【０００１】
【発明の属する技術分野】
本発明は、衝撃入力に対してそのエネルギーを吸収するのに用いられる衝撃吸収装置に関し、例えば、自動車の構造部材として用いられる衝撃吸収装置に関するものである。
【０００２】
【従来の技術】
従来の衝撃吸収装置としては、衝撃エネルギーを吸収する材料として弾性率の高い材料を用いたものがある。しかし、弾性率の高い材料は、高荷重を支持しつつ一定形状を保つことが難しい場合があり、例えば自動車のフロントメンバーのように、エンジン等の重量物を支持する構造体には不向きである。このフロントメンバーの衝撃吸収装置としては、車内側に高強度材を配置すると共に、その前方部に低強度の鋼板を配置し、前方向からの衝撃入力に対して、低強度鋼板を座屈もしくは変形させることで衝撃エネルギーを吸収し、車内側の高強度材で車体骨格を保護するようにしたものがあった。
【０００３】
【発明が解決しようとする課題】
しかしながら、この種の衝撃吸収装置にあっては、鋼板等の材料そのものの高強度化には限界があり、しかも、材料の高強度化に伴って加工性が困難になることが予想されるほか、低強度材料の材料特性によって衝撃入力時の初期の反力が決まることから、材料の選択だけでは衝撃エネルギーの吸収性能を高めることが困難であった。
【０００４】
【発明の目的】
本発明は、上記従来の状況に鑑みて成されたもので、衝撃エネルギーの吸収性能を高めることができる衝撃吸収装置を提供することを目的としている。
【０００５】
【課題を解決するための手段】
本発明に係わる衝撃吸収装置は、衝撃からの保護対象となる構造体に接合する仕切り部材と、仕切り部材に基端部を接合した外筒部材と、仕切り部材に基端部を接合するとともに外筒部材の先端部分に内接し且つ先端部が外筒部材から突出した内筒部材を備え、内筒部材は、外筒部材よりも軸方向圧縮強度が低い基端側の低強度部と、低強度部よりも軸方向圧縮強度が高い先端側の高強度部を備えると共に、低強度部と高強度部を同軸状に突合せ接合して一体化してあり、外筒部材とこれに内接する内筒部材の高強度部との重合部分を周方向の線状溶接により接合したことを特徴とする衝撃吸収装置。
【０００６】
【発明の作用】
本発明に係わる衝撃吸収装置では、衝撃からの保護対象となる構造体に、例えば板状の仕切り部材を接合し、この仕切り部材に対して、例えば断面矩形の外筒部材と同じく断面矩形の内筒部材が軸方向を垂直にして同軸状態で設けてあり、外筒部材から突出した内筒部材の先端部で衝撃を受けるものとなっている。
【０００７】
この衝撃吸収装置は、内筒部材の先端部に衝撃が加わると、反力が増大した後、外筒部材と内筒部材との重合部分を接合している溶接部が破断する。ここで、内筒部材は、外筒部材よりも軸方向圧縮強度が低い基端側の低強度部と、低強度部よりも軸方向圧縮強度が高い先端側の高強度部を備えると共に、これらを同軸状に突合せて溶接等により接合して一体化してあるので、先の溶接部の破断に続いて内筒部材の低強度部が座屈し、これにより反力が減少する。つまり、衝撃エネルギーを吸収する。このとき、内筒部材は、高強度部が外筒部材の先端部分に内接しているので、低強度部の座屈に伴って外筒部材に案内されつつ軸方向に収縮する。
【０００８】
そして、収縮した内筒部材の先端部が外筒部材の先端部に達した後には、外筒部材と内筒部材の高強度部で形状を維持することにより再び反力が増大する。さらに、衝撃入力が大きい場合には、内筒部材の先端部が外筒部材の先端部に達した後、内筒部材の高強度部と外筒部材が座屈して衝撃エネルギーを吸収する。当該衝撃吸収装置は、上記のように衝撃エネルギーを吸収する一方で、外筒部材および内筒部材の各基端部と保護対象である構造体との間に設けた仕切り部材により、構造体を保護する。
【０００９】
【発明の効果】
本発明に係わる衝撃吸収装置によれば、仕切り部材、外筒部材、および高強度部と低強度部から成る内筒部材を備えた簡単な構造で、衝撃エネルギーの吸収性能を高めることができると共に、初期の反力を高めることも可能であり、衝撃から構造体を確実に保護することができる。
【００１０】
【実施例】
図１は本発明に係わる衝撃吸収装置の一実施例を説明する図である。図示の衝撃吸収装置は、例えば自動車の前部または後部に設けるものであって、衝撃からの保護対象となる箱状の構造体（例えば車体キャビン）Ａに対して、同構造体Ａに接合する板状の仕切り部材１と、断面矩形の外筒部材２と、同じく断面矩形の内筒部材３を備えている。これらの部材１〜３は例えば鋼板製である。
【００１１】
外筒部材２は、図中で右側となる基端部から所定の長さＬｂにわたって大断面部２Ａを備えると共に、大断面部の先端にテーパ部２Ｂを介して小断面部２Ｃを連続的に備えており、仕切り部材１に基端部を溶接により接合してある。この外筒部材２は、塑性加工により全体を一体成形したものや、各部２Ａ〜２Ｃを個別に成形して溶接により順次接合したものとすることができる。
【００１２】
内筒部材３は、外筒部材２の小断面部２Ｃの内側空間に対応した断面形状を軸方向全体にわたって有している。この内筒部材３は、外筒部材２よりも軸方向圧縮強度が低い基端側の低強度部３Ａと、低強度部３Ａよりも軸方向圧縮強度が高い先端側の高強度部３Ｂを備えると共に、低強度部３Ａと高強度部３Ｂを同軸状に突合せて溶接することで一体化してある。
【００１３】
内筒部材３は、外筒部材２の内側に挿入して、仕切り部材１に基端部を溶接により接合してあり、この際、外筒部材２の先端部分である小断面部２Ｃに高強度部３Ｂが内接し、外筒部材２から先端部が突出した状態になっている。そして、外筒部材２とこれに内接する内筒部材３の高強度部３Ｂとの重合部分を周方向の線状溶接（溶接部Ｗ）により接合してある。なお、図面上では、内筒部材３における低強度部３Ａと高強度部３Ｂの長さをほぼ等しく示しているが、これに限定されることはない。
【００１４】
ここで、外筒部材２の大断面部２Ａは、内筒部材３の軸方向の長さＬａに対して、同内筒部材３の基端部から軸方向長さの１／３〜１／２の範囲（Ｌｂ）に設けてあり、且つ軸線に直交する断面の面積を内筒部材３の断面積の１．５〜２倍としている。
【００１５】
また、内筒部材３において、低強度部３Ａの降伏点強度と板厚の積に対して、高強度部３Ｂの降伏点強度と板厚の積の比を１．２５以上とし、内筒部材３における高強度部３Ｂの降伏点強度と板厚の積に対して、外筒部材２の降伏点強度と板厚の積の比を１以上としている。
【００１６】
さらに、外筒部材２と内筒部材３の高強度部３Ｂとの重合部分は、周方向の線状溶接として、ＣＯ２レーザやＹＡＧレーザ等のビーム、プラズマおよび電子ビームのいずれかを用いた重ね溶接により接合してあり、内筒部材３の板厚に対して、外筒部材２と内筒部材３の高強度部３Ｂとを接合する溶接幅の比を０．４〜０．８としている。
【００１７】
より具体的な例として、外筒部材２は、降伏点強度２９０Ｍｐａ、板厚１．８ｍｍの鋼板を使用し、軸方向の長さが６００ｍｍであり、大断面部２Ａの外形が１３０ｍｍ×１３０ｍｍであり、小断面部２Ｃの内形が１００ｍｍ×１００ｍｍである。この外筒部材２は、アーク溶接により仕切り部材１に接合してある。なお、仕切り部材１は、外筒部材２と同様の材料を使用し、アーク溶接により構造体Ａに接合してある。
【００１８】
内筒部材３における低強度部３Ａは、降伏点強度１６０Ｍｐａ、板厚１．６ｍｍの鋼板を使用し、軸方向の長さが４００ｍｍであり、外形が１００ｍｍ×１００ｍｍである。他方、高強度部３Ｂは、降伏点強度２９０Ｍｐａ、板厚１．６ｍｍの鋼板を使用し、軸方向の長さが４００ｍｍであり、外形が１００ｍｍ×１００ｍｍである。低強度部３Ａと高強度部３Ｂは、最大出力５ｋＷのＣＯ２レーザにより突合せ溶接してあり、低強度部３Ａの基端部をアーク溶接により仕切り部材１に接合してある。
【００１９】
そして、外筒部材２とこれに内接する内筒部材３の高強度部３Ｂとの重合部分において、外筒部材２の先端部から１０ｍｍの位置をＣＯ２レーザにより周方向に重ね溶接し、この際、レーザ出力と加工速度を調整して溶接部Ｗの溶接幅を１０ｍｍにした。
【００２０】
上記構成を備えた衝撃吸収装置は、内筒部材３の先端部に衝撃が加わると、反力が増大した後、外筒部材２と内筒部材３との溶接部Ｗが破断し、これに続いて内筒部材３の低強度部３Ａが座屈し、これにより反力が減少する。つまり、衝撃エネルギーを吸収する。このとき、内筒部材３は、低強度部３Ａの座屈に伴って、高強度部３Ｂが外筒部材２に案内されつつ軸方向に収縮する。
【００２１】
そして、収縮した内筒部材３の先端部が外筒部材２の先端部に達した後には、外筒部材２と高強度部３Ｂで形状を維持することにより再び反力が増大し、さらに衝撃入力が大きい場合には、内筒部材３の高強度部３Ｂと外筒部材２が座屈して衝撃エネルギーを吸収する。この間、当該衝撃吸収装置では、上記のように衝撃エネルギーを吸収する一方で、仕切り部材１により構造体Ａを保護する。
【００２２】
このように、上記構成を備えた衝撃吸収装置は、仕切り部材１、外筒部材２、および高強度部３Ｂと低強度部３Ａから成る内筒部材３を備えた簡単な構造により、高い衝撃吸収性能を発揮することができ、衝撃から構造体Ａを確実に保護し得るものとなる。
【００２３】
図３は、上記実施例で説明した衝撃吸収装置と、図２に示す比較例としての衝撃吸収装置を用いた落下衝撃試験の結果を示すグラフである。比較例の衝撃吸収装置は、図中で右側である先端側の低強度部１３Ａと基端側の高強度部１３Ｂから成る筒体１３を備えたものである。
【００２４】
低強度部１３Ａは、降伏点強度１６０Ｍｐａ、板厚１．６ｍｍの鋼板を使用し、軸方向の長さが４００ｍｍであり、外形が１００ｍｍ×１００ｍｍである。他方、高強度部１３Ｂは、降伏点強度２９０Ｍｐａ、板厚２．０ｍｍの鋼板を使用し、軸方向の長さが４００ｍｍであり、外形が１００ｍｍ×１００ｍｍである。そして、低強度部１３Ａと高強度部１３Ｂは、レーザビームにより突合せ溶接してあり、高強度部１３Ｂの基端部を構造体Ａに直接接合してある。
【００２５】
そして、実施例の衝撃吸収装置と比較例の衝撃吸収装置をその先端部が上向きとなるように垂直に設置し、これに対して、重量が５００ｋｇｗで且つ装置先端部との接触面が平面である錘を高さ３ｍから落下させ、錘に接続したトルク計により反力を測定した。また、装置の変位は光学式の変位測定装置で測定した。
【００２６】
図３に示すグラフから明らかなように、比較例の衝撃吸収装置では、反力が増大した後、低強度部１３Ａと高強度部１３Ｂが連続的に座屈して反力に１つのピークしか表れない。これに対して、実施例の衝撃吸収装置では、反力が増大して溶接部Ｗが破断した後、低強度部３Ａの座屈により反力が減少し、さらに、外筒部材２と高強度部３Ｂにより再び反力が増大した後、筒部材２と高強度部３Ｂの座屈により再び反力が減少しており、反力に２つのピークが表れている。具体的には、実施例の衝撃吸収装置では、変位量が１２ｍｍ程度で反力が最大になると共に、従来の衝撃吸収装置に対して反力が約３０Ｍｐａ増加しており、高い衝撃吸収性能が得ることが可能である。
【００２７】
ここで、実施例１，２および比較例１〜３として、外筒部材２における大断面部２Ａの断面積と軸方向の長さＬｂを変えたものを用意し、落下衝撃試験により内筒部材３の低強度部３Ａを座屈させて外筒部材２の変形の有無を確認した。その結果を表１に示す。
【００２８】
【表１】
【００２９】
表１から明らかなように、実施例１，２では、外筒部材２の変形は発生しなかったが、比較例１では、大断面部２Ａの断面積が不充分であったため、内筒部材３の低強度部３Ａが座屈により外筒部材２に接触して負荷を与え、外筒部材２の一部に亀裂が発生した。また、比較例２，３では、大断面部２Ａの断面積不足あるいは軸方向長さ不足により、外筒部材２に変形が発生した。
【００３０】
次に、実施例３〜５および比較例４〜９として、内筒部材３における低強度部３Ａおよび高強度部３Ａの条件、外筒部材２の条件、溶接部Ｗの溶接幅を変えたものを用意し、落下衝撃試験により内筒部材３の低強度部３Ａを座屈させて、最大反力と部材の変形状態を確認した。その結果を表２に示す。
【００３１】
【表２】
【００３２】
表２から明らかなように、実施例３〜５では、１４０〜１６０ｋＮの最大反力が得られ、部材の変形状態も良好であった。これに対して、比較例４〜９では、いずれも最大反力が実施例よりも小さく、比較例８を除いて部材の変形に異常が生じた。以上の結果から、実施例の衝撃吸収装置は、初期の最大反力の向上と変位−反力変化から、衝撃入力に対して優れた衝撃吸収性能を有することを確認した。
【００３３】
なお、上記実施例で説明したように、内筒部材３の基端部から軸方向長さの１／３〜１／２の範囲Ｌｂにおいて、内筒部材３の断面積に対して、外筒部材２の断面積を１．５〜２倍としたこと、換言すれば、外筒部材２の大断面部２Ａの軸方向の長さＬｂと断面積の大きさを設定したことにより、内筒部材３との間に低強度部３Ａが座屈する空間を確保することができ、この際、外筒部材２の外形を過大にせずに、且つ座屈した低強度部３Ａが外筒部材２に接触することの無い空間を確保することができ、衝撃吸収と外筒部材２の形状保持を両立させることができる。
【００３４】
また、内筒部材３において、低強度部３Ａの降伏点強度と板厚の積に対して、高強度部３Ｂの降伏点強度と板厚の積の比を１．２５以上にしたことにより、衝撃入力に対して低強度部３Ａが必ず先に座屈変形することとなり、高い衝撃吸収効果を得ることができる。
【００３５】
さらに、内筒部材３における高強度部３Ｂの降伏点強度と板厚の積に対して、外筒部材２の降伏点強度と板厚の積の比を１以上にしたことにより、内筒部材３よりも先に外筒部材２が変形するような事態を未然に防止することができ、高い衝撃吸収効果を得ることができる。
【００３６】
さらに、外筒部材２と内筒部材３の高強度部３Ｂとの重合部分を、周方向の線状溶接として重ね溶接により接合したことにより、衝撃入力で溶接部Ｗを先に破断させるにあたって、溶接強度を制御することが容易になり、外筒部材２や内筒部材３の変形よりも先に溶接部Ｗを確実に破断させることができ、高い衝撃吸収効果を得ることができる。
【００３７】
さらに、内筒部材３の板厚に対して、外筒部材２と内筒部材３の高強度部３Ｂとを接合する溶接幅の比を０．４〜０．８にしたことにより、各部材そのものの形状を保持し得る溶接強度を確保することができると共に、先に溶接部Ｗを確実に破断させることができ、高い衝撃吸収効果を得ることができる。
【００３８】
さらに、外筒部材２と内筒部材３の高強度部３Ｂとの重合部分を、周方向の線状溶接としてレーザビーム、プラズマおよび電子ビームのいずれかを用いた溶接により接合したことにより、外筒部材２の外側からのみの溶接が可能であって、溶接部近傍の熱影響による軟化部位を最小限に抑えることができると共に、衝撃入力時における溶接部近傍の変形を抑制することができ、これにより、溶接部Ｗを確実に破断させて高い衝撃吸収効果を得ることができる。
【００３９】
なお、上記実施例の外筒部材２と内筒部材３の関係とは逆に、外筒部材を低強度部と高強度部で形成し、内筒部材の全体が低強度部よりも高強度である構成にすることも可能であるが、上記実施例で説明した構成にすれば、常態において最も弱い低強度部３Ａを外筒部材２で保護することができると共に、内筒部材３の軸方向の座屈変形がより円滑なものになる。
【図面の簡単な説明】
【図１】本発明に係わる衝撃吸収装置の一実施例を説明する正面図（ａ）および断面図（ｂ）である。
【図２】比較例としての衝撃吸収装置を説明する正面図（ａ）および断面図（ｂ）である。
【図３】実施例と比較例の衝撃吸収装置を用いた落下衝撃試験の結果として反力と変位の関係を示すグラフである。
【符号の説明】
Ａ 構造体
Ｗ 溶接部
１ 仕切り部材
２ 外筒部材
３ 内筒部材
３Ａ 低強度部
３Ｂ 高強度部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a shock absorbing device used to absorb energy of a shock input, for example, to a shock absorbing device used as a structural member of an automobile.
[0002]
[Prior art]
As a conventional shock absorbing device, there is a device using a material having a high elastic modulus as a material for absorbing shock energy. However, a material having a high elastic modulus may be difficult to maintain a constant shape while supporting a high load, and is not suitable for a structure supporting a heavy object such as an engine, for example, a front member of an automobile. . As a shock absorbing device for this front member, a high-strength material is placed inside the vehicle, a low-strength steel plate is placed in front of the high-strength material, and the low-strength steel plate buckles or responds to shock input from the front. Some have absorbed the impact energy by being deformed, and have protected the body frame with high-strength materials inside the vehicle.
[0003]
[Problems to be solved by the invention]
However, in this type of shock absorbing device, there is a limit in increasing the strength of a material such as a steel sheet itself, and it is expected that workability will become more difficult as the material becomes stronger. Since the initial reaction force at the time of impact input is determined by the material properties of the low-strength material, it has been difficult to enhance the impact energy absorption performance only by selecting the material.
[0004]
[Object of the invention]
The present invention has been made in view of the above-described conventional situation, and has as its object to provide an impact absorbing device capable of improving the impact energy absorbing performance.
[0005]
[Means for Solving the Problems]
An impact absorbing device according to the present invention includes a partition member joined to a structure to be protected from an impact, an outer cylinder member joined to a partition member at a base end, and a base member joined to a partition member at a base end. An inner cylinder member inscribed in the distal end portion of the cylinder member and having a distal end portion protruding from the outer cylinder member, wherein the inner cylinder member has a low-strength portion on the base end side having a lower axial compressive strength than the outer cylinder member; It has a high-strength part on the distal end side that has higher axial compressive strength than the high-strength part. An impact absorbing device, wherein a superposed portion of a member and a high-strength portion is joined by linear welding in a circumferential direction.
[0006]
Effect of the Invention
In the shock absorbing device according to the present invention, for example, a plate-shaped partition member is joined to the structure to be protected from the impact, and the partition member has, for example, an inner cylindrical member having the same rectangular cross section as the outer cylindrical member having the rectangular cross section. The cylindrical member is provided coaxially with the axial direction vertical, and receives a shock at the tip of the inner cylindrical member protruding from the outer cylindrical member.
[0007]
In this shock absorbing device, when a shock is applied to the tip of the inner cylinder member, the reaction force increases, and then the welded portion joining the overlapped portion of the outer cylinder member and the inner cylinder member is broken. Here, the inner cylindrical member includes a low-strength portion on the base end side having a lower axial compressive strength than the outer cylindrical member, and a high-strength portion on the distal end having a higher axial compressive strength than the low-strength portion. Are coaxially butted and joined by welding or the like, so that the low-strength portion of the inner cylindrical member buckles following the fracture of the preceding welded portion, thereby reducing the reaction force. That is, it absorbs impact energy. At this time, since the high-strength portion is in contact with the distal end portion of the outer cylinder member, the inner cylinder member contracts in the axial direction while being guided by the outer cylinder member along with the buckling of the low-strength portion.
[0008]
Then, after the contracted distal end of the inner cylindrical member reaches the distal end of the outer cylindrical member, the reaction force increases again by maintaining the shape at the high-strength portions of the outer cylindrical member and the inner cylindrical member. Further, when the impact input is large, after the distal end of the inner cylinder member reaches the distal end of the outer cylinder member, the high strength portion of the inner cylinder member and the outer cylinder member buckle to absorb impact energy. The shock absorbing device absorbs the impact energy as described above, while the structure is formed by a partition member provided between each base end of the outer tube member and the inner tube member and the structure to be protected. Protect.
[0009]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the shock absorbing device which concerns on this invention, while having the simple structure provided with the partition member, the outer cylinder member, and the inner cylinder member which consists of a high-strength part and a low-strength part, the impact energy absorption performance can be improved. Also, the initial reaction force can be increased, and the structure can be reliably protected from impact.
[0010]
【Example】
FIG. 1 is a view for explaining an embodiment of a shock absorbing device according to the present invention. The illustrated shock absorbing device is provided at, for example, a front portion or a rear portion of an automobile, and is bonded to a box-shaped structure (for example, a vehicle body cabin) A to be protected from an impact. A partition member 1 having a plate shape, an outer cylindrical member 2 having a rectangular cross section, and an inner cylindrical member 3 having a rectangular cross section are provided. These members 1 to 3 are made of, for example, a steel plate.
[0011]
The outer cylinder member 2 has a large cross-section 2A over a predetermined length Lb from a base end on the right side in the drawing, and continuously connects a small cross-section 2C to a distal end of the large cross-section via a tapered portion 2B. The base end is joined to the partition member 1 by welding. The outer cylindrical member 2 may be formed by integrally forming the whole by plastic working, or may be formed by individually forming the respective portions 2A to 2C and sequentially joining them by welding.
[0012]
The inner cylinder member 3 has a cross-sectional shape corresponding to the inner space of the small cross-section 2C of the outer cylinder member 2 over the entire axial direction. The inner cylindrical member 3 includes a base-side low-strength portion 3A having lower axial compressive strength than the outer cylindrical member 2 and a distal-side high-strength portion 3B having higher axial compressive strength than the low-strength portion 3A. In addition, the low-strength portion 3A and the high-strength portion 3B are coaxially butted and welded to be integrated.
[0013]
The inner cylinder member 3 is inserted inside the outer cylinder member 2, and the base end is joined to the partition member 1 by welding. The strength portion 3 </ b> B is in inscribed state, and the distal end portion protrudes from the outer cylinder member 2. The overlapping portion of the outer cylinder member 2 and the high-strength portion 3B of the inner cylinder member 3 inscribed therein is joined by circumferential linear welding (welded portion W). In the drawings, the length of the low-strength portion 3A and the length of the high-strength portion 3B of the inner cylindrical member 3 are shown to be substantially equal, but the present invention is not limited to this.
[0014]
Here, the large cross section 2A of the outer cylinder member 2 is 1/3 to 1/1 / of the axial length from the base end of the inner cylinder member 3 to the axial length La of the inner cylinder member 3. 2, and the area of the cross section perpendicular to the axis is 1.5 to 2 times the cross sectional area of the inner cylinder member 3.
[0015]
In the inner cylinder member 3, the ratio of the product of the yield point strength and the thickness of the high-strength portion 3B to the product of the yield point strength and the thickness of the low-strength portion 3A is 1.25 or more. The ratio of the product of the yield point strength and the thickness of the outer cylinder member 2 to the product of the yield point strength and the thickness of the high-strength portion 3B in FIG.
[0016]
Further, at the overlapping portion of the outer cylinder member 2 and the high strength portion 3B of the inner cylinder member 3, any one of a beam such as a CO 2 laser or a YAG laser, a plasma, and an electron beam was used as a linear weld in the circumferential direction. The ratio of the welding width for joining the outer cylinder member 2 and the high-strength portion 3B of the inner cylinder member 3 to the plate thickness of the inner cylinder member 3 is set to 0.4 to 0.8. I have.
[0017]
As a more specific example, the outer cylinder member 2 uses a steel plate with a yield point strength of 290 Mpa and a thickness of 1.8 mm, an axial length of 600 mm, and an outer shape of the large cross section 2A of 130 mm × 130 mm. The inner shape of the small cross section 2C is 100 mm × 100 mm. The outer cylinder member 2 is joined to the partition member 1 by arc welding. In addition, the partition member 1 uses the same material as the outer cylinder member 2 and is joined to the structure A by arc welding.
[0018]
The low-strength portion 3A in the inner cylindrical member 3 uses a steel plate with a yield point strength of 160 Mpa and a thickness of 1.6 mm, an axial length of 400 mm, and an outer shape of 100 mm × 100 mm. On the other hand, the high-strength portion 3B uses a steel plate having a yield point strength of 290 Mpa and a thickness of 1.6 mm, an axial length of 400 mm, and an outer shape of 100 mm × 100 mm. The low-strength portion 3A and the high-strength portion 3B are butt-welded with a CO 2 laser having a maximum output of 5 kW, and the base end of the low-strength portion 3A is joined to the partition member 1 by arc welding.
[0019]
Then, in the overlapping portion of the outer cylinder member 2 and the high-strength portion 3B of the inner cylinder member 3 inscribed in the outer cylinder member 2, a position 10 mm from the tip of the outer cylinder member 2 is overlapped and welded in the circumferential direction by a CO 2 laser. At this time, the laser output and the processing speed were adjusted to make the welding width of the welded portion W 10 mm.
[0020]
In the shock absorbing device having the above configuration, when a shock is applied to the tip of the inner cylinder member 3, the reaction force increases, and then the welded portion W between the outer cylinder member 2 and the inner cylinder member 3 is broken. Subsequently, the low strength portion 3A of the inner cylindrical member 3 buckles, thereby reducing the reaction force. That is, it absorbs impact energy. At this time, the inner cylinder member 3 contracts in the axial direction while the high strength section 3B is guided by the outer cylinder member 2 with the buckling of the low strength section 3A.
[0021]
After the contracted distal end of the inner tubular member 3 reaches the distal end of the outer tubular member 2, the reaction force is increased again by maintaining the shape of the outer tubular member 2 and the high-strength portion 3B, and the impact is further increased. When the input is large, the high strength portion 3B of the inner cylinder member 3 and the outer cylinder member 2 buckle and absorb the impact energy. During this time, the impact absorbing device protects the structure A by the partition member 1 while absorbing the impact energy as described above.
[0022]
As described above, the shock absorbing device having the above-described configuration has a high shock absorbing property due to the simple structure including the partition member 1, the outer cylindrical member 2, and the inner cylindrical member 3 including the high-strength portion 3B and the low-strength portion 3A. Performance can be exhibited, and the structure A can be reliably protected from impact.
[0023]
FIG. 3 is a graph showing the results of a drop impact test using the shock absorbing device described in the above embodiment and the shock absorbing device as a comparative example shown in FIG. The shock absorbing device of the comparative example includes a cylindrical body 13 composed of a low-strength portion 13A on the right end in the drawing and a high-strength portion 13B on the base end.
[0024]
The low-strength portion 13A uses a steel plate having a yield point strength of 160 Mpa and a thickness of 1.6 mm, an axial length of 400 mm, and an outer shape of 100 mm × 100 mm. On the other hand, the high-strength portion 13B uses a steel plate having a yield point strength of 290 Mpa and a thickness of 2.0 mm, an axial length of 400 mm, and an outer shape of 100 mm × 100 mm. The low-strength portion 13A and the high-strength portion 13B are butt-welded with a laser beam, and the base end of the high-strength portion 13B is directly joined to the structure A.
[0025]
Then, the shock absorbing device of the example and the shock absorbing device of the comparative example are installed vertically so that their tips are directed upward, whereas the weight is 500 kgw and the contact surface with the device tip is flat. A certain weight was dropped from a height of 3 m, and the reaction force was measured by a torque meter connected to the weight. The displacement of the device was measured by an optical displacement measuring device.
[0026]
As is clear from the graph shown in FIG. 3, in the shock absorbing device of the comparative example, after the reaction force increases, the low-strength portion 13A and the high-strength portion 13B continuously buckle, and only one peak appears in the reaction force. Absent. On the other hand, in the shock absorbing device of the embodiment, after the reaction force increases and the welded portion W breaks, the reaction force decreases due to the buckling of the low-strength portion 3A. After the reaction force increases again by the portion 3B, the reaction force decreases again due to the buckling of the cylindrical member 2 and the high-strength portion 3B, and two peaks appear in the reaction force. Specifically, in the shock absorbing device of the embodiment, the reaction force is maximized when the displacement amount is about 12 mm, and the reaction force is increased by about 30 Mpa compared to the conventional shock absorbing device. It is possible to get.
[0027]
Here, Examples 1 and 2 and Comparative Examples 1 to 3 were prepared by changing the cross-sectional area of the large cross-section 2A and the length Lb in the axial direction of the outer cylinder member 2 and performing a drop impact test on the inner cylinder member. 3 was buckled, and the presence or absence of deformation of the outer cylindrical member 2 was confirmed. Table 1 shows the results.
[0028]
[Table 1]
[0029]
As is clear from Table 1, in Examples 1 and 2, no deformation of the outer cylindrical member 2 occurred, but in Comparative Example 1, the cross-sectional area of the large cross-sectional portion 2A was insufficient, so that the inner cylindrical member 2 was not deformed. The low-strength portion 3A of No. 3 contacted and applied a load to the outer cylinder member 2 due to buckling, and a crack occurred in a part of the outer cylinder member 2. In Comparative Examples 2 and 3, the outer cylindrical member 2 was deformed due to insufficient cross-sectional area or insufficient axial length of the large cross-section 2A.
[0030]
Next, as Examples 3 to 5 and Comparative Examples 4 to 9, the conditions of the low-strength portion 3A and the high-strength portion 3A in the inner cylinder member 3, the conditions of the outer cylinder member 2, and the welding width of the welded portion W were changed. Was prepared, and the low-strength portion 3A of the inner cylindrical member 3 was buckled by a drop impact test to confirm the maximum reaction force and the deformation state of the member. Table 2 shows the results.
[0031]
[Table 2]
[0032]
As is clear from Table 2, in Examples 3 to 5, the maximum reaction force of 140 to 160 kN was obtained, and the deformation state of the member was also good. On the other hand, in Comparative Examples 4 to 9, the maximum reaction force was smaller than that of Example, and abnormalities occurred in the deformation of the members except for Comparative Example 8. From the above results, it was confirmed that the shock absorbing device of the example had excellent shock absorbing performance against a shock input from the improvement of the initial maximum reaction force and the change in displacement-reaction force.
[0033]
As described in the above embodiment, in the range Lb of 1/3 to 1/2 of the axial length from the base end of the inner cylinder member 3, the outer cylinder By setting the cross-sectional area of the member 2 to 1.5 to 2 times, in other words, by setting the axial length Lb and the size of the cross-sectional area of the large cross-sectional portion 2A of the outer cylindrical member 2, A space in which the low-strength portion 3A buckles can be ensured between the outer tube member 2 and the member 3. The buckled low-strength portion 3A is attached to the outer tube member 2 without increasing the outer shape of the outer tube member 2. A space without contact can be secured, and both impact absorption and shape retention of the outer cylinder member 2 can be achieved.
[0034]
Also, in the inner cylindrical member 3, the ratio of the product of the yield point strength and the thickness of the high strength portion 3B to the product of the yield point strength and the thickness of the low strength portion 3A is set to 1.25 or more. The low-strength portion 3A always buckles and deforms in response to a shock input, and a high shock absorbing effect can be obtained.
[0035]
Further, the ratio of the product of the yield point strength and the thickness of the outer cylinder member 2 to the product of the yield point strength and the thickness of the high-strength portion 3B in the inner cylinder member 3 is 1 or more, so that the inner cylinder member It is possible to prevent a situation in which the outer cylinder member 2 is deformed earlier than the case 3, and a high shock absorbing effect can be obtained.
[0036]
Furthermore, when the overlapping portion of the outer cylinder member 2 and the high-strength portion 3B of the inner cylinder member 3 is joined by lap welding as linear welding in the circumferential direction, the welded portion W is first broken by an impact input. It is easy to control the welding strength, and it is possible to surely break the welded portion W prior to the deformation of the outer tube member 2 and the inner tube member 3, and to obtain a high shock absorbing effect.
[0037]
Furthermore, the ratio of the welding width for joining the outer cylinder member 2 and the high-strength portion 3B of the inner cylinder member 3 to the plate thickness of the inner cylinder member 3 is set to 0.4 to 0.8, so that each member is formed. It is possible to ensure the welding strength that can maintain the shape of itself, and to reliably break the welded portion W first, and to obtain a high shock absorbing effect.
[0038]
Furthermore, the overlapped portion of the outer cylinder member 2 and the high-strength portion 3B of the inner cylinder member 3 is joined by welding using any one of a laser beam, a plasma, and an electron beam as a linear weld in the circumferential direction. Welding can be performed only from the outside of the tubular member 2, and a softened portion due to heat influence near the welded portion can be minimized, and deformation near the welded portion at the time of impact input can be suppressed. Thereby, the welded portion W can be reliably broken, and a high impact absorbing effect can be obtained.
[0039]
In addition, contrary to the relationship between the outer cylinder member 2 and the inner cylinder member 3 in the above embodiment, the outer cylinder member is formed of a low-strength portion and a high-strength portion, and the entire inner cylinder member has a higher strength than the low-strength portion. However, according to the configuration described in the above embodiment, the weakest low-strength portion 3A in the normal state can be protected by the outer cylindrical member 2 and the shaft of the inner cylindrical member 3 can be protected. Buckling deformation in the direction becomes smoother.
[Brief description of the drawings]
FIG. 1 is a front view (a) and a cross-sectional view (b) illustrating an embodiment of a shock absorbing device according to the present invention.
FIG. 2 is a front view (a) and a cross-sectional view (b) illustrating a shock absorbing device as a comparative example.
FIG. 3 is a graph showing a relationship between a reaction force and a displacement as a result of a drop impact test using the impact absorbing devices of the example and the comparative example.
[Explanation of symbols]
A Structure W Welded part 1 Partition member 2 Outer tube member 3 Inner tube member 3A Low strength part 3B High strength part