JP2004155230A

JP2004155230A - Bumper beam for automobile

Info

Publication number: JP2004155230A
Application number: JP2002320452A
Authority: JP
Inventors: Takaharu Amano; 敬治天野; Yoshiya Suzuki; 義也鈴木; Hideo Kamitsuma; 英雄上妻
Original assignee: Mitsubishi Aluminum Co Ltd; Unipres Corp
Current assignee: Unipres Corp; MA Aluminum Corp
Priority date: 2002-11-01
Filing date: 2002-11-01
Publication date: 2004-06-03
Anticipated expiration: 2022-11-01
Also published as: JP4216045B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bumper beam structure for minimizing maximum load generated at the moment of collision. <P>SOLUTION: The bumper beam for an automobile is composed in a "θ-shaped" cross section of a top wall, a bottom wall opposed to the top wall, a pair of lateral walls connecting the top and bottom walls at opposite ends, and a connection rib provided intermediate between the top and bottom walls and connecting the lateral walls. The top wall is thicker than the bottom wall, both corners at opposite ends of the top wall are curved with a radius of curvature of 0.1-0.3 of the length of the top wall, and both corners at opposite ends of the bottom wall are curved with a radius of curvature of 0.5-2.0 of the thickness of the bottom wall. The bumper beam is formed of an extrusion hollow member made of aluminum alloy. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、自動車のバンパーを補強するバンパービームに関するものである。
【０００２】
【従来の技術】
一般に、自動車のバンパーは、車体に連結されるとともにバンパーの強度を保つバンパービームと、このバンパービームに取り付けられて車体の外観を整える樹脂製の表皮材とから概略構成されている。そして、このバンパービームは燃費低減のために軽量化が図られており、近年では軽合金製とする例が多くなってきている。例えば、図８に断面図として示すバンパービーム３０は、アルミ合金材で押し出し成形されたバンパービームの一例で、“日の字型”断面に押し出し成形された中空構造を有している。すなわち、互いに平行な上壁部１１と底壁部１２、及びこれらと直角方向に互いに平行な側壁部１３，１４と、上壁部１１と底壁部１２と平行して、側壁部１３，１４を２分するように中央に設けられた連結リブ１５から構成されている。
【０００３】
バンパービーム３０は、実際にはサイドメンバー１６を介して車両１７の前面または後面に取り付けられ、衝突の際には衝突面側の側壁部１３が図の左方矢印の方向からの衝撃力Ｆを受け止める面となる。従って“日の字型”断面構造の部材の内でも側壁部１３が最も厚さが厚く作られている。また、図８の例では上壁部１１及び底壁部１２と、連結リブ１５は同じ厚さに作られており、図の左方からの衝撃力を均等に受け止めて衝撃力をやわらげる構造となっている。
このようなバンパービームは軽量化を目的として７０００番系高力アルミニウム合金等で作成される。通常、バンパービームには発泡材等からなる緩衝材が取り付けられ、表面はバンパーカバーで覆われている。
【０００４】
バンパービームは自動車の衝突等により外部から衝撃力が加わった時に、その衝撃エネルギーをバンパービーム材料の塑性変形により吸収し、他の部材の損傷を回避すると同時に人体の安全を確保するための重要な部材である。
ところで、自動車の衝突の形態には壁状障害物がバンパービームの壁面の全面に比較的に高速で衝突する形態と、柱状障害物がバンパービームの壁面の一部に比較的に低速で衝突する形態とがある。
前者の衝突形態では、衝突による衝突エネルギーは乗員の負傷やバンパービーム取り付け部材の座屈損傷を招くような大きなものであることが多く、バンパービームに対しては徐々に変形崩壊して大量の衝突エネルギーを吸収できるものであることが望まれている。
一方、後者の衝突形態では、乗員の負傷や取り付け部材の損傷を招くような大きな衝突エネルギーを有する場合は少なく、バンパービームに対しては変形崩壊して衝突エネルギーを吸収するよりも、衝突荷重で変形し難い剛性に富んだものであることが望まれている。
【０００５】
バンパービームには、軽量化を図りつつも形材の曲げ剛性と曲がる時のエネルギー吸収量を大きくすることが求められている。断面形状の改良によりこれらの特性を改良する提案が開示されている（例えば、特許文献１参照。）。
この提案においては、長さ方向に一様な矩形断面形状のアルミ合金形材からなり、衝突方向に対して垂直な壁面を有するように車体側に位置する壁面の両端部が車体に取り付けられるバンパービームであり、上記アルミ合金形材の車体側に位置する角隅部が板厚の２．５倍以上の半径Ｒで湾曲をなしているバンパービームが開示されている。
具体的には図９に示すように、バンパービーム４０は、バンパーカバー内に設けられたアルミ合金形材からなっており、車体４２側に位置する壁面４１ａがサイドメンバー４４を介して車体４２に支持されている。上記のアルミ合金形材は、長さ方向に一様な例えば“日”字形の矩形断面形状に形成されており、一対の横設リブ４１ｂ、４１ｂと、両横設リブ４１ｂ、４１ｂの両端に接続された縦設リブ４１ａ、４１ａと、縦設リブ４１ａ、４１ａ間に接続された補強リブ４１ｃとからなっている。
【０００６】
上記のバンパービーム４０は、縦設リブ４１ａ、４１ａが衝突方向に対して垂直となると共に、横設リブ４１ｂ、４１ｂが衝突方向に対して平行となるように設けられている。そして、車体４２側の角隅部４１ｄ、４１ｄは、縦設リブ４１ａ、４１ａの長さの１／６以下の範囲において板厚の２．５倍以上の半径Ｒで湾曲されている。一方、バンパービーム４０の衝突側の角隅部４１ｅ、４１ｅは、板厚程度の半径ｒで略直角に曲折されている。これにより、バリアー衝突時においては、湾曲された角隅部４１ｄ、４１ｄを座屈の起点に位置させることによって、発生荷重を抑制しながら座屈を促進し、衝突エネルギーを効率良く吸収するようになっている。また、ポール衝突時においては、湾曲された角隅部４１ｄ、４１ｄを座屈の起点の反対側に位置させることによって、大きな発生荷重を生じさせるようになっている。尚、半径Ｒを縦設リブ４１ａ・４１ａの長さの１／６以下に制限した理由は、１／６を越えるとサイドメンバ４４への取り付けが困難になると共に吸収エネルギーが低下するからである。
この構造によれば、上記の二つの衝突形態に対応できるような、徐々に変形崩壊して大量の衝突エネルギーを吸収できる特性と、衝突荷重で変形し難い剛性に富んだ特性とを兼ね備えることができるとされている。
【０００７】
【特許文献１】
特開平８−８０７８９号公報（第１頁、第２図）
【０００８】
【発明が解決しようとする課題】
しかしながら、バンパービームがあまり強すぎると、バンパービームの座屈と共に車体の取り付け金具であるサイドメンバーを損傷させてしまうことになる。サイドメンバーは衝突の瞬間に発生する最大荷重によって損傷する。
例えば、図８に断面で示すような全角隅部が直角に曲折されたバンパービームでは、図１０に示すように衝突によりバンパービームが３．５〜４．５ｍｍ塑性変形する間の平均荷重は５０ｋＮ程度であるのに対して、衝突直後のバンパービームの変位量が１ｍｍに達する以前の０．５ｍｍ程度塑性変形する間に、最大２５０ｋＮもの最大荷重が発生し、その後はほぼ一定の潰し荷重で変形していく。この場合には最大荷重は平均荷重の５．８８倍にも達する。
この最大荷重を低くすることができれば、サイドメンバーを損傷させることなくバンパービームの変形崩壊のみで衝突エネルギーを吸収することができる。
従来はバンパービームが最大３．５〜４．５ｍｍ塑性変形する間に、発生荷重が大幅な変動を伴わない場合の最大荷重と吸収エネルギーの関係を問題としており、衝突の瞬間に発生する最大荷重を下げる試みはなされていなかった。
人身の安全を確保するためにも、衝突の瞬間に発生するこの最大荷重のピークをできる限り低くすることが重要である。
本発明の目的は、上記衝突の瞬間に発生するこの最大荷重のピークをできる限り低くし、バンパービームの取付け金具であるサイドメンバーの損傷を防ぐことのできるバンパービームの構造を提供することにある。
【０００９】
【課題を解決するための手段】
上記課題を解決するため普通乗用車のバンパービームの断面形状を種々検討した結果、サイドメンバーが損傷するのは長さ１００ｍｍのバンパービーム試片に加わる圧潰荷重が１５０ｋＮを越える場合であることが判明した。衝突の瞬間に発生する最大荷重を１５０ｋＮ以下に抑えれば、バンパービームの塑性変形により、サイドメンバーを損傷させることなく衝突エネルギーを吸収できることが判明した。バンパービームの構造を、衝突の後半に発生する衝撃荷重が低くなり過ぎる構造にしてしまうと、バンパービームとしてのエネルギー吸収能が低下してしまうことも判明した。
従って、図１０に示す潰し荷重−変位曲線において、最大ピークのみを引き下げて波形をより矩形波形に近づけることができれば、サイドメンバーを損傷させることなくバンパービームの塑性変形により衝突エネルギーを吸収できることになり、エネルギー吸収材として安定した性能を有するバンパービームとすることができると考えた。そこでバンパービームの断面形状を種々検討した結果、衝撃を受ける面の部材の厚さを厚くし、かつ衝撃を受ける部材面の両端に特定の曲率半径を付与させることにより、上記目的を達成できることを見い出し本発明に至った。
すなわち、本発明のバンパービームでは、断面形状が上壁部と、上壁部に対向する底壁部と、前記上壁部および底壁部の両端部を連結する一対の側壁部と、前記上壁部および底壁部の中間に設けられて２つの側壁部を連結する連結リブとからなる日の字型を呈し、衝突面側の側壁部の厚さが車体取付け面側の側壁部の厚さよりも厚く、衝突面側の側壁部の両角隅部は前記衝突面側の側壁部の長さの０．１〜０．３倍の長さの曲率半径Ｒで湾曲しており、かつ車体取付け面側の側壁部の両角隅部が該車体取付け面側の側壁部の厚さの０．６〜１倍の長さの曲率半径ｒで湾曲したアルミニウム合金製の押し出し中空部材からなるバンパービームとした。この断面形状は衝突面側の側壁部の長さＬ_１が、上壁部及び底壁部の長さＬ_２の２倍よりも短い時に適用される。
【００１０】
一方、側壁部の長さＬ_１が、上壁部及び底壁部の長さＬ_２の２倍よりも長い時には、断面形状が上壁部と、上壁部に対向する底壁部と、前記上壁部および底壁部の両端部を連結する一対の側壁部と、前記上壁部および底壁部の中間に設けられて２つの側壁部を連結する連結リブとからなる日の字型を呈し、衝突面側の側壁部の厚さが車体取付け面側の側壁部の厚さよりも厚く、衝突面側の側壁部の両角隅部は前記底壁部の長さの０．２〜０．６倍の長さの曲率半径で湾曲しており、かつ車体取付け面側の側壁部の両角隅部が該車体取付け面側の側壁部の厚さの０．６〜１倍の長さの曲率半径で湾曲したアルミニウム合金製の押し出し中空部材からなるバンパービームとする。
バンパービームを上記のように構成することにより、衝突した瞬間に発生する最大荷重のピークを効果的に低下させることができ、サイドメンバーを損傷することなしに、衝突エネルギーをバンパービームで吸収し、乗員に与える損傷を飛躍的に少なくすることができるようになる。
【００１１】
本発明においては、前記上壁部と連結リブ及び底壁部の厚さを全て等しく構成することができる。
連結リブの厚さを底壁部の厚さよりも薄く構成する場合には、前記連結リブの厚さは前記底壁部の厚さの０．６〜１倍とすることが好ましい。
連結リブをこのように構成することにより、高い剛性を有すると同時に、衝突時に発生する最大ピーク荷重の飛躍的に低減させることができるようになる。
本発明においては、前記衝突面側の側壁部の両角隅部の曲率半径Ｒを１０〜３０ｍｍとするのが良い。
最大ピーク荷重の飛躍的な低減効果と、押出し加工の容易さを考慮した結果、最も実用的な値である。
【００１２】
【発明の実施の形態】
次に図面を用いて本発明を具体的に説明する。なお、以下の図面においては判りやすく説明するため、各部の縮尺は必ずしも正確には描かれていない。
（第１の実施形態）
図１は本発明のバンパービームの第１の実施形態を示す断面図である。図に示すように本発明のバンパービーム１０は、断面形状が上壁部１と、上壁部１と対向する底壁部２と、上壁部１および底壁部２の両端部を連結する一対の側壁部３、４と、上壁部１および底壁部２の中間に設けられてこれら２つの部位を連結する連結リブ５とからなる“日の字型”を呈するように構成して剛性を確保するようにしている。このバンパービーム１０は、紙面左側の側壁部が衝突面側の側壁部３であり、矢印Ｆで示す衝突の際の衝撃力Ｆが加わる。紙面右側の側壁部が車体取付け面側の側壁部４であり、サイドメンバー６を介して車体７に取り付けられる。図１は、側壁部３，４の長さが上壁部１及び底壁部２の長さの２倍よりも短くて、上壁部１、底壁部２及び連結リブ５の厚さが全て等しい場合を示している。
【００１３】
ここで、図２は本発明のバンパービームの各部の寸法を示す図であり、側壁部の長さをＬ_１、上壁部の長さをＬ_２、衝突面側の側壁部の厚さをｔ_１、車体取付け面側の側壁部の厚さをｔ_２、上壁部及び底壁部の厚さをそれぞれｔ_３、ｔ_４、連結リブの厚さをｔ_５で示している。
この図２を用い上記の関係を説明すれば、Ｌ_１＜２Ｌ_２で、かつｔ_３＝ｔ_４＝ｔ_５の場合を示していることになる。
本実施形態では衝突面側の側壁部３の厚さを車体取付け面側の側壁部４の厚さよりも厚くして衝突エネルギーを受け止め、上壁部１、底壁部２、及び上壁部１と底壁部２との中間に設けられた連結リブ５とで衝撃エネルギーを分担して吸収するようになっている。
【００１４】
実用的な各部の厚さは、例えば上壁部１、底壁部２及び連結リブ５の厚さは２．０ｍｍ〜３．０ｍｍ、衝突面側の側壁部３の厚さは２．０ｍｍ〜４．５ｍｍ、車体取付け面側の側壁部４の厚さは２．０ｍｍ〜３．５ｍｍ程度が適当である。
各部の寸法を示した図２を用いて上記を説明すれば、本第１の実施形態においてはｔ_１＞ｔ_２、ｔ_３＝ｔ_４＝ｔ_５であり、各値の適正値は、ｔ_１＝２．０ｍｍ〜４．５ｍｍ、ｔ_２＝２．０〜３．５ｍｍ、ｔ_３＝ｔ_４＝ｔ_５＝２．０ｍｍ〜３．０ｍｍとなる。
【００１５】
図１は衝突面側の側壁部３及び車体取付け面側の側壁部４の長さが上壁部１及び底壁部２の長さの２倍よりも短い場合を示した。バンパービームの圧潰強度を調整する手段としては、図３に示すように、逆に衝突面側の側壁部３及び車体取付け面側の側壁部４の長さＬ_１を上壁部１及び底壁部２の長さＬ_２の２倍よりも長くすることも考えられる。この場合各部の厚さは、上記の場合と同様でよい。ただし、後に詳述するように隅部の曲率半径Ｒを変える必要がある。
【００１６】
本実施の形態においては、衝突面側の側壁部３の両角隅部と車体取付け面側の側壁部４の両角隅部は、それぞれ曲率半径Ｒ，ｒをもって湾曲して加工する必要がある。“日の字型”の断面の各角隅部に曲率半径を持たせることにより、衝突した瞬間に発生する最大荷重のピークを劇的に低下させることが可能となる。
曲率半径の大きさはごく小さくても最大荷重のピークを低下させる効果を有するが、材料の加工の観点からすれば板厚と同程度以上に大きくするのが実用的である。曲率半径の大きさが大きくなるほど最大荷重のピークを低下させる効果も高くなるが、曲率半径があまり大きくなっても効果は飽和する。適正な曲率半径の大きさは、“日の字型”の断面の長さに関係し、図１に示すように、衝突面側の側壁部３及び車体取付け面側の側壁部４の長さが上壁部１及び底壁部２の長さの２倍よりも短い場合には、衝突面側の側壁部の長さの０．１〜０．３倍の長さの曲率半径とするのが良い。すなわち図２においてＬ_１＜２Ｌ_２で、かつｔ_３＝ｔ_４＝ｔ_５の場合には、曲率半径Ｒは
Ｒ＝（０．１〜０．３）×Ｌ_１・・・・・・（１）
とする。
【００１７】
一方、図３に示すように、衝突面側の側壁部３及び車体取付け面側の側壁部４の長さが上壁部１及び底壁部２の長さの２倍よりも長い場合には、上壁部１及び底壁部２の長さの０．６〜１倍の長さの曲率半径とするのが良い。すなわち図２においてＬ_１＞２Ｌ_２で、かつｔ_３＝ｔ_４＝ｔ_５の場合には、曲率半径Ｒは
Ｒ＝（０．６〜１．０）×Ｌ_２・・・・・・（２）
とするのが適当である。
【００１８】
車体取付け面側の側壁部４の両角隅部の曲率半径ｒは、直接衝撃を受けないので加工精度も配慮して、側壁部４の板厚程度に僅かな曲率半径を与えておけばよい。各部の寸法を示した図２を用いて説明すれば、
ｒ＝（０．６〜１）×ｔ_２・・・・・・（３）
となる。
【００１９】
バンパービームを上記のように構成すれば衝突した瞬間に発生する最大荷重のピークを効果的に低下させることができる。
例えば、図１に示すように、図２に示す寸法図においてｔ_１＝４．５ｍｍ、ｔ_２＝３．５ｍｍ、ｔ_３＝ｔ_４＝ｔ_５＝２．６ｍｍ、Ｌ_１＝１００ｍｍ、Ｌ_２＝７５ｍｍの断面形状が“日の字型”をなしたアルミニウム合金製のバンパービームを押出し成形加工により作成し、長さ１００ｍｍに切断して試験片とし、図１の矢印で示す衝突方向に試験片を押し潰す圧壊試験を行って、衝突時の最大荷重と変位との関係を調べた。曲率半径Ｒは０ｍｍ，５ｍｍ，及び１０ｍｍとした。測定結果を図４に示す。
【００２０】
図４は衝突実験におけるバンパービームの変位量と潰し荷重の関係を示したものである。図に示すように衝突直後の変位量が１ｍｍに達する以前に最大荷重が発生し、その後はほぼ一定の潰し荷重で変形していく。図４の曲線ｊは“日の字型”バンパービームの上壁部両端の曲率半径Ｒを０（曲率半径ナシ）にした場合の変位量曲線であって、変位量が約０．５ｍｍ程度の時に２５０ｋＮの最大荷重が発生している。これに対して曲率半径Ｒを５ｍｍとした曲線ａや、曲率半径Ｒを１０ｍｍとした曲線ｂでは、変位量１ｍｍ前後の時に最大荷重が約１５０ｋＮ前後と大幅に低下して発生し、曲線はより矩形波に近づいている。
このように“日の字型”バンパービームの上壁部両端に曲率半径Ｒを付与することにより衝突時に発生する最大荷重を大幅に低減させることができ、サイドメンバーを損傷することなくバンパービームで衝突エネルギーを有効に吸収することができるので、乗員の安全確保に極めて有効となる。
【００２１】
図５は上記と同じ各部寸法のバンパービームについて上壁部両端の曲率半径Ｒを２０，３０，４０ｍｍに変化させて、同様な最大荷重の測定を行った結果を示している。図中曲線ｃは曲率半径Ｒが２０ｍｍの場合を、曲線ｄは曲率半径Ｒが３０ｍｍの場合を、曲線ｅは曲率半径Ｒが４０ｍｍの場合をそれぞれ示したものである。
図に示すとおり、曲率半径Ｒを大きくすると最大荷重は約１００ｋＮと一層低くなり、より矩形波に近づくものの、曲率半径Ｒが３０ｍｍを越えると最大荷重の低下はほぼ飽和してくる。従ってＲの上限値は４０ｍｍとするのが適当である。Ｒの下限値は最大荷重は約１００ｋＮ以下となる１０ｍｍ程度である。より好ましいＲの範囲は、前記（１）式で示されるＲ＝（０．１〜０．３）×Ｌ_１の範囲で選択すれば良く、実用上は１０〜３０ｍｍ程度である。
【００２２】
（第２の実施形態）
次に、第１の実施形態の変形として“日の字型”断面の上壁部１と底壁部２とは同じ厚さとし、連結リブ５の厚さを薄く変化させた場合の、最大荷重と変位との関係を図６に示す。
図６において、“日の字型”断面各部位の寸法はｔ_５＜ｔ_３＝ｔ_４とした以外は前記第１の実施例の場合と同様で、衝突側の側面部両端の曲率半径Ｒは２０ｍｍとした。図中曲線ｃは第１の実施形態の図５に示す上壁部と底壁部及び連結リブの各厚さが全て等しい（ｔ_５＝ｔ_３＝ｔ_４＝２．６ｍｍ）場合と同じである。また、図中曲線ｆは連結リブの厚さを１５％薄くして、ｔ_３＝ｔ_４＝２．６ｍｍ、ｔ_５＝２．２ｍｍとした場合であり、曲線ｇは連結リブの厚さを３０％薄くして、ｔ_３＝ｔ_４＝２．６ｍｍ、ｔ_５＝１．８ｍｍとした場合である。
図６に示すとおり、連結リブの厚さを上壁部及び底壁部の厚さよりも薄くした場合、薄肉化とともに最大荷重が低下する。これは衝力を受ける方向が連結リブに沿った方向であるため、連結リブの強度が弱くなって衝撃力を和らげるためと推測される。
連結リブの厚さをいろいろ変えたバンパービームを作成して衝突実験を繰り返した結果、連結リブの適正値は“日の字型”断面の側壁部の寸法によって最も影響を受けることが判明した。実験の結果、図２に示す各部寸法で説明すると、連結リブの厚さ（ｔ_５）の適正値は“日の字型”断面の側壁部ｔ_３（＝ｔ_４）との関係において、
ｔ_５＝（０．６〜１）×ｔ_３・・・・・・（４）
とするのが適当であることが判明した。
【００２３】
（比較例）
次に、比較のため、“日の字型”断面において、連結リブの厚さを上壁部及び底壁部の厚さよりも厚くした場合の例を図７に示す。
図７において、“日の字型”断面各部位の寸法はｔ_５＞ｔ_３＝ｔ_４とした以外は前記第１の実施例の場合と同様で、上壁部両端の曲率半径Ｒは２０ｍｍとした。図中曲線ｃは第１の実施形態の図５に示す連結リブの厚さと上壁部及び底壁部の厚さが等しい（ｔ_５＝ｔ_３＝ｔ_４＝２．６ｍｍ）場合と同じである。また、図中曲線ｈは上壁部の厚さを連結リブの厚さよりも１５％薄くして、ｔ_３＝ｔ_４＝２．２ｍｍ、ｔ_５＝２．６ｍｍとした場合であり、曲線ｉは上壁部の厚さを連結リブの厚さよりも３０％薄くして、ｔ_３＝ｔ_４＝１．８ｍｍ、ｔ_５＝２．６ｍｍとした場合である。
図７に示すとおり、側壁部の厚さを連結リブの厚さよりも薄くした場合、曲率半径Ｒの効果により衝突時に発生する最大荷重は低下するものの、薄肉化の程度によって最大荷重が変化することはない。これは側壁部の強度が弱くなって衝撃力を和らげるが、衝力を受ける位置が連結リブ部分であるため、連結リブの強度によって最大荷重が支配されるためと推測される。
【００２４】
次に側壁部と連結リブの厚さが等しい第１の実施形態の結果を表１に纏めてその効果を示す。
【００２５】
【表１】

【００２６】
表１の結果から、側壁部と連結リブの厚さが等しい場合には、最大荷重と平均荷重の比は、曲率半径Ｒが２０ｍｍの時に最も低くなり、Ｒが無い場合の半分程度となることが判る。曲率半径Ｒを５から４０ｍｍの範囲で付与すれば、最大荷重と平均荷重の比が低くなり、最大荷重と平均荷重の比が低いほど乗員の受ける身体的損傷を少なくすることが期待できる。
【００２７】
最後に、側壁部と連結リブの厚さを変化させた場合の第２の実施形態の結果と比較例の結果を表２に纏めてその効果を示す。
【００２８】
【表２】

【００２９】
表２の結果から、連結リブの厚さを側壁部の厚さよりも薄くした方が、衝突の際に発生する最大荷重を下げるためには効果的であることが判る。
【００３０】
【発明の効果】
本発明によれば、バンパービームの断面形状を詳細に検討した結果、衝撃を受ける面の厚さを厚くして剛性を高め、衝撃を受ける面の両端に曲率半径Ｒを付与した形状にしたので、衝突の際バンパービームの変形直後に発生する最大荷重が低くなり、乗員の受ける身体的損傷を少なくすることができるようになる。
本発明のバンパービームを装着した車両は、より安全性の高い車両といえる。
【図面の簡単な説明】
【図１】本発明の自動車用バンパービームの第１の実施形態の断面形状を示す図である。
【図２】本発明の自動車用バンパービームの各部の寸法を示す図である。
【図３】本発明の自動車用バンパービームの第２の実施形態の断面形状を示す図である。
【図４】第１の実施形態におけるバンパービームの変位量と潰し荷重との関係の一例を示す図である。
【図５】第１の実施形態におけるバンパービームの変位量と潰し荷重との関係の他の例を示す図である。
【図６】第２の実施形態におけるバンパービームの変位量と荷重の関係を示す図である。
【図７】比較例におけるバンパービームの変位量と荷重の関係のを示す図である。
【図８】従来の自動車用バンパービームの断面形状の一例を示す図である。
【図９】従来の自動車用バンパービームの断面形状の他の例を示す図である。
【図１０】図８に示す従来の自動車用バンパービームの変位量と荷重の関係を示す図である。
【符号の説明】
１，１１・・・・・・上壁部、２，１２・・・・・・底壁部、３・・・・・・衝突面側の側壁部、４・・・・・・車体取付け面側の側壁部、５，１５・・・・・・連結リブ、１０，２０，３０，４０・・・・・・バンパービーム、１３，１４・・・・・・側壁部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a bumper beam for reinforcing a bumper of an automobile.
[0002]
[Prior art]
2. Description of the Related Art In general, a bumper of an automobile generally includes a bumper beam that is connected to a vehicle body and maintains the strength of the bumper, and a resin skin material that is attached to the bumper beam to adjust the appearance of the vehicle body. The bumper beam has been reduced in weight in order to reduce fuel consumption, and in recent years, the use of light alloys has been increasing. For example, a bumper beam 30 shown as a cross-sectional view in FIG. 8 is an example of a bumper beam extruded from an aluminum alloy material and has a hollow structure extruded in a “sun-shaped” cross section. That is, the upper wall portion 11 and the bottom wall portion 12 which are parallel to each other, the

side wall portions

13 and 14 which are parallel to each other in a direction perpendicular to these, and the

side wall portions

13 and 14 which are parallel to the upper wall portion 11 and the bottom wall portion 12. Is formed by a connecting rib 15 provided at the center so as to divide it into two.
[0003]
The bumper beam 30 is actually attached to the front or rear surface of the vehicle 17 via the side member 16, and in the event of a collision, the side wall 13 on the collision surface side generates an impact force F from the direction of the left arrow in the figure. It is the face to receive. Therefore, the side wall 13 is formed to be the thickest among the members having the "sun-shaped" sectional structure. In the example of FIG. 8, the upper wall 11 and the bottom wall 12 and the connecting rib 15 are formed to have the same thickness, and have a structure in which the impact force from the left side of the figure is evenly received and the impact force is softened. Has become.
Such a bumper beam is made of a 7000 series high-strength aluminum alloy or the like for the purpose of weight reduction. Usually, a cushioning material made of a foam material or the like is attached to the bumper beam, and the surface is covered with a bumper cover.
[0004]
When a bumper beam receives an external impact due to a collision of a car, etc., it absorbs the impact energy by plastic deformation of the bumper beam material, which is important for avoiding damage to other members and ensuring the safety of the human body. It is a member.
By the way, there are two types of collisions of a vehicle: a wall-shaped obstacle collides with the entire surface of the bumper beam at a relatively high speed, and a columnar obstacle collides with a part of the wall of the bumper beam at a relatively low speed. There is a form.
In the former type of collision, the collision energy due to the collision is often large enough to cause injury to the occupant and buckling damage of the bumper beam mounting member, and the bumper beam gradually deforms and collapses, causing a large amount of collision. It is desired that the material can absorb energy.
On the other hand, in the latter type of collision, there are few cases in which the collision energy is large enough to cause injury to the occupant or damage to the mounting member, and the bumper beam is deformed and collapsed to absorb the collision energy rather than absorbing the collision energy. It is desired that the material has high rigidity that is difficult to deform.
[0005]
For the bumper beam, it is required to increase the bending rigidity of the profile and the amount of energy absorbed when bending, while reducing the weight. A proposal for improving these characteristics by improving the cross-sectional shape has been disclosed (for example, see Patent Document 1).
In this proposal, a bumper made of an aluminum alloy material having a rectangular cross-sectional shape that is uniform in the length direction and having both ends of a wall located on the vehicle body side so as to have a wall perpendicular to the collision direction is attached to the vehicle body. A bumper beam, which is a beam and has a corner R located on the vehicle body side of the aluminum alloy profile and having a radius R of 2.5 times or more the plate thickness, is disclosed.
More specifically, as shown in FIG. 9, the bumper beam 40 is made of an aluminum alloy material provided in the bumper cover, and the wall surface 41 a located on the vehicle body 42 side is connected to the vehicle body 42 via the side member 44. Supported. The above-mentioned aluminum alloy material is formed in a rectangular cross section having a uniform shape in the longitudinal direction, for example, a "Japanese" character, and a pair of

horizontal ribs

41b, 41b, and both ends of both

horizontal ribs

41b, 41b. The

vertical ribs

41a, 41a are connected, and the reinforcing ribs 41c are connected between the

vertical ribs

41a, 41a.
[0006]
The bumper beam 40 is provided so that the

vertical ribs

41a and 41a are perpendicular to the collision direction and the

horizontal ribs

41b and 41b are parallel to the collision direction. The

corners

41d, 41d on the vehicle body 42 side are curved with a radius R of 2.5 times or more the plate thickness in a range of 1/6 or less of the length of the

vertical ribs

41a, 41a. On the other hand, the corners 41e on the collision side of the bumper beam 40 are bent substantially at right angles with a radius r of about the plate thickness. Thus, at the time of a barrier collision, the

curved corners

41d, 41d are positioned at the starting point of buckling, thereby promoting buckling while suppressing the generated load and efficiently absorbing the collision energy. Has become. Further, at the time of a pole collision, a large generated load is generated by positioning the

curved corners

41d, 41d on the opposite side of the starting point of buckling. The reason that the radius R is limited to 1/6 or less of the length of the vertical ribs 41a is that if it exceeds 1/6, it becomes difficult to attach the side member 44 and the absorbed energy is reduced. .
According to this structure, it is possible to have both a characteristic capable of absorbing a large amount of collision energy by gradually deforming and collapsing and a characteristic of high rigidity that is difficult to be deformed by a collision load, which can cope with the above two collision modes. It is possible.
[0007]
[Patent Document 1]
JP-A-8-80789 (Page 1, FIG. 2)
[0008]
[Problems to be solved by the invention]
However, if the bumper beam is too strong, the buckling of the bumper beam and the side member, which is the mounting bracket of the vehicle body, will be damaged. The side members are damaged by the maximum load that occurs at the moment of the collision.
For example, in the case of a bumper beam whose all corners are bent at right angles as shown in the cross section in FIG. 8, the average load during the plastic deformation of the bumper beam by 3.5 to 4.5 mm due to collision is 50 kN as shown in FIG. However, a maximum load of 250 kN occurs at the maximum during plastic deformation of about 0.5 mm before the displacement of the bumper beam reaches 1 mm immediately after the collision, and thereafter it is deformed with a substantially constant crushing load I will do it. In this case, the maximum load reaches 5.88 times the average load.
If the maximum load can be reduced, the collision energy can be absorbed only by the deformation and collapse of the bumper beam without damaging the side members.
Conventionally, the relationship between the maximum load and the absorbed energy when the generated load is not accompanied by a significant change during the plastic deformation of the bumper beam at the maximum of 3.5 to 4.5 mm has been a problem. No attempt was made to lower
In order to ensure personal safety, it is important to minimize the peak of the maximum load generated at the moment of a collision as much as possible.
An object of the present invention is to provide a bumper beam structure that can minimize the peak of the maximum load generated at the moment of the collision as much as possible and can prevent damage to a side member that is a mounting bracket for the bumper beam. .
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, various examinations were made on the cross-sectional shape of the bumper beam of the ordinary passenger car. As a result, it was found that the side members were damaged when the crushing load applied to the 100 mm long bumper beam specimen exceeded 150 kN. . It was found that if the maximum load generated at the moment of the collision is suppressed to 150 kN or less, the collision energy can be absorbed without damaging the side members due to the plastic deformation of the bumper beam. It has also been found that if the structure of the bumper beam is configured such that the impact load generated in the latter half of the collision becomes too low, the energy absorption capacity of the bumper beam is reduced.
Therefore, in the crushing load-displacement curve shown in FIG. 10, if only the maximum peak is lowered to make the waveform closer to a rectangular waveform, the collision energy can be absorbed by plastic deformation of the bumper beam without damaging the side members. It was thought that a bumper beam having stable performance as an energy absorbing material could be obtained. Therefore, as a result of various examinations of the cross-sectional shape of the bumper beam, it was found that the above-mentioned object can be achieved by increasing the thickness of the member on the surface subjected to the impact and giving specific radii of curvature to both ends of the surface of the member subjected to the impact. The present invention has been found.
That is, in the bumper beam of the present invention, the cross-sectional shape is an upper wall portion, a bottom wall portion facing the upper wall portion, a pair of side wall portions connecting both ends of the upper wall portion and the bottom wall portion, and A connection rib provided between the wall portion and the bottom wall portion for connecting the two side wall portions, and the thickness of the side wall portion on the collision surface side is the thickness of the side wall portion on the vehicle body mounting surface side. And both corners of the side wall portion on the collision surface side are curved with a radius of curvature R of 0.1 to 0.3 times the length of the side wall portion on the collision surface side, and A bumper beam made of an aluminum alloy extruded hollow member whose both corners of the side wall portion on the surface side are curved with a radius of curvature r of 0.6 to 1 times the thickness of the side wall portion on the vehicle body mounting surface side; did. The cross-sectional shape the length L ₁ of the side wall portion of the collision surface side, is applied when less than twice the length L ₂ of the upper wall portion and bottom wall portion.
[0010]
On the other hand, the length L ₁ of the side wall portion, when longer than twice the length L ₂ of the upper wall portion and the bottom wall portion includes a top wall portion cross section, and a bottom wall portion opposed to the upper wall portion, A sun-shape comprising a pair of side walls connecting both ends of the upper wall and the bottom wall, and a connecting rib provided between the upper wall and the bottom wall and connecting the two side walls. The thickness of the side wall portion on the collision surface side is greater than the thickness of the side wall portion on the vehicle body attachment surface side, and both corners of the side wall portion on the collision surface side are 0.2 to 0 of the length of the bottom wall portion. .6 times as long as the radius of curvature, and both corners of the side wall portion on the vehicle body mounting surface side have a length of 0.6 to 1 times the thickness of the side wall portion on the vehicle body mounting surface side. The bumper beam is made of an extruded hollow member made of an aluminum alloy and curved with a radius of curvature.
By configuring the bumper beam as described above, it is possible to effectively reduce the peak of the maximum load generated at the moment of collision, absorb the collision energy with the bumper beam without damaging the side members, Damage to the occupant can be dramatically reduced.
[0011]
In the present invention, the thicknesses of the upper wall portion, the connection rib, and the bottom wall portion can be all equal.
When the thickness of the connecting rib is configured to be smaller than the thickness of the bottom wall, it is preferable that the thickness of the connecting rib be 0.6 to 1 times the thickness of the bottom wall.
By configuring the connecting ribs in this way, it is possible to have high rigidity and to dramatically reduce the maximum peak load generated at the time of collision.
In the present invention, the radius of curvature R at both corners of the side wall on the collision surface side is preferably set to 10 to 30 mm.
This is the most practical value as a result of taking into account the dramatic reduction effect of the maximum peak load and the ease of extrusion.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be specifically described with reference to the drawings. In the following drawings, the scale of each part is not always drawn accurately for easy understanding.
(1st Embodiment)
FIG. 1 is a sectional view showing a first embodiment of the bumper beam of the present invention. As shown in the figure, a bumper beam 10 of the present invention connects an upper wall 1 with a cross-sectional shape, a bottom wall 2 facing the upper wall 1, and both ends of the upper wall 1 and the bottom wall 2. It is configured so as to exhibit a “sun-shaped” composed of a pair of

side walls

3 and 4 and a connecting rib 5 provided between the upper wall 1 and the bottom wall 2 and connecting these two parts. The rigidity is ensured. In the bumper beam 10, the side wall on the left side of the drawing is the side wall 3 on the collision surface side, and an impact force F at the time of collision indicated by an arrow F is applied. The side wall on the right side of the drawing is the side wall 4 on the vehicle body mounting surface side, and is mounted on the vehicle body 7 via the side member 6. FIG. 1 shows that the length of the

side walls

3 and 4 is shorter than twice the length of the top wall 1 and the bottom wall 2, and the thickness of the top wall 1, the bottom wall 2 and the connecting rib 5 is small. All the cases are equal.
[0013]
Here, FIG. 2 is a diagram showing the dimensions of each part of the bumper beam of the present invention. The length of the side wall is L ₁ , the length of the upper wall is L ₂ , and the thickness of the side wall on the collision surface side is L. At t ₁ , the thickness of the side wall on the vehicle body mounting surface side is denoted by t ₂ , the thickness of the top wall and the bottom wall is denoted by t ₃ and t ₄ , and the thickness of the connecting rib is denoted by t ₅ .
Explaining the above relationship with reference to FIG. 2, the case where L ₁ <2L ₂ and t ₃ = t ₄ = t ₅ is shown.
In the present embodiment, the side wall 3 on the side of the collision surface is made thicker than the side wall 4 on the side of the mounting surface of the vehicle body to receive the collision energy, and the top wall 1, the bottom wall 2, and the top wall 1 are received. The impact energy is shared and absorbed by a connecting rib 5 provided between the bottom wall 2 and the bottom wall 2.
[0014]
Practical thicknesses of the upper wall portion 1, the bottom wall portion 2, and the connecting rib 5 are 2.0 mm to 3.0 mm, and the thickness of the side wall portion 3 on the collision surface side is 2.0 mm to 2.0 mm. The appropriate thickness is 4.5 mm, and the thickness of the side wall portion 4 on the vehicle body mounting surface side is about 2.0 mm to 3.5 mm.
The above will be described with reference to FIG. 2 showing the dimensions of each part. In the first embodiment, t ₁ > t ₂ , t ₃ = t ₄ = t ₅ , and the appropriate value of each value is t ₁ = 2.0 mm to 4.5 mm, t ₂ = 2.0 to 3.5 mm, and t ₃ = t ₄ = t ₅ = 2.0 mm to 3.0 mm.
[0015]
FIG. 1 shows a case where the length of the side wall portion 3 on the collision surface side and the length of the side wall portion 4 on the vehicle body mounting surface side are shorter than twice the length of the upper wall portion 1 and the bottom wall portion 2. As the means for adjusting the crushing intensity of the bumper beam, as shown in FIG. 3, the length L ₁ of the upper wall 1 and bottom wall of the impact surface side wall portion 3 and the side wall 4 of the vehicle body mounting surface of the opposite it is also conceivable to longer than twice the length L ₂ of part 2. In this case, the thickness of each part may be the same as in the above case. However, it is necessary to change the radius of curvature R of the corner as will be described later in detail.
[0016]
In the present embodiment, both corners of the side wall 3 on the collision surface side and both corners of the side wall 4 on the vehicle body mounting surface side need to be curved with curvature radii R and r, respectively. Providing a radius of curvature at each corner of the "sun" cross section can dramatically reduce the peak of the maximum load generated at the moment of collision.
Although the radius of curvature is very small, it has the effect of lowering the peak of the maximum load, but from the viewpoint of material processing, it is practical to increase the radius to the same or greater than the plate thickness. The effect of lowering the peak of the maximum load increases as the radius of curvature increases, but the effect saturates when the radius of curvature is too large. The appropriate radius of curvature is related to the length of the cross section of the "sunshade", and as shown in FIG. 1, the length of the side wall portion 3 on the collision surface side and the side wall portion 4 on the vehicle body mounting surface side. Is smaller than twice the length of the upper wall portion 1 and the bottom wall portion 2, the radius of curvature should be 0.1 to 0.3 times the length of the side wall portion on the collision surface side. Is good. That is, in FIG. 2, when L ₁ <2L ₂ and t ₃ = t ₄ = t ₅ , the radius of curvature R is R = (0.1 to 0.3) × L _1. 1)
And
[0017]
On the other hand, as shown in FIG. 3, when the length of the side wall portion 3 on the collision surface side and the side wall portion 4 on the vehicle body mounting surface side is longer than twice the length of the upper wall portion 1 and the bottom wall portion 2, The radius of curvature is preferably 0.6 to 1 times the length of the upper wall portion 1 and the bottom wall portion 2. That is, in FIG. 2, when L ₁ > 2L ₂ and t ₃ = t ₄ = t ₅ , the radius of curvature R is R = (0.6 to 1.0) × L _2. 2)
Is appropriate.
[0018]
The curvature radius r at both corners of the side wall portion 4 on the vehicle body mounting surface side may be given a slight radius of curvature approximately equal to the thickness of the side wall portion 4 in consideration of processing accuracy since direct impact is not received. With reference to FIG. 2 showing the dimensions of each part,
r = (0.6-1) × t ₂ (3)
It becomes.
[0019]
If the bumper beam is configured as described above, the peak of the maximum load generated at the moment of collision can be effectively reduced.
For example, as shown in FIG. 1, t ₁ = 4.5 mm, t ₂ = 3.5 mm, t ₃ = t ₄ = t ₅ = 2.6 mm, L ₁ = 100 mm, L _{2 in the} dimensions shown in FIG. A bumper beam made of an aluminum alloy having a cross-sectional shape of “sun-shaped” of 75 mm was formed by extrusion molding, cut into a length of 100 mm to form a test piece, and tested in the collision direction indicated by the arrow in FIG. A crush test was performed to crush the piece, and the relationship between the maximum load and the displacement at the time of collision was examined. The radius of curvature R was 0 mm, 5 mm, and 10 mm. FIG. 4 shows the measurement results.
[0020]
FIG. 4 shows the relationship between the displacement of the bumper beam and the crushing load in a collision experiment. As shown in the figure, the maximum load is generated before the displacement immediately after the collision reaches 1 mm, and thereafter, it deforms with a substantially constant crushing load. Curve j in FIG. 4 is a displacement amount curve when the curvature radii R at both ends of the upper wall portion of the “sun-shaped” bumper beam are set to 0 (no curvature radius), and the displacement amount is about 0.5 mm. Sometimes a maximum load of 250 kN occurs. On the other hand, in the curve a with the radius of curvature R of 5 mm and the curve b with the radius of curvature R of 10 mm, the maximum load is significantly reduced to about 150 kN when the displacement amount is about 1 mm, and the curves are more pronounced. Approaching a square wave.
By providing the radius of curvature R at both ends of the upper wall portion of the "sun-shaped" bumper beam in this manner, the maximum load generated at the time of collision can be significantly reduced, and the bumper beam can be used without damaging the side members. Since the collision energy can be effectively absorbed, it is extremely effective for ensuring the safety of the occupants.
[0021]
FIG. 5 shows the same maximum load measurement results obtained by changing the curvature radii R at both ends of the upper wall portion to 20, 30, and 40 mm for the bumper beams having the same dimensions as above. In the figure, a curve c shows a case where the radius of curvature R is 20 mm, a curve d shows a case where the radius of curvature R is 30 mm, and a curve e shows a case where the radius of curvature R is 40 mm.
As shown in the figure, when the radius of curvature R is increased, the maximum load is further reduced to about 100 kN, and the shape approaches a rectangular wave. However, when the radius of curvature R exceeds 30 mm, the decrease in the maximum load is almost saturated. Therefore, it is appropriate that the upper limit value of R is 40 mm. The lower limit value of R is about 10 mm at which the maximum load becomes about 100 kN or less. A more preferred range of R, the (1) may be selected within the range of R = (0.1 to 0.3) × _{L 1} represented by formula, practically is about 10 to 30 mm.
[0022]
(Second embodiment)
Next, as a modification of the first embodiment, the maximum load when the top wall 1 and the bottom wall 2 have the same thickness and the thickness of the connecting rib 5 is changed to be thinner in a “sun-shaped” cross section. FIG. 6 shows the relationship between the displacement and the displacement.
6, the cross-sectional dimension of each part "shaped date" t _{5 <t} 3 ₌ except that the t ₄ is the same as in the first embodiment, the radius of curvature R of the side surface portion at both ends of the collision-side Was 20 mm. The curve c in the figure is the same as the case of the first embodiment shown in FIG. 5 where the thicknesses of the top wall, the bottom wall, and the connecting rib are all equal (t ₅ = t ₃ = t ₄ = 2.6 mm). is there. Further, a curve f in the figure is a case where the thickness of the connecting rib is reduced by 15%, and t ₃ = t ₄ = 2.6 mm and t ₅ = 2.2 mm, and a curve g indicates the thickness of the connecting rib. In this case, the thickness is reduced by 30%, and t ₃ = t ₄ = 2.6 mm and t ₅ = 1.8 mm.
As shown in FIG. 6, when the thickness of the connecting rib is smaller than the thickness of the upper wall portion and the bottom wall portion, the maximum load decreases as the thickness decreases. This is presumed to be because the direction in which the impact is received is along the connecting rib, and the strength of the connecting rib is weakened to reduce the impact force.
A bumper beam with various thicknesses of the connecting ribs was prepared, and repeated collision experiments showed that the appropriate value of the connecting ribs was most affected by the dimensions of the side wall of the "sun-shaped" cross section. As a result of the experiment, to explain the dimensions of each part shown in FIG. 2, the appropriate value of the thickness (t ₅ ) of the connecting rib is determined in relation to the side wall part t ₃ (= t ₄ ) of the “sun-shaped” section.
t ₅ = (0.6 to 1) × t ₃ (4)
Was found to be appropriate.
[0023]
(Comparative example)
Next, for comparison, FIG. 7 shows an example in which the thickness of the connecting rib is larger than the thickness of the upper wall portion and the bottom wall portion in the “sun-shaped” cross section.
7, the cross-sectional dimension of each part "shaped date" t _5> t 3 ₌ except that the t ₄ is the same as in the first embodiment, the radius of curvature R of the upper wall portion at both ends is 20mm And The curve c in the figure is the same as the case of the first embodiment shown in FIG. 5 where the thickness of the connection rib is equal to the thickness of the upper wall and the bottom wall (t ₅ = t ₃ = t ₄ = 2.6 mm). is there. Further, a curve h in the figure is a case where the thickness of the upper wall portion is 15% thinner than the thickness of the connecting rib, and t ₃ = t ₄ = 2.2 mm and t ₅ = 2.6 mm. Is a case where the thickness of the upper wall portion is reduced by 30% from the thickness of the connecting rib, and t ₃ = t ₄ = 1.8 mm and t ₅ = 2.6 mm.
As shown in FIG. 7, when the thickness of the side wall portion is smaller than the thickness of the connecting rib, the maximum load generated at the time of collision decreases due to the effect of the radius of curvature R, but the maximum load changes depending on the degree of thinning. There is no. This is presumed to be due to the fact that the strength of the side wall portion is weakened and the impact force is moderated, but the maximum load is governed by the strength of the connecting rib because the position receiving the impact is the connecting rib portion.
[0024]
Next, the results of the first embodiment in which the thickness of the side wall portion and the thickness of the connecting rib are equal are summarized in Table 1 and the effect is shown.
[0025]
[Table 1]

[0026]
From the results in Table 1, when the thickness of the side wall portion and the connecting rib is equal, the ratio of the maximum load to the average load is the lowest when the radius of curvature R is 20 mm, and is about half that when there is no R. I understand. If the radius of curvature R is given in the range of 5 to 40 mm, the ratio of the maximum load to the average load is reduced, and it can be expected that the lower the ratio of the maximum load to the average load, the less the physical damage to the occupant.
[0027]
Finally, Table 2 summarizes the results of the second embodiment and the results of the comparative example when the thicknesses of the side wall portion and the connection rib are changed, and shows the effects thereof.
[0028]
[Table 2]

[0029]
From the results shown in Table 2, it can be seen that making the thickness of the connecting rib thinner than the thickness of the side wall is more effective in reducing the maximum load generated in the event of a collision.
[0030]
【The invention's effect】
According to the present invention, as a result of examining the cross-sectional shape of the bumper beam in detail, as a result of increasing the thickness of the impact-receiving surface to increase rigidity, the impact-receiving surface is formed to have a radius of curvature R at both ends of the impact-receiving surface. In addition, the maximum load generated immediately after the deformation of the bumper beam in the event of a collision is reduced, so that physical damage to the occupant can be reduced.
A vehicle equipped with the bumper beam of the present invention can be said to be a vehicle with higher safety.
[Brief description of the drawings]
FIG. 1 is a diagram showing a cross-sectional shape of a first embodiment of an automobile bumper beam of the present invention.
FIG. 2 is a view showing dimensions of each part of a bumper beam for an automobile of the present invention.
FIG. 3 is a view showing a cross-sectional shape of a second embodiment of the automotive bumper beam of the present invention.
FIG. 4 is a diagram illustrating an example of a relationship between a displacement amount of a bumper beam and a crushing load in the first embodiment.
FIG. 5 is a diagram illustrating another example of the relationship between the displacement amount of the bumper beam and the crushing load in the first embodiment.
FIG. 6 is a diagram illustrating a relationship between a displacement amount of a bumper beam and a load according to the second embodiment.
FIG. 7 is a diagram illustrating a relationship between a displacement amount of a bumper beam and a load in a comparative example.
FIG. 8 is a diagram showing an example of a cross-sectional shape of a conventional bumper beam for an automobile.
FIG. 9 is a view showing another example of a cross-sectional shape of a conventional bumper beam for an automobile.
FIG. 10 is a diagram showing a relationship between a displacement amount and a load of the conventional automobile bumper beam shown in FIG.
[Explanation of symbols]
1, 11 ... top wall, 2, 12 ... bottom wall, 3 ... side wall on the collision surface side, 4 ... body mounting surface Side wall part, 5, 15 ...

Connection rib

10, 20, 30, 40 ... Bumper beam, 13, 14 ... Side wall part

Claims

The cross-sectional shape is an upper wall portion, a bottom wall portion facing the upper wall portion, a pair of side wall portions connecting both ends of the upper wall portion and the bottom wall portion, and an intermediate portion between the upper wall portion and the bottom wall portion. A side face formed of a connecting rib for connecting the two side wall portions, wherein the side wall portion on the collision surface side is thicker than the side wall portion on the vehicle body mounting surface side, and the side wall on the collision surface side Corners are curved with a radius of curvature R of 0.1 to 0.3 times the length of the side wall on the collision surface side, and both corners of the side wall on the vehicle body mounting surface side Is formed of an extruded hollow member made of an aluminum alloy and curved with a radius of curvature r having a length of 0.6 to 1 times the thickness of the side wall portion on the vehicle body mounting surface side.

The cross-sectional shape is an upper wall portion, a bottom wall portion facing the upper wall portion, a pair of side wall portions connecting both ends of the upper wall portion and the bottom wall portion, and an intermediate portion between the upper wall portion and the bottom wall portion. A side face formed of a connecting rib for connecting the two side wall portions, wherein the side wall portion on the collision surface side is thicker than the side wall portion on the vehicle body mounting surface side, and the side wall on the collision surface side Both corners of the portion are curved with a radius of curvature of 0.2 to 0.6 times the length of the bottom wall, and both corners of the side wall on the vehicle body mounting surface side are attached to the vehicle body mounting surface. A bumper beam for an automobile, comprising an extruded hollow member made of an aluminum alloy and curved with a radius of curvature of 0.6 to 1 times the thickness of the side wall portion on the surface side.

3. The bumper beam for an automobile according to claim 1, wherein the thickness of the upper wall, the connecting rib, and the bottom wall are equal.

3. The bumper beam for an automobile according to claim 1, wherein a thickness of the connecting rib is 0.6 to 1 times a thickness of the bottom wall portion.

The bumper beam for an automobile according to any one of claims 1 to 4, wherein a radius of curvature (R) at both corners of the side wall on the collision surface side is 10 to 30 mm.