JP2004308683A

JP2004308683A - Manufacturing method for sintered oil retaining bearing and sintered oil retaining bearing

Info

Publication number: JP2004308683A
Application number: JP2003099060A
Authority: JP
Inventors: Tsuneo Maruyama; 恒夫丸山; Teruo Shimizu; 輝夫清水
Original assignee: Mitsubishi Materials Corp
Current assignee: Mitsubishi Materials Corp
Priority date: 2003-04-02
Filing date: 2003-04-02
Publication date: 2004-11-04

Abstract

<P>PROBLEM TO BE SOLVED: To effectively control an offset of a bearing by forming a bearing hole at the inside of a sintered body after sintering in a manufacturing process of a sintered oil retaining bearing. <P>SOLUTION: The sintered oil retaining bearing has a bearing hole with a circular cross section supporting a rotary shaft formed on a bearing body made of sintered metal, and is provided with a shaft supporting portion with a uniform diameter having the inside as a frictional surface and a tapered enlarged diameter portion formed continuously with the shaft supporting portion with its diameter increasing outwardly. The bearing hole having a uniform diameter including the shaft supporting portion is formed by pressurizing the inner periphery of the cylindrical sintered body W after the sintering process, and the enlarged diameter portion is formed continuously with the shaft supporting portion by pressurizing again the inner periphery of the sintered body W. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、焼結含油軸受の製造方法および焼結含油軸受に関する。
【０００２】
【従来の技術】
焼結体の内部にあらかじめ潤滑油を含侵させておき、軸の回転によるポンプ作用と摩擦熱による熱膨張で油をしみ出させて摩擦面を潤滑する焼結含油軸受は、無給油で長期間使用できることから、自動車や家電製品、音響機器等の回転軸の軸受として広く採用されている。
【０００３】
上記従来の焼結含油軸受においては、軸受孔に挿通された回転軸を心出し（軸受の中心軸線と回転軸の軸線とを一致させること）するために、軸受孔の一部分を他の部分より小径にし、この部分だけを回転軸に接触させる構造を採用している。
【０００４】
ところで、上記のように軸受孔の一部分を他の部分より小径にすると、軸受全体の長さに対して実際に回転軸に接触する部分の長さが短くなるために軸支持の状態が不安定になり易く、回転軸が心ずれし易いという問題がある。
【０００５】
そこで、従来の焼結含油軸受の中には、軸受孔を、回転軸を支持する軸支部と、軸支部に連なって外方に向かって径が拡大する拡径部とからなる形状とし、さらに拡径部の焼結密度を軸支部より密に形成して回転軸の心ずれを抑制するものがある（例えば下記の特許文献１）。
【０００６】
この構造を採用した軸受においては、回転軸にせん断荷重が作用すると、回転軸に振れが生じることで回転軸と軸支部との間を潤滑していた潤滑油が拡径部側に押し出され、回転軸と拡径部との間に充たされる。回転軸と拡径部との間に充たされた潤滑油は、回転軸が振れることで拡径部に押し付けられるように加圧されるが、拡径部が密に形成されていることから、軸受本体の内部には押し込まれず、回転軸と拡径部との間に残って回転軸に対し反力を作用させる。この反力により回転軸の振れが抑制され、軸受に対する回転軸の心ずれが防止される。
【０００７】
【特許文献１】
特公平８−１９９４１号公報
【０００８】
【発明が解決しようとする課題】
ところで、上記の軸受において拡径部のテーパ角（軸支部の軸線に沿う軸受の長手方向すなわち当該軸受に支持される回転軸の長手方向に対して拡径部の斜面がなす角。軸支部の内面と拡径部の斜面とがなす角にも等しい。）は２〜３°の非常に小さな角度に設定されるので、非常に高い工作精度を要求される。テーパ角の設定が精緻に行えていないと、上記のような回転軸の心ずれ抑制作用が十分に発揮されない可能性がある。
【０００９】
本発明は上記の事情に鑑みてなされたものであり、焼結含油軸受の製造過程において焼結を終えた中間体の内側に軸受孔を高精度に形成することで軸受の心ずれ抑制作用を良好に発揮させることを目的としている。
【００１０】
【課題を解決するための手段】
上記の課題を解決するための手段として、次のような構成の焼結含油軸受の製造方法、および焼結含油軸受を採用する。
すなわち本発明に係る請求項１記載の焼結含油軸受の製造方法は、焼結金属により形成された軸受本体に、回転軸を支持する軸受孔が形成され、該軸受孔が、内面を摩擦面として径の大きさが一定の軸支部と、該軸支部に連なって設けられ、外方に向かって径が拡大してテーパ状をなす拡径部とを備える焼結含油軸受の製造方法であって、
焼結を終えた円筒形状の焼結体の内周面を加圧して前記軸支部を含む径の大きさが一定の軸受孔を形成し、続いて前記焼結体の内周面を再度加圧して前記軸支部に連なるように前記拡径部を形成することを特徴とする。
【００１１】
請求項２記載の焼結含油軸受の製造方法は、請求項１記載の焼結含油軸受の製造方法において、前記拡径部の形成に、基端の径が前記焼結体の内径よりも大きな略円錐形のプレス型を用いることを特徴とする。
【００１２】
請求項３記載の焼結含油軸受の製造方法は、請求項２記載の焼結含油軸受の製造方法において、前記プレス型を、前記焼結体の両側からそれぞれ同時に挿入し、該プレス型の先端どうしを当接させないようにしながら前記焼結体の内周面に押し付けて前記軸支部の両側に前記拡径部を形成することを特徴とする。
【００１３】
請求項４記載の焼結含油軸受は、焼結金属により形成された軸受本体に、回転軸を支持する軸受孔が形成され、該軸受孔が、内面を摩擦面として径の大きさが一定の軸支部と、該軸支部に連なって設けられ、外方に向かって径が拡大してテーパ状をなす拡径部とを備える焼結含油軸受であって、
焼結を終えた円筒形状の焼結体の内周面を加圧して前記軸支部を含む径の大きさが一定の軸受孔を形成し、続いて前記焼結体の内周面を再度加圧して前記軸支部に連なるように前記拡径部を形成したことを特徴とする。
【００１４】
本発明においては、焼結を終えた円筒形状の焼結体の内周面を加圧して軸支部を含む径の大きさが一定の軸受孔を形成し、続いて同焼結体の内周面を再度加圧して軸支部に連なるように拡径部を形成することにより、軸支部の内面と拡径部の斜面とがなす角を正確に形成することが可能である。
焼結を終えた円筒形状の焼結体の内周面を加圧して軸支部を含む径の大きさが一定の軸受孔を形成する工程、および焼結体の内周面を再度加圧して軸支部に連なるように拡径部を形成する工程は、いずれも軸受の寸法精度を高めるためのサイジング（ｓａｉｚｉｎｇ）と呼ばれる工程であるが、このサイジングの工程において、軸支部を含む径の大きさが一定の軸受孔を先に形成し、その軸受孔を基準にして拡径部を形成することで、軸受孔に含まれる軸支部に対する拡径部の位置合わせが正確になされ、これによって軸支部の内面と拡径部の斜面とがなす角が正確に形成される。
【００１５】
本発明においては、拡径部の形成に、基端の径が前記焼結体の内径よりも大きな略円錐形のプレス型を用いることにより、拡径部を高精度に形成することが可能である。拡径部は上記のプレス型の円錐面を転写されるようにして形成されるが、もともと径の大きさが一定の軸受孔を加圧することで、外側に押し広げられた肉の一部が若干軸支部側に移動し、軸支部の内面がせり上がるようにして軸支部の内径を縮めてしまう。このとき、プレス型が略円錐形であるので、せり上がった軸支部の内面がプレス型の円錐面に押し付けられて拡径部となり、軸支部と拡径部との境界が凹凸を生じることなく高精度に形成される。
【００１６】
本発明においては、上記のプレス型を、焼結体の両側からそれぞれ同時に挿入し、該プレス型の先端どうしを当接させないようにしながら焼結体の内周面に押し付けて軸支部の両側に拡径部を形成することにより、軸支部の内面が均一にせり上がり、軸支部の内径がどの部分でも一定になる。
【００１７】
【発明の実施の形態】
本発明に係る第１の実施形態を図１ないし図４に示して説明する。
図１に示す焼結含油軸受（以下では単に軸受とする）は、焼結金属により形成された軸受本体１の内部に、回転軸２が挿通される軸受孔３が形成されている。軸受孔３は、回転軸２の長手方向の軸線Ｏに直交する面内における断面形状が円形をなしており、軸受本体１のほぼ中央にあって回転軸２の直径よりも径が若干大きく、かつ長手方向のいずれの位置においても径の大きさが一定の軸支部３ａと、軸支部３ａに連なって長手方向の両側にそれぞれ設けられ、外方に向かって単調に径が拡大してテーパ状をなす拡径部３ｂ，３ｃとを備えている。いずれの拡径部３ｂ，３ｃも、その傾斜面と軸受本体１の軸方向に平行な直孔部３ａの内面（または回転軸２の軸線Ｏ）とがなす角（テーパ角）θ１は、３°以下に設定されている。なお、図１ではθ１を明確にするために誇張して図示してある。
【００１８】
拡径部３ｂ，３ｃをなす軸受本体１の内壁部４は、軸支部３ａをなす内壁部５よりも焼結密度が高い、すなわち内壁部４の表面および内部に残る気孔が、内壁部５の表面および内部に残る気孔よりも小さく、数も少なくなっている。このような軸受本体１の各部における粗密の違いは、焼結工程の後に行う矯正（再加圧）工程において、該当する部分に対する加圧力を加減することによって実現されている。
【００１９】
上記構成の軸受は、軸受本体１に潤滑油を含侵させたうえで、軸受孔３に回転軸２を挿通されて使用される。軸受に支持された回転軸２を回転させるために比較的小さなトルクが伝達されたときには、回転軸２に作用するせん断荷重も小さく、回転軸２に振れはほとんど生じないので、回転軸２の表面が軸支部３ａに接し、この部分を摩擦面として支持される。軸支部３ａでは、回転軸２の回転によるポンプ作用と摩擦熱による熱膨張とによって軸受本体１の内部から潤滑油がしみ出し、摩擦面を潤滑する。
【００２０】
上記構成の軸受の製造工程を図２ないし図４を参照して説明する。
原料粉末の混合、成形、焼結の各工程を行い、続いてサイジングを行う。サイジングには、軸支部３ａを含む軸受孔３を形成する工程と、軸支部３ａの両側に拡径部３ｂ，３ｃを形成する工程の２つがある。
軸支部３ａを含む軸受孔３を形成する工程では、図２（ａ）〜（ｃ）に示すように、円筒形状の孔１０ａが形成されたダイ１０、孔１０ａに下方から遊びを持って挿入可能な丸棒状の第１のコアロッド１１、孔１０ａに上方から嵌入可能で先端面が単純な円環形状をなす第１の上パンチ１２、同じく孔１０ａに下方から嵌入可能で先端面が単純な円環形状をなす第１の下パンチ１３が用いられる。
【００２１】
第１のコアロッド１１は、基端側と先端側とで２段階に径が変化し、より径の大きな基端側の外径が焼結体Ｗの内径とほぼ同じとなっており、第１の下パンチ１３の内側に挿抜される。ダイ１０は定位置に固定されており、コアロッド１１、第１の上パンチ１２、第２の下パンチ１３は図示しない駆動装置により駆動されるようになっている。
【００２２】
まず、図２（ａ）に示すように、ダイ１０の孔１０ａに第１の下パンチ１３を嵌入し、さらに第１の下パンチ１３を通じて孔１０ａに第１のコアロッド１１を挿入しておく。そして、ダイ１０の上方から孔１０ａに焼結体Ｗを入れる。焼結体Ｗは、内側に第１のコアロッド１１の先細の先端を通されて孔１０ａ内に配置される。
【００２３】
次に、図２（ｂ）に示すように、孔１０ａに第１の上パンチ１１を嵌入し、焼結体Ｗを下方に強く押し下げる。押し下げられた焼結体Ｗは、第１の上パンチ１１と、第１の下パンチ１３とに挟まれて上下から加圧され、上下方向に若干押し縮められる。さらに、外面を孔１０ａの内周面に押し付けられて滑らかな円筒面状に矯正され、内面を第１のコアロッド１１の外周面に押し付けられて滑らかな円筒面状に矯正される（焼結体Ｗの内側には、軸支部３ａを含む径の大きさが一定の軸受孔３が形成される）。
【００２４】
矯正が完了したら、第１の上パンチ１１を孔１０ａから抜き出し、続いて図２（ｃ）に示すように、第１の下パンチ１３を上方に押し上げ、矯正を終えた焼結体Ｗを孔１０ａから取り出す。
【００２５】
軸支部３ａの両側に拡径部３ｂ，３ｃを形成する工程では、図３（ａ）〜（ｃ）に示すように、焼結体Ｗの外径にほぼ等しい内径の孔２０ａが形成されたダイ２０、孔２０ａに上方から遊びを持って挿入可能な丸棒状の第２のコアロッド２１、同じく孔２０ａに下方から遊びを持って挿入可能な丸棒状の第３のコアロッド２２、孔２０ａに上方から嵌入可能で先端面が単純な円環形状をなす第２の上パンチ２３、同じく孔２０ａに下方から嵌入可能で先端面が単純な円環形状をなす第２の下パンチ２４が用いられる。
【００２６】
第２、第３のコアロッド２１，２２は、外径が焼結体Ｗの内径よりも大きく、かつ先端２１ａ，２２ａが円錐台形状のプレス型をなしている。両先端２１ａ，２２ａは同寸法で、基端２１ｂ，２２ｂの径が焼結体Ｗの内径よりも大きく、先端面２１ｃ，２２ｃ（先端）の外径は焼結体Ｗの内径よりも小さく形成されている。第２のコアロッド２１は第２の上パンチ２３の内側に、第３のコアロッド２２は第２の下パンチ２４の内側に挿抜される。
ダイ２０は定位置に固定されており、第２、第３のコアロッド２１，２２、第２の上パンチ２３、第２の下パンチ２４は図示しない駆動装置により駆動されるようになっている。
【００２７】
まず、図３（ａ）に示すように、ダイ２０の孔２０ａに第２の下パンチ２４を嵌入し、さらに第２の下パンチ２４を通じて孔２０ａに第３のコアロッド２２を挿入しておく。また、ダイ２０の上方には、内側に第２のコアロッド２１を挿入した第２の上パンチ２３を待機させておく。そして、ダイ２０の上方から孔２０ａに、軸支部３ａを含む軸受孔３の形成を終えた焼結体Ｗを入れる。
【００２８】
次に、図３（ｂ）に示すように、孔２０ａに第２の上パンチ２３および第２のコアロッド２１を同期させて嵌入し、焼結体Ｗを下方に押し下げる。押し下げられた焼結体Ｗは、第２のコアロッド２１と、第３のコアロッド２２とに挟まれて加圧される。このとき、各コアロッドの先端面２１ｃ，２２ｃどうしを当接させないことを考慮して各コアロッド２１，２２の駆動量や先端形状を決定しておく。
【００２９】
各コアロッドの先端２１ａ，２２ａは、先行して実施されたサイジングによって形成された軸受孔３の両端開口に当接し、軸受孔３の長手方向に案内されるように軸受孔３の内側に押し込まれる。焼結体Ｗは、軸受孔３の内側に各コアロッドの先端２１ａ，２２ａの円錐面をそれぞれ押し付けられて矯正される（軸支部３ａの両側には、拡径部３ｂ，３ｃが形成される）。このとき、拡径部３ｂ，３ｃに当たる部分は２度加圧されることにより焼結密度が高められ、軸支部３ａとの間に粗密の差が与えられる。
【００３０】
矯正が完了したら、第２のコアロッド２１および第２の上パンチ２３を孔２０ａから抜き出し、続いて図３（ｃ）に示すように、第２の下パンチ２４を上方に押し上げ、矯正を終えた焼結体Ｗを孔２０ａから取り出す。
【００３１】
上記のように、サイジングの工程において軸支部３ａを含む径の大きさが一定の軸受孔３を先に形成し、その軸受孔３を基準にして拡径部３ｂ，３ｃを形成することで、軸支部３ａに対する拡径部３ｂ，３ｃの位置合わせが正確になされ、軸支部３ａの内周面と拡径部３ｂ，３ｃの斜面とがなす角θ１が非常に正確に形成される。
【００３２】
また、拡径部３ｂ，３ｃの形成に、先端が円錐台形状のプレス型をなす第２、第３のコアロッド２１，２２を用いると、図４に示すように、拡径部３ｂ，３ｃは各コアロッドの先端２１ａ，２２ａの円錐面を転写されるようにして形成されるが、もともと径の大きさが一定の軸受孔３を加圧することで、外側に押し広げられた肉の一部（図中のＸ部分）が若干軸支部３ａ側に移動し、軸支部３ａの内面がせり上がるようにして軸支部３ａの内径を縮めてしまう。このとき、各コアロッドの先端２１ａ，２２ａが略円錐形であるので、せり上がった軸支部３ａの内面がその円錐面に押し付けられて拡径部３ｂ，３ｃとなり、軸支部３ａと拡径部３ｂ，３ｃとの境界が凹凸を生じることなく高精度に形成される。また、軸支部３ａとなる部分は先行して加圧されて硬さを増しているので、両側からコアロッドを挿入されても内面にうねりのような変形が起こらず、滑らかな円筒面が保たれる。
【００３３】
さらに、第２、第３のコアロッド２１，２２を焼結体Ｗの両側からそれぞれ同時に挿入し、各コアロッドの先端２１ａ，２２ａどうしを当接させないようにしながら焼結体Ｗの内周面に押し付けることにより、軸支部３ａの内面が図４のように均一にせり上がり、軸支部３ａの内径がどの部分でも一定になる。
【００３４】
次に、本発明に係る第２の実施形態を図５および図６に示して説明する。なお、上記実施形態において既に説明した構成要素には同一符号を付して説明は省略する。
本実施形態の軸受には、図５に示すように、拡径部３ｂは軸支部３ａの一側方にのみ設けられており、軸支部３ａの他側方には面取り部３ｄが設けられている。この面取り部３ｄは、主に軸受孔３に回転軸２を通し易くするために設けられたもので、回転軸２との間で心ずれ抑制の機能を発揮するものではない。
【００３５】
上記構成の軸受の製造工程を図６を参照して説明する。なお、原料粉末の混合から焼結までの工程、さらに軸支部３ａを含む軸受孔３を形成するサイジングの工程については上記第１の実施形態と同じなのでその説明は省略する。
軸支部３ａの両側に拡径部３ｂを形成する工程では、図６（ａ）〜（ｃ）に示すように、焼結体Ｗの外径にほぼ等しい内径の孔３０ａが形成されたダイ３０、孔３０ａに上方から遊びを持って挿入可能な丸棒状の第４のコアロッド３１、孔３０ａに上方から嵌入可能で先端面が単純な円環形状をなす第３の上パンチ３２、同じく孔３０ａに下方から嵌入可能で先端面が単純な円環形状をなす第３の下パンチ３３が用いられる。
【００３６】
第４のコアロッド３１は、外径が焼結体Ｗの内径よりも大きく、かつ先端３１ａが円錐台形状のプレス型をなし、基端３１ｂの径が焼結体Ｗの内径よりも大きく、先端面３１ｃの外径は焼結体Ｗの内径よりも小さく形成されており、第３の上パンチ３２の内側に挿抜される。
ダイ３０は定位置に固定されており、第４のコアロッド３１、第３の上パンチ３２、第３の下パンチ３３は図示しない駆動装置により駆動されるようになっている。
【００３７】
まず、図６（ａ）に示すように、ダイ３０の孔３０ａに第３の下パンチ３３を嵌入しておく。また、ダイ３０の上方には、内側に第４のコアロッド３１を挿入した第３の上パンチ３２を待機させておく。そして、ダイ３０の上方から孔３０ａに、軸支部３ａを含む軸受孔３ならびに面取り部３ｄの形成を終えた焼結体Ｗを入れる。
【００３８】
次に、図６（ｂ）に示すように、孔３０ａに第３の上パンチ３２および第４のコアロッド３１を同期させて嵌入し、焼結体Ｗを下方に押し下げる。押し下げられた焼結体Ｗは、第４のコアロッド３１と、第３の下パンチ３３とに挟まれて加圧される。
【００３９】
第４のコアロッド３１の先端３１ａは、先行して実施されたサイジングによって形成された軸受孔３の一端の開口に当接し、軸受孔３の長手方向に案内されるように軸受孔３の内側に押し込まれる。焼結体Ｗは、軸受孔３の内側に第４のコアロッド３１の先端３１ａの円錐面を押し付けられて矯正される（軸支部３ａの一側方には、拡径部３ｂが形成される）。このとき、拡径部３ｂに当たる部分は２度加圧されることにより焼結密度が高められ、軸支部３ａとの間に粗密の差が与えられる。
【００４０】
矯正が完了したら、第３の上パンチ３２および第４のコアロッド３１を孔３０ａから抜き出し、続いて図６（ｃ）に示すように、第３の下パンチ３３を上方に押し上げ、矯正を終えた焼結体Ｗを孔３０ａから取り出す。
【００４１】
上記のように、サイジングの工程において軸支部３ａを含む径の大きさが一定の軸受孔３を先に形成し、その軸受孔３を基準にして拡径部３ｂを形成することで、軸支部３ａに対する拡径部３ｂの位置合わせが正確になされ、軸支部３ａの内周面と拡径部３ｂの斜面とがなす角θ１が非常に正確に形成される。
【００４２】
ところで、上記第１、第２の実施形態の軸受はいずれも、軸受本体１の各部に粗密の違いを設けて回転軸の心ずれを防止する構造を備えているが、本発明はこのような構造を備える焼結含油軸受にのみ適用されるものではなく、軸受本体の焼結密度が均一な焼結含油軸受にも適用可能であることはいうまでもない。
【００４３】
【発明の効果】
以上説明したように、本発明によれば、軸支部を含む径の大きさが一定の軸受孔を先に形成し、その軸受孔を基準にして拡径部を形成することで、軸受孔に含まれる軸支部に対する拡径部の位置合わせが正確になされるので、軸支部の内面と拡径部の斜面とがなす角を正確に形成することができ、結果的に焼結含油軸受の心ずれ抑制作用を良好に発揮させることができる。
【図面の簡単な説明】
【図１】本発明の第１の実施形態を示す図であって、回転軸の軸線方向に沿う平面で断面視した焼結含油軸受である。
【図２】図１の焼結含油軸受を製造する工程のひとつであるサイジングの進め方を段階的に示す状態説明図である。
【図３】同じく、図１の焼結含油軸受を製造する工程のひとつであるサイジングの進め方を段階的に示す状態説明図である。
【図４】サイジングにより変化する軸受の形状を示す状態説明図である。
【図５】本発明の第２の実施形態を示す図であって、回転軸の軸線方向に沿う平面で断面視した焼結含油軸受である。
【図６】図５の焼結含油軸受を製造する工程のひとつであるサイジングの進め方を段階的に示す状態説明図である。
【符号の説明】
１軸受本体
２回転軸
３軸受孔
３ａ軸支部
３ｂ，３ｃ拡径部
２１，２２第１，第２のコアロッド
２１ａ，２２ａ先端（プレス型）
Ｗ焼結体[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a sintered oil-impregnated bearing and a sintered oil-impregnated bearing.
[0002]
[Prior art]
Lubricating oil is impregnated in the sintered body in advance, and the oil is extruded by the pump action due to the rotation of the shaft and the thermal expansion due to frictional heat to lubricate the friction surface. Because it can be used for a period, it is widely used as a bearing for rotating shafts of automobiles, home appliances, audio equipment, and the like.
[0003]
In the above-mentioned conventional sintered oil-impregnated bearing, in order to center the rotating shaft inserted in the bearing hole (to make the center axis of the bearing coincide with the axis of the rotating shaft), a part of the bearing hole is separated from other parts. A structure is adopted in which the diameter is reduced and only this portion is brought into contact with the rotating shaft.
[0004]
By the way, if one part of the bearing hole is made smaller in diameter than the other part as described above, the length of the part that actually contacts the rotating shaft becomes shorter than the entire length of the bearing, and the shaft support state becomes unstable. And there is a problem that the axis of rotation tends to be misaligned.
[0005]
Therefore, in conventional sintered oil-impregnated bearings, the bearing hole is formed of a shaft supporting portion that supports the rotating shaft, and a diameter-enlarging portion that is connected to the shaft supporting portion and whose diameter increases outward. There is one in which the sintering density of the enlarged diameter portion is formed more densely than that of the shaft support portion to suppress misalignment of the rotating shaft (for example, Patent Document 1 below).
[0006]
In a bearing employing this structure, when a shear load is applied to the rotating shaft, a run-out occurs in the rotating shaft, so that the lubricating oil that has lubricated between the rotating shaft and the shaft support portion is pushed out to the enlarged diameter portion side, It is filled between the rotating shaft and the enlarged diameter portion. The lubricating oil filled between the rotating shaft and the enlarged diameter portion is pressurized so as to be pressed against the enlarged diameter portion by swinging the rotating shaft, but because the enlarged diameter portion is formed densely. However, it is not pushed into the inside of the bearing main body, but remains between the rotating shaft and the enlarged diameter portion to exert a reaction force on the rotating shaft. Due to this reaction force, run-out of the rotary shaft is suppressed, and misalignment of the rotary shaft with respect to the bearing is prevented.
[0007]
[Patent Document 1]
Japanese Patent Publication No. 8-19941
[Problems to be solved by the invention]
By the way, in the above bearing, the taper angle of the enlarged diameter portion (the angle formed by the slope of the enlarged diameter portion with respect to the longitudinal direction of the bearing along the axis of the bearing portion, that is, the longitudinal direction of the rotating shaft supported by the bearing. The angle between the inner surface and the slope of the enlarged diameter portion is also set to a very small angle of 2 to 3 °, so that extremely high machining accuracy is required. If the taper angle is not precisely set, the above-described action of suppressing the misalignment of the rotating shaft may not be sufficiently exhibited.
[0009]
The present invention has been made in view of the above circumstances, and in the manufacturing process of a sintered oil-impregnated bearing, a bearing hole is formed with high precision inside an intermediate body after sintering, thereby suppressing the bearing misalignment. The purpose is to show it well.
[0010]
[Means for Solving the Problems]
As means for solving the above problems, a method for manufacturing a sintered oil-impregnated bearing having the following configuration and a sintered oil-impregnated bearing are employed.
That is, in the method for manufacturing a sintered oil-impregnated bearing according to claim 1 of the present invention, a bearing body for supporting a rotating shaft is formed in a bearing body formed of a sintered metal, and the bearing hole has an inner surface having a friction surface. The present invention provides a method for manufacturing a sintered oil-impregnated bearing comprising: a shaft supporting portion having a constant diameter; and a diameter-enlarging portion provided in connection with the shaft supporting portion, the diameter increasing outward and forming a tapered shape. hand,
The inner peripheral surface of the cylindrical sintered body after sintering is pressurized to form a bearing hole having a constant diameter including the shaft support, and then the inner peripheral surface of the sintered body is re-applied. The enlarged diameter portion is formed so as to be connected to the shaft support by pressing.
[0011]
A method for manufacturing a sintered oil-impregnated bearing according to a second aspect is the method for manufacturing a sintered oil-impregnated bearing according to the first aspect, wherein a diameter of a base end is larger than an inner diameter of the sintered body in forming the enlarged diameter portion. It is characterized in that a substantially conical press die is used.
[0012]
A method for manufacturing a sintered oil-impregnated bearing according to a third aspect is the method for manufacturing a sintered oil-impregnated bearing according to the second aspect, wherein the press dies are simultaneously inserted from both sides of the sintered body, respectively, and a tip of the press dies is provided. The enlarged diameter portions are formed on both sides of the shaft support portion by pressing against the inner peripheral surface of the sintered body while preventing them from contacting each other.
[0013]
In the sintered oil-impregnated bearing according to claim 4, a bearing hole for supporting a rotating shaft is formed in a bearing body formed of a sintered metal, and the bearing hole has a constant diameter with an inner surface as a friction surface. A shaft support portion, a sintered oil-impregnated bearing provided with a diameter-enlarging portion that is provided in connection with the shaft support portion and has a diameter that increases outward and forms a tapered shape,
The inner peripheral surface of the cylindrical sintered body after sintering is pressurized to form a bearing hole having a constant diameter including the shaft support, and then the inner peripheral surface of the sintered body is re-applied. The enlarged diameter portion is formed so as to be connected to the shaft support by pressing.
[0014]
In the present invention, the inner peripheral surface of the sintered cylindrical body after the sintering is pressed to form a bearing hole having a constant diameter including the shaft support portion, and then the inner peripheral surface of the sintered body is formed. By forming the enlarged diameter portion so as to be continuous with the pivot portion by pressing the surface again, it is possible to accurately form an angle formed by the inner surface of the pivot portion and the slope of the enlarged diameter portion.
A step of forming a bearing hole having a constant diameter including the shaft support by pressing the inner peripheral surface of the cylindrical sintered body after sintering, and pressing the inner peripheral surface of the sintered body again. The process of forming the enlarged diameter portion so as to be continuous with the shaft support portion is a process called sizing for improving the dimensional accuracy of the bearing. In this sizing process, the size of the diameter including the shaft support portion is large. By first forming a fixed bearing hole and forming the enlarged diameter portion based on the bearing hole, the positioning of the enlarged diameter portion with respect to the bearing portion included in the bearing hole is accurately performed, thereby The angle formed between the inner surface of the diaper and the slope of the enlarged diameter portion is accurately formed.
[0015]
In the present invention, the enlarged diameter portion can be formed with high accuracy by using a substantially conical press die whose base end diameter is larger than the inner diameter of the sintered body. is there. The enlarged diameter part is formed by transferring the conical surface of the above-mentioned press die, but by pressing a bearing hole having a constant diameter from the beginning, a part of the meat expanded outward is The shaft is slightly moved to the side of the shaft support, and the inner surface of the shaft support is raised, thereby reducing the inner diameter of the shaft support. At this time, since the press die has a substantially conical shape, the inner surface of the raised shaft support is pressed against the conical surface of the press die to form an enlarged diameter portion, and the boundary between the shaft support and the enlarged diameter portion does not have irregularities. Formed with high precision.
[0016]
In the present invention, the above-mentioned press dies are simultaneously inserted from both sides of the sintered body, respectively, and pressed against the inner peripheral surface of the sintered body while preventing the tips of the press dies from coming into contact with each other. By forming the enlarged diameter portion, the inner surface of the shaft support portion is uniformly raised, and the inner diameter of the shaft support portion is constant at any portion.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
A first embodiment according to the present invention will be described with reference to FIGS.
In the sintered oil-impregnated bearing shown in FIG. 1 (hereinafter simply referred to as a bearing), a bearing hole 3 through which a rotating shaft 2 is inserted is formed inside a bearing body 1 formed of a sintered metal. The bearing hole 3 has a circular cross section in a plane perpendicular to the longitudinal axis O of the rotating shaft 2, is substantially at the center of the bearing body 1, and has a diameter slightly larger than the diameter of the rotating shaft 2. In addition, a shaft supporting portion 3a having a constant diameter at any position in the longitudinal direction and provided on both sides in the longitudinal direction so as to be continuous with the shaft supporting portion 3a. And enlarged diameter portions 3b and 3c. The angle (taper angle) θ1 between the inclined surface of each of the enlarged diameter portions 3b and 3c and the inner surface of the straight hole portion 3a (or the axis O of the rotating shaft 2) parallel to the axial direction of the bearing body 1 is 3 ° is set below. Note that FIG. 1 is exaggerated in order to clarify θ1.
[0018]
The inner wall portion 4 of the bearing body 1 forming the enlarged diameter portions 3b and 3c has a higher sintering density than the inner wall portion 5 forming the shaft support portion 3a, that is, pores remaining on the surface and inside of the inner wall portion 4 are formed. It is smaller and smaller in number than the pores remaining on the surface and inside. Such a difference in density in each part of the bearing body 1 is realized by increasing or decreasing the pressure applied to the corresponding part in a correction (re-pressurization) step performed after the sintering step.
[0019]
The bearing having the above configuration is used after the bearing body 1 is impregnated with lubricating oil and the rotating shaft 2 is inserted through the bearing hole 3. When a relatively small torque is transmitted to rotate the rotating shaft 2 supported by the bearing, the shear load acting on the rotating shaft 2 is small, and the rotating shaft 2 hardly oscillates. Is in contact with the shaft support 3a, and this portion is supported as a friction surface. In the shaft support 3a, the lubricating oil exudes from the inside of the bearing main body 1 due to the pumping action due to the rotation of the rotating shaft 2 and the thermal expansion due to frictional heat, and lubricates the friction surface.
[0020]
The manufacturing process of the bearing having the above configuration will be described with reference to FIGS.
The respective steps of mixing, molding, and sintering the raw material powder are performed, and then sizing is performed. The sizing includes two steps, a step of forming the bearing hole 3 including the shaft support 3a and a step of forming the enlarged diameter portions 3b and 3c on both sides of the shaft support 3a.
In the step of forming the bearing hole 3 including the shaft support 3a, as shown in FIGS. 2A to 2C, the die 10 having the cylindrical hole 10a formed therein is inserted with play from below into the hole 10a. A possible first core rod 11 having a round rod shape, a first upper punch 12 which can be fitted into the hole 10a from above and has a simple annular end face, and can be fitted into the hole 10a from below and has a simple tip face. A first lower punch 13 having an annular shape is used.
[0021]
The diameter of the first core rod 11 changes in two steps between the base end side and the distal end side, and the outer diameter of the larger base end side is substantially the same as the inner diameter of the sintered body W. Of the lower punch 13. The die 10 is fixed at a fixed position, and the core rod 11, the first upper punch 12, and the second lower punch 13 are driven by a driving device (not shown).
[0022]
First, as shown in FIG. 2A, the first lower punch 13 is fitted into the hole 10a of the die 10, and the first core rod 11 is inserted into the hole 10a through the first lower punch 13. Then, the sintered body W is put into the hole 10a from above the die 10. The sintered body W is placed inside the hole 10a through the tapered tip of the first core rod 11 inside.
[0023]
Next, as shown in FIG. 2B, the first upper punch 11 is fitted into the hole 10a, and the sintered body W is strongly pushed downward. The pressed-down sintered body W is sandwiched between the first upper punch 11 and the first lower punch 13 and is pressed from above and below and is slightly compressed in the vertical direction. Further, the outer surface is pressed against the inner peripheral surface of the hole 10a to be corrected into a smooth cylindrical surface, and the inner surface is pressed against the outer peripheral surface of the first core rod 11 to be corrected into a smooth cylindrical surface (sintered body). A bearing hole 3 having a constant diameter including the shaft support 3a is formed inside W.)
[0024]
When the straightening is completed, the first upper punch 11 is pulled out from the hole 10a, and subsequently, the first lower punch 13 is pushed upward as shown in FIG. Remove from 10a.
[0025]
In the step of forming the enlarged diameter portions 3b and 3c on both sides of the shaft support portion 3a, holes 20a having an inner diameter substantially equal to the outer diameter of the sintered body W were formed as shown in FIGS. A die 20, a round rod-shaped second core rod 21 that can be inserted into the hole 20a with play from above, a third round rod-shaped core rod 22 that can be inserted into the hole 20a with play from below, and an upper part into the hole 20a. A second upper punch 23, which can be fitted into the hole 20a and has a simple annular shape, and a second lower punch 24, which can be fitted into the hole 20a from below and has a simple annular shape, are used.
[0026]
Each of the second and third core rods 21 and 22 has a press die having an outer diameter larger than the inner diameter of the sintered body W and tips 21a and 22a having a truncated cone shape. The two ends 21a and 22a have the same dimensions, the diameter of the base ends 21b and 22b is larger than the inner diameter of the sintered body W, and the outer diameter of the front end faces 21c and 22c (tip) is smaller than the inner diameter of the sintered body W. Have been. The second core rod 21 is inserted inside the second upper punch 23, and the third core rod 22 is inserted inside the second lower punch 24.
The die 20 is fixed at a fixed position, and the second and third core rods 21 and 22, the second upper punch 23, and the second lower punch 24 are driven by a driving device (not shown).
[0027]
First, as shown in FIG. 3A, the second lower punch 24 is fitted into the hole 20a of the die 20, and the third core rod 22 is inserted into the hole 20a through the second lower punch 24. Above the die 20, a second upper punch 23 into which the second core rod 21 is inserted is kept on standby. Then, the sintered body W after the formation of the bearing hole 3 including the shaft support 3a is put into the hole 20a from above the die 20.
[0028]
Next, as shown in FIG. 3B, the second upper punch 23 and the second core rod 21 are synchronously fitted into the holes 20a, and the sintered body W is pushed downward. The pressed-down sintered body W is pressed between the second core rod 21 and the third core rod 22. At this time, the drive amount and the tip shape of each of the core rods 21 and 22 are determined in consideration of preventing the tip surfaces 21c and 22c of the core rods from abutting each other.
[0029]
The tips 21a and 22a of the core rods abut the openings at both ends of the bearing hole 3 formed by sizing performed in advance, and are pushed inside the bearing hole 3 so as to be guided in the longitudinal direction of the bearing hole 3. . The sintered body W is straightened by pressing the conical surfaces of the tips 21a and 22a of the core rods inside the bearing hole 3 (the enlarged diameter portions 3b and 3c are formed on both sides of the shaft support 3a). . At this time, the portions corresponding to the enlarged diameter portions 3b and 3c are pressurized twice so that the sintering density is increased, and a difference in density between the shaft supporting portion 3a and the sintering portion is given.
[0030]
When the straightening is completed, the second core rod 21 and the second upper punch 23 are pulled out from the hole 20a, and then, as shown in FIG. 3C, the second lower punch 24 is pushed upward to complete the straightening. The sintered body W is taken out from the hole 20a.
[0031]
As described above, in the sizing process, the bearing hole 3 having a constant diameter including the shaft support portion 3a is formed first, and the enlarged diameter portions 3b and 3c are formed with the bearing hole 3 as a reference. The positioning of the enlarged diameter portions 3b and 3c with respect to the shaft support portion 3a is accurately performed, and the angle θ1 formed between the inner peripheral surface of the shaft support portion 3a and the inclined surfaces of the enlarged diameter portions 3b and 3c is formed very accurately.
[0032]
When the second and third core rods 21 and 22 each having a truncated cone-shaped press die are used to form the enlarged diameter portions 3b and 3c, as shown in FIG. The conical surfaces of the tips 21a and 22a of the core rods are formed so as to be transferred, and a part of the meat that is spread outward by pressing the bearing hole 3 having a constant diameter is originally applied. (X part in the figure) slightly moves to the side of the shaft support 3a, and the inner surface of the shaft support 3a rises to reduce the inner diameter of the shaft support 3a. At this time, since the tips 21a and 22a of the core rods are substantially conical, the inner surface of the raised shaft support 3a is pressed against the conical surface to become the enlarged diameter portions 3b and 3c, and the shaft support 3a and the enlarged diameter portion 3b , 3c are formed with high accuracy without unevenness. Also, since the portion serving as the shaft support portion 3a is pressurized in advance and has increased hardness, even when the core rod is inserted from both sides, deformation such as undulation does not occur on the inner surface, and a smooth cylindrical surface is maintained. It is.
[0033]
Further, the second and third core rods 21 and 22 are simultaneously inserted from both sides of the sintered body W, respectively, and pressed against the inner peripheral surface of the sintered body W while preventing the tips 21a and 22a of the core rods from coming into contact with each other. As a result, the inner surface of the shaft support 3a is uniformly raised as shown in FIG. 4, and the inner diameter of the shaft support 3a is constant at any portion.
[0034]
Next, a second embodiment according to the present invention will be described with reference to FIGS. Note that components already described in the above embodiment are given the same reference numerals, and description thereof is omitted.
In the bearing of this embodiment, as shown in FIG. 5, the enlarged diameter portion 3b is provided only on one side of the shaft support 3a, and a chamfered portion 3d is provided on the other side of the shaft support 3a. I have. The chamfered portion 3d is provided mainly for facilitating the passage of the rotary shaft 2 through the bearing hole 3, and does not exhibit a function of suppressing misalignment with the rotary shaft 2.
[0035]
The manufacturing process of the bearing having the above configuration will be described with reference to FIG. The steps from the mixing of the raw material powders to the sintering, and the sizing step of forming the bearing hole 3 including the shaft support 3a are the same as those in the first embodiment, and the description thereof will be omitted.
In the step of forming the enlarged diameter portions 3b on both sides of the shaft support 3a, as shown in FIGS. 6 (a) to 6 (c), a die 30 having a hole 30a having an inner diameter substantially equal to the outer diameter of the sintered body W is formed. A fourth core rod 31 in the form of a round bar that can be inserted into the hole 30a with play from above, a third upper punch 32 that can be fitted into the hole 30a from above and has a simple annular end face, and the hole 30a as well. A third lower punch 33 that can be fitted from below and has a simple annular shape at the distal end surface is used.
[0036]
The fourth core rod 31 has an outer diameter larger than the inner diameter of the sintered body W, a tip 31a in the shape of a frustoconical press, a base end 31b larger than the inner diameter of the sintered body W, The outer diameter of the surface 31c is formed smaller than the inner diameter of the sintered body W, and is inserted and removed inside the third upper punch 32.
The die 30 is fixed at a fixed position, and the fourth core rod 31, the third upper punch 32, and the third lower punch 33 are driven by a driving device (not shown).
[0037]
First, as shown in FIG. 6A, the third lower punch 33 is fitted into the hole 30a of the die 30. Above the die 30, a third upper punch 32 into which the fourth core rod 31 is inserted is kept on standby. Then, the sintered body W after the formation of the bearing hole 3 including the shaft support 3a and the chamfered portion 3d is put into the hole 30a from above the die 30.
[0038]
Next, as shown in FIG. 6B, the third upper punch 32 and the fourth core rod 31 are synchronously fitted into the hole 30a, and the sintered body W is pushed downward. The pressed-down sintered body W is pressed between the fourth core rod 31 and the third lower punch 33.
[0039]
The tip 31a of the fourth core rod 31 abuts the opening at one end of the bearing hole 3 formed by sizing performed in advance, and is positioned inside the bearing hole 3 so as to be guided in the longitudinal direction of the bearing hole 3. Pushed. The sintered body W is corrected by pressing the conical surface of the tip 31a of the fourth core rod 31 into the inside of the bearing hole 3 (an enlarged diameter portion 3b is formed on one side of the shaft support 3a). . At this time, the portion corresponding to the enlarged diameter portion 3b is pressurized twice so that the sintering density is increased, and a difference in density between the shaft support 3a and the shaft support 3a is given.
[0040]
When the correction is completed, the third upper punch 32 and the fourth core rod 31 are pulled out from the hole 30a, and subsequently, as shown in FIG. 6C, the third lower punch 33 is pushed upward to complete the correction. The sintered body W is taken out from the hole 30a.
[0041]
As described above, in the sizing step, the bearing hole 3 having a constant diameter including the shaft support portion 3a is formed first, and the enlarged diameter portion 3b is formed based on the bearing hole 3 so that the shaft support portion is formed. The position of the enlarged diameter portion 3b with respect to 3a is accurately adjusted, and the angle θ1 formed by the inner peripheral surface of the shaft support 3a and the inclined surface of the enlarged diameter portion 3b is formed very accurately.
[0042]
By the way, the bearings of the first and second embodiments are both provided with a structure for preventing the misalignment of the rotating shaft by providing a difference in density between each part of the bearing body 1. It goes without saying that the present invention is not only applied to a sintered oil-impregnated bearing having a structure, but is also applicable to a sintered oil-impregnated bearing having a uniform sintered density of the bearing body.
[0043]
【The invention's effect】
As described above, according to the present invention, a bearing hole having a constant diameter including the shaft support portion is formed first, and the enlarged diameter portion is formed based on the bearing hole, so that the bearing hole is formed. Since the positioning of the enlarged diameter portion with respect to the included shaft support portion is accurately performed, the angle between the inner surface of the shaft support portion and the inclined surface of the enlarged diameter portion can be formed accurately, and as a result, the core of the sintered oil-impregnated bearing is formed. The effect of suppressing displacement can be favorably exhibited.
[Brief description of the drawings]
FIG. 1 is a view showing a first embodiment of the present invention, and is a sintered oil-impregnated bearing viewed in cross section along a plane along the axial direction of a rotating shaft.
FIG. 2 is a state explanatory view showing stepwise a sizing procedure which is one of the steps of manufacturing the sintered oil-impregnated bearing of FIG.
3 is a state explanatory view showing stepwise a sizing procedure, which is one of the steps for manufacturing the sintered oil-impregnated bearing of FIG.
FIG. 4 is a state explanatory view showing the shape of a bearing that changes with sizing.
FIG. 5 is a view showing a second embodiment of the present invention, and is a sintered oil-impregnated bearing viewed in cross section along a plane along the axial direction of a rotating shaft.
FIG. 6 is a state explanatory view showing stepwise a sizing procedure, which is one of the steps for manufacturing the sintered oil-impregnated bearing of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Bearing main body 2 Rotating shaft 3 Bearing hole 3a Shaft support part 3b, 3c Enlarged diameter part 21, 22 First and second core rods 21a, 22a Tip (press type)
W sintered body

Claims

A bearing hole for supporting the rotating shaft is formed in a bearing body formed of a sintered metal, and the bearing hole is provided continuously with the shaft support portion having a constant diameter with the inner surface as a friction surface. A method for manufacturing a sintered oil-impregnated bearing comprising: a diameter-enlarging portion whose diameter increases outward and forms a tapered shape,
The inner peripheral surface of the cylindrical sintered body after sintering is pressurized to form a bearing hole having a constant diameter including the shaft support, and then the inner peripheral surface of the sintered body is re-applied. A method for manufacturing a sintered oil-impregnated bearing, comprising forming the enlarged diameter portion so as to be connected to the shaft support portion by pressing.

The method for manufacturing a sintered oil-impregnated bearing according to claim 1, wherein a substantially conical press die whose base end is larger than the inner diameter of the sintered body is used for forming the enlarged diameter portion.

The press dies are simultaneously inserted from both sides of the sintered body, respectively, and pressed against the inner peripheral surface of the sintered body while preventing the tips of the press dies from coming into contact with each other. 3. The method for manufacturing a sintered oil-impregnated bearing according to claim 2, wherein a portion is formed.

A bearing hole for supporting the rotating shaft is formed in a bearing body formed of a sintered metal, and the bearing hole is provided continuously with the shaft support portion having a constant diameter with the inner surface as a friction surface. Is a sintered oil-impregnated bearing having a diameter-enlarging portion whose diameter increases outward and forms a tapered shape,
The inner peripheral surface of the cylindrical sintered body after sintering is pressurized to form a bearing hole having a constant diameter including the shaft support, and then the inner peripheral surface of the sintered body is re-applied. The sintered oil-impregnated bearing, wherein the enlarged diameter portion is formed so as to be connected to the shaft support portion by pressing.