Abstract:
A motor vehicle structural energy absorbing member ( 12 ) is light weight and is made in a manner to produce random or directionally oriented, elongated pores or voids ( 16 ) in a structural matrix ( 14 ) in a manner that permits tailoring of impact energy absorption in one or more direction(s) to provide an integral energy absorbing region.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to motor vehicle energy absorbing structural members for absorbing impact energy. 
     2. Description of Related Art 
     Modern motor vehicles are known to incorporate energy absorbing structural members that are designed to absorb impact energy when the vehicle is involved in a crash. Such energy absorbing members include steel door beams residing inside the doors of the vehicle to absorb a side impact and bumper extensions and frame members which are designed to have collapsible zones to collapse on impact. Various materials have been used to fabricate such energy absorbing members including bulky steel and aluminum alloy plates and beams, non-metallic materials such as polymers and other plastics, and composite materials that include a metal-metal composites, metal-polymer composites and others. 
     An object of the present invention is to provide an improved vehicle structural energy absorbing member. 
     SUMMARY OF THE INVENTION 
     The present invention provides a structural energy absorbing member that is light weight and that is made in a manner to produce pores or voids in a structural matrix to provide an integral energy absorbing region and that permits tailoring of impact energy absorption in one or more anticipated directions of impact. The pore or void structure, geometry, distribution, and concentration in the structural matrix can be controlled to provide energy absorption tailored to particular impact situations. The structural matrix can comprise metallic materials and ceramic materials. The energy absorbing structural member can comprise a frame rail member, bumper member, door beam and other structural energy absorbing member connected to a second structural member of the motor vehicle. Not only are the structural energy absorbing member pursuant to the invention advantageous as a result of their light weight, but also smaller structural energy absorbing members pursuant to the invention may be used in lieu of larger hollow structural components of the motor vehicle ad a result of the structural matrix thereof providing greater load carrying capacity compared to a similar sized hollow component. The structural energy absorbing members pursuant to the invention may be used as sound dampening structural members incorporated into the vehicle frame, strut frames, control arm links, engine and transmission mounts, and the like of a motor vehicle. 
     The above objects and advantages of the present invention will become more readily apparent from the following description taken with the following drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of a motor vehicle bumper frame extension and a bumper including energy absorbing structural frame members pursuant to embodiments of the invention. 
     FIGS. 1A,  1 B,  1 C,  1 D, and  1 E are partial perspective views of energy absorbing members pursuant to various embodiments of the invention. 
     FIG. 2 is a plan view of a motor vehicle frame including energy absorbing frame members pursuant to embodiments of the invention. 
     FIG. 3 is a perspective view of a motor vehicle door having an energy absorbing door side beam pursuant to an embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, motor vehicle bumper frame extensions  10  and bumper assembly  22  including respective energy absorbing structural frame members  12  and  26  pursuant to embodiments of the invention are illustrated. The bumper frame extensions  10  include respective tubular elongated structural members  10   a,    10   b  between which a respective energy absorbing structural member  12  pursuant to the invention is connected by welding, mechanical fasteners or other fastening technique. The tubular bumper frame extension members  10   a,    10   b  typically are formed of steel or aluminum alloy tubes with the extension members  10   b  having a respective flange  10   c  fastened thereon for attachment to the bumper assembly  22 . In FIG. 1, the tubular bumper frame extension members  10   a,    10   b  are shown welded by welds W to the opposite axial ends of the respective energy absorbing structural members  12  for purposes of illustration only. 
     The energy absorbing structural members  12  each comprise a solid structural matrix  14  having a plurality of directionally oriented, elongated pores or voids  16  therein. The structural matrix  14  can comprise metallic, ceramic and plastic materials. For example only, for joining to the steel or aluminum alloy bumper frame extension members  10   a,    10   b,  the matrix  14  can comprise steel or aluminum alloy, respectively, that is readily weldable to the frame extension members  10   a,    10   b.  The structural matrix  14  typically is a solid material to impart needed mechanical properties to the energy absorbing members  12 , although the matrix  14  may contain some porosity so long as adequate structural properties are exhibited by the energy absorbing members  12 . 
     The elongated pores  16  are illustrated in FIG. 1 as extending parallel to one another preferentially along the longitudinal axis of the energy absorbing members  12  to define an integral energy absorbing region that can axially collapse in a frontal impact of the motor vehicle to absorb impact energy. That is, the elongated pores or voids  16  are aligned generally parallel to the direction of anticipated frontal impact of the motor vehicle. However, the pores or voids  16  can be oriented in other directions relative to the energy absorbing members  12  to permit tailoring of impact energy absorption in an anticipated impact direction(s). The pore or void structure, geometry, distribution, and concentration in the structural matrix  14  also can be controlled to this end to provide energy absorption tailored to particular impact situations. The energy absorbing members  12  can be made with controlled pore or void orientation, structure, geometry, distribution, and concentration in the structural matrix  14  as described in U.S. Pat. No. 5,181,549 wherein a gas is dissolved in a molten matrix material under pressure and then the molten matrix material is cooled in a manner to form the elongated pores and voids  16  as a solidification front progresses through the molten matrix material in a mold. The teachings of U.S. Pat. No. 5,181,549 are incorporated herein by reference with respect to manufacture of porous members. 
     The energy absorbing members  12  can be made as taught in the aforementioned patent to include solid end regions  12   a,    12   b  where the energy absorbing members  12  are welded to the bumper frame extension members  10   a,    10   b.  Such solid end regions  12   a,    12   b  facilitate welding or other fastening of the energy absorbing members  12  to the structural members  10   a,    10   b.    
     Referring again to FIG. 1, the bumper assembly  22  is shown including an energy absorbing bumper beam  26  that is fastened to a decorative, resilient plastic (e.g. molded polyurethane) bumper fascia  24  and to the flanges  10   c  of the bumper frame extension by mechanical fasteners (not shown) or other fastening means. The energy absorbing bumper beam  26  includes a plurality of elongated pores or voids  28  extending parallel to one another preferentially along the longitudinal axis thereof in a solid structural matrix  29  to define an energy absorbing region that can collapse from front-to-back laterally in an anticipated frontal impact of the motor vehicle to absorb impact energy. That is, the elongated pores or voids  28  are aligned generally transverse or perpendicular to the direction of anticipated frontal impact of the motor vehicle. The energy absorbing bumper beam  26  can be made in the manner taught in aforementioned U.S. Pat. No. 5,181,549 already incorporated herein by reference. 
     Although n FIGS. 1 and 1A the energy absorbing members  12  and  26  are illustrated as having a rectangular cross-section, the invention is not so limited. The energy absorbing members can have any suitable cross-section suited to a particular application as a motor vehicle structural member. For example, referring to FIGS. 1B through 1D, energy absorbing member  12 ′ can include a triangular cross-section, FIG. 1B, with pores or voids  16 ′ elongated along a longitudinal axis of the solid matrix  14 ′. The matrix  14 ′ can include a solid central region  18 ′ or attachment by welding, mechanical fasteners, and the like to a second motor vehicle structural member (not shown) or to provide a support region for mounting of a motor vehicle component thereon. Alternately, energy absorbing member  12 ″ can include a circular cross-section, FIG. 1C, with pores or voids  16 ″ elongated along a longitudinal axis of the solid matrix  14 ″. Further, energy absorbing member  12 ′″ can include a circular cross-section, FIG. 1C, with pores or voids  16 ′″ elongated along a radial direction of the solid matrix  14 ′″. A solid outer casing or housing  15 ′″ comprising metal, ceramic and other materials can be provided about the matrix  14 ′″ for attachment to a second motor vehicle structural member (not shown) or to provide a support region for mounting of a motor vehicle component thereon. Energy absorbing member  12 ″″ also can include randomly oriented, spherical pore or voids  16 ″″ in a solid structural matrix  14 ″″ rather than the directionally oriented, elongated pores or voids shown in the other figures. 
     Referring to FIG. 2, a frame  30  for a motor vehicle is illustrated as including forward side frame members  31 , bumper assembly  33 , rearward side frame members  41 , and cross frame members  35 ,  37 . The side frame members  31 ,  41  can include respective energy absorbing members  32 ,  42  of the type described hereabove pursuant to the invention having multiple elongated pores or voids  36 ,  46  extending through a solid structural matrix  34 ,  44  in a manner similar to that shown in FIG.  1 A. 
     Referring to FIG. 3, a door  50  for a motor vehicle is illustrated as including an energy absorbing door beam or member  52  pursuant to the invention having multiple elongated pores or voids  56  extending through a solid structural matrix  54 . The voids  56  extend along the longitudinal axis of the door beam  52  so as to be oriented perpendicular to the direction of anticipated impact force on the door. The energy absorbing door beam  5 , is mounted on a brackets  52   a,    52   b  that are welded or mechanically fastened to the door  50 . 
     While the invention has been described in terms of specific embodiments thereof, it is not intended to be limited thereto but rather only as set forth in the appended claims.