Battery pack

Abstract

The panel material located directly beneath the battery case provides a battery pack that exhibits high heat resistance and high impact resistance against collisions. [Solution] The battery case houses a battery module having multiple battery cells and is mounted on a vehicle, and the panel material 50 is provided directly below the battery case and is exposed to the outside of the vehicle, and the cross section of the panel material cut by a plane perpendicular to the horizontal direction has a shape with multiple holes 53, the size of which gradually decreases from bottom to top.

Description

[[Technical Field]]

[0001] The present invention relates to a battery pack. [[Background Art]]

[0002] The following Patent Document 1 discloses a battery pack in which a battery module (battery array) is housed in a battery case. [[Prior Art Documents]] [[Patent Documents]]

[0003] [[Patent Document 1]] Japanese Patent Laid-Open No. 2023-503506 [[Summary of the Invention]] [[Problems to be Solved by the Invention]]

[0004] The battery pack disclosed in the above-mentioned Patent Document 1 has room for improvement in achieving both heat resistance and impact resistance against collision objects.

[0005] In view of the above facts, an object of the present invention is to provide a battery pack in which a panel member provided directly under a battery case can exhibit high heat resistance and high impact resistance against collision objects. [[Means for Solving the Problems]]

[0006] The battery pack according to a first aspect comprises: a battery case that houses a battery module having a plurality of battery cells and is mounted on a vehicle; and a panel member that is provided directly under the battery case and exposed to the outside of the vehicle, wherein a cross-section of the panel member cut along a plane orthogonal to the horizontal direction has a shape having a plurality of holes, and the size of the holes gradually decreases from the lower side to the upper side.

[0007] In the battery pack of the first embodiment, a panel material is provided directly below the battery case, and the cross-section of the panel material, when cut by a plane perpendicular to the horizontal direction, has a shape with multiple holes. Furthermore, the size of each hole gradually decreases from bottom to top.

[0008] Therefore, the upper part of the panel material has greater heat resistance than the lower part. As a result, even if the area around the battery case becomes hot, the upper part of the panel material can prevent this heat from reaching the battery case.

[0009] Furthermore, if an object collides with the panel material, the lower part of the panel can exhibit higher impact resistance than the upper part. Therefore, when an object (collision object) collides with the lower surface of the panel material, the lower part of the panel can deform flexibly and absorb the impact in this case.

[0010] Thus, the panel material provided directly below the battery case in the battery pack of the first embodiment can exhibit high heat resistance and high impact resistance against collisions.

[0011] In the second embodiment of the battery pack, the hole is hexagonal in the first embodiment.

[0012] In the battery pack of the second embodiment, each hole in the panel material is hexagonal. That is, the internal structure of the panel material is a honeycomb structure. Therefore, the panel material can exhibit higher shock absorption compared to panels with holes of shapes other than hexagons.

[0013] In the third embodiment of the battery pack, the panel material is made of iron, as in the first or second embodiment.

[0014] In the third embodiment of the battery pack, the panel material is made of iron. Therefore, the heat resistance of the panel material is higher compared to the case where the panel material is made of aluminum. [Effects of the Invention]

[0015] As described above, the battery pack according to the present invention has an excellent effect that the panel member provided directly under the battery case can exhibit high heat resistance and high impact resistance against impact objects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] [Figure 1] Fig. 1 is a cross-sectional view cut at the center in the vehicle width direction of a vehicle including the battery pack according to the embodiment. [Figure 2] Fig. 2 is a schematic exploded perspective view of the battery pack. [Figure 3] Fig. 3 is a schematic cross-sectional view of the panel member. MODES FOR CARRYING OUT THE INVENTION

[0017] Hereinafter, the battery pack according to the embodiment will be described with reference to the accompanying drawings. Note that arrow UP, arrow FR and arrow LH in each drawing respectively indicate the upper side in the vehicle vertical direction, the front side in the vehicle front-rear direction, and the left side in the vehicle left-right direction.

[0018] As shown in Fig. 1, the battery pack 20 of the present embodiment is mounted on a vehicle (electric vehicle) 10. The vehicle 10 of the present embodiment is a battery electric vehicle (BEV).

[0019] The vehicle 10 includes a pair of left and right front wheels 11F, a pair of left and right rear wheels 11R, a pair of left and right rockers 12 which are part of a vehicle body frame member and extend in the vehicle front-rear direction, and a pair of front and rear cross members 14 which are part of a vehicle body frame member extending in the vehicle width direction (left-right direction) and having both end portions fixed to the left and right rockers 12.

[0020] The battery pack 20 of the present embodiment includes a battery case 22, a battery module 40, and a panel member 50. The electric power of the battery pack 20 (battery cells 43) is supplied to, for example, an electric motor (not shown) that applies driving force to driving wheels which are at least one of the front wheels 11F and the rear wheels 11R.

[0021] As shown in Figures 1 and 2, the battery case 22 includes a lower case 24 and an upper case 35.

[0022] The lower case 24 is a hollow body with an opening 25 formed on an upper surface thereof. The lower case 24 includes a bottom plate portion 26, a peripheral wall portion 27, and an outer peripheral flange 28. The planar shape of the peripheral wall portion 27 is annular, and a lower end portion of the peripheral wall portion 27 is connected to an outer peripheral edge portion of the bottom plate portion 26. The planar shape of the outer peripheral flange 28 is annular, and an inner peripheral edge portion of the outer peripheral flange 28 is connected to an upper end portion of the peripheral wall portion 27.

[0023] The upper case 35 is a hollow body with an opening 36 formed on a lower surface thereof. The upper case 35 includes a top plate portion 37, a peripheral wall portion 38, and an outer peripheral flange 39. The planar shape of the peripheral wall portion 38 is annular, and an upper end portion of the peripheral wall portion 38 is connected to an outer peripheral edge portion of the top plate portion 37. The planar shape of the outer peripheral flange 39 is annular, and an inner peripheral edge portion of the outer peripheral flange 39 is connected to a lower end portion of the peripheral wall portion 38.

[0024] As shown in Figure 1, a battery module 40 is provided inside the lower case 24. The battery module 40 includes a battery stack 41, end plates 48, and a restraining member (not shown).

[0025] As shown in Figure 1, the battery stack 41 extending in the front-rear direction includes a plurality of battery cells 43 that are lithium-ion batteries, and a plurality of insulating members (spacers, not shown) positioned between adjacent battery cells 43. A positive electrode and a negative electrode (both not shown) are provided in each battery cell 43.

[0026] The battery module 40 includes a pair of front and rear end plates 48. The front end plate 48 is positioned immediately before the most front battery cell 43, and the rear end plate 48 is positioned immediately after the most rear battery cell 43.

[0027] The front and rear ends of multiple restraining members are fixed to the front and rear end plates 48, respectively, and the front-to-rear length of each restraining member becomes shorter than when it is in a free state. That is, each restraining member pulls the front and rear end plates 48 toward each other, and as a result the front and rear end plates 48 sandwich the battery stack 41 from the front and rear. The battery module 40 is thus constructed.

[0028] Furthermore, the battery module 40 includes a number of busbars (not shown) connected to the positive and negative electrodes of each battery cell 43.

[0029] As shown in Figures 1 and 2, the panel material 50 is a flat plate-shaped member with a roughly rectangular planar shape. The panel material 50 is made of iron. As shown in Figure 1, the upper surface of the panel material 50 is fixed to the lower surface of the lower case 24.

[0030] As shown in Figure 3, the interior of the panel material 50 is composed of a honeycomb structure 52. That is, numerous holes 53 with a hexagonal cross-sectional shape are formed inside the panel material 50. This "hexagon" includes regular hexagons and approximate regular hexagons. Each hexagonal hole 53 extends in the left-right direction. That is, each hole 53 extends across the entire width of the panel material 50.

[0031] Furthermore, the size of each hexagonal hole 53 gradually decreases from bottom to top. In addition, the left and right sides of the panel material 50 are covered by side portions 55, the top surface of the panel material 50 is covered by a top portion 56, the bottom surface of the panel material 50 is covered by a bottom portion 57, the front surface of the panel material 50 is covered by a front portion 58, and the rear surface of the panel material 50 is covered by a rear portion 59. In other words, although the panel material 50 is exposed to the outside of the vehicle, the honeycomb structure 52 is not exposed to the outside of the panel material 50.

[0032] Furthermore, the outer flange 39 of the upper case 35 is placed on the entire upper surface of the outer flange 28 of the lower case 24, which houses the battery module 40 and is integrated with the panel material 50, via a sealing material (not shown), thereby fixing the outer flange 28 and outer flange 39 to each other. This completes the battery pack 20.

[0033] Furthermore, as shown in Figure 1, the battery case 22 of the completed battery pack 20 is supported by the rocker 12 and the cross member 14.

[0034] (Mechanism of action and effect) Next, the operation and effects of the embodiment will be described.

[0035] The battery pack 20 of this embodiment includes a panel material 50 fixed to the lower surface of the lower case 24 (battery case 22). Since the panel material 50 is made of iron, it has superior heat resistance compared to the case made of aluminum. Furthermore, the cross-section of the panel material 50 cut by a plane perpendicular to the left-right direction (horizontal direction) is a honeycomb structure 52 having a large number of hexagonal holes 53. Moreover, the size of each hexagonal hole 53 gradually decreases from the bottom to the top. Therefore, the upper part of the panel material 50 has greater heat resistance than the lower part. As a result, flames generated around the panel material 50 are prevented from reaching the lower surface of the battery case 22 (lower case 24) by the upper part of the panel material 50 (where the holes 53 are smaller).

[0036] Furthermore, if an object collides with the panel material 50, the lower part of the panel material 50 can exhibit higher impact resistance than the upper part. In other words, the larger holes 53 on the lower side of the panel material 50 deform more easily than the smaller holes 53 on the upper side. Therefore, for example, if a stone on the road surface collides with the lower surface 57 of the panel material 50, the deformation of the multiple large holes 53 on the lower side of the panel material 50 allows it to absorb the force applied to the panel material 50 from the stone (more efficiently than the smaller holes 53 on the upper side).

[0037] Furthermore, the internal structure of the panel material 50 is a honeycomb structure. As a result, the panel material 50 can exhibit higher shock absorption compared to cases where the holes 53 are of a shape other than hexagons. In addition, although the panel material 50 is made of iron, which has a higher specific gravity than aluminum, the internal structure of the panel material 50 is a honeycomb structure (hollow structure), which suppresses an increase in the weight of the panel material 50.

[0038] In this way, the panel material 50 provided directly below the battery case 22 (lower case 24) in the battery pack 20 can exhibit high heat resistance and high impact resistance against collision objects.

[0039] Although the battery packs according to the embodiments have been described above, these can be modified as appropriate without departing from the spirit of the present invention.

[0040] For example, a battery pack may have multiple battery modules.

[0041] Furthermore, the cross-sectional shape of the holes 53 in the panel material 50 does not have to be hexagonal, as long as the diameter of each hole 53 gradually decreases from bottom to top. For example, the internal structure of the panel material 50 may be a structure in which polyhedra (e.g., dodecahedrons) with a shape close to a sphere are arranged and integrated (fixed) with respect to each other, and the diameter of each polyhedron may gradually decrease from bottom to top. In this case as well, the panel material 50 can exhibit high heat resistance and high impact resistance against collisions.

[0042] A component different from the battery case 22 (lower case 24) may be interposed between the lower surface of the battery case 22 (lower case 24) and the panel material 50 located directly below the battery case 22.

[0043] The vehicle may be an electric vehicle that is different from an electric vehicle and is equipped with an electric motor that utilizes the power of the battery pack 20. For example, the vehicle may be a hybrid electric vehicle (HEV) or a plug-in hybrid electric vehicle (PHEV). [Explanation of Symbols]

[0044] 10 vehicles 20 battery packs 22 Battery Case 40 Battery Modules 43 battery cells 50 Panel materials 52 Honeycomb structure 53 holes

Claims

1. A battery case that houses a battery module having multiple battery cells and is mounted on a vehicle, A panel material provided directly below the battery case and exposed to the outside of the vehicle, Equipped with, The cross-section of the panel material, when cut by a plane perpendicular to the horizontal direction, has a shape with multiple holes. A battery pack in which the size of the aforementioned holes gradually decreases from bottom to top.

2. The battery pack according to claim 1, wherein the hole is a hexagonal hole.

3. The battery pack according to claim 1 or claim 2, wherein the panel material is made of iron.

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