JP2004132402A - Fluid bearing device and its manufacturing method - Google Patents

Fluid bearing device and its manufacturing method Download PDF

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Publication number
JP2004132402A
JP2004132402A JP2002295249A JP2002295249A JP2004132402A JP 2004132402 A JP2004132402 A JP 2004132402A JP 2002295249 A JP2002295249 A JP 2002295249A JP 2002295249 A JP2002295249 A JP 2002295249A JP 2004132402 A JP2004132402 A JP 2004132402A
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JP
Japan
Prior art keywords
bearing
housing
peripheral surface
shaft member
bearing sleeve
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JP2002295249A
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Japanese (ja)
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JP4152712B2 (en
Inventor
Isao Komori
古森 功
Masaji Shimizu
清水 政次
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NTN Corp
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NTN Corp
NTN Toyo Bearing Co Ltd
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  • Sliding-Contact Bearings (AREA)
  • Mounting Of Bearings Or Others (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid bearing device having a small number of components, low in cost and high in reliability and capable of surely preventing the mixture of foreign matters into a bearing gap. <P>SOLUTION: A housing 7 is formed by resin molding using a bearing sleeve 8 as an insert component. The bearing sleeve 8 is formed of a sintered alloy with a herringbone dynamic pressure groove in the inner periphery. Burrs formed at a P point following the molding are deposited on the upper end face 7d of the housing 7 at the glass transition point or higher and the melting point or lower of a resin. <P>COPYRIGHT: (C)2004,JPO

Description

【0001】
【発明の属する技術分野】
本発明は、ラジアル軸受隙間に生じる潤滑油の油膜によって回転部材を非接触支持する流体軸受装置に関する。この軸受装置は、情報機器、例えばHDD、FDD等の磁気ディスク装置、CD−ROM、CD−R/RW、DVD−ROM/RAM等の光ディスク装置、MD、MO等の光磁気ディスク装置などのスピンドルモータ、レーザビームプリンタ(LBP)のポリゴンスキャナモータ、あるいは電気機器、例えば軸流ファンなどの小型モータ用として好適である。
【0002】
【従来の技術】
上記各種モータには、高回転精度の他、高速化、低コスト化、低騒音化などが求められている。これらの要求性能を決定づける構成要素の一つに当該モータのスピンドルを支持する軸受があり、近年では、上記要求性能に優れた特性を有する流体軸受の使用が検討され、あるいは実際に使用されている。
【0003】
この種の流体軸受は、軸受隙間内の潤滑油に動圧を発生させる動圧発生手段を備えたいわゆる動圧軸受と、動圧発生手段を備えていないいわゆる真円軸受(軸受面が真円形状である軸受)とに大別される。
【0004】
例えば、HDD等のディスク装置のスピンドルモータやレーザビームプリンタ(LBP)のポリゴンスキャナモータに組込まれる流体軸受装置では、軸部材をラジアル方向に回転自在に非接触支持するラジアル軸受部と、軸部材をスラスト方向に回転自在に支持するスラスト軸受部とが設けられ、ラジアル軸受部として、軸受スリーブの内周面又は軸部材の外周面に動圧発生用の溝(動圧溝)を設けた動圧軸受が用いられる。スラスト軸受部としては、例えば、軸部材の一端面をスラストプレートによって接触支持する構造の軸受(いわゆるピボット軸受)が用いられる。通常、軸受スリーブはハウジングの内周の所定位置に固定され、また、ハウジングの内部空間に注油した潤滑油が外部に漏れるのを防止するため、ハウジングの開口部にシール部材を配設する場合が多い(例えば特許文献1参照)。
【0005】
【特許文献1】
特開平11−191945号公報
【0006】
【発明が解決しようとする課題】
上記構成の流体軸受装置は、ハウジング、軸受スリーブ、軸部材、スラストプレート、及びシール部材といった多くの部品で構成され、情報機器の益々の高性能化に伴って必要とされる高い軸受性能を確保すべく、各部品の加工精度や組立精度を高める努力がなされている。その一方で、情報機器の低価格化・小型化の傾向に伴い、この種の流体軸受装置に対するコスト低減の要求も益々厳しくなっている。
【0007】
また、この種の流体軸受装置では、軸受性能の確保のために、軸受隙間の精度は厳密に管理する必要があり、この軸受隙間への異物の混入は極力排除する必要がある。
【0008】
そこで、本発明は、部品点数が少なく、低コストでかつ信頼性が高く、さらには軸受隙間への異物の混入を確実に防止することのできる流体軸受装置を提供することを目的とする。
【0009】
【課題を解決するための手段】
上記課題を解決するため、本発明にかかる流体軸受装置は、樹脂製のハウジングと、ハウジングの内部に設けられた軸受スリーブと、軸受スリーブの内周面に挿入された軸部材と、軸受スリーブの内周面と軸部材の外周面との間に設けられ、軸受隙間に生じる潤滑油の油膜で軸部材をラジアル方向で非接触支持するラジアル軸受部とを少なくとも備え、前記ハウジングを、軸受スリーブをインサート部品とする樹脂の型成形で形成し、かつこの型成形に伴って形成されたバリを、ハウジング表面に溶着したものである。
【0010】
ハウジングを、軸受スリーブをインサート部品として樹脂の型成形(インサート成形)で形成することにより、ハウジングを金属材で形成する場合に比べて、ハウジングの製造コストを低減することができる。また、流体軸受装置に、軸部材をスラスト方向で支持するスラスト軸受部を設ける場合、スラスト軸受部は、軸部材の一端側端面をハウジングの底部で直接支持する構造とすることができる。従って、従来、この種の流体軸受装置に設けられていたスラストプレートを不要として、部品点数の削減を図ることができる。さらに、ハウジングに対する軸受スリーブの組立作業が不要であるので、組立コストも低減する。
【0011】
ところで、インサート成形後の成形品表面には、型と型の間の隙間に入り込んだ溶融樹脂が固化することによってバリが形成される。このバリを放置すると、何らかの要因でバリが脱落した際に、これが軸受スリーブの内周面に入り込んで軸受性能に重大な影響を与えるおそれがある。従って、この種のバリは、その発生防止を防止するか、あるいは脱型後に何らかの方法で除去する必要がある。
【0012】
しかしながら、インサート成形においてバリの発生を完全に防止することは難しい。従って、上記バリ対策としては、後者の方法をとらざるを得ず、具体的には例えば機械加工によってバリを削り取る方法が考えられる。しかしながら、削り取る場合には、その破片が軸受スリーブの内周面に入り込んだり、あるいは加工時の加圧力でバリ発生部周辺の寸法精度が崩れる等の不具合の発生が懸念される。
【0013】
そこで、本発明では、型成形に伴って形成されたバリを、ハウジング表面に溶着した。このようにバリを除去するのではなく、ハウジング表面に溶着することで、バリの脱落を確実に防止することができ、その一方で、機械加工のようにバリの加工に際して破片が発生することはないので、その軸受スリーブ内周への侵入を確実に防止することができる。また、熱溶着に際しては、機械加工のようにバリ発生部に高い加圧力が作用することもなく、また、仮に変形したとしても、熱溶着用の治具でその変形部分を寸法矯正することもできるので、この部分を高精度に成形することができる。以上から、バリの発生に由来する軸受性能の低下を確実に防止し、高い軸受性能を確保することができる。
【0014】
上記の溶着は、樹脂のガラス転位点以上、融点温度以下の温度で行うのが望ましい。
【0015】
ハウジングは、その一端に、軸部材の外周面との間でシール空間を形成するシール部を有するものとすることができる。このシール部は、インサート成形によってハウジングと一体形成することができる。
【0016】
図2は、シール部7aを有するハウジング7をインサート成形するための射出成形装置の一例を示すものである。図示のように、この装置は、可動型10と固定型20とを備え、一方の型、例えば可動型10は、円筒状の軸部11とその外周に嵌合した外周部16とで構成される。軸受スリーブ8の周囲のキャビティ30にゲート部31から溶融樹脂を射出してキャビティ30に充填し、樹脂が硬化したところで、先ず、可動型10の軸部11を軸受スリーブ8の内周から抜き、さらに外周部16を固定型20から離反させて型開きすれば、軸受スリーブ8を樹脂でモールドしたシール部7a付のハウジング7が得られる。
【0017】
この射出成形装置において、シール部7aの内周面7a2は、シール部7aの内周に挿入した軸部11(詳しくはシール成形部13)の外周面で成形することができる。バリは、主として型同士の摺動部位に形成されるので、型開き時に互いに摺動する、軸部11の外周面とその外周に嵌合した型(図示例では外周部16)の内周面との間の摺動部A、すなわちシール部7aの内周面7a2の軸方向延長方向にバリが形成されることとなる。この場合、図3に示すように、シール部7aの内周に溶着治具40を挿入してハウジング7の端面7dに押し付けることにより、バリ41が軟化・屈曲してハウジング7の端面7dと一体化され(溶着)(図4(a)(b)参照)、バリ41の突出部分が消滅する。従って、上述したバリの発生に由来する不具合を確実に防止することができる。
【0018】
このようにシール部を一体に有するハウジングをインサート成形する場合、バリが、シール部の内周面よりも外径側に形成されるものであるのが望ましい。これにより、溶着に伴う変形でシール部の寸法精度が狂う事態を防止することができると共に、溶着時にバリが脱落して軸受スリーブ内周面に入り込む危険性を回避することができる。
【0019】
流体軸受装置の用途に応じ、ラジアル軸受部は、軸受隙間内の潤滑油の動圧作用で圧力を発生させる動圧軸受で構成することもできる。
【0020】
【発明の実施の形態】
以下、本発明の実施形態について説明する。
【0021】
図1は、この実施形態に係る流体軸受装置(流体動圧軸受装置)1を示している。この流体軸受装置1は、例えば、HDD等のディスク装置のスピンドルモータやレーザビームプリンタ(LBP)のポリゴンスキャナモータに組込まれるもので、ハウジング7と、軸受スリーブ8と、軸部材2とを構成部品して構成される。
【0022】
軸受スリーブ8の内周面8aと軸部材2の外周面2aとの間に第1ラジアル軸受部R1と第2ラジアル軸受部R2とが軸方向に離隔して設けられる。また、軸部材2の下側端面2bとハウジング7の底部7cの内底面7c1との間にスラスト軸受部Tが設けられる。尚、説明の便宜上、スラスト軸受部Tの側を下側、スラストTと反対の側を上側として説明を進める。
【0023】
軸部材2は、例えば、ステンレス鋼等の金属材で形成され、その下側端面2bは凸球状に形成される。
【0024】
軸受スリーブ8は、焼結金属からなる多孔質体で円筒状に形成される。焼結金属としては、例えば、銅、鉄、及びアルミニウムの中から選択される1種以上の金属粉末、若しくは銅被覆鉄粉などの被覆処理を施した金属粉末や合金粉末を主原料とし、必要に応じて、すず、亜鉛、鉛、黒鉛、二硫化モリブデン等の粉末又はこれらの合金粉末を混合し、成形し、焼結して得られたものを用いることができる。このような焼結金属は、内部に多数の気孔(内部組織としての気孔)を備えていると共に、これら気孔が外表面に通じて形成される多数の開孔を備えている。この焼結金属は、潤滑油や潤滑グリースを含浸させた含油焼結金属として用いられる。なお、焼結金属に限らず、軟質金属等の他の金属材料で軸受スリーブ8を形成することも可能である。
【0025】
軸受スリーブ8の内周面8aには、第1ラジアル軸受部R1と第2ラジアル軸受部R2のラジアル軸受面となる上下2つの領域が軸方向に離隔して設けられ、該2つの領域には、動圧発生手段として、例えばヘリングボーン形状の動圧溝がそれぞれ形成される。尚、動圧発生手段として、スパイラル形状や軸方向の溝を形成したり、あるいは三円弧軸受等を採用しても良い。また、軸受スリーブ8の内周上端側部分には面取り部8dが形成され、内周下端側部分には面取り部8fが形成されている。
【0026】
ハウジング7は、後述のように、上記軸受スリーブ8をインサート部品として、66ナイロン等の樹脂を射出成形(インサート成形)して形成される。このハウジング7は、一端を開口すると共に、他端を閉じた有底筒状で、円筒状の側部7bと、側部7bの上端から内径側に一体に延びた環状のシール部7aと、側部7bの下端と一体に連続した底部7cとを備えている。シール部7aの内周面7a2は、軸部材2の外周面2aと所定のシール空間Sを介して対向する。尚、この実施形態では、シール部7aの内周面7a2と対向してシール空間Sを形成する軸部材2の外周面2aを、上方(ハウジング7の外方向)に向かって漸次縮径するテーパ形状に形成している。軸部材2の回転時、テーパ形状の外周面2aは、いわゆる遠心力シールとしても機能する。シール空間Sは、このようなテーパ状の空間とする他、軸方向で同径の円筒状に形成することもできる。
【0027】
図2は、ハウジング7をインサート成形するための射出成形装置を概念的に示している。この射出成形装置は、可動型10と固定型20とを有する。
【0028】
可動型10または固定型20の何れか一方、例えば可動型10は、円形断面の軸部11とその外周に嵌合された外周部16とを有する。軸部11は、軸受スリーブ8の内周面8aに嵌合される嵌合部12と、ハウジング7のシール部7aの内周面7a2を成形するシール成形部13とを有し、シール成形部13の外径寸法は嵌合部12の外形寸法よりも大きい。嵌合部12とシール成形部13との境界には、テーパ状の当接部14が形成される。この当接部14が、軸受スリーブ8の内周上端側部分に形成された面取り部8dと当接することにより、キャビティ30内における軸受スリーブ8の位置決めが行われる。
【0029】
固定型20は、中空円筒状の成形部21を有するもので、可動型10との同軸状態を維持しつつ、その衝合面22を可動型10の衝合面15と衝合させることにより、軸受スリーブ8の周囲にキャビティ30が形成される。このキャビティ30にゲート31から溶融樹脂を射出してキャビティ30に充填し、その後、樹脂が硬化したところで型開きを行えば、軸受スリーブ8を樹脂でモールドしたハウジング7が得られる。型開きは、例えば、先ず可動型10の軸部11を軸受スリーブ8の内周から抜き、次いで可動型10の外周部16を固定型20から離反させることにより行われる。
【0030】
ハウジング7と軸受スリーブ8とは、上記のインサート成形により、別段の固定工程を経ることなく、相互に固定される。図1に示すように、ハウジング7の内部において、シール部7aの内側面7a1と軸受スリーブ8の上側端面8b、側部7bの内周面7b1と軸受スリーブ8の外周面8g、底部7cの内底面7c1と軸受スリーブ8の下側端面8cおよび内周下端側部分の面取り部8fがそれぞれ密着している。尚、軸受スリーブ8の内周面8aや内周上端側部分の面取り部8dは樹脂に覆われていない。
【0031】
この実施形態の動圧軸受装置1は、インサート成形により相互に固定されたハウジング7および軸受スリーブ8に対して、軸部材2を装着することによって組立ることができる。すなわち、軸部材2を軸受スリーブ8の内周面8aに挿入して、その下側端面2bをハウジング7の内底面7c1に接触させる。そして、例えば真空引きの状態で、シール部7aで密封されたハウジング7の内部に潤滑油を注油し、軸受隙間等のハウジング内部空間を油で満たすと共に、軸受スリーブ8の気孔に油を含浸させる。
【0032】
軸部材2の回転時、軸受スリーブ8の内周面8aのラジアル軸受面となる領域(上下2箇所の領域)は、それぞれ、軸部材2の外周面2aとラジアル軸受隙間を介して対向する。そして、軸部材2の回転に伴い、上記ラジアル軸受隙間に潤滑油の動圧作用が発生し、軸部材2が上記ラジアル軸受隙間内に形成される潤滑油の油膜によってラジアル方向に回転自在に非接触支持される。これにより、軸部材2をラジアル方向に回転自在に非接触支持する第1ラジアル軸受部R1と第2ラジアル軸受部R2とが構成される。同時に、軸部材2の下側端面2bがハウジング7の内底面7c1によって接触支持される。これにより、軸部材2をスラスト方向に回転自在に支持するスラスト軸受部Tが構成される。
【0033】
上述のようにインサート成形の際、可動型10では、軸部11と外周部16との間で摺動が生じる。この摺動部Aには、キャビティ30への樹脂の充填に伴って溶融樹脂が入り込み、図4(a)に示すように、固化後はこの部分が軸方向に突出するバリ41となる。このバリ41は、ハウジング7の上端面7dの内周縁部Pに沿って形成される(バリ41の長さ・大きさ等は誇張して描いている)。
【0034】
このバリ41は、ハウジング7の表面(本実施形態では上端面7d)に溶着される。溶着は、図3に示すように、ハウジング7の上端開口部(図面では上下が図1と逆になっている)の内周に溶着治具40を挿入することにより行われる。溶着治具40は、ハウジング7のシール部7aの内周面7a2に嵌合する小径部40aと、これよりも大径に形成され、端面をハウジング7の上端面7dと係合させた大径部40bとを備える。この治具40を加熱してハウジング7の上端開口部に押込むことにより、同図(b)に示すようにバリ41が軟化屈曲して外径側に折り曲がった状態でハウジング7の上端面7dに溶着され(符号41’で示す)、これによりバリ41による軸方向の突出部が消滅する。
【0035】
このバリ41の溶着に際しては、機械加工のようにバリの破片が発生することはない。従って、バリやその破片の軸受スリーブ8内周(ラジアル軸受隙間)への侵入を確実に防止することができる。また、熱溶着用の治具40がバリ41の発生部P周辺、本実施形態であればハウジング7の上端面7dやシール部内周面7a2を寸法矯正するので、これらの部分の精度を高めることができる。以上から、本発明によれば、バリの発生に起因した軸受性能の低下を確実に防止し、高い軸受性能を確保することができる。
【0036】
上述のように熱溶着に際しては、溶着治具40を加熱するが、その時の溶着温度は、ハウジング7の素材樹脂のガラス転位点以上で融点以下の温度とする。ガラス転位点温度よりも小さいとバリ41を軟化させることができず、融点を超えると溶着治具40との接触部の樹脂が溶融状態となり、却って精度低下を招く。例えば、ハウジング7を66ナイロンで成形する場合、そのガラス転位点は80℃であり、融点は200℃であるから、溶着はその間の温度(80〜200℃)で行う。
【0037】
ところで、バリの溶着時における異物の軸受スリーブ8内周への侵入やシール部7aの寸法劣化を防止するためには、バリ41の発生部Pができるだけシール部内周面7a2よりも外径側に存在しているのが好ましい。図5は、これを実現するための手段の一例を示すもので、可動型10の軸部11’と外周型16’の摺動部A’が、ハウジング7のシール部内周面7a2よりも外径側に位置するように金型構造を変更したものである。具体的には、軸部11’のシール成形部13に隣接してこれよりも大径の大径部18を形成し、大径部18の端面18aをハウジング上端面7dに接触させると共に、大径部18の外周に内型10の外周部16’を嵌合したものである。この場合、大径部18の外周面と外周部16の内周面との間が摺動部A’となり、その延長線上のハウジング上端面7dにバリの発生部P’が形成される。
【0038】
以上の説明では、スラスト軸受部Tとして、軸部材2の端部を接触支持するピボット軸受を例示しているが、この軸受部Tとしては、ラジアル軸受部R1、R2と同様に、動圧溝等の動圧発生手段で軸受隙間に生じた潤滑油の動圧効果により圧力を発生させて軸部材2をスラスト方向で非接触支持する動圧軸受を使用することもできる。
【0039】
また、本発明は、ラジアル軸受部R1、R2の何れか一方または双方をいわゆる真円軸受で構成した流体軸受装置にも同様に適用可能である。
【0040】
【発明の効果】
本発明によれば、コンパクトで部品点数が少なく、より一層低コストで、且つ信頼性の高い流体軸受装置を提供することができる。
【0041】
また、ハウジングのインサート成形に伴って形成されるバリをハウジング表面に溶着しているので、バリの破片が軸受スリーブの内周面に入り込んだり、あるいはバリ発生部の寸法精度が低下する等の不具合を回避することができる。
【図面の簡単な説明】
【図1】本発明にかかる流体軸受装置を示す断面図である。
【図2】ハウジングを射出成形するための射出成形装置を概念的に示す断面図である。
【図3】バリの溶着工程を示す断面図である。
【図4】図4(a)は溶着前のバリを概念的に示す拡大断面図、同図(b)は、溶着後の状態を概念的に示す拡大断面図である。
【図5】射出成形装置の他の実施形態を示す断面図である。
【符号の説明】
1  流体軸受装置
2  軸部材
7  ハウジング
7a シール部
7a2 内周面
7b 側部
7c 底部
8  軸受スリーブ
8a 内周面
40 熱溶着治具
41 バリ
P、P’ バリ発生部
A、A’ 摺動部
R1 第1ラジアル軸受部
R2 第2ラジアル軸受部
S  シール空間
T  スラスト軸受部
[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hydrodynamic bearing device that supports a rotating member in a non-contact manner by an oil film of lubricating oil generated in a radial bearing gap. This bearing device is a spindle for information equipment, for example, a magnetic disk device such as an HDD or FDD, an optical disk device such as a CD-ROM, a CD-R / RW, a DVD-ROM / RAM, or a magneto-optical disk device such as an MD or MO. It is suitable for a motor, a polygon scanner motor of a laser beam printer (LBP), or a small motor such as an electric device such as an axial fan.
[0002]
[Prior art]
The above various motors are required to have high speed, low cost, low noise, etc. in addition to high rotational accuracy. One of the components that determine the required performance is a bearing that supports the spindle of the motor.In recent years, the use of a fluid bearing having characteristics excellent in the required performance has been studied or actually used. .
[0003]
Fluid bearings of this type include a so-called dynamic pressure bearing having a dynamic pressure generating means for generating dynamic pressure in lubricating oil in a bearing gap, and a so-called circular bearing without a dynamic pressure generating means (the bearing surface is a perfect circle). Bearings).
[0004]
For example, in a fluid bearing device incorporated in a spindle motor of a disk device such as an HDD or a polygon scanner motor of a laser beam printer (LBP), a radial bearing portion that rotatably supports a shaft member in a radial direction in a non-contact manner, and a shaft member A thrust bearing portion rotatably supported in the thrust direction is provided, and a dynamic pressure generating groove (dynamic pressure groove) is provided as a radial bearing portion on the inner peripheral surface of the bearing sleeve or the outer peripheral surface of the shaft member. Bearings are used. As the thrust bearing portion, for example, a bearing (a so-called pivot bearing) having a structure in which one end surface of a shaft member is supported in contact with a thrust plate is used. Normally, the bearing sleeve is fixed at a predetermined position on the inner circumference of the housing, and a seal member may be provided at the opening of the housing to prevent the lubricating oil injected into the internal space of the housing from leaking outside. Many (see, for example, Patent Document 1).
[0005]
[Patent Document 1]
JP-A-11-191945 [0006]
[Problems to be solved by the invention]
The hydrodynamic bearing device having the above configuration is composed of many parts such as a housing, a bearing sleeve, a shaft member, a thrust plate, and a seal member, and secures a high bearing performance required as information devices become more and more sophisticated. Efforts have been made to increase the processing accuracy and assembly accuracy of each part. On the other hand, with the trend toward lower price and smaller size of information equipment, demands for cost reduction of this type of hydrodynamic bearing device are becoming more and more severe.
[0007]
In addition, in this type of hydrodynamic bearing device, it is necessary to strictly control the accuracy of the bearing gap in order to ensure the bearing performance, and it is necessary to minimize the entry of foreign matter into the bearing gap.
[0008]
Therefore, an object of the present invention is to provide a hydrodynamic bearing device which has a small number of parts, is low in cost, has high reliability, and can reliably prevent foreign substances from being mixed into a bearing gap.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, a fluid bearing device according to the present invention includes a resin housing, a bearing sleeve provided inside the housing, a shaft member inserted into an inner peripheral surface of the bearing sleeve, and a bearing sleeve. A radial bearing portion that is provided between the inner peripheral surface and the outer peripheral surface of the shaft member and that non-contactly supports the shaft member in a radial direction with an oil film of lubricating oil generated in a bearing gap; and It is formed by molding a resin as an insert part, and burrs formed along with the molding are welded to the surface of the housing.
[0010]
By forming the housing by resin molding (insert molding) with the bearing sleeve as an insert part, the manufacturing cost of the housing can be reduced as compared with the case where the housing is formed of a metal material. When the fluid bearing device is provided with a thrust bearing portion for supporting the shaft member in the thrust direction, the thrust bearing portion may have a structure in which one end surface of the shaft member is directly supported by the bottom of the housing. Therefore, the thrust plate conventionally provided in this type of hydrodynamic bearing device becomes unnecessary, and the number of parts can be reduced. Further, since the operation of assembling the bearing sleeve to the housing is unnecessary, the assembly cost is reduced.
[0011]
Meanwhile, burrs are formed on the surface of the molded product after the insert molding by solidifying the molten resin that has entered the gap between the dies. If the burrs are left unattended, if the burrs fall off for some reason, they may enter the inner peripheral surface of the bearing sleeve and seriously affect bearing performance. Therefore, it is necessary to prevent such burrs from being prevented from being generated, or to remove the burrs by some method after demolding.
[0012]
However, it is difficult to completely prevent generation of burrs in insert molding. Therefore, the latter method must be taken as the above-described countermeasure against burrs. Specifically, a method of removing burrs by, for example, mechanical processing can be considered. However, in the case of shaving, there is a concern that a debris may enter the inner peripheral surface of the bearing sleeve, or a dimensional accuracy around the burr generating portion may be lost due to a pressing force at the time of working.
[0013]
Therefore, in the present invention, burrs formed during the molding are welded to the housing surface. Instead of removing burrs in this way, by welding to the surface of the housing, it is possible to reliably prevent the burrs from falling off.On the other hand, debris is not generated when processing burrs like machining. Therefore, it is possible to reliably prevent the bearing sleeve from entering the inner periphery. Also, at the time of heat welding, a high pressing force does not act on the burr generating portion unlike machining, and even if it is deformed, it is also possible to correct the dimension of the deformed portion with a jig for heat welding. Therefore, this part can be molded with high precision. As described above, it is possible to reliably prevent a decrease in bearing performance due to the occurrence of burrs, and to ensure high bearing performance.
[0014]
The above-mentioned welding is desirably performed at a temperature equal to or higher than the glass transition point of the resin and equal to or lower than the melting point temperature.
[0015]
The housing may have, at one end, a seal portion that forms a seal space with the outer peripheral surface of the shaft member. This seal portion can be formed integrally with the housing by insert molding.
[0016]
FIG. 2 shows an example of an injection molding apparatus for insert-molding the housing 7 having the seal portion 7a. As shown in the drawing, the apparatus includes a movable mold 10 and a fixed mold 20. One mold, for example, the movable mold 10 is configured by a cylindrical shaft portion 11 and an outer peripheral portion 16 fitted on the outer periphery thereof. You. The molten resin is injected from the gate portion 31 into the cavity 30 around the bearing sleeve 8 to fill the cavity 30, and when the resin is cured, first, the shaft portion 11 of the movable mold 10 is pulled out from the inner periphery of the bearing sleeve 8, Further, when the outer peripheral portion 16 is separated from the fixed mold 20 and opened, the housing 7 with the seal portion 7a in which the bearing sleeve 8 is molded with resin is obtained.
[0017]
In this injection molding apparatus, the inner peripheral surface 7a2 of the seal portion 7a can be molded on the outer peripheral surface of the shaft portion 11 (specifically, the seal molding portion 13) inserted into the inner periphery of the seal portion 7a. Since the burrs are formed mainly at the sliding portions of the dies, the burrs slide on each other when the dies are opened, and the inner peripheral surface of the outer peripheral surface of the shaft portion 11 and the outer peripheral portion 16 fitted in the outer periphery thereof (in the illustrated example, the outer peripheral portion 16). Is formed in the axial direction of the sliding portion A, that is, the inner peripheral surface 7a2 of the seal portion 7a. In this case, as shown in FIG. 3, the welding jig 40 is inserted into the inner periphery of the seal portion 7a and pressed against the end surface 7d of the housing 7, so that the burr 41 is softened and bent to be integrated with the end surface 7d of the housing 7. (Welding) (see FIGS. 4A and 4B), and the protruding portion of the burr 41 disappears. Therefore, it is possible to surely prevent the above-mentioned problems caused by the occurrence of burrs.
[0018]
When insert-molding a housing integrally having a seal portion as described above, it is preferable that the burr is formed on the outer diameter side of the inner peripheral surface of the seal portion. Thereby, it is possible to prevent a situation in which the dimensional accuracy of the seal portion is degraded due to deformation due to welding, and it is possible to avoid a risk that burrs fall off during welding and enter the inner peripheral surface of the bearing sleeve.
[0019]
Depending on the application of the fluid dynamic bearing device, the radial bearing portion may be constituted by a dynamic pressure bearing that generates pressure by dynamic pressure action of lubricating oil in a bearing gap.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0021]
FIG. 1 shows a hydrodynamic bearing device (fluid dynamic bearing device) 1 according to this embodiment. The hydrodynamic bearing device 1 is incorporated in, for example, a spindle motor of a disk device such as an HDD or a polygon scanner motor of a laser beam printer (LBP), and includes a housing 7, a bearing sleeve 8, and a shaft member 2. It is composed.
[0022]
A first radial bearing portion R1 and a second radial bearing portion R2 are provided between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a of the shaft member 2 so as to be separated in the axial direction. A thrust bearing portion T is provided between the lower end surface 2b of the shaft member 2 and the inner bottom surface 7c1 of the bottom 7c of the housing 7. For convenience of description, the description will be made with the side of the thrust bearing portion T being the lower side and the side opposite to the thrust T being the upper side.
[0023]
The shaft member 2 is formed of, for example, a metal material such as stainless steel, and its lower end surface 2b is formed in a convex spherical shape.
[0024]
The bearing sleeve 8 is formed in a cylindrical shape with a porous body made of a sintered metal. As the sintered metal, for example, one or more metal powders selected from copper, iron, and aluminum, or metal powder or alloy powder that has been subjected to a coating treatment such as copper-coated iron powder as a main raw material, According to the above, a powder obtained by mixing, molding, and sintering a powder of tin, zinc, lead, graphite, molybdenum disulfide or the like, or an alloy powder thereof can be used. Such a sintered metal has a large number of pores (pores as an internal structure) inside, and also has a large number of openings formed through these pores to the outer surface. This sintered metal is used as an oil-impregnated sintered metal impregnated with lubricating oil or lubricating grease. The bearing sleeve 8 can be formed of not only a sintered metal but also another metal material such as a soft metal.
[0025]
On the inner peripheral surface 8a of the bearing sleeve 8, two upper and lower regions serving as radial bearing surfaces of a first radial bearing portion R1 and a second radial bearing portion R2 are provided axially separated from each other. As the dynamic pressure generating means, for example, a herringbone-shaped dynamic pressure groove is formed. As the dynamic pressure generating means, a spiral shape or an axial groove may be formed, or a three-arc bearing may be used. Further, a chamfered portion 8d is formed on the inner peripheral upper end portion of the bearing sleeve 8, and a chamfered portion 8f is formed on the inner peripheral lower end portion.
[0026]
The housing 7 is formed by injection molding (insert molding) a resin such as nylon 66 using the bearing sleeve 8 as an insert part, as described later. The housing 7 has a bottomed cylindrical shape having one end opened and the other end closed, a cylindrical side portion 7b, and an annular seal portion 7a integrally extending from the upper end of the side portion 7b to the inner diameter side. It has a bottom part 7c which is continuous with the lower end of the side part 7b. The inner peripheral surface 7a2 of the seal portion 7a faces the outer peripheral surface 2a of the shaft member 2 via a predetermined seal space S. In this embodiment, the outer peripheral surface 2a of the shaft member 2, which faces the inner peripheral surface 7a2 of the seal portion 7a and forms the seal space S, is tapered so as to gradually reduce its diameter upward (outward of the housing 7). It is formed in a shape. When the shaft member 2 rotates, the tapered outer peripheral surface 2a also functions as a so-called centrifugal seal. The seal space S may be formed in a cylindrical shape having the same diameter in the axial direction, in addition to the tapered space.
[0027]
FIG. 2 conceptually shows an injection molding apparatus for insert-molding the housing 7. This injection molding apparatus has a movable mold 10 and a fixed mold 20.
[0028]
Either the movable mold 10 or the fixed mold 20, for example, the movable mold 10 has a shaft portion 11 having a circular cross section and an outer peripheral portion 16 fitted around the shaft portion 11. The shaft portion 11 has a fitting portion 12 fitted to the inner peripheral surface 8a of the bearing sleeve 8, and a seal molding portion 13 for molding the inner peripheral surface 7a2 of the seal portion 7a of the housing 7. The outer diameter of 13 is larger than the outer dimension of the fitting portion 12. A tapered contact portion 14 is formed at the boundary between the fitting portion 12 and the seal forming portion 13. The contact portion 14 comes into contact with a chamfered portion 8 d formed on the inner peripheral upper end portion of the bearing sleeve 8, thereby positioning the bearing sleeve 8 in the cavity 30.
[0029]
The fixed mold 20 has a hollow cylindrical molded part 21, and by maintaining its coaxial state with the movable mold 10, the abutment surface 22 abuts against the abutment surface 15 of the movable mold 10, A cavity 30 is formed around the bearing sleeve 8. A molten resin is injected into the cavity 30 from the gate 31 to fill the cavity 30, and then, when the resin is cured, the mold is opened to obtain the housing 7 in which the bearing sleeve 8 is molded with the resin. The mold opening is performed, for example, by first removing the shaft portion 11 of the movable mold 10 from the inner periphery of the bearing sleeve 8 and then separating the outer peripheral portion 16 of the movable mold 10 from the fixed mold 20.
[0030]
The housing 7 and the bearing sleeve 8 are mutually fixed by the above-mentioned insert molding without going through a separate fixing step. As shown in FIG. 1, inside the housing 7, the inner surface 7 a 1 of the seal portion 7 a and the upper end surface 8 b of the bearing sleeve 8, the inner peripheral surface 7 b 1 of the side portion 7 b, the outer peripheral surface 8 g of the bearing sleeve 8, and the bottom 7 c The bottom surface 7c1, the lower end surface 8c of the bearing sleeve 8, and the chamfered portion 8f of the inner peripheral lower end portion are in close contact with each other. Note that the inner peripheral surface 8a of the bearing sleeve 8 and the chamfered portion 8d on the inner peripheral upper end side are not covered with the resin.
[0031]
The dynamic pressure bearing device 1 of this embodiment can be assembled by mounting the shaft member 2 to the housing 7 and the bearing sleeve 8 fixed to each other by insert molding. That is, the shaft member 2 is inserted into the inner peripheral surface 8a of the bearing sleeve 8, and the lower end surface 2b is brought into contact with the inner bottom surface 7c1 of the housing 7. Then, for example, in a state of vacuum evacuation, lubricating oil is injected into the inside of the housing 7 sealed by the seal portion 7a, and the space inside the housing such as a bearing gap is filled with oil, and the pores of the bearing sleeve 8 are impregnated with oil. .
[0032]
When the shaft member 2 rotates, regions (two upper and lower regions) of the inner peripheral surface 8a of the bearing sleeve 8 to be radial bearing surfaces respectively oppose the outer peripheral surface 2a of the shaft member 2 via the radial bearing gap. Then, with the rotation of the shaft member 2, a dynamic pressure action of the lubricating oil is generated in the radial bearing gap, and the shaft member 2 is non-rotatably rotatable in the radial direction by an oil film of the lubricating oil formed in the radial bearing gap. Contact supported. Thus, a first radial bearing portion R1 and a second radial bearing portion R2 that rotatably support the shaft member 2 in the radial direction in a non-contact manner are configured. At the same time, the lower end surface 2b of the shaft member 2 is contacted and supported by the inner bottom surface 7c1 of the housing 7. Thus, a thrust bearing portion T that rotatably supports the shaft member 2 in the thrust direction is configured.
[0033]
As described above, in the movable mold 10, sliding occurs between the shaft portion 11 and the outer peripheral portion 16 during insert molding. The molten resin enters the sliding portion A with the filling of the resin into the cavity 30, and as shown in FIG. 4A, after solidification, this portion becomes a burr 41 projecting in the axial direction. The burr 41 is formed along the inner peripheral edge P of the upper end surface 7d of the housing 7 (the length, size, and the like of the burr 41 are exaggerated).
[0034]
The burr 41 is welded to the surface of the housing 7 (the upper end surface 7d in the present embodiment). As shown in FIG. 3, the welding is performed by inserting a welding jig 40 into the inner periphery of the upper end opening of the housing 7 (the upper and lower sides are inverted in FIG. 1 in the drawing). The welding jig 40 has a small-diameter portion 40a fitted to the inner peripheral surface 7a2 of the seal portion 7a of the housing 7, and a large-diameter portion formed with a larger diameter than the small-diameter portion 40a. Unit 40b. By heating the jig 40 and pushing it into the upper end opening of the housing 7, the burr 41 is softened and bent as shown in FIG. 7d (denoted by reference numeral 41 '), whereby the axial projection of the burr 41 disappears.
[0035]
When welding the burrs 41, no burrs are generated as in the case of machining. Therefore, it is possible to reliably prevent the burrs and their debris from entering the inner periphery of the bearing sleeve 8 (radial bearing gap). In addition, since the jig 40 for heat welding corrects the size of the vicinity of the generation portion P of the burr 41, in this embodiment, the upper end surface 7d of the housing 7 and the inner peripheral surface 7a2 of the seal portion, the accuracy of these portions can be improved. Can be. As described above, according to the present invention, it is possible to reliably prevent a decrease in bearing performance due to the occurrence of burrs, and to ensure high bearing performance.
[0036]
As described above, during the heat welding, the welding jig 40 is heated, and the welding temperature at that time is set to a temperature equal to or higher than the glass transition point of the material resin of the housing 7 and equal to or lower than the melting point. If the temperature is lower than the glass transition point temperature, the burr 41 cannot be softened. If the temperature exceeds the melting point, the resin at the contact portion with the welding jig 40 is in a molten state, and the accuracy is rather lowered. For example, when the housing 7 is molded from 66 nylon, the glass transition point is 80 ° C. and the melting point is 200 ° C., so that the welding is performed at the temperature (80 to 200 ° C.) therebetween.
[0037]
By the way, in order to prevent intrusion of foreign matter into the inner periphery of the bearing sleeve 8 and deterioration of the size of the seal portion 7a during welding of the burr, the generation portion P of the burr 41 should be as far as possible outside the seal portion inner peripheral surface 7a2. Preferably it is present. FIG. 5 shows an example of a means for achieving this, in which the shaft portion 11 'of the movable die 10 and the sliding portion A' of the outer peripheral die 16 'are located outside the inner peripheral surface 7a2 of the seal portion of the housing 7. The mold structure is changed so as to be located on the radial side. Specifically, a large-diameter portion 18 having a larger diameter than the seal forming portion 13 of the shaft portion 11 'is formed, and the end surface 18a of the large-diameter portion 18 is brought into contact with the housing upper end surface 7d. The outer periphery 16 ′ of the inner mold 10 is fitted to the outer periphery of the diameter portion 18. In this case, a portion between the outer peripheral surface of the large-diameter portion 18 and the inner peripheral surface of the outer peripheral portion 16 serves as a sliding portion A ′, and a burr generation portion P ′ is formed on an upper end surface 7 d of the housing on an extension thereof.
[0038]
In the above description, as the thrust bearing portion T, a pivot bearing that contacts and supports the end of the shaft member 2 is exemplified. However, as this bearing portion T, as in the case of the radial bearing portions R1 and R2, a dynamic pressure groove is used. It is also possible to use a dynamic pressure bearing that generates the pressure by the dynamic pressure effect of the lubricating oil generated in the bearing gap by a dynamic pressure generating means such as the above and supports the shaft member 2 in a non-contact manner in the thrust direction.
[0039]
In addition, the present invention can be similarly applied to a fluid bearing device in which one or both of the radial bearing portions R1 and R2 are configured as so-called perfect bearings.
[0040]
【The invention's effect】
According to the present invention, it is possible to provide a highly reliable hydrodynamic bearing device that is compact, has a small number of parts, is even lower in cost.
[0041]
In addition, since burrs formed during insert molding of the housing are welded to the surface of the housing, debris of the burrs may enter the inner peripheral surface of the bearing sleeve, or the dimensional accuracy of the burrs may be reduced. Can be avoided.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a hydrodynamic bearing device according to the present invention.
FIG. 2 is a sectional view conceptually showing an injection molding apparatus for injection molding a housing.
FIG. 3 is a cross-sectional view showing a step of welding burrs.
FIG. 4 (a) is an enlarged sectional view conceptually showing a burr before welding, and FIG. 4 (b) is an enlarged sectional view conceptually showing a state after welding.
FIG. 5 is a sectional view showing another embodiment of the injection molding apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fluid bearing device 2 Shaft member 7 Housing 7a Seal part 7a2 Inner peripheral surface 7b Side part 7c Bottom part 8 Bearing sleeve 8a Inner peripheral surface 40 Heat welding jig 41 Burrs P, P 'Burrs generating part A, A' Sliding part R1 First radial bearing portion R2 Second radial bearing portion S Seal space T Thrust bearing portion

Claims (6)

樹脂製のハウジングと、ハウジングの内部に設けられた軸受スリーブと、軸受スリーブの内周面に挿入された軸部材と、軸受スリーブの内周面と軸部材の外周面との間に設けられ、軸受隙間に生じる潤滑油の油膜で軸部材をラジアル方向で非接触支持するラジアル軸受部とを少なくとも備え、
前記ハウジングが、軸受スリーブをインサート部品とする樹脂の型成形で形成され、
かつこの型成形に伴って形成されたバリをハウジング表面に溶着したことを特徴とする流体軸受装置。
A housing made of resin, a bearing sleeve provided inside the housing, a shaft member inserted into the inner peripheral surface of the bearing sleeve, and provided between the inner peripheral surface of the bearing sleeve and the outer peripheral surface of the shaft member, A radial bearing portion for supporting the shaft member in a radial direction in a non-contact manner with an oil film of lubricating oil generated in the bearing gap,
The housing is formed by resin molding using a bearing sleeve as an insert part,
And a burr formed by the molding is welded to a surface of the housing.
樹脂のガラス転位点以上、融点温度以下で溶着した請求項1記載の流体軸受装置。The hydrodynamic bearing device according to claim 1, wherein the resin is welded at a temperature equal to or higher than the glass transition point of the resin and equal to or lower than the melting point temperature. ハウジングが、その一端に、軸部材の外周面との間でシール空間を形成するシール部を有する請求項1または2記載の流体軸受装置。3. The hydrodynamic bearing device according to claim 1, wherein the housing has at one end a seal portion that forms a seal space with an outer peripheral surface of the shaft member. 樹脂製バリが、シール部の内周面よりも外径側に形成されるものである請求項3記載の流体軸受装置。4. The hydrodynamic bearing device according to claim 3, wherein the resin burr is formed on an outer diameter side of the inner peripheral surface of the seal portion. ラジアル軸受部が、軸受隙間内の潤滑油の動圧作用で圧力を発生させる動圧軸受である請求項1〜4何れか記載の流体軸受装置。The fluid bearing device according to any one of claims 1 to 4, wherein the radial bearing portion is a dynamic pressure bearing that generates pressure by a dynamic pressure action of lubricating oil in a bearing gap. 樹脂製のハウジングと、ハウジングの内部に設けられた軸受スリーブと、軸受スリーブの内周面に挿入された軸部材と、軸受スリーブの内周面と軸部材の外周面との間に設けられ、軸受隙間に生じる潤滑油の油膜で軸部材をラジアル方向で非接触支持するラジアル軸受部とを少なくとも備える流体軸受装置を製造するための方法であって、
ハウジングを、軸受スリーブをインサート部品とする樹脂の型成形で形成し、型成形に伴って形成されたバリを、ハウジング表面に溶着することを特徴とする流体軸受装置の製造方法。
A housing made of resin, a bearing sleeve provided inside the housing, a shaft member inserted into the inner peripheral surface of the bearing sleeve, and provided between the inner peripheral surface of the bearing sleeve and the outer peripheral surface of the shaft member, A method for manufacturing a fluid bearing device including at least a radial bearing portion that supports a shaft member in a radial direction in a non-contact manner with an oil film of lubricating oil generated in a bearing gap,
A method for manufacturing a hydrodynamic bearing device, wherein a housing is formed by molding a resin having a bearing sleeve as an insert part, and burrs formed during the molding are welded to a surface of the housing.
JP2002295249A 2002-10-08 2002-10-08 Hydrodynamic bearing device and manufacturing method thereof Expired - Fee Related JP4152712B2 (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007102312A1 (en) * 2006-03-06 2007-09-13 Ntn Corporation Fluid bearing device
JP2007239794A (en) * 2006-03-06 2007-09-20 Ntn Corp Fluid bearing device
JP2007263169A (en) * 2006-03-27 2007-10-11 Ntn Corp Fluid bearing device
US8215843B2 (en) 2006-03-24 2012-07-10 Ntn Corporation Fluid dynamic bearing device

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007102312A1 (en) * 2006-03-06 2007-09-13 Ntn Corporation Fluid bearing device
JP2007239794A (en) * 2006-03-06 2007-09-20 Ntn Corp Fluid bearing device
US8092090B2 (en) 2006-03-06 2012-01-10 Ntn Corporation Fluid dynamic bearing device
US8215843B2 (en) 2006-03-24 2012-07-10 Ntn Corporation Fluid dynamic bearing device
US8562219B2 (en) 2006-03-24 2013-10-22 Ntn Corporation Fluid dynamic bearing device
JP2007263169A (en) * 2006-03-27 2007-10-11 Ntn Corp Fluid bearing device

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