Battery pack

Abstract

To provide a battery pack capable of suppressing a local load from being applied to a battery cell when a load is applied to a side wall of the battery case.SOLUTION: A disclosed battery pack includes a battery case that accommodates multiple stacked battery cells. The battery case includes: a bottom wall that opposes the bottom of multiple battery cells; and four side walls connected to the bottom wall and opposed to the side faces of multiple battery cells. At least one of the four side walls includes a central part opposing the multiple battery cells and a peripheral part located around the central part. The peripheral part is formed in a frame shape to cover the central part and has a weak part with lower rigidity than the central part.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a battery case that houses a battery stack which is a laminate of a plurality of battery cells. This battery case has a bottom wall facing the bottom surface of the battery stack, and four side walls connected to the bottom wall and facing the side surfaces of the battery stack.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a load is input to any of the side walls of the battery case, the side wall deforms starting from the connection portion with the bottom wall. Along with such deformation of the side wall, a local load is input to the battery cell.

[0005] The present disclosure has been made in view of the above - mentioned problems, and an object thereof is to provide a battery pack capable of suppressing the input of a local load to a battery cell when a load is input to the side wall of the battery case.

Means for Solving the Problems

[0006] The battery pack according to the present disclosure includes a battery case that houses a plurality of stacked battery cells. The battery case includes a bottom wall facing the bottom surfaces of the plurality of battery cells, and four side walls connected to the bottom wall and facing the side surfaces of the plurality of battery cells. At least one of the four side walls includes a central portion facing the plurality of battery cells and a peripheral portion located around the central portion. The peripheral portion is provided in a frame shape so as to cover the central portion and includes a fragile portion that is less rigid than the central portion.

[0007] The fragile portion may be a recess formed in a frame shape.

[0008] The fragile portion may be a stepped portion located between a central portion and a peripheral portion formed to be thicker than the peripheral portion.

Advantages of the Invention

[0009] According to the battery pack of the present disclosure, by providing the above-described fragile portion, when a load is input to the side wall of the battery case, stress can be concentrated on the fragile portion. As a result, the fragile portion provided in a frame shape breaks, and an external load acts in a state where a wide area of the side wall (that is, the central portion) is in contact with the plurality of battery cells. Therefore, input of a local load to the plurality of battery cells can be suppressed.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Best Mode for Carrying Out the Invention

[0011] Hereinafter, with reference to the accompanying drawings, a battery pack according to an embodiment of the present disclosure will be described. In the drawings, common elements are denoted by the same reference numerals, and redundant descriptions are omitted or simplified.

[0012] 1. Structure of the Battery Pack FIG. 1 is a perspective view schematically showing the structure of a battery pack 1 according to an embodiment. FIG. 2 is a plan view of the battery pack 1 shown in FIG. 1 viewed from above.

[0013] The battery pack 1 includes a battery stack 10 that is a laminate of a plurality of battery cells 12, and a battery case 20 that houses the battery stack 10. The battery pack 1 is mounted on an electric vehicle such as a hybrid vehicle (HEV) or a battery electric vehicle (BEV), and supplies power to the electric vehicle.

[0014] More specifically, as an example, the battery stack 10 is configured by alternately laminating a plurality of rectangular battery cells 12 and spacers 14, and includes a pair of end plates 16 arranged so as to sandwich the assembly of the battery cells 12 and the spacers 14 from both sides in the stacking direction D1. The spacer 14 is formed of an insulating resin, ensures the insulation between adjacent battery cells 12, and functions as a heat dissipation path for the battery cells 12. The battery stack 10 having such a configuration is housed in the battery case 20 in a state where a compressive load is applied from the sides of the pair of end plates 16 located at both ends thereof.

[0015] In the example of the battery pack 1, the battery stacks 10 are arranged in two rows, but may be arranged in one row or multiple rows of three or more rows. Also, in the example of the battery pack 1, the stacking direction D1 of the battery cells 12 is parallel to the longitudinal direction of the battery case 20, but may be parallel to the short-side direction of the battery case 20.

[0016] The battery case 20 is made of, for example, metal and has a substantially rectangular parallelepiped shape. The battery case 20 is composed of an upper cover (not shown) that constitutes the upper wall of the battery case 20 and a lower case. The lower case constitutes a bottom wall 22 (see FIG. 3), and four side walls 24, 26, 28, and 30. The bottom wall 22 faces the bottom surface of the battery stack 10 (each battery cell 12). The four side walls 24 to 30 are respectively connected to the bottom wall 22 and face the respective side surfaces of the battery stack 10. In FIGS. 1 and 2, the lower case is shown as the battery case 20. That is, the lower case has a substantially rectangular parallelepiped shape with an open upper surface.

[0017] Next, with reference to FIGS. 3 and 4 together with FIGS. 1 and 2, the configuration of the battery case 20 (lower case) will be described. FIG. 3 is a cross-sectional view taken along line A-A in FIG. 2, and is a cross-sectional view of the battery cell 12 and the battery case 20 as seen from a direction orthogonal to the stacking direction D1. In FIG. 3, the configuration around the battery stack 10 closer to the side wall 24 among the two rows of battery stacks 10 is shown, and the illustration of the configuration around the other battery stack 10 is omitted. FIG. 4 is a schematic side view of the battery case 20 shown in FIG. 1 as seen from the side of the side wall 24.

[0018] The side wall 24 of the battery case 20 is one of the side walls extending along the stacking direction D1. As shown in FIG. 4 and the like, the side wall 24 includes a central portion 24a (general surface) facing the battery stack 10 and a peripheral portion 24b located around the central portion 24a. More specifically, in a side view of the battery case 20 as seen from the side of the side wall 24 (see FIG. 4), the central portion 24a here corresponds to the central region of the side wall 24 that overlaps the plurality of battery cells 12 constituting the battery stack 10. And the peripheral portion 24b is a part of the side wall 24 other than the central portion 24a.

[0019] Furthermore, as shown in FIG. 4, the peripheral portion 24b includes a fragile portion 24b1 provided in a frame shape so as to cover the central portion 24a. The fragile portion 24b1 is a portion having lower rigidity than the central portion 24a.

[0020] Specifically, the weak part 24b1 is a concave part formed in a frame shape (more specifically, a U shape) so as to cover the central part 24a. In other words, it is formed in a groove shape on the outer surface of the side wall 24. Additionally, the weak part 24b1 is a thin part with a smaller thickness compared to the periphery of the weak part 24b1. For this reason, the weak part 24b1 is not only the central part 24a but also a part with lower rigidity than the parts other than the weak part 24b1 in the peripheral part 24b. Note that the concave weak part 24b1 may be formed on the inner surface of the side wall 24.

[0021] More specifically, as shown in FIG. 2, when the side wall 24 is viewed from above, the weak part 24b1 is located outside the side wall 24 in the stacking direction D1 compared to the outer end positions P1 and P2 of the battery cells 12 located at each end in the stacking direction D1, and extends along the vertical direction D2 (see FIG. 3) of the battery case 20. That is, the weak part 24b1 is provided in the peripheral part 24b near each of the side walls 26 and 30 adjacent to the side wall 24. And as shown in FIG. 3, when the side wall 24 is viewed from a direction orthogonal to the stacking direction D1, the weak part 24b1 is located below the side wall 24 compared to the lower end position P3 of the battery cell 12 in the vertical direction D2, and extends along the stacking direction D1. That is, the weak part 24b1 is provided in the peripheral part 24b near the bottom wall 22.

[0022] 2. Effects FIGS. 5(A) and 5(B) are diagrams for explaining the problems of the battery pack 100 according to the comparative example. The effects of the battery pack 1 according to the embodiment will be described while comparing with the battery pack 100 according to this comparative example. The battery pack 100 includes a battery case 102. The battery case 102 is formed in the same manner as the battery case 20 except that it does not have the weak part 24b1.

[0023] The curve C shown in FIG. 5(A) schematically shows the deformation of the side wall 104 of the battery case 102 when a load is input from the direction of arrow B to the side wall 104 by a crusher in a crushing test. Specifically, as represented by the curve C, the overall deflection of the side wall 104 leads to the input of a local load to the side surface portion of the battery stack 10 (a plurality of battery cells 12). The reason is as follows. That is, the side wall 104 without the weak portion 24b1 has a uniform wall surface rigidity. Therefore, as shown by the curve C in FIG. 5(A), deformation of the side wall 104 occurs, and accordingly, the side wall 104 deforms starting from the connection portion between the side wall 104 and the bottom wall 106 indicated by the circled E in FIG. 5(B). As a result, a local load is input to the battery stack 10 (a plurality of battery cells 12).

[0024] On the other hand, according to the battery pack 1 according to the present embodiment, the side wall 24 of the battery case 20 is provided in a frame shape so as to cover the central portion 24a facing the battery stack 10 and includes a weak portion 24b1 having a lower rigidity than the central portion 24a. Thereby, when a load is input from the outside by a crusher, stress can be concentrated on the weak portion 24b1. As a result, the frame-shaped weak portion 24b1 breaks, and an external load acts in a state where a wide range of the side wall 24 (that is, the central portion 24a) is in contact with the battery stack 10 (a plurality of battery cells 12). Therefore, it is possible to suppress the input of a local load to the battery stack 10 (a plurality of battery cells 12). In other words, it is possible to receive an external load by utilizing the overall rigidity of the plurality of battery cells 12.

[0025] Further, in the present embodiment, the weak portion 24b1 is a "recess" formed in a frame shape so as to cover the central portion 24a. Thereby, it is possible to suppress the input of a local load to the battery stack 10 (a plurality of battery cells 12) using a simple structure without the need to add another member.

[0026] 3. Modification Figs. 6(A) and 6(B) are diagrams schematically showing the structure of the battery pack 2 according to a modified example of the embodiment. The battery pack 2 according to this modified example includes a battery case 40. The battery case 40 is different from the battery case 20 shown in Fig. 1 in the configuration of the weak part (in other words, the stress concentration part).

[0027] Specifically, the battery case 40 includes a side wall 42. The side wall 42 includes a central part 42a (general surface) facing the battery stack 10 and a peripheral part 42b located around the central part 42a. And the peripheral part 42b includes a weak part 42b1. Note that the "central part" according to the present disclosure is a part facing a plurality of stacked battery cells (that is, the battery stack), but as long as it includes a part facing a plurality of battery cells, it is not strictly limited to only the part facing a plurality of battery cells. That is, like the example of the central part 42a shown in Fig. 6, the central part may include a part facing a plurality of cells and a peripheral part thereof.

[0028] Moreover, as shown in Figs. 6(A) and 6(B), the central part 42a is formed to be thicker than the peripheral part 42b. And the weak part 42b1 corresponds to a stepped part located between the central part 42a and the peripheral part 42b.

[0029] According to the battery case 40 configured as described above, the rigidity of the central part 42a is relatively increased with respect to the peripheral part 42b. For this reason, a rigidity difference can be generated between the central part 42a and the weak part 42b1. Thereby, when a load is input to the side wall 42 from the outside in the crushing test, stress can be concentrated on the weak part 42b1 having a stepped shape. As a result, the weak part 42b1 provided in a frame shape breaks, and local load input to the battery stack 10 (a plurality of battery cells 12) can be suppressed.

[0030] Incidentally, in the above-described embodiment, the weak part 24b1 (see FIG. 2) is provided only on the side wall 24 parallel to the stacking direction D1 of the plurality of battery cells 12 among the four side walls 24, 26, 28, and 30 of the battery case 20. However, the "weak part" according to the present disclosure may be provided in the same manner on the other side wall 28 parallel to the stacking direction D1 instead of or together with the side wall 24. Further, the weak part 24b1 may be provided in the same manner on at least one of the side walls 26 and 30 extending along the direction orthogonal to the stacking direction D1 instead of or together with at least one of the side walls 24 and 28. Note that the same applies to the battery case 40 shown in FIG. 6(A).

Explanation of Reference Numerals

[0031] 1, 2, 100 Battery Pack 10 Battery Stack 12 Battery Cell 20, 40, 102 Battery Case 22, 106 Bottom Wall of Battery Case 24, 26, 28, 30, 42, 104 Side Wall of Battery Case 24a, 42a Central Portion of Side Wall 24b, 42b Peripheral Portion of Side Wall 24b1, 42b1 Weak Part

Claims

1. A battery pack comprising a battery case for housing a plurality of stacked battery cells, wherein the battery case includes a bottom wall facing the bottom surfaces of the plurality of battery cells, and four side walls connected to the bottom wall and facing the side surfaces of the plurality of battery cells, and at least one of the four side walls includes a central portion facing the plurality of battery cells, and a peripheral portion located around the central portion, and the peripheral portion is provided in a frame shape so as to cover the central portion and includes a fragile portion having lower rigidity than the central portion battery pack.

2. The battery pack according to claim 1, wherein the fragile portion is a recess formed in the frame shape.

3. The battery pack according to claim 1, wherein the fragile portion is a stepped portion located between the central portion and the peripheral portion formed to be thicker than the peripheral portion.

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