Battery pack

Abstract

Provided is a battery pack in which, if abnormal heating occurs in a cylindrical cell, the container of an embedding member is opened early. A battery pack according to the present disclosure comprises: a plurality of cylindrical cells arranged such that the electrode terminals face in the same direction; and an embedding member disposed between the plurality of cylindrical cells. The embedding member includes a container, and a heat absorbing agent and a gas accommodated within the container. The container is provided with a protrusion disposed between two adjacent cylindrical cells when viewed from the longitudinal direction of the cylindrical cells, and extending in the longitudinal direction of the cylindrical cells. The protrusion has a heat absorbing agent accommodation part in which the heat absorbing agent is accommodated, and a gas housing part in which the gas is accommodated. The gas accommodation part is positioned at the tip of the protrusion and comes into contact with each of the two adjacent cylindrical cells.

Description

Technical Field

[0001] The present disclosure relates to a battery pack.

Background Art

[0002] A battery unit equipped in a battery pack has a plurality of cells. When the cells are cylindrical cells, the plurality of cylindrical cells are arranged in a direction orthogonal to the longitudinal direction of the cylindrical cells. Further, the plurality of cylindrical cells are arranged such that the electrode terminals are located on the same plane. If abnormal heat generation occurs in one cylindrical cell, there is a possibility that the adjacent cylindrical cell is heated and catches fire. In order to prevent such induced explosion (the adjacent cylindrical cell is heated and catches fire), an embedding member may be arranged between the cylindrical cells. Further, the embedding member in the following patent document has a resin container and a heat-absorbing agent housed in the container. When abnormal heat generation occurs in the cylindrical cell, a part of the container melts (opens), and the heat-absorbing agent is discharged.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, according to the above embedding member, since the heat transmitted from the cylindrical cell to the container is absorbed by the heat-absorbing agent housed inside, the temperature rise of the container is suppressed. That is, the melting of the container is delayed, and the container is not opened promptly.

[0005] In view of the above problems, an object of the present disclosure is to provide a battery pack in which the container of the embedding member is opened early when abnormal heat generation occurs in the cylindrical cell.

Means for Solving the Problems

[0006] A battery pack according to one aspect of the present disclosure includes a plurality of cylindrical cells arranged such that electrode terminals face the same direction, and an embedded member disposed between the plurality of cylindrical cells. The embedded member has a container, and a heat-absorbing agent and a gas accommodated inside the container. The container is provided with a convex portion that is disposed between two adjacent cylindrical cells when viewed from the longitudinal direction of the cylindrical cells and extends in the longitudinal direction of the cylindrical cells. The convex portion has a heat-absorbing agent accommodating portion in which the heat-absorbing agent is accommodated and a gas accommodating portion in which the gas is accommodated. The gas accommodating portion is disposed at the tip of the convex portion and contacts each of two adjacent cylindrical cells.

Advantages of the Invention

[0007] According to the battery pack of the present disclosure, the gas accommodating portion melts early, and the supply of the heat-absorbing agent is accelerated. Thereby, detonation is suppressed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

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[0009] Hereinafter, the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited by the following embodiments for carrying out the invention (hereinafter referred to as embodiments). Further, the constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those within the so-called equivalent range. Furthermore, the constituent elements disclosed in the following embodiments can be combined as appropriate.

[0010] (Embodiment 1) FIG. 1 is an exploded perspective view of a battery pack 100 according to Embodiment 1. As shown in FIG. 1, the battery pack 100 includes a battery unit 1 and a case 101 that houses the battery unit 1.

[0011] The case 101 is a resin housing. The case 101 has a first case 102 and a second case 103 that are vertically divided. The first case 102 is disposed above the second case 103 in the vertical direction. Hereinafter, the upper side in the vertical direction is referred to as the upper Z1. The lower side in the vertical direction is referred to as the lower Z2. Also, the direction orthogonal to the vertical direction is referred to as the horizontal direction.

[0012] The first case 102 forms a bottomed cylindrical shape that opens downward Z2. The second case 103 forms a bottomed cylindrical shape that opens upward Z1. The first case 102 and the second case 103 are fastened by bolts (not shown). An external terminal 110 is provided on the wall of the second case 103. The external terminal 110 is connected to the two electrode tabs 25 of the battery unit 1.

[0013] FIG. 2 is an exploded perspective view of the battery unit. As shown in FIG. 2, the battery unit 1 includes four cylindrical cells 2, a cell holder 10, tabs 20, a control board 26, and an embedded member 30. Hereinafter, the direction in which the cylindrical cell 2 extends is referred to as the longitudinal direction. Electrode terminals 3 are provided at both ends in the longitudinal direction of the cylindrical cell 2.

[0014] The four cylindrical cells 2 are each arranged to be parallel to the horizontal direction. Also, the four cylindrical cells 2 are arranged such that the electrode terminals 3 face the same direction. Also, the four cylindrical cells 2 are arranged in order in the direction orthogonal to both the vertical direction and the longitudinal direction (hereinafter referred to as the width direction). Further, the four cylindrical cells 2 are arranged such that their respective electrode terminals 3 are located on the same plane. Note that the same plane is a plane extending in the width direction and the vertical direction. Hereinafter, the direction parallel to the same plane is referred to as the plane direction. In addition, in the battery pack of the present disclosure, a plurality of electrode terminals 3 may not be arranged on the same plane. That is, a plurality of electrode terminals 3 may be arranged offset in the longitudinal direction.

[0015] The width direction in which the four cylindrical cells 2 are arranged is the direction in which the external terminal 110 is disposed when viewed from the inside of the case 101 (see FIG. 1). Hereinafter, the direction in which the external terminal 110 is disposed when viewed from the cylindrical cell 2 is referred to as the first width direction Y1, and the direction opposite to the first width direction Y1 is referred to as the second width direction Y2. Further, with respect to the four cylindrical cells 2, they may be referred to as the first cylindrical cell 2a, the second cylindrical cell 2b, the third cylindrical cell 2c, and the fourth cylindrical cell 2d in order from the first width direction Y1.

[0016] The cell holder 10 includes a first cell holder 11 and a second cell holder 12. The first cell holder 11 is disposed on one side in the longitudinal direction with respect to the four cylindrical cells 2. Further, the first cell holder 11 is a resin product. The second cell holder 12 is disposed on the other side in the longitudinal direction with respect to the four cylindrical cells 2. Further, the second cell holder 12 is a resin product. Hereinafter, the direction in which the first cell holder 11 is disposed when viewed from the four cylindrical cells 2 is referred to as the first longitudinal direction X1, and the opposite direction is referred to as the second longitudinal direction X2.

[0017] The first cell holder 11 and the second cell holder 12 are each provided with a cell accommodating portion 13. The cell accommodating portion 13 is a hole extending in the longitudinal direction, and the end portion of the cylindrical cell 2 is accommodated therein. Further, the cell accommodating portion 13 extends in the width direction so as to accommodate the four cylindrical cells 2.

[0018] The upper wall portion 14 above the cell accommodating portion 13 in the Z1 direction is formed by four arc-shaped walls continuous in the width direction. That is, the upper wall portion 14 extends along the outer peripheral surface of the four cylindrical cells 2. On the other hand, the lower wall portion 15 below the cell accommodating portion 13 in the Z2 direction is linear in the width direction. Therefore, a space for disposing the embedding member 30 is provided between the cylindrical cell 2 and the lower wall portion 15.

[0019] The tab 20 is a metal plate extending in the planar direction. The plurality of tabs 20 includes a plurality of first tabs 21 and a plurality of second tabs 22. The first tab 21 connects the electrode terminals 3 of two adjacent cylindrical cells 2 in the width direction. The second tab 22 is provided with an electrode tab 25. The first tab 21 and the second tab are each welded to the electrode terminal 3 of the cylindrical cell 2.

[0020] The control board 26 is arranged above the cell holder 10 in the Z1 direction and fixed to the cell holder 10 by screws. The control board 26 suppresses over-discharge and over-charging of the cylindrical cell 2.

[0021] FIG. 3 is a perspective view of the embedded member according to Embodiment 1. FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. 3. As shown in FIGS. 3 and 4, the embedded member 30 includes a container 40 having a sealed internal space, and a heat-absorbing agent 7 and a gas 8 (see FIG. 4) accommodated inside the container 40.

[0022] The container 40 is a resin housing. The resin preferably includes a thermoplastic resin that is easily melted by abnormal heat generation of the cylindrical cell 2. Specifically, polypropylene (PP), polystyrene (PS), and polyethylene (PE) can be mentioned.

[0023] The heat-absorbing agent 7 is a liquid mainly composed of water. When applying a gel as the form of the heat-absorbing agent 7, it is desirable to use a synthetic polymer gel. As the synthetic polymer gel, for example, sodium polyacrylate, polyvinyl alcohol, polyhydroxyethyl methacrylate, and silicone hydrogel can be used. In addition, the form of the heat-absorbing agent 7 may be a sol.

[0024] The gas 8 includes, for example, air, but the type of the gas 8 is not particularly limited. The gas 8 has a specific gravity smaller than that of the heat-absorbing agent 7. Therefore, when accommodated inside the container 40, the gas 8 is arranged in the upper Z1 direction, and the heat-absorbing agent 7 is arranged in the lower Z2 direction of the gas 8. Further, the gas 8 absorbs an extremely small amount of heat compared to the heat-absorbing agent 7.

[0025] Also, the gas 8 is stored in the container 40 in the following manner. The heat absorbent 7 is sufficiently stirred and the gas 8 is mixed into the heat absorbent 7, and then they are stored in the container. Alternatively, when storing the heat absorbent 7 in the container 40, the heat absorbent 7 does not fill all the spaces in the container 40, but a part of the space is left for storage.

[0026] As shown in FIG. 4, the container 40 includes a lower member 45 that extends horizontally along the lower wall portion 15 of the cell accommodating portion 13, and an upper member 46 that covers the upper side Z1 of the lower member 45. An internal space is formed between the lower member 45 and the upper member 46. Note that FIG. 4 is a view in which only the embedded member 30 is extracted from the battery pack 100. Therefore, the cylindrical cell 2 and the lower wall portion 15 disposed near the embedded member 30 are illustrated by phantom lines.

[0027] The upper member 46 is provided with three convex portions 47 that protrude upward in the Z1 direction. The three convex portions 47 are disposed between two adjacent cylindrical cells 2. That is, the container 40 is provided with a first convex portion 41 disposed between the first cylindrical cell 2a and the second cylindrical cell 2b, a second convex portion 42 disposed between the second cylindrical cell 2b and the third cylindrical cell 2c, and a third convex portion 43 disposed between the third cylindrical cell 2c and the fourth cylindrical cell 2d. Further, the internal spaces of the first convex portion 41, the second convex portion 42, and the third convex portion 43 are continuous with each other. Hereinafter, the first convex portion 41 will be described as a representative example, and the description of the second convex portion 42 and the third convex portion 43 will be omitted.

[0028] FIG. 5 is an exploded perspective view of the embedded member according to Embodiment 1. As shown in FIG. 5, the upper member 46 is provided with a frame-shaped frame portion 48. The convex portion 47 of the upper member 46 is arranged so as to face downward in the Z2 direction, and the heat absorbent 7 and the gas 8 are stored inside the frame portion 48. Then, the lower member 45 is overlapped from above the frame portion 48 in the Z1 direction. Then, the frame portion 48 and the lower member 45 are joined by heat welding or the like. Thereby, the lower member 45 and the upper member 46 are integrated, and the inside of the container 40 is sealed.

[0029] FIG. 6 is an enlarged view of the first convex portion of Embodiment 1. Note that FIG. 6 is a view in which only the embedded member 30 is extracted from the battery pack 100. For this reason, the cylindrical cell 2 and the lower wall portion 15 arranged in the vicinity of the embedded member 30 are illustrated by virtual lines. As shown in FIG. 6, the first convex portion 41 has a first arc wall 51, a second arc wall 52, and a connecting portion 53. The connecting portion 53 is arranged between the first cylindrical cell 2a and the second cylindrical cell 2b and extends in the width direction.

[0030] The first arc wall 51 is arranged in the first width direction Y1 with respect to the connecting portion 53. The first arc wall 51 has an arc shape. The first arc wall 51 extends along the outer peripheral surface of the first cylindrical cell 2a. That is, all of the outer peripheral side surfaces of the first arc wall 51 are in contact with the outer peripheral surface of the first cylindrical cell 2a.

[0031] The second arc wall 52 is arranged in the second width direction Y2 with respect to the connecting portion 53. The second arc wall 52 has an arc shape. The second arc wall 52 extends along the outer peripheral surface of the second cylindrical cell 2b. That is, all of the outer peripheral side surfaces of the second arc wall 52 are in contact with the outer peripheral surface of the second cylindrical cell 2b.

[0032] The space between the first arc wall 51 and the second arc wall 52 gradually narrows as it goes upward in the Z1 direction. The end portion 51a of the first arc wall 51 in the first width direction Y1 is continuous with the lower member 45. The end portion 52a of the second arc wall 52 in the second width direction Y2 is connected to the end portion 51a of the first arc wall 51 in the first width direction Y1 of the second convex portion 42. And the internal space of the first convex portion 41 and the internal space of the second convex portion 42 are continuous.

[0033] Inside the first convex portion 41, a heat-absorbing agent 7 and a gas 8 are accommodated. The gas 8, which has a lower specific gravity than the heat-absorbing agent 7, is disposed above Z1 inside the first convex portion 41. Therefore, when viewed from the longitudinal direction, the first convex portion 41 is divided into a gas accommodation portion 60 that is disposed at the tip of the first convex portion 41 and houses the gas 8 inside, and a heat-absorbing agent accommodation portion 61 that is disposed below Z2 the gas accommodation portion 60 and houses the heat-absorbing agent 7 inside. That is, the first convex portion 41 has a heat-absorbing agent accommodation portion 61 that houses the heat-absorbing agent 7 and a gas accommodation portion 60 that houses the gas 8.

[0034] Note that the gas accommodation portion 60 is composed of an end portion 51b of the first arc wall 51 near the connection portion 53, an end portion 52b of the second arc wall 52 near the connection portion 53, and the connection portion 53. Therefore, the gas accommodation portion 60 is in contact with each of two adjacent cylindrical cells 2 (the first cylindrical cell 2a and the second cylindrical cell 2b). Hereinafter, for convenience of explanation, the portion of the first arc wall 51 excluding the end portion 51b (the portion constituting the heat-absorbing agent accommodation portion 61) is referred to as a heat-absorbing agent wall portion 51c.

[0035] The connection portion 53 is disposed between the center O1 of the first cylindrical cell 2a and the center O2 of the second cylindrical cell 2b. Therefore, the connection portion 53 (the gas accommodation portion 60) is disposed at the narrowest position between the outer peripheral surface of the first cylindrical cell 2a and the outer peripheral surface of the second cylindrical cell 2b.

[0036] FIG. 7 is a cross-sectional view taken along the line VII-VII of FIG. 4. Note that FIG. 7 is a view in which only the embedded member 30 is extracted from the battery pack 100. For this reason, the cylindrical cell 2 and the lower wall portion 15 disposed in the vicinity of the embedded member 30 are illustrated by phantom lines. As shown in FIG. 7, the first convex portion 41 extends in the longitudinal direction. The first convex portion 41 has the same length as the length of the cylindrical cell 2 in the longitudinal direction. Therefore, the gas accommodation portion 60 is in contact with the first cylindrical cell 2a and the second cylindrical cell 2b over the entire length in the longitudinal direction. Also, inside the gas accommodation portion 60, the gas 8 is continuous in the longitudinal direction. More specifically, the gas 8 is continuous over the entire length in the longitudinal direction of the gas accommodation portion 60.

[0037] FIG. 8 is a view when abnormal heat generation occurs in the first cell in Embodiment 1. Note that FIG. 8 is a view in which only the embedded member 30 is extracted from the battery pack 100. For this reason, the cylindrical cell 2 and the lower wall portion 15 disposed in the vicinity of the embedded member 30 are illustrated by virtual lines. Next, the case where abnormal heat generation occurs in the cylindrical cell 2 will be described. In the following description, the case where abnormal heat generation occurs in the first cylindrical cell 2a among the four cylindrical cells 2 will be taken as an example.

[0038] When abnormal heat generation occurs in the first cylindrical cell 2a, heat is transferred to the first convex portion 41 that abuts on the outer peripheral surface of the first cylindrical cell 2a. Specifically, it is transferred to the first arc wall 51 among the first convex portions 41. Here, the heat absorption agent wall portion 51c of the first arc wall 51 constitutes the wall portion of the heat absorption agent housing portion 61 and is in contact with the heat absorption agent 7. Therefore, the heat transferred to the heat absorption agent wall portion 51c is absorbed by the heat absorption agent 7. On the other hand, the end portion 51b of the first arc wall 51 constitutes the wall portion of the gas housing portion 60 and is in contact with the gas 8 (see FIG. 6). Further, the gas 8 absorbs an extremely small amount of heat compared to the heat absorption agent 7. For this reason, as shown in FIG. 8, the end portion 51b of the first arc wall 51 melts earlier than the heat absorption agent wall portion 51c. That is, a crack 62 is generated in the gas housing portion 60 of the first convex portion 41, and the container 40 is opened.

[0039] Also, the inside of the container 40 is heated by the first cylindrical cell 2a, and the internal pressure is rising. Therefore, the heat absorption agent 7 is discharged from the crack 62 of the gas housing portion 60 and flows out between the first cylindrical cell 2a and the second cylindrical cell 2b.

[0040] Then, the heat absorption agent 7 comes into contact with the outer peripheral surface of the first cylindrical cell 2a and absorbs heat from the first cylindrical cell 2a. Thereby, the rise of the first cylindrical cell 2a is suppressed. Further, the heat absorption agent 7 comes into contact with the outer peripheral surface of the second cylindrical cell 2b and absorbs heat from the second cylindrical cell 2b. Thereby, the heat applied to the second cylindrical cell 2b by the first cylindrical cell 2a is absorbed by the heat absorption agent 7, and the heating of the second cylindrical cell 2b is suppressed.

[0041] Further, the gas storage portion 60 is in contact with the entire length of the first cylindrical cell 2a and the second cylindrical cell 2b. Therefore, even if abnormal heat generation occurs at any location in the longitudinal direction of the cylindrical cells 2a and 2b, a crack will occur in the gas storage portion 60, allowing the heat-absorbing material 7 to flow out.

[0042] As described above, according to Embodiment 1, the gas storage portion 60 is opened earlier than the heat-absorbing agent storage portion 61. Along with this, the supply of the heat-absorbing agent 7 also becomes earlier, and as a result, the detonation of the cylindrical cell 2 is suppressed.

[0043] As described above, Embodiment 1 has been explained, but the present disclosure is not limited to the example shown in Embodiment 1. For example, in Embodiment 1, the tip of the first convex portion 41 has the gas 8 continuously stored throughout the entire length direction. However, in the present disclosure, the gas 8 does not necessarily have to be continuous throughout the entire longitudinal direction of the gas storage portion 60 (convex portion 47). Hereinafter, an explanation will be given using the embedded member 30A of Modification 1.

[0044] (Modification 1) FIG. 9 is a cross-sectional view of the embedded member of Modification 1 cut in the longitudinal direction. Note that FIG. 9 is a view in which only the embedded member 30A is extracted from the battery pack. Therefore, the cylindrical cell 2 and the lower wall portion 15 disposed in the vicinity of the embedded member 30A are illustrated by phantom lines. The heat-absorbing agent 7 has high adhesiveness. Thus, as shown in FIG. 9, in the case of the embedded member 30A of Modification 1, a part 7a of the heat-absorbing agent 7 may adhere to the inner surface of the connection portion 53. For this reason, the gas 8 and the heat-absorbing agent 7 may be stored inside the wall portion surrounded by the tip of the first convex portion 41 (the end 51b of the first arc wall 51, the end 52b of the second arc wall 52, and the connection portion 53). That is, the tip of the first convex portion 41 may include a gas storage portion 60 that stores the gas 8 and a heat-absorbing agent storage portion 61 that stores a part 7a of the heat-absorbing agent 7.

[0045] According to this Modification 1, although there is a portion at the tip of the first convex portion 41 where heat is absorbed by a part 7a of the heat-absorbing agent 7, on the other hand, there is also a portion that houses the gas 8 and does not absorb heat. Therefore, when abnormal heat generation occurs in the cylindrical cell 2, the gas housing portion 60, which is a part of the tip of the first convex portion 41, melts early. Thus, also in Modification 1, early supply of the heat-absorbing agent 7 is possible as in Embodiment 1, and detonation is suppressed.

[0046] Also, in the present disclosure, the gas 8 housed in the gas housing portion 60 may be in the form of bubbles. In other words, the bubbles (gas 8) may be scattered in the length direction within the gas housing portion 60. Even in such an example, the portion where the bubbles (gas 8) are arranged melts early. From the above, in the present disclosure, the gas 8 housed in the gas housing portion 60 may be in the form of bubbles, and there is no particular limitation on the length of the gas 8 that is continuous in the longitudinal direction.

[0047] Further, the gas housing portion 60 of the present disclosure is not limited to the case where the gas 8 is in contact with the inner surface of the wall portion (the end portion 51b of the first arc wall 51, the end portion 52b of the second arc wall 52, and the connecting portion 53) that constitutes the gas housing portion 60. That is, the gas housing portion 60 includes the case where the heat-absorbing agent 7 is attached to the inner surface of the wall portion that constitutes the gas housing portion 60. More specifically, the gas 8 housed in the gas housing portion 60 includes the case where it is not in contact with the inner surface of the wall portion that constitutes the gas housing portion 60 due to the heat-absorbing agent 7 attached to the inner surface of the wall portion that constitutes the gas housing portion 60. Even in such a gas housing portion 60, although heat is absorbed by the heat-absorbing agent 7 attached to the inner surface of the wall portion that constitutes the gas housing portion 60, the amount of heat is extremely small. Therefore, early melting of the gas housing portion 60 can be achieved in the same manner as in the case of the embodiment. Note that in the present disclosure, it is preferable that the heat-absorbing agent 7 is not attached to the inner surface of the wall portion that constitutes the gas housing portion 60 because the melting of the gas housing portion 60 can be made earlier.

[0048] (Modification 2) Next, the embedding member 30B of Modification 2 will be described. FIG. 10 is a perspective view of the embedding member of Modification 2. As shown in FIG. 10, the embedding member 30B of Modification 2 is different from the embedding member 30 of Embodiment 1 in that the convex portion 47 of the container 40B is single. According to this Modification 2, detonation of two cylindrical cells 2 arranged in the width direction can be suppressed. Further, when three embedding members 30B of Modification 2 are arranged in the width direction, detonation of four cylindrical cells 2 arranged in the width direction can be suppressed in the same manner as the embedding member 30 of Embodiment 1.

[0049] (Modification 3) FIG. 11 is a perspective view of the embedding member of Modification 3. As shown in FIG. 11, the embedding member 30C of Modification 3 is different from the embedding member 30 of Embodiment 1 in that a protruding portion 55 is provided on the convex portion 47. The protruding portion 55 is provided on each of the first convex portion 41, the second convex portion 42, and the third convex portion 43. Hereinafter, the protruding portion 55 provided on the first convex portion 41 will be described as a representative example.

[0050] FIG. 12 is a cross-sectional view of the first convex portion of Modification 3. Note that FIG. 12 is a view in which only the embedding member 30C is extracted from the battery pack. For this reason, the cylindrical cell 2 and the lower wall portion 15 arranged in the vicinity of the embedding member 30C are illustrated by phantom lines. As shown in FIG. 12, the protruding portion 55 includes a first protruding portion 55a formed by protruding a part of the first arc wall 51 into the container 40C, and a second protruding portion 55b formed by protruding a part of the second arc wall 52 into the container 40C. The first protruding portion 55a and the second protruding portion 55b extend over the entire longitudinal direction of the first arc wall 51 and the second arc wall 52 (see FIG. 11).

[0051] The first protruding portion 55a and the second protruding portion 55b are in the same vertical position. That is, the first protruding portion 55a and the second protruding portion 55b face each other in the width direction. Thereby, a minute gap S is formed between the first protruding portion 55a and the second protruding portion 55b inside the first convex portion 41. Note that in FIG. 12, the minute space S is shown relatively large in order to make the minute gap S easier to see.

[0052] Further, the first protrusion 55a and the second protrusion 55b are arranged at positions in the vertical direction at the boundary between the gas storage portion 60 and the heat absorbent storage portion 61. Therefore, the minute gap S is a space that communicates the inside of the gas storage portion 60 and the inside of the heat absorbent storage portion 61.

[0053] Also, the minute gap S (the distance between the first protrusion 55a and the second protrusion 55b) has a width such that it is difficult for the heat absorbent 7 to pass through. In other words, when the heat absorbent 7 is accommodated inside the frame portion 48 of the upper member 46 (see FIG. 5), it is a width such that the heat absorbent 7 does not move toward the gas storage portion 60. When the viscosity of the heat absorbent 7 to be used is high, the minute gap S becomes relatively large, and when the viscosity of the heat absorbent 7 to be used is low, the minute gap S becomes relatively small.

[0054] According to the embedded member 30C of this Modification 3, it becomes difficult to accommodate the heat absorbent 7 inside the gas storage portion 60. Therefore, when abnormal heat generation occurs in the cylindrical cell 2, early opening by the gas storage portion 60 is ensured. Further, since the internal pressure of the container 40C increases due to abnormal heat generation in the cylindrical cell 2, when the heat absorbent 7 moves from the heat absorbent storage portion 61 to the gas storage portion 60, the space between the first protrusion 55a and the second protrusion 55b is expanded. Therefore, it is suppressed that the protruding amount of the heat absorbent 7 decreases. Also, according to Modification 3, there is no restriction on arranging the tip portion (gas storage portion 60) of the convex portion 47 upward in the Z1 direction. That is, since the gas 8 is held inside the gas storage portion 60, the direction of the tip portion (gas storage portion 60) of the convex portion 47 can be freely set. Hereinafter, a case where the tip portion of the convex portion 47 faces downward in the Z2 direction will be described using Modification 4.

[0055] (Modification 4) FIG. 13 is a view of the battery unit of Modification 4 as seen in the longitudinal direction. As shown in FIG. 13, the battery unit 1D of Modification 4 includes eight cylindrical cells 2. The eight cylindrical cells 2 are arranged in two columns in the vertical direction and four columns in the width direction. The battery unit 1D also has two embedded members. One of the two embedded members is the embedded member 30 of Embodiment 1. The other of the two embedded members is the embedded member 30C of Modification 3.

[0056] The embedded member 30C is arranged in a posture such that the lower member 45 is located above Z1 than the upper member 46. That is, the tip of the convex portion 47 is arranged facing downward Z2. Above Z1 of the lower member 45 of the embedded member 30C, the embedded member 30 is stacked. The first convex portion 41, the second convex portion 42, and the third convex portion 43 of the embedded member 30 are arranged between four of the eight cylindrical cells 2 arranged above Z1. On the other hand, the first convex portion 41, the second convex portion 42, and the third convex portion 43 of the embedded member 30C are arranged between four of the eight cylindrical cells 2 arranged below Z2.

[0057] According to this Modification 4, the four cylindrical cells 2 arranged above Z1 among the eight cylindrical cells 2 are suppressed from being detonated by the embedded member 30. Also, in the embedded member 30C, the gas 8 is held inside the gas storage portion 60 by the plurality of protruding portions 55. Therefore, the four cylindrical cells 2 arranged below Z2 among the eight cylindrical cells 2 are suppressed from being detonated by the embedded member 30C.

[0058] (Modification 5) FIG. 14 is an enlarged view of the first convex portion of Modification 5. As shown in FIG. 14, the container 40E of the embedded member 30E of Modification 5 is different from the embedded member 30C of Modification 3 in that the number of protruding portions 55E is decreased. Specifically, in the first convex portion 41 of the container 40E, the protruding portion 55E is provided toward the first arc wall 51. That is, the protruding portion 55E is not provided on the second arc wall 52. And a minute gap S is formed between the second arc wall 52 and the protruding portion 55E. Even in this Modification 5, similar to Modification 3, it is possible to prevent the heat absorbent 7 from being accommodated inside the gas accommodation portion 60. Note that in the present disclosure, the protruding portion 55E may be provided on the second arc wall 52 instead of the first arc wall 51.

[0059] Regarding Modification 3, an example in which a minute gap S is formed between the first protruding portion 55a and the second protruding portion 55b has been described. However, in the present disclosure, the first protruding portion 55a and the second protruding portion 55b may be in contact with each other inside the container 40. According to this, it is possible to surely prevent the heat absorbent 7 from being accommodated in the gas accommodation portion 60. Further, even when the first protruding portion 55a and the second protruding portion 55b are in contact with each other, the internal pressure of the container 40 increases due to abnormal heat generation of the cylindrical cell 2, and the first protruding portion 55a and the second protruding portion 55b are expanded. Therefore, the heat absorbent 7 can smoothly move toward the gas accommodation portion 60 and be discharged from the container 40. In addition, a part of the first protruding portion 55a and the second protruding portion 55b in the longitudinal direction may be in contact with each other. Further, in the present disclosure, the protruding portion 55E mentioned in Modification 5 may be in contact with the first arc wall 51 or the second arc wall 52.

[0060] As described above, Embodiment 1 and Modifications 1 to 5 have been described. These are examples of suppressing detonation of adjacent cylindrical cells 2 in the width direction. Next, an embedded member capable of suppressing detonation of adjacent cylindrical cells 2 in the vertical direction will be described.

[0061] (Embodiment 2) FIG. 15 is a perspective view of the embedded member according to Embodiment 2. FIG. 16 is a cross-sectional view of the embedded member according to Embodiment 2 cut in the planar direction. FIG. 17 is a view of the battery unit according to Embodiment 2 as viewed from the longitudinal direction. Note that FIG. 17 is a view in which only the embedded member 130 is extracted from the battery pack. For this reason, the cylindrical cell 2 arranged in the vicinity of the embedded member 130 is illustrated by a phantom line. Note that the embedded member 130 according to Embodiment 2 is used for the battery unit 1F having eight cylindrical cells 2 as shown in Modification 4 (see FIG. 17).

[0062] In FIG. 15, the container 140 of the embedded member 130 has two side walls 145 (only one is illustrated in FIG. 15) arranged at both longitudinal ends in the longitudinal direction. A joining portion 146 is provided on the side wall 145 arranged in the second longitudinal direction X2 among the two side walls 145. This joining portion 146 is formed by closing the storage port by heat welding. That is, before being heat welded, the joining portion 146 forms a cylindrical storage port that communicates the inside and the outside of the container 140. Note that the heat absorption agent 7 and the gas 8 are stored in the container 140 through the storage port (joining portion 146).

[0063] When viewed from the longitudinal direction, the container 140 is provided with four convex portions 147 protruding in four directions. The four convex portions 147 are arranged at 90° intervals around the joining portion 146. Thus, the four convex portions 147 include a first convex portion 141 protruding upward in the Z1 direction, a second convex portion 142 protruding downward in the Z2 direction, a third convex portion 143 protruding in the first width direction Y1, and a fourth convex portion 144 protruding in the second width direction Y2.

[0064] The first convex portion 141, the second convex portion 142, the third convex portion 143, and the fourth convex portion 144 all have the same shape.

[0065] As shown in FIG. 16, the first convex portion 141 has the same shape as the first convex portion 41 of Modification 3. That is, the first convex portion 141 has a connecting portion 153 extending in the width direction, a first arc wall 151 disposed in the first width direction Y with respect to the connecting portion 153, and a second arc wall 152 disposed in the second width direction Y2 with respect to the connecting portion 153. A first protruding portion 155a is provided on the first arc wall 151. A second protruding portion 155b is provided on the second arc wall 152.

[0066] Further, the first arc wall 151 of the first convex portion 141 forms the second arc wall 152 of the third convex portion 143. The second arc wall 152 of the first convex portion 141 forms the first arc wall 151 of the fourth convex portion 144. That is, the first convex portion 141, the second convex portion 142, the third convex portion 143, and the fourth convex portion 144 share the first arc wall 151 and the second arc wall 152 with respect to the adjacent convex portions 147, respectively.

[0067] From the above, the upper Z1 end portion of the first convex portion 141 forms the first gas storage portion 161. The lower Z2 end portion of the second convex portion 142 forms the second gas storage portion 162. The end portion in the first width direction Y1 of the third convex portion 143 forms the third gas storage portion 163. The end portion in the second width direction Y2 of the fourth convex portion 144 forms the fourth gas storage portion 164. And the portion of the container 140 other than the first gas storage portion 161, the second gas storage portion 162, the third gas storage portion 163, and the fourth gas storage portion 164 forms the heat absorbent storage portion 165.

[0068] As shown in FIG. 17, in the battery unit 1F, three embedding members 130 are prepared for eight cylindrical cells 2. The embedding members 130 are respectively arranged between four adjacent cylindrical cells 2 in the vertical direction and the width direction. Therefore, the first gas storage portion 161 is arranged between two adjacent cylindrical cells 2 in the width direction among the four cylindrical cells 2 and arranged above Z1. The second gas storage portion 162 is arranged between two adjacent cylindrical cells 2 in the width direction among the four cylindrical cells 2 and arranged below Z2. The third gas storage portion 163 is arranged between two adjacent cylindrical cells 2 in the vertical direction among the four cylindrical cells 2 and arranged in the first width direction Y1. The fourth gas storage portion 164 is arranged between two adjacent cylindrical cells 2 in the vertical direction among the four cylindrical cells 2 and arranged in the second width direction Y2. From the above, according to the second embodiment, the detonation of two adjacent cylindrical cells 2 in the vertical direction can also be suppressed.

[0069] (Modification Example 6) FIG. 18 is a cross-sectional view of the embedding member of Modification Example 6. The embedding member 130G of Modification Example 6 is different from the embedding member 130 of the second embodiment in that a protruding portion 155G is provided on either the first arc wall 151 or the second arc wall 152. Even in this Modification Example 6, the detonation of two adjacent cylindrical cells 2 in the vertical direction can also be suppressed.

[0070] (Embodiment 3) FIG. 19 is a perspective view of the embedding member of Embodiment 3. FIG. 20 is a cross-sectional view of the embedding member of Embodiment 3 cut in the plane direction. FIG. 21 is a view of the battery unit of Embodiment 3 viewed from the longitudinal direction. Note that FIG. 21 is a view in which only the embedding member 230 is extracted from the battery pack. Therefore, the cylindrical cells 2 arranged in the vicinity of the embedding member 230 are illustrated by phantom lines. The embedding member 230 of Embodiment 3 is used for a battery unit in which the cylindrical cells 2 arranged above Z1 and the cylindrical cells 2 arranged below Z2 are displaced in the width direction as shown in FIG. 21. Note that the arrangement of the cylindrical cells 2 shown in FIG. 21 may be referred to as a stack-like or triangular lattice-like arrangement.

[0071] As shown in Fig. 19, the container 240 of the embedded member 230 is provided with three convex portions 247 protruding in three directions when viewed from the longitudinal direction. The three convex portions 147 are arranged at intervals of 120° when viewed from the longitudinal direction. Therefore, the three convex portions 247 have a first convex portion 241, a second convex portion 242, and a third convex portion 243 arranged in order in the clockwise direction (see the arrow T in Figs. 19 and 20) when viewed from the second longitudinal direction X2. The first convex portion 241, the second convex portion 242, and the third convex portion 243 have the same shape respectively.

[0072] As shown in Fig. 20, the first convex portion 241 has a connecting portion 253, a first arc wall 251 arranged in the clockwise direction T with respect to the connecting portion 253, and a second arc wall 252 arranged in the counterclockwise direction with respect to the connecting portion 253. A first protruding portion 255a is provided on the first arc wall 251. A second protruding portion 255b is provided on the second arc wall 252. In Embodiment 3 as well, the first convex portion 241, the second convex portion 242, and the third convex portion 247c share the first arc wall 251 and the second arc wall 252 with respect to adjacent convex portions 247 respectively.

[0073] From the above, a first gas storage portion 261 is provided at the tip of the first convex portion 241. A second gas storage portion 262 is provided at the tip of the second convex portion 242. A third gas storage portion 263 is provided at the tip of the third convex portion 243. The portion of the container 240 other than the first gas storage portion 261, the second gas storage portion 262, and the third gas storage portion 263 forms a heat absorbent storage portion 265.

[0074] As shown in Fig. 21, six embedded members 230 are prepared for eight cylindrical cells 2. The embedded member 230 is arranged between three cylindrical cells 2 arranged in a triangular lattice. These three cylindrical cells 2 are two adjacent cylindrical cells 2 in the width direction and one cylindrical cell 2 that is in the middle in the width direction and is displaced in the vertical direction with respect to these two cylindrical cells 2. That is, one of the three cylindrical cells 2 is adjacent in the width direction, and the other two are adjacent in the diagonal direction. The diagonal direction is a direction in which the vertical position changes as it goes in the width direction.

[0075] And in Embodiment 3, when the first gas storage portion 261 is disposed between adjacent cylindrical cells in the width direction, the remaining second gas storage portion 262 and third gas storage portion 263 are disposed between two adjacent cylindrical cells 2 in the diagonal direction. From the above, according to Embodiment 3, it is also possible to prevent the detonation of two adjacent cylindrical cells 2 in the diagonal direction.

[0076] As described above, each embodiment and each modification have been described. In the present disclosure, the connection portion (gas storage portion) may be disposed offset from the narrowest portion between two adjacent cylindrical cells 2. Further, in the present disclosure, the wall thickness of the wall portion constituting the gas storage portion may be made smaller than the wall thickness of the wall portion constituting the heat absorbent storage portion so that the gas storage portion is more easily opened. Note that the gas storage portion is constituted by the wall portions of the connection portion 53, the end portion 51b of the first arc wall 51 closer to the connection portion 53, and the end portion 52b of the second arc wall 52 closer to the connection portion 53 (see FIG. 6). Further, the heat absorbent storage portion is constituted by the wall portions of the portion of the first arc wall 51 excluding the end portion 51b and the portion of the second arc wall 52 excluding the end portion 52b (see FIG. 6).

Description of Reference Numerals

[0077] 1, 1D, 1F, 1H Battery unit 2 Cylindrical cell 7 Heat absorbent 8 Gas 10 Cell holder 20 Tab 30, 30A, 30B, 30C, 30E, 130, 230 Embedded member 40, 40B, 40E, 140, 240 Container 41, 141, 241 First convex portion 42, 142, 242 Second convex portion 43, 143, 243 Third convex portion 45 Lower member 46 Upper member 47, 147, 247 Convex portion 48 Frame portion 51, 151, 251 First arc wall 52, 152, 252 Second arc wall 53, 153, 253 Connection part 55, 55E Protrusion 55a, 155a, 255a First protrusion 55b, 155b, 255b Second protrusion 60 Gas storage part 61, 165, 265 Heat absorber storage part 62 Crack 100 Battery pack 101 Case 144 Fourth convex part 161, 261 First gas storage part 162, 262 Second gas storage part 163, 263 Third gas storage part 164 Fourth gas storage part S Micro gap

Claims

1. A plurality of cylindrical cells arranged such that the electrode terminals face the same direction, An embedding member disposed between the plurality of cylindrical cells, Comprising, The embedding member has a container, a heat-absorbing agent and a gas accommodated inside the container, The container is provided with a convex portion that is disposed between two adjacent cylindrical cells as viewed from the longitudinal direction of the cylindrical cell and extends in the longitudinal direction of the cylindrical cell, The convex portion is, A heat-absorbing agent accommodating portion in which the heat-absorbing agent is accommodated, A gas accommodating portion in which the gas is accommodated, Having, The gas accommodating portion is disposed at the tip of the convex portion and contacts each of the two adjacent cylindrical cells Battery pack.

2. The inner surface of the wall portion constituting the gas accommodating portion has no adhesion of the heat-absorbing agent The battery pack according to claim 1.

3. The gas accommodating portion is disposed at the narrowest portion between two adjacent cylindrical cells The battery pack according to claim 1.

4. The gas accommodating portion is in contact with the entire longitudinal direction of the side surfaces of two adjacent cylindrical cells The battery pack according to claim 1.

5. The gas accommodated in the gas accommodating portion is continuous in the longitudinal direction The battery pack according to claim 1.

6. The gas accommodated in the gas accommodating portion is continuous over the entire longitudinal direction of the convex portion The battery pack according to claim 1.

7. The wall thickness of the wall portion constituting the gas accommodating portion is smaller than the wall thickness of the wall portion constituting the heat-absorbing agent accommodating portion The battery pack according to claim 1.

8. The convex portion is, A first arc wall extending along the outer peripheral surface of one of the two adjacent cylindrical cells, A second arc wall extending along the outer peripheral surface of the other of the two adjacent cylindrical cells, A connecting wall disposed between two adjacent cylindrical cells and connecting the first arc wall and the second arc wall, Having at least The battery pack according to claim 1.

9. At least one of the first arc wall and the second arc wall is provided with a protruding portion protruding into the interior of the container, The protruding portion is provided at the boundary between the heat-absorbing agent accommodating portion and the gas accommodating portion The battery pack according to claim 8.

10. The container is made of resin The battery pack according to claim 1.

11. The heat-absorbing agent is mainly composed of water The battery pack according to claim 1.

12. The form of the heat-absorbing agent is a gel or a sol The battery pack according to any one of claims 1 to 11.

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