Battery-pack enclosure and method for producing battery-pack enclosure

Abstract

A battery-pack enclosure according to the present invention is a battery-pack enclosure 1 that is mounted under the floor of a vehicle body and that is constituted by a steel sheet, the battery-pack enclosure 1 comprising: a body 2 that is constituted by a bottomed frame having a pair of side walls 11, 12 which face each other in the vehicle width direction; and a cross member 3 that extends in the vehicle width direction so as to reach the pair of side walls 11, 12 inside the body 2, wherein the body 2 has a structure in which side surface members forming the side walls 11, 12 and a bottom surface member forming the bottom 15 of the body 2 are integrated together, the side walls 11, 12 extend in the vehicle height direction, the inner surfaces of the side surfaces 11, 12 are formed as vertical surfaces along the vehicle height direction, and the cross member 3 is bonded to the side walls 11, 12 in the state in which the ends of the cross member 3 in the vehicle width direction continuously abut the inner surfaces of the side walls 11, 12 in the vehicle height direction.

Description

Battery Case and Method for Manufacturing Battery Case

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

[0002] In order to achieve carbon neutrality, the electrification of transportation equipment is progressing. In electric vehicles, it is required to install a large-capacity battery in order to increase the cruising range. A battery case that houses a large-capacity battery becomes large in size. Therefore, in order to secure a large space in the vehicle interior, many electric vehicles mount the battery case below the floor panel.

[0003] In addition, electric vehicles need to have members and structures for protecting the battery so that the battery can be protected during a collision. As an important performance of the battery case, high collision strength for protecting the internal battery is required. In existing electric vehicles, as a structure for protecting the battery, a frame style in which the side surface of the battery case is constituted by an aluminum alloy extrusion member is often seen.

[0004] However, in the aluminum frame type battery case, the material cost is high compared to the case where it is made of automotive steel sheets that occupy a large part as the material of the vehicle body. In addition, there is a demerit that the number of joining steps for assembling the frames is large. Therefore, Patent Document 1 and Patent Document 2 disclose that a battery case made of a steel sheet with a cost lower than that of aluminum is configured. In an all steel structure, a structure in which a battery and an electrical component are housed in a tray formed from a single steel sheet is mainstream.

[0005] Japanese Unexamined Patent Application Publication No. 2017-226353, Japanese Unexamined Patent Application Publication No. 2019-202747

[0006] In a battery case with a tray formed from a single sheet of steel, if the tray is manufactured by deep drawing, the side walls of the tray will be sloped rather than vertical. Furthermore, the portion continuing from the side walls to the bottom of the tray will always have a fillet geometry cross-section. Since batteries are usually rectangular in shape, they cannot be mounted in the vicinity of the side walls inside the battery case, making it impossible to effectively utilize the internal space of the battery case and maximize battery capacity.

[0007] Furthermore, to improve the side impact performance of the battery case, in order to prevent collision loads from the side walls from being transmitted to the battery, reinforcing members such as cross members installed inside the tray need to be fixed to the sloped side walls. One method of fixing this is to use brackets, but this leads to an increase in the number of components. Alternatively, one method is to butt the cross members against the side walls and fix them with continuous welding, but because the side walls are sloped, the cost of trimming the ends of the cross members at an angle and the welding costs increase.

[0008] The present invention has been made to solve the above problems, and aims to provide a battery case and a method for manufacturing a battery case in which an internal cross member can be fixed to the side wall of a tray having a steel plate tray.

[0009] The battery case according to the present invention is a steel plate battery case that is mounted under the floor of a vehicle body to house a battery, and comprises a main body consisting of a frame structure with a bottom having a pair of side walls that face each other in the vehicle width direction when mounted on the vehicle body, and a cross member that extends in the vehicle width direction so as to span the pair of side walls inside the main body and reinforces the main body, wherein the main body has a structure in which a side member that forms the side wall and a bottom member that forms the bottom of the main body are integrated, the side wall is integrated with the bottom member so as to extend along the vehicle height direction when mounted on the vehicle body, the inner surface of the side wall is formed as a vertical surface along the vehicle height direction, and the cross member is joined to the side wall with its end in the vehicle width direction in continuous contact with the inner surface of the side wall in the vehicle height direction.

[0010] In the battery case according to the present invention, the main body has a projection (protrusion area) that protrudes from the inner surface of the side wall in the vehicle width direction for positioning and fixing the cross member, and the cross member is fixed to the side wall in a position determined by the projection.

[0011] In the battery case according to the present invention, the side member is formed of a steel plate, and the projection is formed of a separate material from the side member and attached to the side wall.

[0012] In the battery case according to the present invention, the side member is formed of a steel plate, and the projection is formed by the side member and is a portion that protrudes in the vehicle width direction from the inner surface.

[0013] In the battery case according to the present invention, the projection is preferably formed by bending the inside of a slit provided in the side member in the vehicle width direction.

[0014] In the battery case according to the present invention, the side member has a structure in which a plurality of side members are joined in the front-rear direction of the vehicle, and the projection is preferably an L-shaped portion extending in the vehicle width direction from the end of the portion where the side members are joined together.

[0015] In the battery case according to the present invention, the projection is preferably a portion formed by bending the steel plate and protruding from the inner surface in the vehicle width direction.

[0016] In the battery case according to the present invention, the projection is preferably a portion formed on the side member by press working.

[0017] In the battery case according to the present invention, the cross member has a fixing portion that is positioned and fixed to the projection, and the fixing portion is preferably joined to the projection by welding after sliding from above in the vehicle height direction and being positioned on the projection.

[0018] In the battery case according to the present invention, it is preferable that the cross member has its end in the vehicle width direction continuously joined to the side wall by welding.

[0019] The present invention relates to a method for manufacturing a battery case, which is a steel plate battery case mounted under the floor of a vehicle body and houses a battery, and includes an integration step of integrating a bottom member that forms the bottom of a tray and a side member that forms a pair of side walls facing each other in the vehicle width direction when mounted on the vehicle body, such that the side walls are perpendicular to the bottom; an arrangement step of arranging a cross member that reinforces the tray inside the tray such that the cross member extends across the pair of side walls inside the tray; and a joining step of joining both ends of the cross member that is arranged inside the tray to the pair of side walls.

[0020] In the battery case manufacturing method according to the present invention, the arrangement step may include a step of positioning and fixing the cross member by a projection that protrudes from the inner surface of the side wall in the vehicle width direction.

[0021] In the battery case manufacturing method according to the present invention, the joining step may include a step of continuously joining both ends of the cross member to the side wall by welding.

[0022] According to the present invention, since the internal cross member is fixed to the side wall of the tray, the battery case has excellent side impact resistance when mounted on an electric vehicle. Furthermore, because the side wall is a vertical surface, the volume that can accommodate the battery inside the battery case is larger compared to the case with a sloped surface. In addition, a battery case made of steel plate can be made more cost-effective compared to one made of aluminum.

[0023] Figure 1 is a diagram showing the overall configuration of the battery case in the embodiment. Figure 2 is an exploded view illustrating the structure of the battery case. Figure 3 is a diagram illustrating the state in which the battery is housed in the tray. Figure 4 is a diagram illustrating the state in which the projection is attached to the inner surface of the side wall. Figure 5 is a diagram illustrating the state in which the cross member is joined to the projection. Figure 6 is a diagram illustrating the method of joining the cross member and the projection. Figure 7 is a diagram illustrating that the cross member is continuously joined to the side wall. Figure 8 is a diagram illustrating the structure of the projection in the first modified example. Figure 9 is a diagram illustrating the state in which the cross member is joined to the projection in the first modified example. Figure 10 is a diagram illustrating the structure of the projection in the second modified example. Figure 11 is a diagram illustrating the structure of the side member in the third modified example. Figure 12 is a diagram illustrating the structure of the projection in the third modified example. Figure 13 is a diagram illustrating the structure of the projection in the fourth modified example.

[0024] Hereinafter, with reference to the drawings, a battery case and a method for manufacturing the battery case in an embodiment of the present invention will be specifically described. The components in the embodiments shown below include those that are substituted and easily replaceable by those skilled in the art, or that are substantially identical.

[0025] Figure 1 shows the overall configuration of the battery case in the embodiment. The battery case 1 is a battery case made of steel plate. The battery case 1 comprises a main body 2 that houses the battery, a cross member 3 provided inside the main body 2, and a side frame 4 provided outside the main body 2.

[0026] The battery case 1 is the case portion of the battery pack and houses multiple batteries inside. The battery case 1 has a structure in which the main body 2, cross member 3, and side frame parts 4 are integrated. The battery case 1 is mounted on an electric vehicle with batteries housed inside. Electric vehicles are electric vehicles and plug-in hybrid vehicles. Electric vehicles are equipped with a battery pack to supply power to the motor. In this description, the structure and arrangement may be described using the orientation of the battery case 1 when it is mounted on an electric vehicle. The front and rear of the vehicle are referred to as the front and rear sides. The left and right sides are referred to as the left and right sides in the vehicle width direction. When viewing an electric vehicle from the rear to the front, the left side is the left side in the vehicle width direction, and the right side in that case is the right side in the vehicle width direction. The upper and lower sides are referred to as the upper and lower sides in the vehicle height direction.

[0027] The main body 2 is the main body of the battery case 1. The battery is housed inside the main body 2 and mounted on the electric vehicle. The internal space of the main body 2 becomes the battery housing chamber that houses the battery. The main body 2 has a tray 10 made of a bottomed frame and a cover that closes the upper opening of the tray 10. In Figure 1, etc., the cover is not shown. The tray 10 has a pair of side walls 11 and 12 that face each other in the vehicle width direction when mounted on the vehicle body, a front wall 13 and a rear wall 14 that face each other in the vehicle front-rear direction, and a rectangular bottom 15. The side walls 11 and 12 form the sides of the tray 10. The pair of side walls 11 and 12 have a symmetrical structure. The front wall 13 forms the front of the tray 10. The rear wall 14 forms the rear of the tray 10. The bottom 15 forms the bottom of the tray 10. The main body 2 has a structure in which the tray 10 and the cover are integrated. The upper part of the tray 10 is where the cover is attached, and is a flange portion formed in the shape of a rectangular frame. The cover is attached to the flange portion of the tray 10 by bolts or the like so as to cover the upper opening of the tray 10. The battery case 1 is formed into a structure that increases the rigidity of the main body 2 by the cross member 3 and side frame 4 which are integrated with the main body 2. The cross member 3 and side frame 4 are fixed to the tray 10.

[0028] The cross member 3 is a reinforcing member positioned inside the tray 10 to reinforce the main body 2. The cross member 3 is fixed to the inner surface of the tray 10. The cross member 3 is integrated with the tray 10 to reinforce the tray 10. The cross member 3 is provided so as to span a pair of opposing side walls 11 and 12 in the vehicle width direction, and both ends in the vehicle width direction are joined to the side walls 11 and 12. Multiple cross members 3 are arranged at predetermined intervals in the vehicle longitudinal direction. In the example shown in Figure 1, three cross members 3 are provided inside the tray 10, arranged at equal intervals in the vehicle longitudinal direction. Each of the three cross members 3 extends along the vehicle width direction so as to span the left and right side walls 11 and 12. The cross member 3 extends along the vehicle width direction inside the tray 10 and receives loads in the vehicle width direction that are input to the main body 2 from outside the main body 2 and act on the tray 10.

[0029] The side frame 4 is a reinforcing member positioned outside the tray 10 and reinforces the main body 2. The side frame 4 is fixed to the outer surface of the tray 10. The side frame 4 is integrated with the tray 10 to reinforce it. The side frame 4 is fixed to the outer surface of the tray 10. The side frame 4 extends along the longitudinal direction of the vehicle and faces the outer surfaces of the side walls 11 and 12 in the vehicle width direction. Two side frames 4 are arranged so as to sandwich the tray 10 from both sides in the vehicle width direction. The battery case 1 comprises a left side frame 4 attached to the outer surface of the side wall 11 and a right side frame 4 attached to the outer surface of the side wall 12. The side frame 4 extends along the longitudinal direction of the vehicle outside the tray 10 and receives loads in the vehicle width direction that are input to the tray 10 from outside the main body 2.

[0030] The side frame 4 is constructed from a steel plate structure. The side frame 4 includes multiple bends that extend along the longitudinal direction of the vehicle, formed by repeatedly folding the steel plate in mountain and / or valley directions. Because the side frame 4 has multiple cross-sections that extend in the vehicle width direction, it has high bending rigidity against loads applied from the outside in the vehicle width direction. In other words, the side frame 4 has high load-bearing capacity against side impact loads from the vehicle width direction. This can increase the resistance to collision loads applied to the battery case 1 through the side sill during a side collision of an electric vehicle.

[0031] In electric vehicles equipped with a battery case 1, it is necessary to withstand the collision load transmitted to the battery case 1 via the vehicle body during a collision and protect the battery inside the battery case 1. A structure capable of protecting the battery is one that prevents the tray 10, which is deformed by the collision load, from coming into contact with the battery. To prevent the collision load from being transmitted to the battery, the cross member 3 inside the tray 10 is fixed to the inner surface of the side walls 11 and 12. However, in conventional battery cases with a drawn steel plate structure, since the tray is manufactured by drawing a single steel plate, the side walls cannot be formed into 90° vertical walls, and a fillet shape is required, resulting in excess space in the vicinity of the side walls when a rectangular battery is mounted on the tray. To increase the driving range, it is desirable to make more effective use of the internal space of the tray to increase the battery capacity. Also, if the inner surface of the side wall is an inclined surface, the cross member will be butted against the inclined surface and continuously welded, so the ends of the cross member must be trimmed at an angle, which increases costs. Therefore, in the battery case 1, the tray 10 is not formed from a single sheet of steel that has been drawn into shape. Instead, the bottom portion 15 and the side walls 11 and 12 are made from separate materials, and the cross members 3 are directly joined to the side walls 11 and 12. In the battery case 1, the bottom surface and left and right sides of the tray 10 are made from separate materials, and the battery housing chamber formed by the bottom surface, left and right sides, and front and rear sides of the tray 10 is divided by the cross members 3 fixed to the left and right sides.

[0032] As shown in Figure 2, the tray 10 has a bottom member 21 that forms the bottom 15 and side members 22 that form the side walls 12. In Figure 2, only the right side member 22 that forms the side wall 12 is shown, but the tray 10 also has a side member 22 that forms the left side wall 11. In Figure 2, the left side member 22 is omitted. The tray 10 has a structure in which two side members 22, 22 are integrated into a single bottom member 21. Regarding the pair of side walls 11, 12, the description of the right side wall 12 may be given, and the description of the left side wall 11 may be omitted. The same applies to the left side member 22 and the right side member 22.

[0033] The bottom member 21 is made of a single steel plate. The bottom member 21 is a steel plate member that forms the front wall portion 13, the rear wall portion 14, and the bottom portion 15, and is formed in a rectangular shape. The front wall portion 13 and the rear wall portion 14 are erected vertically from the ends of the bottom portion 15 in the vehicle's front-rear direction upward in the vehicle's height direction. The front wall portion 13 and the rear wall portion 14 extend along the vehicle's width direction.

[0034] Furthermore, the bottom member 21 has a fixing portion 23 that is joined to the side member 22. The fixing portion 23 includes a left fixing portion that is joined to the side member 22 that forms the left side wall portion 11, and a left fixing portion that is joined to the side member 22 that forms the right side wall portion 12. The fixing portion 23 is erected vertically from the end of the bottom portion 15 in the vehicle width direction upward in the vehicle height direction. The fixing portion 23 extends along the vehicle's longitudinal direction. The height of the fixing portion 23 is lower than the front wall portion 13 and the rear wall portion 14.

[0035] The side member 22 is made of a single steel plate. The side member 22 has a flat surface that forms the inner surface 12a of the side wall portion 12. The inner surface 12a is the surface that faces the vehicle width direction inside the tray 10 and is a vertical surface aligned with the vehicle height direction. The upper part 22a of the side member 22 is the part that forms the flange portion of the tray 10. The lower part 22b of the side member 22 is the part that is joined to the fixing portion 23 of the bottom member 21. The side member 22 is joined to the bottom member 21 such that its inner surface is a vertical surface.

[0036] As shown in Figure 3, the fixing portion 23 is positioned outward in the vehicle width direction from the lower portion 22b and is joined to the lower portion 22b by a welded portion 24 and adhesive. The welded portion 24 is formed by spot welding. Adhesive is interposed between the fixing portion 23 and the lower portion 22b. A sealing material 25 is provided at the joint between the fixing portion 23 and the lower portion 22b. The sealing material 25 is a member that seals the space between the bottom member 21 and the side member 22 and is provided along the longitudinal direction of the vehicle.

[0037] As shown in Figure 3, with the side member 22 joined to the bottom member 21, the inner surface 12a of the side wall portion 12 is formed as a vertical surface. The bottom surface 15a of the bottom portion 15 is formed as a horizontal surface. The battery 100 is bonded to the bottom surface 15a with a highly thermally conductive adhesive 101. The battery 100 is placed on the bottom surface 15a and positioned within the vicinity of the inner surface 12a. Although the inner surface 12a faces the battery 100, it does not contact the battery 100. The positional relationship between the side member 22 and the battery 100 is the same for the side wall portion 11 as for the side wall portion 12. This prevents the creation of excess space in the vicinity of the side wall portion 11 and the vicinity of the side wall portion 12.

[0038] The end portion 30 of the cross member 3 is joined to the inner surface of the side wall portion 11 and the inner surface 12a of the side wall portion 12 by welding. As shown in Figure 2, a projection 26 for positioning and fixing the cross member 3 is provided on the inside of the side member 22.

[0039] The projection 26 is made of a separate component from the side member 22. The projection 26 is made of a steel plate. The inner surface of the side member 22 is provided with a recess 12b to which the projection 26 is attached. The recess 12b is formed in a shape that is recessed more than the inner surface 12a of the side wall 12. Multiple recesses 12b are formed on the side wall 12 at predetermined intervals in the vehicle's longitudinal direction. The position of the cross member 3 in the vehicle's longitudinal direction is determined by the projection 26.

[0040] As shown in Figure 4, the projection 26 is joined to the recess 12b by a welded portion 27. The welded portion 27 is formed by spot welding. The projection 26 includes a fixed portion joined to the recess 12b of the side wall portion 12 and a projection portion that protrudes inward in the vehicle width direction from the inner surface 12a of the side wall portion 12. The projection portion of the projection 26 extends in the vehicle height direction and has a flat surface facing the vehicle front-rear direction. As shown in Figure 5, the projection 26 is joined to the cross member 3 by a welded portion 28. The welded portion 28 is formed by spot welding or laser beam welding. The cross member 3 is joined to the projection 26 by the welded portion 28 while positioned relative to the projection 26.

[0041] As shown in Figure 6, the cross member 3 is welded to the projection 26, positioned to sandwich it from both sides in the front-rear direction of the vehicle. The cross member 3 has a fixing portion 31 that is joined to the projection 26. The fixing portion 31 has a surface for joining to the projection 26 in accordance with its shape.

[0042] The cross member 3 has a vertical wall portion 32 and a flange portion 33. The vertical wall portion 32 is a pair of wall portions formed front and rear. The fixing portion 31 is formed in a shape that is recessed from the vertical wall portion 32 in the front-rear direction of the vehicle. The flange portion 33 is the part that is joined to the bottom portion 15. As shown in Figure 4, the cross member 3 is slid from above the open tray 10 toward the projection portion 26 so that the fixing portion 31 comes into contact with the projection portion 26 and the cross member 3 is positioned. It is preferable that the projection portion 26 and the cross member 3 are joined with spot joints. The joining of the fixing portion 31 to the projection portion 26 stabilizes the load-bearing capacity during a collision.

[0043] The cross member 3 is joined to the side walls 11 and 12 by welding. As shown in Figures 5 and 7, the cross member 3 is joined to the side walls 12 by a welded joint 29 with its end 30 in contact with the inner surface 12a of the side wall 12. The welded joint 29 is formed by laser welding or electric arc welding.

[0044] The welded joint 29 includes a left-side welded joint 29 that joins the left end 30 of the cross member 3 in the vehicle width direction to the side wall 11, and a right-side welded joint 29 that joins the right end 30 of the cross member 3 in the vehicle width direction to the side wall 12. The vehicle width direction end 30 of the cross member 3 is formed perpendicularly to the inner surface shape of the side wall 11 and 12 and is in contact with the side wall 11 and 12. In this contact state, the cross member 3 is attached to the side wall 11 and 12 by the welded joint 29. The end 30 joined by the welded joint 29 is the vehicle width direction end of the vertical wall 32. The vertical wall 32 and the side wall 11 and 12 are joined by the welded joint 29. Of the end 30, the vertical wall 32 is continuously joined to the side wall 11 and 12 by welding. The continuous joining of the end 30 to the side wall 11 and 12 stabilizes the load-bearing capacity during a collision.

[0045] A manufacturing method of the battery case 1 will be described. The manufacturing method of the battery case 1 includes an integration process, an arrangement process, and a joining process.

[0046] The integration process is a process of integrating the members constituting the tray 10. The integration process includes a frame joining process of joining the bottom member 21 and the side member 22 by welding, and a protrusion joining process of joining the protrusion 26 to the side member 22 by welding. In the frame joining process, the side member 22 is joined to the bottom member 21 so that the side walls 11, 12 are perpendicular to the bottom 15. The side member 22 is joined to the fixing portion 23 and is joined to the front wall portion 13 and the rear wall portion 14 by welding. The four corners of the bottomed frame in the tray 10 are joined by continuous welding. In the frame joining process, the front end of the side wall 11 is joined to the left end of the front wall portion 13 by continuous welding, and the rear end is joined to the left end of the rear wall portion 14 by continuous welding. Similarly, in the frame joining process, the front end of the side wall 11 is joined to the left end of the front wall portion 13 by continuous welding, and the rear end is joined to the left end of the rear wall portion 14 by continuous welding. In the protrusion joining process, the protrusion 26 is joined to the side member 22 by welding. In the integration process, either the frame joining process or the protrusion joining process may be performed first. The order of the frame joining process and the protrusion joining process is not particularly limited.

[0047] The arrangement process is a process of arranging the cross member 3 inside the tray 10. The arrangement process includes a process of positioning and fixing the cross member 3 by the protrusions 26 protruding in the vehicle width direction from the inner surfaces of the side walls 11, 12. In the arrangement process, the cross member 3 is slid from above the tray 10 toward the protrusion 26, and the cross member 3 is arranged inside the tray 10 so as to be positioned by the protrusion 26. At that time, the cross member 3 is arranged so as to extend across the pair of side walls 11, 12 inside the tray 10.

[0048] The joining step is a step of joining the end portions 30 on both sides in the vehicle width direction of the cross member 3 disposed inside the tray 10 to a pair of side wall portions 11 and 12. The joining step includes a step of continuously joining the end portions 30 of the cross member 3 to the side wall portions 11 and 12 by welding.

[0049] As described above, according to the embodiment, since the cross member 3 provided inside the tray 10 is fixed to the inner surfaces of the side wall portions 11 and 12, the structure has excellent side collision resistance. Further, compared with the structure in which a single steel plate of the conventional structure is drawn and formed, the battery 100 can be accommodated up to the vicinity regions of the side wall portions 11 and 12, so that the capacity of the battery 100 can be increased.

[0050] The method of mounting the battery case 1 below the vehicle may be a method of setting a bracket on the lower surface of the battery case 1 and fastening the bracket and the lower surface of the side sill.

[0051] Further, the battery case 1 is not limited to the structure in which the cross member 3 is joined to the protrusion 26 by welding, and the cross member 3 may not be joined to the protrusion 26. Even in the structure in which the cross member 3 is not joined to the protrusion 26, the load resistance during a collision can be obtained.

[0052] Further, the battery case 1 is not limited to the structure in which the end portions 30 of the cross member 3 are joined to the side wall portions 11 and 12 by welding, and the cross member 3 may not be joined to the side wall portions 11 and 12. Even in the structure in which the end portions 30 of the cross member 3 are not joined to the side wall portions 11 and 12, the load resistance during a collision can be obtained.

[0053] Further, the battery case 1 is not limited to the structure having the protrusion 26 as a separate member from the side member 22, and a part of the side member 22 may function as a protrusion. As the battery case 1 of the modified example, it is possible to adopt a structure in which protrusions are provided on the side wall portions 11 and 12.

[0054] As shown in Figure 8, the main body 2 of the first modified example has a projection 41 provided on the side wall portion 12. The side wall portion 12 has a U-shaped slit 40 on its inner surface 12a. The slit 40 is formed in a horizontal U-shape and is not provided on the rear side in the vehicle's longitudinal direction. The inner portion of the slit 40 is formed on the same plane as the inner surface 12a. The inner portion of the slit 40 is bent to form a projection 41 that protrudes in the vehicle width direction. The projection 41 includes a vertical surface facing the vehicle's longitudinal direction. As shown in Figure 9, the cross member 3 is aligned by the projection 41 and joined to the projection 41 by a welded portion 28. The welded portion 28 is formed by spot welding.

[0055] As shown in Figure 10, the main body 2 of the second modified example has a structure in which the side wall portion 12 is composed of a plurality of side members 22. The side members 22 are provided with projections 42 formed from a part of the side member 22. The projections 42 are L-shaped portions that extend in the vehicle width direction from the end of the portion where the side members are joined together. The side members 22 have a structure in which four side members are connected in the front-rear direction of the vehicle. With respect to the side members that are connected, the side member 22 on the relative front side will be described as side member 22A, and the side member 22 on the relative rear side will be described as side member 22B. Figure 10 shows the portion where the front side member 22A and the rear side member 22B are joined together.

[0056] As shown in Figure 10, the rear end of the side member 22A and the front end of the side member 22B overlap, and the side member 22A and the side member 22B are joined by a weld 43. The weld 43 is formed by spot welding. A sealant is applied to the boundary where the side member 22A and the side member 22B overlap to prevent water ingress. In addition, the space between the side member 22A and the bottom member 21, and the space between the side member 22B and the bottom member 21 are sealed with a sealant 25. As a result, the overlapping portions of the side member 22A, the side member 22B, and the bottom member 21 are sealed. The projection 42 protrudes in the vehicle width direction from the rear end of the front side member 22A. The projection 42 includes a vertical surface facing the vehicle's front-rear direction. The cross member 3 is aligned by the projection 42 and joined to the projection 42 by a weld. This weld is formed by spot welding.

[0057] As shown in Figures 11 and 12, in the third modified example, the side member 22 is formed from a blank-shaped steel plate. The side member 22 has a blank portion 44 and a bridge portion (bridge area) 45. By bending this side member 22, a side wall portion 12 having a projection 46 is formed, as shown in Figure 12. The projection 46 is formed by bending the bridge portion 45. The projection 46 is part of the side member 22. The projection 46 includes a vertical surface facing the front-rear direction of the vehicle. The cross member 3 is aligned with the projection 46 and joined to the projection 46 by a weld. This weld is formed by spot welding. A sealing material 47 is provided in the gap portion of the side wall portion 12 formed by the blank portion 44. The side wall portion 12 is sealed by the sealing material 47.

[0058] As shown in Figure 13, in the fourth modification, a projection 48 formed by overhang molding is provided on the side member 22. The projection 48 has a convex shape that protrudes from the inner surface 12a. The cross member 3 is slid from above the tray 10 toward the projection 48, and the cross member 3 is positioned by the projection 48.

[0059] According to the present invention, since the internal cross member is fixed to the side wall of the tray, the battery case has excellent side impact resistance when mounted on an electric vehicle. Furthermore, because the side wall is a vertical surface, the volume that can accommodate the battery inside the battery case is larger compared to the case with a sloped surface. In addition, a battery case made of steel plate can be made more cost-effective compared to one made of aluminum.

[0060] 1 Battery case 2 Main body 3 Cross member 4 Side frame 10 Tray 11, 12 Side wall 12a Inner surface 13 Front wall 14 Rear wall 15 Bottom 15a Bottom surface 21 Bottom surface member 22 Side member 26 Protrusion

Claims

1. A battery case made of steel plate, mounted under the floor of a vehicle body to house a battery, comprising: a main body consisting of a bottomed frame having a pair of side walls facing each other in the vehicle width direction when mounted on the vehicle body; and a cross member extending in the vehicle width direction within the main body so as to span the pair of side walls and reinforcing the main body, wherein the main body has a structure in which a side member forming the side wall and a bottom member forming the bottom of the main body are integrated, the side wall is integrated with the bottom member so as to extend along the vehicle height direction when mounted on the vehicle body, the inner surface of the side wall is formed as a vertical surface along the vehicle height direction, and the cross member is joined to the side wall with its end in the vehicle width direction in continuous contact with the inner surface of the side wall in the vehicle height direction.

2. The battery case according to claim 1, wherein the main body has projections that protrude from the inner surface of the side wall in the vehicle width direction for positioning and fixing the cross member, and the cross member is fixed to the side wall in a position determined by the projections.

3. The battery case according to claim 2, wherein the side member is formed of a steel plate, and the projection is formed of a separate material from the side member and attached to the side wall.

4. The battery case according to claim 2, wherein the side member is formed of a steel plate, and the projection is formed by the side member and is a portion that protrudes in the vehicle width direction from the inner surface.

5. The battery case according to claim 4, wherein the projection is formed by bending the inside of a slit provided in the side member in the vehicle width direction.

6. The battery case according to claim 4, wherein the side member has a structure in which a plurality of side members are joined in the longitudinal direction of the vehicle, and the projection is an L-shaped portion extending in the vehicle width direction from the end of the portion where the side members are joined together.

7. The battery case according to claim 4, wherein the projection is formed by bending the steel plate and protrudes from the inner surface in the vehicle width direction.

8. The battery case according to claim 4, wherein the projection is a portion formed on the side member by press working.

9. The battery case according to any one of claims 2 to 8, wherein the cross member has a fixing portion that is positioned and fixed to the projection, and the fixing portion is joined to the projection by welding while slid from above in the vehicle height direction and positioned to the projection.

10. The battery case according to any one of claims 2 to 9, wherein the cross member is continuously joined to the side wall portion by welding at its end in the vehicle width direction.

11. A method for manufacturing a steel plate battery case for which a battery is mounted under the floor of a vehicle body, comprising: an integration step of integrating a bottom member that forms the bottom of a tray and a side member that forms a pair of side walls facing each other in the vehicle width direction when mounted on the vehicle body, such that the side walls are perpendicular to the bottom; an arrangement step of arranging a cross member that reinforces the tray inside the tray such that the cross member extends across the pair of side walls inside the tray; and a joining step of joining both ends of the cross member that is arranged inside the tray to the pair of side walls.

12. The method for manufacturing a battery case according to claim 11, wherein the arrangement step includes a step of positioning and fixing the cross member with a projection that protrudes from the inner surface of the side wall in the vehicle width direction.

13. The method for manufacturing a battery case according to claim 11 or 12, wherein the joining step includes a step of continuously joining both ends of the cross member to the side wall by welding.

Images