JP2004026941A - Lubricating grease and roller bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricating grease which is excellent in high-temperature durability, exhibits a low dust generation, a low volatility, and a high fretting resistance in high-speed applications, and is cheaper than a fluorine-based grease; and a roller bearing with the lubricating grease confined therein. <P>SOLUTION: The lubricating grease is a grease mixture of a fluorine-based lubricating grease comprising a perfluoropolyether oil as the base oil and a fluororesin powder as the thickening agent and a urea-based lubricating grease comprising a synthetic oil other than a perfluoropolyether oil as the base oil and a urea compound as the thickening agent. When the grease mixture is left standing at 200°C for 250 hr, its evaporation amount is 15 wt% or lower. <P>COPYRIGHT: (C)2004,JPO

Description

【化２】

【化３】

【化４】

【化５】

【００１９】
増ちょう剤であるフッ素樹脂粉は上記パーフルオロポリエーテル油と親和性が高く、高温安定性、耐薬品性を有する粉末が使用できる。
フッ素樹脂を例示すれば、ポリテトラフルオロエチレン（ＰＴＦＥ）、テトラフルオロエチレン−パーフルオロアルキルビニルエーテル共重合体（ＰＦＡ）、テトラフルオロエチレン−ヘキサフルオロプロピレン共重合体（ＦＥＰ）などのパーフルオロ系フッ素樹脂が好ましく、特にポリテトラフルオロエチレン（ＰＴＦＥ）が高温安定性、耐薬品性が優れているため好ましい。
【００２０】
フッ素系潤滑グリースは、フッ素系潤滑グリース全体量に対して、パーフルオロポリエーテル油を　７０〜９０　重量％、フッ素樹脂粉を　１０〜３０　重量％配合することが好ましい。この範囲の配合とすることにより、転がり軸受封入グリースとして洩れが少なく、長時間トルクを下げられる好ましいちょう度に調整できる。
【００２１】
本発明に使用できるウレア系潤滑グリースは増ちょう剤としてウレア化合物を用いる。
ウレア化合物は尿素結合を分子内に　２　個有するジウレアが好ましく、以下の化６で示される。
【化６】

ここで、Ｒ_１、Ｒ_２およびＲ_３は、脂肪族基、脂環族基または芳香族基をそれぞれ表す。Ｒ_１およびＲ_２が脂環族基および／または芳香族基である脂環族ウレア、芳香族ウレアが優れた高温性を有するため好ましい。なお、ウレア化合物の製造方法の一例としては、ジイソシアナート化合物にイソシアナート基当量のアミン化合物を反応させて得られる。
【００２２】
第１のウレア系潤滑グリースは、上記ウレア化合物を増ちょう剤として、炭素数　７〜２２　の脂肪族一価アルコールと芳香族多価カルボン酸とのエステル、および炭素数　７〜２２　の脂肪族一価カルボン酸と脂肪族多価アルコールとのエステルから選ばれた少なくとも一つのエステル油を基油として用いる。脂肪族一価アルコールおよび脂肪族一価カルボン酸において、炭素数　７　未満および炭素数　２２　をこえると潤滑性が劣る。
炭素数　７〜２２　の脂肪族一価アルコールとしては、ヘプチルアルコール、オクチルアルコール、ノニルアルコール、デシルアルコール、ウンデシルアルコール、ラウリルアルコール、オレイルアルコール、ステアリルアルコール等が挙げらる。
【００２３】
また、炭素数　７〜２２　の脂肪族一価カルボン酸は、上記脂肪族一価アルコールの−ＣＨ_２ＯＨを−ＣＯＯＨに代えた一価カルボン酸が挙げられる。
【００２４】
芳香族多価カルボン酸としては、フタル酸、イソフタル酸、テレフタル酸、トリメリット酸、トリメシン酸、ピロメリット酸、ジフェニルテトラカルボン酸、ベンゾフェノンテトラカルボン酸などが挙げられる。
【００２５】
脂肪族多価アルコールとしては、１，３　ブチレングリコール、グリセリン、プロピレングリコール、エチレングリコール、ペンタジオール、ジエチレングリコール、ポリエチレングリコール、ポリプロピレングリコール、トリメチロールプロパン、ペンタエリスリトール、ジペンタエリスリトール、ソルビトールなどが挙げられる。
【００２６】
第１のウレア系潤滑グリースは、ウレア系潤滑グリース全体量に対して、上記エステル油を　７０〜９５　重量％、ウレア化合物を　３０〜５　重量％配合することが好ましい。この範囲の配合とすることにより、軸受封入グリースとして漏れが少なく、長時間潤滑性の良好なちょう度に調整できる。
【００２７】
第２のウレア系潤滑グリースは、上記化６で示されるウレア化合物を増ちょう剤とする潤滑グリースである。
基油としては、ポリオレフィン油、アルキルジフェニルエーテル油またはエステル油を用いることができる。
【００２８】
ポリオレフィン油は、以下の化７、化８で示される液状のポリオレフィンが使用できる。
【化７】

ここで、ｎは　４〜１６　の整数、ｍは　１〜６　の整数である。
【化８】

ここで、ｎは　１〜８　の整数、ｍは　１〜３　の整数、ｑは　１〜３　の整数、ｐはポリオレフィン油の粘度により異なる整数である。
【００２９】
ポリオレフィン油は、室温で液状を示し、動粘度が１００ｍｍ^２／ｓ　（４０℃）以上のものが好ましい。１００ｍｍ^２／ｓ　未満の動粘度であると潤滑グリースとした場合に蒸発損失が大きく長時間での潤滑性が期待できない。
【００３０】
アルキルジフェニルエーテル油は、以下の化９で示されるモノアルキルジフェニルエーテル油、および／または化１０で示されるジアルキルジフェニルエーテル油が使用できる。
【化９】

【化１０】

ここで、Ｒ_４、Ｒ_５、Ｒ_６は、それぞれ炭素数　８〜２０　のアルキル側鎖であり、一つのフェニル環に結合しているか、あるいは二つのフェニル環にそれぞれ結合している。
これらの中で、耐熱性、蒸発特性を考慮するとアルキル側鎖Ｒ_５およびＲ_６を有するジアルキルジフェニルエーテル油が好ましい。
【００３１】
エステル油は、ジエステル油、ポリオールエステル油またはこれらのコンプレックスエステル油、芳香族エステル油などが使用できる。
ポリオールエステル油としては、脂肪族一価アルコールと芳香族多価カルボン酸とのエステル、および脂肪族一価カルボン酸と脂肪族多価アルコールとのエステル等が挙げられる。
【００３２】
第２のウレア系潤滑グリースは、上記ポリオレフィン油を基油とし、化６で示すウレア化合物を増ちょう剤とする潤滑グリース、上記アルキルジフェニルエーテル油を基油とし、化６で示すウレア化合物を増ちょう剤とする潤滑グリース、および上記エステル油を基油とし、化６で示すウレア化合物を増ちょう剤とする潤滑グリースの中から選ばれた少なくとも一つの潤滑グリースである。
【００３３】
ポリオレフィン油を基油とする潤滑グリースは、グリース全体量に対して、ポリオレフィン油を　７０〜９５　重量％、化６で示すウレア化合物を　３０〜５　重量％配合することが好ましい。この範囲の配合とすることにより、軸受封入グリースとして好ましいちょう度に調整できる。
また、アルキルジフェニルエーテル油を基油とする潤滑グリースは、グリース全体量に対して、アルキルジフェニルエーテル油を　７０〜９５　重量％、化６で示すウレア化合物を　３０〜５　重量％配合することが好ましい。この範囲の配合とすることにより、軸受封入グリースとして好ましいちょう度に調整できる。
また、エステル油を基油とする潤滑グリースは、グリース全体量に対して、エステル油を　７０〜９５　重量％、化６で示すウレア化合物を　３０〜５　重量％配合することが好ましい。この範囲の配合とすることにより、軸受封入グリースとして漏れが少なく、長時間潤滑性の良好なちょう度に調整できる。
【００３４】
フッ素系潤滑グリースと、ウレア系潤滑グリースとを混合したときの混合グリースは、該混合グリースを　２００℃で　２５０　時間放置したときの蒸発量が　１５　重量％以下である。　１５　重量％をこえると高温耐久性が低下し、また発塵しやすくなる。
蒸発量は日本工業規格（ＪＩＳ）Ｒ３５０３に準拠した　５０ｍｌ　ガラス製ビーカにグリースを約　５ｇ　採取して、　２００℃に設定された熱風循環式の恒温槽（内容積：９０　リットル、風量：５．１ｍ^３／分、風速：０．４２ｍ／秒）内に　２５０　時間放置して、グリースの初期重量と放置後の重量を測定して次式で求める。
蒸発量（％）＝［（初期重量−放置後の重量）／初期重量］×１００
【００３５】
第１および第２のウレア系潤滑グリースは、上記方法で測定したとき、それぞれのウレア系潤滑グリースの蒸発量が　２５　重量％以下である。蒸発量が　２５　重量％をこえると、フッ素系潤滑グリースと混合したとき、混合グリースの蒸発量を１５　重量％以下とすることができない。
【００３６】
ウレア系潤滑グリースは、それぞれ混合グリース全体に対して　３０〜７５　重量％配合される。ウレア系潤滑グリースの混合割合が　７５　重量％をこえると、混合グリースの蒸発量が　１５　重量％をこえ、　３０　重量％未満であると、潤滑グリースの製造原価を低下させることができない。
【００３７】
また上記各潤滑グリースまたは混合グリースには、必要に応じて公知の添加剤を含有させることができる。この添加剤として、例えば、アミン系、フェノール系、イオウ系、ジチオりん酸亜鉛などの酸化防止剤、塩素系、イオウ系、りん系、ジチオりん酸亜鉛、有機モリブデンなどの極圧剤、ベンゾトリアゾール、亜硝酸ソーダなどの金属不活性剤、ポリメタクリレート、ポリイソブチレン、ポリスチレンなどの粘度指数向上剤、摩耗抑制剤、清浄分散剤などが挙げられる。
さらに、混合グリースに対しては、フッ素系グリースでは使用できなかった防錆性の優れた炭化水素（鉱油）系防錆添加剤、石油スルホネート、ジノナニルナフタレンスルホネート、アミン、ソルビタンエステルなどを用いることができる。
また、これらの添加剤は単独または　２　種類以上組み合わせて添加できる。
【００３８】
本発明に係る転がり軸受の一例を図１に示す。図１は小径転がり軸受の断面図である。
転がり軸受１は、外周面に内輪転走面を有する内輪２と内周面に外輪転走面を有する外輪３とが同心に配置され、内輪転走面と外輪転走面との間に介在される複数個の転動体４および図示を省略した保持器およびシール部材とにより構成される。少なくとも転動体４の周囲に潤滑グリース５が封入される。
【００３９】
潤滑グリース５の中で、フッ素系潤滑グリースと、上記第１のウレア系潤滑グリースとの混合グリースは耐熱耐久性に優れるため、電装補機または定着ローラに使用される転がり軸受に好適に使用できる。
また、潤滑グリース５の中で、フッ素系潤滑グリースと、上記第１のウレア系潤滑グリースとの混合グリースは低発塵性、フレッティング性、低揮発性に優れるため、光学式ロータリーエンコーダを内蔵したサーボモータに使用される転がり軸受に好適に使用できる。
【００４０】
【実施例】
参考例１：グリース１の作製
グリース全体に対して、パーフルオロポリエーテル油（デュポン社製商品名、クライトックス２４０ＡＣ）　６７　重量％に、フッ素樹脂粉（デュポン社製商品名、バイダックス）　３３　重量％を加え撹拌した後、ロールミルに通し「増ちょう剤にフッ素樹脂粉、基油にパーフルオロポリエーテル油を用いたグリース」である半固形状のグリース１を得た。
【００４１】
参考例２：グリース２の作製
グリース全体に対して、芳香族エステル油（旭電化工業社製商品名、プルーバーＴ９０）　８８　重量％の半量に　１　モルのジイソシアネートを溶かし、残りの半量に　２　モルのモノアミンを溶かして上記半量の基油に攪拌しながら加えた後、１００〜１２０℃で　３０　分間攪拌を続けて反応させ、ウレア化合物　１２　重量％を基油に折出した。その後、ロールミルに通し「増ちょう剤にウレア化合物、基油に合成油を用いたグリース」である半固形状のグリース２を得た。
【００４２】
参考例３：グリース３の作製
グリース全体に対して、アルキルジフェニールエーテル油（松村石油社製商品名、モレスコＬＢ１００、動粘度　９７ｍｍ^２／ｓ（ａｔ４０℃））　７７　重量％の半量に　１　モルのジイソシアネートを溶かし、残りの半量に　２　モルのモノアミンを溶かして上記半量の基油に攪拌しながら加えた後、１００〜１２０℃で　３０　分間攪拌を続けて反応させ、ウレア化合物　２３　重量％を基油に折出した。その後、ロールミルに通し「増ちょう剤にウレア化合物、基油に合成油を用いたグリース」である半固形状のグリース３を得た。
【００４３】
参考例４：グリース４の作製
グリース全体に対して、ポリオレフィン油（三井化学社製商品名、ルーカントＨＣ−２０、動粘度　１５５ｍｍ^２／ｓ（ａｔ４０℃））　８２　重量％の半量に　１　モルのジイソシアネートを溶かし、残りの半量に　２　モルのモノアミンを溶かして上記半量の基油に攪拌しながら加えた後、１００〜１２０℃で　３０　分間攪拌を続けて反応させ、ウレア化合物　１８　重量％を基油に折出した。その後、ロールミルに通し「増ちょう剤にウレア化合物、基油に合成油を用いたグリース」である半固形状のグリース４を得た。
【００４４】
実施例１〜実施例３および比較例１〜比較例６
表１に示す割合で各グリースをそれぞれ混合撹拌して潤滑グリースを得た。配合比率はグリース全体に対する重量％である。実施例１には鉱油をベースにしたアミン系防錆添加剤を添加している。
比較例１〜比較例４のグリースは参考例１〜参考例４で作製したものであり、比較例５、６は表１に示す割合で各グリースをそれぞれ混合攪拌して混合グリースとした。
得られた混合グリースの混和ちょう度、滴点、体積当たりのコストを比較例１を　１　として算出した。その結果を表１に示す。
また、日本工業規格（ＪＩＳ）Ｒ３５０３に準拠した　５０ｍｌ　ガラス製ビーカにグリースを約　５ｇ　採取して、　２００℃に設定された熱風循環式の恒温槽（内容積：９０　リットル、風量：５．１ｍ^３／分、風速：０．４２ｍ／秒）内に　２５０　時間放置したときの蒸発量を測定して表１に示す。
【００４５】
石油ベンジンで洗浄した軸受　６２０４ＺＺに全空間容積の　３８　％となる各実施例の潤滑グリースを封入して転がり軸受を作製した。得られた転がり軸受を高温耐久試験にて評価した。
高温耐久試験は、ラジアル荷重　６７Ｎ　、スラスト荷重　６７Ｎ　、回転数　１００００ｒｐｍ　、雰囲気温度　２００℃にて軸受を回転させ、過負荷によりモータが停止するまでの時間を測定した。結果を表１に示す。
【００４６】
また、石油ベンジンで洗浄した軸受　３０２０４に全空間容積の　４４　％となる各実施例の潤滑グリースを封入して転がり軸受を作製した。得られた転がり軸受をスラスト荷重　９８Ｎ　、回転数　１８００ｒｐｍ　、室温にて慣らし運転させた後、１　％食塩水に　１０　秒間浸漬させ、４０℃で　４８　時間放置した後の錆の発生を観察した。錆の観察は外輪転走面を周方向に　３２　等分し、錆の発生した区分を数え、パーセントで表した。結果を表１に示す。
【００４７】
【表１】

表１に示すように、実施例１〜実施例３の潤滑グリースは高温耐久試験に優れ、低コストであった。
【００４８】
実施例４〜実施例６および比較例７〜比較例８
表２に示す割合で各グリースをそれぞれ混合撹拌して潤滑グリースを得た。配合比率はグリース全体に対する重量％である。比較例７はリチウム石鹸−ポリオレフィン油系の低発塵グリース、比較例８はリチウム石鹸−エステル油系の汎用サーボモータ用グリースである。なお、比較例１および比較例４を表２に併記する。
得られた潤滑グリースの混和ちょう度、滴点、体積当たりのコストを比較例１を１として算出した。その結果を表２に示す。また、実施例１と同様にして測定した蒸発量を表２に示す。
【００４９】
石油ベンジンで洗浄した試験軸受　６０００ＬＬＢに全空間容積の　２９　％となる各実施例の潤滑グリースを封入して転がり軸受を作製した。
得られた転がり軸受を用いて、図２に示す発塵量測定試験装置を用いて発塵性を評価した。試験台６を貫通する回転軸７の上部に２つの試験用軸受８をそれぞれ挿通するように取付け、クランプ型治具９にコイルばね１０を介して２つの試験用軸受にスラスト荷重を負荷し、クランプ型治具９を試験台６上に固定された係止具１１で回転不能の状態に固定した。
また、試験台６の上面には、クランプ型治具９を覆う大きさの箱型の気密性カバー１２を設け、この気密性カバー１２には、クリーンエア（塵埃を含まない清浄空気）の導入ダクト１３及び排気ダクト１４を接続し、排気ダクト１４は吸気ポンプを内蔵するダストカウンタ１５（パーティクルカウンタとも呼ばれる。）に接続した。なお、回転軸７は試験台６の下方に設置した電動モータ１６で回転駆動し、試験台６の下面と回転軸７は磁性流体シール１７で密封した。
試験条件は、回転軸の回転速度を　１８００ｒｐｍ　、スラスト荷重　１５Ｎ　、雰囲気温度は室温、清浄空気流量　０．４７５リットル／分、運転開始から　７〜８　時間後の　０．５μｍ　以上の塵総数を計測した。結果を表２に示す。
【００５０】
ＡＳＴＭＤ　４１７０に準拠したＦａｆｎｉｒ微動摩耗試験を行ない微動摩耗量を測定してフレッティング性を評価した。測定条件を以下に、結果を表２に示す。
軸受　　　　　：５１２０４Ｊ
グリース封入量：１±０．１ｇ
荷重　　　　　：２４５０Ｎ（１．７ＧＰａ）
遥動角　　　　：１２゜
サイクル　　　：３０Ｈｚ
温度　　　　　：室温
時間　　　　　：２時間
測定量　　　　：内外輪の摩耗量（ｍｇ）
【００５１】
【表２】

表２に示すように、実施例４〜実施例６の潤滑グリースは比較例８に比較して低発塵性を示し、かつ優れたフレッティング性を示した。
【００５２】
【発明の効果】
本発明の潤滑グリースは、フッ素系潤滑グリースとウレア系潤滑グリースとの混合グリースであり、蒸発量が　１５　重量％以下であるので、高温耐久性および発塵性に優れ、かつ低コストの潤滑グリースが得られる。
また、ウレア系潤滑グリースを代えることにより、高温耐久性により優れた潤滑グリース、または発塵性により優れた潤滑グリースが得られる。
その結果、上記潤滑グリースを封入することにより、電装補機や定着ローラ等に使用できる転がり軸受、光学式ロータリーエンコーダを内蔵したサーボモータに使用できる転がり軸受が得られる。
【図面の簡単な説明】
【図１】小径転がり軸受の断面図である。
【図２】発塵量測定試験装置を示す図である。
【符号の説明】
１　　転がり軸受
２　　内輪
３　　外輪
４　　転動体
５　　潤滑グリース
６　　試験台
７　　回転軸
８　　試験軸受
９　　クランプ型治具
１０　コイルばね
１１　係止具
１２　気密性カバー
１３　導入ダクト
１４　排気ダクト
１５　ダストカウンタ
１６　電動モータ
１７　磁性流体シール[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a lubricating grease and a rolling bearing, and in particular, a lubricating grease excellent in high-temperature durability used for an electric auxiliary machine, a fixing roller, and the like, a rolling bearing filled with the lubricating grease, or a servo incorporating an optical rotary encoder. The present invention relates to a lubricating grease excellent in low dust generation used for a motor and the like, and a rolling bearing in which the lubricating grease is sealed.
[0002]
[Prior art]
Lubricating grease is sealed in the rolling bearing to provide lubrication. This lubricating grease is obtained by kneading a base oil and a thickener as main components, and a synthetic oil such as a mineral oil, an ester oil, a silicone oil or an ether oil as a base oil, and a lithium soap or the like as a thickener. Metal soaps and urea compounds are generally used. Further, various additives such as an antioxidant, a rust inhibitor, a metal deactivator, and a viscosity index improver are added to the lubricating grease as needed.
[0003]
In recent years, the demand for lighter vehicles has led to smaller and lighter automotive electrical components, but on the other hand, the performance of electrical components requires higher output and higher efficiency. A technique has been adopted to compensate for the decrease in output by rotating at high speed.
For this reason, rolling bearings used for electrical accessories such as electromagnetic clutches, alternators, and flywheel dampers have been required to withstand high-speed rotation and high loads. The life of grease sealed in a bearing is usually shorter than the service life due to fatigue of the bearing itself. As a result, the life of the bearing itself depends on the life of the grease, and there is a need for grease having excellent high-temperature durability such as seizure life under high speed and high load.
[0004]
In general, urea-based grease is used as the grease for rolling bearings used in electrical accessories. In addition, the grease for rolling bearings used in fan clutches, which become extremely hot at around 200 ° C, uses fluorine resin powder as a thickener and uses perfluoropolyether oil as the base oil. Is used.
[0005]
The heat roller of the copier has a heater inserted into the roller axis to heat and melt the toner consisting of thermoplastic resin and colorant and fix it on the paper surface by pressure. Becomes extremely high around 200 ° C. Therefore, the above-mentioned fluorine-based grease is sealed in the rolling bearing supporting the heat roller.
[0006]
On the other hand, in the case of servo motors with built-in optical rotary encoders, dust and volatile vapor scattered from the grease of sealed ball bearings may fog the slits and lenses of the rotary encoder in high-speed applications. There is a need for a rolling bearing in which grease is sealed.
Conventionally, lubricating grease having low consistency is generally used to obtain excellent low dust generation. Further, in order to obtain excellent low volatility, a fluorine-based grease is used.
[0007]
[Problems to be solved by the invention]
However, in recent years, with the demand for miniaturization, weight reduction, and improvement in quietness of automobiles, the electric accessory has been reduced in size, weight, and hermetically sealed in an engine room. On the other hand, there is an increasing demand for higher output and higher efficiency in the performance of the apparatus itself.
For this reason, there is a problem that the lubricating grease sealed in the rolling bearing used in the electric component auxiliary equipment must withstand high temperatures higher than urea-based grease.
The above-mentioned fluorine-based grease is used as the grease for the rolling bearing that supports a fan clutch or a heat roller of a copying machine that is heated to an extremely high temperature of about 200 ° C. The fluorine-based grease is expensive, and the cost of the rolling bearing is high. There is a problem that hinders down.
Furthermore, fluorine-based grease has poor rust resistance, does not disperse in hydrocarbon solvents, and when sealed in bearings treated with rust preventive oil using mineral oil as a base oil, a large amount of grease leaks at the beginning of rotation. is there.
[0008]
Further, when lubricating grease having a high degree of consistency is used for a bearing such as an optical rotary encoder, there is a problem that dust, volatile vapor, and the like are liable to be scattered from the grease around the bearing. The dust and volatile vapor may fog the slits and lenses of the rotary encoder and cause a malfunction.
In addition, servo motors often have start-stop and frequent changes in the direction of rotation.Fretting resistance is required for rolling bearings, but lubricating grease with low consistency has high channeling properties, There is a problem that grease is easily removed from the oil, and the fretting property is inferior.
[0009]
The present invention has been made to address such problems, and has excellent high-temperature durability, and has excellent low-dusting properties, low volatility, and fretting resistance in high-speed applications, and is a fluorine-based grease. It is an object of the present invention to provide a lubricating grease which is less expensive and a rolling bearing in which the lubricating grease is sealed.
[0010]
[Means for Solving the Problems]
The lubricating grease according to the present invention comprises a perfluoropolyether oil as a base oil, a fluorine-based lubricating grease using a fluororesin powder as a thickener, and a synthetic oil excluding the perfluoropolyether oil as a base oil, and a urea compound. A grease mixed with a urea-based lubricating grease using as a thickener, characterized in that the mixed grease has an evaporation amount of 15% by weight or less when left at 200 ° C. for 250 hours.
Further, the urea-based lubricating grease is characterized in that the amount of evaporation when left at 200 ° C. for 250 hours is 25% by weight or less.
[0011]
In the present invention, the amount of evaporation refers to the amount of evaporation (%) based on the original weight when about 5 g of grease is sampled and measured in a 50 ml glass beaker based on Japanese Industrial Standard (JIS) R3503.
[0012]
Among the urea-based lubricating greases, a first urea-based lubricating grease is an ester of an aliphatic monohydric alcohol having 7 to 22 carbon atoms and an aromatic polycarboxylic acid, and an aliphatic monohydric grease having 7 to 22 carbon atoms. At least one ester oil selected from esters of a carboxylic acid and an aliphatic polyhydric alcohol is used as a base oil, and a urea compound is used as a thickener.
Further, the second urea-based lubricating grease is a lubricating grease using a polyolefin oil as a base oil and a urea compound as a thickener, a lubricating grease using an alkyl diphenyl ether oil as a base oil and a urea compound as a thickener, and an ester. At least one lubricating grease selected from lubricating greases using oil as a base oil and a urea compound as a thickener.
[0013]
A rolling bearing according to the present invention is a rolling bearing comprising concentrically disposed inner and outer rings, a plurality of rolling elements interposed between the inner and outer rings, and lubricating grease sealed around the rolling elements. The lubricating grease to be enclosed is the first or second lubricating grease described above.
[0014]
The rolling bearing enclosing the first lubricating grease is a rolling bearing used for an electric auxiliary machine or a fixing roller.
The rolling bearing in which the second lubricating grease is sealed is a rolling bearing used for a servomotor having a built-in optical rotary encoder.
[0015]
By using the first urea-based lubricating grease using an ester oil having a specific structure as a base oil, the amount of evaporation of the lubricating grease in a high-temperature atmosphere can be reduced. By mixing the first urea-based lubricating grease and the fluorine-based lubricating grease, the heat resistance of the grease is improved. The mixed grease achieves both heat resistance and cost reduction, and makes it possible to use a hydrocarbon-based rust inhibitor having excellent rust-preventive properties, which could not be mixed with the fluorine-based lubricating grease alone. As a result, the lubricating grease according to the present invention has improved rust prevention.
[0016]
Lithium soap-ester oil-based lubricating grease, urea-ester oil or synthetic hydrocarbon oil-based lubricating grease used in sealed ball bearings for servo motors with built-in optical rotary encoders is satisfactory in terms of price, Lithium soap-ester oil-based lubricating greases are inferior in dusting and fretting properties, and urea-ester oil or synthetic hydrocarbon oil-based lubricating greases may be poor in dusting and volatility under severe conditions.
By mixing the second urea-based lubricating grease and the fluorine-based lubricating grease, a lubricating grease having excellent low dust generation, fretting properties and low volatility was obtained.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
The fluorine-based lubricating grease that can be used in the present invention is a perfluoropolyether oil that uses a perfluoropolyether oil as a base oil and a fluororesin powder as a thickening agent, in which a hydrogen atom of an aliphatic hydrocarbon polyether is replaced with a fluorine atom. Any compound can be used. As an example of such a perfluoropolyether oil, a perfluoropolyether having a side chain represented by the following chemical formulas 1 and 2 and a linear perfluoropolyether represented by the chemical formulas 3 to 5 There is. These can be used alone or in combination. n and m are integers.
As a commercial product of Chemical Formula 1, Fomblin Y (trade name of Montedison), as a commercial product of Chemical Formula 2, Krytox (trade name of DuPont) or Valierta J Oil (trade name of Cleaver Company), and a commercial product of Chemical Formula 3 As a commercial product of Chemical Formula 4, Fomblin M (a product name of Montedison Company), and as a commercial product of Chemical Formula 5, Demnum (trade name of Daikin), etc. .
[0018]
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[0019]
As the fluororesin powder as a thickener, a powder having high affinity with the above-mentioned perfluoropolyether oil, high temperature stability and chemical resistance can be used.
Examples of the fluororesin include perfluorofluororesins such as polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA), and tetrafluoroethylene-hexafluoropropylene copolymer (FEP). Is preferred, and polytetrafluoroethylene (PTFE) is particularly preferred because of its excellent high-temperature stability and chemical resistance.
[0020]
The fluorine-based lubricating grease preferably contains 70 to 90% by weight of a perfluoropolyether oil and 10 to 30% by weight of a fluororesin powder based on the total amount of the fluorine-based lubricating grease. By setting the blending ratio in this range, it is possible to adjust to a preferable consistency in which the leakage of the rolling bearing sealed grease is small and the torque can be reduced for a long time.
[0021]
The urea-based lubricating grease that can be used in the present invention uses a urea compound as a thickener.
The urea compound is preferably diurea having two urea bonds in the molecule, and is represented by the following chemical formula (6).
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Here, R ₁ , R ₂ and R ₃ represent an aliphatic group, an alicyclic group or an aromatic group, respectively. An alicyclic urea or an aromatic urea in which R ₁ and R ₂ are an alicyclic group and / or an aromatic group is preferable because of having excellent high-temperature properties. In addition, as an example of the production method of the urea compound, the urea compound is obtained by reacting a diisocyanate compound with an amine compound having an isocyanate group equivalent.
[0022]
The first urea-based lubricating grease comprises an ester of an aliphatic monohydric alcohol having 7 to 22 carbon atoms and an aromatic polycarboxylic acid, and an aliphatic monohydric alcohol having 7 to 22 carbon atoms, using the urea compound as a thickener. At least one ester oil selected from esters of a polycarboxylic acid and an aliphatic polyhydric alcohol is used as a base oil. When the aliphatic monohydric alcohol and the aliphatic monohydric carboxylic acid have less than 7 carbon atoms and more than 22 carbon atoms, lubricity is poor.
Examples of the aliphatic monohydric alcohol having 7 to 22 carbon atoms include heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, undecyl alcohol, lauryl alcohol, oleyl alcohol, and stearyl alcohol.
[0023]
Further, aliphatic monocarboxylic acids 7 to 22 carbon atoms, a _-CH 2 OH of the aliphatic monohydric alcohol is monovalent carboxylic acid was replaced with -COOH like.
[0024]
Examples of the aromatic polycarboxylic acid include phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, trimesic acid, pyromellitic acid, diphenyltetracarboxylic acid, and benzophenonetetracarboxylic acid.
[0025]
Examples of the aliphatic polyhydric alcohol include 1,3-butylene glycol, glycerin, propylene glycol, ethylene glycol, pentadiol, diethylene glycol, polyethylene glycol, polypropylene glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, and sorbitol.
[0026]
The first urea-based lubricating grease preferably contains 70 to 95% by weight of the ester oil and 30 to 5% by weight of the urea compound, based on the total amount of the urea-based lubricating grease. By setting the blending ratio in this range, the leakage is reduced as the bearing-enclosed grease, and the lubrication can be adjusted to a good consistency for a long time.
[0027]
The second urea-based lubricating grease is a lubricating grease using a urea compound represented by Chemical Formula 6 as a thickener.
As the base oil, polyolefin oil, alkyl diphenyl ether oil or ester oil can be used.
[0028]
As the polyolefin oil, a liquid polyolefin represented by the following chemical formulas 7 and 8 can be used.
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Here, n is an integer of 4 to 16, and m is an integer of 1 to 6.
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Here, n is an integer of 1 to 8, m is an integer of 1 to 3, q is an integer of 1 to 3, and p is an integer that varies depending on the viscosity of the polyolefin oil.
[0029]
The polyolefin oil is preferably liquid at room temperature and has a kinematic viscosity of 100 mm ² / s (40 ° C.) or more. When the kinematic viscosity is less than 100 mm ² / s, evaporation loss is large when lubricating grease is used, and lubricating properties cannot be expected for a long time.
[0030]
As the alkyl diphenyl ether oil, a monoalkyl diphenyl ether oil represented by the following chemical formula 9 and / or a dialkyl diphenyl ether oil represented by the following chemical formula 10 can be used.
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Here, R ₄ , R ₅ , and R ₆ are each an alkyl side chain having 8 to 20 carbon atoms, and are bonded to one phenyl ring or two phenyl rings.
Among them, dialkyl diphenyl ether oils having alkyl side chains R ₅ and R ₆ are preferable in consideration of heat resistance and evaporation characteristics.
[0031]
As the ester oil, a diester oil, a polyol ester oil, or a complex ester oil or an aromatic ester oil thereof can be used.
Examples of the polyol ester oil include an ester of an aliphatic monohydric alcohol and an aromatic polycarboxylic acid, and an ester of an aliphatic monohydric carboxylic acid and an aliphatic polyhydric alcohol.
[0032]
The second urea-based lubricating grease is a lubricating grease using the above-mentioned polyolefin oil as a base oil, using a urea compound represented by Chemical Formula 6 as a thickener, and using the above-mentioned alkyldiphenyl ether oil as a base oil, increasing the urea compound represented by Chemical Formula 6 At least one lubricating grease selected from lubricating grease as a lubricant and lubricating grease using the above ester oil as a base oil and a urea compound represented by Chemical Formula 6 as a thickener.
[0033]
The lubricating grease containing a polyolefin oil as a base oil preferably contains 70 to 95% by weight of the polyolefin oil and 30 to 5% by weight of the urea compound represented by Chemical Formula 6, based on the total amount of the grease. By setting the content in this range, the consistency can be adjusted to a preferable value as the bearing-enclosed grease.
The lubricating grease containing an alkyl diphenyl ether oil as a base oil preferably contains 70 to 95% by weight of an alkyl diphenyl ether oil and 30 to 5% by weight of a urea compound represented by Chemical Formula 6, based on the total amount of the grease. By setting the content in this range, the consistency can be adjusted to a preferable value as the bearing-enclosed grease.
In addition, the lubricating grease using an ester oil as a base oil preferably contains 70 to 95% by weight of the ester oil and 30 to 5% by weight of the urea compound represented by Chemical Formula 6, based on the total amount of the grease. By setting the blending ratio in this range, the leakage is reduced as the bearing-enclosed grease, and the lubrication can be adjusted to a good consistency for a long time.
[0034]
The mixed grease obtained by mixing the fluorine-based lubricating grease and the urea-based lubricating grease has an evaporation amount of 15% by weight or less when the mixed grease is left at 200 ° C. for 250 hours. If the content exceeds 15% by weight, high-temperature durability is reduced and dust is easily generated.
About 5 g of grease was collected in a 50 ml glass beaker compliant with Japanese Industrial Standards (JIS) R3503, and the amount of evaporation was set at 200 ° C. in a hot-air circulating thermostat (volume: 90 liters, air volume: 5.1 m). ³ / min, wind speed: 0.42 m / sec) for 250 hours, and measure the initial weight of the grease and the weight after leaving the grease, and determine the grease by the following formula.
Evaporation amount (%) = [(initial weight−weight after standing) / initial weight] × 100
[0035]
The first and second urea-based lubricating greases have an evaporation amount of 25% by weight or less when measured by the above method. If the amount of evaporation exceeds 25% by weight, when mixed with fluorine-based lubricating grease, the amount of evaporation of the mixed grease cannot be reduced to 15% by weight or less.
[0036]
The urea-based lubricating grease is blended in an amount of 30 to 75% by weight based on the whole mixed grease. If the mixing ratio of the urea-based lubricating grease exceeds 75% by weight, the amount of evaporation of the mixed grease exceeds 15% by weight, and if it is less than 30% by weight, the production cost of the lubricating grease cannot be reduced.
[0037]
Known additives can be added to the lubricating grease or mixed grease as needed. Examples of the additives include antioxidants such as amines, phenols, sulfurs, and zinc dithiophosphate, extreme pressure agents such as chlorine, sulfur, phosphorus, zinc dithiophosphate, and organic molybdenum, and benzotriazole. And a metal deactivator such as sodium nitrite, a viscosity index improver such as polymethacrylate, polyisobutylene, and polystyrene, a wear inhibitor, a cleaning dispersant, and the like.
For mixed greases, use hydrocarbon (mineral oil) -based rust-preventive additives, petroleum sulfonates, dinonanylnaphthalenesulfonates, amines, sorbitan esters, etc., which could not be used with fluorine-based greases. Can be.
These additives can be added alone or in combination of two or more.
[0038]
FIG. 1 shows an example of the rolling bearing according to the present invention. FIG. 1 is a sectional view of a small-diameter rolling bearing.
In a rolling bearing 1, an inner ring 2 having an inner ring rolling surface on an outer peripheral surface and an outer ring 3 having an outer ring rolling surface on an inner peripheral surface are arranged concentrically, and interposed between the inner ring rolling surface and the outer ring rolling surface. And a plurality of rolling elements 4 and a retainer and a seal member (not shown). Lubricating grease 5 is sealed at least around the rolling elements 4.
[0039]
Among the lubricating greases 5, the mixed grease of the fluorine-based lubricating grease and the first urea-based lubricating grease has excellent heat resistance and durability, and thus can be suitably used for a rolling bearing used for an electric auxiliary machine or a fixing roller. .
Also, among the lubricating greases 5, the mixed grease of the fluorine-based lubricating grease and the first urea-based lubricating grease is excellent in low dust generation, fretting, and low volatility. The present invention can be suitably used for a rolling bearing used for a servomotor.
[0040]
【Example】
Reference Example 1: Preparation of grease 1 Perfluoropolyether oil (trade name, manufactured by DuPont, Krytox 240AC) was 67% by weight, and fluororesin powder (trade name, manufactured by DuPont, Vidax) was 33% by weight based on the entire grease. % And stirred, and then passed through a roll mill to obtain a semi-solid grease 1 which is "grease using a fluororesin powder as a thickener and a perfluoropolyether oil as a base oil".
[0041]
Reference Example 2: Preparation of Grease 2 1 mole of diisocyanate was dissolved in 88% by weight of an aromatic ester oil (produced by Asahi Denka Kogyo Co., Ltd., Prover T90), and 2 moles in the remaining half of the grease. After dissolving the monoamine and adding it to the above half amount of the base oil with stirring, the mixture was allowed to react with stirring at 100 to 120 ° C. for 30 minutes, and 12% by weight of the urea compound was separated into base oil. Thereafter, the mixture was passed through a roll mill to obtain a semi-solid grease 2 which was a “grease using a urea compound as a thickener and a synthetic oil as a base oil”.
[0042]
Reference Example 3: Production of Grease 3 1 mol of the alkyl diphenyl ether oil (trade name, manufactured by Matsumura Sekiyu KK, Moresco LB100, kinematic viscosity 97 mm ² / s (at 40 ° C.)) of 77% by weight based on the entire grease. Dissolve the diisocyanate, dissolve 2 moles of monoamine in the remaining half, add to the above half of the base oil with stirring, and continue the reaction by stirring at 100 to 120 ° C. for 30 minutes to make 23% by weight of the urea compound into the base oil. I started out. Thereafter, the resultant was passed through a roll mill to obtain a semi-solid grease 3 which is a “grease using a urea compound as a thickener and a synthetic oil as a base oil”.
[0043]
Reference Example 4: Preparation of Grease 4 With respect to the entire grease, polyolefin oil (trade name, manufactured by Mitsui Chemicals, Lucant HC-20, kinematic viscosity: 155 mm ² / s (at 40 ° C.)) 1 mol of diisocyanate in half of 82% by weight Is dissolved in the remaining half, and 2 mol of the monoamine is dissolved and added to the above-mentioned half of the base oil with stirring. Then, the mixture is allowed to react with stirring at 100 to 120 ° C. for 30 minutes, and 18% by weight of the urea compound is converted into the base oil. I started. Thereafter, the resultant was passed through a roll mill to obtain a semi-solid grease 4 which is a “grease using a urea compound as a thickener and a synthetic oil as a base oil”.
[0044]
Examples 1 to 3 and Comparative Examples 1 to 6
Each grease was mixed and stirred at a ratio shown in Table 1 to obtain a lubricating grease. The mixing ratio is% by weight based on the entire grease. In Example 1, an amine-based rust preventive additive based on mineral oil was added.
The greases of Comparative Examples 1 to 4 were produced in Reference Examples 1 to 4. In Comparative Examples 5 and 6, each grease was mixed and stirred at a ratio shown in Table 1 to obtain a mixed grease.
The mixing consistency, dropping point, and cost per volume of the obtained mixed grease were calculated with Comparative Example 1 as 1. Table 1 shows the results.
In addition, about 5 g of grease was collected in a 50 ml glass beaker compliant with Japanese Industrial Standards (JIS) R3503, and a hot-air circulating thermostat set at 200 ° C. (inner volume: 90 liters, air volume: 5.1 m ³⁾ / Min, wind speed: 0.42 m / sec) and the amount of evaporation when left for 250 hours is shown in Table 1.
[0045]
Rolling bearings were produced by enclosing the lubricating grease of each Example, which is 38% of the total space volume, in a bearing 6204ZZ washed with petroleum benzine. The obtained rolling bearing was evaluated by a high-temperature durability test.
In the high-temperature endurance test, the bearing was rotated at a radial load of 67 N, a thrust load of 67 N, a rotation speed of 10,000 rpm, an ambient temperature of 200 ° C., and the time until the motor stopped due to overload was measured. Table 1 shows the results.
[0046]
A rolling bearing was manufactured by filling the lubricating grease of each embodiment, which occupies 44% of the total space volume, in a bearing 30204 washed with petroleum benzene. The obtained rolling bearing was conditioned at a thrust load of 98 N, a rotation speed of 1800 rpm and room temperature, immersed in 1% saline for 10 seconds, and left standing at 40 ° C. for 48 hours to observe rusting. The rust was observed by dividing the outer ring rolling surface into 32 equal parts in the circumferential direction, counting the sections where rust occurred, and expressing the percentage. Table 1 shows the results.
[0047]
[Table 1]

As shown in Table 1, the lubricating greases of Examples 1 to 3 were excellent in the high-temperature durability test and low in cost.
[0048]
Examples 4 to 6 and Comparative Examples 7 to 8
Each grease was mixed and stirred at a ratio shown in Table 2 to obtain a lubricating grease. The mixing ratio is% by weight based on the entire grease. Comparative Example 7 is a lithium soap-polyolefin oil type low dusting grease, and Comparative Example 8 is a lithium soap-ester oil type grease for a general-purpose servomotor. Table 2 also shows Comparative Example 1 and Comparative Example 4.
The mixing penetration, dropping point, and cost per volume of the obtained lubricating grease were calculated with Comparative Example 1 as 1. Table 2 shows the results. Table 2 shows the amount of evaporation measured in the same manner as in Example 1.
[0049]
A test bearing 6000 LLB washed with petroleum benzine was filled with the lubricating grease of each example, which occupies 29% of the total space volume, to produce a rolling bearing.
Using the obtained rolling bearing, dust generation was evaluated using a dust generation amount measurement test apparatus shown in FIG. Two test bearings 8 are mounted on the upper part of a rotating shaft 7 penetrating the test table 6 so as to be inserted respectively, and a thrust load is applied to the two test bearings via a coil spring 10 on a clamp-type jig 9. The clamp-type jig 9 was fixed in a non-rotatable state by a lock 11 fixed on the test table 6.
A box-shaped airtight cover 12 is provided on the upper surface of the test stand 6 so as to cover the clamp jig 9, and clean air (clean air containing no dust) is introduced into the airtight cover 12. The duct 13 and the exhaust duct 14 were connected, and the exhaust duct 14 was connected to a dust counter 15 (also called a particle counter) having a built-in intake pump. The rotating shaft 7 was driven to rotate by an electric motor 16 installed below the test table 6, and the lower surface of the test table 6 and the rotating shaft 7 were sealed with a magnetic fluid seal 17.
The test conditions were as follows: the rotational speed of the rotating shaft was 1800 rpm, the thrust load was 15 N, the ambient temperature was room temperature, the clean air flow rate was 0.475 l / min, and the total number of dust particles of 0.5 μm or more after 7 to 8 hours from the start of operation was measured. . Table 2 shows the results.
[0050]
A Fafnir fine motion wear test based on ASTM D 4170 was performed, and the fine motion wear amount was measured to evaluate the fretting property. The measurement conditions are shown below, and the results are shown in Table 2.
Bearing: 51204J
Grease filling amount: 1 ± 0.1g
Load: 2450N (1.7 GPa)
Harmonic angle: 12 ° cycle: 30 Hz
Temperature: Room temperature Time: 2 hours Measured amount: Wear of inner and outer rings (mg)
[0051]
[Table 2]

As shown in Table 2, the lubricating greases of Examples 4 to 6 exhibited low dust generation and excellent fretting properties as compared with Comparative Example 8.
[0052]
【The invention's effect】
The lubricating grease of the present invention is a mixed grease of a fluorine-based lubricating grease and a urea-based lubricating grease. Since the amount of evaporation is 15% by weight or less, the lubricating grease is excellent in high-temperature durability and dust generation and has low cost. Is obtained.
Further, by replacing the urea-based lubricating grease, a lubricating grease excellent in high-temperature durability or a lubricating grease excellent in dust generation can be obtained.
As a result, by enclosing the lubricating grease, a rolling bearing that can be used for an electric accessory and a fixing roller, and a rolling bearing that can be used for a servomotor having a built-in optical rotary encoder can be obtained.
[Brief description of the drawings]
FIG. 1 is a sectional view of a small-diameter rolling bearing.
FIG. 2 is a diagram showing a dust generation amount measurement test apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rolling bearing 2 Inner ring 3 Outer ring 4 Rolling element 5 Lubricating grease 6 Test stand 7 Rotary shaft 8 Test bearing 9 Clamp type jig 10 Coil spring 11 Locking tool 12 Hermetic cover 13 Introductory duct 14 Exhaust duct 15 Dust counter 16 Electric motor 17 Magnetic fluid seal

Claims (8)

Fluorine-based lubricating grease using perfluoropolyether oil as a base oil and a fluororesin powder as a thickener, and urea using a synthetic oil excluding the perfluoropolyether oil as a base oil and a urea compound as a thickener A lubricating grease, which is a mixed grease with a system-based lubricating grease, wherein an amount of evaporation of the mixed grease when left at {200 ° C.} for {250} hours is {15} wt% or less. 2. The lubricating grease according to claim 1, wherein the urea-based lubricating grease has an evaporation amount of not more than {25}% by weight when left at 200 ° C. for {250} hours. 2. The lubricating grease according to claim 1, wherein said urea-based lubricating grease is blended in {30-75}% by weight based on the whole mixed grease. The urea-based lubricating grease includes an ester of an aliphatic monohydric alcohol having 7 to 22 carbon atoms and an aromatic polycarboxylic acid, and an ester of an aliphatic monohydric carboxylic acid having 7 to 22 carbon atoms and an aliphatic polyhydric alcohol. 4. The lubricating grease according to claim 1, wherein at least one ester oil selected from esters is used as a base oil, and a urea compound is used as a thickener. The urea-based lubricating grease is a polyolefin oil as a base oil, a lubricating grease using a urea compound as a thickener, a lubricating grease using an alkyl diphenyl ether oil as a base oil, a lubricating grease using a urea compound as a thickener, and an ester oil as a base oil. The lubricating grease according to claim 1, wherein the lubricating grease is at least one lubricating grease selected from lubricating greases containing a urea compound as a thickener. An inner ring and an outer ring arranged concentrically, a plurality of rolling elements interposed between the inner ring and the outer ring, and a rolling bearing in which lubricating grease is sealed around the rolling elements,
A rolling bearing, wherein the lubricating grease is the lubricating grease according to claim 4 or 5. An inner ring and an outer ring arranged concentrically, a plurality of rolling elements interposed between the inner ring and the outer ring, and a rolling bearing in which lubricating grease is sealed around the rolling elements, wherein the lubricating grease is used. A rolling bearing, which is the lubricating grease according to the above, and is used for an electric auxiliary machine or a fixing roller. 6. A rolling bearing comprising concentrically disposed inner and outer rings, a plurality of rolling elements interposed between the inner and outer rings, and a lubricating grease sealed around the rolling elements, wherein the lubricating grease is used. A rolling bearing, which is used for a servomotor having a built-in optical rotary encoder.

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