Abstract:
A floor module is provided for installation in the rear area of a motor vehicle. A rear area of the floor module facing the tail of the vehicle includes a first plastic composition, and a front area facing away from the tail includes a second plastic composition, wherein the first plastic composition imparts a higher elastic deformability to the rear area than to the front area.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to German Patent Application No. 102015008727.4, filed Jul. 7, 2015, which is incorporated herein by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The present disclosure pertains to a floor module for use in a motor vehicle, and the motor vehicle incorporating same. 
       BACKGROUND 
       [0003]    Population growth in congested urban centers is leading to a continuously growing vehicle density, and to a correspondingly rising demand for parking and transport areas that can only be satisfied on a limited available space at ever greater costs. In order to keep land usage and fuel consumption by private transport within reasonable limits, extremely compact vehicles with a low weight and correspondingly low fuel consumption must be more-readily available. 
         [0004]    One way of minimizing weight involves no longer manufacturing parts of a motor vehicle body that have no supporting or passenger compartment-reinforcing function out of metal, but rather out of plastic. For example, DE 10 2010 054 693 A1 discloses a floor module for a motor vehicle that encompasses a base trough injection molded out of plastic as a single piece. 
         [0005]    The trough must be stiff enough to support a vehicle battery and spare tire. If it is made stiffer, however, the greater the danger that it will break when deformed in an accident, and then has to be replaced. In the known floor module, the danger of such breakage is limited by the fact that it does not reach directly up to a rear cross member of the vehicle body, so that the latter can be deformed during an accident without also affecting the floor module. In an extremely compact urban vehicle, it is virtually impossible to secure a floor module far enough away from the outer skin of the body as to keep it from deforming and breaking during a minor accident. However, if the floor module is broken, it must be removed and replaced with a new one. The high repair costs associated therewith can result in an unfavorable classification of the vehicle at insurance companies, and thus lead to correspondingly operating costs for the vehicle owner. 
         [0006]    Therefore, there exists a demand for a motor vehicle or components for the latter that minimize the repair expenses after an accident, even given a compact and weight-saving construction. 
       SUMMARY 
       [0007]    In one embodiment of the present disclosure, this demand is satisfied by a floor module to be installed in the rear area of a motor vehicle, in which a rear area of the floor module facing the tail of the vehicle includes a first plastic composition, and a front area facing away from the tail includes a second plastic composition. The first plastic composition imparts a higher elastic deformability to the rear area than to the front area. As a consequence, because the front area that is at best minimally endangered during a minor accident can be relatively stiff so as to impart the mechanical resilience to the floor module required for transporting goods thereon, the rear area can be deformed to a great extent in light of its elasticity, without this posing a danger of breakage or in some other way impairing the mechanical integrity of the floor module. 
         [0008]    The front and rear areas of the floor module are preferably designed as a single piece with each other, for example by coextruding the first and second plastic composition in a shared mold, or by deep-drawing flat material cuts consisting of the first and second plastic composition together in an identical forming tool, and welding them together in the process. 
         [0009]    The entire floor module is typically shaped like a trough. One part of a flat floor plate of the floor module can consist of the relatively slightly deformable front area, and the other part of the highly deformable rear area. A horizontal mounting flange for attaching the floor module to other parts of the body of the motor vehicle can extend around the floor plate. In order to create the aforementioned trough shape, one wall can extend around the floor plate. It makes sense for the mounting flange to be stiffened by ribs, which extend between a lower side of the mounting flange and an exterior side of this wall that joins together the floor plate and flange. 
         [0010]    A receptacle for a motor vehicle battery is preferably formed in the relatively slightly deformable front area of the floor module. In order to secure the battery in the receptacle, the receptacle can be bordered from behind by a rib that protrudes upward from the front area of the floor module. In addition, the receptacle can be bordered laterally by a projection that protrudes from the front area of the floor module and onto which can be secured, in particular plugged, a hook for encompassing a rear side of the battery. The projection can encompass a threaded bolt, to which the hook can be attached by screwing on a nut. In order to simplify vehicle assembly, the floor module and vehicle battery pre-installed in the receptacle of the floor plate can together form an assembly, which can be built into the vehicle body according to the present disclosure as one unit. 
         [0011]    In another embodiment of the present disclosure, the demand is satisfied by an assembly with a floor module as described above, and by a vehicle battery pre-installed in the receptacle of the floor module. 
         [0012]    In another embodiment of the present disclosure, the demand is satisfied by a motor vehicle with a floor module or an assembly as described above, in which a front edge of the floor module is anchored to a central, rear cross member of the motor vehicle. Storage space can be created between the cross member and floor module by having the front area of the floor module extend under the front cross member, and used in particular to accommodate the vehicle battery. A rear edge of the floor module can be anchored to a rear cross member of the motor vehicle. Even if its exposed position puts this rear cross member at great risk of being deformed during a collision between the rear of the motor vehicle and an obstacle, damage to the floor module can be averted by this deformation due to the elasticity of the rear area. 
         [0013]    The floor module is preferably detachably anchored by fasteners such as screws or bolts, on the one hand so that the latter can be easily detached from the floor module and repaired or replaced given a deformation of the rearmost cross member, without having to also remove the floor module for this purpose, and on the other hand so that the floor module can also be quickly and inexpensively replaced if a collision was strong enough to damage the floor module, e.g., by deforming it all the way into its front area. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The present disclosure will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements. 
           [0015]      FIG. 1  is a view of the rear section of a motor vehicle according to the present disclosure; 
           [0016]      FIG. 2  is the floor module of the vehicle, viewed from the same direction as on  FIG. 1 ; 
           [0017]      FIG. 3  is a view of the floor module, inclined from the front; 
           [0018]      FIG. 4  is an assembly included of the floor module and a vehicle battery mounted thereto; 
           [0019]      FIG. 5  is a section through the floor module in the vehicle transverse direction, along the plane marked V-V on  FIG. 4 ; 
           [0020]      FIG. 6  is a section in the vehicle transverse direction along the VI-VI plane on  FIG. 1 ; 
           [0021]      FIG. 7  is a section in the vehicle longitudinal direction along the plane on  FIG. 1 ; 
           [0022]      FIG. 8  is a section in the vehicle longitudinal direction along the vehicle center plane in an intact state; and 
           [0023]      FIG. 9  is a section similar to  FIG. 8  in the deformed state after a collision. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description. 
         [0025]      FIG. 1  shows a perspective view of the rear area of the body of a compact motor vehicle according to the present disclosure. The body has a ladder-like support structure with two side members  4  extending along the flanks of the vehicle and several cross members joining the side members together. A tailgate of the body has been omitted on the figure, so that, of these cross members, a rear cross member  2  and a central rear cross member  3  are visible through the tailgate opening between two side walls  1  of the body. The two cross members  2 ,  3  and the side members  4  together include a rectangular frame, under which a trough-shaped floor module  5  is attached. 
         [0026]      FIG. 2  shows the floor module  5  separate from the body. The floor module  5  is injection molded as a single piece out of two different plastic compositions, wherein a line  6  extending in the vehicle transverse direction establishes the boundary between a front area  7 —relative to the traveling direction of the vehicle—included of a relatively stiff, dimensionally stable plastic and a rear area  8  included of a plastic that to a large extent is elastically deformable. An essentially flat base plate  9  belongs in part to the front area  7 , and in part to the rear area  8 . A rib  10  elongated in the vehicle transverse direction extends parallel to the line  6  in the front, stiff area of the base plate  9  over part of its width. Located opposite the rib  10  is a bulge  11  on a front edge of the base plate; the storage space between the bulge  11  and rib  10  is provided to accommodate a battery  12  of the vehicle, as depicted on  FIGS. 1 and 4 . 
         [0027]    A projection at a central location of the stiff area of the base plate  9  is formed by crafting an elevation  13  from the stiff plastic, and anchoring an upwardly protruding threaded bolt  14  therein. As visible in particular on  FIG. 6 , the threaded bolt  14  can consist of a screw, the head of which was embedded into the stiff plastic of the front area  7  while injection molding the floor module  5 . 
         [0028]    A continuous wall  15  extends all the way around the rectangular base plate  9 , and also includes the stiff plastic in the front area  7 , and the elastically deformable plastic in the rear area  8 . A seamless, continuous flange  16  extends along the upper edge of the wall  15 . An inwardly protruding, horizontally elongated projection  17  is formed on the wall  15  in proximity to the base plate  9  in the area of the bulge  11 , so that the battery  12  can latch positively in place in front of the rib  10  and under the projection  17 . 
         [0029]    In order to secure the battery  12  in this latched position, a hook  18  injection molded out of plastic is plugged onto the threaded bolt  14 , and, as depicted on  FIG. 4 , abuts against a narrow side  19  of the battery and its broadside  20  facing the vehicle rear, and is fixed in its position by a nut  21  screwed onto the threaded bolt  14 . 
         [0030]      FIG. 5  presents a schematic section through the floor module  5  and battery  12  along the plane marked V-V on  FIG. 4  and running through the bulge  11 . The flange  16  extends above the bulge  10  from the upper edge of the wall  15  over the base plate  9 , so that the storage space formed between the flange  16  and base plate  9  is shaped like a niche  24 , into which the battery  12  is pushed from behind in the sequence of motions shown on  FIG. 7 , and secured among other things via positive engagement under the projection  17 . 
         [0031]    The flange  16  extends outwardly from a side section of the wall  15  profiled on  FIG. 5 , and is stiffened by triangular ribs  22  that extend between the lower side of the flange  16  and the wall  15 . Such ribs  22  are distributed along the flange  16  on all four sides of the floor module  5 , in particular so as to stiffen those areas of the flange  16  recessed to form a screw hole  23 . The screw holes  23  are used to attach the floor module  5  to the lower sides of the side and cross members  2 ,  3 ,  4  by means of screws, which pass through the screw holes  23  from below and engage threads on the side and cross members  2 ,  3 ,  4 . 
         [0032]      FIG. 6  presents a section through the floor module  5 , the battery  12  and a side member  4  along the plane marked VI-VI on  FIG. 1  and runs through the axis of the threaded bolt  14 . The side member  4  includes two metal sheets  25 ,  26 , which are welded together on flanges  27 ,  28  extending in the vehicle longitudinal direction. The flange  16  of the floor module  5  touches the lower side of the flange  27  facing the vehicle interior, and is detachably secured to the latter by screws  29  extending through the screw holes  23  from below. 
         [0033]    As evident from  FIG. 7 , the rear cross member  2  also encompasses two metal sheets  30 ,  31 , which are welded together on a flange  32 . This flange  32  lies at the same height as the flange  27  of the side member  4 , and the flange  16  of the floor module  5  is also secured thereto by screws  29 . 
         [0034]    Below the central, rear cross member  3 , the flange  16  of the floor module  5  runs at a deeper level than along the side member  4  and the rear cross member  2 . While the central, rear cross member  3  also encompasses two metal sheets  35 ,  36  welded together along flanges  33 ,  34 , the flange  16  here is not bolted to the flanges  33 ,  34 , but rather at a lower level to the lower side of the metal sheet  36 . 
         [0035]      FIG. 8  shows the floor module  5  bolted to the rear cross member  2  and central, rear cross member  3  in an intact, non-deformed state. On  FIG. 9 , a portion of the rear cross member  2  is forwardly displaced toward the central, rear cross member  3  by a collision. The resultant deformation of the floor module  5  is concentrated on the slightly deformable, elastic rear area  8 ; the stiff front area  7  is essentially not deformed. If the deflected rear cross member  2  is again aligned or replaced during repairs, the elasticity of the rear area  8  allows it to return to the configuration on  FIG. 8 , without requiring any further action for this purpose. 
         [0036]    While at least one exemplary embodiment has been presented in the foregoing 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 of the invention in any way. Rather, the foregoing 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 of the invention as set forth in the appended claims and their legal equivalents.