Lower part structure of vehicle

Abstract

To provide a lower part structure of a vehicle 1 which enables improvement of vehicle body rigidity in the vehicle 1 in which a floor surface of a passenger compartment is formed by a substantially flat front floor panel 5.SOLUTION: A lower structure of a vehicle 1 includes a battery unit 20 disposed at the lower side of a vehicle relative to a front floor panel 5. The battery unit 20 includes: a battery frame 23 which is fastened to a high rigid portion of a vehicle body; and second frame reinforcement members 27 which connect widthwise frames 232 of the battery frame 23 in a vehicle front-rear direction. The second frame reinforcement member 27 comprises: main parts 28 which are provided in parallel to each other while spaced apart from each other in the vehicle front-rear direction; and connection parts 29 each of which is fixed to the main parts 28 located adjacent to each other in the vehicle front-rear direction and connected to a floor cross member through the front floor panel 5.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a vehicle undercarriage structure in which a battery unit is provided on the vehicle lower side of a floor panel in a vehicle that does not have a floor tunnel extending in the longitudinal direction of the vehicle, for example. [Background technology]

[0002] In vehicles such as automobiles, in electric vehicles that use the output of a rotating electric motor as driving force, the battery unit that supplies power to the rotating electric motor is arranged below the vehicle on the floor panel that forms the floor surface of the passenger compartment, and is fastened and fixed to a high-rigidity part of the vehicle.

[0003] For example, in Patent Document 1, in an electric vehicle equipped with a floor tunnel extending in the fore-and-aft direction of the vehicle at approximately the center of the floor panel in the vehicle width direction, a battery unit is fastened and fixed from below the vehicle to a floor frame extending in the fore-and-aft direction of the vehicle, connecting the underside of the floor tunnel and floor panel.

[0004] Incidentally, the above-mentioned floor tunnel has traditionally been used as a space for arranging an exhaust pipe that discharges exhaust generated by the internal combustion engine outside the vehicle from the rear, but this is no longer necessary in electric vehicles, which do not require an exhaust pipe.

[0005] Therefore, in a vehicle in which a battery unit is disposed below the floor panel, the vehicle interior floor surface may be formed by a relatively flat front floor panel that does not have a floor tunnel. However, in this case, the rigidity of the relatively flat floor panel is lower than that of a floor panel having a floor tunnel, which may result in a decrease in the rigidity of the vehicle body. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-160506 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above-mentioned problems, an object of the present invention is to provide a vehicle undercarriage structure that can improve the vehicle body rigidity in a vehicle whose cabin floor surface is configured with a substantially flat floor panel. [Means for solving the problem]

[0008] This invention is a vehicle undercarriage structure comprising a substantially flat floor panel arranged between left and right side sills of a vehicle, and a floor cross member arranged on the upper surface of the floor panel and connecting the left and right side sills in the vehicle width direction, and further comprising a battery unit arranged on the lower side of the vehicle relative to the floor panel, the battery unit being substantially annular in shape and forming the outer shape of the battery unit and comprising a high-rigidity battery frame fastened to a high-rigidity portion of the body of the vehicle, and a high-rigidity frame reinforcement member connecting opposing portions of the battery frame in a predetermined direction in the predetermined direction, the frame reinforcement member being composed of a main body portion arranged side by side at a predetermined interval in the predetermined direction, and a connecting portion fixed to both of the main body portions adjacent in the predetermined direction and connected to the floor cross member via the floor panel.

[0009] The floor cross member may be an open cross-sectional floor cross member that forms a closed cross section together with a floor panel, or a cylindrical floor cross member that has a closed cross-sectional shape. The high-rigidity portion is a portion whose longitudinal cross-sectional shape along the vehicle longitudinal direction or vehicle width direction is a closed cross-sectional shape, more preferably a body frame member that forms the body frame of the vehicle, such as a side sill, a floor frame, a floor cross member that connects the left and right side sills in the vehicle width direction, the rear of the front side frame, or a torque box that connects the front side frame to the side sill. The battery frame may be a battery frame that is generally rectangular in plan view or a battery frame that is generally trapezoidal in plan view.

[0010] According to this invention, a highly rigid battery frame is connected to a highly rigid portion of the vehicle, and a highly rigid frame reinforcement member is connected to the floor cross member, so that the battery frame and frame reinforcement member of the battery unit can function as reinforcement members that reinforce the floor panel.

[0011] Furthermore, the vehicle's lower structure can be configured with a main body having a reduced length in a specified direction, compared to when opposing parts of a battery frame in a specified direction are connected by a single main body, thereby improving the bending rigidity of the frame reinforcement member against input loads from a specified direction (e.g., collision loads from a specified direction).

[0012] Therefore, the vehicle undercarriage can reliably allow the frame reinforcing member to function as a reinforcing member that reinforces the floor panel. As a result, the vehicle's undercarriage can improve the vehicle body rigidity by using the battery unit in a vehicle whose passenger compartment floor surface is configured with a substantially flat floor panel.

[0013] In addition, the vehicle's undercarriage can stably support the heavy battery unit compared to when only the battery frame is fastened to the vehicle body, and can suppress vibrations transmitted, for example, to the interior of the vehicle due to the weight of the battery unit connected to the vehicle body.

[0014] As an aspect of the present invention, the connecting portion may be composed of a fastened member fixed to the main body portion and a fastening member fastened to the fastened member, sandwiching the floor panel and the floor cross member. This configuration allows the main body to be firmly fixed to the floor cross member using a simply configured connecting portion, thereby improving the vehicle body rigidity while minimizing weight increase in the vehicle undercarriage.

[0015] In another aspect of the present invention, the battery unit may include a bottom plate portion that closes the opening in the battery frame below the vehicle, and a top plate portion that closes the opening in the battery frame above the vehicle, and the fastened member may be configured to abut against the underside of the top plate portion.

[0016] With this configuration, the top plate portion covering the opening on the upper side of the vehicle of the battery frame can be stably supported by the connecting portion, so that shaking of the top plate portion due to unevenness of the road surface, for example, can be suppressed. This allows the vehicle's undercarriage to stably support the battery unit while preventing the generation of unintended noise and vibration.

[0017] In another aspect of the present invention, the connecting portion may include an intermediate member that is arranged between the floor panel and the top plate portion of the battery unit and fastened to the fastened member across the top plate portion.

[0018] The intermediate member is a member that screws into the fastened member through an opening provided in the top plate portion and has a through hole through which the fastening member is inserted, or a member that screws into the fastened member protruding from the opening in the top plate portion.

[0019] With this configuration, the opening provided in the part of the top plate portion facing the fastened member is not exposed to the outside by the intermediate member, thereby preventing moisture from entering the inside of the battery unit through the opening in the top plate portion. This allows the vehicle's undercarriage structure to ensure watertightness of the battery unit even when the frame reinforcing member is connected to the floor cross member.

[0020] In another aspect of the present invention, the battery unit may include a plurality of battery modules arranged side by side inside the battery frame with the frame reinforcement member sandwiched therebetween, and the battery modules may have flange portions that protrude toward the frame reinforcement member and are fastened and fixed to the upper surface of the main body portion.

[0021] With this configuration, the size of the battery module can be made closer to the frame reinforcing member than, for example, when the battery module is fixed to a bracket of a frame reinforcing member that protrudes toward the battery module. This allows the vehicle's undercarriage to improve the vehicle body rigidity without compromising battery capacity.

[0022] As another aspect of the present invention, the frame reinforcing member may be configured to connect portions of the battery frame that face each other in the vehicle longitudinal direction in the vehicle longitudinal direction. According to this configuration, the frame reinforcing member can improve the rigidity of the battery unit against loads in the vehicle's longitudinal direction.

[0023] Therefore, in a vehicle in which the passenger compartment floor is constructed of a substantially flat floor panel, the vehicle's lower structure can improve the body rigidity against, for example, a collision load from the front of the vehicle or a collision load from the rear of the vehicle, by using a battery unit connected to the vehicle body.

[0024] Furthermore, for example, if multiple floor cross members are arranged on the upper surface of the floor panel at a predetermined interval in the fore-and-aft direction of the vehicle, the vehicle's lower structure can have one frame reinforcement member arranged crosswise to the multiple floor cross members.

[0025] This allows the vehicle's undercarriage to easily connect multiple floor cross members to a single frame reinforcing member, thereby improving the support rigidity of the battery unit.

[0026] In another aspect of the present invention, the floor cross member may be formed in a cross-sectional shape in a longitudinal section along the vehicle's fore-and-aft direction, having two trapezoidal sections with an approximately trapezoidal cross section that protrude upwardly of the vehicle at a predetermined distance in the vehicle's fore-and-aft direction, and a valley bottom portion that connects the lower ends of the trapezoidal sections, and the connecting portion may be configured to connect the main body portion to the valley bottom portion of the floor cross member.

[0027] With this configuration, the rigidity of the floor cross member to which the battery unit is connected can be made higher than that of a floor cross member having a generally hat-shaped cross section with one trapezoidal portion.

[0028] This allows the vehicle's undercarriage to improve the support rigidity of the battery unit and further improve the body rigidity of the vehicle to which the battery unit is connected. [Effects of the Invention]

[0029] The present invention can provide a vehicle underbody structure that can improve the body rigidity of a vehicle whose passenger compartment floor surface is configured with a substantially flat floor panel. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 2 is an external perspective view showing the external appearance of the vehicle undercarriage as seen from above and in front of the vehicle. [Figure 2] FIG. 2 is a cross-sectional view showing a cross section near the torque box in a longitudinal section along the vehicle front-rear direction. [Figure 3] FIG. 2 is a cross-sectional view showing a cross section near a side sill in a longitudinal cross section along the vehicle width direction. [Figure 4] 3 is a cross-sectional view showing a cross section of a first floor cross member and a second floor cross member in a longitudinal section along the vehicle front-rear direction. FIG. [Figure 5] FIG. 10 is a cross-sectional view showing a cross section of a fourth floor cross member in a longitudinal section along the vehicle front-rear direction. [Figure 6] FIG. 2 is an exploded perspective view showing the external appearance of the battery unit as viewed from above and in front of the vehicle. [Figure 7] FIG. 2 is a plan view showing the appearance of the battery unit with the top panel removed. [Figure 8] FIG. [Figure 9] FIG. 4 is a cross-sectional view showing a cross section of a connecting portion in a longitudinal cross section along the vehicle width direction. [Figure 10] FIG. 10 is a cross-sectional view showing a cross section of a connecting portion in another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0031] An embodiment of the present invention will be described below with reference to the drawings. The vehicle 1 of this embodiment is an electric vehicle that uses the output of a rotating electric machine as a driving force, and a battery unit 20 that supplies power to the rotating electric machine is disposed outside the passenger compartment below the front floor panel 5. The undercarriage structure of such a vehicle 1 will be described with reference to FIGS. 1 to 9.

[0032] FIG. 1 shows an external perspective view of the undercarriage of a vehicle 1 as viewed from above and in front of the vehicle, FIG. 2 shows a cross-sectional view of the vicinity of the torque box 14 in a longitudinal section along the vehicle longitudinal direction, and FIG. 3 shows a cross-sectional view of the vicinity of the side sill 3 in a longitudinal section along the vehicle width direction.

[0033] Furthermore, Figure 4 shows a cross-sectional view of the first floor cross member 7 and the second floor cross member 8 in a longitudinal section along the fore-and-aft direction of the vehicle, and Figure 5 shows a cross-sectional view of the fourth floor cross member 10 in a longitudinal section along the fore-and-aft direction of the vehicle.

[0034] In addition, Figure 6 shows an exploded oblique view of the battery unit 20 viewed from above and in front of the vehicle, Figure 7 shows a plan view of the battery unit 20 with the top plate portion 25 removed, Figure 8 shows an oblique view of the exterior of the connecting portion 29, and Figure 9 shows a cross-sectional view of the connecting portion 29 in a longitudinal section along the vehicle width direction.

[0035] More specifically, Figure 2 shows a cross-sectional view of a longitudinal section along the vehicle's fore-and-aft direction passing through a position outside the front side frame 12 in the vehicle width direction, Figure 3 shows a cross-sectional view of a longitudinal section along the vehicle width direction passing through the valley bottom 72 of the first floor cross member 7, and Figure 4 shows a cross-sectional view of a longitudinal section along the vehicle's fore-and-aft direction passing through the second frame reinforcement member 27.

[0036] For clarity of illustration, the portion of the vehicle forward of the dash panel 2 is omitted in FIG. 1, and the vicinity of the center in the vehicle width direction is omitted in FIG. Furthermore, for clarity of illustration, the battery module 21 is omitted in FIG. 6, and part of the fastened member 30 is shown in a see-through state in FIG.

[0037] In the drawings, arrows Fr and Rr indicate the longitudinal direction of the vehicle, with arrow Fr indicating the front of the vehicle and arrow Rr indicating the rear of the vehicle. Furthermore, arrows Rh and Lh indicate the width direction of the vehicle, with arrow Rh indicating the right side in the width direction of the vehicle and arrow Lh indicating the left side in the width direction of the vehicle.

[0038] First, as shown in FIG. 1, vehicle 1, which is an electric vehicle, is equipped with a dash panel 2 that forms the front wall of the passenger compartment (reference numeral omitted) where occupants get in, a pair of left and right side sills 3 that extend rearward from the lower portions of both ends of the dash panel 2 in the vehicle width direction, and a pair of left and right rear side frames 4 that are connected to the rear of the side sills 3 and extend rearward of the vehicle.

[0039] Furthermore, the vehicle 1 is provided with a front floor panel 5 that forms the floor surface of the vehicle 1 between the side sills 3, and a rear floor panel 6 that forms the floor surface of the vehicle 1 between the rear side frames 4. In addition, the vehicle 1 is equipped with a first floor cross member 7, a second floor cross member 8 and a third floor cross member 9 that connect the left and right side sills 3 in the vehicle width direction, and a fourth floor cross member 10 that connects the left and right rear side frames 4 in the vehicle width direction.

[0040] As shown in FIG. 1, the vehicle 1 includes a battery unit 20 that is fixed to a body frame member that forms the body frame of the vehicle 1 below the front floor panel 5 and that supplies power to the rotating electric machine.

[0041] More specifically, the dash panel 2 is a panel member having a thickness in the longitudinal direction of the vehicle, and both ends in the vehicle width direction are connected to hinge pillars (not shown) erected at the front ends of the side sills 3 . As shown in FIG. 2, a dash cross member 11 is joined to the front surface of the dash panel 2, extending from the lower end of the dash panel 2 in the vehicle width direction and connected to the hinge pillar.

[0042] The dash cross member 11 is an open section member that, together with the dash panel 2, forms a body frame member extending in the vehicle width direction, and its cross section in a longitudinal section along the vehicle fore-and-aft direction is formed to be approximately hat-shaped, protruding toward the front of the vehicle. Furthermore, as shown in FIG. 2, a pair of left and right front side frames 12 are joined to the dash panel 2 at positions spaced a predetermined distance apart in the vehicle width direction and extending toward the front of the vehicle.

[0043] The left and right side sills 3 are body frame members whose cross-sectional shape in a longitudinal section along the vehicle width direction is a closed cross-section, and as shown in FIG. 3, are composed of a side sill inner 3a having a generally hat-shaped cross section that protrudes inward in the vehicle width direction, and a side sill outer 3b having a generally hat-shaped cross section that protrudes outward in the vehicle width direction.

[0044] The side sill 3 is configured by joining together in the vehicle width direction a side sill inner 3a located on the inner side in the vehicle width direction and a side sill outer 3b located on the outer side in the vehicle width direction relative to the side sill inner 3a.

[0045] The left and right rear side frames 4 are body frame members whose cross-sectional shape in a longitudinal section along the vehicle width direction is a closed cross section, and their front ends are joined to the inside of the rear part of the side sill 3 in the vehicle width direction.

[0046] Although detailed illustrations are omitted, the rear side frame 4 forms a closed cross-sectional shape extending in the fore-and-aft direction of the vehicle by joining, for example, a side frame upper located above the vehicle and a side frame lower located below the side frame upper in the vertical direction of the vehicle.

[0047] As shown in FIG. 1, a damper support member 13 that supports the upper end of a rear suspension damper (not shown) is joined to the rear side frame 4 at a position rearward of a fourth floor cross member 10 (described later) in the vehicle.

[0048] As shown in FIG. 1, the front floor panel 5 is formed in a substantially flat plate shape that bulges out toward the top of the vehicle and does not have a floor tunnel that extends in the front-rear direction of the vehicle. The front end of the front floor panel 5 is joined to the lower end of the dash panel 2, and both ends in the vehicle width direction are joined to the side sills 3.

[0049] Furthermore, as shown in FIG. 2, a pair of left and right torque boxes 14 are provided in front of the front floor panel 5 outside the vehicle compartment to connect the front side frames 12 and the side sills 3 in the vehicle width direction.

[0050] The torque box 14 is an open-section member that, together with the front floor panel 5, forms a body frame member extending in the vehicle width direction, and its cross-sectional shape in a longitudinal section along the vehicle fore-and-aft direction is formed to be approximately hat-shaped, protruding downward from the vehicle.

[0051] In addition, the rear floor panel 6 is composed of a kick-up portion (not shown) that stands above the vehicle from its front end joined to the rear end of the front floor panel 5, and a rear floor main body (symbol omitted) that extends from the upper end of the kick-up portion toward the rear of the vehicle.

[0052] In addition, as shown in Figure 1, the left and right first floor cross members 7 are joined to the upper surface of the front floor panel 5 near the approximate center of the front floor panel 5 in the vehicle's fore-and-aft direction, and connect the left and right side sills 3 in the vehicle width direction.

[0053] This first floor cross member 7 is an open section member that forms a body frame member extending in the vehicle width direction together with the approximately flat front floor panel 5, and is formed so that its cross-sectional shape in a longitudinal section along the fore-and-aft direction of the vehicle is approximately M-shaped.

[0054] Specifically, as shown in Figure 4, the first floor cross member 7 has, in a longitudinal cross section along the vehicle's fore-and-aft direction, two trapezoidal portions 71 that protrude upward in an approximately trapezoidal shape at positions spaced a predetermined distance apart in the vehicle's fore-and-aft direction, and a valley bottom portion 72 that connects the lower ends of the two trapezoidal portions 71 and is joined to the upper surface of the front floor panel 5.

[0055] Furthermore, the first floor cross member 7 has a front flange portion 73 that extends from the front lower end of the trapezoidal portion 71 on the front side of the vehicle toward the front of the vehicle and is joined to the upper surface of the front floor panel 5, and a rear flange portion 74 that extends from the rear lower end of the trapezoidal portion 71 on the rear side of the vehicle toward the rear of the vehicle and is joined to the upper surface of the front floor panel 5.

[0056] As shown in Figure 4, the valley bottom 72 of this first floor cross member 7 has two insertion holes 7a formed at a predetermined distance in the vehicle width direction, through which fastening bolts 32 of the connecting portion 29 described later can be inserted.

[0057] In addition, as shown in Figure 1, the second floor cross member 8 is joined to the upper surface of the front floor panel 5 at a position a predetermined distance rearward of the vehicle from the first floor cross member 7, and connects the left and right side sills 3 in the vehicle width direction.

[0058] This second floor cross member 8 is an open section member that forms a body frame member extending in the vehicle width direction together with the approximately flat front floor panel 5, and is formed so that its cross-sectional shape in a longitudinal section along the fore-and-aft direction of the vehicle is approximately M-shaped.

[0059] Specifically, as shown in Figure 4, the second floor cross member 8 has, in a longitudinal cross section along the vehicle's fore-and-aft direction, two trapezoidal portions 81 that protrude upward in an approximately trapezoidal shape at positions spaced a predetermined distance apart in the vehicle's fore-and-aft direction, and a valley bottom portion 82 that connects the lower ends of the two trapezoidal portions 81 and is joined to the upper surface of the front floor panel 5.

[0060] Furthermore, the second floor cross member 8 has a front flange portion 83 that extends from the front lower end of the trapezoidal portion 81 on the front side of the vehicle toward the front of the vehicle and is joined to the upper surface of the front floor panel 5, and a rear flange portion 84 that extends from the rear lower end of the trapezoidal portion 81 on the rear side of the vehicle toward the rear of the vehicle and is joined to the upper surface of the front floor panel 5.

[0061] Similar to the valley bottom 72 of the first floor cross member 7, the valley bottom 82 of this second floor cross member 8 has two insertion holes (numeral omitted) formed at a predetermined distance in the vehicle width direction, through which the fastening bolts 32 of the connecting portion 29 described later are inserted.

[0062] As shown in FIG. 1, the third floor cross member 9 is joined to the upper surface of the rear floor panel 6 rearward of the second floor cross member 8, and connects the left and right side sills 3 in the vehicle width direction.

[0063] This third floor cross member 9 is an open section member that forms a body frame member extending in the vehicle width direction together with the kick-up portion of the rear floor panel 6, and its cross-sectional shape in a longitudinal section along the fore-and-aft direction of the vehicle is formed in a shape that, together with the kick-up portion of the rear floor panel 6, forms a closed section with an approximately rectangular cross section.

[0064] In addition, as shown in Figure 1, the fourth floor cross member 10 is joined to the upper surface of the rear floor panel 6 rearward of the third floor cross member 9 and forward of the damper support member 13, and connects the left and right rear side frames 4 in the vehicle width direction. This fourth floor cross member 10, together with the rear floor main body of the rear floor panel 6, constitutes a vehicle body frame member extending in the vehicle width direction.

[0065] Specifically, as shown in Figure 5, the fourth floor cross member 10 is composed of a cross member upper 101 located above the vehicle relative to the rear floor panel 6, and a cross member lower 102 located below the vehicle relative to the rear floor panel 6.

[0066] 5, the cross member upper 101 has a cross section in a longitudinal section along the vehicle front-rear direction that is generally hat-shaped and protrudes upward toward the vehicle. Both ends of the cross member upper 101 in the vehicle width direction are joined to the rear side frames 4 and are also joined to the lower parts of rear side panels (not shown) that form the interior walls of the vehicle at the rear of the vehicle 1.

[0067] On the other hand, the cross member lower 102 has a cross section in a longitudinal section along the vehicle front-rear direction that is generally hat-shaped and protrudes downward toward the vehicle, as shown in Figure 5. The cross member lower 102 is joined to the cross member upper 101 with the rear floor panel 6 sandwiched therebetween.

[0068] The fourth floor cross member 10 configured as described above has an opening at the top of the vehicle, and two approximately box-shaped support legs 15 that are long in the vertical direction of the vehicle are joined at a predetermined distance in the width direction of the vehicle, as shown in Figure 5. These support legs 15 are provided as high-rigidity parts that connect and support a battery unit 20 (described later) to the fourth floor cross member 10.

[0069] As shown in Figures 6 and 7, the battery unit 20 is a structure that is approximately rectangular in plan view, and is composed of four battery modules 21 arranged side by side in the vehicle width direction, and a housing 22 that houses and holds the battery modules 21 inside.

[0070] Specifically, the battery module 21 is, for example, a lithium ion battery in which a plurality of battery cells are electrically connected, and as shown in FIG. 7, is formed in a generally rectangular shape in plan view that is long in the vehicle front-rear direction.

[0071] As shown in Figure 7, the four battery modules 21 are arranged inside the housing 22 in four storage spaces (reference numerals omitted) that are approximately rectangular in plan view and elongated in the fore-and-aft direction of the vehicle, separated by a first frame reinforcing member 26 and a second frame reinforcing member 27 described later.

[0072] Furthermore, although not shown in detail, the battery module 21 is provided with a plurality of flange portions 21a that protrude in the vehicle width direction at positions spaced apart at predetermined intervals in the vehicle longitudinal direction. The flange portion 21 a of the battery module 21 is provided to fasten and fix the battery module 21 to a fastening portion provided on the housing 22 .

[0073] More specifically, of the four battery modules 21, the two battery modules 21 located furthest outward in the vehicle width direction have flange portions 21a that protrude outward in the vehicle width direction and are fastened and fixed to fastening portions 23a of the longitudinal frame 231 described later, as shown in Figure 7, and flange portions 21a that protrude inward in the vehicle width direction and are fastened and fixed to the upper surface of the second frame reinforcing member 27 described later.

[0074] On the other hand, the two battery modules 21 located on the inner side in the vehicle width direction have flange portions 21a that protrude outward in the vehicle width direction and are fastened to the upper surface of the adjacent second frame reinforcing member 27 on the outer side in the vehicle width direction, as shown in Figure 7.

[0075] The flange portion 21a fastened to the second frame reinforcing member 27 is formed at approximately the same position in the vehicle longitudinal direction as the flange portion 21a of the adjacent battery module 21, and is formed so as to overlap the flange portion 21a of the adjacent battery module 21 in the vehicle vertical direction (see Figure 4).

[0076] As shown in Figures 6 and 7, the housing 22 includes a battery frame 23 formed in a generally annular shape that is generally rectangular in plan view and serves as the frame body of the battery unit 20, a bottom plate portion 24 that closes the opening in the battery frame 23 on the lower side of the vehicle, and a top plate portion 25 that closes the opening in the battery frame 23 on the upper side of the vehicle.

[0077] Furthermore, inside the battery frame 23, the housing 22 is provided with one first frame reinforcement member 26 extending in the fore-and-aft direction of the vehicle at approximately the center in the vehicle width direction, and a pair of second frame reinforcement members 27 extending in the fore-and-aft direction of the vehicle on the outer side of the first frame reinforcement member 26 in the vehicle width direction. The single first frame reinforcing member 26 and the pair of second frame reinforcing members 27 define four compartmentalized storage spaces inside the housing 22.

[0078] Specifically, the battery frame 23 is configured as a highly rigid frame body that is generally rectangular in plan view and is made by combining extruded aluminum alloy members, for example. The battery frame 23 is formed with a length in the vehicle vertical direction that is shorter than the length of the battery module 21 in the vehicle vertical direction.

[0079] More specifically, the battery frame 23 is composed of a pair of left and right longitudinal frames 231 extending in the fore-and-aft direction of the vehicle at positions spaced a predetermined distance apart in the vehicle width direction, and a pair of front and rear width frames 232 connecting the ends of the longitudinal frames 231 in the vehicle width direction at positions spaced a predetermined distance apart in the vehicle width direction.

[0080] Furthermore, as shown in Figures 6 and 7, the left and right longitudinal frames 231 have multiple fastening portions 23a for fastening and fixing the battery module 21 joined to the inner surfaces facing the other longitudinal frame 231 at predetermined intervals in the longitudinal direction of the vehicle.

[0081] As shown in Figures 2 and 3, the battery frame 23 configured as described above has the width direction frame 232 on the vehicle front side fastened and fixed to the torque box 14, and the left and right longitudinal direction frames 231 fastened and fixed to the side sills 3. In addition, as shown in FIG. 5, the width direction frame 232 of the battery frame 23 on the vehicle rear side is fastened and fixed to the support leg 15, and is connected to the fourth floor cross member 10 via the support leg 15.

[0082] As shown in FIG. 3, the bottom plate portion 24 is a plate material having a thickness in the vertical direction, and is integrally formed with a roughly box-shaped main body portion (reference numeral omitted) that is open at the top of the vehicle, and a flange portion (reference numeral omitted) that extends from the upper edge of the main body portion and is fastened and fixed to the underside of the battery frame 23. The main body of the bottom plate portion 24 is fixed to the lower surfaces of the first frame reinforcing member 26 and the second frame reinforcing member 27 by welding or fastening.

[0083] On the other hand, as shown in Figures 3 and 6, the top plate portion 25 is a plate material having a thickness in the vertical direction, and is integrally formed with a roughly box-shaped main body portion (symbol omitted) that is open toward the bottom of the vehicle, and a flange portion (symbol omitted) that extends from the lower edge of the main body portion and is fastened and fixed to the upper surface of the battery frame 23.

[0084] The main body of the top panel 25 is fixed to the upper surface of the second frame reinforcing member 27 (a member 30 to be fastened to the second frame reinforcing member 27, which will be described later). For this reason, as shown in Figure 6, an opening 25a is formed in the main body portion of the top plate portion 25 in the vertical direction of the vehicle at a position opposite to the fastened member 30 of the second frame reinforcing member 27 described later in the vertical direction of the vehicle, through which the intermediate member 31 described later can be inserted.

[0085] The first frame reinforcing member 26 is an extruded member made of, for example, an aluminum alloy, and is formed into a generally rectangular cross section that extends in the vehicle longitudinal direction and has a length in the vehicle vertical direction that is generally the same as that of the battery frame 23.

[0086] As shown in FIGS. 6 and 7, the first frame reinforcing member 26 is joined to the width direction frame 232 at approximately the center in the vehicle width direction, thereby connecting the front and rear width direction frames 232 in the vehicle longitudinal direction.

[0087] In addition, as shown in Figure 7, the pair of second frame reinforcement members 27 are highly rigid members that connect the widthwise frame 232 in the fore-and-aft direction of the vehicle at approximately the center in the vehicle width direction between the longitudinal frame 231 and the first frame reinforcement member 26.

[0088] As shown in Figures 6 and 7, this second frame reinforcement member 27 is composed of three main body portions 28 arranged side by side at a predetermined interval in the fore-and-aft direction of the vehicle, and two connecting portions 29 that connect adjacent main body portions 28 in the fore-and-aft direction of the vehicle and are connected to the body frame members of the vehicle 1.

[0089] Specifically, the main body 28 is an extruded member made of, for example, an aluminum alloy, and is formed with a roughly rectangular cross section that extends in the fore-and-aft direction of the vehicle and has roughly the same length in the up-and-down direction of the vehicle as the battery frame 23. On the upper surface of the main body 28, screw holes 28a (see FIG. 4) are formed as fastening portions to which the flange portions 21a of the battery modules 21 are fastened.

[0090] On the other hand, the two connecting portions 29 are composed of a connecting portion 29 that connects the second frame reinforcement member 27 to the first floor cross member 7 via the front floor panel 5, and a connecting portion 29 that connects the second frame reinforcement member 27 to the second floor cross member 8 via the front floor panel 5, as shown in Figure 4.

[0091] As shown in Figures 6, 8 and 9, this connecting portion 29 is composed of a fastened member 30 fixed by welding to the main body portion 28 adjacent in the fore-and-aft direction of the vehicle, an intermediate member 31 fastened to the fastened member 30 across the top plate portion 25, and a fastening bolt 32 fastened to the fastened member 30 via the intermediate member 31.

[0092] Since the two connecting portions 29 that make up the second frame reinforcing member 27 have the same configuration, in this embodiment, the connecting portion 29 that connects the main body portion 28 to the first floor cross member 7 will be used for detailed description.

[0093] More specifically, as shown in Figures 8 and 9, the fastened member 30 is formed as a columnar body with an approximately rectangular cross section that extends in the vertical direction of the vehicle and has a length in the vertical direction of the vehicle that is longer than the main body portion 28 adjacent to it in the fore-and-aft direction of the vehicle.

[0094] In addition, when the second frame reinforcement member 27 and the first floor cross member 7 are connected, the fastened member 30 has an upper end surface abutting the underside of the top plate portion 25, and is formed with a length in the vertical direction of the vehicle that supports the top plate portion 25 from below the vehicle.

[0095] As shown in Figures 8 and 9, the upper part of this fastened member 30 is formed with a large-diameter screw hole 30a recessed from the upper end surface toward the bottom of the vehicle, and a small-diameter screw hole 30b recessed from the bottom of the screw hole 30a further toward the bottom of the vehicle, on the same axis.

[0096] Specifically, the screw hole 30a of the fastened member 30 is formed to have a size that allows the intermediate member 31 to be screwed into it from above the vehicle. On the other hand, the screw hole 30b of the fastened member 30 is a screw hole into which the fastening bolt 32 is screwed from above the vehicle, and is formed with a smaller diameter than the screw hole 30a.

[0097] As shown in Figures 8 and 9, the intermediate member 31 is approximately cylindrical and has a smaller diameter than the opening 25a of the top plate portion 25, and is integrally formed with a shaft portion 311 that screws into the screw hole 30a of the fastened member 30, and a head portion 312 that has a larger diameter than the shaft portion 311.

[0098] Specifically, the shaft portion 311 of the intermediate member 31 is formed in a generally cylindrical shape with a screw thread on the outer circumferential surface that screws into the screw hole 30a of the fastened member 30, as shown in FIGS. On the other hand, as shown in Figures 8 and 9, the head 312 of the intermediate member 31 is formed in an approximately circular shape in a plan view, with its lower surface abutting against the upper surface of the top plate portion 25 and having an axial length that allows its upper surface to abut against the lower surface of the front floor panel 5.

[0099] The axial length of the head portion 312 of the intermediate member 31 is set to a length that provides a desired distance between the front floor panel 5 and the top plate portion 25 of the battery unit 20 in the vertical direction of the vehicle. The intermediate member 31 has a through hole 31a that is generally circular in plan view and has a larger diameter than the fastening bolt 32 (a shaft portion 32a of the fastening bolt 32, which will be described later), penetrating in the vehicle vertical direction.

[0100] As shown in Figures 8 and 9, the fastening bolt 32 is a hexagonal bolt having a shaft 32a that is smaller in diameter than the through hole 31a of the intermediate member 31 and that screws into the screw hole 30b of the fastened member 30 via the through hole 31a of the intermediate member 31.

[0101] As shown in Figure 9, the fastening bolt 32 is inserted through the insertion hole 7a of the first floor cross member 7 and the opening 5a provided in the front floor panel 5, into the through hole 31a of the intermediate member 31, and is screwed into the screw hole 30b of the fastened member 30 via the through hole 31a.

[0102] As shown in Figure 9, the lower structure of the vehicle 1 having such a configuration has a housing 22 that houses and holds a battery module 21 inside, and the intermediate member 31 is screwed into the screw hole 30a of the fastened member 30 through the opening 25a of the top plate portion 25, thereby fixing the top plate portion 25 to the fastened member 30.

[0103] In addition, the lower structure of the vehicle 1 connects and fixes the second frame reinforcement member 27 of the housing 22 to the first floor cross member 7 and the second floor cross member 8 by fastening bolts 32 threaded from inside the vehicle cabin through the through holes 31a of the intermediate member 31 and into the screw holes 30b of the fastened members 30 for the battery unit 20 connected to the left and right side sills 3, the torque box 14 and the fourth floor cross member 10.

[0104] In this way, by connecting and fixing the battery unit 20 not only to the left and right side sills 3, torque box 14 and fourth floor cross member 10, which are body frame members of the vehicle 1, but also to the first floor cross member 7 and second floor cross member 8, which are body frame members, the lower structure of the vehicle 1 improves the body rigidity of the vehicle 1, which has a substantially flat front floor panel 5.

[0105] As described above, the lower structure of the vehicle 1 in this embodiment comprises a substantially flat front floor panel 5 arranged between the left and right side sills 3 of the vehicle 1, and floor cross members (first floor cross member 7, second floor cross member 8) arranged on the upper surface of the front floor panel 5 and connecting the left and right side sills 3 in the vehicle width direction. Furthermore, the undercarriage of the vehicle 1 includes a battery unit 20 disposed below the front floor panel 5 of the vehicle.

[0106] This battery unit 20 is provided with a highly rigid battery frame 23 that is roughly annular and forms the outer shape of the battery unit 20, and is fastened to a highly rigid portion of the body of the vehicle 1 (body skeletal member, support leg portion 15), and a highly rigid second frame reinforcement member 27 that connects opposing widthwise frames 232 of the battery frame 23 in the fore-and-aft direction of the vehicle in the fore-and-aft direction of the vehicle.

[0107] The second frame reinforcement member 27 is composed of main body portions 28 arranged side by side at a predetermined interval in the fore-and-aft direction of the vehicle, and connecting portions 29 fixed to both adjacent main body portions 28 in the fore-and-aft direction of the vehicle and connected to the floor cross members (first floor cross member 7, second floor cross member 8) via the front floor panel 5.

[0108] According to this configuration, the highly rigid battery frame 23 is connected to the body frame member and the support leg 15, and the highly rigid second frame reinforcement member 27 is connected to the first floor cross member 7 and the second floor cross member 8, so that the battery frame 23 and second frame reinforcement member 27 of the battery unit 20 can function as reinforcement members that reinforce the front floor panel 5.

[0109] Furthermore, the lower structure of the vehicle 1 can be configured with a main body 28 having a reduced length in the vehicle's fore-and-aft direction compared to when, for example, the widthwise frames 232 of the battery frame 23 are connected together with a single main body, thereby improving the bending rigidity of the second frame reinforcement member 27 against input loads from the vehicle's fore-and-aft direction (for example, collision loads from the vehicle's fore-and-aft direction).

[0110] Therefore, the undercarriage of the vehicle 1 can reliably cause the second frame reinforcing member 27 to function as a reinforcing member that reinforces the front floor panel 5. As a result, the battery unit 20 can improve the vehicle body rigidity of the undercarriage of the vehicle 1, which has a substantially flat passenger compartment floor surface constituted by the front floor panel 5.

[0111] In addition, the lower structure of the vehicle 1 can stably support the heavy battery unit 20 compared to when only the battery frame 23 is fastened to the vehicle body, and can suppress vibrations transmitted, for example, to the interior of the vehicle due to the weight of the battery unit 20 connected to the vehicle body.

[0112] In addition, the connecting portion 29 is composed of a fastened member 30 fixed to the main body portion 28 and a fastening bolt 32 fastened to the fastened member 30, sandwiching the front floor panel 5 and floor cross members (first floor cross member 7, second floor cross member 8).

[0113] According to this configuration, the main body 28 can be firmly fixed to the first floor cross member 7 and the second floor cross member 8 by the simply configured connecting portion 29. This allows the lower structure of the vehicle 1 to improve the body rigidity of the vehicle 1 while suppressing weight increase.

[0114] The battery unit 20 also includes a bottom plate portion 24 that closes the opening of the battery frame 23 below the vehicle, and a top plate portion 25 that closes the opening of the battery frame 23 above the vehicle. The fastened member 30 is configured to abut against the lower surface of the top plate portion 25.

[0115] According to this configuration, the top plate portion 25 covering the opening on the upper side of the vehicle of the battery frame 23 can be stably supported by the connecting portion 29, so that shaking of the top plate portion 25 due to unevenness of the road surface, for example, can be suppressed. This allows the undercarriage of the vehicle 1 to stably support the battery unit 20 while preventing the generation of unintended abnormal noise and vibration.

[0116] The connecting portion 29 is disposed between the front floor panel 5 and the top plate portion 25 of the battery unit 20, and includes an intermediate member 31 that is fastened to the fastened member 30 with the top plate portion 25 sandwiched therebetween. According to this configuration, the opening 25a provided in the part of the top plate portion 25 facing the fastened member 30 is not exposed to the outside by the intermediate member 31, so that the intrusion of moisture into the inside of the battery unit 20 through the opening 25a of the top plate portion 25 can be prevented.

[0117] As a result, the lower structure of the vehicle 1 can ensure waterproofing of the battery unit 20 even when the second frame reinforcement member 27 is connected to the floor cross members (first floor cross member 7, second floor cross member 8).

[0118] Furthermore, when fastening bolts 32 to fastened members 30 located inside battery unit 20, fastening bolts 32 can be fastened to fastened members 30 while being guided by through holes 31a of intermediate member 31. Therefore, the undercarriage of vehicle 1 can improve the ease of assembling fastening bolts 32 to fastened members 30 that cannot be seen from the outside.

[0119] The battery unit 20 also includes a plurality of battery modules 21 arranged side by side inside the battery frame 23 with a second frame reinforcing member 27 sandwiched therebetween. The battery module 21 includes a flange portion 21a that protrudes toward the second frame reinforcing member 27 and is fastened to the upper surface of the main body portion .

[0120] According to this configuration, the size of the battery module 21 can be made closer to the second frame reinforcing member 27 than, for example, when the battery module 21 is fixed to a bracket of the second frame reinforcing member 27 that protrudes toward the battery module 21. This allows the undercarriage of the vehicle 1 to improve the body rigidity of the vehicle 1 without compromising the battery capacity.

[0121] The second frame reinforcing member 27 is configured to connect the widthwise frames 232 of the battery frame 23 that face each other in the vehicle front-rear direction. According to this configuration, the second frame reinforcing member 27 can improve the rigidity of the battery unit 20 against loads in the vehicle longitudinal direction.

[0122] Therefore, in a vehicle 1 in which the passenger compartment floor surface is constructed of a substantially flat front floor panel 5, the lower structure of the vehicle 1 can improve the body rigidity against, for example, a collision load from the front of the vehicle or a collision load from the rear of the vehicle, by using a battery unit 20 connected to the body.

[0123] Furthermore, the undercarriage of the vehicle 1 can have one second frame reinforcing member 27 disposed so as to intersect with the first floor cross member 7 and the second floor cross member 8. This allows the undercarriage of the vehicle 1 to easily connect the first floor cross member 7 and the second floor cross member 8 to one second frame reinforcing member 27, thereby improving the support rigidity of the battery unit 20.

[0124] In addition, the floor cross members (first floor cross member 7 and second floor cross member 8) are formed in a cross-sectional shape in a longitudinal section along the vehicle's fore-and-aft direction, having two trapezoidal sections 71, 81 with approximately trapezoidal cross sections that protrude upwardly of the vehicle at a predetermined distance in the vehicle's fore-and-aft direction, and valley bottom sections 72, 82 that connect the lower ends of the trapezoidal sections 71, 81. The connecting portion 29 is configured to connect the main body portion 28 to the valley bottom portions 72, 82 of the floor cross members (first floor cross member 7, second floor cross member 8).

[0125] According to this configuration, the rigidity of the floor cross members (first floor cross member 7 and second floor cross member 8) to which the battery unit 20 is connected can be made higher than that of a floor cross member having a cross section that is approximately hat-shaped and has one trapezoidal portion.

[0126] This allows the lower structure of the vehicle 1 to improve the support rigidity of the battery unit 20 and further improve the vehicle body rigidity of the vehicle 1 to which the battery unit 20 is connected.

[0127] In correspondence between the configuration of this invention and the above-mentioned embodiment, The floor panel of the present invention corresponds to the front floor panel 5 of the embodiment, Similarly, The floor cross members correspond to the first floor cross member 7 and the second floor cross member 8, The high-rigidity portions correspond to the side sill 3, the torque box 14, and the support leg 15. The portions of the battery frame facing each other in a predetermined direction correspond to the width direction frame 232, The predetermined direction corresponds to the front-rear direction of the vehicle, The frame reinforcing member corresponds to the second frame reinforcing member 27, The fastening member corresponds to the fastening bolt 32, The present invention is not limited to the configurations of the above-described embodiments, and many other embodiments can be obtained.

[0128] For example, in the above-described embodiment, the parts to which the battery unit 20 is fastened are the left and right side sills 3, the torque box 14, and the support leg 15, but this is not limited to this, and the parts to which the battery unit 20 is fastened may be any suitable part of the vehicle 1 that has high rigidity, preferably a body frame member of the vehicle 1.

[0129] Furthermore, the first floor cross member 7 and the second floor cross member 8 have a cross-sectional shape that is approximately M-shaped in a longitudinal section along the fore-and-aft direction of the vehicle, but this is not limited to this, and the first floor cross member and the second floor cross member may also have a cross-sectional shape that is approximately hat-shaped as long as they have an open cross-sectional shape that forms a closed cross section together with the front floor panel 5. Alternatively, the first floor cross member 7 and the second floor cross member 8 may be cylindrical bodies whose cross section in a longitudinal cross section along the vehicle front-rear direction has a closed cross section.

[0130] Furthermore, although both the first floor cross member 7 and the second floor cross member 8 have an approximately M-shaped cross section, this is not limited to this, and the cross-sectional shape of the first floor cross member 7 and the cross-sectional shape of the second floor cross member 8 may be different.

[0131] For example, one of the first floor cross member 7 and the second floor cross member 8 may have a generally M-shaped cross section, and the other floor cross member may have a generally hat-shaped or rectangular closed cross section.

[0132] Furthermore, although the battery unit 20 has a generally rectangular shape in plan view, the present invention is not limited to this, and the battery unit may have, for example, a generally trapezoidal shape in plan view. Furthermore, the first frame reinforcement member 26 and the second frame reinforcement member 27 are used to connect the widthwise frame 232 in the battery unit 20 in the fore-and-aft direction of the vehicle, but this is not limited to this and the frame reinforcement member may also be used to connect the fore-and-aft direction frame 231 in the vehicle width direction.

[0133] Furthermore, the battery unit 20 is provided with one first frame reinforcement member 26 and a pair of second frame reinforcement members 27, but this is not limited to this, and the number of frame reinforcement members connecting the widthwise frame 232 in the fore-and-aft direction of the vehicle may be any appropriate number. Furthermore, the main body portions 28 of the battery frame 23, the first frame reinforcing member 26, and the second frame reinforcing member 27 are made of extruded members, but this is not limited to this, and any suitable configuration may be used as long as the member is highly rigid, such as an aluminum die-cast member or a member with a closed cross-section shape similar to the body frame member.

[0134] Furthermore, the flange portion 21a of the battery module 21 is formed so as to overlap the flange portion 21a of the adjacent battery module 21, but this is not limited to this, and the flange portion 21a of the battery module 21 may be configured to be spaced apart in the fore-and-aft direction of the vehicle from the flange portion 21a of the adjacent battery module 21.

[0135] Furthermore, although the connecting portion 29 is configured from the fastened members 30, the intermediate member 31, and the fastening bolt 32, this is not limited to this, and the connecting portion may be configured from the fastened members 30 and the fastening bolt 32. Furthermore, the head 312 of the intermediate member 31 has a generally circular shape in plan view, but is not limited to this, and the head 312 may have a generally hexagonal shape in plan view.

[0136] Furthermore, although the fastened members 30 have screw holes 30a into which the intermediate member 31 is screwed, the present invention is not limited to this. For example, as shown in Fig. 10, which shows a cross-sectional view of a connecting portion in another embodiment, the connecting portion may be composed of a fastened member 40 having a shaft portion at the upper end, an intermediate member 41, and a fastening bolt 42. In FIG. 10, for clarity of illustration, the main body portion 28 of the second frame reinforcing member 27 is omitted.

[0137] Specifically, as shown in FIG. 10, the fastened member 40 is integrally formed of a substantially columnar columnar portion 411 fixed to the adjacent main body portion 28 in the fore-and-aft direction of the vehicle, and a shaft portion 412 extending from the upper end of the columnar portion 411 toward the top of the vehicle and onto which the intermediate member 41 is screwed. The columnar portion 411 of this fastened member 40 has substantially the same configuration as the fastened member 30 in the above-described embodiment, except that it does not have a screw hole 30a, and therefore detailed description thereof will be omitted.

[0138] On the other hand, the shaft portion 412 of the fastened member 40 is approximately cylindrical with an axial length that protrudes above the vehicle beyond the opening 25a of the top plate portion 25, and has a screw thread formed on its outer surface for threading onto which the intermediate member 41 is screwed. The fastened member 40 is recessed from the upper end surface of the shaft portion 412 toward the bottom of the vehicle and has a screw hole 40a into which the fastening bolt 42 is screwed.

[0139] The intermediate member 41 is formed of, for example, a hexagonal nut that is screwed onto the shaft portion 412 of the fastened member 40 . The fastening bolt 42 is a hexagonal bolt, similar to the fastening bolt 32 in the above embodiment.

[0140] Even with a connection portion configured in this manner, the lower structure of the vehicle 1 can connect the second frame reinforcement member 27 to the first floor cross member 7 and the second floor cross member 8 by fastening, and can prevent the opening 25a of the top plate portion 25 from being exposed to the outside, thereby achieving the same effect as the above-mentioned embodiment. [Explanation of symbols]

[0141] 1...Vehicle 3...Side sill 5...Front floor panel 7...First floor cross member 8...Second floor cross member 14...Torque box 15...Support leg 20...Battery unit 21...Battery module 21a...Flange part 23...Battery frame 24…Bottom plate part 25...Top plate 27...Second frame reinforcing member 28...Main body 29...Connection part 30,40…Parts to be fastened 31, 41...Intermediate parts 32, 42... Fastening bolts 71, 81... Trapezoidal section 72,82...Bottom of the valley 232...Width direction frame

Claims

1. A vehicle undercarriage structure including a substantially flat floor panel disposed between left and right side sills of a vehicle, and a floor cross member disposed on an upper surface of the floor panel and connecting the left and right side sills in a vehicle width direction, a battery unit disposed below the floor panel, The battery unit comprises: a highly rigid battery frame that is substantially annular and forms the outer shape of the battery unit and is fastened to a highly rigid portion of a body of the vehicle; a highly rigid frame reinforcing member that connects portions of the battery frame that face each other in a predetermined direction, The frame reinforcing member is main body portions arranged in parallel at a predetermined interval in the predetermined direction; a connecting portion that is fixed to both of the main body portions that are adjacent in the predetermined direction and that is connected to the floor cross member via the floor panel; Vehicle undercarriage.

2. The connecting portion is a fastened member fixed to the main body; and a fastening member that is fastened to the fastened member by sandwiching the floor panel and the floor cross member therebetween. The vehicle undercarriage according to claim 1 .

3. The battery unit includes: a bottom plate portion that closes an opening in the battery frame below the vehicle; a top plate portion that closes an opening in the battery frame above the vehicle, The fastened member is configured to abut against the underside of the top plate portion. The vehicle undercarriage according to claim 2.

4. The connecting portion is an intermediate member that is disposed between the floor panel and the top plate portion of the battery unit and is fastened to the fastened member with the top plate portion sandwiched therebetween; The vehicle undercarriage according to claim 3.

5. The battery unit includes: a plurality of battery modules arranged side by side with the frame reinforcing member sandwiched between them inside the battery frame; The battery module comprises: a flange portion that projects toward the frame reinforcing member and is fastened to the upper surface of the main body portion; The vehicle undercarriage according to claim 1 .

6. The frame reinforcing member is The battery frame is configured to connect portions of the battery frame facing each other in the vehicle longitudinal direction. The vehicle undercarriage according to claim 1 .

7. The floor cross member is two trapezoidal sections having a substantially trapezoidal cross section protruding upward from the vehicle at a predetermined interval in the vehicle longitudinal direction; a valley bottom portion connecting the lower ends of the trapezoidal portions, The connecting portion is The main body is configured to be connected to the valley bottom of the floor cross member. The vehicle undercarriage according to claim 1 .

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