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 part 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; highly rigid frame reinforcement member 24 which connect widthwise frames 232 of the battery frame 23; and connection members 30 which connect the frame reinforcement members 24 with floor cross members. The connection member 30 comprises: a first fastening member 31 which is fastened to an upper surface of the frame reinforcement member 24; and a second fastening member 37 which is fastened to the first fastening member 31 while sandwiching the front floor panel 5 and the floor cross member.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 machine as driving force, the battery unit that supplies power to the rotating electric machine 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 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, comprising a high-rigidity battery frame fastened to a high-rigidity portion of the vehicle body, a high-rigidity frame reinforcement member connecting opposing portions of the battery frame in a predetermined direction in the predetermined direction, and a connecting member connecting the frame reinforcement member to the floor cross member, the connecting member being composed of a first fastening member fastened to the upper surface of the frame reinforcement member, and a second fastening member fastened to the first fastening member between the floor panel and the floor cross member.

[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, the highly rigid frame reinforcement member can be connected to the floor cross member by fastening using a connecting member, so that the battery unit can be firmly fixed to the highly rigid floor cross member.

[0011] In this case, since the highly rigid battery frame is also fastened and fixed to a highly rigid portion of the vehicle body, the vehicle's undercarriage structure can allow the battery frame and frame reinforcement member of the battery unit to function as reinforcement members that reinforce the floor panel.

[0012] 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. Furthermore, 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 firmly connected to the vehicle body.

[0013] As an aspect of this 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, the battery modules having flange portions that protrude toward the frame reinforcement member and are fixed to the upper surface of the frame reinforcement member, and the first fastening member may be configured to be fastened to the frame reinforcement member via the flange portions of the battery modules.

[0014] The flange portion of the above-mentioned battery module refers to a flange portion formed to overlap the flange portion of another battery module arranged side by side with a frame reinforcing member therebetween, or a flange portion formed at a predetermined distance in a predetermined direction from the flange portion of the other battery module.

[0015] 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.

[0016] Furthermore, in the vehicle undercarriage structure, the battery module can be fixed to the frame reinforcing member at approximately the same time as the first fastening member is fastened to the frame reinforcing member, allowing the battery unit to be assembled efficiently. This allows the vehicle's undercarriage to improve the vehicle body rigidity without compromising the battery capacity or the assembly efficiency of the battery unit.

[0017] As a further 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] In another aspect of the present invention, the first fastening member may be integrally formed with a threaded portion that screws into the screw hole of the frame reinforcing member, and a head that extends to one axial side of the threaded portion and has a screw hole into which the second fastening member screws.

[0022] With this configuration, the head of the first fastening member can function as a boss portion into which the second fastening member is threaded. As a result, the vehicle undercarriage can firmly connect the frame reinforcing member to the floor cross member using a simply configured connecting member.

[0023] In another aspect of the 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 upward from the vehicle at a predetermined distance in the vehicle's fore-and-aft direction, and a valley bottom that connects the lower ends of the trapezoidal sections, and the second fastening member may be fastened to the first fastening member via the valley bottom of the floor cross member.

[0024] With this configuration, the rigidity of the floor cross member to which the battery unit is fastened can be made higher than that of a floor cross member having a generally hat-shaped cross section with one trapezoidal portion. 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.

[0025] In addition, because the second fastening members are fastened to the first fastening members via the valley bottoms of the floor cross member, the second fastening members are less likely to be exposed above the vehicle above the upper end of the trapezoidal portion, which prevents the second fastening members from interfering with maintaining a gap between the floor cross member and surrounding areas.

[0026] 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 first fastening member may be configured to abut against the underside of the top plate portion.

[0027] 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 member, 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.

[0028] In another aspect of the present invention, the connecting member 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 first fastening member across the top plate portion.

[0029] The intermediate member is a member that screws onto the first fastening member through an opening provided in the top plate portion and has a through hole through which the second fastening member is inserted, or a member that screws onto the first fastening member protruding from the opening in the top plate portion.

[0030] According to this configuration, the opening provided in the portion of the top plate portion facing the first fastening 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. [Effects of the Invention]

[0031] 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]

[0032] [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. 4 is an external perspective view showing the external appearance of a connecting member. [Figure 9] FIG. 4 is a cross-sectional view showing a cross section of the connecting member 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 member in another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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 26 removed, Figure 8 shows an oblique view of the exterior of the connecting member 30, and Figure 9 shows a cross-sectional view of the connecting member 30 in a longitudinal section along the vehicle width direction.

[0037] More specifically, Figure 2 shows a cross-sectional view of a longitudinal section along the fore-and-aft direction of the vehicle 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 fore-and-aft direction of the vehicle passing through the frame reinforcement member 24.

[0038] 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 from FIG. 6, and part of the first fastening member 31 is shown in a see-through state in FIG.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] As shown in Figure 4, two insertion holes 7a are formed in the valley bottom 72 of this first floor cross member 7, spaced a predetermined distance apart in the vehicle width direction, through which the second fastening member 37 of the connecting member 30 described later can be inserted.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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 second fastening member 37 of the connecting member 30 described later can be inserted.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] As shown in FIG. 7, the four battery modules 21 are arranged inside the housing 22 in four accommodation spaces (reference numerals omitted) that are generally rectangular in plan view and elongated in the vehicle longitudinal direction and that are separated by frame reinforcing members 24 described later.

[0074] 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 .

[0075] 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 frame reinforcing member 24.

[0076] 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 frame reinforcement member 24 on the outer side in the vehicle width direction, as shown in Figure 7.

[0077] The flange portion 21a fastened to the frame reinforcing member 24 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 9).

[0078] As shown in Figures 6 and 7, the housing 22 also 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, and three frame reinforcing members 24 that divide the interior of the battery frame 23 into four storage spaces.

[0079] Furthermore, as shown in Figure 6, the housing 22 has a bottom plate portion 25 that closes the opening on the lower side of the vehicle in the battery frame 23, a top plate portion 26 that closes the opening on the upper side of the vehicle in the battery frame 23, and four connecting members 30 that connect the frame reinforcing member 24 to the body frame members of the vehicle 1.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] The three frame reinforcing members 24 are extruded members made of, for example, an aluminum alloy, and are formed with a generally rectangular cross section that extends in the longitudinal direction of the vehicle and has a length in the vertical direction of the vehicle that is generally the same as that of the battery frame 23.

[0085] 6 and 7, the three frame reinforcing members 24 are joined to the front and rear width direction frames 232 at positions spaced a predetermined distance apart in the vehicle width direction, thereby connecting the front and rear width direction frames 232 in the fore-and-aft direction of the vehicle. Therefore, the interior of the housing 22 is formed with four storage spaces divided by the frame reinforcing members 24.

[0086] Furthermore, on the upper surfaces of the two frame reinforcement members 24 located furthest outward in the vehicle width direction, a plurality of screw holes 24a (see Figure 4) are formed at a predetermined interval in the fore-and-aft direction of the vehicle as fastening portions to which the flange portions 21a of the battery module 21 are fastened.

[0087] As shown in FIG. 3, the bottom 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 (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 25 is fixed to the lower surface of the frame reinforcing member 24 by welding or fastening.

[0088] On the other hand, as shown in Figures 3 and 6, the top plate portion 26 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.

[0089] The main body of the top plate 26 is fixed to the upper surface of the frame reinforcing member 24 by a connecting member 30, which will be described later. For this reason, as shown in Figure 6, an opening 26a through which the connecting member 30 (intermediate member 34 described later) is inserted is formed in the main body portion of the top plate portion 26 in the vertical direction of the vehicle at a position opposite the screw hole 24a of the frame reinforcing member 24 in the vertical direction of the vehicle.

[0090] As shown in Figures 4 and 6, the four connecting members 30 are composed of two connecting members 30 that connect one frame reinforcement member 24 located at the outermost position in the vehicle width direction to the first floor cross member 7 and the second floor cross member 8 across the front floor panel 5, and two connecting members 30 that connect the other frame reinforcement member 24 located at the outermost position in the vehicle width direction to the first floor cross member 7 and the second floor cross member 8 across the front floor panel 5.

[0091] As shown in Figures 6, 8 and 9, this connecting member 30 is composed of a first fastening member 31 fastened to the frame reinforcing member 24, an intermediate member 34 fastened to the first fastening member 31 across the top plate portion 26, and a second fastening member 37 fastened to the first fastening member 31 via the intermediate member 34.

[0092] Since the four connecting members 30 have the same configuration, the connecting member 30 that connects the frame reinforcing member 24 to the first floor cross member 7 will be used in the detailed description of this embodiment. More specifically, as shown in Figures 8 and 9, the first fastening member 31 is integrally formed with a shaft portion 32 that screws into the screw hole 24a of the frame reinforcement member 24, and a head portion 33 that extends to one side of the shaft portion 32 in the axial direction, with the vehicle's vertical direction as the axial direction.

[0093] As shown in Figure 9, when the frame reinforcement member 24 and the first floor cross member 7 are connected, the head 33 of this first fastening member 31 abuts against the underside of the top plate portion 26, thereby supporting the top plate portion 26 from below the vehicle.

[0094] 8 and 9, the shaft portion 32 of the first fastening member 31 is formed in a generally cylindrical shape having threads on its outer circumferential surface that screw into the screw holes 24a of the frame reinforcing member 24. The shaft portion 32 of this first fastening member 31 is formed to have an axial length that is longer than the flange portions 21a of the battery modules 21 stacked in the vehicle vertical direction and that allows it to screw into the screw holes 24a of the frame reinforcing member 24.

[0095] On the other hand, as shown in Figure 9, the head 33 of the first fastening member 31 is formed with an axial length that allows its lower end surface to abut against the upper surface of the overlapping flange portion 21a and its upper end surface to abut against the lower surface of the top plate portion 26.

[0096] As shown in Figure 8, the head 33 of this first fastening member 31 is formed of a cylindrical portion 331 that is approximately cylindrical and has a diameter larger than the diameter of the shaft portion 32 and extends from the shaft portion 32, and a hexagonal column portion 332 that is approximately hexagonal and has a diameter larger than that of the cylindrical portion 331 and extends from the cylindrical portion 331.

[0097] As shown in FIG. 9, the head 33 is formed with a vertical length such that the upper end of the cylindrical portion 331 is positioned lower in the vehicle than the upper end of the battery module 21 when fastened to the frame reinforcing member 24.

[0098] As shown in Figures 8 and 9, the head 33 of such a first fastening member 31 is formed with a large-diameter screw hole 33a recessed in the axial direction from the upper end surface of the hexagonal column portion 332, and a small-diameter screw hole 33b recessed further in the axial direction from the bottom of the screw hole 33a.

[0099] Specifically, the screw hole 33a of the head 33 is a screw hole into which the intermediate member 34 is screwed from above the vehicle, and is formed from the upper end surface of the hexagonal column portion 332 to approximately the center of the hexagonal column portion 332 in the axial direction. On the other hand, the screw hole 33b of the head 33 is a screw hole into which the second fastening member 37 is screwed from above the vehicle, and is formed from the bottom of the screw hole 33a to approximately the center of the columnar portion 331 in the axial direction.

[0100] As shown in Figures 8 and 9, the intermediate member 34 is approximately cylindrical and has a diameter smaller than the opening 26a of the top plate portion 26, and is integrally formed with a shaft portion 35 that screws into the screw hole 33a of the first fastening member 31, and a head portion 36 that has a diameter larger than that of the shaft portion 35.

[0101] Specifically, as shown in FIGS. 8 and 9, the shaft portion 35 of the intermediate member 34 is formed in a generally cylindrical shape having a thread on its outer circumferential surface that screws into the screw hole 33a of the first fastening member 31. On the other hand, as shown in Figures 8 and 9, the head 36 of the intermediate member 34 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 26 and having an axial length that allows its upper surface to abut against the lower surface of the front floor panel 5.

[0102] The axial length of the head portion 36 of the intermediate member 34 is set to a length that provides a desired distance between the front floor panel 5 and the top plate portion 26 of the battery unit 20 in the vertical direction of the vehicle. The intermediate member 34 has a through hole 34a that is larger in diameter than the second fastening member 37 (a shaft portion 38 of the second fastening member 37, which will be described later) and has a generally circular shape in plan view that penetrates in the vehicle up-down direction.

[0103] As shown in Figures 8 and 9, the second fastening member 37 is composed of a hexagonal bolt having a smaller diameter than the through hole 34a of the intermediate member 34 and a shaft 38 that screws into the screw hole 33b of the first fastening member 31 via the through hole 34a of the intermediate member 34.

[0104] As shown in Figure 9, the second fastening member 37 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 34a of the intermediate member 34, and is screwed into the screw hole 33b of the first fastening member 31 via the through hole 34a.

[0105] As shown in Figure 9, the undercarriage structure of the vehicle 1 configured in this manner fastens and fixes the battery modules 21 to the housing 22 by screwing the first fastening members 31 into the screw holes 24a of the frame reinforcement members 24 of the housing 22 via the flange portions 21a of the battery modules 21 that are stacked in the vertical direction of the vehicle.

[0106] Furthermore, the lower structure of the vehicle 1 fixes the top plate portion 26 to the first fastening member 31 by screwing the intermediate member 34 into the screw hole 33a of the first fastening member 31 through the opening 26a of the top plate portion 26 with respect to the housing 22 which houses and holds the battery module 21 inside.

[0107] In addition, the lower structure of the vehicle 1 is such that the frame reinforcement member 24 of the housing 22 is connected and fixed to the first floor cross member 7 and the second floor cross member 8 by the second fastening member 37 screwing into the screw hole 33b of the first fastening member 31 from inside the vehicle cabin through the through hole 34a of the intermediate member 34, 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.

[0108] 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.

[0109] 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.

[0110] Furthermore, the undercarriage of the vehicle 1 includes a battery unit 20 disposed below the front floor panel 5 of the vehicle. The battery unit 20 has a substantially annular shape that defines the outer shape of the battery unit 20, and includes a highly rigid battery frame 23 that is fastened to highly rigid portions of the body of the vehicle 1 (body frame members and support legs 15).

[0111] Furthermore, the battery unit 20 is equipped with a highly rigid frame reinforcement member 24 that connects the widthwise frame 232 of the battery frame 23 in the fore-and-aft direction of the vehicle, and a connecting member 30 that connects the frame reinforcement member 24 to the floor cross members (first floor cross member 7, second floor cross member 8).

[0112] This connecting member 30 is composed of a first fastening member 31 that is fastened to the upper surface of the frame reinforcement member 24, and a second fastening member 37 that is fastened to the first fastening member 31 across the front floor panel 5 and floor cross member (first floor cross member 7, second floor cross member 8).

[0113] According to this configuration, the highly rigid frame reinforcement member 24 can be connected to the floor cross members (first floor cross member 7, second floor cross member 8) by fastening using the connecting member 30, so that the battery unit 20 can be firmly fixed to the highly rigid floor cross members (first floor cross member 7, second floor cross member 8).

[0114] In this case, since the highly rigid battery frame 23 is also fastened and fixed to a highly rigid portion of the vehicle body, the lower structure of the vehicle 1 can make the battery frame 23 and frame reinforcing member 24 of the battery unit 20 function as reinforcing members that reinforce the front floor panel 5.

[0115] 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. Furthermore, 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 firmly connected to the vehicle body.

[0116] The battery unit 20 also includes a plurality of battery modules 21 arranged side by side inside a battery frame 23 with a frame reinforcing member 24 sandwiched therebetween. The battery module 21 includes a flange portion 21a that protrudes toward the frame reinforcing member 24 and is fixed to the upper surface of the frame reinforcing member 24. The first fastening member 31 is fastened to the frame reinforcing member 24 via the flange portion 21a of the battery module 21.

[0117] According to this configuration, the size of the battery module 21 can be made closer to the frame reinforcing member 24 than, for example, when the battery module is fixed to a bracket of the frame reinforcing member 24 that protrudes toward the battery module.

[0118] Furthermore, in the undercarriage of the vehicle 1, the battery module 21 can be fixed to the frame reinforcing member 24 at approximately the same time as the first fastening members 31 are fastened to the frame reinforcing member 24, so that the battery unit 20 can be assembled efficiently. As a result, the lower structure of the vehicle 1 can improve the body rigidity of the vehicle 1 without compromising the battery capacity or the assembly efficiency of the battery unit 20.

[0119] The frame reinforcing member 24 is configured to connect the width direction frames 232 of the battery frame 23 in the vehicle front-rear direction. According to this configuration, the frame reinforcing member 24 can improve the rigidity of the battery unit 20 against loads in the vehicle longitudinal direction.

[0120] 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.

[0121] Furthermore, the undercarriage of the vehicle 1 can have one frame reinforcing member 24 disposed crosswise to 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 frame reinforcing member 24, thereby improving the support rigidity of the battery unit 20.

[0122] In addition, the first fastening member 31 is integrally formed with a shaft portion 32 that screws into the screw hole 24a of the frame reinforcement member 24, and a head portion 33 that extends to one axial side of the shaft portion 32 and has a screw hole 33a into which the second fastening member 37 screws.

[0123] According to this configuration, the head 33 of the first fastening member 31 can function as a boss portion into which the second fastening member 37 is screwed. Therefore, the lower structure of the vehicle 1 can firmly connect the frame reinforcing member 24 to the floor cross members (first floor cross member 7, second floor cross member 8) using the simply configured connecting member 30.

[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 second fastening member 37 is fastened to the first fastening member 31 via the valley bottoms 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 fastened 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. 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.

[0126] In addition, because the second fastening members 37 are fastened to the first fastening members 31 via the valley bottoms 72, 82 of the floor cross member, the second fastening members 37 are less likely to be exposed above the vehicle than the upper end surfaces of the trapezoidal portions 71, 81. Therefore, the undercarriage of the vehicle 1 can prevent the second fastening members 37 from interfering with maintaining a gap between the floor cross member and surrounding areas.

[0127] The battery unit 20 also includes a bottom plate portion 25 that closes the opening of the battery frame 23 below the vehicle, and a top plate portion 26 that closes the opening of the battery frame 23 above the vehicle. The first fastening member 31 is configured to come into contact with the lower surface of the top plate portion .

[0128] According to this configuration, the top plate portion 26 covering the opening on the upper side of the vehicle of the battery frame 23 can be stably supported by the connecting member 30, so that shaking of the top plate portion 26 due to, for example, unevenness in the road surface 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.

[0129] The connecting member 30 is disposed between the front floor panel 5 and the top plate portion 26 of the battery unit 20, and includes an intermediate member 34 that is fastened to the first fastening member 31 with the top plate portion 26 sandwiched therebetween.

[0130] According to this configuration, the opening 26a of the top panel 26 is not exposed to the outside by the intermediate member 34, so that the intrusion of moisture into the inside of the battery unit 20 through the opening 26a of the top panel 26 can be suppressed.

[0131] This allows the undercarriage structure of the vehicle 1 to ensure waterproofing of the battery unit 20 even when the frame reinforcement member 24 is connected to the floor cross members (first floor cross member 7, second floor cross member 8).

[0132] Furthermore, when fastening the second fastening member 37 to the first fastening member 31 located inside the battery unit 20, the second fastening member 37 can be fastened to the first fastening member 31 while being guided by the through-hole 34a of the intermediate member 34. Therefore, the undercarriage of the vehicle 1 can improve the ease of assembling the second fastening member 37 to the first fastening member 31, which cannot be seen from the outside.

[0133] 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 threaded portion corresponds to the shank 32, The present invention is not limited to the configurations of the above-described embodiments, and many other embodiments can be obtained.

[0134] 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.

[0135] 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-sectional shape in a longitudinal cross section along the vehicle front-rear direction is a closed cross-sectional shape.

[0136] 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.

[0137] 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.

[0138] Furthermore, although the battery unit 20 has a generally rectangular shape in plan view, the present invention is not limited to this, and may have, for example, a generally trapezoidal shape in plan view. Furthermore, the frame reinforcing member 24 connects the widthwise frames 232 of the battery unit 20 in the vehicle longitudinal direction, but is not limited to this, and may be a frame reinforcing member connecting the longitudinal frames 231 in the vehicle width direction.

[0139] Furthermore, although the battery unit 20 is provided with three frame reinforcing members 24, the number of the frame reinforcing members 24 is not limited to three, and any appropriate number of the frame reinforcing members 24 may be used. Furthermore, although the battery frame 23 and the frame reinforcing member 24 are constructed from extruded members, 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.

[0140] 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.

[0141] Furthermore, although the first fastening member 31 of the connecting member 30 is fastened to the frame reinforcing member 24 via the flange portion 21a of the battery module 21, this is not limited to this, and the first fastening member 31 of the connecting member 30 may also be fastened directly to the frame reinforcing member 24. In this case, the flange portion 21a of the battery module 21 is fastened and fixed using a bolt at a position on the frame reinforcing member 24 that is different from the fastening position of the first fastening member 31.

[0142] Furthermore, among the multiple flange portions 21a provided on the battery module 21, some of the flange portions 21a may be fixed to the frame reinforcing member 24 by the first fastening members 31, and the remaining flange portions 21a may be fixed to the frame reinforcing member 24 by bolts.

[0143] Furthermore, although the connecting member 30 is composed of the first fastening member 31, the intermediate member 34, and the second fastening member 37, this is not limited to this, and the connecting member may be composed of the first fastening member 31 and the second fastening member 37. Furthermore, the head 33 of the first fastening member 31 is configured from the cylindrical portion 331 and the hexagonal column portion 332, but is not limited to this and may be a head configured from the hexagonal column portion 332. Furthermore, the head 36 of the intermediate member 34 has a generally circular shape in plan view, but is not limited to this, and the head 36 may have a generally hexagonal shape in plan view.

[0144] Furthermore, although the head 33 of the first fastening member 31 has the screw hole 33a into which the intermediate member 34 screws, the present invention is not limited to this. For example, as shown in Fig. 10, which shows a cross-sectional view of a connecting member in another embodiment, the connecting member may be composed of a first fastening member 41 having two shaft portions, an intermediate member 45, and a second fastening member 46.

[0145] Specifically, as shown in Figure 10, the first fastening member 41 is integrally formed of a first shaft portion 42 that screws into the frame reinforcing member 24, a head portion 43 that extends from the first shaft portion 42 to one side in the axial direction, and a second shaft portion 44 that extends from the head portion 43 to one side in the axial direction and into which an intermediate member 45 screws.

[0146] The first shaft portion 42 and head portion 43 of the first fastening member 41 have substantially the same configuration as the shaft portion 32 and head portion 33 of the first fastening member 31 in the above-described embodiment, and therefore detailed description thereof will be omitted. The second shaft portion 44 is approximately cylindrical in shape with an axial length that protrudes above the vehicle beyond the opening 26a of the top plate portion 26, and has a screw thread formed on its outer surface into which the intermediate member 45 screws.

[0147] Furthermore, the first fastening member 41 is formed with a screw hole 41a extending from the upper end surface of the second shaft portion 44 to the head portion 43, into which the second fastening member 46 is screwed. The intermediate member 45 is formed of, for example, a hexagonal nut that is screwed onto the second shaft portion 44 of the first fastening member 41. Similarly to the second fastening member 37 in the above embodiment, the second fastening member 46 is configured as a hexagon bolt.

[0148] Even with a connecting member of this configuration, the lower structure of the vehicle 1 can connect the frame reinforcement member 24 to the first floor cross member 7 and the second floor cross member 8 by fastening, and can prevent the opening 26a of the top plate portion 26 from being exposed to the outside, thereby achieving the same effect as the above-mentioned embodiment. [Explanation of symbols]

[0149] 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...Frame reinforcement member 24a...Screw hole 25...Bottom plate part 26...Top plate 30...Connecting member 31, 41...First fastening member 32, 42...Shaft 33,43…Head 33b, 41a...Screw holes 34, 45...Intermediate parts 37, 46...Second fastening member 71...Trapezoidal section 72...Valley bottom 81...Trapezoidal section 82...Valley bottom 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 in the predetermined direction; a connecting member that connects the frame reinforcing member to the floor cross member, The connecting member is a first fastening member fastened to an upper surface of the frame reinforcing member; a second fastening member fastened to the first fastening member with the floor panel and the floor cross member sandwiched therebetween; Vehicle undercarriage.

2. 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 protrudes toward the frame reinforcing member and is fixed to an upper surface of the frame reinforcing member, The first fastening member is The battery module is fastened to the frame reinforcing member via the flange portion. The vehicle undercarriage according to claim 1 .

3. 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 .

4. The first fastening member is a threaded portion that is screwed into the screw hole of the frame reinforcing member; The screw thread portion extends to one side in the axial direction and is integrally formed with a head portion having a screw hole into which the second fastening member is screwed. The vehicle undercarriage according to claim 1 .

5. 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 second fastening member is The floor cross member is fastened to the first fastening member via the valley bottom portion. The vehicle undercarriage according to claim 1 .

6. 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 first fastening member is configured to abut against the lower surface of the top plate portion. The vehicle undercarriage according to claim 1 .

7. The connecting member 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 first fastening member with the top plate portion sandwiched therebetween; 7. The vehicle undercarriage according to claim 6.

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