Bumper system for a motor vehicle

Abstract: A bumper system (10) for a motor vehicle includes an energy absorber (44) and a bumper beam (16) interconnecting the energy absorber (44) and vehicle structure (18). The bumper system (10) includes a push bar (52) disposed below and operatively connected to the bumper beam (16) to deflect and rotate during an impact with an object by the bumper system.

Description: Field of the Invention The present invention relates a bumper system for a motor vehicle. Description of the Related Art It is known to provide a bumper system for a front end or rear end of a motor vehicle. For a front end of the motor vehicle, the bumper system typically includes a bumper beam extending transversely and secured to a forward end of a pair of front rails, which extend longitudinally and are spaced transversely. The bumper system also includes an energy absorber extending transversely and in front of the bumper beam. The bumper system may include a fascia disposed over and covering the energy absorber. It is also known that the bumper system protects a body of the motor vehicle from low speed impact with an object through elastic or semi-plastic deformation of the energy absorber. It is further known that the bumper system is an absorber for high-speed impact with an object through major plastic deformation of the bumper beam. It is further known that a bumper system may have a mechanical device which either lowers down or pushes forward during certain vehicle travel speed to contain the low push bar design within the vehicle approach angle requirement. United States Patent No. 1,347,372 describes what is called a life-saving device attached to the front of a motor vehicle and which acts not only as a fender but also as a means for grasping, holding and supporting the body of a pedestrian encountered by the vehicle. The device consists of laterally movable co-operating grappling arms for grasping the person with which the vehicle collides and an impact member movable rearwardly and which is yieldingly held and which can return to its advanced position subsequent to impact with the pedestrian. It is desirable to provide a bumper system with a lower leg push bar that uses rotation of the push bar instead of its longitudinal deformation to reduce the under side intrusion of lower leg into the vehicle. It is also desirable to prevent a pedestrian's lower leg from being over-ridden by the bumper during an impact. It is further desirable to provide a bumper system with a pedestrian friendly device on a motor vehicle attached to a bumper beam made of spring steel that stores and resists impact energies. Therefore, there is a need in the art to provide a bumper system for a motor vehicle that meets these desires. Summary Of The Invention According to the present invention, we provide a bumper system for a motor vehicle comprising: an energy absorber of a deformable material extending laterally across the front end of the motor vehicle; a bumper beam connected to said energy absorber and extending laterally across the front end of the motor vehicle, said bumper beam being connected to the vehicle structure; and a push bar extending laterally across the front end of the motor vehicle and being disposed below and operatively connected to said bumper beam to deflect and rotate during an impact with an object by said bumper system. The preferred embodiments of the invention provide a bumper system for a motor vehicle that includes a lower leg push bar to prevent a pedestrian's leg from being over-ridden by the bumper during an impact. The lower leg push bar rotates downward in the occurrence of vehicle impact with a leg of a pedestrian. The lower leg push bar is also capable of rotating up and down in the case of curb or speed bump contact. An advantage of the preferred embodiments of the present invention is that the bumper assembly includes a pedestrian friendly device attached to a bumper beam made of spring steel that stores internal energies rather than resist energies which may damage a pedestrian's leg during incidental vehicle impact. Brief description of the drawings The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: FIG. 1 is a perspective view of a bumper system, according to the present invention, illustrated in operational relationship with a motor vehicle. FIG. 2 is a partial perspective view of the bumper system of FIG. 1. FIG. 3 is a fragmentary bottom view of the bumper system of FIG. 1. FIG. 4 is a fragmentary side elevational view of the bumper system of FIG. 1. FIG. 5 is a side elevational view of the bumper system of FIG. 1 with a fascia removed. FIG. 6 is a fragmentary elevational view of the bumper system of FIG. 1 illustrating a first stage of a low- speed curb impact. FIG. 7 is a view similar to FIG. 6 illustrating a second stage of a low-speed curb impact. FIG. 8 is a view similar to FIG. 6 illustrating a first stage of a high-speed pedestrian impact. FIG. 9 is a view similar to FIG. 6 illustrating a second stage of a high-speed pedestrian impact. FIG. 10 is a fragmentary elevational view of another embodiment, according to the present invention, of the bumper system of FIG. 1. FIG. 11 is a perspective view of a portion of the bumper system of FIG. 10. FIG. 12 is a perspective view of a portion of the bumper system of FIG. 10. FIG. 13 is a side elevational view of a portion of the bumper system of FIG. 10. Description Of The Preferred Embodiments Referring to the drawings and in particular FIG. 1, one embodiment of a bumper system 10, according to the present invention, is illustrated in operational relationship with a motor vehicle 12. The bumper system 10 is disposed at a front or forward end of the motor vehicle 12. It should be appreciated that the bumper system 10 may be disposed at a rear or rearward end of the motor vehicle 12. It should also be appreciated that, except for the bumper system 10, the motor vehicle 12 is conventional and known in the art. As illustrated in FIGS. 2 through 5, the bumper system 10 includes a bumper beam, generally indicated at 16. The bumper beam 16 extends laterally and is secured to a forward end 17 of a pair of front rails 18 by suitable means such as welding or mechanical fastening. It should be appreciated that the bumper beam 16 may have any suitable cross-sectional shape. In the embodiment illustrated, the bumper beam 16 is a hollow member having a general "B" cross-sectional shape. The bumper beam 16 has a front or impact wall 20 extending generally vertically and laterally. The bumper beam 16 also has an upper or top wall 22 and a lower or bottom wall 24 inclined from the impact wall 20 and extending laterally. The bumper beam 16 has a curved or arcuate forward corner wall 26 interconnecting the impact wall 20 and the upper and lower walls 22 and 24. The bumper beam 16 also has a rear or supporting wall 28 extending generally vertically and laterally from the upper and lower walls 22 and 24. The bumper beam 16 has a curved or arcuate rear corner wall 30 interconnecting the supporting wall 28 and the upper and lower walls 22 and 24. It should be appreciated that the impact wall 20 has a height greater than the supporting wall 28. The bumper beam 16 also has a plurality of, preferably two generally horizontal interior walls 32 extending laterally and longitudinally forward toward the impact wall 20. The bumper beam 16 has a curved or arcuate inner corner wall 34 interconnecting the interior walls 32 and supporting wall 28. The bumper beam 16 has an inclined transition wall 36 extending laterally and longitudinally forward from the interior walls 32 and toward a centre of the impact wall 20 and a curved or arcuate projection wall 38 interconnecting the ends of the transition walls 36. The impact wall 20 may be formed as two portions with each portion extending from the front corner walls 26 and spaced vertically from each other to form a gap (not shown) therebetween. The projection wall 38 is secured to the upper and lower portions of the impact wall 20 by suitable means such as welding or mechanical fastening to increase a stability of the bumper beam 16 against a "match boxing" behaviour. The upper and lower portions of the impact wall 20 may have a plurality of apertures (not shown) extending therethrough and spaced laterally for a function to be described. As illustrated in FIG. 5, a top wall of the rail 18 is located between the upper wall 22 and the top interior wall 32 of the bumper beam 16 and a lower wall of the rail 18 is located between the lower wall 24 and the lower interior wall 32 of the bumper beam 16 in a symmetrical manner. As a result, the stiffness of the rail 18 causes the two interior walls 32 to collapse prior to the upper and lower walls 22 and 24 collapse. It should be appreciated that this overlapping collapse assures a uniform energy absorption characteristic in high-speed impacts. It should also be appreciated that the walls 22, 24, and 32 may have a plurality of apertures (not shown) extending therethrough to achieve a desired crush stiffness of the bumper beam 16. The bumper beam 16 is made of a relatively rigid material such as metal. The bumper beam 16 is integral, unitary, and formed as one-piece by manufacturing processes such as roll forming which a conventional process known in the art. It should also be appreciated that other manufacturing processes such as extruding and stamping may be used to form the bumper beam 16. It should also be appreciated that the bumper beam 16 may be attached to a rearward end (not shown) of a pair of rear rails (not shown) of the motor vehicle 12 by suitable means such as welding. The bumper system 10 includes an energy absorber 44. The energy absorber 44 extends laterally and is secured to the bumper beam 16. The energy absorber 44 may have a plurality of projections (not shown) extending rearward therefrom and through the apertures in the impact wall 20. The energy absorber 44 is a solid member having a generally trapezoidal shape with rear upper and lower lips 48 and 50 extending rearward. The upper and lower lips 48 and 50 have a generally arcuate or curved shape to extend over the front corner walls 26 of the bumper beam 16. The energy absorber 44 is made of a relatively deformable material such as foam. The bumper beam 16 may have a horizontal sweep to reduce the depth of the deformable material of the energy absorber 44. It should be appreciated that the apertures in the impact wall 20 allows the energy absorber 44 to have local penetration in order to avoid excess compacting of the deformable material during a high-speed impact with an object (not shown) Referring to FIGS. 1 and 4, the bumper system 10 further includes a fascia 50 extending laterally and vertically to cover the energy absorber 44. The fascia 50 is secured to vehicle structure (not shown) by suitable means such as fasteners (not shown) .The fascia 50 is made of a relatively rigid material such as plastic. It should be appreciated that the fascia 50 is conventional and known in the art. Referring to FIGS. 2 through 5, the bumper system 10 includes a pedestrian lower leg push bar, generally indicated at 52, to limit a maximum lateral bending angle of a knee of a pedestrian 70 (FIGS. 7 and 8) who contacts the vehicle 12. As illustrated, the lower leg push bar 52 includes a push bar member 54 extending laterally across a front end of the vehicle 12 below or under the bumper beam 16 and energy absorber 44. The push bar member 54 is generally planar and rectangular in shape. The push bar member 54 may have an arcuate or generally "U" shaped portion 56 at a forward end thereof to contact the pedestrian. The push bar member 54 also includes at least one, preferably a plurality of attachment portions 58 extending at a rear end thereof and spaced laterally for attachment to either the bumper beam 16 or rails 18 in a manner to be described. The push bar member 54 is made of a relatively rigid material such as a composite or metal material. The push bar member 54 is a monolithic structure being integral, unitary, and one-piece. It should be appreciated that the push bar member 54 has a pre-designed horizontal downward angle. The lower leg push bar 52 includes at least one, preferably a plurality of mechanical attachment devices 60 to attach the push bar member 54 to vehicle structure such as a lower face of the bumper beam 16 or the rails 18. The mechanical attachment devices 60 include a housing 62 attached to either the bumper beam 16 or rails 18 by suitable means such as welding. The mechanical attachment devices 60 also include a pin 64 extending through the attachment portions 58 of the push bar member 54 and the housing 62 to allow the push bar member 54 to rotate relative to the bumper beam 16 or rails 18. It should be appreciated that the mechanical attachment devices 60 are conventional and known in the art. The lower leg push bar 52 includes at least one, preferably a plurality of springs 66 to urge the push bar member 54 toward a forward position and to control the stiffness of the lower leg push bar 52. The springs 66 are of a rotational or torsional type. One of the springs 66 is disposed in each of the housings 62 to cooperate with the pin 64. It should be appreciated that the springs 66 are conventional and known in the art. In operation, the bumper system 10 has a first stage or mode as illustrated in FIGS. 6 and 7. In the first mode at low speeds (i.e., less than or equal to approximately ten miles per hour), the bumper system 10 impacts an object such as a pothole or curb 68. In this case, the lower leg push bar 52 contacts the curb 68 and the impact force rotates the lower leg push bar 52 backward or counter-clockwise to yield to the incoming object. It should be appreciated that during a backup of the vehicle 12 from a steep driveway onto a relatively flat road surface, the front end of the vehicle 12 will have a mild "dive down" motion and the lower leg push bar 52 will be allowed to have clockwise rotation to avoid damage during this impact condition. Referring to FIGS. 8 and 9, the bumper system 10 has a second stage or mode as illustrated. In the second mode at high speeds (i.e., greater than approximately ten miles per hour), the bumper system 10 impacts an object such as a pedestrian 70. When a lower leg 72 of the pedestrian 70 contacts the lower leg push bar 52, this impact causes the push bar member 54 to deform and initiates a downward counterclockwise movement. The force required to rotate the base member 54 will be controlled by the stiffness of the springs 66 located in the mechanical attachment devices 60. The deformation and the rotation of the push bar member 54 will absorb most of the impact energy on the lower leg 72. A knee joint of the pedestrian 70 will compress the energy absorber 44 to minimise the acceleration of the knee joint. The energy absorber 44 will cover the knee height in order to minimise the shear deformation of the knee joint. An upper leg 74 of the pedestrian 70 will impact the top of the bumper through either the fascia 50 or grille 76. The deformation of either the fascia 50 or grille 76 will minimise intrusion of the upper leg 74 to the exterior surface of the vehicle 12. After the leg has been accelerated to the vehicle's speed, the springs 66 will rotate the push bar member 54 back to its pre- impact position. It should be appreciated that the knee joint angle will be limited throughout the impact by the intrusion of the knee into the energy absorbing member 44, the lower leg 72 intrusion under the bumper beam 16 controlled by the push bar member 54, and the intrusion of the upper leg 74 into the fascia 50 or grill 76. Referring to FIGS. 10 through 13, another embodiment 110, according to the present invention, of the bumper system 10 is shown. Like parts of the bumper system 10 have like reference numerals increased by one hundred (100) .In this embodiment, the bumper system 110 includes a spring device, generally indicated at 180, attaching the lower leg push bar 152 to the bumper beam 116. The spring device 180 has a base wall 182 and side walls 184 extending generally perpendicular from the base wall 182 to form an inverted "U" shaped cross- section with a notch 185. The spring device 180 also has a reaction flange 186 extending generally perpendicular to the base wall 184. The spring device 180 includes at least one preferably a pair of apertures 188 extending through the base wall 182 to receive fasteners 190 for attaching the spring device 180 to the lower leg push bar 152 and bumper beam 116. The spring device 180 is made of a metal material such as spring steel, preferably a high strength steel that is above 50 ksi. The spring device 180 is made by a stamping process in which the side walls 184 have cuts for the notch 185 stamped therein and the spring device 180 is folded into shape with the flanges of the cuts mechanically joined by spot welding or fasteners (not shown) to form the notch 185. It should be appreciated that the adjoined flanges will bulk out of plane in order to be compatible with the deflection and to achieve a constant spring rate throughout the yielding of the flanges. In operation, upon impact with a lower leg of a pedestrian, the push bar member 154 of the lower leg push bar 152 begins to rotate and applies a reaction force to the lower leg of the pedestrian. During this build up of forces, the spring device 180 reacts with a controlled resistive force storing energy applied by the leg of the pedestrian. The spring device 180 then applies a rebound force to the push bar member 154 and leg controlling the angularity of the pedestrian leg at the knee joint below a predetermined level. It should be appreciated that the spring device 180 allows the lower point of the push bar member 154 to be positioned farther aft in the vehicle 12 than a non-spring supported push bar member 154, which is beneficial to vehicle packaging and styling flexibility during new vehicle definition. Accordingly, the spring device 180 provides attachment and joint strength for fastening a lower leg push bar 152 to a bumper beam 116 or other armature positioned at the front of the vehicle 12. The spring device 180 also provides strength and reaction forces to the push bar member 154 to resist breakage during incidental contact with any object in the external environment such as curbs, driveways, etc. The spring device 180 is tunable by changing its geometry length, width, material thickness, and shape and is a simple structure to manufacture. The spring device 180 provides elastic reaction and storage of internal energies during an impact with a lower leg of a pedestrian, which lengthens the time of contact between the push bar 162 and the lower leg of the pedestrian, in turn, lowering the peak forces applied to the leg. The spring device 180 uses a high strength spring steel to "store" energy temporarily during the impact event instead of relying on permanent material deformation to dissipate energy.

Claims: A bumper system for a motor vehicle comprising: an energy absorber (44); a bumper beam (16) connected to said energy absorber (44) and extending laterally across the front end of the motor vehicle, said bumper beam (16) being connected to the vehicle structure (18); and a push bar (52) extending laterally across the front end of the motor vehicle and being disposed below and operatively connected to said bumper beam (16) to deflect and rotate during an impact with an object by said bumper system, caracterized in that the energy absorber (44) is of a deformable material extending laterally across the front end of the motor vehicle. A bumper system as claimed in claim 1, wherein said bumper beam (16) is made of a metal material. A bumper system as claimed in claim 1 or 2, wherein said push bar (52) has a push bar member (54) extending laterally. A bumper system as claimed in claim 3, wherein said push bar (52) includes at least one attachment device (60) interconnecting at least one attachment portion (58) projecting from the push bar (54) to the bumper beam (16). A bumper system as claimed in claim 4, wherein said at least one attachment device (60) includes a housing (62) attached to said bumper beam (16) and the vehicle structure and a pin (64) extending through said at least one attachment portion (58) and said housing (62) to allow said push bar member (54) to rotate. A bumper system as claimed in any of claim 3 to 5, in claim 3, including at least one spring (66) to urge said push bar member (54) forward. A bumper system as claimed in claim 3, including a spring device (180) connected to said push bar (152) and to said bumper beam (116) or to the vehicle structure.

Inventors: BLADOW JEFFREY LEONARD, CHOU SHUL-FANG, MANSOOR DHAFER, SCHUSTER PETER JOHN, BLADOW, JEFFREY LEONARD, CHOU, SHUL-FANG, MANSOOR, DHAFER, SCHUSTER, PETER JOHN
Applicants: FORD GLOBAL TECH INC, FORD GLOBAL TECHNOLOGIES, INC.
Application year: 2000
Main classification: B60R19
IPC codes: B60R19, B60R21