Pressure relief valve

Abstract

To provide technology to realize a small pressure relief valve.SOLUTION: A pressure relief valve is provided in a case of a battery pack and closes a cylindrical opening communicating with the exhaust hole of the battery pack, and communicates the opening with the outside space as the pressure inside the battery pack increases. The pressure relief valve includes a cover connected to the case and a valve that is biased in the direction to close the opening by an elastic body attached to the cover and is movable along the central axis of the opening. The cover is also provided with an opening exhaust hole that exhausts gas flowing out from the opening, and the cover and the valve are formed such that when the opening is in a fully open state, the flow path of the gas from the opening to the opening exhaust hole changes continuously in the central axis direction in a direction away from the opening, and also changes continuously in a direction from the center of the opening toward the outer periphery of the opening.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] This specification discloses technology relating to a pressure relief valve. [Background technology]

[0002] Patent Document 1 discloses a pressure relief valve that releases pressure in a battery pack when the pressure in the battery pack increases. The pressure relief valve in Patent Document 1 is a so-called swing valve, and a double torsion spring is disposed on the circumferential outside of a valve body that closes the opening of the battery pack. The extension of the double torsion spring is fixed to the center of the valve body. Therefore, in the pressure relief valve in Patent Document 1, when the pressure in the battery pack increases, the valve opens while the pressure receiving surface of the valve body tilts. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-194719 A Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, when the pressure relief valve of Patent Document 1 opens, the valve body opens while the pressure receiving surface of the valve body is inclined. Therefore, the valve body cannot efficiently receive the pressure in the battery pack, and when the pressure in the battery pack rises, the valve body may not open immediately. As a result, when the pressure in the battery pack rises, it takes a long time for the pressure in the battery pack to decrease (the time when the battery pack is in a high-pressure state becomes longer), and the battery pack may be damaged. Therefore, a technology is required to immediately reduce the pressure in the battery pack when the pressure in the battery pack rises. The present specification aims to realize a pressure relief valve that quickly reduces the pressure in the battery pack. [Means for solving the problem]

[0005] The first technology disclosed in this specification may be a pressure relief valve that is provided in a battery pack case and closes a cylindrical opening that is in communication with a discharge hole of the battery pack, and that communicates the opening with an external space as pressure inside the battery pack increases. This pressure relief valve may include a cover connected to the case, and a valve that is biased in a direction to close the opening by an elastic body attached to the cover and is movable along a central axis of the opening. The cover may be provided with an opening discharge hole that discharges gas flowing out from the opening, and the cover and the valve may be formed so that, when the opening is in a fully open state, the flow path of the gas from the opening to the opening discharge hole changes continuously in the direction away from the opening in the central axis direction and continuously changes in the direction from the center of the opening to the outer periphery of the opening.

[0006] A second technology disclosed in this specification is the pressure relief valve of the first technology, wherein the flow passage may be conical.

[0007] A third technology disclosed in this specification is a pressure relief valve of the first or second technology, wherein when a cross section of the cover located in a direction perpendicular to the central axis is observed from the central axis direction, the inside of the cover is arc-shaped and the area decreases from the middle of the cover toward the outside.

[0008] A fourth technology disclosed in this specification is a pressure relief valve of any of the first to third technologies above, wherein a gap may be provided between an outer peripheral surface of the opening and an inner surface of the cover.

[0009] A fifth technology disclosed in this specification is a pressure relief valve of the first technology, wherein, when a cross section including the central axis of the valve is observed, the side of the valve has a curve, and when the valve is open, the distance between an inner edge of the opening and the valve is greater than the distance between the opening and the valve at an end face of the opening.

[0010] A sixth technology disclosed in this specification is a pressure relief valve of any of the first to fourth technologies, wherein when the direction in which the valve moves when closing the opening is downward and the direction in which the valve moves when opening the opening is upward, the opening discharge hole is provided in a side wall of the cover and is inclined upward as it moves away from the central axis, and the side surface of the valve is inclined upward as it moves away from the central axis so that the end face comes into contact with the opening, which is inclined upward as it moves away from the central axis.

[0011] The seventh technology disclosed in this specification is the pressure relief valve of the sixth technology, wherein the valve has a conical shape.

[0012] The eighth technology disclosed in this specification is a pressure relief valve of any of the first to seventh technologies above, wherein a recess is provided above the valve, and the elastic body is connected to the valve within the recess.

[0013] A ninth technology disclosed in this specification is a pressure relief valve of any of the first to eighth technologies above, which is provided with a communication hole connecting an upper side of the valve with a side of the valve, and which may generate negative pressure on the upper side of the valve when the valve opens.

[0014] A tenth technology disclosed in this specification is a pressure relief valve of any of the first to ninth technologies above, wherein the angle of a side of the valve is adjusted so that the side of the valve contacts the inner edge of the opening when the valve is blocking the opening. Effect of the Invention

[0015] According to the first technique, when the pressure inside the battery pack rises and the valve opens the opening, a gas flow path with low flow resistance is formed from the opening to the opening exhaust hole. As a result, when the valve is opened, the gas exhaust flow rate increases, and the pressure inside the battery pack can be quickly reduced.

[0016] According to the second technique, a gas flow path with even lower flow resistance is formed, and the pressure inside the battery pack can be reduced even more quickly.

[0017] According to the third technique, it is possible to suppress an increase in flow path resistance of the gas when the gas moves from the inside to the outside of the cover.

[0018] According to the fourth technology, moisture that has entered the cover through the opening exhaust hole can be exhausted to the outside of the cover. By exhausting moisture from inside the cover to the outside of the cover, deterioration of the components (elastic body, valve) embedded in the cover can be suppressed. In addition, by exhausting moisture from inside the cover to the outside of the cover, it is also possible to suppress moisture from entering the battery pack from inside the cover when the opening is opened.

[0019] According to the fifth technology, the travel distance of the valve when opening can be shortened, and the pressure relief valve can be made smaller.

[0020] According to the sixth technology, the flow of gas from the opening to the opening exhaust hole becomes smooth, and a gas flow path with low flow resistance (high flow coefficient) is easily formed. As a result, the gas exhaust flow rate can be further increased when the valve is opened.

[0021] According to the seventh technique, the gas that has moved through the center of the opening can be reliably guided toward the exhaust hole of the opening without being stagnated by the side surface of the valve.

[0022] According to the eighth technology, the height of the cover can be reduced, and the pressure relief valve can be made smaller.

[0023] According to the ninth technology, negative pressure can be generated in the space above the valve, which can increase the valve opening speed. The pressure release valve can be quickly brought to a fully open state, and the pressure inside the battery pack can be quickly reduced.

[0024] According to the tenth technology, the pressure-receiving area of ​​the valve can be minimized while the valve is closing the opening. This allows the biasing force of the elastic body to be reduced when biasing the valve to the opening. In addition, when the valve moves away from the opening to open it, the side of the valve can also receive pressure. As a result, when the opening is opened, the pressure-receiving area of ​​the valve increases, the valve opening speed can be increased, and the pressure inside the battery pack can be quickly reduced. [Brief description of the drawings]

[0025] [Figure 1] 1 is a cross-sectional view of a pressure relief valve according to a first embodiment (closed state). [Diagram 2] 1 is a cross-sectional view of a pressure relief valve according to a first embodiment (open state). [Diagram 3] FIG. 2 is a cross-sectional view taken along line III-III in FIG. [Figure 4] An enlarged view of the area surrounded by dashed line IV in FIG. 1 is shown. [Diagram 5] FIG. 13 is a diagram for explaining the relationship between the valve and the opening in a closed state. [Figure 6] 4 is a cross-sectional view of a pressure relief valve according to a second embodiment. [Figure 7] 13 is a cross-sectional view of a pressure relief valve according to a third embodiment. [Figure 8] 1 shows modified examples of the covers of the first to third embodiments. [Figure 9] 13 is a cross-sectional view of a pressure relief valve according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] (First Example) The pressure relief valve 100 will be described with reference to Figs. 1 to 5. As shown in Figs. 1 and 2, the pressure relief valve 100 is fixed to a case 50 of a battery pack by a bolt 40. An overall view of the battery pack is omitted. The case 50 has a cylindrical opening 52 extending in the direction of a central axis CL. The central axis CL is the central axis of the opening 52. The opening 52 communicates with a discharge hole (not shown) of the battery pack. An end face 56 of the opening 52 functions as a valve seat on which the valve 30 is seated. Fig. 1 shows a state in which the pressure relief valve 100 (valve 30) closes the opening 52, and Fig. 2 shows a state in which the pressure relief valve 100 (valve 30) opens the opening 52.

[0027] The pressure relief valve 100 includes a cover 10 fixed to a case 50 by a bolt 40, a coil spring 20 attached to the cover 10, and a valve 30 biased toward an opening 52 by the coil spring 20. The coil spring 20 and the valve 30 are disposed in a space 70 within the cover 10. The coil spring 20 is an example of an elastic body. The cover 10 has a fixed part 12 extending in a direction perpendicular to the central axis CL, a cover upper part 18 extending in a direction perpendicular to the central axis CL at a position spaced apart from the fixed part 12 in the direction of the central axis CL, and a cylindrical cover side part 16 connecting the fixed part 12 and the cover upper part 18. The fixed part 12 is fixed to the case 50 by a bolt 40. A gap 72 is provided between the fixed part 12 and the case 50 except for the part fixed by the bolt 40. The cover side part 16 is provided with an opening discharge hole 14 communicating the inside and outside of the cover side part 16.

[0028] 3, four opening discharge holes 14 are provided in the cover side portion 16. The opening discharge holes 14 are arranged at equal intervals in the circumferential direction of the cover side portion 16. That is, the opening discharge holes 14 are arranged so that the angle between the central axis CL and adjacent opening discharge holes 14 is 90 degrees.

[0029] 4, a gap 74 is provided between the outer peripheral surface 54 of the opening 52 and the inner surface 17 of the cover 10 (cover side portion 16). The gap 74 allows the space 70 and the gap 72 to communicate with each other.

[0030] As shown in FIG. 1, the coil spring 20 is disposed inside the cover side portion 16 (space 70) and provided between the cover upper portion 18 and the valve 30. More specifically, one end of the coil spring 20 is attached to the lower surface of the cover upper portion 18 (the surface of the cover upper portion 18 on the valve 30 side). The other end of the coil spring 20 is attached to the upper surface of the valve 30 (the surface of the valve 30 on the cover upper portion 18 side). The lower surface of the valve 30 (the surface opposite to the upper surface of the valve 30) is flat. The valve 30 has a substantially truncated cone shape. The valve 30 is biased in a direction to close the opening 52 by the tension force of the coil spring 20. When the pressure inside the battery pack 80 is normal (less than a predetermined value), the valve 30 is biased toward the opening 52 by the coil spring 20, and the side surface 32 of the valve 30 contacts (seats) the end surface 56 (seat surface) of the opening 52.

[0031] As shown in FIG. 2, when the pressure inside the battery pack 80 rises (above a predetermined value), the pressure on the lower surface of the valve 30 (the surface of the valve 30 opposite the cover upper portion 18 side) becomes higher than the pressure on the upper surface of the valve 30. As a result, the valve 30 moves toward the cover upper portion 18 side against the biasing force of the coil spring 20, and the valve 30 moves away from the opening 52. As a result, the opening 52 and the opening exhaust hole 14 communicate with each other, and the gas inside the battery pack 80 flows out into the cover 10 through the opening 52. The gas that has flowed into the cover 10 from the battery pack 80 moves toward the opening exhaust hole 14 and is exhausted to the outside of the pressure relief valve 100. When the gas inside the battery pack 80 is exhausted and the pressure inside the battery pack 80 returns to normal, the valve 30 is biased toward the opening 52 by the tension force of the coil spring 20, and the side surface 32 of the valve 30 is seated on the end surface 56 of the opening 52 (state of FIG. 1).

[0032] In the pressure relief valve 100, the valve 30 moves along the central axis CL to block or open the opening 52 depending on the pressure inside the battery pack 80. In the following description, the direction in which the valve 30 moves when opening the opening 52 (Fig. 1 → Fig. 2) may be referred to as "upward," and the direction in which the valve 30 moves when closing the opening 52 (Fig. 2 → Fig. 1) may be referred to as "downward."

[0033] As shown in FIG. 1 and FIG. 2, the opening exhaust hole 14 is inclined so as to face upward as it moves away from the central axis CL. In addition, the end surface 56 of the opening 52 is also inclined so as to face upward as it moves away from the central axis CL. Similarly, the side surface 32 of the valve 30 is also inclined so as to face upward as it moves away from the central axis CL. Therefore, when the opening 52 is in a fully open state (the state of FIG. 2), the gas flow path 82 from the opening 52 to the opening exhaust hole 14 forms a substantially conical flow path. More specifically, the flow path 82 changes continuously in the direction away from the opening 52 in the direction of the central axis CL. In addition, the flow path 82 also changes continuously in the direction from the center of the opening 52 toward the outer periphery of the opening 52. Therefore, the flow path 82 can move from the opening 52 to the opening exhaust hole 14 with low resistance.

[0034] 5, the relationship between the valve 30 and the opening 52 when the opening 52 is closed (the state of FIG. 1) will be described. When the valve 30 closes the opening 52, the side surface 32 of the valve 30 contacts an edge 57 of an inner side surface 58 of the opening 52. In other words, the angles of the side surface 32 and the end surface 56 are adjusted so that the angle θ1 between the side surface 32 of the valve 30 and the central axis CL is smaller than the angle θ2 between the end surface 56 of the opening 52 and the central axis CL.

[0035] (Advantages of Pressure Relief Valve 100) The advantages of the pressure relief valve 100 are listed below. (1) In the pressure relief valve 100, the valve 30, the opening 52, and the opening exhaust hole 14 are formed so that the gas flow path 82 forms a substantially conical flow path. As a result, when the pressure inside the battery pack 80 rises and the valve 30 opens the opening 52 (when the opening 52 and the opening exhaust hole 14 communicate with each other), the flow path 82 with low flow resistance (high flow coefficient) is formed. As a result, when the valve 30 opens the opening 52, the gas exhaust flow rate increases, and the pressure inside the battery pack 80 can be quickly reduced. (2) A gap 74 is provided between the outer peripheral surface 54 of the opening 52 and the inner surface 17 of the cover side portion 16. For example, when moisture enters the interior (space 70) of the cover 10 from the opening exhaust hole 14, the moisture can be discharged from the space 70 to the gap 72. This can suppress deterioration of the coil spring 20, the valve 30, etc., and can also suppress the intrusion of moisture into the interior 80 of the battery pack when the opening 52 is open. (3) The opening discharge hole 14, the end face 56 of the opening 52, and the side face 32 of the valve 30 are inclined upward with increasing distance from the central axis CL. Therefore, a flow path 82 with low flow resistance (high flow coefficient) is easily formed. (4) When the valve 30 closes the opening 52, the side surface 32 of the valve 30 contacts the edge 57 of the inner surface 58 of the opening 52. As a result, when the valve 30 closes the opening 52, the valve 30 receives the pressure of the inside 80 of the battery pack only on the central axis CL side of the inner surface 58 of the opening 52. That is, while the opening 52 is closed, the pressure-receiving area of ​​the valve 30 can be minimized. As a result, the tension (biasing force) of the coil spring 20 can be reduced. In addition, when the pressure inside the battery pack 80 increases and the valve 30 moves upward away from the opening 52, pressure is also applied to the side surface 32 of the valve 30. Therefore, when the valve 30 moves upward, the pressure-receiving area of ​​the valve 30 is larger than when the valve 30 closed the opening 52. Since a larger pressure is applied to the valve 30, the valve 30 opens faster, and the pressure inside the battery pack 80 can be reduced quickly.

[0036] (Second Example) The pressure relief valve 200 will be described with reference to Fig. 6. The pressure relief valve 200 is a modified example of the pressure relief valve 100. Regarding the pressure relief valve 200, the structures substantially the same as those of the pressure relief valve 100 are denoted by the same reference numbers as those of the pressure relief valve 100, and descriptions thereof may be omitted.

[0037] The pressure relief valve 200 includes a cone-shaped valve 230. More specifically, a side surface 232 of the valve 230 forms a cone shape. Also, a recess 236 is provided in an upper surface (upper surface) 234 of the valve 230. The coil spring 20 is attached to the upper surface 234 of the valve 230 within the recess 236.

[0038] (Advantages of Pressure Relief Valve 200) The pressure relief valve 200 has the same advantages (1) to (4) as the pressure relief valve 100. In addition, the pressure relief valve 200 has the following advantages. (5) Since the side surface 232 of the valve 230 forms a conical shape, the gas flow path 82 is more likely to become a conical flow path. That is, the gas that has moved through the central portion (portion close to the central axis CL) of the opening 52 can be reliably guided toward the opening exhaust hole 14 without stagnation. (6) The coil spring 20 is attached to the valve 230 in a recess 236 provided in the upper surface 234 of the valve 230. This makes it possible to shorten the distance between the cover upper part 18 and the fixed part 12. In other words, the length of the cover side part 16 in the direction of the central axis CL is shortened, so that the pressure relief valve 200 can be made smaller (reduced in height).

[0039] (Third Example) The pressure relief valve 300 will be described with reference to Fig. 7. The pressure relief valve 300 is a modified example of the pressure relief valve 200. Regarding the pressure relief valve 300, the structures substantially the same as those of the pressure relief valve 200 are denoted by the same reference numbers as those of the pressure relief valve 200, and descriptions thereof may be omitted.

[0040] The pressure relief valve 300 includes a cone-shaped valve 330. An upwardly extending rib 335 is provided at the circumferential end of the upper surface 234 of the valve 330. Also, a communication hole 333 is provided to communicate the upper surface 234 and the side surface 232 of the valve 330. The communication hole 333 communicates the space above the valve 330 (the space surrounded by the upper surface 234 and the cover 10) with the space on the side surface of the valve 330 (the space where the flow path 82 is formed). In the pressure relief valve 300, when the pressure in the battery pack interior 80 increases and the valve 330 separates from the opening 52 and gas flows from the opening 52 to the opening exhaust hole 14, the air present in the space above the valve 330 moves to the space on the side surface of the valve 330 through the communication hole 333 due to the Bernoulli effect. As a result, the pressure in the space above the valve 330 decreases (negative pressure occurs). Incidentally, by providing the rib 335, it is possible to prevent the space above the valve 330 from directly communicating with the opening discharge hole 14.

[0041] (Advantages of Pressure Relief Valve 300) The pressure relief valve 300 has the same advantages (1) to (6) as the pressure relief valve 200. In addition, the pressure relief valve 300 has the following advantages. (7) When the opening 52 is opened, a negative pressure can be generated in the space above the valve 330. The generation of negative pressure causes an upward force to act on the valve 330. As a result, the valve 330 opens faster, and when the pressure inside the battery pack 80 rises, the pressure release valve 300 can be quickly brought to a fully open state.

[0042] (Modification of cover 10) The cover 10a will be described with reference to Fig. 8. The cover 10a can be used in place of the cover 10 used in the pressure relief valves 100, 200, and 300. The cover 10a connects the fixed portion 12 and the cover upper portion 18 with four cover side portions 16a. Each cover side portion 16a is columnar and is provided at equal intervals in the circumferential direction of the cover upper portion 18. That is, the cover side portions 16a are provided so that the angle between the central axis CL and the adjacent cover side portion 16a is 90 degrees. A gap is provided between the cover side portions 16a, 16a, and functions as the opening discharge hole 14a.

[0043] The cover side portion 16a has an arc shape on the inside (the side of the central axis CL) and has a shape in which the area decreases from the middle portion toward the outside. By using the cover side portion 16a having such a shape, it is possible to suppress an increase in the flow resistance of the gas when the gas moves from the inside to the outside of the cover 10a (when the gas passes through the opening discharge hole 14a).

[0044] (Fourth Example) The pressure relief valve 400 will be described with reference to Fig. 9. The pressure relief valve 400 is a modified example of the pressure relief valve 200. Regarding the pressure relief valve 400, the structures substantially the same as those of the pressure relief valve 200 are denoted by the same reference numbers as those of the pressure relief valve 200, and descriptions thereof may be omitted.

[0045] In the pressure relief valve 400, the end face 56 of the opening 52 spreads in a direction perpendicular to the central axis CL (horizontal direction). In addition, the area between the end face of the opening 52 and the inner side surface 58 (the edge of the inner side surface 58) is curved to have a radius. Furthermore, the opening discharge hole 14 extends in a direction perpendicular to the central axis CL (horizontal direction). In the pressure relief valve 400, a valve 430 is used in which the side surface 432 appears as a curve in a cross section including the central axis CL (cross section shown in FIG. 8). The side surface 432 of the valve 430 has a downwardly convex curve from the central axis CL to the middle part toward the outer periphery. In addition, the curve of the side surface 432 shows an inflection point at the middle part, and has an upwardly convex curve from the middle part to the outer periphery. When the valve 430 closes the opening 52, the edge of the inner side surface 58 of the opening 52 (the part curved to have a radius) comes into contact with the part of the side surface 432 of the valve 430 having an upwardly convex curve.

[0046] In the pressure relief valve 400, when the opening 52 is in a fully open state, a flow path 482 is formed that follows the shape of the side surface 432 of the valve 430. The flow path 482 changes continuously in the direction of the central axis CL in a direction away from the opening 52, and also changes continuously in a direction from the center of the opening 52 toward the outer periphery of the opening 52. A recess 436 is provided in the upper surface 434 of the valve 430, and the coil spring 20 is attached to the upper surface 434 of the valve 430 within the recess 436.

[0047] In the pressure relief valve 400, the end face 56 of the opening 52 spreads in the horizontal direction. In addition, the opening 52 and the valve 430 come into contact with the edge of the inner surface 58, which is machined to have a rounded curve, and the side surface 432 of the upwardly convex curved portion. Therefore, when the valve 430 is open, the distance between the edge of the inner surface 58 and the valve 430 (the gas flow path area) is greater than the distance between the end face 56 and the valve 430 (the movement distance of the valve 430 when the valve 430 is opened).

[0048] (Advantages of Pressure Relief Valve 400) The pressure relief valve 400 has the same advantages as the advantages (2) and (4) of the pressure relief valve 200. In addition, the pressure relief valve 400 has the following advantages. (8) When the pressure inside the battery pack 80 increases and the valve 430 opens the opening 52, a flow path 482 with low flow resistance is formed along the shape of the side surface 432 of the valve 430. As a result, when the valve 430 opens the opening 52, the exhaust flow rate of the gas increases, and the pressure inside the battery pack 80 can be quickly reduced. (9) Since the distance between the edge of the inner surface 58 and the valve 430 is greater than the distance between the end surface 56 and the valve 430, the moving distance of the valve 430 when opening can be shortened, and the pressure relief valve 400 can be made smaller (reduced in height).

[0049] (Other embodiments) In the above embodiment, the pressure relief valves 100 to 400 are described in which the cover 10 (cover side portion 16) is provided with four opening discharge holes 14, but the number of opening discharge holes 14 may be three or less, or five or more. The number of opening discharge holes 14 can be appropriately changed as needed. Similarly, in the cover 10a, the number of cover side portions 16a can be appropriately changed as needed, and may be three or less, or five or more.

[0050] In the above embodiment, the coil spring is used as the elastic body, but a leaf spring, a disc spring, rubber, or the like may be used instead of the coil spring.

[0051] In the pressure relief valve 100, a recess may be provided in the upper surface of the valve 30, and the coil spring 20 may be attached to the valve 30 within the recess, similarly to the pressure relief valve 200. The pressure relief valve 100 can be made smaller.

[0052] In the pressure relief valves 200, 300, and 400, the upper surface of the valve may be flat and the coil spring may be attached to the flat surface. In other words, the recess provided on the upper surface of the valve may be omitted. This improves the strength of the valve and makes it easier to manufacture the valve.

[0053] The gap provided between the outer peripheral surface of the opening and the inner surface of the cover is not essential in the pressure relief valves 100 to 400. If necessary, the gap between the outer peripheral surface of the opening and the inner surface of the cover may be eliminated.

[0054] In the pressure relief valves 100 to 300, the angle of the side surface of the valve does not have to be adjusted so that the side surface of the valve contacts the inner edge of the opening when the valve closes the opening. For example, the angle of the side surface of the valve may be adjusted so that the side surface of the valve contacts the entire end face of the opening.

[0055] Although the embodiments of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples exemplified above. Furthermore, the technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings achieves multiple objectives simultaneously, and achieving one of the objectives itself has technical utility. [Explanation of symbols]

[0056] 10:Cover 14: Opening discharge hole 20: Elastic body 30: Valve 50: Case 52: Opening 82: Flow path 100: Pressure relief valve

Claims

1. a pressure relief valve that is provided in a case of a battery pack, closes a cylindrical opening that is in communication with a discharge hole of the battery pack, and communicates the opening with an external space as pressure in the battery pack increases, a cover connected to the case; a valve that is biased in a direction to close the opening by an elastic body attached to the cover and is movable along a central axis of the opening, The cover is provided with an opening exhaust hole for exhausting gas flowing out from the opening, a pressure relief valve, the cover and the valve being formed so that, when the opening is fully open, the gas flow path from the opening to the opening exhaust hole changes continuously in the direction away from the opening in the central axis direction, and also changes continuously in the direction from the center of the opening toward the outer periphery of the opening.

2. 2. The pressure relief valve of claim 1, A pressure relief valve, wherein the flow passage forms a conical flow passage.

3. 2. The pressure relief valve of claim 1, When a cross section of the cover positioned in a direction perpendicular to the central axis is observed from the central axis direction, The inside of the cover is arc-shaped, and the area of ​​the pressure relief valve decreases from the middle to the outside of the cover.

4. 2. The pressure relief valve of claim 1, A pressure relief valve having a gap between an outer peripheral surface of the opening and an inner surface of the cover.

5. 2. The pressure relief valve of claim 1, When a cross section including the central axis of the valve is observed, The valve has a curved side, A pressure relief valve in which, when the valve is open, the distance between an inner edge of the opening and the valve is greater than the distance between the opening and the valve at an end face of the opening.

6. 2. The pressure relief valve of claim 1, When the direction in which the valve moves when closing the opening is defined as a downward direction, and the direction in which the valve moves when opening the opening is defined as an upward direction, The opening discharge hole is provided in a side wall of the cover and is inclined upward as it moves away from the central axis, A pressure relief valve in which the side surface of the valve is inclined upward as it moves away from the central axis so that the end surface comes into contact with the opening, which is inclined upward as it moves away from the central axis.

7. 7. The pressure relief valve of claim 6, A pressure relief valve, wherein the valve is cone shaped.

8. 8. The pressure relief valve of claim 7, A recess is provided above the valve, A pressure relief valve, the elastic body being connected to the valve within the recess.

9. 9. The pressure relief valve of claim 8, A communication hole is provided to communicate an upper side of the valve with a side surface of the valve, A pressure relief valve that creates negative pressure above the valve when the valve opens.

10. 10. A pressure relief valve according to any one of claims 1 to 9, A pressure relief valve in which the angle of a side surface of the valve is adjusted so that the side surface of the valve contacts the inner edge of the opening when the valve is closing the opening.

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