Abstract:
A vehicle bumper system includes a bumper beam and a polymeric energy absorber positioned on a front of the bumper beam. The energy absorber has multiple box-shaped sections and also has interconnecting sections positioned along the length that interconnect adjacent ones of the box-shaped sections. The box-shaped sections of the energy absorber, when cross-sectioned by a transverse plane, include top and bottom U-shaped sections formed by top parallel legs and a top vertical leg and by bottom parallel legs and a bottom vertical leg, respectively. End walls close ends of the box-shaped sections and stabilize the top and bottom U-shaped sections. The interconnecting sections include a tying wall that connects the end walls together. By this arrangement, the box-shaped sections provide a stable and reliable energy absorbing mechanism.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims benefit of provisional application serial No. 60/284,058, filed Apr. 16, 2001, entitled BUMPER SYSTEM WITH FACE-ABUTTING ENERGY ABSORBER under 35 USC 119. 
    
    
     BACKGROUND OF THE PRESENT INVENTION 
     The present invention relates to automotive bumper systems having beams and energy absorbers located on faces of the beams. 
     Many vehicle designs use energy absorbers positioned on a face or front surface of a steel bumper beam to improve energy absorption of a bumper system. The energy absorbers provide an initial level of energy absorption for low impact, including reducing damage during low impact, and also provide a supplemental level of energy absorption during high impact (i.e. before and-at the time that the beam and vehicle begin to absorb substantial amounts of energy). Usually, the energy absorbers are fastened to the bumper beam with fasteners that assure accurate positioning of the energy absorber on the beam. The reasoning includes accurately positioning the energy absorber on the bumper beam to assure consistent performance, as well as to assure accurate positioning for aesthetics and assembly (e.g. to assure a good fit of the front-end fascia over the energy absorber and beam during assembly). 
     However, improvements are desired in terms of temporary and permanent attachment, and for improved and more reliable energy absorption. Typically, attachment of the energy absorbers to bumper beams requires a plurality of fasteners. This is disadvantageous since fasteners require manual labor to install, which can add undesirably to cost. Also, the fasteners can result in localized and non-uniform stress distribution during impact, resulting in inconsistent collapse of the bumper system and poor energy absorption on impact. Further, fixing the energy absorber to the beams results in an inability of the energy absorber to shift and adjust to non-perpendicular and uneven loads transmitted from the impacting bodies. At the same time, depending on the bumper system, sometimes shifting of an energy absorber is not good since it can result in unpredictable, premature and non-uniform collapse, resulting in poor or inconsistent energy absorption by the bumper system. 
     For all of the above reasons, there is a desire for bumper systems that yield a better, more consistent, more reliable, and greater impact energy absorption, both for low and high impact events, and also for square and skewed impact directions. Also, there is a desire for improvements facilitating assembly of an energy absorber to a beam, with lower cost and fewer parts, and with less labor. Still further, there is a desire for energy absorber designs that allow adjustment and tuning for optimal front-end and corner impact strengths, even late in the bumper development program, and yet that does not require expensive or complex molding techniques or assembly techniques. Still further, there is a desire for energy absorber designs that are adaptable for use with many different bumper beam cross-sectional shapes and sizes. Also, energy absorber designs are desired that are flexible and usable on non-linear bumper beams having different curvatures and longitudinal sweeps, and having different cross sections. 
     SUMMARY OF THE PRESENT INVENTION 
     In one aspect of the present invention, a bumper system for vehicles includes a bumper beam having a continuous cross section with a front surface that extends vertically when the bumper beam is in a car-mounted position, and a polymeric energy absorber having a length. The energy absorber includes a rear surface abutting the front surface of the bumper beam. The energy absorber has multiple box-shaped sections and also has interconnecting sections positioned along the length that interconnect adjacent ones of the box-shaped sections. The box-shaped sections of the energy absorber, when cross-sectioned by a transverse plane that extends perpendicular to the length, include a top U-shaped section formed by top parallel legs and a top vertical leg, and further include a bottom U-shaped section formed by bottom parallel legs and a bottom vertical leg. The box-shaped sections further include end walls at each end that are attached to the parallel and vertical legs of the top and bottom U-shaped sections to close ends of the box-shaped sections and to stabilize the top and bottom U-shaped sections relative to each other. The interconnecting sections include a tying wall that connects the end walls together, whereby the box-shaped sections provide a stable and reliable energy absorbing mechanism with the energy-absorbing U-shaped sections being stabilized by the end walls and with adjacent box-shaped sections being held together by interconnecting sections. 
     In yet another aspect of the present invention, a bumper system for vehicles includes a bumper beam having a continuous cross section with a front surface that extends vertically when the bumper beam is in a car-mounted position. A polymeric energy absorber has a length and includes a rear surface abutting the front surface of the bumper beam. The energy absorber has first, second, third, and fourth parallel walls that extend horizontally, the first parallel wall being at a top location and the fourth parallel wall being at a bottom location. The energy absorber further includes a top front wall interconnecting the first and second parallel walls to form a rearwardly-facing U-shaped top channel, and includes a bottom front wall interconnecting the third and fourth parallel walls to form a rearwardly-facing U-shaped bottom channel, the energy absorber further having stabilizing walls that interconnect at least the first and fourth parallel walls to stabilize the top and bottom channels on the bumper beam. 
     In yet another aspect of the present invention, a bumper system for vehicles includes a bumper beam and an energy absorber for the bumper beam. The bumper beam has a front surface that extends vertically when the bumper beam is in a car-mounted position and has a pair of attachment features. The polymeric energy absorber has a length and includes a rear surface abutting the front surface of the bumper beam. The energy absorber further has a pair of protrusions adapted to engage the attachment features to temporarily loosely hold the energy absorber on the bumper beam during assembly of the energy absorber to the bumper beam. 
     In a narrower aspect, the protrusions include a hooked end, and are integrally molded as contiguous material of the energy absorber. Also, the protrusions extend from an upper portion of the energy absorber and hook onto a feature on a top of the bumper beam. 
     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 
     FIGS. 1 and 2 are fragmentary perspective views of a bumper system of the present invention, including a bumper beam and an energy absorber; 
     FIGS. 3-6 are cross-sectional views of the energy absorber taken along the lines III—III, IV—IV, V—V, and VI—VI in FIG. 2; and 
     FIGS. 7 and 8 are front and rear perspective views of the energy absorber shown in FIG. 2, and FIG. 8A is a fragmentary perspective view of a portion of FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention is described as utilizing a B-shaped double-tube bumper beam that is rollformed and swept. The present B-shaped bumper beam is sufficiently described herein for a person skilled in the art to understand and practice the present invention, but it is noted that the process and method of making the illustrated B-shaped bumper beam is described in greater detail in Sturrus patent U.S. Pat. No. 5,454,504, if the reader desires such information. It is specifically contemplated that the present invention could be used in combination with a bumper beam having a shallower channel instead of the deep channel illustrated. For example, the present invention would work on a D-shaped bumper where the bumper beam had a vertically-extending surface extending across a significant vertical portion of a front face of the bumper beam but does not extend completely across a vertical front face of the bumper beam. On the merits, the teachings of U.S. Pat. No. 5,454,504 are incorporated herein in its entirety for the purpose of providing a complete disclosure of the entire bumper system. 
     In regard to the illustrated preferred embodiment, a bumper system  20  (FIGS. 1-6) for vehicles includes a bumper beam  21  and an energy absorber  22  attached to a face of the bumper beam  21 . The illustrated beam is rollformed and swept (see Sturrus patent U.S. Pat. No. 5,454,504) and has a continuous B-shaped double-tubular cross section (FIG.  2 ). The double tubes are spaced vertically apart and include top and bottom mid-walls  23  and  24  defining a longitudinally-extending channel  25  along its rear surface. A polymeric energy absorber  22  has a length with multiple box-shaped sections  27  (five box-shaped sections are shown, but not all are the same length) that abut the front surface  26  of the bumper beam  21 . The energy absorber  22  further includes a plurality of tying sections  28  that extend longitudinally between the box-shaped sections  27  and also vertically between top and bottom portions  27 ′ and  27 ″ of the box-shaped sections  27 , as discussed below. 
     The B-shaped section of the bumper beam  21  (FIG. 3) includes, in addition to top and bottom mid-walls  23  and  24 , a top wall  34 , a rear upper wall  35 , a bottom wall  36 , a rear lower wall  37 , a primary front wall  38  and a channel-forming overlapping front wall  39 . The top tube of the bumper beam  21  is formed by the walls  23 ,  34 ,  35 , and  38 . The bottom tube of the bumper beam  21  is formed by the walls  24 ,  36 ,  37 , and  38 . The top and bottom tubes are interconnected by front walls  38  and  39 . Each of these walls  23 - 24  and  34 - 39  can be flat or non-flat. For example, in some bumper systems (such as the illustrated bumper beam), it has been found to be beneficial to make the horizontal walls  23 ,  24 ,  34 , and  36  slightly bent or curved (in a front-to-rear direction), both for purposes of providing a bumper beam that is less likely to prematurely kink and more likely to reliably and consistently bend, but also for the purpose of ease of manufacture of the bumper beam. As illustrated, the mid-walls  23  and  24  include rear portions that are angled to created a tapered throat. 
     The energy absorber  22  is a molded component of non-foam polymer, such as a blend of PC/ABS/TPE. For example, it is contemplated that General Electric&#39;s XENOY polymer will work for this purpose. The energy absorber  22  includes five box-shaped sections  27  that abut a front of the front wall  38 . Tying walls  28  hold the box-shaped sections  27  together. The illustrated box-shaped sections  27  (FIG. 8A) each include a top wall  41 , a bottom wall  42 , and opposing sidewalls  43  and  44 . A front wall  45  extends around walls  41 - 44  and forms a perimeter flange around them. Additionally, the box-shaped sections  27  include a top wall  41 A, a bottom wall  42 A, and opposing end walls  43 A and  44 A that extend from the outer edges of front wall  45  and extend parallel the walls  41 - 44 , respectively. A rear wall  46  extends outwardly from the walls  41 A- 44 A forming a perimeter. The section  28  is that part of wall  46  that interconnects and ties adjacent box-like sections  27  together. All walls of sections  27  (and wall  28 ) are about 1.5 to 3.5 mm thick, or more preferably about 2.0 mm to 2.5 mm thick. It is noted that the top and bottom walls  41 ,  41 A,  42 ,  42 A, when viewed from a position in front of the bumper system, can be wavy and undulating or otherwise non-linear and non-flat in shape. The other walls can also be wavy or undulating. This provides the walls with increased strength for resisting buckling, and also helps eliminate distortions, such as snaking, that occur when molding a long part. It is also noted that the walls  41 ,  41 A,  42 , and  42 A extend longitudinally on the bumper beam  21 , but are discontinuous and further include non-blind surfaces to prevent die lock when molding. (i.e. This allows mold tooling to pass through the plane of one wall to form another wall.) In other words, the energy absorber  22  can be made by using male and female molds, neither of which require secondary or movable die components for forming the energy absorber  22 . 
     The box-shaped sections  27  of the illustrated energy absorber  22  are able to absorb significant energy without failure, such as may be incurred in a low energy impact. Thus, in a low energy impact, the energy absorber  22  absorbs the impact energy, and the bumper beam  21  does not permanently or temporarily deform. In an intermediate energy impact, the bumper beam  21  and the energy absorber  22  do deflect and absorb energy, but do not permanently deform. However, the walls  23 - 24  and  34 - 39  of the energy absorber  22  may permanently deform. In a high energy impact, both the energy absorber  22  and the bumper beam  21  initially absorb energy and then buckle as they approach a maximum amount of deflection. The point of buckling is designed into the bumper system  20  to cause a maximum amount of energy to be absorbed without damaging the vehicle, while considering all relevant factors such as occupant safety, government standards, and the like. 
     A top lip  53  extends rearwardly from the top of wall  46  of the box section  27 , and a bottom lip  54  extends rearwardly from the bottom of wall  46  of the box section  27 . The lips  53  and  54  engage top and bottom surfaces on the bumper beam  21 . Optionally, the lips  53  and  54  can include attachment tabs or hooks (see hook tab  55  in FIG.  7  and hook tab  56  in FIG. 8) for engaging apertures or features in the bumper beam  21  for retaining (temporarily or permanently) to the bumper beam  21 . These lips  53  and  54  are advantageous in that all (or most) fasteners can be eliminated for attaching the energy absorber  22  to the bumper beam  21 . It is contemplated that the vehicle front fascia  57  (FIG. 5) can be used to hold the energy absorber  22  on the bumper beam  21  without any fasteners, if desired, as noted below. 
     It is noted that the present arrangement faces a “flat side” of the B-shaped cross section of the bumper beam  21  toward the energy absorber  22 , although it is contemplated that the present inventive energy absorber  22  can be positioned against the lobed part of the B-shaped bumper beam  21  and function satisfactorily. In such case, the B-shaped bumper beam  21  would be swept with its “flat” face on the vehicle side of the bumper beam and facing rearwardly. 
     In the present bumper system, the energy absorber  22  is relatively loosely supported on the bumper beam  21 . This is unusual in that historically, automobile manufacturers want the position of the energy absorbers closely controlled and well-fastened to the bumper beam. However, testing has shown that a relatively loose energy absorber can, if properly designed, actually assist in preventing premature collapse of the energy absorber by allowing the energy absorber to adjust to the impacting object to better “face” the impacting object as the impact collision occurs. 
     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.