JP4285896B2 - Energy absorbing member for automobile frame structure made of extruded aluminum alloy material with excellent axial crushing characteristics - Google Patents

Description

【０００１】
【発明の属する技術分野】
本発明は、アルミニウム合金の中空押出形材からなり、その押出軸方向に圧縮の衝撃荷重あるいは圧縮の静的負荷を受けたとき、その衝撃荷重及び静的負荷を吸収する作用を持つエネルギー吸収部材に関する。
【０００２】
【従来の技術】
自動車のフレーム構造において、サイドメンバやバンパーステイなどのエネルギー吸収部材として、アルミニウム合金の中空押出形材の適用が検討されている（例えば特開平７−３１０１５６号公報、特開平７−１１８７８２号公報、特開平８−２１６９１７号公報、特開平６−２４７３３８号公報参照）。軸方向に圧縮の衝撃荷重を受けるこれらのエネルギー吸収部材に要求される特性の１つは、上記公報にも記載されているように、部材が押出軸方向に荷重を受けたとき形材全体がオイラー座屈（形材全体がくの字形に曲がる座屈）を起こさず、かつ圧壊割れを発生することなく蛇腹状に収縮変形して、安定したエネルギー吸収を得ることである。
【０００３】
上記公報のうち、例えば特開平６−２４７３３８号公報では、矩形断面の中空形材からなるサイドメンバにオイラー座屈を抑えて蛇腹状の収縮変形を起こさせるために、断面においてＸ軸回りの断面二次モーメント（剛性）とＹ軸回りの断面二次モーメントに意識的に差を付け、サイドメンバの蛇腹状に座屈する確率の高いパネルが衝突の始めに他のパネルよりも先に座屈するように、その断面形状が設定されている。そして、いったんどれかのパネルが座屈すると他のパネルに蛇腹状の座屈が次々に伝搬し、サイドメンバの全長が長くなってもその全長にわたり蛇腹状の座屈が安定して起こるとされている。
【０００４】
【発明が解決しようとする課題】
本発明は、軸方向に圧縮荷重を受ける自動車のサイドメンバ等のエネルギー吸収部材において、上記特開平６−２４７３３８号公報の技術と同じく断面形状に工夫を加え、オイラー座屈を抑えて蛇腹状の収縮変形を誘発し、安定したエネルギー吸収を得ることを目的とする。
【０００５】
【課題を解決するための手段】
本発明に係る軸圧壊特性に優れたエネルギー吸収部材は、▲１▼外周部とその外周部に接続する内側のリブを有するアルミニウム合金の中空押出形材からなり、リブと外周部が接続する部位のコーナーＲをリブの厚さの１／２以下としたこと、▲２▼外周部とその外周部に接続しかつ互いに交差する複数の内側のリブを有するアルミニウム合金の中空押出形材からなり、複数のリブが交差する部位のコーナーＲを１ｍｍ以下としたこと、あるいは、▲３▼外周部とその外周部に接続する内側のリブを有するアルミニウム合金の中空押出形材からなり、内側のリブの厚さを外周部の厚さより薄く形成したこと、のいずれかの特徴を備える。これらの特徴のうち２以上の特徴を同時に備えることもできる。
【０００６】
【発明の実施の形態】
本発明者らは、外周部と外周部に接続する内側のリブを有する中空押出形材において、その断面形状を外周部と内側のリブに分けて捉え、外周部を構成する板と内側のリブを構成する板の接続部の剛性、内側のリブを構成する板同士の交差部の剛性、あるいは内側のリブの剛性が、オイラー座屈又は蛇腹状変形の起こりやすさに関係していること、そして、この部分の剛性が小さいと外周部又はリブを構成する板の座屈が起こりやすく、蛇腹状の変形が誘発されやすいことを見いだした。本発明はこの知見に基づいてなされたものである。
【０００７】
図１（ａ）、（ｂ）は、本発明に係る中空押出形材を例示するもので、これらは断面形状において基本的に均一な厚さａをもつ矩形の外周部と、同じく基本的に均一な厚さｂをもつリブを備えている。ここで、基本的に均一な厚さとは、外周部とリブそれぞれについて接続部、交差部及びコーナー部以外の厚さが均一という意味である。しかし、本発明に係る中空押出形材はこのような特定の断面形状に限定されるわけではない。
【０００８】
中空押出形材の外周部とリブの接続部のコーナーＲ（Ｒａ）がリブの厚さｂの１／２より小さい（Ｒａ≦ｂ／２）と、当該接続部の剛性が低くなり、外周部又はリブを構成する板の座屈が起こりやすく、蛇腹状の変形が誘発されやすい。ここで、リブの厚さが板幅方向に変化する場合もあり得るが、その場合は当該リブの厚さｂは前記接続部又は交差部を除く部分で最も厚い部位の厚みとする。また、リブ同士の交差部のコーナーＲ（Ｒｂ）が１ｍｍより小さい（Ｒｂ≦１）と、当該交差部の剛性が低くなり、リブを構成する板の座屈が起こりやすく、蛇腹状の変形が誘発されやすい。これら２つの要件のうちいずれかを満たす中空押出形材の外周部とリブのそれぞれの厚さについては、リブの厚さｂを外周部の厚さａと同一又は小さく（ｂ≦ａ）形成することが望ましい。
さらに、中空押出形材の外周部の板厚ａよりリブの厚さｂが薄く（ｂ＜ａ）形成されていると、剛性が小さくなってリブの座屈が起こりやすく、蛇腹状の変形が誘発されやすい。そして、リブの厚さｂをより薄く形成することで蛇腹状の変形が一層安定する。
アルミニウム合金からなる中空押出形材が上記の３つの要件のいずれか１つ又は複数を満たす場合、外周部又はリブを構成する板の一部が座屈し、それに伴い他の板の座屈が誘発され、オイラー座屈が抑制され蛇腹状の変形が起こりやすくなる。
【０００９】
【実施例】
以下、図２〜図５を参照して本発明の実施例を説明する。
図２のＡ〜Ｃに示す断面形状を有する全長２００ｍｍの６０６３−Ｔ５アルミニウム合金中空押出形材に対し軸方向に圧縮荷重を加え、荷重と変位量の関係を調査した。Ａ〜Ｃの外周部の形状はすべて同じ形状で、外形が４５ｍｍ×５５ｍｍ、厚さが２ｍｍである。また、ＡはＲａ、Ｒｂが全て６ｍｍ、リブの厚さｂが２ｍｍ、ＢはＲａ、Ｒｂが全て１ｍｍ、リブの厚さｂが２ｍｍ、ＣはＲａ、Ｒｂが全て１ｍｍ、リブの厚さｂが１．５ｍｍである。
【００１０】
Ａ〜Ｃそれぞれの荷重−変位曲線を図３〜図５に、また、図３〜図５から読み取った最大荷重、エネルギー吸収量、有効変位、及びそれぞれの座屈形態を表１に示す。なお、表１中の有効変位は、実施例のものは軸方向に蛇腹状に潰れきって荷重が再度上昇し、初期の最大荷重と同等の荷重値まで達したときの変位量を意味し、表１中のエネルギー吸収量は、上記有効変位に達するまでのエネルギー吸収量を意味する。一方、比較例のものはオイラー座屈が始まって荷重が単調に減少していくため、実施例と同じ意味での有効変位を定義できないことから、適当な変位で試験をストップさせ、これを表１の有効変位の欄に参考値として記載し、エネルギー吸収量の欄にその変位に達するまでのエネルギー吸収量を参考値として記載した。
【００１１】
【表１】

【００１２】
比較例Ａは、外周部とリブの接続部のコーナーＲ（Ｒａ）が６ｍｍ、リブ同士の交差部のコーナーＲ（Ｒｂ）が６ｍｍであり、断面積が大きいため最大荷重が大きくなっているが、オイラー座屈を起こしたため、有効変位（参考値）が小さくエネルギー吸収量（参考値）が小さくなっている。一方、実施例Ｂは、外周部とリブの接続部のコーナーＲ（Ｒａ）が１ｍｍ、リブ同士のコーナーＲ（Ｒｂ）が１ｍｍでいずれも本発明の規定を満たしており、蛇腹状に圧縮変形を起こし、有効変位及びエネルギー吸収量が大きくなっている。また、実施例Ｃは、外周部とリブの接続部のコーナーＲ（Ｒａ）が１ｍｍで本発明の規定を満たさない（Ｒａ＞ｂ／２）が、リブ同士のコーナーＲ（Ｒｂ）が１ｍｍで本発明の規定を満たし、さらにリブの板厚が外周部の板厚より薄く形成されて本発明の規定を満たし、蛇腹状に圧縮変形を起こし、有効変位及びエネルギー吸収量が大きくなっている。なお、実施例Ｃを実施例Ｂと比較したとき、最大荷重が小さいのは断面積が小さいためと考えられる。
【００１３】
【発明の効果】
本発明によれば、軸方向に圧縮の衝撃荷重あるいは圧縮の静的負荷を受けたとき、オイラー座屈を起こさずに蛇腹状に収縮変形し、有効変位及びエネルギー吸収量の大きい、軸圧壊特性に優れたエネルギー吸収部材を得ることができる。
【図面の簡単な説明】
【図１】 本発明に係る中空押出形材の断面形状を説明する図である。
【図２】 比較例Ａ、実施例Ｂ、Ｃの中空押出形材の断面形状である。
【図３】 比較例Ａの荷重−変位曲線である。
【図４】 実施例Ｂの荷重−変位曲線である。
【図５】 実施例Ｃの荷重−変位曲線である。[0001]
BACKGROUND OF THE INVENTION
The present invention comprises an aluminum alloy hollow extruded shape, and an energy absorbing member having an action of absorbing the impact load and static load when subjected to a compression impact load or compression static load in the direction of the extrusion axis. About.
[0002]
[Prior art]
In an automobile frame structure, application of an aluminum alloy hollow extruded shape as an energy absorbing member such as a side member or a bumper stay has been studied (for example, Japanese Patent Laid-Open Nos. 7-310156 and 7-118782). JP-A-8-216171, JP-A-6-247338). One of the characteristics required for these energy absorbing members that are subjected to a compressive impact load in the axial direction is that, as described in the above-mentioned publication, the entire shape is affected when the member receives a load in the axial direction of the extrusion. It does not cause Euler buckling (buckling in which the entire shape bends in a U-shape) and contracts and deforms in a bellows shape without causing crushing cracks to obtain stable energy absorption.
[0003]
Among the above publications, for example, in Japanese Patent Application Laid-Open No. 6-247338, a cross section around the X axis in the cross section in order to suppress Euler buckling and cause a bellows-like contraction deformation in a side member made of a hollow section having a rectangular cross section. A panel that has a high probability of buckling in a bellows-like shape of the side member buckles ahead of other panels at the beginning of a collision by intentionally making a difference between the secondary moment (rigidity) and the secondary moment of inertia about the Y axis. Further, the cross-sectional shape is set. Once one of the panels buckles, bellows-like buckling propagates one after another to the other panel, and even if the length of the side member becomes long, bellows-like buckling occurs stably over the entire length. ing.
[0004]
[Problems to be solved by the invention]
In the energy absorbing member such as a side member of an automobile that receives a compressive load in the axial direction, the present invention adds a contrivance to the cross-sectional shape in the same manner as the technique of the above-mentioned Japanese Patent Application Laid-Open No. 6-247338, and suppresses Euler buckling and It aims at inducing shrinkage deformation and obtaining stable energy absorption.
[0005]
[Means for Solving the Problems]
The energy absorbing member having excellent axial crushing characteristics according to the present invention comprises: (1) a hollow extruded profile of an aluminum alloy having an outer peripheral portion and an inner rib connected to the outer peripheral portion, and a portion where the rib and the outer peripheral portion are connected. The corner R of the aluminum alloy was made to be 1/2 or less of the thickness of the rib, and (2) an aluminum alloy hollow extruded shape having an outer peripheral portion and a plurality of inner ribs connected to the outer peripheral portion and intersecting each other, The corner R of the portion where the plurality of ribs intersect is set to 1 mm or less, or (3) an aluminum alloy hollow extruded shape having an outer peripheral portion and an inner rib connected to the outer peripheral portion. Any one of the features that the thickness is formed thinner than the thickness of the outer peripheral portion is provided. Two or more of these features can be provided simultaneously.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
In the hollow extruded shape member having the outer peripheral portion and the inner rib connected to the outer peripheral portion, the present inventors grasp the cross-sectional shape separately into the outer peripheral portion and the inner rib, and the plate constituting the outer peripheral portion and the inner rib The rigidity of the connecting portion of the plate constituting the inner rib, the rigidity of the crossing portion of the plates constituting the inner rib, or the rigidity of the inner rib is related to the likelihood of Euler buckling or bellows deformation, And when the rigidity of this part was small, it discovered that the buckling of the board which comprises an outer peripheral part or a rib would occur easily, and a bellows-shaped deformation | transformation was easy to be induced. The present invention has been made based on this finding.
[0007]
1 (a) and 1 (b) illustrate hollow extruded profiles according to the present invention, and these are basically the same as a rectangular outer peripheral portion having a basically uniform thickness a in cross-sectional shape. A rib having a uniform thickness b is provided. Here, the basically uniform thickness means that the thickness other than the connecting portion, the intersecting portion, and the corner portion is uniform for each of the outer peripheral portion and the rib. However, the hollow extruded profile according to the present invention is not limited to such a specific cross-sectional shape.
[0008]
When the corner R (Ra) between the outer peripheral portion of the hollow extruded shape member and the rib is smaller than ½ of the rib thickness b (Ra ≦ b / 2), the rigidity of the connecting portion is reduced, and the outer peripheral portion Alternatively, buckling of the plates constituting the ribs is likely to occur, and bellows-like deformation is likely to be induced. Here, the thickness of the rib may change in the plate width direction. In this case, the thickness b of the rib is the thickness of the thickest portion excluding the connecting portion or the intersection. Further, when the corner R (Rb) of the intersecting portion of the ribs is smaller than 1 mm (Rb ≦ 1), the rigidity of the intersecting portion is lowered, the buckling of the plate constituting the rib is likely to occur, and the bellows-like deformation occurs. Easy to be triggered. About the thickness of the outer peripheral part of the hollow extrusion shape material which satisfy | fills either of these two requirements, and the thickness of a rib, the thickness b of a rib is formed the same as or smaller than the thickness a of an outer peripheral part (b <= a). It is desirable.
Further, when the rib thickness b is thinner (b <a) than the plate thickness a of the outer peripheral portion of the hollow extruded shape member, the rigidity is reduced and the rib tends to buckle, and the bellows-like deformation occurs. Easy to be triggered. Further, by forming the rib thickness b thinner, the bellows-like deformation is further stabilized.
When a hollow extruded shape made of an aluminum alloy satisfies one or more of the above three requirements, a part of the plate constituting the outer periphery or the rib is buckled, and the buckling of other plates is induced accordingly. As a result, Euler buckling is suppressed and bellows-like deformation is likely to occur.
[0009]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
A compression load was applied in the axial direction to a 6063-T5 aluminum alloy hollow extruded profile having a total length of 200 mm having the cross-sectional shapes shown in FIGS. 2A to 2C, and the relationship between the load and the displacement was investigated. The outer peripheral portions A to C are all the same shape, and the outer shape is 45 mm × 55 mm and the thickness is 2 mm. In addition, A is Ra and Rb are all 6 mm, rib thickness b is 2 mm, B is Ra and Rb are all 1 mm, rib thickness b is 2 mm, C is Ra and Rb are all 1 mm, rib thickness b Is 1.5 mm.
[0010]
The load-displacement curves of A to C are shown in FIGS. 3 to 5, and the maximum load, energy absorption amount, effective displacement, and respective buckling modes read from FIGS. 3 to 5 are shown in Table 1. The effective displacement in Table 1 means the amount of displacement when the example is crushed in a bellows shape in the axial direction and the load rises again and reaches a load value equivalent to the initial maximum load, The energy absorption amount in Table 1 means the amount of energy absorption until the effective displacement is reached. On the other hand, in the comparative example, Euler buckling starts and the load decreases monotonously, so the effective displacement in the same meaning as the example cannot be defined. In the column of 1 effective displacement, it described as a reference value, and in the column of energy absorption amount, the energy absorption amount until reaching the displacement was described as a reference value.
[0011]
[Table 1]

[0012]
In Comparative Example A, the corner R (Ra) of the connecting portion between the outer peripheral portion and the rib is 6 mm, and the corner R (Rb) of the intersecting portion of the ribs is 6 mm. Because Euler buckling occurred, the effective displacement (reference value) was small and the energy absorption amount (reference value) was small. On the other hand, in Example B, the corner R (Ra) of the connecting portion between the outer peripheral portion and the rib is 1 mm, and the corner R (Rb) between the ribs is 1 mm, both of which satisfy the provisions of the present invention, and are compressed and deformed in a bellows shape. The effective displacement and the amount of energy absorption are increased. Further, in Example C, the corner R (Ra) of the connection portion between the outer peripheral portion and the rib is 1 mm and does not satisfy the definition of the present invention (Ra> b / 2), but the corner R (Rb) between the ribs is 1 mm. The ribs are formed so that the thickness of the rib is thinner than the thickness of the outer peripheral portion to satisfy the requirements of the present invention, causing compression deformation in a bellows shape, and the effective displacement and the energy absorption amount are large. In addition, when Example C is compared with Example B, it is considered that the maximum load is small because the cross-sectional area is small.
[0013]
【The invention's effect】
According to the present invention, when subjected to a compressive impact load or a compressive static load in the axial direction, it contracts and deforms in a bellows shape without causing Euler buckling, and has an effective displacement and a large amount of energy absorption. It is possible to obtain an energy absorbing member excellent in the above.
[Brief description of the drawings]
FIG. 1 is a view for explaining a cross-sectional shape of a hollow extruded profile according to the present invention.
FIG. 2 is a cross-sectional shape of a hollow extruded profile of Comparative Example A, Examples B and C.
3 is a load-displacement curve of Comparative Example A. FIG.
4 is a load-displacement curve of Example B. FIG.
5 is a load-displacement curve of Example C. FIG.

Claims (2)

外周部とその外周部に接続する内側のリブを有するアルミニウム合金の中空押出形材からなり、前記外周部とリブがそれぞれ基本的に均一な厚さを有し、前記リブの厚さをｂとし前記外周部の厚さをａとしたときｂ＜ａであり、前記リブと外周部が接続する部位のコーナーＲが前記リブの厚さの１／２以下であることを特徴とする軸圧壊特性に優れた自動車のフレーム構造におけるエネルギー吸収部材。An aluminum alloy hollow extruded member having an outer peripheral part and an inner rib connected to the outer peripheral part, each of the outer peripheral part and the rib has a basically uniform thickness, and the thickness of the rib is b the thickness of the outer peripheral portion is b <a when the a, axial collapse characteristic, wherein the corner R portion of the rib and the outer peripheral portion is connected is 1/2 or less of the thickness of the rib An energy absorbing member in an automobile frame structure that is excellent in performance. 外周部とその外周部に接続しかつ互いに交差する複数の内側のリブを有するアルミニウム合金の中空押出形材からなり、前記外周部とリブがそれぞれ基本的に均一な厚さを有し、前記リブの厚さをｂとし前記外周部の厚さをａとしたときｂ＜ａであり、前記複数のリブが交差する部位のコーナーＲが１ｍｍ以下であることを特徴とする軸圧壊特性に優れた自動車のフレーム構造におけるエネルギー吸収部材。An aluminum alloy hollow extruded section having an outer peripheral portion and a plurality of inner ribs connected to the outer peripheral portion and intersecting with each other, each of the outer peripheral portion and the rib having a basically uniform thickness, And b <a where b is the thickness of the outer peripheral portion and a is the thickness of the outer peripheral portion, and the corner R of the portion where the plurality of ribs intersect is 1 mm or less. Energy absorbing member in automobile frame structure.

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