Vehicle fenders – Buffer or bumper type – Bumper having impact force absorbing means directly...
Reexamination Certificate
1999-12-23
2001-05-15
Pape, Joseph D. (Department: 3612)
Vehicle fenders
Buffer or bumper type
Bumper having impact force absorbing means directly...
C188S371000, C188S376000, C188S377000
Reexamination Certificate
active
06231095
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an impact absorption apparatus and especially to an energy absorption device for a vehicle bumper impact system.
It is typical for an automotive bumper system to include three key components. The first is a decorative fascia, usually of plastic, mounted on the exterior of the front end module. The second is a rigid impact beam, typically constructed of roll formed or stamped steel. And the third is an energy absorption device connecting the impact beam to the vehicle frame rails. These three components are designed together to meet the performance requirements for low and high speed impacts.
It is beneficial to design the bumper system in such a way that limited damage is transferred to the vehicle frame rails under impact by properly engineering the energy absorption device. One guideline provided for this design process is for the bumper system to have a peak loading capability equivalent to 85% of the combined rail capacity. This assures that the energy absorption unit will crush first upon impact before loading is imparted on the rails. It is also beneficial to design the bumper system to provide this energy absorption in a controlled and repeatable manner. This allows for consistency in vehicle crash behavior.
There is substantial prior art regarding energy absorption units and bumper systems including U.S. Pat. Nos. 5,427,214; 5,732,801; and 4,272,114. These disclosures depict various methods of meeting the energy absorption targets for the bumper system. Shortcomings of these designs include inconsistency in deformation and resultant energy absorption, instability in lateral loading, high associated manufacturing costs, and post impact damage visibility.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a vehicle energy absorption unit which achieves a controlled and consistent energy absorption characteristic in a bumper impact system.
A cylindrical tube, preferably of steel or aluminum metal, and preferably round in cross section, is preferably grooved, i.e., scored, to provide channels in multiple locations around its periphery to a controlled depth of the tube thickness, but extending lengthwise, i.e., axially of the tube. These channels or grooves can significantly influence the deformation and energy absorption characteristics, to achieve a predetermined load deflection curve. Deformation control is further achieved by the depth of the channels, their locations and quantity, the material of the tube and the thickness of the tube. The tube is partially slit or notched, and flared, preferably along these grooves, at one end of the tube, to form extending mounting flanges, i.e., flange segments. The tube is placed at an opening in an inner reinforcement plate which is of substantially rigid material, usually steel, or alternatively at the forward end of the vehicle frame rail, and the flared end flanges are welded to this plate or frame rail. The opposite outer end of the tube is welded to a secondary outer plate of substantially rigid material such as steel, or directly to the rigid impact beam. If the inner plate is used, it is fastened to the forward end of a hollow vehicle frame rail, with the tube and outer plate being outward of the frame rail. The tube is axially aligned with the hollow interior of the vehicle frame rail. Two of these energy absorption units, i.e., crush boxes, are to be used as portions of a vehicle bumper assembly, usually a front bumper assembly, and are secured as by welding or mechanical attachment to the rigid bumper impact beam, on opposite sides of the vehicle, so as to be in alignment with the two frame rails.
When an impact force is applied to the impact beam, the load is transferred to the outer plates of the two energy absorption units. The tubes are compressed by the load, causing each of them to have portions progressively radially outwardly deflecting and tearing from the cylinder and inverting so the tube passes axially through the inner plate opening. The tube inverts, i.e., turns inside out, through this deflection and tearing process, being contained within the hollow body of the frame rail. The grooved channels in the tube cause the tube to split and tear in a controlled manner along these channels during deformation. The resultant deformation can create a load deflection curve with generally square wave characteristics to allow a controlled peak load near 85% of the rail capacity. This resultant generally square load curve, and the controlled failure mechanism that causes it, are believed particularly unique in the industry.
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Chou Shui Fang
Libriani Alessandro
Tjoelker Todd W. J.
Benteler Automotive Corporation
Pape Joseph D.
Patel Kiran
Price Heneveld Cooper DeWitt & Litton
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