Battery pack mounting structure

Abstract

Provided is a battery pack mounting structure capable of suppressing fluctuations in a constraint load due to temperature fluctuations. A battery pack mounting structure (1) in which a battery pack (10) and a vehicle body (20) are fastened by means of a plurality of brackets (21), the battery pack being provided with a battery module (11) in which a plurality of battery cells are stacked, and a case (12) that accommodates the battery module in a constrained state. Each of the plurality of brackets has a case fastening point (23) for fastening the case and the bracket and a vehicle body fastening point (22) for fastening the vehicle body and the bracket, and the vehicle body fastening point is positioned further inward than the case fastening point with respect to a first direction (100) in which the plurality of battery cells are stacked.

Description

Technical Field

[0001] The present invention relates to a battery pack mounting structure, and more particularly to a battery pack mounting structure in which a battery pack is fastened to a vehicle body via a plurality of brackets. Background Art

[0002] A battery pack formed by stacking a plurality of battery cells can be used as a large-capacity power supply device used in electric vehicles, etc. Since such a battery pack has a small footprint and is lightweight, it can be mounted in a limited space such as in a vehicle.

[0003] Patent Document 1 discloses a battery pack including a battery module having a stacked body in which a plurality of battery cells are stacked, a bracket for fixing the battery module to a case at the battery cells at both ends of the stacked body, and a heat conducting member interposed between the stacked body and the case.

[0004] Patent document 1: Japanese Patent Application Publication No. 2018-041653.

[0005] In order to form a stack, it is necessary to apply an appropriate restraining load to the battery cell to hold it in the housing. On the other hand, in a battery pack having a battery module in which a plurality of battery cells are stacked, sometimes the restraining load may vary greatly due to the change in ambient temperature or the thermal expansion of the battery cell, which may cause the battery module to bend.

[0006] In order to suppress the deflection of the battery module, the battery module disclosed in Patent Document 1 is provided with a heat-conducting component to promote heat dissipation of the battery cell. In addition, it is also disclosed that when the stack is fixed to the housing, an elastic component is provided to suppress the deflection of the stack caused by the reaction force applied to the stack by the heat-conducting component, and when the battery cell expands, the elastic component is compressed to allow a certain amount of expansion of the battery cell.

[0007] On the other hand, the structure of the battery module disclosed in Patent Document 1 requires components such as a heat conductive member and an elastic member, and is therefore disadvantageous in terms of cost. Summary of the invention

[0008] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to provide a battery pack mounting structure that can suppress the variation of the restraint load due to temperature variation.

[0009] The battery pack mounting structure disclosed in the present invention is a battery pack mounting structure that fastens the battery pack to the vehicle body through a plurality of brackets, the battery pack having a battery module stacked with a plurality of battery cells and a housing that accommodates the battery module in a restrained state, the plurality of brackets respectively having a housing fastening point that fastens the housing to the bracket and a vehicle body fastening point that fastens the vehicle body to the bracket, the vehicle body fastening point being located at a position that is closer to the inside than the housing fastening point with respect to a first direction in which the plurality of battery cells are stacked. Thus, a battery pack mounting structure that can suppress changes in restraint loads caused by temperature changes can be provided.

[0010] In addition, the thermal expansion coefficient of the battery module may be greater than the thermal expansion coefficient of the housing. Thus, it is possible to provide a battery pack mounting structure that can suppress changes in restraint load due to temperature changes.

[0011] According to the present disclosure, it is possible to provide a battery pack mounting structure capable of suppressing fluctuations in restraint load due to temperature fluctuations. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a top view of the battery pack mounting structure involved in the present disclosure.

[0013] Figure 2A and Figure 2B It is a graph schematically illustrating the load change when the temperature changes according to the present disclosure.

[0014] Figure 3 It is a diagram for explaining the positional relationship of the bracket involved in the present disclosure. DETAILED DESCRIPTION

[0015] use Figure 1 A configuration example of a battery pack mounting structure according to the present disclosure will be described. Figure 1 The battery pack 10 shown in the figure has at least a battery module 11 in which a plurality of battery cells are stacked and a housing 12 in which the battery module 11 is received in a restrained state. Figure 1 The battery module 11 is pressurized and constrained by applying a restraining load on the battery module 11 (indicated by the arrow in FIG. 1 ). The direction in which the restraining load is applied is referred to as the first direction 100 hereinafter.

[0016] The battery pack mounting structure 1 according to the present disclosure is a structure in which a battery pack 10 is fastened to a vehicle body 20 by a plurality of brackets 21. The plurality of brackets 21 are fastened to the vehicle body 20 at vehicle body fastening points 22 and to the housing 12 at housing fastening points 23. Here, it is preferred that the vehicle body fastening points 22 are located inside the housing fastening points 23 with respect to the first direction.

[0017] By adopting the above configuration, bracket 21 thermally expands in first direction 100 due to temperature rise, thereby assisting thermal expansion of case 12. Thus, a battery pack mounting structure that can suppress changes in restraint load due to temperature changes can be provided.

[0018] use Figures 2A to 3 Explain the mechanism. Figure 2A In order to schematically illustrate the load variation when the temperature changes, the graph is plotted with the dimensions of the battery module 11 and the housing 12 as the horizontal axis and the load applied to them as the vertical axis. The intersection of the constraint load variation 111 of the battery module 11 and the constraint load variation 121 of the housing 12 is represented as the constraint load 101 at 25°C. Figure 2A This indicates that the thermal expansion coefficient of the battery module 11 is larger than the thermal expansion coefficient of the case 12 .

[0019] When the ambient temperature rises from 25° C. to 60° C., the size of the battery module 11 increases due to the temperature change, as shown by the restraint load change 112 . This increase is represented by the thermal expansion 110 of the battery module 11 .

[0020] Likewise, due to the temperature change, the size of the housing 12 may increase, as shown by the restraint load change 122. This increase is represented by the thermal expansion 120 of the housing 12.

[0021] The intersection of the restraint load variation 112 of the battery module 11 and the restraint load variation 122 of the case 12 is represented as a restraint load 202 at 60° C. It can be seen that the restraint load increases due to the difference in expansion between the battery module 11 and the case 12 caused by the temperature rise.

[0022] The housing 12 of the present disclosure is further Figure 3 The thermal expansion 210 between brackets 21A and 21B shown, when the ambient temperature rises from 25° C. to 60° C., will increase in size due to the temperature change, as shown by the restraint load change 123. The details of brackets 21A and 21B will be described later.

[0023] Depending on the presence or absence of thermal expansion 210 between the brackets 21A and 21B, the intersections of the restraint load variation 112 of the battery module 11 and the restraint load variations 122 and 123 of the housing 12 are represented as restraint loads 202 and 102 at 60° C., respectively. The restraint load 202 can be regarded as a restraint load when the vehicle body fastening point 22 is located at the same position as the housing fastening point 23 or at an outer side than the housing fastening point 23 with respect to the first direction 100.

[0024] On the other hand, the restraint load 102 is a restraint load when the thermal expansion 210 between the brackets 21A and 21B is added by positioning the housing 12, i.e., the vehicle body fastening point 22, inward relative to the first direction 100 relative to the housing fastening point 23. Comparing the restraint loads 202 and 102, it can be seen that the increase in the restraint load can be suppressed by positioning the vehicle body fastening point 22 inward relative to the first direction 100 relative to the housing fastening point 23. Therefore, it can be seen that if the thermal expansion coefficient of the battery module 11 is greater than the thermal expansion coefficient of the housing 12, the effect of the battery pack mounting structure in the present disclosure can be obtained.

[0025] in addition, Figure 2B This shows a case where the thermal expansion coefficient of the battery module 11 is smaller than the thermal expansion coefficient of the case 12. Even in this case, by comparing the restraint loads 202 and 102, it can be seen that the battery pack mounting structure according to the present disclosure can suppress an increase in the restraint load.

[0026] Figure 3 It is explained in Figure 1 The diagram shows the positional relationship of the brackets in the battery pack mounting structure 1. The brackets 21A and 21B according to the present disclosure can be made of various materials, but as an example, a bracket made of cast iron is considered.

[0027] In any bracket 21A, assuming that the distance L between the vehicle body fastening point 22A and the housing fastening point 23A in the first direction 100 is 50 mm and the ambient temperature rises from 25° C. to 60° C., the expansion amount ΔL (mm) of the bracket 21 is calculated as follows: 0.0184 (mm).

[0028] ΔL=αLΔT=10.5×10 6 ×50×(60-25)≈0.0184(mm) Among them, α is the linear expansion coefficient of cast iron, and ΔT is the temperature difference.

[0029] The distance between the vehicle body fastening points 22A and 22B of the pair of brackets 21A and 21B of the housing 12 facing each other in the first direction 100 expands by 0.0368 (=0.0184×2) (mm). The load variation reduction ΔF obtained by this expansion is calculated as 46 (N) as shown below.

[0030] ΔF=kΔL×2=2500×0.0184×2=46 (N) Where k is the module spring constant (N / mm).

[0031] Therefore, by applying the battery pack mounting structure involved in the present disclosure, the change in the restraint load can be reduced by 46 (N). It should be noted that although this is an effect calculated when the temperature rises, the same effect is also achieved when the temperature drops. In addition, the battery pack mounting structure of the present disclosure can achieve a higher effect in a configuration in which the restraint load increases when the temperature rises and decreases when the temperature drops.

[0032] In this way, it is possible to provide a battery pack mounting structure that can suppress changes in the restraint load due to temperature changes.

[0033] In addition, the present disclosure is not limited to the above contents, and can be appropriately modified within the scope not departing from the gist.

Claims

1. A battery pack mounting structure for fastening a battery pack to a vehicle body through a plurality of brackets, characterized in that: The battery pack comprises: A battery module in which a plurality of battery cells are stacked; and a housing for accommodating the battery module in a restrained state, The plurality of brackets respectively have: A housing fastening point for fastening the housing to the bracket; and A body fastening point for fastening the body and the bracket, The vehicle body fastening point is located on the inner side than the case fastening point with respect to a first direction in which the plurality of battery cells are stacked.

2. The battery pack mounting structure according to claim 1, characterized in that: The thermal expansion coefficient of the battery module is greater than the thermal expansion coefficient of the housing.

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