JP4216045B2

JP4216045B2 - Bumper beam for automobile

Info

Publication number: JP4216045B2
Application number: JP2002320452A
Authority: JP
Inventors: 敬治天野; 義也鈴木; 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: 2009-01-28
Anticipated expiration: 2022-11-01
Also published as: JP2004155230A

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は、自動車の車体に取り付けられるとともにバンパーの強度を保つ自動車用バンパービームであって、上壁部と、前記上壁部に対向する底壁部と、前記上壁部及び前記底壁部の両端部を連結する一対の側壁部と、前記上壁部及び前記底壁部の中間に設けられて前記一対の側壁部を連結する連結リブとから構成されるアルミニウム合金製の押し出し中空部材からなり、前記中空部材は、前記車体に取り付けられる車体取付け面とは反対側に位置する衝突面側の側壁部の厚さｔ _１が前記車体取付け面側の側壁部の厚さｔ _２よりも厚く、前記衝突面側の側壁部の幅方向の両側に位置する角隅部が前記一対の側壁部側の幅寸法Ｌ _１に対して０．１〜０．３倍の長さの曲率半径Ｒで湾曲し、前記車体取付け側の側壁部の幅方向の両側に位置する角隅部が前記車体取付け側の側壁部の厚さｔ _２の０．６〜１倍の長さの曲率半径ｒで湾曲した形状を有することを特徴とする。この中空部材の形状は、一対の側壁部側の幅寸法Ｌ_１が、上壁部及び底壁部側の幅寸法Ｌ_２の２倍よりも短い時に適用される。
【００１０】
一方、一対の側壁部側の幅寸法Ｌ_１が、上壁部及び底壁部側の幅寸法Ｌ_２の２倍よりも長い時には、前記中空部材は、前記車体に取り付けられる車体取付け面とは反対側に位置する衝突面側の側壁部の厚さｔ _１が前記車体取付け面側の側壁部の厚さｔ _２よりも厚く、前記衝突面側の側壁部の幅方向の両側に位置する角隅部が前記上壁部及び前記底壁部側の幅寸法Ｌ _２に対して０．２〜０．６倍の長さの曲率半径Ｒで湾曲し、前記車体取付け側の側壁部の幅方向の両側に位置する角隅部が前記車体取付け側の側壁部の厚さｔ _２の０．６〜１倍の長さの曲率半径ｒで湾曲した形状とする。
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側の幅寸法Ｌ _１が上壁部１及び底壁部２側の幅寸法Ｌ _２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、一対の側壁部３、４側の幅寸法をＬ_１、上壁部１及び底壁部２側の幅寸法を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は一対の側壁部側３、４の幅寸法が上壁部１及び底壁部２側の幅寸法の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、逆に一対の側壁部３、４側の幅寸法Ｌ_１を上壁部１及び底壁部２側の幅寸法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、一対の側壁部３、４側の幅寸法Ｌ _１が上壁部１及び底壁部２側の幅寸法Ｌ _２の２倍よりも短い場合には、一対の側壁部３、４側の幅寸法Ｌ _１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、一対の側壁部側３、４の幅寸法Ｌ _１が上壁部１及び底壁部２側の幅寸法Ｌ _２の２倍よりも長い場合には、上壁部１及び底壁部２側の幅寸法Ｌ _２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]
BACKGROUND OF THE INVENTION
The present invention relates to a bumper beam for reinforcing a bumper of an automobile.
[0002]
[Prior art]
In general, a bumper of an automobile is roughly constituted by 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 and adjusts the appearance of the vehicle body. The bumper beam has been reduced in weight to reduce fuel consumption, and in recent years, there have been an increasing number of examples made of a light alloy. For example, a bumper beam 30 shown as a cross-sectional view in FIG. 8 is an example of a bumper beam extruded with an aluminum alloy material, and has a hollow structure extruded into a “Japanese character” cross section. That is, the upper wall portion 11 and the bottom wall portion 12 that are parallel to each other, the

side wall portions

13 and 14 that are parallel to each other in the direction perpendicular thereto, and the

side wall portions

13 and 14 that are parallel to the upper wall portion 11 and the bottom wall portion 12. It is comprised from the connection rib 15 provided in the center so that can be divided 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 the side wall portion 13 on the collision surface side receives an impact force F from the direction of the left arrow in the figure in the event of a collision. It becomes a catching surface. Accordingly, the side wall portion 13 is formed to be the thickest among the members having the “day-shaped” cross-sectional structure. Further, in the example of FIG. 8, the upper wall portion 11 and the bottom wall portion 12 and the connecting rib 15 are made to have the same thickness, and the structure is such that the impact force from the left side of the figure is received evenly to soften the impact force. It has become.
Such a bumper beam is made of 7000 series high strength aluminum alloy or the like for the purpose of weight reduction. Usually, a bumper beam is provided with a cushioning material made of foam or the like, and the surface is covered with a bumper cover.
[0004]
Bumper beams are important for ensuring the safety of the human body while absorbing impact energy by plastic deformation of the bumper beam material when impact force is applied from the outside due to automobile collisions, etc., and avoiding damage to other members. It is a member.
By the way, in the form of a car collision, a wall-like obstacle collides with the entire surface of the bumper beam wall at a relatively high speed, and a columnar obstacle collides with a part of the wall surface 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 occupant injury and buckling damage to the bumper beam mounting member. It is desired to be able to absorb energy.
On the other hand, in the latter type of collision, there are few cases where there is a large collision energy that causes injury to the occupant or damage to the mounting member. It is desired that the material is hard to be deformed and rich in rigidity.
[0005]
Bumper beams are required to increase the bending rigidity of the shape 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 is made of an aluminum alloy shape having a uniform rectangular cross section in the length direction, and both ends of the wall surface located on the vehicle body side are attached to the vehicle body so as to have a wall surface perpendicular to the collision direction. There is disclosed a bumper beam which is a beam and has a corner portion located on the vehicle body side of the aluminum alloy shape member curved with a radius R which is 2.5 times or more the plate thickness.
Specifically, as shown in FIG. 9, the bumper beam 40 is made of an aluminum alloy profile provided in the bumper cover, and a wall surface 41 a located on the vehicle body 42 side is connected to the vehicle body 42 via the side member 44. It is supported. The aluminum alloy profile is formed in a rectangular cross-sectional shape that is uniform in the length direction, for example, a “day” shape, and is formed at both ends of the pair of

lateral ribs

41b and 41b and both

lateral ribs

41b and 41b. It consists of connected

vertical ribs

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

vertical ribs

41a, 41a.
[0006]
The bumper beam 40 is provided such 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 and 41d on the vehicle body 42 side are curved with a radius R of 2.5 times or more of the plate thickness in a range of 1/6 or less of the length of the

longitudinal ribs

41a and 41a. On the other hand, the

corners

41e and 41e on the collision side of the bumper beam 40 are bent at a substantially right angle with a radius r about the plate thickness. As a result, at the time of a barrier collision, the

curved corner portions

41d and 41d are positioned at the buckling starting point so as to promote buckling while suppressing the generated load and efficiently absorb the collision energy. It has become. Further, at the time of a pole collision, a large generated load is generated by positioning the

curved corner portions

41d and 41d on the opposite side of the buckling starting point. The reason why the radius R is limited to 1/6 or less of the length of the

longitudinal ribs

41a and 41a is that if it exceeds 1/6, the attachment to the side member 44 becomes difficult and the absorbed energy decreases. .
According to this structure, it is possible to combine the characteristics capable of absorbing a large amount of collision energy by gradually deforming and collapsing, and the characteristics rich in rigidity that are difficult to be deformed by a collision load, so as to correspond to the above two collision modes. It is supposed to be possible.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 8-80789 (first page, FIG. 2)
[0008]
[Problems to be solved by the invention]
However, if the bumper beam is too strong, the side member, which is the mounting bracket of the vehicle body, will be damaged along with the buckling of the bumper beam. Side members are damaged by the maximum load generated at the moment of impact.
For example, in a bumper beam whose full-angle 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 the collision is 50 kN as shown in FIG. However, a maximum load of 250 kN is generated during the plastic deformation of about 0.5 mm before the bumper beam displacement reaches 1 mm immediately after the collision, and then the deformation is performed with a substantially constant crushing load. I will do it. In this case, the maximum load reaches 5.88 times the average load.
If this 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 member.
Conventionally, the problem is the relationship between the maximum load and the absorbed energy when the generated load does not fluctuate significantly during the plastic deformation of the bumper beam up to 3.5 to 4.5 mm. No attempt has been made to lower it.
In order to ensure personal safety, it is important to minimize the peak of this maximum load that occurs at the moment of collision.
An object of the present invention is to provide a bumper beam structure that can reduce the peak of the maximum load generated at the moment of the collision as much as possible and prevent damage to a side member that is a mounting member of the bumper beam. .
[0009]
[Means for Solving the Problems]
As a result of various examinations of the cross-sectional shape of the bumper beam of a normal passenger car to solve the above-mentioned problem, it was found that the side member was damaged when the crushing load applied to the bumper beam specimen having a length of 100 mm 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 member due to the plastic deformation of the bumper beam. It has also been found that if the structure of the bumper beam is made so that the impact load generated in the second half of the collision becomes too low, the energy absorption capability of the bumper beam is reduced.
Therefore, in the crushing load-displacement curve shown in FIG. 10, if the waveform can be made closer to a rectangular waveform by reducing only the maximum peak, the collision energy can be absorbed by plastic deformation of the bumper beam without damaging the side member. Therefore, it was considered that a bumper beam having stable performance as an energy absorbing material can be obtained. Therefore, as a result of various examinations of the cross-sectional shape of the bumper beam, the above object can be achieved by increasing the thickness of the member on the impacted surface and giving a specific radius of curvature to both ends of the impacted member surface. The present invention has been found.
That is, the bumper beam of the present invention, together with attached to the vehicle body of the motor vehicle The vehicle bumper beam to maintain the strength of the bumper, the upper wall portion, a bottom wall portion opposed to the upper wall, the upper wall portion And a pair of side wall portions that connect both end portions of the bottom wall portion, and a connecting rib that is provided between the upper wall portion and the bottom wall portion and connects the pair of side wall portions . consists extruded hollow member, said hollow member, the vehicle body mounting surface to be attached to the vehicle body side wall portion of the thickness t ₁ of the side wall portion of the collision surface located opposite said body mounting surface thickness thicker than t _2, the length of 0.1 to 0.3 times the corner portion of the width dimension L ₁ of the pair of side wall portion located on both sides in the width direction of the side wall portion of the collision surface curvature curved at a radius R, the side walls of the vehicle body mounting side of the Corners located on both sides in the width direction and having the vehicle body mounting side of the side wall portion of the thickness t ₂ of 0.6 to 1 times the length shape curved with a radius of curvature r of the. The shape of this hollow member has a width dimension L ₁ of the pair of side wall portion side is applied when less than twice the width dimension of the upper wall portion and the bottom wall side L _2.
[0010]
On the other hand, the width L ₁ of the pair of side wall portion side, when longer than twice the width of the upper wall portion and the bottom wall side L _2, the hollow member includes a vehicle body mounting surface attached to the vehicle body greater than the thickness t ₂ of the side wall portion of the thickness t ₁ of the side wall portion of the collision surface located opposite said body mounting surface, corner positioned on both sides in the width direction of the side wall portion of the collision surface corner is curved with a radius of curvature R of the upper wall portion and 0.2 to 0.6 times as long as the width dimension L ₂ of the bottom wall portion, the width direction of the side wall portion of the vehicle body mounting side corner portions located on both sides and curved shape with a radius of curvature r of 0.6-1 times the length of the thickness t ₂ of the side wall portion of the vehicle body mounting side.
By configuring the bumper beam as described above, it is possible to effectively reduce the peak of the maximum load that occurs at the moment of collision, absorb the collision energy with the bumper beam without damaging the side member, Damage to passengers can be greatly reduced.
[0011]
In the present invention, the thicknesses of the upper wall portion, the connecting rib, and the bottom wall portion can all be made equal.
In the case where the thickness of the connecting rib is made thinner than the thickness of the bottom wall portion, the thickness of the connecting rib is preferably 0.6 to 1 times the thickness of the bottom wall portion.
By configuring the connecting rib in this way, the maximum peak load generated at the time of collision can be drastically reduced while having high rigidity.
In the present invention, the radius of curvature R at both corners of the side wall on the collision surface side is preferably 10 to 30 mm.
It is the most practical value as a result of considering the dramatic reduction effect of the maximum peak load and the ease of extrusion.
[0012]
DETAILED DESCRIPTION OF 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 necessarily accurately drawn for easy understanding.
(First embodiment)
FIG. 1 is a cross-sectional view showing a first embodiment of a bumper beam of the present invention. As shown in the figure, the bumper beam 10 of the present invention has a cross-sectional shape that connects an upper wall portion 1, a bottom wall portion 2 facing the upper wall portion 1, and both ends of the upper wall portion 1 and the bottom wall portion 2. A pair of

side wall portions

3 and 4 and a connecting rib 5 provided between the upper wall portion 1 and the bottom wall portion 2 to connect these two portions are configured so as to exhibit a “Japanese character shape”. The rigidity is ensured. In the bumper beam 10, the side wall portion on the left side of the drawing is the side wall portion 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 portion on the right side of the drawing is the side wall portion 4 on the vehicle body attachment surface side, and is attached to the vehicle body 7 via the side member 6. In FIG. 1, the width L ₁ on the

side

walls

3 and 4 side is shorter than twice the width L ₂ on the side of the top wall 1 and the bottom wall 2, and the top wall 1, the bottom wall 2, and the connection The case where the thickness of all the ribs 5 is equal is shown.
[0013]
Here, FIG. 2 is a diagram showing the dimensions of each part of the bumper beam of the present invention. The width dimension of the pair of

side wall parts

3 and 4 is L ₁ , and the width dimension of the upper wall part 1 and the bottom wall part 2 side. L ₂ , the thickness of the side wall portion on the collision surface side is t ₁ , the thickness of the side wall portion on the vehicle body mounting surface side is t ₂ , and the thicknesses of the upper wall portion and the bottom wall portion are t ₃ and t ₄ , respectively. It shows the thickness of at t _5.
The above relationship will be described with reference to FIG. 2 and shows a case where L ₁ <2L ₂ and t ₃ = t ₄ = t ₅ .
In this embodiment, the thickness of the side wall portion 3 on the collision surface side is made larger than the thickness of the side wall portion 4 on the vehicle body mounting surface side to receive the collision energy, and the upper wall portion 1, the bottom wall portion 2, and the upper wall portion 1 are received. And the connecting rib 5 provided in the middle of the bottom wall 2 share and absorb the impact energy.
[0014]
The thickness of each practical part is, for example, 2.0 mm to 3.0 mm for the top wall 1, bottom wall 2 and connecting rib 5, and 2.0 mm to the thickness for the side wall 3 on the collision surface side. The thickness of the side wall 4 on the side of the vehicle body mounting surface is suitably about 4.5 mm to 2.0 mm to 3.5 mm. The above description will be made with reference to FIG. 2 showing the dimensions of each part. In the first embodiment, t ₁ > t ₂ and 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, t ₃ = t ₄ = t ₅ = 2.0 mm to 3.0 mm.
[0015]
FIG. 1 shows a case where the width dimension of the pair of

side wall parts

3 and 4 is shorter than twice the width dimension of the upper wall part 1 and the bottom wall part 2 side . As the means for adjusting the crushing intensity of the bumper beam, as shown in FIG. 3, the width dimension of the width L ₁ of the pair of

side wall portions

3 and 4 side in the opposite upper wall 1 and a bottom wall portion 2 L ₂ It is also possible to make it longer than 2 times. In this case, the thickness of each part may be the same as in the above case. However, it is necessary to change the curvature radius R of the corner as will be described in detail later.
[0016]
In the present embodiment, both corners of the side wall portion 3 on the collision surface side and both corners of the side wall portion 4 on the vehicle body mounting surface side must be curved and processed with curvature radii R and r, respectively. By providing a radius of curvature at each corner of the “Sun-shaped” cross section, it is possible to dramatically reduce the peak of the maximum load that occurs at the moment of collision.
Even if the radius of curvature is very small, it has the effect of reducing the peak of the maximum load, but from the viewpoint of processing the material, it is practical to make it larger than the plate thickness. The larger the radius of curvature, the higher the effect of lowering the peak of the maximum load, but the effect is saturated even if the radius of curvature is too large. The size of the proper radius of curvature, related to the length of the cross-section of the "day-shaped", as shown in FIG. 1, the width L ₁ of the pair of

side wall portions

3 and 4 side upper wall portion 1 and If less than 2 times the width L ₂ of the bottom wall 2 side, and the radius of curvature of 0.1 to 0.3 times the length of the width dimension L ₁ of the pair of

side wall portions

3 and 4 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 width dimension L ₁ of the pair of

side wall portion

3, 4 is longer than twice the width L ₂ of the upper wall portion 1 and the bottom wall 2 side, top wall part amount may be 1 and 0.6 to 1 times the length of curvature radius of the width L ₂ of the bottom wall 2 side. 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]
Since the radius of curvature r at both corners of the side wall portion 4 on the vehicle body mounting surface side is not directly impacted, a slight radius of curvature should be given to the thickness of the side wall portion 4 in consideration of machining accuracy. If it demonstrates using FIG. 2 which showed the dimension 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 that occurs at the moment of collision can be effectively reduced.
For example, as shown in FIG. 1, in the dimensional diagram shown in FIG. 2, 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 = A bumper beam made of aluminum alloy with a cross-sectional shape of 75 mm in the form of a “Japanese character” was prepared by extrusion molding, cut to a length of 100 mm to obtain a test piece, and tested in the collision direction indicated by the arrow in FIG. A crushing test was conducted to crush the piece, and the relationship between the maximum load and displacement at the time of collision was investigated. The curvature radius R was 0 mm, 5 mm, and 10 mm. The measurement results are shown in FIG.
[0020]
FIG. 4 shows the relationship between the bumper beam displacement and the crushing load in the collision experiment. As shown in the figure, the maximum load is generated before the displacement immediately after the collision reaches 1 mm, and thereafter, the deformation is performed with a substantially constant crushing load. A curve j in FIG. 4 is a displacement curve when the curvature radius R of both ends of the upper wall portion of the “day-shaped” bumper beam is 0 (no curvature radius), and the displacement is approximately 0.5 mm. Sometimes a maximum load of 250 kN is generated. On the other hand, in the curve a having a curvature radius R of 5 mm and the curve b having a curvature radius R of 10 mm, the maximum load is greatly reduced to about 150 kN when the displacement is about 1 mm, and the curve is more Approaching a square wave.
In this way, the radius of curvature R is applied to both ends of the upper wall of the “sun-shaped” bumper beam, so that the maximum load generated during a collision can be greatly reduced, and the bumper beam can be used without damaging the side members. Since collision energy can be absorbed effectively, it is extremely effective in ensuring the safety of passengers.
[0021]
FIG. 5 shows the result of measuring the same maximum load by changing the radius of curvature R at both ends of the upper wall portion to 20, 30, and 40 mm for the bumper beams having the same dimensions as described above. In the figure, the curve c shows the case where the radius of curvature R is 20 mm, the curve d shows the case where the radius of curvature R is 30 mm, and the curve e shows the 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 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 of R is about 10 mm where the maximum load is about 100 kN or less. A more preferable range of R may be selected within the range of R = (0.1 to 0.3) × L _{1 represented by} the formula (1), and is practically about 10 to 30 mm.
[0022]
(Second Embodiment)
Next, as a modification of the first embodiment, the maximum load when the upper wall portion 1 and the bottom wall portion 2 of the “Japanese character” cross section have the same thickness and the thickness of the connecting rib 5 is changed thinly. FIG. 6 shows the relationship between the displacement and the displacement.
In FIG. 6, the dimensions of each part of the “sun-shaped” cross section are the same as those in the first embodiment except that t ₅ <t ₃ = t _4. Was 20 mm. Curve c in the figure is the same as the case where the thicknesses of the upper wall portion, the bottom wall portion, and the connecting rib shown in FIG. 5 of the first embodiment are all equal (t ₅ = t ₃ = t ₄ = 2.6 mm). is there. Curve f in the figure is the 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 curve g shows the thickness of the connecting rib. This is a case where 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 made thinner than the thickness of the upper wall portion and the bottom wall portion, the maximum load is reduced as the thickness is reduced. This is presumed to be because the direction of receiving the impulsive force is the direction along the connecting rib, so that the strength of the connecting rib is weakened to reduce the impact force.
As a result of repeated collision experiments with bumper beams with various thicknesses of the connecting ribs, it was found that the appropriate value of the connecting ribs was most affected by the size of the side wall of the “Japanese character” cross section. As a result of the experiment, the dimensions of each part shown in FIG. 2 will be described. The appropriate value of the thickness (t ₅ ) of the connecting rib is related to the side wall part t ₃ (= t ₄ ) of the “day-shaped” cross section.
t ₅ = (0.6-1) × t ₃ (4)
It turned out 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 “day-shaped” cross section.
In FIG. 7, the dimensions of each part of the “sun-shaped” cross section are the same as those in the first embodiment except that t ₅ > t ₃ = t _4, and the radius of curvature R at both ends of the upper wall portion is 20 mm. It was. Curve c in the figure is the same as the case where the thickness of the connecting rib shown in FIG. 5 of the first embodiment is equal to the thickness of the upper wall portion and the bottom wall portion (t ₅ = t ₃ = t ₄ = 2.6 mm). is there. 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 the case where the thickness of the upper wall portion is 30% thinner than 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 is made thinner than the thickness of the connecting rib, the maximum load generated at the time of collision is reduced 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 presumably because the strength of the side wall portion is weakened and the impact force is reduced, but the position where the impact force is received is the connecting rib portion, and therefore the maximum load is governed by the strength of the connecting rib.
[0024]
Next, the results of the first embodiment in which the thickness of the side wall portion and the connecting rib are equal are summarized in Table 1, and the effect is shown.
[0025]
[Table 1]

[0026]
From the results of Table 1, when the thickness of the side wall 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 applied in the range of 5 to 40 mm, the ratio of the maximum load to the average load becomes low, and the lower the ratio of the maximum load and the average load, it can be expected that the physical damage received by the passenger is reduced.
[0027]
Finally, Table 2 summarizes the results of the second embodiment and the results of the comparative example when the thickness of the side wall portion and the connecting rib is changed.
[0028]
[Table 2]

[0029]
From the results in Table 2, it can be seen that it is more effective to reduce the maximum load generated at the time of collision when the thickness of the connecting rib is smaller than the thickness of the side wall.
[0030]
【The invention's effect】
According to the present invention, as a result of detailed examination of the cross-sectional shape of the bumper beam, the thickness of the impacted surface is increased to increase the rigidity, and the curvature radius R is given to both ends of the impacted surface. In the event of a collision, the maximum load generated immediately after the deformation of the bumper beam is reduced, and the 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 safer vehicle.
[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 diagram showing dimensions of each part of a bumper beam for automobiles according to the present invention.
FIG. 3 is a diagram showing a cross-sectional shape of a second embodiment of a bumper beam for an automobile according to 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 showing 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 showing a relationship between a displacement amount of a bumper beam and a load in the second embodiment.
FIG. 7 is a diagram showing 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 automobile bumper beam.
FIG. 9 is a diagram showing another example of a cross-sectional shape of a conventional automobile bumper beam.
10 is a diagram showing the relationship between the amount of displacement and load of the conventional bumper beam for an automobile shown in FIG.
[Explanation of symbols]
1, 11 ········ Upper wall portion, 2, 12 ······· Bottom wall portion, 3 ······ Side wall portion on the collision surface side Side wall portion, 5, 15 ···

Connection ribs

10, 20, 30, 40 ··· Bumper beam, 13, 14 ··· Side wall portion

Claims

Together is attached to the vehicle body by a motor vehicle bumper beam to maintain the strength of the bumper, the upper wall portion, a bottom wall portion opposed to the upper wall portion, both end portions of the upper wall portion and the bottom wall portion It consists of an extruded hollow member made of aluminum alloy composed of a pair of side wall parts to be connected, and a connecting rib provided in the middle of the upper wall part and the bottom wall part to connect the pair of side wall parts ,
Said hollow member, the vehicle body mounting surface to be attached to the vehicle body thicker opposite the thickness of the sidewall portion of the collision surface located on the side t ₁ than the vehicle body mounting the thickness of the sidewall portion of the surface t _2, the corners located on both sides in the width direction of the side wall portion of the collision surface side with respect to the width dimension L ₁ of the pair of side wall portion side curved at 0.1 to 0.3 times the length of the radius of curvature R a shape corners located on both sides in the width direction of the side wall portion of the vehicle body mounting side is curved in 0.6-1 times the length of the radius of curvature r of the vehicle body mounting the thickness of the side wall portion of the side t ₂ A bumper beam for automobiles, characterized by comprising:

Together is attached to the vehicle body by a motor vehicle bumper beam to maintain the strength of the bumper, the upper wall portion, a bottom wall portion opposed to the upper wall portion, both end portions of the upper wall portion and the bottom wall portion It consists of an extruded hollow member made of aluminum alloy composed of a pair of side wall parts to be connected, and a connecting rib provided in the middle of the upper wall part and the bottom wall part to connect the pair of side wall parts ,
Said hollow member, the vehicle body mounting surface to be attached to the vehicle body thicker opposite the thickness of the sidewall portion of the collision surface located on the side t ₁ than the vehicle body mounting the thickness of the sidewall portion of the surface t _2, the The corner radius located on both sides in the width direction of the side wall portion on the collision surface side is a curvature radius of 0.2 to 0.6 times the length L ₂ on the upper wall portion and the bottom wall portion side. curved at R, the vehicle body mounting side 0.6-1 times the length of the radius of curvature r of the thickness t ₂ of the corner portion located on both sides in the width direction of the side wall portion is the vehicle body mounting side of the side wall portion of the A bumper beam for automobiles, characterized by having a curved shape .

The automobile bumper beam according to claim 1 or 2, wherein the upper wall portion, the connecting rib, and the bottom wall portion have the same thickness.

The automobile bumper beam according to claim 1 or 2, wherein a thickness of the connecting rib is 0.6 to 1 times a thickness of the bottom wall portion.

The automobile bumper beam according to any one of claims 1 to 4, wherein a radius of curvature R of each corner portion of the side wall portion on the collision surface side is 10 to 30 mm.