Vehicle floor structure

A vehicle floor structure is provided in which a plurality of cross-members are extended between left and right floor frame members at predetermined longitudinal intervals, and a floor panel is mounted to the left and right floor frame members and the crossmembers. A corrugated sheet having a plurality of longitudinally oriented ridges is disposed in a space formed by the left and right floor frame members and the crossmembers. Left and right side portions of the corrugated sheet are connected to the left and right floor frame members. Front and rear edge portions of the corrugated sheet are connected to opposite ones of the crossmembers. If the right floor frame member, for example, is subjected to a load upon an offset collision of the vehicle, the load is transmitted to the left floor frame via the corrugated sheet for dispersion.

FIELD OF THE INVENTION

The present invention relates to vehicle floor structures in which a plurality of crossmembers are extended between left and right floor frame members at certain intervals and a floor panel is provided over the floor frame members and the crossmembers.

BACKGROUND OF THE INVENTION

FIG. 19hereof illustrates a conventional vehicle floor structure.

The vehicle floor structure includes longitudinally extending left and right floor frame members200,201, a plurality of crossmembers202,203,204,205,206,207,208and209extended between the left and right floor frame members200,201at predetermined intervals, and a floor panel210placed over the left and right floor frame members200,201and the crossmembers202,203,204,205,206,207,208and209.

Side frame members211are connected to the front ends of the left and right floor frame members200,201.

In the vehicle floor structure, the left and right floor frame members200,201are merely connected together by the crossmembers202to209. If the right floor frame member201, 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 member200.

Almost all the large load f exerted on the right floor frame member201is thus absorbed by the right floor frame member201. To prevent deformation of the right floor frame member201due to the large load f, it is required to increase the strength of the right floor frame member201.

An uneven load f, however, is not necessarily exerted only on the right floor frame member201and may also be exerted on the left floor frame member200. It is thus necessary to design the left and right floor frame members200,201to have enough strength to be able to withstand a large load, which results in increased weights of the floor frame members200,201.

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 toFIGS. 20A and 20B.

A vehicle floor structure220shown inFIGS. 20A and 20Bconsists of left and right underframe members221,222arranged below a cab floor (not shown) and a reinforcing member223arranged between the underframe members221,222. The reinforcing member223is attached at its left and right side edge portions to the left and right underframe members221,222.

The reinforcing member223is a corrugated panel formed with a plurality of raised portions224provided in parallel to have an uneven cross-sectional shape as shown in FIG.20B. The reinforcing member223provided between the left and right underframe members221,222reinforces the left and right underframe members221,222against a load evenly exerted on the left and right underframe members221,222, for example.

The vehicle floor structure220is configured with the reinforcing member223merely attached at its left and right side edge portions225,226to the left and right underframe members221,222. If, upon an offset collision of the vehicle, a large load f is imposed on the right underframe member222as shown inFIG. 20A, for example, the load f is hardly transmitted to the left underframe member221, as described above. Almost all the large load f imposed on the right underframe member222is received by the right underframe member222. To prevent deformation of the right underframe member222due to a large load f, it is required to increase the strength of the right underframe member222.

An uneven load is not necessarily exerted only on the right underframe member222and may also be exerted on the left underframe member221. It is thus necessary to design the right and left underframe members221,222to have enough strength to be able to withstand a large load f, which results in increased weights of the left and right underframe members221,222.

Thus, there is a demand for a vehicle floor structure which can avoid weight increase while maintaining the frame strength.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided a vehicle floor structure which comprises: left and right floor frame members; a plurality of crossmembers extended between the left and right floor frame members at certain longitudinal intervals; a floor panel mounted to the left and right floor frame members and the crossmembers; and a corrugated sheet in a wave form having a plurality of longitudinally oriented ridges disposed in a substantially rectangular space formed by the left and right floor frame members and opposite ones of the crossmembers; wherein, left and right side portions of the corrugated sheet are connected to the left and right floor frame members, respectively, front and rear edge portions of the corrugated sheet are connected to the opposite crossmembers, and the ridges of the corrugated sheet are connected to the floor panel.

As described above, the floor structure of the present invention forms a space by the left and right floor frame members and the crossmembers. The corrugated sheet is disposed in the space in such a manner that its ridges are oriented longitudinally. The corrugated sheet is connected at the left and right side portions to the left and right floor frame members, and is connected at the front and rear edge portions to the opposite crossmembers, and is connected at the ridges to the floor panel. That is, the corrugated sheet occupies the space formed by the left and right floor frame members and the crossmembers and is arranged with the ridges oriented longitudinally. If a large load is imposed rearward on the right floor frame member, for example, upon an offset collision of the vehicle, the load is transmitted from the right floor frame member to the left floor frame member via the corrugated sheet. The large load imposed on the right floor frame member can thus be dispersed to be received by the left and right floor frame members, and the floor panel and the corrugated sheet located therebetween. If the right floor frame member is reduced in strength to some degree, the right floor frame member can still be prevented from deformation, accordingly.

An uneven load is not necessarily exerted on the right floor frame member and may also be exerted on the left floor frame member. In such a case, a large load can be dispersed into and received by the right floor frame member, the floor panel and the corrugated sheet located therebetween. If the left floor frame member is reduced in strength to some degree, the left floor frame member can still be prevented from deformation, accordingly.

The floor panel of the present invention is preferably mounted on the top of or to the bottom of the left and right floor frame members and the crossmembers. The vehicle floor structure is supported in the vicinities of axles of front and rear wheels and can be curved downward on supporting points in the vicinities of the axles of the front and rear wheels. At that time, the vehicle floor structure is compressed at its upper surface and is stretched at its lower surface. The corrugated sheet having a higher strength is disposed especially on the floor panel to dispose a member of higher strength on the compressed surface. As a result, the bending strength of the vehicle floor structure can be increased.

The ridges of the corrugated sheet are upward- or downward-protruded portions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Discussion will be made first as to a vehicle floor structure according to a first embodiment of the present invention, referring toFIGS. 1to5A and5B.

As shown inFIG. 1, a vehicle floor structure10includes left and right floor frame members11,12, side frame members13,13, a plurality of crossmembers21,22,23,24,25,26and27, a corrugated sheet30, a floor panel15, left and right side sills40,41, and left and right reinforcing plates43,45.

The left and right floor frame members11,12extend longitudinally with a certain space therebetween.

The side frame members13are attached to the front ends of the left and right floor frame members11,12.

The crossmembers21,22,23,24,25,26and27of the first to seventh crossmembers are extended between the left and right floor frame members11,12at predetermined longitudinal intervals.

The corrugated sheet30is formed in a waved section shape. The corrugated sheet30is disposed in a substantially rectangular space28formed by the left and right floor frame members11,12, the first crossmember21and the second crossmember22in such a manner that its upper ridges (ridges)35are oriented longitudinally. The first crossmember21and second crossmember22constitute opposite crossmembers. Left and right side portions31,32of the corrugated sheet30are connected to the left and right floor frame members11,12, respectively. Front and rear edge portions33,34of the corrugated sheet30are connected to the first and second crossmembers21,22, respectively.

The floor panel15is placed over the left and right floor frame members11,12and the first to seventh crossmembers21,22,23,24,25,26and27.

The ridges35of the corrugated sheet30are joined to the undersurface of the floor panel15.

The left and right side sills40,41are arranged outside of the left and right floor frame members11,12, respectively.

A left reinforcing plate43is disposed in a substantially rectangular space42formed by the left side sill40, left floor frame member11, first crossmember21and second crossmember22.

A right reinforcing plate45is disposed in a substantially rectangular space44formed by the right side sill41, right floor frame member12, first crossmember21and second crossmember22.

Front and rear end portions16,17of the floor panel15are connected to the first crossmember21and the fifth crossmember25, respectively. Left and right edge portions18,19of the floor panel15are connected to the left and right side sills40,41, respectively.

As shown inFIGS. 2A and 2B, the first and second crossmembers21and22are formed in a substantially U-shaped section shape.FIG. 2Ashows the front edge portion33of the corrugated sheet30connected to the first crossmember21. The floor panel15is connected to front and rear flat flanges46,47formed at upper portions of the first crossmember21and to the ridges35of the corrugated sheet30.

The rear edge portion34of the corrugated sheet30is connected to the second crossmember22in the same manner as the front edge portion33of the corrugated sheet30is connected to the first crossmember21. Therefore, the structure of connecting the rear edge portion34of the corrugated sheet30to the second crossmember22will not be described.

As shown inFIG. 3, the first crossmember21is formed in a substantially U-shaped section shape, including a bottom48extending transversely, a front wall49extending vertically upward from the front edge of the bottom48, a rear wall50extending vertically upward from the rear edge of the bottom48, and the front and rear flat flanges46,47formed at the top of the front and rear walls49,50, respectively.

The corrugated panel sheet30is a member of increased strength formed with a plurality of raised strips52extending longitudinally at certain intervals, to be in a wave form with the raised strips52and a plurality of flat portions53.

Each raised strip52includes an upper surface (hereinafter referred to as a ridge)35and left and right side walls54,55. A step56is formed in a front end portion of the ridge35. A front end of the left side wall54is bent leftward to form a left flap57. A front end of the right side wall55is bent rightward to form a right flap58. Each flat portion53has a step59formed in its front end.

The front edge portion33of the corrugated sheet30is brought into contact with the rear wall50of the first crossmember21as shown by arrows, thereby to cause the left and right flaps57,58at the raised strips52to abut on the rear wall50, the steps56in the raised strips52to abut on the rear surface of the flat rear flange47, and the steps59in the flat portions53to abut on the bottom48of the first crossmember21(see also FIG.5A).

As shown inFIG. 4, the corrugated sheet30is disposed in the space28between the left and right floor frame members11,12. The ridges35of the corrugated sheet30are connected to the floor panel15by spot welding, for example.

When the ridges35at the left and right side portions31,32of the corrugated sheet30are connected to the floor panel15, the ridges35at the left and right side portions31,32are connected to inside upper edges11a,12aof the left and right floor frame members11,12, respectively.

The left reinforcing plate43is disposed in the space42formed by the left floor frame member11and the left side sill40. An inside upper edge43aof the left reinforcing plate43is connected to the floor panel15by spot welding, for example. An outside lower edge43bof the left reinforcing plate43is connected to the left side sill40by spot welding, for example.

When the inside upper edge43aof the left reinforcing plate43is connected to the floor panel15, an outside upper edge11bof the left floor frame member11is connected to the inside upper edge43aof the left reinforcing plate43. The left reinforcing plate43is bent in a dogleg for increased strength.

The right reinforcing plate45is disposed in the space44formed by the right floor frame member12and the right side sill41. An inside upper edge45aof the right reinforcing plate45is connected to the floor panel15by spot welding, for example. An outside lower edge45bof the right reinforcing plate45is connected to the right side sill41by spot welding, for example.

When the inside upper edge45aof the right reinforcing plate45is connected to the floor panel15, an outside upper edge12bof the right floor frame member12is connected to the inside upper edge45aof the right reinforcing plate45. The right reinforcing plate45is bent in a dogleg for increased strength.

The left edge portion18of the floor panel15is connected to the left side sill40by spot welding, for example. The right edge portion19of the floor panel15is connected to the right side sill41by spot welding, for example.

In the corrugated sheet30, the number of the raised strips52is four and the number of the flat portions53is three. The raised strips52and the flat portions53are not limited to those numbers and the numbers thereof may be determined as desired to desirably change the strength of the corrugated sheet30.

As shown inFIG. 5A, the front and rear flat flanges46,47of the first crossmember21are connected to the floor panel15by spot welding, for example. The left flap57of the corrugated sheet30is connected to the rear wall50of the first crossmember21by spot welding, for example. The step59in the corrugated sheet30is connected to the bottom48of the first crossmember21by spot welding, for example.

As shown inFIG. 5B, the rear flange47of the first crossmember21is connected to the step56in the corrugated sheet30by spot welding, for example. The ridge35is connected to the floor panel15by spot welding, for example. The right flap58of the corrugated sheet30is connected to the rear wall50of the first crossmember21by spot welding, for example. In this manner, the front edge portion33of the corrugated sheet30is connected to the first crossmember21.

As shown inFIG. 1, the corrugated sheet30is disposed in the space28formed by the left and right floor frame members11,12and the first and second crossmembers21,22with the ridges35longitudinally oriented. The corrugated sheet30is connected at the left and right side portions31,32to the left and right floor frame members11,12, and is connected at the front and rear edge portions33,34to the first and second crossmembers21,22, and is connected at the ridges35to the floor panel15. The space formed by the left and right floor frame members11,12and the first and second crossmembers21,22is thus occupied by the corrugated sheet30. The longitudinal arrangement of the ridges35of the corrugated sheet30allows transmission of a large load F imposed rearward on the right floor frame member12, for example, upon an offset collision of the vehicle from the right floor frame member12to the left floor frame member11via the corrugated sheet30.

The large load F imposed on the right floor frame member12can thus be dispersed to be received by the left and right floor frame members11,12, and the floor panel15and the corrugated sheet30located therebetween. If the right floor frame member12is reduced in strength to some degree, the right floor frame member12can still be prevented from deformation, accordingly.

Such an uneven load is not necessarily exerted only on the right floor frame member12and may also be exerted on the left floor frame member11. In such a case, a large load F can be dispersed into and received by the left and right floor frame members11,12, and the floor panel15and the corrugated sheet30located therebetween. If the left floor frame member11is reduced in strength to some degree, the left floor frame member11can be prevented from deformation, accordingly.

Reduction in strength of the left and right floor frame members11,12leads to prevention of weight increase while maintaining the strength of the left and right floor frame members11,12.

Now, first to fourth modifications of the first embodiment will be described with reference toFIGS. 6to9.

A vehicle floor structure60in a first modification shown inFIG. 6differs from the vehicle floor structure10in the first embodiment only in that recesses63are formed in flat portions62of a corrugated sheet61. The other structural elements are identical to those of the vehicle floor structure10in the first embodiment.

The vehicle floor structure60in the first modification has the recesses63formed in the flat portions62of the corrugated sheet61to further facilitate adjustment in strength of the corrugated sheet61suitably for the sizes of vehicles.

A vehicle floor structure65in a second modification shown inFIG. 7differs from the vehicle floor structure10in the first embodiment only in that curved depressions68are formed in flat portions67of a corrugated sheet66. The other structural elements are identical to those of the vehicle floor structure10in the first embodiment.

The vehicle floor structure65in the second modification has the curved depressions68formed in the flat portions67of the corrugated sheet66to further facilitate adjustment in strength of the corrugated sheet66suitably for the sizes of vehicles.

A vehicle floor structure70in a third modification shown inFIG. 8differs from the vehicle floor structure10in the first embodiment only in that the left and right reinforcing plates43,45are eliminated from the vehicle floor structure10shown in the first embodiment and the outside upper edge11bof the left floor frame member11is connected to the floor panel15and the outside upper edge12bof the right floor frame member12is connected to the floor panel15. The number of components is thus reduced, resulting in a simplified structure. The other components are identical to those of the vehicle floor structure10in the first embodiment.

A vehicle floor structure75in a fourth modification shown inFIG. 9differs from the vehicle floor structure10in the first embodiment only in that the left and right floor frame members11,12, the corrugated sheet30and the left and right reinforcing members43,45of the vehicle floor structure10(seeFIG. 4) are integrally formed into an underfloor member76. The other structural elements are identical to those of the vehicle floor structure10in the first embodiment.

The vehicle floor structure75in the fourth modification has a reduced number of components and a simplified structure, simplifying assembly process.

Now, a vehicle floor structure according to a second embodiment of the present invention will be described with reference toFIGS. 10,11,12A and12B. Components in the second embodiment identical to those in the first embodiment are given the identical numbers and will not be described.

Referring toFIG. 10, a vehicle floor structure80in the second embodiment includes a first crossmember21formed in a U-shaped section shape, a corrugated sheet81connected at its front edge portion82to the first crossmember21via a mounting bracket83, and a floor panel15connected to front and rear flat flanges46,47formed at upper portions of the first crossmember21and a plurality of ridges84of the corrugated sheet81.

A rear edge portion of the corrugated sheet81is connected to a second crossmember22(seeFIG. 1) in the same manner as the front edge portion82of the corrugated sheet81is connected to the first crossmember21, so that only the connection between the corrugated sheet81and the first crossmember21will be described.

As shown inFIG. 11, the corrugated sheet81has a plurality of longitudinally extending raised strips85formed at certain intervals, to be in a wave form with the raised strips85and flat portions86for increased strength.

Each raised strip85includes an upper surface (hereinafter referred to as a ridge)84and left and right side walls87,88.

The mounting bracket83is a strip member extended between right and left floor frame members11,12(see FIG.1). The mounting bracket83includes flat surfaces90corresponding to the flat portions86of the corrugated sheet81, protrusions91formed in the positions corresponding to the positions of the ridges84of the corrugated sheet81, and steps92extending forward from the flat surfaces90.

Each protrusion91includes a front wall94to abut against a rear wall50of the first crossmember21, left and right walls95,96to abut against the left and right side walls87,88of the corrugated sheet81, and an upper surface97to abut against the ridge84of the corrugated sheet81.

The steps92are to abut against a bottom48of the first crossmember21(see FIG.10).

Front end portions of the raised strips85of the corrugated sheet81are put over the protrusions91of the mounting bracket83. Specifically, the ridges84and the left and right side walls87,88of the corrugated sheet81are brought into contact with the upper surfaces97and the left and right walls95,96of the protrusions91, and also the flat portions86of the corrugated sheet81are brought into contact with the flat surfaces90, thereby to fit the mounting bracket83to the front edge portion82of the corrugated sheet81.

The front walls94of the protrusions91are made to abut on the rear wall50of the first crossmember21and the steps92are made to abut on the bottom48of the first crossmember21to fit the mounting bracket83to the first crossmember21.

As shown inFIG. 12A, the floor panel15is connected to the front and rear flanges46,47of the first crossmember21by spot welding, for example. The flat portion86of the corrugated sheet81is connected to the flat surface90of the mounting bracket83by spot welding, for example. The step92of the mounting bracket83is connected to the bottom48of the first crossmember21by spot welding, for example.

Also, as shown inFIG. 12B, the front wall94of the mounting bracket83is connected to the rear wall50of the first crossmember21by spot welding, for example. The ridge84is connected the floor panel15by spot welding, for example. The upper surface97of the mounting bracket83is connected to the ridge84by spot welding, for example.

In this manner, the front edge portion82of the corrugated sheet81is connected to the first crossmember21via the mounting bracket83.

The vehicle floor structure80in the second embodiment has the mounting bracket83to simplify the shapes of the front edge portion82and the rear edge portion of the corrugated sheet81as shown inFIG. 11, facilitating the production of the corrugated sheet81, and resulting in cost reduction.

Now, a vehicle floor structure100according to a third embodiment of the present invention will be described with reference toFIGS. 13,14,15A and15B. Components identical to those in the first embodiment are given the identical symbols and will not be described.

Referring toFIG. 13, a vehicle floor structure100in the third embodiment includes a first crossmember101formed in a substantially L-shaped section shape, a corrugated sheet102, a mounting bracket104interposed therebetween for connecting the first crossmember101and a front edge portion103of the corrugated sheet102, and a floor panel15connected to a flat flange106formed at a front-upper edge of the first crossmember101, a flange-like upper edge107of the mounting bracket104, and ridges108of the corrugated sheet102.

A rear edge portion of the corrugated sheet102is connected to a second crossmember (seeFIG. 1) in the same manner as the front edge portion103of the corrugated sheet102is connected to the first crossmember101, so that only the structure of connecting the front edge portion103of the corrugated sheet102to the first crossmember101will be described.

As shown inFIG. 14, the corrugated sheet102has a plurality of longitudinally extending raised strips110formed at certain intervals, to be in a wave form with the raised strips110and flat portions111for increased strength.

Each raised strip110includes an upper surface (hereinafter referred to as a ridge)108and left and right side walls112,113.

The flat portion111is formed in its center with a raised strip114lower in height than the raised strip110in a parallel relationship with the raised strip110.

The first crossmember101is formed in a substantially L-shaped section shape, including a bottom surface116extending transversely, a front wall117raised at the front edge of the bottom surface116, the flat front flange106formed at the upper edge of the front wall117, and protrusions118formed in the positions corresponding to the positions of the raised strips110of the corrugated sheet102.

Each protrusion118has a front wall120raised opposite to the front wall117, left and right walls121,122to abut against the left and right side walls112,113of the corrugated sheet102, and an upper surface123to abut against the ridge108of the corrugated sheet102.

In substantially the center of each front wall120, an opening120ais formed. The formation of the openings120ain the front walls120leads to a reduced weight of the first crossmember101. The upper edge107of the mounting bracket104and the floor panel15are easily connected together by spot welding, for example.

The mounting bracket104is a substantially crank section member extended between the right and left floor frame members11,12(see FIG.1). The mounting member104includes a lower edge124to abut against the bottom surface101of the first crossmember116, a well125raised upward from the rear edge of the lower edge124, and the upper edge107extending rearward from the wall125.

The first crossmember101, corrugated sheet102and mounting bracket104are formed as described above to make the lower edge124of the mounting bracket104abut on the bottom surface116of the first crossmember101.

The ridges108and the left and right side walls112,113of the corrugated sheet102are brought into contact with the upper surfaces123and the left and right walls121,122of the protrusions118. The undersurfaces of the flat portions111of the corrugated sheet102are brought into contact with the bottom surface116of the first crossmember101.

As shown inFIG. 13, the floor panel15abuts on the flat front flange106of the first crossmember101, the upper edge107of the mounting bracket104, and the ridges108of the corrugated sheet102.

As shown inFIG. 15A, the lower edge124of the mounting bracket104and the flat portion111of the corrugated sheet102are connected to the bottom surface116of the first crossmember101by spot welding, for example. The floor panel15is connected to the front flange106of the first crossmember101and the upper edge107of the mounting bracket104by spot welding, for example.

As shown inFIG. 15B, the upper surfaces123of the protrusions118formed at the first crossmember101are connected to the inside of the ridges108of the corrugated sheet102by spot welding, for example. The upper surfaces of the ridges108are connected to the floor panel15by spot welding, for example.

As shown inFIG. 13, the front edge portion103of the corrugated sheet102is connected to the first crossmember101via the mounting bracket104.

The vehicle floor structure100in the third embodiment has the mounting bracket104to simplify the form of the front edge portion103and the rear edge portion of the corrugated sheet102, facilitating the production of the corrugated sheet102, and resulting in cost reduction.

As shown inFIG. 14, the raised strips114are formed in the flat portions111of the corrugated sheet102to increase the strength of the corrugated sheet102.

Now, a vehicle floor structure130according to a fourth embodiment of the present invention will be described with reference to FIG.16. Components identical to those in the first embodiment are given the identical symbols and will not be described.

Referring toFIG. 16, the vehicle floor structure130in the fourth embodiment includes, like the vehicle floor structure10in the first embodiment, a first corrugated sheet30with ridges oriented longitudinally, disposed in a substantially rectangular space28formed by left and right floor frame members11,12and first and second crossmembers21,22.

Left and right side portions31,32of the corrugated sheet30are connected to the left and right floor frame members11,12, respectively. Front and rear edge portions33,34of the corrugated sheet30are connected to the first and second crossmembers21,22, respectively.

A left reinforcing plate43is disposed in a substantially rectangular space42formed by a left side sill40, the left floor frame member11, the first crossmember21and the second crossmember22.

A right reinforcing plate45is disposed in a substantially rectangular space44formed by a right side sill41, the right floor frame member12, the first crossmember21and the second crossmember22.

A second corrugated sheet132in a wave form is disposed in a substantially rectangular space131formed by the left and right floor frame members11,12, the second crossmember22, and a fourth crossmember24, having ridges oriented longitudinally. In this embodiment, the third crossmember23in the first embodiment shown inFIG. 1is eliminated. For correspondence with the first embodiment inFIG. 1, the crossmember24is given the ordinal number “fourth” instead of “third” in description.

Left and right side portions133,134of the second corrugated sheet132are connected to the left and right floor frame members11,12. Front and rear edge portions135,136of the second corrugated sheet132are connected to the second and fourth crossmembers22,24, respectively.

A left reinforcing plate139is disposed in a substantially rectangular space138formed by the left side sill40, the left floor frame member11, the second crossmember22and the fourth crossmember24.

A right reinforcing plate141is disposed in a substantially rectangular space140formed by the right side sill41, the right floor frame member12, the second crossmember22and the fourth crossmember24.

A third corrugated sheet144in a wave form is disposed in a substantially rectangular space143formed by the left and right floor frame members11,12, the fourth crossmember24and a fifth crossmember25, having ridges oriented longitudinally.

Left and right side portions145,146of the third corrugated sheet144are connected to the left and right floor frame members11,12. Front and rear edge portions147,148of the third corrugated sheet144are connected to the fourth and fifth crossmembers24,25, respectively.

Front and rear end portions16,17of a floor panel15are connected to the first and fifth crossmembers21,25, respectively. Left and right edge portions18,19of the floor panel15are connected to the left and right side sills40,41, respectively.

In this manner, the vehicle floor structure130in the fourth embodiment uses more corrugated sheets than the vehicle floor structure10in the first embodiment, further increasing rigidity. A large load F exerted on the right floor frame member12of the vehicle floor structure130is more effectively dispersed to be received by the left and right floor frame members11,12, and the floor panel15and the three corrugated sheets30,132and144located therebetween. If the right floor frame member12is reduced in strength to some degree, the right floor frame member12is still prevented from deformation.

Now, a vehicle floor structure150according to a fifth embodiment of the present invention will be described with reference toFIGS. 17,18A and18B. Components identical to those in the first embodiment are given the identical symbols and will not be described.

In this embodiment, a floor panel151corresponds to the floor panel15in the first embodiment turned upside down, and left and right floor frame members152,153correspond to the left and right floor frame members11,12in the first embodiment turned upside down. A first to seventh crossmembers used in this embodiment correspond to the first to seventh crossmembers21,22,23,24,25,26and27merely turned upside down, and the symbols shown inFIG. 1are used therefor. A corrugated sheet154corresponds to the corrugated sheet30in the first embodiment turned upside down.

Referring toFIG. 17, in the vehicle floor structure150in the fifth embodiment, the left and right floor frame members152,153, the first to seventh crossmembers21to27, and the corrugated sheet154with a plurality of downward facing ridges (bottom ridges)156elongated longitudinally are placed on top of the floor panel151by spot welding, for example.

The corrugated sheet154is disposed in a space155between the left and right floor frame members152,153, and the ridges156of the corrugated sheet154are connected to the floor panel151by spot welding, for example.

When the ridges156at left and right side portions157,158of the corrugated sheet154are connected to the floor panel151, inside lower edges152a,153aof the left and right floor frame members152,153are connected to the ridges156at the left and right side portions157,158.

A left reinforcing plate161is disposed in a space160formed between the left floor frame member152and a left side sill40. An inside lower edge161aof the left reinforcing plate161is connected to the floor panel151by spot welding, for example. An outside edge161bof the left reinforcing plate161is connected to the left side sill40by spot welding, for example.

When the inside lower edge161aof the left reinforcing plate161is connected to the floor panel151, the inside lower edge161aof the left reinforcing plate161is connected to an outside lower edge152bof the left floor frame member152. The left reinforcing plate161is a member bent substantially in a dogleg for increased strength.

A right reinforcing plate163is disposed in a space162formed between the right floor frame member153and a right side sill41. An inside lower edge163aof the right reinforcing plate163is connected to the floor panel151by spot welding, for example. An outside edge163bof the right reinforcing plate163is connected to the right side sill41by spot welding, for example.

When the inside lower edge163aof the right reinforcing plate163is connected to the floor panel151, the inside lower edge163aof the right reinforcing plate163is connected to an outside lower edge153bof the right floor frame member153. The right reinforcing plate163is a member bent substantially in a dogleg for increased strength.

A left side portion164of the floor panel151is connected to the left side sill40by spot welding, for example. A right side portion165of the floor panel151is connected to the right side sill41by spot welding, for example.

The corrugated sheet154includes three raised strips166and four grooves167. The numbers of the raised strips166and grooves167are not limited thereto and may be desirably set to change the strength of the corrugated sheet154as desired.

The vehicle floor structure150in the fifth embodiment provides effects as described with reference toFIGS. 18A and 18B.

Referring toFIG. 18A, the vehicle floor structure150in the fifth embodiment is supported in the vicinities of axles of front and rear wheels170,171and can be deformed downward in a curve (shown by imaginary lines174) on supporting points172,173in the vicinities of the axles of the front and rear wheels170,171.

Referring toFIG. 18B, the corrugated sheet154in the vehicle floor structure150is a member in a wave form and has a higher longitudinal bending strength than the floor panel151. For this reason, the vehicle floor structure150in the fifth embodiment has the corrugated sheet154with the raised strips166oriented longitudinally, disposed on top of the floor panel151.

If a load F1is imposed on the vehicle floor structure150as shown by an arrow and the vehicle floor structure150is deformed in a curve (shown by the imaginary lines174), the vehicle floor structure150can have increased bending strength by the corrugated sheet154having higher strength provided at the compressed side. The vehicle floor structure150in the fifth embodiment can thus be further reduced in weight while maintaining the strength of the left and right floor frame members152,153(see FIG.17).

The corrugated sheets30,61,66,81,102,132,144and154described in the above several embodiments are not limited to the uneven shapes and the shapes may be desirably determined.

Obviously, various minor changes and modifications of the present invention are possible in the light of the above teaching. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.