Abstract:
A rear floor structure for a motor vehicle includes, but is not limited to two longitudinal girders extending between rear wheel houses. A downwardly open pocket for receiving a shock absorber is formed in each of the longitudinal girders.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to German Patent Application No. 102010048849.6, filed Oct. 19, 2010, which is incorporated herein by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The technical field relates to the construction of a rear floor structure for a motor vehicle, in particular a floor structure for a small car that is optimized in regard to its collision behavior. 
       BACKGROUND 
       [0003]    The floor structure of a motor vehicle typically comprises a grid of longitudinal girders and crossbeams, which can be implemented as assembled or integral, for example, as a cast part. Forces which occur in the travel direction in the event of a collision must largely be absorbed and dissipated by the longitudinal girders in order to prevent a deformation of the passenger compartment which endangers the occupants. The stiffness of the longitudinal girders required for this purpose is to be achieved at the least possible weight, on the one hand, for reasons of cost-effectiveness of the manufacturing, and on the other hand, in order to allow fuel-saving operation of the vehicle. 
         [0004]    The more compact the vehicle body of the vehicle is to be, the more difficult the requirements for the longitudinal girders are to meet. At the height of the passenger compartment, the longitudinal girders are to run on the outside along the flanks of the vehicle, so as not to restrict the foot well of the passenger compartment and to contribute to the stability of the passenger compartment against side impact. However, the longitudinal girders must run in a curve in front of and behind the passenger compartment in order to avoid the wheel houses and leave space for a spring-mounted suspension of the wheels and for shock absorbers. Roomy wheel houses which offer space for wheels and associated shock absorbers restrict the space in the vehicle body which is usable for seats of the passenger compartment or as baggage space. In addition, they make it necessary for the longitudinal girders to run offset strongly inward, which impairs their resistance against the longitudinal forces occurring in the event of a collision. 
         [0005]    In view of the foregoing, at least one object is to provide a rear floor structure for a motor vehicle, which has a high carrying capacity at low weight and allows efficient space utilization. In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background. 
       SUMMARY 
       [0006]    A rear floor structure is provided that has two longitudinal girders extending between rear wheel houses, a downwardly open pocket is formed in each of the longitudinal girders to receive a shock absorber associated with one of the rear wheels. Since the rear wheel houses no longer have to provide space for the shock absorber of the wheel received therein, they may be compact, and the longitudinal girders can run at the height of the rear wheel houses with little offset to the lateral surfaces of the vehicle body. Therefore, the curvature of the longitudinal girders can be kept small, which both benefits their carrying capacity and also enlarges the usable space in the interior of the vehicle body. 
         [0007]    If the longitudinal girders are hollow profiles having an upper wall and a lower wall, the shock absorbers can each cross one opening of the lower wall, in order to be supported on the lower wall. The otherwise nonfunctional, empty interior of the longitudinal girders can thus be used to house at least a part of the shock absorbers, which further improves the compactness of the vehicle body construction. 
         [0008]    In order to allow sufficient spring deflection, the length of the shock absorbers cannot be excessively small. In order to be able to house these shock absorbers in a sufficient length, but not unnecessarily increase the distance of the longitudinal girders from the roadway, on the other hand, it is expedient if an area of the upper wall on which the shock absorber is supported is higher than adjacent areas of the upper wall. In particular, the area of the upper wall on which the shock absorber is supported can form the apex of a bulge of the upper wall in the form of a cupola or half-cupola. The longitudinal girders can extend linearly in the vehicle longitudinal direction between the rear wheel houses. 
         [0009]    In order that the pocket receiving the shock absorber does not form a weak point of the longitudinal girder, it can be expedient to incorporate a support wall between the upper wall and the lower wall of each longitudinal girder, which extends in each case at least partially around the shock absorber engaging in the longitudinal girder. The longitudinal girders preferably have a hat-shaped cross-section which is open to the side, i.e., toward the rear wheel houses, at least in the area of the rear wheel houses. The hat-shaped cross-sections can each have two brim sections fastened on the wheel houses. The wheel houses thus supplement the hat-shaped cross-sections to form a highly bending-resistant closed profile, which is capable of dissipating a large quantity of impact energy. 
         [0010]    The longitudinal girders are preferably connected to one another by floor plates, which can form a luggage compartment floor or the floor of the rear part of the passenger compartment, for example. As a result of the engagement of the shock absorbers in the pockets of the longitudinal girders, they may be situated at a relatively small distance above the roadway, so that the floor plates no longer have to extend in a trough down to below the longitudinal girders, but rather can run essentially linearly at the height of the longitudinal girders. The strength resulting therefrom against tensile forces acting the vehicle transverse direction contributes to the stability of the floor structure. 
         [0011]    Furthermore, a crossbar can contribute to the stability of the longitudinal girders at the height of the pockets receiving the shock absorbers, which connects the longitudinal girders to one another at the height of these pockets and thus makes it more difficult for the longitudinal girders to buckle toward one another under load. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and: 
           [0013]      FIG. 1  shows a perspective view of a rear floor structure according to an embodiment; 
           [0014]      FIG. 2  shows a top view of the girders of the rear floor structure; and 
           [0015]      FIG. 3  shows a schematic cross-section through a part of the rear floor structure. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The following detailed description is merely exemplary in nature and is not intended to limit application and uses. Furthermore, there is no intention to be bound by any theory presented in the preceding background or summary or the following detailed description. 
         [0017]      FIG. 1  shows a perspective transparent view of a rear floor structure for a motor vehicle. The lateral flanks of this floor structure are formed by two longitudinal girders  1 . The two longitudinal girders  1  are each profiles open toward the vehicle outer side having a hat-shaped cross-section, which, as may be seen better in  FIG. 3 , each have an essentially horizontal upper wall  2 , a lower wall  3 , a side wall  4 , which connects the walls  2 ,  3  and forms the brim of the hat-shaped cross-section, and struts  5 , which are essentially vertical like the side wall  4 . The longitudinal girders  1  shown in  FIG. 1  each carry flanges  6  on their rear end for fastening a shock absorber support (not shown). A crossbeam  7 , which connects the front ends of the longitudinal girders  1 , to one another is under the front edge of the seat cushions of a rear row of seats in the completely assembled vehicle and forms a rear wall of the foot well for the passengers in the backseat. A rear floor plate  8 , a trough  35 , and a front floor plate  9  fill up the area bounded by the longitudinal girders  1  and crossbeams  7 . 
         [0018]    As may be seen most clearly in  FIG. 2 , the linear rear sections  10  of the longitudinal girders  1 , which are parallel to one another, extend along recesses  11 , which are provided to receive wheel houses (not shown in  FIG. 1  and  FIG. 2 ). Front sections  12  of the longitudinal girders  1  run divergently from a front edge of the recesses  11  to the crossbeam  7 . While the lower edge of the longitudinal girders  1  runs essentially horizontally along the recess  11 , the upper wall  2  locally forms an upwardly curved cupola  13 . The cupola  13  is not complete, a part of its side wall is missing on its side facing toward the adjacent recess  11 . An opening  14  at the apex of the cupola  13  is provided to receive the head end of a shock absorber (not shown in  FIG. 1  and  FIG. 2 ) therein, which engages on a rear wheel of the vehicle, which is housed in the adjacent recess  11 . The body of the shock absorber extends freely through an opening  15  cut in the lower wall  3 . Two sections of a support wall  16 , which connect the walls  2 ,  3  to one another by extending the side walls of the cupola  13 , can be recognized in front of and behind the opening  15  in  FIG. 1 . An angled lower fastening flange  17  of the support wall  16  is welded to the lower wall  3 . An upper edge of the support wall  16  contacts a pedestal zone of the side wall of the cupola  13  from the inside and is welded thereto. The support wall  16  can extend integrally in the curve around the opening  15  and the shock absorber, or it can be divided into two sections, which each cross the free cross-section of the longitudinal girder  1  and have an edge fastened on its side wall  4 . 
         [0019]      FIG. 2  shows a top view of the substructure of  FIG. 1 , in which the floor plates  8 ,  9  are left out. It may be seen here that the longitudinal girders  1  are additionally connected at the height of their two cupolas  13  by a crossbeam  18  running below the floor plates  8 ,  9 . The crossbeam  18  has a hat-shaped cross-section like the longitudinal girder  1 , whose opening is oriented upward, however, so that the webs  19  of the crossbeam  18  are on top and are welded to the essentially level rear floor plate  8 . Arms  20  extending forward from the crossbeam  18  support the three-dimensionally structured floor plate  9 , which extends under the rear row of seats in the completely assembled vehicle. 
         [0020]      FIG. 3  shows a schematic partial cross-section of the floor structure, whose section plane runs through the cupola  13  of one of the longitudinal girders  1  and shows the shock absorber anchored therein, identified here by  21 . Furthermore, it may be seen here that the longitudinal girder  1  is assembled from two elongate elements  22 ,  23 , of which the upper element  22  forms the upper wall  2 , including the cupola  13 , and a part of the side wall  4 , and the lower element  23  forms the lower wall  3  and the remainder of the side wall  4 . Both are connected to one another on webs  24  protruding toward the vehicle interior, which are in turn used as a support surface on which the floor plate  8  is welded. 
         [0021]    A wheel house  25  is welded to the webs  5  of the elements  22 ,  23  and the support wall  16 . The wheel house  25  closes the open side of the longitudinal girder  1 , so that a dimensionally-stable hollow profile having closed cross-section is obtained. The cupola  13 , the support wall  16  extending downward, and the opening  15  together form a pocket  26  open to the bottom, which receives a large part of the shock absorber  21 . 
         [0022]    While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.