A vechicle body structure for an automotive vehicle comprising front side frames (21, 21) provided left and right at a front portion of a vehicle body (10) so as to hold a longitudinal center line of the vehicle body therebetween, rear side frames (26, 26) provided left and right at a rear portion of the vehicle body so as to hold the longitudinal center line of the vehicle body therebetween and side sills (23, 23) or floor frames (27, 27) provided left and right so as to hold the longitudinal center line of the vehicle body therebetween and lower than the front side frames and rear side frames when viewed from the side of the vehicle body, the front side frames, rear side frames and side sills or floor frames being connected to each other, and further a floor tunnel having the bottom-open U-shaped cross-sectional structure which extends along the longitudinal center line of the vehicle body between said front side frames and said rear side frames and protrudes upwardly of the side sills (23, 23) or floor frames (27, 27). Auxiliary frames (52, 52) each having a closed cross-sectional structure are provided at an upper portion of the floor tunnel. The auxiliary frames are joined to the front side frames and the rear side frames via extensions (53, 53, 54, 54), each having a closed cross-sectional structure.

A vehiclelongitudinally extending front side member (1) has a rearwardly descending inclined portion (6) configured in an enclosure form in section with an upper wall (3) and a lower wall (4), the upper wall (3) being more rigid than the lower wall (4).

Disclosed is an automobile underbody structure, wherein a pair of laterally-spaced floor frames 10 are disposed to extend longitudinally in such a manner as to interpose a tunnel region 6 of a front floor portion 2 therebetween and joined to a bottom surface of the front floor portion 2, and a cross member 15, 16 is disposed to extend laterally so as to connect each side-sill 7 and the tunnel region 6 and joined to a top surface of the front floor portion 2. Each of the floor frames 10 is gradually inclined laterally inward toward the rear end thereof so as to be obliquely disposed relative to the cross member 15, 16 in top plan view. A rearward displacement of the floor frames 10 during a head-on collision exerts a compressive force on a region of the cross member 15, 16 located on the laterally outward side relative to each of the floor frames 10, and a tensile force on a region of the cross member 15, 16 located on the laterally inward side relative to each of the floor frames 10. The automobile underbody structure of the present invention makes it possible to effectively receive a shock during a head-on collision by the cross member.

A middle branch frame portion is configured such that a front end portion is connected to a front side frame via s suspension-frame attaching bolt to fasten a suspension frame, a middle portion extends to a tunnel portion that is provided at the center portion in the vehicle width direction so as to project upward, and a rear portion is provided below (vehicle outside) an upper corner portion of the tunnel portion so as to extend along the upper corner portion. Accordingly, there can be provided a vehicle front structure with a pair of front side frames provided at both sides of a vehicle body so as to extend in a vehicle longitudinal direction that can disperse the load properly even when a larger fontal-crash impact load acts.

A vehicle body structure comprise a cross member and a floor. Two parallel side members extend along a longitudinal central line of a vehicle and outwardly from the cross member. The cross member is formed by extrusion in a first direction lying in parallel to a transverse line crossing the longitudinal central line. The floor is formed by extrusion in a second direction lying in parallel to the longitudinal central line. The floor includes a recess recessed inwardly and a floor panel portion that defines at least a portion of the recess defining edge. The cross member has an integral tooth fitted into the recess and connected to said floor along the recess defining edge.