Vehicle underbody structure

Abstract

The present invention includes: a pair of side members that extend in the front-rear direction of a vehicle; a battery that is disposed between the pair of side members and that has a lower case which protrudes further downward than the lower surfaces of the pair of side members and which houses battery cells; and a support member that extends in the front-rear direction of the vehicle so as to run along the side walls of the lower case and that connects the bottom surfaces of the side members and the side walls of the lower case such that the battery is supported by the pair of side members.

Description

Vehicle undercarriage

[0001] The present invention relates to a vehicle underbody structure having a battery between a pair of side members.

[0002] 2. Description of the Related Art Electrically driven vehicles such as electric vehicles and hybrid vehicles that have a traction motor that drives wheels are equipped with a battery that houses battery cells that supply power to the traction motor.

[0003] Patent Document 1 discloses an electric vehicle that aims to lower the center of gravity of the vehicle while ensuring installation space for the battery by mounting the battery, which is a heavy object, between a pair of left and right side members located at the bottom of the vehicle and below the floor panel.

[0004] Japanese Patent Application Publication No. 2013-67334

[0005] The battery described in Patent Document 1 has a bracket attached to the side member to secure the case to the flange portion that protrudes outward in the vehicle width direction on the side of the case. This creates the problem that the case may be deformed from the flange portion due to a side impact load transmitted from the side member, or the battery may become unintentionally detached from the bracket, which could damage the battery cells inside the battery.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a vehicle underbody structure that can protect a battery from a side collision load.

[0007] The above object of the present invention is achieved by the following configuration: [1] A vehicle underbody structure comprising: a pair of side members extending in a vehicle longitudinal direction, a battery disposed between the pair of side members and having a lower case portion projecting downwardly from lower surfaces of the pair of side members and accommodating a battery cell, and a support member extending in the vehicle longitudinal direction along a side wall portion of the lower case portion, connecting a bottom surface of the side member to the side wall portion of the lower case portion, and supporting the battery on the pair of side members.

[0008] According to the present invention, the side of the battery stably receives the side impact load, and the battery itself acts as a reinforcing member that prevents the pair of side members from collapsing inward due to the side impact load, thereby protecting the battery from the side impact load.

[0009] FIG. 1 is a bottom perspective view of the main parts of a vehicle according to this embodiment. FIG. 2 is a bottom view of a vehicle body showing the vehicle undercarriage. FIG. 3 is a bottom perspective view of the main parts showing the vehicle undercarriage. FIG. 4 is an enlarged view of FIG. 3 showing a support member. FIG. 5 is a perspective view showing the inside of a battery. FIG. 6 is an exploded perspective view of the support member removed from the battery. FIG. 7 is a cross-sectional view taken along line A-A in FIG. 5. FIG. 8 is a cross-sectional view taken along line B-B in FIG. 5. FIG. 9 is a perspective view showing a case reinforcing member inside the battery. FIG. 10 is an exploded perspective view of the case reinforcing member.

[0010] Hereinafter, a vehicle undercarriage according to an embodiment of the present invention will be described with reference to the drawings. This embodiment shows only one example of the present invention, and the present invention is not limited to this embodiment. Various modifications and improvements can be made to this embodiment, and such modifications and improvements can also be included in the present invention.

[0011] In this embodiment, the direction of travel of the vehicle is referred to as "front," and the rear of the vehicle when traveling backward is referred to as "rear." The left side of the vehicle in the direction of travel is referred to as "left," and the right side of the vehicle in the direction of travel is referred to as "right." Furthermore, the left-right direction and the vehicle width direction are synonymous, and the front-rear direction and the vehicle direction are synonymous.

[0012] The vehicle underbody structure will be described with reference to Figures 1 to 4. Figure 1 is a bottom perspective view of the main parts of a vehicle according to this embodiment. Figure 2 is a bottom view of a vehicle body showing the vehicle underbody structure. Figure 3 is a bottom perspective view of the main parts showing the vehicle underbody structure. Figure 4 is an enlarged view of Figure 3 showing a support member.

[0013] 1, a vehicle 100 has a cabin 2 in which occupants ride. The cabin 2 is supported by a chassis frame 10 that forms the framework of the vehicle undercarriage. The vehicle undercarriage includes the chassis frame 10, a battery 30 that is disposed below a floor panel of the cabin 2 and supplies power to a traction motor (not shown) as an on-board device, and a support member 20 that supports the battery 30 on the chassis frame 10 side.

[0014] The chassis frame 10 includes a pair of left and right side members 11 extending in the longitudinal direction, and a plurality of cross members 12, 13, and 14 extending in the vehicle width direction, connecting the pair of left and right side members 11 together, and arranged in the longitudinal direction. A plurality of support brackets 15 are arranged in the longitudinal direction on the undersides of the side members 11 for attaching the battery 30 to the chassis frame 10 via support members 20. In this embodiment, five support brackets 15 are provided at a predetermined interval in the longitudinal center of each side member 11. The number and spacing of the support brackets 15 are set appropriately depending on the shape and longitudinal length of the battery 30.

[0015] Next, the mounting structure of the battery 30 mounted to the side member 11 via the support member 20 will be described with reference to Figures 1 to 6. Figure 5 is a perspective view showing the inside of the battery. Figure 6 is an exploded perspective view of the support member 20 removed from the battery.

[0016] (Battery 30) The battery 30 includes a plurality of battery cells 5, a lower case portion 31 formed in a box shape with an open top and accommodating the plurality of battery cells 5, a cover portion 32 covering the upper side of the lower case portion 31, and a battery control portion 33 controlling the battery 30. The outer side surface of the side wall portion 31a of the lower case portion 31 in the vehicle width direction is referred to as the outer side surface of the lower case portion 31, and the inner side surface of the side wall portion 31a of the lower case portion 31 in the vehicle width direction is referred to as the inner side surface of the lower case portion 31. In addition, a case reinforcing member 50, which will be described in detail later, is provided within the lower case portion 31 to protect the battery cells 5 from a side collision load transmitted to the battery 30. This configuration can be seen in FIG. 5 .

[0017] The battery 30 is supported on the side members 11 via support members 20 attached and fixed to the outer surfaces of the lower case portions 31. The battery 30 is disposed between a pair of side members 11 arranged side by side in the vehicle width direction, with the upper surface of the cover portion 32 located near the bottom of the floor panel and the lower case portion 31 protruding downward from the lower end of the side members 11. The battery 30 protrudes vertically from the lower surface of the floor panel to below the side members 11. The ends of the battery 30 in the vehicle width direction extend to the vicinity of the inner surfaces of the pair of side members 11. The battery 30 extends longitudinally from the vicinity of the rear ends of the front wheels (not shown) to the vicinity of the rear wheels (not shown). This configuration can be seen in FIGS. 1 to 4.

[0018] The battery 30 is further provided with electrical equipment such as an inverter (not shown) and an interface (not shown) for connecting to a traction motor, etc., thereby forming a battery. In this embodiment, this battery state is referred to as the battery 30. In this embodiment, as shown in FIG. 5 , the battery 30 houses battery cells 5 in two upper and lower tiers. Specifically, the battery 30 houses a first lower cell 5A in the front part of the lower case portion 31 and a second lower cell 5B in the rear part of the lower case portion 31. An upper cell 5C placed on the second lower cell 5B and a battery control unit 33 placed on the first lower cell 5A are covered by a cover portion 32.

[0019] The arrangement of the battery cells 5 and the battery control unit 33 in the battery 30 is not limited to the above. Furthermore, the battery 30 need only have a portion corresponding to the lower case portion 31 that protrudes below the side member 11 (support bracket 15), and does not need to be separated into the lower case portion 31 and the cover portion 32. For example, instead of the lower case portion 31 and the cover portion 32, a box-shaped member with an openable top surface may be used, or a box-shaped cover portion with an open bottom surface may be configured to surround a mounting plate (not shown) on which the battery cells 5 and the like are mounted.

[0020] (Support Member 20) The support member 20 has connecting brackets 21, 22 connected to the support bracket 15, an outer side member 23 attached to the outer surface of the lower case portion 31 of the battery 30, and a plurality of first bulkheads 24 installed between the outer side member 23 and the outer surface of the lower case portion 31. This configuration can be seen in Figures 4 and 6.

[0021] The connection brackets 21, 22 include a front connection bracket 21 attached to the front portion of the outer surface of the lower case portion 31, and a rear connection bracket 22 attached to the rear portion of the outer surface of the lower case portion 31. The front connection bracket 21 extends in the front-to-rear direction across the two front support brackets 15, and the rear connection bracket 22 extends in the front-to-rear direction across the three rear support brackets 15. This configuration can be seen in Figures 1 to 4. This allows the connection brackets 21, 22 to be stably attached and fixed to the side member 11 (support bracket 15) even in a portion of the side member 11 that is curved in the vehicle width direction and vertical direction midway in the front-to-rear direction.

[0022] Each connecting bracket 21, 22 has an L-shaped cross-sectional shape and is a member extending in the fore-and-aft direction along the outer surface of the lower case portion 31, and has an upper surface portion 21a, 22a extending horizontally and fixed to the lower surface of the support bracket 15 (the bottom surface side of the side member 11), a side surface portion 21b, 22b extending vertically and fixed to the outer side member 23 (the side wall portion 31a side of the lower case portion), and reinforcing ribs 21c, 22c provided between the upper surface portion 21a, 22a and the side surface portion 21b, 22b and whose surface direction intersects with the upper surface portion 21a, 22a and the side surface portion 21b, 22b.

[0023] The reinforcing ribs 21c, 22c are arranged side by side in the front-rear direction so as to sandwich the support bracket 15 fixed to at least the upper surface portions 21a, 22a from the front and rear. This configuration can be seen in Figures 3 and 4. This configuration can more efficiently prevent the L-shaped cross-section connecting brackets 21, 22 from being broken when a side impact load is transmitted from the vehicle width direction outer side to the connecting brackets 21, 22 via the support bracket 15. This ensures that the side impact load transmitted from the support bracket 15 is transmitted reliably to the outer side member 23 connected to the side surface portions 21b, 22b on the vehicle width direction inner side. This configuration can be seen in Figure 3, etc.

[0024] The outer side member 23 is a reinforcing member that extends in the front-to-rear direction from the front end to the rear end of the outer surface of the lower case portion 31. The outer side member 23 is formed by bending a plate-like member that is long in the front-to-rear direction, and has a U-shaped cross section in a front view that is open on the inner side in the vehicle width direction and on the front and rear ends, and is formed with an outer fixing portion 23a, an upper end fixing portion 23b, a lower end fixing portion 23c, and a recessed portion 23d.

[0025] The outer fixing portion 23a is a flat surface formed on the outer side member 23 facing outward in the vehicle width direction, and the side surface portions 21b, 22b of the connecting brackets 21, 22 that abut against the outer fixing portion 23a are fixed to the outer fixing portion 23a by welding or the like. The upper end fixing portion 23b is formed by bending its upper end upward so as to abut against the outer surface of the lower case portion 31, and is fixed to the upper part of the outer surface of the lower case portion 31 by welding or the like. The lower end fixing portion 23c is formed by extending its lower end inward to the left and right to a position where it overlaps with the bottom plate portion of the lower case portion 31, and is fixed to the lower surface of the bottom plate portion of the lower case portion 31 by welding or the like. Note that by attaching the outer side member 23 to the outer surface of the lower case portion 31, a space in which the first bulkhead 24 is attached is formed between the inner circumferential surface of the recessed portion 23d of the outer side member 23 and the outer surface of the lower case portion 31.

[0026] The first bulkhead 24 is formed by bending a plate-like member to have a U-shaped cross-section in plan view, with the vehicle width directional outer side and upper and lower ends open. The first bulkhead 24 has a recessed portion 24a formed on the vehicle width directional inner side and a pair of flanges 24b, 24b bent in the front-rear direction at the front and rear end edges. The vertical width of the first bulkhead 24 is formed to fit within the recessed portion 23d of the outer side member 23, and the pair of flanges 24b, 24b are fixed to the inner surface of the outer fixing portion 23a of the outer side member 23 by welding or other means. This brings the recessed portion 24a of the first bulkhead 24 into contact with or close to the outer surface of the lower case portion 31. For details of this configuration, see FIG. 7 (described later). The first bulkhead 24 may be fixed by any method other than welding or other means, such as bolts.

[0027] A plurality of first bulkheads 24 are arranged in a row in the front-rear direction along the outer side member 23. In the present embodiment, the first bulkheads 24 are arranged in a row at three locations in total: the front end, the rear end, and the center in the front-rear direction of the outer side member 23.

[0028] Next, the case reinforcing member 50 will be described with reference to Figures 7 to 10. Figure 7 is a cross-sectional view taken along line A-A in Figure 5. Figure 8 is a cross-sectional view taken along line B-B in Figure 5. Figure 9 is a perspective view showing the case reinforcing member inside the battery. Figure 10 is an exploded perspective view of the case reinforcing member.

[0029] (Case reinforcement member 50) The case reinforcement member 50 includes a pair of inner side members 51, 51 attached to the inner surface of the lower case portion 31 of the battery 30, a plurality of inner cross members 52 extending in the vehicle width direction so as to connect the pair of inner side members 51, 51, and a plurality of second bulkheads 53 installed between the inner side members 51 and the inner surface of the lower case portion 31. This configuration can be seen in FIGS. 7 to 10 .

[0030] The inner side member 51 is a reinforcing member that extends in the longitudinal direction from the front end to the rear end of the inner surface of the lower case portion 31. The inner side member 51 is formed with a bracing portion 51a that connects the top and bottom surfaces of the inner surface of the lower case portion 31, an upper end fixing portion 51b, a lower end fixing portion 51c, and a recessed portion 51d for installing the second bulkhead 53.

[0031] The tensioning portion 51a is inclined downward and inward in the vehicle width direction relative to the vertical direction, thereby connecting the upper part of the inner surface and the bottom surface of the lower case portion 31. When a side collision load acts on the side member 11, the tensioning portion 51a acts like a tension rod, preventing the upper parts of the connecting brackets 21, 22 from tipping inward in the vehicle width direction toward the lower case portion 31. This configuration can be seen in FIG. 8 .

[0032] The upper end fixing portion 51b is formed by bending its upper end upward so as to abut against the upper part of the inner surface of the lower case portion 31, and is fixed to the upper part of the inner surface of the lower case portion 31 by welding or the like. In this embodiment, the upper end fixing portion 51b of the inner side member 51 and the upper end fixing portion 23b of the outer side member 23 are arranged to sandwich the side wall portion 31a of the lower case portion 31, and the inner side member 51, the outer side member 23, and the lower case portion 31 are spot-welded in a state where the three members are stacked in the vehicle width direction. This configuration can be seen in Figures 7 and 8.

[0033] The lower end fixing portion 51c is formed by bending its lower end inward in the vehicle width direction along the upper surface (bottom surface) of the bottom plate portion of the lower case portion 31, and is fixed to the upper surface of the bottom plate portion of the lower case portion 31 by welding or the like. In the present embodiment, the lower end fixing portion 51c of the inner side member 51 and the lower end fixing portion 23c of the outer side member 23 are arranged to sandwich the bottom plate of the lower case portion 31, and the inner side member 51, the outer side member 23, and the lower case portion 31 are spot-welded together in a vertically stacked state. This configuration can be seen in Figures 7 and 8.

[0034] The recessed portions 51d are formed by recessing a portion of the tensioning portion 51a extending in the front-rear direction inward in the vehicle width direction, thereby ensuring space for installing the second bulkhead 53 in the space between the inner side member 51 and the inner surface of the lower case portion 31. This configuration can be seen in Figures 7 and 10. Similar to the first bulkhead 24 provided on the outer side member 23, the recessed portions 51d are formed in three locations on the inner side member 51: the front end, the rear end, and the center in the front-rear direction.

[0035] The inner cross member 52 is a reinforcing member that extends in the vehicle width direction within the lower case portion 31. The inner cross member 52 is formed by bending a plate-like member that is long in the vehicle width direction, and has an inverted U-shaped cross section in side view that is open at the bottom and both ends in the vehicle width direction, and is formed with a pair of left and right end fixing portions 52a, 52a and a lower end fixing portion 52b that fixes the lower surface to the bottom surface side of the lower case portion 31. This configuration can be seen in Figure 10.

[0036] The left and right end fixing portions 52a, 52a of the inner cross member 52 are connected to the inner side member 51, more specifically, to recessed portions 51d formed in the inner side member 51. As a result, the inner cross member 52 is provided with a total of three fixing portions, similar to the first bulkhead 24 provided on the outer side member 23 and the recessed portions 51d formed in the inner side member 51. Specifically, the inner cross member 52 includes a front cross member 52A connecting the front ends of the pair of inner side members 51, 51, an intermediate cross member 52B connecting the longitudinal centers of the pair of inner side members 51, 51, and a rear cross member 52C connecting the rear ends of the pair of inner side members 51, 51. This configuration can be seen in FIGS. 9 and 10 .

[0037] The second bulkhead 53 is formed by bending a plate-like member to have a U-shaped cross-section in plan view, with the vehicle width directional inner side and upper and lower ends open. The second bulkhead 53 has a recessed portion 53a formed on the vehicle width directional inner side and a pair of flanges 53b, 53b bent in the front-rear direction at its front and rear end edges. The second bulkhead 53 is sized to fit within the recessed portion 51d of the inner side member 51, and the pair of flanges 53b, 53b are fixed to the inner surface of the recessed portion 51d of the inner side member 51 by welding or other means. This brings the recessed portion 53a of the second bulkhead 53 into contact with or close to the inner surface of the lower case portion 31. This configuration can be seen in FIG. 7 . The second bulkhead 53 may be fixed by other means than welding or other means, such as bolts.

[0038] A plurality of second bulkheads 53 are arranged in the front-rear direction along the inner side member 51. In the present embodiment, a total of three second bulkheads 53 are provided, similar to the first bulkheads 24 provided on the outer side member 23, the recessed portions 51d formed in the inner side member 51, and the inner cross members 52 arranged in the front-rear direction.

[0039] (Operation and Effect) According to the above-described vehicle underbody structure, the outer surface of the lower case portion 31 of the battery 30 disposed between the pair of side members 11, 11 can be supported by the support brackets 15 provided on the underside of the side member 11 via the support members 20. Therefore, a large-capacity battery 30 with its lower portion protruding below the underside of the side member 11 as much as possible can be installed with greater space efficiency.

[0040] As shown in FIG. 7 , in the A-A cross section of the above-described vehicle underbody structure, the side collision load transmitted to the support bracket 15 of the side member 11 is transmitted directly in the following order: connecting brackets 21, 22 → outer side member 23 → first bulkhead 24 → lower case portion 31 → second bulkhead 53 → inner side member 51 → inner cross member 52.

[0041] This allows the side collision load transmitted to the side member 11 or the connecting brackets 21, 22 to be transmitted smoothly and reliably to the inner cross member 52 in the lower case portion 31 extending in the vehicle width direction, thereby efficiently preventing the battery 30 (lower case portion 31) from being deformed in a direction that would cause it to collapse in the vehicle width direction. As described above, the battery 30 itself also functions as a reinforcing member attached so as to bridge between the pair of side members 11, 11, which efficiently prevents the side member 11 from being deformed in such a way that it falls inward in the vehicle width direction due to the side collision load.

[0042] As shown in FIG. 8 , in the cross section B-B of the above-described vehicle underbody structure, the side collision load transmitted to the support bracket 15 of the side member 11 is transmitted in the following order: connecting brackets 21, 22 → upper part of the outer side member 23 → upper part of the side wall portion 31 a of the lower case portion 31 → tension portion 51 a of the inner side member 51.

[0043] As a result, when a side collision load acts from the outer side in the vehicle width direction toward the inner side in the vehicle width direction on the upper surface portions 21 a, 22 a of the connecting brackets 21, 22, the bracing portions 51 a of the inner side members 51 can restrict the upper portions of the side wall portions 31 a of the lower case portion 31 from rotating and deforming so as to fall inward in the vehicle width direction. In other words, the bracing portions 51 a efficiently reinforce the side wall portions 31 a of the lower case portion 31, preventing damage to the battery cells in the battery 30.

[0044] Furthermore, in Figures 7 and 8, the outer side member 23, the first bulkhead 24, and the second bulkhead 53 have a U-shaped cross section when viewed from the front, so that in the event of a side collision, they are compressively deformed in the vehicle width direction, thereby efficiently absorbing the side collision load.

[0045] The present invention is not limited to the above-described embodiment, and modifications and improvements can be made as appropriate.

[0046] As described above, this specification discloses the following: (1) A vehicle undercarriage structure comprising: a pair of side members extending in the fore-and-aft direction of the vehicle; a battery disposed between the pair of side members, the battery having a lower case portion projecting below the lower surfaces of the pair of side members and accommodating a battery cell; and a support member extending in the fore-and-aft direction of the vehicle along a side wall portion of the lower case portion, connecting a bottom surface of the side member to the side wall portion of the lower case portion, and supporting the battery to the pair of side members. With this configuration, a larger battery can be supported between the side members, and by stably receiving a side impact load on the side surfaces of the battery, the battery itself can function as a reinforcing member that prevents the pair of side members from tipping inward due to the side impact load.

[0047] (2) The vehicle undercarriage structure according to (1), wherein the support member is connected to the bottom surface of the lower case portion. According to this configuration, since the support member supports both edges of the bottom surface of the lower case portion in the vehicle width direction, a heavy battery can be stably supported.

[0048] (3) The vehicle undercarriage structure according to (1) or (2), wherein the support member includes an outer side member having a C-shaped cross section that is open on the inner side in the vehicle width direction and joined to the outer surface of the side wall of the lower case portion in the vehicle width direction, and a connecting bracket having an L-shaped cross section that connects the outer side member to the bottom surface of the side member. According to this configuration, by providing the outer side member on the outer surface of the side wall of the lower case portion in the vehicle width direction that protrudes below the side member, it is possible to absorb a side collision load transmitted from the connecting bracket.

[0049] (4) The vehicle undercarriage structure according to (3), wherein the connecting bracket has a side portion corresponding to the outer side member and an upper surface portion corresponding to the bottom surface of the side member, and a rib is provided between the side portion and the upper surface portion so as to intersect with the side portion and the upper surface portion in a planar direction. According to this configuration, the provision of the rib on the connecting bracket prevents the upper surface portion from undergoing unintended deformation, such as being crushed in the vehicle width direction, due to a side impact load transmitted from the side member 11, and enables the side impact load transmitted to the upper surface portion of the connecting bracket to be reliably transmitted to the side portion connected to the support member.

[0050] (5) The vehicle understructure according to (3) or (4), wherein the support member further includes a first bulkhead formed with a hat-shaped cross section between the side wall portion of the lower case portion and the outer side member. According to this configuration, by disposing the first bulkhead between the outer side member and the side wall portion of the lower case portion, the side impact load transmitted from the connecting bracket to the outer side member can be more reliably transmitted to the side wall portion of the lower case portion.

[0051] (6) The vehicle underbody structure according to any one of (1) to (5), further comprising an inner side member extending in the front-rear direction of the vehicle, provided on an inner side in the vehicle width direction of the side wall of the lower case portion. With this configuration, the side wall of the lower case portion to which a side impact load is transmitted can be reinforced.

[0052] (7) The vehicle undercarriage structure according to (6), wherein the inner side member has a bracing portion that is inclined downward relative to the vertical direction and inward in the vehicle width direction, and that connects the upper and bottom surfaces of the side wall portions of the lower case portion. This configuration can efficiently prevent the side wall portions of the lower case portion from being deformed inward in the vehicle width direction due to a side collision load.

[0053] (8) The vehicle underbody structure according to any one of (1) to (7), further comprising an inner cross member extending from one end to the other end in the vehicle width direction within the lower case portion. With this configuration, the inner cross member extending in the vehicle width direction acts like a tension rod during a side collision to transmit a side impact load to the lower case portion, making it difficult for the battery to deform.

[0054] (9) The vehicle undercarriage structure according to (8), wherein the inner cross member has a hat-shaped cross section that is open downward when viewed from the vehicle width direction, and a lower end thereof is fixed to the bottom surface of the lower case portion. With this configuration, it is possible to obtain high rigidity against a side impact load acting along the longitudinal direction while reducing the weight and cost of the inner cross member.

[0055] (10) The vehicle undercarriage structure according to (5), further comprising: an inner cross member extending from one end to the other end in the vehicle width direction; an inner side member disposed between the inner cross member and a side wall of the lower case portion and extending in the vehicle fore-and-aft direction; and a second bulkhead connecting the inner side member and the side wall of the lower case portion, wherein the first bulkhead, the second bulkhead, and the inner cross member are aligned in the vehicle width direction. This configuration efficiently and reliably transmits a side impact load to the inner cross member, preventing deformation of the lower case portion due to the side impact load. Furthermore, during a side impact, the cross sections of the outer side member, the first bulkhead, the second bulkhead, and the inner side member deform, thereby absorbing the side impact load.

[0056] DESCRIPTION OF SYMBOLS 2 Cabin 5 Battery cell 5A First lower cell 5B Second lower cell 5C Upper cell 10 Chassis frame 11 Side members 12, 13, 14 Cross members 15 Support bracket 20 Support member 21 Front connection bracket (connection bracket) 21a Upper surface portion 21b Side surface portion 21c Reinforcement rib 22 Rear connection bracket (connection bracket) 22a Upper surface portion 22b Side surface portion 22c Reinforcement rib 23 Outer side member 23a Outer fixing portion 23b Upper end fixing portion 23c Lower end fixing portion 23d Recessed portion 24 First bulkhead 24a Recessed portion 24b Flange portion 30 Battery 31 Lower case portion 31a Side wall portion 32 Cover portion 33 Battery control unit 50 Case reinforcing member 51 Inner side member 51a Tension portion 51b Upper end fixing portion 51c Lower end fixing portion 51d Recessed portion 52 Inner cross member 52A Front cross member 52B Intermediate cross member 52C Rear cross member 52a Left and right end fixing portions 52b Lower end fixing portion 53 Second bulkhead 53a Recessed portion 53b Flange portion 100 Vehicle

Claims

1. A vehicle undercarriage structure comprising: a pair of side members extending in the fore-and-aft direction of a vehicle; a battery disposed between the pair of side members, the battery having a lower case portion that protrudes below the lower surfaces of the pair of side members and that houses a battery cell; and a support member that extends in the fore-and-aft direction of the vehicle along the side wall portions of the lower case portion, connects the bottom surface of the side member to the side wall portion of the lower case portion, and supports the battery on the pair of side members.

2. The vehicle undercarriage structure according to claim 1, wherein the support member is connected to the bottom surface of the lower case portion.

3. A vehicle undercarriage structure as set forth in claim 1 or 2, wherein the support member has an outer side member having a C-shaped cross section that is open on the inner side in the vehicle width direction and that is joined to the outer surface in the vehicle width direction of the side wall portion of the lower case portion, and a connecting bracket having an L-shaped cross section that connects the outer side member to the bottom surface of the side member.

4. A vehicle undercarriage structure as set forth in claim 3, wherein the connecting bracket has a side surface portion corresponding to the outer side member and an upper surface portion corresponding to the bottom surface of the side member, and a rib is provided between the side surface portion and the upper surface portion so that the surface direction intersects with the side surface portion and the upper surface portion.

5. A vehicle undercarriage structure according to claim 3 or 4, wherein the support member further has a first bulkhead formed with a hat-shaped cross section between the side wall of the lower case portion and the outer side member.

6. A vehicle underbody structure as claimed in any one of claims 1 to 5, wherein an inner side member extending in the longitudinal direction of the vehicle is provided on the inner side of the side wall of the lower case portion in the vehicle width direction.

7. A vehicle undercarriage structure as set forth in claim 6, wherein the inner side member has a bracing portion that is inclined downward relative to the vertical direction and inward in the vehicle width direction, and that connects the upper and bottom surfaces of the side wall portions of the lower case portion.

8. A vehicle underbody structure as claimed in any one of claims 1 to 7, wherein an inner cross member extending from one end to the other end in the vehicle width direction is provided within the lower case portion.

9. A vehicle undercarriage structure as set forth in claim 8, wherein the inner cross member has a hat-shaped cross section that is open downward when viewed in the vehicle width direction, and the lower end is fixed to the bottom surface of the lower case portion.

10. A vehicle undercarriage structure as described in claim 5, wherein the battery is provided with an inner cross member extending from one end to the other in the vehicle width direction, an inner side member disposed between the inner cross member and the side wall portion of the lower case portion and extending in the fore-and-aft direction of the vehicle, and a second bulkhead connecting the inner side member and the side wall portion of the lower case portion, and the first bulkhead, the second bulkhead, and the inner cross member are arranged side by side in the vehicle width direction.

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