JP3856363B2

JP3856363B2 - Manufacturing method of bearing

Info

Publication number: JP3856363B2
Application number: JP21661699A
Authority: JP
Inventors: 元博宮坂; 敏一竹花; 健栗原; 秀和徳島
Original assignee: Hitachi Powdered Metals Co Ltd
Current assignee: Hitachi Powdered Metals Co Ltd
Priority date: 1999-07-30
Filing date: 1999-07-30
Publication date: 2006-12-13
Anticipated expiration: 2019-07-30
Also published as: JP2001041245A

Description

【０００１】
【発明の属する技術分野】
本発明は、精密機器に内蔵されるスピンドルモータの駆動軸等、比較的高速で回転する軸を高精度で支持する場合に用いて好適な軸受の製造方法に関する。本発明は、素材を圧縮することにより塑性変形を生じさせて所望形状の軸受を得る技術であって、素材としては、主に、圧粉体を焼結させた焼結体あるいは焼結体にサイジング（再圧縮）を施してなる円筒状の多孔質体が用いられる。また、本発明によって製造された軸受は、潤滑油が含浸され、焼結含油軸受として好適に用いられる。
【０００２】
【従来の技術】
上記焼結含油軸受は、焼結体に含浸された潤滑油が内径面にしみ出し、内径面と回転軸との間に油膜が形成されることにより、摩擦抵抗が低減して騒音や振動が抑えられるといった特性を有する。また、振動や騒音の抑制効果をさらに高めた焼結含油軸受として、軸方向中央部の内径面に、内径が回転軸の外径より僅かに大きく回転軸と接触しない隙間（以下、中逃げ部と称する）を形成し、回転軸の軸支面を両端部の内径面に限定した２点支持構造として摩擦抵抗の低減効果と回転軸の支持力をより安定化させたものがある。
【０００３】
焼結含油軸受は、通常、原料の金属粉末を圧縮成形して得た円筒状の圧粉体を焼結し、焼結体をサイジングして最終形状に仕上げるといった工程を主体として製造されている。ところで、上記中逃げ部を有する軸受を製造する場合、その中逃げ部を焼結体への機械加工で形成すると、内径面に表出している気孔が潰れて潤滑油の循環作用に支障を来すことになる。このため、焼結体のサイジング工程で中逃げ部を同時に形成するか、もしくはサイジング後にもう１度焼結体を圧縮して中逃げ部を独自に形成する方法が好ましい。いずれの場合も、軸方向両端部の内径面が径方向内側に突出したり、軸方向中央部が径方向外側に膨出したりする塑性変形を、素材である焼結体に生じさせることにより、離間する２つの軸支面とこれらの間の中逃げ部が内径面に同時に形成される。
【０００４】
【発明が解決しようとする課題】
上記２点支持構造の軸受においては、前述した摩擦抵抗の低減や回転軸の支持力向上といった軸受性能を高める上で、離間する２つの軸支面の内径および同軸度が高い精度で一致していることが要求される。また、軸支面への潤滑油の供給量が十分になされることも重要である。ところが、従来より焼結体の塑性変形のさせ方は様々提案されているものの、比較的簡素で、軸受性能向上のための要求が十分満たされる一定の製造方法は見い出されていないのが現状であった。
【０００５】
したがって本発明は、軸方向中央部の内径面に回転軸が接触しない中逃げ部を有し、なおかつその中逃げ部の中逃げ量が比較的大きく、軸方向両端部の内径面が回転軸を支持する軸支面として機能する２点支持構造の軸受を、比較的簡素な方法で効率よく製造することができるとともに、その軸受性能（２つの軸支面の内径の同一性や同軸度に伴う回転軸の支持力、潤滑性、耐摩耗性等）の向上も達成し得る軸受の製造方法を提供することを目的としている。
【０００６】
【課題を解決するための手段】
本発明は、円筒状で、軸方向一端部に内径小径部を有するとともに外径均一または外径面の一部に外径大径部を備え、かつ、前記内径小径部の内径がコアロッドの外径よりも大きい形状である焼結された多孔質体からなる素材を、前記コアロッドを挿入させた状態で軸方向に圧縮することにより、前記素材の前記内径小径部を有する軸方向一端部とは反対側の端部の外径を縮小させるとともに中央部および前記内径小径部を有する軸方向一端部の外径を拡大させ、この変形に伴い、両端部内径面を前記コアロッドに圧接させて回転軸を支持する軸支面に形成するとともに、中央部内径面に中逃げ部を形成することを特徴としている。本発明に係る素材は、前述の如く焼結体あるいは焼結体にサイジングを施してなる多孔質体が用いられ、製造後は、潤滑油が含浸され、焼結含油軸受として好適に用いられる。
【０００７】
本発明では、例えば、外径均一の円筒状素材を、ダイに形成された円筒状成形孔に、コアロッドを挿入した状態を保持しながら、パンチにより圧入するとともに軸方向に圧縮するといった成形方法が採られる。その場合、素材の内径は、内径面とコアロッドとの間に隙間が形成される大きさに設定する。また、成形孔を、入口側および中央部が素材の外径よりも大きく、そこから奥が段部を経て素材の外径よりも小さく縮径された孔とする。
【０００８】
このような成形孔に素材が圧入されると、圧入方向先端側の一端部が成形孔の縮径部に圧入されて外径面が内径側に圧縮され、外径が縮小した絞り部が造形される。一方、中央部と、これに続く圧入方向後端側の他端部は、軸方向に圧縮されることにより、その外径面が成形孔の内径面に圧接するまで膨出し、外径が拡大する。また、素材が軸方向に圧縮されることにより、軸方向両端部の内径面が内径側に膨出してコアロッドに圧接し、軸支面に形成されるとともに、これら軸支面間の内径面は、コアロッドとの間の隙間が残存して中逃げ部とされる。本発明は、このような変形態様が適宜になされる素材と成形型の組み合わせを採ることにより、中逃げ量が比較的大きな中逃げ部を有する２点支持構造の軸受を、比較的簡素な方法で効率よく製造することができる。
【０００９】
本発明によれば、回転軸を支持する軸支面は、素材の内径面がコアロッドに強く圧接させられることにより形成されるので、その内径および同軸度が高い精度で一致する。また、軸支面の密度を高くすることができるので、耐摩耗性の向上が図られる。一方、中逃げ部が形成される内径面の密度を軸支面よりも低くすることができ、また、中逃げ部の直径を比較的大きく形成することができるので、潤滑油の含有量を多くすることができ、潤滑性の向上が図られる。これらの結果、高レベルの軸受性能を有する軸受を製造することができる。
【００１０】
本発明の素材としては、特に次に挙げる形状のものが用いられる。
▲１▼外径均一、かつ、軸方向一端部に内径小径部を有する。
▲２▼軸方向一端部に内径小径部を有し、かつ、他端部に外径大径部を有する。
【００１１】
また、本発明では、素材の軸方向両端部の内径面が圧接させられるコアロッドの外径面に、動圧溝形成用の凸部または凹部が形成されていることを特徴としている。これによると、前者の凸部の場合では、軸支面には凸部形状に応じた動圧溝が形成される。また、後者の凹部の場合では、凹部形状に応じて刻設された軸支面と軸支面間の動圧溝とが同時に形成される。軸支面に動圧溝を形成すると、両端部の各軸支面により回転軸を支持する２点支持構造に加え、動圧溝に発生する動圧効果（動圧溝に流入する潤滑油の高圧化に伴う剛性向上）によって回転軸の支持力が相乗的に高まり、回転軸の支持力がより安定する。
【００１２】
【発明の実施の形態】
以下、図面を参照して本発明の実施形態を説明する。
（１）第１実施形態−図１
図１（ａ）の符合１Ａは、焼結体もしくは焼結体にサイジングを施してなる素材である。なお、後に説明する全ての実施形態の素材の材質も、同様の焼結体であることを予め述べておく。素材１Ａは、外径均一で、軸方向一端部に内径小径部３が形成された円筒状のものである。
【００１３】
図１に示す成形装置は、成形孔２０を有するダイ２１と、コアロッド２２と、上下のパンチ２３，２４とを備えている。成形孔２０は奥部の内径が１段階縮径しており、入口側（上側）の主部２０ａと、奥部の絞り形成部２０ｂとから構成されている。主部２０ａから絞り形成部２０ｂへの移行部は、なだらかなテーパ状に形成されている。上パンチ２３は開口部２０ｃに挿入され、下パンチ２４は絞り形成部２０ｂに挿入されるようになされている。
【００１４】
素材１Ａの外径は、外径面と成形孔２０の主部２０ａの内径面との間に隙間が形成される大きさであって、かつ、絞り形成部２０ｂの内径よりも大きく設定されている。また、内径小径部３の内径は、その内径面とコアロッド２２との間に隙間が形成される大きさに設定されている。この隙間は、微小であることが望ましい。
【００１５】
上記成形装置により素材１Ａを圧縮成形するには、図１（ａ）に示すように、まず、下パンチ２４を成形孔２０の絞り形成部２０ｂの途中まで挿入して保持し、下パンチ２４に挿入したコアロッド２２の上端をダイ２１の上面と同レベルになる位置に保持して、成形孔２０にキャビティを形成する。次いで、内径小径部３を上にして素材１Ａをコアロッド２２に嵌め込み、キャビティ内に挿入する。この状態から、図１（ｂ）に示すように上パンチ２３を降下させ、上パンチ２３によって素材１Ａをキャビティ内に圧入するとともに、軸方向に圧縮する。
【００１６】
この操作により、素材１Ａの下端部が成形孔２０の絞り形成部２０ｂに圧入してその外径面が内径側に圧縮され、外径が縮小して絞り部１１が造形される。また、素材１Ａの軸方向中央部と上端部は、軸方向に圧縮されることにより、その外径面が成形孔２０の主部２０ａの内径面に圧接するまで外径側に膨出し、外径が拡大する。一方、素材１Ａの軸方向両端部の内径面は、圧縮作用により内径側に膨出し、コアロッド２２に圧接して軸支面１２に形成される。さらに、これら軸支面１２間の内径面においては、コアロッド２２との間の隙間が残存し、中逃げ部１３とされる。このようにして素材１Ａが塑性変形させられ、軸受１０Ａが成形される。軸受１０Ａは、上パンチ２３を上昇させ、次いで下パンチ２４を上昇させることにより脱型される。
【００１７】
上記第１実施形態によれば、素材１Ａをダイ２１の成形孔２０に圧入するとともに軸方向に圧縮するといった簡素な方法により、中逃げ量が比較的大きな中逃げ部１３を有する２点支持構造の軸受１０Ａを効率よく製造することができる。
【００１８】
軸受１０Ａの軸支面１２は、素材１Ａの内径面をコアロッド２２に強く圧接させることにより形成されるので、その内径および同軸度が高い精度で一致し、加えて高密度化する故、耐摩耗性に優れる。一方、中逃げ部１３はコアロッド２２に圧接しないことから軸支面１２よりも密度は低く、このため潤滑油の含有量を多くすることができ、潤滑性が向上する。これらの結果、軸受１０Ａは優れた軸受性能を発揮する。また、両端部の内径側への圧縮度がほぼ等しいことから、両端部の軸支面１２の気孔率が均等化され、このため、両端部の軸支面１２に生じる油圧も均等となって回転軸をバランスよく支持することができる。
【００１９】
（２）第２実施形態−図２
次に、上記第１実施形態と同様の成形装置を用いて、第１実施形態とは形状の異なる素材から軸受を製造する第２実施形態を説明する。図２（ａ）の符合１Ｂで示す第２実施形態の素材は、軸方向一端部に外径大径部２が、また、他端部に内径小径部３が形成された円筒状のものである。外径大径部２の外径は、成形孔２０の絞り形成部２０ｂの内径よりも大きく、かつ、主部２０ａの内径面との間に隙間が形成される大きさに設定されている。また、外径大径部２以外の外径も絞り形成部２０ｂの内径よりも大きく設定されている。また、内径小径部３の内径は、その内径面とコアロッド２２との間に隙間が形成される大きさに設定されている。
【００２０】
素材１Ｂを圧縮成形するには、図２（ａ）に示すように、内径小径部３を上にして素材１Ｂをコアロッド２２に嵌め込み、成形孔２０のキャビティ内に挿入する。この状態から、図２（ｂ）に示すように、第１実施形態と同様に上パンチ２３を降下させ、上パンチ２３により素材１Ｂを成形孔２０のキャビティに圧入するとともに、軸方向に圧縮する。素材１Ｂは、成形孔２０の内径面に倣って第１実施形態と同様に塑性変形し、軸受１０Ｂに成形される。この場合、外径大径部２は絞り形成部２０ｂに圧入することにより消滅する。
【００２１】
次に、フランジ付きの軸受を製造する第３、第４実施形態を説明する。
（３）第３実施形態−図３
図３（ａ）の符合１Ｃは、第３実施形態で用いる素材である。この素材１Ｃは、軸方向一端部に、第２実施形態の素材１Ｂが有する外径大径部２よりも大径のフランジ５（外径大径部）および内径小径部３が形成された円筒状のものである。なお、第２実施形態の外径大径部２は、圧縮成形後には圧縮されて消滅するものであったが、フランジ５は圧縮成形後も残存し、例えば、固定手段や位置決め手段として利用される。
【００２２】
素材１Ｃを圧縮成形する成形装置は、図３に示すように、成形孔３０を有するダイ３１と、コアロッド２２と、上下のパンチ３３，３４とを備えている。ダイ３１の成形孔３０は、入口側（上側）から奥部に向かって内径が２段階縮小する段状に形成されている。すなわち、成形孔３０は、軸方向中央部の円筒状の主部３０ａと、主部３０ａよりも小径の奥部の絞り形成部３０ｂと、主部３０ａよりも大径でフランジを成形する部分である入口側の開口部３０ｃとから構成されている。開口部３０ｃから主部３０ａへの移行部は水平な段部３０ｄに形成され、主部３０ｃから絞り形成部３０ｂへの移行部はなだらかなテーパ状に形成されている。上パンチ３３は成形孔３０の開口部３０ｃに挿入され、下パンチ３４は絞り形成部３０ｂに挿入されるようになされている。
【００２３】
素材１Ｃのフランジ５の外径は、その外径面と成形孔３０の開口部３０ｃの内径面との間に隙間が形成される大きさに設定されている。また、フランジ５以外の外径は、その外径面と主部３０ａの内径面との間に隙間が形成される大きさであって、かつ、絞り形成部３０ｂの内径よりも大きく設定されている。また、内径小径部３の内径は、その内径面とコアロッド２２との間に隙間が形成される大きさに設定されている。
【００２４】
上記成形装置により素材１Ｃを圧縮成形するには、まず、図３（ａ）に示すように、まず、下パンチ３４を成形孔３０の絞り形成部３０ｂの途中まで挿入して保持し、下パンチ３４に挿入したコアロッド２２を上端がダイ３１の上面より若干突出する位置に保持して、成形孔３０にキャビティを形成する。次いで、フランジ５を上にして素材１Ｃをコアロッド２２に嵌め込んでキャビティ内に挿入する。この状態から、図３（ｂ）に示すように、上パンチ３３を降下させ、上パンチ３３により素材１Ｃを成形孔３０のキャビティに圧入するとともに、軸方向に圧縮する。
【００２５】
この操作により、素材１Ｃの下端部が成形孔３０の絞り形成部３０ｂに圧入して外径面が内径側に圧縮され、外径が縮小して絞り部１１が造形される。また、軸方向に圧縮されることにより、軸方向中央部は、外径面が成形孔３０の主部３０ａの内径面に圧接するまで外径側に膨出し、外径が拡大する。素材１Ｃの上端部であるフランジ５は、成形孔３０の段部３０ｄに拘束されて上パンチ３３により軸方向に圧縮され、その外径面が開口部３０ｃの内径面に圧接するまで外径側に膨出し、外径が拡大したフランジ５Ａに形成される。
【００２６】
一方、素材１Ｃの軸方向両端部の内径面は、圧縮作用により内径側に膨出し、コアロッド２２に圧接して軸支面１２に形成される。さらに、これら軸支面１２間の内径面においては、コアロッド２２との間の隙間が残存し、中逃げ部１３とされる。このようにして素材１Ｃが塑性変形させられ、軸受１０Ｃが成形される。軸受１０Ｃは、上パンチ２３を上昇させ、次いで下パンチ２４を上昇させることにより脱型される。
【００２７】
（４）第４実施形態−図４
上記第３実施形態は、軸方向一端部にフランジを備えた軸受の製造方法であったが、次の第４実施形態は、軸方向中央部にフランジを備えた軸受を成形する例である。
【００２８】
図４に示す成形装置は、第３実施形態の成形装置と同様のダイ３１、コアロッド２２および下パンチ３４と、上パンチ３３に代わる上パンチ４３とを備えている。この場合のダイ３１は、素材１Ｄの形状に対応して、成形孔３０の主部３０ａが第１実施形態の主部３０ａよりも短く設定されている。上パンチ４３は、外側パンチ４４と、外側パンチ４４に挿入される内側パンチ４５との組み合わせからなるものであり、外側パンチ４４の内径は、ダイ３１の成形孔３０の主部３０ａの内径と同一に設定されている。
【００２９】
図４（ａ）に示す第４実施形態の素材１Ｄは、軸方向中央部にフランジ５が形成され、一端部に内径小径部３が形成されたものである。フランジ５の外径は、その外径面と成形孔３０の開口部３０ｃの内径面との間に隙間が形成される大きさに設定されている。また、フランジ５以外の外径は、成形孔３０の主部３０ａおよび外側パンチ４４の内径よりも小さく、これらの内径面との間に隙間が形成される大きさで、かつ、成形孔３０の絞り形成部３０ｂの内径よりも大きく設定されている。素材１Ｄの内径小径部３の内径は、その内径面とコアロッド２２との間に隙間が形成される大きさに設定されている。
【００３０】
上記成形装置により素材１Ｄを圧縮成形するには、まず、下パンチ３４を成形孔３０の絞り形成部３０ｂの途中まで挿入して保持し、下パンチ３４に挿入したコアロッド２２を上端がダイ３１の上面から所定量突出する位置に保持して、成形孔３０にキャビティを形成する。次いで、内径小径部３を上にして素材１Ｄをコアロッド２２に嵌め込んでキャビティ内に挿入する。この状態から、図４（ｂ）に示すように、内側パンチ４５を外側パンチ４４内に所定量後退させた状態とした上パンチ４３を降下させ、上パンチ４３により素材１Ｄを成形孔３０のキャビティに圧入するとともに、軸方向に圧縮する。
【００３１】
この操作により、素材１Ｄの下端部が成形孔３０の絞り形成部３０ｂに圧入して外径が縮小し、絞り部１１に造形される。この絞り部１１からフランジ５までの間の部分の外径面は、主部３０ａの内径面に圧接するまで外径側に膨出し、外径が拡大する。また、軸方向中央部のフランジ５は、成形孔３０の段部３０ｄに拘束されて上パンチ４３の外側パンチ４４により軸方向に圧縮され、その外径面が開口部３０ｃの内径面に圧接するまで外径側に膨出し、外径が拡大したフランジ５Ａに形成される。さらに、フランジ５の上側である素材１Ｄの上端部は、軸方向に圧縮されることにより、外径面が外側パンチ４４の内径面に圧接するまで外径側に膨出し、外径が拡大する。一方、素材１Ｄの内径面には、上記第３実施形態と同様に、軸方向両端部の軸支面１２ならびにこれらの間の中逃げ部１３が形成される。このようにして素材１Ｄは塑性変形させられ、軸受１０Ｄが成形される。軸受１０Ｄは、上パンチ４３を上昇させ、次いで下パンチ２４を上昇させることにより脱型される。
【００３２】
次に、軸支面に動圧溝が形成された軸受を製造する第５、第６実施形態を説明する。
（５）第５実施形態−図５，図６
第５実施形態は、図５に示すように、上記コアロッド２２に代えた動圧溝形成用のコアロッド２２Ａを上記第１実施形態に適用して素材１Ａを圧縮成形し、軸支面１２に動圧溝が形成された軸受を成形する例である。そのコアロッド２２Ａは、図６（ａ）に示すように、素材１Ａの両端部内径面の圧接を受ける外径面に、複数のＶ字状の凸部２２ａが周方向に等間隔をおいてヘリングボーン状に形成されたものである。凸部２２ａは、コアロッド２２Ａの切削やメッキ等の手段によって形成することができるものであり、その高さは、数μｍ程度である。
【００３３】
素材１Ａを圧縮成形するには、図５（ａ）に示すように、素材１Ａの両端部内径面をコアロッド２２Ａの凸部２２ａが形成された部分に対応させた状態から、図５（ｂ）に示すようにコアロッド２２Ａとともに上パンチ２３を降下させ、上パンチ２３により素材１Ａをダイ２１の成形孔２０のキャビティ内に圧入するとともに、軸方向に圧縮する。
【００３４】
素材１Ａは、第１実施形態と同様に塑性変形し、軸受１０Ｅに成形される。軸受１０Ｅの軸支面１２には、図６（ｂ）に示すように、コアロッド２２Ａの凸部２２ａによってヘリングボーン状の動圧溝１４が刻設される。軸受１０Ｅは、上パンチ２３を上昇させ、次いでコアロッド２２Ａとともに下パンチ２４を上昇させてダイ２１から脱型することにより得られる。脱型された軸受１０Ｅには、ダイ２１による外径面の拘束が開放されて全体が僅かに拡径するスプリングバックが生じるので、動圧溝１４間の凸部を摩滅することなくコアロッド２２Ａから軸受１０Ｅを抜くことができる。
【００３５】
第５実施形態によって製造された軸受１０Ｅによれば、軸支面１２で回転軸を支持する２点支持構造に加え、動圧溝１４に発生する動圧効果（動圧溝に流入する潤滑油の高圧化に伴う剛性向上）によって回転軸の支持力が相乗的に高まり、回転軸の支持力がより安定する。なお、潤滑油が動圧溝１４の一部に集中して動圧が上昇する効果が十分に期待される観点から、軸受１０Ｅは、回転軸の回転方向が動圧溝１４のＶ字の先端方向（図６（ｂ）で矢印Ｒ方向）に向くようにセットされることが好ましい。
【００３６】
（６）第６実施形態−図７，図８
第６実施形態は、図７に示すように、上記第３実施形態に上記コアロッド２２Ａを適用して素材１Ｃを圧縮成形し、軸支面１２に動圧溝を形成する例である。素材１Ｃを圧縮成形するには、図７（ａ）に示すように、素材１Ｃの両端部内径面をコアロッド２２Ａの凸部２２ａが形成された部分に対応させた状態から、図７（ｂ）に示すようにコアロッド２２Ａとともに上パンチ３３を降下させ、上パンチ３３により素材１Ｃをダイ３１の成形孔３０のキャビティ内に圧入するとともに、軸方向に圧縮する。
【００３７】
素材１Ｃは、第１実施形態と同様に塑性変形し、軸受１０Ｆに成形される。軸受１０Ｆの軸支面１２には、図８に示すように、コアロッド２２Ａの凸部２２ａによってヘリングボーン状の動圧溝１４が刻設される。軸受１０Ｆは、上パンチ３３を上昇させ、次いでコアロッド２２Ａとともに下パンチ３４を上昇させてダイ３１から脱型することにより得られる。なお、図８の矢印Ｒは、前述した回転軸の好ましい回転方向である。
【００３８】
上記第５、第６実施形態のように、動圧溝形成用のコアロッド２２Ａを用いて軸支面に動圧溝を形成する形態は、第２、第４実施形態にも勿論適用することができる。
【００３９】
（７）他の形態
本発明は、上記第１〜第６実施形態に限定されるものではなく、例えば、素材や製造後の軸受の形状、あるいは動圧溝の形状等は、様々な形態に変更可能である。以下に、他の形態例を示す。なお、各図面において上記実施形態と同一の構成要素には同一の符合を付してある。
【００４０】
Ａ．素材の形状
図９（ａ）は、軸方向一端部にフランジ５を有し、他端部に内径小径部３が形成された素材を示している。フランジ５の位置は任意であり、例えば第３実施形態の素材１Ｃ（図３（ａ）参照）のように、軸方向中央部に形成されていてもよい。さらに、フランジ以外の部分の外径が異なるような円筒状の素材を用いることもできる。
【００４１】
図９（ｂ），（ｃ）は、軸孔の開口周縁に、座ぐり状のテーパ面６が形成された素材を示している。各素材には、外径大径部２あるいは内径小径部３が適宜形成されている。図９（ｄ）に示す素材は、軸方向一端部に内径小径部３が形成され、同端部の外径面が、端部に向かってしだいに縮径するテーパ状小径部８に形成されている。
【００４２】
なお、上記各実施形態を含めて、いずれの場合も内径面における内径小径部３と他の部分との境界部分は画然としている（直角で移行している）が、両者の境界部分を斜面に形成してもよい。図９（ｅ）は、図９（ｂ）の素材をそのようにアレンジした素材であり、さらに、図９（ｆ）に示すように、外径面の周縁を面取りした形状であってもよい。
【００４３】
Ｂ．軸受の形状
次に、軸受の変更例を説明する。
図１０（ａ）は外径均一の軸受、図１０（ｂ）は軸方向両端部に絞り部１１が形成された軸受をそれぞれ示しており、図１０（ｃ），（ｄ）は、これら軸受の軸孔の開口周縁にテーパ面１６が形成されたものである。図１０（ｅ）に示す軸受は、第１、第２実施形態で示した軸受１０Ａ，１０Ｂの軸孔の開口周縁にテーパ面１６が形成され、さらに、外径面の周縁が面取りされたものである。図１０（ｆ）に示す軸受は、一端部にフランジ５Ａが形成されたものである。なお、軸孔の開口周縁にテーパ面を形成する態様は、フランジを備えた軸受にも勿論適用することができる。図１０（ｇ）に示す軸受は、全体的に球状で、軸方向端面が平坦に、かつ、側面が円筒状に形成されている。図１０（ｈ）の軸受は、図１０（ｇ）の軸受の一端部に絞り部１１が形成されたものである。
【００４４】
Ｃ．動圧溝の形状
第５、第６実施形態で示した動圧溝の形状は任意であり、その数も適宜に選択されるが、回転軸をより安定して支持する観点から、複数が軸支面の周方向に沿って等間隔をおいて配置されると好ましい。上記各実施形態では、ヘリングボーン状として、つまり形状によって、動圧上昇が生じる効果を得るようにしているが、深さの断面形状によってもその効果を得ることができる。
【００４５】
それには、概略形状を軸方向に沿って延びる溝とし、回転軸が一方向のみに回転する場合には、回転軸の回転方向の逆方向側の端部を最深部とし、この最深部から回転軸の回転方向に向かってしだいに浅くなるよう傾斜させる。また、回転軸が正逆双方向に回転する場合には、周方向の中間部を最深部とし、この最深部から周方向両端部に向かってしだいに浅くなるよう傾斜させる。このように形成された動圧溝は、横断面（輪切りにした場合の断面）形状が回転軸の回転方向に向かって浅くなるくさび状の隙間となり、溝の浅い先端部に潤滑油が集中するくさび効果を得ることができる。
【００４６】
Ｄ．動圧溝形成用のコアロッド
第５、第６実施形態で示した動圧溝１４は、コアロッド２２Ａに形成した凸部２２ａにより形成されているが、このような凸部に代え、凹部によって動圧溝を形成することができる。すなわち、第５、第６実施形態と刻設のパターンが逆であって、素材の内径小径部の内径面がコアロッドに圧接させられるとコアロッドに形成した凹部に導入されて凸部が突設され、この凸部の内径面が軸支面に、また、凸部間の溝が動圧溝として機能する。この場合、凸部がさらに突設されることにより、その高さだけ中逃げ量が大きい軸受が得られる。なお、コアロッドに形成する凹部は、放電加工や電解腐食といった手段により形成することができる。
【００４７】
【発明の効果】
以上説明したように、本発明によれば、比較的大きな中逃げ部を有する２点支持構造の軸受を、比較的簡素な方法で効率よく製造することができる。
また、本発明によって製造された軸受は、軸方向両端部の軸支面においては、内径および同軸度が高い精度で一致するとともに高密度化されて耐摩耗性の向上が図られ、一方、中逃げ部が形成された軸方向中央部においては、密度が低いことから潤滑油の含有量が十分に確保される。これらの結果、優れた軸受性能を発揮する。
【図面の簡単な説明】
【図１】本発明の第１実施形態に係る軸受の製造方法の工程を（ａ），（ｂ）の順に示す縦断面図である。
【図２】本発明の第２実施形態に係る軸受の製造方法の工程を（ａ），（ｂ）の順に示す縦断面図である。
【図３】本発明の第３実施形態に係る軸受の製造方法の工程を（ａ），（ｂ）の順に示す縦断面図である。
【図４】本発明の第４実施形態に係る軸受の製造方法の工程を（ａ），（ｂ）の順に示す縦断面図である。
【図５】本発明の第５実施形態に係る軸受の製造方法の工程を（ａ），（ｂ）の順に示す縦断面図である。
【図６】（ａ）は本発明の第５実施形態で用いるコアロッドの一部斜視図、（ｂ）は本発明の第５実施形態で製造された軸受の一部を示す縦割り斜視図である。
【図７】本発明の第６実施形態に係る軸受の製造方法の工程を（ａ），（ｂ）の順に示す縦断面図である。
【図８】本発明の第６実施形態で製造された軸受の一部を示す縦割り斜視図である。
【図９】本発明で用いる軸受素材の他の形態例を示す縦断面図である。
【図１０】本発明で製造される軸受の他の形態例を示す縦断面図である。
【符号の説明】
１Ａ〜１Ｄ…素材、２…外径大径部、３…内径小径部、
５…素材のフランジ（外径大径部）、１０Ａ〜１０Ｆ…軸受、
１２…軸支面、１３…中逃げ部、１４…動圧溝、２２，２２Ａ…コアロッド、
２２ａ…動圧溝形成用の凸部。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a bearing suitable for use in supporting a shaft rotating at a relatively high speed, such as a drive shaft of a spindle motor built in a precision instrument, with high accuracy. The present invention is a technique for obtaining a bearing having a desired shape by causing plastic deformation by compressing a material. The material is mainly a sintered body or a sintered body obtained by sintering a green compact. A cylindrical porous body formed by sizing (recompression) is used. Moreover, the bearing manufactured by this invention is impregnated with lubricating oil, and is suitably used as a sintered oil-impregnated bearing.
[0002]
[Prior art]
In the above-mentioned sintered oil-impregnated bearing, the lubricating oil impregnated in the sintered body oozes out to the inner diameter surface, and an oil film is formed between the inner diameter surface and the rotating shaft, so that the frictional resistance is reduced and noise and vibration are generated. It has the characteristic of being suppressed. In addition, as a sintered oil-impregnated bearing that further enhances the effect of suppressing vibration and noise, the inner diameter surface of the axial center portion is slightly larger than the outer diameter of the rotating shaft and does not contact the rotating shaft (hereinafter referred to as the intermediate relief portion). The two-point support structure in which the shaft support surface of the rotary shaft is limited to the inner diameter surfaces of both ends, and the effect of reducing frictional resistance and the support force of the rotary shaft are further stabilized.
[0003]
Sintered oil-impregnated bearings are usually manufactured mainly with the steps of sintering a cylindrical green compact obtained by compression molding a raw metal powder and sizing the sintered body to finish it into a final shape. . By the way, when manufacturing a bearing having the above-described intermediate relief portion, if the intermediate relief portion is formed by machining the sintered body, the pores exposed on the inner diameter surface are crushed, which hinders the circulation of the lubricating oil. Will be. For this reason, it is preferable to form the middle relief portion at the same time in the sizing step of the sintered body, or to compress the sintered body once again after sizing and form the middle relief portion independently. In either case, the inner surface of the axial ends protrudes radially inward, or plastic deformation in which the axial central portion bulges outward in the radial direction is generated in the sintered material, thereby separating the inner surfaces. The two shaft support surfaces and the intermediate escape portion between them are formed simultaneously on the inner diameter surface.
[0004]
[Problems to be solved by the invention]
In the bearing with the above two-point support structure, in order to improve the bearing performance such as the reduction of the frictional resistance and the improvement of the supporting force of the rotating shaft, the inner diameter and the coaxiality of the two separated shaft support surfaces coincide with each other with high accuracy. It is required to be. It is also important that a sufficient amount of lubricating oil is supplied to the shaft support surface. However, although various methods of plastic deformation of the sintered body have been proposed conventionally, there is no constant manufacturing method that is relatively simple and sufficiently satisfies the requirements for improving bearing performance. there were.
[0005]
Therefore, the present invention has a middle relief portion where the rotary shaft does not contact the inner diameter surface of the central portion in the axial direction, and the middle relief amount of the middle relief portion is relatively large. A bearing with a two-point support structure that functions as a supporting shaft for supporting can be efficiently manufactured by a relatively simple method, and the bearing performance (with the same inner diameter and coaxiality of the two supporting surfaces) It is an object of the present invention to provide a method for manufacturing a bearing capable of achieving improvement in the bearing capacity, lubricity, wear resistance, etc. of the rotating shaft.
[0006]
[Means for Solving the Problems]
The present invention is cylindrical, has an inner diameter small diameter portion at one end in the axial direction, has an outer diameter uniform or has an outer diameter large diameter portion at a part of the outer diameter surface, and the inner diameter of the inner diameter small diameter portion is outside the core rod. By compressing a material made of a sintered porous body having a shape larger than the diameter in the axial direction with the core rod inserted,On the opposite side to the one axial end having the small inner diameter portion.The outer diameter of the end is reduced and the center andOne axial end portion having the small inner diameter portionIn accordance with this deformation, both inner diameter surfaces are pressed against the core rod to form a shaft support surface that supports the rotating shaft, and a middle relief portion is formed on the inner diameter surface of the central portion. It is said. As the material according to the present invention, a sintered body or a porous body formed by sizing the sintered body is used as described above. After production, the material is impregnated with a lubricating oil and is suitably used as a sintered oil-impregnated bearing.
[0007]
In the present invention, for example, there is a molding method in which a cylindrical material having a uniform outer diameter is press-fitted by a punch and compressed in the axial direction while maintaining a state where a core rod is inserted into a cylindrical molding hole formed in a die. Taken. In that case, the inner diameter of the material is set to such a size that a gap is formed between the inner diameter surface and the core rod. In addition, the forming hole is a hole whose entrance side and the central part are larger than the outer diameter of the material and from which the depth is reduced through the stepped portion and smaller than the outer diameter of the material.
[0008]
When the material is press-fitted into such a molding hole, one end portion on the front end side in the press-fitting direction is press-fitted into the reduced diameter portion of the molding hole, the outer diameter surface is compressed to the inner diameter side, and the narrowed portion having a reduced outer diameter is formed. Is done. On the other hand, the central portion and the other end portion on the rear end side in the press-fitting direction following this are compressed in the axial direction, so that the outer diameter surface expands until the inner diameter surface of the molding hole comes into pressure contact, and the outer diameter increases. To do. In addition, when the material is compressed in the axial direction, the inner diameter surfaces at both ends in the axial direction bulge toward the inner diameter side, press against the core rod, and are formed on the shaft support surface. The gap between the core rod remains and becomes a middle escape portion. According to the present invention, a bearing having a two-point support structure having a middle relief portion with a relatively large middle relief amount is obtained by adopting a combination of a material and a mold in which such a modification is appropriately performed. Can be manufactured efficiently.
[0009]
According to the present invention, since the shaft support surface that supports the rotating shaft is formed by strongly pressing the inner diameter surface of the material against the core rod, the inner diameter and the coaxiality coincide with each other with high accuracy. Further, since the density of the shaft support surface can be increased, the wear resistance can be improved. On the other hand, the density of the inner diameter surface where the intermediate relief portion is formed can be made lower than that of the shaft support surface, and the diameter of the intermediate relief portion can be made relatively large, so that the content of lubricating oil is increased. This improves the lubricity. As a result, a bearing having a high level of bearing performance can be manufactured.
[0010]
As the material of the present invention, those having the following shapes are used.
(1) It has a uniform outer diameter and a small inner diameter portion at one axial end.
{Circle around (2)} One end portion in the axial direction has a small inner diameter portion and the other end portion has a large outer diameter portion.
[0011]
Further, the present invention is characterized in that a convex portion or a concave portion for forming a dynamic pressure groove is formed on the outer diameter surface of the core rod to which the inner diameter surfaces of both end portions in the axial direction of the material are pressed. According to this, in the case of the former convex part, the dynamic pressure groove according to the convex part shape is formed in the shaft support surface. Moreover, in the case of the latter recessed part, the shaft support surface carved according to the recessed part shape and the dynamic pressure groove between shaft support surfaces are formed simultaneously. When the dynamic pressure groove is formed on the shaft support surface, in addition to the two-point support structure that supports the rotating shaft by the shaft support surfaces at both ends, the dynamic pressure effect generated in the dynamic pressure groove (the lubricating oil flowing into the dynamic pressure groove) As the pressure increases, the support force of the rotary shaft increases synergistically, and the support force of the rotary shaft becomes more stable.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(1) First embodiment-FIG.
1A in FIG. 1A is a sintered body or a material formed by sizing a sintered body. It should be noted in advance that the materials of all the embodiments described later are similar sintered bodies. The material 1 A has a uniform outer diameter and a cylindrical shape in which a small inner diameter portion 3 is formed at one end in the axial direction.
[0013]
The molding apparatus shown in FIG. 1 includes a die 21 having a molding hole 20, a core rod 22, and upper and lower punches 23 and 24. The inner diameter of the forming hole 20 is reduced by one step, and the forming hole 20 includes a main portion 20a on the inlet side (upper side) and a narrowed portion 20b on the inner side. The transition portion from the main portion 20a to the aperture forming portion 20b is formed in a gentle taper shape. The upper punch 23 is inserted into the opening 20c, and the lower punch 24 is inserted into the aperture forming part 20b.
[0014]
The outer diameter of the material 1A is such that a gap is formed between the outer diameter surface and the inner diameter surface of the main portion 20a of the molding hole 20, and is set to be larger than the inner diameter of the aperture forming portion 20b. Yes. In addition, the inner diameter of the inner diameter small diameter portion 3 is set to such a size that a gap is formed between the inner diameter surface and the core rod 22. This gap is desirably very small.
[0015]
In order to compression-mold the material 1A by the molding apparatus, as shown in FIG. 1A, first, the lower punch 24 is inserted and held partway in the drawing forming portion 20b of the molding hole 20, and is held on the lower punch 24. A cavity is formed in the molding hole 20 by holding the upper end of the inserted core rod 22 at the same level as the upper surface of the die 21. Next, the material 1A is fitted into the core rod 22 with the inner diameter small diameter portion 3 facing upward and inserted into the cavity. From this state, as shown in FIG. 1B, the upper punch 23 is lowered, and the upper punch 23 presses the material 1A into the cavity and compresses it in the axial direction.
[0016]
By this operation, the lower end portion of the material 1A is press-fitted into the restriction forming portion 20b of the forming hole 20, the outer diameter surface is compressed to the inner diameter side, the outer diameter is reduced, and the restriction portion 11 is formed. Further, the axially central portion and the upper end portion of the material 1A are compressed in the axial direction, so that the outer diameter surface bulges to the outer diameter side until the outer diameter surface comes into pressure contact with the inner diameter surface of the main portion 20a of the molding hole 20, and the outer The diameter increases. On the other hand, the inner diameter surfaces of both end portions in the axial direction of the material 1A bulge toward the inner diameter side by a compression action, and are formed on the shaft support surface 12 in pressure contact with the core rod 22. Further, in the inner diameter surface between the shaft support surfaces 12, a gap with the core rod 22 remains and serves as a middle escape portion 13. In this way, the material 1A is plastically deformed, and the bearing 10A is formed. The bearing 10 A is removed from the mold by raising the upper punch 23 and then raising the lower punch 24.
[0017]
According to the first embodiment, the two-point support structure having the middle escape portion 13 having a relatively large middle escape amount by a simple method of press-fitting the material 1A into the forming hole 20 of the die 21 and compressing in the axial direction. The bearing 10A can be efficiently manufactured.
[0018]
Since the shaft support surface 12 of the bearing 10A is formed by strongly pressing the inner diameter surface of the material 1A to the core rod 22, the inner diameter and the coaxiality coincide with each other with high accuracy, and in addition, the wear density is increased. Excellent in properties. On the other hand, since the intermediate escape portion 13 is not pressed against the core rod 22, the density is lower than that of the shaft support surface 12. Therefore, the content of the lubricating oil can be increased, and the lubricity is improved. As a result, the bearing 10A exhibits excellent bearing performance. Moreover, since the compressibility to the inner diameter side of both ends is substantially equal, the porosity of the shaft support surfaces 12 at both ends is equalized, and therefore the hydraulic pressure generated on the shaft support surfaces 12 at both ends is also equalized. The rotating shaft can be supported with good balance.
[0019]
(2) Second embodiment-FIG.
Next, a second embodiment in which a bearing is manufactured from a material having a shape different from that of the first embodiment using the same molding apparatus as that of the first embodiment will be described. The material of the second embodiment indicated by reference numeral 1B in FIG. 2A is a cylindrical material in which an outer diameter large diameter portion 2 is formed at one end in the axial direction and an inner diameter small diameter portion 3 is formed at the other end. is there. The outer diameter of the outer diameter large diameter portion 2 is set to a size that is larger than the inner diameter of the drawing forming portion 20b of the molding hole 20 and that a gap is formed between the inner diameter surface of the main portion 20a. Moreover, the outer diameters other than the outer diameter large diameter part 2 are also set larger than the inner diameter of the diaphragm forming part 20b. In addition, the inner diameter of the inner diameter small diameter portion 3 is set to such a size that a gap is formed between the inner diameter surface and the core rod 22.
[0020]
In order to compression-mold the material 1B, as shown in FIG. 2A, the material 1B is fitted into the core rod 22 with the inner diameter small diameter portion 3 facing up, and inserted into the cavity of the molding hole 20. From this state, as shown in FIG. 2B, the upper punch 23 is lowered as in the first embodiment, and the material 1B is pressed into the cavity of the molding hole 20 by the upper punch 23 and is compressed in the axial direction. . The material 1B is plastically deformed in the same manner as in the first embodiment along the inner diameter surface of the molding hole 20, and is molded into the bearing 10B. In this case, the outer diameter / large diameter portion 2 disappears by being press-fitted into the throttle forming portion 20b.
[0021]
Next, 3rd, 4th embodiment which manufactures a bearing with a flange is described.
(3) Third embodiment-FIG.
Reference numeral 1C in FIG. 3A is a material used in the third embodiment. This material 1C is a cylinder in which a flange 5 (outer diameter large diameter portion) and an inner diameter small diameter portion 3 larger in diameter than the outer diameter large diameter portion 2 included in the material 1B of the second embodiment are formed at one axial end portion. It is a shape. The outer diameter / large diameter portion 2 of the second embodiment is compressed and disappears after compression molding, but the flange 5 remains after compression molding, and is used, for example, as a fixing means or positioning means. The
[0022]
As shown in FIG. 3, the molding apparatus that compresses the material 1 C includes a die 31 having a molding hole 30, a core rod 22, and upper and lower punches 33 and 34. The forming hole 30 of the die 31 is formed in a step shape in which the inner diameter is reduced by two steps from the inlet side (upper side) toward the inner part. That is, the forming hole 30 is a cylindrical main portion 30a in the central portion in the axial direction, a deeper drawing forming portion 30b having a smaller diameter than the main portion 30a, and a portion for forming a flange with a larger diameter than the main portion 30a. It is comprised from the opening part 30c of a certain entrance side. A transition part from the opening 30c to the main part 30a is formed in a horizontal step part 30d, and a transition part from the main part 30c to the aperture forming part 30b is formed in a gentle taper shape. The upper punch 33 is inserted into the opening 30c of the molding hole 30, and the lower punch 34 is inserted into the aperture forming part 30b.
[0023]
The outer diameter of the flange 5 of the material 1 C is set such that a gap is formed between the outer diameter surface and the inner diameter surface of the opening 30 c of the molding hole 30. The outer diameters other than the flange 5 are such that a gap is formed between the outer diameter surface and the inner diameter surface of the main portion 30a, and are set larger than the inner diameter of the aperture forming portion 30b. Yes. In addition, the inner diameter of the inner diameter small diameter portion 3 is set to such a size that a gap is formed between the inner diameter surface and the core rod 22.
[0024]
In order to compression-mold the material 1C by the molding apparatus, first, as shown in FIG. 3A, first, the lower punch 34 is inserted and held partway in the drawing forming portion 30b of the molding hole 30, and the lower punch The core rod 22 inserted into 34 is held at a position where the upper end slightly protrudes from the upper surface of the die 31 to form a cavity in the molding hole 30. Next, the material 1C is fitted into the core rod 22 with the flange 5 facing up and inserted into the cavity. From this state, as shown in FIG. 3B, the upper punch 33 is lowered, and the material 1C is press-fitted into the cavity of the forming hole 30 by the upper punch 33 and is compressed in the axial direction.
[0025]
By this operation, the lower end portion of the material 1C is press-fitted into the restriction forming portion 30b of the forming hole 30, the outer diameter surface is compressed to the inner diameter side, the outer diameter is reduced, and the restriction portion 11 is formed. Further, by being compressed in the axial direction, the central portion in the axial direction bulges toward the outer diameter side until the outer diameter surface comes into pressure contact with the inner diameter surface of the main portion 30a of the molding hole 30, and the outer diameter increases. The flange 5 which is the upper end portion of the material 1C is constrained by the step 30d of the forming hole 30 and compressed in the axial direction by the upper punch 33, and the outer diameter side is pressed against the inner diameter surface of the opening 30c. It is formed on the flange 5A that bulges out and has an enlarged outer diameter.
[0026]
On the other hand, the inner diameter surfaces of both end portions in the axial direction of the material 1 C bulge toward the inner diameter side by the compression action, and are formed on the shaft support surface 12 in pressure contact with the core rod 22. Further, in the inner diameter surface between the shaft support surfaces 12, a gap with the core rod 22 remains and serves as a middle escape portion 13. In this way, the material 1C is plastically deformed, and the bearing 10C is formed. The bearing 10 C is removed by raising the upper punch 23 and then raising the lower punch 24.
[0027]
(4) Fourth Embodiment-FIG.
Although the said 3rd Embodiment was a manufacturing method of the bearing provided with the flange in the axial direction one end part, the following 4th Embodiment is an example which shape | molds the bearing provided with the flange in the axial direction center part.
[0028]
The molding apparatus shown in FIG. 4 includes a die 31, a core rod 22 and a lower punch 34 that are the same as the molding apparatus of the third embodiment, and an upper punch 43 that replaces the upper punch 33. In this case, the die 31 is set such that the main portion 30a of the molding hole 30 is shorter than the main portion 30a of the first embodiment, corresponding to the shape of the material 1D. The upper punch 43 is a combination of an outer punch 44 and an inner punch 45 inserted into the outer punch 44, and the inner diameter of the outer punch 44 is the same as the inner diameter of the main portion 30 a of the forming hole 30 of the die 31. Is set to
[0029]
A material 1D according to the fourth embodiment shown in FIG. 4A has a flange 5 formed at the center in the axial direction and a small inner diameter portion 3 formed at one end. The outer diameter of the flange 5 is set such that a gap is formed between the outer diameter surface and the inner diameter surface of the opening 30 c of the molding hole 30. The outer diameter other than the flange 5 is smaller than the inner diameter of the main portion 30a of the molding hole 30 and the outer punch 44, and is large enough to form a gap between these inner diameter surfaces. It is set larger than the inner diameter of the aperture forming part 30b. The inner diameter of the inner diameter small diameter portion 3 of the material 1D is set to such a size that a gap is formed between the inner diameter surface and the core rod 22.
[0030]
In order to compression-mold the material 1D by the molding apparatus, first, the lower punch 34 is inserted and held partway in the drawing forming portion 30b of the molding hole 30, and the core rod 22 inserted into the lower punch 34 has an upper end of the die 31. A cavity is formed in the molding hole 30 while being held at a position protruding a predetermined amount from the upper surface. Next, the material 1D is fitted into the core rod 22 with the inner diameter small diameter portion 3 facing upward and inserted into the cavity. From this state, as shown in FIG. 4 (b), the upper punch 43 with the inner punch 45 retracted into the outer punch 44 by a predetermined amount is lowered, and the upper punch 43 causes the material 1D to move into the cavity of the molding hole 30. And press in the axial direction.
[0031]
By this operation, the lower end portion of the material 1D is press-fitted into the drawing forming portion 30b of the forming hole 30, the outer diameter is reduced, and the drawing portion 11 is formed. The outer diameter surface of the portion between the narrowed portion 11 and the flange 5 bulges toward the outer diameter side until it comes into pressure contact with the inner diameter surface of the main portion 30a, and the outer diameter increases. Further, the flange 5 at the central portion in the axial direction is constrained by the step portion 30d of the forming hole 30 and compressed in the axial direction by the outer punch 44 of the upper punch 43, and its outer diameter surface is in pressure contact with the inner diameter surface of the opening 30c. The flange 5A is expanded to the outer diameter side and the outer diameter is increased. Furthermore, the upper end portion of the material 1D, which is the upper side of the flange 5, is compressed in the axial direction, so that the outer diameter surface bulges to the outer diameter side until it presses against the inner diameter surface of the outer punch 44, and the outer diameter increases. . On the other hand, on the inner diameter surface of the material 1D, as in the third embodiment, the shaft support surfaces 12 at both ends in the axial direction and the intermediate escape portions 13 between these are formed. In this way, the material 1D is plastically deformed, and the bearing 10D is formed. The bearing 10 D is removed from the mold by raising the upper punch 43 and then raising the lower punch 24.
[0032]
Next, fifth and sixth embodiments for manufacturing a bearing in which a dynamic pressure groove is formed on a shaft support surface will be described.
(5) Fifth embodiment-FIGS. 5 and 6
In the fifth embodiment, as shown in FIG. 5, the core rod 22A for forming dynamic pressure grooves instead of the core rod 22 is applied to the first embodiment, and the material 1A is compression-molded. It is an example which shape | molds the bearing in which the pressure groove was formed. As shown in FIG. 6 (a), the core rod 22A has a plurality of V-shaped convex portions 22a at equal intervals in the circumferential direction on the outer diameter surface that receives pressure contact between the inner diameter surfaces of both ends of the material 1A. It is formed in a bone shape. The convex portion 22a can be formed by means such as cutting or plating of the core rod 22A, and its height is about several μm.
[0033]
In order to compression-mold the material 1A, as shown in FIG. 5A, from the state in which the inner diameter surfaces of both ends of the material 1A correspond to the portions where the convex portions 22a of the core rod 22A are formed, FIG. The upper punch 23 is lowered together with the core rod 22A, and the upper punch 23 presses the material 1A into the cavity of the forming hole 20 of the die 21 and compresses it in the axial direction.
[0034]
The material 1A is plastically deformed and molded into the bearing 10E as in the first embodiment. As shown in FIG. 6B, a herringbone-shaped dynamic pressure groove 14 is formed on the shaft support surface 12 of the bearing 10E by the convex portion 22a of the core rod 22A. The bearing 10E is obtained by lifting the upper punch 23 and then lifting the lower punch 24 together with the core rod 22A to remove the die from the die 21. In the removed bearing 10E, the outer diameter surface restraint by the die 21 is released, and a spring back that slightly expands in diameter is generated, so that the protruding portion between the dynamic pressure grooves 14 does not wear out from the core rod 22A. The bearing 10E can be removed.
[0035]
According to the bearing 10E manufactured according to the fifth embodiment, in addition to the two-point support structure that supports the rotating shaft by the shaft support surface 12, the dynamic pressure effect generated in the dynamic pressure groove 14 (the lubricating oil flowing into the dynamic pressure groove) As the pressure increases, the bearing force of the rotating shaft increases synergistically, and the supporting force of the rotating shaft becomes more stable. From the viewpoint of sufficiently expecting the effect that the lubricating oil is concentrated on a part of the dynamic pressure groove 14 and the dynamic pressure is increased, the bearing 10E has the rotation direction of the rotation shaft of the V-shaped tip of the dynamic pressure groove 14. It is preferably set so as to face in the direction (the direction of arrow R in FIG. 6B).
[0036]
(6) Sixth embodiment-FIGS. 7 and 8
As shown in FIG. 7, the sixth embodiment is an example in which the core rod 22 A is applied to the third embodiment to compress the material 1 C and form the dynamic pressure grooves on the shaft support surface 12. In order to compression-mold the material 1C, as shown in FIG. 7A, from the state in which the inner diameter surfaces of both ends of the material 1C correspond to the portions where the convex portions 22a of the core rod 22A are formed, FIG. The upper punch 33 is lowered together with the core rod 22A, and the upper punch 33 presses the material 1C into the cavity of the forming hole 30 of the die 31 and compresses it in the axial direction.
[0037]
The material 1C is plastically deformed as in the first embodiment, and is formed into the bearing 10F. As shown in FIG. 8, a herringbone-shaped dynamic pressure groove 14 is formed on the shaft support surface 12 of the bearing 10F by the convex portion 22a of the core rod 22A. The bearing 10F is obtained by lifting the upper punch 33 and then lifting the lower punch 34 together with the core rod 22A to remove the die from the die 31. Note that an arrow R in FIG. 8 is a preferable rotation direction of the above-described rotation shaft.
[0038]
Of course, the configuration in which the dynamic pressure groove is formed on the shaft support surface using the core rod 22A for forming the dynamic pressure groove as in the fifth and sixth embodiments can be applied to the second and fourth embodiments. it can.
[0039]
(7) Other forms
The present invention is not limited to the first to sixth embodiments. For example, the shape of the material, the bearing after manufacture, the shape of the dynamic pressure groove, and the like can be changed to various forms. Other embodiments are shown below. In addition, in each drawing, the same code | symbol is attached | subjected to the component same as the said embodiment.
[0040]
A. Material shape
FIG. 9A shows a material having a flange 5 at one end in the axial direction and a small inner diameter portion 3 formed at the other end. The position of the flange 5 is arbitrary, and may be formed in the central portion in the axial direction as in the material 1C of the third embodiment (see FIG. 3A), for example. Furthermore, it is also possible to use a cylindrical material whose outer diameters other than the flanges are different.
[0041]
FIGS. 9B and 9C show a material in which a counterbore tapered surface 6 is formed on the periphery of the opening of the shaft hole. Each material is appropriately formed with an outer diameter large diameter portion 2 or an inner diameter small diameter portion 3. The material shown in FIG. 9D has an inner diameter small diameter portion 3 formed at one end in the axial direction, and the outer diameter surface of the end is formed into a tapered small diameter portion 8 that gradually decreases in diameter toward the end. ing.
[0042]
In each case, including the above-described embodiments, the boundary portion between the inner diameter small diameter portion 3 and the other portion on the inner diameter surface is obvious (move at a right angle), but the boundary portion between the two is inclined. You may form in. FIG. 9 (e) is a material obtained by arranging the materials of FIG. 9 (b) as such, and as shown in FIG. 9 (f), the outer peripheral surface may be chamfered. .
[0043]
B. Bearing shape
Next, a modification example of the bearing will be described.
FIG. 10 (a) shows a bearing with a uniform outer diameter, FIG. 10 (b) shows a bearing in which the throttle portions 11 are formed at both ends in the axial direction, and FIGS. 10 (c) and 10 (d) show these bearings. A tapered surface 16 is formed on the opening periphery of the shaft hole. The bearing shown in FIG. 10 (e) has a tapered surface 16 formed at the opening periphery of the shaft hole of the bearing 10A, 10B shown in the first and second embodiments, and the outer peripheral surface is chamfered. It is. The bearing shown in FIG. 10 (f) has a flange 5A formed at one end. In addition, the aspect which forms a taper surface in the opening periphery of a shaft hole is naturally applicable also to the bearing provided with the flange. The bearing shown in FIG. 10 (g) is generally spherical, has an axial end face that is flat, and a side face that is cylindrical. The bearing shown in FIG. 10 (h) has a constricted portion 11 formed at one end of the bearing shown in FIG. 10 (g).
[0044]
C. Dynamic pressure groove shape
The shape of the dynamic pressure grooves shown in the fifth and sixth embodiments is arbitrary, and the number thereof is appropriately selected. From the viewpoint of supporting the rotating shaft more stably, a plurality of the dynamic pressure grooves are arranged in the circumferential direction of the shaft support surface. It is preferable that they are arranged at equal intervals along. In each of the above embodiments, the effect of increasing the dynamic pressure is obtained as a herringbone shape, that is, depending on the shape, but the effect can also be obtained by a cross-sectional shape of depth.
[0045]
For this purpose, the rough shape is a groove extending along the axial direction, and when the rotating shaft rotates in only one direction, the end on the opposite side of the rotating shaft in the rotating direction is the deepest portion, and the rotation starts from this deepest portion. Tilt so that it gradually becomes shallower in the direction of rotation of the shaft. In addition, when the rotating shaft rotates in both forward and reverse directions, the intermediate portion in the circumferential direction is set as the deepest portion, and is inclined so as to gradually become shallower from the deepest portion toward both ends in the circumferential direction. The dynamic pressure groove formed in this way becomes a wedge-shaped gap whose cross section (cross section when cut into a circle) becomes shallower in the rotation direction of the rotary shaft, and the lubricating oil concentrates at the shallow tip of the groove. A wedge effect can be obtained.
[0046]
D. Core rod for forming dynamic pressure grooves
The dynamic pressure grooves 14 shown in the fifth and sixth embodiments are formed by the convex portions 22a formed in the core rod 22A, but instead of such convex portions, the dynamic pressure grooves can be formed by concave portions. . In other words, the engraving pattern is the reverse of the fifth and sixth embodiments, and when the inner diameter surface of the inner diameter small diameter portion of the material is brought into pressure contact with the core rod, it is introduced into the recess formed in the core rod and the projection is projected. The inner diameter surface of the convex portion functions as a shaft support surface, and the groove between the convex portions functions as a dynamic pressure groove. In this case, by further projecting the convex portion, a bearing having a large intermediate escape amount by the height can be obtained. The concave portion formed in the core rod can be formed by means such as electric discharge machining or electrolytic corrosion.
[0047]
【The invention's effect】
As described above, according to the present invention, it is possible to efficiently manufacture a bearing having a two-point support structure having a relatively large middle escape portion by a relatively simple method.
In addition, the bearing manufactured according to the present invention has an inner diameter and a coaxiality that coincide with each other with high accuracy at the axial support surfaces at both ends in the axial direction and is densified to improve wear resistance. In the central portion in the axial direction where the relief portion is formed, the density of the lubricating oil is sufficiently ensured because the density is low. As a result, excellent bearing performance is exhibited.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing steps of a method for manufacturing a bearing according to a first embodiment of the present invention in the order of (a) and (b).
FIG. 2 is a longitudinal sectional view showing steps of a method for manufacturing a bearing according to a second embodiment of the present invention in the order of (a) and (b).
FIG. 3 is a longitudinal sectional view showing steps of a method for manufacturing a bearing according to a third embodiment of the present invention in the order of (a) and (b).
FIG. 4 is a longitudinal sectional view showing steps of a method for manufacturing a bearing according to a fourth embodiment of the present invention in the order of (a) and (b).
FIG. 5 is a longitudinal sectional view showing steps of a method for manufacturing a bearing according to a fifth embodiment of the present invention in the order of (a) and (b).
6A is a partial perspective view of a core rod used in a fifth embodiment of the present invention, and FIG. 6B is a vertical perspective view showing a part of a bearing manufactured in the fifth embodiment of the present invention. is there.
FIG. 7 is a longitudinal sectional view showing steps of a method for manufacturing a bearing according to a sixth embodiment of the present invention in the order of (a) and (b).
FIG. 8 is a longitudinally divided perspective view showing a part of a bearing manufactured in a sixth embodiment of the present invention.
FIG. 9 is a longitudinal sectional view showing another embodiment of the bearing material used in the present invention.
FIG. 10 is a longitudinal sectional view showing another embodiment of the bearing manufactured according to the present invention.
[Explanation of symbols]
1A to 1D ... material, 2 ... outer diameter large diameter part, 3 ... inner diameter small diameter part,
5 ... Material flange (outer diameter large diameter portion), 10A to 10F ... Bearing,
12 ... Shaft support surface, 13 ... Middle escape portion, 14 ... Dynamic pressure groove, 22, 22A ... Core rod,
22a: convex portions for forming dynamic pressure grooves.

Claims

It is cylindrical, has an inner diameter small diameter portion at one end in the axial direction, and has an outer diameter uniform or an outer diameter large diameter portion at a part of the outer diameter surface, and the inner diameter of the inner diameter small diameter portion is larger than the outer diameter of the core rod A material made of a sintered porous body having a shape is compressed in the axial direction with the core rod inserted therein, so that the end of the material opposite to the one axial end portion having the small inner diameter portion Reducing the outer diameter of the part and increasing the outer diameter of one end in the axial direction having the central part and the inner diameter small diameter part ,
In accordance with this deformation, a bearing manufacturing method characterized in that both inner diameter surfaces are pressed against the core rod to form a shaft support surface that supports the rotating shaft, and a center relief portion is formed on the inner diameter surface of the central portion.

The bearing manufacturing method according to claim 1, wherein the material has a uniform outer diameter and a shape having a small inner diameter portion at one axial end portion.

The bearing manufacturing method according to claim 1, wherein the material has a shape having a small inner diameter portion at one axial end portion and a large outer diameter portion at the other axial end portion.

4. A convex portion or a concave portion for forming a dynamic pressure groove is formed on the outer diameter surface of the core rod to which the inner diameter surfaces of both end portions in the axial direction of the material are pressed. The manufacturing method of the bearing as described in 2 ..