Static structures (e.g. – buildings) – Machine or implement
Reexamination Certificate
1999-03-26
2002-06-25
Friedman, Carl D. (Department: 3635)
Static structures (e.g., buildings)
Machine or implement
C052S749100, C052S749100, C052S749100, C296S182100, C296S182100
Reexamination Certificate
active
06408591
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a door beam of an aluminum alloy as a member to reinforce a door for a vehicle such as an automobile, truck and the like, disposed in a door along a front-to-rear direction thereof for securing safety of a passenger and a driver by absorbing a crash shock from a side.
2. Description of the Prior Art
Under the situation in which environmental protection on earth has been regarded as important on a global scale, for example, enforcement of the regulations on reduction of exhaust gas and carbon dioxide gas, etc from automobiles have been stricter in various countries for suppressing global warming, leading to lightweight automobiles rapidly.
A door beam for an automobile, also referred to as an impact beam, an impact bar, a guard bar or a door side beam, mounted in the interior of a door along its front-to-rear direction, functions to absorb a shock in crash. As material, steel (for example, high tensile steel of a 150 kgf/mm
2
class) has been employed, recently in view of weight saving, application of an extrusion of aluminum alloy has been studied.
In a condition that a door beam of an aluminum alloy is held at its both ends, as a load at a central portion is increased, a central portion of the door beam causes bending deformation being pushed down. In the deformation, a tensile-strain is produced in a flange located in the tension-side (hereinafter simply referred to as a tension-side flange, and while a flange in the side where a load is imposed is hereinafter termed as a flange located in the compression-side or simply referred to as a compression-side flange, the tension-side flange is a flange opposed to the compression-side flange) and as a displacement of the central portion is further increased, a tensile-strain eventually exceeds a critical value for rupture and rupture occurs in the tension-side flange.
In order to increase the displacement when the rupture occurs (hereinafter simply referred to as rupture displacement), a method is disclosed in the published Unexamined Japanese Patent Application No. Hei 5-246242, that a position of a neutral axis of bending is shifted toward the tension-side by a necessary distance and another method is also disclosed in the published Unexamined Japanese Patent Application No. Hei 6-171362, that in addition to the shift of a neutral axis, a local buckling is induced in a compression-side flange after the maximal bending strength is cleared and a stress on the tension-side flange is rapidly reduced.
For securing safety of a passenger and a driver, door beams tend to be applied to the field of compact cars, where the length of the door beams needs to be shortened. For example, when applied to the rear doors of a compact type 4 door car, a length of a door beam are sometimes 800 mm or less (the objective of the Unexamined Japanese Patent Application No. Hei 6-171362 is door beams of 800 mm long or more), causing rupture at a smaller displacement than in a conventional long door beam. On the other hand, it is conceivable that a strength of an aluminum alloy constituting the door beams is reduced in order to allow a rupture displacement to a higher extent. In that case, there arises a problem that a maximal load and an energy absorption both required at the given weight of the door beam cannot be attained.
The Unexamined Japanese Patent Applications Nos. Hei 5-330450 and Hei 5-319092 are directed to a door beam composed of a pair of flanges and a pair of webs, where a strength of the web is set so that a beam cross-section is changed according to an impact load and thereby preventing a rupture of a tension-side flange from occurring. Concretely, the means are such that one web is thinner than the other, a corner fillet section or a notch portion is provided on one of joints between a compression-side-flange and both webs, for enabling a cross-section of a beam to be deformed into a rhombic shape (both webs are to be fallen sidelong). These enables to prevent rupture of a tension-side flange from occurring and to attain a large bending deformation and a high energy absorption. Where a door length is short, however, deformation of a cross-section is not stably produced, causing a rupture.
The rupture of door beams has to be avoided in an absolute sense since it has a possibility to injure a passenger or a driver.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made in light of such problems, accordingly aims at providing a door beam to obtain the required maximal load and energy absorption in no need of weight increase without occurrence of rupture thereof and to have the deformation of a cross-section effected in a stable manner even when a length of the door beam is shortened.
A door beam of an aluminum alloy according to the present invention has, as a feature, a cross-section that a compression-side flange and a tension-side flange are connected parallel to each other, by at least one web in a section perpendicular to a length direction and central lines of the compression-side flange and the tension-side flange are shifted from each other. In other words, a door beam of an aluminum alloy according to the present invention has, as a feature, a cross-section that a compression-side flange and a tension-side flange are connected parallel to each other, by at least one web in a section perpendicular to a length direction and that extensions in both sides of the compression-side flange are different in length and extensions in both sides of the tension-side flange are also different in length, while longer side ends of the extensions of the compression-side flange and the extensions of the tension-side flange are in one diagonal. Further, in a door beam of an aluminum alloy according to the present invention, a principal axis is inclined from a loading direction by an angle in the range from 5 degrees to 25 degrees in a section perpendicular to a length direction.
A door beam according to the present invention will be described by taking the case of a door beam which has a cross-section that a compression-side flange
1
and a tension-side flange
2
are connected by a pair of webs
3
,
4
as an example (see FIG.
1
). A central line (a) of the compression-side-flange
1
{a straight line drawn along a loading direction passing through the center of the compression-side flange, wherein in a flange of a uniform thickness, a center of the flange is located at a point which is inward spaced along a width direction (a lateral direction in
FIG. 1
) from one end of the flange by a half width and in
FIG. 1
, a pair of a flange are in parallel to each other and a pair of webs are also in parallel to each other, and the flanges are perpendicular to the webs, so that a loading direction is parallel to a direction of the webs} and a center (b) of the tension-side flange are shifted from each other. In other words, lengths c
1
, c
2
of extensions (in detail, portions extending from the webs, left and right) in the both sides of the compression-side flange
1
are different from each other and lengths d
1
, d
2
of extensions in both sides of the tension-side flange
2
are also different from each other, while ends c
1
, d
2
of the longer side extensions are located in one diagonal (needless to say that ends c
2
, d
1
of the shorter side extensions are located in the other diagonal).
Furthermore, a principal axis (C) is inclined from a loading direction (P), indicated by an arrow, by an angle in the range from 5 degrees to 25 degrees (see FIG.
11
). Two principal axes are those which pass through the center of gravity (as same as the center of figure) of a section and are always perpendicular to each other, and, in any section, a moment of inertia is maximal about one of the axes, while a moment of inertia is minimal about the other of the axes. The angle referred to in the present invention is a smaller one of angles between the two principal axes and the loading direction.
Conventional door beams of an aluminum alloy described in t
Hirano Masakazu
Takeuchi Hisashi
Yamashita Hiroyuki
Friedman Carl D.
Horton Yvonne M.
Kabushiki Kaisha Kobe Seiko Sho
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