Battery case and method for manufacturing the battery case

Abstract

To provide a battery case which is lightweight and low in cost, and a method for manufacturing a battery case.SOLUTION: A battery case 10 includes a rectangular frame-like part 11, and at least one cross member extending toward a pair of parallel wall surfaces of the frame-like part 11 so as to partition inside the frame-like part 11. The frame-like part 11 is made of aluminum or an aluminum alloy, the cross member 20 is made of steel, a steel plate 30 is joined to the wall surface of the frame-like part 11 by welding, the steel plate 30 has a first hole 31 facing the wall surface of the frame-like part 11, the steel plate 30 and the wall surface of the frame-like part 11 are joined to each other in the first hole 31 by welding, the first hole 31 is filled with weld metal WA of aluminum or an aluminum alloy, and the steel plate 30 and one end in the longitudinal direction of the cross member 20 are welded to each other by welding.SELECTED DRAWING: Figure 2

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 electrically powered vehicles (including electric vehicles, hybrid vehicles, etc.) has progressed. The battery systems installed in such vehicles generally have a structure in which a large number of batteries (cells, battery cells) are housed in a battery case formed by a predetermined frame or the like.

[0003] Battery cases that house batteries need to be strong enough to protect the batteries from impacts caused by collisions, etc. In addition, from the perspective of improving fuel efficiency to combat global environmental issues caused by exhaust gases, etc., battery cases also need to be lightweight.

[0004] 31, a typical battery case 100 has a rectangular frame portion 101 composed of four frame members 102, a plate-shaped floor portion 103 disposed on the underside of the frame portion 101, and a plurality of cross members 104 whose both ends are joined to the frame portion 101 to increase strength. For the frame members 102 and cross members 104, aluminum extrusions are often used because they are lightweight and highly rigid.

[0005] Patent Document 1 describes an automobile body frame in which a side frame having a closed cross-sectional structure made of aluminum material and a cross member having a closed cross-sectional structure made of aluminum material are fastened via a fastening member to prevent a decrease in the joining strength of the frame members. Specifically, the fastening member is made of aluminum material and is a π-shaped extruded profile having a flat base and a pair of support parts extending perpendicularly to the base. The base is fastened to the side surface of the side frame by a bolt, the pair of support parts hold the end of the cross member, and the cross member and the support parts are welded at a welded part. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2007-269123 A Summary of the Invention [Problem to be solved by the invention]

[0007] In this way, if the frame members 102 and cross members 104 constituting the frame-shaped portion 101 are all made of aluminum, it is possible to reduce weight, but the cost is higher than when materials such as steel or iron are used. On the other hand, if the frame members 102 and cross members 104 are all made of steel, the cost can be reduced, but the weight increases.

[0008] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a lightweight, low-cost battery case and a method for manufacturing the battery case. [Means for solving the problem]

[0009] The above object of the present invention is achieved by the following configuration [1] relating to a battery case. [1] A rectangular frame portion, At least one cross member extending toward a pair of parallel wall surfaces of the frame portion so as to divide the inside of the frame portion; Equipped with The frame-shaped portion is made of aluminum or an aluminum alloy, The cross member is made of steel; A battery case in which a steel plate is joined to the wall surface of the frame-shaped portion by welding, The steel plate has a first hole facing the wall surface, The steel plate and the wall surface are joined by welding at the first hole, the first hole is filled with an aluminum or aluminum alloy weld metal; The steel plate and one end of the cross member in the longitudinal direction are joined by welding. A battery case characterized by:

[0010] The above object of the present invention can be achieved by the following configuration [2] relating to a manufacturing method of a battery case. [2] A rectangular frame portion, At least one cross member extending toward a pair of parallel wall surfaces of the frame portion so as to divide the inside of the frame portion; Equipped with The frame-shaped portion is made of aluminum or an aluminum alloy, The cross member is made of steel; A manufacturing method of a battery case in which a steel plate is joined to the wall surface of the frame-shaped portion by welding, The steel plate has a first hole facing the wall surface, The first hole is filled with a weld metal of aluminum or an aluminum alloy to join the steel plate and the wall surface; The steel plate and one end of the cross member in the longitudinal direction are joined by welding. A manufacturing method of a battery case comprising the steps of: Effect of the Invention

[0011] According to the present invention, a lightweight, low-cost battery case and a method for manufacturing the battery case can be provided. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view of a battery case according to the first embodiment. [Diagram 2] 2(a) to (e) are diagrams illustrating a manufacturing method of the battery case. [Diagram 3] FIG. 3 is a view for explaining a method of welding the steel plate and the first frame member. [Figure 4] FIG. 4 is a cross-sectional view of a joint between a steel plate and a first frame member. [Diagram 5] FIG. 5 is a cross-sectional view of the joint between the cross member and the floor section. [Figure 6] 6(a) to (d) are views for explaining a manufacturing method of a battery case according to a first modified example of the first embodiment. [Figure 7] 7(a) to (e) are views for explaining a manufacturing method of a battery case according to the second embodiment. [Figure 8] 8(a) to (e) are views for explaining a manufacturing method of a battery case according to a first modified example of the second embodiment. [Figure 9] 9(a) to (e) are views for explaining a manufacturing method of a battery case according to a second modified example of the second embodiment. [Figure 10] 10(a) to (g) are views for explaining a manufacturing method of a battery case according to a third modified example of the second embodiment. [Figure 11] 11(a) to (g) are views for explaining a manufacturing method of a battery case according to a fourth modified example of the second embodiment. [Figure 12] 12(a) to (e) are views for explaining a manufacturing method of a battery case according to a fifth modified example of the second embodiment. [Figure 13] 13(a) to (e) are views for explaining a manufacturing method of a battery case according to the third embodiment. [Figure 14] FIG. 14 is a cross-sectional view taken along line XIV-XIV of FIG. [Figure 15] 15(a) to (d) are views for explaining a manufacturing method of a battery case according to a first modified example of the third embodiment. [Figure 16] 16(a) to (e) are views for explaining a manufacturing method of a battery case according to a second modified example of the third embodiment. [Figure 17] FIG. 17 is a cross-sectional view taken along line XVII-XVII of FIG. [Figure 18] 18(a) to (e) are diagrams showing modified examples of steel sheets. [Figure 19] 19(a) to (d) are views for explaining a manufacturing method of a battery case according to a third modified example of the third embodiment. [Figure 20] 20(a) to (e) are views for explaining a manufacturing method of a battery case according to a fourth modified example of the third embodiment. [Figure 21] 21(a) to (d) are views for explaining a manufacturing method of a battery case according to a fifth modified example of the third embodiment. [Figure 22] 22(a) to (e) are views for explaining a manufacturing method of a battery case according to the fourth embodiment. [Figure 23] FIG. 23 is a cross-sectional view taken along line XXIII-XXIII of FIG. 22(e). [Figure 24] 24(a) to (e) are views for explaining a manufacturing method of a battery case according to a first modified example of the fourth embodiment. [Diagram 25] 25(a) to (e) are views for explaining a manufacturing method of a battery case according to a second modified example of the fourth embodiment. [Figure 26] 26(a) to (e) are views for explaining a manufacturing method of a battery case according to the fifth embodiment. [Figure 27] 27(a) to (e) are views for explaining a manufacturing method of a battery case according to a modified example of the fifth embodiment. [Figure 28] FIG. 28 is a cross-sectional view taken along line XXVIII-XXVIII of FIG. 27(e). [Figure 29A] FIG. 29A is a perspective view showing an example of a method for manufacturing a steel plate. [Figure 29B] FIG. 29B is a perspective view showing an example of a method for manufacturing a steel plate. [Figure 30A] FIG. 30A is a perspective view showing an example of a steel plate. [Figure 30B] FIG. 30B is a perspective view showing an example of a steel plate. [Figure 30C] FIG. 30C is a perspective view showing an example of a steel plate. [Figure 30D]FIG. 30D is a perspective view showing an example of a steel plate. [Figure 30E] FIG. 30E is a perspective view showing an example of a steel plate. [Figure 30F] FIG. 30F is a perspective view showing an example of a steel plate. [Figure 30G] FIG. 30G is a perspective view showing an example of a steel plate. [Diagram 31] FIG. 31 is a perspective view of a conventional battery case. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a battery case and a manufacturing method for a battery case according to the present invention will be described in detail with reference to the drawings.

[0014] First embodiment Fig. 1 is a perspective view of a battery case 10 according to the first embodiment. As shown in Fig. 1, the battery case 10 of this embodiment includes a rectangular frame portion 11 formed of a plurality of first and second frame members 12, 13, at least one cross member 20 (two in this embodiment) disposed inside the frame portion 11, and a floor portion 40 connected to the frame portion 11 so as to form the bottom surface of the battery case 10.

[0015] The first and second frame members 12, 13 constituting the frame-shaped portion 11 and the floor-shaped portion 40 are all made of aluminum or an aluminum alloy (hereinafter also referred to as aluminum material). The cross member 20 is made of steel. In this way, among the components of the battery case 10, the frame-shaped portion 11 and the floor-shaped portion 40 are made of aluminum material, while the cross member 20 is made of steel, thereby achieving both weight reduction and cost reduction.

[0016] The frame-shaped portion 11 is formed in a rectangular shape in a plan view by a pair of first frame members 12 arranged parallel to each other and a pair of second frame members 13 whose both ends are joined to both ends of the pair of first frame members 12.

[0017] 2(a) to (e) are diagrams for explaining a manufacturing method of the battery case 10. Specifically, as shown in Fig. 2(b), in a state in which an end face of the second frame member 13 is abutted against a side face 12a of an end portion of the first frame member 12, a corner formed by an edge portion of the end face of the second frame member 13 and the side face 12a of the first frame member 12 is line-welded by arc welding, thereby joining the first frame member 12 and the second frame member 13. Therefore, a pair of parallel wall surfaces of the frame-shaped portion 11 is formed by a pair of side faces 12a of a pair of opposing first frame members 12.

[0018] The first frame member 12 and the second frame member 13 are welded together by a MIG welding device 50 (hereinafter also referred to as an "aluminum MIG welding device") that uses aluminum or an aluminum alloy as a consumable electrode (welding wire). Therefore, the first frame member 12 and the second frame member 13 are joined together by a weld metal WA of aluminum or an aluminum alloy (hereinafter also referred to as an "aluminum weld metal").

[0019] In this embodiment, the first frame member 12 and the second frame member 13 are disposed on a floor-like portion 40 made of a plate material. Then, as shown in Fig. 2(b), corners formed by the lower surfaces of the first frame member 12 and the second frame member 13 and the upper surface of the floor-like portion 40 are also line-welded by the aluminum MIG welding device 50. Therefore, aluminum weld metal WA is formed at these welded locations as well.

[0020] In addition, flanges (not shown) extending along the floor-like portion 40 may be formed on the undersides of the first frame member 12 and the second frame member 13, and the flanges of the first and second frame members 12, 13 and the floor-like portion 40 may be line welded by an aluminum MIG welding apparatus 50.

[0021] Each cross member 20 is a member for improving the strength of the battery case 10, and extends toward a pair of parallel wall surfaces (opposing side surfaces 12a of a pair of first frame members 12) of the frame portion 11 so as to partition the inside of the frame portion 11 defined by the four first and second frame members 12, 13.

[0022] As shown in Figure 2(d), the longitudinal length (left-right direction in the figure) of the cross member 20 is slightly shorter than the longitudinal length of the second frame member 13, and steel plates 30 are arranged between both longitudinal ends of the cross member 20 and the side surfaces 12a of a pair of first frame members 12.

[0023] The steel plate 30 is a plate-like member made of steel extending along the side surface 12a of the first frame member 12, and is joined to the side surface 12a by welding. A plurality of first holes 31 are formed in the steel plate 30 at positions avoiding the positions where the cross member 20 is joined. In this embodiment, the plurality of first holes 31 are formed on both sides in the width direction (upper right and lower left directions in the drawing) perpendicular to the thickness direction (left and right direction in the drawing) and the height direction (up and down direction in the drawing) of the steel plate 30, with six first holes 31 formed on each side. Then, as described later, the cross member 20 is joined between the first holes 31 formed on both sides in the width direction of the steel plate 30, i.e., to the middle part in the width direction of the steel plate 30. The first holes 31 are through holes that penetrate the steel plate 30 in the thickness direction and face the side surface 12a of the first frame member 12. The first holes 31 are holes for joining the steel plate 30 to the side surface 12a by welding.

[0024] Since the steel plate 30 is made of steel, whereas the first frame member 12 is made of aluminum, when attempting to join the two dissimilar materials by normal arc welding, intermetallic compounds formed at the joining interface between the steel and aluminum become a problem. Intermetallic compounds (Al3Fe, Al5Fe2, etc.) between Fe (steel) and Al (aluminum) are brittle, so there is a possibility that cracks will occur in the welded portion.

[0025] In addition, because the battery case 10 is large in size, it is physically difficult to insert a C-clamp, which is necessary in many dissimilar metal joining methods, and a dissimilar metal joining method that does not use a C-clamp is required.

[0026] Furthermore, since the battery case is extremely sensitive to water infiltration, a joining method that requires providing through holes in the frame portion 11 or floor portion 40 for the insertion of bolts, screws, or rivets cannot be used.

[0027] FIG. 3 is a diagram for explaining a method for welding a steel plate 30 and a first frame member 12. In this embodiment, as shown in FIG. 3, a steel plate 30 having a first hole 31 is placed on the side surface 12a of the first frame member 12, and spot welding is performed by an aluminum MIG welding device 50 to obtain penetration through the first hole 31 of the steel plate 30. Hereinafter, a method of spot welding a steel member and an aluminum member through a through hole provided in the steel member using the aluminum MIG welding device 50 is called "dissimilar material MIG spot welding". In addition, a known inert gas such as argon or helium is used as the shielding gas G. Since welding is performed with a low current that does not melt the steel plate 30 and penetration is obtained between the aluminum weld metal WA and the first frame member 12, the above-mentioned problem due to intermetallic compounds does not occur. In addition, unlike the conventional dissimilar metal joining method, a C-type clamp is not required, and there is no need to provide a through hole in the first frame member 12, and water intrusion into the battery case 10 can be prevented.

[0028] 4 is a cross-sectional view of a joint between the steel plate 30 and the first frame member 12. As shown in FIG. 4, after welding the steel plate 30 and the first frame member 12, the first hole 31 is filled with aluminum weld metal WA. The aluminum weld metal WA has a rivet shape having a shaft portion WA1 that extends in the thickness direction of the steel plate 30 and reaches the first frame member 12, a head portion WA2 that bulges outward from a tip portion of the shaft portion WA1 that protrudes outside the steel plate 30, and a flange portion WA3 that bulges outward from a base portion of the shaft portion WA1 that protrudes inside the first frame member 12. The steel plate 30 and the first frame member 12 are sandwiched and fixed by the head portion WA1 and the flange portion WA3.

[0029] In this manner, the steel plate 30 and the side surface 12a of the first frame member 12 are joined by dissimilar material MIG spot welding at the multiple first holes 31. Note that the number, arrangement, etc. of the first holes 31 are not particularly limited.

[0030] 2(c)-(d), the cross member 20 has an inverted U-shaped cross section with an opening at the lower end in the height direction (up-down direction in the figure), and also has openings at both ends in the longitudinal direction (left-right direction in the figure). A pair of flanges 21, 21 extending along the floor-like portion 40 is provided at the lower end in the height direction of the cross member 20. The pair of flanges 21, 21 extend in the width direction (upper right-lower left direction in the figure) perpendicular to the height direction and the longitudinal direction over the entire longitudinal length of the cross member 20. Thus, the cross member 20 has an upper surface 26, a pair of side surfaces 24 extending downward from both ends in the width direction of the upper surface 26, and flanges 21 extending vertically from the lower ends of each side surface 24.

[0031] The flange portion 21 has a plurality of third holes 22 that penetrate the flange portion 21 in the up-down direction and face the floor-like portion 40. In this embodiment, the multiple third holes 22 are arranged at equal intervals in the longitudinal direction of the cross member 20, but the number and arrangement of the third holes 22 are not particularly limited.

[0032] Since the cross member 20 is made of steel, whereas the floor portion 40 is made of aluminum, dissimilar MIG spot welding is performed using an aluminum MIG welding device 50, similar to the welding of the steel plate 30 and the first frame member 12 described above. FIG. 5 is a cross-sectional view of the joint between the cross member 20 and the floor portion 40. As shown in FIG. 5, after welding the flange portion 21 and the floor portion 40, the third hole 22 is filled with aluminum weld metal WA. The aluminum weld metal WA has a rivet shape having a shaft portion WA1 that extends in the thickness direction of the flange portion 21 and reaches the floor portion 40, a head portion WA2 that bulges outward from the tip end of the shaft portion WA1 that protrudes outside the flange portion 21, and a flange portion WA3 that bulges outward from the base end of the shaft portion WA1 that protrudes outside the floor portion 40. The flange portion 21 and the floor portion 40 are sandwiched and fixed by the head portion WA1 and the flange portion WA3.

[0033] In this manner, the cross member 20 and the floor portion 40 are joined together at the multiple third holes 22 by dissimilar material MIG spot welding.

[0034] Both longitudinal ends of the cross member 20 are joined to the steel plate 30 joined to the side surfaces 12a of the pair of first frame members 12 by welding. Specifically, as shown in Fig. 2(e), one longitudinal end of the cross member 20 is butted against the steel plate 30, and a corner formed by an edge of the longitudinal end of the cross member 20 and the steel plate 30 is line-welded by arc welding. The other longitudinal end of the cross member 20 is also joined to the steel plate 30 by welding in a similar manner.

[0035] The cross member 20 and the steel plate 30 are welded by a MAG welding device 60 (hereinafter also referred to as a "steel MAG welding device") using steel as a consumable electrode (welding wire). Therefore, the cross member 20 and the steel plate 30 are joined by a steel weld metal WS (hereinafter also referred to as a "steel weld metal").

[0036] A battery (not shown) is housed in each compartment of the battery case 10, which is separated by the frame-shaped portion 11 and the multiple cross members 20.

[0037] Further, in the present embodiment, the first and second frame members 12 and 13 are made of a hollow extrusion profile of an aluminum material having a thickness of about 2 to 5 mm. The type of aluminum alloy used is an aluminum alloy of the 5000 series, 6000 series, 7000 series, etc. according to JIS or AA in terms of excellent strength and the possibility of further thinning. The hollow extrusion profile of the aluminum alloy is manufactured by an ordinary profile manufacturing process in which casting such as DC casting method or continuous casting method, homogenization heat treatment, hot extrusion, solution treatment and quenching treatment, and tempering treatment such as artificial aging treatment if necessary are appropriately combined. Note that by manufacturing the first and second frame members 12 and 13 by extrusion molding using an aluminum material, weight reduction can be achieved.

[0038] Also, the cross member 20 can be manufactured by bending a plate of general carbon steel or high-strength steel into an Ω shape, or by crushing a circular steel pipe into a mouth shape. Further, for example, a rib plate can be welded and added in a Π-shaped cross section, or bent into an S shape or a B shape and the joined portion can be welded to form a "day" shape. Further, the steel plate can be subjected to surface treatment such as various plating such as zinc or electrodeposition coating for corrosion prevention purposes.

[0039] Next, the manufacturing method of the battery case of the present embodiment will be described.

[0040] In the manufacturing method of the battery case of the present embodiment, first, as shown in FIGS. 2(a) to 2(b), a steel plate 30 is welded to the side surface 12a of the first frame member 12 through a first hole 31 by an aluminum MIG welding apparatus 50. Subsequently, the first and second frame members 12 and 13 are welded to each other by the aluminum MIG welding apparatus 50 which is a common welding apparatus to form a frame portion 11. Further, the frame portion 11 is welded to the floor portion 40 by the aluminum MIG welding apparatus 50 which is a common welding apparatus. Note that the order of welding of the steel plate 30 and the side surface 12a of the first frame member 12, welding of the first frame member 12 and the second frame member 13, and welding of the frame portion 11 and the floor portion 40 by the aluminum MIG welding apparatus 50 is not particularly limited.

[0041] Next, as shown in Figures 2(c) to (d), with the cross member 20 positioned against the steel plate 30 on the floor-like portion 40, the flange portion 21 of the cross member 20 is welded to the floor-like portion 40 using an aluminum MIG welding device 50.

[0042] Furthermore, as shown in FIG. 2( e ), the longitudinal ends of the cross members 20 are welded to the steel plates 30 by a steel MAG welding device 60 .

[0043] Through these steps, the battery case 10 is manufactured. Note that the order of the welding steps may be changed as appropriate, but the welding steps performed using the aluminum MIG welding device 50, which is a common welding device, may be performed consecutively to shorten the working time.

[0044] As described above, according to the battery case 10 of this embodiment, the frame-shaped portion 11 is made of aluminum or aluminum alloy, the cross member 20 is made of steel, the steel plate 30 is joined by welding to the side surface 12a (wall surface of the frame-shaped portion 11) of the first frame member 12, and the steel plate 30 is joined by welding to one end of the cross member 20 in the longitudinal direction. Therefore, among the components of the battery case 10, the frame-shaped portion 11 is made of aluminum material, while the cross member 20 is made of steel, so that it is possible to achieve both weight reduction and cost reduction. In addition, since the steel plate 30 is joined by welding to the wall surface of the frame-shaped portion 11, and then the cross member 20 is joined to the steel plate 30 by welding, the cross member 20 can be firmly fixed to the frame-shaped portion 11 via the steel plate 30.

[0045] Further, a first hole 31 facing the side surface 12a of the first frame member 12 is formed in the steel plate 30, and the steel plate 30 and the side surface 12a are joined by welding at the first hole 31. Therefore, the steel plate 30, which is made of steel, and the first frame member 12, which is made of aluminum, can be reliably joined by welding via the first hole 31. Furthermore, unlike conventional dissimilar metal joining methods, a C-clamp is not required, and there is no need to provide a through hole in the frame-shaped portion 11, so water can be prevented from entering the battery case 10.

[0046] Furthermore, since the first holes 31 are filled with the aluminum weld metal WA, the steel plate 30, which is made of steel, and the first frame member 12, which is made of aluminum, can be reliably joined by welding via the first holes 31.

[0047] The battery case 10 further has a floor portion 40 connected to the frame portion 11 and constituting a floor surface, the floor portion 40 being made of aluminum or an aluminum alloy, and the cross member 20 and the floor portion 40 being joined by welding. Therefore, among the components of the battery case 10, the frame portion 11 and the floor portion 40 are made of aluminum material, while the cross member 20 is made of steel, making it possible to achieve both weight reduction and cost reduction. Furthermore, the cross member 20 and the floor portion 40 are firmly joined by welding.

[0048] The cross member 20 has a flange portion 21 extending along the floor portion 40, and a third hole 22 facing the floor portion 40 is formed in the flange portion 21, and the flange portion 21 and the floor portion 40 are joined by welding at the third hole 22. Therefore, the cross member 20, which is made of steel, and the floor portion 40, which is made of aluminum, can be reliably joined by welding via the third hole 22. Unlike conventional dissimilar metal joining methods, a C-clamp is not required, and there is no need to provide a through hole in the floor portion 40, and water intrusion into the battery case 10 can be prevented.

[0049] Furthermore, since the third hole 22 is filled with aluminum weld metal WA, the cross member 20, which is made of steel, and the floor portion 40, which is made of aluminum material, can be reliably joined by welding via the third hole 22.

[0050] (First Modification of the First Embodiment) 6(a) to (d) are diagrams for explaining a manufacturing method of the battery case 10 according to a first modified example of the first embodiment. In the manufacturing method of the battery case 10 according to the first embodiment shown in Figs. 2(a) to (e), the steel plate 30 is joined to the side surface 12a of the first frame member 12 by welding, and then the cross member 20 is joined to the steel plate 30 by welding. However, as in the first modified example shown in Figs. 6(a) to (d), the cross member 20 and the steel plate 30 may be joined to be integrated in advance by welding, and then the steel plate 30 may be joined to the side surface 12a of the first frame member 12 by welding. Hereinafter, the manufacturing method of the battery case 10 according to the first modified example will be specifically described.

[0051] 6(a), the frame-shaped portion 11 is formed by welding the first and second frame members 12, 13 together using an aluminum MIG welding device 50. Furthermore, the frame-shaped portion 11 is welded to the floor-shaped portion 40 by the aluminum MIG welding device 50, which is a common welding device.

[0052] 6(b), the longitudinal ends of the cross member 20 are welded to the steel plate 30 by a steel MAG welding device 60. As a result, the cross member 20 and the steel plate 30 are integrated together.

[0053] The order of the welding step shown in FIG. 6(a) and the welding step shown in FIG. 6(b) is not particularly limited.

[0054] 6(c)-(d), with the steel plate 30 joined integrally with the cross member 20 butted against the side surface 12a of the first frame member 12 on the floor-like portion 40 and positioned thereon, the flange portion 21 of the cross member 20 is welded to the floor-like portion 40 by an aluminum MIG welding device 50. The common aluminum MIG welding device 50 also welds the steel plate 30 to the side surface 12a of the first frame member 12 through the first hole 31.

[0055] Through these steps, the battery case 10 is manufactured. Note that the order of the welding steps may be changed as appropriate.

[0056] Second Embodiment 7(a) to (e) are views for explaining a manufacturing method of a battery case 10 according to the second embodiment. As shown in Fig. 7(a), a first rib 14 and a second rib 15 are provided on the upper and lower parts in the height direction of the side surface 12a of the first frame member 12. The first rib 14 and the second rib 15 are formed on the side surface 12a of the first frame member 12 so as to extend in the longitudinal direction of the first frame member 12 (from the upper right to the lower left in the figure).

[0057] The first rib 14 has a first base 14a extending perpendicularly from the side surface 12a toward the cross member 20, and a first protruding portion 14b protruding downward from a tip of the first base 14a. A first groove 16 having an inverted U-shaped cross section is defined between the side surface 12a, the first base 14a, and the first protruding portion 14b.

[0058] The second rib 15 has a second base 15a extending vertically from the side surface 12a toward the cross member 20, and a second protruding portion 15b protruding upward from a tip of the second base 15a. A second groove 17 having a U-shaped cross section is defined between the side surface 12a, the second base 15a, and the second protruding portion 15b.

[0059] In the height direction, the first protruding portion 14b and the second protruding portion 15b face each other with a gap S therebetween, and it is through this gap S that the steel plate 30 and the cross member 20 can be joined to each other.

[0060] In this embodiment, as shown in Fig. 7(a), the steel plate 30 is inserted into the first groove portion 16 and the second groove portion 17 in the longitudinal direction of the first frame member 12 (from the upper right to the lower left in the figure). When the steel plate 30 is inserted into the first groove portion 16 and the second groove portion 17, the multiple first holes 31 of the steel plate 30 are exposed to the inside of the frame-shaped portion 11 via the gaps S. Then, as shown in Fig. 7(b), the steel plate 30 is welded to the side surface 12a of the first frame member 12 via the first holes 31 by an aluminum MIG welding device 50.

[0061] The first rib 14 and the second rib 15 are formed on the side surface 12a excluding the ends in the longitudinal direction (upper right and lower left directions in the figure) of the first frame member 12. As a result, steps 12b, 12c are formed between the side surface 12a and the first rib 14 and the second rib 15. Such steps 12b, 12c may be formed by providing the first rib 14 and the second rib 15 over the entire length of the side surface 12a and then cutting out the ends of the first rib 14 and the second rib 15.

[0062] Then, as shown in FIG. 7(b), with the end face of the second frame member 13 abutting against the side face 12a and steps 12b, 12c of the first frame member 12, the corner formed by the edge of the end face of the second frame member 13 and the side face 12a of the first frame member 12 is line welded by an aluminum MIG welding apparatus 50, thereby joining the first frame member 12 and the second frame member 13.

[0063] In addition, the corners formed by the second rib 15 of the first frame member 12 and the lower surface of the second frame member 13 and the upper surface of the floor-like portion 40 are also line-welded by the aluminum MIG welding device 50.

[0064] As shown in FIG. 7(c), a convex portion 23 is formed at the longitudinal end of the cross member 20, protruding toward the steel plate 30, in the gap S (see FIG. 7(a)) between the first protruding portion 14b of the first rib 14 and the second protruding portion 15b of the second rib 15. Then, as shown in FIGS. 7(c) to 7(d), with the cross member 20 placed on the floor-like portion 40, the convex portion 23 is butted against the steel plate 30 so as to fill the gap S. Here, it is preferable to set the height dimension of the convex portion 23 of the cross member 20 larger than the gap S, and to fit and fix the convex portion 23 to the first and second protruding portions 14b, 15b of the first and second ribs 14, 15. This improves the fixing force between the cross member 20 and the first frame member 12.

[0065] Then, as shown in FIG. 7( d ), the cross member 20 and the floor portion 40 are joined together at the multiple third holes 22 by dissimilar material MIG spot welding using an aluminum MIG welding device 50 .

[0066] Furthermore, as shown in FIG. 7( e ), a corner formed by the edge of the protrusion 23 of the cross member 20 and the steel plate 30 is line-welded by a steel MAG welding device 60 .

[0067] Through these steps, the battery case 10 is manufactured. Note that the order of the welding steps may be changed as appropriate.

[0068] According to the battery case 10 of the present embodiment, the steel plate 30 is inserted into the first groove portion 16 and the second groove portion 17. Therefore, it is possible to prevent the steel plate 30 welded to the side surface 12a of the first frame member 12 from peeling off.

[0069] Furthermore, a convex portion 23 that protrudes toward the steel plate 30 is formed between the first protruding portion 14b and the second protruding portion 15b at one end of the cross member 20 in the longitudinal direction, and the convex portion 23 and the steel plate 30 are joined by welding. Therefore, even when the first rib 14 and the second rib 15 are provided, the cross member 20 and the steel plate 30 can be joined by welding via the convex portion 23.

[0070] (First Modification of the Second Embodiment) 8(a) to 8(e) are diagrams for explaining a manufacturing method of the battery case 10 according to a first modified example of the second embodiment. In the manufacturing method of the battery case 10 according to the second embodiment shown in Figs. 7(a) to 7(e), the steel plate 30 is joined to the side surface 12a of the first frame member 12 by welding, and then the cross member 20 is joined to the steel plate 30 by welding. However, as in the first modified example shown in Figs. 7(a) to 7(e), the cross member 20 and the steel plate 30 may be joined to be integrated in advance by welding, and then the steel plate 30 may be joined to the side surface 12a of the first frame member 12 by welding. Hereinafter, the manufacturing method of the battery case 10 according to the first modified example will be specifically described.

[0071] As shown in Fig. 8(a), the protruding portion 23 of the cross member 20 is welded to the steel plate 30 by a steel MAG welding device 60. This integrates the cross member 20 and the steel plate 30. Then, as shown in Fig. 8(b), the steel plate 30 joined and integrated with the cross member 20 is inserted into the first groove portion 16 and the second groove portion 17.

[0072] 8(c)-(d), with the end face of the second frame member 13 abutting against the side face 12a and steps 12b, 12c of the first frame member 12, the corner formed by the edge of the end face of the second frame member 13 and the side face 12a of the first frame member 12 is line-welded by an aluminum MIG welding apparatus 50. In addition, the corner formed by the second rib 15 of the first frame member 12 and the lower face of the second frame member 13 and the upper face of the floor-like portion 40 is also line-welded by the aluminum MIG welding apparatus 50.

[0073] 8(e), the flange portion 21 of the cross member 20 is welded to the floor portion 40 through the third hole 22 by aluminum MIG welding equipment 50. In addition, the steel plate 30 is welded to the side surface 12a of the first frame member 12 through the first hole 31 by the common aluminum MIG welding equipment 50.

[0074] Through these steps, the battery case 10 is manufactured. Note that the order of the welding steps may be changed as appropriate.

[0075] (Second Modification of the Second Embodiment) 9(a) to 9(e) are diagrams for explaining a manufacturing method of a battery case 10 according to a second modified example of the second embodiment. In the battery case 10 according to the second embodiment shown in Figs. 7(a) to 7(e), a convex portion 23 protruding toward the steel plate 30 was formed at the longitudinal end of the cross member 20 between the first protruding portion 14b of the first rib 14 and the second protruding portion 15b of the second rib 15. In this modified example, the convex portion 23 is not formed on the cross member 20, and a protrusion 32 protruding toward the cross member 20 is formed on the steel plate 30 between the first protruding portion 14b of the first rib 14 and the second protruding portion 15b of the second rib 15. Hereinafter, a manufacturing method of the battery case 10 according to the second modified example will be specifically explained.

[0076] 9(a), the protrusions 32 are formed between the first holes 31 (six on each side in the width direction of the steel plate 30), i.e., in the middle part in the width direction of the steel plate 30. The height of the protrusions 32 is approximately equal to or slightly smaller than the dimension of the gap S between the first protrusions 14b and the second protrusions 15b. The steel plate 30 is inserted into the first grooves 16 and the second grooves 17 in the longitudinal direction of the first frame member 12 (from the upper right to the lower left in the figure).

[0077] When the steel plate 30 is inserted into the first groove portion 16 and the second groove portion 17, the multiple first holes 31 of the steel plate 30 are exposed to the inside of the frame-shaped portion 11 through the gap S. In addition, the contact surface of the protrusion 32 of the steel plate 30 that contacts the cross member 20 is flush with the contact surfaces of the first protrusion 14b and the second protrusion 15b that contact the cross member 20.

[0078] Then, as shown in FIG. 9( b ), the steel plate 30 is dissimilarly MIG spot welded to the side surface 12 a of the first frame member 12 through the first hole 31 by an aluminum MIG welding device 50 .

[0079] In addition, with the end face of the second frame member 13 abutting against the side face 12a and steps 12b, 12c of the first frame member 12, the corner formed by the edge of the end face of the second frame member 13 and the side face 12a of the first frame member 12 is line welded by an aluminum MIG welding apparatus 50.

[0080] In addition, the corners formed by the second rib 15 of the first frame member 12 and the lower surface of the second frame member 13 and the upper surface of the floor-like portion 40 are also line-welded by the aluminum MIG welding device 50.

[0081] 9(c)-(d), with the cross member 20 placed on the floor-like portion 40, both end faces of the cross member 20 are butted against the abutment surfaces of the protrusions 32 of the steel plate 30 and the abutment surfaces of the first protrusions 14b and the second protrusions 15b. Then, the cross member 20 and the floor-like portion 40 are joined by dissimilar material MIG spot welding at the multiple third holes 22 using an aluminum MIG welding device 50.

[0082] Furthermore, as shown in FIG. 9( e ), the corners formed by the longitudinal ends of the cross members 20 and the protrusions 32 of the steel plates 30 are line-welded by a steel MAG welding device 60 .

[0083] Through these steps, the battery case 10 is manufactured. Note that the order of the welding steps may be changed as appropriate.

[0084] According to the battery case 10 of this embodiment, the steel plate 30 has a protrusion 32 that protrudes toward the cross member 20 between the first protrusion 14b and the second protrusion 15b, and the protrusion 32 is joined to the longitudinal direction and one end of the cross member 20 by welding. Therefore, even when the first rib 14 and the second rib 15 are provided, the cross member 20 and the steel plate 30 can be joined by welding via the protrusion 32.

[0085] In this modified example, as in the first modified example (see Figures 8(a) to (e)), the cross member 20 and the steel plate 30 may be joined together by welding in advance to form an integrated unit, and then the steel plate 30 may be inserted into the first and second groove portions 16, 17 and the steel plate 30 may be joined to the side surface 12a of the first frame member 12 by welding.

[0086] (Third Modification of the Second Embodiment) 10(a)-(g) are views for explaining a manufacturing method for a battery case 10 according to a third modified example of the second embodiment. The manufacturing method of this modified example differs from the second embodiment (see FIGS. 7(a)-(e)) in that the steel plate 30 is fixed to the first groove portion 16 and the second groove portion 17 by the first protruding portion 14b and the second protruding portion 15b that have been plastically deformed toward the steel plate 30, as shown in FIGS. 10(b)-(c).

[0087] In this modification, as shown in FIG. 10(a), first, the steel plate 30 is inserted into the first groove 16 and the second groove 17. FIGS. 10(b)-(c) show cross-sectional views of the first frame member 12 and the steel plate 30 before and after the first protruding portion 14b and the second protruding portion 15b are plastically deformed. As shown in FIG. 10(b), the thickness of the steel plate 30 is set slightly shorter than the width of the first groove 16 and the second groove (the width between the side surface 12a and the first protruding portion 14b and the second protruding portion 15b), ensuring smooth insertion of the steel plate 30. Therefore, a gap H is generated between the steel plate 30 and the side surface 12a or the first protruding portion 14b and the second protruding portion 15b.

[0088] 10(c), in order to eliminate the gap H, the first protruding portion 14b and the second protruding portion 15b are plastically deformed toward the steel plate 30 by a plastic deformation device such as a hammer 70, thereby bringing the first protruding portion 14b and the second protruding portion 15b into contact with the steel plate 30. As a result, the steel plate 30 is sandwiched between the side surface 12a of the first frame member 12 and the first protruding portion 14b and the second protruding portion 15b, and is fixed to the first groove portion 16 and the second groove portion 17.

[0089] The subsequent steps shown in FIGS. 10(d) to (g) are similar to the steps described with reference to FIGS. 7(b) to (e), and therefore will not be described.

[0090] As described above, according to the battery case 10 of this embodiment, the steel plate 30 is fixed to the first groove portion 16 and the second groove portion 17 by the first protrusion portion 14b and the second protrusion portion 15b, which are plastically deformed toward the steel plate 30, so that the steel plate 30 can be prevented from moving in the first groove portion 16 and the second groove portion 17 and the steel plate 30 can be securely fixed to the first frame member 12. As in a first modified example (see Figs. 8(a) to (e)), the cross member 20 and the steel plate 30 may be joined by welding to be integrated in advance, and then the steel plate 30 may be joined by welding to the side surface 12a of the first frame member 12. As in a second modified example (see Figs. 9(a) to (e)), the cross member 20 may not be formed with the convex portion 23, and the steel plate 30 may be formed with a protrusion 32 that protrudes toward the cross member 20 between the first protruding portion 14b of the first rib 14 and the second protruding portion 15b of the second rib 15.

[0091] (Fourth Modification of the Second Embodiment) 11(a) to (g) are views for explaining a manufacturing method of a battery case 10 according to a sixth modified example of the second embodiment. The manufacturing method of this modified example differs from the second embodiment (see FIGS. 7(a) to (e)) in that second holes 18 facing the steel plate 30 are formed in the first protruding portion 14b and the second protruding portion 15b, and the steel plate 30 is fixed to the first groove portion 16 and the second groove portion 17 by fastening members fastened toward the steel plate 30 through the second holes 18.

[0092] As shown in FIG. 11(a), the first protruding portion 14b and the second protruding portion 15b each have eight second holes 18, two of which are spaced apart in the longitudinal direction of the first frame member 12 (upper right and lower left directions in the figure). The number and positions of the second holes 18 are not particularly limited, but the second holes 18 are formed in positions that do not overlap with the cross member 20 when the cross member 20 is joined to the steel plate 30 (see FIG. 11(g)). In the illustrated example, the second holes 18 are arranged in positions that are aligned in the vertical direction with the first holes 31 of the steel plate 30. The second holes 18 are screw holes in which female threads are formed for screwing in the bolts 71.

[0093] In this modification, as shown in FIG. 11(a), first, the steel plate 30 is inserted into the first groove 16 and the second groove 17. FIGS. 11(b)-(c) show cross-sectional views of the first frame member 12 and the steel plate 30 before and after a bolt 71 as a fastening member is fastened to the steel plate 30 through the second hole 18. As shown in FIG. 11(b), the thickness of the steel plate 30 is set slightly shorter than the width of the first groove 16 and the second groove (the width between the side surface 12a and the first protruding portion 14b and the second protruding portion 15b), ensuring smooth insertion of the steel plate 30. Therefore, a gap H is generated between the steel plate 30 and the side surface 12a or the first protruding portion 14b and the second protruding portion 15b.

[0094] In order to reliably position the steel plate 30 even if the gap H occurs, as shown in Fig. 11(c), the bolt 71 is inserted into the second hole 18 and fastened toward the steel plate 30. As a result, the steel plate 30 is sandwiched between the side surface 12a of the first frame member 12 and the bolt 71, and is fixed to the first groove portion 16 and the second groove portion 17.

[0095] The subsequent steps shown in FIGS. 11(d) to (g) are similar to the steps described with reference to FIGS. 7(b) to (e), and therefore will not be described.

[0096] As described above, according to the battery case 10 of this embodiment, the second holes 18 facing the steel plate 30 are formed in the first protruding portion 14b and the second protruding portion 15b, and the steel plate 30 is fixed to the first groove portion 16 and the second groove portion 17 by fastening members fastened toward the steel plate 30 through the second holes 18. Therefore, it is possible to prevent the steel plate 30 from moving in the first groove portion 16 and the second groove portion 17, and the steel plate 30 can be securely fixed to the first frame member 12. As in a first modified example (see Figs. 8(a) to (e)), the cross member 20 and the steel plate 30 may be joined by welding to be integrated in advance, and then the steel plate 30 may be joined by welding to the side surface 12a of the first frame member 12. As in a second modified example (see Figs. 9(a) to (e)), the cross member 20 may not be formed with the convex portion 23, and the steel plate 30 may be formed with a protrusion 32 that protrudes toward the cross member 20 between the first protruding portion 14b of the first rib 14 and the second protruding portion 15b of the second rib 15.

[0097] (Fifth Modification of the Second Embodiment) 12(a) to (e) are views for explaining a manufacturing method of a battery case 10 according to a ninth modified example of the second embodiment. The manufacturing method of this modified example differs from the second embodiment (see FIGS. 7(a) to (e)) in that second holes 18 facing the steel plate 30 are formed in the first protruding portions 14b and the second protruding portions 15b, and the first protruding portions 14b and the second protruding portions 15b are joined to the steel plate 30 at the second holes 18 by welding, thereby fixing the steel plate 30 to the first groove portions 16 and the second groove portions 17.

[0098] As shown in Fig. 12(a), eight second holes 18 are formed in each of the first protruding portion 14b and the second protruding portion 15b, two of which are spaced apart in the longitudinal direction of the first frame member 12 (upper right and lower left in the figure). The number and positions of the second holes 18 are not particularly limited, but the second holes 18 are formed in positions that do not overlap with the cross member 20 when the cross member 20 is joined to the steel plate 30 (see Fig. 12(e)). In the illustrated example, the second holes 18 are arranged in positions that are aligned in the vertical direction with the first holes 31 of the steel plate 30.

[0099] In this modification, as shown in Fig. 12(a), first, the steel plate 30 is inserted into the first groove portion 16 and the second groove portion 17. Then, as shown in Fig. 12(b), the steel plate 30 is welded to the side surface 12a of the first frame member 12 through the first hole 31 by an aluminum MIG welding device 50.

[0100] With the end face of the second frame member 13 abutting against the side face 12a and steps 12b, 12c of the first frame member 12, the corner formed by the edge of the end face of the second frame member 13 and the side face 12a of the first frame member 12 is line welded by an aluminum MIG welding apparatus 50, thereby joining the first frame member 12 and the second frame member 13.

[0101] In addition, the corners formed by the second rib 15 of the first frame member 12 and the lower surface of the second frame member 13 and the upper surface of the floor-like portion 40 are also line-welded by the aluminum MIG welding device 50.

[0102] 12(c)-(d), with the cross member 20 placed on the floor-like portion 40, the convex portion 23 is butted against the steel plate 30 so as to fill the gap S between the first protruding portion 14b and the second protruding portion 15b. Then, the flange portion 21 of the cross member 20 and the floor-like portion 40 are joined together at the multiple third holes 22 by dissimilar material MIG spot welding using an aluminum MIG welding device 50.

[0103] Then, as shown in FIG. 12( e ), the corner formed by the edge of the protrusion 23 of the cross member 20 and the steel plate 30 is line-welded by a steel MAG welding device 60 .

[0104] Furthermore, the first protruding portion 14b and the second protruding portion 15b of the first frame member 12 and the steel plate 30 are joined by welding at the second holes 18, but since the first frame member 12 is made of aluminum material and the steel plate 30 is made of steel, it is not preferable to apply normal arc welding. Therefore, in this modified example, arc spot welding for joining dissimilar materials, which will be described below, is applied.

[0105] First, the joining auxiliary member 80 is inserted into the second hole 18 provided in the first protruding portion 14b and the second protruding portion 15b. The joining auxiliary member 80 has a stepped outer shape with a hollow shaft-shaped inserting portion 81 inserted into the second hole 18 and a flange-shaped non-inserting portion 83 disposed on the surface of the first protruding portion 14b and the second protruding portion 15b facing the cross member 20. In addition, a hollow portion 85 is formed in the joining auxiliary member 80, penetrating the inserting portion 81 and the non-inserting portion 83. The outer shape of the non-inserting portion 83 is not limited to a circular shape as shown in FIG. 12(e) and can be any shape. The shape of the hollow portion 85 is also not limited to a circular shape and can be any shape. The material of the steel joining auxiliary member 80 is not particularly limited as long as it is pure iron or an iron alloy, and examples thereof include mild steel, carbon steel, and stainless steel.

[0106] Furthermore, the hollow portion 85 of the joining auxiliary member 80 is filled with a weld metal of an iron alloy or Ni alloy in which a filler material (welding material) is melted by the dissimilar material arc spot welding device 90. As a result, a molten portion is formed in the hollow portion 85 by the weld metal, the molten steel plate 30, and a part of the joining auxiliary member 80. As a result, the first protruding portion 14b and the second protruding portion 15b are joined to the steel plate 30.

[0107] In the illustrated example, the second holes 18 are formed in advance in the first protruding portion 14b and the second protruding portion 15b, and then the auxiliary joining member 80 is inserted into the second holes 18. However, the auxiliary joining member 80 itself may be used as a punch to bring an upper base to which the auxiliary joining member 80 is fixed close to a lower base on which the first protruding portion 14b and the second protruding portion 15b are arranged, and punching may be performed to simultaneously perform the step of providing the second holes 18 in the first protruding portion 14b and the second protruding portion 15b and the step of inserting the auxiliary joining member 80 into the second holes 18.

[0108] According to the battery case 10 of this modified example, second holes 18 facing the steel plate 30 are formed in the first protruding portion 14b and the second protruding portion 15b, and the first protruding portion 14b and the second protruding portion 15b are joined to the steel plate 30 by welding at the second holes 18, thereby fixing the steel plate 30 to the first groove portion 16 and the second groove portion 17. This prevents the steel plate 30 from moving in the first groove portion 16 and the second groove portion 17, and allows the steel plate 30 to be securely fixed to the first frame member 12. As in a first modified example (see Figs. 8(a) to (e)), the cross member 20 and the steel plate 30 may be joined by welding to be integrated in advance, and then the steel plate 30 may be joined by welding to the side surface 12a of the first frame member 12. As in a second modified example (see Figs. 9(a) to (e)), the cross member 20 may not be formed with the convex portion 23, and the steel plate 30 may be formed with a protrusion 32 that protrudes toward the cross member 20 between the first protruding portion 14b of the first rib 14 and the second protruding portion 15b of the second rib 15.

[0109] Third embodiment In the above-mentioned battery case 1, a steel plate 30 is joined by welding to the side surface 12a (wall surface of the frame-shaped portion 11) of the first frame member 12, and the steel plate 30 is joined by welding to one end of the cross member 20 in the longitudinal direction. However, the battery case 1 is a structure of a relatively large size for an automobile part, and the dimensional accuracy of the aluminum extrusion molding from which the first frame member 12 is made is not necessarily high, so that the unavoidable accuracy error can result in a large displacement. For this reason, a gap is generated between the steel plate 30 joined to the side surface 12a of the first frame member 12 and the cross member 20, and there is a risk that welding will be impossible with a simple butt joint structure of the respective members.

[0110] Therefore, in this embodiment, a lightweight, highly rigid battery case 1 that can flexibly respond to and be joined to gaps that may occur at the butt joint between the steel plate 30 joined to the side 12a of the first frame member 12 and the cross member 20, and a manufacturing method for the battery case 1 are described.

[0111] 13(a) to 13(e) are diagrams for explaining a manufacturing method of a battery case 10 according to a third embodiment. In this embodiment, the length of the cross member 20 is designed to be shorter than the length between the pair of first protruding portions 14b or the pair of second protruding portions 15b facing each other in the longitudinal direction of the cross member 20, and a gap A is formed between the first protruding portion 14b and the second protruding portion 15b and the longitudinal end of the cross member 20. A bracket portion 33 formed on a steel plate 30 is disposed in this gap A. The bracket portion 33 is joined to one longitudinal end of the cross member 20, and the joining position with the cross member 20 is adjustable. That is, the cross member 20 and the first frame member 12 are connected via the bracket portion 33 of the steel plate 30.

[0112] The bracket portion 33 of the steel plate 30 is formed between the first holes 31 formed six on each side in the width direction of the steel plate 30, i.e., in the middle portion in the width direction of the steel plate 30. The bracket portion 33 is a flat plate extending perpendicularly to the side surface 12a of the first frame member 12. The height of the bracket portion 33 is approximately equal to or slightly smaller than the dimension of the gap S between the first protruding portion 14b and the second protruding portion 15b. As shown in Figs. 13(a) and 13(b), when the steel plate 30 is inserted into the first groove portion 16 and the second groove portion 17, the bracket portion 33 protrudes toward the cross member 20 side more than the first protruding portion 14b and the second protruding portion 15b.

[0113] As described above, the cross member 20 has an inverted U-shaped cross section with an opening at the lower end, and also has openings at both ends in the longitudinal direction (left-right direction in the figure). A pair of flanges 21, 21 extending along the floor-like portion 40 are provided at the lower end of the cross member 20 in the height direction. Thus, the cross member 20 has an upper surface 26, a pair of side surfaces 24 extending downward from both ends in the width direction of the upper surface 26, and flanges 21 extending vertically from the lower end of each side surface 24.

[0114] Fig. 14 is a cross-sectional view taken along line XIV-XIV of Fig. 13(e). As shown in Figs. 13(c)-(e) and 14, the bracket portion 33 is inserted into the cross member 20 and is formed so as to be movable forward and backward in the longitudinal direction relative to the cross member 20. That is, the bracket portion 33 has an outer surface 33a that can come into contact with the inner surface of the cross member 20 and is relatively slidable inside the cross member 20. In addition, rectangular openings 25 that are elongated holes perpendicular to the longitudinal direction of the cross member 20 are formed on the end sides of both side surfaces 24 of the cross member 20. Therefore, when the bracket portion 33 is disposed inside the cross member 20, the outer surfaces 33a of the bracket portion 33 are exposed through the openings 25.

[0115] Then, the outer surface 33 a of the bracket portion facing the opening 25 and the edge portion 25 a of the opening 25 on the first frame member 12 side are line-welded and joined by a steel MAG welding device 60 .

[0116] In this manner, the side surface 12a of the first frame member 12 is joined to the steel plate 30 and the bracket portion 3 of the steel plate 30 is joined to the cross member 20, thereby connecting the first frame member 12 to the cross member 20. Therefore, even if the gap A between the first protruding portion 14b and the second protruding portion 15b and the longitudinal end portion of the cross member 20 changes, the gap A can be filled by joining the cross member 20 to the bracket portion 33 with the overlapping length of the cross member 20 and the bracket portion 33 changed, and the strength of the battery case 10 can be improved.

[0117] Next, a manufacturing method of the battery case of this embodiment will be described.

[0118] First, as shown in FIG. 13(a), the steel plate 30 is inserted into the first groove portion 16 and the second groove portion 17 in the longitudinal direction of the first frame member 12 (from the upper right to the lower left in the figure).

[0119] 13(b), the side surface 12a of the first frame member 12 and the steel plate 30 are joined through the first holes 31 by dissimilar material MIG spot welding by an aluminum MIG welding device 50. The first frame member 12 and the second frame member 13 are joined by line welding by the aluminum MIG welding device 50. The second rib 15 of the first frame member 12 and the corner formed by the lower surface of the second frame member 13 and the upper surface of the floor-like portion 40 are also line-welded and joined by the aluminum MIG welding device 50.

[0120] 13(c), the cross member 20 is inserted toward the bracket portion 33 of the steel plate 30, and the cross member 20 is placed at a desired position on the floor-like portion 40. Next, as shown in FIG 13(d), the flange portion 21 of the cross member 20 and the floor-like portion 40 are joined through the third hole 22 by dissimilar material MIG spot welding using an aluminum MIG welding device 50.

[0121] 13(e) and 14, an outer surface 33a of the bracket portion 33 facing through the opening 25 of the cross member 20 and an edge portion 25a of the opening 25 on the first frame member 12 side are line-welded by a steel MAG welding device 60 to form a steel weld metal WS. By welding the edge portion 25a of the opening 25 on the first frame member 12 side in this manner, the first frame member 12 does not interfere with the welding torch and become an obstacle to the welding operation, compared to the case where the edge portion of the opening 25 on the opposite side to the first frame member 12 is welded, and the welding operation is made easier.

[0122] As a method for joining the bracket portion 33 and the cross member 20 at the opening 25, a weld bead may be formed so as to close the opening 25, i.e., to straddle the periphery of the opening 25, and the opening 25 may be filled with the steel weld metal WS to join them. This further improves the resistance of the cross member 20 to forces acting in the longitudinal direction.

[0123] As described above, with the battery case 10 of this embodiment, even if the dimensions between the side surfaces 12a of a pair of first frame members 12 at the position where the cross member 20 is connected differ depending on the dimensional accuracy of the frame members 12, it is possible to eliminate problems such as the inability to join the cross member 20 to the steel plate 30 joined to the side surfaces 12a of the first frame member 12. Furthermore, the cross member 20 and the steel plate 30 joined to the side surfaces 12a of the frame members 12 can be reliably joined using the bracket portion 33, and the strength of the battery case 1 can be improved.

[0124] In addition, according to the battery case 10 of this embodiment, an opening 25 is formed at the end of the cross member 20 facing the outer surface 33a of the bracket portion 33 arranged inside it, and the bracket portion 33 and the cross member 20 are joined by welding at the opening 25, so that the bracket portion 33 and the cross member 20 can be welded together without the welding torch interfering with the first frame member 12.

[0125] In the battery case 10 of this embodiment, the first frame member 12 includes the first and second ribs 14, 15, but the present invention is also applicable to a case where the first frame member 12 does not include the first and second ribs 14, 15. In addition, the first and second ribs 14, 15 may be plastically deformed toward the steel plate 30 as shown in Figures 10(b) to (c), and the first frame member 12 may be fastened or welded through second holes 18 formed in the first and second ribs 14, 15 as shown in Figures 11(b) to (c) and Figures 12(b) to (c).

[0126] Furthermore, the shape of the bracket portion 33 can be changed as appropriate.

[0127] (First Modification of the Third Embodiment) 15(a) to (d) are diagrams for explaining a manufacturing method of a battery case 10 according to a first modified example of the third embodiment. In this modified example, as shown in FIG. 15(a), the bracket portion 33 of the steel plate 30 is inserted into the inside of the cross member 20 to temporarily assemble the steel plate 30 and the bracket portion 33. In this manner, in a state in which the bracket portion 33 of the steel plate 30 is assembled to at least one end portion of the cross member 20, the steel plate 30 is inserted into the first and second groove portions 16, 17. As a result, the cross member 20 to which the bracket portion 33 is assembled is disposed relative to the frame-shaped portion 11. At this time, the bracket portion 33 is loosely fitted in the cross member 20, and the bracket portion 33 and the cross member 20 can freely advance and retreat relative to each other.

[0128] 15(b), the cross member 20 is moved while being guided by the bracket portion 33, and placed in a desired position on the floor-like portion 40. Then, the outer surface 33a of the bracket portion 33 facing through the opening 25 of the cross member 20 is welded and joined to the opening 25 by a steel MAG welding device.

[0129] 15(c), the first frame member 12 and the second frame member 13 are joined by line welding using an aluminum MIG welding apparatus 50. In addition, the second rib 15 of the first frame member 12 and the corner formed by the lower surface of the second frame member 13 and the upper surface of the floor-like portion 40 are also joined by line welding using the aluminum MIG welding apparatus 50.

[0130] 15(d), the flange portion 21 and the floor portion 40 of the cross member 20 are joined through the third hole 22 by dissimilar material MIG spot welding by the aluminum MIG welding device 50. Also, the side surface 12a of the first frame member 12 and the steel plate 30 are joined through the first hole 31 by dissimilar material MIG spot welding by the aluminum MIG welding device 50.

[0131] (Second Modification of the Third Embodiment) 16(a) to (e) are views for explaining a manufacturing method of a battery case 10 according to a second modified example of the third embodiment. In this modified example, a steel plate 30 has two bracket portions 33 formed between six first holes 31 formed on each side in the width direction of the steel plate 30. The two bracket portions 33 are spaced apart from each other in the width direction of the steel plate, and each has a flat plate shape extending perpendicular to the side surface 12a of the first frame member 12. The two bracket portions 33 each have inner surfaces 33b facing each other in the width direction of the steel plate 30, and the cross member 20 is sandwiched between these facing inner surfaces 33b.

[0132] First, as shown in Fig. 16(a), the steel plate 30 is inserted into the first groove 16 and the second groove 17 in the longitudinal direction of the first frame member 12 (upper right to lower left direction in the figure). Here, the height of each bracket portion 33 is approximately equal to or slightly smaller than the dimension of the gap S between the first protruding portion 14b and the second protruding portion 15b. Then, with the steel plate 30 inserted into the first groove 16 and the second groove 17, each bracket portion 33 protrudes toward the cross member 20 side further than the first protruding portion 14b and the second protruding portion 15b.

[0133] 16(b), the side surface 12a of the first frame member 12 and the steel plate 30 are joined through the first holes 31 by dissimilar material MIG spot welding by an aluminum MIG welding device 50. The first frame member 12 and the second frame member 13 are joined by line welding by the aluminum MIG welding device 50. The second rib 15 of the first frame member 12 and the corner formed by the lower surface of the second frame member 13 and the upper surface of the floor-like portion 40 are also line-welded and joined by the aluminum MIG welding device 50.

[0134] 16(c), the cross member 20 is inserted between the inner surfaces 33b of the pair of bracket portions 33 of the steel plate 30, and the cross member 20 is placed at a desired position on the floor-like portion 40. In other words, the bracket portions 33 have inner surfaces 33b that can come into contact with a pair of side surfaces (outer surfaces) 24) of the cross member 20, and the pair of side surfaces (outer surfaces) 24 of the cross member 20 can slide relatively.

[0135] Next, as shown in FIG. 16( d ), the flange portion 21 of the cross member 20 and the floor portion 40 are joined through the third holes 22 by dissimilar material MIG spot welding using an aluminum MIG welding device 50 .

[0136] Fig. 17 is a cross-sectional view taken along the line XVII-XVII of Fig. 16(e). As shown in Fig. 16(e) and Fig. 17, a corner formed by the bracket portion 33 and the side surface 24 (outer surface) of the cross member 20 is line-welded by a steel MAG welding device 60 to form a steel weld metal WS. In this manner, the steel plate 30 and the cross member 20 are joined via the bracket portion 33.

[0137] As described above, with the battery case 10 of this embodiment, even if the dimensions between the side surfaces 12a of a pair of first frame members 12 at the position where the cross member 20 is connected differ depending on the dimensional accuracy of the frame member 12, it is possible to eliminate problems such as the inability to join the cross member 20 to the steel plate 30 joined to the side surfaces 12a of the frame member 12. Furthermore, the cross member 20 and the steel plate 30 joined to the side surfaces 12a of the frame member 12 can be reliably joined using the bracket portion 33, and the strength of the battery case 1 can be improved.

[0138] 18(a) to (e) show modified examples of the steel plate 30. As shown in Fig. 18(a) to (e), the steel plate 30 may be composed of two steel plate pieces 30a divided in the width direction. In this case, each steel plate piece 30a has a plurality of first holes 31 and a bracket portion 33. Then, the cross member 20 is inserted between the bracket portions 33 of the pair of steel plate pieces 30a, and each bracket portion 33 and a side surface 24 of the cross member 20 are welded and joined.

[0139] (Third Modification of the Third Embodiment) 19(a) to (d) are views for explaining a manufacturing method of a battery case 10 according to a third modified example of the third embodiment. In this modified example, as shown in Fig. 19(a), the cross member 20 is inserted between a pair of bracket portions 33 of a steel plate 30 of the second modified example, so that the steel plate 30 and the bracket portions 33 are temporarily assembled, and then the steel plate 30 is inserted into the first and second groove portions 16, 17. At this time, the cross member 20 is loosely fitted between the pair of bracket portions 33, and the cross member 20 and the pair of bracket portions 33 can freely advance and retreat relative to each other.

[0140] 19(b), the cross member 20 is moved while being guided by the pair of bracket portions 33, and placed in a desired position on the floor-like portion 40. Then, the corners formed by the bracket portions 33 and the side surfaces 24 of the cross member 20 are welded and joined by a steel MAG welding device 60.

[0141] 19(c), the first frame member 12 and the second frame member 13 are joined by line welding using an aluminum MIG welding apparatus 50. In addition, the second rib 15 of the first frame member 12 and the corner formed by the lower surface of the second frame member 13 and the upper surface of the floor-like portion 40 are also joined by line welding using the aluminum MIG welding apparatus 50.

[0142] 19(d), the flange portion 21 and the floor portion 40 of the cross member 20 are joined through the third hole 22 by dissimilar material MIG spot welding by the aluminum MIG welding device 50. Also, the side surface 12a of the first frame member 12 and the steel plate 30 are joined through the first hole 31 by dissimilar material MIG spot welding by the aluminum MIG welding device 50.

[0143] In this modified example, the steel plate 30 consisting of two steel plate pieces 30a shown in FIG. 18 can also be applied.

[0144] (Fourth Modification of the Third Embodiment) 20(a) to (e) are views for explaining a manufacturing method of a battery case 10 according to a second modified example of the third embodiment. In this modified example, a steel plate 30 has bracket portions 33 formed between first holes 31, six of which are formed on each side in the width direction of the steel plate 30. The bracket portions 33 are in an inverted U-shape with an opening at the lower end. The bracket portions 33 also have openings at both ends in the longitudinal direction of the cross member 20.

[0145] First, as shown in Fig. 20(a), the steel plate 30 is inserted into the first groove 16 and the second groove 17 in the longitudinal direction of the first frame member 12 (upper right to lower left direction in the figure). Here, the height of the bracket portion 33 is approximately equal to or slightly smaller than the dimension of the gap S between the first protruding portion 14b and the second protruding portion 15b. Then, with the steel plate 30 inserted into the first groove 16 and the second groove 17, the bracket portion 33 protrudes toward the cross member 20 side beyond the first protruding portion 14b and the second protruding portion 15b.

[0146] 20(b), the side surface 12a of the first frame member 12 and the steel plate 30 are joined through the first holes 31 by dissimilar material MIG spot welding by an aluminum MIG welding device 50. The first frame member 12 and the second frame member 13 are joined by line welding by the aluminum MIG welding device 50. The second rib 15 of the first frame member 12 and the corner formed by the lower surface of the second frame member 13 and the upper surface of the floor-like portion 40 are also line-welded and joined by the aluminum MIG welding device 50.

[0147] 20(c), the cross member 20 is inserted between the inner surfaces 33b of the pair of bracket portions 33 of the steel plate 30, and the cross member 20 is placed at a desired position on the floor-like portion 40. That is, the bracket portions 33 have inner surfaces 33b that can come into contact with the pair of side surfaces (outer surfaces) 24 and the top surface 26 of the cross member 20, and the pair of side surfaces (outer surfaces) 24 and the top surface 26 of the cross member 20 can slide relative to each other.

[0148] Next, as shown in FIG. 20( d ), the flange portion 21 of the cross member 20 and the floor portion 40 are joined through the third holes 22 by dissimilar material MIG spot welding using an aluminum MIG welding device 50 .

[0149] 20(e), the corners formed by the bracket portion 33 and the pair of side surfaces 24 of the cross member 20 are line-welded by a steel MAG welding device 60 to form a steel weld metal WS. In this manner, the steel plate 30 and the cross member 20 are joined via the bracket portion 33.

[0150] (Fifth Modification of the Third Embodiment) Figures 21(a) to (d) are views for explaining a manufacturing method of a battery case 10 according to a fifth modified example of the third embodiment. In this modified example, as shown in Figure 21(a), the cross member 20 is inserted into the bracket portion 33 of the steel plate 30 of the fourth modified example (see Figures 20(a) to (e)) to temporarily assemble the steel plate 30 and the bracket portion 33, and then the steel plate 30 is inserted into the first and second groove portions 16, 17. At this time, the cross member 20 is loosely fitted into the bracket portion 33, and the cross member 20 and the bracket portion 33 can freely advance and retreat relative to each other.

[0151] 21(b), the cross member 20 is moved while being guided by the bracket portion 33, and placed in a desired position on the floor-like portion 40. Then, the corner formed by the bracket portion 33 and the side surface 24 of the cross member 20 is welded and joined by a steel MAG welding device 60.

[0152] 21(c), the first frame member 12 and the second frame member 13 are joined by line welding using an aluminum MIG welding apparatus 50. In addition, the second rib 15 of the first frame member 12 and the corner formed by the lower surface of the second frame member 13 and the upper surface of the floor-like portion 40 are also joined by line welding using the aluminum MIG welding apparatus 50.

[0153] 21(d), the flange portion 21 and the floor portion 40 of the cross member 20 are joined through the third hole 22 by dissimilar material MIG spot welding by the aluminum MIG welding device 50. Also, the side surface 12a of the first frame member 12 and the steel plate 30 are joined through the first hole 31 by dissimilar material MIG spot welding by the aluminum MIG welding device 50.

[0154] (Manufacturing methods for various brackets) Next, a method for manufacturing steel plates 30 of various shapes having a bracket portion 33 will be described. Fig. 29A to Fig. 29B are perspective views showing an example of a method for manufacturing a steel plate 30. For example, the π-shaped steel plate 30 shown in Fig. 16(a) to (e) is formed by vertically welding two steel plates 37 that will become the bracket portion 33 to one side of a single steel plate 36, as shown in Fig. 29A and Fig. 29B. In addition to such a method of welding plates together, the steel plate 30 can be manufactured by cutting from a plate, casting, using a 3D printer, rolling, and machining such as cutting and drilling.

[0155] 13(a) to (e) and 30A may be modified into similar shapes as shown in Fig. 30B to 30G. In other words, modifications such as forming chamfers at the orthogonal portions between the plates or forming hollows may be appropriately performed as long as the object of the present application can be achieved.

[0156] (Fourth embodiment) 22(a) to (e) are diagrams for explaining a manufacturing method of a battery case 10 according to a fourth embodiment. As in the third embodiment, the present embodiment aims to eliminate a problem such as the inability to join the cross member 20 to the steel plate 30 joined to the side surface 12a of the first frame member 12 even if the dimensions between the side surfaces 12a of the pair of first frame members 12 at the position where the cross member 20 is joined are different. However, while in the third embodiment, the steel plate 30 and the cross member 20 are joined using the bracket portion 33 formed on the steel plate 30, in this embodiment, the steel plate 30 and the cross member 20 are joined using a steel wedge-shaped member 75 arranged between the steel plate 30 and the cross member 20. Hereinafter, a manufacturing method of the battery case 10 of this embodiment will be described.

[0157] As shown in Fig. 22(a), a protrusion 32 is formed in the widthwise intermediate portion of the steel plate 30. The protrusions 32 are arranged between first holes 31, six of which are formed on each side of the steel plate 30 in the widthwise direction. The height of the protrusions 32 is approximately equal to or slightly smaller than the dimension of the gap S between the first protrusion 14b and the second protrusion 15b. The steel plate 30 is inserted into the first groove 16 and the second groove 17 in the longitudinal direction of the first frame member 12 (from the upper right to the lower left in the figure).

[0158] When the steel plate 30 is inserted into the first groove portion 16 and the second groove portion 17, the multiple first holes 31 of the steel plate 30 are exposed to the inside of the frame-shaped portion 11 via the gap S. In addition, the abutment surface of the protrusion 32 of the steel plate 30 that abuts against the wedge-shaped member 75 is flush with the abutment surfaces of the first protrusion 14b and the second protrusion 15b that abut against the wedge-shaped member 75.

[0159] Then, as shown in FIG. 22( b ), the steel plate 30 is dissimilar-material MIG spot welded to the side surface 12 a of the first frame member 12 through the first hole 31 by an aluminum MIG welding device 50 .

[0160] In addition, with the end face of the second frame member 13 abutting against the side face 12a and steps 12b, 12c of the first frame member 12, the corner formed by the edge of the end face of the second frame member 13 and the side face 12a of the first frame member 12 is line welded by an aluminum MIG welding apparatus 50.

[0161] In addition, the corners formed by the second rib 15 of the first frame member 12 and the lower surface of the second frame member 13 and the upper surface of the floor-like portion 40 are also line-welded by the aluminum MIG welding device 50.

[0162] 22(c), one end face 27 of the cross member 20 in the longitudinal direction is inclined with respect to the height direction of the steel plate 30. In other words, one end face 27 of the cross member 20 is an inclined surface that is inclined so that the gap between the end face 27 and the protrusion 32 of the steel plate 30 becomes smaller from the upper surface 26 toward the floor-like portion 40 (from above to below).

[0163] Then, the cross member 20 is placed on the floor-like portion 40 so that one end surface 27 of the cross member 20 is separated from the protrusion 32 and the first and second protrusions 14b, 15b of the steel plate 30 via a gap. Next, a steel wedge-shaped member 75 is inserted from above downward between one end surface 27 of the cross member 20 and the abutment surfaces of the protrusion 32 of the steel plate 30 and the abutment surfaces of the first and second protrusions 14b, 15b.

[0164] The wedge-shaped member 75 has a shape corresponding to the member to be fitted. The wedge-shaped member 75 of this embodiment has a first side surface 75a that abuts against one end surface 27 of the cross member 20, and a second side surface 75b that abuts against the abutment surface of the protrusion 32 of the steel plate 30 and the abutment surfaces of the first and second protrusions 14b, 15b. The first side surface 75a is an inclined surface that inclines toward the steel plate 30 from above to below, similar to the one end surface 27 of the cross member 20. The second side surface 75b is flat, similar to the abutment surface of the protrusion 32 of the steel plate 30 and the abutment surfaces of the first and second protrusions 14b, 15b. In this way, the wedge-shaped member 75 has a wedge shape in which the width in the longitudinal direction of the cross member 20 decreases from above to below.

[0165] Furthermore, in order to reduce weight, the wedge-shaped member 75 is provided with a plurality of through holes 76 that penetrate the wedge-shaped member 75 in the width direction (from the upper right to the lower left in the drawing). In the illustrated example, three through holes 76 are provided, but the number is not particularly limited, and it does not matter if no through holes are provided. That is, the wedge-shaped member 75 has a cross-sectional shape that is solid or has a space inside. With this configuration, if it is solid, the strength can be increased, and if a space is provided inside, the weight can be reduced.

[0166] In this way, the wedge-shaped member 75 is inserted from above downward between one end face 27 of the cross member 20 and the protrusion 32 and the first and second protrusions 14b, 15b of the steel plate 30, thereby fixing the cross member 20 between a pair of first frame members 12.

[0167] Next, as shown in FIG. 22( d ), the cross member 20 and the floor portion 40 are joined at the multiple third holes 22 by dissimilar material MIG spot welding using an aluminum MIG welding device 50 .

[0168] Fig. 23 is a cross-sectional view taken along line XXIII-XXIII of Fig. 22(e). As shown in Fig. 22(e) and Fig. 23, the steel MAG welding device 60 line-welds the corner formed by one end face 27 of the cross member 20 and the first side face 75a of the wedge-shaped member 75, and line-welds the corner formed by the second side face 75b of the wedge-shaped member 75 and the protrusion 32 of the steel plate 30. As a result, the steel plate 30 and the cross member 20 are firmly connected via the wedge-shaped member 75.

[0169] Through these steps, the battery case 10 is manufactured. Note that the order of the welding steps may be changed as appropriate.

[0170] As described above, with the battery case 10 of this embodiment, even if the dimensions between the side surfaces 12a of a pair of first frame members 12 at the position where the cross member 20 is connected differ depending on the dimensional accuracy of the frame members 12, it is possible to eliminate problems such as the inability to join the cross member 20 to the steel plate 30 joined to the side surfaces 12a of the first frame members 12. Furthermore, the cross member 20 and the steel plate 30 joined to the side surfaces 12a of the frame members 12 can be reliably joined using the wedge-shaped members 75, thereby improving the strength of the battery case 1.

[0171] Furthermore, the wedge-shaped member 75 has a cross-sectional shape that is solid or has an internal space, so if it is solid, the strength can be increased, and if there is an internal space, the weight can be reduced.

[0172] (First Modification of the Fourth Embodiment) 24(a) to (e) are views for explaining a manufacturing method of a battery case 10 according to a first modified example of the fourth embodiment. In the fourth embodiment (see FIGS. 22(a) to (e)), the first and second ribs 14, 15 were provided on the first frame member 12, and therefore the protrusions 32 were formed on the steel plate 30. However, when the first and second ribs 14, 15 are not provided on the first frame member 12 as in the present embodiment, the protrusions 32 do not need to be provided on the steel plate 30.

[0173] In this case, first, as shown in FIGS. 24(a) and 24(b), the steel plate 30 is welded to the side surface 12a of the first frame member 12 through the first hole 31 by an aluminum MIG welding device 50.

[0174] In addition, the corner formed by the edge of the end face of the second frame member 13 and the side face 12a of the first frame member 12 is line welded by the aluminum MIG welding apparatus 50. In addition, the corner formed by the second rib 15 of the first frame member 12 and the lower face of the second frame member 13 and the upper face of the floor-like portion 40 is also line welded by the aluminum MIG welding apparatus 50.

[0175] 24(c), the cross member 20 is placed on the floor-like portion 40 so that one end surface 27 of the cross member 20 and the steel plate 30 are separated by a gap. Next, a steel wedge-shaped member 75 is inserted from above downward between one end surface 27 of the cross member 20 and the steel plate 30. In this way, the cross member 20 is fixed between the pair of first frame members 12.

[0176] Next, as shown in FIG. 24( d ), the cross member 20 and the floor portion 40 are joined at the multiple third holes 22 by dissimilar material MIG spot welding using an aluminum MIG welding device 50 .

[0177] 24(e), the steel MAG welding device 60 line-welds the corner formed by one end face 27 of the cross member 20 and the first side face 75a of the wedge-shaped member 75, and line-welds the corner formed by the second side face 75b of the wedge-shaped member 75 and the steel plate 30. As a result, the steel plate 30 and the cross member 20 are firmly connected via the wedge-shaped member 75.

[0178] Through these steps, the battery case 10 is manufactured. Note that the order of the welding steps may be changed as appropriate.

[0179] (Second Modification of the Fourth Embodiment) 25(a) to (e) are views for explaining a manufacturing method of a battery case 10 according to a second modified example of the fourth embodiment. In a first modified example of the fourth embodiment, a steel wedge-shaped member 75 is inserted from above downward between one end face 27 of the cross member 20 and the steel plate 30 (FIG. 24(c)). However, as shown in FIG. 25(c), the wedge-shaped member 75 may be inserted between one end face 27 of the cross member 20 and the steel plate 30 in the width direction of the steel plate 30 (upper right to lower left in the figure).

[0180] In this modified example, the wedge-shaped member 75 is inserted in the width direction of the steel plate 30, so that the steel plate 30 is extended in the width direction so that the wedge-shaped member 75 does not interfere with the excess aluminum weld metal WA filled in the first hole 31 of the steel plate 30, and thereby the distance between the first holes 31 formed on both sides of the steel plate 30 in the width direction is extended.

[0181] 25(c), one end face 27 of the cross member 20 in the longitudinal direction is inclined with respect to the width direction of the steel plate 30, i.e., the extending direction of the side surface 12a of the first frame member 12. In other words, one end face 27 of the cross member 20 is an inclined surface that inclines so that the gap with the steel plate 30 becomes smaller from one side in the width direction to the other side (from the upper right to the lower left in the figure).

[0182] Then, the cross member 20 is placed on the floor-like portion 40 so that one end surface 27 of the cross member 20 and the steel plate 30 are separated by a gap. Next, a wedge-shaped member 75 is inserted between one end surface 27 of the cross member 20 and the steel plate 30 from one side in the width direction of the steel plate 30 to the other side (from the upper right to the lower left in the figure).

[0183] The wedge-shaped member 75 has a shape corresponding to the member to be fitted thereto. The wedge-shaped member 75 of this modified example has a first side surface 75a that abuts against one end surface 27 of the cross member 20 and a second side surface 75b that abuts against the steel plate 30. The first side surface 75a is an inclined surface that inclines toward the steel plate 30 as it moves from one side in the width direction of the steel plate 30 to the other side (from the upper right to the lower left in the figure) like the one end surface 27 of the cross member 20. Also, the second side surface 75b is flat like the steel plate 30. In this way, the wedge-shaped member 75 has a wedge shape in which the width in the longitudinal direction of the cross member 20 becomes smaller as it moves from one side in the width direction of the steel plate 30 to the other side (from the upper right to the lower left in the figure).

[0184] Then, the wedge-shaped member 75 is moved from above toward below so as to enter inside in the width direction of the aluminum weld metal WA so as not to interfere with the excess aluminum weld metal WA filled in the first holes 31 on both sides in the width direction of the steel plate 30. Next, the wedge-shaped member 75 is inserted between one end face 27 of the cross member 20 and the steel plate 30 in the width direction of the steel plate 30. In this way, the cross member 20 is fixed between the pair of first frame members 12.

[0185] Next, as shown in FIG. 25( d ), the cross member 20 and the floor portion 40 are joined at the multiple third holes 22 by dissimilar material MIG spot welding using an aluminum MIG welding device 50 .

[0186] 25(e), the steel MAG welding device 60 line-welds the corner formed by one end face 27 of the cross member 20 and the first side surface 75a of the wedge-shaped member 75, and line-welds the corner formed by the second side surface 75b of the wedge-shaped member 75 and the steel plate 30. As a result, the steel plate 30 and the cross member 20 are firmly connected via the wedge-shaped member 75.

[0187] Through these steps, the battery case 10 is manufactured. The order of the welding steps may be changed as appropriate. When wedge-shaped members 75 are inserted between both longitudinal end faces of the cross member 20 and the steel plate 30, the insertion directions of the wedge-shaped members 75 may be the same or reversed.

[0188] Fifth embodiment 26(a) to 26(e) are diagrams for explaining a manufacturing method for a battery case 10 according to a fifth embodiment. As with the third and fourth embodiments, this modification aims to eliminate problems such as the inability to connect the cross member 20 to the side surface 12a of the first frame member 12 even if the dimensions between the side surfaces 12a of the pair of first frame members 12 at the position where the cross member 20 is connected are different.

[0189] In this embodiment, steel plates 30 of different thicknesses are prepared in advance, and a steel plate 30 corresponding to the gap A between the first frame member 12 and the cross member 20 is selected and placed in the gap. Then, the first frame member 12 and the cross member 20 are connected via the steel plate 30. A manufacturing method for the battery case 10 of this embodiment will be described below.

[0190] As shown in FIG. 26(a), in this embodiment, a first frame member 12 that does not have the first and second ribs 14, 15 is used.

[0191] 26(b), the corners formed by the edge of the end face of the second frame member 13 and the side surface 12a of the first frame member 12 are line-welded by the aluminum MIG welding apparatus 50. In addition, the corners formed by the lower surfaces of the first frame member 12 and the second frame member 13 and the upper surface of the floor-like portion 40 are also line-welded by the aluminum MIG welding apparatus 50.

[0192] Next, the flange portion 21 and the floor portion 40 of the cross member 20 are joined by dissimilar material MIG spot welding at the multiple third holes 22 using an aluminum MIG welding device 50. Here, the longitudinal length of the cross member 20 is shorter than the longitudinal length of the second frame member 13, and gaps A are formed between both longitudinal ends of the cross member 20 and the side surfaces 12a of the pair of first frame members 12.

[0193] As shown in Fig. 26(c), a plurality of steel plates 30 with different thicknesses are prepared in advance. Then, as shown in Fig. 26(d), a steel plate 30 having a thickness corresponding to the gap A between the side surface 12a of the first frame member 12 and the cross member 20 is selected, and the steel plate 30 is placed in the gap A. Then, the steel plate 30 is welded to the side surface 12a of the first frame member 12 through the first hole 31 by an aluminum MIG welding device 50.

[0194] 26(e), a steel MAG welding device 60 line-welds a corner formed by one end of the cross member 20 and the steel plate 30. As a result, the first frame member 12 and the cross member 20 are connected via the steel plate 30.

[0195] Through these steps, the battery case 10 is manufactured. Note that the order of the welding steps may be changed as appropriate.

[0196] As described above, according to the battery case 10 of this embodiment, even if the dimension between the side surfaces 12a of a pair of first frame members 12 at the position where the cross member 20 is connected differs depending on the dimensional accuracy of the frame member 12, a steel plate 30 having a thickness corresponding to the gap A between the side surfaces 12a of the first frame member 12 and the cross member 20 is selected and positioned, thereby eliminating problems such as the inability to connect the cross member 20 to the side surfaces 12a of the first frame member 12.

[0197] (First Modification of Fifth Embodiment) 27(a) to (e) are views for explaining a manufacturing method of the battery case 10 according to a modified example of the fifth embodiment.

[0198] 27(a), in this embodiment, a first frame member 12 is used that has first and second ribs 14, 15. Then, a steel plate 30 is inserted into the first groove portion 16 and the second groove portion 17.

[0199] 27(b), an end of the second frame member 13 is abutted against the step portion 12b of the first frame member 12. In addition, an end of the cross member 20 is abutted against the first and second ribs 14, 15.

[0200] 27(c), a corner formed by an edge of the end face of the second frame member 13 and the side surface 12a of the first frame member 12 is line-welded by the aluminum MIG welding device 50. Also, a corner formed by the second rib 15 of the first frame member 12 and the lower surface of the second frame member 13 and the upper surface of the floor-like portion 40 is line-welded by the aluminum MIG welding device 50. Also, the aluminum MIG welding device 50 welds the steel plate 30 to the side surface 12a of the first frame member 12 through the first hole 31.

[0201] Next, the flange portion 21 and the floor portion 40 of the cross member 20 are joined by dissimilar material MIG spot welding using an aluminum MIG welding device 50 at the multiple third holes 22. Here, gaps B are formed between both longitudinal ends of the cross member 20 and the steel plate 30.

[0202] As shown in FIG. 27(d), a plurality of steel plate-shaped members 35 of different thicknesses are prepared in advance. Then, as shown in FIG. 27(d), a plate-shaped member 35 having a thickness corresponding to the gap B between the cross member 20 and the steel plate 30 is selected, and the plate-shaped member 35 is placed in the gap B. Then,

[0203] Fig. 28 shows a cross-sectional view taken along line XXVIII-XXVIII of Fig. 27(e). As shown in Fig. 27(e) and Fig. 28, a steel MAG welding device 60 line-welds a corner formed between one end of the cross member 20 and the plate-shaped member 35, and line-welds a corner formed between the plate-shaped member 35 and the steel plate 30. As a result, the steel plate 30 and the cross member 20 are firmly connected via the plate-shaped member 35.

[0204] Through these steps, the battery case 10 is manufactured. Note that the order of the welding steps may be changed as appropriate.

[0205] As described above, according to the battery case 10 of this embodiment, even if the dimension between the side surfaces 12a of a pair of first frame members 12 at the position where the cross member 20 is connected differs depending on the dimensional accuracy of the frame members 12, a plate-shaped member 35 having a thickness corresponding to the gap B between the steel plate 30 and the cross member 20 is selected and positioned, thereby eliminating problems such as the inability to connect the cross member 20 to the side surface 12a of the first frame member 12.

[0206] Although the battery case according to each embodiment has been described in detail above, the present invention is not limited to the above-mentioned embodiments and modifications, and can be modified, improved, etc., as appropriate. For example, in the fourth or fifth embodiment, the first and second ribs 14, 15 may be plastically deformed toward the steel plate 30 as shown in Figs. 10(b) to (c), and the first frame member 12 may be fastened or welded through the second holes 18 formed in the first and second ribs 14, 15 as shown in Figs. 11(b) to (c) and 12(b) to (c). In addition, the order of the welding steps in each embodiment and modification is not limited to the above-mentioned order, and may be changed as appropriate.

[0207] As described above, the present specification discloses the following:

[0208] (1) a rectangular frame portion; At least one cross member extending toward a pair of parallel wall surfaces of the frame portion so as to divide the inside of the frame portion; Equipped with The frame-shaped portion is made of aluminum or an aluminum alloy, The cross member is made of steel; A battery case in which a steel plate is joined to the wall surface of the frame-shaped portion by welding, The steel plate has a first hole facing the wall surface, The steel plate and the wall surface are joined by welding at the first hole, the first hole is filled with an aluminum or aluminum alloy weld metal; The steel plate and one end of the cross member in the longitudinal direction are joined by welding. A battery case characterized by: According to this configuration, among the components of the battery case, the frame-shaped portion is made of aluminum material, while the cross member is made of steel, so that it is possible to achieve both weight reduction and cost reduction. In addition, since the steel plate is welded to the wall surface of the frame-shaped portion, and then the cross member is welded to the steel plate, the cross member can be firmly fixed to the frame-shaped portion via the steel plate. In addition, the steel plate and the aluminum frame portion can be reliably joined by welding through the first hole.

[0209] (2) A first rib and a second rib are provided on the upper and lower parts of the wall surface, The first rib has a first base portion extending from the wall surface toward the cross member and a first protruding portion protruding downward from a tip end of the first base portion, A first groove is defined between the wall surface, the first base portion, and the first protruding portion, The second rib has a second base portion extending from the wall surface toward the cross member and a second protruding portion protruding upward from a tip of the second base portion, A second groove is defined between the wall surface, the second base portion, and the second protruding portion, The steel plate is disposed in the first groove portion and the second groove portion. A battery case according to any one of (1). This configuration can prevent the steel plate welded to the wall surface from peeling off.

[0210] (3) A protrusion protruding toward the cross member is formed on the steel plate between the first protruding portion and the second protruding portion, The protrusion and the one end of the cross member in the longitudinal direction are joined by welding. (2) A battery case as described in (1). According to this configuration, even if the first rib and the second rib are provided, the cross member and the steel plate can be joined by welding via the protrusion.

[0211] (4) A convex portion that protrudes toward the steel plate is formed between the first protruding portion and the second protruding portion at the one end portion in the longitudinal direction of the cross member, The protrusion and the steel plate are joined by welding. (2) A battery case as described in (1). According to this configuration, even if the first rib and the second rib are provided, the cross member and the steel plate can be joined by welding via the convex portion.

[0212] (5) The steel plate is formed with a bracket portion extending toward the cross member, the bracket portion has an outer surface that can come into contact with an inner surface of the cross member and is relatively slidable inside the cross member; The cross member has an opening facing the outer surface of the bracket portion disposed therein, The bracket portion and the cross member are joined by welding at the opening. A battery case as described in (1) or (2). This configuration makes it possible to eliminate problems such as the inability to join the cross member to the steel plate joined to the wall surfaces even if the dimensions between the pair of wall surfaces at the position where the cross member is connected differ due to the dimensional accuracy of the frame-shaped portion. Furthermore, the cross member and the steel plate joined to the wall surfaces can be reliably joined using the bracket portion, thereby improving the strength of the battery case.

[0213] (6) The steel plate is formed with a bracket portion extending toward the cross member, the bracket portion has an inner surface capable of abutting against an outer surface of the cross member and is capable of sliding relatively on the outer surface of the cross member; The bracket portion and the cross member are joined by welding. A battery case as described in (1) or (2). This configuration makes it possible to eliminate problems such as the inability to join the cross member to the steel plate joined to the wall surfaces even if the dimensions between the pair of wall surfaces at the position where the cross member is connected differ due to the dimensional accuracy of the frame-shaped portion. Furthermore, the cross member and the steel plate joined to the wall surfaces can be reliably joined using the bracket portion, thereby improving the strength of the battery case.

[0214] (7) One end surface of the cross member in the longitudinal direction is inclined with respect to the height direction of the steel plate or the extending direction of the wall surface, A steel wedge-shaped member is disposed between the one end surface of the cross member and the steel plate, The wedge-shaped member is joined to the cross member and the steel plate by welding. A battery case according to any one of (1) to (3). This configuration makes it possible to eliminate problems such as the inability to join the cross member to the steel plate joined to the wall surface even if the dimension between the pair of wall surfaces at the position where the cross member is connected differs due to the dimensional accuracy of the frame-shaped portion. Furthermore, the cross member and the steel plate joined to the wall surface can be reliably joined using the wedge-shaped member, thereby improving the strength of the battery case.

[0215] (8) The device further includes a floor portion connected to the frame portion and constituting a floor surface, The floor portion is made of aluminum or an aluminum alloy, The cross member and the floor portion are joined by welding. A battery case according to any one of (1) to (7). According to this configuration, the frame and floor of the battery case are made of aluminum, while the cross member is made of steel, making it possible to achieve both weight reduction and cost reduction. Furthermore, the cross member and the floor are firmly joined by welding.

[0216] (9) The cross member has a flange portion extending along the floor portion, The flange portion is formed with a third hole facing the floor portion, The flange portion and the floor portion are joined by welding at the third hole, The third hole is filled with an aluminum or aluminum alloy weld metal. (8) A battery case as described in (8). With this configuration, the cross member, which is made of steel, and the floor portion, which is made of aluminum material, can be reliably joined by welding through the third hole.

[0217] (10) a rectangular frame portion; At least one cross member extending toward a pair of parallel wall surfaces of the frame portion so as to divide the inside of the frame portion; Equipped with The frame-shaped portion is made of aluminum or an aluminum alloy, The cross member is made of steel; A manufacturing method of a battery case in which a steel plate is joined to the wall surface of the frame-shaped portion by welding, The steel plate has a first hole facing the wall surface, The first hole is filled with a weld metal of aluminum or an aluminum alloy to join the steel plate and the wall surface; The steel plate and one end of the cross member in the longitudinal direction are joined by welding. A manufacturing method of a battery case comprising the steps of: According to this configuration, among the components of the battery case, the frame-shaped portion is made of aluminum material, while the cross member is made of steel, so that it is possible to achieve both weight reduction and cost reduction. In addition, since the steel plate is welded to the wall surface of the frame-shaped portion, and then the cross member is welded to the steel plate, the cross member can be firmly fixed to the frame-shaped portion via the steel plate.

[0218] (11) A first rib and a second rib are provided on the upper and lower parts of the wall surface, The first rib has a first base portion extending from the wall surface toward the cross member and a first protruding portion protruding downward from a tip end of the first base portion, A first groove is defined between the wall surface, the first base portion, and the first protruding portion, The second rib has a second base portion extending from the wall surface toward the cross member and a second protruding portion protruding upward from a tip of the second base portion, A second groove is defined between the wall surface, the second base portion, and the second protruding portion, The steel plate is placed in the first groove portion and the second groove portion. A method for manufacturing the battery case according to (10). This configuration can prevent the steel plate welded to the wall surface from peeling off.

[0219] (12) The steel plate is fixed to the first groove portion and the second groove portion by plastically deforming the first protruding portion and the second protruding portion toward the steel plate. A method for manufacturing the battery case according to (11). According to this configuration, the steel plate can be prevented from moving in the first groove portion and the second groove portion, and the steel plate can be reliably fixed to the frame-shaped portion.

[0220] (13) A second hole facing the steel plate is formed in each of the first protruding portion and the second protruding portion, A fastening member is fastened toward the steel plate through the second hole to fix the steel plate to the first groove portion and the second groove portion. A method for manufacturing the battery case according to (11). According to this configuration, the steel plate can be prevented from moving in the first groove portion and the second groove portion, and the steel plate can be reliably fixed to the frame-shaped portion.

[0221] (14) A second hole facing the steel plate is formed in each of the first protruding portion and the second protruding portion, The first protruding portion and the second protruding portion are joined to the steel plate by welding at the second hole, thereby fixing the steel plate to the first groove portion and the second groove portion. A method for manufacturing the battery case according to (11). According to this configuration, the steel plate can be prevented from moving in the first groove portion and the second groove portion, and the steel plate can be reliably fixed to the frame-shaped portion.

[0222] (15) The steel plate is formed with a bracket portion extending toward the cross member, the bracket portion has an outer surface that can come into contact with an inner surface of the cross member and is relatively slidable inside the cross member; The cross member has an opening facing the outer surface of the bracket portion disposed therein, The bracket portion and the cross member are joined by welding at the opening. A method for manufacturing a battery case according to any one of (10) to (14). This configuration makes it possible to eliminate problems such as the inability to join the cross member to the steel plate joined to the wall surfaces even if the dimensions between the pair of wall surfaces at the position where the cross member is connected differ due to the dimensional accuracy of the frame-shaped portion. Furthermore, the cross member and the steel plate joined to the wall surfaces can be reliably joined using the bracket portion, thereby improving the strength of the battery case.

[0223] (16) The steel plate is formed with a bracket portion extending toward the cross member, the bracket portion has an inner surface capable of abutting against an outer surface of the cross member and is capable of sliding relatively on the outer surface of the cross member; The bracket portion and the cross member are joined by welding. A method for manufacturing a battery case according to any one of (10) to (14). This configuration makes it possible to eliminate problems such as the inability to join the cross member to the steel plate joined to the wall surfaces even if the dimensions between the pair of wall surfaces at the position where the cross member is connected differ due to the dimensional accuracy of the frame-shaped portion. Furthermore, the cross member and the steel plate joined to the wall surfaces can be reliably joined using the bracket portion, thereby improving the strength of the battery case.

[0224] (17) a step of assembling the bracket portion of the steel plate to at least one end of the cross member; a step of placing the cross member to which the bracket portion is attached relative to the frame-shaped portion; a step of joining the bracket portion to the cross member by welding; a step of joining the steel plate to the wall surface of the frame-shaped portion by welding; The method for manufacturing a battery case according to (15) or (16), comprising: According to this configuration, the cross member can be firmly fixed to the frame-like portion via the steel plate.

[0225] (18) After the steel plate is joined to the wall surface of the frame-shaped portion by welding, the steel plate is joined to one end of the cross member in the longitudinal direction by welding. A method for manufacturing a battery case according to any one of (10) to (14). According to this configuration, the cross member can be firmly fixed to the frame-like portion via the steel plate.

[0226] (19) After the steel plate and one end of the cross member in the longitudinal direction are joined by welding, the steel plate is joined to the wall surface of the frame-shaped portion by welding. A method for manufacturing a battery case according to any one of (10) to (14). According to this configuration, the cross member can be firmly fixed to the frame-like portion via the steel plate.

[0227] (20) One end surface of the cross member in the longitudinal direction is inclined with respect to the height direction of the steel plate or the extending direction of the wall surface, A steel wedge-shaped member is disposed between the one end surface of the cross member and the steel plate, The wedge-shaped member is joined to the cross member and the steel plate by welding. A method for manufacturing a battery case according to any one of (10) to (14). This configuration makes it possible to eliminate problems such as the inability to join the cross member to the steel plate joined to the wall surface even if the dimension between the pair of wall surfaces at the position where the cross member is connected differs due to the dimensional accuracy of the frame-shaped portion. Furthermore, the cross member and the steel plate joined to the wall surface can be reliably joined using the wedge-shaped member, thereby improving the strength of the battery case.

[0228] (21) The steel plate having a thickness corresponding to the gap between the wall surface of the frame portion and the cross member is selected, and the steel plate is disposed in the gap. A method for manufacturing the battery case according to (10). With this configuration, even if the dimensions between a pair of wall surfaces at the position where the cross member is connected differ depending on the dimensional accuracy of the frame-shaped portion, a steel plate having a thickness corresponding to the gap between the wall surfaces and the cross member is selected and positioned, thereby eliminating problems such as the inability to connect the cross member to the wall surface.

[0229] (22) A plate-like member having a thickness corresponding to the gap between the cross member and the steel plate is selected, and the plate-like member is disposed in the gap. A method for manufacturing a battery case according to any one of (11) to (14). With this configuration, even if the dimensions between a pair of wall surfaces at the position where the cross member is connected differ depending on the dimensional accuracy of the frame-shaped portion, a plate-shaped member having a thickness corresponding to the gap between the steel plate and the cross member is selected and positioned, thereby eliminating problems such as the inability to connect the cross member to a wall surface. [Explanation of symbols]

[0230] 10 Battery case 11 Frame-shaped part 12 First frame member 12a Side (wall) 12b, 12c Stepped section 13 Second frame member 14 First Rib 14a First base 14b First protrusion 15 Second Rib 15a Second base 15b Second protrusion 16 First groove 17 Second groove 18 Second hole 20 Cross member 21 Flange 22 Third hole 23 Convex 24 Side (outer surface) 25 Opening 25a Edge 26 Top side 27 One end face 30 steel plate 30a steel plate piece 31 First hole 32 Protrusion 33 Bracket part 33a Exterior 33b Inside 35 Plate-shaped members 36,37 board 40 Floor part 50 Aluminum MIG welding equipment 60 Steel MAG welding equipment 70 Hammer 71 Bolts (fastening members) 75 Wedge-shaped member 75a First aspect 75b Second aspect 76 Through hole 80 Joint auxiliary parts 81 Insertion section 83 Non-insertion part 85 Hollow part 90 Dissimilar material arc spot welding equipment A,B gap G Shielding gas H-Gap S void WA Aluminum Welding Metal WA1 Shaft WA2 head WA3 flange WS steel weld metal

Claims

1. A rectangular frame portion, At least one cross member extending toward a pair of parallel wall surfaces of the frame portion so as to divide the inside of the frame portion; Equipped with The frame-shaped portion is made of aluminum or an aluminum alloy, The cross member is made of steel; A battery case in which a steel plate is joined to the wall surface of the frame-shaped portion by welding, The steel plate has a first hole facing the wall surface, The steel plate and the wall surface are joined by welding at the first hole, the first hole is filled with an aluminum or aluminum alloy weld metal; The steel plate and one end of the cross member in the longitudinal direction are joined by welding. A battery case characterized by:

2. A first rib and a second rib are provided on the upper and lower parts of the wall surface, The first rib has a first base portion extending from the wall surface toward the cross member and a first protruding portion protruding downward from a tip end of the first base portion, A first groove is defined between the wall surface, the first base portion, and the first protruding portion, The second rib has a second base portion extending from the wall surface toward the cross member and a second protruding portion protruding upward from a tip of the second base portion, A second groove is defined between the wall surface, the second base portion, and the second protruding portion, The steel plate is disposed in the first groove portion and the second groove portion. The battery case according to claim 1 .

3. A protrusion portion protruding toward the cross member is formed on the steel plate between the first protruding portion and the second protruding portion, The protrusion and the one end of the cross member in the longitudinal direction are joined by welding. The battery case according to claim 2.

4. A convex portion protruding toward the steel plate is formed between the first protruding portion and the second protruding portion at one end of the cross member in the longitudinal direction, The protrusion and the steel plate are joined by welding. The battery case according to claim 2.

5. The steel plate is formed with a bracket portion extending toward the cross member, the bracket portion has an outer surface that can come into contact with an inner surface of the cross member and is relatively slidable inside the cross member; The cross member has an opening facing the outer surface of the bracket portion disposed therein, The bracket portion and the cross member are joined by welding at the opening. The battery case according to claim 1 or 2.

6. The steel plate is formed with a bracket portion extending toward the cross member, the bracket portion has an inner surface capable of abutting against an outer surface of the cross member and is capable of sliding relatively on the outer surface of the cross member; The bracket portion and the cross member are joined by welding. The battery case according to claim 1 or 2.

7. One end surface of the cross member in the longitudinal direction is inclined with respect to the height direction of the steel plate or the extension direction of the wall surface, A steel wedge-shaped member is disposed between the one end surface of the cross member and the steel plate, The battery case according to any one of claims 1 to 3, wherein the wedge-shaped member is joined to the cross member and the steel plate by welding.

8. The floor portion is connected to the frame portion and forms a floor surface. The floor portion is made of aluminum or an aluminum alloy, The cross member and the floor portion are joined by welding, The cross member has a flange portion extending along the floor portion, The flange portion is formed with a third hole facing the floor portion, The flange portion and the floor portion are joined by welding at the third hole, The battery case according to any one of claims 1 to 7, wherein the third hole is filled with a weld metal of aluminum or an aluminum alloy.

9. A rectangular frame portion, At least one cross member extending toward a pair of parallel wall surfaces of the frame portion so as to divide the inside of the frame portion; Equipped with The frame-shaped portion is made of aluminum or an aluminum alloy, The cross member is made of steel; A manufacturing method of a battery case in which a steel plate is joined to the wall surface of the frame-shaped portion by welding, The steel plate has a first hole facing the wall surface, The first hole is filled with a weld metal of aluminum or an aluminum alloy to join the steel plate and the wall surface; The steel plate and one end of the cross member in the longitudinal direction are joined by welding. A manufacturing method of a battery case comprising the steps of:

10. A first rib and a second rib are provided on the upper and lower parts of the wall surface, The first rib has a first base portion extending from the wall surface toward the cross member and a first protruding portion protruding downward from a tip end of the first base portion, A first groove is defined between the wall surface, the first base portion, and the first protruding portion, The second rib has a second base portion extending from the wall surface toward the cross member and a second protruding portion protruding upward from a tip of the second base portion, A second groove is defined between the wall surface, the second base portion, and the second protruding portion, The steel plate is placed in the first groove portion and the second groove portion. A method for manufacturing the battery case according to claim 9.

11. The steel plate is fixed to the first groove portion and the second groove portion by plastically deforming the first protruding portion and the second protruding portion toward the steel plate. The method for manufacturing the battery case according to claim 10.

12. A second hole facing the steel plate is formed in each of the first protruding portion and the second protruding portion, A fastening member is fastened toward the steel plate through the second hole to fix the steel plate to the first groove portion and the second groove portion. The method for manufacturing the battery case according to claim 10.

13. The steel plate is formed with a bracket portion extending toward the cross member, the bracket portion has an outer surface that can come into contact with an inner surface of the cross member and is relatively slidable inside the cross member; The cross member has an opening facing the outer surface of the bracket portion disposed therein, The bracket portion and the cross member are joined by welding at the opening. A method for manufacturing the battery case according to any one of claims 9 to 12.

14. The steel plate is formed with a bracket portion extending toward the cross member, the bracket portion has an inner surface capable of abutting against an outer surface of the cross member and is capable of sliding relatively on the outer surface of the cross member; The bracket portion and the cross member are joined by welding. A method for manufacturing the battery case according to any one of claims 9 to 12.

15. a step of assembling the bracket portion of the steel plate to at least one end of the cross member; a step of placing the cross member to which the bracket portion is attached relative to the frame-shaped portion; a step of joining the bracket portion to the cross member by welding; a step of joining the steel plate to the wall surface of the frame-shaped portion by welding; The method for manufacturing a battery case according to claim 13 or 14, comprising:

16. a steel plate having a thickness corresponding to a gap between the wall surface of the frame portion and the cross member is selected, and the steel plate is disposed in the gap; A method for manufacturing the battery case according to claim 9.

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