FIG. 19 hereof illustrates a conventional vehicle floor structure.
The vehicle floor structure includes longitudinally extending left and right floor frame members 200, 201, a plurality of crossmembers 202, 203, 204, 205, 206, 207, 208 and 209 extended between the left and right floor frame members 200, 201 at predetermined intervals, and a floor panel 210 placed over the left and right floor frame members 200, 201 and the crossmembers 202, 203, 204, 205, 206, 207, 208 and 209.
Side frame members 211 are connected to the front ends of the left and right floor frame members 200, 201.
In the vehicle floor structure, the left and right floor frame members 200, 201 are merely connected together by the crossmembers 202 to 209. If the right floor frame member 201, for example, is subjected to a large load f upon an offset collision of the vehicle, the load f is hardly transmitted to the left floor frame member 200.
Almost all the large load f exerted on the right floor frame member 201 is thus absorbed by the right floor frame member 201. To prevent deformation of the right floor frame member 201 due to the large load f, it is required to increase the strength of the right floor frame member 201.
An uneven load f, however, is not necessarily exerted only on the right floor frame member 201 and may also be exerted on the left floor frame member 200. It is thus necessary to design the left and right floor frame members 200, 201 to have enough strength to be able to withstand a large load, which results in increased weights of the floor frame members 200, 201.
For reinforcement of vehicle floor structures, an art of arranging a reinforcing member between left and right frame members is known (e.g., JP-A-2000-135990).
Such a vehicle floor structure will be described with reference to FIGS. 20A and 20B.
A vehicle floor structure 220 shown in FIGS. 20A and 20B consists of left and right underframe members 221, 222 arranged below a cab floor (not shown) and a reinforcing member 223 arranged between the underframe members 221, 222. The reinforcing member 223 is attached at its left and right side edge portions to the left and right underframe members 221, 222.
The reinforcing member 223 is a corrugated panel formed with a plurality of raised portions 224 provided in parallel to have an uneven cross-sectional shape as shown in FIG. 20B. The reinforcing member 223 provided between the left and right underframe members 221, 222 reinforces the left and right underframe members 221, 222 against a load evenly exerted on the left and right underframe members 221, 222, for example.
The vehicle floor structure 220 is configured with the reinforcing member 223 merely attached at its left and right side edge portions 225, 226 to the left and right underframe members 221, 222. If, upon an offset collision of the vehicle, a large load f is imposed on the right underframe member 222 as shown in FIG. 20A, for example, the load f is hardly transmitted to the left underframe member 221, as described above. Almost all the large load f imposed on the right underframe member 222 is received by the right underframe member 222. To prevent deformation of the right underframe member 222 due to a large load f, it is required to increase the strength of the right underframe member 222.
An uneven load is not necessarily exerted only on the right underframe member 222 and may also be exerted on the left underframe member 221. It is thus necessary to design the right and left underframe members 221, 222 to have enough strength to be able to withstand a large load f, which results in increased weights of the left and right underframe members 221, 222.
Thus, there is a demand for a vehicle floor structure which can avoid weight increase while maintaining the frame strength.