JP3572459B2

JP3572459B2 - Body front structure

Info

Publication number: JP3572459B2
Application number: JP2001371738A
Authority: JP
Inventors: 秀司佐伯
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 2001-12-05
Filing date: 2001-12-05
Publication date: 2004-10-06
Anticipated expiration: 2021-12-05
Also published as: JP2003170860A

Description

【０００１】
【発明の属する技術分野】
本発明は、自動車の車体前部構造に関する。
【０００２】
【従来の技術】
車両の衝突対策としては、車体前部のサイドメンバを軸圧潰させることにより衝突エネルギーを吸収するようにしており、例えば特開２００１−１５８３７７号公報にその車体前部構造が示されている。
【０００３】
この車体前部構造は、多角形断面を有するサイドメンバ前部の壁部にビードを配置することにより、サイドメンバに軸方向入力が作用した際に軸圧潰を前方から促進して、衝突エネルギーを吸収するようにしたものである。
【０００４】
【発明が解決しようとする課題】
しかしながら、かかる従来の車体前部構造では、サイドメンバに軸方向に入力する衝突荷重に対してはエネルギー吸収を良好に行うことができるが、この衝突が車両片側のみのオフセット衝突である場合は、オフセット衝突された片側のサイドメンバのみの前端部が変形して車両方向に後退することになる。
【０００５】
このため、バンパーレインフォースとサイドメンバとの間には、バンパーレインフォースが斜めになるような塑性ヒンジが形成され、非衝突側のサイドメンバへの入力分散効率が低下してしまい、オフセット衝突時における車体の変形量を抑制する為の重量投資が増して車体重量の増加が懸念される。
【０００６】
そこで、本発明は、いかなる方向からの前面衝突にあっても、衝突荷重を両側のサイドメンバに効果的に分散することができて、衝突エネルギーの吸収効率を高められる車体前部構造を提供するものである。
【０００７】
【課題を解決するための手段】
請求項１の発明にあっては、フロントコンパートメントの左右両側部に車体前後方向に配設したサイドメンバに車両ユニット部品を搭載するための補強部分を設け、これらサイドメンバの前端に跨って車幅方向に延在するバンパーレインフォースを結合した車体前部構造において、
前記サイドメンバの前記補強部分から前方となるサイドメンバ前方領域に、長手方向に連なる仮想断面の前部と後部に発生する最大応力が、前部よりも後部が大きくなる強度となるような強度調整手段を設けたことを特徴としている。
【０００８】
請求項２の発明にあっては、請求項１に記載の車体前部構造において、前記強度調整手段による最大応力の上限値を、サイドメンバを構成する素材の降伏強度を基準に設定したことを特徴としている。
【０００９】
請求項３の発明にあっては、請求項１，２に記載の車体前部構造において、前記強度調整手段は、前記サイドメンバ前方領域の板厚分布を長手方向に変化させたサイドメンバ板厚変化構造であることを特徴としている。
【００１０】
請求項４の発明にあっては、請求項３に記載の車体前部構造において、前記サイドメンバ板厚変化構造は、板厚の異なる複数の板材をそれらの板厚が段階的に変化するように接合した複合パネル材を、板厚の変化方向が長手方向となるようにして構成したことを特徴としている。
【００１１】
請求項５の発明にあっては、請求項１，２に記載の車体前部構造において、前記強度調整手段は、前記サイドメンバ前方領域の閉断面内に長手方向に適宜間隔をもって複数の仕切り板を配置し、各仕切り板の板厚を前方に行くに従って増厚するようにサイドメンバの長手方向に変化させた仕切り板厚変化構造であることを特徴としている。
【００１２】
請求項６の発明にあっては、請求項１〜５に記載の車体前部構造において、前記強度調整手段は、前記サイドメンバ前方領域の断面寸法を長手方向に変化させた断面寸法変化構造であることを特徴としている。
【００１３】
請求項７の発明にあっては、請求項１，２に記載の車体前部構造において、押出し板厚や押出し断面寸法が押出し方向に連続して変化する押出し材によりサイドメンバ前方領域を形成して、該サイドメンバ前方領域の板厚変化または断面寸法を変化させ、若しくは板厚と断面寸法の両者を変化させて強度調整手段を構成したことを特徴としている。
【００１４】
請求項８の発明にあっては、請求項１〜７に記載の車体前部構造において、前記バンパーレインフォースを閉断面構造とし、この閉断面となったバンパーレインフォースの部材断面の車両上下方向軸に対する断面二次モーメントの断面係数Ｚを、サイドメンバ前部の圧壊時最大反力Ｆｍａｘと、サイドメンバ前方領域のスパンＬに対するバンパーレインフォース構成素材の降伏応力σｙ−ｂｍｐｒの商と、の積より大きく（Ｚ＞Ｆｍａｘ×Ｌ／σｙ−ｂｍｐｒ）設定するとともに、バンパーレインフォースの結合部強度Ｓｊｏｉｎｔを、サイドメンバ前方領域のスパンＬとサイドメンバ前部の圧壊時最大反力Ｆｍａｘとの積より大きく（Ｓｊｏｉｎｔ＞Ｌ×Ｆｍａｘ）設定したことを特徴としている。
【００１５】
請求項９の発明にあっては、請求項１〜８に記載の車体前部構造において、前記左右のサイドメンバのサイドメンバ前方領域は、それぞれ車体前後方向に直状に形成して相互に平行に配置したことを特徴としている。
【００１６】
【発明の効果】
請求項１に記載の発明によれば、車両前方から衝突荷重が入力した際に、サイドメンバ前方領域に設けた強度調整手段によって、このサイドメンバ前方領域の後方から前方に向かって圧壊が誘発され、その圧壊をサイドメンバ前方領域の前端部まで持続的に伝播させて、衝突エネルギーの吸収効率を高めることができる。
【００１７】
また、このときサイドメンバの圧壊はサイドメンバ前方領域の後方から誘発されるため、バンパーレインフォースに連結したサイドメンバの前端部の剛性は高く保持されて、バンパーレインフォースとサイドメンバとの取付け角度は一定に保持される状態にある。
【００１８】
従って、オフセット衝突時に車両片側に衝突荷重が入力した場合に、衝突側のサイドメンバに軸方向入力が作用し、この軸方向入力によってバンパーレインフォースおよびこのバンパーレインフォースと非衝突側のサイドメンバの連結部にそれぞれモーメントを発生させることができるため、結果的にバンパーレインフォースは車両後方に平行移動する状態となって、前記非衝突側のサイドメンバにも軸方向入力を作用させることができるようになり、衝突による荷重分散を効果的に行って衝突エネルギーの吸収効率を高めることができる。
【００１９】
請求項２に記載の発明によれば、請求項１の発明の効果に加えて、前記強度調整手段による最大応力の上限値を、サイドメンバを構成する素材の降伏強度を基準に設定したので、サイドメンバの前端部への入力時には、先ず、最大応力を大きくしたサイドメンバ前方領域の後部が素材の降伏域に達して塑性変形が生じるため、衝突時にはサイドメンバ前方領域の後部から圧壊をより確実に誘発させることができる。
【００２０】
請求項３に記載の発明によれば、請求項１，２の発明の効果に加えて、前記強度調整手段を、前記サイドメンバ前方領域の板厚分布を長手方向に変化させたサイドメンバ板厚変化構造としたので、衝突荷重がサイドメンバに入力した際に、サイドメンバ前方領域の長手方向に連なる仮想断面で発生する最大応力の制御がし易くなり、ひいては強度バランスの調整が容易となって、衝突時におけるサイドメンバ前方領域の後端部からの圧壊をより確実に誘発させることができる。
【００２１】
請求項４に記載の発明によれば、請求項３の発明の効果に加えて、前記サイドメンバ板厚変化構造を、板厚の異なる複数の板材をそれらの板厚が段階的に変化するように接合した複合パネル材を、板厚の変化方向が長手方向となるようにして構成したので、サイドメンバ前方領域の長手方向に連なる仮想断面で発生する最大応力の制御を近似的に行って、サイドメンバ前方領域の後端部からの圧壊を支障無く誘発することができるとともに、このような強度調整手段を備えたサイドメンバ前方領域を容易に形成することができる。
【００２２】
請求項５に記載の発明によれば、請求項１，２の発明の効果に加えて、前記強度調整手段を、前記サイドメンバ前方領域の閉断面内に長手方向に適宜間隔をもって複数の仕切り板を配置し、各仕切り板の板厚を前方に行くに従って増厚するようにサイドメンバの長手方向に変化させた仕切り板厚変化構造としたので、衝突荷重がサイドメンバの前端部に入力した際に、サイドメンバ前方領域の長手方向に連なる仮想断面で発生する最大応力の制御を各仕切り板で行うことができ、ひいては強度バランスの調整が容易となって、衝突時におけるサイドメンバ前方領域の後端部からの圧壊を確実に誘発することができる。
【００２３】
請求項６に記載の発明によれば、請求項１〜５の発明の効果に加えて、強度調整手段を、前記サイドメンバ前方領域の断面寸法を長手方向に変化させた断面寸法変化構造としたので、衝突荷重がサイドメンバに入力した際に、サイドメンバ前方領域の長手方向に連なる仮想断面で発生する最大応力の制御がし易くなり、ひいては強度バランスの調整が容易となって、衝突時におけるサイドメンバ前方領域の後端部からの圧壊をより確実に誘発させることができるとともに、板厚に比較して部材断面定数への感度が高い断面寸法を変化することで、サイドメンバのより一層の軽量化を図ることができる。
【００２４】
請求項７に記載の発明によれば、請求項１，２の発明の効果に加えて、サイドメンバ前方領域を、押出し板厚や押出し断面寸法が押出し方向に連続して変化する押出し材により形成して強度調整手段を構成するようにしたので、板厚分布または断面寸法を長手方向に自在に調整することができるとともに、その変化を連続的に行うことができるため、板厚変化を高精度に行えてサイドメンバ前方領域の長手方向に連なる仮想断面で発生する最大応力を精度良く調整することができるとともに、より一層の構造合理化および軽量化を図ることができる。
【００２５】
請求項８に記載の発明によれば、請求項１〜７の発明の効果に加えて、閉断面となったバンパーレインフォースの部材断面の車両上下方向軸に対する断面二次モーメントの断面係数Ｚを、サイドメンバ前部の圧壊時最大反力Ｆｍａｘ、サイドメンバ前方領域のスパンＬ、バンパーレインフォース構成素材の降伏応力σｙ−ｂｍｐｒに対してＺ＞Ｆｍａｘ×Ｌ／σｙ−ｂｍｐｒとして設定するとともに、バンパーレインフォースの結合部強度Ｓｊｏｉｎｔを、Ｓｊｏｉｎｔ＞Ｌ×Ｆｍａｘとして設定したので、バンパーレインフォース自体の剛性を高く維持して折れを抑制するとともに、バンパーレインフォースとサイドメンバとの結合強度を十分に確保して一定の角度を保持できることにより、オフセット衝突時に非衝突側のサイドメンバへの荷重分散を効率良く行うことができる。
【００２６】
請求項９に記載の発明によれば、請求項１〜８の発明の効果に加えて、左右のサイドメンバのサイドメンバ前方領域を、車体前後方向に直状に形成して相互に平行に配置したので、フルラップ衝突時は勿論のこと、オフセット衝突に対してもサイドメンバ前方領域を後端部から持続的に圧壊させることができ、良好なエネルギー吸収特性を確保することができる。
【００２７】
【発明の実施の形態】
以下、本発明の実施形態を図面と共に詳述する。
【００２８】
（第１実施形態）
図１〜図１０は本発明の車体前部構造の第１実施形態を示し、図１は本発明の対象とする自動車の外観斜視図、図２は車体前部右側の骨格構造を示す略示的平面説明図、図３はサイドメンバ前方領域の斜視図、図４は図３中Ａ−Ａ線に沿った拡大断面図、図５は強度調整手段の入力形態モデルを示す説明図、図６は強度調整手段の概念を示す応力分布図、図７は前方からの衝突荷重の入力形態を示す車体前部右側の略示的平面説明図、図８はサイドメンバの変形モードを示す説明図、図９はオフセット衝突時の荷重分散形態を示す車体前部の略示的平面説明図、図１０はオフセット衝突時におけるサイドメンバの変形モードを示す車体前部の略示的平面説明図である。
【００２９】
本実施形態の車体前部構造は図１に示す車体１０のフロントコンパートメントＦ・Ｃに適用され、その骨格構造は図２に示すように、左右両側部に車体前後方向に直状に配設したサイドメンバ１１を備え、これらサイドメンバ１１は平行に配置されており、かつ、それぞれのサイドメンバ１１の前端部に跨って図外のバンパーの骨格を成すバンパーレインフォース１２を結合してある。
【００３０】
また、それぞれのサイドメンバ１１の後方にはダッシュパネル１７からフロアパネル１８の下面側に廻り込むエクステンションサイドメンバ１３を連設してあり、それぞれのエクステンションサイドメンバ１３の車幅方向外側には略平行にサイドシル１４を配設してあって、これらエクステンションサイドメンバ１３とサイドシル１４のそれぞれの前端部をアウトリガー１５で結合してある。
【００３１】
前記各サイドメンバ１１とエクステンションサイドメンバ１３の連設部間に跨ってダッシュクロスメンバ１６を結合してある。
【００３２】
前記サイドメンバ１１の後側部には前輪２０を支持するサスペンションアーム２１が、直接若しくは図外のサスペンションメンバなどを介して取り付けられるとともに、左右のサイドメンバ１１間には車両ユニット部品としてのエンジン等のパワーユニット３０がマウントブラケット３１を介して搭載される。
【００３３】
サイドメンバ１１には、図３に示すように前記マウントブラケット３１の取付部分に、パワーユニット３０を支持するのに十分な強度を備えた補強部分１１Ｒ（図３中梨地部分で示す）が形成される。
【００３４】
つまり、サイドメンバ１１は、図３に示したように平板帯状の第１プレート１１ａに、断面コ字状の第２プレート１１ｂの両側フランジ部をスポット溶接などで固設することにより閉断面構造として形成されており、前記補強部分１１Ｒは内周面に補強プレートを接合配置する等により形成される。
【００３５】
ここで、本実施形態では前記サイドメンバ１１の前記補強部分１１Ｒから前方となるサイドメンバ前方領域１１Ｆに、長手方向に連なる仮想断面Ｉａ，Ｉｂ…Ｉｅの前部と後部に発生する最大応力が、前部よりも後部が大きくなる強度となるような強度調整手段としてのサイドメンバ板厚変化構造５０を構成し、前記サイドメンバ前方領域１１Ｆの板厚分布を長手方向に変化させてある。
【００３６】
即ち、サイドメンバ板厚変化構造５０は、図４に示すようにサイドメンバ前方領域１１Ｆの前端方向から板厚ｔ１，ｔ２…ｔ６の異なる複数の板材５１ａ，５１ｂ…５１ｆを、それらの板厚が前方から後方に向かって段階的に減厚変化（ｔ１＞ｔ２＞…＞ｔ６）するように全周溶接して接合した複合パネル材５２で構成している。
【００３７】
つまり、前記板材５１ａ，５１ｂ…５１ｆでは板材５１ｆが最も薄肉化されており、この板材５１ｆが前記補強部分１１Ｒに配置されるが、勿論、この補強部分１１Ｒは上述したようにパワーユニット３０を支持するに十分な強度を備えている。
【００３８】
また、このサイドメンバ前方領域１１Ｆは、図５に示すようにサイドメンバ前方領域１１Ｆの前端部に、前方からの衝突荷重Ｆが静的に作用した場合に、サイドメンバ板厚変化構造５０における最大応力の上限値を、サイドメンバ１１を構成する素材の降伏強度を基準に設定し、図６に示すように各板材５１ａ，５１ｂ，５１ｃ…５１ｆに対する降伏強度σ（ｙ）の分布が得られるようにしてある。
【００３９】
ところで、前記サイドメンバ１１の前端から各面を延設したフランジ部１１ｃ，１１ｄ，１１ｆ，１１ｅのうち、上下二面から延設したフランジ部１１ｃ，１１ｄはバンパーレインフォース１２の上下面１２ａ，１２ｂに溶接されるとともに、サイドメンバ１１の左右二面から延設したフランジ部１１ｅ，１１ｆはバンパーレインフォース１２の後面１２ｃに溶接されて、バンパーレインフォース１２とサイドメンバ１１との連結強度を高めるようになっている。
【００４０】
ここで、閉断面構造としたバンパーレインフォース１２の部材断面の車両上下方向軸に対する断面二次モーメントの断面係数をＺ、サイドメンバ１１前部の圧壊時最大反力をＦｍａｘ、サイドメンバ前方領域１１ＦのスパンをＬ、バンパーレインフォース１２の構成素材の降伏応力をσｙ−ｂｍｐｒとした場合に、次の式１を満足するように構成してある。
【００４１】
Ｚ＞Ｆｍａｘ×Ｌ／σｙ−ｂｍｐｒ ……式１
つまり、前記断面係数Ｚを、前記圧壊時最大反力Ｆｍａｘと、前記スパンＬに対する前記降伏応力σｙ−ｂｍｐｒの商と、の積より大きく設定してある。
【００４２】
また、これと同時にバンパーレインフォース１２の結合部強度をＳｊｏｉｎｔとすると、次の式２を満足する構成となっている。
【００４３】
Ｓｊｏｉｎｔ＞Ｌ×Ｆｍａｘ ……式２
つまり、前記結合部強度Ｓｊｏｉｎｔを、前記スパンＬと前記圧壊時最大反力Ｆｍａｘとの積より大きく設定してある。
【００４４】
（作用）
以上の構成によりこの第１実施形態の車体前部構造によれば、図７に示すように車両前方から衝突荷重Ｆが入力した際に、サイドメンバ板厚変化構造５０によって先ず、図８に示すようにサイドメンバ前方領域１１Ｆの後方に圧壊Ｋが発生し、この圧壊Ｋが前方に向かって誘発され、その圧壊Ｋをサイドメンバ前方領域１１Ｆの前端部まで持続的に伝播させて、衝突エネルギーの吸収効率を高めることができる。
【００４５】
このとき、サイドメンバ１１の圧壊は、サイドメンバ前方領域１１Ｆの後方から誘発されるため、バンパーレインフォース１２に連結したサイドメンバ１１の前端部の剛性は高く保持されて、バンパーレインフォース１２とサイドメンバ１１との取付け角度θは一定に保持される状態にある。
【００４６】
従って、図９に示すようにオフセット衝突時に車両片側に衝突荷重Ｆが入力した場合に、衝突側（右側）のサイドメンバ１１に軸方向入力Ｆｎが作用し、この軸方向入力Ｆｎによってバンパーレインフォース１２に相対するモーメントＭｂｍｐｒを発生させるとともに、このバンパーレインフォース１２と非衝突側（左側）のサイドメンバ１２の連結部にモーメントＭｊｎｔを発生させることができる。
【００４７】
このため、結果的に前記バンパーレインフォース１２は車両後方に平行移動する状態となって、前記非衝突側のサイドメンバ１１にも軸方向入力Ｆｎ′を作用させることができるようになり、衝突による荷重分散を効果的に行うことができる。
【００４８】
ここで、バンパーレインフォース１２の断面係数Ｚを、サイドメンバ１１前部の圧壊時最大反力Ｆｍａｘと、サイドメンバ前方領域１１ＦのスパンＬに対するバンパーレインフォース１２の構成素材の降伏応力σｙ−ｂｍｐｒの商と、の積より大きく（Ｚ＞Ｆｍａｘ×Ｌ／σｙ−ｂｍｐｒ）設定してあり、かつ、バンパーレインフォース１２の結合部強度Ｓｊｏｉｎｔを、前記スパンＬと前記圧壊時最大反力Ｆｍａｘとの積より大きく（Ｓｊｏｉｎｔ＞Ｌ×Ｆｍａｘ）設定してあるので、図１０に示すようにバンパーレインフォース１２自体の剛性を高く維持して折れを抑制するとともに、バンパーレインフォース１２とサイドメンバ１１との結合強度を十分に確保して一定の角度θを保持できる。
【００４９】
従って、衝突側のサイドメンバ前方領域１１Ｆは軸方向入力Ｆｎにより、また、非衝突側のサイドメンバ前方領域１１Ｆは軸方向入力Ｆｎ′によって、それぞれの後方部から圧壊Ｋを効果的に発生させることができるため、オフセット衝突時にあっても衝突エネルギーの吸収効率を高めることができる。
【００５０】
特に、前述したように車幅方向に対向する１対のサイドメンバ前方領域１１Ｆは車体前後方向に直状に形成して、それぞれを平行に配置してあるため、前記取付け角度θは直角となっており、従って、フルラップ衝突時は勿論のこと、オフセット衝突に対してもサイドメンバ前方領域１１Ｆの後部からの持続的な圧壊を良好に行わせることができてエネルギー吸収特性を向上することができる。
【００５１】
また、前記サイドメンバ板厚変化構造５０における最大応力の上限値を、サイドメンバ１１を構成する素材の降伏強度を基準に設定したので、サイドメンバ１１の前端部への入力時には、先ず、最大応力を大きくしたサイドメンバ前方領域１１Ｆの後部が素材の降伏域に達して塑性変形が生じるため、衝突時にはサイドメンバ前方領域の後部から圧壊をより確実に誘発させることができる。
【００５２】
更に、前記サイドメンバ板厚変化構造５０は、前記サイドメンバ前方領域１１Ｆの板厚分布を長手方向に変化させた構造であるため、衝突荷重Ｆがサイドメンバ１１に入力した際に、サイドメンバ前方領域１１Ｆの長手方向に連なる仮想断面Ｉａ，Ｉｂ…Ｉｅで発生する最大応力の制御がし易くなり、ひいては強度バランスの調整が容易となって、衝突時におけるサイドメンバ前方領域１１Ｆの後端部からの圧壊Ｋをより確実に誘発させることができる。
【００５３】
更にまた、前記サイドメンバ板厚変化構造５０を、板厚ｔ１，ｔ２…ｔ６と板厚の異なる複数の板材５１ａ，５１ｂ…５１ｆをそれらの板厚が段階的に変化するように接合した複合パネル材５２を用いて、板厚の変化方向が長手方向となるように構成したので、サイドメンバ前方領域１１Ｆの長手方向に連なる仮想断面Ｉａ，Ｉｂ…Ｉｅで発生する最大応力の制御を近似的に行って、サイドメンバ前方領域１１Ｆの後端部からの圧壊を支障無く誘発することができるとともに、単に板厚ｔ１，ｔ２…ｔ６の異なる複数の板材５１ａ，５１ｂ…５１ｆの接合であるため、サイドメンバ前方領域１１Ｆを容易に形成することができる。
【００５４】
尚、前記板材５１ａ，５１ｂ，５１ｃ…５１ｆの数は本実施形態に限定されることはなく、その数はサイドメンバ前方領域１１Ｆの要求圧壊特性に応じて決定すればよい。
【００５５】
（第２実施形態）
図１１は本発明の本発明の第２実施形態を示し、前記第１実施形態と同一構成部分に同一符号を付して重複する説明を省略して述べる。尚、図１１はサイドメンバ前方領域の拡大断面図である。
【００５６】
この第２実施形態では、図１１に示すように強度調整手段を、サイドメンバ前方領域１１Ｆの閉断面内に長手方向に適宜間隔をもって複数の仕切り板６１ａ，６１ｂ…６１ｅを配置し、各仕切り板６１ａ，６１ｂ…６１ｅの板厚ｔ１，ｔ２…ｔ５を、前方に行くに従って増厚（ｔ１＞ｔ２＞…＞ｔ５）するようにサイドメンバ１１の長手方向に変化させた仕切り板厚変化構造６０として構成してある。
【００５７】
即ち、前記仕切り板６１ａ，６１ｂ…６１ｅは、閉断面構造となったサイドメンバ前方領域１１Ｆの内側に固設して一体化されており、これら仕切り板６１ａ，６１ｂ…６１ｅの配置箇所でサイドメンバ前方領域１１Ｆの剛性を高めるとともに、その剛性の増大率はそれぞれの板厚ｔ１，ｔ２…ｔ５に応じて前方に行くに従って増大される。
【００５８】
このとき、パワーユニット３０（図２参照）を搭載する補強部分１１Ｒの剛性は、仕切り板６１ｅの板厚ｔ５によって確保できるようになっており、また、この第２実施形態ではサイドメンバ前方領域１１Ｆの周壁の板厚ｔは、全区間に亘って一定として構成してある。
【００５９】
従って、この第２実施形態の車体前部構造では、衝突荷重Ｆがサイドメンバ１１の前端部に入力された際に、サイドメンバ前方領域１１Ｆの長手方向に連なる仮想断面で発生する最大応力の制御を各仕切り板６１ａ，６１ｂ…６１ｅで行うことができ、ひいては強度バランスの調整が容易となって、衝突時におけるサイドメンバ前方領域１１Ｆの後端部からの圧壊Ｋを確実に誘発することができ、前記第１実施形態と同様の効果を奏することができる。
【００６０】
また、この実施形態ではサイドメンバ前方領域１１Ｆの周壁の板厚ｔを全区間に亘って一定としたが、前記第１実施形態のように板厚を段階的に変化させたサイドメンバ板厚変化構造５０と組み合わせることもできる。
【００６１】
（第３実施形態）
図１２〜図１４は本発明の第３実施形態を示し、前記各実施形態と同一構成部分に同一符号を付して重複する説明を省略して述べる。尚、図１２はサイドメンバ前方領域の斜視図、図１３は図１２中Ｂ−Ｂ線に沿った拡大断面図、図１４は強度調整手段の概念を示す応力分布図である。
【００６２】
この第３実施形態の車体前部構造は、図１２に示すように強度調整手段を、サイドメンバ前方領域１１Ｆの断面寸法ｘ，ｙが前端に行くに従って幅広となるように長手方向で変化させた断面寸法変化構造７０として構成してある。
【００６３】
前記断面寸法変化構造７０は、図１３に示すようにサイドメンバ前方領域１１Ｆで板厚ｔ分布を前端に行くに従って増厚するように変化させてあり、前記断面寸法ｘ，ｙおよび板厚ｔは連続的に変化される。
【００６４】
この実施形態ではサイドメンバ１１を全体的にアルミニウム合金などの軽合金による押出し材で形成してある。
【００６５】
従って、この実施形態の車体前部構造は、前記第１実施形態と同様の機能を奏するとともに、サイドメンバ前方領域１１Ｆは板厚ｔのみならず断面寸法ｘ，ｙを変化させてあり、このように断面寸法ｘ，ｙを変化させることにより、材料力学の観点から板厚ｔ変化に比較して部材断面定数への感度を高くすることができる。
【００６６】
また、サイドメンバ前方領域１１Ｆを、断面寸法ｘ，ｙおよび板厚ｔを長手方向に連続的に変化させることができる押出し材で構成したので、板厚の調整が容易になり、より一層の構造合理化および軽量化を図ることができる。
【００６７】
更に、この実施形態では断面寸法ｘ，ｙおよび板厚ｔを連続的に変化させてあるので、図１４に示すように応力分布はサイドメンバ前方領域１１Ｆの全区間に亘って略一定となっている。
【００６８】
ところで、本発明の車体前部構造は前記各実施形態を例にとって説明したが、本発明の要旨を逸脱しない範囲内でその他の実施形態をとることができる。
【図面の簡単な説明】
【図１】本発明の対象とする自動車の外観斜視図。
【図２】本発明の第１実施形態における車体前部右側の骨格構造を示す略示的平面説明図。
【図３】本発明の第１実施形態におけるサイドメンバ前方領域の斜視図。
【図４】図３中Ａ−Ａ線に沿った拡大断面図。
【図５】本発明の第１実施形態における強度調整手段の入力形態モデルを示す説明図。
【図６】本発明の第１実施形態における強度調整手段の概念を示す応力分布図。
【図７】本発明の第１実施形態における前方からの衝突荷重の入力形態を示す車体前部右側の略示的平面説明図。
【図８】本発明の第１実施形態におけるサイドメンバの変形モードを示す説明図。
【図９】本発明の第１実施形態におけるオフセット衝突時の荷重分散形態を示す車体前部の略示的平面説明図。
【図１０】本発明の第１実施形態におけるオフセット衝突時におけるサイドメンバの変形モードを示す車体前部の略示的平面説明図。
【図１１】本発明の第２実施形態におけるサイドメンバ前方領域の拡大断面図。
【図１２】本発明の第３実施形態におけるサイドメンバ前方領域の斜視図。
【図１３】図１２中Ｂ−Ｂ線に沿った拡大断面図。
【図１４】本発明の第３実施形態における強度調整手段の概念を示す応力分布図。
【符号の説明】
Ｆ・Ｃフロントコンパートメント
１０車体
１１サイドメンバ
１１Ｆサイドメンバ前方領域
１１Ｒ補強部分
３０パワーユニット（車両ユニット部品）
５０サイドメンバ板厚変化構造（強度調整手段）
５１ａ，５１ｂ，５１ｃ…５１ｆ板材
５２複合パネル材
６０仕切り板厚変化構造
６１ａ，６１ｂ…６１ｅ仕切り板
７０断面寸法変化構造
Ｉａ，Ｉｂ…Ｉｅ仮想断面
ｘ，ｙ断面寸法
ｔ板厚[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vehicle body front structure of an automobile.
[0002]
[Prior art]
As a countermeasure against a vehicle collision, the collision energy is absorbed by crushing a side member at a front portion of the vehicle body with an axis. For example, Japanese Patent Application Laid-Open No. 2001-158377 discloses the vehicle body front structure.
[0003]
This front body structure has a bead on the front wall of the side member having a polygonal cross section, thereby promoting axial crushing from the front when an axial input is applied to the side member, thereby reducing collision energy. It is intended to be absorbed.
[0004]
[Problems to be solved by the invention]
However, in such a conventional vehicle body front structure, energy can be favorably absorbed with respect to a collision load input to the side member in the axial direction. However, when the collision is an offset collision on only one side of the vehicle, The front end of only one of the side members subjected to the offset collision is deformed and retreats in the vehicle direction.
[0005]
For this reason, a plastic hinge is formed between the bumper reinforce and the side member so that the bumper reinforce is oblique, and the efficiency of input dispersion to the side member on the non-collision side is reduced. There is a concern that the weight investment for suppressing the deformation amount of the vehicle body in the above will increase and the vehicle body weight will increase.
[0006]
Therefore, the present invention provides a vehicle body front structure capable of effectively dispersing a collision load to the side members on both sides even in a frontal collision from any direction and improving the efficiency of absorbing collision energy. Things.
[0007]
[Means for Solving the Problems]
According to the first aspect of the present invention, reinforcing members for mounting vehicle unit components are provided on side members arranged in the front-rear direction of the vehicle body on both left and right sides of the front compartment, and the vehicle width spans the front ends of these side members. In the vehicle body front structure combining the bumper reinforce extending in the direction,
In the side member front region of the side member forward from the reinforcement portion of the side member, the maximum stress generated in the front and rear portions of the imaginary cross section continuous in the longitudinal direction is adjusted so that the rear portion is larger than the front portion. It is characterized in that means are provided.
[0008]
According to a second aspect of the present invention, in the vehicle body front structure according to the first aspect, an upper limit value of a maximum stress by the strength adjusting means is set based on a yield strength of a material forming a side member. Features.
[0009]
According to a third aspect of the present invention, in the vehicle body front structure according to the first or second aspect, the strength adjusting means changes a thickness distribution of the front region of the side member in a longitudinal direction. It is characterized by a variable structure.
[0010]
According to the fourth aspect of the present invention, in the vehicle body front structure according to the third aspect, the side member thickness changing structure is configured to change a plurality of plate materials having different thicknesses stepwise. Is characterized in that the composite panel material joined to the above is configured such that the direction of change in the plate thickness is the longitudinal direction.
[0011]
According to a fifth aspect of the present invention, in the vehicle body front structure according to the first or second aspect, the strength adjusting means includes a plurality of partition plates provided at appropriate intervals in a longitudinal direction in a closed cross section of the side member front region. , And a partition plate thickness changing structure in which the thickness of each partition plate is changed in the longitudinal direction of the side member so as to increase as going forward.
[0012]
According to a sixth aspect of the present invention, in the vehicle body front structure according to the first to fifth aspects, the strength adjusting means is a cross-sectional dimension changing structure in which a cross-sectional dimension of the front region of the side member is changed in a longitudinal direction. It is characterized by having.
[0013]
According to the invention of claim 7, in the vehicle body front structure according to claims 1 and 2, the side member front region is formed by an extruded material whose extruded plate thickness or extruded cross-sectional dimension continuously changes in the extruding direction. The strength adjusting means is constituted by changing the thickness or the cross-sectional dimension of the front region of the side member, or changing both the thickness and the cross-sectional dimension.
[0014]
According to an eighth aspect of the present invention, in the vehicle body front structure according to any one of the first to seventh aspects, the bumper reinforce has a closed cross-sectional structure, and a member cross section of the bumper reinforce having the closed cross section has a vehicle vertical direction. The sectional coefficient Z of the second moment of area with respect to the axis is the product of the maximum reaction force Fmax at the time of crushing at the front part of the side member and the quotient of the yield stress σy-bmpr of the material constituting the bumper reinforcement with respect to the span L in the front region of the side member. A larger value (Z> Fmax × L / σy-bmpr) is set, and the joint strength Sjoint of the bumper reinforce is calculated from the product of the span L of the front region of the side member and the maximum reaction force Fmax at the time of crushing of the front portion of the side member. It is characterized in that it is set to be large (Sjoint> L × Fmax).
[0015]
According to a ninth aspect of the present invention, in the vehicle body front structure according to any one of the first to eighth aspects, the side member front regions of the left and right side members are each formed in a straight line in the vehicle front-rear direction and are parallel to each other. It is characterized by being arranged in.
[0016]
【The invention's effect】
According to the first aspect of the present invention, when a collision load is input from the front of the vehicle, the strength adjusting means provided in the front region of the side member induces crush from the rear of the side member front region toward the front. The crush can be continuously propagated to the front end of the front region of the side member, so that the efficiency of absorbing collision energy can be increased.
[0017]
Also, at this time, since the side members are crushed from behind the front region of the side members, the rigidity of the front end of the side members connected to the bumper reinforce is kept high, and the mounting angle between the bumper reinforce and the side members is increased. Is kept constant.
[0018]
Therefore, when a collision load is input to one side of the vehicle at the time of an offset collision, an axial input acts on the side member on the collision side, and the axial input causes the bumper reinforce and the bumper reinforce and the side member on the non-collision side to act. Since a moment can be generated in each of the connecting portions, the bumper reinforce is consequently moved parallel to the rear of the vehicle, so that an axial input can be applied to the side member on the non-collision side. Thus, the load distribution due to the collision can be effectively performed, and the efficiency of absorbing the collision energy can be increased.
[0019]
According to the second aspect of the invention, in addition to the effect of the first aspect, the upper limit of the maximum stress by the strength adjusting means is set based on the yield strength of the material constituting the side member. At the time of input to the front end of the side member, first, the rear portion of the front region of the side member where the maximum stress is increased reaches the yield region of the material and plastic deformation occurs. Can be triggered.
[0020]
According to the third aspect of the present invention, in addition to the effects of the first and second aspects of the present invention, the strength adjusting means is provided by changing the thickness distribution of the front region of the side member in the longitudinal direction. Because of the variable structure, when a collision load is input to the side member, it becomes easier to control the maximum stress that occurs in the virtual cross-section that extends in the longitudinal direction of the front region of the side member, and thus it becomes easier to adjust the strength balance. Thus, the crush from the rear end of the front region of the side member at the time of collision can be more reliably induced.
[0021]
According to the fourth aspect of the present invention, in addition to the effect of the third aspect of the present invention, the side member thickness changing structure is configured such that a plurality of plate materials having different thicknesses change stepwise. Since the composite panel material joined to was formed so that the direction of change in the plate thickness was the longitudinal direction, the control of the maximum stress generated in the virtual cross-section in the longitudinal direction of the side member front region was performed approximately, The crush from the rear end portion of the side member front region can be induced without any trouble, and the side member front region provided with such strength adjusting means can be easily formed.
[0022]
According to the fifth aspect of the present invention, in addition to the effects of the first and second aspects of the present invention, the plurality of partitioning plates are provided at appropriate intervals in the longitudinal direction within the closed cross section of the front region of the side member. Is arranged, and the thickness of each partition plate is changed in the longitudinal direction of the side member so as to increase as going forward, so that when a collision load is input to the front end of the side member. In addition, it is possible to control the maximum stress generated in the imaginary cross section extending in the longitudinal direction of the side member front region by each partition plate, thereby easily adjusting the strength balance, and after the side member front region at the time of a collision. Crushing from the end can be reliably induced.
[0023]
According to the sixth aspect of the invention, in addition to the effects of the first to fifth aspects, the strength adjusting means has a cross-sectional dimension changing structure in which the cross-sectional dimension of the front region of the side member is changed in the longitudinal direction. Therefore, when a collision load is input to the side member, it becomes easy to control the maximum stress generated in a virtual cross section extending in the longitudinal direction of the front region of the side member, and thus it becomes easy to adjust the strength balance, and at the time of a collision, Crushing from the rear end of the front region of the side member can be more reliably induced, and by changing the cross-sectional dimension having a higher sensitivity to the member cross-sectional constant than the plate thickness, the side member can be further improved. The weight can be reduced.
[0024]
According to the seventh aspect of the invention, in addition to the effects of the first and second aspects, the front region of the side member is formed of an extruded material whose extruded plate thickness and extruded cross-sectional dimension continuously change in the extruding direction. As a result, the thickness adjustment or the cross-sectional dimension can be freely adjusted in the longitudinal direction, and the change can be continuously performed. In addition, it is possible to accurately adjust the maximum stress generated in the virtual cross-section that is continuous in the longitudinal direction of the side member front region, and it is possible to further simplify the structure and reduce the weight.
[0025]
According to the eighth aspect of the invention, in addition to the effects of the first to seventh aspects, in addition to the effect of the first to seventh aspects, the section modulus Z of the second moment of area of the member cross section of the closed bumper reinforce with respect to the vehicle vertical axis is obtained. The maximum reaction force Fmax at the time of crushing of the front part of the side member, the span L of the front region of the side member, and the yield stress σy-bmpr of the bumper reinforcement component are set as Z> Fmax × L / σy-bmpr, and the bumper is set. Since the joint strength Sjoint of the reinforcement is set as Sjoint> L × Fmax, the rigidity of the bumper reinforce itself is kept high to suppress breakage, and the joint strength between the bumper reinforce and the side member is sufficiently ensured. To maintain a certain angle, the side member on the non-collision side can be It is possible to perform a heavy dispersion efficiently.
[0026]
According to the ninth aspect of the invention, in addition to the effects of the first to eighth aspects, the side member front regions of the left and right side members are formed straight in the vehicle body front-rear direction and arranged parallel to each other. Therefore, the front region of the side member can be continuously crushed from the rear end portion not only at the time of a full lap collision but also at the time of an offset collision, so that good energy absorption characteristics can be secured.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0028]
(1st Embodiment)
1 to 10 show a first embodiment of a vehicle body front structure of the present invention, FIG. 1 is an external perspective view of an automobile to which the present invention is applied, and FIG. 3 is a perspective view of the front region of the side member, FIG. 4 is an enlarged sectional view taken along line AA in FIG. 3, FIG. 5 is an explanatory view showing an input form model of the strength adjusting means, and FIG. 7 is a stress distribution diagram showing the concept of the strength adjusting means, FIG. 7 is a schematic plan explanatory view of the front right side of the vehicle body showing an input form of a collision load from the front, FIG. 8 is an explanatory diagram showing a deformation mode of the side member, FIG. 9 is a schematic plan explanatory view of a front portion of the vehicle body showing a load distribution mode at the time of an offset collision, and FIG. 10 is a schematic plan explanatory view of a front portion of the vehicle body showing a deformation mode of a side member at the time of an offset collision.
[0029]
The vehicle body front structure of the present embodiment is applied to the front compartments F and C of the vehicle body 10 shown in FIG. 1, and its skeletal structure is disposed on both right and left sides in the vehicle front-rear direction as shown in FIG. Side members 11 are arranged in parallel with each other, and a bumper reinforce 12 forming a skeleton of a bumper (not shown) is connected across the front end of each side member 11.
[0030]
An extension side member 13 that extends from the dash panel 17 to the lower surface side of the floor panel 18 is connected to the rear of each side member 11 and is substantially parallel to the outside of the extension side member 13 in the vehicle width direction. A side sill 14 is disposed at the front end of each of the extension side members 13 and the side sill 14.
[0031]
A dash cross member 16 is connected between the connected portions of the side members 11 and the extension side members 13.
[0032]
A suspension arm 21 for supporting a front wheel 20 is attached to the rear side of the side member 11 directly or via a suspension member (not shown), and an engine or the like as a vehicle unit component is provided between the left and right side members 11. Are mounted via a mount bracket 31.
[0033]
As shown in FIG. 3, a reinforcing portion 11R (shown by a satin portion in FIG. 3) having sufficient strength to support the power unit 30 is formed on the side bracket 11 at the mounting portion of the mount bracket 31, as shown in FIG. .
[0034]
That is, as shown in FIG. 3, the side member 11 has a closed sectional structure by fixing both side flange portions of the second plate 11b having a U-shaped cross section to the first plate 11a having a flat plate shape by spot welding or the like. The reinforcing portion 11R is formed by joining and arranging a reinforcing plate on the inner peripheral surface.
[0035]
Here, in the present embodiment, the maximum stress generated in the front and rear portions of the imaginary cross sections Ia, Ib... Ie extending in the longitudinal direction is formed in the side member front region 11F forward from the reinforcing portion 11R of the side member 11. A side member thickness changing structure 50 is formed as a strength adjusting means so that the rear portion becomes larger than the front portion, and the thickness distribution of the side member front region 11F is changed in the longitudinal direction.
[0036]
That is, as shown in FIG. 4, the side member plate thickness changing structure 50 includes a plurality of plate members 51a, 51b... 51f having different plate thicknesses t1, t2... T6 from the front end direction of the side member front region 11F. It is composed of a composite panel material 52 welded and joined all around so that the thickness changes stepwise (t1>t2>...> T6) from the front to the rear.
[0037]
That is, in the plate members 51a, 51b,... 51f, the plate member 51f is the thinnest, and the plate member 51f is disposed on the reinforcing portion 11R. Of course, the reinforcing portion 11R supports the power unit 30 as described above. It has enough strength.
[0038]
Further, as shown in FIG. 5, when the collision load F from the front statically acts on the front end of the side member front region 11F, the side member front region 11F has a maximum value in the side member plate thickness change structure 50. The upper limit value of the stress is set based on the yield strength of the material constituting the side member 11 so that the distribution of the yield strength σ (y) for each of the plate members 51a, 51b, 51c... 51f is obtained as shown in FIG. It is.
[0039]
Among the flanges 11c, 11d, 11f, 11e extending from the front end of the side member 11, the flanges 11c, 11d extending from the upper and lower surfaces are upper and lower surfaces 12a, 12b of the bumper reinforcement 12. And the flange portions 11e and 11f extending from the two left and right surfaces of the side member 11 are welded to the rear surface 12c of the bumper reinforce 12 so as to increase the connection strength between the bumper reinforce 12 and the side member 11. It has become.
[0040]
Here, the section coefficient of the second moment of area of the member section of the bumper reinforce 12 having the closed section structure with respect to the vehicle vertical axis is Z, the maximum reaction force at the time of crushing of the front portion of the side member 11 is Fmax, and the side member front area 11F. Is L and the yield stress of the constituent material of the bumper reinforce 12 is σy-bmpr, the following equation 1 is satisfied.
[0041]
Z> Fmax × L / σy-bmpr Equation 1
That is, the sectional modulus Z is set to be larger than the product of the maximum reaction force Fmax during crushing and the quotient of the yield stress σy-bmpr with respect to the span L.
[0042]
At the same time, assuming that the joint strength of the bumper reinforcement 12 is Sjoint, the structure satisfies the following expression (2).
[0043]
Sjoint> L × Fmax Expression 2
That is, the joint strength Sjoint is set to be larger than the product of the span L and the maximum reaction force Fmax at the time of crush.
[0044]
(Action)
According to the vehicle body front structure of the first embodiment having the above configuration, when the collision load F is input from the front of the vehicle as shown in FIG. As described above, the crush K occurs behind the side member front region 11F, and the crush K is induced toward the front, and the crush K is continuously propagated to the front end of the side member front region 11F to reduce the collision energy. Absorption efficiency can be increased.
[0045]
At this time, since the crush of the side member 11 is induced from behind the front region 11F of the side member 11, the rigidity of the front end of the side member 11 connected to the bumper reinforcement 12 is kept high, and The attachment angle θ with the member 11 is kept constant.
[0046]
Accordingly, when a collision load F is input to one side of the vehicle at the time of an offset collision as shown in FIG. 9, an axial input Fn acts on the side member 11 on the collision side (right side), and the bumper reinforcement F is applied by the axial input Fn. In addition to the generation of the moment Mbmpr relative to the bumper 12, the moment Mjnt can be generated at the connection between the bumper reinforce 12 and the side member 12 on the non-collision side (left side).
[0047]
As a result, the bumper reinforce 12 moves parallel to the rear of the vehicle, and the axial input Fn 'can also act on the side member 11 on the non-collision side. Load distribution can be performed effectively.
[0048]
Here, the section modulus Z of the bumper reinforce 12 is calculated by calculating the maximum reaction force Fmax at the time of crushing at the front part of the side member 11 and the yield stress σy-bmpr of the constituent material of the bumper reinforce 12 with respect to the span L of the front region 11F of the side member 11. And the product of the quotient and (Z> Fmax × L / σy-bmpr), and the joint strength Sjoint of the bumper reinforce 12 is calculated by multiplying the span L by the maximum reaction force Fmax during crushing. Since it is set to be larger (Sjoint> L × Fmax), the rigidity of the bumper reinforce 12 itself is kept high as shown in FIG. 10 to suppress breakage and the connection between the bumper reinforce 12 and the side member 11. The strength can be sufficiently ensured to maintain a constant angle θ.
[0049]
Therefore, the crushing K can be effectively generated from the respective rear portions of the front side region 11F of the collision side by the axial input Fn and the front side region 11F of the non-collision side by the axial input Fn '. Therefore, even at the time of the offset collision, the efficiency of absorbing the collision energy can be increased.
[0050]
In particular, as described above, the pair of side member front regions 11F opposed to each other in the vehicle width direction is formed in a straight line in the vehicle front-rear direction, and is disposed in parallel with each other, so that the mounting angle θ is a right angle. Therefore, not only at the time of a full lap collision but also at the time of an offset collision, it is possible to favorably perform continuous crushing from the rear portion of the side member front region 11F and improve energy absorption characteristics. .
[0051]
In addition, since the upper limit of the maximum stress in the side member plate thickness change structure 50 is set based on the yield strength of the material forming the side member 11, when inputting to the front end of the side member 11, the maximum stress is first set. Since the rear portion of the side member front region 11 </ b> F in which the height is increased reaches the yield region of the material and plastic deformation occurs, crush can be more reliably induced from the rear portion of the side member front region at the time of collision.
[0052]
Further, since the side member thickness changing structure 50 is a structure in which the thickness distribution of the side member front region 11F is changed in the longitudinal direction, when the collision load F is input to the side member 11, the side member front thickness changing structure 50 is formed. The maximum stress generated in the virtual cross sections Ia, Ib... Ie continuous in the longitudinal direction of the region 11F can be easily controlled, and the strength balance can be easily adjusted. Can be induced more reliably.
[0053]
Furthermore, the side member plate thickness changing structure 50 is joined to a plurality of plate members 51a, 51b... 51f having different plate thicknesses from the plate thicknesses t1, t2... T6 so that the plate thicknesses change stepwise. Since the plate 52 is configured so that the change direction of the plate thickness becomes the longitudinal direction by using the material 52, the control of the maximum stress generated in the imaginary sections Ia, Ib,. As a result, crushing from the rear end of the front region 11F of the side member can be induced without any trouble, and a plurality of plate members 51a, 51b... 51f having different plate thicknesses t1, t2. The member front region 11F can be easily formed.
[0054]
The number of the plate members 51a, 51b, 51c... 51f is not limited to the present embodiment, and the number may be determined according to the required crushing characteristics of the front region 11F of the side member.
[0055]
(2nd Embodiment)
FIG. 11 shows a second embodiment of the present invention, in which the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description will be omitted. FIG. 11 is an enlarged sectional view of the front region of the side member.
[0056]
In the second embodiment, as shown in FIG. 11, a plurality of partition plates 61a, 61b... 61e are arranged at appropriate intervals in the longitudinal direction in the closed cross section of the side member front region 11F as shown in FIG. The partition plate thickness changing structure 60 in which the plate thicknesses t1, t2... T5 of 61a, 61b... 61e are changed in the longitudinal direction of the side member 11 so as to increase (t1> t2 >>. It is composed.
[0057]
That is, the partition plates 61a, 61b... 61e are fixed and integrated inside the side member front area 11F having a closed cross-sectional structure, and the side members are disposed at the positions where these partition plates 61a, 61b. The rigidity of the front region 11F is increased, and the rate of increase in the rigidity is increased as going forward in accordance with the respective plate thicknesses t1, t2... T5.
[0058]
At this time, the rigidity of the reinforcing portion 11R on which the power unit 30 (see FIG. 2) is mounted can be secured by the plate thickness t5 of the partition plate 61e, and in the second embodiment, the side member front region 11F is provided. The thickness t of the peripheral wall is configured to be constant over the entire section.
[0059]
Therefore, in the vehicle body front structure according to the second embodiment, when the collision load F is input to the front end of the side member 11, the control of the maximum stress generated in the virtual cross section extending in the longitudinal direction of the side member front region 11F is performed. 61e, the adjustment of the strength balance is facilitated, and the crush K from the rear end of the side member front area 11F at the time of collision can be reliably induced. The same effects as those of the first embodiment can be obtained.
[0060]
Further, in this embodiment, the thickness t of the peripheral wall of the side member front region 11F is constant over the entire section. However, as in the first embodiment, the side member thickness change is obtained by changing the thickness stepwise. It can also be combined with the structure 50.
[0061]
(Third embodiment)
FIGS. 12 to 14 show a third embodiment of the present invention, in which the same components as those in the above embodiments are denoted by the same reference numerals, and redundant description will be omitted. FIG. 12 is a perspective view of the front region of the side member, FIG. 13 is an enlarged sectional view taken along line BB in FIG. 12, and FIG. 14 is a stress distribution diagram showing the concept of the strength adjusting means.
[0062]
In the vehicle body front structure of the third embodiment, as shown in FIG. 12, the strength adjusting means is changed in the longitudinal direction such that the cross-sectional dimensions x, y of the side member front region 11F become wider toward the front end. It is configured as a cross-sectional dimension changing structure 70.
[0063]
As shown in FIG. 13, the cross-sectional dimension changing structure 70 changes the thickness t distribution in the front region 11F of the side member so as to increase in thickness toward the front end, and the cross-sectional dimensions x, y and the thickness t are changed. Changed continuously.
[0064]
In this embodiment, the side member 11 is entirely formed of an extruded material of a light alloy such as an aluminum alloy.
[0065]
Therefore, the vehicle body front structure of this embodiment has the same function as that of the first embodiment, and the side member front region 11F is changed not only in the plate thickness t but also in the cross-sectional dimensions x and y. By changing the cross-sectional dimensions x and y, the sensitivity to the member cross-sectional constant can be increased from the viewpoint of material mechanics as compared with the change in the plate thickness t.
[0066]
Further, since the side member front region 11F is made of an extruded material capable of continuously changing the cross-sectional dimensions x and y and the plate thickness t in the longitudinal direction, the plate thickness can be easily adjusted, and the structure is further improved. Rationalization and weight reduction can be achieved.
[0067]
Further, in this embodiment, since the cross-sectional dimensions x and y and the plate thickness t are continuously changed, the stress distribution becomes substantially constant over the entire section of the side member front region 11F as shown in FIG. I have.
[0068]
By the way, the vehicle body front structure of the present invention has been described by taking each of the above embodiments as an example, but other embodiments can be adopted without departing from the gist of the present invention.
[Brief description of the drawings]
FIG. 1 is an external perspective view of an automobile to which the present invention is applied.
FIG. 2 is a schematic plan explanatory view showing a skeletal structure of a vehicle body front right side in the first embodiment of the present invention.
FIG. 3 is a perspective view of a front region of a side member according to the first embodiment of the present invention.
FIG. 4 is an enlarged sectional view taken along line AA in FIG. 3;
FIG. 5 is an explanatory diagram showing an input mode model of an intensity adjusting unit according to the first embodiment of the present invention.
FIG. 6 is a stress distribution diagram illustrating a concept of a strength adjusting unit according to the first embodiment of the present invention.
FIG. 7 is a schematic plan explanatory view of the right front portion of the vehicle body showing an input form of a collision load from the front according to the first embodiment of the present invention.
FIG. 8 is an explanatory diagram showing a deformation mode of the side member according to the first embodiment of the present invention.
FIG. 9 is a schematic plan explanatory view of a front portion of the vehicle body showing a load distribution mode at the time of an offset collision in the first embodiment of the present invention.
FIG. 10 is a schematic plan view of a front portion of the vehicle body showing a deformation mode of a side member at the time of an offset collision according to the first embodiment of the present invention.
FIG. 11 is an enlarged sectional view of a front region of a side member according to a second embodiment of the present invention.
FIG. 12 is a perspective view of a front region of a side member according to a third embodiment of the present invention.
FIG. 13 is an enlarged sectional view taken along line BB in FIG. 12;
FIG. 14 is a stress distribution diagram illustrating the concept of a strength adjusting unit according to a third embodiment of the present invention.
[Explanation of symbols]
FC front compartment
10 Body
11 Side member
11F Side member front area
11R reinforcement part
30 Power unit (vehicle unit parts)
50 Side member thickness change structure (strength adjusting means)
51a, 51b, 51c ... 51f plate material
52 Composite panel materials
60 Partition thickness change structure
61a, 61b ... 61e Partition plate
70 Cross-sectional dimension change structure
Ia, Ib ... Ie Virtual cross section
x, y Cross-sectional dimensions
t Sheet thickness

Claims

Reinforcing parts for mounting vehicle unit parts are provided on side members arranged in the front-rear direction on both left and right sides of the front compartment, and bumper reinforcements extending in the vehicle width direction across the front ends of these side members are connected. In the car body front structure
Strength adjustment in which the maximum stress generated in the front part and the rear part of the imaginary cross-section that extends in the longitudinal direction in the front part of the side member that is forward from the reinforcing part of the side member is such that the rear part is larger than the front part. A vehicle body front structure provided with means.

The vehicle body front structure according to claim 1, wherein an upper limit value of the maximum stress by the strength adjusting means is set based on a yield strength of a material forming the side member.

The vehicle body front structure according to claim 1 or 2, wherein the strength adjusting means is a side member thickness changing structure in which a thickness distribution of the side member front region is changed in a longitudinal direction.

The side member plate thickness change structure is configured such that a composite panel material in which a plurality of plate materials having different plate thicknesses are joined such that the plate thickness changes stepwise is formed such that the change direction of the plate thickness becomes the longitudinal direction. The vehicle body front part structure according to claim 3, wherein:

Strength adjusting means arranges a plurality of partition plates in the closed cross section of the side member front region at appropriate intervals in the longitudinal direction, and increases the thickness of each partition plate in the longitudinal direction of the side member so as to increase in thickness as going forward. The vehicle body front structure according to claim 1 or 2, wherein the partition plate thickness is changed.

The vehicle body front structure according to any one of claims 1 to 5, wherein the strength adjusting means is a cross-sectional dimension changing structure in which a cross-sectional dimension of the front region of the side member is changed in a longitudinal direction.

The extruded material whose extruded sheet thickness and extruded cross-sectional dimension continuously change in the extrusion direction is used to form the side member front region, and the thickness or cross-sectional size of the side member front region is changed, or the thickness and cross-sectional size are changed. The vehicle body front structure according to claim 1 or 2, wherein the strength adjustment means is configured by changing both of them.

The bumper reinforce has a closed cross-sectional structure, and the section coefficient Z of the second moment of area of the member cross section of the bumper reinforce with the closed cross section with respect to the vertical axis of the vehicle, the maximum reaction force Fmax at the time of crushing of the front part of the side member, It is set to be larger than the product of the quotient of the yield stress σy-bmpr of the material forming the bumper reinforce and the span L of the region in front of the side member (Z> Fmax × L / σy-bmpr), and the joint strength Sjoint of the bumper reinforce 8 is set to be larger than the product of the span L of the front region of the side member and the maximum reaction force Fmax at the time of crushing of the front portion of the side member (Sjoint> L × Fmax). Body front structure.

The vehicle body front structure according to any one of claims 1 to 8, wherein the side member front regions of the left and right side members are respectively formed in a straight shape in the vehicle front-rear direction and arranged in parallel with each other.