Reexamination Certificate
2001-02-15
2002-11-19
Patel, Kiran (Department: 3612)
C293S120000, C293S102000, C296S182100
Reexamination Certificate
active
06481690
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to energy absorbers as extruded shapes made of aluminum alloy which have a high strength to resist a car body's collision against a pole (aluminum is hereinafter called Al). It is also concerned with bumper stays to be attached to the body side face of the curved end portions of a bumper reinforcement having curved portions at both ends.
2. Description of Related Art
A car body incorporates body energy absorbers such as bumper reinforcements and door beams. The bumper fitted to the front or rear of the body has, in its inside, a bumper reinforcing member called a bumper reinforcement or bumper reinforce.
Recently, for the sake of lightness, there has been an increasing tendency to use extruded shapes of high-strength aluminum alloys (which have the same sectional profile in the longitudinal direction) such as JIS 5000, 6000 and 7000 series instead of steel shapes which were often used formerly.
Al alloys are higher in such energy absorption as mentioned above than steel if they have the same weight. As an Al alloy extruded shape which has the same sectional profile in the longitudinal direction, it is possible to efficiently mass-produce a rigid hollow structure whose sectional profile is virtually rectangular. For this reason, Al alloys are widely used for bumper reinforcements, bumper stays, door beams and so on.
However, a body energy absorber which consists of an Al alloy extruded hollow shape with a virtually rectangular sectional profile has the following problem: if it is used for rear bumper reinforcement, its bending strength may be insufficient with respect to the virtually horizontal force (of vehicle collision) applied to the body energy absorber when the body collides against a pole.
In order to prevent the body from being bent upon collision against a pole as mentioned above, the bending strength of the bumper reinforcement must be increased. There are various ways to increase it: increasing the strength of Al alloy itself as the material for the bumper reinforcement; increasing the thickness of web, front wall and/or rear wall; increasing the width of the bumper reinforcement and so on.
However, if the strength of the Al alloy shape is increased, it might be more difficult to make shapes by extrusion or bending and such shapes might be more likely to crack, resulting in less collision energy absorption. Also, an increase in the thickness of the Al alloy shape or the width of the bumper reinforcement will lead to an increase in weight, which means that the lightness of Al alloy is traded off for increased strength. If the thickness of the Al alloy shape should be simply increased, the maximum load (force) of a collapsing bumper reinforcement might be larger than the permissible maximum load for side members, and it would be very likely to damage body members such as front side members.
J-P-A-No. 286536/1994 discloses a reinforcement structure in which an auxiliary hollow shape reinforcement made of Al alloy (which has, for example, a semicircular sectional profile at the front and a planar one at the rear and incorporates two props or ribs) is glued to the longitudinal center of the bumper reinforcement front side.
If an auxiliary steel reinforcement as mentioned above is used, the auxiliary reinforcement weight to obtain a satisfactory reinforcing effect is added, which offsets the advantage of lightness offered by the use of Al alloy for an energy absorber.
The auxiliary reinforcement in the form of a hollow shape of Al alloy as described in the above-said J-P-A-No. 286536/1994 may be lighter than the above-said steel reinforcement. Yet still, because the weight of the hollow shape reinforcement with a closed sectional profile is added, the problem of weight increase remains in comparison with the case of absence of an auxiliary reinforcement.
According to the above-said gazette, it is possible to lighten the bumper reinforcement main body as an Al alloy hollow shape by using an auxiliary reinforcement and decreasing its wall thickness. However, the auxiliary reinforcement has a hollow structure with a closed sectional profile and uses inner ribs (props) to reinforce it, so the collapse strength of the auxiliary reinforcement is rather high. Therefore, if the wall thickness of the bumper reinforcement main body is decreased as stated above, upon collision against a pole or in a similar situation, the bumper reinforcement main body might collapse earlier than the auxiliary reinforcement.
Further, because the auxiliary reinforcement is a hollow shape with a closed sectional profile, it is virtually impossible to join it to the bumper reinforcement main body mechanically or using bolts or the like or by welding. Consequently, the fixing method which uses glue as described in the gazette is unavoidable. However, gluing is much more unreliable as a method for fixing a vehicle structural member than a mechanical fixing method or welding.
It is thus demanded that a car body energy absorber such as a rear bumper reinforcement should have a sufficient bending strength without its lightness being unfavorably affected and without a decline in energy absorption upon body collision against a pole, and never bend horizontally from its center or cause buckling upon such collision.
Usually, the bumper reinforcement is fixed to the car body through car body couplers such as bumper stays. In case of a bumper reinforcement which has a curved (or curved) portion at each end, the surface of the bumper stay to come into contact with the bumper reinforcement must match the curved surface of the latter in attaching the former to the latter. Even when the contact surfaces of both are matched, there still remains another problem: how they should be joined and fixed. One known approach as the prior art is that bolts are passed through both the hollow of the curved portion of the bumper reinforcement and that of the bumper stay to connect them with the top and bottom of the bolts staying in these hollows. A conventional technique for joining and fixing a bumper stay to a side member on the bumper stay's car body side is that a hollow attachment as an integral part of the bumper stay is provided and the stay is joined and fixed to the side member through the attachment. This attachment has a width that matches the width of the side member.
Then this hollow attachment is placed in position on the side member and engaged with it. Bolts are passed through this engagement horizontally from the side of the car body and the stay and side member are fixed with the top or bottom of the bolts staying in the hollow of the side member or attachment.
However, these conventional joining/fixing methods have drawbacks. First of all, they are impractical and sometimes even ineffective.
In the above-said conventional methods, it is practically difficult to put a bolt into the inside of the bumper reinforcement and stay which are both hollow and have a closed sectional profile. It is even more difficult for a bumper reinforcement with a curved portion at each end. It is also practically difficult to let the bolt's top and bottom stay in the hollows with the bolt passed through them as suggested by the conventional methods.
Further, it is unrealistic to join and fix the stay to the front of the side member according to the prior art for the following reasons. One reason is that it is difficult to position the above-said hollow attachment on the side member in the car body widthwise direction.
Besides, even if the hollow attachment is once positioned on and engaged with the side member, it is difficult to let the bolt's top or bottom stay in the hollow of the side member or stay attachment with the bolt passed through them horizontally from the side of the car body.
BRIEF SUMMARY OF THE INVENTION
A first object of this invention is to provide a car body energy absorber as a strengthened version of Al alloy car body energy absorber which does not damage the car body as it bends upon car body collision against a po
Hashimura Toru
Kariatsumari Koji
Nimura Satoshi
(Kobe Steel, Ltd.)
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Patel Kiran
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