Overpressure valve

Abstract

A pressure relief valve allows a fluid within an encapsulation to escape through an opening in the encapsulation when the internal pressure of the fluid increases. The pressure relief valve comprises a body attached to the encapsulation, a valve element that is movable relative to the body from a closed position (where the opening is closed) to an open position (where the opening is open), and an elastic element that pushes the valve element toward the closed position. The valve element includes a cover that directly or indirectly covers the opening in the closed position. The cover comprises an inner surface facing the encapsulation and an outer surface located on a side opposite the inner surface.The cover part comprises a first element, which is arranged on at least part of the inner surface, and a second element, which is arranged on one side of the outer surface relative to the first element and is made of plastic. The melting point of the first element is higher than the melting point of the second element.

Description

pressure relief valve

[0001] The present invention relates to a pressure relief valve for regulating the pressure inside a housing.

[0002] A pressure relief valve is a device for adjusting the pressure inside a housing. The housing is, for example, a battery pack installed in an automobile. Devices such as battery cells are housed and sealed inside the battery pack. The pressure relief valve is attached to a housing such as a battery pack. For example, the pressure relief valve is arranged to cover an opening formed in the housing. When the pressure inside the housing exceeds a threshold, the pressure relief valve operates to release fluid inside the housing to the outside. The pressure relief valve can prevent damage to devices inside the housing due to an increase in pressure. This improves the safety of the battery pack.

[0003] Patent Document 1 discloses a pressure relief valve that includes a base member attached to an opening in a housing and a valve member that covers the opening. A biasing force is applied to the valve member toward the base member. When the internal pressure exceeds a threshold, the valve member moves in a direction away from the base member. Fluid inside the housing is released to the outside through a gap between the base member and the valve member.

[0004] JP 2023-18341 A

[0005] If the valve member is made of resin, there is a risk that the valve member may be damaged when the temperature inside the housing rises. For example, the valve member may melt. If the valve member is damaged, the opening of the housing may open more than expected.

[0006] An object of the present invention is to provide a pressure relief valve that can solve these problems.

[0007] The present invention relates to the following items [1] to

[10] : [1] A pressure relief valve that releases a fluid from an opening of a housing when the internal pressure of the fluid inside the housing increases, comprising: a main body attached to the housing; a valve member that is movable relative to the main body from a closed position that closes the opening to an open position that opens the opening; and an elastic member that biases the valve member toward the closed position, wherein the valve member includes a cover part that directly or indirectly covers the opening at the closed position, the cover part includes an inner surface facing the housing and an outer surface located opposite the inner surface, and the cover part includes a first member located on at least a part of the inner surface, and a second member made of resin that is located closer to the outer surface than the first member, and wherein the melting point of the first member is higher than the melting point of the second member.

[0008] [2] In the pressure release valve described in [1], the cover part may be divided into a central part that directly or indirectly covers the opening, and a peripheral part that is located around the central part. The inner surface of the central part may be at least partially constituted by the first member. The inner surface of the peripheral part may be at least partially constituted by the second member.

[0009] [3] In the pressure release valve according to [1] or [2], the melting point of the first member may be 400° C. or higher.

[0010] [4] In the pressure release valve according to any one of [1] to [3], the first member may be made of metal.

[0011] [5] In the pressure release valve according to any one of [1] to [4], the first member may extend to overlap an outer edge of the opening of the housing in a plan view. Alternatively, the first member may extend to overlap an outer edge of an opening of the main body that communicates with the opening of the housing in a plan view.

[0012] [6] In the pressure release valve according to any one of [1] to [5], the second member may include a plurality of ribs located on the outer surface.

[0013] [7] In the pressure release valve according to any one of [1] to [6], the second member may include a protrusion that protrudes from the inner surface toward the housing, and the first member may include a tip that engages with the protrusion.

[0014] [8] In the pressure release valve according to any one of [1] to [7], the valve member may include a shaft extending from the inner surface of the cover portion toward the housing, and the elastic member may be located around the shaft.

[0015] [9] In the pressure relief valve according to any one of [1] to [8], the shaft may contain metal.

[0016]

[10] In the pressure release valve described in [8] or [9], the main body may include a beam portion extending across the opening of the housing or an opening of the main body that communicates with the opening of the housing, the beam portion may include a through hole into which the shaft is inserted, and the beam portion may include metal.

[0017] According to the present invention, damage to the valve member when the temperature inside the housing rises can be suppressed.

[0018] FIG. 1 is a perspective view showing an example of a pressure release valve attached to a housing. FIG. 2 is an exploded view showing an example of a pressure release valve. FIG. 3 is a perspective view showing an example of a pressure release valve. FIG. 4 is a longitudinal sectional view showing an example of a pressure release valve. FIG. 5 is a longitudinal sectional view showing the pressure release valve and the housing in a closed position. FIG. 6 is a longitudinal sectional view showing the pressure release valve and the housing in an open position. FIG. 7 is a longitudinal sectional view showing a pressure release valve according to a first modified example. FIG. 8 is a perspective view showing a pressure release valve according to a second modified example. FIG. 9 is a longitudinal sectional view showing the pressure release valve and the housing in a closed position. FIG. 10 is a longitudinal sectional view showing the pressure release valve and the housing in an open position. FIG. 11 is a longitudinal sectional view showing another example of the second modified example.

[0019] The present invention will be described with reference to the accompanying drawings, in which the scale and aspect ratios of the drawings have been appropriately changed and exaggerated from those of the actual objects for ease of understanding.

[0020] FIG. 1 is a perspective view showing an example of a pressure release valve 10. The pressure release valve 10 is attached to the surface of a housing 100. The housing 100 is, for example, a battery pack mounted on an automobile. Devices such as battery cells are housed and sealed inside the battery pack. The housing 100 includes a front surface 101 and a back surface 102. The front surface 101 is in contact with the atmosphere outside the housing 100. The back surface 102 is in contact with the internal space sealed by the housing 100.

[0021] The housing 100 includes an opening 103 penetrating the housing 100. The pressure release valve 10 is attached to the housing 100 so as to cover the opening 103. The pressure release valve 10 is located above a surface 101 of the housing 100. The pressure release valve 10 overlaps an outer edge 103e of the opening 103 in a plan view. A plan view means viewing an object along the normal direction of the surface 101 of the housing 100. The housing 100 may have fastening holes 105 formed therein into which fasteners are inserted.

[0022] The pressure relief valve 10 operates to release fluid such as gas inside the housing 100 to the outside when the pressure inside the housing 100 exceeds a threshold value. The pressure inside the housing 100 is also referred to as internal pressure.

[0023] 2 is an exploded view showing the pressure relief valve 10. The pressure relief valve 10 includes at least a main body 20, a valve member 30, and an elastic member 40. By assembling the main body 20, the valve member 30, and the elastic member 40, the modularized pressure relief valve 10 is obtained. The pressure relief valve 10 may be attached to the housing 100 in a modularized state. The pressure relief valve 10 may include a first seal member 27 and a second seal member 28.

[0024] When the housing 100, such as a battery pack, is operating normally, the opening 103 of the housing 100 is closed by the valve member 30. This state is also referred to as a closed state. The position of the valve member 30 in the closed state is also referred to as a closed position.

[0025] When the pressure inside the housing 100 increases and exceeds a threshold value, the valve member 30 moves from the closed position to the open position in the first direction D1 relative to the main body 20. This opens the opening 103 of the housing 100, and fluid such as gas inside the housing 100 is released to the outside. The state in which the valve member 30 is in the open position is also referred to as the open state.

[0026] When the fluid is released to the outside, the pressure inside the housing 100 decreases. When the pressure falls below the threshold, the valve member 30 may move relative to the body 20 in the first direction D1 from the open position back to the closed position, causing the opening 103 of the housing 100 to be closed again by the valve member 30.

[0027] Each component of the pressure release valve 10 will be described in detail with reference to Figures 1 to 4. Figure 3 is a perspective view showing the pressure release valve 10 as seen from the housing 100 side. Figure 4 is a vertical cross-sectional view showing the pressure release valve 10.

[0028] (Main Body) The main body 20 is attached to the housing 100 so as to partially overlap the opening 103 of the housing 100 in a plan view. As shown in FIGS. 2 to 4 , the main body 20 may include a base 21, a side wall 22, and a beam portion 23.

[0029] 4 , the base 21 includes an inner surface 211 facing the housing 100, an outer surface 212 located on the opposite side of the inner surface 211, and an opening 213 penetrating from the inner surface 211 to the outer surface 212. The inner surface 211 may be in contact with the surface 101 of the housing 100. The opening 213 communicates with the opening 103 of the housing 100. In a plan view, the opening 213 overlaps the opening 103. Fluid inside the housing 100 is discharged to the outside through the opening 103 of the housing 100 and the opening 213 of the base 21.

[0030] The base 21 may include a fastening portion 214. The fastening portion 214 is a hole into which a fastener is inserted. The fastener is, for example, a bolt. The fastener is inserted into the fastening portion 214 of the base 21 and the fastening hole 105 of the housing 100, and the fastener is fixed with a nut or the like, thereby fixing the main body 20 to the housing 100.

[0031] The sidewall 22 forms a flow path through which a fluid passes inside the housing 100. The sidewall 22 widens from the base 21 toward the housing 100. The sidewall 22 may have a circular outline in a plan view. For example, the sidewall 22 may have a cylindrical shape. The opening 213 is surrounded by the sidewall 22 in a plan view.

[0032] In a plan view, the beam portion 23 extends across the opening 213. The beam portion 23 may include a through-hole 231 into which a shaft 37 (described later) is inserted.

[0033] 2 and 4, the beam portion 23 may include a first member 241 and a second member 242. Both the first member 241 and the second member 242 may include a through hole 231 into which the shaft 37 is inserted.

[0034] The first member 241 may be located on the inner surface of the beam portion 23. The inner surface of the beam portion 23 is the surface of the beam portion 23 facing the inside of the housing 100. The second member 242 may be stacked on the first member 241 in the first direction D1 so as to be located on the outer surface of the beam portion 23.

[0035] The material of the first member 241 is different from the material of the second member 242. The melting point of the first member 241 may be higher than the melting point of the second member 242. The fluid being discharged from the inside of the housing 100 to the outside collides with the inner surface of the beam portion 23 during the discharge process. The high melting point of the first member 241 can prevent the beam portion 23 from being damaged by the heat of the fluid. For example, the beam portion 23 can be prevented from melting. The difference between the melting point of the first member 241 and the melting point of the second member 242 is, for example, 10°C or more, or may be 30°C or more, 50°C or more, or 100°C or more.

[0036] The through-hole 231 of the beam portion 23 can serve to guide the shaft 37 of the valve member 30 in the first direction D1. By suppressing damage to the beam portion 23, the stability of the movement of the valve member 30 is maintained.

[0037] The melting point of the first member 241 is, for example, 400° C. or higher, or may be 500° C. or higher, or may be 600° C. or higher. The first member 241 may contain a metal. The entire first member 241 may be made of a metal.

[0038] The second member 242 may contain resin. The entire second member 242 may be made of resin. Since resin is used in the second member 242, the beam portion 23 becomes lighter than when the entire beam portion 23 is made of metal.

[0039] (Valve Member) The valve member 30 includes at least a cover portion 31 that directly or indirectly covers the opening 103 of the housing 100 in the closed position. "Directly cover" means that the cover portion 31 covers the opening 103 of the housing 100. "Indirectly cover" means that the cover portion 31 covers the opening 213 of the base 21 that communicates with the opening 103 of the housing 100. In the example of Fig. 4, the cover portion 31 covers the opening 213 of the base 21 that communicates with the opening 103 of the housing 100. In other words, the cover portion 31 in Fig. 4 indirectly covers the opening 103 of the housing 100. The cover portion 31 includes an inner surface 311 facing the surface 101 of the housing 100 and an outer surface 312 located on the opposite side of the inner surface 311.

[0040] As with the beam portion 23 described above, fluid being discharged from inside the housing 100 to the outside collides with the inner surface 311 of the cover portion 31 during the discharge process. If the cover portion 31 is made entirely of resin, the heat of the fluid may damage the cover portion 31. For example, the cover portion 31 may melt. If the cover portion 31 is damaged, the opening 103 of the housing 100 opens more than expected. This makes it easier for external oxygen to flow into the housing 100. If a fire is occurring inside the housing 100, the inflow of oxygen may intensify the fire.

[0041] One possible way to prevent damage to the cover portion 31 is to use a metal cover portion 31. However, the weight of the metal cover portion 31 is large. The heavier the cover portion 31 is, the more the movement of the cover portion 31 in the first direction D1 is hindered.

[0042] In order to reduce the weight of the cover portion 31, it is possible to form the cover portion 31 from a thin metal plate. However, in this case, the rigidity of the cover portion 31 will be reduced.

[0043] In view of these problems, this embodiment proposes the use of a cover unit 31 including a first member 321 and a second member 322. The first member 321 and the second member 322 are stacked in a first direction D1. The first member 321 is located on at least a portion of the inner surface 311. The second member 322 is located closer to the outer surface 312 than the first member 321. In other words, in the portion where the first member 321 and the second member 322 overlap in a plan view, the distance from the second member 322 to the outer surface 312 is shorter than the distance from the first member 321 to the outer surface 312. As shown in FIG. 4 , the second member 322 may constitute the outer surface 312.

[0044] The material of the first member 321 is different from the material of the second member 322. The melting point of the first member 321 is higher than the melting point of the second member 322. For example, the first member 321 is made of metal, and the second member 322 is made of resin. The high melting point of the first member 321 can prevent the cover portion 31 from being damaged by the heat of the fluid. For example, the cover portion 31 can be prevented from melting. Furthermore, because the cover portion 31 includes the second member 322 made of resin, the weight of the cover portion 31 is reduced compared to when a metal cover portion 31 is used. The melting point of the first member 321 is, for example, 400°C or higher, or may be 500°C or higher, or may be 600°C or higher. The difference between the melting points of the first member 321 and the second member 322 can be, for example, 10°C or higher, 30°C or higher, 50°C or higher, or 100°C or higher.

[0045] As shown in Fig. 4 , the cover portion 31 may be divided into a central portion 331 and a peripheral portion 332 in a plan view. In the example shown in Fig. 4 , the central portion 331 is a portion of the cover portion 31 that covers the opening 213 of the base 21. The peripheral portion 332 is located around the central portion 331 in a plan view. In the example shown in Fig. 4 , an outer edge 213e of the opening 213 of the base 21 defines the boundary between the central portion 331 and the peripheral portion 332.

[0046] 4, it is preferable that the inner surface 311 of the central portion 331 is at least partially constituted by the first member 321. Preferably, the first member 321 extends so as to overlap the outer edge 213e of the opening 213 in a plan view.

[0047] 4, the inner surface 311 of the peripheral portion 332 may be at least partially formed of the second member 322. For example, it is preferable that the inner surface 311 of the peripheral portion 332 that contacts the second seal member 28 (described later) is formed of the second member 322. When the inner surface 311 of the peripheral portion 332 that contacts the second seal member 28 is made of resin, the degree of freedom in designing the second seal member 28 is increased. For example, the degree of freedom in the shape of the second seal member 28 is increased. For example, the second seal member 28 is easily provided on the cover portion 31. For example, the degree of freedom in the direction of sealing achieved by the second seal member 28 is increased.

[0048] 4 , the second member 322 may include a protrusion 34 that protrudes from the inner surface 311 toward the housing 100. The protrusion 34 protrudes toward the housing 100, for example, from a portion of the inner surface 311 that is closest to or in contact with the outer surface 212 of the base 21. The protrusion 34 supports a shaft 37, which will be described later. The first member 321 may extend from the protrusion 34 to reach the outer edge 213 e of the opening 213 of the base 21 in a plan view.

[0049] The manufacturing method of the cover portion 31 is not particularly limited. For example, the cover portion 31 may be manufactured by combining the first member 321 and the second member 322 that are manufactured separately. For example, the cover portion 31 may be manufactured as a single unit by insert molding. In insert molding, for example, the cover portion 31 is manufactured by injecting a resin that constitutes the second member 322 into a mold in which the first member 321 is placed.

[0050] As shown in Fig. 4, the valve member 30 may include a shaft 37 extending from the inner surface 311 of the cover portion 31 toward the housing 100. The shaft 37 is attached to the cover portion 31. For example, the shaft 37 is inserted into a through-hole located in the center of the cover portion 31. The shaft 37 may be supported by the above-mentioned protrusion 34. The shaft 37 is inserted into the elastic member 40. By inserting the shaft 37 into the elastic member 40, the expansion and contraction movement of the elastic member 40 is stabilized. For example, the biasing force applied by the elastic member 40 to the cover portion 31 is prevented from varying depending on the position.

[0051] As shown in FIG. 4, an end lock 38 may be attached to the tip of the shaft 37.

[0052] The shaft 37 may contain a metal, which increases the heat resistance of the shaft 37. This prevents the shaft 37 from melting due to the heat from the high-temperature fluid discharged from inside the housing 100.

[0053] When the shaft 37 contains metal, the strength of the shaft 37 can be ensured even if the diameter of the shaft 37 is small. The smaller the diameter of the shaft 37, the wider the fluid flow path, so that the fluid can be smoothly discharged from the inside of the housing 100 to the outside.

[0054] (Elastic Member) The elastic member 40 biases the valve member 30 toward the housing 100 in the first direction D1. The elastic member 40 expands and contracts in the first direction D1 in response to movement of the valve member 30 in the first direction D1. The elastic member 40 is, for example, a coil spring. The elastic member 40 is positioned around the shaft 37.

[0055] The elastic member 40 includes a first end and a second end. The first end of the elastic member 40 contacts the main body 20. For example, the first end of the elastic member 40 contacts the inner surface of the beam portion 23 of the main body 20. The second end of the elastic member 40 contacts the end lock 38.

[0056] (First sealing member) The first sealing member 27 is located between the housing 100 and the pressure release valve 10. In the example shown in Fig. 4, the first sealing member 27 is located between the surface 101 of the housing 100 and the inner surface 211 of the base 21 of the pressure release valve 10. The first sealing member 27 is, for example, a gasket.

[0057] (Second sealing member) The second sealing member 28 is located between the main body 20 and the valve member 30. In the example shown in Fig. 4, the second sealing member 28 is located between the outer surface 212 of the base 21 of the main body 20 and the inner surface 311 of the cover portion 31 of the valve member 30. When the pressure release valve 10 is in the closed state, the second sealing member 28 contacts the outer surface 212 of the base 21 and the inner surface 311 of the cover portion 31. The second sealing member 28 is, for example, a gasket.

[0058] The operation of the pressure release valve 10 will be described with reference to Figures 5 and 6. Figure 5 is a vertical cross-sectional view showing the pressure release valve 10 and the housing 100 in the closed state. The elastic member 40 generates a biasing force that biases the valve member 30 toward the housing 100 in the first direction D1. For example, the elastic member 40 is in a contracted state. Therefore, a restoring force is generated in the elastic member 40. The restoring force of the elastic member 40 presses the end lock 38 toward the housing 100, and the cover part 31, which is connected to the end lock 38 via the shaft 37, is also biased toward the housing 100. As a result, the opening 213 of the base 21 is covered by the cover part 31.

[0059] 6 is a longitudinal cross-sectional view showing the pressure release valve 10 and the housing 100 in the open state. When the internal pressure of the housing 100 exceeds a predetermined threshold due to a fire inside the housing 100 or the like, the force applied by the internal pressure to the cover portion 31 becomes greater than the force applied by the elastic member 40 to the cover portion 31. As a result, the cover portion 31 moves in the first direction D1 away from the housing 100. The cover portion 31 moves in the first direction D1 until the force applied by the internal pressure to the cover portion 31 and the force applied by the elastic member 40 to the cover portion 31 are balanced. In the open state, the elastic member 40 is more compressed than the elastic member 40 in the closed state.

[0060] When the cover portion 31 moves, a gap is generated between the inner surface 311 of the cover portion 31 and the outer surface 212 of the base 21. The inner surface 311 of the cover portion 31 overlaps the outer edge 213e of the opening 213 of the base 21. The gap between the inner surface 311 of the cover portion 31 and the outer surface 212 of the base 21 is formed over the entire outer edge 213e of the opening 213. This increases the flow rate of the fluid that passes through the gap and is released to the outside.

[0061] 6 , the fluid F being discharged from the inside to the outside of the housing 100 collides with the inner surface 311 of the cover part 31 during the discharge process. The cover part 31 includes a first member 321 located on at least a part of the inner surface 311. The melting point of the first member 321 is higher than the melting point of the second member 322, and therefore damage to the cover part 31 is suppressed.

[0062] As the fluid is released to the outside, the internal pressure decreases. When the force that the internal pressure applies to the cover portion 31 becomes smaller than the force that the elastic member 40 applies to the cover portion 31, the restoring force of the elastic member 40 causes the cover portion 31 to move toward the housing 100. Because the first member 321 prevents the cover portion 31 from being damaged, the cover portion 31 can close the opening 213 of the base 21 again.

[0063] Various modifications can be made to the above-described embodiment. Below, modifications will be described with reference to the drawings as necessary. In the following description and the drawings used in the following description, parts that can be configured similarly to the above-described embodiment will be designated by the same reference numerals as those used for corresponding parts in the above-described embodiment, and duplicated descriptions will be omitted. Furthermore, if it is clear that the effects obtained in the above-described embodiment can also be obtained in the modified embodiment, the description of the same effect may be omitted.

[0064] (First Modification) Fig. 7 is a longitudinal cross-sectional view showing a pressure release valve 10 according to a first modification. As shown in Fig. 7, the first member 321 may include a tip 321e that engages with the protrusion 34. For example, the tip 321e of the first member 321 may be bent toward the housing 100. For example, the side surface of the protrusion 34 may include a step 34s with which the tip 321e of the first member 321 comes into contact. By having the tip 321e of the first member 321 engage with the protrusion 34, the first member 321 is easily fixed to the second member 322. This facilitates the manufacture of the cover 31. For example, the performance requirements for manufacturing equipment for manufacturing the cover 31 are relaxed.

[0065] (Second Modification) Fig. 8 is a perspective view showing a pressure release valve 10 according to a first modification. As shown in Fig. 8, the cover part 31 of the pressure release valve 10 may directly cover the opening 103 of the housing 100.

[0066] 9 is a vertical cross-sectional view showing the pressure relief valve 10 and the housing 100 in a closed state. The main body 20 includes at least a side wall 22 and a beam portion 23. The beam portion 23 extends across the opening 103 of the housing 100 in a plan view. The beam portion 23 may be fixed to the housing 100 by a fastener or the like.

[0067] 9 , the first seal member 27 is located between the surface 101 of the housing 100 and the inner surface 311 of the cover portion 31 of the pressure release valve 10. In the closed state, the first seal member 27 contacts the surface 101 of the housing 100 and the inner surface 311 of the cover portion 31.

[0068] As in the above-described embodiment, the cover portion 31 of the valve member 30 includes a first member 321 and a second member 322. In this modification, the cover portion 31 also includes the first member 321, which prevents the cover portion 31 from being damaged by the heat of the fluid.

[0069] 9 , the cover unit 31 may be divided into a central portion 331 and a peripheral portion 332 in a plan view. In the example shown in Fig. 9 , the central portion 331 is a portion of the cover unit 31 that covers the opening 103 of the housing 100. In the example shown in Fig. 9 , an outer edge 103e of the opening 103 of the housing 100 defines the boundary between the central portion 331 and the peripheral portion 332.

[0070] In this modification as well, it is preferable that the inner surface 311 of the central portion 331 is at least partially constituted by the first member 321. Preferably, the first member 321 extends so as to overlap the outer edge 103e of the opening 103 in plan view.

[0071] In this modification, the inner surface 311 of the surrounding portion 332 may also be at least partially formed of the second member 322. For example, it is preferable that the inner surface 311 of the surrounding portion 332 that contacts the first seal member 27 is formed of the second member 322. When the inner surface 311 of the surrounding portion 332 that contacts the first seal member 27 is made of resin, the degree of freedom in designing the first seal member 27 is increased. For example, the degree of freedom in the shape of the first seal member 27 is increased. For example, the first seal member 27 is easily provided on the cover portion 31. For example, the degree of freedom in the direction of sealing achieved by the first seal member 27 is increased.

[0072] 10 is a vertical cross-sectional view showing the pressure release valve 10 in an open state and the housing 100. When the internal pressure of the housing 100 exceeds a predetermined threshold, the cover part 31 moves in the first direction D1 so as to move away from the housing 100.

[0073] When the cover part 31 moves, a gap is created between the inner surface 311 of the cover part 31 and the surface 101 of the housing 100. The inner surface 311 of the cover part 31 overlaps the outer edge 103e of the opening 103 of the housing 100. The gap between the inner surface 311 of the cover part 31 and the surface 101 of the housing 100 is formed over the entire outer edge 103e of the opening 103. This increases the flow rate of the fluid that passes through the gap and is released to the outside.

[0074] 10 , the fluid F being discharged from the inside to the outside of the housing 100 collides with the inner surface 311 of the cover part 31 during the discharge process. The cover part 31 includes a first member 321 located on at least a part of the inner surface 311. The melting point of the first member 321 is higher than the melting point of the second member 322, and therefore damage to the cover part 31 is suppressed.

[0075] As the fluid is released to the outside, the internal pressure decreases. When the force that the internal pressure applies to the cover portion 31 becomes smaller than the force that the elastic member 40 applies to the cover portion 31, the restoring force of the elastic member 40 causes the cover portion 31 to move toward the housing 100. Because the first member 321 prevents the cover portion 31 from being damaged, the cover portion 31 can close the opening 103 of the housing 100 again.

[0076] 8 , the cover portion 31 may include a plurality of ribs 35 located on the outer surface 312. The ribs 35 may extend radially from the center of the cover portion 31 toward the periphery. Including the ribs 35 in the cover portion 31 increases the strength of the cover portion 31. Therefore, even if the thickness of the first member 321 is small, deformation of the cover portion 31 is suppressed.

[0077] Fig. 11 is a vertical cross-sectional view showing another example of the second modified example. As shown in Fig. 11, the first member 321 may be exposed on a part of the outer surface 312 of the cover portion 31. In other words, the first member 321 may be configured continuously in the thickness direction from the inner surface 311 to the outer surface 312 of the cover portion 31. This makes it possible to suppress deformation of the first member 321.

[0078] (Other Modifications) A plurality of modifications may be combined with the above-described embodiment. A plurality of modifications may be combined with each other.

[0079] REFERENCE SIGNS LIST 10 Pressure release valve 20 Main body 21 Base 211 Inner surface 212 Outer surface 213 Opening 22 Side wall 23 Beam portion 241 First member 242 Second member 27 First sealing member 28 Second sealing member 30 Valve member 31 Cover portion 311 Inner surface 312 Outer surface 321 First member 322 Second member 331 Central portion 332 Peripheral portion 34 Protrusion 35 Rib 37 Shaft 38 End lock 40 Elastic member 100 Housing 101 Surface 102 Back surface 103 Opening 103e Outer edge 105 Fastening hole

Claims

1. A pressure relief valve which releases fluid from an opening of a housing when the internal pressure of the fluid inside the housing rises, comprising: a main body attached to the housing; a valve member which is movable relative to the main body from a closed position which closes the opening to an open position which opens the opening; and an elastic member which urges the valve member towards the closed position, wherein the valve member includes a cover part which directly or indirectly covers the opening in the closed position, wherein the cover part includes an inner surface facing the housing and an outer surface located opposite the inner surface, wherein the cover part includes a first member located on at least a part of the inner surface, and a second member made of resin which is located closer to the outer surface than the first member, wherein the melting point of the first member is higher than the melting point of the second member.

2. A pressure relief valve as described in claim 1, wherein the cover portion is partitioned, in a plan view, into a central portion that directly or indirectly covers the opening, and a peripheral portion located around the central portion, the inner surface of the central portion being at least partially constituted by the first member, and the inner surface of the peripheral portion being at least partially constituted by the second member.

3. A pressure relief valve as described in claim 1 or 2, wherein the melting point of the first member is 400°C or higher.

4. The pressure relief valve of claim 3, wherein the first member is made of metal.

5. A pressure relief valve as described in claim 1 or 2, wherein the first member extends so as to overlap, in a plan view, with the outer edge of the opening in the housing, or the first member extends so as to overlap, in a plan view, with the outer edge of an opening in the main body that communicates with the opening in the housing.

6. The pressure relief valve of claim 1 or 2, wherein said second member includes a plurality of ribs located on said outer surface.

7. A pressure relief valve as described in claim 1 or 2, wherein the second member includes a protrusion that protrudes from the inner surface toward the housing, and the first member includes a tip that engages with the protrusion.

8. A pressure relief valve as described in claim 1 or 2, wherein the valve member includes a shaft extending from the inner surface of the cover portion toward the housing, and the elastic member is positioned around the shaft.

9. The pressure relief valve of claim 8, wherein the shaft comprises metal.

10. The pressure relief valve as described in claim 8, wherein the main body includes a beam portion extending across the opening of the housing or an opening of the main body that communicates with the opening of the housing, the beam portion includes a through hole through which the shaft is inserted, and the beam portion includes metal.

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