Vehicle underbody structure

Abstract

The present invention comprises: a side sill extending in the vehicle longitudinal direction; a side sill reinforcement provided along the side sill; and a bulkhead disposed inside the side sill and joined to an inner surface of the side sill. The bulkhead and the side sill reinforcement are joined to each other.

Description

Vehicle underbody structure

[0001] The present invention relates to a vehicle underbody structure.

[0002] In a vehicle in which a heavy object such as an on-vehicle device is mounted on a lower portion of the vehicle, a configuration is known in which the heavy object is disposed between a pair of left and right side sills and is attached and fixed to the side sills. For example, in an electric vehicle such as an electric vehicle or a hybrid vehicle having a traveling motor that drives wheels, a battery case on which battery cells, which are heavy objects, are mounted is supported between a pair of side sills at a lower portion of the vehicle.

[0003] Patent Document 1 discloses a vehicle underbody structure including a side sill extending along a vehicle longitudinal direction and a battery pack fixed to the side sill, wherein a bulkhead for reinforcing a cross section of the side sill from an inner side is provided at positions in the vehicle longitudinal direction sandwiching a fixing point for the battery pack provided inside the side sill.

[0004] Japanese Patent Laid-Open No.2019-202743

[0005] The vehicle underbody structure described in the above Patent Document 1 is intended to suppress deformation of the side sill in the vicinity of the fixing point of the battery pack by reinforcing the side sill with the bulkhead. However, while the bulkhead has a large number of parts, which increases the installation work and cost, only a part of the side sill that is long in the front-rear direction is reinforced, so there is a problem that the strength of the side sill may be partially insufficient.

[0006] The present invention has been made in view of such circumstances, and an object of the present invention is to provide a vehicle underbody structure that can efficiently reinforce a side sill with a simple configuration.

[0007] The above object of the present invention is achieved by the following configuration. [1] A vehicle underbody structure, comprising: a side sill extending in a vehicle longitudinal direction; a side sill reinforcement provided along the side sill; and a bulkhead disposed inside the side sill and joined to an inner surface of the side sill, wherein the bulkhead and the side sill reinforcement are joined to each other.

[0008] According to the present invention, the side sill can be reinforced more efficiently and at a low cost by joining a side sill reinforcement provided along the side sill with a bulkhead joined to the inner surface of the side sill.

[0009] Figure 1 is a perspective view of the vehicle structure according to this embodiment, viewed from below. Figure 2 is a bottom view of the vehicle structure, viewed from below. Figure 3 is a bottom view showing the battery case installed in Figure 2. Figure 4 is a top view of the vehicle structure, viewed from above. Figure 5 is a perspective view of the main part showing the side sill. Figure 6 is a side view of the main part showing the side sill. Figure 7 is a cross-sectional view taken along line A-A in Figure 6, showing the cross-sectional shape of the side sill. Figure 8 is a cross-sectional view taken along line B-B in Figure 6, showing the cross-sectional shape of the side sill. Figure 9 is a perspective view of the bulkhead.

[0010] Hereinafter, a vehicle understructure according to one embodiment of the present invention will be described with reference to the drawings. Furthermore, this embodiment is merely an example of the present invention, and the present invention is not limited to this embodiment. In addition, various modifications or improvements can be made to this embodiment, and such modified or improved forms may also be included in the present invention.

[0011] In the following drawings, the symbol FR indicates the front of the vehicle, the symbol UP indicates the top of the vehicle, and the symbol LH indicates the left side in the vehicle width direction (left side in the direction of travel). The opposite direction of symbol FR is the rear of the vehicle, the opposite direction of symbol UP is the bottom of the vehicle, and the opposite direction of symbol LH is the right side in the vehicle width direction (right side in the direction of travel). Hereinafter, these directions may simply be referred to as front, rear, top, bottom, left side, and right side.

[0012] Figure 1 is a perspective view of the vehicle structure according to this embodiment, viewed from below. Figure 2 is a bottom view of the vehicle structure, viewed from below. Figure 3 is a bottom view showing the state in Figure 2 with the battery case attached. Figure 4 is a top view of the vehicle structure, viewed from above.

[0013] The vehicle understructure 1 according to this embodiment is mainly applied to the structural parts of vehicles such as automobiles. The type of automobile to which the vehicle understructure 1 is applied is not limited and may be an internal combustion engine vehicle (ICEV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or an electric vehicle (BEV).

[0014] As shown in Figures 1 to 4, the vehicle understructure 1 comprises a dash panel 3 located at its front, a floor pan 5 located behind the dash panel 3, a tunnel-shaped backbone 7 located in the center of the floor pan 5 in the vehicle width direction, projecting upward and extending in the front-rear direction, and a pair of side sills 40 provided at both ends of the floor pan 5 in the vehicle width direction.

[0015] The dash panel 3 is a partition plate that separates the passenger compartment from the front area of ​​the passenger compartment (e.g., the engine compartment) at the front end of the passenger compartment, and is formed, for example, by pressing a steel plate. The floor pan 5 is a plate material that constitutes the lower part of the passenger compartment, and is formed, for example, by pressing a steel plate. The front end of the floor pan 5 is connected to the rear end of the dash panel 3 and extends almost horizontally towards the rear of the vehicle.

[0016] As shown in Figure 1, the pair of side sills 40 extend in the longitudinal direction at both ends of the floor pan 5 in the vehicle width direction. The lower part of the front pillar 8 and the rear end of the front side member 13 are connected to the front ends of the front side members 13, respectively. The front ends of the rear side members 33 are connected to the rear ends of the rear side members 33, respectively. The specific configuration of the side sills 40 will be described later.

[0017] The front part 1A and the rear part 1B of the vehicle understructure 1 will be described below. The front part 1A of the vehicle understructure 1 includes a dash cross member 11, a backbone cross member 12, a pair of front side members 13, a pair of front stringers 14, and a battery case 20. The rear part 1B of the vehicle understructure 1 includes a first rear cross member 31, a second rear cross member 32, a pair of rear side members 33, a pair of rear stringers 34, and a battery case 20.

[0018] (Front part 1A of the vehicle understructure 1) As shown in Figures 1 to 4, the front part 1A of the vehicle understructure 1 includes a dash cross member 11 as a first cross member extending in the vehicle width direction, a backbone cross member 12 as a second cross member positioned behind the dash cross member 11 and extending in the vehicle width direction, a pair of front side members 13 positioned spaced apart from each other in the vehicle width direction and extending in the front-rear direction to connect the dash cross member 11 and the backbone cross member 12, a front stringer 14 as a connecting member positioned between the pair of front side members 13 in the vehicle width direction and extending in the front-rear direction to connect the dash cross member 11 and the backbone cross member 12, and a battery case 20 for housing the battery.

[0019] By adopting this front section 1A structure, the load applied to the pair of front side members 13 on the outer side in the vehicle width direction during a frontal collision can be distributed to the front stringer 14 on the inner side in the vehicle width direction via the dash cross member 11. In this way, the load from the front can be transmitted to the backbone cross member 12 via multiple paths. Therefore, even when an impact is applied from the front of the vehicle, the collision energy can be efficiently distributed, and localized load concentration can be suppressed.

[0020] The front side member 13 has a hat-shaped cross-section that extends in the front-rear direction, and its rear side is welded to the front surface 3b of the dash panel 3 and the lower surface 5a of the floor pan 5. The front side member 13 has a front-rear extension portion 13a that extends in the front-rear direction, and an inclined portion 13b that is connected to the rear end of the front-rear extension portion 13a and inclined outward in the vehicle width direction as it extends towards the rear.

[0021] The inclined portion 13b that constitutes the rear end of the front side member 13 extends rearward and outward in the vehicle width direction from the rear end of the longitudinal extension portion 13a and is welded and fixed to the front end of the side sill 40. In this way, the rear ends of the pair of front side members 13 are each connected to the front ends of the pair of side sills 40. Therefore, load can be transmitted from the pair of front side members 13 to the pair of side sills 40, increasing the load transmission path and enabling load distribution.

[0022] The inclined portions 13b of the pair of front side members 13 are welded and connected to both ends of the backbone cross member 12 in the vehicle width direction. Therefore, load transmission in the vehicle width direction from the pair of front side members 13 to the backbone cross member 12 can be facilitated. Furthermore, load transmission in the vehicle width direction can also be made toward the pair of side sills 40 which are connected to the vehicle width direction outwards of both ends (inclined portions 13b) of the pair of front side members 13. In this way, load can be distributed from the pair of front side members 13 toward the vehicle width direction outwards and inwards.

[0023] The battery case 20 is a roughly rectangular parallelepiped shape positioned along the lower surface 5a of the floor pan 5. In the illustrated example, the battery case 20 has both sides in the vehicle width direction overlapping with a pair of side sills 40, its front end overlapping with the backbone cross member 12, and its rear end overlapping with the second rear cross member 32 and a pair of rear stringers 34, which will be described later.

[0024] The battery case 20 is fixed to a pair of side sills 40 at both ends in the vehicle width direction by a plurality of bolts 91 arranged at predetermined intervals in the front-rear direction. This allows the load applied to the pair of side sills 40 to be transmitted to and distributed to the battery case 20.

[0025] The front end of the battery case 20, in the vehicle width direction, is fixed to a pair of bases of the backbone cross member 12 by a pair of brackets 101, 101. Therefore, the load applied to the backbone cross member 12 can be transmitted to and distributed to the battery case 20.

[0026] The front end of the battery case 20 is fixed to the inclined portion 13b of a pair of front side members 13 by a pair of brackets 103, 103 on both sides in the vehicle width direction. Therefore, the load applied to the pair of front side members 13 can be transmitted to and distributed to the battery case 20. In particular, the inclined portion 13b of the front side member 13 is the base part that connects to the side sill 40, so load tends to concentrate there. By fixing the battery case 20 to this inclined portion 13b, the load can be distributed to the battery case 20, and the concentration of load on the inclined portion 13b can be suppressed.

[0027] (Rear part 1B of the vehicle understructure 1) As shown in Figures 1 to 4, the rear part 1B of the vehicle understructure 1 includes a first rear cross member 31 as a first cross member extending in the vehicle width direction, a second rear cross member 32 as a second cross member positioned in front of or behind the first cross member and extending in the vehicle width direction, a pair of rear side members 33 positioned spaced apart from each other in the vehicle width direction and extending in the front-rear direction to connect the first rear cross member 31 and the second rear cross member 32, and a rear stringer 34 as a connecting member positioned between the pair of rear side members 33 in the vehicle width direction and extending in the front-rear direction to connect the first rear cross member 31 and the second rear cross member 32.

[0028] By adopting this rear section 1B structure, in the event of a rear collision, the load applied to the pair of rear side members 33 on the outer side in the vehicle width direction can be distributed to the rear stringer 34 on the inner side in the vehicle width direction via the first rear cross member 31. In this way, the load from the rear can be transmitted to the second rear cross member 32 via multiple paths. Therefore, even when an impact is applied from the rear of the vehicle, the collision energy can be efficiently distributed, and localized load concentration can be suppressed.

[0029] The rear side member 33 has a hat-shaped cross-section extending in the front-rear direction and is welded to the lower surface 5a of the floor pan 5. The rear side member 33 has a front-rear extension portion 33a that extends in the front-rear direction and an inclined portion 33b that is connected to the front end of the front-rear extension portion 33a and inclined outward in the vehicle width direction as it extends towards the rear.

[0030] The longitudinal extensions 33a of a pair of rear side members 33 are connected by a third rear cross member 35 and a fourth rear cross member 36, which are positioned behind the first rear cross member 31. The third rear cross member 35 and the fourth rear cross member 36 extend in the vehicle width direction, and both ends of these in the vehicle width direction are welded to the pair of longitudinal extensions 33a. The third rear cross member 35 and the fourth rear cross member 36 also have a hat-shaped cross section that extends in the vehicle width direction and are welded to the lower surface 5a of the floor pan 5.

[0031] The inclined portions 33b of the pair of rear side members 33 extend forward and outward in the vehicle width direction from the front end of the longitudinal extension portion 33a and are welded and fixed to the rear end of the side sill 40. In this way, the front ends of the pair of rear side members 33 are each connected to the rear ends of the pair of side sills 40. Therefore, load can be transmitted from the pair of rear side members 33 to the pair of side sills 40, increasing the load transmission path.

[0032] The inclined portions 33b of the pair of rear side members 33 are welded and connected to both ends in the vehicle width direction of the first rear cross member 31 and the second rear cross member 32, respectively. Therefore, load transmission in the vehicle width direction from the pair of rear side members 33 to the first rear cross member 31 and the second rear cross member 32 can be facilitated. Furthermore, load transmission in the vehicle width direction can also be made toward the pair of side sills 40 connected to both ends (inclined portions 33b) of the pair of rear side members 33. In this way, load can be distributed from the pair of rear side members 33 toward the outward and inward ends in the vehicle width direction.

[0033] As described above, Figure 3 shows a battery case 20 for housing a battery (not shown). The rear end of the battery case 20, in the vehicle width direction, is fixed to a pair of rear stringers 34 via a pair of brackets 105. In the example of Figure 3, the brackets 105 are fixed to the rear stringers 34 in front of the first rear cross member 31 and behind the second rear cross member 32.

[0034] The rear end of the battery case 20 is fixed to the inclined portions 33b of a pair of rear side members 33 by a pair of brackets 107 on both sides in the vehicle width direction. Therefore, the load applied to the pair of rear side members 33 can be transmitted to and distributed to the battery case 20. In particular, the inclined portion 33b of the rear side member 33 is the base part that connects to the side sill 40, so load tends to concentrate there. By fixing the battery case 20 to this inclined portion 33b, the load can be distributed to the battery case 20, and the concentration of load on the inclined portion 33b can be suppressed.

[0035] (Side sill 40) Next, the specific configuration of the side sill 40 will be described based on Figures 5 to 9. Figure 5 is a perspective view of the main part showing the side sill. Figure 6 is a side view of the main part showing the side sill. Figure 7 is a cross-sectional view taken along line A-A in Figure 6, showing the cross-sectional shape of the side sill. Figure 8 is a cross-sectional view taken along line B-B in Figure 6, showing the cross-sectional shape of the side sill. Figure 9 is a perspective view showing the bulkhead.

[0036] The side sill 40 extends in the longitudinal direction along the outer side of the floor pan 5 in the vehicle width direction, with the inclined portion 13b of the rear end of the front side member 13 connected at its front end and the inclined portion 33b of the front end of the rear side member 33 connected at its rear end. The side sill 40 includes a side sill inner 41, a side sill outer 42, a side sill reinforcement 43, a locking hole reinforcing member 44, and a bulkhead 50.

[0037] The side sill inner 41 is a member that constitutes the inner side of the side sill 40 in the vehicle width direction, and has a hat-shaped cross-section that extends in the front-rear direction and is open on the outer side in the vehicle width direction. The side sill inner 41 has an inner bottom surface 41a that extends in the vehicle width direction, an inner side surface 41b that extends upward from the inner end of the inner bottom surface 41a in the vehicle width direction, an inner top surface 41c that extends outward in the vehicle width direction from the upper end of the inner side surface 41b, an upper flange 41d that protrudes upward from the outer side of the inner top surface 41c in the vehicle width direction, and a lower flange 41e that protrudes downward from the outer side of the inner bottom surface 41a in the vehicle width direction.

[0038] The side sill outer 42 is a member that constitutes the outer side of the side sill 40 in the vehicle width direction, and has a hat-shaped cross-section that extends in the front-rear direction and is open on the inner side in the vehicle width direction. The side sill outer 42 has an outer bottom surface 42a extending in the vehicle width direction, an outer side surface 42b extending upward from the outer end in the vehicle width direction of the outer bottom surface 42a, an outer top surface 42c extending outward in the vehicle width direction from the upper end of the outer side surface 42b, an upper flange 42d projecting upward from the outer side in the vehicle width direction of the outer top surface 42c, and a lower flange 42e projecting downward from the outer side in the vehicle width direction of the outer bottom surface 42a.

[0039] By joining the upper flanges 41d and 42d of the side sill inner 41 and the side sill outer 42 together, and the lower flanges 41e and 42e of the side sill inner 41 and the side sill outer 42 together, 41e and 42e are joined by welding or the like, a rectangular prism-shaped side sill 40 extending in the front-rear direction is formed.

[0040] The inclined portion 13b of the rear end of the front side member 13 is connected to the inner side surface in the vehicle width direction on the outer circumferential surface of the front end of the side sill 40, in other words, to the inner surface in the vehicle width direction of the inner side surface 41b of the side sill inner 41. The inclined portion 33b of the front end of the rear side member 33 is connected to the inner side surface in the vehicle width direction on the outer circumferential surface of the rear end of the side sill 40, in other words, to the inner surface in the vehicle width direction of the inner side surface 41b of the side sill inner 41.

[0041] The bulkhead 50 is a reinforcing member provided on the inner circumferential surface of the side sill inner 41 of the side sill 40. In this embodiment, it is provided so as to overlap with the position where the front end of the rear side member 33 is connected at the rear end of the side sill 40. This configuration can be seen by referring to Figures 5 and 6, etc.

[0042] The bulkhead 50 has a main body portion 51 which is a first surface portion perpendicular to the inner circumferential surface of the side sill 40, a mounting portion 52 which extends forward from the outer edge of the main body portion 51, and a plate portion 53 which extends rearward from the outer end in the vehicle width direction of the main body portion 51.

[0043] The mounting portion 52 has a bottom mounting portion 52a, a side mounting portion 52b, and an upper mounting portion 52c. The bottom mounting portion 52a is a second surface portion that extends forward from the lower end of the main body portion 51, which is the first surface portion, along the inner bottom surface 41a, and is joined to the inner bottom surface 41a by welding or the like. The side mounting portion 52b is a third surface portion that extends forward from the inner end in the vehicle width direction of the main body portion 51, which is the first surface portion, along the inner side surface 41b, and is joined to the inner side surface 41b by welding or the like. A pair of upper and lower reinforcing ribs 54 are formed between the side mounting portion 52b and the main body portion 51. The upper mounting portion 52c is a fourth surface portion that extends forward from the upper end of the main body portion 51, which is the first surface portion, along the inner upper surface 41c, and is joined to the inner upper surface 41c by welding or the like.

[0044] The side attachment portion 52b is arranged at a position overlapping the front end portion of the rear side member 33 in the left-right direction, as shown in Figs. 5 to 7. Accordingly, the side sill inner 41 of the side sill 40 is sandwiched between the side attachment portion 52b of the bulkhead 50 and the inclined portion 33b at the front end of the rear side member 33, and is joined by welding or the like in a three-layer overlapping manner.

[0045] The plate portion 53 extends across from the upper end to the lower end of the side sill 40, and includes an upper end fixing portion 53a and a lower end fixing portion 53b, which are fifth surface portions fixed to the side sill 40 side. The upper end fixing portion 53a extends along the upper flanges 41d and 42d, which are the mating surfaces of the side sill inner 41 and the side sill outer 42, and is sandwiched between the upper flanges 41d and 42d, so that it is joined by welding or the like in a three-layer overlapping manner. The lower end fixing portion 53b extends along the lower flanges 41e and 42e, which are the mating surfaces of the side sill inner 41 and the side sill outer 42, and is sandwiched between the lower flanges 41e and 42e, so that it is joined by welding or the like in a three-layer overlapping manner. Refer to Fig. 8 for this configuration.

[0046] The side sill reinforcement 43 extends in the front-rear direction along the side sill 40 and is provided on the inner peripheral surface of the side sill 40. Specifically, the side sill reinforcement 43 is formed with an L-shaped cross section, and includes a reinforcement bottom surface 43a joined along the inner bottom surface 41a of the side sill inner 41, and a reinforcement side surface 43b joined along the inner side surface 41b. The rear end of the side sill reinforcement 43 extends to a position overlapping the bottom attachment portion 52a and the side attachment portion 52b of the bulkhead 50. Accordingly, the bulkhead 50 is sandwiched between the side sill reinforcement 43 and the side sill inner 41 of the side sill 40, so that the bottom surface and the side surface are respectively joined by welding or the like in a three-layer overlapping manner. According to this configuration, the bulkhead 50, which is a member to which a collision load or the like is transmitted, is clamped between the side sill reinforcement 43 and the side sill inner 41, so the collision load can be more efficiently transmitted between the members via the bulkhead 50.

[0047] On the reinforcement bottom surface 43a of the side sill reinforcement 43, a plurality of bolts 91 for fixing both ends of the battery case 20 in the vehicle width direction to the lower surface of the side sill 40 are arranged side by side in the front-rear direction at predetermined intervals. According to this configuration, when an in-vehicle device such as the battery case 20, which is a heavy object, is supported on the side sill 40 at the lower part of the vehicle, the lower part of the side sill 40 where the bolts 91 are provided can be reinforced. Accordingly, bending and resonance of the side sill 40 can be efficiently prevented.

[0048] As shown in FIG. 5, the locking hole reinforcing member 44 is a plate-shaped member having an L-shaped cross section provided on the inner peripheral surface of the rear end portion of the side sill inner 41, and is arranged further rearward of the bulkhead 50. A locking hole for hooking a towing hook is formed at the rear end of the inner bottom surface 41a of the side sill inner 41, so the locking hole reinforcing member 44 can reinforce the periphery of the locking hole on the inner bottom surface 41a. Further, the locking hole reinforcing member 44 is formed with a reinforcing-side locking hole 44a drilled along the locking hole of the inner bottom surface 41a.

[0049] (Operational effect) According to the vehicle lower structure described above, by providing the bulkhead 50 inside the rear end portion of the side sill 40 to which the front end portion of the rear side member 33 is joined, the joint portion between the side sill 40 and the rear side member 33 can be efficiently reinforced.

[0050] The bulkhead 50 is attached to the inner peripheral surface of the side sill inner 41 constituting the side sill 40 via an attachment portion 52, and the side sill outer 42 side is a space. That is, as shown in FIG. 8, at a predetermined position of the side sill 40, the bulkhead 50 is provided in the inner half portion in the vehicle width direction, and a shock absorbing space S is formed in the outer half portion in the vehicle width direction with the plate portion 53 as a boundary. Accordingly, when a side collision of the vehicle occurs, the shock absorbing space S of the side sill 40 is crushed to efficiently absorb shock energy, and the load can be supported by the bulkhead 50, so that the strength of the side sill 40 can be efficiently enhanced.

[0051] By attaching the bulkhead 50 to the side sill inner 41, the front end of the rear side member 33, the side sill inner 41, and the bulkhead 50 can be joined together in a three-layer configuration. This allows the rearward thrust load transmitted to the rear side member 33 to be efficiently transferred to the bulkhead 50.

[0052] The bulkhead 50 extends across the upper and lower ends of the side sill 40 and has a plate portion 53 whose upper and lower ends are sandwiched between the side sill inner 41 and the side sill outer 42, respectively. With this configuration, the plate portion 53 acts like a bracing rod within the side sill 40, making it difficult for the cross-sectional shape of the side sill 40 to deform even when a collision load is applied to the vehicle. As a result, battery resonance is reduced, and vibrations of the steering wheel and floor caused by input from the road surface are reduced, thus improving quietness.

[0053] The mounting portion 52 of the bulkhead 50 overlaps with the rear end of the side sill reinforcement 43, which is provided along the side sill inner 41. The bulkhead 50 is joined in a triple layer by being sandwiched between the side sill reinforcement 43 and the side sill inner 41. With this configuration, for example, the rearward protruding load transmitted from the rear side member 33 can be transmitted to the side sill 40 more efficiently.

[0054] It should be noted that the present invention is not limited to the embodiments described above, and can be modified or improved as appropriate.

[0055] As described above, the following is disclosed in this specification: (1) A vehicle understructure comprising: a side sill extending in the longitudinal direction of the vehicle; a side sill reinforcement provided along the side sill; and a bulkhead disposed inside the side sill and joined to the inner surface of the side sill, wherein the bulkhead and the side sill reinforcement are joined. With this configuration, the side sill can be reinforced more efficiently and at a lower cost by joining the side sill reinforcement provided along the side sill and the bulkhead joined to the inner surface of the side sill.

[0056] (2) The vehicle understructure described in (1), wherein the side sill, the bulkhead, and the side sill reinforcement are joined together in a three-layer stack. With this configuration, the side sill is reinforced by the side sill reinforcement and the bulkhead.

[0057] (3) The vehicle understructure as described in (2), wherein the bulkhead is joined in a triple layer while sandwiched between the side sill and the side sill reinforcement. With this configuration, the load is transmitted more efficiently between the side sill and the side sill reinforcement, so that deformation and resonance of the side sill can be suppressed more efficiently.

[0058] (4) The vehicle understructure according to (2) or (3), wherein the side sill reinforcement is arranged along the bottom and sides of the side sill, and the side sill, the bulkhead, and the side sill reinforcement are joined in a triple layer at the bottom and sides of the side sill. With this configuration, the side sill becomes stronger and the cross-sectional shape of the side sill becomes less prone to deformation.

[0059] (5) A vehicle understructure according to any one of (1) to (4), further comprising a side member connected to one end of the side sill in the front-rear direction and extending in the front-rear direction of the vehicle, wherein the side sill, the bulkhead, and the side member are joined in a three-layer stack. With this configuration, the strength of the connection portion between the side sill and the side member, which is relatively prone to deformation, is improved with a simple structure.

[0060] (6) The vehicle understructure as described in (5), wherein the side members are arranged on the inside in the vehicle width direction of a pair of side sills, the tip of which is inclined outward in the vehicle width direction and connected to the side members. With this configuration, the space between the pair of side members can be made wider, so that larger in-vehicle equipment can be mounted between the pair of side members.

[0061] (7) The vehicle understructure according to any one of (1) to (6), wherein the side sill reinforcement has a fixing portion for fixing in-vehicle equipment positioned between a pair of side sills. With this configuration, the in-vehicle equipment is fixed by the side sill and the side sill reinforcement, so that heavier in-vehicle equipment can be mounted more stably.

[0062] (8) The vehicle understructure as described in (7), wherein the vehicle-mounted equipment is fixed together with the side sill and the side sill reinforcement at the fixing portion. With this configuration, large vehicle-mounted equipment can be fixed in a more stable state.

[0063] (9) The vehicle understructure according to any one of (1) to (8), wherein the bulkhead has a first surface portion perpendicular to the inner surface of the side sill, a second surface portion extending from the first surface portion along the bottom surface of the side sill, a third surface portion extending from the first surface portion along the side surface of the side sill, and a fourth surface portion extending from the first surface portion along the top surface of the side sill. With this configuration, the bulkhead, which is positioned to cover a part of the cross-section inside the side sill, is attached to the bottom surface, side surface, and top surface inside the side sill, so that the side sill can be efficiently reinforced.

[0064] (10) The vehicle understructure according to (9), wherein the side sill has a side sill inner disposed on the inside in the vehicle width direction and a side sill outer disposed on the outside in the vehicle width direction, the second surface portion extends along the bottom surface of the side sill inner, the third surface portion extends along the side surface of the side sill inner, the fourth surface portion extends along the top surface of the side sill inner, and the bulkhead further has a fifth surface portion that extends along the mating surface between the side sill inner and the side sill outer. With this configuration, since the bulkhead is attached to the side sill inner side which constitutes the inside in the vehicle width direction of the side sill, the load transmitted from the side member side to the side sill is efficiently transmitted to the bulkhead. In addition, the bulkhead is efficiently positioned within the side sill and the work of attaching the bulkhead to the side sill is also made easier, so costs can be kept low.

[0065] (11) The vehicle understructure according to (10), wherein a pair of the fifth surfaces are provided above and below the first surface. With this configuration, the bulkhead is provided so that it is sandwiched between the upper and lower ends of the side sill inner and side sill outer by the pair of upper and lower fifth surfaces, making it more difficult for the cross-sectional shape of the side sill to deform.

[0066] 1 Vehicle understructure 1A Front of vehicle understructure 1B Rear of vehicle understructure 3 Dash panel 3b Front 5 Floor pan 5a Underside 7 Backbone 8 Front pillar 11 Dash cross member 12 Backbone cross member 13 Front side member 13a Front-rear extension 13b Inclined section 14 Front stringer 20 Battery case 31 First rear cross member 32 Second rear cross member 33 Rear side member 33a Front-rear extension 33b Inclined section 34 Rear stringer 35 Third rear cross member 36 Fourth rear cross member 40 Side sill 41 Side sill inner 41a Inner bottom surface 41b Inner side surface 41c Inner top surface 41d Upper flange 41e Lower flange 42 Side sill outer 42a Outer bottom surface 42b Outer side surface 42c Outer top surface 42d Upper flange 42e Lower flange 43 Side sill reinforcement 43a Reinforcement bottom surface 43b Reinforcement side surface 44 Locking hole reinforcement member 50 Bulkhead 51 Main body 52 Mounting part 52a Bottom mounting part 52b Side mounting part 52c Top mounting part 53 Plate part 53a Upper end fixing part 53b Lower end fixing part 54 Reinforcement rib 91 Bolt 101 Bracket 103 Bracket 105 Bracket 107 Bracket S Impact absorption space (space)

Claims

1. A vehicle understructure comprising: a side sill extending in the longitudinal direction of the vehicle; a side sill reinforcement provided along the side sill; and a bulkhead disposed inside the side sill and joined to the inner surface of the side sill, wherein the bulkhead and the side sill reinforcement are joined together.

2. The vehicle understructure according to claim 1, wherein the side sill, the bulkhead, and the side sill reinforcement are joined together in a three-layer stack.

3. The vehicle understructure according to claim 2, wherein the bulkhead is joined in a three-layer configuration while sandwiched between the side sill and the side sill reinforcement.

4. The vehicle understructure according to claim 2 or 3, wherein the side sill reinforcement is arranged along the bottom and side surfaces of the side sill, and the side sill, the bulkhead, and the side sill reinforcement are joined in a triple layer at the bottom and side surfaces of the side sill.

5. The vehicle understructure according to any one of claims 1 to 4, further comprising a side member connected to one end of the side sill in the front-rear direction and extending in the front-rear direction of the vehicle, wherein the side sill, the bulkhead, and the side member are joined together in a three-layer stack.

6. The vehicle understructure according to claim 5, wherein the side member is positioned on the inside in the vehicle width direction of a pair of side sills, its tip is inclined outward in the vehicle width direction, and is connected to the side member.

7. The vehicle understructure according to any one of claims 1 to 6, wherein the side sill reinforcement has a fixing portion for fixing in-vehicle equipment positioned between a pair of side sills.

8. The vehicle understructure according to claim 7, wherein the in-vehicle equipment is fixed together with the side sill and the side sill reinforcement at the fixing portion.

9. The vehicle understructure according to any one of claims 1 to 8, wherein the bulkhead has a first surface portion perpendicular to the inner surface of the side sill, a second surface portion extending from the first surface portion along the bottom surface of the side sill, a third surface portion extending from the first surface portion along the side surface of the side sill, and a fourth surface portion extending from the first surface portion along the top surface of the side sill.

10. The vehicle understructure according to claim 9, wherein the side sill comprises a side sill inner disposed inward in the vehicle width direction and a side sill outer disposed outward in the vehicle width direction, the second surface portion extending along the bottom surface of the side sill inner, the third surface portion extending along the side surface of the side sill inner, the fourth surface portion extending along the top surface of the side sill inner, and the bulkhead further comprises a fifth surface portion extending along the mating surface between the side sill inner and the side sill outer.

11. The vehicle understructure according to claim 10, wherein a pair of the fifth surfaces are provided above and below the first surface.

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