Stock material or miscellaneous articles – All metal or with adjacent metals – Defined configuration of both thickness and nonthickness...
Reexamination Certificate
1998-07-08
2001-07-10
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Defined configuration of both thickness and nonthickness...
C428S598000, C428S595000, C428S586000, C420S535000, C420S544000, C420S552000, C072S711000, C072S700000, C148S690000, C148S702000
Reexamination Certificate
active
06258465
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention:
The present invention relates to an energy absorbing member comprising an extrusion made of an aluminum alloy, and having a function that in receiving a compressive impact load or a compressive static load in the extruding axial direction the impact load or the static load can be absorbed.
2. Related Arts:
Recently, the global environment has bee regarded as being of worldwide importance. For example, regulations for reducing gas emissions including carbon dioxide and exhaust gas from automobiles have been strengthened in may countries in order to suppress global warming. Accordingly, lightweight automobiles have been rapidly developed.
Thus, investigations have been made on application of an extrusion made of an aluminum alloy to frames of an automobile and the like.
Into an automobile, incorporated are various energy absorbing members for relieving an impact caused when the automobile collides or contacts another automobile or an object. Recently, attempts have been made to relieve impacts provided to persons in an automobile by using structural members such as a side frame and a bumper stay as an energy absorbing member for absorbing impacts in collision and crushing the member into a form of bellows.
One requirement for such an energy absorbing member is that when a load is applied to the member in the extruding axial direction, in the whole of the member an Euler's buckle (the buckle that the whole of an object is bent into an “L”-like shape) and squeezing cracks (or pressing cracks) do not break out but the member is contracted and deformed into a form of bellows so as to absorb the impact energy stably. When a squeezing crack breaks out, for example, in a side frame of an automobile, contraction and deformation into a form of bellows are disturbed so that energy may not be absorbed stably. Furthermore, broken pieces are scattered in a small engine room and a tip of the pieces is projected out to damage other parts and wirings or penetrate through an outer plate of the car body. Thus, such a material cannot be regarded as a reliable material.
Hitherto, various investigations have been made on development of members having a stable energy absorbability. For example, Japanese Patent Laid-Open (JP-A-) No. 6-247338 discloses a technique of intentionally making different between the sectional secondary moment (rigidity) around the X axis and that around the Y axis in the cross section of a side member comprising a hollow member having a rectangular section, in order to cause the hollow member to be contacted and deformed into a form of bellows, with Euler's buckle being restrained; and setting the section shape of the panel, in the side member, which may be probably buckled into a form of bellows into such a shape that after collision of the panel, the panel will be buckled previously to buckles of other panels. This publication states that once any one of panels is buckled, the buckle into a form of bellows is transmitted to other panels in succession, and that even if the whole of the side member is long, the buckle into a form of bellows occurs stably over the whole length. Besides, JP-A-6-25783, JP-A-7-118782, JP-A-7-310156, JP-A-8-216917, JP-A-8-310440 and others disclose a technique for improving energy absorbability by investigating and adjusting the composition of an aluminum alloy for use as an energy absorbing member, and its structure.
SUMMARY OF THE INVENTION
The first object of the present invention is to provide an energy absorbing member, for a side frame of an automobile or the like to which compressive load in its axial direction is applied, in which a sectional shape thereof is invented so as to induce contraction and deformation into a form of bellows, with Euler's buckle being restrained, and to attain stable energy absorption with large effective displacement and absorbed energy.
The second object of the present invention is to provide an energy absorbing member making best use of the strength and energy absorbability of 6000 series aluminum alloy (Al—Mg—Si alloy) extrusion itself, which has a relatively excellent resistance to corrosion, among high strength aluminum alloys, and is more advantageous from the viewpoint of recycling than other series aluminum alloys.
About the section shape of a hollow extrusion having an outer portion and an inner rib connected to the outer portion, the inventors have considered the sectional shape of the outer portion and that of the rib separately and consequently have found that the liability that Euler's buckle or deformation into a form of bellows breaks out is related to the rigidity of the portion where the plate constituting the outer portion is connected to the plate constituting the rib, that of the portion where the inner ribs cross each other, and that of the inner rib(s); and that when the rigidity of these portions is small, buckles are liable to break out in the plates constituting the outer portion and the rib(s) so as to easily induce deformation into a form of bellows. The present invention based on these findings has at least one characteristic of the following (1) and (2).
(1) An energy absorbing member comprises a hollow extrusion which is made of an aluminum alloy and has an outer portion and an inner rib connected to the outer portion, and the radius of the corner where the rib and the outer portion are connected to each other is not more than a half of the thickness of the rib.
(2) An energy absorbing member comprises a hollow extrusion which is made of an aluminum alloy and has an outer portion and plural inner ribs which are connected to the outer portion and cross each other, and the radius of the corner where the ribs cross each other is 1 mm or less.
Satisfying these characteristics simultaneously is very useful.
Besides satisfying the aforementioned shape, the aluminum alloy constituting the energy absorbing member may be a heat treated aluminum alloy subjected to averaging treatment, so that resistance to squeezing cracks is more efficiently improved. A criterion for an appropriate degree of overaging treatment is as follows. Namely, when &sgr; max represents the maximum value of the proof stress (&sgr; 0.2) obtained by aging-treating an extrusion subjected to quenching treatment involving heating at not less than solution treating temperature and subsequent quenching, or press quenching treatment involving the steps of quenching by rapid cooling on line using temperature for hot processing, it is preferred that the member according to the invention is subjected to overaging treatment so that the proof stress thereof is 0.5 to 0.9 times the &sgr; max. The condition for obtaining the energy absorbing member having this proof stress in the overaging treatment may be as follows: from 210 to 230° C.×from 150 to 240 minutes. The heat treated aluminum alloy subjected to the overaging treatment is preferably an Al—Mg—Si alloy, and more preferably comprises 0.35 to 1.6% by weight of Mg, and 0.2 to 1.6% by weight of Si, or comprises 0.35 to 1.1% by weight of Mg, 0.5 to 1.3% by weight of Si, 0.15 to 0.7% by weight of Cu, 0.005 to 0.2% by weight of Ti, and 0.06 to 0.2% by weight of Zr; at least one element selected from the group consisting of 0.05 to 0.5% by weight of Mn and 0.05 to 0.15% by weight of Cr; and the balance being Al and inevitable impurities. Besides satisfying the aforementioned composition, it is recommendable to contain 0.3% or less by weight of Fe.
The inventors have also found that in the case wherein an energy absorbing member is made of an aluminum alloy extrusion which is subjected to overaging treatment and comprises such a specific composition as above, that is, 0.35 to 1.1% by weight of Mg, 0.5 to 1.3% by weight of Si, 0.15 to 0.7% by weight of Cu, 0.005 to 0.2% by weight of Ti, and 0.06 to 0.2% by weight of Zr; at least one element selected from the group consisting of 0.05 to 0.5% by weight of Mn and 0.05 to 0.15% by weight of Cr; and the balance being Al and inevitable impurities, larger resist
Hirano Masakazu
Oka Takashi
Yamashita Hiroyuki
Boss Wendy
Jones Deborah
Kabushiki Kaisha Kobe Seiko Sho
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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