JP3797465B2

JP3797465B2 - Manufacturing method of bearing

Info

Publication number: JP3797465B2
Application number: JP22621299A
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: 1999-08-10
Filing date: 1999-08-10
Publication date: 2006-07-19
Anticipated expiration: 2019-08-10
Also published as: JP2001050276A

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であって、特に、回転軸が接触しない中逃げ部を有する軸受本体がハウジング内に組み込まれたタイプの軸受を製造する方法に関する。軸受本体は、焼結体あるいは焼結体にサイジングを施した多孔質体からなる素材を成形したものであり、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が、軸受としては、焼結体単体の他に、焼結体がハウジング内に組み込まれたタイプのものがある。ところで、上記中逃げ部を形成する場合、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度焼結体を変形させ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や、軸支面への潤滑油の供給量が十分になされることが要求される。ところが、従来より焼結体の塑性変形のさせ方は種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。また、焼結体をハウジング内に組み込んだタイプの軸受にあっては、焼結体に軸支面および中逃げ部を形成してからハウジングに組み込んでも、焼結体に変形が生じて軸支面の内径に差異が生じたり同軸度が損なわれたりすることが多く、さりとて、組み込んだ後に焼結体をサイジングして軸支面および中逃げ部を形成することは、きわめて困難であった。
【０００５】
したがって本発明は、焼結体がハウジング内に組み込まれた２点支持構造の軸受を、比較的簡素な方法で効率よく、かつ、優れた軸受性能（２つの軸支面の内径や同軸度の同一性に伴う回転軸の支持力、潤滑性、耐摩耗性等）を有するものに製造することができる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、円筒状の軸受本体を円筒状のハウジング内に組み込んでなる軸受の製造方法であって、軸受本体に成形される円筒状の軸受素材を成形孔内に配置するとともに、軸受素材に外径均一のコアロッドを挿入するセット工程と、ハウジング素材を成形孔内に押し込んでハウジング素材内に軸受素材を圧入させる圧入工程とを備え、該圧入工程において、ハウジング素材の外径面を成形孔の内径面に倣って塑性変形させるとともに、少なくとも軸受素材の軸方向両端部の外径面にハウジング素材の内径面を圧迫させることにより、軸受素材をハウジング素材に圧着させる一方、軸受素材の軸方向両端部を縮径させ、その内径面を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、これら軸支面間に、回転軸と接触しない中逃げ部を形成することを特徴としている。本発明に係る軸受素材は、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、軸受本体とされた製造後は、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】
上記セット工程では、例えば、ハウジング素材の外径形状に応じて円筒状に形成された成形孔内に軸受素材を同軸的に配置し、かつ、成形孔に挿入した下パンチ上に載せる。そして、下パンチに貫通させたコアロッドを軸受素材に挿入する。軸受素材の内径は、中逃げ部を形成するために、その内径面とコアロッドとの間に微小な隙間が形成される寸法に設定する。また、軸受素材とハウジング素材は、軸方向長さが等しいと好ましい。
【０００８】
上記圧入工程では、ハウジング素材を軸方向に沿って成形孔に押し込むとともに、ハウジング素材内に軸受素材を圧入させる。この圧入と同時に、両者を軸方向に圧縮してもよい。本発明では、ハウジング素材が成形孔に押し込まれるにつれ、ハウジング素材の内径面が少なくとも軸受素材の軸方向両端部の外径面を圧迫して縮径させる関係が、ハウジング素材、軸受素材および成形孔の形状および寸法に求められる。
【０００９】
そのためには、例えば、押し込み方向先端側の成形孔の内径をハウジング素材の外径よりも小としておく一方、押し込み方向後端側のハウジング素材の内径を、軸受素材の外径よりも小としておく。この場合、ハウジング素材を成形孔に押し込むと、ハウジング素材の先端側は成形孔の内径面に圧迫されて縮径し、縮径するハウジング素材によってさらに軸受素材が圧迫されて縮径し、その部分の軸受素材の外径面がハウジング素材の内径面に圧着するとともに、軸受素材の内径面がコアロッドに圧接させられる。一方、ハウジング素材の後端側の内径面は軸受素材の後端側の外径面を圧迫し、軸受素材は縮径してその内径面がコアロッドに圧接させられる。軸受素材の両端部はハウジング素材によって縮径されて内径面がコアロッドに圧接し、それら内径面が、回転軸を支持する離間した２つの軸支面とされる。また、軸支面間の内径面においてはコアロッドとの間に隙間が残存し、回転軸と接触しない中逃げ部となる。このようにハウジング素材および軸受素材が塑性変形することにより、軸受素材が軸受本体に成形され、かつ、この軸受本体がハウジング素材の内径面に圧着して両者が一体化した軸受に成形される。
【００１０】
本発明は、上記のような変形態様が適宜になされる軸受素材およびハウジング素材と成形孔との組み合わせを採ることにより、軸受本体がハウジング内に組み込まれた構成であって、かつ、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。
【００１１】
また、軸受本体に形成される軸支面は、軸受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、ならびに中逃げ部の直径を比較的大きく形成することが可能なので、潤滑油の含有量や保油量を増大させることができ、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。
【００１２】
また、本発明では、軸受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、回転軸の支持力をより安定させることができる。
【００１３】
【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。
これら実施形態では、注釈しない限りにおいて、本発明に係る軸受素材を素材と称し、ハウジング素材をハウジングと称している。本発明で言う軸受素材およびハウジング素材は、製造前および製造過程のものを言っており、これら素材は製造過程で変形させられ、製造後において、軸受素材は軸受本体となり、ハウジング素材はハウジングとなる。
（１）第１実施形態−図１
図１は、第１実施形態に係る軸受の成形工程を（ａ），（ｂ）の順に示している。第１実施形態では、素材１Ａを成形装置のダイ３１内にセットし、次いで、ハウジング２１をダイ３１内に押し込むと同時にハウジング２１内に素材１Ａを圧入し、軸受２０Ａを製造する。
【００１４】
成形装置は、図１に示すように、ハウジング２１が圧入される成形孔３０を有するダイ３１と、外径均一のコアロッド３２と、上下のパンチ３３，３４とから構成されている。ダイ３１の成形孔３０はハウジング２１に略対応する円筒状であって、図１（ａ）に示すように、主部３０ａと、主部３０ａの奥部（下部）に形成された小径部３０ｂと、主部３０ａの入口側（上側）に形成された開口部３０ｃと、主部３０ａと開口部３０ｃとの間の水平な段部３０ｄとから構成されている。小径部３０ｂの径は主部３０ａよりも小さく、開口部３０ｃの径は主部３０ａよりも大きい。主部３０ａから小径部３０ｂへの移行部は、なだらかなテーパ面に形成されている。
【００１５】
図１（ｂ）に示すように、上パンチ３３は、成形孔３０の開口部３０ｃに摺動自在に挿入されるようになされ、また、下パンチ３４は、成形孔３０の小径部３０ｂに摺動自在に挿入されるようになされている。コアロッド３２は、上下のパンチ３３，３４に摺動自在に貫通するようになされている。
【００１６】
ハウジング２１は、図１（ａ）に示すように、主体をなす円筒部２２の一端部にフランジ２３が形成された円筒状のものである。ハウジング２１の内径は不均一であって、フランジ２３側の端部に内径小径部２４ａが形成され、他の内径部分が内径大径部２４ｂとなっている。円筒部２２の外径は成形孔３０の主部３０ａの径よりも僅かに小さく、その外径面と主部３０ａの内径面との間に微小な隙間が形成される寸法に設定されている。また、フランジ２３の外径は成形孔３０の開口部３０ｃの径よりも僅かに小さく、その外径面と開口部３０ｃの内径面との間に微小な隙間が形成される寸法に設定されている。また、軸方向長さ（高さ）に関しては、円筒部２２は成形孔３０の主部３０ａから小径部３０ｂにかかる長さを有し、フランジ２３は開口部３０ｃよりも短く設定されている。
【００１７】
ハウジング２１は、成形孔３０に塑性変形しながら圧入され得る材質が選択され、例えば、青銅、黄銅、アルミニウム合金、鋼の他、焼結材が用いられる。焼結材の場合、素材１Ａよりも気孔が大きいものを用いると、ハウジング２１に含浸させた油が、毛細管力によって軸受本体側に効果的に供給されるので、軸受寿命を長くすることができ好ましい。
【００１８】
素材１Ａは、焼結体もしくは焼結体にサイジングを施して成形された多孔質体であって、内径および外径がともに均一の単純な円筒状のものである。素材１Ａの外径はハウジング２１の内径大径部２４ｂの径よりも小さく、かつ、内径小径部２４ａの径よりも大きく、その外径面と内径大径部２４ｂとの間に微小な隙間が形成される寸法に設定されている。また、素材１Ａの内径はコアロッド３２の直径よりも大きく、その内径面とコアロッド３２との間に微小な隙間が形成される寸法に設定されている。素材１Ａの軸方向長さは、ハウジング２１のそれと等しく設定されている。
【００１９】
次に、成形装置により軸受を製造する手順を説明する。
［工程１−素材のセット］
図１（ａ）に示すように、下パンチ３４を成形孔３０の小径部３０ｂの途中まで挿入し、コアロッド３２の上端をダイ３１の上面と同一レベルに位置させる。そして、素材１Ａをコアロッド３２に同軸的に嵌め込んで下パンチ３４上にセットする。
【００２０】
［工程２−ハウジング内への素材の圧入］
図１（ａ）に示すように、フランジ２３を上にしてハウジング２１を成形孔３０上に同軸的に配置してから、図１（ｂ）に示すように上パンチ３３を降下させ、上パンチ３３によりハウジング２１を成形孔３０に押し込み、ハウジング２１および素材１Ａを軸方向に圧縮する。下パンチ３４は、ハウジング２１とともに降下させる。
【００２１】
ハウジング２１が成形孔３０に押し込まれ、ハウジング２１および素材１Ａが軸方向に圧縮されると、ハウジング２１の外径面は成形孔３０の内径面に倣って塑性変形する。また、素材１Ａの外径面はハウジング２１の内径面に倣って塑性変形し、ハウジング２１の内径面に圧着する。ハウジング２１の円筒部２２の下端部は、成形孔３０の小径部３０ｂに圧入して縮径し、絞り部２５が造形される。これにより、素材１Ａの下端部も内径側に圧迫されて縮径し、絞り部１１ａが造形される。一方、素材１Ａの上端部は、ハウジング２１の内径小径部２４ａに圧入し、内径小径部２４ａからの圧迫を受けて縮径することにより絞り部１１ｂが造形される。
【００２２】
素材１Ａの上下の絞り部１１ａ，１１ｂの外径面はハウジング２１の内径面にそれぞれ強く圧着し、内径面はコアロッド３２に圧接して軸支面１２に形成される。そして、これら軸支面１２間の内径面においてはコアロッド３２との間に隙間が残存し、中逃げ部１３が形成される。このようにハウジング２１および素材１Ａが塑性変形することにより、素材１Ａが軸受本体１０Ａに成形され、かつ、この軸受本体１０Ａがハウジング２１の内径面に圧着して両者が一体化した軸受２０Ａに成形される。軸受２０Ａは、上パンチ３３を上昇させて退避させ、下パンチ３４を上昇させてダイ３１から押し出すことにより脱型され、この後、コアロッド３２を降下させて軸受２０Ａを得る。
【００２３】
この場合、図１（ａ）に示すような素材１Ａとハウジング２１の位置から上パンチ３３を降下させる方法によれば、素材１Ａの上端部はハウジング２１の内径小径部２４ａに上端面側から軸方向中央部方向に順次圧入され、一方、素材１Ａの下端部は軸方向中央部側から下端面側に向けて縮径されていく。このため、素材１Ａの上端部と下端部は、ともに下パンチ３４方向に塑性変形し、その結果、コアロッド３２に圧接して形成される軸支面１２は、各端面寄りの気孔状態が僅かではあるが異なったものとなる。素材１Ａの両端とも端面側から軸方向中央部に向かって塑性変形させたいときは、まず、図１（ａ）における下パンチ３４の上面を成形孔３０の小径部３０ｂの領域またはそれよりも上方に位置させておき、素材１Ａおよびハウジング２１を同軸的に配置する。次いで、上パンチ３３によりハウジング２１を降下させ、内径小径部２４ａに素材１Ａの上端部を圧入させ、この後、ハウジング２１および素材１Ａを図１（ｂ）に示すように成形孔３０に圧入する手順が採られる。
【００２４】
上記第１実施形態によれば、素材１Ａをダイ３１内にセットし、次いで、ハウジング２１をダイ２１内に押し込んでハウジング２１内に素材１Ａを圧入させるといった簡素な方法により、焼結体からなる軸受本体１０Ａがハウジング（ハウジング素材２１が変形した後のハウジング）２１内に組み込まれた２点支持構造の軸受２０Ａを、効率よく製造することができる。
【００２５】
軸受２０Ａの軸支面１２は、素材１Ａの内径面をコアロッド３２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、耐摩耗性および回転軸の支持力に優れる。一方、中逃げ部１３はコアロッド３２に圧接しないことから軸支面１２よりも密度は低く、かつ、その中逃げ量を比較的大きなものとすることができるので、潤滑油の含有量や保油量を増大させることができ、潤滑性が向上する。これらの結果、軸受２０Ａは優れた軸受性能を発揮する。また、双方の軸支面１２の圧縮度をほぼ等しくすることができることから、それら軸支面１２の気孔率が均等化され、その結果、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。
【００２６】
（２）第２実施形態−図２
次に、本発明の第２実施形態を説明する。
第２実施形態では、図２に示すように、第１実施形態の素材１Ａとは異なる形状の素材１Ｂを成形装置のダイ３１内にセットし、次いで、第１実施形態と同様のハウジング２１をダイ３１内に押し込むと同時にハウジング２１内に素材１Ｂを圧入し、軸受２０Ｂを製造する。
【００２７】
第２実施形態の成形装置は、第１実施形態で用いたダイ３１の成形孔３０および下パンチ３４を変更したものである。成形孔３０は、図２（ａ）に示すように、上記小径部３０ｂが形成されておらず、主部３０ａがダイ３１の下面まで貫通しており、この主部３０ａに、下パンチ３４が挿入されるようになされている。
【００２８】
図２（ａ）の符合１Ｂで示す第２実施形態の素材は、内径均一で、軸方向一端部に外径大径部４ｂが形成された円筒状のものである。外径大径部４ｂの外径は、ハウジング２１の内径大径部２４ｂの径よりも大きく設定されている。また、外径大径部４ｂ以外の外径部分である外径小径部４ａの外径は、ハウジング２１の内径小径部２４ａの径よりも大きく、かつ、内径大径部２４ｂよりも小さくてその外径面と内径大径部２４ｂの内径面との間に微小な隙間が形成される寸法に設定されている。また、素材１Ｂの内径はコアロッド３２の直径よりも大きく、その内径面とコアロッド３２との間に微小な隙間が形成される寸法に設定されている。
【００２９】
次に、成形装置により軸受を製造する手順を説明する。
［工程１−素材のセット］
図２（ａ）に示すように、外径大径部４ｂを下にして素材１Ｂをコアロッド３２に嵌め込み、下パンチ３４上にセットする。
【００３０】
［工程２−ハウジング内への素材の圧入］
図２（ａ）〜（ｂ）に示すように、第１実施形態と同様にしてハウジング２１を上パンチ３３により成形孔３０に押し込み、ハウジング２１および素材１Ｂを軸方向に圧縮する。
【００３１】
ハウジング２１が成形孔３０に押し込まれ、ハウジング２１および素材１Ｂが軸方向に圧縮されると、ハウジング２１の外径面は成形孔３０の内径面に倣って塑性変形する。また、素材１Ｂの外径面はハウジング２１の内径面に倣って塑性変形し、ハウジング２１の内径面に圧着する。素材１Ｂの下端部の外径大径部４ｂは、ハウジング２１の外径大径部２４ｂに圧入して縮径し、消滅させられる。一方、素材１Ｂの上端部は、ハウジング２１の内径小径部２４ａに圧入して縮径し、絞り部１１ｂが造形される。
【００３２】
素材１Ｂの上端部に造形された絞り部１１ｂと下端部の外径面は、それぞれハウジング２１の内径面に強く圧着し、これら部分の内径面はコアロッド３２に圧接して軸支面１２に形成される。そして、これら軸支面１２間の内径面においてはコアロッド３２との間に隙間が残存し、中逃げ部１３が形成される。このようにハウジング２１および素材１Ｂが塑性変形することにより、素材１Ｂが軸受本体１０Ｂに成形され、かつ、この軸受本体１０Ｂがハウジング（ハウジング素材２１が変形した後のハウジング）２１の内径面に圧着して両者が一体化した軸受２０Ｂに成形される。軸受２０Ｂは、上パンチ３３を上昇させて退避させ、下パンチ３４を上昇させてダイ３１から押し出すことにより脱型され、この後、コアロッド３２を降下させて軸受２０Ｂを得る。
【００３３】
（３）第３実施形態−図３，図４
第３実施形態は、図３に示すように、上記コアロッド３２に代えた動圧溝形成用のコアロッド３２Ａを、上記第１実施形態に適用して素材１Ａを成形し、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３２Ａは、図４（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３２ａ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３２ａは、コアロッド３２Ａ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。
【００３４】
軸受を成形するには、まず、図３（ａ）に示すように、素材１Ａを成形装置にセットし、コアロッド３２Ａの凸部３２ａが形成された部分を素材１Ａの両端部内径面に対応させる。この状態から、第１実施形態と同様の操作（図３（ａ）〜（ｂ））を行い、軸受本体１０Ｃがハウジング（ハウジング素材２１が変形した後のハウジング）２１内に組み込まれた軸受２０Ｃを得る。
【００３５】
軸受本体１０Ｃの軸支面１２には、図４（ｂ）に示すように（同図はハウジング２１を省略している）、コアロッド３２Ａの凸部３２ａによってヘリングボーン状の動圧溝１４が刻設される。脱型された軸受２０Ｃには、ダイ３１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３２Ａから軸受２０Ｃを抜くことができる。
【００３６】
第３実施形態によって製造された軸受２０Ｃ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２０Ｃは、回転軸の回転方向が動圧溝１４のＶ字の先端方向（図４（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。
【００３７】
上記第３実施形態のように動圧溝形成用のコアロッド３２Ａを用いて軸支面に動圧溝を形成する形態は、第２実施形態にも勿論適用することができる。
【００３８】
なお、第３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。第３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。
【００３９】
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。
【００４０】
また、第３実施形態で示した動圧溝１４は、コアロッド３２Ａに形成した凸部３２ａ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３実施形態と刻設のパターンが逆であって、素材１Ａ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。
【００４１】
【発明の効果】
以上説明したように、本発明によれば、軸受本体がハウジング内に組み込まれた構成であって、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や保油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工程を（ａ），（ｂ）の順に示す縦断面図である。
【図４】（ａ）は本発明の第３実施形態で用いるコアロッドの一部斜視図、（ｂ）は第３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。
【符号の説明】
１Ａ，１Ｂ…軸受素材、１０Ａ，１０Ｂ，１０Ｃ…軸受本体、１２…軸支面、
１３…中逃げ部、１４…動圧溝、２０Ａ，２０Ｂ，２０Ｃ…軸受、
２１…ハウジング（ハウジング素材）、３０…成形孔、３２，３２Ａ…コアロッド、
３２ａ…動圧溝形成用の凸部。[0001]
BACKGROUND OF THE INVENTION
The present invention is a bearing suitable for use when supporting a shaft that rotates at a relatively high speed, such as a drive shaft of a spindle motor built in a precision instrument, with a high degree of accuracy. The present invention relates to a method of manufacturing a type of bearing in which a bearing body having a portion is incorporated in a housing. The bearing body is formed by molding a sintered body or a material made of a porous body obtained by sizing the sintered body, impregnated with a 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. However, as a bearing, there is a type in which a sintered body is incorporated in a housing in addition to a sintered body alone. By the way, in the case of forming the intermediate relief portion, if the intermediate relief portion is formed by machining the sintered body, the pores exposed on the inner diameter surface may be crushed and hinder the circulation function of the lubricating oil. Become. 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 form the middle relief portion independently by deforming the sintered body again after sizing. In any case, two shafts that are separated from each other by causing plastic deformation in which the inner diameter surfaces of both axial end portions protrude radially inward or the axial central portion bulges outward in the radial direction. A supporting surface and a middle escape portion between them are simultaneously formed 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. And sufficient supply of lubricating oil to the shaft support surface is required. However, although various methods for plastic deformation of the sintered body have been proposed in the past, there is no constant manufacturing method that is relatively simple and sufficiently satisfies the requirements for improving bearing performance. there were. Also, in the case of a type of bearing in which the sintered body is incorporated in the housing, even if the sintered body is formed in the housing after the shaft support surface and the intermediate relief portion are formed, the sintered body is deformed and the shaft support is formed. In many cases, a difference occurs in the inner diameter of the surface or the coaxiality is impaired, and it is very difficult to size the sintered body after the assembly to form the shaft support surface and the intermediate relief portion.
[0005]
Therefore, according to the present invention, a bearing having a two-point support structure in which a sintered body is incorporated in a housing can be efficiently and excellently performed with a relatively simple method (the inner diameter and coaxiality of two shaft support surfaces). It is an object of the present invention to provide a method capable of producing a rotating shaft bearing force, lubricity, wear resistance, and the like associated with the sameness.
[0006]
[Means for Solving the Problems]
The present invention, a cylindrical bearing body a cylindrical bearing manufacturing method comprising incorporating into the housing, together with placing the cylindrical bearing material to be molded to the bearing body forming the hole, the bearing material A setting process for inserting a core rod having a uniform outer diameter, and a press-fitting process for pressing the housing material into the molding hole and press-fitting the bearing material into the housing material . In the press-fitting process, the outer diameter surface of the housing material is formed into the molding hole. The bearing material is pressed against the housing material by compressing the inner diameter surface of the housing material against at least the outer diameter surfaces of both ends in the axial direction of the bearing material, while the bearing material is crimped to the housing material. Both ends are reduced in diameter, and the inner diameter surface is pressed against the core rod to form a shaft support surface that supports the rotation shaft, and the rotation shaft does not contact between the shaft support surfaces. It is characterized by forming a relief portion. As described above, the bearing material according to the present invention uses a sintered body or a porous body formed by sizing the sintered body, and after manufacturing the bearing body , the bearing body is impregnated with a lubricating oil, and a sintered oil-impregnated bearing. Is preferably used.
[0007]
In the setting step, for example, the bearing material is coaxially disposed in a cylindrically formed molding hole in accordance with the outer diameter shape of the housing material and placed on the lower punch inserted into the molding hole. And the core rod penetrated by the lower punch is inserted into the bearing material. The inner diameter of the bearing material is set to such a dimension that a minute gap is formed between the inner diameter surface and the core rod in order to form a middle relief portion. Further, it is preferable that the bearing material and the housing material have the same axial length.
[0008]
In the press-fitting step, the housing material is pushed into the forming hole along the axial direction, and the bearing material is press-fitted into the housing material . Simultaneously with this press-fitting, both may be compressed in the axial direction. In the present invention, as the housing material is pushed into the molded hole, relationship to diameter inner diameter surface of the housing material to compress the outer diameter surface of the axial end portions of at least the bearing material, housing material, bearing material and forming pores It is required for the shape and dimensions.
[0009]
For this purpose, for example, one to keep smaller than the outer diameter of the housing material an inner diameter of the push-in direction front end side of the forming hole, the inner diameter of the housing material pushing direction rear end side, keep smaller than the outer diameter of the bearing material . In this case, when the housing material is pushed into the molding hole, the distal end side of the housing material is compressed by the inner diameter surface of the molding hole to reduce the diameter, and the bearing material is further compressed by the reduced diameter housing material to reduce the diameter. together with the outer diameter surface of the bearing material is pressed against the inner surface of the housing material, the inner diameter surface of the bearing material is brought into pressure contact with the core rod. On the other hand, the inner diameter surface of the rear end side of the housing material to compress the outer surface of the rear end side of the bearing material, the bearing material the inner surface decreases in diameter is brought into pressure contact with the core rod. Both end portions of the bearing material are reduced in diameter by the housing material so that the inner diameter surface is pressed against the core rod, and the inner diameter surfaces serve as two spaced shaft support surfaces that support the rotating shaft. In addition, a gap remains between the inner diameter surface between the shaft support surfaces and the core rod, which becomes a middle escape portion that does not contact the rotating shaft. As the housing material and the bearing material are plastically deformed in this manner, the bearing material is molded into the bearing body, and the bearing body is pressed against the inner diameter surface of the housing material to form a bearing in which both are integrated.
[0010]
The present invention has a structure in which a bearing body is incorporated in a housing by adopting a combination of a bearing material and a housing material and a molding hole in which the above-described deformation mode is appropriately performed, and a medium escape amount. However, it is possible to efficiently manufacture a bearing having a two-point support structure having a relatively large middle clearance portion by a relatively simple method.
[0011]
Further, since the shaft support surface formed on the bearing body is formed by strongly pressing the inner diameter surface of the bearing 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. It can be increased and the lubricity can be improved. As a result, a bearing having a high level of bearing performance can be manufactured.
[0012]
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 bearing 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 can be made more stable.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In these embodiments, unless otherwise noted, the bearing material according to the present invention is referred to as a material, and the housing material is referred to as a housing. The bearing material and the housing material referred to in the present invention are those before and during the manufacturing process, and these materials are deformed during the manufacturing process. After the manufacturing, the bearing material becomes the bearing body and the housing material becomes the housing. .
(1) First embodiment-FIG.
FIG. 1 illustrates a bearing molding process according to the first embodiment in the order of (a) and (b). In the first embodiment, the material 1A is set in the die 31 of the molding apparatus, and then the housing 21 is pushed into the die 31 and simultaneously the material 1A is press-fitted into the housing 21 to manufacture the bearing 20A.
[0014]
As shown in FIG. 1, the molding apparatus includes a die 31 having a molding hole 30 into which the housing 21 is press-fitted, a core rod 32 having a uniform outer diameter, and upper and lower punches 33 and 34. The forming hole 30 of the die 31 has a cylindrical shape substantially corresponding to the housing 21, and as shown in FIG. 1A, a main portion 30a and a small-diameter portion 30b formed in the back portion (lower portion) of the main portion 30a. And an opening 30c formed on the inlet side (upper side) of the main portion 30a, and a horizontal step portion 30d between the main portion 30a and the opening 30c. The diameter of the small diameter portion 30b is smaller than the main portion 30a, and the diameter of the opening 30c is larger than the main portion 30a. The transition portion from the main portion 30a to the small diameter portion 30b is formed on a gentle tapered surface.
[0015]
As shown in FIG. 1B, the upper punch 33 is slidably inserted into the opening 30 c of the molding hole 30, and the lower punch 34 is slid onto the small diameter part 30 b of the molding hole 30. It is designed to be inserted freely. The core rod 32 penetrates the upper and lower punches 33 and 34 in a slidable manner.
[0016]
As shown in FIG. 1A, the housing 21 has a cylindrical shape in which a flange 23 is formed at one end of a cylindrical portion 22 that forms the main body. The inner diameter of the housing 21 is not uniform, an inner diameter small diameter portion 24a is formed at the end on the flange 23 side, and the other inner diameter portion is an inner diameter large diameter portion 24b. The outer diameter of the cylindrical portion 22 is slightly smaller than the diameter of the main portion 30a of the molding hole 30, and is set to a dimension that forms a minute gap between the outer diameter surface and the inner diameter surface of the main portion 30a. . Further, the outer diameter of the flange 23 is slightly smaller than the diameter of the opening 30c of the molding hole 30, and the dimension is set such that a minute gap is formed between the outer diameter surface and the inner diameter surface of the opening 30c. Yes. Regarding the axial length (height), the cylindrical portion 22 has a length extending from the main portion 30a of the molding hole 30 to the small diameter portion 30b, and the flange 23 is set to be shorter than the opening portion 30c.
[0017]
For the housing 21, a material that can be press-fitted while being plastically deformed into the molding hole 30 is selected. For example, in addition to bronze, brass, aluminum alloy, steel, a sintered material is used. In the case of a sintered material, if a material having pores larger than that of the material 1A is used, the oil impregnated in the housing 21 is effectively supplied to the bearing body side by the capillary force, so that the bearing life can be extended. preferable.
[0018]
The material 1A is a sintered body or a porous body formed by sizing the sintered body, and has a simple cylindrical shape with uniform inner and outer diameters. The outer diameter of the material 1A is smaller than the diameter of the inner diameter large diameter portion 24b of the housing 21 and larger than the diameter of the inner diameter small diameter portion 24a, and a minute gap is formed between the outer diameter surface and the inner diameter large diameter portion 24b. The dimension to be formed is set. The inner diameter of the material 1 A is larger than the diameter of the core rod 32, and the dimension is set such that a minute gap is formed between the inner diameter surface and the core rod 32. The axial length of the material 1 A is set equal to that of the housing 21.
[0019]
Next, a procedure for manufacturing a bearing using a molding apparatus will be described.
[Step 1-Material setting]
As shown in FIG. 1A, the lower punch 34 is inserted halfway through the small diameter portion 30 b of the forming hole 30, and the upper end of the core rod 32 is positioned at the same level as the upper surface of the die 31. Then, the material 1A is coaxially fitted into the core rod 32 and set on the lower punch 34.
[0020]
[Step 2-Material press-fitting into the housing]
As shown in FIG. 1A, the housing 21 is coaxially arranged on the molding hole 30 with the flange 23 facing up, and then the upper punch 33 is lowered as shown in FIG. The housing 21 is pushed into the molding hole 30 by 33, and the housing 21 and the material 1A are compressed in the axial direction. The lower punch 34 is lowered together with the housing 21.
[0021]
When the housing 21 is pushed into the molding hole 30 and the housing 21 and the material 1A are compressed in the axial direction, the outer diameter surface of the housing 21 is plastically deformed following the inner diameter surface of the molding hole 30. Further, the outer diameter surface of the material 1 A is plastically deformed following the inner diameter surface of the housing 21, and is crimped to the inner diameter surface of the housing 21. The lower end portion of the cylindrical portion 22 of the housing 21 is press-fitted into the small diameter portion 30 b of the molding hole 30 to reduce the diameter, and the throttle portion 25 is formed. Thereby, the lower end part of the raw material 1A is also compressed toward the inner diameter side to reduce the diameter, and the throttle part 11a is formed. On the other hand, the upper end portion of the material 1A is press-fitted into the inner diameter small diameter portion 24a of the housing 21, and the diameter is reduced by receiving pressure from the inner diameter small diameter portion 24a, thereby forming the throttle portion 11b.
[0022]
The outer diameter surfaces of the upper and lower restricting portions 11 a and 11 b of the material 1 A are strongly pressed against the inner diameter surface of the housing 21. Then, a gap remains between the shaft support surface 12 and the core rod 32 on the inner diameter surface, and the middle escape portion 13 is formed. As the housing 21 and the material 1A are plastically deformed in this way, the material 1A is molded into the bearing body 10A, and the bearing body 10A is crimped to the inner diameter surface of the housing 21 to form a bearing 20A in which both are integrated. Is done. The bearing 20A is removed by raising the upper punch 33 and retracting it, raising the lower punch 34 and pushing it out from the die 31, and then lowering the core rod 32 to obtain the bearing 20A.
[0023]
In this case, according to the method of lowering the upper punch 33 from the position of the material 1A and the housing 21 as shown in FIG. 1A, the upper end portion of the material 1A is pivoted to the inner diameter small diameter portion 24a of the housing 21 from the upper end surface side. The lower end portion of the material 1A is reduced in diameter from the axial direction central portion side toward the lower end surface side. For this reason, both the upper end portion and the lower end portion of the material 1A are plastically deformed in the direction of the lower punch 34, and as a result, the shaft support surface 12 formed in pressure contact with the core rod 32 has a slight pore state near each end surface. There are different things. When it is desired to plastically deform both ends of the material 1A from the end face side toward the axial center, first, the upper surface of the lower punch 34 in FIG. The material 1A and the housing 21 are arranged coaxially. Next, the housing 21 is lowered by the upper punch 33 to press-fit the upper end portion of the material 1A into the small inner diameter portion 24a, and then the housing 21 and the material 1A are press-fitted into the forming hole 30 as shown in FIG. Procedures are taken.
[0024]
According to the first embodiment, the material 1A is set in the die 31, and then the housing 21 is pushed into the die 21 and the material 1A is press-fitted into the housing 21 by a simple method. The bearing 20 A having a two-point support structure in which the bearing body 10 A is incorporated in the housing (housing after the housing material 21 is deformed) 21 can be efficiently manufactured.
[0025]
Since the shaft support surface 12 of the bearing 20A is formed by strongly pressing the inner diameter surface of the material 1A to the core rod 32, the inner diameter and the coaxiality coincide with each other with high accuracy, and in addition, the wear density is increased. Excellent in supporting properties and rotating shaft support. On the other hand, since the intermediate escape portion 13 is not pressed against the core rod 32, the density thereof is lower than that of the shaft support surface 12, and the intermediate escape amount can be made relatively large. The amount can be increased and the lubricity is improved. As a result, the bearing 20A exhibits excellent bearing performance. In addition, since the degree of compression of both the shaft support surfaces 12 can be made substantially equal, the porosity of the shaft support surfaces 12 is equalized, and as a result, the hydraulic pressure generated on the shaft support surfaces 12 is also equalized and the rotation shaft Can be supported in a balanced manner.
[0026]
(2) Second embodiment-FIG.
Next, a second embodiment of the present invention will be described.
In the second embodiment, as shown in FIG. 2, a material 1B having a shape different from that of the material 1A of the first embodiment is set in the die 31 of the molding apparatus, and then a housing 21 similar to that of the first embodiment is provided. The material 1B is press-fitted into the housing 21 at the same time as being pushed into the die 31 to manufacture the bearing 20B.
[0027]
The molding apparatus of the second embodiment is obtained by changing the molding hole 30 and the lower punch 34 of the die 31 used in the first embodiment. As shown in FIG. 2A, the molding hole 30 is not formed with the small diameter portion 30b, and the main portion 30a penetrates to the lower surface of the die 31, and the lower punch 34 is formed in the main portion 30a. It is designed to be inserted.
[0028]
The material of the second embodiment indicated by reference numeral 1B in FIG. 2A has a cylindrical shape with a uniform inner diameter and an outer diameter large diameter portion 4b formed at one end in the axial direction. The outer diameter of the outer diameter large diameter portion 4b is set larger than the diameter of the inner diameter large diameter portion 24b of the housing 21. The outer diameter of the outer diameter small diameter portion 4a, which is an outer diameter portion other than the outer diameter large diameter portion 4b, is larger than the diameter of the inner diameter small diameter portion 24a of the housing 21 and smaller than the inner diameter large diameter portion 24b. The dimension is set such that a minute gap is formed between the outer diameter surface and the inner diameter surface of the inner diameter large diameter portion 24b. Further, the inner diameter of the material 1B is larger than the diameter of the core rod 32, and the dimension is set such that a minute gap is formed between the inner diameter surface and the core rod 32.
[0029]
Next, a procedure for manufacturing a bearing using a molding apparatus will be described.
[Step 1-Material setting]
As shown in FIG. 2A, the material 1 B is fitted into the core rod 32 with the outer diameter large diameter portion 4 b facing down and set on the lower punch 34.
[0030]
[Step 2-Material press-fitting into the housing]
As shown in FIGS. 2A to 2B, the housing 21 is pushed into the forming hole 30 by the upper punch 33 in the same manner as in the first embodiment, and the housing 21 and the material 1B are compressed in the axial direction.
[0031]
When the housing 21 is pushed into the molding hole 30 and the housing 21 and the material 1B are compressed in the axial direction, the outer diameter surface of the housing 21 is plastically deformed following the inner diameter surface of the molding hole 30. Further, the outer diameter surface of the material 1B is plastically deformed following the inner diameter surface of the housing 21, and is crimped to the inner diameter surface of the housing 21. The outer diameter large diameter portion 4b at the lower end portion of the material 1B is press-fitted into the outer diameter large diameter portion 24b of the housing 21 to be reduced in diameter and disappear. On the other hand, the upper end portion of the material 1B is press-fitted into the inner diameter small diameter portion 24a of the housing 21 to reduce the diameter, and the throttle portion 11b is formed.
[0032]
The narrowed portion 11b and the outer diameter surface of the lower end portion formed on the upper end portion of the material 1B are strongly pressed against the inner diameter surface of the housing 21, and the inner diameter surfaces of these portions are formed on the shaft support surface 12 by pressing against the core rod 32. Is done. Then, a gap remains between the shaft support surface 12 and the core rod 32 on the inner diameter surface, and the middle escape portion 13 is formed. As the housing 21 and the material 1B are plastically deformed in this way, the material 1B is molded into the bearing body 10B, and the bearing body 10B is crimped to the inner diameter surface of the housing (the housing after the housing material 21 is deformed) 21. Then, both are formed into a bearing 20B integrated. The bearing 20B is removed by raising the upper punch 33 and retracting it, raising the lower punch 34 and pushing it out from the die 31, and thereafter lowering the core rod 32 to obtain the bearing 20B.
[0033]
(3) Third Embodiment-FIGS. 3 and 4
In the third embodiment, as shown in FIG. 3, a core rod 32A for forming a dynamic pressure groove instead of the core rod 32 is applied to the first embodiment to form the material 1A and move to the shaft support surface 12. It is an example which shape | molds the bearing in which the pressure groove was formed. As shown in FIG. 4A, the core rod 32A has a plurality of V-shaped projections 32a 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 32a can be formed by means such as cutting or plating of the core rod 32A, and the height thereof is about several μm.
[0034]
In order to mold the bearing, first, as shown in FIG. 3A, the material 1A is set in a molding apparatus, and the portions where the convex portions 32a of the core rod 32A are formed correspond to the inner diameter surfaces at both ends of the material 1A. . From this state, the same operation as in the first embodiment (FIGS. 3A to 3B) is performed, and the bearing body 10C is incorporated in the housing (housing after the housing material 21 is deformed) 21C. Get.
[0035]
As shown in FIG. 4B (the housing 21 is omitted in the figure), a herringbone-like dynamic pressure groove 14 is formed on the shaft support surface 12 of the bearing body 10C by the convex portion 32a of the core rod 32A. Established. In the removed bearing 20C, the outer diameter surface restraint by the die 31 is released, and a springback that slightly expands the entire diameter is generated, so that the convex portion between the dynamic pressure grooves 14 is not worn away from the core rod 32A. The bearing 20C can be removed.
[0036]
According to the bearing 20C manufactured according to the third 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 20C 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 (direction of arrow R in FIG. 4B).
[0037]
Of course, the form in which the dynamic pressure groove is formed on the shaft support surface using the core rod 32A for forming the dynamic pressure groove as in the third embodiment can also be applied to the second embodiment.
[0038]
The shape of the dynamic pressure grooves shown in the third embodiment is arbitrary, and the number thereof is appropriately selected. From the viewpoint of supporting the rotating shaft more stably, a plurality of 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 the third embodiment, 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 the cross-sectional shape of the depth.
[0039]
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.
[0040]
Moreover, although the dynamic pressure groove 14 shown in the third embodiment is formed by the convex portion 32a formed in the core rod 32A, the dynamic pressure groove can be formed by a concave portion instead of such a convex portion. That is, the engraving pattern is opposite to that in the third embodiment, and when the inner diameter surface of the inner diameter small diameter portion of the material 1A 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.
[0041]
【The invention's effect】
As described above, according to the present invention, a bearing having a two-point support structure having a bearing body incorporated in a housing and having a relatively large middle escape portion can be efficiently obtained in a relatively simple manner. Can be manufactured.
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 part in the axial direction where the relief portion is formed, the density and the oil retention amount are 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 a manufacturing process of 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 a manufacturing process of 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 a manufacturing process of a bearing according to a third embodiment of the present invention in the order of (a) and (b).
4A is a partial perspective view of a core rod used in a third embodiment of the present invention, and FIG. 4B is a vertical perspective view showing a part of a bearing manufactured in the third embodiment.
[Explanation of symbols]
1A, 1B ... bearing material, 10A, 10B, 10C ... bearing body, 12 ... shaft support surface,
13 ... Middle escape portion, 14 ... Dynamic pressure groove, 20A, 20B, 20C ... Bearing,
21 ... Housing (housing material) , 30 ... Molding hole, 32, 32A ... Core rod,
32a: convex portion for forming a dynamic pressure groove.

Claims

A method for manufacturing a bearing in which a cylindrical bearing body is incorporated in a cylindrical housing,
With placing a cylindrical bearing material to be molded to the bearing body forming the hole, a setting step of inserting the core rod of the outer size uniformity to the bearing material,
A press-in process for pressing the housing material into the molding hole and press-fitting the bearing material into the housing material ,
In the press-fitting process,
While plastically deforming the outer diameter surface of the housing material following the inner diameter surface of the molding hole,
By pressing the inner diameter surface of the housing material against at least the outer diameter surface of both axial ends of the bearing material,
While the bearing material is crimped to the housing material ,
Both ends in the axial direction of the bearing material are reduced in diameter, and the inner diameter surface thereof is pressed against the core rod to form a shaft supporting surface that supports the rotating shaft, and the intermediate relief portion that does not contact the rotating shaft between these shaft supporting surfaces Forming a bearing.

The bearing according to claim 1, wherein 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 bearing material are pressed. Manufacturing method.