Battery pack

Abstract

To provide a battery pack that is reinforced without the need for providing a reinforcing member to a battery case.SOLUTION: The battery pack includes a battery cell group and a battery case. The battery cell group includes a plurality of battery cells. The battery case houses the battery cell group. The battery case includes a pair of cross members arranged to sandwich the battery cell group therebetween in a first direction and extending along a second direction orthogonal to the first direction. The plurality of battery cells is stacked along the second direction. The battery cell group includes a reinforcement plate stacked together with the plurality of battery cells at a position closer to the center of the battery cell group than each end of the battery cell group in the second direction. The reinforcement plate is arranged to bridge between the pair of cross members.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Patent Document 1 discloses a battery pack mounted on a vehicle. In this battery pack, a group of cells is arranged on both sides of a reinforcement that is arranged to extend in the front-rear direction of the vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-111531 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the battery pack described in Patent Document 1, the cell group does not have a reinforcing member as a single unit. Therefore, in the structure described in Patent Document 1, it becomes necessary to provide a reinforcing member (reinforcement) in the battery case that houses the cell group.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and has an object to provide a battery pack that is reinforced without the need to provide a reinforcing member in the battery case. [Means for solving the problem]

[0006] A battery pack according to the present disclosure includes a battery cell group and a battery case. The battery cell group includes a plurality of battery cells. The battery case houses the battery cell group. The battery case includes a pair of cross members disposed to sandwich the battery cell group in a first direction and extending along a second direction perpendicular to the first direction. The plurality of battery cells are stacked along the second direction. The battery cell group includes a reinforcing plate stacked together with the plurality of battery cells at a position closer to a center of the battery cell group than each end of the battery cell group in the second direction. The reinforcing plate is disposed to bridge between the pair of cross members. Effect of the Invention

[0007] According to the battery pack according to the present disclosure, a battery pack having a reinforcing structure against a load from a first direction is realized without the need to provide a reinforcing member in the battery case. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing a configuration of a battery pack according to an embodiment; [Diagram 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Diagram 3] 4 is a diagram for explaining electrical connection paths between a plurality of battery cells in a battery pack according to an embodiment. FIG. [Figure 4] 5A and 5B are diagrams illustrating an example of a heat insulating structure of a battery cell group according to an embodiment. [Diagram 5] 11A and 11B are diagrams illustrating another example of a heat insulating structure for a battery cell group according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] 1. Basic configuration of the battery pack Fig. 1 is a diagram showing the configuration of a battery pack 1 according to an embodiment. The battery pack 1 is mounted on an electric vehicle such as a battery electric vehicle (BEV). The "FR" direction shown in Fig. 1 corresponds to the front direction of the vehicle in which the battery pack 1 is mounted. The "RH" direction corresponds to the right direction of the vehicle.

[0010] The battery pack 1 includes multiple battery cells 10 and a battery case 20. The battery case 20 houses the multiple battery cells 10. The battery case 20 includes a lower case 21 and an upper case 22 (see FIG. 2 described below). FIG. 1 includes a view of the multiple battery cells 10 placed on the lower case 21 looking down from above the electric vehicle (the direction of "UPR" shown in FIG. 2), as well as an exploded perspective view for explaining the restraint structure for the multiple battery cells 10.

[0011] The plurality of battery cells 10 are, for example, rectangular cells. If a predetermined number of battery cells 10 stacked along the second direction D2 are referred to as a battery cell group 12, in the example shown in FIG. 1, a plurality of (for example, four) battery cell groups 12 are arranged in line along the first direction D1 as the plurality of battery cells 10. More specifically, each of the plurality of battery cells 10 is housed in the battery case 20 in a state in which it is placed on the lower case 21 without being modularized. In this manner, the battery pack 1 according to this embodiment has a so-called CTP (Cell To Pack) structure. The CTP structure does not require a structure associated with modularization, and therefore the space utilization rate and energy density of the battery pack 1 can be effectively improved.

[0012] In the example shown in Fig. 1, the first direction D1 is parallel to the vehicle front-rear direction. When the battery pack 1 is viewed from above as in Fig. 1, the first direction D1 is perpendicular to the second direction D2, which is the stacking direction of the battery cells 10 in each battery cell group 12. The second direction D2 is parallel to the vehicle left-right direction (vehicle width direction). The reinforcing plate 13 shown in Fig. 12 relates to a "reinforcing structure against front-rear loads" described later, and the details of the reinforcing plate 13 will be described later.

[0013] The lower case 21 includes a pair of side reinforcements 23 and a plurality of cross members 24 as members that reinforce the lower case 21. These side reinforcements 23 and cross members 24 are fixed to the main body of the lower case 21 so as to surround each of the plurality of battery cells 10 (each battery cell group 12).

[0014] More specifically, as shown in FIG. 1, the side reinforcements 23 are disposed on the outer sides of the ends of the battery cell groups 12 in the second direction D2 (vehicle width direction) and extend along the first direction D1 (vehicle front-rear direction). Some of the cross members 24 are disposed between two battery cell groups 12 adjacent to each other in the first direction D1 and extend along the second direction D2. The rest of the cross members 24 extend along the second direction D2 adjacent to the battery cell groups 12 located at each end of the first direction D1. Both ends of each cross member 24 are connected to a pair of side reinforcements 23. In other words, focusing on one battery cell group 12, the lower case 21 includes a pair of cross members 24 disposed to sandwich the battery cell group 12 in the first direction D1 and formed to extend along the second direction D2 perpendicular to the first direction D1.

[0015] In order to restrain the multiple battery cells 10 (each battery cell group 12) in the second direction D2 (stacking direction), the battery pack 1 has a hybrid restraint structure that integrally includes a cross member as a reinforcing member and a restraint band for the battery cell group 12 as the cross member 24.

[0016] 1, each cross member 24 has an opposing wall 24a that faces the adjacent battery cell group 12. In addition, the cross member 24 located between two battery cell groups 12 in the first direction D1 has two opposing walls 24a. The cross member 24 is joined to the battery cell group 12 via an adhesive 30 applied to the opposing walls 24a.

[0017] Additionally, an engagement portion 24b is formed at each end of each cross member 24 in the second direction D2. The engagement portion 24b engages with an engagement portion 31a of the restraining member 31 on the battery cell group 12 side. The restraining member 31 is provided at each end of the battery cell group 12 in the second direction D2. By engaging the engagement portion 24b with the engagement portion 31a in a state in which a compressive load is applied to the battery cell group 12 along the second direction D2, the battery cell group 12 is restrained by the cross member 24 in the second direction D2 with a predetermined restraining force.

[0018] As described above, according to the hybrid restraint structure, the battery cell group 12 is restrained in the second direction D2 (stacking direction) by restraint using the adhesive 30 and mechanical restraint using the engagement portions 24b and 31a (double structure). This makes it possible to reduce the number of parts while effectively reducing the gap between the cross member 24 and the battery cell group 12, thereby realizing restraint in the second direction D2 in a space-efficient manner.

[0019] Furthermore, a restraint band 32 may be used to restrain the battery cell group 12 in the second direction D2. The restraint band 32 can restrain the battery cell group 12 from above as well by engaging engagement portions 32a at each end of the restraint band 32 with engagement portions 31b of the restraint member 31. Furthermore, to achieve more reliable restraint, the restraint band 32 may be joined to the upper surface 10a of each battery cell 10 included in the battery cell group 12 via an adhesive 33 (see FIG. 2).

[0020] Next, the relationship between the battery cells 10 and the battery case 20 (lower case 21) will be described. The lower surface 10b of each battery cell 10 is joined to the lower case 21 via a thermally conductive adhesive 34 (see FIG. 2). That is, each battery cell 10 is restrained from separating from the lower case 21 by the adhesive force of the thermally conductive adhesive 34. In addition, as shown in FIG. 2, each cross member 24 is disposed on the lower case 21 (more specifically, for example, the reinforcing member 25 included in the lower case 21). In order to more reliably restrain the assembly of the battery cell group 12 and the cross member 24, each cross member 24 may be fixed to the lower case 21 (reinforcing member 25) using fasteners such as bolts and nuts. Furthermore, by using the thermally conductive adhesive 34, when a cooler 40 is provided so as to contact the lower surface of the lower case 21 as in the example shown in FIG. 2, the thermally conductive adhesive 34 can be used to promote heat dissipation from the lower surface 10b of each battery cell 10.

[0021] Furthermore, to achieve more reliable restraint, the top surface 10a of each battery cell 10 may be joined to the upper case 22 via a thermally conductive adhesive 35 (see FIG. 2). With this configuration, when a cooler 41 is provided so as to contact the top surface of the upper case 22 as in the example shown in FIG. 2, the thermally conductive adhesive 35 can be used to promote heat dissipation from the top surface 10a of each battery cell 10. Note that, to restrain the top surface 10a side of each battery cell 10, only the thermally conductive adhesive 35 may be used without using the adhesive 33 in combination.

[0022] 2. Reinforcement structure against front and rear loads For the explanation of the reinforcing plate 13, Fig. 2 is additionally referred to in addition to Fig. 1. Fig. 2 is a cross-sectional view taken along line AA in Fig. 1, and shows the configuration of the reinforcing plate 13 and its surroundings as viewed from a second direction D2.

[0023] Each battery cell group 12 includes a reinforcing plate 13. As shown in FIG. 1, the reinforcing plate 13 is disposed at the center of the battery cell group 12 in the second direction D2, and is stacked together with the battery cells 10 that constitute the battery cell group 12. The reinforcing plate 13 is formed, for example, using a metal material. The location of the reinforcing plate 13 in the battery cell group 12 is not necessarily limited to the center in the second direction D2, but may be any position closer to the center of the battery cell group 12 than each end of the battery cell group 12 in the second direction D2. In addition, the location of the reinforcing plate 13 in the second direction D2 being closer to the center as described above is preferable in terms of effectively receiving a front-rear load together with the skeletal structural members (side reinforcements 23 and cross members 24) on the battery case 20 side, compared to an example in which the location is closer to one end of the battery cell group 12.

[0024] Each reinforcing plate 13 is disposed so as to bridge between a pair of cross members 24. More specifically, the reinforcing plate 13 has a size equivalent to that of the battery cell 10 at least in the first direction D1 and the vehicle front-rear direction (height direction). Similarly to the battery cell 10, the reinforcing plate 13 is joined to the cross members 24 (a pair of cross members) located at each end in the first direction D1 as shown in FIG. 2. In the example shown in FIG. 2, the joining of the reinforcing plate 13 and the cross member 24 is also performed by bonding using an adhesive 30 as shown in FIG. 2. It should be noted that, broadly speaking, the joining of the reinforcing plate 13 and the cross member 24 does not necessarily have to be performed by bonding, and may be performed by using other joining methods such as fastening using fasteners (e.g., bolts and nuts).

[0025] (effect) As described above, in the battery pack 1 according to this embodiment, the battery cell group 12 includes the reinforcing plate 13 stacked together with the multiple battery cells 10 at a position closer to the center of the battery cell group 12 than each end of the battery cell group 12 in the second direction D2. The reinforcing plate 13 is disposed so as to bridge between the pair of cross members 24. As a result, when a load (front-rear load) acts on the battery pack 1 from the vehicle front-rear direction (first direction D1), each reinforcing plate 13 functions as a reinforcing member that receives the load. In this way, in the battery pack 1, the battery cell group 12 itself is provided with a reinforcing structure against the front-rear load. Therefore, a battery pack 1 having a reinforcing structure against the front-rear load can be suitably realized without the need to provide a reinforcing member in the battery case 20.

[0026] Moreover, in the battery pack 1 according to this embodiment, the reinforcing plate 13 is joined to each of the pair of cross members 24 together with the multiple battery cells 10 via an adhesive 30. That is, like the multiple battery cells 10, the reinforcing plate 13 is arranged with no gap between each of the pair of cross members 24. More specifically, as shown in FIG. 2, in the first direction D1 (vehicle front-rear direction), the multiple reinforcing plates 13 are arranged continuously with no gap between the cross members 24 interposed between the individual reinforcing plates 13. This reinforcing structure provides an excellent effect in improving the resistance of the battery pack 1 to crushing due to front-rear loads or to front-rear collisions (frontal or rear-end collisions of electric vehicles) as follows.

[0027] For the explanation of the above-mentioned effect, a battery pack in which a group of battery cells including a reinforcing plate similar to the reinforcing plate 13 is modularized as a battery module without a CTP structure is referred to as a comparative example. In the battery pack according to this comparative example, in order to assemble the battery module in the space in the battery case partitioned by a plurality of cross members, it is necessary to secure a gap between the battery module and the cross member. This gap is generated between each of the battery modules arranged side by side in the first direction D1 (vehicle front-rear direction) and the cross member. As a result, when the above-mentioned front-rear load acts on the battery pack, the reinforcing plate in each battery module that receives the front-rear load strokes in the first direction D1 by the amount of the above-mentioned gap. The stroke of the reinforcing plate causes deformation of the battery module. More specifically, when the battery pack is viewed from above, the battery module is deformed into a dogleg shape. For this reason, it is difficult to appropriately improve the resistance to crushing or front-rear collision associated with the front-rear load with the structure of this comparative example. In contrast, according to the reinforcing structure of the battery pack 1 according to this embodiment, the reinforcing plate 13 is arranged without a gap with the cross member 24. Therefore, in comparison with the comparative example, it is possible to significantly improve resistance to crushing caused by front and rear loads or resistance to front and rear collisions.

[0028] Next, another effect obtained by providing each battery cell group 12 with a reinforcing plate 13 will be described with reference to Fig. 3. Fig. 3 is a diagram for explaining an electrical connection path between the multiple battery cells 10 in the battery pack 1 according to the embodiment. The electrical connection path here is formed by a bus bar 54 that connects between the positive terminal 50 and the negative terminal 52 of the battery pack 1.

[0029] As an electrical connection path in a battery pack including a plurality of battery cell groups such as battery cell group 12, it is also possible to adopt the following configuration, different from the configuration shown in FIG. 3. That is, first, the plurality of battery cells included in each battery cell group are electrically connected in series. Next, adjacent battery cell groups are electrically connected in series. However, when such a configuration is adopted, the length of the bus bars connecting the battery cell groups becomes large. Increasing the length of the bus bars in the entire battery pack is undesirable, for example, from the viewpoint of increasing the cost of the battery pack and protecting the bus bars from external inputs.

[0030] In contrast, in the electrical connection path according to the present embodiment, as shown in Fig. 3, the bus bar 54 electrically connects the battery cells 10 in series not for each battery cell group 12, but for each of the eight sections A to H divided by the cross member 24 and the reinforcing plate 13. The bus bar 54 sequentially connects the sections A to H in series. With the electrical connection path formed in this manner, the length of the bus bar 54 of the battery pack 1 as a whole can be effectively shortened. More specifically, the bus bar 54 is formed to sequentially connect in series the four sections A, B, C, and D located on one side of the reinforcing plate 13 of each battery cell group 12 in the second direction D2, and then sequentially connect in series the four sections E, F, G, and H located on the other side of the second direction D2.

[0031] In addition, according to the electrical connection path shown in FIG. 3, the potential difference between the distant compartments (for example, between compartment A and compartment H, between compartment B and compartment G, and between compartment C and compartment F) is large as an electrical connection path. Therefore, when an electrical short circuit occurs due to the action of an external input or thermal runaway of the battery cell 10, a thermal chain reaction or spark generation of the battery cell 10 due to the high potential difference may easily occur. Regarding such a problem, in the battery pack 1 according to this embodiment, a reinforcing plate 13 is interposed between the compartments where a high potential difference occurs. Therefore, the presence of the reinforcing plate 13 can ensure a sufficient insulation distance between the battery cells 10 in the two compartments where a high potential difference occurs, and can also strengthen resistance to the above-mentioned thermal chain reaction and spark generation.

[0032] 3. Thermal insulation structure of battery cell group When the battery pack 1 includes a bus bar 54 having the electrical connection path shown in FIG. 3, the battery pack 1 may include a battery cell group 14 shown in FIG. 4 or a battery cell group 16 shown in FIG.

[0033] Fig. 4 is a diagram showing an example of a heat insulating structure of a battery cell group according to an embodiment. The battery cell group 14 shown in Fig. 4 includes a heat insulating material 15 interposed between the reinforcing plate 13 and the battery cells 10 in the second direction D2 (stacking direction). More specifically, the heat insulating material 15 is disposed between each of the battery cells 10 adjacent to both ends of the reinforcing plate 13 in the second direction D2. The heat insulating structure using the heat insulating material 15 can more reliably prevent a thermal chain reaction from occurring across compartments in the same battery cell group 12 when thermal runaway occurs in a battery cell 10.

[0034] Fig. 5 is a diagram showing another example of a heat insulating structure for a battery cell group according to an embodiment. A battery cell group 16 shown in Fig. 5 includes a reinforcing plate 17 instead of the reinforcing plate 13. The reinforcing plate 17 is formed using a resin material. More specifically, the reinforcing plate 17 is formed using, for example, a fiber-reinforced resin material with high thermal resistance. This heat insulating structure using the reinforcing plate 17 with higher thermal resistance than the metallic reinforcing plate 13 can also more reliably prevent a thermal chain reaction from occurring across compartments in the same battery cell group 12 when a thermal runaway occurs in a battery cell 10. [Explanation of symbols]

[0035] 1 battery pack, 10 battery cell, 12, 14, 16 battery cell group, 13, 17 reinforcing plate, 15 heat insulating material, 20 battery case, 21 lower case, 22 upper case, 23 side reinforcement, 24 cross member, 30 adhesive, 50 positive terminal, 52 negative terminal, 54 bus bar

Claims

1. A battery cell group including a plurality of battery cells; a battery case that houses the battery cell group; Equipped with the battery case includes a pair of cross members disposed to sandwich the battery cell group in a first direction and extending along a second direction perpendicular to the first direction, the plurality of battery cells are stacked along the second direction, the battery cell group includes a reinforcing plate stacked together with the plurality of battery cells at a position closer to a center of the battery cell group than to each end of the battery cell group in the second direction, The reinforcing plate is disposed so as to bridge the space between the pair of cross members. A battery pack characterized by:

2. The plurality of battery cells and the reinforcing plate are joined to the pair of cross members.

2. The battery pack according to claim 1 .

3. The battery cells and the reinforcing plate are joined to the pair of cross members via an adhesive.

3. The battery pack according to claim 2.

4. The battery cell group includes a thermal insulator interposed between the reinforcing plate and the battery cells in the second direction.

4. The battery pack according to claim 1, wherein the first and second electrodes are electrically connected to each other.

5. The reinforcing plate is formed using a resin material.

4. The battery pack according to claim 1, wherein the first and second electrodes are electrically connected to each other.

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