Abstract:
A crash structure for a vehicle includes a crash can having a plurality of indents and a support rail aligned longitudinally with the crash can. The support rail has an inboard surface region having a further indent to facilitate inward deformation of the crash structure, and an opposite surface region having a continuous surface opposite the further indent. A method of manufacturing a crash structure is also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims foreign priority benefits under 35 U.S.C. §119(a)-(d) to GB 1520996.8 filed Nov. 27, 2015, which is hereby incorporated by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The present disclosure relates to a structural member for absorbing energy in a motor vehicle crash. 
       BACKGROUND 
       [0003]    Vehicles, such as motor vehicles, often include one or more crash structures configured to sacrificially deform in the case of a collision to prevent injury to vehicle occupants and/or damage to other components of a vehicle. Crash structures are often configured to dissipate as much energy as possible during their deformation. It is often desirable to minimize the deceleration of the vehicle during a collision, by minimizing the peak force experienced during deformation of the crash structure. 
         [0004]    Many vehicles comprise an internal combustion engine, which is often provided towards the front of the vehicle. In the case of the vehicle colliding front on with an obstacle, the engine may collide with the obstacle before the crash structure has fully deformed. The momentum of the engine may represent a significant proportion of the momentum of the vehicle and hence, an impact between the engine and the obstacle may greatly reduce the momentum of the vehicle. 
         [0005]    In vehicles with rear mounted engines, the momentum of the engine contributes to the total momentum of the vehicle throughout the full duration of a front on collision. Providing a crash structure for a vehicle with a rear mounted engine can therefore be challenging. 
       SUMMARY 
       [0006]    According to a first approach, there is provided a structural member for a front of a motor vehicle, the structural member being configured to extend in a longitudinal direction of the vehicle, wherein the structural member has a polygonal cross-sectional shape, the longitudinal projection of which defines a plurality of surfaces, wherein at least one of the surfaces has a plurality of indents provided on the surface, the indents being spaced apart from one another in the longitudinal direction, wherein a first indent on the at least one surface is larger in size than a second indent on the at least one surface, the second indent being further from the front of the vehicle than the first indent. For example, the indents may successively decrease in size from the front of the vehicle. The indents may encourage the successive collapse of the structural member during a collision event. 
         [0007]    The indents may have a depth relative to the surrounding surface. The depth of the first indent may be greater than the depth of the second indent. 
         [0008]    The indents may have a width extending in a direction perpendicular to the longitudinal direction of the vehicle. The width of the first indent may be greater than the width of the second indent. 
         [0009]    One or more of the indents on the at least one surface may extend over part of the width of the surface. Alternatively or additionally, one or more of the indents on the at least one surface may extend over the entire width of the surface. For example, a particular surface may comprise indents extending over part of the surface width and indents that extend over entire surface width. 
         [0010]    The indents on a first surface may be longitudinally interspersed with indents from a second, e.g. neighboring, surface. 
         [0011]    Each surface may have a plurality of indents provided thereon. Alternatively, alternate surfaces may have a plurality of indents provided thereon. Corresponding indents may be provided on opposite surfaces of the structural member. 
         [0012]    A further indent may be provided on an inboard side of the structural member. A corresponding indent may not be provided on an opposite outboard side of the structural member. The further indent may extend across one or more of the surfaces. The further indent may be provided near an end of the structural member that is furthest from the front of the vehicle. 
         [0013]    The structural member may form a support rail, e.g. forming a sub-frame of the vehicle. Additionally or alternatively, the structural member may form a crash can provided between a support rail and bumper of the vehicle. 
         [0014]    The structural member may have a substantially constant, e.g. constant, cross-sectional size and/or shape. The structural member may be tubular, e.g. hollow. The structural member may have a square, hexagonal or octagonal cross-sectional shape. The surfaces may be formed by walls defining edges of the cross-sectional shape. 
         [0015]    A vehicle may comprise a first pair of structural members as mentioned above. The first pair of structural members may be laterally spaced apart from one another. The first pair of structural members may be support rails forming a sub-frame of the vehicle or crash cans provided between a support rail and bumper of the vehicle. 
         [0016]    The vehicle may further comprise a second pair of structural members as described above. The second pair of structural members may be laterally spaced apart from one another. The second pair of structural members may be coupled to respective structural members of the first pair. The second pair of structural members may be the other of support rails forming a sub-frame of the vehicle or crash cans provided between a support rail and bumper of the vehicle. 
         [0017]    The structural members may be provided inboard of wheel arches of the vehicle. 
         [0018]    The structural members may be provided at the front of the vehicle. A powertrain, e.g. engine, transmission and/or motor, of the vehicle may be provided at a rear of the vehicle. 
         [0019]    In another approach, a method of manufacturing a structural member for a front of a motor vehicle is provided, the structural member being configured to extend in a longitudinal direction of the vehicle. The method includes: 
         [0020]    folding and joining one or more sheets of material to form a polygonal cross-sectional shape, the longitudinal projection of which defines a plurality of surfaces; and 
         [0021]    forming a plurality of indents on at least one of the surfaces, the indents being spaced apart from one another in the longitudinal direction, wherein a first indent on the at least one surface is larger in size than a second indent on the at least one surface, the second indent being further from the front of the vehicle than the first indent, e.g. such that the indents encourage the successive collapse of the structural member during a collision event. 
         [0022]    The method may further comprise folding two or more sheets of material to form respective portions of the polygonal cross-sectional shape. The method may further comprise joining the two or more sheets together. 
         [0023]    The method may further comprise placing the structural member in a mandrel. The method may further comprise stamping or striking the structural member to form the indents. 
         [0024]    In another approach, a crash structure for a vehicle includes a crash can having a plurality of indents and a support rail aligned longitudinally with the crash can. The support rail has an inboard surface region having a further indent to facilitate inward deformation of the crash structure, and an opposite surface region having a continuous surface opposite the further indent. 
         [0025]    The plurality of indents may include a first indent and a second indent spaced from the first indent in a longitudinal direction. In some approaches, the first indent extends over an entire width of a planar face, and the second indent extends over less than the entire width of the planar face. In other approaches, a depth of the first indent is greater than a depth of the second indent. In still other approaches, a width of the first indent is greater than a width of the second indent. In still other approaches, the first indent and the second indent are disposed on a first planar surface, and the plurality of indents further includes a third indent disposed on a second planar surface angularly offset with respect to the first planar surface. The third indent may be longitudinally interspersed between the first indent and the second indent. 
         [0026]    The crash can may be disposed between the support rail and a bumper of the vehicle. The support rail may be disposed between the crash can and a cross member of the vehicle. A joint plate disposed between the crash can and the support rail. 
         [0027]    At least one of the crash can and the support rail may have a hexagonal or octagonal cross-sectional shape. At least one of the crash can and the support rail may be formed from two or more discrete plates. 
         [0028]    In some approaches, the plurality of indents is a first plurality of indents. The crash structure may include a second plurality of indents provided on opposite surfaces of the crash structure form the first plurality of indents, the second plurality of indents corresponding to the first plurality of indents. Indents of the second plurality of indents may have an indent dimension corresponding to indent dimensions of the first plurality of indents. The second plurality of indents may have a longitudinal spacing corresponding to a longitudinal spacing of the first plurality of indents. 
         [0029]    In another approach, a crash structure for a vehicle includes a polygonal beam including a first planar surface having a first plurality of indents spaced apart by continuous regions of the first planar surface, and a second planar surface adjacent to and angularly offset from the first planar surface. The second planar surface may have a second plurality of indents adjacent to the continuous regions of the first planar surface and longitudinally offset from the first plurality of indents. 
         [0030]    In some approaches, the first plurality of indents includes a first indent that extends over an entire width of the first planar surface and a second indent extends over less than the entire width of the first planar surface. The crash structure may further include an inboard surface region having a further indent to facilitate inward deformation of the crash structure, and an opposite surface region having a continuous surface opposite the further indent. 
         [0031]    In another approach, a method of manufacturing a crash structure for a front of a vehicle includes folding and joining one or more sheets of material to form a substantially constant polygonal cross-sectional shape. A longitudinal projection of which defines a plurality of surfaces. The method further includes forming a plurality of indents on at least one of the surfaces, the indents being spaced apart from one another in the longitudinal direction. The method further includes forming a further indent on an inboard side of the crash structure, wherein an opposite outboard side of the crash structure is a continuous surface not provided with a corresponding further indent. 
         [0032]    In some approaches, the method further includes forming a first indent on the at least one surface and forming a second indent on the at least one surface. The second indent may be smaller in size than the first indent, and may be further from the front of the vehicle than the first indent such that the first and second indents encourage successive collapse of the crash structure during a collision event. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0033]      FIG. 1  shows a crash structure for a vehicle in an undeformed condition; 
           [0034]      FIG. 2 a    shows a crash can and support rail of the crash structure in an undeformed condition; 
           [0035]      FIG. 2 b    shows a crash can and support rail of the crash structure in an undeformed condition; 
           [0036]      FIG. 2 c    is a cross-sectional view of a crash can or support rail of the crash structure in an undeformed condition; 
           [0037]      FIG. 3  shows the crash structure for the vehicle following a full frontal collision; 
           [0038]      FIG. 4  shows the crash structure for the vehicle following a collision with a laterally offset obstacle; and 
           [0039]      FIG. 5  shows a method for manufacturing a structural member. 
       
    
    
     DETAILED DESCRIPTION 
       [0040]    As required, detailed embodiments are disclosed herein; however, it is to be understood that the disclosed embodiments are merely representative and may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the claimed subject matter. 
         [0041]    With reference to  FIG. 1 , a vehicle, such as a motor vehicle  2 , may comprise a front bumper  4  supported by a crash structure  10 . The crash structure may be coupled to a cross member  6  of the vehicle. The vehicle may also comprise a plurality of wheels  8  configured to drive the vehicle. 
         [0042]    The crash structure  10  may comprises one or more structural members, such as one or more crash cans  14  and/or one or more support rails  12 . As depicted in  FIG. 1 , a pair of support rails  12  is provided and each support rail  12  may be coupled at a first end  12   a  of the support rail to the cross member  6 . The support rails  12  may extend away from the cross member  6 . The support rails  12  may extend in a longitudinal direction of the vehicle. For example, as shown in  FIG. 1 , the support rails may extend from the cross member  6  towards the front of the vehicle, e.g. towards the front bumper  4 . 
         [0043]    A second end  12   b  of each of the support rails may be coupled to a first end  14   a  of a respective crash cans  14 . As shown in  FIG. 1 , the support rails  12  and/or the crash cans  14  may comprise one of more flanges configured to allow the crash cans  14  and the support rails  12  to be coupled using mechanical fasteners, such as bolts or rivets. Additionally or alternatively, the support rails  12  may be coupled to the crash cans  14  using any other method, such as welding or brazing or using an adhesive. However, it may be desirable to use a temporary fastening method to couple the support rail  12  to the crash can  14  to allow the crash can to be replaced if necessary. 
         [0044]    A joint plate  15  may be provided at the interface between the second end  12   b  of each the support rails  12  and the first end  14   a  of each of the crash cans  14 . The joint plate  15  may be coupled to the support rail and the crash can at their interface. Alternatively, the joint plate  15  may be omitted. As shown in  FIG. 1 , each of the crash cans  14  may be axially aligned, e.g. on a longitudinal axis, with the support rail  12  to which they are coupled. Alternatively, the crash cans  14  may not be aligned with the support rails  14 . For example the crash cans may be laterally or vertically offset from the support rails. 
         [0045]    A second end  14   b  of each of the crash cans  14  may be coupled to the front bumper  4 . The front bumper  4  may be configured to receive a load from an obstacle (not shown) during a collision of the vehicle with the obstacle, and transfer the load to the crash structure  10 . The front bumper  4  may be configured to receive substantially all of the load applied to the vehicle during a front on collision. 
         [0046]    As shown in  FIG. 1 , the structural members  14 ,  12  of the crash structure may be provided between the wheels  8  of the vehicle  2 , e.g. inboard of each of the wheels. The structural members  14 ,  12  may be provided inboard of wheel arches of the vehicle (not shown), which may be formed in one or more body panels of the vehicle. The arrangement of the structural members  14 ,  12  of the crash structure  10  shown in  FIG. 1  may be possible when the powertrain of the vehicle, e.g. an engine and/or motor and transmission (not shown), is not provided at the front of the vehicle. For example, the powertrain may be provided at a rear of the vehicle and/or at one or more wheels  8  of the vehicle. 
         [0047]    With reference the  FIGS. 2 a , 2 b  and 2 c    the structural members  14 ,  12  may have a substantially constant cross-sectional shape. For example, as shown in  FIG. 2 c   , the structural members may have a substantially constant octagonal shape in cross-section. However, it is equally envisaged that the structural member may have a square, hexagonal or any other polygonal shape in cross-section. In another approach (not shown) the size, e.g. area, of the cross-section may vary from one end of the structural member to the other. For example, the structural members  14 ,  12  may be tapered. 
         [0048]    The cross-sections of the crash cans  14  and the supports rails  12  may be the same shape. Alternatively, the cross-section of the crash cans  14  may be a different shape from the cross-section of the support rails  12 . 
         [0049]    As shown in  FIGS. 2 a  and 2 b   , one or more surfaces  12   c,    14   c  may be defined by the longitudinal projection of the cross-section of the structural member  14 ,  12 . At least one of the surfaces  12   c,    14   c,  may comprise one or more indents  16 ,  18 . As depicted in  FIGS. 2 a  and 2 b   , each of the surfaces  12   c,    14   c  may comprise one or more indents  18 . The indents  16 ,  18  may be spaced apart from each other, e.g. longitudinally, along the support member. 
         [0050]    The indents  16 ,  18  may extend at least partially across a width of one or more surfaces  12   c,    14   c  of the structural member, e.g. in a direction perpendicular to the longitudinal direction of the vehicle. One or more of the indents may extend over substantially the entire width of the surface  12   c,    14   c.  In other words, the indents  16 ,  18  may have a width (measured in the direction perpendicular to the longitudinal direction of the vehicle), which is less than or equal to the width of the surface  12   c,    14   c  in which they are formed. 
         [0051]    The indents  16 ,  18  may have a depth relative to the surrounding surface  12   c,    14   c.  The indents may be rounded and/or comprise rounded bottoms, e.g. a cross-section of the indents in a plane parallel to the longitudinal direction of the vehicle may be substantially semi-circular or comprise a sector of a circle or ellipse. Alternatively, the cross-section of the indent  16 ,  18  may be any other shape, such as substantially triangular or substantially square. 
         [0052]    As shown in  FIGS. 2 a  and 2 b   , the indents  16 ,  18  may be provided on each of the surfaces  12   c,    14   c  of the crash can  14  and the support rail  12 . Each surface may comprise a plurality of indents. The indents  16 ,  18  formed in opposite surfaces of the support members may correspond. For example, the indents  16 ,  18  in opposite surfaces may be the same width and/or depth and/or may be provided at the same longitudinal locations. In contrast, the indents  16 ,  18  formed in adjacent, e.g. neighbouring, surfaces may be dissimilar. Indents  16 ,  18  on one or more surfaces may have a different width and/or depth and/or may be provided at different longitudinal locations to those provided on one or more adjacent surface. For example, indents provided on one or more surfaces  12   c,    14   c  may be longitudinally interspersed with the indents provided on one or more adjacent surfaces. 
         [0053]    As shown in  FIGS. 2 a  and 2 b   , the size, e.g. the depth, span and/or width of the indents  16 ,  18  provided on the surfaces  12   c,    14   c  may vary along the length, e.g. longitudinal length, of the surfaces  12   c,    14   c  (the indent span may be measured in the longitudinal direction of the vehicle). The size, e.g. depth, span and/or width, of successive indents may decrease from the front of the crash structure  10  towards the rear of the crash structure  10 . For example, a first indent  18   a  provided towards the front of the vehicle  2 , e.g. towards a second end  12   b  of the crash can, may have a greater depth than a second indent  18   b  provided towards the first end  12   a  of the crash can, e.g. further from the front of the vehicle  2 . Additionally or alternatively, the first indent  18   a  may have a greater width and/or span than the second indent  18   b.  In some embodiments, two or more of the indents  16 ,  18  spaced apart along one of the surfaces  12   c,    14   c  may be grouped into pairs, threes or larger groups, which may be the same size as the others in the group. 
         [0054]    With reference to  FIG. 2 c   , the structural members  12 ,  14  may be formed from one or more folded sheets  22 ,  24 , which may be joined at or near their ends to provide the structural member. As shown in  FIG. 2 c   , the structural member may be formed from two folded sheets, however it is equally envisaged that one or more than two folded sheets may be used to form the structural member. 
         [0055]    As depicted in  FIG. 2 c   , the structural member  12 ,  14  may be formed from a first side sheet  22  and a second side sheet  24 . The first and second side sheets  22 ,  24  may be substantially the same size and/or shape. In order to join the first and second side sheets, one or more end surfaces  22   a,    24   a  at each end of one of the side sheets  22 ,  24  may be overlapped with one or more end surfaces  22   a,    24   a  provided at each end of the other of the side sheets to form first and second joints  26 ,  28 . The side sheets may be joined at the joints  26 ,  28  using any appropriate method. For example the first and second side sheets may be bolted, riveted, welded and/or brazed together. 
         [0056]    As each of the side sheets may be the same size, the side sheets  22 ,  24  may be vertically or laterally offset, such that the at one of the joints the end surfaces  22   a  of the first side sheet  22  are provided on the outside of the structural member  12 ,  14  and at the other of the joints, the end surfaces  22   a  of the first side sheet  22  are provided on an inside of the structural member  12 ,  14 . In an alternative embodiment (not shown), the first and second side sheets may be different sizes and the end surfaces of one of the side sheets may be provided on the outside of the structural member  12 ,  14  at each of the joints. 
         [0057]    With reference to  FIG. 5 , a method  500  of manufacturing a structure member will now be described. The method  500  comprises a first step  502  in which one or more sheets of material are folded and a second step  504  in which the folded sheet are joined (at their ends), e.g. as described above with reference to  FIG. 2 c   , to form a substantially constant polygonal cross-sectional shape, the longitudinal projection of which defines a plurality of surfaces. 
         [0058]    The method  500  further comprises a third step  506 , in which a plurality of indents are formed on at least one of the surfaces of the structural member. As described above with reference to  FIGS. 2 a  and 2 b   , the indents may vary in size, e.g. depth, span and/or width along the length of the structural member. The indents may be produced using a pressing, forming or forging process. The indents may be formed by striking the structural member with a tool configured to provide the desired, shape, depth, span and/or width of indent. 
         [0059]    With reference to  FIGS. 3 and 4 , when the vehicle  2  is involved in a collision with an obstacle (not shown) the structural members  12 ,  14  may be configured to collapse in order to dissipate the kinetic energy lost by the vehicles  2  and/or the obstacle during the collision. For example, the surfaces  12   a,    14   a  of the structural members may be configured to buckle locally and fold in order to dissipate energy. 
         [0060]    By providing the indents  16 ,  18  such that the size, e.g. depth, span and/or width, of the indents varies along the longitudinal length of the structural member, the indents may encourage the structural member to collapse in a successive manner during an impact between the vehicle  2  and the obstacle. For example, the indents  18  in the crash can  14  may be configured such that the crash can  14  initially begins to collapse at or towards the second end  14   b  of the crash can. The collapse of the crash can  14  may propagate towards the first end  14   a,  e.g. such that the crash can  14  collapses successively from the front of the vehicle  2  rearwards. The indents  16 , provided in the support rail  12  may be configured such that, once the crash can  14  has substantially completely collapsed, the support rail  12  begins to collapse at or towards the second end  12   b  of the support rail  12 . Similar to the crash can  14 , the indents  16  in the support rail  12  may be configured to encourage the successive collapse of the support rail  12  from the second end  12   b  towards the first end  12   a.    
         [0061]    Encouraging successive collapse of the structural members  12 ,  14 , as described above, may lead to more complete collapse of the structural members such that a greater amount of energy may be dissipated by the crash structure  10 . 
         [0062]    As shown in  FIG. 1 , the support rail  12  may be provided with a further indent  17 . The further indent  17  may be provided on an inboard side of the support rail  12  at or towards the first end  12   a  of the support rail. The further indent may extend at least partially over the width of the surface  12   c.  As shown in  FIG. 1 , the further indent may extend over one or more surfaces  12   c  of the support rail. The further indent  17  may be configured to affect the direction in which the support rail collapses during a side or offset impact with an obstacle (not shown).  FIG. 4  depicts the crash structure  10  following an impact with an offset obstacle. As shown in  FIG. 4 , the further indent  17  has been configured to encourage the support rail to collapse inwards (relative to the vehicle  2 ) during the collision. The inwards collapsing of the support rail  12  may increase the energy dissipated by the collapsing of the crash structure  10  and/or may reduce the deceleration of the vehicle  2  during the collision. As the further indent  17  is configured to encourage the support rail  12  to collapse inwards during the collision, a corresponding indent may not be provided on an opposite outboard side of the support rail. 
         [0063]    It will be appreciated by those skilled in the art that although the claimed subject matter has been described by way of example, with reference to one or more examples, it is not limited to the disclosed examples and alternative examples may be constructed without departing from the scope of the appended claims. 
         [0064]    While representative embodiments are described above, it is not intended that these embodiments describe all possible forms of the claimed subject matter. The words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the claimed subject matter. Additionally, the features of various implementing embodiments may be combined to form further embodiments not explicitly illustrated or described.