Patent Publication Number: US-2023141662-A1

Title: Vehicle Load Distribution System

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 10-2021-0153396, filed on Nov. 9, 2021, which application is hereby incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a vehicle load distribution system. 
     BACKGROUND 
     A vehicle frame, which is a structure designed to install chassis components or a vehicle body, should be sufficiently protected from local or overall damages due to deformation, torsion, tension, compression, and/or vibration caused by the vehicle&#39;s propulsion force, brake action, a centrifugal force during steering, an impact from a road surface, a vertical load due to the weight of the vehicle body, and various reaction forces. It should be of a structure that can sufficiently absorb impact energy applied to the vehicle in the event of a collision. 
     Due to diversification of the vehicle market, the vehicle frame is being changed in various ways from an existing monocoque structure to a novel structure such as a purpose built vehicle (PBV) frame and a space frame, to meet each vehicle&#39;s purpose. In particular, a low-cost electric vehicle (EV) requires a vehicle body structure which is created by breaking an existing method in order to maximize profitability. 
     Existing vehicles use pressed steel materials and aluminum materials for the frame, and thus the material cost and investment cost thereof may be relatively high. 
     In addition, since a joint portion between structural members constituting the existing vehicle frame is made by welding, the joint portion between the structural members may be easily damaged by an impact load during a frontal collision of the vehicle. In addition, it may be difficult to uniformly distribute a load transferred from the front of the vehicle body. Thus, it may be difficult to safely protect a passenger compartment and a vehicle battery. 
     The above information described in this background section is provided to assist in understanding the background of the inventive concept, and may include any technical concept which is not considered as the prior art that is already known to those skilled in the art. 
     SUMMARY 
     The present disclosure relates to a vehicle load distribution system. Particular embodiments relate to a vehicle load distribution system designed to uniformly distribute a load transferred to the front of the vehicle. 
     Embodiments of the present disclosure can solve problems occurring in the prior art while advantages achieved by the prior art are maintained intact. 
     An embodiment of the present disclosure provides a vehicle load distribution system uniformly distributing a load in the event of a frontal collision of the vehicle, and using a relatively inexpensive material such as mass-produced steel pipes, thereby significantly reducing the manufacturing cost thereof, compared to when using pressed steel materials and aluminum materials. 
     According to an embodiment of the present disclosure, a vehicle load distribution system may include a dash crossmember, a pair of front side members extending from the dash crossmember toward the front of the vehicle, and a pair of rear lower members extending from the dash crossmember toward the rear of the vehicle. A front end of each rear lower member may be aligned with a rear end of a corresponding front side member. 
     The pair of front side members may be connected to the dash crossmember so that the dash crossmember may primarily support a load transferred through the front side members. In particular, the rear lower members may be aligned with the corresponding front side members so that the load may be stably transferred and distributed to the front side members, the dash crossmember, and the rear lower members. 
     The vehicle load distribution system may further include a front crossmember located behind the dash crossmember. The pair of rear lower members may connect the dash crossmember and the front crossmember in a longitudinal direction of the vehicle. 
     The pair of rear lower members may connect the dash crossmember and the front crossmember so that the front crossmember may secondarily support the load transferred through the rear lower members. 
     The vehicle load distribution system may further include a seat crossmember located behind the front crossmember and a central longitudinal member connecting the dash crossmember and the seat crossmember. The central longitudinal member may extend along a central longitudinal axis of the vehicle. 
     The central longitudinal member may connect the dash crossmember and the seat crossmember so that the seat crossmember may thirdly support the load transferred through the central longitudinal member. 
     Each front side member may have an opening provided in the rear end thereof, and the dash crossmember may be fitted and joined to the opening of the front side member. 
     The opening of the front side member may include a top engaging portion joined to a top surface of the dash crossmember and a front engaging portion joined to a front surface of the dash crossmember. 
     The rear end of the front side member may be mechanically joined to the dash crossmember. That is, the rear end of the front side member may be very firmly joined to the dash crossmember through a mechanical joint system. 
     Each rear lower member may include a front engaging portion provided on the front end thereof, and the front engaging portion may be joined to a rear surface of the dash crossmember. 
     The rear lower member may further include a bracket integrally connected to the front end thereof, and the bracket may include a bottom engaging portion joined to a bottom surface of the dash crossmember. 
     The front end of the rear lower member may be mechanically joined to the dash crossmember. That is, the front end of the rear lower member may be very firmly joined to the dash crossmember through a mechanical joint system. 
     Each rear lower member may have an opening provided in a rear end thereof, and the front crossmember may be fitted and joined to the opening of the rear lower member. 
     The opening of the rear lower member may include a top engaging portion joined to a top surface of the front crossmember, a front engaging portion joined to a front surface of the front crossmember, and a bottom engaging portion joined to a bottom surface of the front crossmember. 
     The rear end of the rear lower member may be mechanically joined to the front crossmember. That is, the rear end of the rear lower member may be very firmly joined to the front crossmember through a mechanical joint system. 
     The central longitudinal member may have a front opening provided in a front end thereof, and the dash crossmember may be fitted and joined to the front opening of the central longitudinal member. 
     The front opening may include a front engaging portion joined to a rear surface of the dash crossmember, and a bottom engaging portion joined to a bottom surface of the dash crossmember. 
     The front end of the central longitudinal member may be mechanically joined to the dash crossmember. That is, the front end of the central longitudinal member may be very firmly joined to the dash crossmember through a mechanical joint system. 
     The central longitudinal member may have a rear opening provided in a rear end thereof, and the seat crossmember may be fitted and joined to the rear opening of the central longitudinal member. 
     The rear opening may include a top engaging portion joined to a top surface of the seat crossmember, a rear engaging portion joined to a front surface of the seat crossmember, and a bottom engaging portion joined to a bottom surface of the seat crossmember. 
     The rear end of the central longitudinal member may be mechanically joined to the seat crossmember. That is, the rear end of the central longitudinal member may be very firmly joined to the seat crossmember through a mechanical joint system. 
     The front crossmember may have a pair of side openings provided in both end portions thereof, respectively, and each side sill may be fitted and joined to a corresponding side opening of the front crossmember. 
     Each side opening may include a side engaging portion joined to an inboard side surface of the side sill, and a bottom engaging portion joined to a bottom surface of the side sill. 
     Each end portion of the front crossmember may be mechanically joined to the side sill. That is, both end portions of the front crossmember may be very firmly joined to the pair of side sills through a mechanical joint system. 
     The front crossmember may have a central opening provided in a central portion thereof, and the central longitudinal member may be fitted and joined to the central opening of the front crossmember. 
     The central opening may include a bottom engaging portion joined to a bottom surface of the central longitudinal member, a first side engaging portion joined to a first side surface of the central longitudinal member, and a second side engaging portion joined to a second side surface of the central longitudinal member. 
     The central longitudinal member may be mechanically joined to the central portion of the front crossmember. That is, the central longitudinal member may be very firmly joined to the central portion of the front crossmember through a mechanical joint system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of embodiments of the present disclosure will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG.  1    illustrates a vehicle frame to which a vehicle load distribution system according to an exemplary embodiment of the present disclosure is applied; 
         FIG.  2    illustrates a perspective view of a front portion of the vehicle frame illustrated in  FIG.  1   ; 
         FIG.  3    illustrates a plan view of the vehicle frame illustrated in  FIG.  1   , from which a pair of roof rails are removed; 
         FIG.  4    illustrates an enlarged view of portion A of  FIG.  3   ; 
         FIG.  5    illustrates a cross-sectional view, taken along line B-B of  FIG.  4   ; 
         FIG.  6    illustrates a cross-sectional view, taken along line C-C of  FIG.  4   ; and 
         FIG.  7    illustrates a cross-sectional view, taken along line D-D of  FIG.  4   . 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals will be used throughout to designate the same or equivalent elements. In addition, a detailed description of well-known techniques associated with the present disclosure will be omitted in order not to unnecessarily obscure the gist of the present disclosure. 
     Terms such as first, second, A, B, (a), and (b) may be used to describe the elements in exemplary embodiments of the present disclosure. These terms are only used to distinguish one element from another element, and the intrinsic features, sequence or order, and the like of the corresponding elements are not limited by the terms. Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meanings as those generally understood by those with ordinary knowledge in the field of art to which the present disclosure belongs. Such terms as those defined in a generally used dictionary are to be interpreted as having meanings equal to the contextual meanings in the relevant field of art, and are not to be interpreted as having ideal or excessively formal meanings unless clearly defined as having such in the present application. 
       FIG.  1    illustrates a vehicle frame  1  to which a vehicle load distribution system according to an exemplary embodiment of the present disclosure is applied. 
     Referring to  FIG.  1   , the vehicle frame  1  may include a center frame module  2 , a front structure  6  connected to the front of the center frame module  2 , a rear frame module  9  connected to the rear of the center frame module  2 , and an intermediate structure  20  disposed between the center frame module  2  and the rear frame module  9 . 
     A pair of front pillars  5   a  may extend from the front of the center frame module  2  in a height direction of the vehicle, and the pair of front pillars  5   a  may be spaced apart from each other in a width direction of the vehicle. 
     A pair of center pillars  5   b  may extend from the center of the center frame module  2  in the height direction of the vehicle, and the pair of center pillars  5   b  may be spaced apart from each other in the width direction of the vehicle. 
     A pair of rear pillars  5   c  may extend from the rear of the center frame module  2  in the height direction of the vehicle, and the pair of rear pillars  5   c  may be spaced apart from each other in the width direction of the vehicle. 
     A pair of roof rails  3  may be disposed above the center frame module  2 , and each roof rail  3  may extend in a longitudinal direction of the vehicle. Each roof rail  3  may connect a top end of the corresponding front pillar  5   a , a top end of the corresponding center pillar  5   b , and a top end of the corresponding rear pillar  5   c . Each roof rail  3  may have a front extension portion  3   a  extending obliquely from a front end thereof, and a rear extension portion  3   b  extending obliquely from a rear end thereof. 
     Referring to  FIGS.  3  and  4   , the center frame module  2  may include a pair of side sills  30  disposed on both side edges thereof, a plurality of crossmembers  12 ,  14 ,  16 , and  18  connecting the pair of side sills  30  in the width direction of the vehicle, and a plurality of longitudinal members  13 ,  15 ,  17   a , and  17   b  extending in the longitudinal direction of the vehicle. 
     The pair of side sills  30  may be spaced apart from each other in the width direction of the vehicle, and each side sill  30  may extend in the longitudinal direction of the vehicle. Referring to  FIG.  7   , each side sill  30  may include a side sill inner  31  facing the interior of the vehicle, and a side sill outer  32  facing the exterior of the vehicle. 
     The side sill inner  31  may have an angular cross section or a circular cross section with a cavity defined therein, and accordingly the side sill inner  31  may have a closed cross section. 
     An inboard side surface of the side sill outer  32  may be fixed to an outboard side surface of the side sill inner  31  using fasteners, welding, and/or the like. The side sill outer  32  may be made of a mass-produced steel pipe having an angular cross section or a circular cross section with a cavity defined therein, and accordingly the side sill outer  32  may have a closed cross section. For example, the mass-produced steel pipe may be SGH400, SGH490, or the like. 
     Each of the side sill inner  31  and the side sill outer  32  may have a closed cross section, and the cavity of the side sill outer  32  may be separated from the cavity of the side sill inner  31 . Since the cavity of the side sill inner  31  and the cavity of the side sill outer  32  are separated from each other, the side sill  30  may have a double closed cross section, thereby enhancing strength and stiffness thereof. 
     The side sill inner  31  may be made of a material having higher strength and stiffness than a material of the side sill outer  32 . As the material of the side sill inner  31  has higher strength and stiffness than the material of the side sill outer  32 , side stiffness of the center frame module  2  may be significantly improved. 
     According to an exemplary embodiment, the side sill inner  31  may be made of a high-tensile strength steel plate such as SPFC1180Y through hot stamping, hot forming, press hardening, and/or roll forming. Accordingly, side crash performance (crashworthiness) of the side sills  30  may be improved so that a battery and a passenger compartment may be safely protected in the event of a side collision. 
     The cross-sectional areas and thicknesses of the side sill inner  31  and the side sill outer  32  may be determined to have the same or similar moment of inertia compared to an existing side sill according to the related art. 
     According to an exemplary embodiment, as illustrated in  FIG.  7   , the cross-sectional area of the side sill inner  31  may be greater than the cross-sectional area of the side sill outer  32 . In addition, the thickness of the side sill inner  31  may be greater than the thickness of the side sill outer  32 . 
     The side sill inner  31  and the side sill outer  32  may be joined to form a stepped structure. Referring to  FIG.  7   , a bottom surface of the side sill outer  32  may be located lower than a bottom surface of the side sill inner  31 . Accordingly, the side sill inner  31  and the side sill outer  32  may more safely protect a battery case located under the center frame module  2  in the event of a side collision of the vehicle. 
     Each side edge of an upper body may be directly mounted on the side sill outer  32  of the corresponding side sill  30 . Referring to  FIG.  7   , a top surface of the side sill outer  32  may be located lower than a top surface of the side sill inner  31 , and accordingly a mounting space of the upper body may be sufficiently secured. 
     The plurality of crossmembers  12 ,  14 ,  16 , and  18  may include a dash crossmember  12  mounted on a dash panel, a front crossmember  14  located behind the dash crossmember  12 , a first seat crossmember  16  located behind the front crossmember  14 , and a second seat crossmember  18  located behind the first seat crossmember  16 . The front crossmember  14 , the first seat crossmember  16 , and the second seat crossmember  18  may extend in the width direction of the vehicle. The front crossmember  14 , the first seat crossmember  16 , and the second seat crossmember  18  may be parallel to each other. 
     The dash crossmember  12  may block the dash panel from intruding into the passenger compartment in the event of a frontal collision of the vehicle. Referring to  FIG.  1   , the dash crossmember  12  may connect lower portions of the pair of front pillars  5   a  in the width direction of the vehicle. The dash crossmember  12  may be mounted under the dash panel, and the dash panel may serve as a partition between a front compartment and the passenger compartment. In addition, both end portions of the dash crossmember  12  may be joined to the pair of side sills  30  using fasteners, welding, and/or the like, respectively. According to an exemplary embodiment, the dash crossmember  12  may be made of a mass-produced steel pipe having an angular cross section or a circular cross section with a cavity defined therein, and accordingly the dash crossmember  12  may have a closed cross section. For example, the mass-produced steel pipe may be SGH400, SGH490, or the like. 
     The front crossmember  14  may be spaced apart from the dash crossmember  12  toward the rear of the vehicle, and be adjacent to a front end of the center frame module  2 . Both end portions of the front crossmember  14  may be joined to the pair of side sills  30 , respectively. 
     The front crossmember  14  may have an angular cross section or a circular cross section with a cavity defined therein, and accordingly the front crossmember  14  may have a closed cross section. According to an exemplary embodiment, the front crossmember  14  may be made of a high-tensile strength steel plate such as SPFC1180Y through hot stamping, hot forming, press hardening, and/or roll forming. Accordingly, the high-strength front crossmember  14  may improve crashworthiness and stiffness of the center frame module  2 , thereby safely protecting the battery and the passenger compartment in the event of a collision of the vehicle. 
     The first seat crossmember  16  may be spaced apart from the front crossmember  14  toward the rear of the vehicle, and be located in the middle of the center frame module  2 . A vehicle seat may be mounted on the first seat crossmember  16  through brackets, and thus the first seat crossmember  16  may support the vehicle seat. 
     The first seat crossmember  16  may have an angular cross section or a circular cross section with a cavity defined therein, and accordingly the first seat crossmember  16  may have a closed cross section. According to an exemplary embodiment, the first seat crossmember  16  may be made of a high-tensile strength steel plate such as SPFC1180Y through hot stamping, hot forming, press hardening, and/or roll forming. Accordingly, the high-strength first seat crossmember  16  may improve crashworthiness and stiffness of the center frame module  2 , thereby safely protecting the battery and the passenger compartment in the event of a collision of the vehicle. 
     The second seat crossmember  18  may be spaced apart from the first seat crossmember  16  toward the rear of the vehicle, and be adjacent to a rear end of the center frame module  2 . A vehicle seat may be mounted on the second seat crossmember  18  through brackets, and thus the second seat crossmember  18  may support the vehicle seat. 
     The second seat crossmember  18  may have an angular cross section or a circular cross section with a cavity defined therein, and accordingly the second seat crossmember  18  may have a closed cross section. According to an exemplary embodiment, the second seat crossmember  18  may be made of a high-tensile strength steel plate such as SPFC1180Y through hot stamping, hot forming, press hardening, and/or roll forming. Accordingly, the high-strength second seat crossmember  18  may improve crashworthiness and stiffness of the center frame module  2 , thereby safely protecting the battery and the passenger compartment in the event of a collision of the vehicle. 
     The plurality of longitudinal members  13 ,  15 ,  17   a , and  17   b  may include a pair of rear lower members  13  extending from the dash crossmember  12  to the front crossmember  14 , a central longitudinal member  15  extending from the dash crossmember  12  to the first seat crossmember  16 , a pair of first side longitudinal members  17   a  extending from the first seat crossmember  16  to the second seat crossmember  18 , and a pair of second side longitudinal members  17   b  extending from the second seat crossmember  18  to the intermediate structure  20 . 
     The pair of rear lower members  13  may be spaced apart from each other in the width direction of the vehicle, and each of the rear lower members  13  may extend in the longitudinal direction of the vehicle. According to an exemplary embodiment, the rear lower members  13  may be made of a high-tensile strength steel plate such as SPFC1470 through hot stamping, hot forming, press hardening, and/or roll forming, whereby front crash performance (crashworthiness) of the vehicle may be improved, and thus the battery and the passenger compartment may be safely protected in the event of a frontal collision. 
     The central longitudinal member  15  may extend along a central longitudinal axis of the vehicle. 
     The pair of first side longitudinal members  17   a  may be spaced apart from each other in the width direction of the vehicle, and each first side longitudinal member  17   a  may extend in the longitudinal direction of the vehicle. A front end of each first side longitudinal member  17   a  may be joined to the first seat crossmember  16  using fasteners, welding, and/or the like, and a rear end of the first side longitudinal member  17   a  may be joined to the second seat crossmember  18  using fasteners, welding, and/or the like. 
     The pair of second side longitudinal members  17   b  may be spaced apart from each other in the width direction of the vehicle, and each second side longitudinal member  17   b  may extend in the longitudinal direction of the vehicle. A front end of each second side longitudinal member  17   b  may be joined to the second seat crossmember  18  using fasteners, welding, and/or the like, and a rear end of the second side longitudinal member  17   b  may be joined to the intermediate structure  20  using fasteners, welding, and/or the like. 
     Each second side longitudinal member  17   b  may be aligned with the corresponding first side longitudinal member  17   a  in the longitudinal direction of the vehicle. In particular, the front end of each second side longitudinal member  17   b  and the rear end of the corresponding first side longitudinal member  17   a  may face each other with the second seat crossmember  18  disposed therebetween. A longitudinal axis of the second side longitudinal member  17   b  may be aligned with a longitudinal axis of the corresponding first side longitudinal member  17   a.    
     According to an exemplary embodiment, the central longitudinal member  15 , the first side longitudinal member  17   a , and the second side longitudinal member  17   b  may be made of a mass-produced steel pipe having an angular cross section or a circular cross section with a cavity defined therein, and accordingly the central longitudinal member  15 , the first side longitudinal member  17   a , and the second side longitudinal member  17   b  may have a closed cross section. For example, the mass-produced steel pipe may be SGH400, SGH490, or the like. 
     Referring to  FIGS.  1  and  2   , the front structure  6  may be connected to the center frame module  2 , the pair of front pillars  5   a , and the pair of front extension portions  3   a . The front structure  6  may include a pair of front side members  11 , a pair of fender upper members  62  located above the pair of front side members  11 , respectively, a bumper back beam  63  connecting front ends of the pair of front side members  11 , a front end module  64  connected to the pair of front side members  11  and the pair of fender upper members  62 , and an upper crossmember  65  connecting the pair of front pillars  5   a.    
     The pair of front side members  11  may be spaced apart from each other in the width direction of the vehicle on the front of the vehicle, and each front side member  11  may extend in the longitudinal direction of the vehicle. The front side member  11  may extend from the dash crossmember  12  of the center frame module  2  to the front of the vehicle. A rear end of the front side member  11  may be joined to the dash crossmember  12  of the center frame module  2  using fasteners, welding, and/or the like, and the front end of the front side member  11  may be joined to a corresponding end portion of the bumper back beam  63  using fasteners, welding, and/or the like. According to an exemplary embodiment, the front side member  11  may be made of a mass-produced steel pipe having an angular cross section or a circular cross section with a cavity defined therein, and accordingly the front side member  11  may have a closed cross section. For example, the mass-produced steel pipe may be SGH400, SGH490, or the like. 
     The pair of fender upper members  62  may be spaced apart from each other in the width direction of the vehicle, and each fender upper member  62  may extend in the longitudinal direction of the vehicle. Each fender upper member  62  may be upwardly spaced apart from the corresponding front side member  11 . According to an exemplary embodiment, the fender upper member  62  may be made of a mass-produced steel pipe having an angular cross section or a circular cross section with a cavity defined therein, and accordingly the fender upper member  62  may have a closed cross section. For example, the mass-produced steel pipe may be SGH400, SGH490, or the like. 
     The bumper back beam  63  may extend in the width direction of the vehicle, and the bumper back beam  63  may connect the front ends of the pair of front side members  11 . Each end portion of the bumper back beam  63  may be joined to the front end of the corresponding front side member  11 . According to an exemplary embodiment, the bumper back beam  63  may be made of a high-tensile strength steel plate through hot stamping, hot forming, press hardening, and/or roll forming. 
     The front end module  64  may be a frame supporting a heat exchanger such as a radiator, a condenser, and an intercooler. According to an exemplary embodiment, the front end module  64  may be made of a plurality of mass-produced steel pipes. 
     The upper crossmember  65  may extend in the width direction of the vehicle, and each end portion of the upper crossmember  65  may be joined to the corresponding front pillar  5   a . Referring to  FIGS.  1  and  2   , a pair of strut bars  66  may extend from the upper crossmember  65  to the pair of fender upper members  62 , respectively, and the pair of strut bars  66  may be spaced apart from each other in a longitudinal direction of the upper crossmember  65 . A top end of each strut bar  66  may be joined to a portion of the upper crossmember  65  adjacent to the end portion of the upper crossmember  65 , and a bottom end of the strut bar  66  may be joined to the corresponding fender upper member  62 . That is, the pair of fender upper members  62  may be connected to the upper crossmember  65  through the pair of strut bars  66 . According to an exemplary embodiment, the upper crossmember  65  and the strut bar  66  may be made of a mass-produced steel pipe having an angular cross section or a circular cross section with a cavity defined therein, and accordingly the upper crossmember  65  and the strut bar  66  may have a closed cross section. For example, the mass-produced steel pipe may be SGH400, SGH490, or the like. 
     Referring to  FIG.  3   , the rear frame module  9  may include a pair of rear side members  91 , a rear crossmember  92  connecting the pair of rear side members  91 , and a rear back beam  93  connecting rear ends of the rear side members  91 . 
     The pair of rear side members  91  may be spaced apart from each other in the width direction of the vehicle on the rear of the vehicle, and each rear side member  91  may extend in the longitudinal direction of the vehicle. Each rear side member  91  may extend from a rear portion of the corresponding side sill  30  to the rear of the vehicle, and a front portion of the rear side member  91  may be joined to the inboard side surface of the rear portion of the corresponding side sill  30  using fasteners, welding, and/or the like. That is, the pair of rear side members  91  may be connected to the inboard side surfaces of the pair of side sills  30 , respectively. The rear crossmember  92  and the rear back beam  93  may extend in the width direction of the vehicle. 
     According to an exemplary embodiment, the rear side member  91  may be made of a mass-produced steel pipe having an angular cross section or a circular cross section with a cavity defined therein, and accordingly the rear side member  91  may have a closed cross section. For example, the mass-produced steel pipe may be SGH400, SGH490, or the like. 
     Referring to  FIG.  1   , the rear frame module  9  may be located higher than the center frame module  2 , and the intermediate structure  20  may connect the center frame module  2  and the rear frame module  9 . 
     Referring to  FIG.  3   , the vehicle frame  1  according to an exemplary embodiment of the present disclosure may further include a rear subframe  80  mounted on the rear frame module  9 . The rear subframe  80  may include a pair of front mounting portions  81  mounted on the front portions of the pair of rear side members  91 , respectively, and a pair of rear mounting portions  82  mounted on the rear portions of the pair of rear side members  91 , respectively. 
     According to an exemplary embodiment of the present disclosure, except for the strength members or stiffness members such as the bumper back beam  63 , the front crossmember  14 , the first seat crossmember  16 , the second seat crossmember  18 , the rear lower member  13 , and the side sill inner  31 , most of the members constituting the center frame module  2 , the front structure  6 , and the rear frame module  9  may be made of mass-produced steel pipes. In particular, the mass-produced steel pipe may have an angular cross section or a circular cross section with a cavity defined therein, and the shape and size thereof may be standardized. Each member made of the mass-produced steel pipe may have a closed cross section. Thus, the vehicle frame  1  according to an exemplary embodiment of the present disclosure may form a relatively inexpensive and stable space frame. 
     The vehicle frame  1  according to an exemplary embodiment of the present disclosure may include a vehicle load distribution system  10  uniformly distributing a load in the event of a frontal collision of the vehicle. The vehicle load distribution system  10  may be disposed between the front structure  6  and the center frame module  2 . According to an exemplary embodiment of the present disclosure, the pair of front side members  11 , the dash crossmember  12 , the pair of rear lower members  13 , and the central longitudinal member  15  may constitute the vehicle load distribution system  10 . 
     As illustrated in  FIG.  4   , the rear end of each front side member  11  may be joined to the dash crossmember  12 , and each rear lower member  13  may be joined to the dash crossmember  12  while being aligned with the rear portion of the corresponding front side member it A front end of each rear lower member  13  may be joined to the dash crossmember  12  using fasteners, welding, and/or the like, and a rear end of the rear lower member  13  may be joined to the front crossmember  14  using fasteners, welding, and/or the like. That is, the rear lower member  13  may connect the dash crossmember  12  and the front crossmember  14 . The front end of the rear lower member  13  may face the rear end of the front side member  11  with the dash crossmember  12  disposed therebetween. That is, the front end of the rear lower member  13  may be aligned with the rear end of the corresponding front side member  11 . 
     A longitudinal axis of the rear lower member  13  may be aligned with a longitudinal axis of the rear portion of the corresponding front side member  11 . Referring to  FIG.  4   , the rear portion of each front side member  11  may extend diagonally toward the dash crossmember  12  while being inclined at a predetermined angle, and each rear lower member  13  may extend diagonally from the dash crossmember  12  toward the front crossmember  14  while being inclined at a predetermined angle. The rear lower member  13  may be inclined at the same angle as that of the rear portion of the front side member  11  so that the front end of the rear lower member  13  may be aligned with the rear end of the front side member  11 . As the rear lower member  13  is aligned with the corresponding front side member  11 , a load may be stably transferred and distributed to the front side member  11 , the dash crossmember  12 , and the rear lower member  13 . 
     Referring to  FIG.  5   , each front side member  11  may have an opening  41  provided in the rear end thereof, and the dash crossmember  12  may be fitted into the opening  41  of the front side member  11 . 
     According to an exemplary embodiment, the opening  41  may include a top engaging portion  41   a  joined to a top surface of the dash crossmember  12 , and a front engaging portion  41   b  joined to a front surface of the dash crossmember  12 . The top engaging portion  41   a  may be horizontally flat to match the top surface of the dash crossmember  12 , and the top engaging portion  41   a  may be joined to the top surface of the dash crossmember  12  by welding (CO 2  welding or the like), using fasteners, and/or the like. The front engaging portion  41   b  may be vertically flat to match the front surface of the dash crossmember  12 , and the front engaging portion  41   b  may be joined to the front surface of the dash crossmember  12  by welding (CO 2  welding or the like), using fasteners, and/or the like. Accordingly, the opening  41  of the front side member  11  may have an L-shaped cross section, and thus the rear end of the front side member  11  may be mechanically joined to the dash crossmember  12 . That is, the rear end of the front side member  11  may be very firmly joined to the dash crossmember  12  through a mechanical joint system. According to another exemplary embodiment of the present disclosure, the opening  41  of the front side member  11  may have a U-shaped cross section, and thus the rear end of the front side member  11  may be more firmly joined to the dash crossmember  12 . 
     Referring to  FIG.  5   , each rear lower member  13  may have a front engaging portion  42  provided on the front end thereof. The front engaging portion  42  may be vertically flat to match a rear surface of the dash crossmember  12 , and the front engaging portion  42  may be joined to the rear surface of the dash crossmember  12  by welding (CO 2  welding or the like), using fasteners, and/or the like. A bracket  43  may be integrally connected to the front end of the rear lower member  13  using fasteners, welding, and/or the like, and the bracket  43  may have a bottom engaging portion  43   a  that is horizontally flat to match a bottom surface of the dash crossmember  12 . Accordingly, the front engaging portion  42  of the rear lower member  13  and the bottom engaging portion  43   a  of the bracket  43  may form an L-shaped cross section, and thus the front end of the rear lower member  13  may be mechanically joined to the dash crossmember  12 . That is, the front end of the rear lower member  13  may be very firmly joined to the dash crossmember  12  through a mechanical joint system. Accordingly, the front engaging portion  41   b  of the opening  41  of the front side member  11  and the front engaging portion  42  of the rear lower member  13  may face each other with the dash crossmember  12  disposed therebetween. The top engaging portion  41   a  of the opening  41  of the front side member  11  and the bottom engaging portion  43   a  of the bracket  43  may face each other with the dash crossmember  12  disposed therebetween. 
     As described above, the rear end of the front side member  11  and the front end of the rear lower member  13  may be joined and supported to the dash crossmember  12  through the mechanical joint system, and thus a load transferred to the front side member  11  may be uniformly distributed and transferred to the dash crossmember  12  and the rear lower member  13 . 
     Referring to  FIG.  5   , each rear lower member  13  may have an opening  44  provided in the rear end thereof, and the front crossmember  14  may be fitted into the opening  44  of the rear lower member  13 . 
     According to an exemplary embodiment, the opening  44  may include a top engaging portion  44   a  joined to a top surface of the front crossmember  14 , a front engaging portion  44   b  joined to a front surface of the front crossmember  14 , and a bottom engaging portion  44   c  joined to a bottom surface of the front crossmember  14 . The top engaging portion  44   a  may be horizontally flat to match the top surface of the front crossmember  14 , and the top engaging portion  44   a  may be joined to the top surface of the front crossmember  14  by welding (CO 2  welding or the like), using fasteners, and/or the like. The front engaging portion  44   b  may be vertically flat to match the front surface of the front crossmember  14 , and the front engaging portion  44   b  may be joined to the front surface of the front crossmember  14  by welding (CO 2  welding or the like), using fasteners, and/or the like. The bottom engaging portion  44   c  may be horizontally flat to match the bottom surface of the front crossmember  14 , and the bottom engaging portion  44   c  may be joined to the bottom surface of the front crossmember  14  by welding (CO 2  welding or the like), using fasteners, and/or the like. The opening  44  of the rear lower member  13  may have a U-shaped cross section, and thus the rear end of the rear lower member  13  may be mechanically joined to the front crossmember  14 . That is, the rear end of the rear lower member  13  may be very firmly joined to the front crossmember  14  through a mechanical joint system. 
     In the vehicle load distribution system according to an exemplary embodiment of the present disclosure, as illustrated in  FIG.  4   , a front end of the central longitudinal member  15  may be joined to a central portion of the dash crossmember  12  using fasteners, welding, and/or the like, and a rear end of the central longitudinal member  15  may be joined to a central portion of the first seat crossmember  16  using fasteners, welding, and/or the like. The pair of rear lower members  13  may be symmetrical to each other with respect to the central longitudinal member  15 . 
     Referring to  FIG.  6   , the central longitudinal member  15  may have a front opening  45  provided in the front end thereof, and a rear opening  46  provided in the rear end thereof. 
     The dash crossmember  12  may be fitted into the front opening  45  of the central longitudinal member  15 . According to an exemplary embodiment, the front opening  45  may include a front engaging portion  45   a  joined to the rear surface of the dash crossmember  12 , and a bottom engaging portion  45   b  joined to the bottom surface of the dash crossmember  12 . The front engaging portion  45   a  may be vertically flat to match the rear surface of the dash crossmember  12 , and the front engaging portion  45   a  may be joined to the rear surface of the dash crossmember  12  by welding (CO 2  welding or the like), using fasteners, and/or the like. The bottom engaging portion  45   b  may be horizontally flat to match the bottom surface of the dash crossmember  12 , and the bottom engaging portion  45   b  may be joined to the bottom surface of the dash crossmember  12  by welding (CO 2  welding or the like), using fasteners, and/or the like. Accordingly, the front opening  45  of the central longitudinal member  15  may have an L-shaped cross section, and thus the front end of the central longitudinal member  15  may be mechanically joined to the dash crossmember  12 . That is, the front end of the central longitudinal member  15  may be very firmly joined to the dash crossmember  12  through a mechanical joint system. 
     The first seat crossmember  16  may be fitted into the rear opening  46  of the central longitudinal member  15 . According to an exemplary embodiment, the rear opening  46  may include a top engaging portion  46   a  joined to a top surface of the first seat crossmember  16 , a rear engaging portion  46   b  joined to a front surface of the first seat crossmember  16 , and a bottom engaging portion  46   c  joined to a bottom surface of the first seat crossmember  16 . The top engaging portion  46   a  may be horizontally flat to match the top surface of the first seat crossmember  16 , and the top engaging portion  46   a  may be joined to the top surface of the first seat crossmember  16  by welding (CO 2  welding or the like), using fasteners, and/or the like. The rear engaging portion  46   b  may be vertically flat to match the front surface of the first seat crossmember  16 , and the rear engaging portion  46   b  may be joined to the front surface of the first seat crossmember  16  by welding (CO 2  welding or the like), using fasteners, and/or the like. The bottom engaging portion  46   c  may be horizontally flat to match the bottom surface of the first seat crossmember  16 , and the bottom engaging portion  46   c  may be joined to the bottom surface of the first seat crossmember  16  by welding (CO 2  welding or the like), using fasteners, and/or the like. Accordingly, the rear opening  46  of the central longitudinal member  15  may have a U-shaped cross section, and thus the rear end of the central longitudinal member  15  may be mechanically joined to the first seat crossmember  16 . That is, the rear end of the central longitudinal member  15  may be very firmly joined to the first seat crossmember  16  through a mechanical joint system. 
     In the vehicle load distribution system according to an exemplary embodiment of the present disclosure, as illustrated in  FIG.  4   , both end portions of the front crossmember  14  may be joined to the pair of side sills  30  using fasteners, welding, and/or the like, respectively. 
     Referring to  FIG.  7   , the front crossmember  14  may have a pair of side openings  48  provided in both end portions thereof, respectively. The side sill inner  31  of each side sill  30  may be fitted into the corresponding side opening  48  of the front crossmember  14 . According to an exemplary embodiment, each side opening  48  may include a side engaging portion  48   a  joined to the inboard side surface of the side sill inner  31  of the side sill  30 , and a bottom engaging portion  48   b  joined to the bottom surface of the side sill inner  31  of the side sill  30 . The side engaging portion  48   a  may be vertically flat to match the inboard side surface of the side sill inner  31  of the side sill  30 , and the side engaging portion  48   a  may be joined to the inboard side surface of the side sill inner  31  of the side sill  30  by welding (CO 2  welding or the like), using fasteners, and/or the like. The bottom engaging portion  48   b  may be horizontally flat to match the bottom surface of the side sill inner  31  of the side sill  30 , and the bottom engaging portion  48   b  may be joined to the bottom surface of the side sill inner  31  of the side sill  30  by welding (CO 2  welding or the like), using fasteners, and/or the like. Accordingly, the side opening  48  of the front crossmember  14  may have an L-shaped cross section, and thus each end portion of the front crossmember  14  may be mechanically joined to the side sill  30 . That is, both end portions of the front crossmember  14  may be very firmly joined to the pair of side sills  30  through a mechanical joint system. 
     Referring to  FIG.  7   , the front crossmember  14  may include a central opening  47  provided in a central portion thereof. The central longitudinal member  15  may be fitted into the central opening  47  of the front crossmember  14 . According to an exemplary embodiment, the central opening  47  may include a bottom engaging portion  47   a  joined to a bottom surface of the central longitudinal member  15 , a first side engaging portion  47   b  joined to a first side surface of the central longitudinal member  15 , and a second side engaging portion  47   c  joined to a second side surface of the central longitudinal member  15 . The bottom engaging portion  47   a  may be horizontally flat to match the bottom surface of the central longitudinal member  15 , and the bottom engaging portion  47   a  may be joined to the bottom surface of the central longitudinal member  15  by welding (CO 2  welding or the like), using fasteners, and/or the like. The first side engaging portion  47   b  may be vertically flat to match the first side surface of the central longitudinal member  15 , and the first side engaging portion  47   b , may be joined to the first side surface of the central longitudinal member  15  by welding (CO 2  welding or the like), using fasteners, and/or the like. The second side engaging portion  47   c  may be vertically flat to match the second side surface of the central longitudinal member  15 , and the second side engaging portion  47   c  may be joined to the second side surface of the central longitudinal member  15  by welding (CO 2  welding or the like), using fasteners, and/or the like. Accordingly, the central opening  47  of the front crossmember  14  may have a U-shaped cross section, and thus the central longitudinal member  15  may be mechanically joined to the central portion of the front crossmember  14 . That is, the central longitudinal member  15  may be very firmly joined to the central portion of the front crossmember  14  through a mechanical joint system. 
     During a frontal collision of the vehicle, the pair of front side members  11  may define a load path through which an impact load is primarily transferred, and the pair of rear lower members  13  may define a load path through which the impact load is secondarily transferred. 
     The pair of front side members  11  may be symmetrically connected to the dash crossmember  12  so that the dash crossmember  12  may primarily support the load transferred through the front side members  11 . That is, the impact load may be transferred to the dash crossmember  12  through the pair of front side members  11 , and the dash crossmember  12  may primarily support the transferred impact load so that the dash crossmember  12  may serve as a primary impact load support. 
     The pair of rear lower members  13  may connect the dash crossmember  12  and the front crossmember  14  so that the front crossmember  14  may secondarily support the load transferred through the rear lower members  13 . The impact load may be transferred to the front crossmember  14  through the pair of rear lower members  13 , and the front crossmember  14  may secondarily support the transferred impact load so that the front crossmember  14  may serve as a secondary impact load support. In particular, the rear lower members  13  may be made of a high-strength material, thus safely protecting the passenger compartment. 
     The central longitudinal member  15  may connect the dash crossmember  12  and the first seat crossmember  16  so that the first seat crossmember  16  may thirdly support the load transferred through the central longitudinal member  15 . The impact load may be transferred to the first seat crossmember  16  through the central longitudinal member  15 , and the first seat crossmember  16  may thirdly support the transferred impact load so that the first seat crossmember  16  may serve as a third impact load support. In particular, the first seat crossmember  16  may be made of a high-strength material, thus safely protecting the passenger compartment. 
     As set forth above, the vehicle load distribution system according to exemplary embodiments of the present disclosure may use a relatively inexpensive material such as mass-produced steel pipes, thereby significantly reducing the manufacturing cost thereof, compared to when using pressed steel materials and aluminum materials, and may uniformly distribute a load in the event of a frontal collision of the vehicle. 
     According to exemplary embodiments of the present disclosure, the pair of front side members may define a load path through which an impact load is primarily transferred during a frontal collision of the vehicle. The pair of front side members may be symmetrically connected to the dash crossmember so that the dash crossmember may primarily support the load transferred through the front side members. That is, the impact load may be transferred to the dash crossmember through the pair of front side members, and the dash crossmember may primarily support the transferred impact load. Accordingly, the dash crossmember may block the dash panel from intruding into the passenger compartment in the event of the frontal collision of the vehicle. 
     According to exemplary embodiments of the present disclosure, the pair of rear lower members may connect the dash crossmember and the front crossmember so that the front crossmember may secondarily support the load transferred through the rear lower members. The impact load may be transferred to the front crossmember through the pair of rear lower members, and the front crossmember may secondarily support the transferred impact load. According to exemplary embodiments of the present disclosure, the central longitudinal member may connect the dash crossmember and the seat crossmember so that the seat crossmember may thirdly support the load transferred through the central longitudinal member. The impact load may be transferred to the seat crossmember through the central longitudinal member, and the seat crossmember may thirdly support the transferred impact load. 
     Hereinabove, although the present disclosure has been described with reference to exemplary embodiments and the accompanying drawings, the present disclosure is not limited thereto, but may be variously modified and altered by those skilled in the art to which the present disclosure pertains without departing from the spirit and scope of the present disclosure claimed in the following claims.