Lower structure of vehicle body

Abstract

To reduce air resistance in the periphery of a rear tire by a simple structure.SOLUTION: A lower structure 1 of a vehicle body includes a battery case 4 which is arranged below a floor part of a vehicle, a side sill 6 extending in a vehicle longitudinal direction along a vehicle width direction outer side of the floor part, a battery side member 7 which extends in a vehicle longitudinal direction on the vehicle width direction outer side of the battery case 4 and connects the battery case 4 and the side sill 6, and a side part cover member 20 which is fixed to a rear end of the battery side member 7 and a rear side angle part 4x of the battery case 4, wherein the side part cover member 20 has a lateral wall part 23 extending in parallel with the lower surface of the battery case 4, and a guide wall part 33 which projects downward from the rear end of the lateral wall part 23 and extends in a vehicle width direction, and the lower end of the guide wall part 33 projects to the lower side of a lower surface 7b of the battery side member 7, and projects to the lower side of the lower surface of the battery case 4 or to the lower side of a lower surface 5b of a battery undercover 5.SELECTED DRAWING: Figure 12

Description

[Technical Field]

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

[0002] One known example of an automobile underbody structure is the underbody structure described in Patent Document 1. The underbody structure described in Patent Document 1 has a battery undercover that is placed under the floor in the center of the vehicle in the longitudinal direction and covers the underside of the battery unit, and water that flows from the road surface toward the battery unit while the vehicle is in motion is received by the battery undercover, thereby preventing the battery unit from getting wet.

[0003] In the vehicle underbody structure described in Patent Document 1, a rear deflector (also called a strake) is provided in front of the rear tire to reduce air resistance under the floor and from the entire tire, and a running straightening surface with a straightening function is provided on the battery undercover. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-219042 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the vehicle underbody structure described in Patent Document 1 only reduces air resistance around the rear tires using a typical rear deflector (strake), so further reduction in air resistance is desired. Furthermore, a rear suspension is disposed around the rear tires, and the rear suspension is typically exposed to the road surface. Therefore, air flowing along the underside of the battery undercover (driving wind) hits the rear suspension, potentially increasing air resistance. Furthermore, parts or members other than the rear suspension may be disposed around the rear tires so that they are exposed to the road surface and protrude downward. Thus, the vehicle underbody structure described in Patent Document 1 leaves room for improvement in reducing air resistance. Note that a battery undercover covering the underside of the battery case may not be provided, and even in this case, there is similarly room for improvement in reducing air resistance.

[0006] SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a vehicle underbody structure that can reduce air resistance around the rear tire with a simple structure. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, according to one aspect of the present invention, a battery case is arranged below a floor portion of a vehicle, and a side sill extends in the fore-and-aft direction of the vehicle along the outer portion of the floor portion in the vehicle width direction, the battery side member extends in the fore-and-aft direction of the vehicle on the outer side of the battery case in the vehicle width direction and connects the battery case to the side sill, and a side cover member is fixed to the rear end portion of the battery side member and the rear corner portion of the battery case, the side cover member having a lateral wall portion extending parallel to the underside of the battery case, and a guide wall portion protruding downward from the rear end of the lateral wall portion and extending in the vehicle width direction, the lower end of the guide wall portion protruding downward below the underside of the battery side member and protruding downward below the underside of the battery case or the underside of a battery undercover covering the underside of the battery case. [Effects of the Invention]

[0008] According to one aspect of the present invention, it is possible to provide a vehicle underbody structure that can reduce air resistance around a rear tire with a simple structure. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a bottom view of a vehicle body including a vehicle underbody structure according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged bottom view of a main part of the vehicle body underbody structure. [Figure 3] FIG. 3 is a cross-sectional view taken along line AA shown in FIG. 2. [Figure 4] 3 is an enlarged perspective view of a portion of the vehicle body undercarriage including a side cover member and a reinforcing member, as viewed from above. FIG. [Figure 5A] FIG. 4 is a perspective view of a first cover member of the side cover member as viewed from above. [Figure 5B] FIG. 4 is a perspective view of a first cover member of the side cover member as viewed from below. [Figure 6] 10 is a perspective view showing a state in which a second cover member and a reinforcing member of the side cover member are joined together. FIG. [Figure 7A] FIG. 2 is an enlarged perspective view of a main part of the vehicle body underbody structure as viewed from below. [Figure 7B] FIG. 2 is an enlarged perspective view of a main portion of the vehicle underbody structure from which the side cover members and the reinforcing members have been removed, as viewed from below. [Figure 7C] FIG. 2 is an enlarged perspective view of a main portion of the vehicle underbody structure from which the side cover members have been removed, as viewed from below. [Figure 7D] 1 is an enlarged perspective view of a main part of the vehicle body underbody structure from which a first cover member has been removed, as viewed from below. FIG. [Figure 8] FIG. 3 is a cross-sectional view taken along line BB shown in FIG. 2. [Figure 9] FIG. 3 is a cross-sectional view taken along line CC shown in FIG. 2. [Figure 10] FIG. 9 is a perspective view of a cut model taken along line DD shown in FIG. 8. [Figure 11]3 is a cross-sectional view taken along line EE shown in FIG. 2. [Figure 12] FIG. 2 is an enlarged perspective view of a main part of the vehicle body underbody structure as viewed from below. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a bottom view of a vehicle body including a vehicle body understructure 1 according to one embodiment of the present invention, FIG. 2 is an enlarged bottom view of a main portion of the vehicle body understructure 1, and FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. In the drawings, the arrow Fr indicates the front in the longitudinal direction of the vehicle, the arrow O indicates the outside of the vehicle in the width direction of the vehicle, and the arrow U indicates the upside in the vertical direction of the vehicle. In the following description, "front" and "rear" correspond to the front and rear in the longitudinal direction of the vehicle, "up" and "down" correspond to the up and down in the vertical direction of the vehicle, and "left" and "right" correspond to the left and right in the width direction of the vehicle when a vehicle occupant is facing forward of the vehicle. The vehicle body understructure 1 has a bilaterally symmetrical structure. Below, the left side of the vehicle body understructure 1 will be mainly described, and a description of the right side of the vehicle body understructure 1 will be omitted. The vehicle to which the vehicle body understructure 1 is applied is an electric vehicle or a hybrid vehicle equipped with both an engine and a motor. In this embodiment, the vehicle is an electric vehicle, although not particularly limited thereto.

[0011] 1 to 3, a vehicle body 2 has a floor section that separates the vehicle interior from a battery arrangement area. The floor section is composed of a floor panel 3 made of a metal sheet. The vehicle body understructure 1 includes a battery case 4 disposed below the floor section (floor panel 3). The underside of the battery case 4 is covered by a battery undercover 5. Side sills 6 extending in the vehicle longitudinal direction are provided on the outer sides of the floor section (floor panel 3) in the vehicle width direction. Battery side members 7 extending in the vehicle longitudinal direction are provided on the outer sides of the battery case 4 in the vehicle width direction. Side skirts 8 extending in the vehicle longitudinal direction are provided on the outer sides of the battery side members 7 in the vehicle width direction. The battery side members 7 are disposed between the battery case 4 and the side skirts 8 in the vehicle width direction and below the side sills 6 in the vertical direction. The battery side members 7 connect the battery case 4 and the side sills 6, and the battery case 4 is fixed to the side sills 6 via the battery side members 7. An opening 9 is formed behind the battery side members 7 to allow access to the interior of the vehicle during vehicle maintenance, etc.

[0012] Thus, the vehicle body understructure 1 includes a battery case 4 arranged below the floor portion of the vehicle (here, floor panel 3), a side sill 6 extending in the fore-and-aft direction of the vehicle along the outer portion of the floor portion in the vehicle width direction, and a battery side member 7 extending in the fore-and-aft direction of the vehicle on the outer side of the battery case 4 in the vehicle width direction and connecting the battery case 4 and the side sill 6.

[0013] The battery case 4 has a generally rectangular parallelepiped appearance. The battery case 4 includes a lower case 4a and an upper case 4b attached to the lower case 4a from above. The battery case 4 is a case in which an accommodation space for accommodating a battery and the like is formed by vertically joining the upper case 4b and the lower case 4a. The battery is accommodated in the accommodation space inside the battery case 4. A sealing material such as a packing (not shown) is provided between a mating surface 4c of the lower case 4a with the upper case 4b and a mating surface of the upper case 4b with the lower case 4a. The interior of the battery case 4 is sealed by the sealing material. In the illustrated example, the outer edges of the mating surface 4c of the lower case 4a and the outer edges of the mating surface of the upper case 4b run around the battery case 4 along the front, right, rear, and left sides of the battery case 4 and are exposed to the outside of the battery case 4.

[0014] The battery undercover 5 is fixed to the underside of the battery case 4. By covering the underside of the battery case 4, the battery undercover 5 protects the battery case 4 from water and pebbles that may flow onto the battery case 4 from the road surface while the vehicle is in motion. The battery undercover 5 is formed in roughly the same shape as the underside of the battery case 4. However, the four corners (four corner portions) of the battery undercover 5 are cut out at an angle. Therefore, when the battery undercover 5 is fixed to the underside of the battery case 4, the four corners of the battery case 4 are not covered by the battery undercover 5. Figure 7B, which will be described later, shows a state in which the rear corners 4x, which are the corners on the rear side of the battery case 4 on the outer side in the vehicle width direction, are not covered by the battery undercover 5 and are exposed to the outside of the battery case 4. The rear corner portion 4x is a triangular prism-shaped region and has a side (right side or left side) facing outward in the vehicle width direction, a rear side facing rearward in the vehicle longitudinal direction, an upper surface facing upward in the vehicle vertical direction, and a lower surface facing downward in the vehicle vertical direction.

[0015] 2, a plate-shaped reinforcing member 10 extending in the vehicle longitudinal direction and vehicle width direction is fixed to the rear corner 4x of the battery case 4. The reinforcing member 10 is made of a thin metal plate and, in the illustrated example, is formed in a generally triangular shape in a plan view. The reinforcing member 10 is fixed to a holding bracket 12 (described later) fixed to the vehicle body. In other words, the reinforcing member 10 is a plate-shaped member that connects the rear corner 4x of the battery case 4 and the holding bracket 12 and extends in the vehicle longitudinal direction and vehicle width direction. More specifically, the reinforcing member 10 is provided so as to bridge between the rear corner 4x of the battery case 4 and the holding bracket 12. As a result, the battery case 4 is fixed to the vehicle body 2 via the reinforcing member 10. In this way, in this embodiment, the vehicle underbody structure 1 includes the reinforcing member 10 and the holding bracket 12 in addition to the battery case 4, the side sill 6, and the battery side member 7.

[0016] Arranged behind the battery side member 7 are a rear tire T, a fairing P, a rear suspension 11, and a retaining bracket 12 (described later). The rear suspension 11 is, for example, a trailing arm suspension. The fairing P is attached to the front lower end of the rear wheel housing H that covers the rear tire T from above and extends downward. The fairing P is an aerodynamic component that regulates the airflow (air current) during driving, and is also called a strake or deflector. The fairing P blocks the air (driving wind) that flows along the lower surface 7b of the battery side member 7 during driving, thereby preventing the air from flowing into the rear tire T. In other words, the fairing P has the function of preventing air from flowing into the front lower portion of the rear tire T during driving, thereby reducing air resistance around the rear tire T.

[0017] The retaining bracket 12 is provided around the rear end of the side sill 6 and is a bracket that holds the tip of the arm 11a of the rear suspension, and is joined to the vehicle body. The joint portion of the retaining bracket 12 is a relatively rigid part of the vehicle body. In the illustrated example, the retaining bracket 12 is located inside the rear end of the side sill 6 in the vehicle width direction, and is located near the rear end of the side sill 6. The retaining bracket 12 is also located rearward of the rear end surface 7a of the battery side member 7.

[0018] The tip of an arm (more specifically, a trailing arm) 11a of the rear suspension 11 is swingably held by a holding bracket 12 fixed to the vehicle body, and is supported (connected) to the vehicle body. A bolt hole for fixing a reinforcing member 10 is formed in the underside of the holding bracket 12. The rear suspension 11 is disposed inward in the vehicle width direction from the rear tire T. A rear undercover 13 is disposed behind the battery case 4, and the front end of the rear undercover 13 is adjacent to the rear end of the battery case 4. A rear floor cover 14 is disposed behind the rear undercover 13. The rear undercover 13 is a cover that covers the underside and side of battery accessories and high-voltage devices (not shown) disposed behind the battery case 4.

[0019] The rear tire T and the air deflector P protrude downward from the lower surface 7b of the battery side member 7, and the rear suspension 11 and the retaining bracket 12 protrude downward from at least the lower surface of the battery case 4 (in the illustrated example, the lower surface 5b of the battery undercover 5).

[0020] The rear end surfaces 7a of the battery side members 7 are inclined forward from the inner side toward the outer side in the vehicle width direction. When the battery undercover 5 is fixed to the underside of the battery case 4, the obliquely cut-out rear inclined portion 5a of the battery undercover 5 and the rear end surfaces 7a of the battery side members 7 are arranged so as to roughly follow a common imaginary plane. More specifically, as shown in FIG. 7B (described later), the battery undercover 5 has an upper cover wall 5a1 on the battery case 4 side and a lower cover wall 5a2 below the upper cover wall 5a1. The upper cover wall 5a1 protrudes slightly rearward and outward in the vehicle width direction beyond the lower cover wall 5a2 at the rear inclined portion 5a. The rear end surfaces of the lower cover wall 5a2 of the rear inclined portion 5a of the battery undercover 5 and the rear end surfaces 7a of the battery side members 7 are arranged so as to roughly follow a common imaginary plane.

[0021] The battery side member 7 is made of aluminum material. The battery side member 7 is, for example, a rectangular cylindrical member extending in the longitudinal direction of the vehicle. In the illustrated example, the battery side member 7 has a plurality of ribs therein that are spaced apart in the vehicle width direction. The battery side member 7 is made of, for example, an aluminum alloy and formed by pultrusion. The battery side member 7 is an impact absorbing member in the event of a side collision. In other words, when an impact load is applied from the outside in the vehicle width direction during a side collision, the battery side member 7 deforms due to the impact load, thereby absorbing the energy of the impact load.

[0022] The vehicle body understructure 1 also includes side cover members 20 fixed to rear end portions of the battery side members 7 and rear corner portions 4x of the battery case 4. A rear suspension 11 and a rear tire T are arranged behind the side cover members 20. The outer portions of the front end portions of the side cover members 20 in the vehicle width direction are fixed to the rear end portions of the battery side members 7. The inner portions of the rear portions of the side cover members 20 in the vehicle width direction are fixed to the underside of the rear corner portions 4x of the battery case 4 via reinforcing members 10. The intermediate portions of the side cover members 20 in the vehicle fore-and-aft direction are fixed to the side sills 6 via side sill brackets 15 (see FIG. 9 described later) described later.

[0023] The rear end surface 7a of the battery side member 7, the rear inclined portion 5a of the battery undercover 5, and the underside of the rear corner 4x of the battery case 4 are each covered by the side cover member 20. In the illustrated example, approximately half of the inner side of the rear end surface 7a of the battery side member 7 in the vehicle width direction and most of the rear inclined portion 5a of the battery undercover 5 are each covered from the rear by the side cover member 20, and most of the underside of the rear corner 4x of the battery case 4, among the underside of the battery case 4, is covered from below by the side cover member 20.

[0024] Next, the side cover member 20 will be described in detail with reference to Figures 2, 4, 5A, 5B, and 6. Figure 4 is an enlarged perspective view of a portion of the vehicle body understructure 1 including the side cover member 20 and the reinforcing member 10, viewed from above. Figures 5A and 5B are perspective views of a first cover member 21 (described below) of the side cover member 20, with Figure 5A being a perspective view viewed from above and Figure 5B being a perspective view viewed from below. Figure 6 is a perspective view showing a state in which a second cover member 22 (described below) of the side cover member 20 is joined to the reinforcing member 10. In Figure 4, the battery case 4 and the battery undercover 5 have been removed, and the outline of the battery case 4 is indicated by a two-dot chain line, and the outline of the battery undercover 5 is indicated by a dashed line.

[0025] As shown in FIG. 4 and FIG. 10 described later, the side cover member 20 has a first opposing wall portion 20A facing the rear end surface 7a of the battery side member 7, and a second opposing wall portion 20B facing the side surface at the rear corner portion 4x of the battery case 4.

[0026] The side cover member 20 has a first cover member 21 made of resin and a second cover member 22 made of thin metal plate. That is, in this embodiment, the side cover member 20 is separated into two parts, the first cover member 21 and the second cover member 22, which are connected to each other (21 and 22).

[0027] The first opposing wall portion 20A is provided on at least the first cover member 21, and the second opposing wall portion 20B is provided on at least the second cover member 22. Specifically, the first opposing wall portion 20A is provided only on the first cover member 21, and the second opposing wall portion 20B is also provided on the first cover member 21. More specifically, the first opposing wall portion 20A is formed by a first wall portion 24a of a first vertical wall portion 24 (described later) of the first cover member 21, and the second opposing wall portion 20B is formed by a second vertical wall portion 26 (described later) of the second cover member 22 and a cross wall portion 24b of the first vertical wall portion 24 (described later) of the first cover member 21.

[0028] When the side cover members 20 are fixed to the battery side members 7 and the battery case 4, the first cover member 21 has a first horizontal wall portion 23 extending parallel to the lower surface of the battery case 4 and a first vertical wall portion 24 protruding upward from the upper surface of the first horizontal wall portion 23. In other words, the first horizontal wall portion 23 extends in the vehicle longitudinal direction and vehicle width direction from the lower end of the first vertical wall portion 24. Furthermore, the first horizontal wall portion 23 extends in the vehicle longitudinal direction and vehicle width direction from the lower end of the first opposing wall portion 20A. Note that the lower surface of the battery case 4 is parallel to the road surface, i.e., extends horizontally, when mounted on the vehicle body. Here, "parallel" to the lower surface of the battery case 4 is not limited to being strictly parallel, but may also include being roughly parallel and being slightly inclined. It is sufficient that the majority of the first lateral wall portion 23 extends parallel to the underside of the battery case 4, and it is not necessary that the entire first lateral wall portion 23 be parallel to the underside of the battery case 4. In this embodiment, the first lateral wall portion 23 corresponds to the "lateral wall portion" according to the present invention.

[0029] When the side cover member 20 is fixed to the battery side member 7 and the battery case 4, the second cover member 22 has a second horizontal wall portion 25 that is generally parallel to the lower surface of the battery case 4, and a second vertical wall portion 26 that protrudes upward from the upper surface of the second horizontal wall portion 25.

[0030] The first lateral wall portion 23 has a first lateral wall portion upper portion 23a located on the outer side in the vehicle width direction and a first lateral wall portion lower portion 23b located on the inner side in the vehicle width direction. The first lateral wall portion upper portion 23a is located above the first lateral wall portion lower portion 23b in the up-down direction.

[0031] Although not particularly limited, in the illustrated example, the first lateral wall portion 23 has a shape that, in a top view, is roughly a right-angled isosceles triangle with the right-angled vertex removed to form a rectangle. The first lateral wall portion 23 has a base portion 27, a first outer hypotenuse portion 28, a first rear hypotenuse portion 29, a second rear hypotenuse portion 30, and a second outer hypotenuse portion 31. The base portion 27 corresponds to the base of the right-angled isosceles triangle. The first outer hypotenuse portion 28 extends from the outer end of the base portion 27 in the vehicle width direction and corresponds to a portion of one hypotenuse of the isosceles triangle. The first rear hypotenuse portion 29 extends from the inner end of the base portion 27 in the vehicle width direction and corresponds to a portion of the other hypotenuse of the isosceles triangle. The second rear oblique side portion 30 extends from the rear end of the first outer oblique side portion 28 toward the bottom side portion 27 and parallel to the first rear oblique side portion 29. The second outer oblique side portion 31 extends from the outer end of the first rear oblique side portion 29 in the vehicle width direction toward the bottom side portion 27 and parallel to the first outer oblique side portion 28.

[0032] The bottom edge portion 27 is disposed so as to follow the diagonally chamfered rear inclined portion 5a of the battery undercover 5 and the diagonally chamfered rear end surface 7a of the battery side member 7. The bottom edge portion 27 is slightly bent up and down at the boundary between the first horizontal wall portion upper portion 23a and the first horizontal wall portion lower portion 23b, and upper and lower steps 27a are provided at the boundary. The steps 27a are provided at a position corresponding to the boundary between the battery undercover 5 and the battery side member 7. In the portion of the bottom edge portion 27 corresponding to the battery side member 7 (i.e., the first horizontal wall portion upper portion 23a), the bottom edge portion 27 follows the lower surface 7b of the battery side member 7 near the rear end surface 7a of the battery side member 7. In the portion of the bottom edge portion 27 corresponding to the battery undercover 5 (i.e., the first horizontal wall portion lower portion 23b), the bottom edge portion 27 follows the lower surface of the cover upper wall 5a1 of the rear inclined portion 5a of the battery undercover 5.

[0033] The first outer oblique side portion 28 is disposed along a portion of the vehicle width direction inner portion of the side skirt 8 that includes the rear end. When the side cover member 20 is fixed to the battery side member 7 and the battery case 4, the rear portion of the side cover member 20 (more specifically, the first rear oblique side portion 29, the second rear oblique side portion 30, and the second outer edge portion 31) forms the front portion of the opening edge that forms the opening 9 for accessing the interior of the vehicle. In the illustrated example, the vehicle width direction outer portion of the rear undercover 13 forms the vehicle width direction inner edge of the opening edge that forms the opening 9, and extends from the rear of the side cover member 20 to the area of ​​the rear suspension 11 and the retaining bracket 12.

[0034] 5A, the first cover member 21 has a guard wall portion 32 that extends from the middle of the extension direction of the bottom side portion 27 toward the inside in the vehicle width direction along the bottom side portion 27 and protrudes upward. In other words, the side cover member 20 has the guard wall portion 32 that protrudes upward from the front end (bottom side portion 27) of the lateral wall portion (here, the first lateral wall portion 23) and extends in the vehicle width direction.

[0035] The first vertical wall portion 24 is provided on the first horizontal wall portion upper portion 23a. The first vertical wall portion 24 has a first wall portion 24a that extends linearly in a top view, an intersecting wall portion 24b that extends linearly in a direction intersecting with the first wall portion 24a in a top view, and a curved portion 24c that extends in a curved manner to connect the first wall portion 24a and the intersecting wall portion 24b.

[0036] The first wall portion 24a is spaced rearward from the bottom side portion 27 and extends generally parallel to the bottom side portion 27. The first wall portion 24a extends from the first outer oblique side portion 28 to the periphery of the middle position of the bottom side portion 27 in the extension direction.

[0037] The cross wall portion 24b is generally parallel to the first outer oblique side portion 28 and extends linearly in the front-to-rear direction to connect to the second outer oblique side portion 31. The cross wall portion 24b extends rearward from the curved portion 24c. A rear portion of the cross wall portion 24b is cut out.

[0038] A fixing portion 24d for fixing to the vehicle body side is provided on the upper portion of the cross wall portion 24b. The fixing portion 24d has a through hole formed therein for fixing with a fastening member such as a screw or a pin.

[0039] The first cover member 21 has a first pedestal portion 21a, a second pedestal portion 21b, a third pedestal portion 21c, and a fourth pedestal portion 21d. The first pedestal portion 21a is a pedestal portion for fixing a front end portion of a first lateral wall portion 23 of the first cover member 21 to a rear end portion of the battery side member 7. The first pedestal portion 21a protrudes from the bottom portion 27 near the outer side in the vehicle width direction of the first lateral wall portion upper portion 23a. A through hole is formed in the first pedestal portion 21a for fastening to the battery side member 7. The second pedestal portion 21b is a pedestal portion for fixing a vehicle longitudinal direction intermediate portion of the first lateral wall portion 23 of the first cover member 21 to the side sill 6. As shown in FIG. 9 (described later), a side-sill bracket 15 is joined to the underside 6a of the side sill 6 by spot welding or the like, and the second pedestal portion 21b functions as a pedestal for fixing a vehicle longitudinally intermediate portion of the first lateral wall portion 23 to the side sill 6 via the side-sill bracket 15. The second pedestal portion 21b is formed in a vehicle longitudinally intermediate portion of the first lateral wall portion upper portion 23a and bulges upward. The second pedestal portion 21b is positioned along the first outer oblique side portion 28 and toward the second rear oblique side portion 30. A through-hole is formed in the second pedestal portion 21b for fastening to the side-sill bracket 15. The third pedestal portion 21c is a pedestal for fixing the first cover member 21 to the reinforcing member 10. The third pedestal portion 21c bulges upward at the rear end side of the first lateral wall portion lower portion 23b. A through-hole is formed in the third pedestal portion 21c for fastening to the reinforcing member 10. The fourth pedestal portion 21d is a pedestal portion for fixing the second cover member 22 to the first cover member 21. The fourth pedestal portion 21d bulges upward from the first horizontal wall portion upper portion 23a near the first horizontal wall portion lower portion 23b. A through hole for fixing the second cover member 22 is formed in the fourth pedestal portion 21d. The top surface of each pedestal portion (21a-21d) is formed as a flat surface. A fastening member such as a screw or a clip is inserted into the through hole of each pedestal portion (21a-21d).

[0040] 5B, the side cover member 20 has a guide wall portion 33 in the first cover member 21 that protrudes downward from the rear end of a lateral wall portion (here, the first lateral wall portion 23) and extends in the vehicle width direction. In the illustrated example, the guide wall portion 33 has a first guide wall portion 35 and a second guide wall portion 36. Furthermore, the side cover member 20 further has a first front / rear wall portion 37 and a second front / rear wall portion 38 in the first cover member 21.

[0041] Each wall portion (35, 36, 37, 38) protrudes downward from an edge portion (corresponding side portion) of the first lateral wall portion 23. The base end of the first guide wall portion 35 is connected to the rear end of the top plate of the second base portion 21b and to the second rear oblique side portion 30, which is the rear end of the first lateral wall portion upper portion 23a. The base end of the second guide wall portion 36 is connected to the first rear oblique side portion 29.

[0042] With the side cover member 20 fixed to the battery side member 7 and the battery case 4, the first guide wall portion 35 is located rearward of the rear end surface 7a of the battery side member 7 and outward in the vehicle width direction from the rear corner 4x of the battery case 4. The second guide wall portion 36 is located inward in the vehicle width direction from the first guide wall portion 35. A portion of the second guide wall portion 36 is formed so as to overlap with the position of the rear corner 4x of the battery case 4 and the position of the rear inclined portion 5a of the battery undercover 5 in the vehicle width direction.

[0043] A component X1 that protrudes downward from the lower surface 7b of the battery side member 7 is disposed behind the first guide wall portion 35, and another component X2 that protrudes downward from at least the lower surface of the battery case 4 (here, the lower surface 5b of the battery undercover 5) and is different from component X1 is disposed behind the second guide wall portion 36. In the illustrated example, the component X1 behind the first guide wall portion 35 includes at least the rear tire T and the air straightening vane P, and the other component X2 behind the second guide wall portion 36 includes at least the rear suspension 11 and the holding bracket 12.

[0044] In the illustrated example, the distance between the second guide wall portion 36 and the holding bracket 12 is shorter than the distance between the first guide wall portion 35 and the rectifying plate P.

[0045] The first guide wall portion 35 protrudes in a direction different from the protruding direction of the second guide wall portion 36 relative to the lateral wall portion (first lateral wall portion 23). In the illustrated example, the first guide wall portion 35 is located forward of the second guide wall portion 36 in the vehicle longitudinal direction, and protrudes so as to incline rearward from the lateral wall portion (first lateral wall portion 23) toward the lower end of the first guide wall portion 35. In other words, the first guide wall portion 35 inclines rearward from the base end toward the tip end (i.e., the lower end, or further, the rear end). The second guide wall portion 36 protrudes perpendicular to the lateral wall portion (first lateral wall portion 23).

[0046] The length in the extension direction from the base end to the tip (lower end / rear end) of the first guide wall portion 35 is longer than the length in the extension direction from the base end to the tip (lower end) of the second guide wall portion 36. The tip position of the first guide wall portion 35 coincides with the tip position of the second guide wall portion 36 in the up-down direction.

[0047] The guard wall portion 32 is formed from the inner end of the front end (bottom portion 27) of the lateral wall portion (first lateral wall portion 23) in the vehicle width direction toward the outer side in the vehicle width direction, and the formation position of the guard wall portion 32 overlaps at least the formation position of the second guide wall portion 36 in the vehicle width direction. In the illustrated example, the guard wall portion 32 is provided in a portion of the bottom portion 27 (front end of the first lateral wall portion 23) that corresponds to the first lateral wall portion lower portion 23b (more specifically, a portion of the bottom portion 27 that is more inward in the vehicle width direction than the stepped portion 27a). As shown in FIG. 11 , which will be described later, the guard wall portion 32 is provided along the lower surface of the cover upper wall 5a1 of the rear inclined portion 5a of the battery undercover 5.

[0048] The first front-rear wall portion 37 extends forward from the outer end of the first guide wall portion 35 in the vehicle width direction. With the side cover member 20 fixed to the battery side member 7 and the battery case 4, the first front-rear wall portion 37 extends along the edge of the side skirt 8 extending in the front-rear direction. The lower end position (tip position) of the first front-rear wall portion 37 coincides with the lower end position of the side skirt 8 in the up-down direction, or is located lower than the lower end position of the side skirt 8 in the up-down direction. The second front-rear wall portion 38 extends forward from the outer end of the second guide wall portion 36 in the vehicle width direction, and is connected to the inner end of the first guide wall portion 35 in the vehicle width direction.

[0049] The rear end of the first front / rear wall portion 37 is connected to the outer end of the first guide wall portion 35 in the vehicle width direction, the inner end of the first guide wall portion 35 is connected to the front end of the second front / rear wall portion 38, and the rear end of the second front / rear wall portion 38 is connected to the inner end of the second guide wall portion 36 in the vehicle width direction. As a result, the first front / rear wall portion 37, the first guide wall portion 35, the second front / rear wall portion 38, and the second guide wall portion 36 extend continuously. The lower end positions of the first guide wall portion 35, the second front / rear wall portion 38, and the second guide wall portion 36 are aligned in the up / down direction.

[0050] The cross wall portion 24b of the first vertical wall portion 24 protruding upward from the first horizontal wall portion 23 (horizontal wall portion) is disposed between the first guide wall portion 35 and the second guide wall portion 36 in the vehicle width direction. As described above, the cross wall portion 24b is provided with a fixing portion 24d for fixing to the vehicle body side.

[0051] Next, the second cover member 22 and the reinforcing member 10 will be described in detail with reference to FIGS. 4 and 6. The second cover member 22 has a second lateral wall portion 25 extending in the vehicle longitudinal direction and the vehicle width direction, and a second vertical wall portion 26 protruding upward from the upper surface of the second lateral wall portion 25. The base end of the second vertical wall portion 26 is connected to the outer end of the second lateral wall portion 25 in the vehicle width direction. The second cover member 22 has a generally L-shaped cross section and extends generally in the vehicle longitudinal direction. A first connecting hole 26a, which is a through hole, is formed in the front portion of the second vertical wall portion 26. The front portion of the second vertical wall portion 26 is connected to the first vertical wall portion 24 (the fixing portion 24d of the intersecting portion 24b) via the first connecting hole 26a with a fastening member such as a bolt. As a result, the first cover member 21 of the side cover member 20 is fixed to the vehicle body on the retaining bracket 12 side via the fixing portion 24d, the second cover member 22, and the reinforcing member 10.

[0052] The reinforcing member 10 is formed in a generally triangular shape when viewed from above. First, second, and third fixing holes 10a, 10b, and 10c, which are through-holes, are formed at each vertex of the reinforcing member 10, and a fourth fixing hole 10d is formed in the center. A fastening member such as a bolt is inserted into each fixing hole (10a, 10b, 10c). The reinforcing member 10 is fixed to the underside of the rear corner 4x of the battery case 4 by the fastening member such as a bolt. Specifically, the portion of the upper surface of the reinforcing member 10 that faces the second and third fixing holes 10b and 10c is in contact with the underside of the rear corner 4x of the battery case 4. The reinforcing member 10 is then fixed to the underside of the battery case 4 via the fastening members that are inserted into the second and third fixing holes 10b and 10c. A portion of the reinforcing member 10 on the side of the first fixing hole 10a protrudes rearward from the rear end of the battery case 4 and is fixed to the holding bracket 12 via a fastening member inserted into the first fixing hole 10a. A portion of the reinforcing member 10 around the fourth fixing hole 10d is fixed to the first cover member 21 via a fastening member inserted into the fourth fixing hole 10d and a through-hole in the third base portion 21c of the first cover member 21.

[0053] The second cover member 22 is fixed to the upper surface of the reinforcing member 10. In the illustrated example, the second cover member 22 is joined to the upper surface of the reinforcing member 10 by spot welding. The second lateral wall portion 25 is arranged so that the outer end of the second lateral wall portion 25 in the vehicle width direction is generally along the long side portion of the reinforcing member 10 extending in the vehicle front-rear direction. The side of the second cover member 22 in the longitudinal direction where the first connection hole 26a is formed protrudes forward from the reinforcing member 10.

[0054] A portion of the second vertical wall portion 26 of the second cover member 22 on the side of the first connection hole 26a is overlapped with the cross wall portion 24b of the first vertical wall portion 24 of the first cover member 21 from the inner side in the vehicle width direction and is connected to the cross wall portion 24b. As a result, the first wall portion 24a of the first cover member 21 and the second vertical wall portion 26 of the second cover member 22 are connected to extend continuously with each other via the curved portion 24c and the cross wall portion 24b of the first cover member 21. In other words, the first opposing wall portion 20A (in the illustrated example, the first wall portion 24a) and the second opposing wall portion 20B (in the illustrated example, the cross wall portion 24b and the second vertical wall portion 26) are connected to extend continuously with each other.

[0055] Next, with reference to Fig. 2 and Fig. 7A to Fig. 7D, a state in which the side cover member 20 is fixed to the rear end portion of the battery side member 7 and the rear corner portion 4x of the battery case 4 will be described. Fig. 7A to Fig. 7D are enlarged perspective views of essential parts of the vehicle body underbody structure 1 viewed from below, with Fig. 7A showing a state in which the side cover member 20 and the reinforcing member 10 are attached, Fig. 7B showing a state in which the side cover member 20 and the reinforcing member 10 have been removed, Fig. 7C showing a state in which the side cover member 20 has been removed, and Fig. 7D showing a state in which the first cover member 21 has been removed.

[0056] 2 and 7A, the side cover members 20 are fixed to the rear end portions of the battery side members 7 and the rear corners 4x of the battery case 4 via the reinforcing members 10, so that most of the rear end surfaces 7a of the battery side members 7 and most of the undersides of the rear corners 4x of the battery case 4 are covered by the first cover members 21 so as not to be directly exposed to the road surface. As shown in Fig. 7B, when the side cover members 20 and the reinforcing members 10 are removed, the rear end surfaces 7a of the battery side members 7, the undersides of the rear corners 4x of the battery case 4, and the undersides of the holding brackets 12 are exposed to the outside.

[0057] 7C, the reinforcing member 10 is fixed to the lower surface of the holding bracket 12 and also to the lower surface of the rear corner 4x of the battery case 4. As shown in Fig. 7D, the second cover member 22 fixed to the reinforcing member 10 is arranged so as to cover the rear end portion of the left side surface of the battery case 4 (i.e., the left side surface of the rear corner 4x).

[0058] The first vertical wall portion 24 of the first cover member 21 and the second vertical wall portion 26 of the second cover member 22 will be described with reference to Figures 8 to 10. Figure 8 is a cross-sectional view taken along line BB in Figure 2, Figure 9 is a cross-sectional view taken along line CC in Figure 2, and Figure 10 is a perspective view of a cut model taken along line DD in Figure 8.

[0059] 8 to 10 , the first wall portion 24a of the first vertical wall portion 24 of the first cover member 21 faces the vehicle width direction inner portion of the rear end surface 7a of the battery side member 7 and functions as the first opposing wall portion 20A, partially covering the rear end surface 7a of the battery side member 7. As a result, the first cover member 21 (particularly the first opposing wall portion 20A) effectively prevents water and flying stones from entering the rear end surface 7a of the battery side member 7. As described above, the bottom edge portion 27 of the first cover member 21, in the portion corresponding to the battery side member 7 (in other words, the first lateral wall portion upper portion 23a), is aligned along the underside 7b of the battery side member 7 in the vicinity of the rear end surface 7a of the battery side member 7. As a result, the rear end surface 7a of the battery side member 7 is not directly exposed to the road surface. Therefore, the first lateral wall portion 23 of the first cover member 21 more effectively prevents water and flying stones from entering the rear end surface 7a of the battery side member 7.

[0060] The second vertical wall portion 26 of the second cover member 22 faces the side surface of the rear corner 4x of the battery case 4 and functions as the second opposing wall portion 20B, covering the lower portion of the side surface of the rear corner 4x of the battery case 4. As a result, even if high-pressure water or pebbles enter from below through the opening 9 and head toward the battery case 4 during driving or maintenance, the second opposing wall portion 20B effectively prevents water from splashing (water damage) or pebbles from hitting the side surface of the battery case 4. As a result, high-pressure water from splashing or pebbles from hitting the side surface of the battery case 4, where the edge portion (mating surface portion) of the mating surface between the lower case 4a and the upper case 4b is exposed, are effectively prevented from splashing high-pressure water or pebbles from hitting the side surface of the battery case 4, and direct water from splashing or pebbles from hitting the edge portion of the sealant provided between the lower case 4a and the upper case 4b are effectively prevented. This prevents water from entering the interior of the battery case 4, damage to the sealant of the battery case 4, and deterioration of the sealant, thereby maintaining sealing performance. Furthermore, since the opening 9 is allowed to be provided, the undercover (5, 13, 14) can be made lighter than when it covers the entire underside of the vehicle body, and assembly and maintenance can be improved.

[0061] The sealing structure of the battery case 4 can be a general structure in which a sealant is provided between the upper and lower mating surfaces, and the second opposing wall portion 20B can be formed using a cover member (side cover member 20) that protects the rear end surface 7a of the battery side member 7, which serves as an impact absorbing member. Therefore, the vehicle underbody structure 1 can prevent water from getting on the battery case 4 with a simple structure.

[0062] 8, when the mating surface 4c of the lower case 4a is higher than the lower surface 6a of the side sill 6 in the vehicle vertical direction, the upper end of the second opposing wall portion 20B has at least a portion that coincides with the position of the lower surface 6a of the side sill 6 or a portion that is higher than the position of the lower surface 6a of the side sill 6 in the vehicle vertical direction. In the illustrated example, the uppermost end of the second opposing wall portion 20B is approximately aligned with the height position of the mating surface 4c of the lower case 4a. This more effectively prevents water from splashing directly on the edge of the sealing material or pebbles from hitting it.

[0063] The side cover member 20 has a first cover member 21 fixed to the rear end of the battery side member 7 and a second cover member 22 fixed to the rear corner 4x of the battery case 4, with the first opposing wall portion 20A being provided on at least the first cover member 21 and the second opposing wall portion 20B being provided on at least the second cover member 22. This allows the side cover member 20 to be formed separately for the battery side member 7 side and the battery case 4 side, making it easy to optimize the structure of the side cover member 20.

[0064] The first cover member 21 fixed to the rear end of the battery side member 7 is made of resin, and the battery side member 7 is an impact absorbing member in the event of a side collision. This makes it easier for the first cover member 21 to deform together with the battery side member 7 in the event of a side collision, and prevents the first cover member 21 from interfering with the absorption of impact load energy in the event of a side collision.

[0065] The second cover member 22, which is fixed to the rear corner portion 4x of the battery case 4 via the reinforcing member 10, is made of a thin metal plate. This ensures the holding rigidity of the battery case 4 and can protect the battery case 4 from flying stones and the like.

[0066] The first opposing wall portion 20A and the second opposing wall portion 20B are connected to each other so as to extend continuously. This provides a continuous protective wall around the corners, including the rear corners 4x, of the battery case 4 without any gaps. As a result, direct splashing of water on the edges of the sealing material of the battery case 4 and collisions with pebbles are more reliably prevented.

[0067] The first cover member 21 has a first lateral wall portion 23 extending in the vehicle longitudinal direction and the vehicle width direction from the lower end of the first opposing wall portion 20A (first wall portion 24a of the first vertical wall portion 24). The front end of the first lateral wall portion 23 is fixed to the rear end of the battery side member 7 via the first pedestal portion 21a, and the vehicle longitudinal direction intermediate portion of the first lateral wall portion 23 is fixed to the side sill 6 via the second pedestal portion 21b. As a result, the rigidity of the resin first cover member 21 is ensured by the first opposing wall portion 20A (first wall portion 24a) and the first lateral wall portion 23, and the mounting rigidity of the side cover member 20 to the vehicle body 2 is ensured, thereby stabilizing the side cover member 20. As a result, detachment of the side cover member 20 due to splashing of high-pressure water, collision with pebbles, and vibration during driving is reliably suppressed.

[0068] A retaining bracket 12 that retains the tip of an arm 11a of a rear suspension 11 is provided around the rear end of the side sill 6 (inside in the vehicle width direction in the illustrated example). The rear corner 4x of the battery case 4 and the retaining bracket 12 are connected by a plate-shaped reinforcing member 10 that extends in the vehicle longitudinal direction and the vehicle width direction, and the second cover member 22 is fixed to the upper surface of the reinforcing member 10. In other words, the second cover member 22 is fixed to the battery case 4 via the retaining bracket 12 joined to the vehicle body and the reinforcing member 10 that is fixed to the lower surface of the rear corner 4x of the battery case 4. As a result, the second cover member 22, which has a second vertical wall portion 26 that extends in the vehicle vertical direction (vertical direction), is fixed to the reinforcing member 10 that extends in the vehicle longitudinal direction and the vehicle width direction (approximately horizontal direction). As a result, the rigidity of the reinforcing member 10 is further improved, thereby improving the retaining rigidity of the battery case 4 and the rear suspension 11.

[0069] Next, the structure and operation relating to the reduction of air resistance around the rear tire T will be mainly described with reference to Figures 2, 11, 12, etc. Figure 11 is a cross-sectional view taken along line EE shown in Figure 2, and Figure 12 is an enlarged perspective view of the main parts including the side cover member 20 of the vehicle body underbody structure 1 as viewed from below.

[0070] As mentioned above, the rear tire T, the air deflector P, the rear suspension 11, and the retaining bracket 12 are arranged behind the battery side member 7, and the rear tire T and the air deflector P protrude downward from the lower surface 7b of the battery side member 7, and the rear suspension 11 and the retaining bracket 12 protrude downward from the lower surface 5b of the battery undercover 5.

[0071] 11 and 12, the lower ends of the guide wall portions 33 (first guide wall portion 35, second guide wall portion 36) of the first cover member 21 of the side cover member 20 protrude downward from the lower surface 7b of the battery side member 7 and also protrude downward from the lower surface 5b of the battery undercover 5. Therefore, as shown by the thick arrows in FIGS. 11 and 12, air that flows along the lower surface 7b of the battery side member 7 and the lower surface 5b of the battery undercover 5 and reaches the side cover member 20 is blocked by the guide wall portions 33 and directed downward. As a result, air is prevented from flowing into parts or members around the rear tire, such as the rear tire T, the fairing P, the rear suspension 11, and the retaining bracket 12. Therefore, the guide wall portions 33 reduce air resistance caused by the parts or members around the rear tire. Furthermore, the opening 9 is allowed to be provided around the rear tire, the entire underside of the vehicle body does not need to be covered by a complex structure, and the guide wall portion 33 can be formed by utilizing the cover member (side cover member 20) as an impact absorbing member. Therefore, the vehicle body understructure 1 can reduce air resistance around the rear tire with a simple structure.

[0072] In this embodiment, the guide wall portion 33 has a first guide wall portion 35 located rearward of the rear end surface 7a of the battery side member 7 and a second guide wall portion 36 located inward in the vehicle width direction from the first guide wall portion 35. A component X1 (P, T) that protrudes downward from the lower surface 7b of the battery side member 7 is disposed rearward of the first guide wall portion 35, and another component X2 (11, 12) that protrudes downward from at least the lower surface of the battery case 4 and is different from the component X1 is disposed rearward of the second guide wall portion 36. The first guide wall portion 35 protrudes in a direction different from the protruding direction of the second guide wall portion 36 relative to the lateral wall portion (first lateral wall portion 23). As a result, the guide wall portion 33 can individually control and optimize the direction of the air (traveling wind) flow by the first guide wall portion 35 and the second guide wall portion 36 according to the components (X1, X2) that differ in size and shape.

[0073] However, the rear tire T and the air fairing P (component X1) protrude downward significantly compared to the rear suspension 11 and the retaining bracket 12 (component X2), and the area of ​​the protruding portion is also large when viewed in the front-to-rear direction of the vehicle, so air resistance is likely to increase due to the inflow of air that interferes with (collides with) the rear tire T and the air fairing P (component X1). In light of this point, the guide wall portion 33 is configured as follows to effectively reduce air resistance that may occur on the rear tire T side.

[0074] In this embodiment, in order to effectively reduce air resistance on the side of the rear tire T, the first guide wall portion 35 is located forward of the second guide wall portion 36 in the vehicle longitudinal direction and protrudes so as to incline rearward from the lateral wall portion (first lateral wall portion 23) toward the lower end of the first guide wall portion 35, the second guide wall portion 36 protrudes perpendicular to the lateral wall portion (first lateral wall portion 23), the component X1 behind the first guide wall portion 35 includes at least the rear tire T and the air straightening vane P, the other component X2 behind the second guide wall portion 36 includes at least the rear suspension 11 and the holding bracket 12, and the distance between the second guide wall portion 36 and the holding bracket 12 is shorter than the distance between the first guide wall portion 35 and the air straightening vane P. The length of the first guide wall portion 35 in the extension direction from its base end to its tip end is longer than the length of the second guide wall portion 36 in the extension direction from its base end to its tip end. This allows the guide wall portion 33 to guide air further downward in front of the air deflector P and rear tire T while suppressing air resistance generated at the first guide wall portion 35. As a result, air resistance caused by the air deflector P and rear tire T is more effectively reduced on the side of the rear tire T and air deflector P where air resistance is likely to occur. In addition, the second guide wall portion 36 also suppresses air from flowing into the rear suspension 11 and the holding bracket 12, and suppresses the generation of air resistance caused by the rear suspension 11 and the holding bracket 12.

[0075] In this embodiment, the side cover member 20 has a guard wall portion 32 that protrudes upward from the lateral wall portion (first lateral wall portion 23) and extends in the vehicle width direction. The guard wall portion 32 is formed from the inner end of the front end (bottom portion 27) of the lateral wall portion (first lateral wall portion 23) in the vehicle width direction toward the outer side in the vehicle width direction. Therefore, the guard wall portion 32 extends from the inner end of the side cover member 20 in the vehicle width direction, which is the end portion of the side cover member 20 that is fixed to the battery case 4, toward the outer side in the vehicle width direction. In other words, the guard wall portion 32 extends from a portion corresponding to the underside of the rear corner portion 4x of the battery case 4. As a result, as shown in FIG. 11 , even if there is a gap between the side cover member 20 (first lateral wall portion 23) and the battery undercover 5 (cover lower wall 5a2), the gap between the side cover member 20 and the battery undercover 5 is effectively blocked by the guard wall portion 32. As a result, the generation of an upward air flow that would enter the interior of the vehicle through the gap between the side cover member 20 and the battery undercover 5 is effectively suppressed. Therefore, the generation of unnecessary air resistance is suppressed, and a downward air flow is reliably generated. Furthermore, because the formation position of the guard wall portion 32 overlaps with the formation position of at least the second guide wall portion 36 in the vehicle width direction, the guard wall portion 32 promotes the flow toward the second guide wall portion 36, and the air guidance effect of the second guide wall portion 36 can be reliably ensured.

[0076] In this embodiment, the side cover member 20 has a first front-rear wall portion 37 extending forward from the vehicle width direction outer end of the first guide wall portion 35, and a second front-rear wall portion 38 extending forward from the vehicle width direction outer end of the second guide wall portion 36 and connecting to the vehicle width direction inner end of the first guide wall portion 35. The first front-rear wall portion 37 extends along the edge of the side skirt 8 extending in the front-rear direction, and the lower end position of the first front-rear wall portion 37 coincides with the lower end position of the side skirt 8 in the vertical direction or is located lower than the lower end position of the side skirt 8 in the vertical direction. As a result, the first front-rear wall portion 37 and the second front-rear wall portion 38 suppress the generation of air flow in the vehicle width direction in the side cover member 20, and air flow toward the rear of the vehicle toward the first guide wall portion 35 and the second guide wall portion 36 is more reliably generated. As a result, the first guide wall portion 35 and the second guide wall portion 36 more effectively reduce air resistance. In addition, the second front and rear wall portion 38 extends forward from the outer end of the second guide wall portion 36 in the vehicle width direction and connects to the inner end of the first guide wall portion 35 in the vehicle width direction, thereby improving the strength and rigidity of the side cover member 20.

[0077] In this embodiment, the side cover member 20 is disposed between the first guide wall portion 35 and the second guide wall portion 36 in the vehicle width direction, and has a cross wall portion 24b that protrudes upward from the lateral wall portion (first lateral wall portion 23), and the cross wall portion 24b is provided with a portion 24d that is fixed to the vehicle body side. This ensures a holding force for the side cover member 20, stabilizes the posture of the side cover member 20 during travel, and reliably suppresses the occurrence of turbulence in the air flow caused by, for example, tilting of the walls (35, 36, 37, 38, etc.) of the side cover member 20, thereby reliably reducing air resistance.

[0078] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes are possible within the scope of the present invention.

[0079] For example, although not shown, if the position of the mating surface 4c of the lower case 4a relative to the upper case 4b is lower than the position of the lower surface 6a of the side sill 6 in the vertical direction of the vehicle, the upper end of the second opposing wall portion 20B may have at least a portion that coincides with the position of the mating surface 4c of the lower case 4a or a portion that is higher than the position of the mating surface 4c in the vertical direction of the vehicle. This similarly more effectively prevents water from splashing directly on the edge of the sealing material or pebbles from hitting it.

[0080] Furthermore, in the vehicle shown in the figure, the underside of the battery case 4 is covered by the battery undercover 5, but there are cases where the underside of the battery case 4 is not covered by the battery undercover 5. In this case, the lower ends of the guide wall portions 33 (first guide wall portion 35, second guide wall portion 36) only need to protrude downward from the underside 7b of the battery side member 7 and from the underside of the battery case 4. [Explanation of symbols]

[0081] 1 Underbody structure 2. Body 3 Floor panel (floor section) 4 Battery case 4a Lower case 4b Upper case 4c Mating surface 4x rear corners 5 Battery under cover 5a Back slope 5a1 Cover upper wall 5a2 Cover bottom wall 5b Bottom side 6 Side sill 6a Bottom side 7 Battery side member 7a Rear end surface 7b Bottom side 8 Side Skirts 9 aperture 10 Reinforcement member 10a 1st fixing hole 10b 2nd fixing hole 10c 3rd fixing hole 10d 4th fixing hole 11 Rear suspension 11a Arm 12 Retaining bracket 13 Rear under cover 14 Rear floor cover 15 Side sill bracket 20 Side cover member 20A First opposing wall 20B 2nd opposing wall 21 first cover member 21a First base 21b Second pedestal 21c Third pedestal 21d 4th pedestal 22 second cover member 23 First side wall (side wall) 23a Upper part of the first side wall 23b Lower part of 1st side wall 24 1st vertical wall section 24a 1st wall 24b Cross wall 24c curved section 24d Fixed part 25 Second side wall 26 2nd vertical wall section 26a First connection hole 27 Bottom 27a Step 28 First outer hypotenuse 29 First rear oblique side 30 Second rear oblique side 31 Second outer oblique side 32 Guard wall 33 Guide wall 35 First guide wall 36 Second guide wall 37 First front and rear walls 38 2nd front and rear walls H Rear wheel house P rectifier plate T Rear tire X1 Parts X2 Other parts

Claims

1. A vehicle body underbody structure including: a battery case disposed under a floor portion of a vehicle; and a side sill extending in a front-rear direction of the vehicle along a vehicle width direction outer portion of the floor portion, a battery side member extending in the vehicle front-rear direction on the outer side of the battery case in the vehicle width direction and connecting the battery case and the side sill; a side cover member fixed to a rear end portion of the battery side member and a rear corner portion of the battery case; Including, The side cover member has a lateral wall portion extending parallel to a lower surface of the battery case, and a guide wall portion protruding downward from a rear end of the lateral wall portion and extending in a vehicle width direction, a lower end of the guide wall portion protruding downwardly from a lower surface of the battery side member and from a lower surface of the battery case or a lower surface of a battery undercover covering the lower surface of the battery case.

2. the guide wall portion includes a first guide wall portion located rearward of a rear end surface of the battery side member, and a second guide wall portion located inward in the vehicle width direction of the first guide wall portion, a component that protrudes downward beyond a lower surface of the battery side member is disposed behind the first guide wall portion, and another component that protrudes downward beyond at least a lower surface of the battery case and is different from the component is disposed behind the second guide wall portion, The vehicle underbody structure according to claim 1 , wherein the first guide wall portion protrudes in a direction different from a direction in which the second guide wall portion protrudes relative to the lateral wall portion.

3. the first guide wall portion is located forward of the second guide wall portion in the vehicle longitudinal direction, and protrudes in a manner inclined rearward from the lateral wall portion toward a lower end of the first guide wall portion, the second guide wall portion protrudes perpendicular to the lateral wall portion, the component behind the first guide wall portion includes at least a rear tire and a straightening vane attached to a front lower end of a rear wheel housing that covers the rear tire from above and extends downward; the other components behind the second guide wall portion include at least a rear suspension and a holding bracket that holds a tip end of an arm of the rear suspension, a separation distance between the second guide wall portion and the holding bracket is shorter than a separation distance between the first guide wall portion and the rectifying plate; The vehicle underbody structure according to claim 2 , wherein a length from a base end to a tip end of the first guide wall portion in an extension direction is longer than a length from a base end to a tip end of the second guide wall portion in an extension direction.

4. The side cover member has a guard wall portion that protrudes upward from a front end of the lateral wall portion and extends in the vehicle width direction, the guard wall portion is formed from an inner end of a front end of the lateral wall portion in the vehicle width direction toward an outer side in the vehicle width direction, The vehicle underbody structure according to claim 2 , wherein a position where the guard wall portion is formed overlaps at least a position where the second guide wall portion is formed in the vehicle width direction.

5. A side skirt extending in the front-rear direction of the vehicle is provided on the outer side of the side sill in the vehicle width direction, the side cover member has a first front / rear wall portion extending forward from a vehicle width direction outer end of the first guide wall portion, and a second front / rear wall portion extending forward from the vehicle width direction outer end of the second guide wall portion and connected to a vehicle width direction inner end of the first guide wall portion, The first front and rear wall portions extend along edges of the side skirts extending in the front-rear direction, 3. The vehicle body understructure according to claim 2, wherein a lower end position of the first front and rear wall portions is aligned with a lower end position of the side skirt in the vertical direction or is positioned lower than the lower end position of the side skirt in the vertical direction.

6. the side cover member is disposed between the first guide wall portion and the second guide wall portion in the vehicle width direction and has a cross wall portion protruding upward from the lateral wall portion, The vehicle underbody structure according to claim 2 , wherein the cross wall portion is provided with a fixing portion for fixing to the vehicle body side.

Images