Battery pack structure

Abstract

The objective is to obtain a battery pack structure that allows the battery module to be connected to the lower case with low rigidity when the battery is in use, and to be connected to the lower case with high rigidity during a collision. [Solution] The battery pack structure comprises a battery module 20 comprising a plurality of battery cells 16 arranged in parallel in a predetermined direction and an end plate 18 positioned on the outside in the direction of arrangement of the plurality of battery cells 16; a lower case 26 in which the lower part of the battery module 20 is housed; and a module bracket 24 which fixes the end plate 18 to the lower case 26 such that a gap is formed between it and the inner wall surface of the lower case 26, and has a bend point 32 that bends toward the end plate 18 in the portion facing the end plate 18, and further has a contact surface 34 formed that extends along the end plate 18 from the bend point 32 and faces the end plate 18.

Description

TECHNICAL FIELD

[0001] The present invention relates to a battery pack structure. BACKGROUND ART

[0002] Patent Document 1 below discloses an example of a battery module fixing structure.

[0003] Briefly described, in this battery module fixing structure, by devising the shapes of the end plate and the side plate, load fluctuations caused by expansion and contraction of cells due to temperature changes and aged deterioration are prevented from being transmitted to the module fixing points. PRIOR ART DOCUMENTS PATENT DOCUMENTS

[0004] PATENT DOCUMENT 1 Japanese Unexamined Patent Application Publication No. 2018-073542 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] However, the technique described in the above Patent Document 1 still has room for improvement in the following points. That is, in order to simplify the energy absorption mechanism at the time of collision, it is necessary to utilize the load in the stacking direction of the modules, but in the case of this structure, the connection between the lower case and the module has low rigidity. In other words, the connection from the module mounting point to the cells is connected with low rigidity. For this reason, it becomes difficult to transmit an external collision load to the module.

[0006] In consideration of the above facts, the present invention aims to obtain a battery pack structure that can connect the battery module to the lower case with low rigidity during battery use, and can connect the battery module to the lower case with high rigidity at the time of collision. MEANS FOR SOLVING THE PROBLEMS

[0007] The battery pack structure according to claim 1 comprises a battery module comprising a plurality of battery cells arranged in parallel in a predetermined direction and an end plate positioned on the outside in the direction of arrangement of the plurality of battery cells; a lower case in which the lower part of the battery module is housed; and a module bracket that fixes the end plate to the lower case such that a gap is formed between it and the inner wall surface of the lower case, and has a bend point in the portion facing the end plate that bends toward the end plate, and further extends along the end plate from the bend point and has a contact surface facing the end plate.

[0008] According to the present invention as described in claim 1, the end plate of the battery module is fixed to the lower case via a module bracket, and a bending point is provided in the portion of the module bracket facing the end plate, which bends toward the end plate. Therefore, during normal use of the battery pack, load fluctuations caused by the expansion and contraction of the battery cells are absorbed by the displacement of the bending point and are less likely to be transmitted to the fixing point between the module bracket and the lower case. In other words, the fixing structure of the battery module is made less rigid.

[0009] On the other hand, the portion of the module bracket facing the end plate has a contact surface that extends from the bend point along the end plate and faces the end plate. Therefore, when a collision load is applied from the module bracket side to the end plate side during a collision, the contact surface first contacts the end plate, resulting in a highly rigid connection between the battery module and the lower case via the module bracket, and a reaction force against the collision load is quickly generated. In other words, it becomes possible to reproduce a state in which the battery module and the lower case are connected with high rigidity during a collision.

[0010] In the battery pack structure according to claim 2, in the invention described in claim 1, a protrusion is provided on the end plate at a position facing the lower case, which protrudes toward the lower case.

[0011] According to the present invention as described in claim 2, a protrusion is provided on the end plate at a position facing the lower case, so that the lower case deforms and hits the protrusion during a collision. This allows a reaction force to be generated from the end plate towards the lower case via the protrusion. As a result, a reaction force can be generated quickly not only on the contact surface but also on the protrusion.

[0012] In the battery pack structure according to claim 3, in the invention described in claim 2, a protrusion is provided in the lower case at a position opposite to the protruding portion, projecting toward the end plate side.

[0013] According to the present invention as described in claim 3, a convex portion is provided in the lower case at a position opposite to the protrusion provided on the end plate, projecting toward the end plate. Therefore, the distance between the convex portion and the protrusion is shorter than in areas without a convex portion. As a result, during a collision, the convex portion of the lower case and the protrusion of the end plate come into contact quickly, generating a reaction force. This allows for the rapid generation of a collision reaction force outside the battery pack during a collision. For example, if an energy absorbing member is located outside the lower case, the reaction force can be rapidly applied to the energy absorbing member, causing it to undergo plastic deformation.

[0014] In the battery pack structure according to claim 4, in the invention according to claim 3, a reinforcing rib is provided on the end plate facing the lower case, connecting the fixing portion that fixes the end plate and the lower case with the protruding portion.

[0015] According to the present invention as described in claim 4, a reinforcing rib connecting the fixed portion and the protruding portion is provided on the surface of the end plate facing the lower case, so that the collision load applied during a collision is distributed throughout the end plate via the reinforcing rib. [Effects of the Invention]

[0016] As described above, the battery pack structure according to the present invention recited in claim 1 has an excellent effect that the battery module can be connected to the lower case with low rigidity when the battery is in use, and the battery module can be connected to the lower case with high rigidity at the time of collision.

[0017] The battery pack structure according to the present invention recited in claim 2 has an excellent effect that the portion that generates reaction force at the time of collision can be increased, and the high rigidity characteristic required at the time of collision can be enhanced.

[0018] The battery pack structure according to the present invention recited in claim 3 has an excellent effect that the energy absorption performance at the time of collision can be improved.

[0019] The battery pack structure according to the present invention recited in claim 4 has an excellent effect that the collision reaction force can be rapidly generated while suppressing the input of collision load to the battery cell side. [Brief Description of the Drawings]

[0020] [Figure 1] It is a schematic vertical cross-sectional view showing the entire structure of the battery pack structure according to the present embodiment, cut along the vehicle width direction. [Figure 2] It is an enlarged cross-sectional view of the main part of the battery pack structure shown in Figure 1. [Figure 3] It is an enlarged front view of the end plate shown in Figure 1. [Figure 4] It is a transverse cross-sectional view showing a state in which the main part structure of the battery pack structure shown in Figure 2 is cut along line 4-4. [Mode for Carrying Out the Invention]

[0021] Hereinafter, the battery pack structure according to the present embodiment will be described with reference to Figure 1 to Figure 4. In these drawings, the arrow UP appropriately indicated points to the vehicle upper side, the arrow LH points to the left side in the vehicle width direction, and the arrow FR points to the vehicle front side.

[0022] (Overall Structure of Battery Pack Structure) Figure 1 is a schematic vertical cross-sectional view showing the entire battery pack structure according to the present embodiment, cut along the vehicle width direction. As shown in this figure, a substantially rectangular battery pack 12 in plan view is disposed on the lower side of the cabin of the vehicle 10 (on the vehicle lower side of the vehicle body floor). Further, on the outer side of the battery pack 12 in the vehicle width direction, an elongated energy absorbing member 14 whose longitudinal direction is the vehicle front-rear direction is disposed. Although only the energy absorbing member 14 on the left side of the battery pack 12 in the vehicle width direction is illustrated in Figure 1, a similar energy absorbing member is also disposed on the right side of the battery pack 12 in the vehicle width direction. The energy absorbing member 14 has a rectangular closed cross-sectional shape, and two partition walls are formed inside. As an example, the energy absorbing member 14 is constituted by an extruded material.

[0023] As shown in Figure 1 and Figure 2, the battery pack 12 includes a plurality of battery modules 20 each configured to include a plurality of battery cells 16 stacked with a predetermined direction as the stacking direction, and end plates 18 arranged at ends in the stacking direction.

[0024] The plurality of battery modules 20 described above are accommodated in a case 22. The case 22 is configured to include a lower case 26 having a hat-shaped cross section and constituting the lower portion of the case 22, and an unillustrated upper case fitted to the lower case 26 and constituting the upper portion of the case 22.

[0025] Further, the lower case 26 is configured to include a main body portion 26A having a hat-shaped cross section, and a reinforcement 26B having a substantially Z-shaped cross section that forms a rectangular closed cross-sectional structure with a side wall portion 26A1 and a bottom wall portion 26A2 located on the outer side of the main body portion 26A in the vehicle width direction.

[0026] (Main Part Structure of Battery Pack Structure) The battery module 20 described above is attached to the reinforcement 26B of the lower case 26 via a module bracket 24. Specifically, as shown in Figure 2, the module bracket 24 is formed in an L-shape when viewed in the vehicle's longitudinal direction, and consists of a lateral wall portion 24A extending along the vehicle's width direction and a longitudinal wall portion 24B that is bent upward from the inner end of the lateral wall portion 24A and extends in the vehicle's vertical direction. The lateral wall portion 24A is fastened and fixed to the horizontal flange portion 26B1 of the reinforcement 26B with a first bolt 30A and a weld nut (not shown). The longitudinal wall portion 24B is fastened and fixed to a boss 31 formed on the side surface of the end plate 18 with a second bolt 30B.

[0027] Here, the vertical wall portion 24B of the module bracket 24 described above is bent diagonally downward towards the end plate 18 at a predetermined position at its lower end, and then bent downward along the side of the end plate 18 toward the bottom wall portion 26A2 of the lower case 26. Hereafter, the endpoint of the diagonally downward bend will be referred to as the "bend point 32," and the inner wall surface bent downward from this bend point 32 will be referred to as the "contact surface 34." The contact surface 34 is positioned opposite the center of the side of the end plate 18 with a small gap between them.

[0028] Furthermore, as shown in Figures 1 to 3, multiple cylindrical protrusions 36 are integrally formed at predetermined intervals in the vehicle's longitudinal direction on the lower part of the outer side surface of the end plate 18 in the vehicle's width direction. The protrusions 36 are preferably solid, but may be hollow. Also, the shape of the protrusions 36 is not necessarily limited to a cylindrical shape; it may be a rectangular prism shape. In this embodiment, protrusions 36 are formed in a total of three places on the end plate 18: both the front and rear ends and the central part. The protrusion height of the protrusions 36 is set to be the same as that of the boss 31, and their size is also set to be approximately the same.

[0029] Furthermore, a roughly grid-like reinforcing rib 38 extending in the vertical and horizontal directions is integrally formed on the outer side surface of the end plate 18 in the vehicle width direction. The three protrusions 36 are interconnected by the reinforcing rib 38. The four bosses 31 are also interconnected by the reinforcing rib 38. In other words, the multiple protrusions 36 and bosses 31 are interconnected by the reinforcing rib 38.

[0030] As shown in Figure 4, the vertical wall 26B2 of the reinforcement 26B in the lower case 26 described above is formed with an uneven shape in plan cross-sectional view. As a result, a protrusion 42 is positioned close to the vertical wall 26B2 at a position opposite to the protrusion 36 in the vehicle width direction. A small gap 44 is provided between the top of the protrusion 42 and the end face of the protrusion 36. However, the gap 44 is set to be wider than the gap between the contact surface 34 and the end plate 18.

[0031] (Mechanism of Action and Effects) Next, the operation and effects of the battery pack structure according to this embodiment will be described.

[0032] According to this embodiment, the end plate 18 of the battery module 20 is fixed to the lower case 26 via a module bracket 24, and a bending point 32 is provided in the portion of the module bracket 24 that faces the end plate 18, causing it to bend toward the end plate 18.

[0033] Therefore, during normal use of the battery pack 12, load fluctuations caused by the expansion and contraction of the battery cells 16 are absorbed by the displacement of the bending point 32, and are less likely to be transmitted to the first bolt 30A between the module bracket 24 and the lower case 26. In other words, the fixing structure of the battery module 20 is made less rigid.

[0034] On the other hand, in the portion of the module bracket 24 facing the end plate 18, a contact surface 34 is formed that extends from the bending point 32 along the end plate 18 and faces the end plate 18.

[0035] Therefore, when a collision load F is input from the module bracket 24 to the end plate 18 during a collision, the contact surface 34 first contacts the end plate 18 (reinforcement rib 38, indicated by dots in Figure 3), thereby creating a highly rigid connection between the battery module 20 and the lower case 26 via the module bracket 24, and quickly generating a reaction force against the collision load F1. In other words, during a collision, it becomes possible to reproduce a state in which the battery module 20 and the lower case 26 are connected with high rigidity.

[0036] As described above, the battery pack structure according to this embodiment can connect the battery module 20 to the lower case 26 with low rigidity when the battery is in use, and connect the battery module 20 to the lower case 26 with high rigidity when a collision occurs.

[0037] Furthermore, in this embodiment, a protrusion 36 is provided on the end plate 18 at a position facing the lower case 26, projecting toward the lower case 26. Therefore, during a collision, the lower case 26 deforms and hits the protrusion 36, and a collision load F2 is input. This allows a reaction force to be generated from the end plate 18 toward the lower case 26 via the protrusion 36. As a result, a reaction force can be quickly generated not only on the contact surface 34 but also on the protrusion 36. Consequently, the battery pack structure according to this embodiment can increase the portion that generates a reaction force during a collision, thereby enhancing the high rigidity characteristics required during a collision.

[0038] Furthermore, in this embodiment, a protrusion 42 is provided in the lower case 26 at a position opposite to the protrusion 36 provided on the end plate 18, so that the distance between the protrusion 42 and the protrusion 36 is shorter than in the area where the protrusion 42 is not present.

[0039] Therefore, during a collision, the protrusion 42 of the lower case 26 and the projection 36 of the end plate 18 come into contact quickly, generating a reaction force. As a result, a collision reaction force can be quickly generated outside the battery pack 12 during a collision. For example, if an energy absorber 14 is located outside the lower case 26, the reaction force can be quickly applied to the energy absorber 14, causing it to undergo plastic deformation. Consequently, the battery pack structure according to this embodiment can improve the energy absorption performance during a collision.

[0040] Furthermore, in this embodiment, a reinforcing rib 38 connecting the boss 31 and the protruding portion 36 is provided on the end plate 18 facing the lower case 26. As a result, the impact load F input during a collision is distributed across the entire end plate 18 in a planar direction via the reinforcing rib 38. Consequently, the battery pack structure according to this embodiment can quickly generate an impact reaction force while suppressing the input of the impact load F to the battery cell 16.

[0041] (Supplementary explanation of the embodiment) In the embodiment described above, the fold point 32 and contact surface 34 formed on the module bracket 24 are formed at one location. However, the invention is not limited to this, and multiple fold points may be formed on the module bracket, or multiple fold points may be provided on a single contact surface.

[0042] Furthermore, in this embodiment, the protrusions 36 are formed in three cylindrical locations on the end plate 18, but this is not limited to this. The protrusions may be formed in one or more locations other than three, and the shape may also be other than cylindrical, as mentioned above.

[0043] In addition, although the reinforcing ribs 38 are arranged in a grid pattern in this embodiment, they are not limited to this and may be formed in a slanted or honeycomb shape. [Explanation of Symbols]

[0044] 12 battery packs 16 battery cells 18 End Plates 20 Battery Modules 24 Module Brackets 26 Lower Cases 31 Boss (fixed part) 32 Inflection points 34. Contact surface 36 Protrusion 38 Reinforcement Ribs

Claims

1. A battery module comprising a plurality of battery cells arranged in parallel in a predetermined direction, and an end plate positioned on the outside of the arrangement direction of the plurality of battery cells, A lower case in which the lower part of the aforementioned battery module is housed, The module bracket is fixed to the lower case such that a gap is formed between the end plate and the inner wall surface of the lower case, and has a bend point that bends toward the end plate at the portion facing the end plate, and further extends from the bend point along the end plate to form a contact surface that faces the end plate, A battery pack structure having the following characteristics.

2. A projection is provided on the end plate at a position facing the lower case, projecting toward the lower case. The battery pack structure according to claim 1.

3. A protrusion is provided in the lower case at a position opposite to the protruding portion, projecting toward the end plate side. The battery pack structure according to claim 2.

4. The end plate is provided with a reinforcing rib on the surface facing the lower case, connecting the fixing portion that secures the end plate and the lower case with the protruding portion. The battery pack structure according to claim 3.

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