JP4032464B2 - Rolling bearing - Google Patents

Description

【００４０】
これらの主として耐クリープ性向上のための繊維材〔Ａ〕の添加量は、混合物全体の１０〜５５重量％であり、好ましくは２０〜４０重量％である。５５重量％を越えると成形性が悪くなり、１０重量％未満では耐クリープ性が悪くなる。
【００４１】
本発明の磁性充填材〔Ｂ〕は、リング状絶縁部材の電気絶縁性の維持と伝熱性の向上とを同時に満たすために用いられ、その熱伝導率は高い程好ましいが、少なくともガラス繊維と同程度の５〜１０Ｗ／ｍ・Ｋであれば良い。一方、電気絶縁性についても高い方がよいが、比抵抗値で１×１０³ Ω・ｃｍ以上、より好ましくは１×１０⁴ Ω・ｃｍ以上であれば使用上問題はない。さらに、飽和磁化については、２０ｅｍｕ／ｇ以上、より好ましくは５０ｅｍｕ／ｇ以上が磁気吸引力が大きくなるので好適である。２０ｅｍｕ／ｇ未満では磁気吸引力が小さすぎて所期の伝熱性の向上が得られない。
【００４２】
このような条件を満たし得る磁性充填材は、例えばＭｇＦｅ₂ ０₄ （マグネシウムフェライト），ＭｎＦｅ₂ Ｏ₄ （マンガンフェライト），Ｆｅ₃ Ｏ₄ （マグネタイト），ＣｏＦｅ₂ Ｏ₄ （コバルトフェライト），ＮｉＦｅ₂ Ｏ₄ （ニッケルフェライト），ＣｕＦｅ₂ Ｏ₄ （銅フェライト），γ−Ｆｅ₂ Ｏ₃ （マグヘマイト）などの粒状粉体から選定される。表２にこれらの充填材物質の飽和磁化と比抵抗を示す。
【００４３】
【表２】

【００４４】
磁性充填材〔Ｂ〕の添加量は、リング状絶縁部材を形成する合成樹脂組成物全体の２０〜６５重量％であり、好ましくは２５〜５５重量％の範囲で選定される。６５重量％を越えると耐クリープ性，成形性を満たすことが困難となり、一方、２０重量％未満では伝熱性の向上が期待できず、そのため本願発明の電気絶縁性，伝熱性，耐クリープ性の３拍子そろった向上という効果が期待できなくなる。
【００４５】
更に、本発明の非磁性高熱伝導性充填材〔Ｃ〕は、磁性充填材［Ｂ］と同様に、リング状絶縁部材の伝熱性の向上と電気絶縁性の維持とを同時に満たすために用いられるが、その熱伝導率は、磁性充填材［Ｂ］のように粒子同士が磁気吸引力によって積極的につながろうとはしないので、粒子個々により高い熱伝導性が必要になる。具体的には１０Ｗ／ｍ・Ｋ以上さらに好ましくは２０Ｗ／ｍ・Ｋ以上が必要である。一方、電気絶縁性についても高い方がよいが、比抵抗値で１×１０³ Ω・cm以上、より好ましくは１×１０⁴ Ω・cm以上であれば使用上問題ない。
【００４６】
このような条件を満たし得る非磁性高熱伝導性充填材〔Ｃ〕は、例えば、ＳｉＣ（炭化 ケイ素）、ＡｌＮ（窒化アルミニウム）、ＢｅＯ（ベリリア）、ＢＮ（窒化ホウ素）、Ａｌ₂ Ｏ₃ （アルミナ）、ＭｇＯ（マグネシア）などの粉体、繊維またはウィスカー等から選定される。表３に、これらの充填材物質の熱伝導率と比抵抗をＣｕ（銅）、ガラス繊維（Ｅガラス）と比較して示す。
【００４７】
【表３】

【００４８】
なお、表３に示されるもののうち、ＳｉＣ，Ａｌ₂ Ｏ₃ は繊維及びウィスカー（記号〔Ｃ−１〕で示す）もあるが、それ以外は粒状（記号〔Ｃ−２〕で示す）のみである。よって、耐クリープ性が更に要求される場合には、ガラス繊維（ＧＦ）を用いずにＳｉＣ，Ａｌ₂ Ｏ₃ のウィスカー又は繊維〔Ｃ−１〕を使用すれば耐クリープ性が更に向上し、加えて伝熱性の向上も得られる。
【００４９】
この非磁性高熱伝導性充填材〔Ｃ−１〕は、少なくとも一部を磁性充填材〔Ｂ〕の代わりに使用することができる。その場合の添加量は、両者混合（〔Ｂ＋Ｃ−１〕）の場合で合成樹脂組成物全体の３０〜７５重量％、前者のみ単独（〔Ｃ−１〕）の場合で、２０〜７５重量％であり、好ましくは２５〜５０重量％の範囲で選定される。７５重量％を越えると成形性を満たすことが困難となる。一方、２０重量％未満ではリング状絶縁部材の熱伝導性が０．５ｗ／ｍ・ｋ以上にならない。したがって、耐クリープ性，伝熱性の向上が期待できず、そのため本願発明のリング状絶縁部材の電気絶縁性，伝熱性，耐クリープ性の３拍子そろった向上という効果が期待できなくなる。なお、コスト的には、磁性充填材〔Ｂ〕の方が非磁性高熱伝導性充填材〔Ｃ−１〕に比べて安価なため、非磁性高熱伝導性充填材〔Ｃ−１〕単独で用いるよりも磁性充填材〔Ｂ〕のみ或いは両者混合〔Ｂ＋Ｃ−１〕で使用する方が有利である。
【００５０】
以上述べた上記第２の目的を達成する本発明の合成樹脂組成物への各種充填材の単独での充填量をまとめると表−４のようになる。
【００５１】
【表４】

【００５２】
但し、次に述べるように、〔Ｃ−１〕と組合せると〔Ａ〕の充填量は０〜４０重量％、同じく〔Ｂ〕の充填量は０〜５５重量％となる。
【００５３】
これらの各種充填材は組み合わせて使用することも可能である。
その場合に考えられる合成樹脂組成物のマトリッスス中での充填材の組合せ方と充填比率は、次の５通りとなる。
【００５４】
▲１▼ Ａ＋Ｂ ４５〜７５ｗｔ％
▲２▼ Ａ＋Ｃ−２ ４５〜７５ｗｔ％
▲３▼ Ｂ＋Ｃ−１ ３０〜７５ｗｔ％
▲４▼ Ａ＋Ｃ−１ ４５〜７５ｗｔ％
▲５▼ Ａ＋Ｂ＋Ｃ ４５〜７５ｗｔ％
何れも、下限値未満の充填量ではリング状絶縁部材の熱伝導性が０．５ｗ／ｍ・ｋ以上にならない。一方、上限値を超えると成形性が低下する。
【００５５】
それぞれの組合せにおける臨界的意義を、以下に述べる。
（１） 繊維材〔Ａ〕と磁性充填材〔Ｂ〕との組合わせ：
表５に、充填材〔Ａ＋Ｂ〕の場合について、当該充填材の添加比率の違いによるリング状絶縁部材の熱伝導率と比抵抗の測定結果を示す。但し、繊維材〔Ａ〕（ガラス繊維）は２０重量％に固定し、磁性充填材〔Ｂ〕（ＭｎＦｅ₂ Ｏ₄ ）の添加量を変化させた。
【００５６】
【表５】

【００５７】
図１は、表５をグラフにしたものである。この図から明らかなように、合計添加量〔Ａ＋Ｂ〕は、４５〜７５重量％の範囲が好ましい。７５重量％を越えるとリング状絶縁部材の比抵抗が１×１０¹³Ω・ｃｍ未満になってしまう。また、マトリックス樹脂が不足して成形時の流動性低下をまねき、その結果、形成されたリング状絶縁部材の表面粗さが悪くなると共にウエルド強度が低下する。一方、４５重量％未満では、繊維材〔Ａ〕，磁性充填材〔Ｂ〕が共に必要最低量が確保できず、伝熱性，耐クリープ性の両立が困難になり、リング状絶縁部材の熱伝導性が０．５ｗ／ｍ・ｋ以上にならない。更に、高い伝熱性，耐クリープ性を確保するためには、合計添加量〔Ａ＋Ｂ〕が５０〜７５重量％の範囲にあると、より好適である。
【００５８】
なお、このような繊維材〔Ａ〕，磁性充填材〔Ｂ〕を含有する樹脂組成物にあっては、必要に応じて離型剤や、強度向上を目的としてシランカップリング剤等のカップリング剤を添加しても良い。あるいは、カップリング剤などで処理した繊維材又は充填材を使用してもよい。
（２） 繊維材〔Ａ〕と粒状非磁性高熱伝導性充填材〔Ｃ−２〕との組合せ：
表６に、充填材〔Ａ＋Ｃ−２〕の場合について、当該充填材の添加比率の違いによるリング状絶縁部材の熱伝導率と比抵抗の測定結果を示す。但し、繊維材〔Ａ〕（ガラス繊維）は２０重量％に固定し、粒状非磁性高熱伝導性充填材〔Ｃ−２〕（Ａｌ₂ Ｏ₃ ）の添加量を変化させた。
【００５９】
【表６】

【００６０】
図２は、表６をグラフにしたものである。この図から明らかなように、合計添加量〔Ａ＋Ｃ−２〕は、４５〜７５重量％の範囲が好ましい。７５重量％を越えると、比抵抗はなお高いがマトリックス樹脂が不足して成形性が低下する。一方、４５重量％未満では、リング状絶縁部材の熱伝導性が０．５ｗ／ｍ・ｋ以上にならない。
（３） 磁性充填材〔Ｂ〕と繊維またはウィスカ状非磁性高熱伝導性充填材〔Ｃ−１〕との組合せ：
表７に、充填材〔Ｂ＋Ｃ−１〕の場合について、当該充填材の添加比率の違いによるリング状絶縁部材の熱伝導率と比抵抗の測定結果を示す。但し、磁性充填材〔Ｂ〕（ＭｎＦｅ₂ Ｏ₄ ）は２０重量％に固定し、非磁性高熱伝導性充填材〔Ｃ−１〕（Ａｌ₂ Ｏ₃ 繊維）の添加量を変化させた。
【００６１】
【表７】

【００６２】
図３は、表７をグラフにしたものである。この図から明らかなように、合計添加量〔Ｂ＋Ｃ−１〕は、３０〜７５重量％の範囲が好ましい。７５重量％を越えると、比抵抗はなお高いがマトリックス樹脂が不足して成形性が低下する。一方、３０重量％未満では、リング状絶縁部材の熱伝導性が０．５ｗ／ｍ・ｋ以上にならない。
【００６３】
なお、表８に、上記繊維またはウィスカ状非磁性高熱伝導性充填材〔Ｃ−１〕単独の場合について、当該充填材〔Ｃ−１〕（Ｓｉウィスカ使用）の添加比率の違いによるリング状絶縁部材の熱伝導率と比抵抗の測定結果を示す。
【００６４】
【表８】

【００６５】
図４は、表８をグラフにしたものである。この図から明らかなように、〔Ｃ−１〕充填材単独の添加量は、２０〜７５重量％の範囲が好ましい。７５重量％を越えると、比抵抗はなお高いがマトリックス樹脂が不足して成形性が低下する。一方、２０重量％未満では、リング状絶縁部材の熱伝導性が０．５ｗ／ｍ・ｋ以上にならず、伝熱性，耐クリープ性の両立が困難である。
（４） 繊維材〔Ａ〕と繊維またはウィスカ状非磁性高熱伝導性充填材〔Ｃ−１〕との組合せ：
充填材〔Ａ＋Ｃ−１〕の場合について、当該充填材の添加比率の違いによるリング状絶縁部材の熱伝導率と比抵抗の変化を上記同様に測定した結果、図示しないが合計添加量〔Ａ＋Ｃ−１〕は、４５〜７５重量％の範囲が好ましいことが判った。７５重量％を越えると、比抵抗はなお高いがマトリックス樹脂が不足して成形性が低下する。一方、４５重量％未満では、リング状絶縁部材の熱伝導性が０．５ｗ／ｍ・ｋ以上にならない。
（５） 繊維材〔Ａ〕と磁性充填材〔Ｂ〕と非磁性高熱伝導性充填材〔Ｃ〕との組合せ：
繊維材〔Ａ〕と磁性充填材〔Ｂ〕と非磁性高熱伝導性充填材〔Ｃ〕との合計添加量〔Ａ＋Ｂ＋Ｃ〕は、４５〜７５重量％が好ましい。７５重量％を越えるとマトリックス樹脂が不足して成形時の流動性低下をまねき、その結果、成形されたリング状絶縁部材の表面粗さが悪くなると共にウエルド強度が低下する。一方、４５重量％未満では、リング状絶縁部材の熱伝導性が０．５ｗ／ｍ・ｋ以上にならないばかりか、繊維材〔Ａ〕，磁性充填材〔Ｂ〕，非磁性高熱伝導性充填材〔Ｃ〕の各必要最低量が確保できないために、伝熱性，耐クリープ性の両立が困難になる。更に、高い伝熱性，耐クリープ性を確保するためには、合計添加量〔Ａ＋Ｂ＋Ｃ〕が５０〜７５重量％の範囲にあるとより好適である。
【００６６】
上記三者の合計添加量〔Ａ＋Ｂ＋Ｃ〕の内訳は、次のような電食を防止する転がり軸受のリング状絶縁部材として必要な物性が得られるように、それぞれ決められる。
【００６７】
熱伝導率 ：０．５ｗ／ｍ・ｋ以上
比抵抗 ：１×１０¹³Ω・ｃｍ以上
ウエルド強度 ：７０ＭＰａ以上
【００６８】
アイゾット衝撃強度：２ｋJ ／ｍ² 以上、より好ましくは落下時の強度向上のため５ｋJ ／ｍ² 以上とする。これにより電食防止転がり軸受自体の取扱いがより容易になる。すなわち、ウエルド強度７０ＭＰａ以上、アイゾット衝撃強度２ｋJ ／ｍ² 以上であれば軸受をハウジングに挿入する際の絶縁被膜の損傷を防止できる。
【００６９】

【００７０】
【発明の実施の形態】
以下、第１の目的を達成する本発明の実施の形態を図面を参照して説明する。図５に示すものは、本発明の転がり軸受の第１の実施形態の半断面図で、ファンモータのロータ軸に嵌着される内輪１、ハウジングに嵌着される外輪２、内輪１と外輪２との間に介在する転動体のボール３、そのボール３を保持する保持器４を備えた深溝玉軸受に本発明を適用したものである。外輪２の外周面２ｇ及び両側面２ｓ，２ｓからなる外輪外周部は、その略全面が熱可塑性エラストマの被膜状の層５で被覆されている。
【００７１】
この実施形態の熱可塑性エラストマの層５は薄い個所での厚さｔが１．５ｍｍであり、その外周面５ｇに、図６に拡大して示すような断面半円形で高さｈが５０μｍ程の凸部７が円周方向に環状に連続して多数列形成されている。また、熱可塑性エラストマの層５の内周面５ｎ及び内側面には、断面四角形の突起８が円周方向に連続して環状にそれぞれ形成されている。これらの突起８は、外輪２の外周面２ｇ及び両側面２Ｓ，２Ｓに予め形成されている断面四角形で円周方向に連続して環状に形成されている凹溝９に対応させてあり、当該突起８が凹溝９に嵌合して脱落を防止する構造になっている。
【００７２】
前記熱可塑性エラストマの層５は、例えばポリエステル系エラストマであるペルプレン（登録商標），Ｐ−３０Ｂ」を採用し、所定の金型を用いて射出成形されている。その性状は、硬さ：７１［ＨＤ_A ］，熱伝導率：０．２２ｗ／ｍ・ｋ，比抵抗：１×１０¹²Ω・ｃｍである。これを、外輪２に取り付けるに際しては、当該外輪２の外周部に、予め、室温硬化型のエポキシ系弾性接着剤「ＥＰ−００１」を塗布しておき、前記射出成形された熱可塑性エラストマの層５を変形させてその外輪２の外周部に嵌め込み、完全に接着するまで放置するという方法をとった。
【００７３】
いま、上記の深溝玉軸受を、例えば図７に示すようにファンモータに固定側軸受として組み込んで使用する場合に、内輪１をファンモータのロータ軸Ｊに締まり嵌めで嵌着し、外輪２の方はハウジングＨに嵌着し間座Ｋを介して予圧を付与するものとする。このとき、外輪２はその外周部に取り付けてある熱可塑性エラストマの層５を介してハウジングＨの内面に挿入される。かくしてファンモータに装着された本実施形態の転がり軸受は、外輪２の外周部に形成された熱可塑性エラストマの層５により、軸受外輪２の外周面５ｇとハウジングＨとが電気的に絶縁される。且つまた、軸受外輪２の一方の外側面２ｓとの間及び他方の外側面２ｓと同じくハウジングを構成する間座Ｋとの間も介在する熱可塑性エラストマの層５により電気的に絶縁される。したがってインバータ駆動されるファンモータに軸電圧が生じても、軸受の内輪１外輪２間には電位差を生じることがない。すなわち、軸受の内外輪間に電流が流れることがなくなり、内輪１外輪２の各軌道面あるいはボール３の転動面の電食が防止される。
【００７４】
しかして、熱可塑性エラストマの層５は、硬さが７１［ＨＤ_A ］と従来のプラスチックスやセラミックスにより形成された絶縁被膜に比べて材質的に柔らかく変形し易いうえに、外周面５ｇが凸部７で凹凸状になっていてハウジングＨとの接触面積が小さいことから形状的にも変形し易くされているため、ハウジングＨ内への挿入が容易に行われる。しかも、ハウジングＨ内に圧入された熱可塑性エラストマの層５は、今度は突っ張って変形に対して抵抗する。すなわち、本実施形態によれば、軸受の挿入性を損なわずにしかもクリープ発生も防止できるという効果を奏する。
【００７５】
図８，図９に、本発明の転がり軸受の第２の実施形態を示す。
この実施形態では、軸受の外輪２の外周部を被覆している熱可塑性エラストマの被膜状の層５の材質及び外周面５ｇの表面構造が上記第１の実施形態とは異なっている。すなわち、本実施形態例の熱可塑性エラストマの層５の材質は、ポリアミド系エラストマ（詳しくはポリアミド・ポリエーテル系）である「ペバックス，登録商標、２５３３ＳＡ＊＊」（東レ（株）製）硬さ７５［ＨＤ_A ］である。その性状は、硬さ：７５［ＨＤ_A ］，熱伝導率：０．２６ｗ／ｍ・ｋ，比抵抗：１０¹⁴〜１０¹⁵Ω・ｃｍである。成形方法及び外輪２の外周部への接合方法は上記第１の実施形態例の場合と同じである。また、本実施形態例の熱可塑性エラストマの層５の外周面５ｇの表面構造については、図９に示すように、断面半円状の凸部７の代わりに、断面台形状で周方向に深さｈ₁ が３０μｍ程の凹部１１が円周方向に環状に連続して多数列形成されている。
【００７６】
その他の構成及び作用効果は、第１の実施形態と同様である。
図１０，図１１に、本発明の転がり軸受の第３の実施形態を示す。
この実施形態は、軸受の外輪２の外周部を被覆している熱可塑性エラストマの被膜状の層５の材質，外輪外周部への取付け構造及び層の外周面５ｇの表面構造が上記第１，第２の各実施形態とは異なっている。すなわち、本実施形態例の熱可塑性エラストマの層５の材質は、第１の実施形態例の場合と同じポリエステル系エラストマである「ペルプレン（登録商標），Ｐ−３０Ｂ」に、補強材（熱伝導性フィラー）のＳｉＣウィスカを４０重量％添加したものである。また、外輪外周部への取付けについては、図１０に示すように、外輪２の外周面２ｇと両側面２ｓとに断面台形状の溝（アリ溝）１２を円周方向に連続して予め形成し、この外輪２をコアとして金型に装着して熱可塑性エラストマの層５をインサート成形することにより、熱可塑性エラストマの層５の内周面５ｎと内側面５ｓとの前記アリ溝１２に対応する個所を突起１３としてアリ溝１２内に嵌入させ、熱可塑性エラストマの層５の脱落を防止する構造になっている。突起１３を除いた熱可塑性エラストマの層５の厚さｔは１．０ｍｍである。
【００７７】
熱可塑性エラストマの層５の外周面５ｇの表面には、図１１に示すように、外輪２の幅方向に連続する杉綾模様状（ヘリンボン状）の深さ５０μｍの凹部１４が形成されている。この熱可塑性エラストマの層５の性状は、硬さ：７５［ＨＤ_A ］，熱伝導率：０．６ｗ／ｍ・ｋ，比抵抗：１×１０¹⁵Ω・ｃｍである。
【００７８】
その他の構成及び作用効果は、第１の実施形態と同様である。
続いて、本発明の転がり軸受の第４の実施形態（図１２）を説明する。
この実施形態における熱可塑性エラストマの被膜状の層５の材質は、ポリエステル系エラストマである「ペルプレン（登録商標），Ｐ−３０Ｂ」に、熱伝導性フィラーとしてＡｌＮ粉末を３０重量％及び補強材としてガラス繊維（シランカップリング剤処理したもの）２０重量％を含有させたものを用いている。
【００７９】
この実施形態例の熱可塑性エラストマの層５の外輪外周部への取付け構造は、上記図１０に示したものと同じである。
熱可塑性エラストマの層５の外周面５ｇの表面には、図１２に示すように、菱型模様とした深さ５０μｍの帯状の凹部１６が点在している。この熱可塑性エラストマの層５の性状は、硬さ：７７［ＨＤ_A ］，熱伝導率：０．６２ｗ／ｍ・ｋ，比抵抗：９×１０¹⁴Ω・ｃｍである。
【００８０】
その他の構成及び作用効果は、第１の実施形態と同様である。
図１３に、本発明の転がり軸受の第５の実施形態を示す。
この実施形態は、例えば転がり軸受の外輪２の一側面２ｓをバネで押圧して予圧するなどのように、外輪２の外周部としての外周面と一端側とがハウジングに対し電気的導通状態となるような使用態様の場合に好適に利用できるものである。すなわち、熱可塑性エラストマの層５は、外輪２の外周面２ｇを被覆する部分５Ａとこれに直交して外輪２の一側面２ｓを被覆する部分５Ｂとからなる断面ほぼＬ形とされている。この熱可塑性エラストマの層５により、転がり軸受（図示のものは、シール１７を有する密閉型軸受）の外輪２の外周面２ｇ及び一方の側面２ｓが被覆されている。被覆する側面２ｓは、熱可塑性エラストマの層５が無い場合にハウジングと導通する側である。
【００８１】
なお、この実施形態の熱可塑性エラストマの層５の外周面には、図５，図６に示すものと同様の断面半円形の凸部７が、円周方向に環状に連続して多数形成されている。
【００８２】
予め所定の金型を用いて断面Ｌ形に射出成形された熱可塑性エラストマの層５は、その内周面５ｎの被覆しない方の側面２ｓに近い個所に、円周方向に連続した断面四角形の突起８を備えている。一方、外輪２の外周面２ｇには、前記突起８に対応する位置に、円周方向に連続した断面四角形の凹溝９が予め形成してある。
【００８３】
熱可塑性エラストマの層５の装着は、第１の実施形態におけると同様に、外輪２の被覆面に予め弾性接着剤を塗布し、熱可塑性エラストマの層５の前記突起８を外輪の前記凹溝９に嵌合させるようにして熱可塑性エラストマの層５を貼り付ける方法で行う。
【００８４】
ファンモータに装着された本実施形態の転がり軸受は、断面Ｌ形の熱可塑性エラストマの層５のうちの外輪２の外周面２ｇを被覆する部分５Ａにより、ハウジングＨと電気的に絶縁されると共に、外輪の一側面２ｓを被覆する部分５Ｂにより予圧用の部材とも電気的に絶縁される。かくして、インバータ駆動されるファンモータに軸電圧が生じても、軸受の内輪外輪間には電位差がなくしたがって軸電流が流れないから、内輪外輪の軌道面やボール３の転動面の電食が防止される。
【００８５】
その他の構成及び作用効果は、第１の実施形態とほぼ同様である。
図１４に、本発明の転がり軸受の第６の実施形態を示す。
この実施形態は、転がり軸受の外輪２の両側面２ｓ，２ｓがハウジングに接触せず電気的に非導通である使用態様の場合に好適に利用できるものである。すなわち、転がり軸受の外周部である外輪２の外周面２ｇに、円周方向に環状に連続した三列の凹溝１８，１８，１８が平行に形成されており、各凹溝１８に断面長方形の環状の熱可塑性エラストマの層（帯）５が下半部を嵌め込んで接着されている。その熱可塑性エラストマの層５の外周面には、図５，図６に示すものと同様の断面半円形の凸部７が、円周方向に環状に連続して多数形成されている。
【００８６】
本実施形態の転がり軸受をファンモータに装着した場合、外輪２の外周面２ｇに取り付けた帯状の熱可塑性エラストマの層５によりハウジングと電気的に絶縁され、一方、軸受外輪２の両側面２ｓ，２ｓとハウジングとはもともと非接触非導通であるから、上記各実施形態例の場合と同じく内輪外輪の軌道面やボール３の転動面の電食を効果的に防止することができる。
【００８７】
なお、本発明において熱可塑性エラストマの層５の外周面５ｇに形成される凹凸のパターンは上記各実施形態例のものに限らず、その他種々のものが可能である。図１５，図１６はその他のパターン例を示したもので、図１５のものはヘリンボン状の凹部２０が外輪の円周方向に連続しているパターン、図１６のものは不定形の突起２１が不規則に多数散在しているパターンである。
【００８８】
また、上記各実施形態では深溝玉軸受の場合を例にして説明したが、本発明はこれに限らず、アンギュラ玉軸受やころ軸受等のその他の転がり軸受にも同様に適用することができる。
【００８９】
続いて、第２の目的を達成する本発明の実施の形態（第７の実施形態）を説明する。
図１７の転がり軸受Ａには、その外輪２の外周面２ｇと片側の端面２ｓを被うようにしてリング状絶縁部材３０が圧入されている。内輪１の方はそのままになっている。３はボール、４は保持器である。リング状絶縁部材３０の角部には、ハウジングへの当該転がり軸受Ａの挿入性が良くなるように、円周に面取り３０ａが施されている。リング状絶縁部材３０は、その材料として例えばＰＰＳ樹脂４０重量％（以下、ｗｔ％とも記述する）と、強化繊維剤〔Ａ〕であるガラス繊維３５重量％と、磁性充填材〔Ｂ〕であるマンガンフェライト（ＭｎＦｅ₂０₄ ）２５重量％とからなる樹脂組成物を用いて、射出成形により製作した。
【００９０】
すなわち、先ず、予め各材料組成を、ブレンダやヘンシェルミキサ等により混合して二軸押出機等の押出機に供給し、押出機から材料ペレットを得た。次に、金型中に前記ペレットを溶融した材料を射出して所定の時間冷却することにより、厚さ１．０ｍｍのリング状絶縁部材３０を得た。その後、当該リング状絶縁部材３０を外輪２に圧入した。その際、必要に応じてリング状絶縁部材３０を加熱して膨張させてから圧入した。
【００９１】
図１８は、上記図１７に示した第２の目的を達成する本発明の転がり軸受Ａを、２個一対でファン駆動用電動モータ４０内に取り付けた状態を示す断面図である。両転がり軸受Ａの外輪２は、それぞれモータハウジング４１の両端部に形成した保持段部４２或いは保持凹部４３の内側に、リング状絶縁部材３０を介して嵌めこまれている。なお、４１ａはハウジング本体、４１ｂはハウジング前蓋、４１ｃはハウジング後蓋である。また、４４はモータ回転軸、４５はロータ、４６はステータである。そして、リング状絶縁部材３０の大鍔部３０ｂを上記保持段部４２或いは保持凹部４３の奥面に対向させた状態で固定されている。前記大鍔部３０ｂは、軸受外輪２の一端面２ｓと保持段部４２或いは保持凹部４３の奥面とに挟持されて、これら両面が当接するのを阻止する。また、各リング状絶縁部材３０の円筒部３０ｃは、外輪２の外周面２ｇと、保持段部４２或いは保持凹部４３の内周面との間に挟持されて、これら両周面同志が当接するのを阻止する。なお、外輪２の他方の端面２ｓは空気中にさらされた状態になっており、特にリング状絶縁部材３０で被う必要がない。
【００９２】
このように、第２の目的を達成する本発明の転がり軸受をモータ中に組み込むことによって、インバータからステータ４６に印加される高周波電流に基づいてモータ回転軸４４に軸電圧が惹起されても、この回転軸４４とモータハウジング４１との間に電流が流れることを抑えることができる。すなわち、上記回転軸４４を支持する転がり軸受Ａの外輪２と、これらの外輪２を保持している部材であるモータハウジング４１との取付け箇所が絶縁されているので、上記回転軸４４の電位がモータハウジング４１の電位より高くなっても、これら外輪２を組み込んでなる各転がり軸受Ａに電流が流れることがなくなる。従って、これら各転がり軸受Ａに電食が発生することがない。
【００９３】
（実施例）
以下、第２の目的を達成する本発明の実施例と比較例とに付いて実施した比較試験について説明する。
【００９４】
図１７に示したリング状絶縁部材３０を有する転がり軸受において、そのリング状絶縁部材３０の樹脂組成物の材料組成を種々に変えたものを被試験体として用いた。
【００９５】
表９に、リング状絶縁部材３０の各実施例１−１〜１５−２及び比較例１の成分組成を示す。
【００９６】
【表９】

【００９７】
また、表９に示す樹脂，繊維材〔Ａ〕，磁性充填材〔Ｂ〕，非磁性高熱伝導性充填材〔Ｃ〕の具体的な商品名（登録商標には^R を付す），メーカを下記に記す。
【００９８】
樹脂：
ＰＰＳ（ポリフェニレンサルファイド樹脂）；呉羽化学工業（株）「フォートロンＫＰＳ」。
【００９９】
芳香族ＰＡ（芳香族ポリアミド樹脂）；三井石油化学「アーレン^R 」。
【０１００】
強化繊維材〔Ａ〕：
ガラス繊維；日東紡績（株）「ＣＳ３Ｊ−２７３」（シランカップリング剤処理ガラスチョップドストランド）。
【０１０１】
６チタン酸カリウムウィスカー；大塚化学（株）「ティスモ−Ｄ」。
【０１０２】
ホウ酸アルミニウムウィスカー；四国化成工業（株）「アルボレックスＹＳ３」（シランカップリング剤処理済）。
【０１０３】
炭酸カルシウムウィスカー；丸尾カルシウム（株）「ウィスカルＡ」。
【０１０４】
磁性充填材〔Ｂ〕：
ＭｎＦｅ₂Ｏ₄ ；（株）高純度化学研究所。
【０１０５】
ＣｏＦｅ₂Ｏ₄ ；（株）高純度化学研究所。
ＮｉＦｅ₂Ｏ₄ ；（株）高純度化学研究所。
【０１０６】
非磁性高熱伝導性充填材〔Ｃ〕：
ＳｉＣウィスカー；出光マテリアル（株），Ｍグレード。
【０１０７】
ＡｌＮ ；出光マテリアル（株），ＡＧＳＤ−１００。
【０１０８】
ＢＮ（ｈ−ＢＮ）；出光マテリアル（株），Ｆグレード。
【０１０９】
Ａｌ₂Ｏ₃ ；日本アエロジル（株），Aluminium Oxide Ｃ。
【０１１０】
Ａｌ₂Ｏ₃ 繊維 ；ニチアス（株） ，ルビール^R バルクファイバーＴ／５４７０−ＲＳ。
ＭｇＯ ；協和化学工業（株） ，パイロキスマ５３０１Ｋ。
それらの絶縁被膜に関して以下の特性評価を実施した。
【０１１１】
▲１▼熱伝導率と比抵抗の測定：
表９の実施例１−１〜１５−２および比較例１に示す樹脂組成物について、レーザフラッシュ法で２０℃における熱伝導率（Ｗ／ｍ・Ｋ）及び比抵抗（Ω・ｃｍ）の測定を行った。その結果を表５に示す。
【０１１２】
【表１０】

【０１１３】
実施例１−１〜１５−２は熱伝導率が比較例１に比べて大きく、いずれも０．５ｗ／ｍ・ｋ以上と、通常のプラスチック材料（0.2 〜0.4 w/m ・k ）よりも良好な伝熱性を示している。特に、ガラス繊維を用いずにＳｉＣウィスカー又はＡｌ₂ Ｏ₃ 繊維を使用した実施例１１−１〜１２−２において、顕著な熱伝導率が得られている。
【０１１４】
また、各実施例１−１〜１５−２の比抵抗は比較例１よりも小さくなっているが、いずれも１×１０¹³Ω・ｃｍ以上を有しており、十分な電気絶縁性を備えていることがわかる。
【０１１５】
▲２▼ウエルド強度，アイゾット衝撃強度の測定：
表９の実施例１−１〜１５−２および比較例１の組成を有する樹脂組成物について所定の試験片を成形し、２３℃でウエルド強度及びアイゾット衝撃強度の測定を行った。すなわちウエルド強度は、金型キャビティの両端から絶縁被膜樹脂組成物を注入させてその樹脂組成物の会合部（ウエルド部）を中央に持つＪＩＳ１号試験片（ｔ＝３ｍｍ）を成形し、これを用いて引張り速度５ｍｍ／ｍｉｎで測定した。また、アイゾット衝撃強度は、ノッチ付試験片で測定した。
【０１１６】
それらの測定結果を表６に示す。
【０１１７】
【表１１】

【０１１８】
なお、実施例１−１〜１０−２では、マトリックス樹脂の充填材として強化性の高いガラス繊維を用い、実施例１３−１〜実施例１５−２では同じく強化繊維材〔Ａ〕に属するウィスカー類を用いているので、ウエルド強度は差異が少なく、いずれも７０ＭＰａ以上であった。これに対して、実施例１１−１，１１─２は強化繊維材〔Ａ〕ではなく非磁性高熱伝導性充填材〔Ｃ〕であるＳｉＣウィスカーを、また実施例１２−１，１２−２ではアルミナ繊維を用いているが、やはり７０ＭＰａ以上のウエルド強度が得られている。
【０１１９】
また、アイゾット衝撃強度は、ガラス繊維〔Ａ〕を減らして粉体系の充填材〔Ｂ〕，〔Ｃ〕を添加することによって比較例１（ガラス繊維４０重量％）より少し低めになっているが、いずれも２．０ＫＪ／ｍ² を越えており、使用上問題ないことがわかった。
【０１２０】
▲３▼耐クリープ性の把握：
実施例１−１〜１５−２及び比較例１の組成を有する樹脂組成物について円柱状の試験片を成形し、図１９に示す試験装置を用いて圧縮クリープ試験を行った。測定は、当該試験片を試験装置ごと、１２０℃に設定された恒温槽にいれて１００時間放置（面圧２．９ｋｇ／ｍｍ² ）し、その後取り出して１時間室温に保持した後に当該試験片ＴＰの高さ変化率を測定した。測定結果を表１２に示す。
【０１２１】
【表１２】

【０１２２】
各実施例とも、比較例１よりも高さ変化率は小さく、耐クリープ性は良好である。特に、磁性充填材〔Ｂ〕をガラス繊維と併用した実施例１−１〜４−２、非磁性高熱伝導性充填材〔Ｃ〕のうちのアルミナ繊維をガラス繊維と併用した実施例１０−１，１０−２及びガラス繊維を使わずにＳｉＣウィスカーやアルミナ繊維を単独で充填した実施例１１−１〜１２−２は、高さ変化率が小さくて顕著な耐クリープ性を示している。
【０１２３】
なお、図示しないが、図５，図８，図１０，図１３，図１４，図１７のような外輪２の外周面又は端面２ｓに施した本願発明の絶縁被膜を、内輪１の内周面又は内輪１の端面の少なくとも１つの面に選択的に施しても、本願発明の目的が達せられる。
【０１２４】
【発明の効果】
以上説明したように、第１の目的を達成する本発明の転がり軸受によれば、外輪の外周部を被覆する熱可塑性エラストマの層がモータハウジングと外輪間の電気的導通を阻止するため、この軸受をインバータ駆動されるファンモータに用いると、従来のように電気的導通性を有する特殊なグリースを使用したり、塵埃が発生し易い電気的ブラシを設置することなく、軸受内外輪間を電流が流れることを阻止することができ、その結果、内外輪軌道面あるいは転動体転動面の電食を防止できるという効果を奏する。
【０１２５】
また、外周面に凹凸を有する変形し易い熱可塑性エラストマの層にすると、上記の効果に加えて更に、軸受のハウジングへの挿入が容易で且つハウジング内で突っ張ってクリープ防止機能を発揮するという効果も得られる。
【０１２６】
更に、熱可塑性エラストマに熱伝導性フィラーを含有させると、熱可塑性エラストマの層自体の熱伝導性が向上する結果、良好な絶縁性を維持しつつ、十分な放熱性も維持できてエラストマの熱劣化を抑制できるという効果をも奏する。
【０１２７】
また、第２の目的を達成する本発明の転がり軸受によれば、外輪の外周部に圧入されたリング状絶縁部材がモータハウジングと外輪間の電気的導通を阻止するため、この軸受をインバータ駆動されるファンモータに用いると、従来のように電気的導通性を有する特殊なグリースを使用したり、塵埃が発生し易い電気的ブラシを設置することなく、軸受内外輪間を電流が流れることを阻止することができ、その結果、内外輪軌道面あるいは転動体転動面の電食を防止できるという効果を奏する。
【０１２８】
また、リング状絶縁部材を、比抵抗が１×１０¹³Ω・ｃｍ以上で且つ熱伝導率が０．５Ｗ／ｍ・Ｋ以上の合成樹脂組成物からなるものとしたため、電気絶縁性，耐クリープ性のみでなく放熱性にも優れた転がり軸受を提供できるという効果が得られる。
【０１２９】
また、前記リング状絶縁部材の合成樹脂組成物として、マトリックス樹脂に耐クリープ性の大きい繊維材〔Ａ〕と、飽和磁化及び比抵抗が一定値以上の磁性充填材〔Ｂ〕とを両者の合計〔Ａ＋Ｂ〕３０〜７５重量％の範囲で混合したものにすると、磁性充填材〔Ｂ〕の電気絶縁性向上作用及び伝熱性向上作用により、耐クリープ性，伝熱性，成形性及び電気絶縁性に一層優れた絶縁被膜が得られて、高速回転で高温にさらされる使用条件下でも安定した性能が保証できる電食防止転がり軸受を提供できるという効果を奏する。
【０１３０】
さらに、前記リング状絶縁部材の合成樹脂組成物の磁性充填材〔Ｂ〕の少なくとも一部を非磁性高熱伝導性充填材〔Ｃ〕で置換しても、上記同様の効果を奏する。
【０１３１】
また、磁性充填材〔Ｂ〕及び非磁性高熱伝導性充填材〔Ｃ〕の含有量を当該充填材の種類に応じて単独もしくは合わせて２０〜６５重量％の範囲内で任意に調整すると、リング状絶縁部材の耐クリープ性，伝熱性，成形性及び電気絶縁性の諸特性のバランスを調整できて、軸受の使用条件等に応じて製品に多様性を持たせることができる。
【図面の簡単な説明】
【図１】本発明の絶縁材の組成と熱伝導率及び比抵抗との関係を示す図である。
【図２】本発明の絶縁材の組成と熱伝導率及び比抵抗との関係を示す図である。
【図３】本発明の絶縁材の組成と熱伝導率及び比抵抗との関係を示す図である。
【図４】本発明の絶縁材の組成と熱伝導率及び比抵抗との関係を示す図である。
【図５】本発明の転がり軸受の第１の実施形態の半断面図である。
【図６】図５に示す熱可塑性エラストマの層の表面の部分拡大断面図である。
【図７】図５に示す転がり軸受のモータへの取付け態様を示す模式図である。
【図８】本発明の転がり軸受の第２の実施形態の半断面図である。
【図９】図８に示す熱可塑性エラストマの層の表面の部分拡大断面図である。
【図１０】本発明の転がり軸受の第３の実施形態の半断面図である。
【図１１】図１０に示す熱可塑性エラストマの層の表面の部分拡大平面図である。
【図１２】本発明の転がり軸受の第４の実施形態における、熱可塑性エラストマの層の表面の部分拡大平面図である。
【図１３】本発明の転がり軸受の第５の実施形態の半断面図である。
【図１４】本発明の転がり軸受の第６の実施形態の半断面図である。
【図１５】本発明の転がり軸受における熱可塑性エラストマの層の表面パターンの他の例を示す平面図である。
【図１６】本発明の転がり軸受における熱可塑性エラストマの層の表面パターンのさらに他の例を示す平面図である。
【図１７】本発明の転がり軸受の第７の実施形態の半断面図である。
【図１８】図１７に示す転がり軸受のモータへの取付け態様を示す断面図である。
【図１９】耐クリープ性試験装置の模式側面図である。
【符号の説明】
１ 内輪
２ 外輪
２ｇ 外周部（外輪の外周面）
２ｓ 外周部（外輪の側面）
３ 転動体（ボール）
５ 熱可塑性エラストマの層
３０ リング状絶縁部材
Ａ 転がり軸受[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in a rolling bearing used in a fan motor whose speed is controlled by an inverter.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a rolling bearing (hereinafter also simply referred to as a bearing) incorporated in a fan motor (hereinafter also simply referred to as a motor) is attached with an outer ring mounted on a housing and an inner ring fitted on a rotor shaft of the motor with a clearance fit or an interference fit. Needless to say, it is an interference fit, but even in the case of a clearance fit, the inner ring or the outer ring is pressed against the bearing via a spacer to increase the rigidity of the bearing and prevent vibrations. Since the preload is applied, the outer ring and the bracket, and the inner ring and the rotor shaft are electrically connected to each other.
[0003]
On the other hand, fan motors are increasingly controlled in speed via an inverter that can vary the rotational speed in order to control the air volume. In that case, motor noise due to switching can be reduced by setting the carrier frequency of the inverter high, and it has become possible to set the carrier frequency high by improving the performance of semiconductor elements and circuit technology. For this reason, the carrier frequency of inverters has been set higher. Along with this, the shaft voltage generated in the motor driven by the inverter increases, and a potential difference is generated between the rotor shaft and the housing and thus between the inner and outer rings of the bearing, so that current flows through the rolling elements in the bearing, and as a result, There is an increasing possibility of electrolytic corrosion on the raceway surface of the ring or the rolling surface of the rolling element.
[0004]
Conventionally, when a fan motor driven by an inverter has a risk of electric corrosion, the following measures are taken.
(1) When an electric brush can be installed, the electric brush is brought into contact with the rotor shaft to keep the rotor shaft and the housing at the same potential, thereby preventing current from flowing between the inner and outer rings of the bearing. .
[0005]
(2) Or, by enclosing grease that imparts electrical continuity to the bearing, the current between the inner and outer rings of the bearing is kept at an equipotential to prevent current from flowing.
(3) Alternatively, grease with high base oil viscosity is sealed in the bearing to increase the thickness of the oil film formed between the bearing outer ring and the rolling element, and between the bearing inner ring and the rolling element. Insulate.
[0006]
[Problems to be solved by the invention]
However, each of these conventional electric corrosion prevention measures has the following problems.
[0007]
Regarding the installation of the electric brush, one end of the rotor shaft of the motor is housed in the housing so that there is no space for installing the electric brush, and the other end of the rotor shaft has a fan formed of an insulating material such as synthetic resin. Since it is mounted, it is often difficult to bring the electric brush into contact with the rotor shaft, and as a practical matter, it is often impossible to install the electric brush on the fan motor. Further, even if an electric brush can be installed, there is a problem that the abrasion powder of the brush is discharged from the fan motor and released as dust in the air. For example, when a fan motor provided with an electric brush is used in a clean room, it becomes a fatal defect and cannot be put to practical use.
[0008]
With regard to the sealing of the grease imparted with electrical conductivity, the grease contains a good electrical conductor such as carbon particles, so the rotational noise of the bearing has to be larger than that of normal grease. In addition, the use of such expensive special grease has the disadvantage of increasing the cost of the bearing.
[0009]
When encapsulating grease with a high base oil viscosity, the oil film indicates that the temperature rise is caused by an increase in the bearing torque due to the viscosity of the grease, and that the current passing between the inner and outer rings of the bearing is an alternating current with a high frequency. There is a problem that the current may be conducted in the gap of about the thickness. In addition, the oil film formation state fluctuates due to the deterioration of the enclosed grease over time or the entry of foreign matter into the grease, so there is a possibility that electrical conduction and insulation will occur alternately and electric corrosion may occur. It cannot be.
[0010]
It is also known to form an insulating coating made of plastics or ceramics on the outer ring of the bearing as another measure for preventing electric corrosion. When the insulating coating is plastic, for example, the composition includes PPS resin containing glass fiber, and the thermal conductivity is only about 0.2 to 0.4 W / m · K. Therefore, the heat generated by the rotation of the bearing is difficult to escape and the temperature of the bearing rises. That is, there is a problem that further improvement in heat dissipation of the bearing is desired. Further, when the insulating coating is ceramic, after thermal spraying, it can be cut to a target outer diameter and further polished to improve accuracy, but the cost is higher than that of the resin coating.
[0011]
  Accordingly, the present invention has been made paying attention to the problems of the conventional measures for preventing electric corrosion of rolling bearings, and instead of means such as installation of an electric brush or sealing of special grease, a shaft is provided.Outer ringPerimeterPartIt is an object of the present invention to provide a rolling bearing capable of not only preventing electric corrosion but also improving the insertability of the bearing into the housing and preventing the occurrence of creep by covering the surface with an insulating coating made of a thermoplastic elastomer.
[0012]
Another object of the present invention is to provide a specific resistance of 1 × 10 so as to cover one of the outer peripheral portion and the end face of the outer ring, instead of means such as installing an electric brush or enclosing special grease.¹³A rolling bearing that secures heat dissipation while preventing electrolytic corrosion by press-fitting a ring-shaped insulating member made of a synthetic resin composition having a resistance of Ω · cm or more and a thermal conductivity of 0.5 w / m · k or more. It is to provide.
[0013]
[Means for Solving the Problems]
  In order to achieve the first object, a first aspect of the present invention provides a rolling bearing having at least an outer ring and an inner ring, and a rolling element interposed between the outer ring and the inner ring.Satisfies the following five conditionsIt is characterized by that.
[0014]
    Condition A: A thermoplastic elastomer layer is formed on the entire outer periphery of the outer ring.
    Condition B: The thermoplastic elastomer layer has a hardness of 60 to 90 [HD _A And a thickness of 0.5 to 5 mm.
    Condition C: The thermoplastic elastomer layer has a thermal conductivity of 10 W / m · k or more and a specific resistance of 1 × 10 ^Four Contains a thermally conductive filler of Ω · cm or more.
    Condition D: Concavities and convexities are provided over the entire outer peripheral surface of the thermoplastic elastomer layer.
    Condition E: The unevenness is formed by a herringbone-shaped concave portion that continues in the width direction of the outer ring, a strip-shaped concave portion that continues in a rhombus shape, or irregular projections that are irregularly scattered.
[0015]
  In addition, the present inventionAccording to a second aspect of the present invention, in the rolling bearing according to the first aspect, the thermoplastic elastomer layer has an unevenness height (depth) of the outer peripheral surface of 5 to 100 μm.It is characterized by that.
[0017]
In the rolling bearing according to the present invention, the bearing outer ring and the housing are electrically insulated from each other by a thermoplastic elastomer layer formed on the outer peripheral portion of the outer ring. Therefore, even if a shaft voltage is generated in the motor driven by the inverter, no potential difference is generated between the inner and outer rings of the bearing. Accordingly, no current flows between the inner and outer rings of the bearing, and electrolytic corrosion of the raceway surfaces of the inner and outer rings or the rolling surfaces of the rolling elements is prevented.
[0018]
Hardness of the thermoplastic elastomer layer of the present invention is 60 to 90 [HD_A], Since it is softer and easier to deform than a normal metal thin film layer or plastics layer, it is easy to insert the bearing into the housing. In addition, when the bearing is press-fitted into the housing, the thermoplastic elastomer layer stretches in the housing and functions effectively to prevent creep. Further, if the surface of the thermoplastic elastomer is uneven, the contact area to the housing is smaller than that of a flat one, and therefore, it becomes easier to deform and the bearing can be inserted into the housing more easily.
[0019]
When a thermally conductive filler is added to the thermoplastic elastomer layer of the present invention, heat is effectively radiated from the bearing to the housing without being stored in the elastomer layer, so that thermal degradation of the elastomer can be suppressed.
[0020]
  In addition, in order to achieve the second purpose described above,TomorrowIn a rolling bearing having at least an outer ring and an inner ring, and a rolling element interposed between the outer ring and the inner ring, a specific resistance (such as covering at least one of the outer peripheral portion of the outer ring and both end faces of the bearing) Value) is 1 × 10¹³A ring-shaped insulating member made of a synthetic resin composition having a resistance of Ω · cm or more and a thermal conductivity of 0.5 W / m · k or more is press-fitted.
[0021]
Here, the ring-shaped insulating member has a thermal conductivity of less than 10 w / m · k and a specific resistance of 1 × 10 10 which contributes to the reinforcement of the synthetic resin composition.^ThreeFiber material [A] of Ω · cm or more, saturation magnetization of 20 emu / g or more and specific resistance of 1 × 10^ThreeIt includes a magnetic filler [B] of Ω · cm or more, and the sum of both [A + B] may be 30 to 75% by weight.
[0022]
The content of the magnetic filler [B] can be 20 to 65% by weight.
The magnetic filler [B] can be ferrite.
Further, at least a part of the magnetic filler [B] can be replaced with a heat conduction improving filler.
[0023]
The thermal conductivity improving filler has a thermal conductivity of 10 w / m · k or more and a specific resistance of 1 × 10.^ThreeA nonmagnetic high thermal conductive filler [C] of Ω · cm or more can be used.
Further, the non-magnetic high thermal conductive filler [C] may be selected from any one of inorganic compound powders, fibers and whiskers.
[0024]
In general, since a fiber material such as a resin or glass fiber has a low thermal conductivity, an insulating coating formed from a resin composition obtained by mixing only these two also has a low thermal conductivity. Further, since a fiber material such as glass fiber does not have magnetism in itself, the fibers are not attracted magnetically in the resin and connected. Therefore, if glass fibers are brought into contact with each other to increase the thermal conductivity, a considerable amount must be mixed into the resin, which significantly reduces mechanical strength such as moldability and weld strength, and is used for bearings. It becomes impossible to form an insulating film (ring-shaped insulating member) having a performance higher than that required for this.
[0025]
Therefore, in the present invention to achieve the second object, magnetic particles (saturation magnetization of 20 emu / g or more and specific resistance of 1 × 10^ThreeInsulating filler consisting of Ω · cm or more is separately added to the resin. The magnetic particles of the added magnetic filler attract each other in the resin and easily come into contact with each other, thereby increasing the thermal conductivity of the ring-shaped insulating member and improving the heat dissipation characteristics. Thus, an insulating coating excellent in heat resistance, insulation and heat dissipation as well as creep resistance can be obtained.
[0026]
In the present invention, at least a part of the reinforcing fiber material [A] and the magnetic filler [B] has a thermal conductivity of 10 w / m · k or more and a specific resistance of 1 × 10.^ThreeIt may be replaced with a nonmagnetic high thermal conductive filler [C] of Ω · cm or more. This non-magnetic high thermal conductive filler [C] is added as a thermal conductivity improving filler, and can be used in the same manner as a reinforcing material such as glass fiber if it is fibrous or whisker-like, reducing the strength of the resin itself. It is possible to improve the thermal conductivity without making it even more effective.
[0027]
Details of the present invention will be described below.
Examples of the thermoplastic elastomer that can be used in the rolling bearing of the present invention that achieves the first object include polyester-based elastomers, polyamide-based elastomers, polyurethane-based elastomers, polyolefin-based elastomers, nitrile-based elastomers, acrylic-based elastomers, styrene-based elastomers, and others. There are dynamic cross-link type elastomers. In view of heat resistance, polyester elastomer is particularly preferable.
[0028]
Specific examples of these thermoplastic elastomer materials include: “Mirastoma” (Mitsui Petrochemical Co., Ltd., registered trademark) for olefins, and “Perprene” (manufactured by Toyobo Co., Ltd.) for polyesters. , Registered trademark] and “Hytrel” (registered trademark, manufactured by Toray DuPont Co., Ltd.), and “Pebax” (registered trademark, manufactured by Toray Industries, Inc.) and “UBE polyamide elastomer” [Ube Industries, Ltd. "Elastollan" (manufactured by Takeda Burdish Urethane Kogyo Co., Ltd., registered trademark) for polyurethane, and "Miraplane" (manufactured by Mitsubishi Kasei MKV) for nitrile and acrylic. In addition, “santoprene” [AES Japan Co., Ltd., registered trademark], which is a dynamic cross-linking type, can be exemplified as other special ones.
[0029]
The hardness of the thermoplastic elastomer is 60 to 90 [HD_A] (Durometer A scale hardness), more preferably 70 to 85 [HD_A]. 60 [HD_A] Is too soft, the deformation capacity is large, and when the bearing is press-fitted into the housing, the thermoplastic elastomer layer may be crushed and protrude from the end face of the bearing outer ring main body, and the rigidity against the radial load is deteriorated. On the other hand, the hardness is 90 [HD_A], The deformability is reduced, and the insertability into the housing and the creep resistance are reduced.
[0030]
If the thickness of the thermoplastic elastomer layer is about 0.5 to 5 mm, it is sufficient for insulation and prevention of creep. If it is less than 0.5 mm, the strength as a layer (coating) is lowered. On the other hand, when the thickness exceeds 5 mm, the amount of material used increases, leading to an increase in cost.
[0031]
The height (depth) of the concavo-convex portion of the thermoplastic elastomer layer is preferably 5 to 100 μm, more preferably 10 to 50 μm in view of mold release and deformability during molding and creep prevention. If the thickness is less than 5 μm, a sufficient contribution to the deformability / creep prevention is not required. On the other hand, if the thickness exceeds 100 μm, the releasability from the mold deteriorates and the productivity decreases.
[0032]
For joining the thermoplastic elastomer layer and the outer ring main body, the thermoplastic elastomer part may be separately molded by injection molding, and it may be deformed and fitted into the outer ring, or it may fall off at the outer peripheral part or end face part of the outer ring main body. A groove for prevention (preferably dovetail groove) may be provided, and insert bearing molding may be performed using the bearing body as a core.
[0033]
Moreover, in order to perform the joining more firmly, an adhesive may be interposed between the thermoplastic elastomer layer and the outer peripheral portion or end face portion of the outer ring main body. As the adhesive, an elastic adhesive such as an epoxy is suitable for offsetting the difference in linear expansion between the outer ring main body and the thermoplastic elastomer.
[0034]
Furthermore, for the purpose of improving the thermal conductivity of the thermoplastic elastomer, the thermal conductivity is 10 w / m · k or more and the specific resistance is 1 × 10.^FourA thermally conductive filler of Ω · cm or more may be added to the air stoma. As a result, the heat generated by the operation of the bearing is effectively radiated from the bearing to the housing without being stored in the thermoplastic elastomer layer, and thermal deterioration of the thermoplastic elastomer can be suppressed. The addition amount of the thermally conductive filler is preferably about 10 to 50% by weight, the thermal conductivity of the thermoplastic elastomer layer is 0.5 w / m · k or more, and the specific resistance is 1 × 10.¹³Various fillers are used in combination so as to be Ω · cm or more. When the addition amount of the heat conductive filler is less than 10% by weight, the improvement of the heat conductivity cannot be expected so much. On the other hand, if the added amount exceeds 50% by weight, the moldability of the thermoplastic elastomer layer is lowered.
[0035]
Specific examples of the thermally conductive filler include SiC whisker, Al₂O_Three(Whiskers, fibers, particulates, etc.), AlN (particulates), MgO (particulates), BeO (particulates) and the like.
[0036]
For the purpose of improving the strength of the thermoplastic elastomer layer of the present invention, reinforcing fibers such as glass fibers may be added. In this case, the amount of reinforcing fiber added is 30 to 65% by weight in total with the thermally conductive filler. If the total addition amount is less than 30% by weight, a product with a balance between a certain level of strength and thermal conductivity cannot be obtained. On the other hand, if the total addition amount exceeds 65% by weight, the moldability deteriorates.
[0037]
Subsequently, the present invention for achieving the second object will be described in detail.
As the resin material used for forming the ring-shaped insulating member of the present invention, PPS resin, aromatic nylon (aromatic polyamide resin), 4.6 nylon of aliphatic polyamide resin, or the like can be suitably used. Since the PPS resin has low water absorption and good moldability, a ring-shaped insulating member having low water absorption and excellent dimensional stability can be formed at low cost by injection molding. Aromatic nylon is preferable because it has a high melting point and high strength, and can maintain insulation performance at a high temperature of 120 ° C. when the bearing rotates at high speed. On the other hand, aliphatic polyamide resins such as 4.6 nylon also have good electrical insulation and are suitable for ring-shaped insulating members.
[0038]
However, the above resin cannot satisfy a plurality of functions required for an insulating member for an electric corrosion prevention rolling bearing at the same time, and is used in combination with an additive material described below.
The fiber material [A] of the present invention used for reinforcing the resin material is mainly used for improving the creep resistance of the matrix resin and maintaining the electrical insulation of the ring-shaped insulation member. The higher the better, the specific resistance value is 1 × 10^ThreeΩ · cm or more, preferably 1 × 10^FourΩ · cm or more is good. The higher the thermal conductivity, the better. Specific preferred examples include glass fiber (GF) fibers or potassium titanate whiskers such as potassium 6 titanate and potassium 8 titanate, aluminum borate whiskers, calcium carbonate whiskers (argonite), basic magnesium sulfate whiskers, etc. Is effective, but other aramid fibers can also be used. Table 1 shows these specific resistance values.
[0039]
[Table 1]

[0040]
The addition amount of the fiber material [A] mainly for improving the creep resistance is 10 to 55% by weight, preferably 20 to 40% by weight, based on the entire mixture. If it exceeds 55% by weight, the moldability is deteriorated, and if it is less than 10% by weight, the creep resistance is deteriorated.
[0041]
The magnetic filler [B] of the present invention is used in order to satisfy both the maintenance of the electrical insulation of the ring-shaped insulating member and the improvement of the heat conductivity at the same time. It may be about 5 to 10 W / m · K. On the other hand, the electrical insulation is preferably high, but the specific resistance value is 1 × 10.^ThreeΩ · cm or more, more preferably 1 × 10^FourIf it is Ω · cm or more, there is no problem in use. Further, with respect to the saturation magnetization, 20 emu / g or more, more preferably 50 emu / g or more is preferable because the magnetic attractive force becomes large. If it is less than 20 emu / g, the magnetic attraction force is too small to achieve the expected improvement in heat transfer.
[0042]
Magnetic fillers that can satisfy such conditions are, for example, MgFe₂0_Four(Magnesium ferrite), MnFe₂O_Four(Manganese ferrite), Fe_ThreeO_Four(Magnetite), CoFe₂O_Four(Cobalt ferrite), NiFe₂O_Four(Nickel ferrite), CuFe₂O_Four(Copper ferrite), γ-Fe₂O_ThreeSelected from granular powders such as (maghemite). Table 2 shows the saturation magnetization and specific resistance of these filler materials.
[0043]
[Table 2]

[0044]
The amount of the magnetic filler [B] added is 20 to 65% by weight, preferably 25 to 55% by weight, based on the entire synthetic resin composition forming the ring-shaped insulating member. If it exceeds 65% by weight, it becomes difficult to satisfy creep resistance and moldability. On the other hand, if it is less than 20% by weight, improvement in heat transfer cannot be expected, so that the electric insulation, heat transfer, and creep resistance of the present invention are not expected. The effect of improving all three beats cannot be expected.
[0045]
Furthermore, the non-magnetic high thermal conductive filler [C] of the present invention is used for simultaneously satisfying the improvement of the heat conductivity of the ring-shaped insulating member and the maintenance of the electrical insulation, similarly to the magnetic filler [B]. However, the thermal conductivity of the particles is not higher than that of the magnetic filler [B], so that the particles do not actively connect with each other by the magnetic attractive force. Specifically, 10 W / m · K or more, more preferably 20 W / m · K or more is required. On the other hand, the electrical insulation is preferably high, but the specific resistance value is 1 × 10.^ThreeΩ · cm or more, more preferably 1 × 10^FourIf it is Ω · cm or more, there is no problem in use.
[0046]
Nonmagnetic high thermal conductive fillers [C] that can satisfy such conditions include, for example, SiC (silicon carbide), AlN (aluminum nitride), BeO (beryllia), BN (boron nitride), Al₂O_Three(Alumina), MgO (magnesia) and other powders, fibers or whiskers. Table 3 shows the thermal conductivity and specific resistance of these filler materials in comparison with Cu (copper) and glass fiber (E glass).
[0047]
[Table 3]

[0048]
Of those shown in Table 3, SiC, Al₂O_ThreeThere are fibers and whiskers (indicated by the symbol [C-1]), but the others are only granular (indicated by the symbol [C-2]). Therefore, when creep resistance is further required, SiC and Al are used without using glass fiber (GF).₂O_ThreeWhen the whisker or fiber [C-1] is used, creep resistance is further improved, and in addition, improved heat transfer is obtained.
[0049]
At least a part of this non-magnetic high thermal conductive filler [C-1] can be used instead of the magnetic filler [B]. The addition amount in that case is 30 to 75% by weight of the whole synthetic resin composition in the case of both mixing ([B + C-1]), 20 to 75% by weight in the case of the former alone ([C-1]). Preferably, it is selected in the range of 25 to 50% by weight. If it exceeds 75% by weight, it becomes difficult to satisfy the moldability. On the other hand, if it is less than 20% by weight, the thermal conductivity of the ring-shaped insulating member does not become 0.5 w / m · k or more. Therefore, improvement in creep resistance and heat transfer cannot be expected, and therefore, it is impossible to expect the effect of improving the electric insulation, heat transfer, and creep resistance of the ring-shaped insulating member of the present invention in three beats. In terms of cost, the magnetic filler [B] is less expensive than the nonmagnetic high thermal conductive filler [C-1], and therefore the nonmagnetic high thermal conductive filler [C-1] is used alone. It is more advantageous to use only the magnetic filler [B] or a mixture of both [B + C-1].
[0050]
Table 4 summarizes the amount of each filler alone in the synthetic resin composition of the present invention that achieves the second object described above.
[0051]
[Table 4]

[0052]
However, as described below, when combined with [C-1], the filling amount of [A] is 0 to 40% by weight, and similarly, the filling amount of [B] is 0 to 55% by weight.
[0053]
These various fillers can also be used in combination.
In that case, the combination method and filling ratio of the fillers in the matrix of the synthetic resin composition are as follows.
[0054]
(1) A + B 45-75wt%
(2) A + C-2 45-75 wt%
(3) B + C-1 30-75wt%
(4) A + C-1 45-75 wt%
(5) A + B + C 45-75wt%
In any case, when the filling amount is less than the lower limit, the thermal conductivity of the ring-shaped insulating member does not become 0.5 w / m · k or more. On the other hand, if the upper limit value is exceeded, the moldability decreases.
[0055]
The critical significance of each combination is described below.
(1) Combination of fiber material [A] and magnetic filler [B]:
Table 5 shows the measurement results of the thermal conductivity and specific resistance of the ring-shaped insulating member according to the difference in the addition ratio of the filler in the case of the filler [A + B]. However, the fiber material [A] (glass fiber) is fixed to 20% by weight, and the magnetic filler [B] (MnFe₂O_Four) Was added.
[0056]
[Table 5]

[0057]
FIG. 1 is a graph of Table 5. As is apparent from this figure, the total addition amount [A + B] is preferably in the range of 45 to 75% by weight. If it exceeds 75% by weight, the specific resistance of the ring-shaped insulating member is 1 × 10¹³It becomes less than Ω · cm. In addition, the matrix resin is insufficient, resulting in a decrease in fluidity at the time of molding. As a result, the surface roughness of the formed ring-shaped insulating member is deteriorated and the weld strength is decreased. On the other hand, if it is less than 45% by weight, the necessary minimum amount of both the fiber material [A] and the magnetic filler [B] cannot be ensured, and it becomes difficult to achieve both heat transfer and creep resistance. The property does not exceed 0.5 w / m · k. Furthermore, in order to ensure high heat conductivity and creep resistance, it is more preferable that the total addition amount [A + B] is in the range of 50 to 75% by weight.
[0058]
In addition, in the resin composition containing such a fiber material [A] and a magnetic filler [B], a coupling agent such as a release agent or a silane coupling agent for the purpose of improving the strength is necessary. An agent may be added. Alternatively, a fiber material or a filler treated with a coupling agent or the like may be used.
(2) Combination of fiber material [A] and granular non-magnetic high thermal conductive filler [C-2]:
Table 6 shows the measurement results of the thermal conductivity and specific resistance of the ring-shaped insulating member according to the difference in the addition ratio of the filler in the case of the filler [A + C-2]. However, the fiber material [A] (glass fiber) is fixed at 20% by weight, and the granular non-magnetic high thermal conductive filler [C-2] (Al₂O_Three) Was added.
[0059]
[Table 6]

[0060]
FIG. 2 is a graph of Table 6. As is apparent from this figure, the total addition amount [A + C-2] is preferably in the range of 45 to 75% by weight. If it exceeds 75% by weight, the specific resistance is still high, but the matrix resin is insufficient and the moldability is lowered. On the other hand, if it is less than 45% by weight, the thermal conductivity of the ring-shaped insulating member does not become 0.5 w / m · k or more.
(3) Combination of magnetic filler [B] and fiber or whisker-like nonmagnetic high thermal conductive filler [C-1]:
Table 7 shows the measurement results of the thermal conductivity and specific resistance of the ring-shaped insulating member according to the difference in the addition ratio of the filler in the case of the filler [B + C-1]. However, magnetic filler [B] (MnFe₂O_Four) Is fixed at 20% by weight, non-magnetic high thermal conductive filler [C-1] (Al₂O_ThreeThe amount of fiber) was changed.
[0061]
[Table 7]

[0062]
FIG. 3 is a graph of Table 7. As is apparent from this figure, the total addition amount [B + C-1] is preferably in the range of 30 to 75% by weight. If it exceeds 75% by weight, the specific resistance is still high, but the matrix resin is insufficient and the moldability is lowered. On the other hand, if it is less than 30% by weight, the thermal conductivity of the ring-shaped insulating member does not become 0.5 w / m · k or more.
[0063]
In Table 8, in the case of the above-mentioned fiber or whisker-like non-magnetic high thermal conductive filler [C-1] alone, ring-shaped insulation due to the difference in addition ratio of the filler [C-1] (using Si whisker) The measurement result of the thermal conductivity and specific resistance of a member is shown.
[0064]
[Table 8]

[0065]
FIG. 4 is a graph of Table 8. As apparent from this figure, the addition amount of [C-1] filler alone is preferably in the range of 20 to 75% by weight. If it exceeds 75% by weight, the specific resistance is still high, but the matrix resin is insufficient and the moldability is lowered. On the other hand, if it is less than 20% by weight, the thermal conductivity of the ring-shaped insulating member does not become 0.5 w / m · k or more, and it is difficult to achieve both heat conductivity and creep resistance.
(4) Combination of fiber material [A] and fiber or whisker-like non-magnetic high thermal conductive filler [C-1]:
In the case of the filler [A + C-1], the change in the thermal conductivity and specific resistance of the ring-shaped insulating member due to the difference in the addition ratio of the filler was measured in the same manner as described above. 1] was found to be preferably in the range of 45 to 75% by weight. If it exceeds 75% by weight, the specific resistance is still high, but the matrix resin is insufficient and the moldability is lowered. On the other hand, if it is less than 45% by weight, the thermal conductivity of the ring-shaped insulating member does not become 0.5 w / m · k or more.
(5) Combination of fiber material [A], magnetic filler [B] and non-magnetic high thermal conductive filler [C]:
The total amount [A + B + C] of the fiber material [A], the magnetic filler [B], and the nonmagnetic high thermal conductivity filler [C] is preferably 45 to 75% by weight. If it exceeds 75% by weight, the matrix resin is insufficient and the fluidity during molding is lowered. As a result, the surface roughness of the molded ring-shaped insulating member is deteriorated and the weld strength is lowered. On the other hand, if it is less than 45% by weight, the thermal conductivity of the ring-shaped insulating member does not become 0.5 w / m · k or more, and the fiber material [A], magnetic filler [B], nonmagnetic high thermal conductivity filler Since the necessary minimum amounts of [C] cannot be ensured, it becomes difficult to achieve both heat transfer and creep resistance. Furthermore, in order to ensure high heat conductivity and creep resistance, the total addition amount [A + B + C] is more preferably in the range of 50 to 75% by weight.
[0066]
The breakdown of the total addition amount [A + B + C] of the above three is determined so that the following physical properties required as a ring-shaped insulating member of a rolling bearing for preventing electric corrosion can be obtained.
[0067]
Thermal conductivity: 0.5 w / m · k or more
Specific resistance: 1 × 10¹³Ω · cm or more
Weld strength: 70 MPa or more
[0068]
Izod impact strength: 2 kJ / m²More preferably, 5 kJ / m for improving strength when dropped²That's it. This makes it easier to handle the electric corrosion prevention rolling bearing itself. That is, weld strength of 70 MPa or more, Izod impact strength of 2 kJ / m²If it is above, the damage of the insulating film at the time of inserting a bearing in a housing can be prevented.
[0069]

[0070]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention that achieve the first object will be described below with reference to the drawings. FIG. 5 is a half sectional view of the first embodiment of the rolling bearing according to the present invention. The inner ring 1 is fitted to the rotor shaft of the fan motor, the outer ring 2 is fitted to the housing, the inner ring 1 and the outer ring. The present invention is applied to a deep groove ball bearing provided with a ball 3 of a rolling element interposed between 2 and a cage 4 for holding the ball 3. The outer ring outer peripheral portion composed of the outer peripheral surface 2g of the outer ring 2 and the two side surfaces 2s, 2s is substantially entirely covered with a film layer 5 of a thermoplastic elastomer.
[0071]
The thermoplastic elastomer layer 5 of this embodiment has a thickness t of 1.5 mm at a thin portion, and a semicircular cross section as shown in an enlarged view in FIG. A plurality of convex portions 7 are continuously formed in an annular shape in the circumferential direction. Further, on the inner peripheral surface 5n and the inner side surface of the layer 5 of the thermoplastic elastomer, protrusions 8 having a quadrangular section are formed in an annular shape continuously in the circumferential direction. These protrusions 8 correspond to the concave grooves 9 that are formed in an annular shape continuously in the circumferential direction with a square cross section formed in advance on the outer peripheral surface 2g and both side surfaces 2S, 2S of the outer ring 2, The protrusion 8 is structured to be fitted into the concave groove 9 to prevent dropping.
[0072]
The thermoplastic elastomer layer 5 employs, for example, Perprene (registered trademark), P-30B, which is a polyester elastomer, and is injection-molded using a predetermined mold. Its properties are hardness: 71 [HD_A], Thermal conductivity: 0.22 w / m · k, specific resistance: 1 × 10¹²Ω · cm. When this is attached to the outer ring 2, a room temperature curing type epoxy elastic adhesive “EP-001” is applied in advance to the outer periphery of the outer ring 2, and the injection-molded thermoplastic elastomer layer 5 was deformed and fitted into the outer periphery of the outer ring 2 and left until it was completely adhered.
[0073]
Now, when the deep groove ball bearing is used as a fixed-side bearing in a fan motor as shown in FIG. 7, for example, the inner ring 1 is fitted into the rotor shaft J of the fan motor with an interference fit. The one is fitted to the housing H and preload is applied via the spacer K. At this time, the outer ring 2 is inserted into the inner surface of the housing H through a thermoplastic elastomer layer 5 attached to the outer periphery thereof. Thus, in the rolling bearing of this embodiment mounted on the fan motor, the outer peripheral surface 5g of the bearing outer ring 2 and the housing H are electrically insulated by the thermoplastic elastomer layer 5 formed on the outer peripheral portion of the outer ring 2. . In addition, it is electrically insulated by the thermoplastic elastomer layer 5 interposed between one outer surface 2s of the bearing outer ring 2 and between the other outer surface 2s and the spacer K constituting the housing. Therefore, even if a shaft voltage is generated in the fan motor driven by the inverter, no potential difference is generated between the inner ring 1 and the outer ring 2 of the bearing. That is, current does not flow between the inner and outer rings of the bearing, and electrolytic corrosion of each raceway surface of the inner ring 1 and outer ring 2 or the rolling surface of the ball 3 is prevented.
[0074]
Thus, the layer 5 of thermoplastic elastomer has a hardness of 71 [HD_A] And the material is softer and easier to deform than an insulating coating made of plastics or ceramics, and the outer peripheral surface 5g is uneven at the convex portion 7 and the contact area with the housing H is small. Therefore, the shape can be easily deformed, so that it can be easily inserted into the housing H. Moreover, the layer 5 of thermoplastic elastomer press-fitted into the housing H is now stretched to resist deformation. That is, according to this embodiment, there is an effect that creep can be prevented without impairing the insertability of the bearing.
[0075]
8 and 9 show a second embodiment of the rolling bearing of the present invention.
In this embodiment, the material of the film-like layer 5 of the thermoplastic elastomer covering the outer peripheral portion of the outer ring 2 of the bearing and the surface structure of the outer peripheral surface 5g are different from those of the first embodiment. That is, the material of the thermoplastic elastomer layer 5 in this embodiment is “Pebax, registered trademark, 2533SA **” (manufactured by Toray Industries, Inc.), which is a polyamide-based elastomer (specifically, a polyamide / polyether-based) hardness. 75 [HD_A]. Its properties are hardness: 75 [HD_A], Thermal conductivity: 0.26 w / m · k, specific resistance: 10¹⁴-10¹⁵Ω · cm. The molding method and the method of joining the outer ring 2 to the outer peripheral portion are the same as in the case of the first embodiment. Further, as shown in FIG. 9, the surface structure of the outer peripheral surface 5g of the thermoplastic elastomer layer 5 of the present embodiment example has a trapezoidal cross section and is deep in the circumferential direction instead of the semicircular cross section. H₁A plurality of recesses 11 each having a thickness of about 30 μm are continuously formed in a ring shape in the circumferential direction.
[0076]
Other configurations and operational effects are the same as those of the first embodiment.
10 and 11 show a third embodiment of the rolling bearing of the present invention.
In this embodiment, the material of the coating layer 5 of the thermoplastic elastomer covering the outer peripheral portion of the outer ring 2 of the bearing, the mounting structure to the outer peripheral portion of the outer ring, and the surface structure of the outer peripheral surface 5g of the layer are the first, This is different from each of the second embodiments. That is, the material of the thermoplastic elastomer layer 5 in this embodiment is made of the same polyester elastomer as in the first embodiment, “Perprene (registered trademark), P-30B”, and a reinforcing material (heat conduction). 40% by weight of SiC whisker. In addition, as shown in FIG. 10, the outer ring 2 is attached to the outer ring outer peripheral portion in advance by continuously forming a trapezoidal groove (ant groove) 12 in the circumferential direction on the outer peripheral surface 2g and both side surfaces 2s of the outer ring 2. Then, the outer ring 2 is attached to a mold as a core, and the thermoplastic elastomer layer 5 is insert-molded to correspond to the dovetail groove 12 between the inner peripheral surface 5n and the inner side surface 5s of the thermoplastic elastomer layer 5. This portion is inserted into the dovetail groove 12 as a protrusion 13 to prevent the thermoplastic elastomer layer 5 from falling off. The thickness t of the thermoplastic elastomer layer 5 excluding the protrusions 13 is 1.0 mm.
[0077]
On the surface of the outer peripheral surface 5 g of the thermoplastic elastomer layer 5, as shown in FIG. 11, a concave portion 14 having a depth of 50 μm and a herringbone pattern (herringbone shape) continuous in the width direction of the outer ring 2 is formed. The thermoplastic elastomer layer 5 has a hardness of 75 [HD_A], Thermal conductivity: 0.6 w / m · k, specific resistance: 1 × 10¹⁵Ω · cm.
[0078]
Other configurations and operational effects are the same as those of the first embodiment.
Subsequently, a fourth embodiment (FIG. 12) of the rolling bearing of the present invention will be described.
The material of the thermoplastic elastomer film-like layer 5 in this embodiment is “Perprene (registered trademark), P-30B” which is a polyester elastomer, 30% by weight of AlN powder as a heat conductive filler, and a reinforcing material. A glass fiber (treated with a silane coupling agent) containing 20% by weight is used.
[0079]
The structure for attaching the thermoplastic elastomer layer 5 of this embodiment to the outer ring outer peripheral portion is the same as that shown in FIG.
On the surface of the outer peripheral surface 5g of the thermoplastic elastomer layer 5, as shown in FIG. 12, there are dotted strip-shaped recesses 16 having a depth of 50 μm and having a rhombus pattern. The thermoplastic elastomer layer 5 has a hardness of 77 [HD_A], Thermal conductivity: 0.62 w / m · k, specific resistance: 9 × 10¹⁴Ω · cm.
[0080]
Other configurations and operational effects are the same as those of the first embodiment.
FIG. 13 shows a fifth embodiment of the rolling bearing of the present invention.
In this embodiment, the outer peripheral surface of the outer ring 2 as an outer peripheral portion and one end side are in an electrically conductive state with respect to the housing, for example, by preloading one side 2s of the outer ring 2 of the rolling bearing with a spring. It can utilize suitably in the case of such a use aspect. That is, the thermoplastic elastomer layer 5 has a substantially L-shaped cross section composed of a portion 5A that covers the outer peripheral surface 2g of the outer ring 2 and a portion 5B that covers the one side surface 2s of the outer ring 2 perpendicularly thereto. This thermoplastic elastomer layer 5 covers the outer peripheral surface 2g and one side surface 2s of the outer ring 2 of the rolling bearing (the illustrated one is a sealed bearing having a seal 17). The side surface 2s to be coated is a side that conducts with the housing when the thermoplastic elastomer layer 5 is not provided.
[0081]
In addition, on the outer peripheral surface of the thermoplastic elastomer layer 5 of this embodiment, a plurality of convex portions 7 having a semicircular cross section similar to those shown in FIGS. 5 and 6 are continuously formed in an annular shape in the circumferential direction. ing.
[0082]
The thermoplastic elastomer layer 5 which has been injection-molded into a L-shaped cross-section in advance using a predetermined mold has a quadrangular cross-section continuous in the circumferential direction at a location close to the side surface 2s of the inner peripheral surface 5n that is not covered. A protrusion 8 is provided. On the other hand, on the outer peripheral surface 2g of the outer ring 2, a concave groove 9 having a square cross section continuous in the circumferential direction is formed in advance at a position corresponding to the protrusion 8.
[0083]
As in the first embodiment, the thermoplastic elastomer layer 5 is attached in the same manner as in the first embodiment by applying an elastic adhesive to the coating surface of the outer ring 2 in advance, so that the protrusion 8 of the thermoplastic elastomer layer 5 is inserted into the concave groove of the outer ring. 9 is carried out by a method in which a layer 5 of thermoplastic elastomer is applied so as to be fitted to 9.
[0084]
The rolling bearing of this embodiment mounted on the fan motor is electrically insulated from the housing H by a portion 5A covering the outer peripheral surface 2g of the outer ring 2 of the layer 5 of the thermoplastic elastomer having an L-shaped cross section. The preload member is also electrically insulated by the portion 5B that covers one side surface 2s of the outer ring. Thus, even if an axial voltage is generated in the fan motor driven by the inverter, there is no potential difference between the inner and outer rings of the bearing, and therefore no axial current flows. Therefore, the electric corrosion of the raceway surface of the inner ring and outer ring and the rolling surface of the ball 3 is prevented. Is prevented.
[0085]
Other configurations and operational effects are substantially the same as those of the first embodiment.
FIG. 14 shows a sixth embodiment of the rolling bearing of the present invention.
This embodiment can be suitably used in the case of a usage mode in which both side surfaces 2s, 2s of the outer ring 2 of the rolling bearing do not contact the housing and are electrically non-conductive. That is, three rows of concave grooves 18, 18, 18 that are annularly continuous in the circumferential direction are formed in parallel on the outer peripheral surface 2 g of the outer ring 2 that is the outer peripheral portion of the rolling bearing. An annular thermoplastic elastomer layer (band) 5 is fitted into the lower half and bonded. On the outer peripheral surface of the thermoplastic elastomer layer 5, a plurality of convex portions 7 having a semicircular cross section similar to those shown in FIGS. 5 and 6 are continuously formed in an annular shape in the circumferential direction.
[0086]
When the rolling bearing of the present embodiment is mounted on a fan motor, it is electrically insulated from the housing by a belt-like thermoplastic elastomer layer 5 attached to the outer peripheral surface 2g of the outer ring 2, and on the other hand, both side surfaces 2s, Since 2s and the housing are originally non-contact and non-conductive, the electric corrosion of the raceway surface of the inner ring and the outer ring and the rolling surface of the ball 3 can be effectively prevented as in the above embodiments.
[0087]
In the present invention, the uneven pattern formed on the outer peripheral surface 5g of the thermoplastic elastomer layer 5 is not limited to those in the above embodiments, and various other patterns are possible. FIGS. 15 and 16 show other pattern examples. FIG. 15 shows a pattern in which a herringbone-shaped recess 20 is continuous in the circumferential direction of the outer ring, and FIG. 16 shows an irregular projection 21 in FIG. It is an irregularly scattered pattern.
[0088]
In each of the above embodiments, the case of a deep groove ball bearing has been described as an example. However, the present invention is not limited to this, and can be similarly applied to other rolling bearings such as an angular ball bearing and a roller bearing.
[0089]
Next, an embodiment (seventh embodiment) of the present invention that achieves the second object will be described.
A ring-shaped insulating member 30 is press-fitted into the rolling bearing A of FIG. 17 so as to cover the outer peripheral surface 2g of the outer ring 2 and the end surface 2s on one side. The inner ring 1 is left as it is. 3 is a ball and 4 is a cage. A chamfer 30a is provided at the corner of the ring-shaped insulating member 30 so that the rolling bearing A can be easily inserted into the housing. The ring-shaped insulating member 30 is made of, for example, 40% by weight of PPS resin (hereinafter also referred to as wt%), 35% by weight of glass fiber as a reinforcing fiber agent [A], and magnetic filler [B]. Manganese ferrite (MnFe₂0_Four) It was manufactured by injection molding using a resin composition consisting of 25% by weight.
[0090]
That is, first, each material composition was previously mixed by a blender, a Henschel mixer or the like, and supplied to an extruder such as a twin screw extruder, and material pellets were obtained from the extruder. Next, a ring-shaped insulating member 30 having a thickness of 1.0 mm was obtained by injecting a material obtained by melting the pellets into a mold and cooling the material for a predetermined time. Thereafter, the ring-shaped insulating member 30 was press-fitted into the outer ring 2. At that time, the ring-shaped insulating member 30 was heated and expanded as necessary, and then press-fitted.
[0091]
FIG. 18 is a cross-sectional view showing a state where two pairs of rolling bearings A according to the present invention that achieve the second object shown in FIG. 17 are mounted in the fan driving electric motor 40. The outer rings 2 of the both rolling bearings A are fitted into the holding step portions 42 or holding recess portions 43 formed at both ends of the motor housing 41 via ring-shaped insulating members 30. In addition, 41a is a housing main body, 41b is a housing front cover, 41c is a housing rear cover. Reference numeral 44 denotes a motor rotating shaft, 45 denotes a rotor, and 46 denotes a stator. And the large collar part 30b of the ring-shaped insulation member 30 is being fixed in the state facing the back | inner surface of the said holding | maintenance step part 42 or the holding | maintenance recessed part 43. FIG. The large collar portion 30b is sandwiched between the one end surface 2s of the bearing outer ring 2 and the inner surface of the holding step portion 42 or the holding concave portion 43, and prevents the both surfaces from coming into contact with each other. Further, the cylindrical portion 30c of each ring-shaped insulating member 30 is sandwiched between the outer peripheral surface 2g of the outer ring 2 and the inner peripheral surface of the holding step portion 42 or the holding concave portion 43, and both peripheral surfaces abut against each other. To prevent it. The other end face 2s of the outer ring 2 is exposed to the air and does not need to be covered with the ring-shaped insulating member 30 in particular.
[0092]
Thus, by incorporating the rolling bearing of the present invention that achieves the second object in the motor, even if an axial voltage is induced on the motor rotating shaft 44 based on the high-frequency current applied from the inverter to the stator 46, It is possible to suppress a current from flowing between the rotating shaft 44 and the motor housing 41. That is, since the mounting location of the outer ring 2 of the rolling bearing A that supports the rotating shaft 44 and the motor housing 41 that is a member holding these outer rings 2 is insulated, the potential of the rotating shaft 44 is reduced. Even if the electric potential of the motor housing 41 becomes higher, no current flows through each rolling bearing A incorporating the outer ring 2. Therefore, no electrolytic corrosion occurs in each of the rolling bearings A.
[0093]
(Example)
Hereinafter, a comparative test carried out for the examples of the present invention that achieve the second object and comparative examples will be described.
[0094]
In the rolling bearing having the ring-shaped insulating member 30 shown in FIG. 17, a material in which the material composition of the resin composition of the ring-shaped insulating member 30 was variously changed was used as a test object.
[0095]
Table 9 shows the component compositions of Examples 1-1 to 15-2 and Comparative Example 1 of the ring-shaped insulating member 30.
[0096]
[Table 9]

[0097]
In addition, specific trade names of resin, fiber material [A], magnetic filler [B], and nonmagnetic high thermal conductive filler [C] shown in Table 9^RThe manufacturer is described below.
[0098]
resin:
PPS (polyphenylene sulfide resin); Kureha Chemical Industry Co., Ltd. “Fortron KPS”.
[0099]
Aromatic PA (aromatic polyamide resin); Mitsui Petrochemical "Aalen^R"
[0100]
Reinforcing fiber material [A]:
Glass fiber; Nitto Boseki Co., Ltd. “CS3J-273” (silane coupling agent-treated glass chopped strand).
[0101]
6 Potassium titanate whisker; Otsuka Chemical Co., Ltd. “Tismo-D”.
[0102]
Aluminum borate whisker; Shikoku Kasei Kogyo Co., Ltd. “Arbolex YS3” (treated with silane coupling agent).
[0103]
Calcium carbonate whisker; Maruo Calcium Co., Ltd. “Wiscal A”.
[0104]
Magnetic filler [B]:
MnFe₂O_Four  ; High purity chemical research institute.
[0105]
CoFe₂O_Four  ; High purity chemical research institute.
NiFe₂O_Four  ; High purity chemical research institute.
[0106]
Non-magnetic high thermal conductive filler [C]:
SiC whisker; Idemitsu Material Co., Ltd., M grade.
[0107]
AlN: Idemitsu Material Co., AGSD-100.
[0108]
BN (h-BN); Idemitsu Material Co., Ltd., F grade.
[0109]
Al₂O_Three      Nippon Aerosil Co., Ltd., Aluminum Oxide C.
[0110]
Al₂O_ThreeFiber: NICHIAS, Ruby^RBulk fiber T / 5470-RS.
MgO: Kyowa Chemical Industry Co., Ltd., Pyroxma 5301K.
The following characteristics evaluation was implemented about those insulating films.
[0111]
(1) Measurement of thermal conductivity and specific resistance:
For the resin compositions shown in Examples 1-1 to 15-2 and Comparative Example 1 in Table 9, measurement of thermal conductivity (W / m · K) and specific resistance (Ω · cm) at 20 ° C. by laser flash method Went. The results are shown in Table 5.
[0112]
[Table 10]

[0113]
In Examples 1-1 to 15-2, the thermal conductivity is larger than that of Comparative Example 1, and each is 0.5 w / m · k or more, which is higher than that of a normal plastic material (0.2 to 0.4 w / m · k). It shows good heat conductivity. In particular, SiC whisker or Al without glass fiber₂O_ThreeIn Examples 11-1 to 12-2 using fibers, remarkable thermal conductivity is obtained.
[0114]
Moreover, although the specific resistance of each Example 1-1 to 15-2 is smaller than that of the comparative example 1, all of them are 1 × 10.¹³It can be seen that it has Ω · cm or more and has sufficient electrical insulation.
[0115]
(2) Measurement of weld strength and Izod impact strength:
Predetermined specimens were molded for the resin compositions having the compositions of Examples 1-1 to 15-2 and Comparative Example 1 in Table 9, and the weld strength and Izod impact strength were measured at 23 ° C. That is, the weld strength is obtained by injecting an insulating coating resin composition from both ends of the mold cavity to form a JIS No. 1 test piece (t = 3 mm) having an associated portion (weld portion) of the resin composition in the center. And measured at a pulling speed of 5 mm / min. The Izod impact strength was measured with a notched specimen.
[0116]
Table 6 shows the measurement results.
[0117]
[Table 11]

[0118]
In Examples 1-1 to 10-2, highly reinforcing glass fibers are used as the filler for the matrix resin. In Examples 13-1 to 15-2, whiskers belonging to the same reinforcing fiber material [A] are used. The weld strength was small and all were 70 MPa or more. In contrast, in Examples 11-1 and 11-2, SiC whisker which is not a reinforcing fiber material [A] but a nonmagnetic high thermal conductive filler [C] is used, and in Examples 12-1 and 12-2. Although alumina fibers are used, a weld strength of 70 MPa or more is also obtained.
[0119]
The Izod impact strength is slightly lower than that of Comparative Example 1 (40% by weight of glass fiber) by reducing the glass fiber [A] and adding powder-based fillers [B] and [C]. Both are 2.0KJ / m²It was found that there was no problem in use.
[0120]
(3) Understanding creep resistance:
Cylindrical test pieces were molded for the resin compositions having the compositions of Examples 1-1 to 15-2 and Comparative Example 1, and a compression creep test was performed using the test apparatus shown in FIG. For the measurement, the test piece is placed in a thermostatic chamber set at 120 ° C. for each test apparatus and left for 100 hours (surface pressure of 2.9 kg / mm²Then, after taking out and holding at room temperature for 1 hour, the height change rate of the test piece TP was measured. Table 12 shows the measurement results.
[0121]
[Table 12]

[0122]
In each example, the rate of change in height is smaller than in Comparative Example 1, and the creep resistance is good. In particular, Examples 1-1 to 4-2 in which the magnetic filler [B] is used in combination with the glass fiber, and Example 10-1 in which the alumina fiber of the nonmagnetic high thermal conductive filler [C] is used in combination with the glass fiber. , 10-2 and Examples 11-1 to 12-2 filled with SiC whiskers or alumina fibers alone without using glass fibers have a small rate of change in height and show remarkable creep resistance.
[0123]
Although not shown, the insulating film of the present invention applied to the outer peripheral surface or end surface 2s of the outer ring 2 as shown in FIGS. 5, 8, 10, 13, 14, and 17 is the inner peripheral surface of the inner ring 1. Alternatively, even if it is selectively applied to at least one of the end faces of the inner ring 1, the object of the present invention can be achieved.
[0124]
【The invention's effect】
As described above, according to the rolling bearing of the present invention that achieves the first object, the thermoplastic elastomer layer covering the outer peripheral portion of the outer ring prevents electrical conduction between the motor housing and the outer ring. When the bearing is used for a fan motor driven by an inverter, current is not generated between the inner and outer rings of the bearing without using special grease with electrical conductivity as in the past or installing an electric brush that is likely to generate dust. As a result, it is possible to prevent electrolytic corrosion of the inner and outer ring raceway surfaces or the rolling element rolling surfaces.
[0125]
In addition to the above-described effects, the thermoplastic elastomer layer having irregularities on the outer peripheral surface can be easily inserted into the housing of the bearing and can be stretched in the housing to exhibit a creep preventing function. Can also be obtained.
[0126]
Furthermore, when a thermoplastic elastomer is contained in the thermoplastic elastomer, the thermal conductivity of the thermoplastic elastomer layer itself is improved. As a result, sufficient heat dissipation can be maintained while maintaining good insulation, and the heat of the elastomer can be maintained. There is also an effect that deterioration can be suppressed.
[0127]
Also, according to the rolling bearing of the present invention that achieves the second object, the ring-shaped insulating member press-fitted into the outer peripheral portion of the outer ring prevents electrical conduction between the motor housing and the outer ring. When used in a fan motor, current flows between the inner and outer rings of the bearing without using special grease with electrical conductivity as in the past or installing an electric brush that easily generates dust. As a result, it is possible to prevent electric corrosion of the inner and outer ring raceway surfaces or rolling element rolling surfaces.
[0128]
The ring-shaped insulating member has a specific resistance of 1 × 10¹³Since it is made of a synthetic resin composition having a resistance of Ω · cm or more and a thermal conductivity of 0.5 W / m · K or more, it can provide a rolling bearing that is excellent not only in electrical insulation and creep resistance but also in heat dissipation. The effect is obtained.
[0129]
Further, as the synthetic resin composition of the ring-shaped insulating member, the matrix resin has a high creep resistance fiber material [A] and a saturation filler and a magnetic filler [B] having a specific resistance equal to or higher than a certain value. [A + B] When mixed in the range of 30 to 75% by weight, the creep resistance, heat transfer, moldability, and electrical insulation are improved by the electrical insulation and heat transfer improving actions of the magnetic filler [B]. An even better insulating coating is obtained, and there is an effect that it is possible to provide an electric corrosion-preventing rolling bearing capable of guaranteeing stable performance even under use conditions exposed to high temperature at high speed rotation.
[0130]
Further, even if at least a part of the magnetic filler [B] of the synthetic resin composition of the ring-shaped insulating member is replaced with a non-magnetic high thermal conductive filler [C], the same effect as described above can be obtained.
[0131]
Further, when the contents of the magnetic filler [B] and the nonmagnetic high thermal conductive filler [C] are arbitrarily adjusted within the range of 20 to 65% by weight depending on the type of the filler, The balance of creep resistance, heat transfer, formability, and electrical insulation characteristics of the insulating member can be adjusted, and the product can be varied depending on the use conditions of the bearing.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the composition of an insulating material of the present invention, thermal conductivity, and specific resistance.
FIG. 2 is a diagram showing the relationship between the composition of an insulating material of the present invention, thermal conductivity, and specific resistance.
FIG. 3 is a diagram showing the relationship between the composition of the insulating material of the present invention, thermal conductivity, and specific resistance.
FIG. 4 is a diagram showing the relationship between the composition of the insulating material of the present invention, thermal conductivity, and specific resistance.
FIG. 5 is a half sectional view of the first embodiment of the rolling bearing of the present invention.
6 is a partially enlarged cross-sectional view of the surface of the thermoplastic elastomer layer shown in FIG. 5. FIG.
FIG. 7 is a schematic diagram showing how the rolling bearing shown in FIG. 5 is attached to the motor.
FIG. 8 is a half sectional view of a second embodiment of the rolling bearing of the present invention.
9 is a partially enlarged cross-sectional view of the surface of the thermoplastic elastomer layer shown in FIG. 8. FIG.
FIG. 10 is a half sectional view of a third embodiment of the rolling bearing of the present invention.
FIG. 11 is a partially enlarged plan view of the surface of the thermoplastic elastomer layer shown in FIG. 10;
FIG. 12 is a partially enlarged plan view of a surface of a thermoplastic elastomer layer in a fourth embodiment of the rolling bearing of the present invention.
FIG. 13 is a half sectional view of a fifth embodiment of the rolling bearing of the present invention.
FIG. 14 is a half sectional view of a sixth embodiment of the rolling bearing of the present invention.
FIG. 15 is a plan view showing another example of the surface pattern of the thermoplastic elastomer layer in the rolling bearing of the present invention.
FIG. 16 is a plan view showing still another example of the surface pattern of the thermoplastic elastomer layer in the rolling bearing of the present invention.
FIG. 17 is a half sectional view of a seventh embodiment of the rolling bearing of the present invention.
18 is a cross-sectional view showing how the rolling bearing shown in FIG. 17 is attached to the motor.
FIG. 19 is a schematic side view of a creep resistance test apparatus.
[Explanation of symbols]
1 inner ring
2 Outer ring
2g Outer part (outer ring outer ring)
2s Outer periphery (side surface of outer ring)
3 Rolling elements (ball)
5 Thermoplastic elastomer layer
30 Ring-shaped insulating member
A Rolling bearing

Claims (2)

A rolling bearing having at least an outer ring and an inner ring, and a rolling element interposed between the outer ring and the inner ring , satisfying the following five conditions .
Condition A: A thermoplastic elastomer layer is formed on the entire outer periphery of the outer ring.
Condition B: The thermoplastic elastomer layer has a hardness of 60 to 90 [HD _A ] and a thickness of 0.5 to 5 mm.
Condition C: The thermoplastic elastomer layer contains a thermally conductive filler having a thermal conductivity of 10 W / m · k or more and a specific resistance of 1 × 10 ⁴ Ω · cm or more.
Condition D: Concavities and convexities are provided over the entire outer peripheral surface of the thermoplastic elastomer layer.
Condition E: The unevenness is formed by a herringbone-shaped concave portion that continues in the width direction of the outer ring, a strip-shaped concave portion that continues in a rhombus shape, or irregular projections that are irregularly scattered. The rolling bearing according to claim 1, wherein the thermoplastic elastomer layer has a height (depth) of unevenness of the outer peripheral surface of 5 to 100 μm.

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