Vehicle lower part structure

Abstract

To obtain a vehicle lower part structure which achieves high versatility while securing a battery mounting space.SOLUTION: A vehicle lower part structure includes: a side frame 18 extending in a vehicle front-back direction at the outer side in a vehicle width direction of a battery BT, provided in a position that is overlapped with at least a part of the battery BT in a vehicle side view, and having a closed cross sectional structure; and a side member 40 which is disposed at the outer side in the vehicle width direction of the side frame 18, provided at a position which is overlapped with at least a part of the side frame 18 in the vehicle side view, and fastened to the side frame 18 by a fastening member 46 and has a closed cross sectional structure.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a structure provided with a floor reinforcement extending in the vehicle longitudinal direction inside the vehicle width direction of a rocker that forms the skeleton of a vehicle. In the structure described in this Patent Document 1, a battery is mounted inside the vehicle width direction of the floor reinforcement, and the battery is fastened to the floor reinforcement.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the structure described in the above Patent Document 1, since the floor reinforcement is arranged apart from the rocker, the dimension between the left and right floor reinforcements becomes small, and the mounting space for the battery cannot be expanded. On the other hand, if the battery case is extended to the rocker, the mounting space for the battery can be secured, but since the dimension between the left and right rockers is different for each vehicle type, it is necessary to change the dimension of the battery case for each vehicle type.

[0005] An object of the present invention is to obtain a vehicle underbody structure with high versatility of a battery case while securing a mounting space for the battery.

Means for Solving the Problems

[0006] The vehicle underbody structure according to claim 1 includes a side frame having a closed cross-section structure that extends in the vehicle longitudinal direction on the outside in the vehicle width direction of the battery and is provided at a position overlapping at least a part of the battery in a side view of the vehicle, and a side member having a closed cross-section structure that is disposed on the outside in the vehicle width direction of the side frame, is provided at a position overlapping at least a part of the side frame in a side view of the vehicle, and is fastened to the side frame by a fastening member.

[0007] In the vehicle underbody structure according to claim 1, the side frame extends in the vehicle longitudinal direction on the outside in the vehicle width direction of the battery. Further, the side frame has a closed cross-section structure and is provided at a position overlapping at least a part of the battery in a side view of the vehicle. Thus, when a side collision occurs in the vehicle (hereinafter, appropriately referred to as "side impact"), the side frame can receive the collision load input from the side of the vehicle, and the battery is protected.

[0008] In addition, a side member is disposed on the outside in the vehicle width direction of the side frame, and the side member is fastened to the side frame by a fastening member. By adopting such a structure in which the side frame and the side member are fastened by a fastening member, the side frame approaches the side member, and a mounting space for the battery in the vehicle width direction can be secured.

[0009] Furthermore, the side member has a closed cross-section structure and is provided at a position overlapping at least a part of the side frame in a side view of the vehicle. In this way, the side frame and the side member having a closed cross-section structure fastened by a fastening member can function as a rocker, which is a vehicle skeleton member. And since it can be applied to vehicles with different vehicle classes only by changing the side member, there is no need to change the battery and the side frame, and the structure has high versatility.

[0010] The vehicle underbody structure according to claim 2 is, in claim 1, provided with an outer energy absorption member in the cross-section of the side member.

[0011] In the vehicle underbody structure according to claim 2, by providing an outer energy absorption member within the cross-section of the side member, at least a part of the collision load input from the side of the vehicle during a side impact can be absorbed by the outer energy absorption member.

[0012] The vehicle underbody structure according to claim 3 is, in claim 2, within the cross-section of the side frame, an inner energy absorption member is provided at a position where at least a part thereof overlaps with the outer energy absorption member when viewed from the side of the vehicle.

[0013] In the vehicle underbody structure according to claim 3, by providing an inner energy absorption member within the cross-section of the side frame, at least a part of the collision load input from the side of the vehicle during a side impact can be absorbed by the inner energy absorption member. Also, at least a part of the inner energy absorption member overlaps with the outer energy absorption member when viewed from the side of the vehicle. Therefore, the load can be effectively absorbed by both the outer energy absorption member and the inner energy absorption member, and the load input to the battery can be suppressed.

[0014] The vehicle underbody structure according to claim 4 is, in claim 3, a floor cross member extending in the vehicle width direction is connected to the side frame, and at least a part of the inner energy absorption member is provided at a position where it overlaps with the floor cross member when viewed from the side of the vehicle.

[0015] In the vehicle underbody structure according to claim 4, a floor cross member extending in the vehicle width direction is connected to the side frame. Also, at least a part of the inner energy absorption member is provided at a position where it overlaps with the floor cross member when viewed from the side of the vehicle. Therefore, while the collision load input from the side of the vehicle during a side impact is absorbed by the inner energy absorption member, it can be transmitted to the anti-collision side via the side frame and the floor cross member. As a result, the load input to the battery can be effectively suppressed.

[0016] The vehicle underbody structure according to claim 5 is, in claim 1, a front pillar extending in the vehicle up-and-down direction is connected to the front side of the vehicle in the side member, and a center pillar extending in the vehicle up-and-down direction is connected to the side member on the rear side of the vehicle with respect to the front pillar.

[0017] In the vehicle underbody structure according to claim 5, by connecting the front pillar and the center pillar to the side member, a side module including the side member, the front pillar, and the center pillar is configured. Thereby, the side member, the front pillar, and the center pillar are modularized in advance, and the skeleton of the vehicle can be configured only by fastening the battery and the side frame to the modularized side module.

[0018] The vehicle underbody structure according to claim 6 is, in claim 1, a wall portion on the outer side in the vehicle width direction of the side frame and a wall portion on the inner side in the vehicle width direction of the side member are fastened in the vehicle width direction by the fastening member.

[0019] In the vehicle underbody structure according to claim 6, the side frame and the side member are fastened in the vehicle width direction by the fastening member. Thereby, at the time of a side impact, since a load is input along the axial direction of the fastening member, compared with the case where a load is input in the shear direction of the fastening member at the time of a side impact as in the structure fastened vertically by the fastening member, the fastening state can be maintained well.

[0020] The vehicle underbody structure according to claim 7 is, in claim 3, the outer energy absorption member is disposed at the upper part in the cross section of the side member, the inner energy absorption member is disposed at the upper part in the cross section of the side frame, and the fastening member is disposed below the outer energy absorption member and the inner energy absorption member.

[0021] In the vehicle underbody structure according to claim 7, by vertically dividing the region where the outer energy absorption member and the inner energy absorption member are arranged and the region where the fastening member is arranged, it is possible to prevent the outer energy absorption member and the inner energy absorption member from getting in the way when the side frame and the side member are fastened by the fastening member. Further, by arranging the outer energy absorption member and the inner energy absorption member at the upper part, the collision load can be efficiently transmitted to the floor cross member.

[0022] The vehicle underbody structure according to claim 8 is, in claim 1, wherein the side member includes a flat inner panel arranged to face the side frame, and an outer panel having a hat-shaped cross section arranged outside the inner panel in the vehicle width direction and joined to the inner panel.

[0023] In the vehicle underbody structure according to claim 8, since the side member includes a flat inner panel, the side frame can be brought into surface contact with the side member, and the side frame and the side member can be firmly fastened.

Advantages of the Invention

[0024] As described above, according to the vehicle underbody structure of the present invention, it is possible to enhance the versatility of the battery case while securing the mounting space for the battery.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0026] <First Embodiment> The vehicle underbody structure according to the first embodiment will be described with reference to the drawings.

[0027] FIG. 1 is a perspective view showing a part of the vehicle underbody structure according to the embodiment. The arrows FR, UP, and RH in the figure indicate the vehicle front direction, the vehicle upward direction, and the vehicle right direction in the vehicle 10, respectively. In the following description, when the front-rear, up-down, and left-right directions are used without special mention, the front and rear in the vehicle front-rear direction, the up and down in the vehicle up-down direction, and the left and right in the vehicle left-right direction (width direction) are respectively indicated.

[0028] As shown in FIG. 1, the vehicle underbody structure of the present embodiment includes a battery frame 12. The battery frame 12 is a substantially frame-shaped member surrounding the battery case 20 and is disposed below the passenger compartment (not shown).

[0029] The battery frame 12 includes a front frame 14, a rear frame 16, and a pair of left and right side frames 18. The front frame 14, the rear frame 16, and the side frames 18 may be integrally formed of metal, or may be formed separately. In the present embodiment, as an example, the front frame 14, the rear frame 16, and the side frames 18 are each formed by extrusion molding and have a closed cross-sectional structure, and the battery frame 12 is formed by joining them to each other.

[0030] The front frame 14 is located at the vehicle front part of the vehicle underbody structure and extends in the vehicle width direction along the vehicle front end of the battery case 20. In addition, a front module (not shown) constituting the front part of the vehicle is joined to the front frame 14.

[0031] The rear frame 16 is located at the vehicle rear part of the vehicle underbody structure and extends in the vehicle width direction along the vehicle rear end of the battery case 20. In addition, a rear module (not shown) constituting the rear part of the vehicle is joined to the rear frame 16.

[0032] The right end of the front frame 14 and the right end of the rear frame 16 are connected in the vehicle longitudinal direction by the side frame 18. Also, the left end of the front frame 14 and the left end of the rear frame 16 are connected in the vehicle longitudinal direction by the side frame 18.

[0033] A pair of left and right side frames 18 each extend in the vehicle longitudinal direction outside the battery case 20 in the vehicle width direction. The front end of the side frame 18 is connected to the front frame 14, and the rear end of the side frame 18 is connected to the rear frame 16.

[0034] FIG. 2 is an enlarged cross-sectional view of the main part showing an enlarged state of the cut along the line 2-2 in FIG. 1. As shown in this FIG. 2, the side frame 18 includes an upper wall portion 18A, a lower wall portion 18B, a right wall portion 18C, and a left wall portion 18D, and has a closed cross-sectional structure with a substantially rectangular outer shape in a cross-sectional view seen from the vehicle longitudinal direction.

[0035] The upper wall portion 18A is disposed at a position higher than the battery case 20 and extends in the vehicle width direction and the vehicle longitudinal direction. Also, the lower wall portion 18B is disposed at a position overlapping the battery case 20 in a side view of the vehicle and extends in the vehicle width direction and the vehicle longitudinal direction. In other words, the side frame 18 is provided at a position overlapping at least a part of the battery case 20 in a side view of the vehicle.

[0036] The battery case 20 is configured to include an upper case 22 and a lower case 24, and a battery BT is housed inside the battery case 20. The battery BT stores electric power for supplying to a motor (not shown), and the vehicle is configured to travel by operating a motor (not shown) with the electric power supplied from the battery BT. Also, a power supply unit (not shown) is provided in the vehicle, and the vehicle is configured to be able to supply power to the battery BT from the outside of the vehicle via the power supply unit.

[0037] The upper case 22 is located above the battery case 20 and has a substantially hat shape with a cross-section viewed from the vehicle longitudinal direction being open to the lower side of the vehicle. Further, an upper right flange 22A extending along the lower wall portion 18B of the side frame 18 is formed at the right end of the upper case 22 in the vehicle width direction.

[0038] The lower case 24 is located below the upper case 22 and has a substantially hat shape with a cross-section viewed from the vehicle longitudinal direction being open to the upper side of the vehicle. Further, a lower right flange 24A superposed on the upper right flange 22A of the upper case 22 is formed at the right end of the lower case 24 in the vehicle width direction. Then, in a state where the upper right flange 22A and the lower right flange 24A are superposed vertically, a bolt 30 penetrates from below and is screwed into a weld nut 32 provided on the lower wall portion 18B of the side frame 18.

[0039] A plurality of bolts 30 and weld nuts 32 are provided at intervals in the vehicle longitudinal direction, and the battery case 20 is fastened to the side frame 18 by these plurality of bolts 30 and weld nuts 32.

[0040] The right wall portion 18C of the side frame 18 connects the right ends of the upper wall portion 18A and the lower wall portion 18B vertically and faces the side member 40, which will be described later, in the vehicle width direction. Further, an extension portion 18E extends downward from the lower end of the right wall portion 18C.

[0041] The left wall portion 18D connects the left ends of the upper wall portion 18A and the lower wall portion 18B vertically. Further, a floor cross member 34 is joined to the left wall portion 18D.

[0042] As shown in FIG. 1, in this embodiment, as an example, two floor cross members 34 are provided and arranged side by side in the vehicle longitudinal direction. The floor cross member 34 is formed by pressing sheet metal, but is not limited thereto, and may be formed by extrusion molding, roll forming, casting, or the like.

[0043] Each floor cross member 34 has an upper surface, a front surface, and a rear surface, and is formed in a substantially U-shaped cross section that is open downward in the vehicle width direction when viewed from the vehicle width direction. Further, as shown in FIG. 2, a gap is provided between the floor cross member 34 and the battery case 20. Furthermore, at the vehicle width direction end of the upper surface of the floor cross member 34, a bent portion 34A that is bent upward along the left wall portion 18D of the side frame 18 is formed. The bent portion 34A is joined by welding or the like in a state of being overlapped with the left wall portion 18D of the side frame 18. In the present embodiment, the upper case 22 of the battery case 20 also serves as a floor panel that constitutes the floor portion of the passenger compartment.

[0044] Also, at the vehicle width direction ends of the upper surface and the rear surface of the floor cross member 34, bent portions (not shown) that are bent back and forth along the left wall portion 18D of the side frame 18 are formed, and these bent portions are joined by welding or the like in a state of being overlapped with the left wall portion 18D. Note that the floor cross member 34 and the side frame 18 may be mechanically joined by bolts, rivets, or the like.

[0045] A side member 40 is disposed outside the side frame 18 in the vehicle width direction, and the side member 40 has a closed cross-sectional structure including a side inner panel 42 and a side outer panel 44.

[0046] The side inner panel 42 is a substantially flat plate-shaped member disposed opposite to the side frame 18 in the vehicle width direction, and extends in the vehicle vertical direction and the vehicle front-rear direction. The upper end portion of the side inner panel 42 is located above the vehicle with respect to the upper wall portion 18A of the side frame 18, and the lower end portion of the side inner panel 42 is located below the vehicle with respect to the lower wall portion 18B of the side frame 18.

[0047] The side outer panel 44 is disposed on the outer side in the vehicle width direction of the side inner panel 42, and is formed in a substantially hat-shaped cross section with the inner side in the vehicle width direction open. Further, an upper flange 44A bent upward along the side inner panel 42 is formed at the upper end portion of the side outer panel 44, and the upper flange 44A is joined to the upper end portion 42A of the side inner panel 42 by spot welding or the like in a state where they are overlapped.

[0048] At the lower end portion of the side outer panel 44, a lower flange 44B bent downward along the side inner panel 42 is formed, and the lower flange 44B is joined to the lower end portion 42B of the side inner panel 42 by spot welding or the like in a state where they are overlapped.

[0049] Here, the closed cross section formed by the side inner panel 42 and the side outer panel 44 overlaps at least a part of the side frame 18 in a side view of the vehicle. In this embodiment, as an example, the closed cross section of the side member 40 overlaps the entire side frame 18 in a side view of the vehicle.

[0050] A bolt insertion hole 42C is formed in the side inner panel 42 below the central portion in the vehicle vertical direction. Further, a bolt insertion hole 18F is formed at a position communicating with the bolt insertion hole 42C below the central portion in the vehicle vertical direction in the right wall portion 18C of the side frame 18. Then, a bolt 46 as a fastening member is inserted into the bolt insertion hole 42C and the bolt insertion hole 18F from the outer side in the vehicle width direction, and the bolt 46 is screwed into a weld nut 48 provided on the right wall portion 18C. In this way, the right wall portion 18C, which is the wall portion on the outer side in the vehicle width direction of the side frame 18, and the side inner panel 42, which is the wall portion on the inner side in the vehicle width direction of the side member 40, are fastened in the vehicle width direction by the bolt 46 and the weld nut 48. Note that a work hole (not shown) is formed in the side outer panel 44, and the bolt 46 can be inserted through this work hole.

[0051] Also, in this embodiment, as an example, a sealing material 54 and an adhesive 56 are provided between the side frame 18 and the side member 40. The sealing material 54 is provided between the extension portion 18E and the side member 40 below the bolt 46 in the vehicle vertical direction, and seals the space between the two. The sealing material 54 is not particularly limited as long as it can suppress the intrusion of water between the side frame 18 and the side member 40.

[0052] The adhesive 56 is provided between the right wall portion 18C and the side inner panel 42 above the bolt 46 in the vehicle vertical direction, and adheres the two. Note that, instead of the adhesive 56, a sealing material similar to the sealing material 54 may be provided. In this embodiment, since the bolt 46 is located below the central portion in the vertical direction of the right wall portion 18C, by adhering the upper portion of the right wall portion 18C to the side member 40 with the adhesive 56, the fastening state by the bolt 46 can be maintained well.

[0053] An outer energy absorption member 52 is provided in the cross section of the side member 40. The outer energy absorption member 52 has a cross-sectional shape in which the internal space is partitioned in the vehicle width direction, and is structured to collapse and absorb at least a part of the energy when a load is input from the vehicle width direction. Further, the outer energy absorption member 52 is located at the upper part in the cross section of the side member 40. Specifically, the outer energy absorption member 52 is provided above the bolt 46 and is fixed to the side member 40. The fixing method of the outer energy absorption member 52 is not particularly limited, and it may be mechanically fastened to the side member 40 with bolts, rivets, etc., or adhered to the side member 40 with an adhesive or the like. Also, the outer energy absorption member 52 may be fixed by sandwiching it between the side inner panel 42 and the side outer panel 44.

[0054] Inside the side frame 18 in cross-section, an inner energy absorption member 50 is provided. The inner energy absorption member 50 has a cross-sectional shape in which the internal space is partitioned in the vehicle width direction, and is structured to collapse and absorb at least part of the energy when a load is input from the vehicle width direction. Also, the inner energy absorption member 50 is located at the upper part within the cross-section of the side frame 18. Specifically, the inner energy absorption member 50 is provided above the bolt 46, and is arranged at a position where at least part of it overlaps with the outer energy absorption member 52 in a side view of the vehicle and is fixed to the side frame 18. The fixing method of the inner energy absorption member 50 is not particularly limited, and it may be mechanically fastened to the side frame 18 with bolts, rivets, etc., or may be adhered to the side frame 18 with an adhesive or the like.

[0055] Here, in the present embodiment, the outer energy absorption member 52, the inner energy absorption member 50, and the floor cross member 34 are arranged at positions where they overlap in a side view of the vehicle. Note that, as an example in the present embodiment, the outer energy absorption member 52 and the inner energy absorption member 50 have their internal spaces partitioned into two in the vehicle width direction by a partition wall extending in the vehicle up-and-down direction, but it is not limited to this. For example, two or more partition walls may be provided to have a structure with three or more internal spaces in the vehicle width direction. Also, as long as it has a structure that can collapse and absorb energy when a load is input, other structures may be adopted. For example, a structure without a partition wall or a structure with an inclined partition wall may be adopted.

[0056] Next, an example of a manufacturing method of a vehicle constituting the vehicle lower structure according to the present embodiment will be described. FIG. 3 is a side view showing an example of the side module SM in the present embodiment. In the present embodiment, as an example, the side module SM is formed in advance.

[0057] The side module SM is configured to include a side member 40, a front pillar 60, a center pillar 62, and a roof side rail 64. The front pillar 60 is a skeletal member extending in the vehicle up-and-down direction, and the lower end portion of the front pillar 60 is connected to the front end portion of the side member 40. The front pillar 60 and the side member 40 may be joined by welding or the like, or may be mechanically fastened by bolts, rivets, or the like.

[0058] A center pillar 62 is provided on the vehicle rear side of the front pillar 60. The center pillar 62 is a skeletal member extending in the vehicle up-and-down direction, and the lower end portion of the center pillar 62 is connected to the central portion in the vehicle front-rear direction of the side member 40. The center pillar 62 and the side member 40 may be joined by welding or the like, or may be mechanically fastened by bolts, rivets, or the like.

[0059] The upper end portion of the front pillar 60 and the upper end portion of the center pillar 62 are connected to the roof side rail 64. The roof side rail 64 is a skeletal member extending in the vehicle front-rear direction, and a roof panel (not shown) is fixed to the roof side rail 64.

[0060] On the other hand, as shown in FIG. 1, with the floor cross member 34 joined to the battery frame 12, the battery case 20 is fastened to the side frame 18 of the battery frame 12.

[0061] As shown in FIG. 2, with respect to the side frame 18 to which the battery case 20 is fastened, the side member 40 constituting the side module SM is fastened by bolts 46 and weld nuts 48.

[0062] (Function) Next, the function of the vehicle lower structure according to the present embodiment will be described.

[0063] In the vehicle underbody structure according to this embodiment, as shown in FIG. 1, the side frame 18 extends in the vehicle longitudinal direction on the outside in the vehicle width direction of the battery case 20. Further, as shown in FIG. 2, the side frame 18 has a closed cross-section structure and is provided at a position overlapping at least a part of the battery BT in a side view of the vehicle. Thereby, the collision load input from the side of the vehicle at the time of a side collision of the vehicle can be received by the side frame 18, and the battery BT is protected.

[0064] In addition, a side member 40 is disposed outside the side frame 18 in the vehicle width direction, and the side member 40 is fastened to the side frame 18 by a bolt 46 which is a fastening member. By adopting such a structure in which the side frame 18 and the side member 40 are fastened by the bolt 46, the side frame 18 comes close to the side member 40, and a mounting space for the battery BT in the vehicle width direction can be secured.

[0065] Furthermore, the side member 40 has a closed cross-section structure and is provided at a position overlapping at least a part of the side frame 18 in a side view of the vehicle. In this way, the side frame 18 and the side member 40 having a closed cross-section structure can function as a rocker which is a vehicle skeleton member. And since it can be applied to vehicles with different vehicle classes only by changing the side member 40, it is not necessary to change the battery BT and the side frame 18, and the structure has high versatility. As a result, in the vehicle underbody structure of this embodiment, it is possible to increase the versatility while securing a mounting space for the battery BT.

[0066] In particular, in this embodiment, the side frame 18 and the side member 40 are fastened in the vehicle width direction by the bolt 46. Thereby, at the time of a side collision, since a load is input along the axial direction of the bolt 46, compared with the case where a load is input in the shear direction of the bolt at the time of a side collision as in the structure fastened vertically by the bolt, the fastening state can be maintained well.

[0067] Furthermore, in the present embodiment, by providing the outer energy absorption member 52 within the cross-section of the side member 40, at least a part of the collision load input from the side of the vehicle during a side collision of the vehicle can be absorbed by the outer energy absorption member 52.

[0068] Similar to the side member 40, by providing the inner energy absorption member 50 within the cross-section of the side frame 18, at least a part of the collision load input from the side of the vehicle during a side collision of the vehicle can be absorbed by the inner energy absorption member 50. Also, at least a part of the inner energy absorption member 50 overlaps with the outer energy absorption member 52 in a side view of the vehicle. Therefore, the collision load can be effectively absorbed by both the outer energy absorption member 52 and the inner energy absorption member 50, and the input of load to the battery BT can be suppressed.

[0069] Also, in the present embodiment, the floor cross member 34 extending in the vehicle width direction is connected to the side frame 18. Furthermore, at least a part of the inner energy absorption member 50 is provided at a position overlapping with the floor cross member 34 in a side view of the vehicle. Therefore, while the inner energy absorption member 50 absorbs the collision load input from the side of the vehicle during a side collision, it can be transmitted to the anti-collision side through the side frame 18 and the floor cross member 34. As a result, the input of load to the battery BT can be effectively suppressed.

[0070] Furthermore, in the present embodiment, as shown in FIG. 3, the front pillar 60 and the center pillar 62 are connected to the side member 40, and a side module SM including the side member 40, the front pillar 60, and the center pillar 62 is configured. Thereby, the side member 40, the front pillar 60, and the center pillar 62 are modularized in advance, and the vehicle skeleton can be configured only by fastening the battery BT and the side frame 18 to the modularized side module SM.

[0071] Furthermore, in the present embodiment, as shown in FIG. 2, since the outer energy absorption member 52 and the inner energy absorption member 50 are disposed at the upper part within the cross section and the bolt 46 is inserted through the lower part within the cross section, it is possible to prevent the outer energy absorption member 52 and the inner energy absorption member 50 from getting in the way when the side frame 18 and the side member 40 are fastened by the bolt 46. Also, by disposing the outer energy absorption member 52 and the inner energy absorption member 50 at the upper part, the collision load can be efficiently transmitted to the floor cross member 34.

[0072] In the present embodiment, since the side member 40 includes the flat side inner panel 42, the side frame 18 can be brought into surface contact with the side member 40, and the side frame 18 and the side member 40 can be firmly fastened. In the present embodiment, although the sealing material 54 and the adhesive 56 are provided between the side frame 18 and the side member 40, since both the sealing material 54 and the adhesive 56 are thin, the side frame 18 and the side member 40 are in a state of almost surface contact.

[0073] <Second Embodiment> Next, the vehicle lower structure according to the second embodiment will be described with reference to FIG. 4. Note that the same reference numerals are given to the same configurations as those in the first embodiment, and the description will be omitted as appropriate.

[0074] FIG. 4 is a plan view showing a main part of the vehicle lower structure according to the second embodiment. As shown in this FIG. 4, the vehicle lower structure of the present embodiment has the same configuration as that of the first embodiment except for the side member 70.

[0075] The side member 70 of the present embodiment is disposed on the outer side in the vehicle width direction of the side frame 18, and the side member 70 has a closed cross-sectional structure including a side inner panel 72 and a side outer panel 74.

[0076] The side inner panel 72 is disposed opposite to the side frame 18 in the vehicle width direction, and has a substantially crank-shaped cross section when viewed from the vehicle longitudinal direction. Specifically, the portion of the side inner panel 72 facing the side frame 18 extends in the vehicle vertical direction, and the lower end portion 72B of the side inner panel 72 is located below the vehicle relative to the lower wall portion 18B of the side frame 18.

[0077] Also, the upper portion of the side inner panel 72 extends obliquely outward in the vehicle width direction and upward in the vehicle, and is further bent upward to form an upper flange 72A.

[0078] The side outer panel 74 is disposed outside the side inner panel 72 in the vehicle width direction, and has a substantially hat-shaped cross section with an open inner side in the vehicle width direction. Further, an upper flange 74A bent upward along the upper flange 72A of the side inner panel 72 is formed at the upper end portion of the side outer panel 74, and the upper flange 72A of the side inner panel 72 and the upper flange 74A of the side outer panel 74 are joined by spot welding or the like in a state where they are overlapped.

[0079] A lower flange 74B bent downward along the side inner panel 72 is formed at the lower end portion of the side outer panel 74, and the lower flange 74B is joined to the lower end portion 72B of the side inner panel 72 by spot welding or the like in a state where they are overlapped.

[0080] Here, the closed cross section formed by the side inner panel 72 and the side outer panel 74 overlaps at least a part of the side frame 18 when viewed from the side of the vehicle. In this embodiment, as an example, the closed cross section of the side member 70 overlaps the entire side frame 18 when viewed from the side of the vehicle.

[0081] In the central portion in the vehicle vertical direction of the side inner panel 72, a bolt insertion hole 72C is formed. Further, in the lower portion of the right wall portion 18C of the side frame 18 than the central portion in the vehicle vertical direction, a bolt insertion hole 18F is formed at a position communicating with the bolt insertion hole 72C. And a bolt 46 as a fastening member is inserted into the bolt insertion hole 72C and the bolt insertion hole 18F from the outside in the vehicle width direction, and the bolt 46 is screwed into a weld nut 48 provided on the right wall portion 18C. In this way, the right wall portion 18C which is the wall portion on the outside in the vehicle width direction of the side frame 18 and the side inner panel 72 which is the wall portion on the inside in the vehicle width direction of the side member 70 are fastened in the vehicle width direction by the bolt 46 and the weld nut 48. Note that a work hole (not shown) is formed in the side outer panel 74, and the bolt 46 can be inserted through this work hole.

[0082] Also, between the side frame 18 and the side member 70, a sealing material 54 and an adhesive 56 are provided in the same manner as in the first embodiment. The sealing material 54 is provided between the extension portion 18E and the side member 70 below the vehicle with respect to the bolt 46, and seals between the two. The adhesive 56 is provided between the right wall portion 18C and the side inner panel 72 above the vehicle with respect to the bolt 46, and adheres the two.

[0083] An outer energy absorption member 76 is provided in the cross section of the side member 70. The outer energy absorption member 76 has a cross-sectional shape in which the internal space is partitioned into three in the vehicle width direction, and has a structure in which it collapses and absorbs at least a part of the energy when a load is input from the vehicle width direction. Further, the outer energy absorption member 76 is located at the upper part in the cross section of the side member 70. Specifically, the outer energy absorption member 76 is provided above the bolt 46 and is fixed to the side member 70.

[0084] (Function) Next, the function of the vehicle lower structure according to the present embodiment will be described.

[0085] In this embodiment, the shape of the side member 70 is different from that of the first embodiment, and the dimension of the side member 70 in the vehicle width direction is larger than that of the side member 40 in the first embodiment. Therefore, by applying the side member 70 of this embodiment, even in a vehicle with a large vehicle compartment, it is not necessary to change the shapes of the battery case 20 and the side frame 18. Other operations are the same as those in the first embodiment.

[0086] As described above, the vehicle underbody structure according to the present invention has been described. However, it goes without saying that the present invention can be implemented in various modes without departing from the gist of the present invention. For example, in the above embodiment, the inner energy absorption member 50 is provided inside the side frame 18, and the outer energy absorption member 52 is provided inside the side member 40. However, the present invention is not limited to this, and a configuration without the inner energy absorption member 50 and the outer energy absorption member 52 may be adopted.

[0087] Further, in the above embodiment, a gap is provided between the floor cross member 34 and the battery case 20. However, the present invention is not limited to this, and a configuration in which the floor cross member 34 is attached to the battery case 20 may be adopted.

[0088] Furthermore, in this embodiment, the battery case 20 is configured to accommodate the battery BT. However, the present invention is not limited to this. For example, a structure in which the battery is directly accommodated between the left and right side frames 18 may be adopted. In this case, a structure in which the batteries are arranged on a support cover that supports the batteries from below and a cover that also serves as a floor panel is attached from above the side frames 18 may be adopted.

[0089] Regarding the above embodiment, the following supplementary notes are disclosed.

[0090] (Supplementary Note 1) A side frame having a closed cross-section structure that extends in the vehicle longitudinal direction on the outer side of the battery in the vehicle width direction and is provided at a position that overlaps at least a part of the battery in a side view of the vehicle; A side member having a closed cross-section structure is disposed on the outer side in the vehicle width direction of the side frame and is provided at a position overlapping at least a part of the side frame in a side view of the vehicle, and is fastened to the side frame by a fastening member. A vehicle lower structure having (Appendix 2) The vehicle lower structure according to Appendix 1, wherein an outer energy absorption member is provided in the cross-section of the side member. (Appendix 3) The vehicle lower structure according to Appendix 2, wherein an inner energy absorption member is provided in the cross-section of the side frame at a position where at least a part thereof overlaps the outer energy absorption member in a side view of the vehicle. (Appendix 4) A floor cross member extending in the vehicle width direction is connected to the side frame. The vehicle lower structure according to Appendix 3, wherein at least a part of the inner energy absorption member is provided at a position overlapping the floor cross member in a side view of the vehicle. (Appendix 5) A front pillar extending in the vehicle vertical direction is connected to the front side in the vehicle direction of the side member. A center pillar extending in the vehicle vertical direction is connected to the side member on the rear side of the vehicle with respect to the front pillar. The vehicle lower structure according to any one of Appendices 1 to 4. (Appendix 6) The vehicle lower structure according to any one of Appendices 1 to 5, wherein a wall portion on the outer side in the vehicle width direction of the side frame and a wall portion on the inner side in the vehicle width direction of the side member are fastened in the vehicle width direction by the fastening member. (Appendix 7) The outer energy absorption member is disposed at the upper part in the cross-section of the side member. The inner energy absorption member is disposed at the upper part in the cross-section of the side frame. The vehicle lower structure according to Appendix 3, wherein the fastening member is disposed below the outer energy absorption member and the inner energy absorption member. (Appendix 8) The side member is configured to include a flat inner panel disposed opposite to the side frame, and an outer panel having a hat-shaped cross section disposed outside the inner panel in the vehicle width direction and joined to the inner panel. The vehicle lower structure according to any one of Appendices 1 to 7.

Explanation of Signs

[0091] 18 Side frame 34 Floor cross member 40 Side member 42 Side inner panel (inner panel) 44 Side outer panel (outer panel) 46 Bolt (fastening member) 50 Inner energy absorption member 52 Outer energy absorption member 60 Front pillar 62 Center pillar BT Battery

Claims

1. A side frame with a closed cross-section structure that extends in the vehicle longitudinal direction on the outer side of the battery in the vehicle width direction and is provided at a position overlapping at least a part of the battery in a side view of the vehicle, A side member with a closed cross-section structure that is arranged on the outer side of the side frame in the vehicle width direction, is provided at a position overlapping at least a part of the side frame in a side view of the vehicle, and is fastened to the side frame by a fastening member, A vehicle lower structure having the above.

2. The vehicle lower structure according to claim 1, wherein an outer energy absorption member is provided in the cross-section of the side member.

3. The vehicle lower structure according to claim 2, wherein an inner energy absorption member is provided in the cross-section of the side frame at a position where at least a part thereof overlaps the outer energy absorption member in a side view of the vehicle.

4. A floor cross member extending in the vehicle width direction is connected to the side frame, The vehicle lower structure according to claim 3, wherein at least a part of the inner energy absorption member is provided at a position overlapping the floor cross member in a side view of the vehicle.

5. A front pillar extending in the vehicle vertical direction is connected to the front side of the vehicle of the side member, The vehicle lower structure according to claim 1, wherein a center pillar extending in the vehicle vertical direction is connected to the side member on the rear side of the vehicle with respect to the front pillar.

6. The vehicle lower structure according to claim 1, wherein the wall portion on the outer side in the vehicle width direction of the side frame and the wall portion on the inner side in the vehicle width direction of the side member are fastened in the vehicle width direction by the fastening member.

7. The outer energy absorption member is arranged at the upper part in the cross-section of the side member, The inner energy absorption member is arranged at the upper part in the cross-section of the side frame, The vehicle lower structure according to claim 3, wherein the fastening member is arranged below the outer energy absorption member and the inner energy absorption member.

8. The vehicle lower structure according to claim 1, wherein the side member includes a flat inner panel arranged to face the side frame, and an outer panel having a hat-shaped cross-section arranged on the outer side in the vehicle width direction of the inner panel and joined to the inner panel.

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