Abstract:
A bumper system includes a tubular beam with flattened end sections, and further includes an energy absorber having a rear recess mateably receiving the tubular beam in a nested relationship, with the recess also including flat mating surfaces engaging the flattened end sections. Mounts engage a rear of the flattened end sections, and fasteners secure the tubular beam and energy absorber to the mounts. In one modified bumper system, corner sections on the energy absorber are shaped to slidingly engage a side surface of the mount and simultaneously an end of the beam upon corner impact of the vehicle. In another modified bumper system, offset ends of the tubular beam fit into a recess in an energy absorber, with its center section being between vehicle mounts.

Description:
BACKGROUND  
         [0001]    The present invention relates to vehicle bumper systems, and more particularly relates to a bumper system having an integrated energy absorber and beam, and also relates to novel beam constructions such as are shaped for engagement with mating energy absorbers.  
           [0002]    Bumper systems using integrated energy absorber and bumper beam arrangements are desired to improve assembly of bumper systems to vehicles, to minimize the number and types of mechanical fasteners overall, and to simplify tooling. In particular, it is desirable to provide a design where the beam and energy absorber can be assembled off-line of the main vehicle assembly line into a unitary subassembly, and then manipulated as a unit for attachment to the vehicle. Also, it is desirable to attach fascia to the subassembly, and to integrate and attach other components to the subassembly, such as headlights, grilles, and other functional and ornamental components. At the same time, impact durability and enhanced energy absorption continue to be high priority items in bumper systems, and accordingly, any subassembly should preferably not detract from the same.  
           [0003]    In addition to the above, many vehicle manufacturers and some insurance groups and government entities are pressing for improved crashworthiness of vehicles, and also for bumper systems that will provide for better pedestrian safety. Longer bumper strokes with lower initial energy absorption rates have the possibility of satisfying these desires, but this can result in energy absorbers that are physically larger in size than present bumper systems, and that are not easy to package and carry at a front of the vehicle. Thus, new integrated bumper systems are desired to deal with the conflicting functional and design requirements.  
           [0004]    Improvements are also desired in rear bumper systems on vehicles. In particular, vehicle manufacturers are looking increasingly at energy absorbers for rear bumper systems that are not dissimilar in shape and function to energy absorbers for front bumper systems. However, the energy absorber of any such rear bumper system must be integrated into the bumper system such that it does not interfere with other functional and aesthetic requirements at a rear of the vehicle. For example, many rear bumper systems include a step, and/or are adapted to support a ball hitch for hauling a trailer.  
           [0005]    Accordingly, bumper systems are desired solving the aforementioned problems and having the aforementioned advantages.  
         SUMMARY OF THE PRESENT INVENTION  
         [0006]    In one aspect of the present invention, a bumper system includes a tubular beam with front, rear, top, and bottom walls; the front and rear walls being reformed at ends of the tubular beam to form flattened end sections. The bumper system further includes an energy absorber having a rear surface with a recess mateably receiving the tubular beam, the recess including mating surfaces engaging a front of the flattened end sections. Vehicle mounts engage a rear of the flattened end sections, and fasteners secure the tubular beam and energy absorber to the mounts.  
           [0007]    In another aspect of the present invention, a bumper system includes a beam having front, rear, top, and bottom walls defining a tubular center section and having end sections. The bumper system further includes a one-piece energy absorber having an absorber center section with a rear-facing recess mateably receiving the tubular center section and engaging portions of the front, top and bottom walls; and further having corner sections with an interior surface located proximate an outer end of the end sections of the beam. Mounts engage a rear of the end sections, with the interior surface of the corner sections being positioned to engage the outer end of the beam and to simultaneously engage an outer side surface of the mounts when the vehicle experiences a corner impact. Fasteners secure the tubular beam and energy absorber to the mounts.  
           [0008]    In yet another aspect of the present invention, a bumper system for a vehicle having a passenger compartment includes a tubular bumper beam having a tubular bumper beam that includes a center section, end sections, and bent interconnecting sections that interconnect each end section with an end of the center section, with the center section being at least 25% of a length of the bumper beam and defining a longitudinal primary centerline, and the end sections being at least 15% of the length. The end sections each define a secondary centerline that extends parallel the primary centerline, with the secondary centerline being spaced horizontally from the primary centerline when in a vehicle-mounted position, and with the center section being located partially between the mounts and closer to the passenger compartment than the end sections. An energy absorber is provided that includes at least one recess shaped to receive a portion of the tubular bumper beam. Mounts are provided that are adapted for attachment to a vehicle and that are attached to the end sections.  
           [0009]    An advantage of the present bumper systems is that some of the traditional front-end support structure can be simplified or eliminated. For example, the present inventive bumper system can include an energy absorber with portions that support the front-of-vehicle fascia in areas in front of the vehicle hood. This allows the front end support structure of the vehicle to e simplified, such as by eliminating fascia-supporting struts, by eliminating forwardly-extending flanges on the radiator cross support, by reducing the strength requirements on the radiator cross support and/or by eliminating or reducing strength requirements on a vehicle&#39;s front end panel.  
           [0010]    These and other aspects, objects, and features of the present invention will be understood and appreciated by those skilled in the art upon studying the following specification, claims, and appended drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0011]    [0011]FIG. 1 is a perspective view of a bumper system embodying the present invention, including an energy absorber and a tubular beam with flattened ends positioned within a rear-facing recess in the energy absorber;  
         [0012]    [0012]FIG. 2 is an exploded view of FIG. 1;  
         [0013]    [0013]FIGS. 3 and 4 are cross sections taken along lines III-III and IV-IV in FIG. 2;  
         [0014]    [0014]FIG. 5 is a fragmentary top schematic view of the bumper system of FIG. 1;  
         [0015]    [0015]FIG. 6 is an exploded perspective view of another bumper system embodying the present invention;  
         [0016]    [0016]FIG. 7 is a perspective view of the bumper system of FIG. 6, a portion of the energy absorber being removed to better show engagement of the energy absorber with the beam;  
         [0017]    [0017]FIG. 8 is a cross section taken along line VIII-VIII in FIG. 7;  
         [0018]    [0018]FIG. 9 is a cross section of an alternative bumper system, the cross section being similar to FIG. 8, and FIG. 9A is a fragmentary perspective view of an apertured version of the U-beam shown in FIG. 9;  
         [0019]    [0019]FIG. 10 is a perspective view of a rear bumper system embodying the present invention; and  
         [0020]    [0020]FIG. 11 is an exploded view of FIG. 10. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0021]    A bumper system  20  (FIG. 1) includes a beam  21  with a tubular center section and flattened end sections  23  and  24 , and a molded energy absorber  22  adapted to nestingly receive the beam  21  to form a unitary subassembly that can be handled and assembled as a unit to a vehicle. The flattened end sections  23  and  24  form vertically enlarged attachment members or “hands” on each end of the beam  21  that engage mating flat surfaces on the energy absorber  22 . Mounts  26  abuttingly engage a rear of the flattened end sections  23  and  24 , and fasteners  27  extend through the energy absorber  22  and the flattened end sections  23  and  24  to secure the tubular beam  21  and energy absorber  22  to the mounts  26 . It is contemplated that the term “mount” as used herein includes a rail extending from a vehicle frame, or similar structural frame component.  
         [0022]    The beam  21  (FIG. 1) is described in sufficient detail below for an understanding of the present invention by persons skilled in this art. Nonetheless, if additional discussion is desired, the reader&#39;s attention is directed to application Ser. No. 09/822,658, filed Nov. 1, 2001, entitled METHOD OF FORMING A ONE-PIECE TUBULAR BEAM, and application Ser. No. 09/904,066, filed Mar. 30, 2002, entitled ROLLFORMED AND STAMPED DOOR BEAM, and also U.S. Pat. No. 5,092,512, issued Mar. 3, 1992, entitled METHOD OF ROLLFORMING AN AUTOMOTIVE BUMPER, the entire contents of all of which are incorporated herein in their entireties. Different vehicle mounts can be used with the present invention. The mounts illustrated in FIG. 14 are described in sufficient detail below for an understanding by persons skilled in the art. Nonetheless, if additional discussion is desired, the reader&#39;s attention is directed to application Ser. No. 09/964,914, filed Sep. 27, 2001, entitled BUMPER CRUSH TOWER WITH RINGS OF VARIED STRENGTH, the entire contents of which is incorporated herein in its entirety.  
         [0023]    Beam  21  (FIG. 2) includes a tubular center section  28  having a square cross section defined by front, rear, top, and bottom walls. The beam  21  is rollformed to a desired tubular shape, welded along a weld bead  29  located at a middle of the rear wall, and then swept into a curvilinear shape that matches a front end (or rear end) of a selected model vehicle. It is noted that different cross sections can be used, if desired. The weld bead  29  stops short of an end of the beam  21 , and about 6 to 8 inches of an end of the walls are reformed and “opened up” to a relatively coplanar flat condition to form the flattened end sections  23  and  24 . A pattern of holes  30  are formed in the flattened end sections  23  and  24 , which correspond to attachment holes in the mount  26 .  
         [0024]    Energy absorber  22  (FIG. 2) includes an injection-molded member  32  made from a suitable non-foam polymeric material having good properties for absorbing energy upon impact, such as Xenoy material. The non-foam material substantially forms the structure of energy absorber  22 , including box-shaped sections  33 , which are molded along rail  34  at strategic locations for improved impact properties, as described below. The box-shaped sections  33  include vertical sidewalls  33 ′ and top and bottom walls  33 ″ that combine with front wall  39 ′ to form a hollow internal cavity.  
         [0025]    The center section  28  includes horizontal upper and lower rails  34  and  35 , both of which have rearwardly-facing U-shaped cross sections. The upper rail  34  defines a large portion of the rearwardly-facing recess  25  (FIG. 4), which is shaped to closely receive the center tubular section of the beam  21 . The box-shaped sections  33  are molded onto top, front and bottom surfaces of the upper rail  34  at strategic locations along its length. Two such sections  33  are shown, but more or less can be used. The sections  33  provide improved energy absorbing characteristics to the bumper system  20 , and further the sections  33  have an upper surface shaped to support the vehicle front fascia  36 , which is typically a low stiffness or TPO material that requires support against the forces of gravity.  
         [0026]    The energy absorber  22  (FIG. 2) also includes mounting sections  38  that form integrated crush boxes over the mounts  26  at each end of the center section  28 . The mounting sections  38  (FIG. 3) each include a rectangular ring-shaped planar outer front wall  39 , rearwardly-extending walls  40  forming an open “C” shape that extends rearwardly from the front wall  39 , a rectangular ring-shaped planar rear wall  41  that extends from the rearwardly-extending walls  40 , forwardly-extending walls  42  that form a square tube shape that extends forwardly from the rear wall  41 , a rectangular ring-shaped planar inner front wall  43  that extends from the forwardly-extending walls  42 , and an interior stiffener flange  44  that extends rearwardly from the inner front wall  43 . Additional stiffening webs can be extended between the rearwardly-extending walls  40  and the forwardly-extending walls  42  as needed for stiffness and structure in the energy absorber  22 . A plurality of legs  35 ′ extend below the lower rail  35 , such as for supporting a bottom of the TPO fascia on a front of the vehicle.  
         [0027]    The flattened end section  23  (and  24 ) (FIG. 3) includes a flat front surface that mateably engages the flat rear surface of the planar rear wall  41 . The mount  26  includes a tubular section  47  (e.g. a crush tower for optimal energy absorption in front impact), a rear plate  48  shaped for connection to a vehicle, such as to vehicle frame members, and a front plate  49  shaped to mateably engage a flat rear surface on the end section  23  (and  24 ). Fasteners, such as bolts  50  are extended through aligned holes in the planar rear wall  41 , in the flattened end sections  23  (and  24 ), and the front plate  49 . Notably, the tubular portion of beam  21  (i.e. center section  28 ) extends short of the mounts  26  (see FIG. 5), and further the flattened end sections  23  (and  24 ) extend only to the outer edges of the mounts  26 , for reasons discussed below.  
         [0028]    The energy absorber  22  includes corner sections  52  (FIGS. 2 and 5) having an apertured front wall  53 , an apertured rear wall  54 , and reinforcing walls  55  that extend between the front and rear walls  52  and  53  for structural support. The front wall  53  curves rearwardly at its outer edge to form an aerodynamic shape at a front of the vehicle fenders. Further, the reinforcing walls  55  include a top wall  56  shaped to support portions of an RRIM fascia in the area of a vehicle front fender. Also, the corner section  52  includes a tubular canister portion  57  and canister-mounting structure  58  for adjustably securely supporting a fog lamp assembly  59  (and/or a turn signal assembly).  
         [0029]    As shown in FIG. 5, the corner section(s)  52  include a rearwardly-extending box section  60  that is outboard of the mount  26  and positioned adjacent an end of the flattened end sections  23  (and  24 ). During a corner impact by an object  61 , forces are transmitted along lines  62  and  63  into the corner section  52 . The angled forces  63  are directed through the box section  60  at an angle toward a side surface of the mount  26 . The angled forces cause the corner section  52  to bend rearwardly in direction  64 , sliding rearwardly slightly along line  64 ′ on the mount  26  (depending on the magnitude of the forces  63 ). This action tends to allow the angled forces to relieve themselves, and also tends to cause the object  61  to bounce sideways off the vehicle bumper system  20 .  
         [0030]    When an object  66  is struck in a front impact directly in-line with the mounts  26 , the forces  67  are transmitted directly against the mount  26  in a manner permitting the mount  26  to absorb forces in a telescoping manner like it historically is designed. (I.e. the forces are linear and permit the tubular section  47  to telescopingly crush and collapse in a predictable manner.) When the bumper system  20  is struck in a center area between the mounts  26 , the impact is primarily transmitted linearly into the mounts  26 , due to the strength of the beam  22 . Nonetheless, it is noted that with the present beam  22 , some bending may occur, depending on a width of the impact area on the bumper system  20  and how nearly it is perfectly centered on the bumper system  20 .  
         [0031]    In the modified bumper system  20 A (FIGS.  6 - 8 ), a beam  21 A similar to beam  21  is provided, and a “longer stroke” energy absorber  22 A is attached to its face. The energy absorber  22 A includes upper and lower U-shaped rails  34 A and  35 A that open rearwardly. The rails  34 A and  35 A are connected by vertical webs  65 A that extend fore/aft, and by a rear wall  66 A that extends across a back of the energy absorber  22 A. Flanges  67 A and  68 A extend rearwardly from the rear wall  66 A. The flanges  67 A and  68 A engage and cover top and bottom walls of the beam  21 A, and include fingers  67 A and  68 A′ for snap-locking onto the beam  21 A for temporary securement of the energy absorber  22 A to the beam  21 A. In energy absorber  22 A, the corner sections  52 A also form the mounting section of the energy absorber  22 A. Specifically, the corner sections  52 A include a flat rear wall  70 A, and perpendicular walls  71 A forming a box around the flat rear wall  70 A. The end section  23 A (and  24 A) of the beam  21 A engage a rear surface of the flat rear wall  70 A, and fasteners (i.e. bolts) are extended through aligned holes in the flat rear wall  70 A, the flattened sections  23 A (and  24 A), and the front plate of the mount ( 26 ) to which it is attached.  
         [0032]    A rear “root” portion  72 A of the inner wall of the rails  34 A and  35 A is offset slightly from the flanges  67 A and  68 A (FIG. 8), and also is offset from the corresponding top and bottom walls of the beam  21 A. Upon front impact, the rails  34 A and  35 A are driven rearwardly. Due to the stiffness of the beam  21 A, this causes the “root” portion  72 A of the energy absorber  22 A to buckle and fold onto itself and onto the flanges  67 A and  68 A, as shown by arrows  73 A. The result is a much more predictable and “softer” impact. At such time as the energy absorber  22 A is completely crushed, forces from the impact are directly transmitted to the beam  21 A, providing a force versus deflection force curve increases sharply over the initial force versus deflection curve.  
         [0033]    The bumper system  20 B (FIG. 9) is not unlike the bumper system  20 A (FIGS.  6 - 7 ), but in system  20 B the beam  21 B is U-shaped (i.e. is not tubular), and further it is insert-molded into a center of the energy absorber  22 B. In the bumper system  20 B, the beam  21 B includes a plurality of apertures or holes to allow the plastic material of the energy absorber to flow through and interlock with the metal beam  21 B, thus providing better bonding and preventing de-lamination. It is noted that the apertures  75 B may reduce a bending strength of the beam  21 B, depending on their location. The illustrated apertures  75 B are located only on the vertical flange  76 B of the beam  21 B, such that they do not greatly affect bending strength in a direction parallel an impact force. Nonetheless, the location and shape of the apertures  75 B can be a desirable thing by helping distribute and relieve stress in some specific vehicle applications.  
         [0034]    It is noted that a strength of the tubular portion of the beam  21 B (or beams  21 A or  21 ) can be substantially increased by press-fitting within the tubular portion an internal energy absorber, such as is illustrated in FIGS.  14 - 15 . The internal energy absorber tends to reduce a tendency of the beam to prematurely kink or bend, resulting in a consistently higher and more predictable energy of absorption during impact.  
         [0035]    It is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.