Vehicle body understructure of electric vehicle

Abstract

To ensure the rigidity of a floor panel against a load in a vertical direction in an electric vehicle having a step in the floor panel.SOLUTION: A rear floor panel 10 of an electric vehicle has an inclined part 16 that extends while inclining upward as it heads for backward from a rear end of a plane part 12. A floor cross member 20 is disposed in a front part of the inclined part 16 on the side of an upper surface of the rear floor panel 10. An under-floor reinforcement 30 is disposed in the front part of the inclined part 16 on the side of a lower surface of the rear floor panel 10. A front end of the under-floor reinforcement 30 is disposed ahead of the front end of the inclined part 16, and a rear end of the under-floor reinforcement 30 is disposed on the inclined part 16. The under-floor reinforcement 30 and the floor cross member 20 are joined with the rear floor panel 10 therebetween.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to an underbody structure for an electric vehicle. [Background technology]

[0002] In a vehicle having an internal combustion engine, a fuel tank is usually disposed below the floor of the vehicle. For example, in order to secure a space for disposing the fuel tank, a structure is known in which the rear part of the floor part is disposed above the front part of the floor part in the vertical direction of the vehicle, as disclosed in Patent Document 1. A rear seat is disposed at the rear of the floor part.

[0003] By providing a step between the front and rear of the floor in this manner, a space for arranging a fuel tank, etc. can be secured below the floor panel located at the rear of the floor. In addition, by forming a wall portion that constitutes the step and extends in the vehicle width direction in the floor, the rigidity of the floor can be secured.

[0004] On the other hand, an electric vehicle has a battery pack that supplies power to the electric motor. Even in a structure in which a step is provided in the floor portion as in the above example, the battery pack is often disposed below the floor panel. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-138631 A Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, in an electric vehicle, the battery pack is disposed below the floor panel, and therefore it is necessary to secure a space below the floor panel to install the battery pack. Furthermore, when a structure having a floor panel with a step portion as in the above example is applied to an electric vehicle, it is necessary to dispose the battery pack below the floor panel located at the front of the floor portion.

[0007] In this case, the position of the front part of the floor part is disposed higher than in the structure of the above example. Therefore, the difference in the position of the front part and the rear part of the floor part in the vertical direction of the vehicle is smaller than in the structure of the above example. This leaves room for improvement in terms of ensuring the rigidity of the floor part.

[0008] The present invention has been made to solve the above-mentioned problems, and its object is to provide an underbody structure for an electric vehicle that is capable of ensuring the rigidity of a floor panel against vertical loads in an electric vehicle having a step in the floor panel. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides an underbody structure for an electric vehicle, in which a battery pack is disposed on the underside of a floor panel, and a step is provided on the floor panel so that a rear portion is positioned higher than a front portion. In the underbody structure for an electric vehicle, the floor panel has a flat portion and an inclined portion that extends at an angle upward from a rear end of the flat portion toward the rear of the vehicle, a cross member extending in the vehicle width direction is disposed on the upper surface side of the floor panel in front of the inclined portion, an under-floor reinforcement is disposed on the lower surface side of the floor panel in front of the inclined portion, a front end of the under-floor reinforcement is disposed further forward of the vehicle than a front end of the inclined portion and a rear end of the under-floor reinforcement is disposed on the inclined portion, and the under-floor reinforcement and the cross member are joined to the floor panel with the floor panel sandwiched therebetween. Effect of the Invention

[0010] According to the present invention, in an electric vehicle in which a floor panel has a step, it is possible to ensure the rigidity of the floor panel against a load in the vertical direction. [Brief description of the drawings]

[0011] [Figure 1] 1 is a perspective view showing an embodiment of a vehicle body underbody structure for an electric vehicle according to the present invention; [Diagram 2] FIG. 2 is a perspective view showing a state in which the rear seat in FIG. 1 is removed. [Diagram 3] FIG. 3 is a top view of FIG. 2. [Figure 4] FIG. 3 is a bottom view of FIG. 2. [Diagram 5] FIG. 2 is a schematic cross-sectional view taken along the line AA in FIG. [Figure 6] FIG. 6 is an enlarged cross-sectional view of FIG. [Figure 7] FIG. 4 is a schematic cross-sectional view taken along the line BB in FIG. [Figure 8] FIG. 4 is a schematic cross-sectional view taken along the line CC in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of a vehicle body underbody structure for an electric vehicle according to the present invention will be described with reference to the drawings (FIGS. 1 to 8). In the drawings, the direction of the arrow Fr indicates the front in the vehicle longitudinal direction. In the description of the embodiment, the "front (front end) and rear (rear end)" correspond to the front and rear in the vehicle longitudinal direction. Additionally, the arrows R and L indicate the right and left sides when a passenger looks forward of the vehicle. Additionally, the arrow U indicates the upward direction in the vehicle vertical direction.

[0013] 1 to 4, the vehicle body underbody structure of the electric vehicle of this embodiment has a front floor panel 50, a rear floor panel 10 (floor panel), a floor cross member 20 (cross member), and an under-floor reinforcement 30. The vehicle body underbody structure also includes a side sill 47, a rear side member 45, and the like.

[0014] In the vehicle body underbody structure of this embodiment, a battery pack 55 is disposed on the underside of the rear floor panel 10. A step is provided in the rear floor panel 10 so that the rear portion is positioned higher than the front portion (FIG. 5). The rear floor panel 10 may have a front side flat portion 12 (flat portion) and an inclined portion 16 that extends from the rear end of the front side flat portion 12 toward the rear of the vehicle and inclines upwardly of the vehicle. Furthermore, the floor cross member 20 extends in the vehicle width direction and is disposed in front of the inclined portion 16 on the upper surface side of the rear floor panel 10, and the under-floor reinforcement 30 is disposed in front of the inclined portion 16 on the underside side of the rear floor panel 10.

[0015] In addition, the front end of the under-floor reinforcement 30 is positioned further forward of the vehicle than the front end of the inclined portion 16, and the rear end of the under-floor reinforcement 30 is positioned at the inclined portion 16, and the under-floor reinforcement 30 and the floor cross member 20 are joined with the rear floor panel 10 sandwiched between them.

[0016] Hereinafter, each member of the vehicle underbody structure of this embodiment will be described.

[0017] The floor portion of the electric vehicle of this embodiment has a front floor panel 50 and a rear floor panel 10 arranged along the front-rear direction of the vehicle. The front floor panel 50 is arranged on the vehicle front side of the rear floor panel 10, for example, below the driver's seat. As shown in Figs. 1 and 2, the rear floor panel 10 is arranged on the vehicle rear side of the front floor panel 50, and the front part of the rear floor panel 10 is joined to the rear part of the front floor panel 50 by, for example, spot welding. The rear floor panel 10 of this embodiment is arranged below the rear seat 52, as shown in Fig. 1.

[0018] As shown in Figs. 2 and 5, the front and rear parts of the rear floor panel 10 are configured to be positioned at different positions in the vehicle vertical direction. In this example, the rear floor panel 10 has a front side flat surface portion 12 and a rear side flat surface portion 18 located rearward of the front side flat surface portion 12. The rear side flat surface portion 18 is located higher than the front side flat surface portion 12. The inclined portion 16 extends so as to incline upward toward the vehicle rearward so as to connect the rear end of the front side flat surface portion 12 and the front end of the rear side flat surface portion 18. The range of the inclined portion 16 in the vehicle longitudinal direction is set to the range indicated by L in Figs. 5 and 6. In addition, the floor panel of this embodiment is provided with tunnel portions 13 and 17 as shown in Fig. 2.

[0019] The front side flat surface portion 12 is a flat surface portion located at the front of the rear floor panel 10. In this embodiment, the front side flat surface portion 12 includes a footrest space for an occupant seated on the rear seat 52. A side sill 47 extending in the vehicle front-rear direction is joined to the underside of the front side flat surface portion 12 at the outer side in the vehicle width direction. The side sill 47 in this embodiment is a highly rigid member constituting the vehicle body frame, and is made of a metal material. In addition, a part of the tunnel portion 13, 17 is disposed in the middle of the front side flat surface portion 12 in the vehicle width direction. The tunnel portion 13, 17 will be described later.

[0020] As shown in FIG. 5, the rear side flat surface portion 18 is a portion located rearward of the front side flat surface portion 12, and is disposed higher on the vehicle than the front side flat surface portion 12. The rear side flat surface portion 18 is disposed below the cushion portion 53 of the rear seat 52. The vehicle width direction outer portion of the rear side flat surface portion 18 may be joined to, for example, a rear side member 45 extending in the front-rear direction of the vehicle. The rear side member 45, like the side sill 47, is a highly rigid member constituting the vehicle body frame, and is formed of a metal material. In this example, the rear side member 45 may be joined to the rear of the side sill 47 via a bracket or the like.

[0021] Next, the inclined portion 16 will be described. As shown in FIG. 2, FIG. 3, FIG. 5, and FIG. 6, the inclined portion 16 is a portion that connects the front side flat portion 12 and the rear side flat portion 18, and extends from the rear end of the front side flat portion 12 to the front end of the rear side flat portion 18. The inclined portion 16 extends from the rear of the front side flat portion 12 toward the rear of the vehicle, inclining upward, and is connected to the front end of the rear side flat portion 18. The rear portion of the inclined portion 16 is joined to the rear portion of the side sill 47, for example. In this embodiment, the rear side flat portion 18, the front side flat portion 12, and the inclined portion 16 are integrally formed. That is, they are formed from a single sheet metal. Note that the rear side flat portion 18, the front side flat portion 12, and the inclined portion 16 may be formed from different members and joined by spot welding or the like to form a single rear floor panel 10.

[0022] Next, the tunnel portions 13, 17 of the rear floor panel 10 will be described. As shown in Fig. 2 and Fig. 3, the tunnel portions 13, 17 are provided in the middle of the rear floor panel 10 in the vehicle width direction, and bulge upward in the vehicle front-rear direction. The tunnel portions 13, 17 have top portions 13a, 17a located above the top surfaces 12a, 16a (main surfaces) of the rear floor panel 10, and side wall portions 13b, 17b extending from the top surfaces 12a, 16a toward the top portions 13a, 17a. The tunnel portions 13, 17 will be described in detail below.

[0023] 2 and 3, the tunnel portions 13, 17 of this embodiment are provided in the front flat surface portion 12 and the inclined portion 16 of the rear floor panel 10. The tunnel portions 13, 17 include a front tunnel portion 13 provided in the front flat surface portion 12 and an inclined tunnel portion 17 provided in the inclined portion 16, which are provided so as to be integrally continuous with each other.

[0024] The front tunnel portion 13 is provided in the middle of the front flat surface portion 12 in the vehicle width direction, bulges upward in the vehicle, and extends in the vehicle front-rear direction. In this example, the front tunnel portion 13 is provided in approximately the center of the front flat surface portion 12 in the vehicle width direction. The front tunnel portion 13 is connected to a tunnel portion 51 provided in the front floor panel 50. The front tunnel portion 13 has a front apex portion 13a and a front side wall portion 13b. The front apex portion 13a is located above the vehicle than the upper surface 12a of the front flat surface portion 12 located on the outer side of the front tunnel portion 13 in the vehicle width direction. The front side wall portion 13b is inclined upward from the upper surface 12a toward the inner side in the vehicle width direction. The upper end of the front side wall portion 13b is connected to the outer end of the front apex portion 13a in the vehicle width direction.

[0025] As shown in Figs. 2 and 3, the inclined tunnel section 17 is provided in the middle part (almost the center part in this example) of the inclined section 16 in the vehicle width direction, bulges upward of the vehicle, and extends in the vehicle front-rear direction. The inclined tunnel section 17 has an inclined apex 17a and an inclined side wall 17b. The inclined apex 17a is located above the upper surface of the inclined section 16 located outside the inclined tunnel section 17 in the vehicle width direction. The length of the inclined apex 17a in the vehicle width direction increases toward the rear of the vehicle. In this example, the outer ends on both sides of the inclined apex 17a in the vehicle width direction extend away from each other toward the rear of the vehicle. The front end of the inclined apex 17a is connected to the rear end of the front apex 13a. As shown in Fig. 8, the inclined apex 17a is located below the rear side flat portion 18 located at the rear end of the rear floor panel 10.

[0026] The inclined side wall portion 17b is inclined upward from the side of the inclined portion 16 toward the inside in the vehicle width direction. The upper end of the inclined side wall portion 17b is connected to the outer end of the inclined top portion 17a in the vehicle width direction. The lower end of the inclined side wall portion 17b is inclined along the inclination direction of the inclined portion 16, and is also inclined toward the inside in the vehicle width direction toward the rear of the vehicle. The front end of the inclined side wall portion 17b is connected to the rear end of the front side wall portion 13b.

[0027] As shown in Figures 2 and 3, the floor cross member 20 is a member joined to the upper surface of the rear floor panel 10, and extends in the vehicle width direction from one end of the rear floor panel 10 to the other end in the vehicle width direction. The floor cross member 20 is a highly rigid member that constitutes the vehicle body frame, and is formed from a metal material. The floor cross member 20 increases the rigidity of the floor portion of the electric vehicle by being joined to the rear floor panel 10. The outer portion of the floor cross member 20 in the vehicle width direction is joined to the side sill 47. Moreover, the floor cross member 20 of this embodiment is arranged so as to straddle the tunnel portion (in this example, the inclined tunnel portion 17) from above.

[0028] As shown in Figs. 2, 3, and 6, the floor cross member 20 has a front wall portion 21, upper surface portions 25a, 25b, and 25c, and a rear wall portion 26. The front wall portion 21 is a portion that protrudes upward from the front portion of the upper surface 16a of the inclined portion 16 of the rear floor panel 10 and extends in the vehicle width direction. The front wall portion 21 has a front wall surface that faces the front of the vehicle. The lower end of the front wall portion 21 is formed along the shape of the upper surface 16a of the front portion of the inclined portion 16. In other words, the vehicle width direction intermediate portion of the lower end of the front wall portion 21 has a recessed portion 21a that is cut out in a substantially trapezoidal shape so as to correspond to the shape of the inclined tunnel portion 17 provided in the inclined portion 16.

[0029] 5 and 6, the rear wall portion 26 is a wall portion disposed at a distance from the front wall portion 21 toward the rear of the vehicle, protruding upward from the upper surface 16a of the inclined portion 16 and extending in the vehicle width direction. The rear wall portion 26 has a wall surface facing the rear of the vehicle. The lower end of the rear wall portion 26 is formed along the upper surface of the rear floor panel 10, similar to the lower end of the front wall portion 21. In other words, the vehicle width direction intermediate portion of the lower end of the rear wall portion 26 is cut out in a substantially trapezoidal shape to correspond to the shape of the inclined tunnel portion 17.

[0030] As shown in Fig. 2 and Fig. 6, the upper surface portions 25a, 25b, and 25c face the vehicle upward and extend in the vehicle width direction. The upper surface portions 25a, 25b, and 25c are inclined upward from the upper end of the front wall portion 21 toward the rear of the vehicle, and are connected to the upper end of the rear wall portion 26. In addition, the floor cross member 20 of this embodiment has a middle portion in the vehicle width direction protruding along the shape of the inclined tunnel portion 17. That is, the central upper surface portion 25a located on the upper side of the inclined tunnel portion 17 is disposed higher than the outer upper surface portion 25b located on the outer side of the inclined tunnel portion 17 in the vehicle width direction. Between the central upper surface portion 25a and the outer upper surface portion 25b, an inclined upper surface portion 25c is provided that is inclined downward from the vehicle width direction toward the outer side.

[0031] An inner reinforcement 20a is disposed inside the floor cross member 20. The inner reinforcement 20a is joined to the rear sides of the front wall portion 21, the rear wall portion 26, etc. by spot welding or the like.

[0032] 5 and 6, the floor cross member 20 has a front flange portion 22 and a rear flange portion 27. The front flange portion 22 protrudes from the lower end of the front wall portion 21 toward the front side of the vehicle and extends along the shape of the lower end of the front wall portion 21. The front flange portion 22 is joined to the front portion of the inclined portion 16 of the rear floor panel 10 by, for example, spot welding. The rear flange portion 27 protrudes from the lower end of the rear wall portion 26 toward the rear side of the vehicle and extends along the shape of the lower end of the rear wall portion 26. The rear flange portion 27 is joined to the inclined portion 16 located rearward of the front flange portion 22 by, for example, spot welding.

[0033] 2 and 3, the floor cross member 20 of this embodiment has an extension 23 that extends toward the front of the vehicle from the front end of the middle part of the floor cross member 20 in the vehicle width direction. As shown in Figures 6 and 7, at least a part of the extension 23 and at least a part of the under-floor reinforcement 30 are arranged to overlap in the vehicle up-down direction.

[0034] The floor cross member 20 of this embodiment has two extensions 23, as shown in Figures 2 and 3. The two extensions 23 are arranged at an interval from each other in the vehicle width direction, and each extension 23 protrudes forward of the vehicle from the front end of the front flange portion 22 of the floor cross member 20. The front end of the extension 23 is arranged forward of the front end of the inclined portion 16 and at the rear of the front flat portion 12. In this example, the extension 23 is arranged on the vehicle front side of the vehicle width direction outer portion of the approximately trapezoidal recess 21a of the front wall portion 21.

[0035] The extension portion 23 is disposed so as to cover the side wall portions 13b, 17b of the tunnel portions 13, 17 from above. As shown in Figs. 2 and 3, the extension portion 23 of this embodiment has an inner portion 23a, a middle portion 23b, and an outer portion 23c. The inner portion 23a of the extension portion 23 is a portion located on the inner side of the extension portion 23 in the vehicle width direction and extends in the vehicle front-rear direction. As shown in Figs. 2, 6, and 7, the inner portion 23a of the extension portion 23 covers the inclined apex portion 17a of the inclined tunnel portion 17 and the outer side of the front apex portion 13a of the front-side tunnel portion 13 in the vehicle width direction from above, and may be joined to the inclined apex portion 17a and the front apex portion 13a by spot welding or the like.

[0036] The intermediate portion 23b of the extension portion 23 is inclined downward from the outer end of the inner portion 23a in the vehicle width direction toward the outer side in the vehicle width direction and extends in the front-rear direction of the vehicle. The intermediate portion 23b corresponds to the inclination direction of the inclined side wall portion 17b and the front side wall portion 13b, covers the inclined side wall portion 17b and the front side wall portion 13b from the upper side in the direction perpendicular to the inclination direction of the inclined side wall portion 17b and the front side wall portion 13b, and is joined to the inclined side wall portion 17b and the front side wall portion 13b by spot welding or the like.

[0037] The outer portion 23c of the extension 23 protrudes outward in the vehicle width direction from the outer end of the intermediate portion 23b in the vehicle width direction and extends in the front-rear direction of the vehicle. The outer portion 23c covers, from above, the upper surface 16a of the inclined portion 16 located outside the lower end of the inclined sidewall portion 17b and the upper surface 12a of the front flat surface portion 12 located outside the lower end of the front sidewall portion 13b, and is joined to the upper surfaces 12a, 16a by spot welding or the like.

[0038] Next, the under-floor reinforcement 30 will be described. As shown in Fig. 4, the under-floor reinforcement 30 is a member joined to the underside of the rear floor panel 10, and is formed from a metal material. The under-floor reinforcement 30 is a member extending in the vehicle width direction, and is disposed in the middle part in the vehicle width direction in front of the inclined part 16. In addition, the under-floor reinforcement 30 ensures the rigidity of the floor part of the electric vehicle by being joined to the rear floor panel 10. The configuration of the under-floor reinforcement 30 will be described below.

[0039] As shown in Fig. 4, the under-floor reinforcement 30 has a main body portion 31 extending in the vehicle width direction, and two forward protruding portions 32 protruding forward from a front portion of the main body portion 31. The rear end of the main body portion 31 extends linearly in the vehicle width direction. The side ends of the main body portion 31 extend so as to incline outward in the vehicle width direction toward the rear of the vehicle. The forward protruding portions 32 protrude forward from the vehicle width direction side portions at the front portion of the main body portion 31.

[0040] 6 and 7, the front end of the forward protrusion 32 is disposed at the rear of the front flat surface portion 12, forward of the front end of the inclined portion 16. In this embodiment, the front end of the forward protrusion 32 is disposed on the lower surface 12b of the front flat surface portion 12, which is located further forward of the vehicle than the front end of the extension portion 23. The two forward protrusions 32 are disposed at a distance from each other in the vehicle width direction. The front end of the main body portion 31, which is located between the two forward protrusions 32, extends linearly in the vehicle width direction.

[0041] The main body portion 31 is disposed below the floor cross member 20. That is, the main body portion 31 and the floor cross member 20 are disposed so as to sandwich the front portion of the inclined portion 16. The main body portion 31 is joined to the lower surface 16b of the inclined portion 16 by spot welding or the like. For example, the main body portion 31 of the under-floor reinforcement 30, the inclined portion 16 of the rear floor panel 10, and the rear flange portion 27 of the floor cross member 20 are joined by spot welding or the like in a three-layered state as shown in Figs. 5 and 6.

[0042] The forward protrusion 32 is disposed so as to cover from below the side wall portions 13b, 17b of the tunnel portions 13, 17. As shown in Fig. 4 and Fig. 6, the forward protrusion 32 of this embodiment has an inner portion 32a, a middle portion 32b, and an outer portion 32c, similar to the extension portion 23.

[0043] The inner part 32a of the forward protrusion 32 is a part located on the inner side of the forward protrusion 32 in the vehicle width direction, and extends in the vehicle front-rear direction. The inner part 32a of the forward protrusion 32 covers the outer parts in the vehicle width direction of the inclined apex 17a of the inclined tunnel section 17 and the front apex 13a of the front-side tunnel section 13 from below, and is joined to the inclined apex 17a and the front apex 13a by spot welding or the like. For example, the inner part 32a of the forward protrusion 32, the inclined apex 17a of the inclined tunnel section 17, and the inner part 23a of the extension section 23 may be joined by spot welding in a three-ply state.

[0044] The intermediate portion 32b of the forward protrusion 32 is inclined downward from the outer end of the inner portion 32a in the vehicle width direction toward the outer side in the vehicle width direction, and extends in the front-rear direction of the vehicle. The intermediate portion 32b of the forward protrusion 32 corresponds to the inclination direction of the inclined side wall portion 17b and the front side wall portion 13b, covers the inclined side wall portion 17b and the front side wall portion 13b from the lower side in the direction perpendicular to the inclination direction of the inclined side wall portion 17b and the front side wall portion 13b, and is joined to the inclined side wall portion 17b and the front side wall portion 13b by spot welding or the like. For example, the intermediate portion 32b of the forward protrusion 32, the inclined side wall portion 17b of the inclined tunnel portion 17, and the intermediate portion 23b of the extension portion 23 may be joined by spot welding in a three-ply state.

[0045] The outer part 32c of the forward protruding part 32 protrudes outward in the vehicle width direction from the outer end of the intermediate part 32b in the vehicle width direction and extends in the front-rear direction of the vehicle. The outer part 32c of the forward protruding part 32 covers the lower surface 16a of the inclined part 16 located outside the lower end of the inclined side wall part 17b and the lower surface 12b of the front side flat part 12 located outside the lower end of the front side wall part 13b from below, and is joined to each lower surface 12b, 16b by spot welding or the like. For example, the outer part 32c of the forward protruding part 32, the lower surface 16b located outside the lower end of the inclined side wall part 17b of the inclined tunnel part 17, and the outer part 23c of the extension part 23 may be joined by spot welding in a three-ply state.

[0046] In this embodiment, the under-floor reinforcement 30 and the floor cross member 20 are joined to the rear floor panel 10 with the inclined portion 16 of the rear floor panel 10 sandwiched therebetween. This configuration effectively reinforces the front portion of the inclined portion 16 of the rear floor panel 10, and makes it possible to suppress concentration of stress on the inclined portion 16 when the inclined portion 16 is deformed by, for example, a load in the vertical direction acting on the front portion of the inclined portion 16. Therefore, in an electric vehicle in which a step is provided in the rear floor panel 10, it is possible to ensure the rigidity of the rear floor panel 10 against a load in the vertical direction.

[0047] Although detailed description is omitted, as virtually shown in Fig. 5, a battery pack 55, which is a heavy object, is attached to the underside of the floor panel via a mounting member such as a bracket (not shown). For example, the rear end of the battery pack 55 may be located slightly rearward of the inclined portion 16 of the rear floor panel 10. In such a case, when an impact load acts on the front part of the vehicle body from the front to the rear, a rearward load is also applied to the inclined portion 16 due to the inertia of the battery pack 55.

[0048] In this embodiment, since the inclined portion 16 is effectively reinforced as described above, the load acting on the inclined portion 16 can be transmitted to members constituting the vehicle body frame, such as the floor cross member 20, the side sill 47, and the rear side member 45. This makes it possible to effectively suppress stress concentration on the inclined portion 16.

[0049] In addition, in this embodiment, as described above, at least a part of the extension 23 and at least a part of the under-floor reinforcement 30 are arranged to overlap in the vehicle up-down direction. In detail, the forward protrusion 32 and the extension 23 are arranged to overlap with each other via the side wall 13b, 17b of the front tunnel 13, 17, etc. This makes it possible to effectively reinforce the center of the vehicle floor where the tunnel 13, 17, 51 is located. For example, it is possible to reinforce the bent portion at the boundary between the front side wall 13b of the front tunnel 13 and the upper surface 12 of the rear floor panel 10, and to reduce deformation that occurs when a load is applied. In addition, by reinforcing the step formed by the tunnel 13, 17, it is possible to effectively suppress stress concentration on the step caused by deformation of the step.

[0050] As described above, the extension 23, the front side wall portion 13b, and the forward protrusion 32 are joined in three layers, and therefore have high strength and rigidity. In this embodiment, the front end of the under-floor reinforcement 30 is disposed further forward in the vehicle than the front end of the extension 23 of the floor cross member 20. In this example, the front end of the forward protrusion 32 is disposed further forward in the vehicle than the front end of the extension 23 (FIG. 7).

[0051] This can prevent a sudden difference in strength between the reinforced and unreinforced parts. For example, a two-ply part is arranged on the front side of a three-ply part. Therefore, in this embodiment, the reinforcing effect is gradually increased toward the rear. As a result, an extreme difference in strength does not occur, making it possible to prevent stress concentration.

[0052] In addition, in this embodiment, as shown in Figures 2 and 6, seat brackets 41, 42 that support the front portion of the seat rail 52a of a vehicle seat (in this example, the rear seat 52) ​​are attached to the floor cross member 20, and the seat brackets 41, 42 are arranged next to the extension portion 23 in the fore-and-aft direction of the vehicle.

[0053] As shown in Figs. 2 and 3, the seat brackets 41, 42 of this embodiment include two outer seat brackets 42 and one intermediate seat bracket 41. The outer seat bracket 42 may be attached to the upper surface of the floor cross member 20 at the outer side in the vehicle width direction. The intermediate seat bracket 41 is disposed in the middle of the floor cross member 20 in the vehicle width direction and behind the right extension portion 23. The intermediate seat bracket 41 is disposed so as to cover the inclined upper surface portion 25c located on the right side from above. The intermediate seat bracket 41 is joined to the central upper surface portion 25a and the outer upper surface portion 25b. In addition, the lower part of the front side of the intermediate seat bracket 41 is joined to the wall surface of the front wall portion 21 of the floor cross member 20. Although not shown in the drawings, the lower part of the rear side of the intermediate seat bracket 41 may be joined to the rear wall portion 26. The intermediate seat bracket 41 is disposed in line with the right extension portion 23 along the vehicle front-rear direction.

[0054] By arranging as described above, the load from the intermediate seat bracket 41 can be received by the extension portion 23. This makes it possible to suppress deformation of the floor portion. Also, by reinforcing the intermediate seat bracket 41 (the mounting portion on the front side of the rear seat 52) ​​located on the front side of the rear seat 52, deformation of the seat mounting portion at the rear of the rear seat 52 can be reduced, and as a result, it becomes possible to reduce the stress acting on the floor portion.

[0055] The description of the present embodiment is merely an example for explaining the present invention, and does not limit the invention described in the claims. Furthermore, the configuration of each part of the present invention is not limited to the above embodiment, and various modifications are possible within the technical scope described in the claims.

[0056] For example, in this embodiment, the inclined portion 16 is provided on the rear floor panel 10, but this is not limited to this. For example, the inclined portion 16 may be provided on a floor panel in which the rear floor panel 10 and the front floor panel 50 are integrally formed. [Explanation of symbols]

[0057] 10 Rear floor panel 12 Front side flat part (flat part) 12a Top side 12b Bottom side 13 Front tunnel section 13a Front top 13b Front side wall 16 Slope 16a Top side 16b Bottom side 17 Inclined tunnel section 17a Slope top 17b Slanted side wall section 18 Rear side plane part 20 Floor cross member 20a Inner Reinforcement 21 Front wall 21a Recess 22 Front flange 23 Extension 23a Inside part 23b Middle part 23c outer part 25a Center top section 25b Outer top part 25c Slanted top section 26 Rear wall 27 Rear flange 30 Underfloor reinforcement 30 31 Main body 32 Forward protrusion 32a Inside part 32b middle part 32c outer part 41 Intermediate seat bracket 42 Outer seat bracket 45 Rear side member 47 Side sill 50 Front floor panel 52 Rear seat 52a Seat rail 53 Cushion section 55 Battery Pack

Claims

1. A vehicle body underbody structure for an electric vehicle, the vehicle body underbody structure including a battery pack disposed on a lower surface side of a floor panel, the floor panel having a step such that a rear portion of the floor panel is positioned higher than a front portion of the floor panel, The floor panel has a flat portion and an inclined portion that extends obliquely upward from a rear end of the flat portion toward the rear of the vehicle, A cross member extending in a vehicle width direction is disposed on the upper surface side of the floor panel and in front of the inclined portion, An under-floor reinforcement is disposed on the underside of the floor panel and in front of the inclined portion, A front end of the under-floor reinforcement is disposed on a vehicle front side relative to a front end of the inclined portion, and a rear end of the under-floor reinforcement is disposed on the inclined portion, A vehicle body underbody structure for an electric vehicle, wherein the under-floor reinforcement and the cross member are joined to the floor panel with the floor panel sandwiched therebetween.

2. The cross member has an extension portion extending forward of the vehicle from a front end of a vehicle width direction intermediate portion of the cross member, The under-floor reinforcement extends in a vehicle width direction, 2. The vehicle body underbody structure for an electric vehicle according to claim 1, wherein at least a portion of the extension and at least a portion of the under-floor reinforcement are disposed so as to overlap in the vehicle up-down direction.

3. 3. The vehicle body underbody structure for an electric vehicle according to claim 1, wherein a front end of the under-floor reinforcement is disposed further forward of the vehicle than a front end of the extension of the cross member.

4. A tunnel portion is provided in a vehicle width direction intermediate portion of the floor panel, the tunnel portion bulging upwardly of the vehicle and extending in a vehicle front-rear direction, The tunnel portion has a top portion located above a main surface of the floor panel and a side wall portion extending from the main surface toward the top portion, 3. The vehicle body underbody structure of an electric vehicle as described in claim 1 or 2, characterized in that the side wall portion is covered from above by the extension portion and covered from below by the under-floor reinforcement, and is sandwiched between the extension portion and the under-floor reinforcement.

5. A seat bracket for supporting a front portion of a vehicle seat is attached to the cross member, 3. The vehicle body underbody structure for an electric vehicle according to claim 1, wherein the seat bracket is arranged next to the extension portion in the vehicle front-rear direction.

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