Battery case and method for manufacturing the battery case

Abstract

To provide a battery case which is lightweight and can be produced at low cost and with which higher bonding strength can be obtained, even with a multi-material structure where an aluminum material and a steel material are combined.SOLUTION: Provided is a battery case 100 in which a bonding assistance member 15 is provided between each of end portions 13a of a cross member 13A and each of wall surfaces 11a of a frame body 11 facing the end portion 13a, the frame body 11 and the bonding assistance member 15 are made of aluminum or an aluminum alloy, and the cross member 13A is made of steel. One end portion of the bonding assistance member 15 is welded to the wall surface 11a, and the bonding assistance member 15 has an overlap portion OL extending from the one end portion toward an inside space and overlapping with a side surface of the end portion 13a of the cross member 13A. In the cross member 13A, first through holes 35 passing through to look out on the overlap portion OL of the bonding assistance member 15 are formed. The bonding assistance member 15 and the cross member 13A are bonded with a weld metal of the aluminum or the aluminum alloy formed by welding at positions of the first through holes. 35.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a battery case and a method for manufacturing the battery case. [Background technology]

[0002] In recent years, the development of vehicles that use electric power as a power source, such as electric vehicles and hybrid vehicles, has been actively promoted. The battery systems installed in such vehicles generally employ a configuration in which a large number of batteries are housed in a battery case formed by a predetermined frame or the like.

[0003] Battery cases must be strong enough to protect the stored batteries from impacts such as collisions, while also requiring reduced material and manufacturing costs. Furthermore, from the perspective of improving fuel efficiency and addressing global environmental issues such as exhaust gas emissions, battery cases must also be lightweight.

[0004] For example, a typical battery case shown in Fig. 11 includes a rectangular frame body 83 formed by four frame members 81, a plurality of cross members 85 whose both ends are joined to the frame body 83 for reinforcement, and floor panel members 87 that form the floor surface of the frame body 83. For the frame members 81 and cross members 85, extruded aluminum products are often used because they are lightweight and highly rigid.

[0005] Such a battery case structure is disclosed, for example, in Patent Document 1 as a body frame for an automobile. Patent Document 1 describes that a side frame made of aluminum and having a closed cross-sectional structure and a cross member made of aluminum and having a closed cross-sectional structure are fastened together via a fastening member to prevent a decrease in the bonding strength between the side frame and the cross member. This fastening member has a flat base and a pair of support members extending perpendicular to the base, and is made of an aluminum extrusion that is π-shaped in plan view. The base is fastened to the side of the side frame with bolts, the pair of support members clamp the ends of the cross member, and the cross member and the support members are welded together with welds. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-269123 Summary of the Invention [Problem to be solved by the invention]

[0007] If the frame members 81 and cross members 85 were all made of aluminum, weight reduction would be possible, but material costs would be higher than if they were made of steel. On the other hand, if the frame members 81 and cross members 85 were all made of steel, cost reduction would be achieved, but weight would increase. Therefore, combining aluminum and steel materials is an option, but in that case, welding between aluminum materials, between aluminum and steel materials, and between steel materials would be required. For welding between aluminum materials and between aluminum and steel materials, AC welding equipment using aluminum arc welding rods or aluminum welding wire is used, while for welding between steel materials, spot welding equipment or DC welding equipment using steel welding wire is used. Therefore, at least two welding machines are required in the manufacturing process. Furthermore, for safety reasons, space is required to separate the welding locations of each welding machine, resulting in increased equipment costs and a loss of takt time.

[0008] Furthermore, to join dissimilar materials, such as aluminum frame member 81 and steel cross member 85, it is envisioned to use, for example, MIG arc spot welding between dissimilar metals, but the load applied to the joint by this welding is in the direction of peeling between the members. The joint by the above-mentioned spot welding is strong against loads in the shear direction, but weak against loads in the peeling direction, and there is a problem that a structure in which a load in the peeling direction is applied to the joint is disadvantageous in terms of strength.

[0009] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a battery case and a method for manufacturing a battery case that has a multi-material structure combining aluminum and steel, yet is lightweight and can be produced at low cost, and yet has high joining strength. [Means for solving the problem]

[0010] The present invention comprises the following configurations. (1) A battery case in which at least one cross member is provided between a pair of opposing wall surfaces on the inner circumferential surface of a rectangular frame body so as to divide an inner space surrounded by the frame body, Joint auxiliary members are provided between the end portions of the cross members and the wall surfaces of the frame body facing the end portions, the frame body and the joining auxiliary member are made of aluminum or an aluminum alloy, the cross member is made of steel; Each of the joint auxiliary members has one end welded to the wall surface and an overlapping portion extending from the one end toward the inner space and overlapping with a side surface of the end of the cross member, The cross member has a first through hole formed therein, the first through hole facing the overlapping portion of the joining auxiliary member, The joining auxiliary member and the cross member are joined by a weld metal of aluminum or aluminum alloy formed by welding at the position of the first through hole. Battery case. (2) A method for manufacturing a battery case, comprising: at least one cross member provided between a pair of opposing wall surfaces on the inner circumferential surface of a rectangular frame body so as to divide an inner space surrounded by the frame body; joint auxiliary members provided between ends of the cross member and the wall surface of the frame body facing the ends; the frame body and the joint auxiliary members made of aluminum or an aluminum alloy; and the cross member made of steel; welding one end of the joining auxiliary member to the wall surface of the frame; a step of welding an overlapping portion of the joining auxiliary member that extends from the one end toward the inner space and overlaps with a side surface of the end of the cross member at a position of a first through hole that is formed in the cross member and passes through the overlapping portion, thereby joining the joining auxiliary member and the cross member with a weld metal of aluminum or aluminum alloy formed at the position of the first through hole; A method for manufacturing a battery case comprising: [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a battery case and a method for manufacturing a battery case that has a multi-material structure that combines aluminum and steel materials, yet is lightweight and can be produced at low cost, and yet has high joining strength. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view of a battery case according to a first embodiment. [Figure 2] FIG. 2 is a perspective view of the joining auxiliary member. [Figure 3] FIG. 3 is an enlarged view of a portion P1 of the battery case shown in FIG. 1, showing the state before the cross member is joined. [Figure 4] FIG. 4 is an enlarged view of the P1 portion of the battery case shown in FIG. 1, showing the state after the cross member has been joined. [Figure 5] FIG. 5 is an enlarged perspective view of a portion of the cross member. [Figure 6] FIG. 6 is a schematic cross-sectional view of a joint between a cross member and a joint auxiliary member or a floor panel member. [Figure 7] FIG. 7 is a perspective view showing how a first frame member and a cross member of a battery case according to a second embodiment are joined together via a joining auxiliary member. [Figure 8] FIG. 8 is a perspective view showing a state in which the cross member and the joining auxiliary member shown in FIG. 7 are joined together. [Figure 9]FIG. 9 is a perspective view of the joining auxiliary member. [Figure 10] FIG. 10 is a cross-sectional view taken along the line XX shown in FIG. [Figure 11] FIG. 11 is a perspective view of a conventional battery case. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First Embodiment (Battery case configuration) FIG. 1 is a perspective view of a battery case 100 of the first embodiment. The battery case 100 comprises a rectangular frame body 11, at least one (in this configuration, two, as an example) cross member 13A, 13B arranged inside the frame body 11, a joining auxiliary member 15 connecting the cross member 13 and the frame body 11, and a floor panel member 17.

[0014] The frame 11 is composed of a pair of opposing first frame members 19A, 19B and a pair of opposing second frame members 21A, 21B. One end 19a and the other end 19b of the first frame member 19A are joined to one end 21a of the pair of second frame members 21A, respectively. One end 19a and the other end 19b of the first frame member 19B are joined to the other end 21b of the pair of second frame members 21B, respectively.

[0015] The cross members 13A, 13B are disposed between a pair of opposing wall surfaces 11a on the inner circumferential surface of the rectangular frame body 11 so as to separate the inner space surrounded by the frame body 11. The cross members 13A, 13B are rod-shaped members extending in one axial direction, and are formed slightly shorter than the second frame members 21A, 21B.

[0016] The joining auxiliary members 15 are respectively arranged between each end 13a (a total of four locations in this configuration) of the cross members 13A, 13B and the wall surface 11a of the frame body 11, and join the cross members 13A, 13B and the frame body 11 together.

[0017] The floorboard member 17 is joined to the underside of the frame body 11 and forms the inner bottom surface of the frame body 11.

[0018] In the battery case 100 configured as described above, a plurality of regions (three regions S1, S2, and S3 in this configuration) are defined by the first frame members 19A and 19B, the second frame members 21A and 21B, and the cross members 13A and 13B. Each of the regions S1, S2, and S3 is used to accommodate, for example, a battery pack (not shown).

[0019] The first frame members 19A, 19B and second frame members 21A, 21B constituting the frame body 11, and the floor panel member 17, are all made of aluminum or an aluminum alloy (hereinafter also referred to as aluminum material). More specifically, the first frame members 19A, 19B and the second frame members 21A, 21B are made of hollow aluminum extrusions with a thickness of approximately 2 to 5 mm. Aluminum alloys such as JIS or AA 5000, 6000, or 7000 series aluminum alloys are preferred because of their excellent strength and the ability to be thinned. Aluminum alloy hollow extrusions are manufactured using a standard extrusion manufacturing process that appropriately combines casting (e.g., DC casting or continuous casting), homogenization heat treatment, hot extrusion, solution treatment and quenching, and, if necessary, thermal refining treatments such as artificial aging. The use of extrusions increases the strength of each frame member, thereby easily increasing the rigidity of the battery case 100.

[0020] The cross members 13A, 13B are made of steel, such as general carbon steel or high-strength steel. Specifically, the steel plate may be bent to form a hat-shaped or "Ω"-shaped cross section, or a circular steel pipe may be crushed to form an elliptical or rectangular cross section. Furthermore, the cross section may be a "Π" shape with a rib plate welded to the inside, or an "S" or "B" shape with the steel members welded together. The surfaces of the cross members 13A, 13B may be subjected to various surface treatments, such as zinc plating or electro-deposition coating, for corrosion prevention.

[0021] FIG. 2 is a perspective view of the joining auxiliary member 15. As shown in FIG. The joining auxiliary member 15 is an aluminum member arranged along the longitudinal direction of the cross members 13A and 13B shown in FIG. 1. The joining auxiliary member 15 is preferably a hollow extruded aluminum member having a thickness of approximately 2 to 5 mm, but may also be a plate material. Furthermore, the material is preferably an aluminum alloy such as a 5000 series, 6000 series, or 7000 series aluminum alloy as defined by JIS or AA, because it has excellent strength and can be made thinner. When the joining auxiliary member 15 is a hollow extruded aluminum member, the joining auxiliary member 15 is manufactured by a typical extruded material manufacturing process, similar to that of the frame 11, which involves an appropriate combination of casting, such as DC casting or continuous casting, homogenization heat treatment, hot extrusion, solution treatment and quenching, and, if necessary, thermal refining treatment, such as artificial aging.

[0022] 2 is an extruded member having a trapezoidal outer shape in a cross section perpendicular to the longitudinal direction. Joint auxiliary member 15 has one end face 15a and the other end face 15b, a top face 15c, a pair of side faces 15d connected to top face 15c, and a bottom face 15e, and two hollow portions 23 are formed along the longitudinal direction.

[0023] As described above, the battery case 100 is made of aluminum for its constituent parts, including the frame body 11, the joining auxiliary member 15, and the floor plate member 17, and only the cross members 13A and 13B are made of steel, thereby achieving both lightweight and low cost.

[0024] (Battery case manufacturing method) Next, a method for manufacturing the battery case 100 having this configuration will be described. 1 are prepared, and an end face of one end 21a of the second frame member 21A is butted against a wall surface (side surface) 11a of the end 19a of the first frame member 19A. In this state, a corner 25 formed by the edge of the end face of the second frame member 21A and the wall surface 11a of the first frame member 19A is joined by line welding using arc welding.

[0025] Similarly, the end face of the other end 21b of the second frame member 21A is abutted against the wall surface of the end 19a of the first frame member 19B, and a corner 25 formed between them is line-welded by arc welding. Similarly, the other end 19b of the first frame members 19A, 19B is also line-welded by arc welding at a corner 25 formed when the second frame members 21B are abutted against each other. This forms a rectangular frame body 11. The order of the above-mentioned welding steps is arbitrary.

[0026] The welding between the first frame members 19A, 19B and the second frame members 21A, 21B is performed by, for example, MIG welding (hereinafter also referred to as "aluminum MIG welding") using an aluminum material as a consumable electrode (welding wire).

[0027] The floor plate members 17 are joined to the frame body 11 joined in this manner. To join the floor plate members 17, first, the frame body 11 is placed on the floor plate members 17, and corners 27 formed by the lower surfaces of the first frame members 19A, 19B and the upper surface of the floor plate member 17, and corners 29 formed by the lower surfaces of the second frame members 21A, 21B and the upper surface of the floor plate member 17, are line-welded by aluminum MIG welding in the same manner as above. Note that the welding order is not limited to the above. For example, it is also possible to weld the first frame members 19A, 19B and the bottom plate member 17, and the second frame members 21A, 21B and the bottom plate member 17, respectively, and then weld the first frame members 19A, 19B and the second frame members 21A, 21B.

[0028] 3 and 4 are enlarged partial cross-sectional views showing an enlarged view of portion P1 of battery case 100 shown in Fig. 1, with Fig. 3 showing the state before joining of cross member 13A and Fig. 4 showing the state after joining of cross member 13A. Here, we will explain the joining portion between end 19a of first frame member 19A and end 21a of second frame member 21A, and the portion where one end 13a of cross member 13A and wall surface 11a of first frame member 19A are joined via joining auxiliary member 15, but the same applies to other corresponding joining portions, so explanations thereof will be omitted.

[0029] 3, at corners 25 between the first frame members 19A, 19B and the second frame members 21A, 21B and corners 27, 29 between the first frame members 19A, 19B and the second frame members 21A, 21B and the floor panel member 17, weld metal WA of aluminum material (hereinafter also referred to as "aluminum weld metal") is formed by aluminum MIG welding along each corner 25, 27, 29. Note that floor panel member 17 is sized to cover the entire lower surface of frame body 11, but is not limited to this, and may be sized so that the inner wall surface of frame body 11 forms an outer edge.

[0030] Next, the joining of the frame 11 and the cross members 13A, 13B using the joining auxiliary member 15 will be described in detail. First, the joining auxiliary member 15 is joined to the first frame member 19A before being joined to the cross member 13A. That is, one end face 15a of the joining auxiliary member 15 is pressed against the wall surface 11a of the first frame member 19A, and a corner 31 between the wall surface 11a and the joining auxiliary member 15 is welded by aluminum MIG welding. As a result, aluminum weld metal WA is formed along the top surface 15c and a pair of side surfaces 15d of the one end face 15a of the joining auxiliary member 15.

[0031] 4, the cross member 13A is placed so as to cover the side surface 15d of the auxiliary joining member 15, and the auxiliary joining member 15 and the cross member 13A are joined together, and the cross member 13A is joined together with the floorboard member 17. It is preferable that the upper surface 15c of the auxiliary joining member 15 and the cross member 13 are spaced apart from each other, as this reduces the dimensional accuracy of the cross member 13A in the height direction.

[0032] Figure 5 is a partially enlarged perspective view of the cross member 13A. The cross member 13A shown here has a hat-shaped cross section taken along the longitudinal axis, and includes a top 13b, a pair of side walls 13c, and a pair of flanges 13d. The inner ceiling surface 33 of the top 13b faces the upper surface 15c of the auxiliary joint member 15 shown in Figure 2. The inner surfaces 34 of the pair of side walls 13c are flat opposing surfaces that overlap and face the pair of side surfaces 15d of the auxiliary joint member 15. The pair of flanges 13d are connected to the base end (lower side) of the hat shape and extend along the floor panel member 17.

[0033] A plurality of through holes (first through holes) 35 are formed in a dispersed manner on the surface of the side wall 13c of the cross member 13A facing the side surface 15d of the joint auxiliary member 15. Each through hole 35 is a generally circular hole in a plan view, formed to penetrate the side surface 15d. That is, the joint auxiliary member 15 has an overlapping portion OL extending from one end welded to the wall surface 11a of the first frame member 19A toward the inner space of the frame body 11 and overlapping with the side surface of the end portion 13a of the cross member 13A. A plurality of through holes 35 are formed in the cross member 13A, facing the overlapping portion OL. In addition, a plurality of through holes (second through holes) 37 are formed in the flange portion 13d of the cross member 13A along its longitudinal direction, penetrating the floor panel member 17. It is preferable that the plurality of through holes 35, 37 are arranged at equal intervals from each other to evenly distribute the applied load, but they may be formed at unequal intervals.

[0034] The cross member 13A having the above-described configuration is placed over the joining auxiliary member 15 as shown in FIG. 4, and spot welding is performed by aluminum MIG welding at the positions of the multiple through holes 35 formed in the side wall portion 13c and at the positions of the multiple through holes 37 formed in the flange portion 13d.

[0035] This spot welding is performed with a low current that does not melt the steel cross member 13A, thereby achieving penetration of the aluminum weld metal WA that fills the through holes 35, 37. This method of spot welding steel and aluminum materials is called "dissimilar material MIG spot welding." Note that known inert gases such as argon or helium can be used as the shielding gas G.

[0036] After spot welding, aluminum weld metal WA including penetration of joining auxiliary member 15 is obtained at the position of through hole 35, and aluminum weld metal WA including penetration of floor panel member 17 is obtained at the position of through hole 37. In this way, aluminum weld metal WA fills through holes 35, 37 and is prevented from slipping out of through holes 35, 37, thereby achieving a form in which dissimilar materials are joined together.

[0037] 6 is a schematic cross-sectional view of the joint between the cross member 13A and the joining auxiliary member 15 or the floor plate member 17. After spot welding the steel cross member 13A to the joining auxiliary member 15 or the floor plate member 17, the through holes 35, 37 are filled with aluminum weld metal WA. The aluminum weld metal WA then takes on a rivet shape having a shaft portion WA1, a head portion WA2, and a flange portion WA3. Specifically, the shaft portion WA1 extends in the thickness direction of the cross member 13A and reaches the joining auxiliary member 15 or the floor plate member 17. The head portion WA2 is formed as a portion of the shaft portion WA1 that protrudes outside the cross member 13A and bulges outward from the through holes 35, 37. The flange portion WA3 is formed as a portion of the shaft portion WA1 that protrudes into the joining auxiliary member 15 or the floor plate member 17 and bulges outward. The head portion WA2 and the flange portion WA3 sandwich the cross member 13A and the auxiliary joining member 15 or the floor board member 17 to fix them together.

[0038] In this way, the cross member 13A and the auxiliary joining member 15, and the cross member 13A and the floor panel member 17 are joined by dissimilar material MIG spot welding at the positions of the plurality of through holes 35, 37. The number, arrangement, etc. of the through holes 35, 37 shown here are not particularly limited.

[0039] According to this configuration, the aluminum weld metal WA by line welding and the aluminum weld metal WA by spot welding can be formed using the same welding method, which does not complicate the manufacturing process and allows welding equipment to be placed in a space-saving manner. This reduces increases in equipment costs and losses in takt time, enabling efficient production.

[0040] Furthermore, because dissimilar material MIG spot welding for fixing the cross member 13A is performed on the side surface 15d of the joining support member 15, the load imposed on the weld by an external force acts in the shear direction, thereby improving the joining strength compared to when a load is applied in the peel direction as in the conventional method.

[0041] Furthermore, because the auxiliary joining member 15 is made of aluminum, the material cost is higher than if it were made of steel, but if an extruded shape is used for the auxiliary joining member 15, processing can be completed simply by cutting the extruded shape to the desired length. This makes production easier, and when comparing the total material cost and manufacturing cost, it is actually lower cost.

[0042] Furthermore, the cross member 13A joined to the auxiliary joining member 15 is not directly joined to the first frame members 19A and 19B but is joined to the side surface 15d of the auxiliary joining member 15, so high dimensional accuracy is not required in the longitudinal direction.

[0043] The outer shape of the above-described auxiliary joining member 15 in a cross section perpendicular to the longitudinal direction is trapezoidal, but the cross-sectional shape is not limited to this. Furthermore, if the auxiliary joining member 15 is made of the same extruded material as the first frame members 19A, 19B or the second frame members 21A, 21B, the manufacturing cost can be further reduced.

[0044] Second Embodiment Next, a second embodiment of the battery case will be described. Fig. 7 is a perspective view showing how the first frame member 19A and the cross member 14 of the battery case 200 of the second embodiment are joined via the joining auxiliary member 16. Fig. 8 is a perspective view showing the state in which the cross member 14 and the joining auxiliary member 16 shown in Fig. 7 are joined. The battery case 200 of the second embodiment has the same configuration as the battery case 100 of the first embodiment except that the configurations of the cross member 14 and the joining auxiliary member 16 are different.

[0045] As shown in Figures 7 and 8, the joining auxiliary member 16 is made of aluminum and is an extruded member whose extrusion direction is a direction (vertical direction) perpendicular to the longitudinal directions of the first frame member 19A and the cross member 14. Two hollow portions 24 are formed in the joining auxiliary member 16 along the extrusion direction. One end of the joining auxiliary member 16 is welded to the wall surface 11a of the first frame member 19A using an aluminum MIG welding device. A pair of gaps 41 is formed at the other end opposite to the one end joined to the first frame member 19A. The end portions 14a of the cross member 14 are inserted into the pair of gaps 41.

[0046] The cross member 14 has a hat-shaped cross section taken orthogonally to its longitudinal direction, and includes a top portion 14b, a pair of side wall portions 14c, and a pair of flange portions 14d. The pair of side wall portions 14c are inserted into gaps 41 formed in the auxiliary joint member 16. The pair of flange portions 14d are connected to the base end side (lower side) of the hat shape, and each extend along the floor panel member 17. A slit hole (first through hole) 43 is formed in each of the pair of side wall portions 14c.

[0047] FIG. 9 is a perspective view of the joint auxiliary member 16. The gaps 41 of the joint auxiliary member 16 are formed at both ends of one side of the rectangular cross section perpendicular to the extrusion direction. In other words, the joint auxiliary member 16 has a pair of outer protruding pieces (protruding pieces) 45A, 45B protruding from the first frame member 19A toward the cross member 14, and a central protruding piece 47 provided between the pair of outer protruding pieces 45A, 45B. The central protruding piece 47 has a pillar portion 47a parallel to the outer protruding pieces 45A, 45B, and lateral protruding pieces (protruding pieces) 47b extending from the protruding tip of the pillar portion 47a toward the pair of outer protruding pieces 45A, 45B. The cross member 14 has slit holes 43, which are elongated holes aligned along the protruding pieces, at positions where the pair of outer protruding pieces 45A, 45B and the lateral protruding pieces 47b face each other.

[0048] FIG. 10 is a cross-sectional view taken along line XX in FIG. 8. The side wall 14c of the cross member 14 is inserted into the gap 41 in the joint auxiliary member 16. The protruding tips of the outer projections 45A and 45B face the tips of the lateral projections 47b of the joint auxiliary member 16 through slits 43 formed in the side wall 14c of the cross member 14. The outer projections 45A and 45B are then line-welded to the lateral projections 47b by aluminum MIG welding. This forms aluminum weld metal WA along the slits 43, joining the pair of outer projections 45A and 45B to the lateral projections 47b. Thus, the cross member 14 is joined to the joint auxiliary member 16 through the slits 43. The joint auxiliary member 16 is also joined to the first frame member 19A by the aluminum weld metal WA. In this manner, the joint auxiliary member 16 joins the first frame member 19A and the cross member 14.

[0049] As shown in FIG. 8, the cross member 14 and the floor panel member 17 are joined by the above-mentioned dissimilar material MIG spot welding at the positions of the plurality of through holes 37 formed in the flange portion 14d of the cross member 14.

[0050] According to this configuration, the aluminum weld metal WA by line welding and the aluminum weld metal WA by spot welding can be formed using the same welding method, which does not complicate the manufacturing process and allows the equipment to be placed in a space-saving manner, thereby suppressing increases in equipment costs and losses in takt time and enabling efficient production.

[0051] Furthermore, since the cross member 14 and the first frame member 19A are joined by line welding via the joining auxiliary member 16, the cross member 14 and the first frame member 19A can be joined with high strength.

[0052] The shape of the joining auxiliary member 16 shown here is an example and is not limited to this. Although not shown, for example, a joining auxiliary member 16 made of aluminum may be formed with a slit having a thickness equivalent to that of the cross member 14, and the cross member 14 may be pressed into the slit to be joined. In other words, a fixed form in which a steel material is fitted into an aluminum material may be used.

[0053] Furthermore, although the aluminum weld metal WA formed by line welding described above is formed only at a portion of the corners, it may be formed without gaps over the entire length of the corners, which is preferable because it gives the battery case a liquid-tight structure and improves the sealing performance between the inside and outside of the case.

[0054] As such, the present invention is not limited to the above-described embodiments, and the present invention also contemplates the mutual combination of the various components of the embodiments, as well as modifications and applications by those skilled in the art based on the description in the specification and well-known techniques, and these modifications and applications are included in the scope of protection sought. For example, although the above example shows aluminum MIG welding, other welding methods using heat sources, such as laser welding and laser-arc hybrid welding, may also be used. Laser welding is characterized by low heat input, high precision, high speed, and excellent deep penetration welding. Laser-arc hybrid welding is also expected to produce more efficient and high-quality welding. In addition to using aluminum filler metal, aluminum powder can also be used as the filler metal. Aluminum powder, for example, is widely used in deposition methods and powder bed methods using metal 3D printers. In other words, the welding of aluminum materials in the present invention may be performed using aluminum filler metal.

[0055] As described above, the present specification discloses the following: (1) A battery case in which at least one cross member is provided between a pair of opposing wall surfaces on the inner circumferential surface of a rectangular frame body so as to divide an inner space surrounded by the frame body, Joint auxiliary members are provided between the end portions of the cross members and the wall surfaces of the frame body facing the end portions, the frame body and the joining auxiliary member are made of aluminum or an aluminum alloy, the cross member is made of steel; Each of the joint auxiliary members has one end welded to the wall surface and an overlapping portion extending from the one end toward the inner space and overlapping with a side surface of the end of the cross member, The cross member has a first through hole formed therein, the first through hole facing the overlapping portion of the joining auxiliary member, The joining auxiliary member and the cross member are joined by a weld metal of aluminum or aluminum alloy formed by welding at the position of the first through hole. Battery case. With this battery case, when joining a steel cross member to an aluminum or aluminum alloy frame, an aluminum or aluminum alloy auxiliary joining member is welded to the frame, and the cross member is welded to the side of this auxiliary joining member. As a result, when an external force is applied to the battery case, the load acting on the welded portion with the cross member is in the shear direction rather than the peel direction, improving the joining strength. Furthermore, because only aluminum materials need to be welded together, the manufacturing process is not complicated.

[0056] (2) The battery case according to (1), wherein the first through holes are formed in a plurality of dispersed locations in an area overlapping the overlapping portion of the joining auxiliary member. According to this battery case, the auxiliary joining member and the cross member are welded at the positions of the first through holes provided at a plurality of locations, thereby improving the joining strength between them.

[0057] (3) The joining auxiliary member has at least a pair of protruding pieces arranged on either side of the end of the cross member, The first through hole is formed at a position on the cross member where the tips of the protruding pieces face each other, The battery case described in (1), wherein the joining auxiliary member and the cross member are joined by welding the tips of the protruding pieces formed through the first through hole of the cross member to each other. According to this battery case, the tip ends of the protruding pieces are welded together through the first through-holes, thereby joining the joining auxiliary member and the cross member.

[0058] (4) The battery case according to (3), wherein the first through hole is a long hole that extends along the tip of the protruding piece. According to this battery case, the joining strength can be improved by performing line welding along the first through hole of the elongated hole.

[0059] (5) The battery case according to any one of (1) to (4), wherein the frame is formed from an extruded shape material. According to this battery case, the rigidity can be easily increased by using low-cost, high-strength extruded shapes.

[0060] (6) The battery case according to (5), wherein the joining auxiliary member is formed by an extruded profile. With this battery case, a high-strength joining auxiliary member can be easily obtained at low cost.

[0061] (7) The battery case according to (6), wherein the joining auxiliary member is formed from the same extruded material as the frame body. According to this battery case, the same extruded shape material as that of the frame can be used, further reducing manufacturing costs.

[0062] (8) The battery case according to any one of (1) to (7), further comprising a floor plate member made of aluminum or an aluminum alloy, joined to the lower surface of the frame body and serving as a floor surface inside the frame body. According to this battery case, by providing a floor plate member made of aluminum or an aluminum alloy, it is possible to achieve a lightweight yet high-strength structure.

[0063] (9) The cross member has a flange portion extending along the floor panel member, The flange portion is formed with a plurality of second through holes that face the floorboard member and penetrate the floorboard member, The battery case described in (8), wherein the cross member and the floor panel member are joined by a weld metal of aluminum or aluminum alloy formed by welding at the position of the second through hole. This battery case allows the cross member and floor panel member, which are made of different materials, to be joined with high strength.

[0064] (10) A method for manufacturing a battery case, comprising: at least one cross member provided between a pair of opposing wall surfaces on the inner circumferential surface of a rectangular frame body so as to divide an inner space surrounded by the frame body; joint auxiliary members provided between ends of the cross member and the wall surface of the frame body facing the ends; the frame body and the joint auxiliary members made of aluminum or an aluminum alloy; and the cross member made of steel; welding one end of the joining auxiliary member to the wall surface of the frame; a step of welding an overlapping portion of the joining auxiliary member that extends from the one end toward the inner space and overlaps with a side surface of the end of the cross member at a position of a first through hole that is formed in the cross member and passes through the overlapping portion, thereby joining the joining auxiliary member and the cross member with a weld metal of aluminum or aluminum alloy formed at the position of the first through hole; A method for manufacturing a battery case comprising: According to this battery case manufacturing method, when joining a steel cross member to an aluminum or aluminum alloy frame body, an aluminum or aluminum alloy joining auxiliary member is welded to the frame body, and the cross member is welded to the side of this joining auxiliary member. As a result, when an external force is applied to the battery case, the load acting on the welded portion with the cross member is in the shear direction rather than the peel direction, improving the joining strength. Furthermore, because only aluminum materials need to be welded together, the manufacturing process is not complicated.

[0065] (11) The first through holes are formed at a plurality of locations in a region overlapping the overlapping portion of the joining auxiliary member, The method for manufacturing a battery case according to (10), wherein the welding between the joining auxiliary member and the cross member at the position of the first through hole is performed by welding using an aluminum filler metal. According to this method of manufacturing a battery case, the joint holding member and the cross member can be joined with high quality by welding using an aluminum filler metal.

[0066] (12) The joining auxiliary member has at least a pair of protruding pieces arranged on either side of the end of the cross member, The first through hole is formed at a position on the cross member where the tips of the protruding pieces face each other, The method for manufacturing a battery case according to (10), wherein the welding at the position of the first through hole is performed by welding the tips of the protruding pieces together through the first through hole using an aluminum filler metal. According to this method of manufacturing a battery case, the joint holding member and the cross member can be joined with high quality by welding using an aluminum filler metal. [Explanation of symbols]

[0067] 11 Frame 11a Wall 13A, 13B, 14 Cross members 13a, 14a End 13b,14b Top 13c,14c Side wall part 13d, 14d flange 15 Joint auxiliary parts 15a,15b end face 15c top surface 15d side 15e bottom 17 Flooring 19A, 19B First frame member 19a,19b end 21A, 21B Second frame member 21a, 21b end 23 Hollow part 25, 27, 29, 31 Corners 33 Inner ceiling surface 35 Through hole (first through hole) 37 Through hole (second through hole) 41 Gap 43 Slit hole (first through hole) 45A, 45B Outer protruding piece (protruding piece) 47 Central protruding piece 47a Pillar 47b Lateral protruding piece (protruding piece) 100 Battery Case OL overlapping part S1,S2,S3 area WA Aluminum Weld Metal WA1 shaft WA2 head WA3 Tsuba

Claims

1. A battery case in which at least one cross member is provided between a pair of opposing wall surfaces on the inner circumferential surface of a rectangular frame body so as to divide an inner space surrounded by the frame body, Joint auxiliary members are provided between the end portions of the cross members and the wall surfaces of the frame body facing the end portions, the frame body and the joining auxiliary member are made of aluminum or an aluminum alloy, the cross member is made of steel; Each of the joint auxiliary members has one end welded to the wall surface and an overlapping portion extending from the one end toward the inner space and overlapping with a side surface of the end of the cross member, The cross member has a first through hole formed therein, the first through hole facing the overlapping portion of the joining auxiliary member, The joining auxiliary member and the cross member are joined by a weld metal of aluminum or aluminum alloy formed by welding at the position of the first through hole. Battery case.

2. The first through holes are formed in a plurality of locations in a region overlapping with the overlapping portion of the joining auxiliary member, The battery case according to claim 1 .

3. The joining auxiliary member has at least a pair of protruding pieces arranged on either side of the end portion of the cross member, The first through hole is formed at a position on the cross member where the tips of the protruding pieces face each other, The joining auxiliary member and the cross member are joined by welding the tips of the protruding pieces formed through the first through holes of the cross member to each other. The battery case according to claim 1 .

4. The first through hole is a long hole along the tip of the protruding piece. The battery case according to claim 3 .

5. The frame is formed by an extruded shape material. The battery case according to any one of claims 1 to 4.

6. The joining auxiliary member is formed by an extruded shape material. The battery case according to claim 5 .

7. The joining auxiliary member is formed from the same extruded shape as the frame body. The battery case according to claim 6.

8. A floor plate member made of aluminum or an aluminum alloy is provided which is joined to the underside of the frame body and serves as a floor surface inside the frame body. The battery case according to any one of claims 1 to 7.

9. The cross member has a flange portion extending along the floor panel member, The flange portion is formed with a plurality of second through holes that face the floorboard member and penetrate the floorboard member, The cross member and the floor panel member are joined by a weld metal of aluminum or aluminum alloy formed by welding at the position of the second through hole. The battery case according to claim 8.

10. A method for manufacturing a battery case, comprising: at least one cross member provided between a pair of opposing wall surfaces on the inner circumferential surface of a rectangular frame body so as to divide an inner space surrounded by the frame body; joint auxiliary members provided between ends of the cross member and the wall surfaces of the frame body facing the ends; the frame body and the joint auxiliary members made of aluminum or an aluminum alloy; and the cross member made of steel; welding one end of the joining auxiliary member to the wall surface of the frame; a step of welding an overlapping portion of the joining auxiliary member that extends from the one end toward the inner space and overlaps with a side surface of the end of the cross member at a position of a first through hole that is formed in the cross member and passes through the overlapping portion, thereby joining the joining auxiliary member and the cross member with a weld metal of aluminum or aluminum alloy formed at the position of the first through hole; A method for manufacturing a battery case comprising:

11. The first through holes are formed in a plurality of locations in a region overlapping with the overlapping portion of the joining auxiliary member, The welding between the joining auxiliary member and the cross member at the position of the first through hole is performed using an aluminum filler metal. The method for manufacturing the battery case according to claim 10.

12. The joining auxiliary member has at least a pair of protruding pieces arranged on either side of the end portion of the cross member, The first through hole is formed at a position on the cross member where the tips of the protruding pieces face each other, The welding at the position of the first through hole is performed by welding the tips of the protruding pieces together through the first through hole using an aluminum filler metal. The method for manufacturing the battery case according to claim 10.

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