Abstract:
A body supporting structure for a vehicle body has a passenger-compartment section, a front-structure section and a rear-structure section. In order to form the body supporting structure, at least one supporting-structure body is configured as a three-dimensional flat structure which extends in all vehicle directions (x, y, z direction) and includes flat elements, the flat elements which extend in different vehicle directions (x, y, z direction) are connected with the formation of soft transitions, the flat elements are configured with cross-sectional areas which are structured depending on the applied loads, and flat elements with low applied loads or non-loadbearing regions are configured with apertures.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is the U.S. National Stage of International Application No. PCT/EP2013/001745, filed Jun. 13, 2013, which designated the United States and has been published as International Publication No, WO 2013/185917 and which claims the priority of German Patent Application, Serial No. 10 2012 011 878.3, filed Jun. 13, 2012, pursuant to 35 U.S.C. 119(a)-(d). 
     BACKGROUND OF THE INVENTION 
     The invention relates to a body supporting structure for a vehicle body having a passenger compartment section, a front-structure section and a rear-structure section. 
     The existing state of the art for manufacturing vehicle bodies has long been a unitary body shell construction, in which, by using different joining techniques, profiles, frame parts, reinforcements, sheet metal parts and skins are permanently connected with one another as steel elements and sheet metal elements and form a body-supporting structure. This category also includes the so-called monocoque construction, which is used primarily in motor sport. For example, a single-shell outer skin forms here the supporting structure of a vehicle; driver compartments are also produced using this monocoque construction as a monocoque shells and connected to the body. 
     A new lightweight design concept in body construction was introduced by the applicant in form of the so-called Audi Space Frame (ASF). Here, a unitary body is formed of die-cast aluminum, aluminum profiles and aluminum sheet, into which the load-bearing flat elements are integrated. 
     In these concepts, to optimize the crash performance, longitudinal beam structures which are connected via cross-beam support structures to provide reinforcement and support, for example, by way of cast nodes (see ASF-concept), are optimized as main load paths with regard to occurring load situations. Single load path structures are also designed to receive individual loads, such as crash loads, introduced undercarriage loads or stiffness-enhancing loads. Crash energy is dissipated by wrinkling of the employed metallic material used in these load paths. 
     In the context of lightweight concepts, body parts are increasingly constructed as hybrid components from a combination of metal and fiber-reinforced plastic (FRP) or as a plastic component made of a FRP material. 
     For example, a body-supporting structure is known from EP 1 781 527 B1 which has a modular structure constructed as a central body section with the passenger compartment and a front body section. The central body section is produced as a support frame from aluminum profiles and connected to a base plate. Both the base plate and the front body section are made from a fiber composite material, such as carbon fibers, Kevlar fibers and/or glass fibers. According to EP 1 781 527 B1 it is also proposed to likewise produce the central body partially or completely from a fiber composite material. 
     DE 10 2010 014 574 A1 discloses a vehicle body of modular construction, which also consists of a unitary passenger compartment and a front- and rear-structure section attached thereto, wherein the passenger compartment includes a trough-shaped bottom section made of fiber-reinforced plastic with a front wall and a rear wall. The front-structure section and the rear-structure section are attached to this front wall and rear wall with screws. 
     Although energy absorbing elements made of a fiber composite material have a higher specific energy absorption capability than metallic longitudinal or transverse beams, such structures made of fiber-reinforced plastic exhibit an unfavorable crash behavior, since these structures dissipate crash energy in a progressive compression process (crushing) which causes their complete destruction, so that the residual strength is not sufficient to hold the attached structural elements together. 
     It is also known to take nature as a model for lightweight structures and to replicate nature as a bionic design, which is intended for maximum weight savings while providing optimal stability. 
     Such a concept was pursued by Daimler AG in the development of a concept vehicle, referred to as “Bionic Car”. This vehicle was constructed with an optimized basic structure inside an optimal aerodynamic shell, with a boxfish used as a fluid dynamics model. This optimized basic structure was developed by using software simulating a bone mineralization process, which produces load-oriented structural proposals for technical components. However, this Bionic Car concept was not produced in series. 
     Furthermore, it is also known to develop vehicle body parts with an optimal bionic design, as described for example in DE 10 2009 052 920 A1 in relation to a subcarrier to be attached to a vehicle body. 
     SUMMARY OF THE INVENTION 
     It is the object of the invention to create a body supporting structure for a vehicle body which has at least partially an optimized bionic structure, and in particular an optimized crash performance. 
     This object is solved by a vehicle body supporting structure for a vehicle body having a passenger compartment section, a front-structure section and a rear-structure section. 
     Such a body supporting structure for a vehicle body with a passenger compartment section, a front-structure section and a rear-structure section, is characterized according to the invention in that
         to form the body supporting structure, at least one structural supporting member is formed from flat elements as a three-dimensional surface structure extending in all directions of the vehicle,   the flat elements extending in different directions of the vehicle are interconnected by smooth transitions,   the flat elements are formed with cross-sectional areas that are structured depending on the occurring applied loads, and   the flat elements with low applied loads or non-loadbearing regions are formed with openings.       

     Such an inventive structural supporting member thus represents a surface supporting structure extending in quasi all three spatial directions and which is self-supporting and hence distributes applied loads in all spatial directions, wherein depending on the occurring applied loads the cross-sectional areas are structured in such a way that large applied loads result in large surface cross-sections. 
     By employing such a supporting surface structure, the usual nodes connecting the longitudinal and transverse beams are removed and the longitudinal and transverse structures are seamlessly joined by smooth transitions, i.e. without the formation of sharp edges. Thus, there are no sharp edges in the load paths, thus preventing peak stresses. Detrimental separation lines or joints are also eliminated. Furthermore, such a supporting surface structure forms homogeneous load paths, thus preventing peak stresses under an applied force. Single supports acting only in one spatial direction are also no longer required. 
     Overall, such a structural supporting member according to the invention produces a structure having high stability while minimizing material consumption. 
     According to another advantageous embodiment of the invention, a floor assembly with a common trough-like subfloor for the passenger compartment section and a front-structure section with a trough bottom and trough side members is provided as a supporting structural member, wherein the trough bottom is symmetrically recessed in the region of the front-structure section relative to the region of the passenger compartment section with a smaller width in the transverse vehicle direction and the bottom assembly is formed with the trough side members surrounding the entire horizontal contour of the trough bottom and extending substantially in the vertical direction of the vehicle. 
     Such floor assembly has neither longitudinal nor transverse beams; forces of an applied front load are homogeneously introduced into the surface area of the floor assembly, i.e., in particular in the trough bottom, where they are distributed. The forces acting in the event of a side crash are homogeneously distributed in the floor assembly in the same manner. 
     Advantageously, the trough side members of the passenger compartment section running in the longitudinal vehicle direction are formed in the vertical vehicle direction at a rocker panel height of the vehicle. This defines at the same time the door openings without necessitating any additional parts. 
     According to another embodiment, however, the trough side members of the floor assembly are elevated in the area of the front-structure section relative to the rocker panel height in the vertical vehicle direction. This ensures a high stability of the front-structure section, and more particularly, forces can be introduced there via other attached structural supporting members, which are then also distributed in the floor assembly. Accordingly, openings for front axles can be accommodated in these trough side members, which extend in the longitudinal vehicle direction, in the region of front-structure section. 
     According to another embodiment of the invention, the front-structure trough side member has in the transverse vehicle direction at least one opening for a cooling air supply, where the radiator grille with refrigeration units can be arranged in a space-saving manner. 
     In one embodiment of the invention, the subfloor is formed in the region of the transition of the passenger compartment section to the front-structure section with a raised portion having a cross sectional area in the transverse vehicle direction that is greater than the cross-sectional area of the trough bottom in the region of the passenger compartment section. 
     In this way, a high stability is achieved in the transverse vehicle direction in the front-structure section of the passenger compartment section of the vehicle body, so that large load forces are homogenously introduced into the subfloor via this raised portion. 
     Particularly advantageously, the trough bottom in the region of the front-structure section may be formed with an obtuse angle of at least 135° relative to the trough bottom in the area of the passenger compartment section. Advantageously, this positively affects the drag coefficient (c w -value). 
     In another advantageous embodiment of the invention, the front-structure section may have as structural supporting member a front-structure cell with two front-structure side members oriented in the vertical vehicle direction which are each formed in the longitudinal vehicle direction and which extend, starting from the end region of the passenger compartment section of the contour of the front-structure trough side member, which extends in the transverse vehicle direction; furthermore, the front-structure side members are each formed at the front end of the passenger compartment section with a lower A-pillar section, and a flat element located at the transition of the passenger compartment section to a front-structure section and connecting the front-structure side members is provided as a front wall. 
     This produces a stable and weight-optimized front end in conjunction with the subfloor. A positive connection across an area between the front-structure side members and the trough side members of the subfloor is achieved by an end-side connection. 
     Advantageously, in this front-structure cell, the respective upper ends of the two front-structure side members are each provided with a transitional front-structure flat element extending in the longitudinal vehicle direction and in the transverse vehicle direction, such that for forming a wheel housing its outer boundary edge is aligned in the region of the passenger compartment section with the contour of the trough side member. Preferably, the two front-structure flat elements are formed to transition into each other in the region of the flat element forming the front wall of the passenger compartment section. 
     Such a front-structure cell can accommodate all necessary drive and suspension components without necessitating additional vehicle body parts. 
     According to another embodiment, the front-structure cell may be formed on both sides of its front end with a receiving chamber having an open front, wherein the front-structure side members and the front-structure flat elements each form a side wall of the receiving chamber. In this way, all necessary front lighting components can be accommodated by this receiving chamber of the front-structure cell. 
     According to another embodiment of the invention, a seat element extending substantially in the horizontal direction may be formed on the rear trough side member of the passenger compartment section extending in the transverse vehicle direction for supporting a backseat, wherein the seat element is connected to a flat seatback element extending substantially in the vertical vehicle direction. Preferably, the seat element and the flat seatback element have an angular position relative to one another with an angle that corresponds substantially to the angle between the seat element and the backrest of the backseat. 
     According to another embodiment, a particularly stable and crash-proof floor assembly is furthermore formed by extending the subfloor, starting from the rear trough side section in the rearward direction by way of outside side tunnels, such that the outside tunnel walls of the side tunnels are aligned with the respective trough side member in the region of the passenger compartment section. Preferably, the side tunnel is formed with a bottom tunnel wall that is substantially aligned with the trough bottom, whereas the top side tunnel wall is formed so as to be substantially aligned with the first surface section of the rear trough side member of the subfloor. 
     Furthermore, according to another embodiment of the invention, the two side tunnels are formed so as to terminate frontally in the plane of the rear trough side member. Preferably, the two inner tunnel side walls of the side tunnels aligned in the vertical vehicle direction are constructed to introduce a grid-like pattern in the rear trough side member. The rigidity in this area is improved by connecting the side tunnel to the rear trough side section, whereby less material is required concurrent with the grid-like structure of the trough side member. 
     According to a preferred embodiment of the invention, the rear-structure section includes a subfloor rear-structure section as a supporting structural member, which has a bottom member rearwardly continuing the trough bottom in the area of the passenger compartment bottom section and side members that are stepwise matched to the outer shape of the side tunnel in the transverse vehicle direction. This allows rear axle units to be connected to this subfloor rear member. Preferably, the side members of the rear-structure subfloor section are each formed so as to transition to a flat element forming an inner wall of the wheel housing. 
     According to an advantageous embodiment of the invention, the rear-structure section forming a further structural supporting member may include a storage space cell with a storage space cell bottom having formed thereon storage space cell side walls and a molded front end wall. In this case, this end wall is constructed so as to be aligned with the seat-back flat element. 
     The rear-structure section thus includes only a few structural supporting members for forming the body supporting structure. 
     According to an embodiment of the invention, a roof structure may be formed in each case by a curved truss connecting the lower A-pillar section with the front wall of the storage space cell, wherein in each case a B-pillar element connects the truss to the trough side section of the trough bottom. Preferably, two spaced transverse elements connecting the truss in the transverse vehicle direction are provided, which receive a roof area element between them. 
     To complete the body supporting structure, a side member covering the outside of the lower A-pillar section, the truss, the B-pillar section and a side wall of the storage space cell is provided as a supporting structural member. 
     The structural supporting members according to the invention may each be produced as fiber plastic composites entirely of fiber-reinforced plastic. Suitable processes are for example:
         RTM (Resin Transfer Molding) as high-pressure RTM or low-pressure RTM,   RIM (Resin Injection Molding),   Prepreg Autoclave or Prepreg Out-of-Autoclave,   Wet pressing,   SMC (Sheet Molding Compound) or BMC (Bulk Molding Compound).       

     It is also possible to use structural foams for the structural supporting members according to the invention, wherein the foams are either introduced into the cavities of the structural supporting members or as finished components into the structural supporting members. 
     The structural supporting members are connected by way of adhesive connections. 
     Preferably, these structural supporting members may also be made of aluminum sheet or steel sheet by suitable forming processes, using structural foams like in the manufacture of the structural supporting members. 
     The body supporting structure according to the invention is particularly suited for vehicle bodies of electric vehicles, where a large internal combustion engine can be omitted. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The invention will now be described in detail by way of an exemplary embodiment and with reference to the accompanying drawings, which show in: 
         FIG. 1  a front perspective view of a body supporting structure according to the invention, 
         FIG. 2  a rear perspective view of the body supporting structure according to  FIG. 1 , 
         FIG. 3  a perspective view of a floor assembly of the body supporting structure according to  FIG. 1  with a front-structure cell and a storage space cell, 
         FIG. 4  a perspective sectional view of the body supporting structure sectioned along the line A-A of  FIG. 1 , 
         FIG. 5  a perspective sectional view of the body supporting structure sectioned along the line B-B of  FIG. 1 , 
         FIG. 6  a perspective sectional view of the body supporting structure sectioned along the line C-C of  FIG. 2 , and 
         FIG. 7  a perspective sectional view of the body supporting structure sectioned along the line D-D of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The body supporting structure  1  of a vehicle body illustrated in  FIGS. 1 and 2  includes a passenger compartment section  1   a , a front-structure section  1   b , and a rear-structure section  1   c  and is constructed from a plurality of structural supporting members. In addition, vehicle doors, which are omitted in the subsequent  FIGS. 3 to 7 , are already installed in this body supporting structure  1  according to  FIGS. 1 and 2 . 
     The body supporting structure  1  includes as structural supporting members a floor assembly  10 , a front-structure cell  20 , a subfloor rear-structure section  40 , a storage space cell  50  as well as side members  70   a  and  70   b.    
     These structural supporting members represent a flat supporting structure composed of flat elements and extending in all three vehicle directions, namely the x-, y- and z-direction, which is self-supported so that applied loads are distributed in all spatial directions. Such structural supporting members eliminate the customary nodes connecting the longitudinal and transverse beams and seamlessly join the longitudinal and transverse structures by way of soft transitions without sharp edges. Thus, there are neither sharp edges in the load paths nor undesirable partitions or joints. Homogeneous load paths are hence formed in such a structural supporting member, i.e. locally applied loads spread immediately to the flat elements and are distributed in the spatial structure of the body supporting structure. 
     Such structural supporting members  10 ,  20 ,  40 ,  50 , and  70   a  and  70   b  are entirely made of a fiber composite material. 
     Hereinafter, these structural supporting members  10 ,  20 ,  40 ,  50 , and  70   a  and  70   b , and additional elements completing the body supporting structure  1  will be described below. 
     The floor assembly  10  includes as an essential component a subfloor  11  which extends both across the passenger compartment section  1   a  and across the front-structure section  1   b , and which is illustrated as the structural supporting member  10 , in particular in the sectional views of  FIGS. 4 and 5 , and a subfloor rear member  40  which continues the subfloor  11  in the rearward direction of the body supporting structure  1  according to  FIG. 4 . 
     This subfloor  11  is made of a trough bottom  12  with a circumferential trough side sections  13  substantially extending in the z direction. This trough bottom  13  thus represents a flat element, which continues in the z-direction with the trough side members  13  as additional flat elements. In the region of the front-structure section  1   b , the trough bottom  12   b  is symmetrically recessed in the y-direction relative to the trough bottom  12   a  in the region of the passenger compartment section  1   a . The trough side members  13   a  in the region of the passenger compartment section  1   a  transition in this transition region harmoniously into the trough side members  13   b  of the front-structure section  1   b.    
     The upper end sides of the trough side members  13   a  in the region of the passenger compartment section  1   a  have a height that corresponds to the rocker panel height of the vehicle body. In the transition region from the passenger compartment section  1   a  to the front-structure section  1   b , this rocker panel height of the trough side members  13   a  increases to a much higher value of the height of the upper end of the trough side members  13   b  in the region of the front-structure section  1   b . As a result, openings  16  for receiving the front axles may be provided at that location. 
     The front-structure trough side member  13   c  extending in the y-direction is structured in the center with a rib extending in the z-direction, creating two openings  15   a  and  15   b  for supply of cooling air. 
     The trough bottom  12   b  in the region of the front-structure section  1   b  is slightly angled relative to the trough bottom  12   a  in the region of the passenger compartment section  1   a  in the z-direction with an obtuse angle of at least 135°. 
     The front end of the trough bottom  12   a  belonging to the passenger compartment section  1   a  is formed with a raised portion  14  located opposite the trough bottom  12   a  and extending in the z-direction, thereby forming a region reinforcing the trough bottom  12  with a larger cross-section in the transverse vehicle direction than in the adjacent regions of the trough bottom  12   a  and  12   b . An opening for passage of a steering column can be applied in this area. 
     For supporting a backseat, a flat seat element  28  extending substantially horizontally (x-y plane) is formed on the rear trough side member  13   d  of the passenger compartment section  1   a  running in the y-direction, which is connected to a flat seatback element  29  extending substantially in the z-direction. The seat element  28  and the flat seatback element  29  have an angular position relative to each other with an angle that corresponds substantially to the angle between the seat and the backrest of the backseat. 
     The subfloor  11  of the floor assembly  10  is extended from the rear trough side member  13   d  in the reverse direction by way of side tunnels  30   a  and  30   b  arranged on the outside, so that the outside tunnel walls of the side tunnels  30   a  and  30   b  are aligned with the respective trough side member  13   a  in the region of the passenger compartment section  1   a , the bottom tunnel walls of the two side tunnels  30   a  and  30   b  are aligned with the trough bottom  12   a , and the upper tunnel walls of the two side tunnels  30   a  and  30   b  are aligned with the seat member  28  of the rear side of the trough side member  13   d.    
     The two side tunnels  30   a  and  30   b  end at the front side in the plane of the rear trough side member  13   d , wherein the two inside tunnel side walls of the side tunnels  30   a  and  30   b  aligned in the z direction form the rear trough side member  13   d  with a grid-like structure, creating three openings. 
     As another structural supporting member, a front-structure cell  20  having two front-structure side members  21   a  and  21   b  facing each in the z direction is provided in the region of the front-structure section  1   b , which are formed in the x direction, starting from the end region of the passenger compartment section  1   a  with the trough side member  13   a , transitioning into the trough side member  13   b  in the region of the front-structure section  1   b , and ending at the trough side member  13   b  that runs in the y-direction. At the transition from the passenger compartment section  1   a  to the front-structure section  1   b , i.e. at the front end of the passenger compartment section  1   a , front-structure side members  21   a  and  21   b  are formed as a lower A-pillar section  22   a  and  22   b , wherein a flat element connecting the front-structure side members  21   a  and  21   b  is formed at the transition from the passenger compartment section  1   a  to the front-structure section  1   b  as an end wall  23  with an opening  23   b . These front-structure side members  21   a  and  21   b  form fittingly abut the trough side members  13   a  and  13   b.    
     The two front-structure side members  21   a  and  21   b  of the front-structure cell  20  are each constructed to transition at their upper end into a flat element  24   a  and  24   b  extending in the x- and y-direction, so that for forming a wheel housing  25 , their outside free boundary edge  26  is aligned with the contour of the trough side member  13   a  in the region of the passenger compartment section  1   a . A respective flat element  24   a  and  24   b  each covers the corner region between the front-structure flat element  24   c  and  24   d , so that an arc-shaped profile of the parts forming the wheel housing  25  is produced by the contour and the boundary edge  26 . 
     Furthermore, the two front-structure flat elements  24   a  and  24   b  are formed in the region of the flat elements forming the end wall  23  so as to transition into one another, so that a circular-arc-like opening for an engine hood is formed in the plane of the two front-structure flat elements  24   a  and  24   b.    
     Finally, the front-structure cell  20  is provided at its front end on both sides with a receiving chamber  27   a  and  27   b  open at the front, so that the front-structure side members  21   a  and  21   b  and the front-structure flat elements  24   a  and  24   b  each form a side wall of the receiving chamber  27   a  and  27   b , respectively. 
     The upper end face of the end wall  23  has a curved profile in the forward direction such that the end wall  23  is bridged at the end face in a sector-like fashion by a flat element  23   a.    
     As an additional structural supporting member, a subfloor rear member  40  is arranged in the region of the rear-structure section  1   c , which has a bottom part  41  rearwardly extending the trough bottom  12   a  in the region of the passenger compartment section  1   a , as well as side members  42   a  and  42   b . The side members  42   a  and  42   b  are stepwise adapted in the y-direction to the outer shape of the side tunnels  30   a  and  30   b  and are each formed as a flat element transitioning into a respective wheel housing inner wall  43   a  and  43   b.    
     The rear-structure section  1   c  further includes as another structural supporting member a storage space cell  50 , which has a storage space cell bottom  51  extending substantially in the x-y plane with storage space cells side walls  52   a  and  52   b  molded thereto and extending in the z-direction, and a front end wall  53  molded thereto, whereby this end wall  53  is substantially aligned in the z-direction with the flat seatback element  29 , as evident from  FIGS. 3 and 4 . The edge reinforcements  29   a  and  29   b  of the flat seatback element  29  here transition into corresponding edge reinforcements  52   a  and  52   b.    
     To form a roof structure  60  of the body supporting structure  1 , a respective truss  61   a  and  61   b  connecting the lower A-pillar section  22   a  and  22   b  in an arcuate manner with the end wall  53  of the storage space cell  50  is provided on both sides, so that in each case a respective B-pillar element  62   a ,  62   b  connects the truss  61   a  and  61   b , respectively, with the trough side member  13   a  of the trough bottom  12  in the region of the passenger compartment section  1   a . Furthermore, a roof area element  64  is also provided, which is received between two spaced-apart transverse elements  63   a  and  63   b  connecting the trusses  61   a  and  61   b  in the y-direction. 
     Finally, as a last structural supporting member, a respective side member  70   a  and  70   b  is provided which each covers the outside of the lower A-pillar section  22   a  and  22   b , the truss  61   a  and  61   b , the B-pillar member  62   a  and  62   b , and a storage space cell side wall  52   a  and  52   b  of the storage space cell  50 . 
     For constructing the body supporting structure  1  (without the vehicle doors), the individual structural supporting members made of a fiber-reinforced plastic are connected with each other by an adhesive joint. 
     REFERENCE SYMBOLS 
     
         
           1  body supporting structure 
           1   a  passenger compartment section 
           1   b  front-structure section 
           1   c  rear-structure section 
           10  structural supporting member, floor assembly 
           11  subfloor of the floor assembly  10   
           12  trough bottom of the subfloor  11   
           12   a  trough bottom in the region of the passenger compartment section  1   a    
           12   b  trough bottom in the region of the front-structure section  1   b    
           13  trough side members of the subfloor  11   
           13   a  trough side members of the passenger compartment section  1   a    
           13   b  trough side members in the region of front-structure section  1   b    
           13   c  front-structure trough side member of the front-structure section  1   b    
           13   d  rear trough side member of the passenger compartment section  1   a    
           14  raised portion 
           15   a  opening in the trough side member  13   c    
           15   b  opening in the trough side member  13   c    
           16  openings in the trough side member  13   b    
           20  structural supporting member, front-structure cell 
           21   a  front-structure side member of the front-structure cell  20   
           21   b  front-structure side member of the front-structure cell  20   
           22   a  lower A-pillar section of the front-structure side member  21   a    
           22   b  lower A-pillar section of the front-structure side member  21   b    
           23  end wall of the front-structure cell  20   
           23   a  flat element of the front-structure cell  20   
           23   b  opening of the front wall  23   
           24   a  front-structure flat element of the front-structure cell 
           24   b  front-structure flat element of the front-structure cell 
           24   c  flat element of the front-structure cell  20   
           24   d  flat element of the front-structure cell  20   
           25  wheel housing 
           26  boundary edge of the front-structure flat element  24   a ,  24   b    
           27   a  receiving chamber of the front-structure cell 
           27   b  receiving chamber of the front-structure cell 
           28  seat element of the trough side member  13   d    
           29  flat seatback element 
           29   a  edge reinforcement of the seat backrest flat element  29   
           29   b  edge reinforcement of the seat backrest flat element  29   
           30   a  side tunnel of the floor assembly  10   
           30   b  side tunnel of the floor assembly  10   
           40  supporting structural member, subfloor rear member 
           41  bottom part of the subfloor rear member  40   
           42   a  side member of the subfloor rear member  40   
           42   b  side member of the subfloor rear member  40   
           43   a  wheel housing inner wall of the side member  42   a    
           43   b  wheel housing inner wall of the side member  42   b    
           50  structural supporting member, storage space cell 
           51  storage space cell bottom of the storage space cell  50   
           52   a  storage space cell side wall of the storage space cell  50   
           52   b  storage space cell side wall of the storage space cell  50   
           53  front wall of the storage space cell  50   
           53   a  edge reinforcement of the front wall  52   
           53   b  edge reinforcement of the front wall  52   
           60  roof structure 
           61   a  truss the roof structure  60   
           61   b  truss the roof structure  60   
           62   a  B-pillar element of the roof structure  60   
           62   b  B-pillar element of the roof structure  60   
           63   a  transverse member of the roof structure  60   
           63   b  transverse member of the roof structure  60   
           64  roof area element 
           70   a  structural supporting member, side member 
           70   b  structural supporting member, side member