JP4074703B2 - Sintered oil-impregnated bearing unit - Google Patents

Description

（式中、Ｒ₁ 〜Ｒ₃ は、同一又は異なってもよい水素原子、炭素数１〜１２のアルキル基、アルキレン基、アルコキシ置換アルキル基又は炭素数６〜１２のアリール基若しくはアルキル置換アリール基を示す）
【００１８】
このリン酸エステルの基油に対する配合割合は、０．１〜１０重量％、好ましくは０．５〜３重量％である。リン酸エステルの配合割合が０．１重量％より少ないと耐摩耗性を改善することができず、１０重量％を超えて添加しても大幅な耐摩耗性能力の向上は認められない。
【００１９】
本発明で用いる潤滑油には、油循環補助剤を添加することがよく、この油循環補助剤としては、エチレン・α−オレフィン共重合体若しくはその水素化物又はポリメタクリレート系のものや、ポリブデン（ポリイソブチレン）系のものなどが挙げられる。エチレン・α−オレフィン共重合体若しくはその水素化物は、例えば高分子量のエチレン・プロピレン共重合体（エチレン・プロピレンゴム等）を熱分解する方法と、エチレンと炭素数３〜１０のα−オレフィンとを分子量調整剤の共在下で共重合し、直接低分子量体を得る方法とが知られている。国内では、エチレン・α−オレフィン共重合体若しくはその水素化物は、配位アニオン重合触媒を用い、水素などの分子量調整剤の供給量を変化させることで平均分子量を調整して製造されている。これらは数平均分子量２００〜４，０００程度のものがあり、数平均分子量１，０００〜２，０００程度のものが好ましい。ポリメタクリレート系の数平均分子量は２０，０００〜１，５００，０００程度であるが、せん断安定性との関係から数平均分子量は２０，０００〜１００，０００程度が好ましい。またポリブテン系の数平均分子量は５，０００〜３００，０００程度がよい。油循環補助剤の配合割合は、基油に対して１〜３０重量％、好ましくは１〜５重量％の範囲がよい。油循環補助剤を用いることで、軸受上部から保油部として機能する空間に溜まった潤滑油をその特異なワイゼンベルグ効果によって再度上部へ送ることが可能となる。
【００２０】
本発明で用いる潤滑油には、上記添加剤の他に防錆剤を添加することがよく、この防錆剤としては、カルボン酸エステル又は有機スルフォン酸亜鉛塩が好ましい。カルボン酸エステルとしては防錆剤として知られているカルボン酸エステルであれば制限はないが、アミノ基のついた脂肪族カルボン酸のエステル、例えばアミノコハク酸エステルやその誘導体などが好適である。このカルボン酸エステルは、潤滑油の耐摩耗性を阻害することなく十分な防錆性を発揮する。また、有機スルフォン酸亜鉛塩としては防錆剤として知られている有機スルフォン酸亜鉛塩であれば制限はないが、ジノニルナフタレンスルフォン酸亜鉛塩が好適であり、下記一般式（２）で表される。通常、これのキャリアとして鉱油を用いるが、スラッジが多く発生したり、潤滑性能が低下するため、ＰＡＯ等の基油として用いられる油をキャリアとすることがよい。具体的には、キングインダストリーズ社製ＮＡ−ＳＵＬ ＺＳ／ＰＡＯなどがある。
【００２１】
【化２】

【００２２】
これら防錆剤の基油に対する添加量は、０．０１〜３．０重量％、好ましくは０．０２〜０．５重量％である。防錆剤の添加量が０．０１重量％より少ないと防錆効果がなく、３．０重量％を超えると濁りが発生し、品質不良が発生するため好ましくない。
【００２３】
本発明の焼結含油軸受用潤滑油には、金属不活性剤を配合することができる。金属不活性剤としては、ベンゾトリアゾール及びその誘導体が代表的なものであるが、その他にイミダゾリン、ピリジン誘導体がある。これらは、少なくともＮ−Ｃ−Ｎ結合を有する化合物中に効果のあるものが多く、金属表面に不活性皮膜を作る作用と酸化防止作用を有する。これ以外では、Ｎ−Ｃ−Ｓ結合を有する化合物もあるが、基油への溶解性及び揮発性などから、ベンゾトリアゾール誘導体などが有効である。金属不活性剤の配合割合は、基油に対して０．０５〜５重量％の範囲がよい。
【００２４】
更に、本発明の潤滑油には、酸化防止剤を配合することができる。酸化防止剤としては、遊離基連鎖反応停止剤として働くフェノール系、アミン系あるいは過酸化物分解剤として働く硫黄系酸化防止剤からなる群から選ばれる１種又は２種以上の酸化防止剤を用いることができる。好適にはアミン系とフェノール系の酸化防止剤を併用することが好ましい。フェノール系酸化防止剤としては、例えば２，６−ジ−ｔ−ブチルフェノール、４，４’−メチレンビス（２，６−ジ−ｔ−ブチルフェノール）、２，６，−ジ−ｔ−ブチル−４−エチルフェノール、２，６−ジ−ｔ−４−ｎ−ブチルフェノールが挙げられる。蒸発特性及び基油との相溶性の点からは、４，４’−メチレンビス（２，６−ジ−ｔ−ブチルフェノール）が好適である。また、アミン系酸化防止剤としては、ジオクチルジフェニルアミンやフェニル−α−ナフチルアミンが挙げられる。なお、蒸発特性及び基油との相溶性の点からは、ジオクチルジフェニルアミンが好適である。その配合量は、基油への溶解性を考慮して、基油に対して、アミン系酸化防止剤０．１〜１０重量％、フェノール系酸化防止剤０．１〜１０重量％が好ましい。単独使用の場合は、アミン系酸化防止剤０．１〜１０重量％が好適である。フェノール系酸化防止剤は併用のみに効果がある。
【００２５】
本発明に用いる潤滑油には、上記添加剤の他に、粘度指数向上剤、流動点降下剤、分散剤、金属不活性剤、清浄剤、油性剤、界面活性剤、消泡剤などの添加剤を必要により１種又は２種以上配合することもできる。また、潤滑油をグリースとして使用する場合は、金属石けん系や非金属石けん系の増ちょう剤を配合することもできる。
【００２６】
【発明の実施の形態】
以下、本発明を図面を参照しながら説明する。
図１は、２個の焼結含油軸受からなる焼結含油軸受ユニットを備えた光ディスク駆動装置の一例を示す断面図であり、図２はその軸受ユニット部分の拡大断面図である。図中、１は回転軸、２は焼結含油軸受、３はロータ、４はステータ、５はターンテーブル、６はロータケース、７はロータマグネット、８はハウジング、９はディスク、１０はスラスト受けである。焼結含油軸受２はコイルを有するステータ４と一体とされているハウジング８内に固着されている。回転軸１の上部にはターンテーブル５が固着されており、その下側には円筒状のロータケース６とその内周面にはりつけられたロータマグネット７からなるロータ３が固着され、回転軸とともに回転する。回転軸１は焼結含油軸受２及びスラスト受け１０により摺動支持され、回転する。
【００２７】
ここで、焼結含油軸受２は、ほぼ円筒状であって、その内径が軸方向で異なっている。すなわち、図２に示すように内周面の小径部２ａと大径部２ｂの半径が異なっており、その結果、回転軸との間に生ずる間隙Ｃ１及びＣ２も異なっている。小径部２ａでの間隙Ｃ１は軸受機能を奏するに適した間隙とされるが、大径部２ｂでの間隙Ｃ２は、これよりやや大きく、トルクの上昇が可及的に防止される程度以上の間隙とされている。この間隙をＣ２とＣ１の差で表わせば、０．００５ｍｍ以上、好ましくは０．０１ｍｍ以上、０．５ｍｍ以下である。間隙が狭すぎるとトルクの上昇が大きく、広すぎると流出した潤滑油が下方に配置した軸受の方にたまりやすく、上方に配置した軸受への潤滑油の戻りがなくなったり、減少する。また、軸受面における間隙Ｃ１は、軸半径をＲとしたとき、Ｃ１／Ｒ＝１／２０００〜１／４００の範囲とするのが望ましい。
【００２８】
図２に示す例では、２個の焼結含油軸受を、大径部が相対向するように配置されているが、その軸受端面間の間隙Ｃ３も０．５ｍｍ以下、好ましくは両者が接触する程度とすることがよい。０．５ｍｍ以上とすると、流失した油が端面間のすきまに溜まっても上側の軸受に接触しなくなり、上側の軸受へ油が回収されなくなる。上下の軸受が接触しているか、近接していれば上側の軸受から油が流失しても、毛細管現象によって下側の軸受の油を上側の軸受に吸い上げ、油の減少速度が上下で平均化される。また、この他に焼結含油軸受を３個以上用いたり、この焼結含油軸受に小径部を２つ以上設けたりすることも可能である。
【００２９】
図３は、１個の焼結含油軸受２をハウジング８内に固着したものであり、図中の符合で図１及び２と共通するものは同一のものを示す。図３に示す例では焼結含油軸受２の両端部が軸受面を構成する小径部となり、中間部が大径部となっているが、これらと軸との間隙などについては、前記と同じことがいえる。また、この他に小径部を３つ以上とし、大径部を２つ以上としたりすることも可能である。なお、図４に示した構成は従来例であり、この構成では、軸受２は２個使用されるが、軸方向に離隔してハウジング８に固定されるため、軸受面間に大きな空間領域が生じてしまう。
【００３０】
焼結含油軸受の材質としては、鉄、銅、ニッケル、亜鉛、鉛又はこれらの合金の粉末を発泡成形、焼結等をして得られる均一な多孔質組織を有する焼結体であり、およそ５０μｍ以下の多数の細孔が分布しているのが一般的である。一定面積におけるこの細孔の開孔部の面積比率を表面開孔率とした場合、軸受表面での開孔率が大きすぎると、油が軸受内部に逃げやすく、油膜圧力が発生しにくい。一方、開孔率が小さすぎると、油の滲み出しが少なく潤滑不良となりやすい。一方向にラジアル荷重が加わる場合は、荷重が加わった部分が金属の塑性流動などでなじみ、開孔部が封孔される一方、その他の部分は開孔が維持され油供給孔となるので、良好な潤滑状態となる。したがって、一般的に焼結含油軸受は、このようななじみ現象を期待して開孔率を大きめに設定する。しかし、光ディスク装置のように振れ回り荷重が加わる場合は、開孔率を大きめに設定してなじみ現象が生じると、周方向全体に封孔されてしまうため、油供給孔がなくなってしまう。したがって、初期から開孔率を適切に設定し、流体潤滑により初期なじみをなくす必要がある。開孔率を５％以下にすると、開孔率が小さすぎて油供給不足になりやすい。また、開孔率を２０％以上とすると、開孔率が大きすぎて油膜圧力が生じにくい。したがって、開孔率は５〜２０％（面積比）が適切であり、この範囲に設定すると良好な油膜が形成されて、軸振れ精度、耐久性が向上する。
【００３１】
本発明の焼結含油軸受は各種の軸受に使用することができるが、上記したＣＤ−ＲＯＭなどの光ディスク装置の他、例えばポータブルラジカセ、軸流ファンモータ、ステッピングモータ、ポータブルＣＤプレーヤ、ポータブルＭＤプレーヤ等のキャプスタンモータやスピンドルモータ用軸受に適用することができる。特に、この焼結含油軸受をＣＤ−ＲＯＭなどの光ディスク装置のスピンドルモータに適用すると、回転精度がよく、耐久性の優れるものとすることができる。
【００３２】
このような光ディスク装置のスピンドルモータの構成としては、光ディスクを支持するターンテーブルが装着された回転軸と、この回転軸を支持する軸受と、前記回転軸又は前記回転軸と共に回転する回転部材に設けられたロータと、静止部材に設けられたステータとを有する光ディスク装置のスピンドルモータにおいて、前記軸受が、回転軸の外周面と軸受隙間を介して対向する軸受面を有する焼結含油軸受からなるものが挙げられる。ここで、使用される焼結含油軸受及び潤滑油としては前記したものがよい。
【００３３】
【実施例】
次に、本発明を実施例によりさらに具体的に説明するが、本発明は、これらの例によってなんら限定されるものではない。実施例及び比較例で用いた各成分の略号は次のとおりである。また、配合割合は重量％で示されている。
ＰＡＯＨ：ポリ−α−オレフィン水素化物（新日鐵化学製：シンフルード５０１炭素数３０：９６重量％、炭素数４０：４重量％）
ＰＭＭＡ：ポリメタクリレート（１００℃動粘度：８５０ｃＳｔ）
ＲＣ：エチレン・α−オレフィン共重合体水素化物（１００℃動粘度：１００ｃＳｔ）
ＴＰ：リン酸トリオクチル
ＴＡ：アルキルリン酸エステルアミン塩
Ｌ５７：ジオクチルジフェニルアミン
ＰＯＥ：ポリオールエステル（ＨＡＴＣＯ社製：Ｈ２９３７）
Ｚｎ：ジノニルナフタレンスルフォン酸亜鉛塩
Ｂａ：ジノニルナフタレンスルフォン酸バリウム中性塩
ＢＴＡ：金属不活性剤（ベンゾトリアゾール誘導体）
Ｄ１：diethylenetriamine dinonylnaphthalene sulfonate synergistic blend
Ｄ２：calcium dinonylnaphthalene sulfonate
ＣＥ：アミノコハク酸エステル
【００３４】
実施例１〜５、比較例１〜５
表１に示す各成分を配合して実施例１〜５及び比較例１〜５の焼結含油軸受用潤滑油を調製した。なお、表１中の「Ｂａｌ」は、全体を１００として、数値表示したもの以外の残りがそのものであることを表している。
【００３５】
実施例１〜５と比較例１〜５の潤滑油について以下に示す評価試験を行った。
＜旧ＡＳＴＭ Ｄ２７８３−８８＞
試験機は、旧ＡＳＴＭ Ｄ２７８３−８８に記載されているものを用い、試験条件は、回転数９，０００ｒｐｍ、負荷荷重１０ｋｇ（平均圧力；１４，６５０ｋｇ／ｃｍ² 、すべり速度；３．４６ｍ／ｓｅｃ）とし、測定項目として、摩耗痕径（ｍｍ）と電気抵抗法による油膜形成率の測定を実施した。試験球の材質は上部球にＳＵＪ２を使用し、下部球の３つは黄銅のものを使用した（評価時間は３０分）。
＜熱安定性＞
１７５℃×２４時間の環境下に供試油を置き、粘度変化（ＪＩＳ Ｋ２２８３）、全酸価変化（ＪＩＳ Ｋ２５０１）、スラッジ発生量（ＪＩＳ Ｂ９９３１準拠）を測定した。
＜湿潤試験＞
ＪＩＳ Ｋ２２４６湿潤試験方法に準拠して実施し、焼結含油軸受に試料を含油させて３００時間後の錆の発生有無を確認した。
【００３６】
潤滑油を含浸させた焼結含油軸受をＣＤ−ＲＯＭ実機モータに組み込んで、回転数７０００ｒｐｍ、アンバランス荷重０．５ｇ・ｃｍ、雰囲気温度５０℃の条件下において、耐久試験を実施した。なお、実機モータの軸受構成は、図１に示した軸受構成と同じである。
【００３７】
実施例６、比較例６〜９
実施例５の潤滑油を含浸させた焼結含油軸受を、表２に示す軸受構成のＣＤ−ＲＯＭ実機モータに組み込み、耐久性試験を行った。
表２中の照図の図番は、試験に使用した軸受構成を示す図面番号であり、表２中のＣ３、Ｃ１は図２で定義しているＣ３及びＣ１を表わす。図面を参照して説明すると、軸受２は、銅、鉄、アルミニウムなどを主成分とする焼結合金からなる略円筒状の部材で、内周面には、軸受面となる小径部２ａと、軸受面より内径寸法を大きくした大径部２ｂがある。軸受２は、大径部２ｂ側の端面２ｃが相対向するように２個、ハウジング８に固定されており、端面２ｃ間の間隙Ｃ３は０ｍｍ、若しくは０．５ｍｍ以下に設定される。また、大径部２ｂと小径部２ａとの径差Ｃ２は半径で０．０５ｍｍ以下に設定される。軸受面となる小径部２ａの表面における開孔部の面積比率である表面開孔率は、５〜２０％に設定される。軸受面における間隙Ｃ１は、軸半径をＲとしたとき、Ｃ１／Ｒ＝１／２０００〜１／４００の範囲とされる。なお、軸受２の外径面には空気の通気路として軸方向の溝２ｄが設けられている。この空気の通気溝２ｄを設けることによって、回転軸１を軸受２に挿入する際、回転軸１と軸受２とスラストワッシャ１０で囲まれた空間の空気が通気溝２ｄを通って逃げるため、スムーズに回転軸１を軸受２に挿入することができる。
比較例６は、図４に示した軸受構成（従来例）のものを、本発明に係わる実施例との比較のために同条件で評価試験を行った。
【００３８】
試験結果を表３及び表４に示す。表３中の発錆状況とは、湿潤試験における軸受外観の状態であり、少しでも発錆が認められた場合は「あり」とした。また、耐久試験の結果を表す数値は、電流値及び軸振れを測定し、電流値が初期値の±２０％を超えるか、軸振れが初期値の＋４０％を超えるかした時点を耐久寿命とし、その時間を示してある。なお、試験は３０００ｈｒを目標として行い、３０００ｈｒ問題なく駆動した場合は、その時点で試験を終了している。この場合、試験結果は「３０００以上」と記載した。また、測定は２００ｈｒ毎に行っており、上記規格を満足できなくなった時間を試験結果として記載している。一般的に光ディスク装置のスピンドルモータには２０００ｈｒの耐久寿命が求められるので、２０００ｈｒ以上の耐久寿命がある場合は、実用可能と判断される。
【００３９】
【表１】

【００４０】
【表２】

【００４１】
【表３】

【００４２】
【表４】

【００４３】
比較例１〜５に示すように、リン酸エステルを配合しないと摩耗痕径が大きく、油膜形成率が悪い。これに比べて、実施例１〜５に示すように、耐摩耗剤としてリン酸エステルを配合すると摩耗及び油膜形成率が大幅に改善される。また、比較例１〜５には、防錆剤などの添加剤が配合されているが、防錆性及び熱安定性は改善されるものの、総合性能は実施例に比べ劣っている。なお、実施例１〜２は、リン酸エステルの種類について検討した結果であるが、両者ともに優れた潤滑特性を示した。また、実施例３〜５に示すように、エステル及びエステル系油循環補助剤であるＰＭＭＡを混合することで、スラッジの発生を抑制し、各種性能に悪影響が出ないようになることが認められた。油循環補助剤として用いるＰＭＭＡ及びＲＣは、基油同様それ自身も酸化劣化するが、潤滑性、防錆性などに悪影響を与えないことが認められた。
【００４４】
防錆剤の添加効果を実施例１〜５及び比較例１〜５で確認した。防錆剤を添加すると、防錆性能は向上するが熱安定性に劣るものがあることが確認される。実施例１〜５及び比較例４〜５に示すように、カルボン酸エステル（ＣＥ）又は有機スルフォン酸亜鉛塩（Ｚｎ）を使用することで防錆性、熱安定性は改善され、リン酸エステルと併用することで、総合性能に優れる潤滑油が得られた。従来、焼結含油軸受油に添加される防錆剤のような補助的な添加剤の影響を重要視していなかったが、実用性能を含めて考えると防錆剤などの補助的役割を果たす添加剤の影響も大きく、使用する耐摩耗剤及び基油の性能に影響を与える場合があり、これら諸問題をも解決した本発明の意義は大きい。
【００４５】
実機モータによる耐久試験でも上記の結果が追認されており、実施例１〜５ではいずれも２０００ｈｒ以上の寿命となった。リン酸エステルを配合していない比較例１〜５の寿命は短かった。
図３のように１個の焼結含油軸受の内径面に２個の軸受面を設けた実施例６も３０００ｈｒ以上の寿命となったが、図４のような軸受構成とした比較例６は２０００ｈｒまでには至らず、同じ配合組成の含浸油を使用した実施例５と比較して軸受形状による寿命の差が確認された。
【００４６】
【発明の効果】
本発明の焼結含油軸受用潤滑油組成物は、耐摩耗剤の性能低下を抑制し、熱安定性及び防錆性能等の諸特性を向上させることができる。したがって、焼結含油軸受等の非常に簡易な構造であっても良好な特性を得ることができ、焼結含油軸受及びその軸受装置の設計の容易性及び信頼性を向上させることができる。また、焼結含油軸受の構造を大径部と小径部とを有する形状とし、２個の軸受を突き当てるように使用するか、単体の焼結含油軸受の内径面に複数の軸受面を軸方向に離隔形成するとともに、その軸受面間の領域の内径寸法を軸受面の内径寸法よりも大きくした焼結含油軸受とすると、従来に比べ保油量が増えるとともに、油が流失しにくくなるので耐久性が向上する。更に、本発明の焼結含油軸受用潤滑油組成物に、金属不活性剤、酸化防止剤等を配合することによって、特に蒸発量などを一層向上させることができる。
本発明に係わる光ディスク装置のスピンドルモータによれば、低騒音化及び低コスト化を実現することができ、しかも光ディスク装置の読み取り精度を向上させることができる。
【図面の簡単な説明】
【図１】本発明の焼結含油軸受ユニット（焼結含油軸受２個）を備えた光ディスク駆動装置の一例を示す断面図である。
【図２】図１の軸受ユニット部分の拡大断面図である。
【図３】本発明の焼結含油軸受ユニット（焼結含油軸受１個）を備えた光ディスク駆動装置の一例を示す断面図である。
【図４】従来の焼結含油軸受ユニットを備えた光ディスク駆動装置の一例を示す断面図である。
【符号の説明】
１ ： 回転軸
２ ： 焼結含油軸受
３ ： ロータ
４ ： ステータ
５ ： ターンテーブル
６ ： ロータケース
７ ： ロータマグネット
８ ： ハウジング
９ ： ディスク
１０ ： スラスト受け
２ａ ： 大径部
２ｂ ： 小径部
Ｃ１、Ｃ２、Ｃ３： 間隙[0001]
The present invention relates to a bearing device in which a sintered oil-impregnated bearing is fixed to a housing and unitized. This bearing unit is a bearing device for a device that requires durability under the condition that an unbalance load is applied, such as a spindle motor of an optical disk device such as a CD-ROM, a CD-R, a DVD-ROM, and a DVD-RAM. Suitable as
[Prior art]
[0002]
Since an unbalanced load due to the mounting of a disk is applied to a spindle motor of an optical disk device or the like, durability under an unbalanced load is required. One of the components that determine the required performance is a bearing that supports a spindle. Conventionally, a rolling bearing or a sintered oil-impregnated bearing is used. However, when required performance includes durability, low cost, and low noise, a sintered oil-impregnated bearing is generally selected.
[0003]
Conventionally, as shown in FIG. 4, a sintered oil-impregnated bearing unit is generally used by fixing two cylindrical bearings having a hollow through which a shaft penetrates to a housing with an interval in the axial direction. there were.
[0004]
Since a spindle motor of an optical disk apparatus represented by a CD-ROM or a DVD-ROM has an unbalance load due to the mounting of the disk, a swinging load is applied to the bearing. In these devices, the number of rotations used has been increasing year by year. ² ) Increases dramatically in proportion to the square of the rotational speed. When the rotational speed is high and the runout is large, the load area moves in the circumferential direction with the rotational speed, so the oil film cannot follow this, resulting in poor lubrication and metal contact and wear. Progresses.
[0005]
In addition, in self-lubricated bearings such as sintered oil-impregnated bearings, air is also entrained in the bearing gap as it rotates, but this amount of entrainment increases under high-speed rotation, which hinders oil film formation and further wear. It becomes easy to do. As wear progresses, the amount of swirl increases, and this leads to a vicious circle in which it becomes more difficult to form an oil film. In addition, when two cylindrical bearings are fixed to the housing as shown in FIG. 4, oil easily flows out from the upper bearing, and from this point, lubrication is likely to be poor. Because of such circumstances, there is a problem in durability under high speed conditions of 6000 rpm or higher.
[0006]
On the other hand, it is needless to say that an excellent lubricating oil is required for the lubricating oil used in the sintered oil-impregnated bearing. However, for example, Japanese Patent Application Laid-Open No. 9-4889 discloses a material obtained by adding a specific organic phosphorus compound to a base oil, and Japanese Patent Application Laid-Open No. 9-125086 includes a material obtained by blending a polyolefin and a polyol ester. Although described, it maintains the stand-alone performance such as wear resistance and evaporability, but is required for lubricating oil supply for sintered oil-impregnated bearings, such as the supply performance of lubricant from sintered oil-impregnated bearings and wear resistance and rust resistance. Could not satisfy all the characteristics.
[0007]
In addition, since the production of sintered oil-impregnated bearings is increasing in high temperature and high humidity overseas, there is a demand for better rust prevention for the lubricating oil used. However, the conventional combination causes a problem of impairing the wear resistance, and it is difficult to satisfy both performances at the same time.
[0008]
As conventional lubricating oils for sintered oil-impregnated bearings, various paraffinic and naphthenic mineral oils and synthetic oils such as diesters, polyol esters and poly-α-olefin hydrides are used depending on the properties. There is no special lubricating oil for oil-impregnated bearings, and the current situation is diverting commercially available hydraulic fluids and engine oils. In general, mineral oil-based lubricants contain mineral oil-based base oils containing antioxidants, rust inhibitors, antiwear agents, antifoaming agents, metal deactivators, etc. Additives such as an improver and a pour point depressant are blended, but even if this is done, it has been difficult to satisfy the required performance as a lubricating oil for sintered oil-impregnated bearings.
[0009]
[Problems to be solved by the invention]
An object of the present invention is to provide a sintered oil-impregnated bearing unit that can withstand high-speed rotation with excellent wear resistance and improved rust prevention performance.
[0010]
[Means for Solving the Problems]
That is, the present invention is a hollow body having a hollow through which a shaft passes, and has a structure in which an inner peripheral surface has a small diameter portion constituting a bearing surface and a large diameter portion slightly larger than this. A bearing unit in which one or more oil-impregnated bearings are fixed in a housing, The diameter difference between the large-diameter portion and the small-diameter portion of the sintered oil-impregnated bearing is 0.05 mm or less in radius, and the surface opening ratio, which is the degree of opening on the inner peripheral surface of the sintered oil-impregnated bearing, is the bearing surface portion. When it is adjusted to 5 to 20% and there are two or more sintered oil-impregnated bearings, the two sintered oil-impregnated bearings are fixed in the housing so that the large diameter side faces each other, and between the end faces of each Is set to 0 mm or 0.5 mm or less, and The lubricating oil impregnated in the sintered oil-impregnated bearing is blended with 0.1 to 10% by weight of a phosphate ester as an antiwear agent in the base oil. And an ethylene / α-olefin copolymer or a hydride thereof, polymethacrylate or polybutenes as an oil circulation aid, and the base oil is (a) a poly-α-olefin or a hydride thereof, (b ) It is selected from the group consisting of poly-α-olefins or mixtures of their hydrides and esters. It is characterized by For spindle motors of disk drives that rotate at a speed of 6000 rpm or higher This is a sintered oil-impregnated bearing unit, and the present invention is a spindle motor of an optical disc apparatus provided with the sintered oil-impregnated bearing unit.
[0011]
The hollow through which the shaft penetrates has a circular cross section perpendicular to the shaft, and the radius of the circle is different in the axial direction. Since the small diameter portion acts as a bearing surface of the shaft, it has a radius very close to the radius of the shaft, and the large diameter portion has a slightly larger radius. Therefore, when one or more of such sintered oil-impregnated bearings are fixed in the housing, the gap generated between the shaft and the bearing is large and small, and the gap generated in the portion corresponding to the small diameter portion is several μm. On the other hand, a minute gap is generated in the part corresponding to the large diameter part, and even if there is oil that generates heat during driving and is lost due to thermal expansion, it is retained in this minute gap part, and after stopping, the bearing temperature As it drops, it is again collected inside the bearing. Further, the bearing main body portion corresponding to the large diameter portion functions as an oil retaining material. Therefore, the oil retention amount of oil is remarkably increased as compared with the conventional space except for the portion corresponding to the bearing surface as shown in FIG. This increases the absolute amount of oil and contributes to improved durability. Moreover, since the diameter is large except for the bearing portion, the torque does not increase.
[0012]
When a single sintered oil-impregnated bearing is used, assembly accuracy such as coaxiality and cylindricity can be easily obtained rather than fixing two or more separate bearings to the housing. Further, it can be manufactured at a lower cost than that manufactured by two separate bodies. Moreover, when it is set to two, manufacture and an assembly of a sintered oil-impregnated bearing become easy.
[0013]
The base oil of the lubricating oil for sintered oil-impregnated bearings of the present invention includes paraffinic and naphthenic mineral oils, aromatic hydrocarbons such as alkylnaphthalene, aliphatic hydrocarbons such as polyolefin, and hydrides thereof. Examples thereof include synthetic oils such as naphthenic or hydrogenated aliphatic hydrocarbons and esters, but preferably (a) poly-α-olefin or hydride thereof, (b) poly-α-olefin or hydrogen thereof. It consists of at least 1 or more types chosen from the group which consists of a mixture of a compound and ester.
[0014]
The poly-α-olefin (hereinafter abbreviated as PAO) has a number average molecular weight of 200 to 1600, preferably 350 to 800, and has a carbon number of 3 to 3 having a double bond at the terminal such as ethylene or 1-butene. A linear α-olefin (a component in the vicinity of decene-1) obtained by thermal decomposition of 20, preferably 6 to 15 olefins such as wax was subjected to low polymerization by cationic polymerization in the presence of a Lewis acid catalyst. Things are appropriate. A hydride of PAO is obtained by hydrogenating it in the presence of a hydrogenation catalyst. By using PAO or this hydride as the base oil, the heat resistance can be improved, and the amount of sludge generated from the oil can be extremely suppressed.
[0015]
Esters as base oils are monoesters (monohydric alcohol and monovalent fatty acid esters), diesters (monohydric alcohol and divalent fatty acid esters), polyol esters (polyhydric alcohols having a neopentyl skeleton and monovalent fatty acid esters). Etc.), complex esters (oligomer ester obtained by adding a polyhydric fatty acid to a polyol ester as a raw material and cross-linking the polyol) and the like can be used, but a polyol ester is preferred in terms of compatibility, low viscosity and excellent evaporation properties. . By using an ester together with PAO or a hydride thereof, the solubility, which is a drawback of polyolefins, can be overcome, and further, evaporation characteristics and lubricity can be improved. When the ester is used as a part of the base oil, the blending amount is preferably in the range of 1 to 30% by weight of the base oil.
[0016]
In the lubricating oil used in the present invention, a phosphate ester is blended with the above base oil as an antiwear agent. Examples of the phosphoric acid ester include phosphoric acid triesters such as trioctyl phosphate and tricresyl phosphate represented by the following general formula (1), acidic phosphate esters such as monooctyl phosphate, and dioctyl phosphate, Alkyl phosphate amine salts (partially amine salts) and the like can be mentioned, and phosphoric acid triesters are preferred. More preferred are phosphoric acid trialkyl esters and phosphoric acid tri (alkyl) aryl esters. The use of a phosphate ester can increase the oil film forming ability.
[0017]
[Chemical 1]

(Wherein R ₁ ~ R _Three Are the same or different hydrogen atoms, alkyl groups having 1 to 12 carbon atoms, alkylene groups, alkoxy-substituted alkyl groups, aryl groups having 6 to 12 carbon atoms or alkyl-substituted aryl groups.
[0018]
The blending ratio of the phosphate ester to the base oil is 0.1 to 10% by weight, preferably 0.5 to 3% by weight. If the blending ratio of the phosphate ester is less than 0.1% by weight, the wear resistance cannot be improved, and even if the amount exceeds 10% by weight, no significant improvement in the wear resistance ability is observed.
[0019]
An oil circulation aid is preferably added to the lubricating oil used in the present invention. Examples of the oil circulation aid include an ethylene / α-olefin copolymer or a hydride thereof, a polymethacrylate type, and a polybutene ( Polyisobutylene) -based ones and the like. Examples of the ethylene / α-olefin copolymer or hydride thereof include a method of thermally decomposing a high molecular weight ethylene / propylene copolymer (ethylene / propylene rubber, etc.), ethylene, an α-olefin having 3 to 10 carbon atoms, Is a method in which a low molecular weight product is directly obtained by copolymerization in the presence of a molecular weight modifier. In Japan, an ethylene / α-olefin copolymer or a hydride thereof is produced by adjusting the average molecular weight by changing the supply amount of a molecular weight regulator such as hydrogen using a coordination anion polymerization catalyst. These have a number average molecular weight of about 200 to 4,000, preferably a number average molecular weight of about 1,000 to 2,000. The number average molecular weight of the polymethacrylate series is about 20,000 to 1,500,000, but the number average molecular weight is preferably about 20,000 to 100,000 from the viewpoint of shear stability. The number average molecular weight of the polybutene system is preferably about 5,000 to 300,000. The blending ratio of the oil circulation aid is 1 to 30% by weight, preferably 1 to 5% by weight, based on the base oil. By using the oil circulation auxiliary agent, it is possible to send the lubricating oil accumulated in the space functioning as the oil retaining portion from the upper portion of the bearing to the upper portion again due to its unique Weisenberg effect.
[0020]
In addition to the above-mentioned additives, it is preferable to add a rust inhibitor to the lubricating oil used in the present invention, and the rust inhibitor is preferably a carboxylic acid ester or an organic sulfonate zinc salt. The carboxylic acid ester is not particularly limited as long as it is a carboxylic acid ester known as a rust preventive, but an ester of an aliphatic carboxylic acid having an amino group, such as an amino succinic acid ester or a derivative thereof, is preferable. This carboxylic acid ester exhibits sufficient antirust properties without impairing the wear resistance of the lubricating oil. The organic sulfonic acid zinc salt is not limited as long as it is a known organic sulfonic acid zinc salt as a rust preventive, but dinonyl naphthalene sulfonic acid zinc salt is preferred and is represented by the following general formula (2). Is done. Normally, mineral oil is used as a carrier for this. However, since a lot of sludge is generated or lubrication performance is lowered, oil used as a base oil such as PAO is preferably used as a carrier. Specifically, there is NA-SUL ZS / PAO manufactured by King Industries.
[0021]
[Chemical 2]

[0022]
The amount of these rust inhibitors added to the base oil is 0.01 to 3.0% by weight, preferably 0.02 to 0.5% by weight. When the addition amount of the rust inhibitor is less than 0.01% by weight, there is no rust prevention effect, and when it exceeds 3.0% by weight, turbidity is generated and a quality defect occurs, which is not preferable.
[0023]
A metal deactivator can be blended in the lubricating oil for sintered oil-impregnated bearings of the present invention. Typical examples of the metal deactivator include benzotriazole and its derivatives, but other examples include imidazoline and pyridine derivatives. Many of these compounds are effective among compounds having at least an N—C—N bond, and have an action of forming an inert film on a metal surface and an antioxidant action. Other than these, there are compounds having an N—C—S bond, but benzotriazole derivatives and the like are effective from the viewpoint of solubility in base oil and volatility. The compounding ratio of the metal deactivator is preferably in the range of 0.05 to 5% by weight with respect to the base oil.
[0024]
Furthermore, antioxidant can be mix | blended with the lubricating oil of this invention. As the antioxidant, one or more antioxidants selected from the group consisting of phenolic, amine-based or sulfur-based antioxidants that function as free radical chain reaction terminators are used. be able to. It is preferable to use an amine-based and phenol-based antioxidant in combination. Examples of phenolic antioxidants include 2,6-di-t-butylphenol, 4,4′-methylenebis (2,6-di-t-butylphenol), 2,6, -di-t-butyl-4- Examples include ethylphenol and 2,6-di-t-4-n-butylphenol. From the viewpoint of evaporation characteristics and compatibility with the base oil, 4,4′-methylenebis (2,6-di-t-butylphenol) is preferable. Examples of amine-based antioxidants include dioctyl diphenylamine and phenyl-α-naphthylamine. Dioctyldiphenylamine is preferred from the viewpoint of evaporation characteristics and compatibility with the base oil. The blending amount is preferably 0.1 to 10% by weight of an amine antioxidant and 0.1 to 10% by weight of a phenolic antioxidant with respect to the base oil in consideration of solubility in the base oil. When used alone, 0.1 to 10% by weight of an amine-based antioxidant is suitable. Phenolic antioxidants are effective only in combination.
[0025]
In addition to the above additives, the lubricating oil used in the present invention includes addition of a viscosity index improver, pour point depressant, dispersant, metal deactivator, detergent, oiliness agent, surfactant, antifoaming agent, etc. If necessary, one or more agents can be blended. When lubricating oil is used as grease, a metallic soap-based or non-metallic soap-based thickener can be blended.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view showing an example of an optical disk drive device provided with a sintered oil-impregnated bearing unit composed of two sintered oil-impregnated bearings, and FIG. 2 is an enlarged sectional view of the bearing unit portion. In the figure, 1 is a rotating shaft, 2 is a sintered oil-impregnated bearing, 3 is a rotor, 4 is a stator, 5 is a turntable, 6 is a rotor case, 7 is a rotor magnet, 8 is a housing, 9 is a disk, 10 is a thrust receiver It is. The sintered oil-impregnated bearing 2 is fixed in a housing 8 integrated with a stator 4 having a coil. A turntable 5 is fixed to the upper part of the rotating shaft 1, and a rotor 3 comprising a cylindrical rotor case 6 and a rotor magnet 7 attached to the inner peripheral surface is fixed to the lower side of the turntable 5. Rotate. The rotary shaft 1 is slidably supported by the sintered oil-impregnated bearing 2 and the thrust receiver 10 and rotates.
[0027]
Here, the sintered oil-impregnated bearing 2 has a substantially cylindrical shape, and its inner diameter differs in the axial direction. That is, as shown in FIG. 2, the radiuses of the small-diameter portion 2a and the large-diameter portion 2b on the inner peripheral surface are different, and as a result, the gaps C1 and C2 generated between the rotary shaft and the rotary shaft are also different. The gap C1 in the small diameter portion 2a is a gap suitable for performing a bearing function, but the gap C2 in the large diameter portion 2b is slightly larger than this, and is larger than the extent that an increase in torque is prevented as much as possible. It is a gap. If this gap is expressed by the difference between C2 and C1, it is 0.005 mm or more, preferably 0.01 mm or more and 0.5 mm or less. If the gap is too narrow, the torque increases greatly, and if it is too wide, the lubricating oil that has flowed out tends to accumulate toward the bearing disposed below, and the lubricating oil does not return to the bearing disposed above or decreases. Further, the clearance C1 on the bearing surface is preferably in the range of C1 / R = 1/2000 to 1/400, where R is the shaft radius.
[0028]
In the example shown in FIG. 2, the two sintered oil-impregnated bearings are arranged so that the large diameter portions face each other, but the gap C3 between the bearing end faces is also 0.5 mm or less, preferably the two come into contact with each other. It is good to be about. If it is 0.5 mm or more, even if the lost oil accumulates in the gap between the end faces, it does not come into contact with the upper bearing, and the oil is not recovered to the upper bearing. If the upper and lower bearings are in contact with each other or close to each other, even if oil flows away from the upper bearing, the lower bearing oil is sucked up into the upper bearing by capillary action, and the oil reduction rate is averaged up and down. Is done. In addition, it is also possible to use three or more sintered oil-impregnated bearings, or to provide two or more small-diameter portions in the sintered oil-impregnated bearing.
[0029]
FIG. 3 shows a case where one sintered oil-impregnated bearing 2 is fixed in the housing 8, and the same reference numerals in FIG. In the example shown in FIG. 3, both ends of the sintered oil-impregnated bearing 2 are small-diameter portions constituting the bearing surface, and the intermediate portion is a large-diameter portion. The gap between these and the shaft is the same as described above. I can say. In addition, it is possible to have three or more small diameter portions and two or more large diameter portions. The configuration shown in FIG. 4 is a conventional example, and in this configuration, two bearings 2 are used. However, since they are fixed to the housing 8 in the axial direction, a large space area is formed between the bearing surfaces. It will occur.
[0030]
The material of the sintered oil-impregnated bearing is a sintered body having a uniform porous structure obtained by foaming, sintering, etc. of powder of iron, copper, nickel, zinc, lead or an alloy thereof. In general, a large number of pores of 50 μm or less are distributed. When the area ratio of the opening portions of the pores in a certain area is defined as the surface opening ratio, if the opening ratio on the bearing surface is too large, the oil easily escapes into the bearing and the oil film pressure is hardly generated. On the other hand, if the hole area ratio is too small, oil oozes out and lubrication is likely to be poor. When a radial load is applied in one direction, the part where the load is applied is familiar with the plastic flow of the metal, etc., while the hole is sealed, while the other part is maintained as an oil supply hole. Good lubrication. Therefore, in general, a sintered oil-impregnated bearing is set to have a larger aperture ratio in anticipation of such a familiar phenomenon. However, when a wobbling load is applied as in the optical disc apparatus, if the familiarity phenomenon occurs when the aperture ratio is set to be large, the oil supply hole is lost because the entire circumferential direction is sealed. Therefore, it is necessary to appropriately set the aperture ratio from the beginning and eliminate the initial familiarity by fluid lubrication. If the hole area ratio is 5% or less, the hole area ratio is too small and the oil supply tends to be insufficient. On the other hand, if the opening ratio is 20% or more, the opening ratio is too large and oil film pressure is hardly generated. Therefore, 5 to 20% (area ratio) is appropriate for the hole area ratio, and when it is set within this range, a good oil film is formed and the shaft runout accuracy and durability are improved.
[0031]
The sintered oil-impregnated bearing of the present invention can be used for various types of bearings. In addition to the above-described optical disk device such as a CD-ROM, for example, a portable radio cassette player, an axial fan motor, a stepping motor, a portable CD player, and a portable MD player. It can be applied to a capstan motor or a spindle motor bearing. In particular, when this sintered oil-impregnated bearing is applied to a spindle motor of an optical disc apparatus such as a CD-ROM, the rotational accuracy is good and the durability is excellent.
[0032]
As the configuration of the spindle motor of such an optical disk apparatus, a rotating shaft on which a turntable for supporting an optical disk is mounted, a bearing for supporting the rotating shaft, and a rotating member that rotates together with the rotating shaft or the rotating shaft are provided. In a spindle motor of an optical disk apparatus having a rotor and a stator provided on a stationary member, the bearing comprises a sintered oil-impregnated bearing having a bearing surface facing the outer peripheral surface of the rotating shaft via a bearing gap Is mentioned. Here, the above-described sintered oil-impregnated bearing and lubricating oil are preferably used.
[0033]
【Example】
EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited at all by these examples. Abbreviations of each component used in Examples and Comparative Examples are as follows. Further, the blending ratio is indicated by weight%.
PAOH: poly-α-olefin hydride (manufactured by Nippon Steel Chemical Co., Ltd .: Shinflud 501, carbon number 30:96 wt%, carbon number 40: 4 wt%)
PMMA: Polymethacrylate (100 ° C. kinematic viscosity: 850 cSt)
RC: Hydrogenated ethylene / α-olefin copolymer (100 ° C. kinematic viscosity: 100 cSt)
TP: Trioctyl phosphate
TA: alkyl phosphate ester amine salt
L57: Dioctyldiphenylamine
POE: polyol ester (manufactured by HATCO: H2937)
Zn: zinc dinonylnaphthalene sulfonate
Ba: neutral salt of dinonylnaphthalene sulfonate barium
BTA: Metal deactivator (benzotriazole derivative)
D1: diethylenetriamine dinonylnaphthalene sulfonate synergistic blend
D2: calcium dinonylnaphthalene sulfonate
CE: Amino succinate
[0034]
Examples 1-5, Comparative Examples 1-5
The ingredients shown in Table 1 were blended to prepare sintered oil-impregnated bearing lubricating oils of Examples 1 to 5 and Comparative Examples 1 to 5. Note that “Bal” in Table 1 indicates that the whole is 100, and the rest other than the numerical display is itself.
[0035]
The following evaluation tests were performed on the lubricating oils of Examples 1 to 5 and Comparative Examples 1 to 5.
<Old ASTM D2783-88>
The test machine used was the one described in the former ASTM D2783-88, and the test conditions were a rotation speed of 9,000 rpm, a load of 10 kg (average pressure; 14,650 kg / cm ² , Sliding speed; 3.46 m / sec), and measurement of wear scar diameter (mm) and oil film formation rate by an electric resistance method were performed as measurement items. As the material of the test sphere, SUJ2 was used for the upper sphere, and three of the lower spheres were made of brass (evaluation time was 30 minutes).
<Thermal stability>
The test oil was placed in an environment at 175 ° C. for 24 hours, and the change in viscosity (JIS K2283), change in total acid value (JIS K2501), and sludge generation amount (based on JIS B9931) were measured.
<Wetting test>
The test was carried out in accordance with the JIS K2246 wet test method, and a sample was impregnated in a sintered oil-impregnated bearing, and the presence or absence of rust after 300 hours was confirmed.
[0036]
A sintered oil-impregnated bearing impregnated with lubricating oil was incorporated into a CD-ROM actual motor, and an endurance test was performed under conditions of a rotational speed of 7000 rpm, an unbalance load of 0.5 g · cm, and an ambient temperature of 50 ° C. The bearing configuration of the actual motor is the same as the bearing configuration shown in FIG.
[0037]
Example 6 and Comparative Examples 6-9
The sintered oil-impregnated bearing impregnated with the lubricating oil of Example 5 was incorporated into a CD-ROM actual machine motor having a bearing configuration shown in Table 2, and a durability test was performed.
The reference number in the table in Table 2 is a drawing number indicating the bearing configuration used in the test, and C3 and C1 in Table 2 represent C3 and C1 defined in FIG. Referring to the drawings, the bearing 2 is a substantially cylindrical member made of a sintered alloy mainly composed of copper, iron, aluminum or the like, and an inner peripheral surface has a small diameter portion 2a serving as a bearing surface, There is a large-diameter portion 2b having a larger inner diameter than the bearing surface. Two bearings 2 are fixed to the housing 8 so that the end surfaces 2c on the large diameter portion 2b side face each other, and a gap C3 between the end surfaces 2c is set to 0 mm or 0.5 mm or less. The diameter difference C2 between the large diameter portion 2b and the small diameter portion 2a is set to 0.05 mm or less in radius. The surface aperture ratio, which is the area ratio of the aperture portions on the surface of the small diameter portion 2a that becomes the bearing surface, is set to 5 to 20%. The clearance C1 on the bearing surface is in the range of C1 / R = 1/2000 to 1/400, where R is the shaft radius. An axial groove 2d is provided on the outer diameter surface of the bearing 2 as an air ventilation path. By providing the air ventilation groove 2d, when the rotary shaft 1 is inserted into the bearing 2, the air in the space surrounded by the rotary shaft 1, the bearing 2, and the thrust washer 10 escapes through the ventilation groove 2d. The rotary shaft 1 can be inserted into the bearing 2.
In Comparative Example 6, the bearing test (conventional example) shown in FIG. 4 was subjected to an evaluation test under the same conditions for comparison with the example according to the present invention.
[0038]
The test results are shown in Tables 3 and 4. The rusting situation in Table 3 is the state of the bearing appearance in the wet test, and “Yes” is indicated when rusting is observed even a little. The numerical value representing the result of the endurance test is the endurance life when the current value and shaft runout are measured and the current value exceeds ± 20% of the initial value or the shaft runout exceeds + 40% of the initial value. The time is shown. Note that the test was performed with a target of 3000 hr, and when the test was performed without any problem for 3000 hr, the test was completed at that time. In this case, the test result was described as “3000 or more”. Moreover, the measurement is performed every 200 hr, and the time when the above standard cannot be satisfied is described as a test result. In general, a spindle motor of an optical disc apparatus is required to have a durability life of 2000 hours. Therefore, if it has a durability life of 2000 hours or more, it is determined that it is practical.
[0039]
[Table 1]

[0040]
[Table 2]

[0041]
[Table 3]

[0042]
[Table 4]

[0043]
As shown in Comparative Examples 1 to 5, if a phosphate ester is not blended, the wear scar diameter is large and the oil film formation rate is poor. Compared with this, as shown in Examples 1 to 5, when a phosphate ester is blended as an antiwear agent, the wear and the oil film formation rate are greatly improved. Moreover, although additives, such as a rust inhibitor, are mix | blended with Comparative Examples 1-5, although rust prevention property and thermal stability are improved, the comprehensive performance is inferior compared with an Example. In addition, although Example 1-2 was the result of having examined about the kind of phosphate ester, both showed the outstanding lubrication characteristic. In addition, as shown in Examples 3 to 5, it is recognized that mixing of ester and PMMA which is an ester oil circulation auxiliary agent suppresses the generation of sludge and does not adversely affect various performances. It was. It was recognized that PMMA and RC used as an oil circulation auxiliary agent oxidize and deteriorate themselves as well as the base oil, but do not adversely affect the lubricity and rust prevention properties.
[0044]
The effect of adding the rust inhibitor was confirmed in Examples 1 to 5 and Comparative Examples 1 to 5. When a rust inhibitor is added, the rust prevention performance is improved, but it is confirmed that there is an inferior thermal stability. As shown in Examples 1 to 5 and Comparative Examples 4 to 5, the use of carboxylic acid ester (CE) or organic sulfonic acid zinc salt (Zn) improves rust prevention and thermal stability, and phosphate ester. In combination, a lubricating oil with excellent overall performance was obtained. Conventionally, the influence of auxiliary additives such as rust preventives added to sintered oil-impregnated bearing oils has not been considered important, but considering practical performance, it plays an auxiliary role such as rust preventives. The influence of the additive is also great, which may affect the performance of the antiwear agent and base oil to be used, and the significance of the present invention that solves these problems is great.
[0045]
In the endurance test with an actual motor, the above results were confirmed, and in each of Examples 1 to 5, the lifetime was 2000 hours or more. The lifetimes of Comparative Examples 1 to 5 in which no phosphate ester was blended were short.
Example 6 in which two bearing surfaces were provided on the inner diameter surface of one sintered oil-impregnated bearing as shown in FIG. 3 also had a life of 3000 hours or more. It did not reach 2000 hr, and a difference in the life depending on the bearing shape was confirmed as compared with Example 5 using the impregnated oil having the same composition.
[0046]
【The invention's effect】
The lubricating oil composition for sintered oil-impregnated bearings of the present invention can suppress the performance degradation of the antiwear agent and improve various properties such as thermal stability and rust prevention performance. Therefore, good characteristics can be obtained even with a very simple structure such as a sintered oil-impregnated bearing, and the ease and reliability of the design of the sintered oil-impregnated bearing and its bearing device can be improved. In addition, the structure of the sintered oil-impregnated bearing has a shape having a large-diameter portion and a small-diameter portion. If the oil-impregnated sintered bearings are separated in the direction and the inner diameter of the region between the bearing surfaces is larger than the inner diameter of the bearing surfaces, the oil retention amount increases and oil does not easily flow out. Durability is improved. Furthermore, the amount of evaporation and the like can be further improved by blending a metal deactivator, an antioxidant and the like with the lubricating oil composition for sintered oil-impregnated bearings of the present invention.
According to the spindle motor of the optical disc apparatus according to the present invention, noise reduction and cost reduction can be realized, and the reading accuracy of the optical disc apparatus can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of an optical disk drive device provided with a sintered oil-impregnated bearing unit (two sintered oil-impregnated bearings) according to the present invention.
FIG. 2 is an enlarged cross-sectional view of the bearing unit portion of FIG.
FIG. 3 is a cross-sectional view showing an example of an optical disk drive device provided with a sintered oil-impregnated bearing unit (one sintered oil-impregnated bearing) of the present invention.
FIG. 4 is a cross-sectional view showing an example of an optical disk drive device provided with a conventional sintered oil-impregnated bearing unit.
[Explanation of symbols]
1: Rotation axis
2: Sintered oil-impregnated bearing
3: Rotor
4: Stator
5: Turntable
6: Rotor case
7: Rotor magnet
8: Housing
9: Disc
10: Thrust receiver
2a: Large diameter part
2b: Small diameter part
C1, C2, C3: gap

Claims (6)

1 or a sintered oil-impregnated bearing having a hollow body having a hollow through which a shaft penetrates, the inner circumferential surface of which includes a small diameter portion constituting the bearing surface and a large diameter portion slightly larger than this. Two or more bearing units fixed in the housing, wherein the diameter difference between the large diameter portion and the small diameter portion of the sintered oil impregnated bearing is 0.05 mm or less in radius, and the surface of the inner peripheral surface of the sintered oil impregnated bearing is When the surface opening ratio, which is the degree of opening, is adjusted to 5 to 20% at the bearing surface, and there are two or more sintered oil-impregnated bearings, the two large diameter parts of the two sintered oil-impregnated bearings face each other Thus, the gap between the respective end faces is set to 0 mm or 0.5 mm or less, and the lubricating oil impregnated in the sintered oil-impregnated bearing is used as a wear-resistant agent in the base oil. the ester was blended 0.1 to 10 wt%, and oil circulation aids An ethylene / α-olefin copolymer or a hydride thereof, polymethacrylate or polybutenes, and the base oil is (a) a poly-α-olefin or a hydride thereof, and (b) a poly-α-olefin. Or a sintered oil-impregnated bearing unit for a spindle motor of a disk drive rotating at a speed of 6000 rpm or more, wherein the sintered oil-impregnated bearing unit is selected from the group consisting of a mixture of a hydride and an ester thereof . Sintered oil impregnation having a structure in which the bearing unit has a hollow body having a hollow through which a shaft penetrates, and has an inner peripheral surface having a small diameter portion constituting the bearing surface and a large diameter portion slightly larger than this. Two bearings are fixed in the housing so that the large diameter side faces each other, the gap between the respective end faces is set to 0 mm or 0.5 mm or less, and the large diameter portion and the small diameter portion 2. A sintered oil-impregnated bearing unit for a spindle motor of a disk apparatus according to claim 1, wherein the difference in diameter is 0.05 mm or less in radius . Sintering in which the bearing unit has a plurality of bearing surfaces spaced apart in the axial direction on the inner peripheral surface of one sintered oil-impregnated bearing, and the inner diameter of the region between the bearing surfaces is larger than the inner diameter of the bearing surface 2. A sintered oil-impregnated bearing unit for a spindle motor of a disk apparatus according to claim 1, wherein the oil-impregnated bearing is fixed in the housing . The spindle motor of the disk apparatus according to any one of claims 1 to 3, wherein the lubricating oil contains 0.01 to 3.0 wt% of a carboxylic acid ester or an organic sulfonic acid zinc salt as a rust inhibitor. sintered oil-impregnated bearing unit of use. 5. A spindle motor for a disk apparatus comprising the sintered oil-impregnated bearing unit for the spindle motor of the disk apparatus according to claim 1 . 6. The spindle motor of the disk device according to claim 5, wherein the spindle motor of the disk device is a spindle motor of the optical disk device.

Images