JP2004114146A

JP2004114146A - Press-fitting joining structure and method

Info

Publication number: JP2004114146A
Application number: JP2002285191A
Authority: JP
Inventors: Akira Nozue; 野末　明; Osamu Kanehara; 金原　理
Original assignee: Ohashi Technica Inc
Current assignee: Ohashi Technica Inc
Priority date: 2002-09-30
Filing date: 2002-09-30
Publication date: 2004-04-15
Anticipated expiration: 2022-09-30
Also published as: JP3822853B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a press-fitting joining structure and method which joins members composing a metal component easily and economically with high finishing accuracy and excellent strength. <P>SOLUTION: The press-fitting joining structure uses a first member 2 having an aperture 13 in which an inner wall face being the same as the section of the press-fitted part is formed and a second member 4 which is shaped similarly to the aperture 13 and has a constant section. 0.1mm or more is secured as the allowance for the press-fitting of the second member 4 into the aperture 13 of the first member 2. The second member 4 is pressed into the aperture 13 of the first member 2 at a given pressure, and both members are electrified therebetween so as to generate heat by electrical resistance at the joined part of both members. Then the second member 4 is press-fitted into the aperture 13 so that a boundary face is formed at the joined part between the second member 4 and the inner wall face of the aperture 13 and the joining is brought to a solid phase. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、金属製要素部品を構成する部材同士の圧入接合構造及び圧入接合方法に関する。
【０００２】
【従来の技術】
従来、自動車等に使用される金属製要素部品を製造する場合、通常、アーク溶接等により部材同士を接合している。これは、例えばプレートに軸体（又は筒体）を接合する場合には、プレートに設けた孔に軸体を嵌め込み、アーク溶接等により溶加材を用いて軸体との嵌め合せ部位の全周又は局部的に溶接を行うものである。また、抵抗溶接法として、スポット溶接法、プロジェクション溶接法による接合、或いはかしめ加工により部材同士を接合する方法も行われている。
【０００３】
また、パイプ接続孔に挿入するパイプ部の挿入側元部にビードを形成し、あるいは上記パイプ接続孔の入口側周縁にリップを形成して、抵抗溶接するものもある（例えば、特許文献１参照）。
【０００４】
【特許文献１】
特開平７−４００５８号公報
【特許文献２】
特開２００１−３５３６２８号公報
【０００５】
【発明が解決しようとする課題】
しかし、上記接合方法によれば、アーク溶接の溶接熱による熱変形等により、プレート、軸体等の母材の熱的劣化や、寸法歪みが発生して精度への影響が避けられない。この場合には、溶接後に後加工を加えて製品の精度を高め、また溶接部分の不要な溶加材を削除するなど、溶接後の仕上げ加工に多くの手間と費用を要するといった問題がある。
【０００６】
また、上記抵抗溶接法は重ね抵抗溶接法が主力であり、いずれも接合部にナゲットと呼ばれる溶融組織を形成することで接合している。この重ね抵抗溶接では、溶接を強くするためにはナゲットの数を増やすしかなく、結果として接合母材の熱的劣化や、寸法精度への影響が避けられない。また、上記ビード、或いはリップの形成には製造工程が複雑化し、また後加工等を要することから、費用がかかるという問題がある。
【０００７】
これに対して、本件出願人は先に非全周の圧入接合構造を提案した（特許文献２参照）。しかし、非全周の圧入接合構造の場合には、接合部の気密性の点で例えば流体を通過させるパイプ同士の接合には不向きであるという問題がある。
【０００８】
ここで、全周の圧入接合構造では下記の問題が考えられている。
▲１▼　圧入時のしごきによって削り取られるバリの量が多いため、全周接合を想定したとき、バリが邪魔になって所定の圧入深さの圧入接合を行うことが難しい。
▲２▼　初期通電時の接触面積が増えるため、所要電流が多く必要となり、接合構造の大きさが制限される。これから、先の非全周の圧入接合構造のままの条件で全周接合を行うのは適当でなく、新たな条件が必要となることが予想される。そこで、本件出願人は、上記問題点を解決するため試験行い全周の圧入接合構造の実用化を図った。
【０００９】
本発明は、上記問題点に鑑みてなされたものであり、製造容易で経済効果に優れ、かつ仕上精度が良く強度的にも優れた圧入接合構造及び圧入接合方法を提供することを目的としている。
【００１０】
【課題を解決するための手段】
以上の技術的課題を解決するため、本発明に係る圧入接合構造は、図１に示すように、圧入部分の断面が同一の内壁面部が形成された孔部１３，２１を有する第一の部材２，２２と、上記孔部１３，２１と相似形状で、かつ一定の断面を有する第二の部材４，２４とを用い、上記第一の部材２，２２の孔部１３，２１に対する第二の部材４，２４の圧入代を０．１ｍｍ以上とし、上記第一の部材２，２２の孔部１３，２１内に上記第二の部材４，２４を所定の圧力で押圧するとともに、これら両部材間に通電して両者の接合部に電気抵抗熱を発生させ、上記第二の部材４，２４を上記孔部１３，２１に圧入し、上記第二の部材４，２４と上記孔部１３，２１の内壁面部との接合面部に接合界面を形成させ、かつこの接合を固相状態の接合としたことである。
【００１１】
また、本発明に係る圧入接合構造は、上記圧入接合の後、再度上記第一の部材と上記第二の部材との間に通電し、両者の接合部に電気抵抗熱を発生させて焼き戻しを行うことである。
【００１２】
また、本発明に係る圧入接合構造は、上記圧入代の上限を０．４ｍｍとし、
上記圧入代と、上記第一の部材と上記第二の部材とが接合する圧入深さを（１−２×圧入代）ｍｍ以上として両部材を接合したことである。
【００１３】
また、本発明に係る圧入接合構造は、上記圧入代の上限を０．４ｍｍとし、
上記圧入代と、上記第一の部材と上記第二の部材とが接合する圧入深さを１．０ｍｍ以上として両部材を接合したことである。
【００１４】
また、本発明に係る圧入接合構造は、上記第一の部材と上記第二の部材とが接合する圧入深さの上限を（９−２０×圧入代）ｍｍとして両部材を接合したことである。
【００１５】
また、本発明に係る圧入接合構造は、上記第一の部材を、内部に貫通した円形の孔部を有する筒体に形成したことである。
【００１６】
また、本発明に係る圧入接合構造は、上記第一の部材及び上記第二の部材をそれぞれ円形の筒体に形成し、この第一の部材における上記第二の部材との接合部の内周を一様に拡径して第一の接合部を形成する一方、上記第二の部材の接合部の外周を一様に縮径して第二の接合部を形成し、上記第一の接合部内に上記第二の接合部を接合したことである。
【００１７】
また、本発明に係る圧入接合構造は、上記第一の部材を、板面から垂直方向に内壁面部が形成された円形の孔部を有する板体に形成したことである。また、上記第一の部材と第二の部材との接合部の断面積を２０平方ｃｍ以下としたことである。
【００１８】
本発明に係る圧入接合方法は、圧入部分の断面が同一の内壁面部が形成された孔部１３，２１を有する第一の部材２，２２と、上記孔部１３，２１と相似形状で、かつ一定の断面を有する第二の部材４，２４とを用い、上記第一の部材の孔部１３，２１に対する第二の部材４，２４の圧入代を０．１ｍｍ以上とし、上記第一の部材２，２２の孔部１３，２１内に上記第二の部材４，２４を所定の圧力で押圧するとともに、これら両部材間に通電して両者の接合部に電気抵抗熱を発生させ、上記両部材の軟化によって第二の部材４，２４を上記孔部１３，２１に圧入し、上記第二の部材４，２４と上記孔部１３，２１の内壁面部との接合面部に接合界面を形成させ、かつこの接合を固相状態の接合としたことである。
【００１９】
また、本発明に係る圧入接合方法は、上記圧入代の上限を０．４ｍｍとし、上記圧入代と、上記第一の部材と上記第二の部材とが接合する圧入深さとの関係を、（１≦圧入深さ（ｍｍ）≦９−２０×圧入代）の範囲で、両部材を接合したことである。
【００２０】
また、本発明に係る圧入接合方法は、上記圧入接合の後、再度上記第一の部材と上記第二の部材との間に通電し、両者の接合部に電気抵抗熱を発生させて焼き戻しを行うことである。
【００２１】
【発明の実施の形態】
以下、本発明に係る実施の形態を図面に基づいて説明する。
この実施の形態に係る圧入接合構造及び圧入接合方法では、ワークとして、筒体同士の接合、及びプレートと筒体との接合について説明する。
【００２２】
図１はワークＡとして、冶具を用いて第一の筒体２に第二の筒体４を接合する形態を示している。この冶具は、上部に円柱状の穴部７が設けられたクローム銅製の下型６と、下部に円柱状の穴部９が設けられたクローム銅製の上型８とを有する。これら下型６と上型８とは、それぞれ電極１０，１２としても機能し両型間に通電可能である。
【００２３】
上記下型６には、第一の筒体２が上部の接合部１４を残した状態で上記穴部７内に嵌入され、第一の筒体２の側壁面部２ａと穴部７の側壁部７ａとは通電のため密着している。このように第一の筒体２の側壁面部２ａに電極１０を設ける構成としたのは、第一の筒体２の下面部に電極を設けたのでは、第一の筒体２自体の抵抗が通電に影響するので、これを軽減して通電を良好にするためである。勿論、第一の筒体２に電極を設ける形態は、上記以外の方法、例えば第一の筒体２の筒内に電極を突入する等の方法であってもよく、要は第一の筒体２の接合部１４の近傍に電極を設けることである。そして、上型８には図示しないプレス機構が装備され、上型８を加圧降下する。
【００２４】
上記第一の筒体２は図２（ａ）に示すように、筒の内径φ１（直径）が１９ｍｍ、外径φ２が２２ｍｍ、筒厚ｔが１．５ｍｍの円筒形状である。その接合部１４は、第一の筒体２の端部から一定範囲の内周面が外向に一様に切り欠かれて拡径し、内径がφ３の円周面からなる孔部１３を形成している。
【００２５】
第二の筒体４は図２（ｂ）に示すように、筒の内径φ４が１９ｍｍ、外径φ５が２２ｍｍ、及び筒厚ｔが１．５ｍｍの円筒形状である。その接合部１６は、第二の筒体４の外周面が端部から一定範囲にかけて内向（中心向）に一様に切り欠かれて縮径し、外径がφ６の円周面を形成している。そして、図２（ｃ）に示すように、上記第一の筒体２の接合部１４に上記第二の筒体４の接合部１６を接合する。
【００２６】
このとき図１（ｂ）に示すように、第二の筒体４の外径φ６は第一の筒体２の内径φ３より僅かに大きく、その差（φ６−φ３）が圧入代（ｄ）となる（半径に対してはｄ／２の圧入代）。この圧入代（ｄ）により、第二の筒体４の外周部位が、第一の筒体２の内周部位と接して接合面部を形成する。
【００２７】
これら両筒体の接合部１４，１６に圧入代（ｄ）を設ける場合、それぞれ接合部１４，１６の筒厚を等しくしてバランスをとる。このため、接合部１４の内径φ３の大きさを、２０．５ｍｍ−圧入代（ｄ）／２に、また接合部１６の外径φ６を、２０．５ｍｍ＋圧入代（ｄ）／２とする。
【００２８】
圧入深さについては、通常、図１（ｂ）に示すように両筒体２，４の接合部１４，１６として、段差を形成する部位の全体が圧入深さ（ｈ）となる。試験では、バリ１５等の観測を行う都合上、図１（ｃ）に示すように、接合部１４，１６の一部を残した状態で、圧入深さ（ｈ）とした。
【００２９】
ここで、社内試験により、上記ワークＡとして上記第一の筒体２と上記第二の筒体４とを圧入接合し、接合状態を観察した結果について説明する。この第一の筒体２及び第二の筒体４の材料として、ともにクロムモリブデン鋼（ＳＣＭ４２０）を用いた。他の材料として、ＳＵＳ（ステンレス鋼）を第一の筒体２及び第二の筒体４に用いることができ、ＳＵＳと炭素鋼とを組み合わせて用いることもできる。
【００３０】
さらに他の材料として、機械構造用炭素鋼、機械構造用合金鋼、耐熱鋼、工具鋼、バネ鋼、鋳鉄、快削鋼、軸受鋼、一般加工用鋼材、圧力容器用鋼材、チタン、アルミニウムなどの軽金属等が適用可能である。また、この圧入接合においては、低炭素鋼同士、低炭素鋼と高炭素鋼及び高炭素鋼同士のいずれの組み合わせも可能である。要は、接合部における電気抵抗熱を利用した圧入加工であるから、金属であれば特に制限はされない。特に、同一の材料同士、また融点及び硬度が同程度の材料同士を接合することが、接合界面の組織が均一に形成され、良好な接合が行われる。
【００３１】
実施条件として、印加電流は２２ｋＡとした。加圧力は０．４ＭＰａ（但し、４００ｋｇｆから４５０ｋｇｆの範囲）とした。この加圧力は、母材の応力（ここでは第二の筒体４が第一の筒体２に突入することを妨げる抵抗力）よりも低い圧力としている。したがって、この加圧力が、母材の軟化により低下した応力を上回った時点から、圧入が開始されることになる。
【００３２】
さて、接合に際しては図１に示すように、上記下型６の穴部７に上記第一の筒体２を嵌入する一方、第二の筒体４を上型８の穴部９に嵌入する。そして、上型８を一定の加圧力を付勢して押圧し、併せて第一の筒体２と第二の筒体４間に通電する。すると、電気抵抗熱の発生とともに第二の筒体４の圧入が開始され、第二の筒体４の接合部１６が第一の筒体２の孔部１３の接合部１４内を降下移動する。この場合に、両部材の接合界面にしごきの作用が生じ、しごき加工による製造工程により圧入接合が行われる。
【００３３】
このとき、一定の加圧力、一定の降下速度で圧入接合が行われ、瞬時に接合部が発熱され短時間で第二の筒体４の先端部１７は第一の筒体２の段差部１８に至り接合を完了する。このとき、第一の筒体２の接合部１６と第二の筒体４の接合部１４との間には固相溶接の接合界面１９が形成される。固相溶接においては、その接合面に清浄な表面組織が得られていることが、接合の良否を左右する。この実施の形態に係る圧入接合によれば、上記接合界面１９には第二の筒体４と第一の筒体２との各壁面同士の間が滑り方向の移動によりしごかれ、これにより表面の不純物質層が削られて表面が清浄化され、この清浄な組織に固相溶接が行われる。
【００３４】
図３は、上記接合の過程を、抵抗熱による接合部の温度推移に対する加圧力及び、母材接合部の応力の変化で捉えたものである。ここで、縦軸には、接合部の温度と、接合部の母材応力、横軸には接合プロセスの時間軸をとっている。まず、時間軸に沿って説明すると、スタート時点では、接合部の温度は常温のままであり、母材（第一の筒体２及び第二の筒体４）の硬さも素材の硬さそのままである為、加圧力に対し充分な応力を保っている。したがって、この時点では、加圧されているものの第二の筒体４は第一の筒体２の上部に位置したままである。
【００３５】
時間の経過とともに通電による抵抗熱により接合面部が昇温し、それに伴って接合面部の軟化が始まる。接合面部の軟化によって応力が低下し、加圧力を克服する点が同図の圧入スタートの時点であり、第二の筒体４が第一の筒体２の接合部１４をしごきながら降下移動する。このスタート時点で接合面部の温度は最高点に達していると考えられる。
【００３６】
その後、圧入が進むにつれて、接合面部の接合面積が増加し、反対に断面積差が減少するので電流密度が下がり、結果的に抵抗熱の発生が減少し、接合面部の温度は低下する。このように、母材としての第二の筒体４が第一の筒体２内を移動して接合過程を終了する。以上の、加圧及び通電の開始、圧入スタート、圧入の完了までの全プロセスが、１秒に満たない短時間の間に行われる。そして、圧入の完了後、冷却により接合部の母材の硬さが回復して強固に接合する。
【００３７】
ここで、焼き戻しを行わない場合には、加圧→通電→圧入→放冷（急冷）の経過をたどる。このように圧入後は、そのまま放冷すれば銅製の電極により急速に冷却が行われる。このため、焼き入れ性の良い材料の圧入接合を行った場合、接合部には焼きが入り材質が脆くなる。この焼きが入る理由として、上記圧入接合では局部的にかつ急激に熱が加わるため、接合部と非接合部との温度勾配は大きくなり、鋼の変態点（Ａ３）以上に加熱された接合部は加熱が途絶されると共に急冷され、マルテンサイト組織に変化するためである。このマルテンサイト組織は、材料の炭素当量と接合材料の大きさに比例して増加する。
【００３８】
この実施の形態では、加熱後の急速冷却により接合が行われた直後に、再度、第一の筒体２と第二の筒体４との間にテンパー（熱処理）通電を行って加熱する。この再加熱によって焼き戻し処理が行われ、接合部の靭性が回復する。図４は、上記圧入接合工程に、焼き戻しの工程を加えたときの温度の変化をグラフで示したものである。同図に示すように全体は順に、工程▲１▼　加圧、通電（圧入）、工程▲２▼　放冷（急冷）、工程▲３▼　通電（焼戻し）、工程▲４▼　放冷（徐冷）の４つの工程からなる。
【００３９】
上記焼き戻しとなる理由は、最初の加熱接合時の熱の伝熱により、周辺部材が加熱され、部材の温度が高くなる。このため、少し時間をおいて上記テンパー通電を行うことにより、周辺部材の温度が高められ、２回目の通電によって加熱された接合部は冷却速度が遅くなる。このとき、焼入れ組織であるマルテンサイトは焼き戻しマルテンサイトに変化し、靭性が回復して焼き戻しが行えるのである。これらの工程は短時間で行われるため、最初に部材をセットした治具で行うことが望ましい。上記焼き戻しは、特にワークとしてＳ３０Ｃ以上の炭素含有量の鋼材、または炭素当量０．３％以上の材料を用いた場合に有効である。
【００４０】
図５及び図６は、上記第一の筒体２に第二の筒体４を圧入接合したときの、接合界面における接合部の金属顕微鏡撮影写真である。このときの、圧入代（ｄ）は０．２ｍｍである。ワークを観察した結果、接合部の周囲の熱影響範囲（硬度変化範囲）が比較的狭く、接合部の周囲の熱影響部では、結晶粒が成長せず、不規則で粒状の組織が観察される。そして、接合界面には異常な炭化物や酸化物が見られなく良好な接合状態にあり、これから機械的強度が確保される。
【００４１】
上記観察結果より、圧入の直後は接合面部が狭いことから電流が集中して組織の表層部が軟化或いは限られた薄層だけが溶融するものの、接合状態は、圧入による塑性変形（熱塑性）を伴った固相溶接に至ったものといえる。したがって上記実施の形態に係る圧入接合は、従来の重ね溶接とは異なり、接合部に溶融凝固層が殆ど存在しないことから、固相溶接あるいは固相溶接に近い接合方法である。
【００４２】
特に、上記圧入接合で重要な点は、圧入の工程において、圧入というプロセスの効果として、接合界面には滑り方向の動きが生まれ、これにより表面の不純物質層が削り取られ、かつ除去されるという作用が得られることにある。この作用により、固相溶接に必須の清浄な接合表面が形成されて、両者の接合が強固に行われるものであり、この接合方法における特徴的な作用効果といえる。
【００４３】
ここで、上記ワークＡについて行った、社内における第一の試験について説明をする。この試験では、上記ワークＡにつき上記圧入代（ｄ）が０．１ｍｍ〜０．４ｍｍの範囲で、また圧入深さ（ｈ）を０．５ｍｍ〜１０．０ｍｍの範囲で圧入接合を行なった。下記表１は、そのときの接合部の引き抜き強度、及び接合端部に発生するバリ１５の量、圧入深さについての試験結果をまとめたものである。
【００４４】
【表１】

【００４５】
この試験では、第一の筒体２と第二の筒体４との圧入代（ｄ＝φ６−φ３）が０．１ｍｍ以下については行わなかったが、これは圧入代の削り量が少なく接合が不安定であることが予測されたこと、及び抵抗溶接の際に初期加圧力で圧入されてしまうために試験が困難であり正確なデータを得ることができないことから試験の対象から除外した。また、圧入代（ｄ）が０．５ｍｍ以上の場合には、圧入深さと圧入代による削り量が多すぎるため、仕上りが雑となり接合面の歪みが大きくなって仕上りにむらができ好ましくないので試験対象から除外した。
【００４６】
また同表に示す抜け強度は、試験サンプルの第一の筒体２を固定し、圧入方向と反対方向から、第二の筒体４の端面にオートグラフで静荷重を加え、第二の筒体４が第一の筒体２から剥離して抜ける荷重（接合部の破壊荷重）を測定した結果である。強度の試験機として、引張り試験機オートグラフ（島津製作所製）を用いた。
【００４７】
「抜け強度」の単位は（ｋＮ）であり、「母材」と記入されているのは母材自体が破断したものである。この母材の破断は、母材の接合部と非接合部との境界である熱影響部において発生しており、接合部で破断することは見られなかった。
【００４８】
図７（ａ）は、第一の筒体２に第二の筒体４を圧入接合したときのバリ１５（第一の筒体２の先端部のバリ）、及びバリ１５’（第二の筒体４の先端部のバリ）の形状を示したものである。この第一の筒体２と第二の筒体４の接合のように、接合部が対称的（各断面形状が略同一）な形態の場合には、材料の高温変形抵抗の違いによって、バリの発生状態が異なる。第一の筒体２の高温変形抵抗が第二の筒体４より大の場合には、バリ１５がバリ１５’に比べて大きく形成され、小の場合はバリ１５が小さく、また等しい場合にはバリ１５、１５’は同じ大きさに形成される。図７（ｂ）は、後述するプレート２０に筒体２２を圧入接合したときのバリ３７の形状を示したものである。
【００４９】
バリ１５の量は目視で判定したものである。この目視の判定では図７に示すように、概ね、圧入深さ（ｈ）に対する同方向のバリのはみ出し量（ｖ）を基準とし、この割合が約２割以内であればはみ出し量が少ないと、また２割以上であればはみ出し量が多いと判断した。なお、試験の際には、各接合部材については接触する部位の端部に面取りを施して圧入接合を行ったが、測定の都合上、この面取り部分を加えた深さを圧入深さとした。
【００５０】
表１および下記表２において、「バリ」の判定結果については、「〇」はバリのはみ出しがほとんど無い状態、「△」はバリのはみ出し量が少ない状態、「×」はバリのはみ出し量が多い状態、をそれぞれ示している。また、「圧入深さ」については、その深さまで圧入できたか否かを示し、（〇）は圧入できたこと、（×）はその深さまで圧入できなかったことを示している。
【００５１】
図８は、上記試験結果に基づいて、良好な接合が得られる範囲をグラフで示したものである。ここで、接合が良好といえる目安として、▲１▼接合強度が１０ｋＮ以上であること、▲２▼圧入接合によって生じるバリの量が少ないこと、▲３▼圧入接合により圧入物が挫屈、縮小などの永久変形をしないこと、を考慮した。
【００５２】
試験結果によれば、同図に示すように、圧入代、或いは圧入深さが大きくなるにつれて接合強度が増加する。接合強度の適否の目安は、製品の用途によっても異なるが、通常数ｋＮであることから、「１０ｋＮ程度以上」を、好適な強度としての目安とした。
【００５３】
先ず、圧入代が０．１ｍｍに満たない場合は、圧入代の削り量が少なく接合が不安定であるため排除した。したがって、圧入代の範囲は下記式▲３▼となる。
０．１≦圧入代（ｍｍ）　　　　式▲３▼
圧入代が多いとバリによって接合部の外観が悪くなるので圧入代は少ないほうが良いが、この圧入代を少なくすると接合力が低下する。接合の際、接合界面の清浄度は、圧入時にこの接合部に加えられるしごきがある限り、酸化皮膜除去機能が発揮され接合力は確保される。このしごきが適切に行われる圧入代が、上記式▲３▼の範囲である。
【００５４】
次に、良好な強度（１０ｋＮ程度以上）及び品質（バリ）が得られるための、各圧入代における圧入深さの範囲（下限及び上限）について検討する。上記範囲の下限については、品質（バリ）は良好であり問題とならないので、この場合には接合強度により制限される。表１から、圧入代０．１ｍｍでは圧入深さが１．０ｍｍ、圧入代０．２ｍｍでは圧入深さが１．０ｍｍ、圧入代０．３ｍｍでは圧入深さが０．５ｍｍ、圧入代０．４ｍｍでは圧入深さが０．５ｍｍであり、これらを（△）でプロットした。
【００５５】
これらの、△を特に、圧入代０．１ｍｍ及び圧入代０．３ｍｍに注目して直線で結び、これを圧入深さの下限とすると、
１−２×圧入代≦圧入深さ（ｍｍ）　　　　式▲４▼
なる簡単な式が導かれる。これから、圧入深さの下限はこの式▲４▼の範囲が良好である。圧入深さが式▲４▼の範囲より小さいと、圧入の際の削り量が少ないため接合強度が出ない。
【００５６】
全ての範囲の圧入代（０．１〜０．４ｍｍ）で良好な強度が得られるのは、圧入深さが１．０ｍｍ以上であり、この範囲であればより安定しかつ良好な圧入強度が確保できる。
【００５７】
次に、上記範囲の上限については、接合強度は良好（１０ｋＮ）であり問題とならないので、この場合は、品質（バリ）により制限される。圧入深さの良否については、圧入深さが否（×）の場合であっても、強度は十分得られることから、範囲の判断には圧入深さを考慮しないこととした。品質が良好であることの目安は、製品の仕上げ加工を必要としない範囲として、はみ出し量少（△）までの範囲を良好とした。
【００５８】
この結果、良好な品質が得られるための、各圧入代における圧入深さの上限については、圧入代０．１ｍｍでは圧入深さが１０．０ｍｍ、圧入代０．２ｍｍでは圧入深さが５．０ｍｍ、圧入代０．３ｍｍでは圧入深さが３．０ｍｍ、圧入代０．４ｍｍでは圧入深さが３．０ｍｍであり、これらをプロット（〇）した。
【００５９】
これらの、プロットを特に圧入代０．２ｍｍ及び圧入代０．３ｍｍに注目して直線で結び、これを圧入深さの上限とすると、
圧入深さ（ｍｍ）≦９−２０×圧入代　　　　式▲２▼
なる簡単な式が導かれる。これから、圧入深さの上限はこの式▲２▼の範囲が良好である。
【００６０】
この圧入接合では、圧入によって両部材の接合界面においてしごき加工が行われ、このしごきによって削り取られた部分がバリとなって接合部にたまる。このバリは、製品の外観を損なうため、接合強度に影響のない範囲でできるだけ少ないことが望ましい。圧入深さが式▲２▼の範囲外では、圧入深さと圧入代による削り量が多すぎて仕上りが悪くなる。
【００６１】
したがって、この圧入接合が良好に行えるための、圧入代に対する圧入深さの好適な範囲として、上記範囲▲２▼、範囲▲３▼及び範囲▲４▼で区画された三角形状の範囲▲１▼が導ける。この範囲▲１▼内における圧入代と圧入深さの関係を維持した圧入接合であれば、圧入強度についても、またバリ量についてもともに良好な圧入接合が行える。
【００６２】
さらに、圧入代が０．３ｍｍ以上になると、表１には具体的に表れてないが、０．４ｍｍではバリの量も比較的多くなり、これからすれば圧入代が０．３ｍｍ以下がより好適である。また、圧入深さが３．０ｍｍ以上になると、接合強度は略、母材のレベルとなるので、強度の点からすればこれ以上の圧入深さは必要なく、かえってバリの量を増加させることになることから、圧入深さは３．０ｍｍ以下がより好適である。
【００６３】
上記第二の筒体４は、棒状（中実）であっても、圧入接合における技術的な差異はなく同様な効果が期待できる。ここでのワークの接合部は、製造容易或いは実用上の点で断面を円形としているが、これは他の形状、例えば楕円形、三角、四角等の多角形であっても、技術的には同様であって適用は可能であり、同程度の圧入代を設けた場合には同様の効果が期待できる。
【００６４】
また、ワークの接合部の断面の大きさは、理論的には制限はないが、特に全周接合の場合は電気抵抗が小さくて大容量の電流が必要となり、またアーク溶接等他の溶接との兼ね合いから、実質的には、接合部の断面積が２０平方ｃｍ以下（これは断面が円形の場合の直径５０ｍｍ以下に略相当）が好適である。ワークの接合部の大きさがこれ以上になると、電流供給設備の能力の問題（一般溶接機の最大容量は４５ｋＡ程度）、電極自体の抵抗の影響等の実用上の問題が生じる。
【００６５】
図９は、ワークＢとして円形の孔部２１が設けられた円形状のプレート２０と円形の筒体２２とを接合する形態を示す。この場合も、冶具を用いてプレート２０に筒体２２を接合する。この冶具は、クローム銅製の下型２４と、下部に円柱状の穴部２６が設けられたクローム銅製の上型２８とを有し、これら下型２４と上型２８とは、それぞれ電極３０，３２としても機能する。
【００６６】
上記上型２８には、筒体２２が下部の接合部３４を残した状態で上記穴部２６内に嵌入され、筒体２２の側壁面部２２ａと穴部２６の側壁面部２６ａとは通電のため密着している。このように電極３２を設ける構成とした理由については、上述した通りである。そして、上型２８には図示しないプレス機構が装備され、上型２８を加圧降下する。
【００６７】
図１０に示すように、上記プレート２０は所定の厚さ（ｐ）を有し、このプレート２０に設けられた孔部２１は、断面の直径φ１０の円形であり、プレート２０の板面から垂直方向に孔部２１の内壁面部としての接合部３６が形成されている。
【００６８】
接合に際しては図９に示すように、上記下型２４の上面部３５に上記プレート２０を載置する一方、上記筒体２２を上型２８の穴部２６に嵌入する。そして、上型２８を一定の加圧力を付勢して押圧し、併せて電極３０，３２を介してプレート２０と筒体２２間に通電する。すると、電気抵抗熱の発生とともに筒体２２の圧入が開始され、筒体２２の接合部３４がプレート２０の孔部２１の接合部３６内を降下移動する。この場合、圧入代（ｄ２）により両部材の接合界面にしごきの作用が生じ、圧入接合が行われる。圧入は、図９（ｃ）に示すように、プレート２０の板厚の範囲の圧入深さ（ｈ２）まで行われる。
【００６９】
同図に示すように、上記筒体２２の接合部３４の外径（直径）φ１１は、プレート２０の孔部２１の直径φ１０より僅かに大きく、圧入代（ｄ２）はこれらの差（ｄ２＝φ１１−φ１０）となる（半径に対してはｄ２／２の圧入代）。この圧入代（ｄ２）により、筒体２２の接合部３４の外周部位が、プレート２０の孔部２１の接合部３６と接して接合面部を形成する。具体的には上記筒体２２は、外径φ１１が１７．０＋圧入代（ｄ２）ｍｍの円形形状であり、内径φ１２は１４ｍｍで、肉厚（ｔ２）が略１．５ｍｍの円筒形である。
【００７０】
次に、社内における第二の試験について説明する。この試験では、上記ワークＢとして孔部２１が設けられたプレート２０に筒体２２を圧入接合する。ここでは、上記圧入代（ｄ２）を０．１ｍｍ〜０．４ｍｍの範囲で、また圧入深さ（ｈ２）を１．０ｍｍ〜７．０ｍｍの範囲で圧入接合を行なった。上記第一の試験では、圧入深さが０．５について試験を行ったが、第二の試験では、プレート２０の板厚を０．５ｍｍとして圧入深さ（０．５ｍｍ）を得ることが試験的に困難であり、試験の対象から外した。また、材料の都合で圧入深さが３．２ｍｍについて（３．０ｍｍに代えて）試験を行った。
【００７１】
下記表２は、そのときの接合部の引き抜き強度、及び接合端部に発生するバリ３７の量、圧入深さについての試験結果をまとめたものである。材料については、プレート２０は浸炭処理材、筒体２２はＳ２０Ｃ（炭素鋼）を用いた。また、上記第一の試験と同様に、再通電による焼き戻しを行った。
【００７２】
【表２】

【００７３】
この試験で、圧入代（ｄ２）が０．１ｍｍ以下、０．５ｍｍ以上について行わなかったのは上記第一の試験の場合と同様な理由による。その他の条件及び試験内容は、第一の試験の場合と同様である。
【００７４】
この表２についても、上記表１と略同様な結果が見られ、接合強度、バリの量、圧入深さ等につき上記表１から検討した事項については、この表２においても略当てはまり、これからすれば接合の形態、及び部材が異なっても同様な圧入接合の作用効果が期待できる。
【００７５】
図１０は、上記試験結果に基づいて、良好な接合が得られる範囲をグラフで示したものである。ここで、接合が良好といえる目安として上記第一の試験と同様、▲１▼接合強度が１０ｋＮ以上であること、▲２▼圧入接合によって生じるバリ３７の量が少ないこと、▲３▼圧入接合により圧入物が挫屈、縮小などの永久変形をしないこと、を考慮した。
【００７６】
先ず、圧入代については、上述したように０．１ｍｍに満たない場合は、圧入代の削り量が少なく接合が不安定であるため排除した。したがって、圧入代の範囲は下記式▲３▼’となる。
０．１≦圧入代（ｍｍ）　　　　式▲３▼’
【００７７】
次に、良好な強度（１０ｋＮ程度以上）及び品質（バリ）が得られるための、各圧入代における圧入深さの範囲（下限及び上限）について検討する。上記範囲の下限については、品質（バリ）は良好であり問題とならないので、この場合には接合強度により制限される。表２から、圧入深さが１．０ｍｍの場合には、いずれの圧入代０．１ｍｍ〜０．４ｍｍであっても接合強度は問題ない。
【００７８】
したがって、圧入深さは１．０ｍｍ以上であれば良好であり、下記▲４▼’が得られる。
１．０≦圧入深さ（ｍｍ）　　　　式▲４▼’
圧入深さが式▲４▼’の範囲に満たないと、圧入の際の削り量が少ないため接合強度が出ない。
【００７９】
次に、圧入深さの上限については、接合強度は良好（１０ｋＮ）であり問題とならないので、この場合は、品質（バリ）により制限される。圧入深さの良否については、圧入深さが否（×）の場合であっても、強度は十分得られることから、上記範囲の判断には考慮しないことした。品質が良好の目安は、製品の仕上げ加工を必要としない範囲として、はみ出し量少（△）までを良好とした。
【００８０】
この結果、良好な品質が得られるための、各圧入代における圧入深さの上限については、圧入代０．１ｍｍでは圧入深さが７．０ｍｍ以上、圧入代０．２ｍｍでは圧入深さが５．０ｍｍ、圧入代０．３では圧入深さが３．２ｍｍ、圧入代０．４では圧入深さが３．２ｍｍであり、これらをプロット（〇）した。
【００８１】
これらの、プロットを特に圧入代０．２ｍｍ及び圧入代０．３ｍｍに注目して直線で結び、これを圧入深さの上限とすると、
圧入深さ（ｍｍ）≦９−２０×圧入代　　　　式▲２▼’
なる簡単な式が導かれる。これから、圧入深さの上限はこの式▲２▼’の範囲が良好である。
【００８２】
したがって、この圧入接合が良好に行えるための、圧入代に対する圧入深さの好適な範囲は、上記範囲▲２▼’範囲▲３▼’及び範囲▲４▼’で区画された三角形状の範囲▲１▼’が導ける。この範囲▲１▼’内における圧入代と圧入深さの関係が保てる圧入接合構造であれば、圧入強度及びバリ量について良好な圧入接合が行える。
【００８３】
さらに、表２には具体的に表れてないが、圧入代が０．３ｍｍ以上になるとバリ３７の量も比較的多くなり、これからすれば圧入代が０．３ｍｍ以下がより好適である。また、圧入深さが略３．０ｍｍ以上になると、接合強度は十分得られ、強度の点からすればこれ以上の圧入深さは必要なく、かえってバリの量を増加させることになることから、圧入深さは３．０ｍｍ以下がより好適である。
【００８４】
上記筒体２２は、棒状（中実）であっても、技術的な差異はなく同様な効果が期待できる。ここでのワークの接合部は、断面を円形としているが、これは他の形状、例えば楕円形、三角、四角等の多角形であっても、技術的には同様であって適用は可能であり、同程度の圧入代を設けた場合には同様の効果が期待できる。
【００８５】
上記圧入接合方法は、自動車の要素部品等の製造に用いることができ、例えばトランスミッションのコントロールレバーコンポーネント、シフトレバーコンポーネント等、プレート部に筒体を接合した形態の部品、或いはエンジン部品等の製造に好適である。
【００８６】
従って上記実施の形態に係る圧入接合によれば、圧入と通電のみの簡単な工程で、しかも迅速に接合が行えて製造が容易に行えて製造コストが安価で経済性に優れる。また、接合界面が清浄化されて接合が良好に行われて強度的にも優れ、加えて接合を固相状態の溶接としたことから、母材に与える熱影響範囲が少ないことから、高精度な接合が確保され仕上り精度が良く、後加工が殆ど不要なものとなる等の効果がある。
【００８７】
このため、板体と筒体の各単品精度を向上することでそのまま完成品の精度を高めることができ、部品の直角度、同軸度、穴ピッチなどの溶接後の精度変化を修正することなくそのまま完成品として扱える。また、全周接合では接合部の気密性が確保でき、特にパイプ同士の接合には有効である。
【００８８】
このように上記圧入溶接方法は、母材の熱的劣化が極めて限定的な範囲の為、溶接後の歪取りや、応力除去の熱処理が不要であり、また、寸法精度に与える影響が殆ど無いため、溶接後の仕上げ加工が不要であり、加工費用が大幅に削減できる。また、この溶接の接合強度についても、溶接に匹敵する強度が確保でき、カシメ等の接合方法と異なり、溶接後の熱処理も可能であり、高炭素鋼の溶接も可能であり、費用も安価である。さらに、上記圧入接合方法は、電極を筒体の接合面部近傍の側壁面部に設けたから、筒体自体の抵抗の影響が排除され、通電が良好に行えて適切な電気抵抗熱が確保される。
【００８９】
【発明の効果】
以上説明したように、本発明に係る圧入接合構造は、第一の部材の孔部に対する第二の部材の圧入代を０．１ｍｍ以上とし、第一の部材の孔部内に第二の部材を押圧し通電して電気抵抗熱を発生させ、接合界面の接合を固相状態の接合とした構成としたから、簡単な工程で迅速に接合が行えて経済性に優れ、また接合界面が清浄化されて接合が良好に行われて強度的にも優れ、加えて接合を固相状態の溶接としたことから、接合部の熱的劣化がなく仕上り精度が良いという効果がある。
【００９０】
また、本発明に係る圧入接合構造によれば、圧入代の上限を０．４ｍｍとし、圧入深さの下限を、（１−２×圧入代）ｍｍ、又は１．０ｍｍ以上の範囲内で、両部材を接合したから、上記効果に加え、安定した強度が得られるとともに、仕上り精度が良く後加工の必要がないという効果がある。
【００９１】
また、本発明に係る圧入接合構造は、さらに圧入深さの上限を、（９−２０×圧入代）ｍｍの範囲内で、両部材を接合したから、特に仕上り精度が良く、このため後加工の必要がないので経済的であるという効果がある。
【００９２】
また、本発明に係る圧入接合構造は、第一の部材を、内部に貫通した円形の孔部を有する筒体に形成したから、さらに、パイプ同士の接合が容易かつ迅速に行えかつ仕上がり精度が良く強度的にも優れるという効果がある。
【００９３】
本発明に係る圧入接合方法は、第一の部材の孔部に対する第二の部材の圧入代を０．１ｍｍ以上とし、第一の部材の孔部内に第二の部材を押圧し、通電して電気抵抗熱を発生させ、接合面部に接合界面を形成させ、かつこの接合を固相状態の接合としたから、簡単な工程で製造が容易に行え、また接合界面が清浄化されて接合が良好に行われ強度的にも優れ、加えて仕上り精度が良いという効果がある。
【００９４】
また本発明に係る圧入接合方法は、圧入接合の後、再度第一の部材と第二の部材との間に通電して焼き戻しを行うこととしたから、上記効果に加えて、接合部の靭性が確保でき、優れた品質の接合が行えるという効果がある。
【図面の簡単な説明】
【図１】本発明の実施の形態に係り、ワークＡを用いた圧入接合の説明図であり、（ａ）は治具にセットされた部材を、（ｂ）は部材同士の圧入代を、（ｃ）は部材同士の圧入深さを示す。
【図２】ワークＡを示す図で、（ａ）は第一の筒体を、（ｂ）は第二の筒体を、（ｃ）は部材同士の圧入接合状態を示す。
【図３】実施の形態に係り、接合の過程を温度推移に対する加圧力及び圧力の変化でとらえた説明図である。
【図４】実施の形態に係り、加熱及び再通電による焼き戻しにおける時間と温度との関係を示すグラフである。
【図５】実施の形態に係り、ワークＡの接合界面の金属顕微鏡撮影写真である。
【図６】金属顕微鏡撮影写真の部分拡大写真（ａ）（ｂ）である。
【図７】実施の形態に係り、（ａ）はワークＡを圧入接合したときのバリの形状を示す図であり、（ｂ）はワークＢについてのバリの形状を示す図である。
【図８】実施の形態に係り、ワークＡを用いた第一の試験に基づき、好適な圧入代と圧入深さとの関係を示す図である。
【図９】本発明の実施の形態に係り、ワークＢを用いた圧入接合の説明図であり、（ａ）は治具にセットされた部材を、（ｂ）は部材同士の圧入代を、（ｃ）は部材同士の圧入深さを示す。
【図１０】ワークＢに係るプレート及び筒体を示す図である。
【図１１】実施の形態に係り、ワークＢを用いた第二の試験に基づき、好適な圧入代と圧入深さとの関係を示す図である。
【符号の説明】
２　第一の部材（第一の筒体）
４　第二の部材（第二の筒体）
１３，２１　孔部
２２　第一の部材、板体（プレート）
２４　第二の部材（筒体）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a press-fit joining structure and a press-fit joining method for members constituting a metal element part.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, when manufacturing metal element parts used for automobiles or the like, members are usually joined to each other by arc welding or the like. This is because, for example, when a shaft (or a cylinder) is joined to a plate, the shaft is fitted into a hole provided in the plate, and the entire fitting portion with the shaft is welded by arc welding or the like using a filler material. Welding is performed circumferentially or locally. Further, as a resistance welding method, a method of joining members by a spot welding method, a projection welding method, or a caulking process is also performed.
[0003]
Further, there is a method in which a bead is formed at an insertion-side base portion of a pipe portion to be inserted into a pipe connection hole, or a lip is formed at a periphery of an entrance side of the pipe connection hole and resistance welding is performed (for example, see Patent Document 1). ).
[0004]
[Patent Document 1]
JP-A-7-40058
[Patent Document 2]
JP 2001-353628 A
[0005]
[Problems to be solved by the invention]
However, according to the above joining method, thermal deformation or the like of a base material such as a plate and a shaft body and dimensional distortion occur due to thermal deformation or the like due to welding heat of arc welding, and it is unavoidable to affect accuracy. In this case, there is a problem that much work and cost are required for finishing work after welding, for example, post-working is performed after welding to improve the accuracy of the product, and unnecessary filler material at the welded portion is removed.
[0006]
In addition, the above-described resistance welding method is mainly a lap resistance welding method, and in each case, the joint is formed by forming a molten structure called a nugget at a joint portion. In this lap resistance welding, in order to strengthen the welding, the number of nuggets must be increased, and as a result, thermal deterioration of the joining base material and influence on dimensional accuracy cannot be avoided. Further, the formation of the bead or the lip has a problem that the manufacturing process is complicated and post-processing is required, so that the cost is high.
[0007]
On the other hand, the present applicant has previously proposed a non-peripheral press-fit connection structure (see Patent Document 2). However, in the case of the non-peripheral press-fitting joining structure, there is a problem that the joining portion is not suitable for joining pipes through which a fluid passes, for example, in terms of airtightness.
[0008]
Here, the following problem is considered in the press-fitting joining structure of the entire circumference.
{Circle around (1)} Since a large amount of burrs are scraped off by ironing at the time of press-fitting, it is difficult to perform press-fitting welding at a predetermined press-in depth due to the burrs obstructing all-around welding.
{Circle around (2)} Since the contact area at the time of initial energization increases, a large amount of required current is required, and the size of the joint structure is limited. From this, it is not appropriate to perform the full-circle joining under the condition of the non-full-circumferential press-fit joining structure, and it is expected that new conditions will be required. Therefore, the present applicant conducted a test in order to solve the above-mentioned problems, and aimed at putting the entire circumference of the press-fit joint structure to practical use.
[0009]
The present invention has been made in view of the above problems, and has as its object to provide a press-fit joining structure and a press-fit joining method which are easy to manufacture, have excellent economic effects, and have excellent finishing accuracy and strength. .
[0010]
[Means for Solving the Problems]
In order to solve the above technical problems, the press-fitting joint structure according to the present invention, as shown in FIG. 1, has a first

member having holes

13 and 21 formed with inner wall portions having the same cross-section of a press-fit portion. 2 and 22 and

second members

4 and 24 having a shape similar to that of the

holes

13 and 21 and having a constant cross section. The press-in allowance of the

members

4 and 24 is set to 0.1 mm or more, and the

second members

4 and 24 are pressed into the

holes

13 and 21 of the

first members

2 and 22 with a predetermined pressure. Electric current is applied between the members to generate electric resistance heat at the joint thereof, and the

second members

4 and 24 are press-fitted into the

holes

13 and 21 so that the

second members

4 and 24 and the

holes

13 , 21 are formed at the joint surface with the inner wall surface, and this joint is a solid-phase joint. It is.
[0011]
Further, in the press-fit joining structure according to the present invention, after the press-fit joining, electricity is supplied again between the first member and the second member to generate electric resistance heat at a joint portion between the first member and the second member, thereby tempering. It is to do.
[0012]
Further, in the press-fitting joint structure according to the present invention, the upper limit of the press-fitting margin is 0.4 mm,
The above-mentioned press fitting allowance and the press fitting depth at which the first member and the second member are joined are set to (1-2 × press fitting allowance) mm or more, and the two members are joined.
[0013]
Further, in the press-fitting joint structure according to the present invention, the upper limit of the press-fitting margin is 0.4 mm,
The press fitting allowance and the press fitting depth at which the first member and the second member are joined to each other are set to 1.0 mm or more, and the two members are joined.
[0014]
Further, the press-fit joining structure according to the present invention is that the two members are joined by setting the upper limit of the press-fit depth at which the first member and the second member are joined to (9-20 × press-fit allowance) mm. .
[0015]
Further, in the press-fit joining structure according to the present invention, the first member is formed in a cylindrical body having a circular hole penetrating therein.
[0016]
Further, in the press-fit joint structure according to the present invention, the first member and the second member are each formed in a circular cylindrical body, and an inner periphery of a joint portion of the first member with the second member is formed. Is uniformly expanded to form a first joint, while the outer periphery of the joint of the second member is uniformly reduced in diameter to form a second joint, and the first joint is formed. That is, the above-mentioned second joining portion is joined in the portion.
[0017]
Further, in the press-fitting joining structure according to the present invention, the first member is formed as a plate having a circular hole having an inner wall surface formed in a direction perpendicular to the plate surface. Further, the cross-sectional area of the joint between the first member and the second member is set to 20 cm 2 or less.
[0018]
The press-fitting joining method according to the present invention includes the

first members

2 and 22 having the

holes

13 and 21 in which the inner wall portions having the same cross-section of the press-fit portion are formed; The

second member

4, 24 having a constant cross section is used, and the press-in allowance of the

second member

4, 24 into the

holes

13, 21 of the first member is set to 0.1 mm or more. The

second members

4 and 24 are pressed into the

holes

13 and 21 of the second and second 22 with a predetermined pressure, and electricity is applied between the two members to generate electric resistance heat at a joint between the two members. The

second members

4 and 24 are press-fitted into the

holes

13 and 21 by softening of the members, and a bonding interface is formed at the bonding surface between the

second members

4 and 24 and the inner wall surfaces of the

holes

13 and 21. In addition, this bonding is a bonding in a solid state.
[0019]
In the press-fitting method according to the present invention, the upper limit of the press-fitting margin is set to 0.4 mm, and the relationship between the press-fitting margin and the press-fitting depth at which the first member and the second member are joined is represented by ( That is, both members were joined in a range of 1 ≦ press-in depth (mm) ≦ 9−20 × press-in allowance).
[0020]
Also, in the press-fitting method according to the present invention, after the press-fitting, electricity is supplied again between the first member and the second member to generate electrical resistance heat at a joint between the first member and the temper. It is to do.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
In the press-fitting joining structure and the press-fitting joining method according to this embodiment, joining of the cylinders and joining of the plate and the cylinder will be described as works.
[0022]
FIG. 1 shows a form in which a second cylindrical body 4 is joined to a first cylindrical body 2 using a jig as a work A. This jig has a lower die 6 made of chrome copper having a cylindrical hole 7 provided at an upper part, and an upper die 8 made of chrome copper provided with a cylindrical hole 9 at a lower part. The lower die 6 and the upper die 8 also function as

electrodes

10 and 12, respectively, and current can flow between the two dies.
[0023]
In the lower die 6, the first cylindrical body 2 is fitted into the hole 7 with the upper joint portion 14 left, and the side wall 2a of the first cylindrical body 2 and the side wall of the hole 7 are formed. 7a is in close contact with the power supply. The configuration in which the electrode 10 is provided on the side wall surface portion 2a of the first cylindrical body 2 is such that the electrode is provided on the lower surface of the first cylindrical body 2, so that the resistance of the first cylindrical body 2 itself is reduced. This affects the energization, so that it is reduced to improve the energization. Needless to say, the form in which the electrodes are provided on the first cylinder 2 may be a method other than the above, for example, a method in which the electrodes are inserted into the cylinder of the first cylinder 2. An electrode is provided near the joint 14 of the body 2. The upper die 8 is equipped with a press mechanism (not shown), and presses down the upper die 8.
[0024]
As shown in FIG. 2A, the first cylindrical body 2 has a cylindrical shape having an inner diameter φ1 (diameter) of 19 mm, an outer diameter φ2 of 22 mm, and a thickness t of 1.5 mm. The joint portion 14 is formed such that an inner peripheral surface of a certain range is uniformly cut outwardly from the end of the first cylindrical body 2 and the diameter thereof is increased to form a hole portion 13 having a circular inner surface with an inner diameter of φ3. are doing.
[0025]
As shown in FIG. 2B, the second cylindrical body 4 has a cylindrical shape with an inner diameter φ4 of 19 mm, an outer diameter φ5 of 22 mm, and a thickness t of 1.5 mm. The joint portion 16 is formed such that the outer peripheral surface of the second cylindrical body 4 is uniformly cut inward (toward the center) from the end portion to a certain range and is reduced in diameter to form a circumferential surface having an outer diameter of φ6. ing. Then, as shown in FIG. 2C, the joint 16 of the second cylinder 4 is joined to the joint 14 of the first cylinder 2.
[0026]
At this time, as shown in FIG. 1B, the outer diameter φ6 of the second cylinder 4 is slightly larger than the inner diameter φ3 of the first cylinder 2, and the difference (φ6-φ3) is the press-fit allowance (d). (Pressing allowance of d / 2 for radius). Due to the press-fit allowance (d), the outer peripheral portion of the second cylindrical body 4 comes into contact with the inner peripheral portion of the first cylindrical body 2 to form a joint surface portion.
[0027]
When the press-fit allowances (d) are provided at the

joints

14 and 16 of these two cylinders, the cylinder thicknesses of the

joints

14 and 16 are made equal to achieve a balance. For this reason, the size of the inner diameter φ3 of the joint portion 14 is set to 20.5 mm−press fitting allowance (d) / 2, and the outer diameter φ6 of the joint portion 16 is set to 20.5 mm + press fit allowance (d) / 2.
[0028]
As for the press-fit depth, as shown in FIG. 1 (b), the entirety of the portion forming the step as the

joints

14, 16 of the two

cylindrical bodies

2, 4 is the press-fit depth (h). In the test, for the purpose of observing the burrs 15 and the like, as shown in FIG. 1C, the press-fitting depth (h) was set with a part of the

joints

14 and 16 left.
[0029]
Here, a description will be given of a result of press-fitting the first cylindrical body 2 and the second cylindrical body 4 as the work A by an in-house test and observing a bonded state. Chromium molybdenum steel (SCM420) was used as the material of the first cylinder 2 and the second cylinder 4. As another material, SUS (stainless steel) can be used for the first cylinder 2 and the second cylinder 4, and SUS and carbon steel can be used in combination.
[0030]
Still other materials include carbon steel for machine structures, alloy steel for machine structures, heat-resistant steel, tool steel, spring steel, cast iron, free-cutting steel, bearing steel, steel for general machining, steel for pressure vessels, titanium, aluminum, etc. Light metal or the like is applicable. In this press-fit joining, any combination of low-carbon steel, low-carbon steel and high-carbon steel and high-carbon steel can be used. The point is that press-fitting processing using electric resistance heat at the joint is not particularly limited as long as it is a metal. In particular, joining the same material, or materials having similar melting points and hardness, forms a uniform structure at the joining interface and achieves good joining.
[0031]
As an implementation condition, the applied current was 22 kA. The applied pressure was 0.4 MPa (however, in the range of 400 kgf to 450 kgf). The pressing force is set to a pressure lower than the stress of the base material (here, a resistance force that prevents the second cylinder 4 from entering the first cylinder 2). Therefore, the press-fitting is started from the point in time when the applied pressure exceeds the stress reduced by the softening of the base material.
[0032]
At the time of joining, as shown in FIG. 1, the first cylinder 2 is fitted into the hole 7 of the lower mold 6, while the second cylinder 4 is fitted into the hole 9 of the upper mold 8. . Then, the upper die 8 is urged by applying a constant pressing force, and at the same time, electricity is supplied between the first cylinder 2 and the second cylinder 4. Then, press-fitting of the second cylindrical body 4 is started together with generation of electric resistance heat, and the joint 16 of the second cylindrical body 4 moves down in the joint 14 of the hole 13 of the first cylindrical body 2. . In this case, an ironing action occurs at the joining interface between the two members, and press-fitting is performed by a manufacturing process by ironing.
[0033]
At this time, press-fit welding is performed at a constant pressing force and a constant descending speed, the joint is instantaneously heated, and the distal end portion 17 of the second cylindrical body 4 is quickly turned into the stepped portion 18 of the first cylindrical body 2. To complete the joining. At this time, a joint interface 19 of solid-phase welding is formed between the joint 16 of the first cylinder 2 and the joint 14 of the second cylinder 4. In solid-phase welding, the quality of the joint depends on the fact that a clean surface structure is obtained on the joint surface. According to the press-fit joining according to this embodiment, between the respective wall surfaces of the second cylinder 4 and the first cylinder 2 is squeezed at the joining interface 19 by the movement in the sliding direction. The impurity layer on the surface is scraped to clean the surface, and solid phase welding is performed on this clean structure.
[0034]
FIG. 3 shows the above joining process as a change in the pressure applied to the temperature transition of the joining portion due to resistance heat and the change in the stress of the base material joining portion. Here, the vertical axis indicates the temperature of the joining portion and the base metal stress of the joining portion, and the horizontal axis indicates the time axis of the joining process. First, a description will be given along the time axis. At the time of the start, the temperature of the joining portion remains at room temperature, and the hardness of the base materials (the first cylindrical body 2 and the second cylindrical body 4) remains unchanged. Therefore, a sufficient stress is maintained with respect to the pressing force. Therefore, at this point, the second cylinder 4 remains at the upper part of the first cylinder 2 though it is pressurized.
[0035]
With the passage of time, the temperature of the joint surface rises due to the resistance heat due to energization, and accordingly, the softening of the joint surface starts. The point at which the stress is reduced due to the softening of the joining surface and the pressure is overcome is the time of the press-fitting start shown in the figure, and the second cylinder 4 moves down while squeezing the joint 14 of the first cylinder 2. . At this start point, the temperature of the joint surface is considered to have reached the highest point.
[0036]
Thereafter, as the press-fitting proceeds, the bonding area of the bonding surface increases, and conversely, the difference in cross-sectional area decreases, so that the current density decreases. As a result, the generation of resistance heat decreases, and the temperature of the bonding surface decreases. In this way, the second cylinder 4 as the base material moves in the first cylinder 2 to complete the joining process. The entire process from the start of pressurization and energization, the start of press-fitting, and the completion of press-fitting is performed in a short time of less than 1 second. Then, after the press-fitting is completed, the hardness of the base material at the joining portion is restored by cooling, and the joining is performed firmly.
[0037]
Here, when tempering is not performed, the course of pressurization → energization → press-fit → cooling (rapid cooling) is followed. Thus, after the press-fitting, if it is allowed to cool as it is, cooling is rapidly performed by the copper electrode. Therefore, when a material having good hardenability is press-fitted and joined, the joint is hardened and the material becomes brittle. The reason for this quenching is that, in the press-fitting, heat is locally and rapidly applied, so that the temperature gradient between the bonded portion and the non-bonded portion increases, and the bonded portion heated above the transformation point (A3) of steel. The reason for this is that the heating is interrupted and the material is rapidly cooled to change into a martensite structure. This martensite structure increases in proportion to the carbon equivalent of the material and the size of the joining material.
[0038]
In this embodiment, immediately after the joining is performed by the rapid cooling after the heating, the first cylinder 2 and the second cylinder 4 are heated again by energizing a temper (heat treatment). The tempering process is performed by this reheating, and the toughness of the joint is restored. FIG. 4 is a graph showing a change in temperature when a tempering process is added to the press-fitting bonding process. As shown in the figure, the entire process is performed in the following order: process (1) pressurizing, energizing (press-fitting), process (2) cooling (rapid cooling), process (3) energizing (tempering), process (4) cooling (gradual cooling) )).
[0039]
The reason for the tempering is that the peripheral member is heated by the heat transfer at the time of the first heat bonding, and the temperature of the member increases. For this reason, by performing the above-mentioned tempering with a short time, the temperature of the peripheral member is increased, and the cooling rate of the joint heated by the second energization becomes slow. At this time, the martensite, which is a quenched structure, changes to tempered martensite, and the toughness is recovered and tempering can be performed. Since these steps are performed in a short time, it is desirable to perform the steps using a jig in which members are set first. The tempering is particularly effective when a steel material having a carbon content of S30C or more or a material having a carbon equivalent of 0.3% or more is used as the work.
[0040]
FIG. 5 and FIG. 6 are metallographic micrographs of the joint at the joint interface when the second cylinder 4 is press-fitted to the first cylinder 2. At this time, the press fitting allowance (d) is 0.2 mm. As a result of observing the work, the heat affected zone (hardness change range) around the joint was relatively narrow, and crystal grains did not grow in the heat affected zone around the joint, and an irregular and granular structure was observed. You. The joint interface is in a good joint state without any abnormal carbides or oxides, thereby ensuring the mechanical strength.
[0041]
From the above observation results, immediately after the press-fitting, the current is concentrated because the joining surface is narrow, and the surface layer of the tissue is softened or only a limited thin layer is melted. However, the joining state shows plastic deformation (thermoplasticity) due to the press-fitting. It can be said that the accompanying solid-phase welding was achieved. Therefore, unlike the conventional lap welding, the press-fitting according to the above-described embodiment is a solid-phase welding or a joining method similar to solid-phase welding because there is almost no molten and solidified layer in the joint.
[0042]
In particular, the important point in the press-fitting is that, in the press-fitting step, as a result of the process of the press-fitting, a movement in the sliding direction is generated at the bonding interface, whereby the impurity layer on the surface is scraped off and removed. The effect is obtained. By this action, a clean joining surface essential for solid-phase welding is formed, and the joining is performed firmly. This can be said to be a characteristic action and effect in this joining method.
[0043]
Here, a first in-house test performed on the work A will be described. In this test, the work A was press-fitted with the press-fit allowance (d) in the range of 0.1 mm to 0.4 mm and the press-fit depth (h) in the range of 0.5 mm to 10.0 mm. Table 1 below summarizes test results on the pull-out strength of the joint at that time, the amount of burrs 15 generated at the joint end, and the press-fit depth.
[0044]
[Table 1]

[0045]
In this test, the first cylinder 2 and the second cylinder 4 were not subjected to a press-fit allowance (d = φ6-φ3) of 0.1 mm or less. Was excluded from the test because it was predicted to be unstable, and because it was difficult to obtain accurate data because the test was difficult due to press-fitting with initial pressure during resistance welding. Further, when the press-fitting margin (d) is 0.5 mm or more, since the press-fitting depth and the shaving amount due to the press-fitting margin are too large, the finish is rough, the distortion of the joint surface is large, and the finish is uneven, which is not preferable. Excluded from testing.
[0046]
The detachment strength shown in the same table is obtained by fixing the first cylinder 2 of the test sample, applying a static load to the end face of the second cylinder 4 by an autograph from the direction opposite to the press-fitting direction, and It is a result of measuring a load (a breaking load at a joint) at which the body 4 peels off from the first cylindrical body 2 and comes off. A tensile tester Autograph (manufactured by Shimadzu Corporation) was used as a strength tester.
[0047]
The unit of “stripping strength” is (kN), and “base material” is written when the base material itself is broken. The fracture of the base material occurred in the heat-affected zone, which is the boundary between the joint and the non-joined portion of the base material, and no break was observed at the joint.
[0048]
FIG. 7A shows burrs 15 (burrs at the distal end of the first cylinder 2) and burrs 15 ′ (second burrs) when the second cylinder 4 is press-fitted and joined to the first cylinder 2. 3 shows the shape of a burr at the end of the cylindrical body 4. In the case where the joints are symmetrical (each cross-sectional shape is substantially the same) as in the joining of the first cylinder 2 and the second cylinder 4, the burr is formed due to the difference in the high-temperature deformation resistance of the material. Is different. When the high temperature deformation resistance of the first cylinder 2 is larger than that of the second cylinder 4, the burr 15 is formed larger than the burr 15 ′. The burrs 15 and 15 'are formed in the same size. FIG. 7B shows the shape of the burr 37 when the cylindrical body 22 is press-fitted to the plate 20 described later.
[0049]
The amount of the burrs 15 is visually determined. In this visual judgment, as shown in FIG. 7, generally, the protrusion amount (v) of the burr in the same direction with respect to the press-fit depth (h) is used as a reference, and if this ratio is within about 20%, the protrusion amount is small. If it is 20% or more, it is determined that the amount of protrusion is large. At the time of the test, each of the joining members was chamfered at the end of the contacting portion and press-fitting was performed. For the sake of measurement, the depth including the chamfered portion was defined as the press-fitting depth.
[0050]
In Table 1 and Table 2 below, regarding the judgment result of “burr”, “〇” indicates a state where almost no protrusion of the burr occurred, “△” indicates a state where the amount of protrusion of the burr was small, and “×” indicates a state where the protrusion of the burr was detected. Each state is shown. Further, the “press-fitting depth” indicates whether or not the press-fitting was possible up to that depth, (、) indicates that the press-fitting was possible, and (×) indicates that the press-fitting was not possible to the depth.
[0051]
FIG. 8 is a graph showing a range in which good bonding can be obtained based on the above test results. Here, it can be said that the bonding is good. (1) The bonding strength is 10 kN or more, (2) The amount of burrs generated by press-fitting is small, and (3) The press-fitted material is buckled or reduced by press-fitting. In order to avoid permanent deformation such as,
[0052]
According to the test results, as shown in the figure, the joining strength increases as the press-in allowance or the press-in depth increases. Although the standard of the appropriateness of the bonding strength varies depending on the use of the product, it is usually several kN. Therefore, “approximately 10 kN or more” is set as a standard of a suitable strength.
[0053]
First, when the press-fitting margin was less than 0.1 mm, it was excluded because the shaving amount at the press-fitting margin was small and the joining was unstable. Therefore, the range of the press-in allowance is given by the following equation (3).
0.1 ≦ Press-in allowance (mm) Formula (3)
If the press-in allowance is large, the appearance of the joint is deteriorated by burrs, so it is better to reduce the press-in allowance. However, if the press-in allowance is reduced, the joining force is reduced. At the time of joining, as for the cleanliness of the joining interface, as long as there is ironing applied to this joint at the time of press-fitting, an oxide film removing function is exhibited and the joining force is secured. The press-fit allowance at which the ironing is performed appropriately falls within the range of the above equation (3).
[0054]
Next, the range (lower limit and upper limit) of the press-fitting depth in each press-fitting margin for obtaining good strength (about 10 kN or more) and quality (burr) will be examined. Regarding the lower limit of the above range, since the quality (burr) is good and does not cause any problem, in this case, it is limited by the bonding strength. From Table 1, the press-fit depth is 1.0 mm at the press-fit allowance of 0.1 mm, the press-fit depth is 1.0 mm at the press-fit allowance of 0.2 mm, the press-fit depth is 0.5 mm at the press-fit allowance of 0.3 mm, and the press-fit allowance is 0. At 4 mm, the indentation depth was 0.5 mm, and these were plotted with (△).
[0055]
When these △ are particularly connected with a straight line focusing on the press-fitting allowance of 0.1 mm and the press-fitting allowance of 0.3 mm, and defining this as the lower limit of the press-fitting depth,
1-2 x press-in allowance ≤ press-in depth (mm) Formula (4)
A simple formula is derived. Therefore, the lower limit of the press-fitting depth is preferably in the range of the formula (4). If the press-fit depth is smaller than the range of the formula (4), the amount of shaving at the time of press-fit is small, so that the joining strength is not obtained.
[0056]
Good strength can be obtained with the press-fitting allowance (0.1 to 0.4 mm) in all ranges when the press-fit depth is 1.0 mm or more, and in this range, more stable and good press-fit strength is obtained. Can be secured.
[0057]
Next, as for the upper limit of the above range, since the bonding strength is good (10 kN) and does not cause any problem, in this case, it is limited by quality (burr). Regarding the quality of the press-fitting depth, even when the press-fitting depth was negative (×), sufficient strength was obtained, so that the press-fitting depth was not considered in determining the range. The standard of good quality is defined as a range up to a small amount of protrusion (量) as a range that does not require finishing of the product.
[0058]
As a result, with respect to the upper limit of the press-fitting depth at each press-fitting allowance to obtain good quality, the press-fitting depth is 10.0 mm at a press-fitting allowance of 0.1 mm, and the press-fitting depth is 5.0 mm at a press-fitting allowance of 0.2 mm. The press-fit depth was 3.0 mm at 0 mm and the press-fit allowance of 0.3 mm, and the press-fit depth was 3.0 mm at the press-fit allowance of 0.4 mm, and these were plotted (〇).
[0059]
Focusing these plots on a straight line focusing on the press-fitting allowance of 0.2 mm and the press-fitting allowance of 0.3 mm, and defining this as the upper limit of the press-fitting depth,
Press-in depth (mm) ≤ 9-20 x press-in allowance formula (2)
A simple formula is derived. From this, the upper limit of the press-fitting depth is preferably in the range of the formula (2).
[0060]
In this press-fitting, ironing is performed at the joint interface between the two members by press-fitting, and the portion removed by the ironing becomes burrs and accumulates at the joint. Since this burr impairs the appearance of the product, it is desirable that the burr be as small as possible without affecting the bonding strength. If the press-in depth is out of the range of the formula (2), the shaving amount due to the press-in depth and the press-in allowance is too large, and the finish is deteriorated.
[0061]
Therefore, as a preferable range of the press-fitting depth with respect to the press-fitting allowance in which the press-fitting can be favorably performed, a triangular range (1) divided by the range (2), the range (3), and the range (4). Can lead. If the press-fitting is performed while maintaining the relationship between the press-fitting allowance and the press-fitting depth within the range (1), good press-fitting can be performed with respect to both the press-in strength and the burr amount.
[0062]
Furthermore, when the press-in allowance is 0.3 mm or more, although not specifically shown in Table 1, the amount of burr is relatively large at 0.4 mm, and the press-in allowance is more preferably 0.3 mm or less. It is. In addition, when the press-fit depth is 3.0 mm or more, the joining strength is substantially at the level of the base material. Therefore, from the viewpoint of strength, no further press-fit depth is required, and instead, the amount of burrs should be increased. Therefore, it is more preferable that the press-fit depth is 3.0 mm or less.
[0063]
Even if the second cylinder 4 is rod-shaped (solid), there is no technical difference in press-fitting and similar effects can be expected. The joint portion of the work here has a circular cross section for ease of manufacture or practical use. However, even if it has another shape, for example, an elliptical shape, a triangular shape, a polygonal shape such as a square, technically, The same is applicable and applicable, and the same effect can be expected when the same press-fitting margin is provided.
[0064]
The size of the cross-section of the joint of the work is not theoretically limited, but especially in the case of full-circumferential joining, the electric resistance is small and a large amount of current is required. In view of this, it is preferable that the cross-sectional area of the joint is substantially 20 cm 2 or less (this substantially corresponds to a diameter of 50 mm or less when the cross section is circular). If the size of the joint portion of the work is larger than this, practical problems such as the problem of the capacity of the current supply equipment (the maximum capacity of a general welding machine is about 45 kA) and the influence of the resistance of the electrode itself arise.
[0065]
FIG. 9 shows a form in which a circular plate 20 provided with a circular hole 21 as a work B and a circular cylindrical body 22 are joined. Also in this case, the cylinder 22 is joined to the plate 20 using a jig. This jig has a lower die 24 made of chromium copper, and an upper die 28 made of chrome copper having a cylindrical hole 26 provided at a lower portion. Also functions as 32.
[0066]
In the upper die 28, the cylindrical body 22 is fitted into the hole 26 while leaving the lower joint 34, and the side wall surface 22a of the cylindrical body 22 and the side wall surface 26a of the hole 26 are electrically connected to each other. Adhering. The reason for providing the electrode 32 in this manner is as described above. The upper mold 28 is equipped with a press mechanism (not shown), and presses down the upper mold 28.
[0067]
As shown in FIG. 10, the plate 20 has a predetermined thickness (p), and a hole 21 provided in the plate 20 has a circular cross section having a diameter of φ10 and is perpendicular to the plate surface of the plate 20. A joint 36 is formed in the direction as an inner wall surface of the hole 21.
[0068]
At the time of joining, as shown in FIG. 9, the plate 20 is placed on the upper surface 35 of the lower mold 24, and the cylindrical body 22 is fitted into the hole 26 of the upper mold 28. Then, the upper mold 28 is pressed by applying a constant pressing force, and at the same time, electricity is supplied between the plate 20 and the cylindrical body 22 via the

electrodes

30 and 32. Then, press-fitting of the cylinder 22 is started together with generation of electric resistance heat, and the joint 34 of the cylinder 22 moves down in the joint 36 of the hole 21 of the plate 20. In this case, the press-fitting margin (d2) causes an ironing action at the joint interface between the two members, and press-fitting is performed. The press-fitting is performed up to the press-fitting depth (h2) in the range of the thickness of the plate 20, as shown in FIG.
[0069]
As shown in the drawing, the outer diameter (diameter) φ11 of the joint portion 34 of the cylindrical body 22 is slightly larger than the diameter φ10 of the hole 21 of the plate 20, and the press-fit allowance (d2) is the difference between these (d2 = φ11−φ10) (d2 / 2 press-fitting allowance for the radius). Due to the press-fitting allowance (d2), the outer peripheral portion of the joining portion 34 of the cylindrical body 22 comes into contact with the joining portion 36 of the hole 21 of the plate 20 to form a joining surface portion. Specifically, the cylindrical body 22 is a circular shape having an outer diameter φ11 of 17.0 + a press-fitting allowance (d2) mm, an inner diameter φ12 of 14 mm, and a wall thickness (t2) of about 1.5 mm. .
[0070]
Next, the second test in the company will be described. In this test, the cylindrical body 22 is press-fitted to the plate 20 having the hole 21 as the work B. Here, the press-fitting (d2) was performed in the range of 0.1 mm to 0.4 mm, and the press-in depth (h2) was performed in the range of 1.0 mm to 7.0 mm. In the above-mentioned first test, the test was performed with a press-fit depth of 0.5, but in the second test, it was tested that the press-fit depth (0.5 mm) was obtained with the plate 20 having a thickness of 0.5 mm. And was excluded from the test. Further, a test was performed for a press-fit depth of 3.2 mm (instead of 3.0 mm) due to the material.
[0071]
Table 2 below summarizes test results on the pull-out strength of the joint at that time, the amount of burr 37 generated at the joint end, and the press-fit depth. As for the material, the plate 20 was made of a carburized material, and the cylindrical body 22 was made of S20C (carbon steel). Further, as in the first test, tempering by re-energization was performed.
[0072]
[Table 2]

[0073]
In this test, the reason why the press-in allowance (d2) was not performed for 0.1 mm or less and 0.5 mm or more was not performed for the same reason as in the first test. Other conditions and test contents are the same as those of the first test.
[0074]
In Table 2 as well, substantially the same results as in Table 1 above were observed, and the items examined from Table 1 above regarding the bonding strength, the amount of burrs, the press-fitting depth, etc., were substantially applicable in Table 2 as well. If the joining form and the members are different, the same effect of press-fitting can be expected.
[0075]
FIG. 10 is a graph showing a range in which good bonding can be obtained based on the above test results. Here, similar to the above-mentioned first test, as a guide to be able to say that the bonding is good, (1) the bonding strength is 10 kN or more, (2) the amount of burrs 37 generated by press-fitting is small, and (3) press-fitting. Therefore, it was considered that the press-fitted material did not undergo permanent deformation such as buckling or reduction.
[0076]
First, with respect to the press-fitting margin, when it was less than 0.1 mm as described above, it was excluded because the shaving amount of the press-fitting margin was small and the joining was unstable. Therefore, the range of the press-in allowance is given by the following equation (3) '.
0.1 ≦ Press-in allowance (mm) Formula (3) '
[0077]
Next, the range (lower limit and upper limit) of the press-fitting depth in each press-fitting margin for obtaining good strength (about 10 kN or more) and quality (burr) will be examined. Regarding the lower limit of the above range, since the quality (burr) is good and does not cause any problem, in this case, it is limited by the bonding strength. From Table 2, when the press-fit depth is 1.0 mm, there is no problem in the bonding strength regardless of the press-fit allowance of 0.1 mm to 0.4 mm.
[0078]
Therefore, if the press-fit depth is 1.0 mm or more, it is good, and the following (4) 'is obtained.
1.0 ≤ Press-in depth (mm) Formula (4) '
If the press-fitting depth is less than the range of the formula (4) ', the amount of shaving during press-fitting is small, so that the joining strength is not obtained.
[0079]
Next, as for the upper limit of the press-fitting depth, the bonding strength is good (10 kN) and does not cause any problem. In this case, it is limited by the quality (burr). Regarding the quality of the press-fitting depth, even when the press-fitting depth was negative (x), sufficient strength was obtained, so that it was not considered in the determination of the above range. The standard of good quality was defined as good up to a small amount of protruding (として) as a range that does not require finish processing of the product.
[0080]
As a result, in order to obtain good quality, the upper limit of the press-fitting depth in each press-fitting allowance is 7.0 mm or more at a press-fitting allowance of 0.1 mm, and 5 mm at a press-fitting allowance of 0.2 mm. The press-in depth was 3.2 mm at a press-in allowance of 0.0 mm and a press-in allowance of 0.3, and the press-in depth was 3.2 mm at a press-in allowance of 0.4.
[0081]
Focusing these plots on a straight line focusing on the press-fitting allowance of 0.2 mm and the press-fitting allowance of 0.3 mm, and defining this as the upper limit of the press-fitting depth,
Press-in depth (mm) ≤ 9-20 x press-in allowance formula (2) '
A simple formula is derived. From this, the upper limit of the press-fitting depth is preferably in the range of the formula (2) '.
[0082]
Therefore, a preferable range of the press-fitting depth with respect to the press-fitting margin for performing the press-fitting satisfactorily is a triangular range defined by the ranges (2), (3) and (4). 1 ▼ 'can be led. If the press-fitting joint structure can maintain the relationship between the press-fitting allowance and the press-fitting depth within this range {1} ', good press-fitting can be performed with respect to the press-fitting strength and the amount of burrs.
[0083]
Further, although not specifically shown in Table 2, when the press-in allowance is 0.3 mm or more, the amount of the burr 37 is relatively large, and from this, it is more preferable that the press-in allowance is 0.3 mm or less. Also, when the press-in depth is approximately 3.0 mm or more, sufficient bonding strength can be obtained, and from the viewpoint of strength, no further press-in depth is required, and the amount of burrs is rather increased, so that More preferably, the press-fit depth is 3.0 mm or less.
[0084]
Even if the cylindrical body 22 is rod-shaped (solid), there is no technical difference and similar effects can be expected. The joint portion of the work here has a circular cross section, but this is technically the same and applicable even if the shape is another shape, for example, a polygon such as an ellipse, a triangle, or a square. Yes, the same effect can be expected when the same press-fitting margin is provided.
[0085]
The above-mentioned press-fitting method can be used for the production of element parts and the like of automobiles, for example, for the production of transmission control lever components, shift lever components, etc., parts in which a cylinder is joined to a plate part, or engine parts. It is suitable.
[0086]
Therefore, according to the press-fitting joining according to the above-described embodiment, the joining can be performed quickly and easily by a simple process of only press-fitting and energization, and the manufacturing can be easily performed. The manufacturing cost is low and the economy is excellent. In addition, since the bonding interface is cleaned and the bonding is performed well and the strength is excellent, in addition, since the bonding is in the solid state welding, the range of heat influence on the base material is small, so high precision In addition, there is an effect that a perfect joint is secured, the finishing accuracy is good, and post-processing is almost unnecessary.
[0087]
For this reason, the accuracy of the finished product can be increased as it is by improving the accuracy of each single product of the plate and the cylinder, without correcting the change in accuracy after welding such as the squareness, coaxiality, hole pitch of parts It can be used as a finished product. In addition, the airtightness of the joint can be ensured in the all-around joining, which is particularly effective for joining pipes.
[0088]
As described above, in the press-fit welding method, since the thermal deterioration of the base material is in an extremely limited range, heat treatment for removing distortion and stress after welding is unnecessary, and there is almost no influence on dimensional accuracy. Therefore, finishing work after welding is unnecessary, and the processing cost can be greatly reduced. Also, as for the joining strength of this welding, strength equivalent to welding can be secured, and unlike the joining method such as caulking, heat treatment after welding is also possible, welding of high carbon steel is also possible, and cost is low. is there. Further, in the press-fitting method described above, since the electrodes are provided on the side wall surface near the joint surface of the cylindrical body, the influence of the resistance of the cylindrical body itself is eliminated.
[0089]
【The invention's effect】
As described above, the press-fitting joint structure according to the present invention sets the press-fitting allowance of the second member to the hole of the first member to be 0.1 mm or more, and inserts the second member into the hole of the first member. Pressing and energizing to generate electrical resistance heat, and the joining interface is joined in a solid state, so it can be joined quickly in a simple process and is economical, and the joining interface is cleaned. The joining is performed well and the strength is excellent. In addition, since the joining is performed in a solid state, there is an effect that there is no thermal deterioration of the joining portion and the finishing accuracy is good.
[0090]
In addition, according to the press-fitting joint structure according to the present invention, the upper limit of the press-fitting margin is 0.4 mm, and the lower limit of the press-fitting depth is (1-2 × press-fitting) mm, or within a range of 1.0 mm or more. Since both members are joined, in addition to the above-mentioned effects, there is an effect that stable strength is obtained, finishing accuracy is good, and post-processing is not required.
[0091]
In addition, the press-fitting joint structure according to the present invention further joins both members with the upper limit of the press-fitting depth being within a range of (9-20 × press-fitting allowance) mm, so that the finishing accuracy is particularly good, and therefore, post-processing. It is economical because there is no necessity.
[0092]
Further, in the press-fitting joining structure according to the present invention, since the first member is formed into a cylindrical body having a circular hole penetrating therein, further, the joining between pipes can be performed easily and quickly, and the finishing accuracy is improved. There is an effect that the strength is excellent.
[0093]
In the press-fitting joining method according to the present invention, the press-fitting margin of the second member into the hole of the first member is set to 0.1 mm or more, the second member is pressed into the hole of the first member, and the current is applied. Since electric resistance heat is generated to form a bonding interface at the bonding surface and the bonding is made in a solid state, manufacturing can be easily performed with a simple process, and the bonding interface is cleaned and the bonding is good. In addition, there is an effect that the strength is excellent and the finishing accuracy is good.
[0094]
In addition, in the press-fitting method according to the present invention, after the press-fitting, since the tempering is performed by energizing the first member and the second member again, in addition to the above-described effects, There is an effect that toughness can be secured and joining of excellent quality can be performed.
[Brief description of the drawings]
FIGS. 1A and 1B are explanatory views of press-fit joining using a work A according to an embodiment of the present invention, wherein FIG. 1A shows a member set on a jig, FIG. (C) shows the press-fit depth between the members.
FIGS. 2A and 2B are diagrams showing a work A, wherein FIG. 2A shows a first cylindrical body, FIG. 2B shows a second cylindrical body, and FIG.
FIG. 3 is an explanatory view according to the embodiment, in which a joining process is grasped by a change in a pressing force and a pressure with respect to a temperature transition.
FIG. 4 is a graph showing a relationship between time and temperature in tempering by heating and re-energization according to the embodiment.
FIG. 5 is a photograph taken by a metallurgical microscope of a bonding interface of a work A according to the embodiment.
FIGS. 6A and 6B are partially enlarged photographs (a) and (b) of a photograph taken by a metallurgical microscope.
7A is a diagram illustrating a shape of a burr when a work A is press-fitted and joined, and FIG. 7B is a diagram illustrating a shape of a burr for a work B according to the embodiment;
FIG. 8 is a view showing a preferable relationship between a press-fitting allowance and a press-fitting depth based on a first test using a work A according to the embodiment.
9A and 9B are explanatory diagrams of press-fit joining using a work B according to the embodiment of the present invention, wherein FIG. 9A shows a member set in a jig, FIG. (C) shows the press-fit depth between the members.
FIG. 10 is a view showing a plate and a cylinder relating to a work B;
FIG. 11 is a diagram showing a preferable relationship between a press-fitting allowance and a press-fitting depth based on a second test using a work B according to the embodiment.
[Explanation of symbols]
2 First member (first cylinder)
4 Second member (second cylinder)
13, 21 holes
22 First member, plate (plate)
24 Second member (cylindrical body)

Claims

A first member having a hole in which a cross section of the press-fit portion has the same inner wall surface portion,
Using a second member having a shape similar to the hole and having a constant cross section,
Pressing allowance of the second member into the hole of the first member is 0.1 mm or more,
The second member is pressed into the hole of the first member with a predetermined pressure, and electric current is applied between the two members to generate electric resistance heat at a joint between the two members. A press-fit joint structure characterized by being press-fitted into a hole, forming a joint interface at a joint surface between the second member and the inner wall surface of the hole, and joining the solid-state joint.

The method according to claim 1, wherein after the press-fitting, electricity is supplied again between the first member and the second member to generate electric resistance heat at a joint between the first member and the second member to perform tempering. The press-fit connection structure described.

The upper limit of the press-fitting margin is 0.4 mm,
The said press-fitting, and the press-fitting depth which the said 1st member and the said 2nd member join are (1-2xpress-fitting) mm or more, and both members were joined, The Claim 1 or Claim characterized by the above-mentioned. Item 3. A press-fit joint structure according to Item 2.

The upper limit of the press-fitting margin is 0.4 mm,
The press-fit according to claim 1 or 2, wherein the press-fit margin and the press-fit depth at which the first member and the second member are joined to each other are set to 1.0 mm or more. Joint structure.

The upper part of the press-fitting depth at which the first member and the second member are joined is set to (9-20 × press-fit allowance) mm, and the two members are joined to each other. Press-fit joint structure.

The press-fit joint structure according to any one of claims 1 to 5, wherein the first member is formed in a cylindrical body having a circular hole penetrating therein.

The first member and the second member are each formed in a circular cylindrical body,
The inner diameter of the joint of the first member with the second member is uniformly increased in diameter to form the first joint, while the outer periphery of the joint of the second member is uniform. Reducing the diameter to form a second joint,
The press-fit connection structure according to claim 6, wherein the second connection portion is connected to the first connection portion.

The press-fit joining according to any one of claims 1 to 5, wherein the first member is formed as a plate having a circular hole having an inner wall surface formed in a vertical direction from the plate surface. Construction.

9. The press-fit joint structure according to claim 1, wherein a cross-sectional area of a joint between the first member and the second member is 20 cm 2 or less. 10.

A first member having a hole in which a cross section of the press-fit portion has the same inner wall surface portion,
Using a second member having a shape similar to the hole and having a constant cross section,
Pressing allowance of the second member into the hole of the first member is 0.1 mm or more,
Pressing the second member into the hole of the first member with a predetermined pressure, and applying electric current between these two members to generate electric resistance heat at a joint between the two members,
Pressing the second member into the hole by softening the two members,
A press-fit joining method, wherein a joining interface is formed at a joining surface between the second member and an inner wall surface of the hole, and the joining is performed in a solid state.

The upper limit of the press-fitting margin is 0.4 mm,
The relationship between the press-fitting allowance and the press-fitting depth at which the first member and the second member are joined is set in a range of (1 ≦ press-fitting depth (mm) ≦ 9−20 × press-fitting allowance). The press-fitting method according to claim 10, wherein:

After the press-fitting, a current is again applied between the first member and the second member, and an electric resistance heat is generated at a joint between the two members to perform tempering. The press-fitting method according to claim 11.