compression coil spring 14. The valve opening direction is from the first end to the second end of the housing 11, and is the direction in which the valve body 12A moves axially away from the valve seat 11C. As the piston 12 moves in the valve opening direction, the valve body 12A eventually reaches the valve opening position. The valve opening position is the position of the valve body 12A that is axially separated from the valve seat 11C.
[0039] When the valve body 12A reaches the open position, hydrogen gas flows into the second chamber C2 through the gap between the valve body 12A and the valve seat 11C. The hydrogen gas that has flowed into the second chamber C2 is released to the outside of the housing 11 from the output port 11B. The pressure of the hydrogen gas flowing into the input port 11A decreases as a portion of the hydrogen gas in the secondary port 5B is released to the outside of the housing 11. In other words, the rise in secondary pressure is suppressed by releasing a portion of the hydrogen gas in the secondary port 5B to the outside of the housing 11.
[0040] When the pressure of the hydrogen gas flowing into the input port 11A falls below the set pressure of the relief valve 1, the piston 12 moves in the valve closing direction due to the elastic force of the compression coil spring 14. The valve closing direction is the direction from the second end to the first end of the housing 11, and the direction in which the valve body 12A approaches the valve seat 11C in the axial direction. As the piston 12 moves in the valve closing direction, the valve body 12A eventually reaches the closed position.
[0041] In this way, the relief valve 1 moves the valve body 12A between the closed position and the open position in response to the pressure of the hydrogen gas flowing into the input port 11A, i.e., the secondary pressure, thereby keeping the secondary pressure below the set pressure of the relief valve 1.
[0042] <Operation of the First Embodiment> Next, the operation of the first embodiment will be described. The spring load F0 of the compression coil spring 14 is set to a size necessary to keep the relief valve 1 closed against high-pressure hydrogen gas when the pressure of the hydrogen gas flowing into the input port 11A is below the set pressure of the relief valve 1. For this reason, depending on the usage conditions of the valve device 2, a large spring load F0 may be applied to the valve body 12A. For example, a situation in which no hydrogen gas pressure is applied to the piston 12 can be considered. In this case, there is concern that a large spring load F0 will be applied to the valve body 12A.
[0043] Incidentally, the secondary pressure of the valve device 2 used in a hydrogen engine vehicle is higher than the secondary pressure of the valve device 2 used in a hydrogen fuel cell vehicle. Therefore, the spring load F0 of the compression coil spring 14 used in a hydrogen engine vehicle is set to be larger than the spring load F0 of the compression coil spring 14 used in a hydrogen fuel cell vehicle.
[0044] As a situation where the pressure of hydrogen gas is not applied to the piston 12, for example, when hydrogen gas is used until the gas tank 3 is almost empty, or when hydrogen gas is discharged for maintenance of the valve device 2. Also, after the relief valve 1 or the valve device 2 is manufactured and while the relief valve 1 or the valve device 2 exists alone, the pressure of hydrogen gas is not applied to the piston 12. In this case, due to the spring load F0 of the compression coil spring 14, the valve body 12A is pressed against the valve seat 11C. Therefore, there is a risk that the valve body 12A may be damaged.
[0045] In this regard, in the present embodiment, a load F1 in the valve opening direction by hydrogen gas acts on the portion of the piston 12 that is exposed inside the valve seat 11C. The load F1 in the valve opening direction is a force that pushes the piston 12 in the valve opening direction. The valve opening direction is the direction from the first end portion to the second end portion of the housing 11, and is the direction in which the valve body 12A moves axially away from the valve seat 11C. The load F1 in the valve opening direction is represented by the following formula (2).
[0046] F1 = S2 × PL... (1) However, "S2" is the area of the portion of the piston 12 that is exposed inside the valve seat 11C, and is the pressure receiving area that receives the pressure of hydrogen gas. "PL" is the secondary pressure of hydrogen gas.
[0047] The hydrogen gas flowing into the input port 11A is introduced through the through-hole 12D of the piston 12 into the gap between the tip surface of the fitting projection 12B and the inner end surface of the fitting recess 13D. The gap is formed on the side opposite to the valve body 12A of the piston 12. Therefore, a closing load F2 in the direction of the hydrogen gas acts on the tip surface of the fitting projection 12B. The closing load F2 in the direction is a force that pushes the piston 12 back in the closing direction. The closing direction is the direction from the second end portion to the first end portion of the housing 11, and is the direction in which the valve body 12A approaches the valve seat 11C in the axial direction. The closing load F2 in the direction is represented by the following formula (1).
[0048] F2 = S1 × PL … (2) Here, "S1" is the area of the tip surface of the fitting projection 12B, and is the pressure receiving area that receives the pressure of the hydrogen gas. "PL" is the secondary pressure of the hydrogen gas.
[0049] The magnitude relationship between the area S1 of the tip surface of the fitting projection 12B and the area S2 of the portion of the piston 12 exposed inside the valve seat 11C is represented by the following formula (3). S2 > S1 … (3) From formulas (1), (2), and (3), it can be seen that the opening load F1 in the opening direction is greater than the closing load F2 in the closing direction. Therefore, the function of the relief valve 1 is maintained. That is, when the pressure of the hydrogen gas flowing into the input port 11A exceeds the set pressure of the relief valve 1, the piston 12 moves in the opening direction against the elastic force of the compression coil spring 14.
[0050] A part of the opening load F1 in the opening direction by the hydrogen gas is offset by the closing load F2 in the closing direction by the hydrogen gas. That is, the force in the opening direction acting on the piston 12 is weakened by the force that pushes the piston 12 back in the closing direction. The opening load F3 acting on the piston 12 after a part of the opening load F1 in the opening direction is offset by the closing load F2 in the closing direction is represented by the following formula (4).
[0051] F3 = F1 - F2 = (S2 - S1) × PL … (4) Here, "S1" is the area of the tip surface of the fitting projection 12B, and is the pressure receiving area that receives the pressure of the hydrogen gas. "S2" is the area of the portion of the piston 12 exposed inside the valve seat 11C, and is the pressure receiving area that receives the pressure of the hydrogen gas. "PL" is the secondary pressure of the hydrogen gas.
[0052] Therefore, the spring load F0 of the compression coil spring 14 can be reduced by the amount by which a portion of the valve-opening load F1 due to hydrogen gas is offset by the valve-closing load F2 due to hydrogen gas. The spring load F0 is set to be approximately the same as the valve-opening load F3 that acts on the piston 12 after the valve-opening load F1 is partially offset by the valve-closing load F2. In other words, the spring load F0 of the compression coil spring 14 that presses the valve body 12A against the valve seat 11C is smaller than when the valve-closing load F2 does not act on the piston 12. Therefore, even if a situation occurs where no hydrogen gas pressure is applied to the piston 12, damage to the valve body 12A is suppressed.
[0053] Furthermore, the area of the portion of the piston 12 exposed to the inside of the valve seat 11C, that is, the pressure-receiving area of the piston 12 that receives the pressure of hydrogen gas, is smaller than the pressure-receiving area when the piston 12 does not have a through hole 12D, by the amount of the cross-sectional area when the through hole 12D is cut by a plane perpendicular to the axial direction. Therefore, the load F1 in the valve-opening direction due to hydrogen gas is smaller than the load F1 in the valve-opening direction when the piston 12 does not have a through hole 12D. Consequently, the spring load F0 of the compression coil spring 14 can be further reduced by the amount by which the load F1 in the valve-opening direction due to hydrogen gas is reduced. As the force pressing the valve body 12A against the valve seat 11C is further weakened, damage to the valve body 12A is suppressed even when a situation occurs where no pressure of hydrogen gas is applied to the piston 12.
[0054] <Effects of the First Embodiment> The first embodiment provides the following effects: (1-1) The pressure regulating member 13 has a fitting recess 13D that faces the piston 12 in the axial direction. The pressure regulating member 13 also functions as a second end wall that closes the second end of the housing 11. The piston 12 has a fitting projection 12B that is slidably fitted in the fitting recess 13D in the axial direction. An axial gap is formed between the tip surface of the fitting projection 12B and the inner end surface of the fitting recess 13D. The piston 12 has a through hole 12D that penetrates the piston 12 in the axial direction. The input port 11A communicates with the gap between the tip surface of the fitting projection 12B and the inner end surface of the fitting recess 13D via the through hole 12D. The through hole 12D functions as a guide path that guides hydrogen gas flowing into the input port 11A in order to reduce the force acting on the piston 12 in the direction of valve opening.
[0055] In this configuration, when the relief valve 1 is closed, hydrogen gas flowing in from the input port 11 flows through the through hole 12D into the gap between the tip surface of the fitting projection 12B and the inner end surface of the fitting recess 13D. As a result, the piston 12 is subjected to both a force pushing it in the valve-opening direction and a force pushing it back in the valve-closing direction. That is, the force acting on the piston 12 in the valve-opening direction is weakened by the force pushing it back in the valve-closing direction. Therefore, the spring load F0 required to keep the relief valve 1 closed can be reduced. This makes it possible to suppress damage to the valve body 12A even when there is no hydrogen gas pressure applied to the piston 12. Furthermore, leakage of hydrogen gas from the relief valve 1 to the outside is also suppressed.
[0056] (1-2) The area S1 of the tip surface of the fitting projection 12B is smaller than the area S2 of the portion of the piston 12 that is exposed to the inside of the valve seat 11C. Therefore, the load F1 acting on the piston 12 in the valve opening direction is greater than the load F2 acting on the piston 12 in the valve closing direction. Thus, the function of the relief valve 1 can be maintained.
[0057] <Second Embodiment> Next, a relief valve 1 according to a second embodiment will be described. This embodiment has basically the same configuration as the first embodiment shown in Figure 2. Therefore, the same reference numerals are used for the same members and components as in the first embodiment, and their detailed descriptions are omitted. This embodiment differs from the first embodiment in the configuration of the piston 12.
[0058] As shown in Figure 3, the piston 12 does not have a through hole 12D. That is, the piston 12 is a solid member with no voids or spaces inside. The valve body 12A that constitutes the piston 12 is also a solid member.
[0059] The relief valve 1 has a bypass 16. The bypass 16 is a gas passage through which hydrogen gas flows. The bypass 16 connects, for example, the inside of the input port 11A to the space between the tip surface of the fitting projection 12B and the inner end surface of the fitting recess 13D. This space is the space on the opposite side of the valve body 12A of the piston 12.
[0060] The bypass 16 may be provided so as not to be exposed to the outside of the body 11. The bypass 16, for example, runs from the input port 11A, through the inside of the body 11 and the inside of the pressure regulating member 13, to the space between the tip surface of the fitting projection 12B and the inner end surface of the fitting recess 13D.
[0061] The bypass 16 may be provided so as to be exposed to the outside of the body 11. The bypass 16 extends, for example, from the input port 11A, through the outside of the body 11 and the inside of the pressure regulating member 13, to the space between the tip surface of the fitting projection 12B and the inner end surface of the fitting recess 13D.
[0062] <Operation of the Second Embodiment> Next, the operation of the second embodiment will be described. A portion of the hydrogen gas flowing into the input port 11A is introduced via the bypass 16 into the space between the tip surface of the fitting projection 12B and the inner end surface of the fitting recess 13D. As a result, a load F2 in the valve-closing direction due to the hydrogen gas acts on the tip surface of the fitting projection 12B. Therefore, the spring load F0 of the compression coil spring 14 can be reduced by the amount by which a portion of the valve-opening load F1 due to the hydrogen gas is offset by the valve-closing load F2 due to the hydrogen gas. As the force pressing the valve body 12A against the valve seat 11C is weakened, damage to the valve body 12A is suppressed even if a situation occurs where no hydrogen gas pressure is applied to the piston 12.
[0063] <Effects of the Second Embodiment> The second embodiment provides the following effects: (2-1) The relief valve 1 has a bypass circuit 16 that bypasses the piston 12. The input port 11A communicates with the gap between the tip surface of the fitting projection 12B and the inner end surface of the fitting recess 13D via the bypass circuit 16. The bypass circuit 16 functions as a guide path that guides the hydrogen gas flowing into the input port 11A in order to reduce the force acting on the piston 12 in the direction of valve opening.
[0064] In this configuration, when the relief valve 1 is closed, hydrogen gas flowing in from the input port 11 flows through the bypass 16 into the gap between the tip surface of the fitting projection 12B and the inner end surface of the fitting recess 13D. As a result, the piston 12 is subjected to both a force pushing it in the valve-opening direction and a force pushing it back in the valve-closing direction. That is, the force acting on the piston 12 in the valve-opening direction is weakened by the force pushing it back in the valve-closing direction. Therefore, the spring load F0 required to keep the relief valve 1 closed can be reduced. This suppresses damage to the valve body 12A even when there is no hydrogen gas pressure applied to the piston 12. It also suppresses hydrogen gas leakage from the relief valve 1 to the outside.
[0065] (2-2) The area S1 of the tip surface of the fitting projection 12B is smaller than the area S2 of the portion of the piston 12 that is exposed to the inside of the valve seat 11C. Therefore, the load F1 acting on the piston 12 in the valve opening direction is greater than the load F2 acting on the piston 12 in the valve closing direction. Thus, the function of the relief valve 1 can be maintained.
[0066] (2-3) The bypass 16 bypasses the piston 12 and connects the input port 11A with the gap between the tip surface of the fitting projection 12B and the inner end surface of the fitting recess 13D. Therefore, unlike the first embodiment, it is not necessary to drill a hole in the valve body, and consequently in the piston 12.
[0067] <Third Embodiment> Next, a relief valve 1 according to a third embodiment will be described. This embodiment has basically the same configuration as the first embodiment shown in Figure 2. Therefore, the same reference numerals are used for the same members and components as in the first embodiment, and their detailed descriptions are omitted. This embodiment differs from the first embodiment in the configuration of the pressure regulating member 13.
[0068] As shown in Figure 4, the support shaft portion 13C does not have a fitting recess 13D. The axial length of the support shaft portion 13C is shortened by the axial length of the fitting recess 13D. The support shaft portion 13C has a pressure-receiving shaft portion 13F. The pressure-receiving shaft portion 13F is a columnar body with a circular cross-sectional shape and is provided at the tip of the support shaft portion 13C. The tip is the end of the support shaft portion 13C opposite to the end wall of the pressure adjustment member 13. The pressure-receiving shaft portion 13F is fitted into the through hole 12D of the piston 12. The outer circumferential surface of the pressure-receiving shaft portion 13F is slidable in the axial direction relative to the inner circumferential surface of the through hole 12D.
[0069] When the relief valve 1 is closed, an axial gap is formed between the tip surface of the fitting projection 12B and the tip surface of the support shaft portion 13C. The tip surface of the fitting projection 12B is the end surface of the fitting projection 12B opposite to the valve body 12A. The tip surface of the support shaft portion 13C is the end surface of the support shaft portion 13C on which the pressure receiving shaft portion 13F is provided, and is the end surface of the support shaft portion 13C opposite to the end wall of the pressure regulating member 13.
[0070] The first sealing member 12C is fitted into a groove provided on the inner circumferential surface of the fitting projection 12B. The groove has a rectangular cross-sectional shape and is provided around the entire circumference of the inner circumferential surface of the fitting projection 12B. The first sealing member 12C ensures airtightness between the inner circumferential surface of the fitting projection 12B and the outer circumferential surface of the pressure-receiving shaft portion 13F.
[0071] The third chamber C3, which houses the compression coil spring 14, is in communication with the atmosphere via a vent hole 13E. Therefore, the pressure inside the third chamber C3 is atmospheric pressure. The pressure inside the piston 12, which is in communication with the third chamber C3, is also atmospheric pressure. That is, a load F3 due to atmospheric pressure acts on the piston 12, more specifically on the inner surface of the end wall of the piston 12 and the tip surface of the fitting projection 12B, in the valve closing direction. The load F3 in the valve closing direction is a force that pushes the piston 12 back in the valve closing direction.
[0072] <Operation of the Third Embodiment> Next, the operation of the third embodiment will be described. The portion of the piston 12 that is exposed to the inside of the valve seat 11C is subjected to the pressure of the hydrogen gas flowing into the input port 11A. A load F1 in the valve-opening direction due to the hydrogen gas acts on the portion of the piston 12 that is exposed to the inside of the valve seat 11C. However, the area of the portion of the piston 12 that is exposed to the inside of the valve seat 11C, that is, the pressure-receiving area of the piston 12 that is subjected to the pressure of the hydrogen gas, is smaller than the pressure-receiving area when the piston 12 does not have a through hole 12D, by the amount of the cross-sectional area when the through hole 12D is cut by a plane perpendicular to the axial direction.
[0073] Therefore, the load F1 in the valve-opening direction due to hydrogen gas is smaller than the load F1 in the valve-opening direction when the piston 12 does not have a through hole 12D. Consequently, the spring load F0 of the compression coil spring 14 can be reduced by the amount by which the load F1 in the valve-opening direction due to hydrogen gas is reduced. As the force pressing the valve body 12A against the valve seat 11C is weakened, damage to the valve body 12A is suppressed even when a situation occurs where no hydrogen gas pressure is applied to the piston 12.
[0074] Furthermore, a portion of the hydrogen gas flowing into the input port 11A flows into the through-hole 12D. The pressure regulating member 13 receives the pressure of the hydrogen gas flowing into the through-hole 12D via the tip surface of the pressure receiving shaft portion 13F. Since the pressure regulating member 13 is fixed to the housing 11, the pressure regulating member 13 does not move due to the pressure of the hydrogen gas.
[0075] <Effects of the Third Embodiment> The third embodiment provides the following effects: (3-1) The piston 12 has a through hole 12D that penetrates the piston 12 in the axial direction. The pressure regulating member 13 has a pressure receiving shaft portion 13F that is slidably fitted in the axial direction into the through hole 12D. The tip surface of the pressure receiving shaft portion 13F faces the input port 11A in the axial direction via the valve seat 11C. A portion of the through hole 12D that communicates with the input port 11A via the valve seat 11C functions as a guide path that guides hydrogen gas flowing into the input port 11A in order to reduce the force acting on the piston 12 in the direction of valve opening.
[0076] With this configuration, the pressure-receiving area of the piston 12 is reduced by the cross-sectional area of the through-hole 12D. The pressure-receiving area is the area of the part of the piston 12 that receives the pressure of the hydrogen gas flowing into the input port 11A. Therefore, the force acting on the piston in the valve-opening direction due to the pressure of the hydrogen gas is reduced by the amount by which the pressure-receiving area of the piston 12 is reduced. A portion of the pressure of the hydrogen gas flowing into the input port 11A is received by the pressure regulating member 13 via the pressure-receiving shaft portion 13F. Therefore, the spring load F0 of the compression coil spring 14 can be made smaller than when the piston 12 does not have a through-hole 12D. As a result, even if a situation occurs where no pressure of hydrogen gas is applied to the piston 12, damage to the valve body 12A can be suppressed. In addition, leakage of hydrogen gas from the relief valve 1 to the outside is also suppressed.
[0077] <Other Embodiments> Each embodiment may be implemented with the following modifications: In each embodiment, a configuration in which the pressure regulating member 13 is omitted may be adopted as the relief valve 1. In this case, the second end of the housing 11 is closed by a second end wall. The second end wall is, for example, a simple wall formed integrally with the housing 11 and has a circular cross-sectional shape.
[0078] - In each embodiment, the relief valve 1 may be used to release the pressure of a gas other than hydrogen gas. - In each embodiment, the relief valve 1 and the pressure reducing valve 6 are incorporated into the body 5 to form a single valve device 2. However, the relief valve 1 and the pressure reducing valve 6 may be used as independent valve devices. The relief valve 1 and the pressure reducing valve 6 are installed in the middle of the piping connecting the gas tank 3 and the consumption equipment 4. The relief valve 1 is, for example, located downstream of the pressure reducing valve 6.
Claims
1. A relief valve comprising: a housing which is a cylindrical body having a circular cross-sectional shape, the housing including a peripheral wall having an output port for gas, a first end wall provided at a first end of the peripheral wall and having an input port for gas and a valve seat surrounding the input port, and a second end wall provided at a second end of the peripheral wall; a piston which is axially slidable within the housing and has a valve body configured to open and close the input port by contacting or separating from the valve seat in the axial direction; a biasing member disposed between the piston and the second end wall which is configured to constantly bias the piston in the closing direction; and a guide passage which is configured to guide gas flowing into the input port in order to reduce the force acting on the piston in the opening direction.
2. The relief valve according to claim 1, wherein the second end wall has a fitting recess facing the piston in the axial direction, the piston has a fitting projection that is slidably fitted in the fitting recess in the axial direction, an axial gap is formed between the tip surface of the fitting projection and the inner end surface of the fitting recess, the area of the tip surface of the fitting projection is smaller than the area of the portion of the piston that is exposed to the inside of the valve seat, and the guide passage is configured to communicate the input port and the gap.
3. The relief valve according to claim 2, wherein the guide passage is a through hole that penetrates the piston in the axial direction.
4. The relief valve according to claim 2, wherein the guide path is a bypass route that goes around the piston.
5. The relief valve according to claim 1, wherein the piston has a through hole that penetrates the piston in the axial direction, the second end wall has a pressure-receiving shaft portion that is slidably fitted in the axial direction into the through hole, the tip surface of the pressure-receiving shaft portion faces the input port in the axial direction via the valve seat, and the guide passage is a part of the through hole that communicates with the input port via the valve seat.