Battery case bottom structure

Abstract

To achieve a bottom surface structure of a battery case having a lower surface in a substantially horizontal flat shape, while enhancing rigidity by combining two extrusion materials different in an extrusion direction.SOLUTION: A bottom surface structure of a battery case is mounted at a lower part of a vehicle and is formed by combining extrusion materials, and comprises: a first extrusion material 12 which has a notch part 18 formed by notching an upper surface side of an end part in an extrusion direction; and a second extrusion material 14 which is a hollow shape and on which a rib 20 connecting between an upper surface part and a lower surface part is provided. The first extrusion material 12 and the second extrusion material 14 are joined so that a lower surface of the second extrusion material 14 covers the notch part 18 from an upper side of the notch part 18 of the first extrusion material 12. An extrusion direction of the first extrusion material 12 and an extrusion direction of the second extrusion material 14 are vertical to each other. The rib 20 is disposed just above joined portions 22.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a bottom structure of a battery case mounted on a vehicle. [Background technology]

[0002] BACKGROUND ART Conventionally, for electrically powered vehicles such as battery electric vehicles (BEVs) and plug-in hybrid electric vehicles (PHEVs), battery cases with various structures have been proposed to protect batteries arranged under the vehicle.

[0003] Patent Document 1 discloses a protective structure for a battery module that enhances protection against external input loads by forming a gap with a predetermined clearance between a case body that houses a battery module and a guard member provided below it, and by making the guard member have a hollow cross-sectional shape. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-183222 Summary of the Invention [Problem to be solved by the invention]

[0005] While a vehicle is traveling, objects or flying stones on the road surface may come into contact with the battery located underneath the vehicle, potentially damaging the battery. Therefore, the structure of the battery case that protects the battery requires ingenuity. For example, to increase rigidity, a structure combining an aluminum extrusion with the bottom of the battery case may be adopted. In this case, combining two extrusions with different extrusion directions increases rigidity, but another issue may arise when joining the two extrusions. Specifically, the two extrusions are fitted or butt-joined, which can cause the joint to protrude from the bottom.

[0006] In the bottom structure of a battery case, it is desirable for the bottom surface to be flat (i.e., approximately horizontal) to be able to withstand aerodynamic forces and road interference. However, with the structure described above, the joints protrude from the bottom surface, making it impossible to make the bottom surface flat. In such a configuration, if interference occurs from below the vehicle, the protruding parts will bear the load, but the rigidity of the bottom of the battery case is insufficient, and the battery cannot be adequately protected. An example of such a problem is the bottom structure of a battery case shown in Figures 4 and 5.

[0007] FIG. 4 is a cross-sectional view of the bottom of a battery case having a different structure from the bottom structure of the battery case disclosed herein. More specifically, FIG. 4 is a cross-sectional view of the bottom 10 of the battery case, showing two extrusions 12 and 14 with different extrusion directions fitted together and joined. Hereinafter, the extrusion 12 will be referred to as the first extrusion 12, and the extrusion 14 will be referred to as the second extrusion 14. The same elements will be denoted by the same reference numerals in each figure. As shown in FIG. 4, the first extrusion 12 and the second extrusion 14 are joined at two locations enclosed by dashed lines. This joining is achieved, for example, by arc welding. At this time, as shown in FIG. 4, a recess provided below the side surface of the second extrusion 14 (more specifically, the side surface joined to the first extrusion 12) is fitted with the end of the first extrusion 12. In this configuration, the lower surface 14a of the second extrusion 14 is the lowest surface of the bottom 10 of the battery case. That is, the lowest surface of the bottom surface 10 of the battery case is the lower surface 14a, which is a specific narrow portion rather than a wide area. Therefore, the bottom structure of the battery case shown in Fig. 4 does not achieve the desired structure of a flat bottom surface.

[0008] Next, FIG. 5 is a cross-sectional view showing the bottom of a battery case having a different configuration from the bottom structure of the battery case disclosed herein. More specifically, FIG. 5 is a cross-sectional view of the bottom 10 of the battery case, showing a first extrusion member 12 and a second extrusion member 14, which are extruded in different directions, butt-joined together. For example, when the first extrusion member 12 and the second extrusion member 14 are butt-joined together by high-frequency welding, the welded portion is raised, forming a weld bead 16. As shown in FIG. 5, the weld bead 16 protrudes below the bottom surfaces of the first extrusion member 12 and the second extrusion member 14. Therefore, similar to FIG. 4, the bottom 10 of the battery case shown in FIG. 5 does not achieve the flat bottom structure desired for a battery case.

[0009] Therefore, this specification discloses a bottom structure of a battery case that combines two extruded materials with different extrusion directions to increase rigidity while providing a substantially horizontal lower surface. [Means for solving the problem]

[0010] The bottom structure of a battery case disclosed in this specification is a bottom structure of a battery case that is mounted on the underside of a vehicle and is formed by combining extruded materials, and is characterized in that it comprises a first extruded material having a cutout portion formed by cutting out the upper surface side of the end portion in the extrusion direction, and a second extruded material that is hollow and has a rib connecting the upper surface portion and the lower surface portion, and the first extruded material and the second extruded material are joined from above the cutout portion of the first extruded material so that the lower surface of the second extruded material covers the cutout portion, the extrusion direction of the first extruded material and the extrusion direction of the second extruded material are perpendicular to each other, and the rib is positioned directly above the joined portion.

[0011] According to the above configuration, the second extrusion member is joined to cover the upper side of the notch of the first extrusion member, resulting in a configuration in which the second extrusion member is placed on top of the first extrusion member. Therefore, the lowest surface of the bottom of the battery case is the lower surface of the first extrusion member, allowing for a wide area to be made substantially horizontal. Furthermore, by providing a rib directly above the joint between the first extrusion member and the second extrusion member, the rigidity of the bottom of the battery case can be increased.

[0012] The bottom structure of the battery case is characterized in that the lower surface of the second extrusion member is formed into a seat shape by being composed of a portion that is joined to the cutout portion and a portion that is lower than that portion in the vertical direction of the vehicle, and the lowermost surface of the second extrusion member, which is the lower portion, and the lower surface of the first extrusion member are arranged so as to form an approximately horizontal plane.

[0013] According to the above configuration, the lower surface of the second extrusion member is shaped like a seat, which more effectively increases the rigidity of the bottom surface of the battery case. In addition, the ground clearance of the lowermost surface of the second extrusion member and the lower surface of the first extrusion member can be made the same, allowing the lowermost surface of the bottom surface of the battery case to be approximately horizontal over a wider area.

[0014] In the above configuration, the second extrusion member has a flange portion that protrudes toward the first extrusion member, and the flange portion and the upper surface of the first extrusion member are joined together.

[0015] According to the above configuration, it is possible to improve the positional accuracy when joining the first extruded member and the second extruded member. [Effects of the Invention]

[0016] According to the bottom structure of the battery case disclosed in this specification, by combining two extrusion materials with different extrusion directions, it is possible to increase rigidity while realizing a configuration in which the bottom surface is made approximately horizontal to deal with aerodynamic forces and road interference. [Brief explanation of the drawings]

[0017] [Figure 1]FIG. 2 is a perspective view schematically showing the joining of extrusion members in the bottom structure of the battery case. [Figure 2] 2 is a cross-sectional view taken along the line AA in FIG. 1. [Figure 3] FIG. 10 is a cross-sectional view of the bottom structure of a battery case according to a modified example. [Figure 4] FIG. 2 is a cross-sectional view showing the bottom of a battery case having a different configuration from the bottom structure of the battery case disclosed in this specification. [Figure 5] FIG. 2 is a cross-sectional view showing the bottom of a battery case having a different configuration from the bottom structure of the battery case disclosed in this specification. DETAILED DESCRIPTION OF THE INVENTION

[0018] A battery case that houses multiple battery modules (not shown) that serve as the vehicle's driving power source is disposed in the lower part of the vehicle. The bottom structure of the battery case will be described below with reference to the drawings. In each drawing, "Fr," "Up," and "Rh" indicate the front, top, and right side of the vehicle, respectively.

[0019] FIG. 1 is a perspective view schematically illustrating the joining of extrusion members in the bottom structure of a battery case. In FIG. 1, the upper portion shows the extrusion members before joining, and the lower portion shows the bottom surface of the battery case after joining the extrusion members. As shown in FIG. 1, the bottom surface 10 of the battery case includes first extrusion members 12 (reference numerals are omitted as appropriate) and second extrusion members 14. In FIG. 1, the bottom surface 10 of the battery case is configured by combining four first extrusion members 12 and two second extrusion members 14 located at the left and right ends of the first extrusion members 12, but the number of extrusion members is not limited to this. The first extrusion members 12 are arranged so that the extrusion direction (hereinafter referred to as the "extrusion direction") when molded by an extrusion molding machine (not shown) is parallel to the vehicle width direction. The first extrusion members 12 have notches 18 (reference numerals are omitted as appropriate) formed by cutting out the upper surface of the end portion in the extrusion direction. The second extrusion members 14 are arranged so that the extrusion direction is parallel to the vehicle longitudinal direction. Therefore, the extrusion direction of the first extrusion material 12 and the extrusion direction of the second extrusion material 14 are perpendicular to each other. In this way, by combining two extrusion materials with different extrusion directions, the rigidity of the bottom surface 10 of the battery case is improved. Note that the first extrusion material 12 may be arranged parallel to the vehicle longitudinal direction, and the second extrusion material 14 may be arranged parallel to the vehicle width direction.

[0020] Next, the configuration of the bottom surface 10 of the battery case will be described in more detail with reference to FIG. 2. FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1. The second extrusion 14 is a hollow aluminum material. The second extrusion 14 is formed to have a hollow shape due to the provision of a rib 20 connecting its upper surface and lower surface. The hollow shape of the second extrusion 14 allows for weight reduction. Furthermore, the hollow shape is effective in protecting the battery because it can absorb input loads by deformation of the hollow portion even when interference input occurs from below the vehicle. Note that, as shown in FIG. 2, the first extrusion 12 is also hollow in this example, but this is not limited thereto.

[0021] As shown in FIG. 2 , the first extrusion 12 and the second extrusion 14 are joined together such that the underside of the second extrusion 14 covers the cutout 18 of the first extrusion 12 from above. This joining is performed using arc welding at two locations surrounded by dashed lines. Note, however, that the joining method is not limited to this. Of the two locations, a rib 20 is disposed directly above the lower joint 22. Providing the rib 20 further improves the rigidity of the bottom surface 10 of the battery case. That is, stress tends to concentrate at the joint between the first extrusion 12 and the second extrusion 14, but the presence of the rib 20 improves the rigidity of the second extrusion 14 in particular. Therefore, even if interference input is applied from below the vehicle, deformation of the bottom surface 10 of the battery case is suppressed, thereby protecting the battery.

[0022] 2, the lowest surface of the bottom surface 10 of the battery case is the lower surface of the first extrusion member 12. That is, compared to the bottom surface of the battery case described with reference to FIGS. 4 and 5, the bottom surface structure of the battery case disclosed in this specification has a wide range of the lowest surface that is substantially horizontal.

[0023] Next, a modified example of the bottom structure of the battery case will be described with reference to Fig. 3. Fig. 3 is a cross-sectional view of the bottom structure of the battery case in this modified example. The basic structure is the same as that shown in Fig. 2. That is, the first extrusion member 12 and the second extrusion member 14 are joined from above the notch portion 18 of the first extrusion member 12 so that the underside of the second extrusion member 14 covers the notch portion. The joining is performed using arc welding at two locations surrounded by dashed lines, but as described above, the joining method is not limited to this.

[0024] On the other hand, the shape of the second extrusion member 14 in the bottom surface 10 of the battery case shown in FIG. 3 is different from that shown in FIG. 2. As shown in FIG. 3, the second extrusion member 14 has a lower surface low portion 14a and a lower surface high portion 14b. The lower surface low portion 14a forms the lowest surface of the second extrusion member 14 and is positioned one level lower than the lower surface high portion 14b. The lower surface high portion 14b is the portion that joins with the notch portion 18 of the first extrusion member 12, more specifically, the portion that rests on the notch portion 18. In other words, the lower surface of the second extrusion member 14 has a seat shape formed by two surfaces of different heights, the lower surface low portion 14a and the lower surface high portion 14b. This seat shape can more effectively increase the rigidity of the bottom surface 10 of the battery case. Furthermore, by forming the lower surface of the second extrusion member 14 into a seating surface shape, it is possible to adjust the height above ground of the lower surface lower portion 14a to be the same as that of the lower surface of the first extrusion member 12. As a result, the lowest surface of the bottom surface 10 of the battery case is the lower surface of the lower surface lower portion 14a and the first extrusion member 12, and therefore has a substantially horizontal shape over a wider area.

[0025] Furthermore, the second extrusion material 14 shown in FIG. 3 has a flange portion 14c. The flange portion 14c is a member that protrudes toward the first extrusion material 12, and this flange portion 14c is joined to the upper surface of the first extrusion material 12. The flange portion 14c and the upper surface of the first extrusion material 12 may be joined by a removable means such as bolting, or by welding as described above. Providing the flange portion 14c can improve the positional accuracy when joining the first extrusion material 12 and the second extrusion material 14.

[0026] As described above, the bottom structure of the battery case disclosed in this specification is configured so that the second extrusion member 14 is placed on top of the first extrusion member 12, and therefore the lowest surface of the bottom surface 10 of the battery case becomes the underside of the first extrusion member 12, allowing for a wide area to be made substantially horizontal. Furthermore, by providing the rib 20 directly above the joint 22 between the first extrusion member 12 and the second extrusion member 14, rigidity can be increased.

[0027] The above description is merely an example. In the bottom structure of the battery case disclosed herein, a second extrusion member 14, whose extrusion direction is perpendicular to the first extrusion member 12, is joined to cover the first extrusion member 12, which has a notch 18 on the upper surface of the end portion in the extrusion direction, and a rib 20 is disposed directly above the joint 22. Therefore, other configurations of the bottom structure of the battery case may be modified as appropriate. In FIG. 2 , the lower surface of the first extrusion member 12 is the lowermost surface of the bottom surface 10 of the battery case. However, for example, the lower surface of the second extrusion member 14 may be inclined so that the height of the lowermost surface of the second extrusion member 14 is the same as the height of the lower surface of the first extrusion member 12. In other words, the first extrusion member 12 and the second extrusion member 14 may be joined so that the lower surfaces of both members are substantially horizontal, without one member protruding downward. With this configuration, the lowest surface of the bottom surface 10 of the battery case is the surface where the lower surface of the first extruded member 12 and the lower surface of the second extruded member 14 join together, and can be made wider. [Explanation of symbols]

[0028] 10 bottom surface of battery case, 12 first extrusion member, 14 second extrusion member, 14a lower surface lower portion, 14b lower surface higher portion, 14c flange portion, 18 notch portion, 20 rib, 22 joint portion

Claims

1. A bottom structure of a battery case that is mounted under a vehicle and is formed by combining extruded materials, a plurality of first extrusion members arranged along the vehicle longitudinal direction, each having a hollow rectangular cross section perpendicular to the extrusion direction, each having a plate-like cutout portion at an end in the extrusion direction, where the top and side surfaces of the rectangular cross section are cut out and only the bottom surface remains, with the bottom surface of the bottom surface portion being the bottommost surface of the battery case; a second extrusion member having a hollow shape and provided with a rib connecting an upper surface portion and a lower surface portion; Equipped with The first extruded material and the second extruded material are joined together such that a lower surface of the second extruded material covers the notched portion from above the notched portion of the first extruded material, an extrusion direction of the first extrusion material is a vehicle width direction, an extrusion direction of the second extrusion material is a vehicle front-rear direction, and the extrusion direction of the first extrusion material and the extrusion direction of the second extrusion material are perpendicular to each other; The rib extends in the vehicle front-rear direction, which is the extrusion direction of the second extrusion material, and is disposed directly above the joined portion. The bottom structure of the battery case is characterized by the following.

2. the lower surface of the second extrusion member has a seating surface shape that is configured with a portion that is joined to the notch portion and a portion that is lower than the portion that is joined to the notch portion in the vehicle up-down direction, The lowermost surface of the second extrusion member, which is the lower portion, and the lower surface of the first extrusion member are arranged to form a substantially horizontal plane. The bottom structure of the battery case according to claim 1 .

3. the second extrusion member has a flange portion that protrudes toward the first extrusion member, The flange portion and the upper surface of the first extrusion material are joined together. The bottom structure of the battery case according to claim 1 .

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