Abstract:
An unitary bumper unit is adapted for attachment to a vehicle for absorbing forces generated from an impact and comprises a singularly molded part combining a relatively stiff beam portion for attachment to a vehicle and an impact energy absorber integrally molded together with the beam portion wherein the energy absorber faces in a forward direction for absorbing energy due to an impact with the said energy absorber having a crushable forward projecting members adapted to crush upon impact.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims priority to U.S. Provisional Application Serial No. 60/427844 filed on Nov. 20, 2002, which is incorporated herein by reference in its entirety. 
     
    
     
       FIELD OF INVENTION  
         [0002]    The field of invention is bumper systems that are adaptable to provide pedestrian protection in a bumper on an automotive vehicle.  
         BACKGROUND OF THE INVENTION  
         [0003]    Future legislation in Japan and European countries may require an energy absorbent design for a vehicle bumper system to help protection a pedestrian&#39;s legs from an impact.  
           [0004]    Current bumper impact systems employ several separate components, which are assembled. Generally, these components include a soft energy absorber backed by stiff reinforcing beam to achieve US FMVSS and European ECE42 impact. The component parts of the energy absorber may be a thermoplastic resin or polypropylene foam adjacent a stiff supporting reinforcing beam of steel or aluminum. The bumper assembly typically includes a reinforcing beam, which is configured to attach to vehicle rails, an energy absorber, and an aesthetic fascia attachable to the energy absorber. The fascia typically substantially envelops both the reinforcing beam and energy absorber.  
           [0005]    Traditional vehicle bumper and bumper energy absorber systems have been designed to protect vehicle structures and possibly occupants of the vehicle during low speed, about 5 miles per hour (mph), in a vehicle-to-vehicle or vehicle-to-solid structure impact. The new legislation requires a level of pedestrian protection during impact with the front end of an automotive vehicle. The impact energy levels during such an occurrence are much lower than the traditional 5 mph vehicle bumper impacts. Systems designed for 5 mph vehicle bumper impact are maybe too stiff to provide a sufficient level of pedestrian injury mitigation.  
           [0006]    Desirable features of bumper systems include adaptability of the system to provide for US FMVSS 5 mph impact requirements, European ECE42 legislation, Allianz impact requirements and European Pedestrian Protection for lower and upper leg or legs.  
         SUMMARY OF INVENTION  
         [0007]    According to an embodiment, a unitary bumper unit comprises a singularly molded part combining a relatively stiff beam portion for attachment to a vehicle and an impact energy absorber integrally molded together with the beam portion and facing in a forward direction for absorbing energy due to an impact. In an embodiment, the energy absorber portion comprises a forwardly projection portion extending longitudinally across the beam and adapted to crush upon impact to absorb forces generated during impact. In an embodiment, the beam portion extends longitudinally across the front of a vehicle and is adapted for attachment to forwardly projecting supports or rails that extend outwardly from the front of the vehicle and are typically attached to the frame of the vehicle. In an embodiment, the forwardly projecting portion includes a crushable portion for initiating at least the partial collapse of said forwardly projecting portion for absorbing forces created by an impact. The energy absorber and the beam portion are molded from a thermoplastic resin material wherein energy from an impact is desirable absorbed by energy absorber portion and the beam portion. According to one embodiment, the energy absorbing system has a construction, which promotes enhanced energy absorption efficiency. The system is desirable adaptable for applications where low levels of energy need to be absorbed, such as in the area of pedestrian protection upon impact with the front end of an automotive vehicle. Desirable embodiments include constructions which promotes superior energy absorption efficiency, especially where low levels of energy need to be absorbed as in the area of pedestrian protection upon impact with the front end of an automotive vehicle.  
           [0008]    Traditional vehicle bumper and bumper energy absorber systems have been designed to protect vehicle structures of the vehicle during low speed (about 5 miles per hour (mph)) in a vehicle-to-vehicle or vehicle-to-solid structure impact. New legislation has been introduced in at least Europe and Japan to require a level of pedestrian protection during impact with the front end of an automotive vehicle. The impact energy levels during such an occurrence are much lower than the traditional 5 mph vehicle bumper impacts. Therefore, systems designed for 5 mph vehicle bumper impact are too stiff to provide a sufficient level of mitigating pedestrian injury.  
           [0009]    According to an embodiment, the solitary bumper unit is desirably adapted to minimize or mitigate pedestrian injury at low levels of speed and in particularly mitigate lower and upper leg injuries. The bumper unit comprises a singular injection molded combination of a reinforcing bumper beam and an energy absorber with the energy absorber comprising crushable members such as crush cans for absorbing the energy of impact, preferable at low speeds which may provide for lower and upper pedestrian leg protection. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a perspective view of the singular solitary bumper unit illustrating the integrated energy absorber and reinforcing bumper beam.  
         [0011]    [0011]FIG. 2 is a partial front view of the singular solitary bumper unit of FIG. 1.  
         [0012]    [0012]FIG. 3 a schematic cross sectional view along section  3 - 3  of FIG. 2.  
         [0013]    [0013]FIG. 4 a schematic cross sectional view along section  4 - 4  of FIG. 2.  
         [0014]    [0014]FIG. 5 a schematic cross sectional view along section  5 - 5  of FIG. 2.  
         [0015]    [0015]FIG. 6 a schematic cross sectional view along section  6 - 6  of FIG. 2. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    [0016]FIG. 1 illustrates a bumper unit  11  comprising having an energy absorber portion  13  and a bumper beam portion  15  formed as a singular or solitary thermoplastic unit which is adapted for attached directly to forward projecting supports or rails  19  of a motor vehicle. The combination bumper unit  11  may be adapted to achieve efficient energy absorption upon impact for pedestrian protection to meet FMVSS and ECE 42 type impact forces. Impact forces during low speed FMVSS and ECE 42 impact and the forces on a lower leg during pedestrian impact are maintained just below a predetermined level of deforming the bumper unit  11  until the kinetic energy of the impact event has been absorbed. When the impact is over, the bumper unit  11  is desirably adapted to return substantially to its original shape and still retain sufficient integrity to withstand subsequent impacts. The bumper unit  11  may be adapted for the combination of low speed impact FMVSS and ECE 42 performance, Allianz offset impact, and pedestrian lower and upper leg protection. Functionality in a molded beam portion  15  and energy absorber portion  13  is provided by crushable members  17  which are integrally molded into the single injection molded unit. Some deformation of the beam portion  15  may also occur upon impact. After impact, it is desirable to have deformations in the energy absorbing portion  13  be adapted to return substantially to their original shape. Such performance translates to reduced costs of repair for low speed (so called “fender benders”) and desirable reductions in pedestrian leg injury. The solitary bumper unit  11  incorporates crushable members  17  which are desirably adapted through geometric shape, wall thickness, and other functionality to enhance lower and/or upper pedestrian leg protection during impact. The crushable members  17  are desirably adapted to deform during impact and absorb energy. The energy absorption efficiency of the crushable members  17  desirably reduces the forces translated into a pedestrian&#39;s leg during impact. Variations to the shape, wall thickness, and depth of crushable members  17  tune the energy absorber portion  13  to an impact response for specific impact energy levels. Preferably the crushable members  17  are forwardly projecting thin joined walls  21  formed as hollow sections which may be in the shape of crushable lobes, cans, boxes, H-shaped, or I-shaped.  
         [0017]    The energy absorber portion  13  incorporates forwardly projecting crushable members  17  which may be the form of crush lobes, crush cans or other geometry which incorporates a desired functionality when molded together with the beam portion in the same single molding operation. The crushable members  17  are desirably adapted to provide for protection of pedestrians on impact. Enhanced energy absorption efficiency of the crushable members  17  desirable reduces the forces translated into a pedestrian lower leg during impact. The forwardly projection crushable members  17  may be spaced apart along the length of the elongated beam portion  15 . FIG. 1 illustrates an embodiment where a pair of end crushable members  23  are, respectively, located at the ends of the beam portion  15  over or adjacent to the respective rails  19 . The end crushable members  23  are adapted to absorb energy by deforming to protect the vehicle rail tips from damage during impact such as might occur during an Allianz offset impact test. The integrated beam portion  15  is shown schematically in FIG. 6 as being attached to respective supports or rails  19  which extend outwardly from the front of the vehicle and are typically attached to the vehicle frame. Since both the crushable members  17  and the beam portion  15  are formed in a single molding operation from the same thermoplastic material, the bumper unit  11  may be desirable recycled.  
         [0018]    The engineering thermoplastic resins that can be employed in this practice of this invention can be any of the well-known engineering thermoplastics. This include for example aromatic polycarbonates; copolyester carbonate; polyester such as polybutylene terephthalate, polyethylene terephthalate, polypropylene terephthalate; polyphenylene ether; polyurethene; polyethlenes (high density and low density); polypropylenes; polysulphones; acrylates (homo and copolymers) such as polyethyl meth-acrylate, polymethylmethacrlate and the like; blends of the above engineering polymers and blends thereof with an elastomeric polymer and blends with other polymers such as polycarbonate/polybutylene terephthalate, polyphenylenether/high impact polystyrene, polycarbone/acrylonitrile-butadiene-styrene, and the like The preferred engineering thermoplastic resin is blend of aromatic polycarbonate and a polyester such as polybutylene terephthalate (PBT) or polyethylene terephthalate (PET) or a blend of polycarbonate with a blend of PBT and PET  
         [0019]    Referring to FIG. 1, bumper unit  11  includes bumper beam  15  with integral energy absorber portion  13 , which includes crushable members  17  spaced apart in a lateral direction along the length of the beam portion  15 . Each crushable member  17  comprises a plurality of forwardly projecting molded joined wall portions  21  which extend in different lateral directions. As shown in FIG. 5, joined wall portions  21  form molded hollow thin walled areas of the final molded part, which project forwardly. For purposes of discussion, the terms forwardly and rearward are not intended to be unduly limited but are intended to aid in the description of the relationship of the various features and sections described herein. Forward and rearward direction refers to a direction along an axis extending longitudinally along a forward and rearward aligned direction corresponding to the front and rear of the vehicle. Lateral directions are directions in a plane normal to the longitudinal axis. As shown in FIG. 1, and as previously discussed, end crushable members  17  are positioned adjacent respective ends of the beam portion  15  and have a box shaped configuration with a portion an end wall cut away. Other crushable members  17  are illustrated in FIG. 1 as having an I-shaped configuration. The I-shaped configuration includes a vertical wall portion  29  joining a lateral or horizontal wall portion  27 . The crushable members  17  are spaced along the beam portion  15  intermediate the pair of end crushable members  23 . Various positioning of the crushable members  17  are contemplated including both even and uneven spacing. Other configurations for the crushable members  17  are contemplated, such other configurations include forwardly projecting lobes, cones or other arcuate or joined walls or configurations.  
         [0020]    As illustrated in FIG. 1, the beam portion  15  includes an integrated upper fascia support  31  and integrated lower fascia support  33 . FIG. 3, a schematic view, shows a partial view of the fascia  43  fastened to the upper fascia support  31 . FIG. 4, a schematic view, shows a partial view of the fascia  43  fastened to the lower fascia support  35 . The fascia  43 , which typically envelopes the bumper unit  11  may be a thermoplastic resin and which may be injection molded.  
         [0021]    The box shaped end crushable members  23  are shaped for vehicle rail  19  protection, in particular for offset impact. As illustrated in the FIG. 6 schematic view, along section  6 - 6  of FIG. 2, the beam portion  15  is joined to the rails  19  with fasteners  35  such as bolts and nuts. The rails  19  extend forwardly in a longitudinally direction from the front vehicle. Such rails are well known in the automotive field to provide for attached of the bumper to an automotive vehicle.  
         [0022]    [0022]FIG. 3 is a schematic cross sectional view along cross section of FIG. 2 and illustrates a cross section of the beam portion  15 . The beam portion may include at least one corrugation  37  extending in the lateral direction to provide stiffness to the beam portion  15 .  
         [0023]    [0023]FIG. 5 schematically illustrates the cross section along section  5 - 5  and shows the beam portion  15  having a thicker cross sectional area than the forwardly projecting crushable members  17 . For example, the walls may have a thickness that broadly ranges from about 1.0 mm to about 7.0 mm. More specifically, for certain low speed or pedestrian impact applications the nominal wall thickness may generally range from about 1.0 mm to about 5.0 mm and for other applications, particularly those for a 5 mph FMVSS system, the nominal wall thickness for the side and rear walls would more likely be in the range of about 2.5 mm to 7.0 mm. The beam portion has wall thicknesses that enhance the stiffness of the beam portion so as to resist deformation do to impact. Wall thickness for the beam may be the range from about 3 to about 10, preferable from about 4 to about 6 mm.  
         [0024]    While it will be apparent that the preferred embodiments of this invention as disclosed herein are well calculated to fulfill the objects stated, it will be appreciated that the invention is susceptible to modifications, variations, and changes without departing from the spirit and scope of the present invention being limited only in terms of the appended claims.