Battery pack

Abstract

To provide a battery pack that is easy to fasten and manufacture even when there is variation in the fastening positions of battery cells.SOLUTION: A battery pack 1 according to the disclosed technology includes a battery stack 2 in which multiple battery cells 4 are repeatedly arranged in a certain repeating direction, and a side member 5 arranged along the battery stack across the multiple battery cells 4 included in the battery stack 2, with the side member 5 having a long hole 52 formed in the repeating direction of the battery cells 4 in the battery stack 2, and each battery cell 4 being fixed to the side member 5 by a cell fastening member 7 which passes through the long hole 52.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The disclosed technology relates to a battery pack.

Background Art

[0002] Conventionally, a battery pack in which a plurality of battery cells are stacked has been known. An example is described in Patent Document 1. This document discloses a battery pack that restrains battery cells with a long restraining band. In the technology described in this document, holes corresponding to each battery cell are formed in the restraining band, and each battery cell is fixed to the restraining band by screwing through each hole.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The conventional technology has a problem that screwing may be difficult. For example, this may occur when the battery stack is deformed such as bent during fastening. This is because the position of the hole in the restraining band does not match the position of the battery cell. Also, the number of battery cells in the battery stack varies depending on the specifications of the battery pack. For this reason, the positions of the holes in the restraining band also vary depending on the specifications of the battery pack, and it is difficult to make them common.

[0005] An object of the disclosed technology is to provide a battery pack that is easy to fasten and easy to manufacture even if there is variation in the fastening position of the battery cells.

Means for Solving the Problems

[0006] In one aspect of the disclosed technology, a battery pack includes a battery stack in which a plurality of battery cells are repeatedly arranged in a certain repeating direction, and side members arranged along the battery stack across the plurality of battery cells included in the battery stack. Long holes are formed in the side members in the repeating direction of the battery cells in the battery stack, and the battery cells are fixed to the side members by cell fastening members passing through the long holes.

[0007] In the battery pack according to the above aspect, the battery cells are fixed to the side members by the cell fastening members. Since the shape of the portion where the cell fastening members are fastened in the side members is a long hole, there is a certain degree of freedom in the fastening position of the battery cells with respect to the longitudinal direction of the side members, that is, the repeating direction of the arrangement of the battery cells. Therefore, the battery pack of the above aspect is easy to fasten and easy to manufacture even if there are variations in the fastening positions of the battery cells.

[0008] In the battery pack according to the above aspect, each battery cell has at least a rectangular outer shape including a side surface and a bottom surface that intersects the side surface and has a fastened shape by a fastening member. The side member has a side piece portion facing the side surface of each battery cell and a bottom piece portion facing the bottom surface of each battery cell and having a long hole formed therein. It is desirable that each battery cell included in the battery stack be fixed to the side member with a certain inclination angle inclined with respect to the side piece portion. By arranging the battery cells inclined with respect to the side member in this way, the size of the battery pack in the width direction can be reduced. Therefore, it is not the case that the size of the battery pack in the width direction is almost determined by the longitudinal size of the battery cells.

[0009] In a battery pack in the form of an inclined arrangement, there is one having a cover member provided outside the side piece portion as viewed from the battery stack, and a cover fastening member that fixes the side piece portion and the cover member and partially projects from the side piece portion toward the battery stack. In this case, even if the battery pack is curved by an external force and the cover fastening member hits the battery cell, the battery cell is less likely to be damaged. This is because the cover fastening member often hits the side surface of the battery cell, and the side surface is inclined. Due to the inclination, the pressing force applied to the battery cell is decomposed into a vertical component and a horizontal component, and substantially only the vertical component is applied to the battery cell.

[0010] In a battery pack in an embodiment having a cover member, each battery cell has an outer shape having first and second side surfaces parallel to each other, and a side member and a cover member are respectively provided with respect to the first and second side surfaces. Among the battery cells included in the battery stack, there may be a configuration in which some are fixed only to one of the side members. Although the cover fastening member is likely to hit the side surface of the battery cell that is not fixed to the side member in each battery cell, the battery cell is still less likely to be damaged as described above.

[0011] In the battery pack according to any of the above embodiments, it is further desirable that the long hole has a length that spans two or more battery cells included in the battery stack. In this way, even when the number of repeated arrangements of battery cells differs depending on the specifications of the battery pack, the same side member can be used.

Advantages of the Invention

[0012] According to the disclosed technology, a battery pack is provided that is easy to fasten and easy to manufacture even if there is variation in the fastening positions of the battery cells.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0014] This embodiment embodies the disclosed technology as the battery pack 1 shown in FIG. 1. The battery pack 1 in FIG. 1 houses a battery stack 2 in a case 3. The battery stack 2 is formed by repeatedly arranging a large number of battery cells 4 in a certain repeating direction. The case 3 is formed by assembling an end plate 30, a cover member 31, and a corner post 32 in a box shape. In FIG. 1, the front end plate 30 and the cover member 31 are omitted so that the internal battery stack 2 can be seen. In the battery pack 1 of FIG. 1, two sets of battery stacks 2 are stacked in two upper and lower stages.

[0015] The battery stack 2 in the battery pack 1 is placed on a side member 5. The side member 5 is a long member arranged along the battery stack 2 across a plurality of battery cells 4 included in the battery stack 2. The side member 5 in FIG. 1 has a length that extends over the entire longitudinal direction of the battery pack 1. The longitudinal direction of the battery pack 1 is also the repeating direction of the arrangement of the battery cells 4 in the battery stack 2. For each battery stack 2 in FIG. 1, side members 5 are respectively arranged at two lower positions on both the left and right sides. Each battery cell 4 is fixed to the side member 5.

[0016] The fixing of the battery cell 4 to the side member 5 will be described with reference to FIG. 2. FIG. 2 is a cross-sectional view of the battery cell 4 in the battery stack 2 as seen from the front. In FIG. 2, cover members 31 are provided on both the left and right sides, and the battery cell 4 is positioned between them. The battery cell 4 has a rectangular outer shape. The outer shape of the battery cell 4 includes a side surface 40 and a bottom surface 41. The bottom surface 41 is a surface that intersects the side surface 40. Thread holes 42 are formed in the bottom surface 41. The thread holes 42 are formed at locations near the ends in the longitudinal direction (left-right direction in FIG. 2) on the bottom surface 41. In FIG. 2, the thread holes 42 are depicted as being formed at two locations near both ends, but only one of them may be used. Generally, positive and negative terminals are provided near both ends of the upper surface of the battery cell 4, so the thread holes 42 may be formed only under the terminals of a certain determined polarity, either positive or negative.

[0017] In FIG. 2, the aforementioned side member 5 is attached to the inner surface of each of the cover members 31 on both sides. The side member 5 has a side piece portion 50 and a bottom piece portion 51. In relation to the battery cell 4, the side piece portion 50 is a part that faces the side surface 40, and the bottom piece portion 51 is a part that faces the bottom surface 41.

[0018] The side piece portion 50 is also a part where attachment to the cover member 31 is performed. The cover member 31 is located outside the side piece portion 50 as seen from the battery stack 2. The side piece portion 50 is fixed to the cover member 31 by a screw 6. The screw 6 partially protrudes from the side piece portion 50 toward the battery stack 2 side. The screw 6 is a cover fastening member.

[0019] The bottom piece portion 51 is a part where the battery cell 4 is fixed to the side member 5. The battery cell 4 is fixed to the bottom piece portion 51 by a screw 7. The screw 7 passes through the side member 5 and is fitted into the thread hole 42. The screw 7 is a cell fastening member, and the thread hole 42 is a fastened shape.

[0020] The fixing of the battery cell 4 to the side member 5 will be further described with reference to FIG. 3. FIG. 3 shows the side member 5 and the battery cell 4 as viewed from above. As shown in FIG. 3, a long hole 52 is formed in the bottom plate portion 51. The long hole 52 is a hole elongated in the repeating direction of the battery cells 4 in the battery stack 2. The long hole 52 is a hole having a length spanning a plurality of battery cells 4 in the battery stack 2.

[0021] In FIG. 3, the shaft portion of the screw 7 is indicated by a dashed line. Each screw 7 is within the range of the long hole 52 in FIG. 3. The long hole 52 is a hole for passing the screw 7 therethrough. In FIG. 3, the odd-numbered battery cells 4 from the right are fixed only to the upper side member 5 in the figure by the screws 7, and the even-numbered battery cells 4 from the right are fixed only to the lower side member 5 in the figure by the screws 7. In the case of a configuration in which the screw hole 42 is formed only under the terminal of either the positive or negative determined polarity, when the battery cells 4 are arranged so as to form a series connection as a whole battery stack 2, the battery cells 4 fixed only to the upper side and the battery cells 4 fixed only to the lower side will naturally be arranged alternately as shown in FIG. 3. Each battery cell 4 may be configured to be fixed to the upper and lower side members 5 by two screws 7.

[0022] In the configuration of FIG. 3, since the hole provided in the bottom plate portion 51 is the long hole 52, there are the following advantages. First, it can be said that the degree of freedom with respect to the longitudinal direction of the side member 5 is high regarding the mounting position of the battery cell 4. This is because the battery cell 4 can be fixed to the side member 5 by the screw 7 at any position within the range of the long hole 52.

[0023] Therefore, even if there is some variation in the holding position of the battery cell 4 during the fixing by the screw 7, it does not interfere with the fixing operation. This is because the variation in position is absorbed by the long hole 52. Further, even if the specifications of the battery cell 4 and the overall length of the side member 5 are the same, there is a fairly wide range of adaptability regarding the number of battery cells 4 as the battery stack 2. Thus, even when the number of battery cells 4 differs depending on the specifications of the battery stack 2, it can be accommodated with the same side member 5. This is because the length of the long hole 52 is long enough to span a plurality of battery cells 4 in the battery stack 2.

[0024] Second, it can be mentioned that the long hole 52 contributes to the heat dissipation of the battery cell 4. This is because heat can be dissipated from the long hole 52 as well. In particular, this effect is significant in the long hole 52 on the side where the fixing by the screw 7 is not performed.

[0025] Subsequently, an embodiment according to a modified example of the disclosed technology will be described with reference to FIG. 4. In FIG. 4, compared with FIG. 3, the difference is that each battery cell 4 is inclined. Further, in FIG. 4, the cover member 31 and the screw 6, which were omitted in FIG. 3, are also depicted. The screws 6 are provided at a plurality of locations with respect to the longitudinal direction of the side member 5.

[0026] In the battery pack 11 according to the modified example, as shown in FIG. 4, each battery cell 4 of the battery stack 12 is arranged inclined with respect to the longitudinal direction of the side member 5 when viewed from above. The length of each battery cell 4 in its own longitudinal direction is the same in FIGS. 3 and 4. In the battery pack 11 of FIG. 4, the overall width W2 is smaller than the overall width W1 in FIG. 3. This is due to the inclined arrangement of the battery cells 4.

[0027] Thus, according to the disclosed technology, when there is a requirement to reduce the overall width of the battery pack for mounting on a device, by arranging the battery cells 4 in the inclined manner shown in FIG. 4, this requirement can be met. The overall width W2 can also be adjusted by the inclination angle of the battery cells 4. When the battery cells 4 are arranged inclined, as the end face plate 30 in FIG. 1, one with a width adapted to the overall width W2 in FIG. 4 is used. Thereby, even when the battery cells 4 are arranged inclined, the overall width as the battery pack 11 is stabilized.

[0028] By using the inclined arrangement of the battery cells 4, in addition to the above-described compactness in the width direction, there are further two advantages as follows.

[0029] First, the heat dissipation performance of the battery cell 4 is improved. This is because, while the battery cells 4 are repeatedly arranged and inclined, an exposed region 44 shown by a broken line in FIG. 4 is formed on a part of the main surface 43 of the battery cell 4. In the case of the configuration of FIG. 3 where the battery cells 4 are not inclined, the entire main surface 43 of the battery cell 4 faces the adjacent battery cell 4. In contrast, in FIG. 4, by inclining the battery cell 4, a part of the main surface 43 inevitably becomes an exposed region 44 that does not face the adjacent battery cell 4. The exposed region 44 exists over the entire height direction of the battery cell 4 and there are two such regions for each battery cell 4.

[0030] Also, due to the inclined arrangement of the battery cell 4, the side surface 40 of the battery cell 4 also becomes an exposed region. In the case of a configuration where the battery cell 4 is not inclined, depending on the specifications, the side surface 40 may be very close to the side piece part 50 and may not be an exposed region. In contrast, in the case of the inclined arrangement, there is inevitably a certain gap between the side surface 40 and the side piece part 50. Therefore, in the case of the inclined arrangement, in addition to the above-described region 44, the side surface 40 also becomes an exposed region. For this reason, the heat dissipation performance of the battery cell 4 is high.

[0031] Second, it can be mentioned that the battery cell 4 is less likely to be damaged. As shown by an arrow F in FIG. 4, an external force that bends the side member 5 may be applied to the battery pack 11. In that case, as shown in an enlarged view in FIG. 5, the side piece part 50 and the cover member 31 approach the end of the battery cell 4. In particular, this is likely to occur near the center in the longitudinal direction of the battery pack 11. In this case, furthermore, the screw 6 may come into contact with the side surface 40 of the battery cell 4.

[0032] When the battery cell 4 is disposed in an inclined manner, as described above, the side surface 40 is also inclined. That is, the side surface 40 is inclined with respect to the direction of the force F. Even if the screw 6 hits the inclined side surface 40, the pressing force applied to the battery cell 4 is dispersed into a vertical component F1 and a horizontal component F2 due to the inclination of the side surface 40. Therefore, the force actually applied to the battery cell 4 is only the vertical component F1. The force F1 is smaller than the original force F. For this reason, breakage of the battery cell 4 is less likely to occur.

[0033] In the case of a configuration in which the battery cell 4 is not inclined, the side surface 40 of the battery cell 4 is perpendicular to the force F. For this reason, the force F is directly applied to the battery cell 4. For this reason, breakage of the battery cell 4 is likely to occur. On the other hand, in the configuration of FIG. 4, part of the force F is released as the horizontal component F2 due to the inclined arrangement of the battery cell 4. For this reason, in the battery pack 11, breakage of the battery cell 4 is less likely to occur.

[0034] In the configuration of FIG. 4, further, since each battery cell 4 is fixed only to one of the side members 5, contact between the screw 6 and the side surface 40 is more likely to occur as compared with the case where each battery cell 4 is fixed to both of the side members 5. In particular, of the both side surfaces 40 of the battery cell 4, the side surface 40 farther from the fastening position by the screw 7 is more likely to come into contact with the screw 6 than the side surface 40 closer to the fastening position. Still, in this embodiment, breakage of the battery cell 4 due to contact with the screw 6 is prevented as described above.

[0035] As described in detail above, according to the present embodiment, the long hole 52 is provided in the side member 5 so that the battery cell 4 can be fixed anywhere in the long hole 52. Thereby, a battery pack 1 that is easy to fasten and easy to manufacture is realized even if there is variation in the fastening position of the battery cell 4.

[0036] Furthermore, by making the length of the long hole 52 span two or more battery cells 4 in the battery stack 2, degrees of freedom are also provided in the number of battery cells 4 in the battery stack 2. Further, by providing the long hole 52 in the bottom plate portion 51 of the side member 5, the battery cell 4 can be attached obliquely to the side member 5. As a result, the size in the width direction of the battery pack 1 can be adjusted, and the cooling performance of the battery cell 4 is also improved. Breakage of the battery cell 4 during deformation is also prevented.

[0037] The present embodiment and examples are merely illustrative and do not limit the disclosed technology in any way. Therefore, the disclosed technology can naturally be variously improved and modified without departing from the gist thereof. For example, the long hole 52 does not have to extend over substantially the entire length of the side member 5. That is, the side member 5 may be divided into several sections in the longitudinal direction, and the long hole 52 may be formed in each section. The battery pack 1 is not limited to the two-stage stacked configuration shown in FIG. 1.

[0038] In the above-described embodiment, the long hole 52 is provided in the bottom plate portion 51 of the side member 5, but this is not essential. The long hole 52 may be formed in a portion of the side member 5 that faces the side surface 40 of the battery cell 4. In that case, it is not possible to arrange the battery cell 4 obliquely, but the effect of improving the degree of freedom in the fixing position of the battery cell 4 can be obtained. In that case, the screw hole 42 of the battery cell 4 is provided in the side surface 40 instead of the bottom surface 41. What is referred to as "screw 7" and "screw hole 42" in the above embodiment is not limited to screws and screw holes. Any member that can function as a cell fastening member and a fastened shape may be used.

Description of Reference Numerals

[0039] 1 Battery pack 6 Screw 31 Cover member 44 Exposed area 2 Battery stack 7 Screw 40 Side surface 50 Side piece portion 4 Battery cell 11 Battery pack 41 Bottom surface 51 Bottom plate portion 5 Side member 12 Battery stack 42 Screw hole 52 Long hole

Claims

1. A battery pack having a plurality of battery cells repeatedly arranged in a certain repeating direction, and a side member disposed along the battery stack across the plurality of battery cells included in the battery stack, wherein a long hole in the repeating direction of the battery cells in the battery stack is formed in the side member, and each of the battery cells is fixed to the side member by a cell fastening member passing through the long hole.

2. The battery pack according to claim 1, wherein each of the battery cells has at least a rectangular outer shape including a side surface and a bottom surface intersecting the side surface and having a fastened shape by the fastening member, and the side member has a side piece portion facing the side surface of each of the battery cells, and a bottom piece portion facing the bottom surface of each of the battery cells and having the long hole formed therein, and each of the battery cells included in the battery stack is fixed to the side member with a certain inclination angle inclined with respect to the side piece portion.

3. The battery pack according to claim 2, having a cover member provided outside the side piece portion as viewed from the battery stack, and a cover fastening member that fixes the side piece portion and the cover member and partially projects from the side piece portion toward the battery stack.

4. The battery pack according to claim 3, wherein each of the battery cells has an outer shape having first and second side surfaces parallel to each other, the side member and the cover member are respectively provided with respect to the first and second side surfaces, and among the battery cells included in the battery stack, there are some that are fixed only to one of the side members.

5. The battery pack according to any one of claims 1 to 4, wherein the long hole has a length extending across two or more of the battery cells included in the battery stack.

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