Vehicle underbody structure

Abstract

To prompt a load to be transmitted from a front part of a vehicle to a battery case while securing rigidity of a front part of a battery pack.SOLUTION: A vehicle lower part structure comprises front side members 10 and side sills 18, where a battery case 40A is fixed to a space between the side sills 18 through battery brackets 50. A front part of the battery case 40A has a case straight portion 41 extending in a width direction and case inclined portions 42 extending obliquely rearward as going outward from both outer ends of the case straight portion 41. The case straight portion 41 and the case inclined portions 42 form case corner portions 43, where rear parts of the front side members 10 are joined to the case corner portions 43 through the battery brackets 50.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vehicle undercarriage. [Background technology]

[0002] In an electric vehicle, for example, as disclosed in Patent Document 1, a battery case is fixed to the underside of a floor portion of the vehicle body. In the structure disclosed in Patent Document 1, a front side frame extending forward of the vehicle is provided in the front portion of the floor portion, and a front side frame support portion is provided in the rear portion of the front side frame. The front side frame support portion is attached to a battery case support frame that supports the battery case.

[0003] In this example, a frame portion extending in the vehicle width direction is provided at the front of the battery case support frame, and a battery-side right angle portion is provided on both sides of the frame in the vehicle width direction. The front side frame support portion is fastened by a plurality of front fastening portions provided on the frame portion, and a plurality of lateral fastening portions fastened to the side sill are provided at the sides of the battery case support frame. That is, in this example, the front side frame support portion is fastened to the side sill via a plurality of fastening portions provided around the battery-side right angle portion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-140728 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the above example structure, when an impact load is applied to the front side frame due to, for example, a frontal collision, the impact load is input to the front side frame support portion and then input to the frame portion of the battery case support frame. Since the battery case support frame in the above example is provided with many fastening portions, the impact load transmitted to the front side frame support portion is transmitted to the multiple fastening portions and then to the battery case.

[0006] However, by providing a plurality of fastening parts on the battery case support frame, an impact load is input to the frame part at each fastening part. In such a structure, the load may not be input in the intended direction. When an impact load in an unintended direction is input to the battery case support frame in this way, an unintended load is transmitted to the battery case, and as a result, the battery case may be damaged. Therefore, in the structure having a plurality of fastening parts as in the above example, there is room for improvement in terms of effectively transmitting the impact load input to the front side frame to the battery case.

[0007] On the other hand, the battery pack of an electric vehicle is heavy and therefore accounts for a large proportion of the vehicle body weight. Since the battery pack is heavy and has a large inertial force, if a frontal collision occurs while the vehicle is running, a large load acts in the forward direction of the vehicle on the front part of the battery case that constitutes the outer part of the battery pack and its surroundings due to the inertial force. Therefore, it is necessary to increase the rigidity of the front part of the battery pack.

[0008] The present invention has been made to solve the above-mentioned problems, and its object is to provide a vehicle underbody structure that can ensure the rigidity of the front of the battery pack and further promote load transfer from the front of the vehicle to the battery case. [Means for solving the problem]

[0009] The vehicle underbody structure according to the present invention for achieving the above object includes a front side member extending forward from a front portion of a floor portion of the vehicle, and a side sill provided on the vehicle rear side of the front side member and outboard in the vehicle width direction, extending in the vehicle front-rear direction, and a battery case accommodating a battery is fixed via a battery bracket between the side sills on the underside of the floor portion. In the vehicle underbody structure, the front portion of the battery case has a case straight portion extending in the vehicle width direction, and a case inclined portion extending inclined toward the vehicle rear as it moves outward in the width direction from both ends of the case straight portion on the outer side in the vehicle width direction, the case straight portion and the case inclined portion form case corner portions, and the rear portion of the front side member is joined to the case corner portions via the battery bracket. a front cross member is disposed on the vehicle front side of the battery case, the front cross member having a member straight portion extending in the vehicle width direction to correspond to the case straight portion, and member inclined portions provided on both sides of the member straight portion in the vehicle width direction and inclined to correspond to the case inclined portions, the member straight portions and the member inclined portions forming member corner portions, and the battery bracket is joined to the case corner portions via the member corner portions of the front cross member. There are. Effect of the Invention

[0010] According to the present invention, it is possible to ensure the rigidity of the front part of the battery pack and further promote the transfer of load from the front part of the vehicle to the battery case. [Brief description of the drawings]

[0011] [Figure 1] 1 is a bottom view of a vehicle underbody structure according to the present invention, as viewed from below the vehicle. [Diagram 2] 2 is an enlarged bottom view showing the vicinity of the front part of the battery case in FIG. 1. [Diagram 3] FIG. 3 is a perspective view showing a cross section taken along the line AA in FIG. 2. [Figure 4] FIG. 3 is a cross-sectional view taken along the line BB in FIG. 2. [Diagram 5] 1. FIG. 4 is a bottom view showing a modified example of the front side member of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of a vehicle underbody structure according to the present invention will be described with reference to the drawings (FIGS. 1 to 5). In the drawings, the direction of the arrow Fr indicates the front in the vehicle longitudinal direction. In the description of the embodiment, the "front (front end) and rear (rear end)" correspond to the front and rear in the vehicle longitudinal direction. The directions of the arrows L and R indicate the left and right in the vehicle width direction. In the description of the embodiment, the "left and right" correspond to the left and right when an occupant in the vehicle cabin faces forward of the vehicle. In addition, the arrow U indicates the upper side of the vehicle.

[0013] The vehicle underbody structure of this embodiment is a underbody structure of an electric vehicle having a battery that supplies power to a motor (not shown) for driving wheels. The vehicle underbody structure includes a front side member 10, a side sill 18, a lower member 21, a side brace 16, a battery pack 40, a battery bracket 50, and a front cross member 60.

[0014] As shown in Figures 1 and 2, the front side members 10 are highly rigid components constituting the vehicle body frame. The front side members 10 extend in the vehicle front direction from both outer side portions in the vehicle width direction in the front portion of a floor panel 71 constituting the floor portion. The two front side members 10 are spaced apart from each other in the vehicle width direction, and are disposed on the inner side in the vehicle width direction of a wheel house panel 73 provided on the side portion of the vehicle body. A drive motor and the like are disposed between the two front side members 10.

[0015] Each front side member 10 has a rear inclined portion 12 and a front straight portion 11. The rear inclined portion 12 extends from the front of the floor panel 71 toward the front of the vehicle, inclining outward in the vehicle width direction. A rear portion of the rear inclined portion 12 is joined to a battery bracket 50. The configuration of the rear portion of the rear inclined portion 12 and its surroundings will be described later. The front straight portion 11 extends from the front end of the rear inclined portion 12 toward the front of the vehicle.

[0016] Moreover, the front side member 10 has a U-shaped cross section with an opening toward the upper side of the vehicle. For example, an inner flange (not shown) that protrudes inward in the vehicle width direction and extends in the vehicle front-rear direction is provided on the inner wall of the front side member 10 located at the rear inclined portion 12, and an outer flange (not shown) that protrudes outward in the vehicle width direction and extends in the vehicle front-rear direction is provided on the outer wall. The inner flange and the outer flange are joined to, for example, a dash lower panel 72 that constitutes a part of the floor portion of the vehicle body, or the like. A battery bracket 50 is joined to the rear portions of the inner flange and the outer flange.

[0017] 1 and 2, the side sill 18 is a highly rigid member joined to both outer sides in the vehicle width direction of the floor panel 71, and is disposed on the vehicle rear side of the wheel house panel 73 and further outboard in the vehicle width direction than the front side member 10, and extends in the vehicle front-rear direction. A front portion of the side sill 18 and a rear portion of the rear inclined portion 12 of the front side member 10 are connected by a side brace 16. The relationship between the side sill 18, the rear inclined portion 12, and the side brace 16 will be described later.

[0018] 1 and 2, a floor tunnel 71A is provided in the middle of the floor panel 71 in the vehicle width direction. The floor tunnel 71A is formed so that the approximate center of the floor panel 71 rises upwardly of the vehicle, and extends in the vehicle front-rear direction. In other words, by providing the floor tunnel 71A, an opening extending in the vehicle front-rear direction is formed in the lower surface of the floor panel 71.

[0019] As shown in FIG. 2, the lower member 21 extends from the rear of the rear inclined portion 12 of the front cross member 60 toward the inside in the vehicle width direction. The lower member 21 is a hollow member having a predetermined width in the vehicle front-rear direction and extending in the vehicle width direction, and has a cross-sectional shape with an opening on the upper side of the vehicle as viewed in the vehicle width direction. The outer side of the lower member 21 in the vehicle width direction is joined to the bottom part of the rear inclined portion 12 of the front side member 10 in a state where the outer side covers a part of the bottom part from the lower side of the vehicle. The inner side of the lower member 21 in the vehicle width direction is joined to the floor panel 71 located at the opening edge of the floor tunnel 71A. The inner side of the lower member 21 in the vehicle width direction is joined to the intermediate member 28 extending in the vehicle width direction so as to straddle the floor tunnel 71A. The intermediate member 28 and the left and right lower members 21 constitute one lower cross member 20 extending in the vehicle width direction.

[0020] 1 and 2, the side brace 16 extends inclined toward the rear of the vehicle as it moves outward in the vehicle width direction so as to connect the outer portion of the lower member 21 and the front portion of the side sill 18. Although not shown in detail, the side brace 16 has a U-shaped cross section that opens upward in the vehicle. Flanges 16c, 16d are provided at the upper portions of the front wall 16a and the rear wall 16b that form the U-shaped cross section, and the flange 16c is joined to a floor panel 71. The flange 16c of the front wall 16a is joined to the floor panel 71 located near the rear of the wheel house panel 73.

[0021] In addition, the vehicle width direction inner portion of the underside portion constituting the U-shaped cross section of the side brace 16 is disposed so as to cover the bottom surface portion at the rear of the rear inclined portion 12 of the front side member 10 via the lower member 21. The underside portion covering the front side member 10 is joined to the vehicle width direction outer portion of the bottom surface portion of the rear inclined portion 12 of the front side member 10 by spot welding or the like. In addition, the underside portion is also joined to the outer portion of the lower member 21.

[0022] The battery pack 40 is a heavy object that houses an internal battery and is fixed to the underside of the floor panel 71. The battery housed inside the battery pack 40 supplies power to, for example, a drive motor via a cable (not shown) or the like. The cable is routed, for example, inside the floor tunnel 71A and connected to the motor. The battery pack 40 has a battery and a battery case 40A that houses the battery. An inner cross member 45 and front and rear braces 48 are provided inside the battery case 40A.

[0023] As shown in FIG. 1, the battery case 40A extends in the vehicle front-rear direction and further extends in the vehicle width direction across the entire area between the side sills 18 on both sides. The front part of the battery case 40A has a case straight portion 41 and a case inclined portion 42. The case straight portion 41 is provided in the center of the front part of the battery case 40A in the vehicle width direction and extends in the vehicle width direction. The case inclined portions 42 are provided on both outer sides of the case straight portion 41 in the vehicle width direction and extend obliquely toward the rear of the vehicle as they move from the outer parts of the case straight portion 41 in the vehicle width direction toward the outside in the vehicle width direction. In addition, the case straight portion 41 and the case inclined portion 42 form a case corner portion 43 in the front part of the battery case 40A.

[0024] As shown in Figs. 1 and 2, the front cross member 60 is disposed on the vehicle front side of the battery case 40A, is one of the members constituting the vehicle body frame, and is a member extending in the vehicle width direction as a whole. The front cross member 60 has a member straight portion 61 and a member inclined portion 62. The member straight portion 61 is disposed between the rear inclined portions 12 of the front side members 10 on both sides in the vehicle width direction, and is a portion extending in the vehicle width direction. The member inclined portion 62 is a portion extending at an incline toward the rear of the vehicle as it moves from the outer portion of the member straight portion 61 in the vehicle width direction toward the outer side in the vehicle width direction. In addition, the member straight portion 61 and the member inclined portion 62 form a member corner portion 63 in the front cross member 60. That is, the front cross member 60 is formed so as to be convex toward the front of the vehicle as a whole.

[0025] The member straight portion 61 and the member inclined portions 62 on both sides are arranged so as to cover the case straight portion 41 and the case inclined portions 42 on both sides of the battery case 40A from the front side of the vehicle. Therefore, the inclination angle of the member inclined portions 62 is inclined at approximately the same angle as the inclination angle of the case inclined portions 42.

[0026] 3 and 4, the front cross member 60 has an upper member 65 having an L-shaped cross section constituting a top surface portion 65a and a rear wall 65b, and a lower member 66 having an L-shaped cross section constituting a front wall 66b and a bottom portion 66a, and is formed by joining these together. A flange 65c protruding toward the rear of the vehicle is provided at the lower end of the rear wall 65b of the upper member 65, and the flange 65c is joined to the bottom portion 66a of the lower member 66. Similarly, a flange 66c protruding toward the front of the vehicle is provided at the upper end of the front wall 66b of the lower member 66, and the flange 66c is joined to the top surface portion 65a of the upper member 65, thereby forming a hollow structure.

[0027] 2 and 3, the battery bracket 50 is a member for attaching the battery case 40A to the lower part of the floor portion of the vehicle body. The battery bracket 50 is joined to the battery case 40A via a front cross member 60.

[0028] By providing a case corner 43 at the front of the battery case 40A as the starting point of panel rigidity and arranging the battery bracket 50 at that portion, it is possible to ensure the joint rigidity between the battery pack 40 and the vehicle body. In addition, because the battery bracket 50 is arranged near the rear of the front side member 10, the structure of this embodiment makes it possible to efficiently transmit an impact load due to a frontal collision or the like to the front side member 10 in the vehicle rearward direction toward the battery pack 40.

[0029] 1 and 2, the battery bracket 50 of this embodiment is joined to a member corner 63 of the front cross member 60. In detail, the battery bracket 50 is joined to a front wall 66b located at the member corner 63 of the lower member 66 of the front cross member 60. As shown in FIG. 3, an inner flange 54 is provided on the inner side of the rear part of the battery bracket 50 in the vehicle width direction, which protrudes inward in the vehicle width direction and extends in the vehicle vertical direction, and an outer flange (not shown) is provided on the outer side of the rear part of the battery bracket 50 in the vehicle width direction, which protrudes outward in the vehicle width direction and extends in the vehicle vertical direction. The inner flange 54 is joined by spot welding or the like to the front wall 66b of the case straight part 41 constituting the member corner 63 of the front cross member 60, and the outer flange is joined by spot welding or the like to the front wall 66b of the case inclined part 42 constituting the member corner 63. In other words, the battery bracket 50 is joined to the front walls 66b on both the left and right sides of the member corner 63.

[0030] As described above, the forward convex shape formed by the member straight portions 61 and member inclined portions 62 of the front cross member 60 corresponds to the convex shape formed by the case straight portions 41 and case inclined portions 42 of the battery case 40A. Therefore, the rigidity of the case corner portions 43 and member corner portions 63 can increase the rigidity of the front portion of the battery pack 40, and the battery pack 40 is fixed to the vehicle body by these corner portions 43, 63.

[0031] 1 and 2, in this embodiment, the lower cross member 20 and the side brace 16 have shapes corresponding to the member straight portion 61 and the member inclined portion 62 of the front cross member 60. That is, as described above, the lower cross member 20 extends in the vehicle width direction like the member straight portion 61, and the side brace 16 is inclined like the member inclined portion 62. The lower cross member 20 and the side brace 16 form a corner, and the angle of the corner is formed at approximately the same angle as the angle of the member corner portion 63 of the front cross member 60.

[0032] In addition, the lower cross member 20 and both side braces 16 are disposed so as to cover the member straight portion 61 and both side member inclined portions 62 of the front cross member 60 from the front side of the vehicle. Therefore, the inclination angle of the side braces 16 is inclined at approximately the same angle as the inclination angle of the member inclined portions 62.

[0033] The battery bracket 50 is joined to a joint portion where the rear portion of the front side member 10, the end portion of the lower member 21 in the vehicle width direction, and the front portion of the side brace 16 are joined. In this example, the battery bracket 50 is joined to the rear portion of the lower member 21 of the lower cross member 20 in a state where it is arranged so as to overlap the rear portion of the rear inclined portion 12 of the front side member 10 as viewed from below the vehicle, as shown in Figs. 1 and 2. The battery bracket 50 has a flat planar portion 51 extending forward of the vehicle from a member corner portion 63 as shown in Fig. 3. The planar portion 51 is joined to an outer portion in the vehicle width direction of the lower surface portion of the lower member 21. Here, the lower surface portion of the lower member 21 and the planar portion 51 of the battery bracket 50 may be joined by spot welding or the like in a state where they are in contact with each other. Also, the lower surface portion and the planar portion 51 may be fastened by a bolt or the like.

[0034] The battery bracket 50 of this embodiment is also joined to the lower part of the front side member 10. In this example, a flat portion 51 of the battery bracket 50 is provided with bolt holes 52, and the flat portion 51 is joined to the bottom surface portion 14 of the rear inclined portion 12 of the front side member 10 via a side brace 16 by a bolt or the like.

[0035] By configuring the lower cross member 20 and the side brace 16 as described above, a corner formed at the joint between the lower cross member 20 and the side brace 16 and the member corner 63 are joined via the battery bracket 50. With this configuration, an impact load can be received at the portion where members such as the lower member 21 of the lower cross member 20, the side brace 16, the battery bracket 50, and the front cross member 60 are densely packed together. Furthermore, with this configuration, it becomes possible to distribute the impact load to members surrounding these members.

[0036] In this embodiment, an outer cross member 55 extending in the vehicle width direction is provided on the underside of the battery case 40A. The outer cross member 55 is disposed rearward of the vehicle with a gap from the front end of the battery case 40A. The outer cross member 55 is a plate having projections and recesses when viewed in the vehicle width direction, and the upper convex surface of the outer cross member 55 serves as a joining surface, and is joined to the underside of the battery case 40A by spot welding or the like.

[0037] 3 and 4, the inner cross member 45 inside the battery case 40A is disposed at a distance from the case straight portion 41 on the vehicle rear side, and is provided at a position corresponding to the outer cross member 55 in the vehicle front-rear direction. The inner cross member 45 has a U-shaped cross section that opens downwardly of the vehicle when viewed in the vehicle width direction, and flanges 45b, 45d that protrude forward and backward of the vehicle are provided at the lower end of the front wall 45a and the lower end of the rear wall 45c that constitute the U-shaped cross section, and these flanges 45b, 45d are joined to the bottom surface of the battery case 40A by spot welding or the like. The joint surfaces of the front and rear flanges 45b, 45d of the inner cross member 45 and the outer cross member 55 may be joined in three sheets via the bottom surface (lower surface) of the battery case 40A.

[0038] Additionally, the front and rear braces 48 inside the battery case 40A are members that extend in the front-rear direction of the vehicle and are provided at the front inside the battery case 40A. The inner cross member 45 has a U-shaped cross section that opens downwardly of the vehicle when viewed in the front-rear direction of the vehicle, and flanges 48b that protrude to the left and right are provided at the lower ends of the left and right side walls 48a that form the U-shaped cross section, and these flanges 48b are joined to the bottom surface of the battery case 40A by spot welding or the like.

[0039] In addition, the front end portions of the front and rear braces 48 are positioned adjacent to the vehicle rear side of the case corner portion 43, and the rear end portions of the front and rear braces 48 are positioned adjacent to the vehicle front side of the inner cross member 45.

[0040] Providing the front and rear braces 48 makes it possible to stably support the case corners 43, member corners 63, etc. When the battery bracket 50, the front cross member 60, etc. are deformed due to an impact load, the case corners 43 come into contact with the front ends of the front and rear braces 48, making it possible to strengthen the case corners 43. Furthermore, the front and rear braces 48 make it possible to suppress deformation of the case corners 43.

[0041] Furthermore, by providing the inner cross member 45 as configured above, it becomes possible to stably support the front and rear braces 48 from the rear side of the vehicle. Note that, although in this embodiment, the rear ends of the front and rear braces 48 are disposed with a gap between them and the front wall 45a of the inner cross member 45, the rear ends may be joined to the front wall 45a.

[0042] Furthermore, at least a portion of the front and rear braces 48 and at least a portion of the inner cross member 45 are joined to the outer cross member 55 via the bottom surface of the battery case 40A. For example, the joint surfaces of the front and rear flanges 45b, 45d of the inner cross member 45 and the outer cross member 55 may be joined in three pieces via the bottom surface (lower surface) of the battery case 40A. Furthermore, the rear portions of the left and right flanges 45b of the front and rear braces 48 and the joint surfaces of the outer cross member 55 may be joined in three pieces via the bottom surface (lower surface) of the battery case 40A.

[0043] By joining the front and rear braces 48 and the inner cross member 45 to the outer cross member 55 via the bottom surface of the battery case 40A, the rigidity of the rear portion of the front and rear braces 48 is improved. Therefore, the front and rear braces 48 can more stably support the case corners 43, the member corners 63, etc. from the rear side of the vehicle.

[0044] The description of the present embodiment is merely an example for explaining the present invention, and does not limit the invention described in the claims. Furthermore, the configuration of each part of the present invention is not limited to the above embodiment, and various modifications are possible within the technical scope described in the claims.

[0045] In addition, in this embodiment, the battery bracket 50 is joined to a joint portion where the rear portion of the front side member 10, the end portion in the vehicle width direction of the lower member 21, and the front portion of the side brace 16 are joined, but this is not limited thereto. The flat portion 51 of the battery bracket 50 may be joined to the periphery of the joint portion.

[0046] Furthermore, the battery bracket 50 is joined to the front wall 66b located at the member corner 63 of the front cross member 60, but is not limited to this. As long as it overlaps the member corner 63 or the like, it may be joined to the bottom 66a of the front cross member 60, or to the lower part of the front part of the battery case 40A.

[0047] Further, the front side member 10 of the present embodiment has the rear inclined portion 12, but is not limited to this. For example, as shown in Fig. 5, the front side member 10 may be formed so as to extend linearly in the vehicle front-rear direction. [Explanation of symbols]

[0048] 10 Front side member 11 Front straight section 12 Posterior slope 16 Side brace 16a front wall 16b Back wall 16c flange 16d flange 18 Side sill 20 Lower cross member 21 Lower Member 28 Intermediate parts 40 Battery Pack 40A Battery Case 41 Case straight section 42 Case inclination 43 Case corner 45 Inner cross member 45a front wall 45b flange 45c back wall 45d flange 48 Front and rear braces 48a side wall 48b flange 50 Battery bracket 51 Plane part 52 Bolt holes 54 Inner flange 55 Outer cross member 60 Front cross member 61 Member straight section 62 Member inclined part 63 Member corner 65 Upper member 65a Top section 65b Back wall 65c flange 66 Lower part 66a bottom 66b front wall 66c flange 71 Floor Panel 71A Floor Tunnel 72 Dash lower panel 73 Wheelhouse Panel

Claims

1. a front side member extending from a front portion of a floor portion of the vehicle toward the front of the vehicle; and a side sill provided on a vehicle rear side and on an outer side in a vehicle width direction of the front side member, the side sill extending in a vehicle front-rear direction, A battery case that houses a battery is fixed via a battery bracket between both side sills on the underside of the floor portion, The front portion of the battery case has a case straight portion extending in the vehicle width direction and a case inclined portion extending from both ends of the case straight portion on the outer side in the vehicle width direction toward the outer side in the width direction and inclined toward the rear of the vehicle, and a case corner portion is formed by the case straight portion and the case inclined portion, a rear portion of the front side member is joined to the case corner portion via the battery bracket, A front cross member is disposed on the vehicle front side of the battery case, the front cross member has a member straight portion extending in the vehicle width direction to correspond to the case straight portion, and member inclined portions provided on both sides of the member straight portion in the vehicle width direction and inclined to correspond to the case inclined portions, the member straight portions and the member inclined portions forming member corner portions, a battery bracket joined to the case corner portion via the member corner portion of the front cross member,

2. A lower member extending in a vehicle width direction is disposed on a vehicle front side of the front cross member, A side brace is provided on an outer side of the lower member in a vehicle width direction, the side brace extending obliquely toward the rear of the vehicle as it moves toward the outer side in the vehicle width direction, and the side brace connects the lower member and the side sill, the lower member and the side brace have shapes corresponding to the member straight portion and the member inclined portion of the front cross member, 2. The vehicle underbody structure according to claim 1, wherein the battery bracket is joined to or around a joint where a rear portion of the front side member, an end portion of the lower member in a vehicle width direction, and a front portion of the side brace are joined.

3. An outer cross member extending in the vehicle width direction is provided on the lower surface side of the battery case, An inner cross member extending in a vehicle width direction is provided on the inside of the battery case at a position corresponding to the outer cross member, the inner cross member is disposed on a vehicle rear side of the case straight portion with a gap therebetween, A front-rear brace extending in the front-rear direction of the vehicle is provided at a front portion inside the battery case, The front end portions of the front and rear braces are disposed adjacent to the vehicle rear side of the case corner portions, 3. The vehicle underbody structure according to claim 1, wherein rear end portions of the front and rear braces are disposed adjacent to a vehicle front side of the inner cross member.

4. 4. The vehicle underbody structure according to claim 3, wherein at least a portion of the front and rear braces and at least a portion of the inner cross member are joined to the outer cross member via a bottom portion of the battery case.

Images