Abstract:
A side member of a vehicle chassis structure is disclosed as having a front section, two rear sections running on the same side of the vehicle center, and a branching section that connects the front and rear sections. The branching section includes a y-shaped floor part and at least one side wall part, which extends along an edge of the floor part, and encompasses both a side wall attached to a rising flange of the floor part and a flange angled away from the side wall and attached to a base plate of the floor part.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to German Patent Application No. 102014016045.9, filed Oct. 29, 2014, which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure pertains to a vehicle chassis structure with a side member having a front section, two rear sections running on the same side of the vehicle center, and a branching section that connects the front section and rear sections. 
     BACKGROUND 
     The branching section of a conventional chassis structure such as disclosed in U.S. Pat. No. 5,002,333. The branching section is realized as a single piece through deep drawing. Steels suitable for deep drawing generally have a low strength, so that a sufficient resistance against the loads arising during a vehicle collision can only be achieved for the chassis structure by a high wall thickness and correspondingly high weight of the branching section. 
     SUMMARY 
     In accordance with the present disclosure, a vehicle chassis structure of the kind indicated at the outset is provided that achieves a high load-bearing capacity at a lower weight. For example, in an embodiment of the present disclosure a vehicle chassis structure of the kind indicated at the outset is disclosed and further includes a branching section having a y-shaped floor part and at least one side wall part, which extends along an edge of the floor part, and encompasses both a side wall attached to a rising flange of the floor part and a flange angled away from the side wall and attached to a base plate of the floor part. Attaching the respective side wall and flange of the floor part or flange of the side wall part and the base plate of the floor part to each other doubles the material along an edge of the branching section, which imparts a high strength to the latter and makes it possible to reduce the wall thicknesses of the parts assembled into the branching section in comparison to the conventional one-part branching section, and in so doing decrease its weight, without any losses in strength. 
     The side wall parts can be roll formed. Roll forming can be performed using high-strength alloys that are not suitable for deep drawing. If the at least one side wall part consists of such a high-strength alloy, in particular a high-strength aluminum alloy, the wall thickness of the side wall part and/or the floor part can be further reduced, and additional weight can be economized in this way. 
     A second flange can be angled away along the upper edge of the lateral wall, so that other parts of the chassis structure can be attached thereto. These parts may include in particular a floor plate of a passenger compartment and/or a front wall that separates the passenger compartment from an engine compartment. 
     The roll forming part can extend along an edge of the floor part between connectors for the two rear sections of the side member. The roll forming part can also extend along one of the two edges of the floor part, which each join a connector for one of the rear sections with a connector for the front section. 
     Side wall parts as defined above are preferably provided on all three edges of the floor part. The front section of the side wall part that generally runs between an engine compartment and a front wheel well of the vehicle is preferably designed as a profile with a closed cross section. An inner of the two rear sections of the side member can border a transmission hump of the vehicle. This inner rear section is also preferably designed as a profile with a closed cross section. 
     The inner, rear section may include several parts, which are interconnected along flanges that extend in a longitudinal direction of the inner, rear section. If these flanges are designed so as to project from the cross section of the inner, rear section toward the sides, they can further serve to anchor other parts of the chassis structure thereto, in particular a floor plate of the passenger compartment. An outer of the two rear sections can exhibit a hat-shaped cross section, which is only enhanced to form a closed cross section by mounting the floor plate or another body part thereon. 
     The front section and rear sections of the side member can also be roll formed. Here as well, fabrication through roll forming makes it possible to use high-strength material, so that the required load-bearing capacity of the side member in the event of a collision can be achieved with a low weight. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements. 
         FIG. 1  illustrates the branching section of a vehicle chassis structure according to the present disclosure in an expanded view; 
         FIG. 2  illustrates the side member including the branching section on  FIG. 1 , front section and rear sections in an assembled condition; 
         FIG. 3  illustrates the side member from  FIG. 2 , assembled with a front wheel housing; 
         FIG. 4  is illustrates a complete front section with two side members on either side of the middle of the vehicle; 
         FIG. 5  is a cross section through the front section of a side member and the connector of the branching section that accommodates it along the V-V plane shown in  FIG. 2 ; 
         FIG. 6  is a cross section through the branching section along the VI-VI plane shown in  FIG. 2 ; and 
         FIG. 7  is a cross section through the rear, inner section of the side member along the VII-VII plane shown in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     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. 
       FIG. 1  shows the branching section  1  of a side member of a motor vehicle body in an expanded view. The branching section  1  includes a Y-shaped floor part  2  as viewed from above, and side wall parts  3 ,  4 ,  5 . The floor part  2  is deep drawn in a manner known in the art from flat material, such as sheet steel. It encompasses three arms including a first arm  6  which extends obliquely upward toward the front in the longitudinal direction of the vehicle, and second and third arms  7 ,  8  which extend horizontally toward the back therein, and in so doing diverge in the transverse direction of the vehicle. A floor plate  9  extends over the entire length of the arms  6 ,  7 ,  8  up until the connectors  10 ,  11 ,  12  formed at their free ends. Formed along the edges of the floor plate  9  are vertically rising flanges  13 ,  14 ,  15 , which each extend continuously from one of the connectors  10 ,  11 ,  12  to another. 
     The side wall parts  3 ,  4 ,  5  are roll formed out of high-strength sheet steel, and each encompass a vertical wall  16 , as well as flanges  17 ,  18  angled away from the upper and lower edges of the wall  16  in opposite directions. The lower flange  17  and each of the flanges  13 ,  14 ,  15  extend over the entire length of the wall  16 . The upper flange  18  of side wall part  3  also extends over the entire length of the wall  16 . The upper flange  18  of the side wall parts  4 ,  5  extends from rear connectors  11 ,  12  but do not extend as far as to the front connector  10 . 
     When assembling the branching section  1 , the floor part  2  and side wall parts  3 ,  4 ,  5  are each joined together in such a way that the lower flange  17  abuts against the floor plate  9 , the wall  16  of the side wall part  3  abuts against the flange  13 , the wall  16  of the side wall part  4  abuts against the flange  14 , and the side wall  16  of the side wall part  5  abuts against the flange  15 . These parts are structurally bonded by means of two rows of welding points, one along the side walls  16  and flanges  13 ,  14 ,  15  and the other along the flange  17  and floor plate  9 .  FIG. 2  shows a construction for the branching section  1  in which the side wall parts  3 ,  4 ,  5  are inserted into the floor part  2 , so that the flanges  17  rest upon the floor plate  9 . A configuration in which the side wall parts  3 ,  4 ,  5  of the floor part  2  envelop the floor part  2  from outside would also be possible. 
     The front connector  10  has placed inside of it a carrier section  19 , here in the form of a rectangular profile. As evident from the cross section shown on  FIG. 5 , it is anchored on the areas of the walls  16  that rise over the flanges  14 ,  15  by means of welding points  20 , and contacts the lower flanges  17  of the two side wall parts  4 ,  5 . The welding points of the aforementioned rows connecting the side wall parts  3 ,  4 ,  5  with the floor part  2  are marked  21 . 
     The front carrier section  19  is depicted with a seamless cross section in  FIG. 5 . In practice, it is preferably obtained by roll forming a strip of high-strength sheet steel, wherein a seam on which the two edges of the sheet steel are welded together can be placed at any location of the cross section desired. 
       FIG. 6  shows a section through a central area of the branching section  1  in the transverse direction of the vehicle. As clearly evident here, the material is doubled by overlapping the floor part  9  with the side wall parts  4 ,  5  in the area of the edges of the structure that is exposed to a heavy load during a collision, while the flat wall areas subjected to a weaker load can make do with a single sheet layer whose wall thickness can be distinctly smaller than that of a sheet deep drawn as a single part in a conventional manner. 
     Referring once again to  FIG. 2 , an outer, rear carrier section  22  is inserted into the connector  11 , and welded to the side walls  16  and flanges  17 ,  18  of the side wall parts  3  and  5 . The carrier section  22  has an inversely hat-shaped cross section with an upwardly open central groove  24 , and upwardly facing, elongated flanges  23  on either side of the groove, which each extend and are provided as an elongation of the flange  18  of the side wall parts  3  and  5 , so as to be welded from below to a floor plate of a passenger compartment (not shown on  FIG. 2 ). 
     An inner, rear carrier section  25  is placed inside the connector  12 , and there welded to the walls  16  and flanges  17 ,  18  of the side wall parts  3 ,  4 . Just as the front carrier section  19 , the carrier section  25  has a closed cross section, but as depicted on  FIG. 7  is composed of several parts  26 ,  27 , which are welded among each other along flanges  28  or  29  that extend in the longitudinal direction of the carrier section  25  or in the longitudinal direction of the vehicle. The flanges  28  protruding on the side facing the outer, rear carrier section  22  provide a support for the floor plate  30  of the passenger compartment. The flanges  29  protruding toward the middle of the vehicle can support a cover for a transmission hump or border an outlet opening for a gearshift extending into the transmission hump. The part  26  can serve as a carrier for a rail  31 , in which a front seat of the vehicle is adjustably guided. Due to their simple shape, the parts  26 ,  27  can be easily fabricated via roll forming, and can therefore be made out of a high-strength material that is not suitable for deep drawing or extruding. 
       FIG. 3  shows the side member from  FIG. 2 , enhanced to include a wheel housing  32  and a strut mount  33 , which each include parts of a front wheel well. The wheel housing  32  is welded to the wall  16  of the side wall part  5  before the front end of its upper flange  18 . 
       FIG. 4  shows the left-side assembly from  FIG. 3  and a right-side assembly, which is a mirror-imaged counter piece, joined together by a front wall  34  that differentiates a passenger compartment from the engine compartment and a transmission hump front part  35 , which projects into the passenger compartment from the front wall  34 . A lower edge of the front wall  34  abuts flush against the flange  23  and  28  of the rear carrier sections  22 ,  25 , on which the floor plate  30  not shown on  FIG. 4  rests. 
     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.