Vehicle understructure

Abstract

This prevents vehicle structures from interfering with the battery case during a side collision. [Solution] In the lower structure of a vehicle 1, which includes a floor panel 13 that constitutes the floor surface of the vehicle 1, a pair of side sills 14, 14 arranged on the left and right sides of the floor panel, a cross member 3 provided on the exterior surface of the floor panel, including a flat extending bottom surface 311, extending in the vehicle width direction and connecting the pair of side sills, and a battery case 21 arranged below the floor panel and the cross member for housing the battery, a weak portion 33 is provided at the lower part of the cross member in a cross section perpendicular to the extending direction of the cross member.

Description

[Technical Field]

[0001] The present invention mainly relates to a structure of a lower portion (underbody) of a vehicle. [Background Art]

[0002] As a lower structure of this type of vehicle, there is known a vehicle body side structure including: a side sill formed by joining a side sill inner and a side sill outer at an upper end portion and a lower end portion in a vehicle height direction; a battery pack disposed at a lower portion of the vehicle body on a vehicle inner side in the vehicle width direction relative to the side sill; and a floor cross member extending in the vehicle width direction above the vehicle inner side in the vehicle width direction relative to the side sill (Patent Document 1). In this conventional vehicle body side structure, when a collision load is input to the side sill from the vehicle outer side in the vehicle width direction (side collision), after the side sill outer deforms and crushes, the load input to the side sill is transmitted to the floor cross member, thereby reducing the load transmitted to the battery pack. [Prior Art Document] [Patent Document]

[0003] [Patent Document 1] International Publication WO2023 / 233930 Pamphlet [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] However, in the above-described conventional technology, there is a problem that when the floor cross member undergoes buckling deformation in a downward convex shape, a vehicle structure such as a floor panel interferes with the battery case.

[0005] The problem to be solved by the present invention is to provide a vehicle lower structure capable of suppressing interference of a vehicle structure with a battery case during a side collision. [Means for Solving the Problem]

[0006] The present invention solves the above problem by providing a weak point at the lower part of the cross member in a cross section perpendicular to the extending direction of the cross member, in a vehicle understructure that includes a cross member provided on the exterior surface of the floor panel, including a flat extending bottom surface, connecting a pair of side sills, and a battery case disposed below the floor panel and the cross member for housing a battery. [Effects of the Invention]

[0007] According to the present invention, it is possible to suppress interference between the vehicle structure and the battery case during a side collision. [Brief explanation of the drawing]

[0008] [Figure 1] This is a bottom view of a vehicle showing the understructure of a vehicle according to one embodiment of the present invention. [Figure 2] Figure 1 is an exploded perspective view showing the floor panel, side sill, and cross member. [Figure 3] This is a cross-sectional view of the section along line III-III in Figure 1, shown upside down. [Figure 4] This is a cross-sectional view along the line IV-IV in Figure 3. [Figure 5] (A) to (C) are partially broken perspective views showing section V in Figure 3. [Figure 6] This is a cross-sectional view showing the lower structure of a vehicle according to another embodiment of the present invention, with the cross section along line III-III in Figure 1 shown upside down. [Figure 7] This is a cross-sectional view showing an inverted view of the cross-section along line III-III in Figure 1, illustrating the understructure of a vehicle according to yet another embodiment of the present invention. [Figure 8] (A) and (B) are perspective views showing part VIII of Figure 7, respectively. [Figure 9] This is a cross-sectional view showing an inverted view of the cross-section along line III-III in Figure 1, illustrating the understructure of a vehicle according to yet another embodiment of the present invention. [Figure 10] This is a perspective view showing section X in Figure 9. [Figure 11](A) and (B) are diagrams illustrating the operation of the embodiment shown in Figure 1, respectively. [Figure 12] (A) is a diagram illustrating the operation of the embodiment shown in Figure 7, and (B) is a diagram illustrating the operation of a comparative example thereof. [Modes for carrying out the invention]

[0009] Common configuration of the embodiments Hereinafter, examples of embodiments for carrying out the present invention will be described with reference to the drawings. Figure 1 is a bottom view of vehicle 1 showing the lower structure of vehicle 1 according to one embodiment of the present invention, Figure 2 is an exploded perspective view showing the floor panel 13, side sill 14 and cross member 3 of Figure 1, Figure 3 is a cross-sectional view showing the cross section along line III-III of Figure 1 upside down, and Figure 4 is a cross-sectional view along line IV-IV of Figure 3.

[0010] As shown in Figure 1, the vehicle 1 of this embodiment has an internal combustion engine 11 and a drive motor 12. The type of vehicle 1 of this embodiment is not particularly limited, and it may be a hybrid vehicle that uses both the internal combustion engine 11 and the drive motor 12 as drive sources, or a hybrid vehicle that uses only the drive motor 12 as a drive source and uses the internal combustion engine 11 as a power source for power generation. Furthermore, although the present invention will be explained using a hybrid vehicle as an example in the following embodiments, the vehicle of the present invention may be an electric vehicle that does not have an internal combustion engine 11 and is equipped only with a drive motor 12.

[0011] Vehicle 1 in this embodiment includes a floor panel 13, a pair of left and right side sills 14, a battery 2, and a cross member 3 as the vehicle's underbody structure (also called the automobile's underbody structure). Note that the vehicle according to the present invention may include other underbody components. In the following description, the direction along the front and rear of Vehicle 1 is referred to as the front-rear direction, the direction along the left and right of Vehicle 1 is referred to as the vehicle width direction, and the direction along the top and bottom of Vehicle 1 is referred to as the up-down direction. Figures 1 to 11 show the front-rear, left-right, and up-down directions of Vehicle 1, respectively.

[0012] As shown in FIGS. 1 and 2, the floor panel 13 is a member obtained by press-forming a metal plate material constituting the floor surface of a vehicle compartment. In order to increase panel rigidity against input in the front-rear direction of the vehicle 1, as shown in FIGS. 2 and 3, the floor panel 13 has a portion that extends along the front-rear direction of the vehicle 1 at the center in the vehicle width direction of the vehicle 1, A tunnel portion 131 that bends convexly upward is formed. The boundary portion between the general surface of the floor panel 13 and the tunnel portion 131 is also referred to as a rising start position 132.

[0013] As shown in FIG. 3, the side sill 14 is formed of an assembly component in which a sill outer panel 141 and a sill inner panel 142 are welded and joined in a hollow shape, and is fixed to the left and right ends of the floor panel 13 by welding or the like. The sill outer panel 141 and the sill inner panel 142 constituting the side sill 14 are formed by press-forming a metal plate material, have high rigidity in the front-rear direction among vehicle structures, and constitute a part of the frame member of the lower structure of the vehicle 1. The side sill 14 is provided extending from the rear portion of the front wheel to the front portion of the rear wheel at each of the left and right ends of the floor panel 13.

[0014] The battery 2 has cell modules housed in a battery case 21, and is disposed below the cross member 3 on the vehicle exterior side (under-floor side) of the floor panel 13 as shown in FIGS. 1 and 3 via a battery frame (not shown). The battery 2 supplies electric power to the travel drive motor 12, on-vehicle electrical components, and the like.

[0015] The internal combustion engine 11 includes an exhaust pipe 15 that guides exhaust gas. As shown in FIG. 1, the exhaust pipe 15 extends rearward of the vehicle 1 from the internal combustion engine 11 mounted on the front portion of the vehicle 1, and a part thereof is routed in a space between the battery 2 and the right side sill 14. A first muffler 16 and a second muffler 17 are provided in the middle of the exhaust pipe 15. The first muffler 16 is disposed between the battery 2 and the right side sill 14. Note that the first muffler 16 and the second muffler 17 may include a filter portion and a catalyst portion. Further, the second muffler 17 is not necessarily required, and only the first muffler 16 may be disposed. Furthermore, the battery 2 and the first muffler 16 may be disposed at horizontally reversed positions.

[0016] The cross member 3 of the present embodiment includes: a cross member main body 31 that is provided on an outdoor-side surface of a floor panel 13, includes a flatly extending bottom surface 311, extends in a vehicle width direction, and connects a pair of left and right side sills 14, 14; and a reinforcing member 32 extending in the vehicle width direction, which is provided on the flatly extending bottom surface 311 of the cross member main body 31.

[0017] The cross member main body 31 of the present embodiment is a frame member formed by press-molding a metal plate material, and as shown in the cross-sectional view of FIG. 4, includes the bottom surface 311, vertical wall surfaces 312, 312 rising from the bottom surface 311, and a flange surface 313 bent in a horizontal direction from an upper end of each vertical wall surface 312. The bottom surface 311 extends flat in a range indicated by reference sign R1 in FIG. 3, and inclines toward a sill inner panel 142 in an outer range beyond that. Here, "extends flat" means that the bottom surface 311 extends over at least all or a part of a predetermined range R1 while being horizontal or slightly inclined without curving or bending. In other words, it means that the cross member main body 31 includes a shape or structure that may cause the cross member main body 31 to undergo buckling deformation into a downward convex ridge when a load is input in a side collision. By including the flatly extending bottom surface 311 over all or a part of the predetermined range R1 in the cross member main body 31, the rigidity of the vehicle 1 against a side collision where an input load is applied in the vehicle width direction can be increased.

[0018] In this embodiment, the cross member body 31 only needs to have a bottom surface 311 that extends flat within a predetermined range R1. The upper ends of the flange surface 313 and vertical wall surface 312 may extend flat in the same way as the bottom surface 311, as shown in Figures 2 and 3, or they may curve and extend along the underside of the floor panel 13.

[0019] The reinforcing member 32 in this embodiment is a skeletal member formed by press-forming a metal plate, and as shown in the cross-sectional view of Figure 4, it has a bottom surface 321 and vertical wall surfaces 322 rising from the bottom surface 321. In this embodiment, the reinforcing member 32 is joined by welding or the like in a state where the bottom surface 321 of the reinforcing member 32 is in contact with the bottom surface 311 of the cross member body 31 within the range R1 of the flat bottom surface 311 of the cross member body 31, as shown in Figure 3. Note that the reinforcing member 32 according to the present invention may also be a flat plate-like member consisting only of a bottom surface 321 without vertical wall surfaces 322.

[0020] As shown in Figure 3, the reinforcing member 32 of this embodiment is provided such that its center coincides with the center of the vehicle in the vehicle width direction, and the position P1 of the left end of the reinforcing member 32 is positioned inward from the position P2 of the outer left end of the battery case 21, i.e., towards the center in the vehicle width direction. This allows the side sill 14 and the left end portion of the cross member body 31 to be sufficiently compressed when there is an input in the vehicle width direction, such as a side collision, thereby absorbing collision energy, and at the same time suppressing the early onset of buckling deformation of the cross member 3 in the initial stages of a side collision. If the arrangement of the battery case 21 and the first silencer 16 is reversed left to right, it is preferable to position P1 of the right end of the reinforcing member 32 inward from the position P2 of the outer right end of the battery case 21, i.e., towards the center in the vehicle width direction.

[0021] In this embodiment, the cross member 3 is provided with a weak point 33 at the lower part of the cross member 3 in a cross section perpendicular to the extending direction of the cross member 3, where the buckling deformation load in response to input in the vehicle width direction is smaller than that at the upper part. The weak point 33 in this embodiment refers to a shape and structure in which, when a load in the vehicle width direction, i.e., a side collision load, is applied to the vehicle 1, the cross member 3 buckles and deforms in an upward convex shape starting from the weak point 33.

[0022] In this embodiment, the vulnerable portion 33 is more preferably located inward in the vehicle width direction from the rising start position 132 of the tunnel portion 131 of the floor panel 13, as shown in Figure 3, i.e., in the range indicated by the symbol R2. This is to compensate for the fact that in the event of an input such as a side collision, the entire cross member 3 will buckle in an upward convex shape due to the upward convex buckling deformation of the floor panel 13. Examples of the form of the vulnerable portion 33 of the present invention will be described below.

[0023] 《Example of the first form of a vulnerable area》 Figures 5(A) to 5(C) are partially broken perspective views showing one side of section V in Figure 3. The weak points 33 shown in Figure 5 are all examples of those provided on the reinforcing member 32. The weak point 33 in Figure 5(A) is an example in which the ridge portion between the bottom surface 321 and the vertical wall surface 322 of the reinforcing member 32 is recessed to form a triangular bead-shaped recess. The weak point 33 in Figure 5(B) is an example in which the bottom surface 321 of the reinforcing member 32 is embossed in an upward convex shape. The weak point 33 in Figure 5(C) is an example in which the lower side of the bottom surface 321 and vertical wall surface 322 of the reinforcing member 32 is cut out to form an opening. In all examples, a weak point 33 is formed at the lower part of the reinforcing member 32 in a cross section perpendicular to the extending direction of the reinforcing member 32, where the buckling deformation load in response to input in the vehicle width direction is smaller than at the upper part.

[0024] Next, the operation will be explained. Figures 11(A) and (B) respectively illustrate the operation of the embodiment shown in Figure 1. As shown in Figure 11(A), when a force F in the vehicle width direction, such as a side collision, is applied to the cross member 3, a weak point 33 is provided at the lower part of the reinforcing member 32 in a cross section perpendicular to the extending direction of the reinforcing member 32, where the buckling deformation load against the input in the vehicle width direction is smaller than at the upper part. Therefore, as shown in Figure 11(B), the reinforcing member 32 buckles and deforms in an upward convex shape. Since the cross member body 31 is welded to the reinforcing member 32, it buckles and deforms in an upward convex shape simultaneously with the buckling deformation of the reinforcing member 32. Although not shown in the figure, the floor panel 13 is also welded to the cross member body 31, so the floor panel 13 also buckles and deforms in an upward convex shape. Due to these deformations, both the cross member (cross member body 31 and reinforcing member 32) and the floor panel 13, which are located above the battery case 21, buckle and deform in an upward convex shape, moving away from the battery case 21. As a result, interference between the vehicle structure and the battery case 21 during a side collision can be suppressed.

[0025] 《Example of the second form of the vulnerable area》 Figure 6 is a cross-sectional view showing the lower structure of a vehicle 1 according to another embodiment of the present invention, with the cross section along line III-III in Figure 1 shown upside down. In the first embodiment shown in Figures 3 and 5, a single reinforcing member 32 is provided on the cross member body 31, and a weak portion 33 is formed on the reinforcing member 32. However, in the second embodiment shown in Figure 6, instead, reinforcing members 32, 32 are provided spaced apart on the left and right sides of the cross member body 31 in the vehicle width direction, and the space between these two reinforcing members 32, 32 (i.e., the part of the cross member 3 where no reinforcing member 32 is provided) is made into a weak portion 33.

[0026] In this case, the configuration of the cross member body 31 is the same as the configuration of the cross member body 31 in the embodiments shown in Figures 2 to 4. Furthermore, each of the reinforcing members 32 has a bottom surface 321 and a vertical wall surface 322 rising from this bottom surface 321, as shown in the cross-sectional view in Figure 4. In this embodiment, the reinforcing member 32 is joined by welding or the like in a state where the bottom surface 321 of the reinforcing member 32 is in contact with the bottom surface 311 of the cross member body 31 within the range R1 of the flat bottom surface 311 of the cross member body 31, as shown in Figure 6. Note that the reinforcing member 32 according to the present invention may also be a flat plate-shaped member consisting only of a bottom surface 321 without a vertical wall surface 322.

[0027] However, in this embodiment, the reinforcing member 32 itself does not have a weak point 33, and the space between these two reinforcing members 32, 32 is considered the weak point 33. Here, it is more preferable to position the inner ends of the two reinforcing members 32 inward in the vehicle width direction from the rising start position 132 of the tunnel portion 131 of the floor panel 13, i.e., in the range indicated by the reference numeral R2, as shown in Figure 6.

[0028] As shown in Figure 6, two reinforcing members 32 are provided spaced apart on the left and right sides of the cross member body 31 in the vehicle width direction, and the space between the reinforcing members 32, 32 is made a weak point 33. In this way, the buckling load on the cross member 3 as a whole in response to inputs in the vehicle width direction, such as a side collision, is relatively smaller in the space between the two reinforcing members 32, 32, i.e., the portion of the cross member body 31 without the reinforcing members 32, than in the portion with the reinforcing members 32. Furthermore, since the two reinforcing members 32, 32 are provided at the lower part of the cross member body 31, the buckling load on the cross member 3 as a whole is relatively smaller in the lower part of the cross member body 31 in a cross section perpendicular to the extension direction of the cross member compared to the upper part. As a result, when a force F in the vehicle width direction, such as a side collision, is applied, the cross member deforms in an upward convex shape, starting from the weak point 33, and especially from the inner end of the reinforcing member 32 where the magnitude of the buckling load changes rapidly. This suppresses interference between the vehicle structure and the battery case 21 during a side collision.

[0029] 《Example of the third form of a vulnerable area》 Figure 7 is a cross-sectional view showing the understructure of a vehicle according to yet another embodiment of the present invention, with the cross section along line III-III in Figure 1 shown upside down. In the first embodiment shown in Figures 3 and 5, one reinforcing member 32 is provided on the cross member body 31, and a weak portion 33 is formed on the reinforcing member 32. However, in the third embodiment shown in Figure 7, instead, reinforcing members 32, 32 are provided in contact with each other on the left and right sides in the vehicle width direction of the cross member body 31, and a weak portion 33 is provided at the ends where these two reinforcing members 32, 32 contact each other.

[0030] In this case, the configuration of the cross member body 31 is the same as the configuration of the cross member body 31 in the embodiments shown in Figures 2 to 4. Furthermore, each of the reinforcing members 32 has a bottom surface 321 and a vertical wall surface 322 rising from this bottom surface 321, as shown in the cross-sectional view in Figure 4. In this embodiment, the reinforcing member 32 is joined by welding or the like in a state where the bottom surface 321 of the reinforcing member 32 is in contact with the bottom surface 311 of the cross member body 31 within the range R1 of the flat bottom surface 311 of the cross member body 31, as shown in Figure 7. Note that the reinforcing member 32 according to the present invention may also be a flat plate-shaped member consisting only of a bottom surface 321 without a vertical wall surface 322.

[0031] Figures 8(A) and 8(B) are perspective views showing section VIII of Figure 7, and perspective views showing the inner end of one of the reinforcing members 32. The weak portion 33 in Figure 8(A) is an example in which the bottom surface 321 of the inner end of the reinforcing member 32 is embossed in an upward convex shape. The weak portion 33 in Figure 8(B) is an example in which the bottom surface 321 and the lower side of the vertical wall surface 322 of the inner end of the reinforcing member 32 are cut out. In both examples, a weak portion 33 is formed at the lower part of the reinforcing member 32 in a cross section perpendicular to the extending direction of the reinforcing member 32, where the buckling deformation load to input in the vehicle width direction is smaller than at the upper part.

[0032] Next, the operation will be explained. Figure 12(A) is a diagram illustrating the operation of the embodiment shown in Figure 7, and Figure 12(B) is a diagram illustrating the operation of the embodiment shown in Figure 1 as a comparative example of the embodiment shown in Figure 7. As shown in Figure 12(A), when a force F in the vehicle width direction, such as a side collision, is applied to the cross member 3, the two reinforcing members 32 buckle and deform in an upward convex shape at the contact portion, starting from the weak point 33, where the buckling deformation load in response to the input in the vehicle width direction is smaller than that at the top.

[0033] In this case, if the reinforcing member 32 is composed of a single reinforcing member 32, as in the comparative example shown in Figure 12(B), a tensile force f is generated on the upper part of the reinforcing member 32 when buckling deformation occurs starting from the weak point 33, which may prevent the buckling deformation from progressing smoothly. In contrast, in this embodiment shown in Figure 12(A), the two reinforcing members 32, 32 are only in contact and not joined together, so no tensile force f is generated between these two reinforcing members 32, 32. Therefore, compared to the comparative example shown in Figure 12(B), buckling deformation can be performed more reliably at the intended position.

[0034] As shown in Figure 12(A), when the two reinforcing members 32 buckle in an upward convex shape, the cross member body 31, which is welded to the reinforcing members 32, buckles in an upward convex shape simultaneously with the buckling deformation of the reinforcing members 32. Although not shown in the figure, the floor panel 13 is also welded to the cross member body 31, so the floor panel 13 also buckles in an upward convex shape. Due to these deformations, both the cross member (cross member body 31 and reinforcing members 32) and the floor panel 13, which are located above the battery case 21, buckle in an upward convex shape, moving away from the battery case 21. This suppresses interference between the vehicle structure and the battery case 21 during a side collision.

[0035] 《Example of the fourth form of a vulnerable area》 Figure 9 is a cross-sectional view showing the understructure of a vehicle according to yet another embodiment of the present invention, with the cross section along line III-III in Figure 1 shown upside down, and Figure 10 is a perspective view showing section X in Figure 9. In the first embodiment shown in Figures 3 and 5, one reinforcing member 32 is provided on the cross member body 31, and a weak portion 33 is formed on the reinforcing member 32. However, in the fourth embodiment shown in Figure 9, instead, reinforcing members 32, 32 are provided spaced apart on the left and right sides of the cross member body 31 in the vehicle width direction, and an intermediate reinforcing member 34 is joined between these two reinforcing members 32, 32, with the two joints between the reinforcing member 32 and the intermediate reinforcing member 34 forming the weak portion 33.

[0036] In this case, the configuration of the cross member body 31 is the same as the configuration of the cross member body 31 in the embodiment shown in Figures 2 to 4. Furthermore, each of the reinforcing members 32 has a bottom surface 321 and a vertical wall surface 322 rising from this bottom surface 321, as shown in Figure 10. Similarly, the intermediate reinforcing member 34 has a bottom surface 341 and a vertical wall surface 342 rising from this bottom surface 341, as shown in Figure 10, and has the same cross-sectional shape as the reinforcing member 32. In this embodiment, the reinforcing member 32 and the intermediate reinforcing member 34 are joined by welding or the like within the range R1 of the flat bottom surface 311 of the cross member body 31, with the bottom surface 321 of the reinforcing member 32 and the bottom surface 341 of the intermediate reinforcing member 34 in contact with the bottom surface 311 of the cross member body 31, as shown in Figure 9. Note that the reinforcing member 32 according to the present invention may also be a flat plate-shaped member consisting only of a bottom surface 321 without a vertical wall surface 322. Similarly, the intermediate reinforcing member 34 according to the present invention may be a flat plate-shaped member consisting only of a bottom surface 341 without a vertical wall surface 342.

[0037] However, in this embodiment, neither the reinforcing member 32 nor the intermediate reinforcing member 34 itself has a weak point 33; rather, the weak point 33 is the two joints between the reinforcing member 32 and the intermediate reinforcing member 34. Here, it is more preferable to provide the weak points 33, 33, which are the two joints between the reinforcing member 32 and the intermediate reinforcing member 34, in the vehicle width direction inward from the rising start position 132 of the tunnel portion 131 of the floor panel 13, i.e., in the range indicated by the reference numeral R2, as shown in Figure 9.

[0038] In this embodiment, the reinforcing member 32 and the intermediate reinforcing member 34 are members with different plate thicknesses or materials. A single steel plate (blank material) formed by welding together multiple steel plates of different thicknesses and materials in this manner is also called a tailored blank. For example, in this embodiment, it is possible to use a configuration in which the two reinforcing members 32 are made from thick steel plates, the intermediate reinforcing member 34 is made from thin steel plates, and their ends are welded together. Alternatively, it is possible to use a configuration in which the two reinforcing members 32 are made from steel, the intermediate reinforcing member 34 is made from aluminum of the same plate thickness, and their ends are welded together.

[0039] As shown in Figure 9, two reinforcing members 32 are provided spaced apart on the left and right sides of the cross member body 31 in the vehicle width direction, and an intermediate reinforcing member 34 of a different material or plate thickness is joined between the reinforcing members 32, 32, making the joint a weak point 33. In this case, the buckling load on the cross member 3 as a whole in response to inputs in the vehicle width direction, such as a side collision, is relatively smaller at the joint between the reinforcing members 32 and the intermediate reinforcing member 34, i.e., the weak point 33, than at the parts where the reinforcing members 32 and the intermediate reinforcing member 34 are provided. Furthermore, since the two reinforcing members 32, 32 and the intermediate reinforcing member 34 are provided at the lower part of the cross member body 31, the buckling load on the cross member 3 as a whole is relatively smaller at the lower part of the cross section perpendicular to the extension direction of the cross member compared to the upper part. As a result, when a force F in the vehicle width direction, such as a side collision, is applied, the cross member deforms in an upward convex shape, starting from the weak point 33, which is the joint between the reinforcing members 32 and the intermediate reinforcing member 34. This makes it possible to suppress interference between the vehicle structure and the battery case 21 during a side collision.

[0040] 《Effects of the Embodiment》 As described above, the vehicle substructure of this embodiment includes a floor panel 13 that constitutes the floor surface of the vehicle 1, a pair of side sills 14, 14 arranged on the left and right sides of the floor panel 13, a cross member 3 provided on the exterior surface of the floor panel 13, including a flat, extending bottom surface 311, extending in the vehicle width direction and connecting the pair of side sills 14, 14, and a battery case 21 arranged below the floor panel 13 and the cross member 3 for housing the battery. In this vehicle substructure, a weak point 33 is provided at the lower part of the cross member 3 in a cross section perpendicular to the extending direction of the cross member 3, where the buckling deformation load in response to input in the vehicle width direction is smaller than that at the upper part. Therefore, when an input such as a side collision occurs, stress concentrates at the weak point 33. When an input such as a side collision occurs, the cross member 3 buckles and deforms in an upward convex shape starting from the weak point 33 provided at the lower part. This makes it possible to suppress interference between the vehicle structure and the battery case 21.

[0041] Furthermore, in this embodiment, when a load in the vehicle width direction is applied to the vehicle 1, the cross member 3 buckles and deforms in an upward convex shape starting from the weak point 33, thereby suppressing interference between the vehicle structure and the battery case 21.

[0042] Furthermore, in the vehicle substructure of this embodiment, the cross member 3 includes a reinforcing member 32 extending in the vehicle width direction on the flat bottom surface 311, and the weak portion 33 is provided at the lower part of the reinforcing member 32 in a cross section perpendicular to the direction of extension of the reinforcing member 32. Therefore, when an input such as a side collision occurs, the reinforcing member 32 buckles and deforms in an upward convex shape starting from the weak portion 33 provided at the lower part, and at the same time, the entire cross member 3 buckles and deforms in an upward convex shape. This makes it possible to suppress interference between the vehicle structure and the battery case 21.

[0043] Furthermore, in the vehicle's substructure of this embodiment, the reinforcing members 32 are provided spaced apart on the left and right sides in the vehicle width direction, and the weak portion 33 consists of the space between the reinforcing members 32. Therefore, when an input such as a side collision occurs, the weak portion 33 is used as the starting point, and especially the inner end of the reinforcing member 32, where the magnitude of the buckling load changes rapidly, is used as the starting point for upward convex buckling deformation. Simultaneously, the entire cross member 3 is deformed upward convex buckling deformation. This prevents the vehicle structure from interfering with the battery case 21.

[0044] Furthermore, in the vehicle substructure of this embodiment, the reinforcing members 32 are provided in contact with each other on the left and right sides in the vehicle width direction, and the weak points 33 are provided at the ends where each of the reinforcing members 32 makes contact. Therefore, when an input such as a side collision occurs, the two reinforcing members 32 buckle and deform in an upward convex shape starting from the weak points 33 provided at the contact points, and at the same time, the entire cross member 3 buckles and deforms in an upward convex shape. This makes it possible to suppress interference between the vehicle structure and the battery case 21. At this time, since the two reinforcing members 32, 32 are only in contact and not joined, no tensile force f is generated between these two reinforcing members 32, 32. Therefore, buckling deformation can be more reliably achieved at the intended position.

[0045] Furthermore, in the vehicle substructure of this embodiment, the cross member 3 includes a reinforcing member 32 and an intermediate reinforcing member 34 extending in the vehicle width direction on the flat, extending bottom surface 311. The reinforcing members 32 are spaced apart on the left and right sides in the vehicle width direction, and the intermediate reinforcing member 34 is joined between the left and right reinforcing members 32, 32. The joint between the reinforcing member 32 and the intermediate reinforcing member 34 constitutes the weak point 33. Therefore, when an input such as a side collision occurs, the weak point 33, formed by the joint between the reinforcing member 32 and the intermediate reinforcing member 34, buckles and deforms in an upward convex shape, and at the same time, the entire cross member 3 buckles and deforms in an upward convex shape. This makes it possible to suppress interference between the vehicle structure and the battery case 21.

[0046] Furthermore, in the vehicle's understructure of this embodiment, the vulnerable portion 33 is located in a range R2 in the vehicle width direction that is inward from the starting position 132 of the tunnel portion 131 of the floor panel 13. Therefore, when an input such as a side collision occurs, the floor panel 13 buckles and deforms in an upward convex shape, following the shape of the tunnel portion 131. This buckling deformation of the floor panel 13 can compensate for the buckling deformation of the entire cross member 3 in an upward convex shape.

[0047] Furthermore, in the vehicle's understructure of this embodiment, the position P1 of one outer end of the reinforcing member 32 is located inward from the position P2 of the outer end of the battery case 21 in the vehicle width direction. When there is an input in the vehicle width direction, such as a side collision, the collision energy is absorbed by the crushing of the side sill 14 and the left end portion of the cross member body 31. By positioning the left end P1 of the reinforcing member 32 to be closer to the center in the vehicle width direction than the outer left end P2 of the battery case 21, sufficient absorption of collision energy by the crushing of the left end portion of the side sill 14 and the cross member body 31 can be achieved. In addition, it is possible to suppress the early onset of buckling deformation of the cross member 3 in the initial stages of a side collision. [Explanation of symbols]

[0048] 1…Vehicle 11…Internal combustion engine 12…Motor for driving the vehicle 13…Floor panel 131...Tunnel section 132... Starting position 14... Side sill 141...Sill outer panel 142...Sill inner panel 15… Exhaust pipe 16…1st silencer 17…Second silencer 2… Battery 21…Battery case 3…Cross member 31... Cross member body 311...Bottom 312…Vertical wall surface 313…Flange surface 32…Reinforcement member 321...Bottom 322... Vertical wall surface 33…Vulnerable parts 34…Intermediate reinforcing member 341...Bottom 342…Vertical wall surface R1... The area where the bottom surface of the cross member body extends flat. R2... The area inside the vehicle width direction from the rising point of the tunnel section. P1…Position of the left end of the reinforcing member (one outer end of the reinforcing member) P2…Location of the left outer edge of the battery case (outer edge of the battery case in the vehicle width direction)

Claims

1. The floor panels that make up the floor surface of the vehicle, A pair of side sills are positioned on the left and right sides of the aforementioned floor panel, A cross member is provided on the exterior surface of the floor panel, includes a flat, extending bottom surface, extends in the vehicle width direction, and connects the pair of side sills. In the lower structure of a vehicle, which includes a battery case for housing a battery and is located below the floor panel and the cross member, A vehicle substructure in which a weak portion is provided at the lower part of the cross member in a cross section perpendicular to the extending direction of the cross member.

2. The vehicle substructure according to claim 1, wherein when a load in the width direction is applied to the vehicle, the cross member buckles and deforms in an upward convex shape starting from the weak point.

3. The cross member includes a reinforcing member extending in the vehicle width direction on the flat, extending bottom surface. The vehicle substructure according to claim 1 or 2, wherein the weak portion is provided at the lower part of the reinforcing member in a cross section perpendicular to the extending direction of the reinforcing member.

4. The reinforcing members are provided spaced apart on both the left and right sides in the vehicle width direction. The vehicle substructure according to claim 3, wherein the weak portion is the space between the reinforcing members.

5. The reinforcing members are provided in contact with the left and right sides in the vehicle width direction, The vehicle substructure according to claim 3, wherein the weak portion is provided at the end where each of the reinforcing members makes contact.

6. The cross member includes a reinforcing member and an intermediate reinforcing member extending in the vehicle width direction on the flat, extending bottom surface, The reinforcing members are provided spaced apart on both the left and right sides in the vehicle width direction. The intermediate reinforcing member is joined between the left and right reinforcing members, The vehicle substructure according to claim 1 or 2, wherein the joint between the reinforcing member and the intermediate reinforcing member constitutes the weak portion.

7. The vehicle substructure according to claim 1 or 2, wherein the vulnerable portion is provided inward in the vehicle width direction from the starting position of the rising tunnel portion of the floor panel.

8. The vehicle understructure according to claim 3, wherein one outer end of the reinforcing member is provided inward from the outer end of the battery case in the vehicle width direction.

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