JP7545665B2 - Vehicle underbody structure - Google Patents

Description

The present invention relates to a vehicle undercarriage.

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

In this example, a frame portion extending in the vehicle width direction is provided at the front of the battery pack support frame, and battery-side right-angle portions are 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 that are fastened to the side sill are provided on the sides of the battery pack 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 periphery of the battery-side right-angle portions.

JP 2018-140728 A

In the structure of the above example, 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 pack support frame. Since the battery pack 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 pack.

However, by providing multiple fastening parts on the battery pack support frame, an impact load is input to the frame part at each fastening part. With such a structure, there is a possibility that the load will not be input in the intended direction. If an impact load in an unintended direction is input to the battery pack support frame in this way, an unintended load will be transmitted to the battery pack, which may result in damage to the battery pack. Therefore, with a structure such as the above example having multiple fastening parts, there is room for improvement in terms of effectively transmitting the impact load input to the front side frame to the battery pack.

On the other hand, the battery pack of an electric vehicle is heavy and therefore accounts for a large proportion of the vehicle weight. As the battery pack is heavy, it has a large inertial force. If a frontal collision occurs while the vehicle is running, this inertial force will result in a large load acting in the forward direction of the vehicle on the front part of the battery case, which constitutes the outer part of the battery pack, and its surrounding area. For this reason, it is necessary to increase the rigidity of the front part of the battery pack, etc.

The present invention has been made to solve the above problems, and its purpose is to provide a vehicle underbody structure that ensures the rigidity of the front of the battery pack and can also facilitate the transfer of load from the front of the vehicle body to the battery pack.

The vehicle underbody structure according to the present invention, which is intended to achieve the above object, includes a front side member extending forward from the front of a floor of the vehicle, and a battery pack fixed to the underside of the floor via a battery bracket. In the vehicle underbody structure, a lower member is joined to the rear of the front side member, extending inward in the vehicle width direction from the rear of the front side member, and the battery bracket is joined to the outer portion of the lower member in the vehicle width direction, in a state where it is positioned so as to overlap the rear of the front side member when viewed from below the vehicle.

The present invention makes it possible to ensure the rigidity of the front of the battery pack and to promote the transfer of load from the front of the vehicle body to the battery pack.

1 is a bottom view of a vehicle underbody structure according to the present invention, as viewed from below the vehicle. 2 is an enlarged bottom view showing a portion where a front side member, a lower member, and a side brace are joined in FIG. 1 . FIG. FIG. 3 is a bottom view showing a state in which the side brace in FIG. 2 has been removed. 3 is a side view of the front side member and the like in FIG. 2 as viewed from the outer side in the vehicle width direction. 3 is a cross-sectional view taken along the line AA in FIG. 2. FIG. 2 is a bottom view showing a state in which a suspension frame is attached to the bulging portion of FIG. 1 . 3 is a cross-sectional view taken along the line BB in FIG. 2. 4 is a bottom view showing a modified example of the lower member in which the lower member and the outer lower member in FIG. 3 are integrally formed. FIG.

One embodiment of a vehicle undercarriage according to the present invention will now be described with reference to the drawings (Figs. 1 to 8). In the drawings, the direction of the arrow Fr indicates the front in the longitudinal direction of the vehicle. In the description of the embodiment, the "front (front end) and rear (rear end)" correspond to the front and rear in the longitudinal direction of the vehicle. The directions of the arrows L and R indicate the left and right sides 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. The direction of the arrow U indicates the upper side of the vehicle.

The vehicle underbody structure of this embodiment is the underbody structure of an electric vehicle having a battery that supplies power to a motor (not shown) for driving the wheels. The vehicle underbody structure has 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.

As shown in Figures 1 and 2, the front side members 10 are highly rigid components that make up the vehicle body frame. The front side members 10 extend forward from both outer sides in the vehicle width direction at the front of the floor panel 71 that makes up the floor. 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 of the vehicle body. A drive motor and other components are disposed between the two front side members 10.

Each front side member 10 has a rear inclined portion 12 and a front straight portion 11. The rear inclined portion 12 extends at an incline outward in the vehicle width direction from the front of the floor panel 71 toward the front of the vehicle. The rear portion of the rear inclined portion 12 is joined to the battery bracket 50. The configuration of the rear portion of the rear inclined portion 12 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.

The front side member 10 has a U-shaped cross section with an opening toward the top of the vehicle. For example, the inner wall 12a of the front side member 10 located at the rear inclined portion 12 is provided with an inner flange 12c that protrudes inward in the vehicle width direction and extends in the vehicle front-rear direction, and the outer wall 12b is provided with an outer flange 12d that protrudes outward in the vehicle width direction and extends in the vehicle front-rear direction. As shown in FIG. 2, the inner flange 12c and the outer flange 12d are joined to a dash lower panel 72 that constitutes a part of the floor of the vehicle body (FIG. 7). A battery bracket 50 is joined to the rear of the inner flange 12c and the outer flange 12d. In this embodiment, the bottom surface portion 14 (FIGS. 4 and 5) that constitutes the U-shaped cross section is inclined downward toward the rear of the vehicle.

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

As shown in Figures 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 approximately the center of the floor panel 71 rises upward from 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.

As shown in FIG. 3, the lower member 21 extends from the rear of the rear inclined portion 12 of the front side member 10 toward the inside in the vehicle width direction. In this embodiment, the lower member 21 is composed of an inner lower member 22 and an outer lower member 27 arranged side by side in the vehicle width direction. The inner lower member 22 and the outer lower member 27 are members that extend in the vehicle width direction, and the outer lower member 27 is joined to the outer end of the inner lower member 22.

As shown in FIG. 3, the inner lower member 22 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 vehicle upper side as viewed in the vehicle width direction. In this example, the outer side of the inner lower member 22 in the vehicle width direction is disposed on the inner side in the vehicle width direction at the rear of the rear inclined portion 12 of the front side member 10. Although detailed illustration is omitted, the lower surface of the inner lower member 22 is joined to the bottom surface portion 14 of the rear inclined portion 12, and the rear wall 22a provided at the rear end of the lower surface of the inner lower member 22 is joined to the rear end of the rear inclined portion 12. In addition, the front wall 22b provided at the front end of the lower surface of the inner lower member 22 is provided with a flange 22c that protrudes, for example, forward of the vehicle and extends in the vehicle up-down direction, and the flange 22c is joined to the inner wall 12a of the rear inclined portion 12 by spot welding or the like.

As shown in FIG. 3, the inner side of the inner member 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 inner lower member 22 in the vehicle width direction is joined by spot welding or the like to an intermediate member (not shown) that extends in the vehicle width direction so as to straddle the floor tunnel 71A.

As shown in FIG. 3, the outer lower member 27 is a plate extending in the vehicle width direction, and the inner portion of the outer lower member 27 in the vehicle width direction is joined by spot welding or the like to the outer portion of the lower surface of the inner lower member 22 in the vehicle width direction. The outer lower member 27 is also joined to the bottom surface portion 14 in a state where it covers a part of the bottom surface portion 14 of the rear inclined portion 12 of the front side member 10 from the underside of the vehicle.

Although not shown in the figures, the intermediate member, the left and right inner lower members 22, and the left and right outer lower members 27 form a single lower cross member.

As shown in FIG. 2, the side brace 16 is a highly rigid member that extends at an angle toward the rear of the vehicle as it moves outward in the vehicle width direction, connecting the outer lower member 27 and the front of the side sill 18. Although not shown in detail, the side brace 16 has a U-shaped cross section that opens toward the top of the vehicle. Flanges 16c and 16d are provided on the upper portions of the front wall 16a and rear wall 16b that form the U-shaped cross section, and the flanges 16c and 16d are joined to the floor panel 71 by spot welding or the like. 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.

The inner side of the underside of the side brace 16, which forms the U-shaped cross section, is arranged to cover the bottom 14 at the rear of the rear inclined portion 12 of the front side member 10 via the outer lower member 27. The underside covering the front side member 10 is joined by spot welding or the like to the outer side of the bottom 14 of the rear inclined portion 12 of the front side member 10 in the vehicle width direction. The underside of the side brace 16 is also joined to the outer lower member 27.

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). The cable is routed, for example, inside the floor tunnel 71A and connected to the motor. The battery pack 40 includes a battery and a battery case that houses the battery, and in this embodiment, the battery case will be referred to as the battery pack 40.

As shown in FIG. 1, the battery pack 40 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 of the battery pack 40 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 of the battery pack 40 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 at an incline toward the rear of the vehicle as they move from the outer portions 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 of the battery pack 40.

As shown in FIG. 1, the front cross member 60 is disposed on the vehicle front side of the battery pack 40, is one of the members constituting the vehicle body frame, and is a member that extends 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 that extends in the vehicle width direction. The member inclined portion 62 is a portion that extends 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. In other words, the front cross member 60 is formed so that it is convex toward the front of the vehicle as a whole.

As shown in FIG. 5, the front cross member 60 is formed by joining together an upper member 65 having an L-shaped cross section that constitutes a top surface 65a and a rear wall 65b, and a lower member 66 having an L-shaped cross section that constitutes a front wall 66b and a bottom 66a. A flange 65c that protrudes 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 66a of the lower member 66. Similarly, a flange 66c that protrudes 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 65a of the upper member 65, thereby forming a hollow structure.

As shown in Figures 2 and 3, the battery bracket 50 is a member for attaching the battery pack 40 to the lower part of the floor of the vehicle body. The battery bracket 50 is joined to the battery pack 40 via the front cross member 60.

The battery bracket 50 is joined to a front wall 66b located at a member corner 63 of the front cross member 60. A flange (not shown) that protrudes inward in the vehicle width direction and extends in the vehicle vertical direction is provided on the inside of the rear part of the battery bracket 50 in the vehicle width direction, and a flange (not shown) that protrudes outward in the vehicle width direction and extends in the vehicle vertical direction is provided on the outside of the vehicle width direction. These flanges are joined to the front wall 66b located at the member corner 63 of the front cross member 60 by spot welding or the like.

As shown in Figs. 2 and 3, the battery bracket 50 is joined to the rear of the outer lower member 27 in a state where it is arranged so as to overlap the rear of the rear inclined portion 12 of the front side member 10 when viewed from below the vehicle. In this example, the battery bracket 50 has a flat planar portion 51 extending forward of the vehicle from the member corner portion 63. The planar portion 51 is joined to the outer portion of the lower surface of the lower member 21 in the vehicle width direction. Here, the underside of the outer lower member 27 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. The underside and the planar portion 51 may also be fastened by bolts or the like.

As described above, the lower member 21 (inner lower member 22) extending inward in the vehicle width direction is joined to the rear of the front side member 10, so the joint where these members are joined has improved rigidity in the vehicle width direction and the vehicle front-rear direction. This improved rigidity promotes load transfer from the front side member 10 to the lower member 21. Furthermore, because the battery bracket 50 is disposed on the vehicle rear side of the front side member 10, it becomes possible to efficiently transfer load from the front side member 10 to the battery bracket 50. In addition, the structure in which the battery bracket 50 is joined to the member corner portion 63 also improves the rigidity of the front portion of the battery pack 40.

As shown in FIG. 3, the battery bracket 50 of this embodiment is also joined to the lower part of the front side member 10. In this example, the flat portion 51 of the battery bracket 50 is joined to the bottom surface 14 of the rear inclined portion 12 of the front side member 10 via the side brace 16 by bolts or the like. Although not shown in the figure, for example, two bolt holes 52 are provided in the flat portion 51 of the battery bracket 50 at intervals in the vehicle width direction, and bolt holes are provided in the side brace 16 and the bottom surface 14 of the front side member 10 to correspond to these bolt holes 52. The front side member 10 and the battery bracket 50 are joined with bolts passing through the bolt holes 52.

The flat surface 51 of the battery bracket 50, the side brace 16, and the front side member 10 are fastened together with bolts or the like in a three-layered configuration. This type of joint structure makes it possible to more effectively transmit load to the battery bracket 50 by utilizing the rigidity of the front side member 10 in the vehicle fore-aft direction.

In this embodiment, the rear end of the rear inclined portion 12 of the front side member 10 is joined to the rear wall of the side brace 16 and the rear wall of the inner lower member 22. Furthermore, as shown in Figures 2 and 3, a bulge portion 17 that bulges forward of the vehicle is formed by the front portion of the outer lower member 27 and the inner portion in the vehicle width direction at the front portion of the side brace 16.

The front portion of the outer lower member 27 has a portion that bulges further forward of the vehicle than the front portion of the inner lower member 22. Similarly, the inner portion in the vehicle width direction at the front portion of the side brace 16 has a portion that bulges further forward of the vehicle than the front portion of the inner lower member 22. The bulging portion 17 is formed by the bulging portions of the outer lower member 27 and the side brace 16.

The provision of the bulge 17 improves the rigidity in the longitudinal direction of the vehicle. As a result, the load input from the front side member 10 is transmitted to the rear of the vehicle via the bulge 17. This promotes the transmission of the load to the rear of the vehicle.

As shown in Figures 4 and 5, the bottom surface portion 14 constituting the U-shaped cross section of the front side member 10 is joined to the bulge portion 17, and the bulge portion 17 bulges further downward in the vehicle than the bottom surface portion 14. In other words, the lower end of the bulge portion 17 is located further downward in the vehicle than the bottom surface portion 14. This allows the bulge portion 17 to support the bottom surface portion 14 of the front side member 10 from the lower side of the vehicle.

For example, in the event of a frontal collision, the front side member 10 receives the impact load and absorbs the load. At that time, because the rear end of the front side member 10 is joined to the bulge portion 17, the deformation of the front side member 10 that causes it to fold can be promoted on the vehicle forward side of the bulge portion 17. In other words, deformation of the rear end of the front side member 10 on the vehicle rear side of the bulge portion 17 is suppressed. As a result, it is possible to concentrate the load input direction from the bulge portion 17 toward the battery bracket 50.

In addition, the above-described deformation of the front side member 10 prevents the load from being transmitted to the vehicle body where the passenger compartment is located, and the load transmitted to the battery bracket 50 is sufficiently absorbed. Furthermore, the input direction of the impact load is aligned in the intended direction (e.g., toward the rear of the vehicle). In other words, the transmission of the load in an unintended direction is suppressed.

In addition, as shown in Figures 4 and 5, the bottom surface 14 of the front cross member 60 in this embodiment extends so as to incline downward toward the rear of the vehicle, and the lower end of the rear of the battery bracket 50 is located below the bottom surface 14 of the front side member 10. Note that the upper end of the rear of the battery bracket 50, i.e., the end closest to the battery pack 40, may be located below the bottom surface 14.

Because the bottom surface 14 of the front side member 10 is inclined, the impact load input to the front side member 10 is transmitted along the incline toward the lower side of the vehicle. On the other hand, because the battery bracket 50 is positioned below the front side member 10, it is possible to prevent the battery bracket 50 from being damaged by the impact load.

If the lower end of the rear of the battery bracket 50 were positioned above the vehicle with respect to the bottom surface 14 of the front cross member 60, the impact load transmitted from the front cross member 60 toward the bottom of the vehicle would be transmitted from the battery bracket 50 toward the top of the vehicle. In this case, the battery bracket 50 could bend and break so as to convex toward the top of the vehicle, resulting in insufficient load transmission. Therefore, positioning the battery bracket 50 as described above is effective in preventing damage to the battery bracket 50.

In addition, as shown in Figs. 1 and 2, the front side member 10 of this embodiment has a curved portion 13 that curves inward in the vehicle width direction from the middle portion in the vehicle front-rear direction toward the rear of the vehicle. The curved portion 13 in this example is a portion that connects the front straight portion 11 and the rear inclined portion 12. Furthermore, the battery bracket 50 is joined on the inner side in the vehicle width direction of a reference line L (Fig. 2) that passes through the center of the front side member 10 in the vehicle width direction. In this example, one of the bolt holes 52 in the flat portion 51 of the battery bracket 50 is located to the right of the reference line L (on the inner side in the vehicle width direction, on the left in Fig. 2).

The rear of the front side member 10 curves inward in the vehicle width direction, so the load is transmitted toward the rear of the vehicle and toward the inside in the vehicle width direction. Because the joint between the battery bracket 50 and the front side member 10 is located inside the reference line L, the load input to the vehicle body is more easily input to the battery pack 40. This allows the impact load to be transmitted to the battery pack 40 effectively.

In this embodiment, as shown in Figs. 6 and 7, a suspension frame 75 is joined to the lower part of the bulge 17. The suspension frame 75 is a member that extends in the vehicle width direction. In this example, the outer part of the upper surface of the suspension frame 75 in the vehicle width direction and the lower part of the bulge 17 are fastened with bolts or the like.

The suspension frame 75 is joined to the front of the battery pack 40. The rear of the suspension frame 75 on the outer side in the vehicle width direction protrudes rearward of the vehicle beyond the middle part of the suspension frame 75 in the vehicle width direction. This protruding part is fastened to the member inclined part 62 of the underside of the front cross member 60 by bolts 79 or the like (Figure 7).

By attaching the suspension frame 75 as described above, when an impact load is input to the front side member 10, the load can be transmitted from the bulge 17 to the battery pack 40 via the suspension frame 75. This makes it possible to transmit the impact load to the battery pack 40 more effectively.

The description of this 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.

In this embodiment, the lower member 21 is composed of an inner lower member 22 and an outer lower member 27, but is not limited to this. For example, as shown in FIG. 8, the inner lower member 22 and the outer lower member 27 may be composed as a single member.

10 Front side member 11 Front straight portion 12 Rear inclined portion 12a Inner wall 12b Outer wall 12c Inner flange 12d Outer flange 13 Curved portion 14 Bottom surface portion 16 Side brace 16a Front wall 16b Rear wall 16c Flange 17 Bulging portion 18 Side sill 21 Lower member 22 Inner lower member 22a Rear wall 22b Front wall 22c Flange 27 Outer lower member 40 Battery pack 41 Case straight portion 42 Case inclined portion 43 Case corner portion 50 Battery bracket 51 Flat portion 52 Bolt hole 60 Front cross member 61 Member straight portion 62 Member inclined portion 63 Member corner portion 65 Upper member 65a Top surface portion 65b Rear wall 65c Flange 66 Lower member 66a Bottom portion 66b Front wall 66c Flange 71 Floor panel 71A Floor tunnel 72 Dash lower panel 73 Wheel house panel 75 Suspension frame

Claims (7)

A vehicle underbody structure having a front side member extending from a front portion of a floor portion of a vehicle toward the front of the vehicle, and a battery pack fixed to a lower surface side of the floor portion via a battery bracket,
A lower member is joined to a rear portion of the front side member, the lower member extending inward in a vehicle width direction from the rear portion,
a battery bracket that is joined to a vehicle width direction outer portion of the lower member in a state where the battery bracket overlaps a rear portion of the front side member when viewed from below the vehicle. The vehicle underbody structure according to claim 1, characterized in that the battery bracket is joined to the rear of the front side member. A side brace is joined to the rear portion of the front side member,
The side brace extends obliquely toward the rear of the vehicle as it moves from the rear of the front side member toward the outside in the vehicle width direction, and an upper portion of the side brace is joined to the floor portion,
3. The vehicle underbody structure according to claim 1, wherein a bulging portion that bulges forward of the vehicle is formed by a vehicle width direction outer portion of the lower member and a vehicle width direction inner portion of the side brace. The front side member has a bottom surface portion facing a vehicle lower side,
4. The vehicle underbody structure according to claim 3, wherein the bulging portion bulges downwardly of the vehicle relative to the bottom surface portion. The front side member extends so as to incline downwardly toward the rear of the vehicle,
5. The vehicle underbody structure according to claim 1, wherein the battery bracket is disposed below the front side member. the front side member has a curved portion that curves inwardly in a vehicle width direction from a middle portion in a vehicle front-rear direction toward the rear of the vehicle,
6. The vehicle underbody structure according to claim 1, wherein the battery bracket is joined to the front side member on a vehicle widthwise inner side of a reference line passing through a vehicle widthwise center of the front side member. A vehicle width direction outer portion of a suspension frame extending in the vehicle width direction is joined to a lower portion of the bulging portion,
7. The vehicle underbody structure according to claim 4, wherein the suspension frame is joined to a front portion of the battery pack.