Vehicle body structure

Abstract

A vehicle body structure according to the present disclosure is provided with a pair of side sills (1), a floor panel (2), a backbone (21), a backbone reinforcement (3), and a mount bracket (4). The side sills (1) are provided on both sides of the vehicle body in the vehicle width direction, and extend in the vehicle front-rear direction. The floor panel (2) forms the floor surface of the body and is provided between the pair of side sills (1). The backbone (21) is formed in a tunnel shape at the center of the floor panel (2) in the vehicle width direction. The backbone reinforcement (3) is fixed across the left and right sides of the backbone (21) and reinforces the backbone (21). The mount bracket (4) to which a mount (5) is attached connects the side sills (1) and the backbone reinforcement (3) in the vehicle width direction.

Description

Body structure

[0001] This case relates to the body structure of a frame vehicle.

[0002] Conventionally, frame vehicles have been known in which a body is mounted on a frame via a mount, with the lower end of the mount supported by a frame-side bracket fixed to, for example, a side rail of the chassis frame, and the upper end of the mount supported by a body-side bracket fixed to, for example, a side sill of a cab body (see Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2006-256395

[0004] Noise and vibration generated by the drivetrain and wheels during vehicle operation are transmitted from the frame to the body via the mounts. However, depending on the body structure supporting the upper end of the mount, it can be difficult to suppress the amplification of these noises and vibrations. For example, a deformation mode in which the side sill tilts to the left or right can occur, which can worsen acoustic sensitivity at specific frequencies or seat vibration. Furthermore, due to constraints on the surrounding structure, it is often difficult to add reinforcement to increase the rigidity of the side sill.

[0005] One of the objects of the present invention, which was devised in light of the above-mentioned problems, is to provide a vehicle body structure that can improve the vibration and noise characteristics of a frame vehicle. However, in addition to this object, another object of the present invention is to achieve effects derived from the various configurations shown in the "Description of the Invention" below, which cannot be obtained with conventional technology.

[0006] The disclosed vehicle body structure can be realized as the following disclosed embodiments (application examples), which solve at least part of the above-mentioned problems. Each of the embodiments from embodiment 2 onwards is an embodiment that can be selected as an additional option, and each of the embodiments can be omitted. None of the embodiments from embodiment 2 onwards discloses an embodiment or configuration that is essential to the present invention.

[0007] Aspect 1. The disclosed vehicle body structure is a vehicle body structure for a frame vehicle in which a body is placed on a frame via mounts, and includes a pair of side sills provided on both sides of the body in the vehicle width direction and extending in the front-to-rear direction of the vehicle, a floor panel forming the floor surface of the body and provided between the pair of side sills, a backbone formed in a tunnel shape in the center of the floor panel in the vehicle width direction, a backbone reinforcement fixed across the left and right sides of the backbone and reinforcing the backbone, and a mount bracket connecting the side sills and the backbone reinforcement in the vehicle width direction and to which the mount is attached.

[0008] Aspect 2. With regard to aspects including Aspect 1 above, it is preferable that the floor panel, the backbone reinforcement, and the mount bracket form a closed cross-sectional structure connecting the pair of side sills in the vehicle width direction. Aspect 3. With regard to aspects including Aspect 1 above, it is preferable that the floor panel has a front floor panel on which the backbone is provided, a rear floor panel located rearward and above the front floor panel, and a step surface connecting the front floor panel and the rear floor panel, and that the backbone reinforcement is fixed to the front floor panel, the rear floor panel, and the step surface.

[0009] Aspect 4. With regard to aspects including Aspect 3 above, it is preferable that the floor panel has a base portion shaped such that the boundary between the floor panel and the side sill bulges inward and downward in the vehicle width direction, and the mount bracket is joined to the side sill, the backbone reinforcement, the front floor panel, the rear floor panel, and the base portion. Aspect 5. With regard to aspects including Aspect 4 above, it is preferable that the mount bracket has a vertical extension portion that extends from the boundary between the base portion and the side sill along the inner surface of the side sill in the vehicle width direction to near the underside of the side sill.

[0010] Aspect 6. With regard to the aspects including Aspect 3 above, it is preferable to include a front floor side member provided on the front floor panel and extending in the vehicle fore-and-aft direction, and a front reinforcing member connecting the front floor side member and the backbone reinforcement in the vehicle fore-and-aft direction. Aspect 7. With regard to the aspects including Aspect 3 above, it is preferable to include a rear floor cross member provided on the rear floor panel and extending in the vehicle width direction, and a rear reinforcing member connecting the rear floor cross member and the mount bracket in the vehicle fore-and-aft direction.

[0011] Aspect 8. With regard to aspects including Aspect 7 above, it is preferable to include a rear floor side member that is provided on the rear floor panel, extends in the fore-and-aft direction of the vehicle, is perpendicular to the rear floor cross member, and is connected to the backbone reinforcement. Aspect 9. With regard to aspects including Aspect 3 above, it is preferable that the backbone reinforcement has a first reinforcement that is fixed to the front floor panel, the rear floor panel, and the step surface on the left and right sides of the backbone, and a second reinforcement that is fixed to the first reinforcement so as to create a gap between the first reinforcement and the second reinforcement.

[0012] Aspect 10. With regard to aspects including Aspect 3 above, it is preferable that the mount bracket has a mount support portion that supports the upper end of the mount, a lateral extension portion that extends from the mount support portion inward in the vehicle width direction and is connected to the backbone reinforcement, a rear slope portion that extends from the lateral extension portion rearward and upward toward the vehicle and is connected to the rear floor panel, and a protrusion portion that extends from the lateral extension portion forward and downward toward the vehicle and is connected to the front floor panel.

[0013] According to the disclosed vehicle body structure, by connecting the side sill and the backbone bracket in the vehicle width direction with the mount bracket, the rigidity around the mount bracket can be increased and deformation of the side sill in the lateral direction can be suppressed, thereby improving acoustic sensitivity and seat vibration in the vehicle cabin and improving the vibration and noise characteristics of frame vehicles.

[0014] 3 is an exploded perspective view of the body structure of a frame vehicle; FIG. 4 is an underside view of the body of a frame vehicle; FIG. 5 is an enlarged perspective view of the main parts of FIG. 2; FIG. 6 is an exploded perspective view of the main elements in FIG. 3; FIG. 7 is a perspective view of a backbone reinforcement; FIG. 8 is a cross-sectional view including the backbone reinforcement (cross-sectional view A-A in FIG. 2); (A) and (B) are perspective views of a mount bracket; and FIG. 9 is a cross-sectional view including the mount bracket (cross-sectional view B-B in FIG. 2).

[0015] The disclosed vehicle body structure is applied to a frame vehicle in which a body (also called a cab body, cabin, or vehicle body) is mounted on a frame (also called a chassis or chassis frame) via mounts (also called body mounts, vibration-damping mounts, or vibration-isolating mounts). The powertrain (e.g., engine, motor, transmission, propeller shaft, etc.) and wheel suspension devices of the frame vehicle are attached to the frame. Specific examples of frame vehicles include trucks, buses, vans (minivans), wagons, and SUVs (Sport Utility Vehicles).

[0016] Regarding the definitions of directions in the embodiments, the front-rear direction (vehicle length direction) is determined based on the forward / reverse direction of the frame vehicle, and the left-right direction (vehicle width direction) is determined based on the front-rear direction. The up-down direction is determined based on the state in which the frame vehicle is stopped on a flat road surface. Regarding the inward / outward directions of the frame vehicle, the direction from the outside of the vehicle toward the passenger compartment in the vehicle width direction is the inward direction, and the direction from the passenger compartment toward the outside of the vehicle is the outward direction. To the right of the median plane of the frame vehicle (the vertical plane dividing the frame vehicle into left and right halves), the right direction is the outward direction, and the left direction is the inward direction. To the left of the median plane of the frame vehicle, the left direction is the outward direction, and the right direction is the inward direction.

[0017] [1. Configuration] Fig. 1 is an exploded perspective view of a frame vehicle 50 to which a vehicle body structure according to an embodiment is applied. The frame vehicle 50 includes a frame 51 and a body 52 mounted on the frame 51 via mounts 5. The frame 51 is a skeletal member to which a powertrain and wheel suspension devices are attached. The frame 51 shown in Fig. 1 is a ladder frame formed by connecting a pair of left and right side frames in a ladder-like manner using multiple cross frames. Other specific examples of the frame 51 include an X-type frame, a backbone frame, and a perimeter frame.

[0018] The body 52 is a portion that forms the passenger compartment, living space, luggage compartment, etc., where passengers and luggage are loaded, and is also called the vehicle body. The mounts 5 are shock absorbers that absorb and reduce vibrations and shocks transmitted between the frame 51 and the body 52, and are, for example, rubber mounts or viscous mounts. The mounts 5 are attached to the frame 51 and function to support the body 52 thereon. Although four mounts 5 are shown in FIG. 1 , the number and arrangement positions of the mounts 5 are not limited to this.

[0019] Fig. 2 is a bottom view showing the mount 5 and body 52 as viewed from below. The underside (lower part) of the body 52 is provided with a side sill 1, a floor panel 2, a backbone reinforcement 3, and a mount bracket 4. The front end portion (engine compartment, front bumper) and rear end portion (rear bumper) of the frame vehicle 50 are omitted from Fig. 2. Fig. 3 is an enlarged perspective view of the main parts of Fig. 2, and Fig. 4 is an exploded perspective view of the main elements of Fig. 3, namely, the floor panel 2, the backbone reinforcement 3, the mount bracket 4, and the mount 5.

[0020] [A. Side sills, floor panel] The side sills 1 are a pair of left and right cross members provided on both sides in the vehicle width direction at the bottom of the body 52 and extending in the front-to-rear direction. The side sills 1 serve as thresholds where occupants place or straddle their feet when getting on or off the frame vehicle 50. The side sills 1 are formed, for example, in the shape of a hollow cylinder with a closed cross section. The side sills 1 are positioned approximately horizontally along the lower edge of the side door to connect the front wheel housing and the rear wheel housing.

[0021] The floor panel 2 is a plate-like member that forms the floor surface of the body 52, and is extended substantially horizontally to connect the pair of side sills 1. The floor panel 2 is provided with a front floor panel 22, a rear floor panel 23, and a dash panel 24. The front floor panel 22 is the part that forms the floor surface of the passenger compartment where passengers sit. Passenger seats are attached, for example, to seat rails that are fixed to the upper surface of the front floor panel 22.

[0022] 2 and 3, a front floor side member 53 is attached to the underside of the front floor panel 22. The front floor side member 53 is a reinforcing member that increases the rigidity of the front floor panel 22 and is formed, for example, in the shape of a hollow cylinder with a closed cross section. A pair of front floor side members 53 are provided spaced apart in the vehicle width direction, and each is arranged to extend in the front-to-rear direction.

[0023] The rear floor panel 23 is a portion of the floor rearward of the front floor panel 22. The rear floor panel 23 serves as the floor of a luggage compartment where luggage is loaded, for example. The rear floor panel 23 is disposed above (at a higher position than) the front floor panel 22. The front floor panel 22 and the rear floor panel 23 are connected by a step surface 26 (see FIG. 4 ). The step surface 26 is an inclined surface that connects the rear edge of the front floor panel 22 and the front edge of the rear floor panel 23.

[0024] As shown in Figures 2 and 3, a rear floor cross member 54 and a rear floor side member 55 are provided on the underside of the rear floor panel 23 as reinforcing members for increasing the rigidity of the rear floor panel 23. The rear floor cross member 54 and the rear floor side member 55 are each formed, for example, in the shape of a hollow cylinder with a closed cross section. The rear floor cross member 54 is provided so as to linearly connect the pair of left and right side sills 1 (or the left and right rear wheel housings) and is arranged to extend in the vehicle width direction. A pair of rear floor side members 55 are provided spaced apart in the vehicle width direction and are arranged to extend in the front-to-rear direction.

[0025] The distance between the pair of rear floor side members 55 is set shorter than the distance between the pair of front floor side members 53. In this embodiment, the rear floor cross member 54 and the rear floor side member 55 are integrally connected. The dash panel 24 is a rising portion formed by bending the front end of the front floor panel 22 upward. The dash panel 24 functions as a partition wall that separates the passenger compartment from the engine compartment.

[0026] A tunnel-shaped backbone 21 is provided in the center of the floor panel 2 in the vehicle width direction. In this embodiment, the backbone 21 is formed in a tunnel-like shape by projecting upward from the plate surface of the center of the front floor panel 22 in the vehicle width direction. This backbone 21 is formed in the front floor panel 22 over the entire length of the vehicle in the fore-and-aft direction. The front end of the backbone 21 reaches the dash panel 24, and the rear end of the backbone 21 reaches the step surface 26 (see Figure 4). The width (dimension in the vehicle width direction) of the backbone 21 increases toward the front of the vehicle. A propeller shaft and exhaust system devices extending in the fore-and-aft direction are arranged below the backbone 21.

[0027] As shown in Figures 2 to 4, a pair of base portions 25 are provided on both the left and right ends of the floor panel 2. The base portions 25 are rectangular parallelepiped-shaped portions that bulge outward and downward in the vehicle width direction at the boundary between the floor panel 2 and the side sill 1. The base portions 25 reinforce the boundary between the floor panel 2 and the side sill 1 and function to increase the rigidity of the body 52. ​​As shown in Figure 2, the base portions 25 have a width that completely overlaps with the mount 5 when viewed from below the body 52. ​​Furthermore, as shown in Figure 3, the downward protrusion dimension H of the base portions 25 when the lower surface side of the front floor panel 22 is used as a reference is １ is the downward protrusion dimension H of the side sill 1 ２ As a result, as shown in Figure 4, the lower surface 12 of the side sill 1 is positioned lower than the lower surface 27 of the base portion 25, and the inner surface 11 of the side sill 1 is exposed to the inside in the vehicle width direction.

[0028] [B. Backbone Reinforcement] The backbone reinforcement 3 is a reinforcing member for reinforcing the backbone 21, and is fixed to the floor panel 2 across the left and right sides of the backbone 21. The backbone reinforcement 3 of this embodiment is fixed to the floor panel 2 so as to reinforce the rear end of the backbone 21. The backbone reinforcement 3 of this embodiment is also fixed to the floor panel 2 so as to reinforce a step provided at the rear end of the backbone 21.

[0029] Figure 5 is a perspective view of the backbone reinforcement 3, and Figure 6 is a cross-sectional view (cross-sectional view taken along line A-A in Figure 2) including the backbone reinforcement 3. The backbone reinforcement 3 in this embodiment is composed of two members: a first reinforcement 31 and a second reinforcement 32. The first reinforcement 31 is fixed to the floor panel 2, for example, by welding. The second reinforcement 32 is provided below the first reinforcement 31, and is fixed to the first reinforcement 31 and the floor panel 2, for example, by welding.

[0030] The first reinforcement 31 has a lower reinforcing surface 33, a step reinforcing surface 34, and an upper reinforcing surface 35, and is manufactured, for example, by pressing a plate material. The lower reinforcing surfaces 33 are planar portions fixed to the left and right front floor panels 22 of the backbone 21, and a pair of lower reinforcing surfaces 33 are provided with a gap in the vehicle width direction. The pair of lower reinforcing surfaces 33 are located on approximately the same plane. Each lower reinforcing surface 33 is fixed to the front floor panel 22 in a state of approximately surface contact.

[0031] The step reinforcement surfaces 34 are planar portions extending upward from the rear end edges of the respective lower reinforcement surfaces 33. The step reinforcement surfaces 34 are fixed in a state of substantial surface contact with the step surfaces 26. As shown in Figures 3 and 4 , the convex shape (end face of the tunnel) that occurs at the intersection of the backbone 21 and the step surfaces 26 is closed by the step reinforcement surfaces 34. The upper reinforcement surfaces 35 are planar portions extending rearward from the upper end edges of the step reinforcement surfaces 34. The upper reinforcement surfaces 35 are fixed in a state of substantial surface contact with the rear floor panel 23.

[0032] The second reinforcement 32 has a lower flange portion 36, a horizontal surface portion 37, an inclined surface portion 38, and an upper flange portion 39, and is manufactured by, for example, pressing a plate material. The lower flange portion 36 is a planar portion that is fixed in a state of substantial surface contact with the step reinforcing surface 34 of the first reinforcement 31 and the step surface 26. The dimension of the lower flange portion 36 in the vehicle width direction is set to be larger than the dimension of the step reinforcing surface 34 in the vehicle width direction. The lower flange portion 36 is arranged near the lower ends of the step reinforcing surface 34 and the step surface 26 so as to cross and reinforce the convex shape (end face of the tunnel) that occurs at the intersection of the backbone 21 and the step surface 26.

[0033] The horizontal surface portion 37 is a planar portion extending rearward from the upper end edge of the lower flange portion 36. The horizontal surface portion 37 is disposed approximately parallel to the rear floor panel 23. The inclined surface portion 38 is a planar portion extending diagonally rearward and upward from the rear end edge of the horizontal surface portion 37. The upper flange portion 39 is a planar portion extending rearward from the rear end edge (upper end edge) of the inclined surface portion 38. The upper flange portion 39 is fixed in a state of approximately surface contact with the upper reinforcing surface 35 of the first reinforcement 31 and the rear floor panel 23. The dimension of the upper flange portion 39 in the vehicle width direction is set to be larger than the dimension of the upper reinforcing surface 35 in the vehicle width direction.

[0034] The second reinforcement 32 is fixed to the first reinforcement 31 so as to create a gap between it and the first reinforcement 31. That is, inside the backbone reinforcement 3, as shown in Fig. 6, a rectangular tubular closed cross-sectional structure is formed, surrounded by four surfaces: a step reinforcing surface 34, an upper reinforcing surface 35, a horizontal surface portion 37, and an inclined surface portion 38. The cross-sectional shape of this closed cross-sectional structure is a trapezoid with a long upper base and a short lower base, which is a cross-sectional shape that efficiently improves the rigidity of the rear floor panel 23.

[0035] [C. Mount Bracket] The mount bracket 4 is a portion to which the mount 5 is attached. As shown in FIG. 2 , the mount brackets 4 are arranged in pairs at positions adjacent to each of the left and right side sills 1. In this embodiment, the mount 5, which is arranged near the rear of the passenger compartment (front floor panel 22), is attached to the mount bracket 4. This mount bracket 4 is attached (joined) to connect the side sill 1 and the backbone reinforcement 3 in the vehicle width direction. As shown in FIG. 2 , the mount 5, which is arranged near the front of the passenger compartment (front floor panel 22), is supported by a box-shaped body-side bracket fixed to the side sill 1 and the front floor panel 22.

[0036] 7A and 7B are perspective views of the left and right mount brackets 4, and Fig. 8 is a cross-sectional view (cross-sectional view taken along B-B in Fig. 2) including the right mount bracket 4. The mount bracket 4 of this embodiment has a mount support portion 41, a vertical extension portion 42, a horizontal extension portion 43, a rear slope portion 44, and a protrusion portion 45, and is manufactured, for example, by pressing a plate material. The mount support portion 41 is a flat portion to which the mount 5 is attached, and is provided, for example, substantially horizontally.

[0037] The vertical extension 42 is a flat portion that extends downward from the outer edge of the mount support portion 41 in the vehicle width direction. The vertical extension 42 extends from the boundary between the base portion 25 and the side sill 1 along the inner surface 11 of the side sill 1 to near the underside 12 of the side sill 1. This increases the integration between the mount bracket 4 and the side sill 1 and improves the rigidity of the mount bracket 4 and its surroundings.

[0038] The lateral extension portion 43 is a planar portion that extends upward and inward in the vehicle width direction from the inner end edge of the mount support portion 41. The lateral extension portion 43 is formed in a shape that smoothly connects the mount support portion 41 and the horizontal surface portion 37 of the second reinforcement 32, and is fixed in a state of nearly surface contact with the horizontal surface portion 37. This increases the unity between the mount bracket 4 and the second reinforcement 32, further improving the rigidity of the mount bracket 4 and its surroundings.

[0039] The rear slope portion 44 is a planar portion extending upward and rearward from the rear end edges of the mount support portion 41 and the lateral extension portion 43. The rear slope portion 44 is formed in a shape that follows the slope portion 38 of the second reinforcement 32, and is fixed in a state of substantial surface contact with the slope portion 38. The rear end of the rear slope portion 44 extends along the surface of the base portion 25 to the rear floor panel 23 and is joined to the base portion 25. In addition, the upper end portion of the rear slope portion 44 extends rearward along the upper flange portion 39, and is fixed (joined) in a state of substantial surface contact with the upper flange portion 39 and the rear floor panel 23.

[0040] The protrusion 45 is a stepped portion that extends downward and forward from the lateral extension 43 and is connected to the front floor panel 22. The protrusion 45 is positioned on the front side of the vehicle (the front floor panel 22 side) where the difference in level with the floor panel 2 is small, based on the height of the portion of the lateral extension 43 that is in surface contact with the horizontal surface portion 37. Providing the protrusion 45 on the mount bracket 4 improves the rigidity of the lateral extension 43.

[0041] 8, the mount bracket 4 is attached so as to sandwich the backbone reinforcement 3 between the floor panel 2 and the mount bracket 4, with the mount bracket 4 in contact with the horizontal surface portion 37 and the inclined surface portion 38 of the second reinforcement 32 of the backbone reinforcement 3. As a result, a closed cross-sectional structure is formed inside the mount bracket 4, surrounded by the rear floor panel 23, the step surface 26, the lateral extension portion 43, the rear inclined surface portion 44, and the protrusion portion 45.

[0042] The cross-sectional shape of this closed cross-sectional structure is substantially the same as the cross-sectional shape of the closed cross-sectional structure formed inside the backbone reinforcement 3. In this way, by connecting the closed cross-sectional structure of the backbone reinforcement 3 and the closed cross-sectional structure of the mount bracket 4 in the vehicle width direction, a closed cross-sectional structure that connects a pair of side sills 1 in the vehicle width direction is formed. This closed cross-sectional structure has the function of reinforcing the entire floor panel 2, for example, like a floor cross member disposed between a pair of side sills 1. Therefore, the rigidity of the body 52 around the mount bracket 4 is improved.

[0043] 2 and 3, a front extension 6 (front reinforcing member) that connects the front floor side member 53 and the backbone reinforcement 3 in the longitudinal direction is provided on the underside of the front floor panel 22. The front extension 6 functions to integrally connect the closed cross-sectional structure that connects the pair of side sills 1 in the vehicle width direction with the front floor side member 53. This improves the rigidity of the body 52 around the backbone reinforcement 3 and the mount bracket 4.

[0044] Similarly, a rear extension 7 (rear reinforcing member) is provided on the underside of the rear floor panel 23, connecting the rear floor cross member 54 and the mount bracket 4 in the fore-and-aft direction. The rear extension 7 functions to integrally connect the closed cross-sectional structure that connects the pair of side sills 1 in the vehicle width direction with the rear floor cross member 54. This improves the rigidity of the body 52 around the mount bracket 4.

[0045] [2. Effects] (1) The vehicle body structure of this embodiment is a vehicle body structure for a frame vehicle 50 in which a body 52 is mounted on a frame 51 via mounts 5. This vehicle body structure includes a pair of side sills 1, a floor panel 2, a backbone 21, a backbone reinforcement 3, and a mount bracket 4. The side sills 1 are provided on both sides of the body 52 in the vehicle width direction and extend in the front-to-rear direction. The floor panel 2 forms the floor surface of the body 52 and is provided between the pair of side sills 1.

[0046] The backbone 21 is formed in a tunnel shape in the center of the floor panel 2 in the vehicle width direction. The backbone reinforcement 3 is fixed across the left and right sides of the backbone 21 to reinforce the backbone 21. The mount bracket 4 connects the side sill 1 and the backbone reinforcement 3 in the vehicle width direction. A mount 5 is attached to the mount bracket 4.

[0047] In this way, by connecting the side sill 1 and the backbone reinforcement 3 in the vehicle width direction with the mount bracket 4, the side sills 1 arranged on either side of the backbone 21 can be connected by the backbone reinforcement 3 and the mount bracket 4. This increases the rigidity of the body 52 around the mount bracket 4 and suppresses the collapse deformation of the side sill 1 in the left-right direction. In addition, the acoustic sensitivity and seat vibration in the vehicle cabin can be improved, and the vibration and noise characteristics of the frame vehicle 50 can be improved.

[0048] (2) In the above-described vehicle body structure, the floor panel 2, the backbone reinforcement 3, and the mount bracket 4 form a closed cross-sectional structure that connects the pair of side sills 1 in the vehicle width direction. This closed cross-sectional structure has the function of reinforcing the entire floor panel 2, for example, like a floor cross member disposed between the pair of side sills 1. Therefore, the rigidity of the body 52 around the backbone reinforcement 3 and the mount bracket 4 can be further improved.

[0049] (3) The floor panel 2 has a front floor panel 22 on which the backbone 21 is provided, a rear floor panel 23 located rearward and above the front floor panel 22, and a step surface 26 connecting the front floor panel 22 and the rear floor panel 23. In addition, the backbone reinforcement 3 is fixed to the front floor panel 22, the rear floor panel 23, and the step surface 26.

[0050] This configuration can increase the rigidity around the step surface 26, further improving the acoustic sensitivity and seat vibration inside the vehicle cabin. In addition, in this embodiment, a closed cross-sectional structure is formed along the step surface 26, so the rigidity around the step surface 26 can be further increased. Therefore, the acoustic sensitivity and seat vibration inside the vehicle cabin can be improved, and the vibration and noise characteristics of the frame vehicle 50 can be improved.

[0051] (4) The floor panel 2 has a base portion 25 that bulges downward and inward in the vehicle width direction at the boundary between the floor panel 2 and the side sill 1. The mount bracket 4 is joined to the side sill 1, the backbone reinforcement 3, the front floor panel 22, the rear floor panel 23, and the base portion 25. This configuration further increases the rigidity of the body 52 around the mount bracket 4. As shown in FIG. 2, the base portion 25 in this embodiment has a width that completely overlaps with the mount 5. This allows the mount 5 to comfortably support the weight of the body 52, stabilizing the support state of the body 52.

[0052] (5) The mount bracket 4 has a vertical extension 42 that extends from the boundary between the base portion 25 and the side sill 1 along the inner surface 11 of the side sill 1 in the vehicle width direction to near the underside 12 of the side sill 1. This reinforces the side sill 1 and more reliably suppresses deformation of the side sill 1 in the left-right direction. It also enhances the unity between the side sill 1 and the mount bracket 4, increasing the rigidity around the mount bracket 4. This improves acoustic sensitivity and seat vibration within the vehicle cabin, improving the vibration and noise characteristics of the frame vehicle 50.

[0053] (6) As shown in FIG. 3 , the front floor panel 22 is provided with front floor side members 53 extending in the fore-and-aft direction. Furthermore, a front extension 6 (front reinforcing member) is provided between the front floor side members 53 and the backbone reinforcement 3, connecting them in the fore-and-aft direction. This configuration further improves the rigidity of the body 52 around the backbone reinforcement 3. Furthermore, in this embodiment, the rear end of the front extension 6 is connected to a closed cross-sectional structure, thereby enhancing the reinforcing effect of the entire floor panel 2.

[0054] (7) As shown in FIG. 3 , the rear floor panel 23 is provided with a rear floor cross member 54 extending in the vehicle width direction. Furthermore, a rear extension 7 (rear reinforcing member) is provided between the rear floor cross member 54 and the mount bracket 4, connecting them in the fore-and-aft direction. This configuration further improves the rigidity of the body 52 around the mount bracket 4. Furthermore, in this embodiment, the front end of the rear extension 7 is connected to a closed cross-section structure, thereby enhancing the reinforcing effect of the entire floor panel 2.

[0055] (8) As shown in FIG. 3 , rear floor side members 55 are provided on the rear floor panel 23. The rear floor side members 55 extend in the front-to-rear direction, intersect the rear floor cross member 54 at right angles, and are connected to the backbone reinforcement 3. This configuration further improves the rigidity of the body 52 around the backbone reinforcement 3. In addition, in this embodiment, the rear end of the front extension 6 is connected to a closed cross-sectional structure, which enhances the reinforcing effect of the entire floor panel 2.

[0056] (9) As shown in Fig. 5 , the backbone reinforcement 3 has a first reinforcement 31 and a second reinforcement 32. The first reinforcement 31 is fixed to the front floor panel 22 and the rear floor panel 23 on the left and right sides of the backbone 21 and to the step surface 26. The second reinforcement 32 is fixed to the first reinforcement 31 so that a gap is formed between the first reinforcement 31 and the second reinforcement 32. With this configuration, a closed cross-sectional structure can be formed inside the backbone reinforcement 3, and the rigidity of the backbone reinforcement 3 can be further improved.

[0057] (10) As shown in FIGS. 7A and 7B , the mount bracket 4 has a mount support portion 41 that supports the upper end of the mount 5, a lateral extension portion 43, a rear slope portion 44, and a protrusion portion 45. The lateral extension portion 43 extends inward in the vehicle width direction from the mount support portion 41 and is connected to the backbone reinforcement 3. The rear slope portion 44 extends upward and rearward from the lateral extension portion 43 and is connected to the rear floor panel 23. The protrusion portion 45 extends downward and forward from the lateral extension portion 43 and is connected to the front floor panel 22. This configuration allows a closed cross-sectional structure to be formed on the inside of the mount bracket 4, further improving the rigidity of the mount bracket 4. In addition, providing the protrusion portion 45 on the mount bracket 4 improves the rigidity of the lateral extension portion 43.

[0058] [3. Other] The above-described embodiments are merely illustrative and are not intended to exclude various modifications or applications of techniques not explicitly described in the present embodiments. Each configuration of the present embodiments can be modified in various ways without departing from the spirit of the present embodiments. Furthermore, each configuration of the present embodiments can be selected as needed, or can be appropriately combined with various configurations included in known techniques.

[0059] In the above embodiment, a structure in which the backbone reinforcement 3 is provided in the step portion between the front floor panel 22 and the rear floor panel 23 is illustrated, but the location of the backbone reinforcement 3 is not limited to this. The backbone reinforcement 3 only needs to be fixed across at least the left and right sides of the backbone 21, and its position in the front-to-rear direction can be changed as appropriate. The vehicle body structure according to the present invention can also be applied to a frame vehicle 50 equipped with a floor panel 2 that does not have a step surface 26.

[0060] In the above embodiment, the floor panel 2, the backbone reinforcement 3, and the mount bracket 4 form a closed cross-sectional structure, but such a closed cross-sectional structure is not essential. The same is true for the closed cross-sectional structures shown in Figures 6 and 8, and these closed cross-sectional structures are not essential. The mount bracket 4 only needs to connect at least the side sill 1 and the backbone reinforcement 3 in the vehicle width direction.

[0061] In the above embodiment, the mount brackets 4 are arranged in pairs at positions adjacent to each of the left and right side sills 1, but the mount brackets 4 may be arranged on only one of the left and right sides. The number and arrangement positions of the mount brackets 4 can be set according to the number and arrangement positions of the mounts 5. By arranging the mount brackets 4 at least in positions that connect the side sill 1 and the backbone reinforcement 3 in the vehicle width direction, it is possible to obtain the same effects as in the above embodiment.

[0062] The present invention is applicable to the manufacturing industry of frame vehicles in which a body is mounted on a frame via a mount, and is applicable to the manufacturing industry of body structures of frame vehicles.

[0063] DESCRIPTION OF SYMBOLS 1 Side sill 2 Floor panel 3 Backbone reinforcement 4 Mount bracket 5 Mount 6 Front extension (front reinforcement member) 7 Rear extension (rear reinforcement member) 11 Inner surface 12 Underside 21 Backbone 22 Front floor panel 23 Rear floor panel 24 Dash panel 25 Base portion 26 Step surface 27 Underside 31 First reinforcement 32 Second reinforcement 33 Lower reinforcement surface 34 Step reinforcement surface 35 Upper reinforcement surface 36 Lower flange portion 37 Horizontal surface portion 38 Inclined surface portion 39 Upper flange portion 41 Mount support portion 42 Vertical extension portion 43 Horizontal extension portion 44 Rear slope portion 45 Protruding portion 50 Frame vehicle 51 Frame 52 Body 53 Front floor side member 54 Rear floor cross member 55 Rear floor side member

Claims

1. A body structure for a frame vehicle in which a body is placed on a frame via a mount, comprising: a pair of side sills provided on both sides of the body in the vehicle width direction and extending in the front-to-rear direction of the vehicle; a floor panel forming the floor of the body and provided between the pair of side sills; a backbone formed in a tunnel shape in the center of the floor panel in the vehicle width direction; a backbone reinforcement fixed across the left and right sides of the backbone and reinforcing the backbone; and a mount bracket connecting the side sills and the backbone reinforcement in the vehicle width direction and to which the mount is attached.

2. The vehicle body structure according to claim 1, wherein the floor panel, the backbone reinforcement, and the mount bracket form a closed cross-sectional structure connecting the pair of side sills in the vehicle width direction.

3. The vehicle body structure according to claim 1, wherein the floor panel comprises a front floor panel on which the backbone is provided, a rear floor panel located rearward and above the front floor panel, and a step surface connecting the front floor panel and the rear floor panel, and the backbone reinforcement is fixed to the front floor panel, the rear floor panel, and the step surface.

4. The vehicle body structure according to claim 3, wherein the floor panel has a base portion shaped such that the boundary between the floor panel and the side sill bulges inward and downward in the vehicle width direction, and the mount bracket is joined to the side sill, the backbone reinforcement, the front floor panel, the rear floor panel, and the base portion.

5. The vehicle body structure according to claim 4, wherein the mounting bracket has a vertical extension extending from the boundary between the base and the side sill along the inner surface of the side sill in the vehicle width direction to near the underside of the side sill.

6. The vehicle body structure according to claim 3, further comprising: a front floor side member provided on the front floor panel and extending in the longitudinal direction of the vehicle; and a front reinforcing member connecting the front floor side member and the backbone reinforcement in the longitudinal direction of the vehicle.

7. The vehicle body structure according to claim 3, further comprising: a rear floor cross member provided on the rear floor panel and extending in the vehicle width direction; and a rear reinforcing member connecting the rear floor cross member and the mount bracket in the vehicle longitudinal direction.

8. The vehicle body structure according to claim 7, further comprising rear floor side members that are attached to the rear floor panel, extend in the longitudinal direction of the vehicle, intersect perpendicularly with the rear floor cross member, and are connected to the backbone reinforcement.

9. A vehicle body structure as described in claim 3, characterized in that the backbone reinforcement has a first reinforcement fixed to the front floor panel, the rear floor panel and the step surface on the left and right sides of the backbone, and a second reinforcement fixed to the first reinforcement so as to create a gap between the first reinforcement and the second reinforcement.

10. The vehicle body structure described in claim 3, wherein the mount bracket has a mount support portion that supports the upper end of the mount, a lateral extension portion that extends from the mount support portion toward the inside in the vehicle width direction and is connected to the backbone reinforcement, a rear slope portion that extends from the lateral extension portion toward the rear and upward of the vehicle and is connected to the rear floor panel, and a protrusion portion that extends from the lateral extension portion toward the front and downward of the vehicle and is connected to the front floor panel.

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