Vehicle body lower part structure

Abstract

To reduce influence of an input load on a joined state of fixing parts when a seat belt anchor fixing part and a seat rear fixing part are located close to each other.SOLUTION: In a vehicle body lower part structure 1, a seat belt anchor fixing part 1C is located around a seat rear fixing part 1A reinforced by a seat bracket 20. The vehicle body lower part structure 1 includes: an anchor reinforcement 30 which extends in a front-back direction in front of the seat rear fixing part 1A, has the seat belt anchor fixing part 1C, and is joined to an upper surface of a floor panel 10; and a rear reinforcement 40 which extends in the front-back direction behind the seat rear fixing part 1A. The seat bracket 20 is joined to the floor panel 10 and joined to a rear part of the anchor reinforcement 30 and a front part of the rear reinforcement 40. Rigidity of a metal plate for forming the anchor reinforcement 30 and the rear reinforcement 40 is higher than rigidity of a metal plate for forming the seat bracket 20.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

[0002] A seat belt anchor fixing portion to which a seat belt anchor that supports a seat belt is fixed and a seat rear fixing portion to which a rear portion of the seat, such as a rear portion of a slide rail, is fixed are provided near the seat in the lower part of the vehicle body. A load that pulls each fixing portion forward and diagonally upward may act on each of the seat belt anchor fixing portion and the seat rear fixing portion. For this reason, in order to reinforce each fixing portion, a reinforcing member such as a reinforcement (also called a retainer) is often joined to each fixing portion by spot welding.

[0003] One example of a vehicle underbody structure having a reinforced seatbelt anchor fixing portion and a seat rear fixing portion is disclosed in Patent Document 1. In the structure disclosed in Patent Document 1, a seatbelt anchor retainer is welded to the underside of a floor panel at a location corresponding to the seatbelt anchor fixing portion, and the seatbelt anchor is fastened together with the floor panel by a bolt at the longitudinal center of the retainer. A hat-shaped cross member is welded to the underside of the floor panel at a location corresponding to the seat rear fixing portion, and the rear end of the slide rail can be fastened by a bolt to the closed cross-section formed by the cross member and the floor panel. In the structure disclosed in Patent Document 1, the retainer has a pair of stiffening members extending in the front-rear direction, sandwiching the fastening point to the floor panel by the bolt. The rear end of the retainer is welded to the underside of a flange of the cross member welded to the underside of the floor panel. The retainer is further welded to the underside of the floor panel in a region between the welding point to the cross member flange and the rear end of the stiffening member.

[0004] The structure disclosed in Patent Document 1 has the above configuration, and is intended to prevent separation of the spot weld between the rear end of the retainer and the flange of the cross member when a load is applied to the floor panel upward in the vehicle body, causing the fastening point of the retainer to the floor panel (in other words, the seat belt anchor fixing portion) to move upward and deform, causing the rear end of the rigidity reinforcement portion to lift the floor panel upward.In the structure disclosed in Patent Document 1, the seat belt anchor fixing portion (the fastening point of the retainer to the floor panel) is provided in the longitudinal center of the retainer, and the seat belt anchor fixing portion and the seat rear fixing portion (the fastening point of the rear end of the slide rail to the closed cross-sectional portion) are sufficiently separated from each other. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-218519 Summary of the Invention [Problem to be solved by the invention]

[0006] In some cases, the seat belt anchor fixing portion is disposed in front of and around the seat rear fixing portion in the lower part of the vehicle body, and the seat belt anchor fixing portion and the seat rear fixing portion, which are load input points, are disposed close to each other. In such cases, in order to suppress deformation of the floor panel or the like due to the input load, it is conceivable to increase rigidity by welding reinforcing members such as retainers and cross members to the seat belt anchor fixing portion and the seat rear fixing portion, as in Patent Document 1. However, in a layout in which the seat belt anchor fixing portion and the seat rear fixing portion are disposed close to each other, the rigidity of each fixing portion is increased by the reinforcing members, which may cause stress to concentrate around each fixing portion (seat belt anchor fixing portion, seat rear fixing portion), resulting in greater than expected deformation of the floor panel or the like and possibly affecting the joining condition of the fixing portions.

[0007] Therefore, the present invention aims to provide a vehicle lower body structure having a structure that can reduce the effect of the input load on the joining state of the fixing parts, even if the seat belt anchor fixing part and the seat rear fixing part are arranged close to each other. [Means for solving the problem]

[0008] In order to achieve the above object, according to one aspect of the present invention, there is provided a vehicle underbody structure including a floor panel disposed under a vehicle body and having a seat rear fixing portion, and a seat bracket reinforcing the seat rear fixing portion, wherein a seat belt anchor fixing portion is disposed in the underbody forward of the seat rear fixing portion and around the seat rear fixing portion, the vehicle underbody structure including an anchor force extending in the fore-and-aft direction of the vehicle forward of the seat rear fixing portion and having the seat belt anchor fixing portion and joined to an upper surface of the floor panel, and a rear reinforcement extending in the fore-and-aft direction of the vehicle rear of the seat rear fixing portion, the seat bracket joined to the floor panel and joined to a rear portion of the anchor force and a front portion of the rear reinforcement so as to bridge the gap between the anchor force and the rear reinforcement, and the rigidity of the metal plate material constituting each of the anchor force and the rear reinforcement is higher than the rigidity of the metal plate material constituting the seat bracket. [Effects of the Invention]

[0009] According to one aspect of the present invention, it is possible to provide a vehicle lower body structure having a structure that can reduce the effect of input load on the joining state of the fixing parts, even if the seat belt anchor fixing part and the seat rear fixing part are arranged close to each other. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view of a vehicle underbody structure according to an embodiment of the present invention; [Figure 2] FIG. [Figure 3] FIG. 2 is an enlarged top view of a main part of the vehicle body underbody structure. [Figure 4] FIG. 2 is a perspective view of a main part of the vehicle body underbody structure. [Figure 5] FIG. 2 is a perspective view of a portion of the vehicle body understructure including a seat bracket, as viewed from below. [Figure 6] FIG. 4 is a cross-sectional view taken along line AA shown in FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a perspective view of a vehicle underbody structure 1 according to one embodiment of the present invention, Fig. 2 is a partial bottom view of the vehicle underbody structure 1, Figs. 3 and 4 are views showing essential parts of the vehicle underbody structure 1, Fig. 3 is an enlarged top view, and Fig. 4 is a perspective view. In the drawings, the arrow Fr direction indicates the front in the vehicle longitudinal direction, the arrow O direction indicates the outside of the vehicle in the vehicle width direction, and the arrow U direction indicates the up in the vehicle vertical direction. In the following description, "front" and "rear" correspond to the front and rear in the vehicle longitudinal direction, "up" and "down" correspond to the up and down in the vehicle vertical direction, and "left" and "right" correspond to the left and right in the vehicle width direction when a vehicle occupant is facing forward of the vehicle. In Fig. 3, a seat main body S1 (described later) has been removed, and a fixed rail S2a of a seat rail S2 (described later) is shown by a two-dot chain line. In Fig. 4, a seat S and a seat belt anchor S3 (described later) have been removed.

[0012] (Outline of the underbody structure) 1 to 4, the vehicle underbody structure 1 includes a floor panel 10, a seat bracket 20, an anchoring force 30, a rear reinforcement force 40, a rear side member 50, a side sill 60, a cross member 70, and a brace 80. The vehicle underbody structure 1 of this embodiment is applied to the structure of the underbody of an electric vehicle powered by a power supply unit.

[0013] The floor panel 10 is a panel member disposed under the vehicle body and constituting the floor portion of the vehicle body, and is made of a metal plate material. The floor panel 10 is a plate-shaped member extending from the lower front portion of the vehicle compartment to the rear portion of the vehicle body. The widthwise dimension of the floor panel 10 corresponds approximately to the widthwise dimension of the vehicle body. The floor panel 10 has a main floor panel 10A and a rear floor panel 10B that has a width shorter than the widthwise width of the main floor panel 10A and extends rearward from the rear edge of the main floor panel 10A. In the illustrated example, the front edge of the rear floor panel 10B is joined to the upper surface of the rear edge of the main floor panel 10A.

[0014] A seat S is arranged on the floor panel 10. In this embodiment, the seat S is arranged on the main floor panel 10A. The seat S has a seat body S1 on which an occupant sits and a seat rail S2 that supports the seat body S1 from below. The seat rail S2 extends in the front-to-rear direction of the vehicle between the seat body S1 and the floor panel 10 and is a member that supports the seat body S1 from below so that the seat body S1 can slide in the front-to-rear direction of the vehicle. The seat rail S2 has a fixed rail S2a fixed to the vehicle body side and a movable rail S2b fixed to the bottom of the seat body S1 and attached to the fixed rail S2a so as to be slidable along the fixed rail S2a.

[0015] In the illustrated example, the rear end of the seat rail S2 protrudes rearward relative to the rear of the seat body S1, and the front end of the seat rail S2 is generally located below the front of the seat body S1.

[0016] 1, 3 and 4, the vehicle body understructure 1 is provided at its lower part with a seat rear fixing portion 1A to which the rear end of the fixed rail S2a of the seat rail S2 is fixed, a seat front fixing portion 1B to which the front end of the fixed rail S2a of the seat rail S2 is fixed, and a seat belt anchor fixing portion 1C to which a seat belt anchor S3 is fixed that supports a seat belt (not shown) that protects an occupant seated in the seat S.

[0017] The seat rear fixing portion 1A is provided on the floor panel 10 (main floor panel 10A), and the seat front fixing portion 1B and the seat belt anchor fixing portion 1C are provided on the anchoring force 30. Therefore, the floor panel 10 (main floor panel 10A) has the seat rear fixing portion 1A, and the anchoring force 30 has the seat front fixing portion 1B and the seat belt anchor fixing portion 1C. In other words, the seat rear fixing portion 1A is a fixing portion on the floor panel 10 to which the rear of the seat S is fixed, the seat front fixing portion 1B is a fixing portion on the lower part of the vehicle body (anchor force 30) to which the rear of the seat S is fixed, and the seat belt anchor fixing portion 1C is a fixing portion on the lower part of the vehicle body (anchor force 30) to which the seat belt anchor S3 is fixed.

[0018] The seat bracket 20 is a reinforcing member that reinforces the seat rear fixing portion 1A of the floor panel 10. The seat bracket 20 is joined to the floor panel 10. The seat bracket 20 is formed by performing processing such as press forming on a metal plate material. The seat bracket 20 is joined to the floor panel 10 from the outside of the vehicle compartment by spot welding. In other words, the seat bracket 20 is joined to the underside of the seat rear fixing portion 1A of the floor panel 10. The shape of the seat bracket 20 will be described in detail later.

[0019] The anchoring force 30 is a member that extends in the longitudinal direction of the vehicle in front of the seat rear fixing portion 1A and has a seat belt anchor fixing portion 1C. The anchoring force 30 is formed by processing a metal plate material such as press molding. The anchoring force 30 is formed with high rigidity and reinforces the seat belt anchor fixing portion 1C in the lower part of the vehicle body.

[0020] The anchoring force 30 is disposed on the interior side of the vehicle with respect to the floor panel 10, and is joined to the floor panel 10 (main floor panel 10A) by being spot welded to the upper surface of the floor panel 10.

[0021] 3 and 4, the floor panel 10 (main floor panel 10A) is formed so that, in a vertical view of the vehicle, the portion corresponding to the seat rear fixing portion 1A gradually widens outward in the vehicle width direction toward the front of the vehicle, and then bulges outward in the vehicle width direction significantly in the portion beyond the seat belt anchor fixing portion 1C. The anchoring force 30 has an outer shape that matches the shape of the outer side of the floor panel 10 in the vertical view of the vehicle, is disposed so as to overlap the upper surface of the floor panel 10, and extends in the front-to-rear direction of the vehicle. In other words, the anchoring force 30 is formed so that, in a vertical view of the vehicle, the portion corresponding to the seat belt anchor fixing portion 1C gradually widens outward in the vehicle width direction toward the front of the vehicle, and then bulges outward in the vehicle width direction significantly in the portion beyond the seat belt anchor fixing portion 1C. The inner edge of the anchoring force 30 in the vertical direction extends slightly diagonally so as to move away from the center of the vehicle width direction of the vehicle body as it moves toward the front of the vehicle.

[0022] The seat rear fixing portion 1A is set near the rear of the seat S on the floor panel 10 and near the outer edge of the floor panel 10 in the vehicle width direction. In relation to the anchoring force 30, the seat rear fixing portion 1A is adjacent to the rear end of the anchoring force 30 and rearward of the rear end of the anchoring force 30. In the illustrated example, the rear end of the fixing rail S2a is fastened to the seat rear fixing portion 1A using a rail fastening bolt B, thereby attaching and fixing the rear of the seat S to the floor panel 10.

[0023] The seat front fixing portion 1B is provided in the front part of the anchoring force 30. Specifically, the seat front fixing portion 1B is provided in the vehicle width direction inner portion of the front part of the anchoring force 30. In the illustrated example, a fixed rail front end support S4 is attached to the seat front fixing portion 1B by a fastener such as a bolt not shown, and the front end of the fixed rail S2a is fastened to the upper wall of the fixed rail front end support S4 using bolt B, thereby attaching and fixing the front part of the seat S to the front part of the anchoring force 30 via the fixed rail front end support S4.

[0024] The seat belt anchor fixing portion 1C is provided at the rear of the anchoring force 30. Specifically, the seat belt anchor fixing portion 1C is provided at a portion of the rear of the anchoring force 30 that is on the outer side in the vehicle width direction. In this way, the seat belt anchor fixing portion 1C is arranged in the lower part of the vehicle body, forward of the seat rear fixing portion 1A and around the seat rear fixing portion 1A. In the illustrated example, the seat belt anchor fixing portion 1C and the seat rear fixing portion 1A are arranged close to each other. Furthermore, when viewed from above the vehicle, the seat belt anchor fixing portion 1C is provided at a position close to the seat rear fixing portion 1A and between the seat rear fixing portion 1A and the seat front fixing portion 1B in the fore-and-aft direction of the vehicle. In the illustrated example, the seat belt anchor S3 is attached and fixed to the anchoring force 30 by fastening the seat belt anchor fixing portion 1C using an anchor fastening bolt B.

[0025] The rear reinforcement 40 extends in the longitudinal direction of the vehicle rearward of the seat rear fixing portion 1A. The rear reinforcement 40 is made of a metal plate material that extends along the outer edge of the floor panel 10 in the vehicle width direction. The floor panel 10 is formed so that a portion rearward of the seat rear fixing portion 1A is cut out inward in the vehicle width direction by an amount that roughly corresponds to the seat rear fixing portion 1A. The rear reinforcement 40 extends along the upper surface of the outer edge of the vehicle width direction of the portion of the floor panel 10 rearward of the seat rear fixing portion 1A (i.e., the rear floor panel 10B in the illustrated example), and is joined to the floor panel 10 by spot welding.

[0026] The rear reinforcement 40 has a reinforcement main body 41 extending in the fore-and-aft direction of the vehicle, a reinforcement inner flange 42 extending along the inner edge of the reinforcement main body 41 in the vehicle width direction, and a reinforcement vertical wall 43 extending upward from the outer edge of the reinforcement main body 41 in the vehicle width direction.

[0027] The front edge of the reinforcement main body 41 is joined by spot welding to the upper surface of the vehicle width direction outer portion of the rear edge of the main floor panel 10A of the floor panel 10. The reinforcement inner flange 42 is joined by spot welding to the upper surface of the vehicle width direction outer edge of the rear floor panel 10B of the floor panel 10. In the illustrated example, the vehicle width direction outer edge of the rear floor panel 10B is sandwiched between the reinforcement inner flange 42 and a side member inner flange 53 (described later) of the rear side member 50, and the vehicle width direction outer edge of the rear floor panel 10B, the reinforcement inner flange 42, and the side member inner flange 53 are welded in a triple layer. The reinforcement vertical wall 43 is joined by spot welding to the upper part of the inner surface of a side member outer wall 54 (described later) of the rear side member 50.

[0028] The rear side member 50 is a member that extends in the fore-and-aft direction of the vehicle along the rear reinforcement 40 below the rear reinforcement 40. The rear side member 50 is formed by processing a metal plate material such as by press forming. The rear side member 50 is a member that extends along the outer edge of the floor panel 10 in the vehicle width direction at the rear of the side of the vehicle body, and constitutes part of the vehicle body structural member.

[0029] In the front portion of the vehicle body understructure 1 outside the illustrated range, front side members extending forward of the vehicle are provided on both sides in the vehicle width direction, but the rear side members 50 are not formed to be continuous with these front side members. In the vehicle body understructure 1, the side members are not continuous from the front to the rear of the vehicle body, which can reduce the impact performance of the side members, so the anchoring force 30 also serves as a member to compensate for the reduction in impact performance due to the discontinuity of the side members. In other words, the anchoring force 30 not only functions to reinforce the portion of the vehicle underbody where the seat belt anchor S3 is fixed, but also functions as a vehicle body structural member to satisfy impact performance.

[0030] The rear side member 50 has a rear side member main body portion 50A that fits along the rear reinforcement 40, and a protruding portion 50B that protrudes forward of the vehicle from the front end of the rear reinforcement 40 so as to cover the seat bracket 20 from below. In other words, when divided in the vehicle longitudinal direction, the rear side member 50 is made up of the rear side member main body portion 50A and the protruding portion 50B. In the illustrated example, the protruding portion 50B protrudes forward to a position that exceeds the lower position of the seat belt anchor S3 (seat belt anchor fixing portion 1C).

[0031] The rear side member 50 has a side member bottom wall 51 located below the rear reinforcement 40, a side member inner wall 52 extending upward from the inner end of the side member bottom wall 51 in the vehicle width direction, a side member inner flange 53 extending inward in the vehicle width direction from the upper end of the side member inner wall 52, and a side member outer wall 54 extending upward from the outer end of the side member bottom wall 51 in the vehicle width direction.

[0032] In the illustrated example, the side member outer wall 54 of the rear side member 50 extends along the outer surface of the reinforcement vertical wall 43 of the rear reinforcement 40, the outer surface of a bracket vertical wall 24 (described later) of the seat bracket 20, the outer surface of a panel outer wall 15 (described later) of the main floor panel 10A, and the outer surface of an anchoring force vertical wall 34 (described later) of the anchoring force 30. The side member outer wall 54 is joined to the reinforcement vertical wall 43, the bracket vertical wall 24, the panel outer wall 15, and the anchoring force vertical wall 34 by spot welding.

[0033] The side sill 60 extends in the fore-and-aft direction of the vehicle along the outer edge of the main floor panel 10A in the vehicle width direction and the outer edge of the anchoring force 30 in the vehicle width direction, and is joined to the main floor panel 10A and the anchoring force 30 by spot welding. The side sill 60 is formed by processing a metal plate material, such as press forming. A side sill vertical wall 61 on the outer side of the side sill 60 in the vehicle width direction is joined to the outer surface of the rear end of the side member outer wall 54 of the protruding portion 50B of the rear side member 50 by spot welding.

[0034] The cross member 70 is located below the floor panel 10 and extends in the vehicle width direction at a position corresponding to the seat belt anchor fixing portion 1C in the vehicle longitudinal direction. The cross member 70 is a member that constitutes part of the vehicle body structural member that is along the underside of the main floor panel 10A, and extends in the vehicle width direction so as to bridge the left and right rear side members 50. The cross member 70 is formed into a hat-shaped cross section by processing a metal plate material using press forming or the like. In the illustrated example, the cross member 70 is formed in sections in the vehicle width direction, but this is not limited to this, and it may also be formed as a single unit across the entire vehicle width direction.

[0035] The cross member 70 is joined to the underside of the main floor panel 10A by spot welding. The rear portion of the side sill 60 is joined to the vehicle width direction end of the cross member 70 from the outside of the vehicle width direction by spot welding. In other words, the cross member 70 has an end portion joined to the side sill 60. The front portion of the rear side member 50 is formed to cover the vehicle width direction end of the cross member 70 from below and behind, and is joined to the cross member 70 by spot welding. The vehicle width direction end of the cross member 70 and the main floor panel 10A are sandwiched between the rear portion of the anchoring force 30 and the front portion of the rear side member 50. Therefore, the rear portion of the anchoring force 30 and the front portion of the rear side member 50 are connected via the main floor panel 10A and the cross member 70.

[0036] The brace 80 extends forward from the front of the rear side member 50. The brace 80 is formed to partially cover the front of the rear side member 50, the rear of the side sill 60, and the end of the cross member 70 in the vehicle width direction from below the vehicle, and is joined to the floor panel 10, the rear side member 50, the side sill 60, and the cross member 70 by spot welding.

[0037] The brace 80 has a brace main body 81 that bulges downward in the vehicle, a brace inner flange 82 that extends inward in the vehicle width direction from the inner edge of the brace main body 81 in the vehicle width direction, a brace outer flange 83 that extends outward in the vehicle width direction from the outer edge of the brace main body 81 in the vehicle width direction, and a brace rear flange 84 that extends rearward from the rear edge of the brace main body 81.

[0038] The brace inner flange 82 is joined to the main floor panel 10A and the cross member 70, the brace outer flange 83 is joined to the rear of the side sill 60, and the brace rear flange 84 is joined to the front of the side member bottom wall 51 of the rear side member 50 and the cross member 70.

[0039] (Details of the underbody structure) Next, the detailed structure of the main parts of the vehicle body understructure 1 will be described with reference to Figures 1 to 6. Figure 5 is a perspective view of a portion of the vehicle body understructure 1 including the seat bracket 20, as viewed from below, and Figure 6 is a cross-sectional view taken along line AA shown in Figure 3. In Figure 5, the rear side members 50, side sills 60, cross members 70, and braces 80 are omitted from the illustration.

[0040] Referring to Figures 5 and 6, the seat bracket 20 is joined to the floor panel 10 and is also joined to the rear of the anchoring force 30 and the front of the rear reinforcement 40 so as to bridge the gap between the anchoring force 30 and the rear reinforcement 40.

[0041] Specifically, the front edge of the seat bracket 20 overlaps the underside of the main floor panel 10A in front of and near the seat rear fixing portion 1A, the rear edge of the anchoring force 30 overlaps the upper surface of the main floor panel 10A at a position corresponding to the front edge of the seat bracket 20, and the front edge of the seat bracket 20, the rear edge of the anchoring force 30, and the main floor panel 10A are joined in a three-layer configuration by spot welding. The rear edge of the seat bracket 20 overlaps the underside of the rear edge of the main floor panel 10A, and the front edge of the reinforcement body 41 of the rear reinforcement 40 overlaps the upper surface of the rear edge of the main floor panel 10A, and the rear edge of the seat bracket 20, the front edge of the reinforcement body 41, and the rear edge of the main floor panel 10A are joined in a three-layer configuration by spot welding. The seat bracket 20 has its front edge joined to the rear edge of the anchoring force 30 via the main floor panel 10A, and its rear edge joined to the front edge of the rear reinforcement 40 via the main floor panel 10A, thereby bridging the gap between the anchoring force 30 and the rear reinforcement 40 from front to back.

[0042] In the vehicle body lower structure 1, the rigidity of the metal plate material constituting each of the anchoring force 30 and the rear reinforcement 40 is higher than the rigidity of the metal plate material constituting the seat bracket 20. For example, the metal plate material used for the anchoring force 30 and the rear reinforcement 40 is a high-tensile steel plate, and the metal plate material used for the seat bracket 20 is an ordinary steel plate having a tensile strength lower than that of the high-tensile steel plate. Note that, for example, the rear side member 50, the side sill 60, the cross member 70, and the brace 80 are each made of a high-tensile steel plate like the anchoring force 30 and the rear reinforcement 40, and the floor panel 10 is made of an ordinary steel plate like the seat bracket 20.

[0043] In this embodiment, the main floor panel 10A of the floor panel 10 has a bent portion 11 that bends downward in the vehicle front relative to the seat rear fixing portion 1A. In the illustrated example, the main floor panel 10A also has a rear bent portion 12 that bends downward in the vehicle rear relative to the seat rear fixing portion 1A.

[0044] The seat rear fixing portion 1A of the main floor panel 10A is provided between the bent portion 11 and the rear bent portion 12. The seat rear fixing portion 1A has a width slightly wider than the width of the fixing rail S2a of the seat rail S2, and is formed as a wall extending horizontally so as to connect the bent portion 11 and the rear bent portion 12. A bolt insertion hole 13 is opened in the seat rear fixing portion 1A, through which a bolt B for fastening the seat is inserted.

[0045] In this embodiment, the main floor panel 10A of the floor panel 10 has a bead portion 14 that extends to surround the seat rear fixed portion 1A. In the illustrated example, the bead portion 14 bulges outward from the vehicle. When viewed from above the vehicle, the bead portion 14 extends in a groove shape (U-shape) that is open forward and surrounds the seat rear fixed portion 1A (in other words, the rear end of the fixed rail S2a) from the rear. In other words, the bead portion 14 is made up of an inner bead portion 14a that extends in the front-rear direction on the inner side in the vehicle width direction, an outer bead portion 14b that extends in the front-rear direction on the outer side in the vehicle width direction, and a horizontal bead portion 14c that connects the rear end of the inner bead portion 14a to the rear end of the outer bead portion 14b.

[0046] In the illustrated example, the main floor panel 10A has a panel outer wall 15 that extends upward in the vehicle in a range corresponding to the seat rear fixing portion 1A and the seat belt anchor fixing portion 1C at the outer edge in the vehicle width direction.

[0047] The front portion of the seat bracket 20 is bent to fit along the bent portion 11 of the floor panel 10. A bolt insertion hole that communicates with the bolt insertion hole 13 of the seat rear fixing portion 1A is formed in the center of the seat bracket 20. A bolt B for fastening the seat is inserted from above through the bolt insertion hole formed in the rear end of the fixing rail S2a, the bolt insertion hole 13 of the seat rear fixing portion 1A, and the bolt insertion hole of the seat bracket 20, and is screwed into a weld nut N on the underside of the seat bracket 20. This fastens and fixes the rear end of the fixing rail S2a to the seat rear fixing portion 1A.

[0048] In the illustrated example, the seat bracket 20 has a bracket main body 21 having a flat portion 21a, an inner bulge portion 21b, and an outer bulge portion 21c. The seat bracket 20 further has a bracket rear flange 22 extending rearward from the rear edge of the bracket main body 21, a bracket inner flange 23 extending inward in the vehicle width direction from an inner edge of the bracket main body 21 in the vehicle width direction, and a bracket vertical wall 24 extending upward in the vehicle direction from a part of the outer edge of the bracket main body 21 in the vehicle width direction.

[0049] In this embodiment, the seat bracket 20 is joined to the floor panel 10 (main floor panel 10A) and the anchoring force 30 at the front of the vehicle relative to the front bent portion 11. Specifically, the front edge of the bracket body 21 overlaps the underside of the front part of the bent portion 11 of the main floor panel 10A and is joined together with the rear edge of the anchoring force 30 in a three-layer configuration by spot welding.

[0050] In the illustrated example, the flat portion 21a of the bracket main body 21 abuts against the underside of the seat rear fixing portion 1A of the floor panel 10, extends in the front-rear direction, and is joined to the underside of the seat rear fixing portion 1A by spot welding. Each bulge portion (21b, 21c) bulges upward in the vehicle. The inner bulge portion 21b extends in the front-rear direction along the inner portion of the flat portion 21a in the vehicle width direction, fits into the inner bead portion 14a from below, and is joined to the underside of the inner bead portion 14a by spot welding. The outer bulge portion 21c extends in the front-rear direction along the outer portion of the flat portion 21a in the vehicle width direction, fits into the outer bead portion 14b from below, and is joined to the underside of the outer bead portion 14b by spot welding.

[0051] The seat bracket 20 is joined to the floor panel 10 (main floor panel 10A) and the rear reinforcement 40 at the rear of the vehicle relative to the rear bent portion 12. Specifically, the bracket rear flange 22 overlaps the underside of the rear portion (rear edge) of the rear bent portion 12 of the main floor panel 10A, and is joined together with the front edge of the rear reinforcement 40 in a three-layer configuration by spot welding.

[0052] 2, 4, and 5, in this embodiment, the seat bracket 20 is joined to the protruding portion 50B of the rear side member 50. Specifically, the bracket inner flange 23 is sandwiched between the lower surface of the portion of the inner bead portion 14a of the main floor panel 10A that is along the inner side in the vehicle width direction and the upper surface of the side member inner flange 53 of the rear side member 50, and the bracket inner flange 23, the main floor panel 10A, and the side member inner flange 53 are joined in a three-layer configuration by spot welding. Furthermore, the bracket vertical wall 24 is sandwiched between the outer surface of the panel outer wall 15 of the main floor panel 10A and the inner surface of the side member outer wall 54 of the rear side member 50, and the bracket vertical wall 24, the panel outer wall 15, and the side member outer wall 54 are joined in a three-layer configuration by spot welding. In addition, at the front edge of the rear reinforcement 40, the panel outer wall 15 is sandwiched between the reinforcement vertical wall 43 and the side member outer wall 54, and the front edge of the reinforcement vertical wall 43, the rear edge of the panel outer wall 15, and the side member outer wall 54 are joined in a three-layer configuration by spot welding.

[0053] 5 and 6, in this embodiment, a reinforcing shape portion 25 that bulges in the vehicle vertical direction is formed in a portion of the seat bracket 20 that is located rearward of the vehicle relative to the portion (flat portion 21a) facing the seat rear fixing portion 1A. The reinforcing shape portion 25 of the seat bracket 20 and the bead portion 14 of the floor panel 10 are arranged so as to partially overlap each other vertically. In the illustrated example, the reinforcing shape portion 25 is continuous with the rear portion of the flat portion 21a in the bracket main body 21. The reinforcing shape portion 25 bulges downward so as to be spaced downward from the horizontal bead portions 14c of the bead portion 14. As shown in FIG. 6, a gap is intentionally provided between the horizontal bead portions 14c and the reinforcing shape portion 25. In the illustrated example, the reinforcing shape portion 25 extends in the vehicle width direction, and has hemispherical bulging portions 25a that bulge downward in a hemispherical shape at both ends. The gap between the horizontal bead portion 14c and the reinforcing shape portion 25 narrows in the vertical direction toward the front of the vehicle.

[0054] In the illustrated example, the anchoring force 30 has two bulging portions (31, 31), an anchoring force inner flange 32, an anchoring force outer flange 33, and an anchoring force vertical wall 34.

[0055] The two bulging portions (31, 31) extend in the front-rear direction of the vehicle and are spaced apart from each other in the vehicle width direction, and each bulging portion 31 bulges upward of the vehicle. The bulging portion 31 on the inner side in the vehicle width direction extends to be continuous with the inner bead portion 14a of the floor panel 10, and the bulging portion 31 on the outer side in the vehicle width direction extends to be continuous with the outer bead portion 14b of the floor panel 10.

[0056] In the illustrated example, a seat front fixing portion 1B is provided on the upper wall of the front end portion of the inner bulge portion 31. Also, in the illustrated example, a seat belt anchor fixing portion 1C is provided on the upper wall of the rear end portion of the outer bulge portion 31.

[0057] The seat belt anchor fixing portion 1C is formed as a horizontally extending upper wall of a bulge formed so as to bulge slightly upward on the upper wall of the outer bulge portion 31. A bolt insertion hole 35 is formed in the seat belt anchor fixing portion 1C, and a bolt B for fastening the anchor is inserted through the bolt insertion hole 35 formed in the seat belt anchor S3 and the bolt insertion hole 35 in the seat belt anchor fixing portion 1C from above, and is screwed into a weld nut on the underside of the seat belt anchor fixing portion 1C. This fastens and fixes the seat belt anchor S3 to the seat belt anchor fixing portion 1C.

[0058] The anchoring force inner flange 32 extends inward in the vehicle width direction from the lower end of the inner vertical wall of the inner bulging portion 31 on the vehicle width direction inner side, and is joined to the upper surface of the main floor panel 10A. When viewed from above the vehicle, the anchoring force inner flange 32 is arranged so as to be aligned with the reinforcement inner flange 42 of the rear reinforcement 40, the bracket inner flange 23 of the seat bracket 20, and the side member inner flange 53 of the rear side member 50.

[0059] The anchoring force outer flange 33 extends outward in the vehicle width direction from a portion of the outer edge of the anchoring force 30 that is rearward of the seat belt anchor fixing portion 1C. In the illustrated example, the anchoring force outer flange 33 extends outward in the vehicle width direction from the lower end of the outer vertical wall of the outer bulge portion 31, and is joined to the outer edge of the upper surface of the main floor panel 10A in the vehicle width direction.

[0060] The anchoring force vertical wall 34 extends upward from a portion of the outer edge of the anchoring force 30 in the vehicle width direction that corresponds to the seat belt anchor fixing portion 1C. The anchoring force vertical wall 34 is joined by spot welding to the inner surface of the panel outer wall 15 of the main floor panel 10A and the inner surface of the side member outer wall 54 of the rear side member 50.

[0061] Next, the operation of the vehicle body underbody structure 1 according to this embodiment in the event of a frontal collision or the like will be described.

[0062] As shown by the white arrows in Figures 1 and 6, in the event of a frontal collision or the like, a tensile load acts on the seat rear fixing portion 1A and the seat belt anchor fixing portion 1C, pulling them forward and diagonally upward. Here, the fixing portions of the seat S to the lower part of the vehicle body, the seat rear fixing portion 1A and the seat front fixing portion 1B, are separated by a large distance in the front-to-rear direction of the vehicle by the length of the seat rail S2, and both are provided on the anchoring force 30, and the seat belt anchor fixing portion 1C is disposed in close proximity to the seat rear fixing portion 1A in front of the vehicle and around the seat rear fixing portion 1A. Therefore, when a tensile load acts on the seat rear fixing portion 1A and the seat belt anchor fixing portion 1C, which are close to each other, in the event of a frontal collision or the like, the lower part of the vehicle body (such as the floor panel 10 and the anchoring force 30) may assume a deformation mode in which the rear end of the seat rail S2 (seat rear fixing portion 1A) is lifted forward and diagonally upward, starting from the seat front fixing portion 1B (rotation center).

[0063] With respect to the deformation modes that can occur during a frontal collision, etc., the vehicle body lower structure 1 has a bridge-joint structure in which (1) the anchor force 30 having the seat belt anchor fixing portion 1C extends in the fore-and-aft direction of the vehicle at the front of the vehicle relative to the seat rear fixing portion 1A and is joined to the upper surface of the floor panel 10, the rear reinforcement 40 extends in the fore-and-aft direction of the vehicle at the rear of the vehicle relative to the seat rear fixing portion 1A, and the seat bracket 20 reinforcing the seat rear fixing portion 1A of the floor panel 10 is joined to the floor panel 10 and is joined to the rear of the anchor force 30 and the front of the rear reinforcement 40 so as to bridge the gap between the anchor force 30 and the rear reinforcement 40, and (2) the rigidity of the metal plate material constituting each of the anchor force 30 and the rear reinforcement 40 is higher than the rigidity of the metal plate material constituting the seat bracket 20, thereby providing a rigidity difference.

[0064] Due to the bridge joint structure and the rigidity difference of the vehicle body lower structure 1, the seat bracket 20 is formed with lower rigidity than the anchoring force 30 and the rear reinforcement force 40 located in front and behind the seat bracket 20. As a result, in the deformation mode that can be assumed in the event of a frontal collision, deformation of the seat bracket 20 occurs first, and the anchoring force 30, which has high rigidity, is displaced forward and diagonally upward while maintaining its shape, and the seat bracket 20 deforms upward in response to the input load, and the impact due to the input load is absorbed by the deformation of the seat bracket 20. Therefore, even if the seat belt anchor fixing portion 1C and the seat rear fixing portion 1A are arranged close to each other, deformation of the anchoring force 30 and the like is significantly suppressed in the deformation mode, and peeling of the welded portion of the anchoring force 30 having the seat belt anchor fixing portion 1C to the floor panel 10 is effectively prevented.

[0065] As described above, the vehicle body lower structure 1 of this embodiment has a structure that can reduce the effect of the input load on the joining state of the seat belt anchor fixing portion 1C, even if the seat belt anchor fixing portion 1C and the seat rear fixing portion 1A are arranged close to each other.

[0066] In this embodiment, the seat bracket 20 is joined to the floor panel 10 from the outside of the vehicle cabin. Therefore, even if an input load pulling the seat bracket 20 toward the inside of the vehicle is applied to the seat bracket 20 via the seat rear fixing portion 1A during a frontal collision, for example, no load is generated in the direction of weld separation at the welded portion between the floor panel 10 and the seat bracket 20, and separation of the welded portion of the seat bracket 20 to the floor panel 10 is effectively prevented.

[0067] In this embodiment, the floor panel 10 has a bent portion 11 that bends downward in the vehicle front relative to the seat rear fixing portion 1A, and the seat bracket 20 is joined to the floor panel 10 and the anchoring force 30 in the vehicle front relative to the bent portion 11. Therefore, when a tensile load acts on the seat rear fixing portion 1A and the seat belt anchor fixing portion 1C in the event of a frontal collision, the bending deformation of the floor panel 10 is promoted by the bent portion 11, and the floor panel 10 can be deformed in the intended direction, forward and diagonally upward in the vehicle. As a result, impact absorption is effectively improved, and a decrease in the joining state of the seat belt anchor fixing portion 1C and the seat rear fixing portion 1A in the event of a frontal collision is effectively suppressed, more reliably maintaining the functions of the seat belt anchor fixing portion 1C and the seat rear fixing portion 1A.

[0068] In this embodiment, the vehicle body understructure 1 includes rear side members 50 extending in the fore-and-aft direction of the vehicle along the rear reinforcement 40 below the rear reinforcement 40, and the rear side members 50 have overhanging portions 50B that overhang the vehicle frontward from the front end of the rear reinforcement 40 so as to cover the seat bracket 20 from below, and the seat bracket 20 is joined to the overhanging portions 50B. Therefore, even if a strong impact is applied to the vehicle body from the front during a frontal collision or the like, the overhanging portions 50B of the structure extending in the fore-and-aft direction made up of the rear side members 50 and the rear reinforcement 40 are joined to the seat bracket 20, thereby suppressing breakage of the seat bracket 20. Furthermore, even if the structure made up of the rear side members 50 and the rear reinforcement 40 is deformed by the impact applied during a frontal collision or the like, the seat S can be fixed in place in accordance with this deformation. The rear side member 50 is a component that constitutes part of the vehicle body structure, and its deformation allowance is smaller than that of other parts such as the floor panel 10. Therefore, by covering the seat bracket 20 with the protruding portion 50B of the rear side member 50, movement and breakage of the seat bracket 20 are more effectively suppressed.

[0069] In this embodiment, the floor panel 10 has a bead portion 14 extending to surround the seat rear fixing portion 1A. A reinforcing shape portion 25 bulging in the vehicle vertical direction is formed in a portion of the seat bracket 20 that is located rearward of the portion facing the seat rear fixing portion 1A. The reinforcing shape portion 25 and the bead portion 14 are arranged to partially overlap each other vertically. This effectively enhances the rigidity of the overlapping portion of the vehicle lower body between the reinforcing shape portion 25 of the seat bracket 20 and the bead portion 14 of the floor panel 10. As a result, deformation can be reliably induced in a portion of the vehicle lower body different from the overlapping portion of the reinforcing shape portion 25 and the bead portion 14. For example, when the bent portion 11 is located forward of the overlapping portion, as in this embodiment, deformation at the bent portion 11 is more likely to occur, reliably accelerating impact absorption. This allows deformation of the floor panel 10 to occur in a portion forward of the seat rear fixing portion 1A, thereby reliably maintaining the fixing function of the seat S.

[0070] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and further modifications and changes are possible based on the technical concept of the present invention. [Explanation of symbols]

[0071] 1...Underbody structure 1A...Rear seat fixing part 1C...Seat belt anchor fixing part 10...Floor panel 11...Bend 14...Bead section 20…Seat bracket 25...Reinforced shape part 30...Anchoring Force 40...Rear reinforcement 50...Rear side member 50B...protruding part S...Seat S3...Seatbelt anchor

Claims

1. A vehicle body underbody structure including: a floor panel disposed in a vehicle body underbody and having a seat rear fixing portion; and a seat bracket reinforcing the seat rear fixing portion, wherein a seat belt anchor fixing portion is disposed in the vehicle underbody forward of the seat rear fixing portion and in the periphery of the seat rear fixing portion, an anchoring force extending in the vehicle longitudinal direction in front of the seat rear fixing portion, having the seat belt anchor fixing portion, and joined to an upper surface of the floor panel; a rear reinforcement extending in the vehicle front-rear direction behind the seat rear fixing portion; Including, The seat bracket is joined to the floor panel and is joined to a rear portion of the anchoring force and a front portion of the rear reinforcement so as to bridge between the anchoring force and the rear reinforcement, A vehicle body understructure, characterized in that the rigidity of the metal plate materials constituting each of the anchoring force and the rear reinforcement is higher than the rigidity of the metal plate material constituting the seat bracket.

2. The vehicle underbody structure according to claim 1 , wherein the seat bracket is joined to the floor panel from outside the vehicle compartment.

3. the floor panel has a bent portion that is bent downward in the vehicle front direction relative to the seat rear fixing portion, The vehicle underbody structure according to claim 2 , wherein the seat bracket is joined to the floor panel and the anchoring force at a position forward of the bent portion.

4. a rear side member extending in the vehicle front-rear direction along the rear reinforcement below the rear reinforcement, the rear side member has a protruding portion that protrudes forward of the vehicle relative to a front end of the rear reinforcement so as to cover the seat bracket from below, The vehicle underbody structure according to claim 1 , wherein the seat bracket is joined to the protruding portion.

5. the floor panel has a bead portion extending to surround the seat rear fixing portion, a reinforcing portion that bulges in the vehicle up-down direction is formed in a portion of the seat bracket that is located rearward of the vehicle relative to a portion that faces the seat rear fixing portion, The vehicle underbody structure according to claim 4 , wherein the reinforcing shape portion and the bead portion are arranged so as to partially overlap each other vertically.

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