JP2004051719A - Oil for oil-impregnated bearing, oil-impregnated bearing using the oil, and pressurization motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oil-impregnated bearing oil which is lowly viscous, lowly evaporable, and heat-resistant, does not emit lowly volatile components and outgases when used in a motor, and prevents the friction of an oil-impregnated bearing even in a motor having a special structure in which pressure is applied in a specified direction and to provide an oil-impregnated bearing using the oil, and to provide a pressurization motor. <P>SOLUTION: The oil is prepared by adding a phenolic antioxidant or an amine antioxidant and a friction modifier comprising at least one member selected from among an orthophosphoric ester, an acid phosphoric ester, and an amine salt of an acidic phosphoric ester to a low-viscosity ester base oil. There are also provided the oil-impregnated bearing impregnated with the oil and the pressurization motor, wherein a means for applying a specifically directed side thrust to a motor shaft supported by an oil-impregnated bearing prepared by pressure-sintering a metal powder is the displacement of either side of the cores fixed symmetrically around the motor shaft to the direction of the motor shaft and wherein the oil-impregnated bearing is impregnated with the oil-impregnated bearing oil. <P>COPYRIGHT: (C)2004,JPO

Description

上記式（１）において、Ｒ^１〜Ｒ^３は炭素数４〜３０のアルキル基、アルケニル基、アルキルアリール基又はアリールアルキル基を示し、Ｒ^１〜Ｒ^３は同一でも異なっていてもよい。
【００１３】
正リン酸エステルとしては、トリアリールホスフェート、トリアルキルホスフェート、トリアルキルアリールホスフェート、トリアリールアルキルホスフェート、トリアルケニルホスフェートなどがあり、具体的には、例えば、トリフェニルホスフェート、トリクレジルホスフェート、ベンジルジフェニルホスフェート、エチルジフェニルホスフェート、トリブチルホスフェート、エチルジブチルホスフェート、クレジルジフェニルホスフェート、ジクレジルフェニルホスフェート、エチルフェニルジフェニルホスフェート、ジエチルフェニルフェニルホスフェート、プロピルフェニルジフェニルホスフェート、ジプロピルフェニルフェニルホスフェート、トリエチルフェニルホスフェート、トリプロピルフェニルホスフェート、ブチルフェニルジフェニルホスフェート、ジブチルフェニルフェニルホスフェート、トリブチルフェニルホスフェート、トリヘキシルホスフェート、トリ（２−エチルヘキシル）ホスフェート、トリデシルホスフェート、トリラウリルホスフェート、トリミリスチルホスフェート、トリパルミチルホスフェート、トリステアリルホスフェート、トリオレイルホスフェートなどを挙げることができる。上記の正リン酸エステルは一種又は二種以上を組み合わせて使用してもよい。
これらの正リン酸エステルの中でも、トリクレジルホスフェート、トリフェニルホスフェート、トリプロピルフェニルホスフェート、トリブチルフェニルホスフェートが好ましい。
【００１４】
摩擦調整剤としてこの正リン酸エステルを用いた場合の含油軸受油全量に対する添加量は、０．０１〜１０質量％であると好ましく、０．０５〜５質量％であるとさらに好ましい。正リン酸エステルの添加量が０．０１質量％未満の場合は、他成分との相乗効果による摩擦特性の向上効果が不十分な場合があり、添加量が１０質量％を超えても、添加量に相当する効果の向上がみられない場合がある。
【００１５】
本発明で用いる、摩擦調整剤の酸性リン酸エステルとしては、炭素数１〜２０（アルキル基）のアルキルアシッドフォスフェート又はアルキルハイドロジェンフォスファイトが好ましく、特に下記式（２）又は（３）で表されるものが好ましい。
【化２】

【００１６】
上記式（２）及び（３）において、Ｒ^４及びＲ^５は炭素数１〜３０のアルキル基を表し、具体的には、メチル基，エチル基，ｎ−プロピル基，イソプロピル基，ｎ−ブチル基，イソブチル基，ｓ−ブチル基，ｔ−ブチル基，各種ペンチル基，各種ヘキシル基，各種ヘプチル基，各種オクチル基，各種ノニル基，各種デシル基，各種ウンデシル基，各種ドデシル基，各種トリデシル基，各種テトラデシル基，各種ペンタデシル基，各種ヘキサデシル基，各種ヘプタデシル基，各種オクタデシル基，各種ノナデシル基，各種エイコシル基，各種ヘンエイコシル基，各種ドコシル基，各種トリコシル基，各種テトラコシル基，各種ペンタコシル基，各種ヘキサコシル基，各種ヘプタコシル基，各種オクタコシル基，各種ノナコシル基，各種トリアコンチル基が挙げられ、これらの中でもメチル基が好ましい。Ｒ^４及びＲ^５は同一でも異なっていてもよい。
【００１７】
また、本発明で用いる、摩擦調整剤の酸性リン酸エステルのアミン塩を形成するアミン類としては、下記式（４）
Ｒ^６ _ｎＮＨ_３−ｎ　　　　　・・・（４）
（式中、Ｒ^６は炭素数１〜３０のアルキル基、ｎは１〜３の整数を示す。また、Ｒ^６が複数の場合には、Ｒ^６は同一でも異なっていてもよい。）
で表されるモノ置換アミン（第一級アミン）、ジ置換アミン（第二級アミン）又はトリ置換アミン（第三級アミン）が挙げられる。
一般式（４）におけるＲ^６の炭素数１〜３０のアルキル基としては、前記一般式（２）及び（３）のＲ^４及びＲ^５と同様のものが挙げられ、直鎖又は分岐状のいずれであってもよい。
酸性リン酸エステルのアミン塩としては、モノ−酸性リン酸メチルエステルドデシルアミン塩又はジ−酸性リン酸メチルエステルドデシルアミン塩が好ましい。
【００１８】
摩擦調整剤としてこの酸性リン酸エステル又は酸性リン酸エステルのアミン塩を用いた場合の含油軸受油全量に対する添加量は、０．００５〜１質量％であると好ましく、０．０１〜０．５質量％であるとさらに好ましい。酸性リン酸エステル又は酸性リン酸エステルのアミン塩の添加量が０．００５質量％未満の場合は、他成分との相乗効果による摩擦特性の向上効果が不十分な場合があり、添加量が１質量％を超えても、添加量に相当する効果の向上がみられない場合がある。
【００１９】
本発明の含油軸受油には、必要に応じ抗乳化剤，防錆剤，金属不活性化剤，清浄分散剤，消泡剤などの各種公知の添加剤を本発明の効果を阻害しない範囲で適宜配合することができる。
抗乳化剤としては、ポリアルキレングリコール，金属スルホネートなどを挙げることができ、中でもＥＯ／ＰＯブロック共重合体（ＥＯはエチレンオキサイド、ＰＯはプロピレンオキサイドで、両末端がＯＨのポリアルキレングリコールが好ましい。
防錆剤としては、金属系スルホネート、カルボン酸、アルカノールアミン、アミド、酸アミド、リン酸エステルの金属塩などを挙げることができ、中でもカルボン酸が好ましい。
金属不活性化剤としては、ベンゾトリアゾールなどを挙げることができる。清浄分散剤として、金属スルホネート、金属フェネート、金属サリチレート、金属ホスホネート、コハク酸イミドなど挙げることができる。
消泡剤としては、メチルシリコーン、フルオロシリコーン、ポリアクリレートなどを挙げることができ、中でもメチルシリコーンが好ましい。
【００２０】
本発明の含油軸受は、前述の本発明の含油軸受油を含浸してなるものであり、本発明の与圧モータは、金属粉を圧粉燒結した含油軸受に支承されるモータ軸に対し、特定方向の側圧を付与する手段が、モータ軸を挟んで対象位置に固定された片側のコアを、モータ軸方向に変位させてなるものである与圧モータにおいて、前記含油軸受が本発明の含油軸受油を含浸してなる与圧モータである。
【００２１】
以下、本発明の与圧モータの具体的な構成について、中逃げ・センターフリー型の燒結含油軸受を用いるとともに、軸受フランジ部をハウジングホルダ側に嵌め合わせ結合させたスピンドルモータを、図１を用いて説明する。
同図において、１はハウジングホルダ、３は軸受、５はモータ軸を表す。ハウジングホルダ１は基盤Ｂ等に取り付けられるとともに円筒部２を有し、しかも該円筒部２の外周面にはコイル１０を巻回させた積層コア９が施されている。
【００２２】
軸受３は、銅等の金属粉を、ハウジングホルダ１内に装入可能な大きさに圧粉成型した後、これを燒結し、さらに本発明の含油軸受油を含浸させて構成され、しかも軸穴中間に中逃げ部４が形成されて所謂中逃げ・センターフリー型に構成されており、長さ方向両端にてモータ軸５を支承する構成となっている。
モータ軸５は、上記軸受３内に支承可能な外径の金属棒からなり、モータの出力側に位置する先端寄りの部分には保持材６を介して前記積層コア９及びコイル１０の外側を覆い、しかもその内周側であって上記した積層コア９に対応させた位置にマグネット８を施したロータ７が一体に取り付けられ、さらにその先端部にはＨＤＤの回転メディアＭを取り付けるハブが同じく一体に取り付けられて構成されている。
【００２３】
さらに、金属粉を圧粉燒結した含油軸受３に支承されるモータ軸５に対し、特定方向の側圧を付与する手段として、モータ軸５を挟んで対称位置に固定された積層コア９のうち、片側のコア９を、モータ軸５方向（ターンテーブル１１寄り）に、ａ線位置からｂ線位置にまで距離ｔ−ｔだけ変位させている。このように積層コア６を傾けることにより高速回転するロータ７を常時矢印Ｐ方向に付勢させることができ、その結果モータ軸５に対し、常時特定方向（矢印Ｙ方向）に側圧を付与することができる。
このように、モータ軸に対し、特定方向の側圧を付与することによって、金属粉を圧粉燒結した含油軸受に対する軸振れを抑制することができる。
【００２４】
【実施例】
次に、実施例を用いて本発明をさらに詳しく説明する。
なお、実施例及び比較例で用いる基油の性状及び含油軸受油の性能は、次のようにして測定した。
（１）動粘度
ＪＩＳ　Ｋ　２２８３に従って測定した。
（２）全酸価
ＪＩＳ　Ｋ　２５０１の５項に従って測定した。
（３）引火点
ＪＩＳ　Ｋ　２２６５に従って測定した。
（４）薄膜残さ試験（残油率）
ＪＩＳ　Ｋ　２５４０の潤滑油熱安定度試験に示されている容器及び恒温空気浴を用い、サンプル量を１ｇとして、１２０℃、１４４時間の残さ量を測定した。それを百分率で表し残油率とした。
また、１４４時間後の油剤外観を観察し、油に不溶なスラッジの有無を確認した。
なお、測定中は絶えず空気を１０リットル／ｈｒ流し込んだ。
（５）加水分解試験
試料油７５ｇ、蒸留水２５及び秤量した銅板をガラス瓶に入れて密封する。このガラス瓶を９３℃に保った恒温漕に入れ、一回転中に一度さかさまになる方向に５ｒｐｍで１６８時間回転させる。試験後、銅板の重量減少量と銅板の変色状態を調べ、さらに油層と水層とを分離し、油層について全酸価上昇量及びガスクロマトグラフィー（ＧＣ）によりＣ１４以下の軽質分の検出を行う。
なお、変色状態を示す評価値は、銅板変色度標準版（ＡＳＴＭ　ＣＯＰＰＥＲＳＴＲＩＰ　ＣＯＲＲＯＳＩＯＮ　ＳＴＡＮＤＡＲＤＳ）　ＭＥＴＨＯＤ　Ｄ　１３０／ＩＰ１５４により定義されるものである。
（６）耐荷重性試験
ＡＳＴＭ　Ｄ　２７８３に準拠して、回転数１，８００ｒｐｍ，室温の条件で行った。最大非焼付荷重（ＬＮＬ）と融着荷重（ＷＬ）から荷重摩耗指数（ＬＷＩ）を求めた。この値が大きいほど耐荷重性が良好である。
（７）耐摩耗性試験
ＡＳＴＭ　Ｄ　２７８３に準拠して、荷重３９２Ｎ、回転数１，２００ｒｐｍ、油温８０℃、試験時間６０分の条件で行った。１／２インチ球３個の摩耗痕径を平均して平均摩耗痕径を算出した。
【００２５】
実施例１〜４及び比較例１〜１２
基油として、ジエステル基油として表１に示す性状を有するジオクチルセバケートを用い、この基油に表２に示す成分の酸化防止剤、摩擦調整剤及び金属不活性化剤を添加した含油軸受油を調製し、その性能を評価した。その結果を表２に示す。
なお、表２中、ＤＢＰＣはジターシャルブチルパラクレゾール、Ｚｎ−ＤＴＰはジンク−ジチオフォスフェートである。また、摩擦調整剤のジ（モノ）メチルアシッドフォスフェートアミン塩は、モノ−体：ジ−体＝５０：５０（モル比）の混合物である。
【００２６】
【表１】

【００２７】
【表２】

【００２８】
【発明の効果】
以上詳細に説明したように、本発明の含油軸受油は、低粘度でありながら高い引火点を持ち、蒸発し難く、分解し難いことに加え、モータ使用中にも低揮発成分や分解ガスが発生せず、特定方向より圧力がかかるような特定構造のモータにおいても含油軸受の摩擦を防止することが可能であり、そのようなモータの含油軸受に含浸させて用いることができ、この含油軸受は前記特定構造の部品として有用である。
【図面の簡単な説明】
【図１】本発明の与圧モータの一例を説明する拡大断面図である。
【符号の説明】
１：ハウジングホルダ
２：円筒部
３：軸受
４：中逃げ部
５：モータ軸
６：保持材
７：ロータ
８：マグネット
９：積層コア
１０：コイル
１１：ターンテーブル
Ｂ：基盤
Ｍ：回転メディア[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an oil-impregnated bearing oil, an oil-impregnated bearing using the same, and a pressurized motor. The present invention relates to an oil-impregnated bearing oil useful for a motor having a specific structure in which a volatile component or a decomposition gas is not generated and pressure is applied from a specific direction, an oil-impregnated bearing using the oil, and a pressurized motor.
[0002]
[Prior art]
The accuracy of spindle motors used for information devices (especially CDs and DVDs) is increasing year by year. Conventionally, bearings used for spindle motors for information equipment include rolling bearings, hydrodynamic bearings, and sintered oil-impregnated bearings. From the viewpoint of performance and cost, bearings suitable for each application are used each time. Selected and used.
On the other hand, a spindle motor of an HDD used as a higher-precision and higher-quality recording device is required to have high rotation accuracy and high reliability, and therefore has a certain clearance with respect to the rotation axis and causes uneven rotation. A sintered oil-impregnated bearing could not be used.
However, sintered oil-impregnated bearings are remarkably excellent in workability and can be mass-produced, so that they can be provided to the market at a lower cost than rolling bearings and hydrodynamic bearings. For this reason, the application of sintered oil-impregnated bearings has been awaited even in the field of HDD equipment where cost reduction is progressing.
In order to solve this, for example, a special mechanism has been developed that applies a side pressure in a specific direction to the sintered oil-impregnated bearing while taking advantage of the characteristics of the sintered oil-impregnated bearing to minimize the run-out of the rotating shaft of the motor. (Japanese Patent Laid-Open No. 2001-295844).
[0003]
When pressure is applied to the sintered oil-impregnated bearing from a specific direction in this way and rotation unevenness is suppressed, if the viscosity of the lubricating oil used there is high, an oil film is generated, which in turn causes rotation unevenness. Would. However, when the viscosity of the lubricating oil is easily reduced, the loss of the lubricating oil is caused, and the durability of the bearing is significantly impaired.
Further, since the inner surface of the bearing is always in contact with the rotating shaft at a constant pressure, wear of the bearing increases. Furthermore, in order to prevent damage (head crash) due to friction between the head and the disk, strict management is performed so as not to generate dust and adsorbed substances in the HDD. Therefore, lubricating oils used in HDDs are required to have an oil agent that does not generate low volatile components or decomposition gas (outgas).
Heretofore, as a sintered oil-impregnated bearing oil having a low viscosity and a low evaporation property, a diester, a polyol ester or a lubricating oil obtained by mixing a monoester with these diesters or polyol esters has been disclosed (Japanese Patent Application Laid-Open Nos. 9-125086 and 9-111). 172267, JP-A-2002-146374).
[0004]
However, while these lubricating oils exhibit performance with respect to conventional bearing mechanisms (mechanisms that do not apply pressure in a specific direction), they apply pressure in a specific direction as described above to suppress rotation unevenness. Is not supported.
Furthermore, although conventional lubricating oils are considered for low viscosity, low evaporability, and heat resistance, lubricating properties and decomposability of base oil (ester) have not been studied. In information devices, especially HDDs, it is necessary to suppress not only low volatile components but also decomposition gases during use. It is known that esters readily decompose into fatty acids and alcohols due to the presence of heat and moisture, so when using a lubricating oil based on esters, pay special attention to the decomposition of the esters, Agents must be selected.
As described above, an oil-impregnated bearing oil that is compatible with a special mechanism that suppresses rotation unevenness of a sintered oil-impregnated bearing and that is compatible with an environment requiring cleanliness such as HDD equipment has not been provided so far.
[0005]
[Problems to be solved by the invention]
The present invention has been made in order to solve the above-mentioned problems, and has low viscosity, low evaporation property, heat resistance, low volatile components and decomposition gas are not generated even during use of a motor, and pressure is increased from a specific direction. An object of the present invention is to provide an oil-impregnated bearing oil capable of preventing friction of the oil-impregnated bearing even in a motor having such a specific structure, an oil-impregnated bearing using the oil, and a pressurized motor.
[0006]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to achieve the above object, and as a result, solved the above-mentioned problems by adding a specific antioxidant and a friction modifier to a low-viscosity ester base oil. And completed the present invention.
That is, the present invention
A low-viscosity ester-based base oil, a phenolic antioxidant or an amine-based antioxidant, and a phosphoric acid ester, a friction modifier comprising at least one selected from acidic phosphate esters and amine salts of acidic phosphate esters. Impregnated bearing oil,
Means for applying a side pressure in a specific direction to an oil-impregnated bearing which is impregnated with the oil-impregnated bearing oil, and a motor shaft supported by an oil-impregnated bearing in which metal powder is sintered are fixed at target positions with the motor shaft interposed therebetween. A pressurized motor in which the one-sided core is displaced in the motor axial direction, wherein the oil-impregnated bearing is provided with the oil-impregnated bearing oil impregnated therein.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, the oil-containing bearing oil is a low-viscosity ester-based base oil, a phenolic antioxidant or an amine-based antioxidant, and at least one selected from orthophosphate esters, acidic phosphate esters and amine salts of acidic phosphate esters. It is obtained by adding a kind of friction modifier.
The low-viscosity ester of the base oil used in the present invention has a kinematic viscosity at 40 ° C. of 1 to 15 mm ² / s (preferably 5 to 13 mm ² / s) and a kinematic viscosity at 100 ° C. of 4 mm ² / s. s or less, the flash point is preferably at least one selected from monoesters, diesters and polyol esters having a flash point of 200 ° C. or higher (preferably 220 ° C. or higher).
[0008]
Examples of the monoester include normal butyl oleate, 2-ethylhexyl oleate, 2-ethylhexyl stearate, 2-ethylhexyl palmitate, butoxyethyl oleate, and the like. Examples of the diester include dioctyl adipate and diisononyl adipate. Diisodecyl adipate, di-2-ethylhexyl azelate, diisooctyl azelate, isononyl azelate, di-2-ethylhexyl sebacate, diisooctyl sebacate, diisononyl sebacate, 2-ethylhexyl dodecane diacid, and the like. Examples of the polyol ester include an ester composed of neopentyl glycol and a carboxylic acid having 8 to 10 carbon atoms, and an ester composed of trimethylolpropane and a carboxylic acid having 8 to 10 carbon atoms. And the like. Of these, diester dioctyl sebacate is particularly preferred.
[0009]
Examples of the phenolic antioxidant used in the present invention include monophenolic compounds such as 2,6-di-tert-butyl-4-methylphenol and 2,6-di-tert-butyl-4-ethylphenol. And diphenols such as 2,4'-methylenebis (2,6-di-tert-butylphenol) and 2,2'-methylenebis (4-ethyl-6-tert-butylphenol). This phenolic antioxidant may be used alone or in combination of two or more.
[0010]
Examples of the amine antioxidant used in the present invention include, for example, monoalkyldiphenylamines such as monooctyldiphenylamine and monononyldiphenylamine, 4,4′-dibutyldiphenylamine, 4,4′-dipentyldiphenylamine, and 4,4′-dihexyl. Dialkyldiphenylamines such as diphenylamine, 4,4'-diheptyldiphenylamine, 4,4'-dioctyldiphenylamine, and 4,4'-dinonyldiphenylamine, tetrabutyldiphenylamine, tetrahexyldiphenylamine, tetraoctyldiphenylamine and tetranonyldiphenylamine; Polyalkyldiphenylamine, α-naphthylamine, phenyl-α-naphthylamine, butylphenyl-α-naphthylamine, pentylphenyl-α-naphthylamine , Hexylphenyl -α- naphthylamine, heptylphenyl -α- naphthylamine, octylphenyl -α- naphthylamine, there may be mentioned naphthylamine such as nonylphenyl -α- naphthylamine, among others those of the dialkyl diphenylamine is preferred. The above-mentioned amine antioxidants may be used alone or in combination of two or more.
Among these antioxidants, phenyl-α-naphthylamine or alkylphenyl-α-naphthylamine having 1 to 18 carbon atoms (alkyl group) is preferable.
[0011]
In the present invention, the amount of the antioxidant added to the total amount of the oil-containing bearing oil is preferably 0.05 to 10% by mass, and more preferably 0.3 to 5% by mass. If the amount of the antioxidant is less than 0.05% by mass, the antioxidant effect may not be obtained, and if it exceeds 10% by mass, the effect corresponding to the added amount may not be improved.
[0012]
As the orthophosphate of the friction modifier used in the present invention, a trialkyl phosphate having 1 to 20 carbon atoms (alkyl group) and a triaryl phosphate having 1 to 18 carbon atoms (aryl group) are preferable. Those represented by (1) are preferred.
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In the above formula (1), R ^{1 to} R ³ represent an alkyl group, an alkenyl group, an alkylaryl group or an arylalkyl group having 4 to 30 carbon atoms, and R ^{1 to} R ³ may be the same or different.
[0013]
Examples of the orthophosphate include triaryl phosphate, trialkyl phosphate, trialkylaryl phosphate, triarylalkyl phosphate, trialkenyl phosphate, and the like.Specifically, for example, triphenyl phosphate, tricresyl phosphate, benzyl diphenyl Phosphate, ethyl diphenyl phosphate, tributyl phosphate, ethyl dibutyl phosphate, cresyl diphenyl phosphate, dicresyl phenyl phosphate, ethyl phenyl diphenyl phosphate, diethyl phenyl phenyl phosphate, propyl phenyl diphenyl phosphate, dipropyl phenyl phenyl phosphate, triethyl phenyl phosphate, tripropyl Phenyl phosphate, butyl phosphate Rudiphenyl phosphate, dibutyl phenyl phenyl phosphate, tributyl phenyl phosphate, trihexyl phosphate, tri (2-ethylhexyl) phosphate, tridecyl phosphate, trilauryl phosphate, trimyristyl phosphate, tripalmityl phosphate, tristearyl phosphate, trioleyl phosphate, etc. Can be mentioned. The above orthophosphates may be used alone or in combination of two or more.
Among these orthophosphates, tricresyl phosphate, triphenyl phosphate, tripropylphenyl phosphate, and tributylphenyl phosphate are preferred.
[0014]
When this orthophosphate ester is used as a friction modifier, the amount added to the total amount of the oil-containing bearing oil is preferably 0.01 to 10% by mass, and more preferably 0.05 to 5% by mass. When the amount of the orthophosphoric acid ester is less than 0.01% by mass, the effect of improving the friction characteristics due to the synergistic effect with other components may be insufficient, and even if the amount exceeds 10% by mass, In some cases, the effect corresponding to the amount is not improved.
[0015]
As the acidic phosphoric acid ester of the friction modifier used in the present invention, an alkyl acid phosphate or an alkyl hydrogen phosphite having 1 to 20 carbon atoms (alkyl group) is preferable, and in particular, represented by the following formula (2) or (3): Those represented are preferred.
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[0016]
In the above formulas (2) and (3), R ⁴ and R ⁵ represent an alkyl group having 1 to 30 carbon atoms, specifically, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group. Group, isobutyl group, s-butyl group, t-butyl group, various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, various decyl groups, various undecyl groups, various dodecyl groups, various tridecyl groups , Various tetradecyl groups, various pentadecyl groups, various hexadecyl groups, various heptadecyl groups, various octadecyl groups, various nonadecyl groups, various eicosyl groups, various heneicosyl groups, various docosyl groups, various tricosyl groups, various tetracosyl groups, various pentacosyl groups, various pentacosyl groups, various Hexacosyl group, various heptacosyl groups, various octakosyl groups, various nonacosyl groups, various tria Pentyl group, and a methyl group is preferred among these. R ⁴ and R ⁵ may be the same or different.
[0017]
Further, the amines forming the amine salt of the acidic phosphate ester of the friction modifier used in the present invention include the following formula (4)
R ⁶ _n NH _3-n (4)
(Wherein, ^{R 6} is an alkyl group having 1 to 30 carbon atoms, n represents an integer of 1-3. Furthermore, when ^{R 6} is a plurality, ^{R 6} may be the same or different.)
And a disubstituted amine (secondary amine) or a trisubstituted amine (tertiary amine).
Examples of the alkyl group having 1 to 30 carbon atoms of R ⁶ in the general formula (4) include the same groups as R ⁴ and R ^{5 in the} general formulas (2) and (3), and include straight-chain or branched alkyl groups. Any of them may be used.
As the amine salt of the acidic phosphoric acid ester, mono-acidic phosphoric acid methyl ester dodecylamine salt or di-acidic phosphoric acid methyl ester dodecylamine salt is preferable.
[0018]
When the acidic phosphate ester or the amine salt of the acidic phosphate ester is used as the friction modifier, the amount added to the total amount of the oil-containing bearing oil is preferably 0.005 to 1% by mass, and 0.01 to 0.5% by mass. It is more preferable that the content be mass%. When the amount of the acidic phosphate ester or the amine salt of the acidic phosphate ester is less than 0.005% by mass, the effect of improving the friction characteristics due to the synergistic effect with other components may be insufficient, and the amount of the additive may be 1%. Even when the amount exceeds the mass%, the effect corresponding to the added amount may not be improved in some cases.
[0019]
The oil-impregnated bearing oil of the present invention may optionally contain various known additives such as a demulsifier, a rust inhibitor, a metal deactivator, a detergent / dispersant, and a defoamer as long as the effects of the present invention are not impaired. Can be blended.
Examples of the demulsifier include polyalkylene glycols and metal sulfonates. Among them, EO / PO block copolymers (EO is ethylene oxide, PO is propylene oxide, and polyalkylene glycol having both ends OH are preferable).
Examples of the rust inhibitor include metal sulfonates, carboxylic acids, alkanolamines, amides, acid amides, metal salts of phosphoric acid esters, and the like. Among them, carboxylic acids are preferable.
Benzotriazole etc. can be mentioned as a metal deactivator. Examples of detergent dispersants include metal sulfonates, metal phenates, metal salicylates, metal phosphonates, succinimides, and the like.
Examples of the antifoaming agent include methyl silicone, fluorosilicone, and polyacrylate, and among them, methyl silicone is preferable.
[0020]
The oil-impregnated bearing of the present invention is obtained by impregnating the oil-impregnated bearing oil of the present invention described above. In the pressurized motor, the means for applying the side pressure in a specific direction is obtained by displacing the core on one side fixed to the target position across the motor shaft in the motor axis direction, wherein the oil-impregnated bearing according to the present invention This is a pressurized motor impregnated with bearing oil.
[0021]
Hereinafter, a specific configuration of the pressurized motor according to the present invention will be described with reference to FIG. 1, which shows a spindle motor in which a middle relief / center-free type sintered oil-impregnated bearing is used and a bearing flange portion is fitted and coupled to a housing holder side. Will be explained.
In the figure, 1 is a housing holder, 3 is a bearing, and 5 is a motor shaft. The housing holder 1 is attached to a base B or the like and has a cylindrical portion 2, and the outer peripheral surface of the cylindrical portion 2 is provided with a laminated core 9 around which a coil 10 is wound.
[0022]
The bearing 3 is formed by compacting a metal powder such as copper into a size that can be inserted into the housing holder 1, then sintering it, and further impregnating with the oil-impregnated bearing oil of the present invention. A middle escape portion 4 is formed in the middle of the hole to form a so-called center escape / center-free type. The motor shaft 5 is supported at both ends in the length direction.
The motor shaft 5 is made of a metal rod having an outer diameter that can be supported in the bearing 3, and a portion near the front end located on the output side of the motor is provided with a holding member 6 through the outside of the laminated core 9 and the coil 10. A rotor 7 provided with a magnet 8 is integrally mounted at a position corresponding to the above-described laminated core 9 on the inner peripheral side thereof, and a hub for attaching a rotating medium M of the HDD is also provided at the tip thereof. It is configured to be integrally attached.
[0023]
Further, as means for applying a lateral pressure in a specific direction to the motor shaft 5 supported on the oil-impregnated bearing 3 in which the metal powder is sintered by powder, among the laminated cores 9 fixed at symmetrical positions with the motor shaft 5 interposed therebetween, The core 9 on one side is displaced in the direction of the motor shaft 5 (closer to the turntable 11) by a distance tt from the position of the line a to the position of the line b. By inclining the laminated core 6 in this manner, the rotor 7 rotating at a high speed can always be urged in the direction of the arrow P, and as a result, the lateral pressure is constantly applied to the motor shaft 5 in the specific direction (the direction of the arrow Y). Can be.
As described above, by applying a lateral pressure in a specific direction to the motor shaft, it is possible to suppress the shaft runout with respect to the oil-impregnated bearing in which metal powder is sintered by powder.
[0024]
【Example】
Next, the present invention will be described in more detail using examples.
In addition, the property of the base oil used in the Example and the comparative example and the performance of the oil-containing bearing oil were measured as follows.
(1) Kinematic viscosity Measured according to JIS K 2283.
(2) Total acid value It was measured in accordance with JIS K2501.
(3) Flash point Measured according to JIS K 2265.
(4) Thin film residue test (residual oil rate)
Using the container and the constant temperature air bath indicated in the lubricating oil thermal stability test of JIS K 2540, the amount of the residue was measured at 120 ° C. for 144 hours with the sample amount being 1 g. It was expressed as a percentage and used as the residual oil ratio.
Further, the appearance of the oil agent after 144 hours was observed, and the presence or absence of sludge insoluble in oil was confirmed.
During the measurement, air was constantly supplied at a rate of 10 liter / hr.
(5) Hydrolysis test 75 g of sample oil, 25 distilled water and a weighed copper plate are put in a glass bottle and sealed. This glass bottle is placed in a thermostat kept at 93 ° C., and is rotated once at one rotation during one rotation at 5 rpm for 168 hours. After the test, the amount of weight loss of the copper plate and the discolored state of the copper plate are examined. Further, the oil layer and the aqueous layer are separated, and the oil layer is subjected to a total acid value increase and a light component of C14 or less by gas chromatography (GC). .
The evaluation value indicating the discolored state is defined by the standard value of copper plate discoloration standard (ASTM COPERSTRIP CORROSION STANDARDS) METHOD D 130 / IP154.
(6) Load resistance test According to ASTM D2783, the test was performed under the conditions of a rotation speed of 1,800 rpm and room temperature. The load and wear index (LWI) was determined from the maximum non-seizure load (LNL) and the fusion load (WL). The larger the value, the better the load resistance.
(7) Abrasion resistance test Abrasion resistance test was carried out under the conditions of a load of 392 N, a rotation speed of 1,200 rpm, an oil temperature of 80 ° C., and a test time of 60 minutes in accordance with ASTM D2783. The average wear scar diameter was calculated by averaging the wear scar diameters of three 1/2 inch balls.
[0025]
Examples 1 to 4 and Comparative Examples 1 to 12
Oil-containing bearing oil obtained by using dioctyl sebacate having the properties shown in Table 1 as a diester base oil and adding an antioxidant, a friction modifier and a metal deactivator having the components shown in Table 2 to this base oil Was prepared and its performance was evaluated. Table 2 shows the results.
In Table 2, DBPC is di-tert-butyl paracresol and Zn-DTP is zinc dithiophosphate. The di (mono) methyl acid phosphate amine salt of the friction modifier is a mixture of mono-form: di-form = 50: 50 (molar ratio).
[0026]
[Table 1]

[0027]
[Table 2]

[0028]
【The invention's effect】
As described in detail above, the oil-impregnated bearing oil of the present invention has a low flash point, a high flash point, is difficult to evaporate, is difficult to decompose, and has low volatile components and decomposed gas during use of the motor. It is possible to prevent oil-impregnated bearing friction even in a motor having a specific structure in which pressure does not occur and a pressure is applied from a specific direction, and the oil-impregnated bearing of such a motor can be used by impregnating it. Is useful as a component having the specific structure.
[Brief description of the drawings]
FIG. 1 is an enlarged sectional view illustrating an example of a pressurized motor according to the present invention.
[Explanation of symbols]
1: Housing holder 2: Cylindrical part 3: Bearing 4: Middle relief part 5: Motor shaft 6: Holding member 7: Rotor 8: Magnet 9: Laminated core 10: Coil 11: Turntable B: Base M: Rotating media

Claims (11)

A low-viscosity ester-based base oil, a phenolic antioxidant or an amine-based antioxidant, and a phosphoric acid ester, a friction modifier comprising at least one selected from acidic phosphate esters and amine salts of acidic phosphate esters. Oil-impregnated bearing oil added. Wherein the low viscosity ester, kinematic viscosity at 40 ℃ 1~15mm ² / s, 100 kinematic viscosity at ° C. is ^{4 mm} 2 / s or less, selected flash point 200 ° C. or more monoesters, diesters and polyol esters The oil-impregnated bearing oil according to claim 1, which is at least one kind. 2. The oil-impregnated bearing oil according to claim 1, wherein the low-viscosity ester comprises diester dioctyl sebacate. The addition amount of the phenolic antioxidant or the amine antioxidant is 0.05 to 10% by mass and the addition amount of the friction modifier is 0.01 to 10% by mass based on the total amount of the oil-containing bearing oil. The oil-impregnated bearing oil described in 1. The oil-impregnated bearing oil according to claim 1, wherein the antioxidant comprises phenyl-α-naphthylamine which is an amine-based antioxidant or alkylphenyl-α-naphthylamine having 1 to 18 carbon atoms (alkyl group). The friction modifier comprises a trialkyl phosphate having a carbon number of 1 to 20 (alkyl group) or a triaryl phosphate having a carbon number of 1 to 18 (aryl group), which is an orthophosphate ester, and is added to the total amount of the oil-containing bearing oil. Is 0.1 to 10% by mass. The friction modifier comprises an acid phosphate ester of an alkyl acid phosphate or an alkyl hydrogen phosphite having 1 to 20 carbon atoms (alkyl group), and the addition amount of the oil-containing bearing oil is 0.005 to 1% by mass. The oil-impregnated bearing oil according to claim 1. The friction modifier comprises a mono-acidic acid methyl ester dodecylamine salt or a di-acidic acid methyl ester dodecylamine salt, which is an amine salt of an acidic phosphoric acid ester. The oil-impregnated bearing oil according to claim 1, which is 1% by mass. Means for applying a lateral pressure in a specific direction to a motor shaft supported on an oil-impregnated bearing in which metal powder is sintered by powder is used to displace a core on one side fixed to a target position across the motor shaft in the motor shaft direction. The oil-impregnated bearing oil according to any one of claims 1 to 8, wherein the oil-impregnated bearing oil is used in the oil-impregnated bearing. An oil-impregnated bearing obtained by impregnating the oil-impregnated bearing oil according to claim 1. Means for applying a lateral pressure in a specific direction to a motor shaft supported on an oil-impregnated bearing in which metal powder is sintered by powder is used to displace a core on one side fixed to a target position across the motor shaft in the motor shaft direction. A pressurized motor comprising: a pressurized motor comprising the oil-impregnated bearing oil according to any one of claims 1 to 8.

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