Abstract:
A vehicle front structure includes a bumper beam formed as a hollow body having open ends, and elongation members received within the open ends and extending laterally outward.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to British Patent Application No. 1319254.7 filed Oct. 31, 2013, which is incorporated herein by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The present disclosure relates to a front structure for a motor vehicle including a bumper beam and elongation members connected to lateral ends of the bumper beam. 
       BACKGROUND 
       [0003]    DE 10 2010 014 999 A1 suggests a front structure which combines one type of bumper beam with different types of elongation members such that front structures for vehicles of different widths can be formed using a small number of different parts. 
         [0004]    A problem with this front structure arises from its tripartite structure. If a vehicle equipped with this front structure collides with an obstacle and the overlap between the vehicle&#39;s front structure and the obstacle is small, an elongation member that is subject to most of the force may come loose. As such, additional measures may be required to ensure the front structure exhibits suitable crashworthiness characteristics. 
       SUMMARY 
       [0005]    The present disclosure provides a vehicle front structure which achieves crashworthiness characteristics for such front structures in case of a small overlap collision. According to an embodiment of the present disclosure, a vehicle front structure includes a bumper beam formed as a hollow body having open ends, and elongation members inserted in the open ends. This structure avoids a weak link between the bumper beam and the elongation members. Rather, a bumper including the bumper beam and the elongation members inserted therein according to the present disclosure can only be separated into pieces when a collision is violent enough to shatter at least one of the bumper beam and the elongation members. 
         [0006]    The bumper beam may be formed as an extrusion profile. In such a profile, a moderate bend, as conventional bumper beams usually have, can be formed conveniently during or after extrusion. Since the bumper beam does not have to extend into corners of the vehicle body shell, there is no need to form sharp bends in it. The elongation members may also be extrusion profiles. Since these may extend into the corners of the vehicle body shell, they may need to have sharper bends than the bumper beam. However, since the elongation members are generally shorter than the bumper beam, sharp bends in the elongation members may be formed using smaller and, hence, less expensive tooling. The elongation members may have a horizontal symmetry plane. Such elongation members may be used indifferently at left and right sides of the vehicle, so that only a single set of tools is required for manufacturing elongation members for left and right-hand sides of the vehicle body. 
         [0007]    A light metal such as aluminum or an aluminum alloy can be used for manufacturing the bumper beam and/or the elongation members. For reasons of stability, the bumper beam should include at least two compartments separated by a partition wall. In order to solidly fix the elongation members in the bumper beam, the elongation members should have slit in which the partition wall can be accommodated. 
         [0008]    According to an embodiment of the present disclosure, the slit extends longitudinally within a wall of the elongation member. Such a slit should substantially not extend beyond an overlapping region of the bumper beam and elongation members. In order to accommodate the slit, the wall must be rather thick and sturdy, contributing substantially to the overall rigidity of the vehicle front structure. 
         [0009]    According to a more light-weight embodiment, each elongation member has at least three compartments, the width of a central one of which corresponds to the thickness of the above-mentioned partition wall. In this embodiment, a slit which receives the partition wall of the bumper beam may be formed by cutting away outer walls of the central compartment. 
         [0010]    In the overlapping region of the bumper beam and one of the elongation members, walls of the bumper beam and of the elongation member combine, making the overlapping region more rigid than other regions of the bumper beam and the elongation members. Therefore, longitudinal chassis beams should best be connected to the overlapping region. In particular, connecting members such as screws or rivets may fix the elongation members to the longitudinal chassis beams by extending across a wall of the bumper beam. In order to increase the impact resistance of a distal end of the elongation members, a support may be provided which connects an end portion of one of the elongation members which faces away from the bumper beam to one of the longitudinal chassis beams. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The present disclosure will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements. 
           [0012]      FIG. 1  is a perspective view showing a portion of a vehicle front structure according to the present disclosure; 
           [0013]      FIG. 2  is a perspective view of an elongation member which may be used in the vehicle front structure of  FIG. 1 ; 
           [0014]      FIG. 3  is a perspective view of a second embodiment of an elongation member; 
           [0015]      FIG. 4  is a perspective view of a third embodiment of the elongation member; 
           [0016]      FIG. 5  is a horizontal cross section of part of the vehicle front structure; and 
           [0017]      FIG. 6  is an alternative horizontal cross section of the vehicle front structure. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The following detailed description is merely exemplary in nature and is not intended to limit the present disclosure or the application and uses of the present disclosure. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description. 
         [0019]      FIG. 1  is a perspective view showing a portion of a vehicle front structure according to the present disclosure. The front structure includes a bumper beam  1  extruded from aluminum or aluminum alloy. In  FIG. 1 , only a right-hand end portion of the bumper beam  1  is shown. The bumper beam  1  includes a front wall  2 , a rear wall and three walls  4 ,  5 ,  6  which extend between front wall  2  and rear wall  3 , delimiting upper and lower compartments  7 ,  8 . The stiffness of the front wall  2  is increased by two grooves  3  formed in it, which extend horizontally over the entire length of the bumper beam  1 . 
         [0020]    The rear wall  3  is not visible in the view of  FIG. 1 . It is fixed to a forward end of a longitudinal chassis beam  9 , which extends over a length of the vehicle body. The chassis beam has central portion  10  made of two thick-walled, rigid pieces of sheet metal which combine to form a hollow profile. A hood lock support  11  is connected to a front end central portion  10 . A front end portion of the chassis beam  9  is formed by a crash box  12 , a front wall of which is fixed to the rear wall  3  of bumper beam  1 , and a rear portion of which is inserted into chassis beam central portion  10 . 
         [0021]    An elongation member  13  extruded from the same light metal as bumper beam  1  is shown in a configuration in which it is about to be installed in the vehicle front structure. The elongation member  13  has an inner end portion  14  which, in  FIG. 1 , is just about to be inserted in the compartments  7 ,  8  of bumper beam  1 . When the elongation member  13  has reached its final location, most of the slit  15 , which in  FIG. 1  is still distinctly visible, will have disappeared within bumper beam  1  and will be filled by the partition wall  5  extending between its compartments  7 ,  8 . An outer end portion  16  of elongation member  13  has a support  17  fixed to its rear side, an end of which will finally be connected a chassis beam central portion  10 , close to its front end. Here, the support is a tubular profile of rectangular cross section. 
         [0022]    If in a collision the front structure of  FIG. 1  is hit directly in front of the crash box  12 , it will exhibit a very high bending resistance, since the walls of bumper beam  1  are supported by those of the elongation member  13  inserted in it. If, however, the elongation member  13  is hit in its outer end portion  16 , a substantial part of the load can be transferred to the bumper beam  1 , since the inner end portion  14  is prevented from turning or bending by the fact that it is snugly fitted within compartments  7 ,  8 . Further, another part of the load is transmitted to the chassis beam central portion  10  by support  17 . Therefore, the elongation member  13  will absorb a substantial amount of impact energy, and if it does yield to the collision impact, it will tend to deflect the vehicle laterally, in a direction in which overlap with the obstacle is still further reduced, and in which the vehicle may eventually slip past the obstacle. In this way, a vehicle front wheel located behind the elongation member  13  is effectively protected from the collision impact and from being urged towards the passenger compartment. 
         [0023]      FIG. 2  is a perspective view of an elongation member  13  according to a first embodiment. The elongation member  13 , in this case, is a hollow profile with a single inner compartment  18  and with walls  21 ,  22 , the outer cross section of which closely mates that the cross section of bumper beam compartments  7 ,  8 , so that an inner end portion  14  of elongation member  13 , including slit  15 , will be tightly held in bumper beam  1  when inserted into one of its ends. 
         [0024]    The elongation member  13  has a horizontal symmetry plane, identified by dash-dot lines  19  in  FIG. 2 , so that it can be inserted into bumper beam  1  from both ends alike. 
         [0025]    Inner end portion  14  is bent slightly, matching the curvature of bumper beam  1 . In outer end portion  16 , the bend is more pronounced. 
         [0026]      FIG. 3  is a perspective view of another embodiment of the elongation member  13 . According to this embodiment, there are two partition walls  20  extending between front and rear walls  21 ,  22  of the elongation member, defining upper and lower compartments  23 ,  24  and a central compartment  25  in between. The height of the central compartment  25  corresponds exactly to the thickness of partition wall  5  of bumper beam  1 . In the inner end portion  14  of elongation member  13 , outer walls of the central compartment  25  are removed, whereby the slit  15 , extending all across elongation member  13  in the vehicle longitudinal direction is formed. Here, too, the bend of elongation member  13  is more pronounced in its outer end portion  16 . 
         [0027]    In the embodiment of  FIG. 4 , upper and lower compartments  23 ,  24  are the same as in  FIG. 3 , but instead of the two partition walls  20  and the central compartment  25 , there is just one thick wall  26 , and the slit  15  is cut in wall  26  in the longitudinal direction thereof 
         [0028]      FIG. 5  is a schematic horizontal cross section of a right-hand half of the vehicle front structure (the left-hand half, not shown, being the mirror image thereof). As indicated by a dashed line in  FIG. 5 , the end of bumper beam  1  is cut obliquely, so as to facilitate insertion of the inner end portion  14  of elongation member  13 . The elongation member  13  is fixed by weld seams  27  extending along the edges of bumper beam front wall  2 , bumper beam rear wall  28 , and, optionally, upper and lower walls  4 ,  6 . 
         [0029]    A region  29  in which the bumper beam  1  and the elongation member  13  overlap extends just across crash box  12  in the vehicle transversal direction, welded to rear wall  28 . Support  17  has its front end welded to rear wall  22  of elongation member  13 . It is fixed, although not too rigidly, to chassis beam  9  by being screwed to a sheet metal strip  30 , part of which engages into a gap between a wall of chassis beam central portion  10  and the crash box inserted therein. In case of a collision strip  30  will yield rather easily, but even so, it will prevent a rear end of support from bending away from chassis beam  9 . The rear end of support  17  will abut against a structure  31  projecting laterally from chassis beam central portion  10  and thus prevent elongation member  13  from yielding prematurely. 
         [0030]    In the embodiment of  FIG. 6 , a flange  32  forms a forward end of crash box  12 . Screws  33  extend through holes in the rear walls  22 ,  28  of elongation member  13  and bumper beam  1  and of flange  32  and engage nuts  34  inside crash box  12 . 
         [0031]    In the embodiment shown, the front walls  2 ,  21  of bumper beam  1  and elongation member  13  have holes  35  which are aligned with respect to each other when elongation member  13  is correctly inserted, and by which one of the screws  33  is inserted. Due the oblique cut at the end of the bumper beam  1 , the other screw  33  is accessible by a hole  36  in elongation member  13  alone, although both screws engage the rear walls  22 ,  28  of both the elongation member  13  and the bumper beam  1 . 
         [0032]    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 is only an example, and are not intended to limit the scope, applicability, or configuration of the present disclosure 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 present disclosure as set forth in the appended claims and their legal equivalents.