JP2004245375A - Ball bearing for electric motor for automobile and electric motor for automobile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric motor for an automobile capable of improving acoustic characteristic while reducing rotation torque. <P>SOLUTION: A rotary shaft 2 is rotatably supported by a pair of ball bearings 8, 8 on an inner side of a casing 1a. A holder made of synthetic resin is provided in each ball bearing 8, 8. Grease for ensuring excellent acoustic characteristic is sealed into the inside of each ball bearing 8, 8. Heat treatment for suppressing deterioration with age of surface shape is applied to an inner ring raceway track 13 provided on an outer peripheral face of an inner ring 14, an outer ring raceway track 11 provided on an inner peripheral face of an outer ring 12, and rolling faces of each ball 15, 15. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２５】
この式中のＲ_２ は炭素数６〜１５の芳香族系炭化水素基を、Ｒ_１ 及びＲ_３ は炭素数６〜１２の芳香族系炭化水素基又は炭素数６〜２０の脂肪族炭化水素基を、それぞれ表している。又、Ｒ_１ 及びＲ_３ の全量中に占める芳香族系炭化水素基の割合は、５０〜１００モル％であり、Ｒ_１ 及びＲ_３ は、互いに同一でも異なっても良い。
【００２６】
この様な、芳香族系ジウレア化合物を増ちょう剤に使用し、しかも、この増ちょう剤をグリース中に１５〜３５質量％（好ましくは１５〜３０質量％）配合した場合には、耐剥離性を確保できると共に、グリース漏れの防止を図り易くなる。又、高温で高速回転する状態で使用する玉軸受８、８の耐久寿命を確保できると共に、低温時の異音の発生を防止できる。又、エステル系油を含む基油の油性効果を得られる為、潤滑性の向上を図れて、玉軸受８、８の早期焼き付きの発生を防止できる。
【００２７】
又、上記グリースの混和ちょう度を、好ましくはＮＬＧＩ Ｎｏ．１〜３とする。この為に、例えば、このグリース中に上記増ちょう剤を５〜３５質量％配合する。
【００２８】
又、このグリースに、更に優れた性能を持たせる為、従来から知られている各種の添加剤を必要に応じて含有させる事もできる。この添加剤としては例えば、金属石けん、ベントン、シリカゲル等のゲル化剤、アミン系、フェノール系、イオウ系、ジチオリン酸亜鉛等の酸化防止剤、塩素系、イオウ系、リン系、ジチオリン酸亜鉛、有機モリブテン等の極圧剤、脂肪酸、動植物油等の油性剤、石油スルフォネート、ジノニルナフタレンスルフォネート、ソルビタンエステル等の錆び止め剤、ベンゾトリアゾール、亜硝酸ソーダ等の金属不活性剤、ポリメタクリレート、ポリイソブチレン、ポリスチレン等の粘度指数向上剤等が挙げられ、これらの添加剤を、単独で又は２種以上組み合わせて添加できる。この際、この添加剤の添加量は、本発明の目的を達成できれば特に限定するものではないが、通常は、上記グリース中に添加剤を２０質量％以下含有させる。
【００２９】
又、本発明の自動車用の電動モータ用玉軸受に使用するグリースを調整する方法も、特に限定するものではない。但し、一般的には、このグリースを、基油中で増ちょう剤を反応させる事により得る。又、加熱温度、攪拌、混合時間等の製造条件は、使用する基油や増ちょう剤、添加剤等により適宜設定する。
【００３０】
又、本発明の場合には、前記内輪１４と外輪１２と各玉１５、１５との表面に、当該表面形状の経時劣化を抑える為の熱処理を施している。例えば、上記内、外両輪１４、１２の表面に施す熱処理として、これら内、外両輪１４、１２をＳＵＪ２により造り、従来から行なわれている標準熱処理に加えて、−２０℃での深冷処理を施す。この標準熱処理は、８２０〜８６０℃で焼き入れした後、１６０〜２００℃で焼き戻しするものである。そして、この様に標準熱処理に加えて深冷処理を施す熱処理により、上記内、外両輪１４、１２の残留オーステナイト量を６質量％以下とする。
【００３１】
又、上記内、外両輪１４、１２をＳＵＪ２により造り、焼き入れ後に、２２０℃で焼き戻しを行なう熱処理を施す事により、これら内、外両輪１４、１２の残留オーステナイト量を、４質量％以下とする事もできる。又、これら内、外両輪１４、１２をＳＵＪ２により造り、上記標準熱処理に加えて、−１９６℃での深冷処理を施す事により、これら内、外両輪１４、１２の残留オーステナイト量を４質量％以下とする事もできる。
【００３２】
更に、これら内、外両輪１４、１２をＳＵＪ２により造り、焼き入れ後に、２４０℃で焼き戻しを行なう熱処理を施すか、焼き入れ後に、−８０℃での深冷処理を施してから、２４０℃で焼き戻しを行なう熱処理を施す事により、これら内、外両輪１４、１２の残留オーステナイト量を０％とする事もできる。
【００３３】
更に、これら内、外両輪１４、１２をＳＵＳ４４０Ｃにより造り、１０５０℃での焼き入れ後に、−８０℃での深冷処理を施した後、５２０℃で焼き戻しを行なう熱処理を施す事により、これら内、外両輪１４、１２の残留オーステナイト量を０％とする事もできる。又、これら内、外両輪１４、１２をＳＵＪ２により造り、焼き入れ後に、２２０℃で２回焼き戻しを行なう熱処理を施す事により、これら内、外両輪１４、１２の残留オーステナイト量を２質量％以下とする事もできる。
【００３４】
この様な熱処理を行なう事により、上記内、外両輪１４、１２の残留オーステナイト量を、従来から使用しているものの残留オーステナイト量である、８〜１４質量％よりも小さくした場合には、これら内、外両輪１４、１２の耐荷重性及び耐衝撃性を向上させる事ができ、前記内輪、外輪各軌道１３、１１に有害な永久変形を生じにくくできる。即ち、オーステナイトはマルテンサイトに比べて降伏応力が低い為、残留オーステナイト量が多い場合には、小さな荷重等でも有害な永久変形を生じ易い。これに対して、上述の様な熱処理により残留オーステナイト量を６質量％以下に小さくする場合には、上記内輪、外輪各軌道１３、１１の耐圧痕性が向上し（降伏応力が高くなり）、上記小さな荷重等による、有害な永久変形を生じにくくできる。又、これら各軌道１３、１１の耐圧痕性を向上させる事ができる為、電動モータの製造時に玉軸受８を組み込んだり、この玉軸受８を運搬する（取り扱う）場合等に、この玉軸受８に大きな外力が加わった場合でも、上記内輪、外輪各軌道１３、１１に有害な永久変形（圧痕）を生じにくくできる。次に、上述の様な熱処理により、内、外両輪１４、１２の残留オーステナイト量を小さくした場合に、耐圧痕性を向上できると言った効果を得られる事を確認すべく行なった第一の実験に就いて説明する。実験は、次の表１にその熱処理方法を示す、従来品と本発明品とを用いて行なった。
【００３５】
【表１】

【００３６】
具体的には、従来品として、内輪及び外輪に従来から行なわれている標準焼き入れと標準焼き戻しを施したものを使用し、本発明品として、内輪及び外輪に焼き入れ後に深冷処理を施してから、高温焼き戻ししたものを使用した。そして、本発明品では、この様な熱処理を施す事により、内輪及び外輪の硬さを５９〜６３ＨＲｃとし、残留オーステナイト量を４質量％以下とし、弾性限度を１１００Ｎ／ｍｍ^２ とした。又、従来品及び本発明品の玉軸受は、内径が８ｍｍであり、外径が２２ｍｍであり、幅が７ｍｍである、シールリングを装着したものとした。そして、第一の実験では、この様な従来品と本発明品とを用いて、外輪を固定の部分に内嵌固定し、内輪に所定の軸方向荷重（アキシアル荷重）を付与した後、１８００ｍｉｎ^−１ で回転させた状態での玉軸受の軸方向振動加速度の上昇値を測定した。
【００３７】
この様にして行なった実験結果を、図４に示している。この図４中、実線は本発明品を、破線は従来品を、それぞれ表している。この図４に示した実験結果から明らかな様に、従来品は、アキシアル荷重が１９６Ｎを越えた場合に、軸方向振動加速度が大きく上昇したのに対し、本発明品の場合には、アキシアル荷重が７８４Ｎでも軸方向振動加速度の上昇量は僅かであった。この事から、上述の様な熱処理を施し、硬さと、残留オーステナイト量と、弾性限度とを所定の範囲とした本発明品は、大きな荷重が加わる場合でも耐圧痕性を向上できる事が分かった。特に、本実験で使用した本発明品は、弾性限度を従来品よりも大きくしている為、軌道面に発生する応力を弾性限度以下に抑え易くなり、圧痕の原因となる塑性変形をより生じにくくできる。
【００３８】
又、上記残留オーステナイト量を６質量％以下と小さくする場合には、上記内輪、外輪各軌道１３、１１の表面形状が経時的に劣化する事を抑える事もできる。即ち、これら各軌道１３、１１に存在する残留オーステナイトの量が多いと、各玉軸受８、８の使用に伴ってこれら各軌道１３、１１に繰り返し加わる転がり応力により、この残留オーステナイトが分解する。そして、分解に伴ってこれら各軌道１３、１１の表面形状が劣化する。これに対して、上述の様な熱処理により残留オーステナイト量を６質量％以下に小さくする場合には、残留オーステナイトの分解に伴う表面形状の経時劣化を抑える事ができる。特に、この残留オーステナイト量を４質量％以下に抑える場合には、上記経時劣化をより抑える事ができ、２質量％以下に抑える場合には、この経時劣化を殆どなくす事ができる。
【００３９】
又、上記残留オーステナイト量を６質量％以下と小さくする場合には、周囲が高温になった場合でも、内輪１４及び外輪１２の経時的変形を抑える事ができ、玉軸受８の位置ずれや、回転軸２と内輪１４との間での摩耗や振動を抑える事もできる。即ち、自動車用電動モータでは、組み込んだ玉軸受８が周囲が高温になる状態で使用される事がある。この場合、従来から行なわれている標準熱処理を施したものでは、内輪中の残留オーステナイト量が多い為、この残留オーステナイトが分解しマルテンサイトに変化する事により、この内輪の内径が大きくなる（膨張する）。この為、この内輪を回転軸２に対し、締り嵌めにより固定する事により玉軸受８の位置決めを行なっている場合に、この回転軸２に対するこの内輪の位置がずれたり、この内輪の内周面とこの回転軸２の外周面との間で滑りが生じて、摩耗や振動が生じる原因となる。これに対して、上述の様に残留オーステナイト量を小さくした場合には、高温による内輪１４の経時的変形を抑える事ができ、回転軸２に対する内輪１４の位置ずれや、この回転軸２とこの内輪１４との間での摩耗や振動を抑える事ができる。
【００４０】
次に、上述の様に内輪１４中の残留オーステナイト量を小さくする事により、周囲が高温になった場合でも、この内輪１４の経時的変形を抑える事ができると言った効果を得られる事を確認すべく行なった第二の実験に就いて説明する。この第二の実験は、前述の第一の実験で使用した従来品と本発明品とをそれぞれ構成する内輪を用いた。そして、これら各内輪を、雰囲気温度が１８０℃である恒温槽中に放置した後、所定時間経過毎に取り出して、常温で内径を測定し、初期寸法に対する寸法変化率を求めた。この様にして行なった第二の実験結果を、図５に示している。この図５中、実線は本発明品を、破線は従来品を、それぞれ表している。この図５に示した実験結果から明らかな様に、従来品の場合には、時間の経過に従って、内輪の内径が変化して、１０００時間経過後には寸法変化率が０．０８％以上になった。これに対して本発明品の場合には、１０００時間経過後でも、内輪１４の内径の寸法変化は全く認められなかった。この様な実験結果から、前述の様な所定の熱処理を施し、硬さと、残留オーステナイト量と、弾性限度とを所定の範囲とした本発明品は、高温環境下での内輪１４の経時的変形（膨張）を抑える事ができる事が分かった。尚、前述の表１には、本発明品の耐圧痕性及び高温寸法安定性の欄中に○印を付しているが、これは、本発明品が、従来品よりもこれらの性能で優れた結果を得られた事を表すものである。
【００４１】
又、前記各玉１５、１５の表面に当該表面形状の経時劣化を抑える為に施す熱処理としては、例えば、所定の形状に加工した各玉１５、１５の表面に通常の焼き入れ処理を施し、次いで、表面硬化処理を施してから、焼き戻し処理を施す熱処理がある。この焼き戻し処理は、例えば、１６０℃で１２０分とする。又、この様な熱処理に於いて、焼き入れ処理後、表面硬化処理前に、予備の焼き戻し処理を施す事もできる。この予備の焼き戻し処理は、例えば、１２５℃で１２０分とする。又、上記各玉１５、１５に施す表面硬化処理は、特許文献４に記載されている方法等、従来から知られている各種の方法を使用できる。
【００４２】
又、上記焼き戻し処理の焼き戻し温度の上限並びに下限は、下記の（ａ）〜（ｆ）で規制する事が好ましい。
（ａ） 焼き戻し時間が１０〜１２０分の場合、焼き戻し温度の上限を２００℃とする。
（ｂ） 焼き戻し時間が１２０分を越える場合には焼き戻し温度の上限を、直交座標の一方の軸に焼き戻し温度を表わし、他方の軸に焼き戻し時間を対数目盛で表わした片対数座標に描かれる線により、当該焼き戻し時間に対応して求める。
（ｃ） 上記（ｂ）の線は、２００℃で１２０分の点から始まり、１７５℃で１０００分の点、１６０℃で４０００分の点を通過する。
（ｄ） 焼き戻し時間が１０〜１２０分の場合、焼き戻し温度の下限を１５０℃とする。
（ｅ） 焼き戻し時間が１２０分を越える場合には焼き戻し温度の下限を、直交座標の一方の軸に焼き戻し温度を表わし、他方の軸に焼き戻し時間を対数目盛で表わした片対数座標に描かれる線により、当該焼き戻し時間に対応して求める。
（ｆ） 上記（ｅ）の線は、１５０℃で１２０分の点から始まり、１４０℃で３００分の点、１３０℃で１０００分の点、１２０℃で６０００分の点を通過する。
【００４３】
この様な、前記各玉１５、１５の表面硬化処理後に行なう焼き戻し処理の好ましい温度条件を、図６を用いて、更に詳しく説明する。この図６は、この焼き戻し処理を行なう場合に於ける、焼き戻し条件のうち、焼き戻し時間ｔと、焼き戻し温度Ｔの上限値並びに下限値との関係を表わしている。又、この図６は、縦軸に焼き戻し温度Ｔを表し、横軸に焼き戻し時間ｔを、対数目盛により表わしている。
【００４４】
上記図６の実線ａは、焼き戻し温度Ｔの上限値と焼き戻し時間ｔとの関係を表わしている。この実線ａは、焼き戻し時間ｔが１０〜１２０分の間では、２００℃の一定値を表わす直線部ａ_１ となり、焼き戻し時間ｔが１２０分を越える部分に於いては、焼き戻し時間ｔが増大するに伴って焼き戻し温度Ｔの上限値が次第に低下する事を表わす、曲線部ａ_２ となっている。そしてこの曲線部ａ_２ は、２００℃で１２０分の点から始まり、１７５℃で１０００分の点、１６０℃で４０００分の点を通過する。
【００４５】
又、図６の実線ｂは、焼き戻し温度Ｔの下限値と焼き戻し時間ｔとの関係を表わしている。この実線ｂは、焼き戻し時間ｔが１０〜１２０分の間では、１５０℃の一定値を表わす直線部ｂ_１ となり、焼き戻し時間ｔが１２０分を越える部分に於いては、焼き戻し時間ｔが増大するに伴って焼き戻し温度Ｔの下限値が次第に低下する事を表わす、曲線部ｂ_２ となっている。そしてこの曲線部ｂ_２ は、１５０℃で１２０分の点から始まり、１４０℃で３００分の点、１３０℃で１０００分の点、１２０℃で６０００分の点を通過する。
従って、上記表面硬化処理後の焼き戻し処理は、図６の斜線範囲で行なう事が好ましい。
【００４６】
又、前記予備の焼き戻し処理は、下記の（ｇ）〜（ｉ）を満たす条件で行なう事が好ましい。
（ｇ） 焼き戻し時間が１０〜１２０分の場合、焼き戻し温度の上限を１４０℃とする。
（ｈ） 焼き戻し時間が１２０分を越える場合には焼き戻し温度の上限を、直交座標の一方の軸に焼き戻し温度を表わし、他方の軸に焼き戻し時間を対数目盛で表わした片対数座標に描かれる線により、当該焼き戻し時間に対応して求める。
（ｉ） 上記（ｈ）の線は、１４０℃で１２０分の点から始まり、１３０℃で３００分の点、１２０℃で１０００分の点、１１０℃で６０００分の点を通過する。
【００４７】
この様な予備の焼き戻し処理の好ましい温度条件を、図７を用いて、更に詳しく説明する。この図７は、焼き入れ後、表面硬化処理を行なう前に予備の焼き戻し処理を行なう場合に於ける、焼き戻し条件のうち、焼き戻し時間ｔと、焼き戻し温度Ｔの上限値との関係を表わしている。この図７は、縦軸に焼き戻し温度Ｔを表わし、横軸に焼き戻し時間ｔを、対数目盛により表わしている。
【００４８】
この図７に記載した、焼き戻し温度の上限値を表わす実線ｃは、焼き戻し時間が１０〜１２０分の場合、１４０℃の一定値を表わす直線部ｃ_１ となり、焼き戻し時間が１２０分を越える部分に於いては、焼き戻し時間ｔが増大するに伴って焼き戻し温度Ｔの上限値が次第に低下する事を表わす、曲線部ｃ_２ となっている。そしてこの曲線部ｃ_２ は、１４０℃で１２０分の点から始まり、１３０℃で３００分の点、１２０℃で１０００分の点、１１０℃で６０００分の点を通過する。
従って、上記予備の焼き戻し処理は、図７の斜線範囲で行なう事が好ましい。
【００４９】
上述の様に、各玉１５、１５の表面硬化処理後に焼き戻し処理を行なう場合には、これら各玉１５、１５の表面形状が経時的に劣化する事がなくなる。即ち、表面硬化処理後に焼き戻し処理を行なう事で、表面硬化処理に伴って各玉１５、１５の内部に生じた残留応力を解消でき、上記表面形状が経時的に劣化する事がなくなる。
【００５０】
又、表面硬化処理後に焼き戻し処理を行なう場合に於ける、焼き戻し温度の上限と下限とを前述の様に規制した場合には、各玉１５、１５の表面硬さを高くでき、これら各玉１５、１５の表面に傷を付きにくくできる。又、これら各玉１５、１５の表面硬化処理に伴ってこれら各玉１５、１５の内部に生じた残留応力を解消し易くできる。
【００５１】
又、前記予備の焼き戻し処理を行なう場合の焼き戻し温度の上限を、前述の様に規制した場合には、各玉１５、１５の表面硬さを高くでき、これら各玉１５、１５の表面に傷を付きにくくできる。尚、上記予備の焼き戻し処理は、続いて行なう表面硬化処理の際に、各玉１５、１５の表面に亀裂等の欠損が発生するのを防止する為に行なう。従って、別途この欠損の発生防止を図れれば、上記予備の焼き戻し処理を省略できる。
【００５２】
更に、本例の場合には、前記内輪軌道１３の中心軸を含む仮想平面に関するこの内輪軌道１３の断面形状の曲率半径を、上記各玉１５、１５の直径の５１〜５４％（より好ましくは５１〜５２．５％）とすると共に、前記外輪軌道１１の中心軸を含む仮想平面に関するこの外輪軌道１１の断面形状の曲率半径を、これら各玉１５、１５の直径の５２〜５７％（より好ましくは５２．５〜５７％）としている。又、前記各玉軸受８、８に動定格荷重の０．０２倍のラジアル荷重が加わった場合に於ける、上記各玉１５、１５の転動面と上記内輪軌道１３との接触部の面積の合計をＳ_１ とし、これら各玉１５、１５の転動面と上記外輪軌道１１との接触部の面積の合計をＳ_２ とした場合に、Ｓ_１ ＞Ｓ_２ としている。更に、（Ｓ_１ ＋Ｓ_２ ）を、上記内輪軌道１３及び外輪軌道１１の断面形状の曲率半径がそれぞれ上記各玉１５、１５の直径の５２％である場合よりも小さくしている。
【００５３】
上述の様に構成する本発明の自動車用の電動モータ用玉軸受とこれを組み込んだ自動車用電動モータによれば、自動車用電動モータの回転トルクを小さくしつつ、音響特性を良好にする事ができる。即ち、本発明の自動車用電動モータの場合には、回転軸２の回転支持部に、各構成部材の接触部が転がり接触状態となる玉軸受８、８を使用している。この為、各構成部材の接触部が滑り接触状態となる滑り軸受を使用した、従来構造の場合よりも回転トルクを１／２程度に小さくできる。しかも、玉軸受８、８を使用した本発明の場合には、低温での起動時の異音の発生を、無視できる程度に小さくできる。
【００５４】
又、本例の場合には、上記各玉１５、１５の転動面と内輪、外輪各軌道１３、１１とに当該表面形状の経時劣化を抑える為の熱処理を施している為、当該表面形状の経時劣化による音響特性の劣化を抑える事ができる。又、上記各玉軸受８の内部に、優れた音響特性を確保する為のグリースを封入している為、グリースを使用する事による音響特性の劣化も抑える事ができる。又、上記各玉軸受８、８に組み込んだ保持器１６を合成樹脂製としている為、この保持器１６と各玉１５、１５とが衝突した場合でも、この衝突に基づく異音の発生を抑える事ができる。これらの結果、本発明によれば、自動車用電動モータの回転トルクを小さくする事により、消費電力を抑えつつ、音響特性を良好にする事ができる。
【００５５】
又、本発明の自動車用電動モータの場合には、回転軸２の回転支持部に玉軸受８、８を使用している為、この回転支持部に滑り軸受を使用した従来構造の場合と異なり、スラスト荷重を受ける為の構造を別に設ける必要がなくなる。又、本例の様に、各玉軸受８、８にシールリング１７、１７を設けた場合には、自動車用電動モータの内部に異物が侵入するのを防止する為の構造を、これら各玉軸受８、８と別に設ける必要がなくなる。これらにより、本発明の場合には、組立作業の容易化によるコスト低減を図り易くなる。
【００５６】
又、本例の場合には、上記内輪、外輪各軌道１３、１１と上記各玉１５、１５の転動面との接触面積の合計である、（Ｓ_１ ＋Ｓ_２ ）を、内輪軌道１３及び外輪軌道１１の断面形状の曲率半径が上記各玉１５、１５の直径の５２％である、従来構造の場合よりも小さくしている。この為、自動車用電動モータの回転トルクを、より小さくできる。即ち、上記各玉軸受８、８の回転トルクは、（Ｓ_１ ＋Ｓ_２ ）にほぼ比例する為、この（Ｓ_１ ＋Ｓ_２ ）が小さくなる程、この回転トルクを小さくできる。この為、（Ｓ_１ ＋Ｓ_２ ）を従来構造の場合よりも小さくした本発明の場合には、上記各玉軸受８、８の回転トルクをより小さくでき、上記電動モータの回転トルクをより小さくできる。
【００５７】
又、一般的に、玉軸受では、内輪と外輪とのうちの一方の軌道輪が主体となり、各玉を自転運動及び公転運動させるが、この場合に、主体となる軌道輪は、各玉の転動面と内輪軌道又は外輪軌道との接触面積が大きくなる側の軌道輪となる。そして、この主体となる軌道輪を、使用時に回転する回転輪とした場合には、各玉をより安定して自転運動及び公転運動させる事ができる。本例の場合には、前記内輪１４を回転輪とすると共に、この内輪１４に設けた内輪軌道１３と各玉１５、１５の転動面との接触部の面積Ｓ_１ を、静止輪である外輪１２に設けた外輪軌道１１と各玉１５、１５の転動面との接触部の面積Ｓ_２ よりも大きくしている（Ｓ_１ ＞Ｓ_２ ）。この為、これら各玉１５、１５を、より安定して自転運動及び公転運動させる事ができ、自動車用電動モータの回転の円滑化を図れる。
【００５８】
尚、本発明の対象となる自動車用の電動モータ用玉軸受は、動定格荷重の０．００５〜０．３倍の広い範囲の大きさのラジアル荷重が加わる状態で使用され、通常は、動定格荷重の０．００８〜０．０５倍程度のラジアル荷重が加わる状態で使用される。又、本発明者が、内輪、外輪各軌道１３、１１の断面形状の曲率半径が種々に異なる多くの種類の組み合わせの玉軸受で、加わるラジアル荷重の大きさを異ならせた条件下での玉軸受８の玉１５と、内輪、外輪各軌道１３、１１との接触状態を調べたところ、動定格荷重の０．００５〜０．３倍のラジアル荷重が加わった場合でのＳ_１ 、Ｓ_２ 、Ｓ_１ ＋Ｓ_２ の関係が、動定格荷重の０．０２倍のラジアル荷重が加わった場合でのＳ_１ 、Ｓ_２ 、Ｓ_１ ＋Ｓ_２ の前述した関係と同じになる事が分かった。この為、上記範囲の代表値である、動定格荷重の０．０２倍のラジアル荷重が加わった場合でのＳ_１ 、Ｓ_２ 、Ｓ_１ ＋Ｓ_２ の関係を前述の様に規制する事により、自動車用の電動モータ用玉軸受に加わるラジアル荷重が動定格荷重の０．０２倍以外となる場合でも、自動車用電動モータの回転トルクをより小さくできると共に、回転の円滑化を図れる。
【００５９】
又、本発明の自動車用の電動モータ用玉軸受は、自動車の走行時に回転しない事がある自動車用電動モータに組み込まれるが、回転しない状態で自動車の走行に伴って振動が加わる。本発明によれば、この場合でも、フレッチングの発生を抑えて、内輪、外輪各軌道１３、１１の面荒れに基づく異音の発生を抑える事ができる。この理由は、▲１▼これら各軌道１３、１１に表面形状の経時劣化を抑える為の熱処理を施した事と、▲２▼優れた音響特性を確保する為のグリースを封入した事と、▲３▼内輪軌道１３及び外輪軌道１１と各玉１５の転動面との接触部の面積Ｓ_１ 、Ｓ_２ 、Ｓ_１ ＋Ｓ_２ を適切に規制した事とが、フレッチングを抑える為の効果として、しかも、これらの相乗効果として有効に働いた為である。
【００６０】
又、本例の場合には、上記各玉軸受８、８の両端部に設けた各シールリング１７、１７の内周縁部を、内輪１４の外周面の両端部に摺接させて、これら各シールリング１７、１７を接触シールとしている。この為、内輪、外輪各軌道１３、１１上を各玉１５、１５が転動する事により生じる異音が、上記各玉軸受８、８の外部に漏れにくくなる。従って、本例の場合には、前記音響特性をより良好にする事ができる。
【００６１】
又、上記各シールリング１７、１７を接触シールとしている為、上記各玉軸受８、８内に封入したグリースが、電動モータの内部でロータ４とステータ５、５とが存在する空間内に侵入する事を、より効果的に防止できる。特に、電動モータがブラシ６、６を有する構造の場合、これら各ブラシ６、６と整流子７との間部分にグリース等の異物が入り込むと、これらブラシ６、６と整流子７との導通が妨げられ、電動モータの正常な機能を発揮させる事ができなくなる可能性がある。これに対して、本例の場合には、グリース等の異物が上記間部分に入り込む事をより効果的に防止できる為、電動モータの正常な機能を長期間に亙り発揮できる。又、上記ブラシ６、６を設けた構造の場合には、これら各ブラシ６、６と整流子７とが接触する事により生じた摩耗粉が上記各玉軸受８、８の内部に入り込む可能性がある。そして、この様に摩耗粉が玉軸受８、８内に入り込んだ場合には、これら各玉軸受８、８の内部に存在するグリースが早期に劣化し易くなる。これに対して、本例の場合には、これら各玉軸受８、８に設けたシールリング１７、１７を接触シールとしている為、電動モータが上記ブラシ６、６を有する場合でも、上記グリースを劣化しにくくして耐久性の向上を図れる。
【００６２】
尚、本例の場合と異なり、図８に示す様に、外輪１２の両端部内周面に係止した１対のシールリング１７ａ、１７ａの内周縁部を、内輪１４の外周面に設けた凹部２５、２５の側面及び底面に摺接させず、この側面及び底面と全周に亙り微小隙間を介して対向させた、所謂非接触シールを設けた構造で本発明を実施する事もできる。この様に非接触シールを設けた場合には、上記各玉軸受８で、内輪、外輪各軌道１３、１１上を各玉１５、１５が転動する事により生じる異音が、本例の場合よりも外部に漏れ出し易くはなる。又、この場合には、自動車用電動モータの内部で、ロータ４とステータ５（図１参照）とが存在する空間内に上記グリースが侵入し易くもなる。但し、上述の様に、１対のシールリング１７ａ、１７ａを非接触シールとした場合には、上記自動車用電動モータの回転トルクの更なる低減を図れて、この自動車用電動モータの消費電力をより抑える事ができる。
【００６３】
又、上述の図８に示した構造では、金属板製の断面Ｌ字形の芯金２６に、ゴム、エラストマー等から成る弾性材２７を結合する事により、シールリング１７ａ、１７ａを構成している。但し、図９に示す様に、シールリング１７ｂ、１７ｂを、金属板に塑性加工を施す事のみにより造った構造で、本発明を実施する事もできる。図８に示すシールリング１７ａ、１７ａの場合、弾性材２７を結合している為、成形上の自由度を、図９に示したシールリング１７ｂ、１７ｂよりも大きくできると共に、内輪１４の両端部外周面に設けた凹部２５、２５とシールリング１７ａ、１７ａの内周縁との間の隙間の経路長さを大きくできる。この為、より高い防塵性と耐グリース漏れ性とを確保できる。但し、シールリング１７ａ、１７ａを、使用温度が比較的制限される弾性材２７により構成している為、一般的には、使用温度に応じた適切な材料を選択する必要がある。これに対して、図９に示したシールリング１７ｂ、１７ｂの場合には、安価に造れると共に、適切な材料を選択すると言った面倒を生じる事なく、低温から高温迄の広い温度範囲で使用できる。
【００６４】
尚、図２、８、９に示した構造の場合と異なり、玉軸受の両端部に設けた１対のシールリングのうち、一方のシールリングの内周縁部を内輪の外周面に摺接させると共に、他方のシールリングの内周縁部をこの内輪の外周面から離隔させた構造とする事もできる。
【００６５】
又、本発明の自動車用電動モータは、前述の図１に示した構造の場合と異なり、回転軸の外周面に設けたロータの位相を検出する為のセンサと、このセンサから発する信号に基づいて、ケーシングの内面に固定したステータに設けたコイルに流す電流の向きを切り換える為の制御部とを備えた、所謂ブラシレス構造とする事もできる。そして、この様にブラシレス構造とした自動車用電動モータで本発明を実施した場合には、ブラシの摩耗粉が各玉軸受８の内部に侵入する事を防止する為の考慮を行なう必要がなくなる。この為、例えば、各玉軸受８の両端部に、上述の図８、９に示した様な非接触型のシールリング１７ａ、１７ｂを設けた場合でも、上記摩耗粉が玉軸受８内のグリース中に混入される事がなくなり、回転トルクの低減と、耐久性の向上とを、高度に両立できる。
【００６６】
【発明の効果】
本発明は、以上に述べた通り構成され作用するので、自動車用電動モータの回転トルクを小さくする事により消費電力を抑えつつ、音響特性を良好にする事ができる。
【図面の簡単な説明】
【図１】本発明の自動車用電動モータの１例を示す断面図。
【図２】図１から玉軸受のみを取り出して示す半部断面図。
【図３】玉軸受に組み込んだ保持器を示す斜視図。
【図４】所定の熱処理を施して残留オーステナイト量を小さくした、内輪及び外輪を使用した玉軸受の耐圧痕性を確認すべく行なった、第一の実験結果を示す線図。
【図５】所定の熱処理を施して残留オーステナイト量を小さくした、内輪の高温での寸法安定性を確認すべく行なった、第二の実験結果を示す線図。
【図６】表面硬化処理後に行なう焼き戻し処理の温度と時間との関係を示す線図。
【図７】予備の焼き戻し処理の温度と時間との関係を示す線図。
【図８】玉軸受の別構造の第１例を示す、図２と同様の図。
【図９】同じく第２例を示す、図２と同様の図。
【図１０】従来構造の第１例の自動車用電動モータを示す断面図。
【図１１】同第２例の自動車用電動モータを示す断面図。
【符号の説明】
１、１ａ ケーシング
２ 回転軸
３ 滑り軸受
４ ロータ
５ ステータ
６ ブラシ
７ 整流子
８ 玉軸受
９ ケーシング本体
１０ 端部部材
１１ 外輪軌道
１２ 外輪
１３ 内輪軌道
１４ 内輪
１５ 玉
１６ 保持器
１７、１７ａ、１７ｂ シールリング
１８ シール溝
１９ 側壁面
２０ 主部
２１ ポケット
２２ 弾性片
２３ 凹面部
２４ 空間
２５ 凹部
２６ 芯金
２７ 弾性材[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to, for example, a cooling fan for ventilating a radiator of a vehicle, or a blowing fan incorporated in a vehicle air conditioner, a power window device, a wiper device, a door mirror angle adjusting device, a power seat device, an electric tilt mechanism, or an electric motor. An electric motor for a vehicle for driving a steering device with a telescopic mechanism, a sunroof opening / closing device, and the like, and a ball bearing for an electric motor for a vehicle incorporated in the electric motor for a vehicle and rotatably supporting a rotating shaft inside a casing. Regarding improvement.
[0002]
[Prior art]
An electric motor for a vehicle, which has been conventionally used for driving a cooling fan, a blowing fan, or the like, is configured as shown in FIG. 10, for example. In this electric motor for a vehicle, a rotating shaft 2 is rotatably supported by a pair of sliding bearings 3 at a central portion inside a casing 1. A rotor 4 is fixed between the sliding bearings 3 at an intermediate portion of the rotating shaft 2, and stators 5 and 5 are fixed to a portion of the inner surface of the casing 1 facing the rotor 4. Further, a brush 6 is supported inside the casing 1, and a tip end surface of the brush 6 is slidably contacted with a commutator (not shown) provided at a portion near the inner diameter of the rotor 4. As an electric motor for an automobile, in addition to the structure shown in FIG. 10, as shown in FIG. 11, a motor in which a brush 6 slides on an outer peripheral surface of a commutator 7 provided at an intermediate portion of the rotating shaft 2 is also available. is there. Patent Documents 1 to 4 exist as prior art documents related to the present invention.
[0003]
[Patent Document 1]
JP-A-11-69700
[Patent Document 2]
JP-A-10-225047
[Patent Document 3]
JP 2002-155930 A
[Patent Document 4]
Japanese Patent Publication No. 1-181212
[0004]
[Problems to be solved by the invention]
In the case of the electric motor for a vehicle as described above, the inner peripheral surfaces of the pair of slide bearings 3 and the outer peripheral surface of the rotating shaft 2 are in sliding contact with each other during use, so that the rotational torque increases. For this reason, it is not only difficult to make the performance of the electric motor sufficiently high, but also the power consumption increases. In addition, in the case of each of the sliding bearings 3, 3, the thrust load applied to the rotating shaft 2 cannot be supported. Therefore, in the case of the conventional structure shown in FIGS. 10 to 11 described above, it is necessary to provide a thrust bearing structure (not shown) different from the slide bearing 3 in order to support this thrust load.
[0005]
In view of such circumstances, in recent years, as described in Patent Literatures 1 to 3, it has been considered to support the rotating shaft 2 inside the casing 1 with a ball bearing. When a ball bearing is used for the rotation supporting portion of the rotating shaft 2 in this way, the rotating torque of the electric motor for an automobile can be reduced, and it is not necessary to provide another structure for supporting the thrust load, and the number of parts can be reduced. In addition, costs can be reduced by reducing the number of assembly steps. However, if a ball bearing is used instead of each of the sliding bearings 3, 3, the acoustic characteristics of the electric motor for an automobile are deteriorated, and unpleasant noise is likely to be generated for the occupant of the automobile. The present inventor has considered that the following reasons (1) to (3) are mainly responsible for the deterioration of the acoustic characteristics.
(1) Abnormal noise is generated when multiple balls roll on each of the inner and outer raceways. In particular, the above-mentioned noise is increased due to the deterioration of the surface accuracy of each of the inner ring and outer ring raceways and each ball over a long period of use.
{Circle around (2)} Abnormal noise is generated when the metal ball and the cage collide with each other.
(3) For example, when an automobile electric motor is used as a blower fan to be incorporated in an air conditioner for a car, and when the blower fan stops when the outside air is at an appropriate temperature during the running of the car, for example, when the car is running, The electric motor may not rotate. In the case of such an electric motor for automobiles, vibrations accompanying the traveling of the automobile are applied, so that minute slippages repeatedly occur on the rolling contact surface in a state where the ball bearings incorporated in the electric motor for automobiles do not rotate. For this reason, surface roughening due to fretting occurs, which leads to generation of abnormal noise.
Therefore, when a ball bearing is used in place of the sliding bearing, it is important to suppress these abnormal sounds (1) to (3) in order to ensure good acoustic characteristics of the electric motor for a vehicle.
In view of such circumstances, the present invention has been made to improve the acoustic characteristics while reducing the rotational torque of the electric motor for an automobile.
[0006]
[Means for Solving the Problems]
Among the ball bearings for an electric motor for a motor vehicle and the electric motor for a motor vehicle according to the present invention, the ball bearing for an electric motor for a vehicle according to claim 1 has an outer race having an outer raceway on an inner peripheral surface and an inner race on an outer peripheral surface. An inner ring having a raceway, a plurality of balls rotatably provided between the outer raceway and the inner raceway, and a retainer for holding the balls are provided. Also, with the outer ring fixed inside a part of a casing of an electric motor for an automobile and the inner ring fixed externally to a rotating shaft of the electric motor, the rotating shaft is rotatable inside the casing. I support it.
[0007]
In the ball bearing for an electric motor for an automobile according to the first aspect, the retainer is made of synthetic resin, and the balls are installed between an inner peripheral surface of the outer ring and an outer peripheral surface of the inner ring. Grease to ensure excellent acoustic characteristics is enclosed in the space. In addition, at least one of the inner raceway, the outer raceway, and the rolling surface of each ball is subjected to a heat treatment for suppressing the deterioration of the surface shape (surface accuracy) with time. As the grease for ensuring the above-mentioned excellent acoustic characteristics, a grease having a high lubricating property, for example, by including an ester-based oil in a base oil can be used.
[0008]
Preferably, the curvature radius of the cross-sectional shape of the inner raceway relative to a virtual plane including the center axis of the inner raceway is 51 to 54% of the diameter of each ball (more preferably, 51 to 52.5%), and the radius of curvature of the cross-sectional shape of the outer raceway relative to the virtual plane including the center axis of the outer raceway is 52 to 57% of the diameter of each ball (more preferably 52.5%). ~ 57%). Further, when a radial load of 0.02 times the dynamic load rating is applied, the sum of the area of the contact portion between the rolling surface of each ball and the inner raceway is represented by S. ₁ And the sum of the areas of the contact portions between the rolling surfaces of these balls and the outer raceway is S ₂ , S ₁ > S ₂ And And (S ₁ + S ₂ ) Is made smaller than the case where the radius of curvature of the cross-sectional shape of both the inner ring and outer ring raceways with respect to a virtual plane including the center axes of the inner ring raceway and the outer ring raceway is 52% of the diameter of each ball.
[0009]
Further, preferably, as described in claim 3, between the outer peripheral surface of the inner race and the inner peripheral surface of the outer race, the end of the space where the balls are installed is closed by a non-contact seal.
[0010]
According to a fourth aspect of the present invention, there is provided an electric motor for a vehicle, in which a rotating shaft is rotatably supported by a pair of bearings inside a casing, similarly to the above-described conventional structure, and a rotating shaft is provided at an intermediate portion of the rotating shaft. A rotor is provided between a pair of bearings.
In particular, in the electric motor for a vehicle described in claim 4, at least one of the pair of bearings is a ball bearing for an electric motor for a vehicle according to any one of claims 1 to 3. It is.
Preferably, as described in claim 5, a sensor provided on the outer peripheral surface of the rotating shaft for detecting the phase of the rotor and a stator fixed to the inner surface of the casing based on a signal generated from the sensor. A so-called brushless structure including a control unit for switching the direction of a current flowing through the provided coil.
[0011]
[Action]
ADVANTAGE OF THE INVENTION According to the ball bearing for electric motors for motor vehicles and the electric motor for motor vehicles of the present invention configured as described above, it is possible to improve the acoustic characteristics while reducing the rotational torque of the electric motor for motor vehicles. That is, according to the electric motor for an automobile incorporating the ball bearing for an electric motor for an automobile of the present invention, a ball bearing in which a contact portion of each component is in a rolling contact state is used as a rotation support portion of a rotating shaft. Therefore, the rotational torque can be made smaller than in the case of the conventional structure using a sliding bearing in which the contact portion of each component is in a sliding contact state.
[0012]
Further, in the case of the present invention, at least one of the rolling surface of each ball and each of the inner ring and the outer ring raceways is subjected to a heat treatment for suppressing the deterioration with time of the surface shape. Deterioration of acoustic characteristics due to deterioration can be suppressed. Further, since grease for ensuring excellent acoustic characteristics is sealed inside the ball bearing, deterioration of acoustic characteristics due to use of grease can be suppressed. Further, since the retainer is made of synthetic resin, even when the retainer collides with each ball, generation of abnormal noise due to the collision can be suppressed. As a result, according to the present invention, it is possible to improve the acoustic characteristics while reducing the rotational torque of the electric motor for a vehicle.
[0013]
In addition, in the case of the electric motor for an automobile of the present invention, since a ball bearing is used for the rotation supporting portion of the rotating shaft, the thrust load is different from that of the conventional structure using the sliding bearing for the rotating supporting portion. There is no need to provide a separate receiving structure. When a seal ring is provided at the end of the ball bearing, it is not necessary to provide a structure for preventing foreign matter from entering the inside of the electric motor for a vehicle, separately from the ball bearing. Thus, in the case of the electric motor for a vehicle according to the present invention, it is easy to reduce the cost by facilitating the assembling work.
[0014]
Furthermore, according to the ball bearing for an electric motor for an automobile described in claim 2, it is the total of the contact areas of the inner ring and outer ring raceways with the rolling surfaces of the balls, (S ₁ + S ₂ ) Is smaller than that of the conventional structure in which the radius of curvature of the cross-sectional shape of each of the inner and outer raceways is 52% of the diameter of each ball, so that the rotational torque of the electric motor can be further reduced. Also, the total area S of the contact area between the inner raceway provided on the inner race that rotates during use and the rolling surface of each ball. ₁ Is the total area S of the contact portion between the outer raceway provided on the outer race that does not rotate even during use and the rolling surface of each ball. ₂ Since these are larger than the above, each ball can be more stably rotated and revolved. Therefore, the rotation of the electric motor for the vehicle can be smoothly performed.
Further, in the case of the electric motor for a vehicle according to the third aspect, the rotational torque can be further reduced.
[0015]
Further, in the case of the electric motor for an automobile according to the fifth aspect, it is not necessary to bring the brush into contact with the commutator, so that abrasion powder of the brush is not generated. For this reason, even when the contact type seal structure is not provided at the end of the ball bearing for the electric motor, this abrasion powder is prevented from being mixed into the grease in the ball bearing. Can be improved.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
1 to 3 show an example of an embodiment of the present invention. In the electric motor of the present embodiment, both ends of the rotating shaft 2 are rotatably supported by a pair of ball bearings 8 inside the casing 1a. The casing 1a includes a bottomed cylindrical casing body 9 and an end member 10 that closes an open end of the casing body 9. Further, the rotor 4 is externally fitted and fixed to a portion located between the pair of ball bearings 8 in the intermediate portion of the rotary shaft 2. In addition, stators 5 and 5 made of permanent magnets are fixed to the inner peripheral surface of the casing main body 9 at positions equidistant in the circumferential direction at a portion facing the rotor 4. A commutator 7 is provided near one end of the rotating shaft 2 (close to the left end in FIG. 1), and the leading edges of the brushes 6, 6 supported on a part of the inner surface of the casing body 9 are attached to the commutator 7. Elastic sliding contact. The brushes 6 are electrically connected to a connector (not shown) provided on the outer peripheral surface of the casing body 9.
[0017]
As shown in detail in FIG. 2, each of the ball bearings 8 and 8, which are ball bearings for an electric motor for an automobile, includes an outer race 12 having an outer raceway 11 on an inner circumferential surface and an inner race 12 on an outer circumferential surface. An inner race 14 having a raceway 13, a plurality of balls 15, 15 rotatably provided between the outer raceway 11 and the inner raceway 13, and a retainer 16 for holding the balls 15, 15 are provided. . In addition, the outer diameter side ends of the pair of seal rings 17, 17 are locked to the inner peripheral surfaces of both ends of the outer ring 12, and the inner diameter side edges of the seal rings 17, 17 are connected to both ends of the inner ring 14. The inner peripheral side walls 19, 19 of the seal grooves 18, 18 provided on the outer peripheral surface of the outer peripheral surface are slidably contacted all around.
[0018]
The retainer 16 is called a crown retainer, and is integrally formed as a whole by injection molding synthetic resin as shown in FIG. Such a retainer 16 is provided with pockets 21, 21 for holding the balls 15, 15 at a plurality of positions in the circumferential direction of the annular main portion 20 so as to be able to roll freely. Each of these pockets 21 and 21 has one side surface of a pair of elastic pieces 22 and 22 arranged at an interval on one side in the axial direction of the main portion 20, and one pair of elastic portions 22 and 22 on the one side in the axial direction of the main portion 20. It is composed of spherical concave portions 23 provided between the elastic pieces 22. Then, the balls 15, 15 are pushed between the pair of elastic pieces 22, 22 while elastically expanding the gap between the distal edges of the elastic pieces 22, 22. The retainer 16 rolls the balls 15, 15 between the outer raceway 11 and the inner raceway 13 by holding the balls 15, 15 in the pockets 21, 21 in this manner. Freely holding.
[0019]
In addition, the balls 15, 15 which are present between the inner peripheral surface of the outer ring 12 and the outer peripheral surface of the inner ring 14 and whose both ends are closed by the pair of seal rings 17, 17 are installed. Grease is sealed in the space 24. In the case of the present embodiment, a grease for ensuring excellent acoustic characteristics is used. For this reason, in the case of this example, the base oil of this grease contains at least an ester-based synthetic oil. Preferably, the ester-based synthetic oil is contained in the base oil in an amount of 30% by mass or more (more preferably 50% by mass or more). As the base oil for the grease, a synthetic hydrocarbon oil or an ether-based synthetic oil can be preferably used in addition to the ester-based synthetic oil. These base oils such as synthetic hydrocarbon oils can be used alone or in combination of two or more. The base oil is adjusted to a predetermined kinematic viscosity.
[0020]
Specifically, as the ester oil, diester oils such as dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl glutarate, and methyl acetyl sinolate, or Aromatic ester oils such as trioctyl trimellitate, tridecyl trimellitate, and tetraoctyl pyromellitate; further, trimethylolpropane caprylate, trimethylolpropaneperargonate, pentaerythritol-2-ethylhexanoate, and pentaerythritol Examples thereof include polyol ester oils such as argonate, and complex ester oils which are oligoesters of a polyhydric alcohol and a mixed fatty acid of a dibasic acid / monobasic acid. When such an ester-based oil is contained in the base oil, the ester bond having a good affinity for the metal enhances the oil film holding ability and ensures excellent oil lubrication, so that the grease lubricity and Durability and heat resistance can be improved. Therefore, when grease containing the ester oil is used as the base oil, the excellent acoustic characteristics of the ball bearings 8 can be secured.
[0021]
Examples of the synthetic hydrocarbon oil-based oil that can be preferably used as the base oil include poly-α-olefins such as normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, 1-decene-ethylene co-oligomer and the like. Examples include hydrides, alkylbenzenes such as monoalkylbenzene and dialkylbenzene, and alkylnaphthalenes such as monoalkylnaphthalene, dialkylnaphthalene, and polyalkylnaphthalene.
[0022]
Examples of the ether-based synthetic oil that can be preferably used as the base oil include polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, polyglycol such as polypropylene glycol monoether, or monoalkyl triphenyl ether, alkyl diphenyl ether, dialkyl diphenyl ether, And phenyl ether oils such as pentaphenyl ether, tetraphenyl ether, monoalkyl tetraphenyl ether and dialkyl tetraphenyl ether.
[0023]
The thickening agent for the grease may be used in a wide range as long as it has a gel structure and is capable of retaining the base oil in the gel structure, but lithium soap or urea is preferred. The system can be used. When lithium soap is used as the thickener, the acoustic characteristics of the ball bearings 8 can be improved. When the urea compound is used as a thickener, a diurea compound represented by the following general formula can also be used.
[0024]
Embedded image

[0025]
R in this formula ₂ Represents an aromatic hydrocarbon group having 6 to 15 carbon atoms; ₁ And R ₃ Represents an aromatic hydrocarbon group having 6 to 12 carbon atoms or an aliphatic hydrocarbon group having 6 to 20 carbon atoms, respectively. Also, R ₁ And R ₃ Is from 50 to 100 mol% in the total amount of ₁ And R ₃ May be the same or different.
[0026]
When such an aromatic diurea compound is used as a thickener and the thickener is blended in a grease in an amount of 15 to 35% by mass (preferably 15 to 30% by mass), the peeling resistance is increased. , And grease leakage can be easily prevented. In addition, the durability of the ball bearings 8, 8 used in a state of high-speed rotation at a high temperature can be ensured, and generation of abnormal noise at a low temperature can be prevented. Further, since the oily effect of the base oil including the ester-based oil can be obtained, the lubricity can be improved, and the occurrence of premature seizure of the ball bearings 8 can be prevented.
[0027]
In addition, the mixing consistency of the grease is preferably set to NLGI No. 1 to 3. For this purpose, for example, the thickener is blended in the grease in an amount of 5 to 35% by mass.
[0028]
In order to provide the grease with more excellent performance, conventionally known various additives can be contained as needed. Examples of the additive include metal soaps, benton, gelling agents such as silica gel, amine-based, phenol-based, sulfur-based, antioxidants such as zinc dithiophosphate, chlorine-based, sulfur-based, phosphorus-based, zinc dithiophosphate, Extreme pressure agents such as organic molybdenum, fatty agents such as fatty acids and animal and vegetable oils, rust inhibitors such as petroleum sulfonates, dinonylnaphthalene sulfonates, sorbitan esters, metal deactivators such as benzotriazole and sodium nitrite, polymethacrylates , Polyisobutylene, polystyrene, and other viscosity index improvers, and these additives can be added alone or in combination of two or more. At this time, the amount of the additive is not particularly limited as long as the object of the present invention can be achieved, but usually, the grease contains the additive in an amount of 20% by mass or less.
[0029]
Further, the method of adjusting grease used in the ball bearing for an electric motor for an automobile of the present invention is not particularly limited. However, this grease is generally obtained by reacting a thickener in a base oil. Production conditions such as heating temperature, stirring, and mixing time are appropriately set depending on the base oil, thickener, additive, and the like used.
[0030]
In the case of the present invention, the surfaces of the inner ring 14, the outer ring 12, and the balls 15, 15 are subjected to a heat treatment to suppress the deterioration of the surface shape with time. For example, as the heat treatment to be applied to the surfaces of the inner and outer wheels 14 and 12, the inner and outer wheels 14 and 12 are made of SUJ2, and in addition to the conventional standard heat treatment, a deep cooling process at −20 ° C. Is applied. In this standard heat treatment, after quenching at 820 to 860 ° C, tempering is performed at 160 to 200 ° C. The amount of retained austenite in the inner and outer wheels 14, 12 is reduced to 6% by mass or less by the heat treatment of performing the deep cooling treatment in addition to the standard heat treatment.
[0031]
The inner and outer wheels 14, 12 are made of SUJ2, and after quenching, a heat treatment of tempering at 220 ° C. is performed to reduce the amount of retained austenite in the inner and outer wheels 14, 12 to 4% by mass or less. It can also be. The inner and outer wheels 14, 12 are made of SUJ2 and subjected to a deep cooling process at -196 ° C in addition to the standard heat treatment to reduce the amount of retained austenite in the inner and outer wheels 14, 12 to 4 mass. % Or less.
[0032]
Further, the inner and outer wheels 14 and 12 are made of SUJ2, and after the quenching, heat treatment for performing tempering at 240 ° C. or after quenching, a deep cooling treatment at −80 ° C. By performing a heat treatment for tempering in the above, the amount of retained austenite in the inner and outer wheels 14, 12 can be reduced to 0%.
[0033]
Furthermore, these inner and outer wheels 14, 12 are made of SUS440C, and after quenching at 1050 ° C., subjected to a deep cooling process at −80 ° C., and then subjected to a heat treatment of tempering at 520 ° C. The amount of retained austenite in the inner and outer wheels 14, 12 can be set to 0%. The inner and outer wheels 14, 12 are made of SUJ2 and, after quenching, are subjected to a heat treatment of tempering twice at 220 ° C., so that the amount of retained austenite in the inner and outer wheels 14, 12 is reduced to 2% by mass. It can also be:
[0034]
By performing such a heat treatment, when the amount of retained austenite of the inner and outer wheels 14, 12 is reduced to less than 8 to 14% by mass, which is the amount of retained austenite of those conventionally used. The load resistance and impact resistance of the inner and outer wheels 14 and 12 can be improved, and harmful permanent deformation can hardly occur on the inner and outer raceways 13 and 11. That is, since austenite has a lower yield stress than martensite, if the amount of retained austenite is large, harmful permanent deformation is likely to occur even with a small load or the like. In contrast, when the amount of retained austenite is reduced to 6% by mass or less by the heat treatment as described above, the indentation resistance of the inner ring and outer ring raceways 13 and 11 is improved (yield stress is increased), and Harmful permanent deformation due to the small load or the like can be hardly generated. In addition, since the indentation resistance of each of the tracks 13 and 11 can be improved, the ball bearing 8 is incorporated when the electric motor is manufactured, or when the ball bearing 8 is transported (handled). Harmful permanent deformation (indentation) can be less likely to occur on the inner ring and outer ring raceways 13 and 11 even when a large external force is applied to the inner ring and the outer ring. Next, the first heat treatment was performed to confirm that when the amount of retained austenite in the inner and outer wheels 14 and 12 was reduced by the heat treatment as described above, the effect of improving the indentation resistance was obtained. The experiment will be described. The experiment was carried out using a conventional product and a product of the present invention whose heat treatment method is shown in Table 1 below.
[0035]
[Table 1]

[0036]
Specifically, as a conventional product, a product which has been subjected to conventional standard quenching and standard tempering for the inner ring and the outer ring is used, and as a product of the present invention, a deep cooling treatment is performed after quenching the inner ring and the outer ring. After the application, a material subjected to high-temperature tempering was used. In the product of the present invention, by performing such a heat treatment, the hardness of the inner ring and the outer ring is set to 59 to 63 HRc, the amount of retained austenite is set to 4% by mass or less, and the elastic limit is set to 1100 N / mm. ² And The ball bearings of the conventional product and the product of the present invention had an inner diameter of 8 mm, an outer diameter of 22 mm, and a width of 7 mm, and were provided with a seal ring. In the first experiment, using such a conventional product and the product of the present invention, the outer ring was internally fixed to the fixed portion, and a predetermined axial load (axial load) was applied to the inner ring for 1800 min. ^-1 The value of the increase in the axial vibration acceleration of the ball bearing in the state where it was rotated at was measured.
[0037]
FIG. 4 shows the results of the experiment performed in this manner. In FIG. 4, the solid line represents the product of the present invention, and the broken line represents the conventional product. As is clear from the experimental results shown in FIG. 4, the axial vibration acceleration of the conventional product greatly increased when the axial load exceeded 196 N, whereas the axial load of the product of the present invention increased. 784N, the amount of increase in the axial vibration acceleration was small. From this fact, it was found that the product of the present invention, which was subjected to the heat treatment as described above and had the hardness, the amount of retained austenite, and the elastic limit within a predetermined range, could improve the indentation resistance even when a large load was applied. . In particular, the product of the present invention used in this experiment has a larger elastic limit than the conventional product, so it is easy to suppress the stress generated on the raceway surface to the elastic limit or less, and plastic deformation that causes indentation is more likely to occur. Can be difficult.
[0038]
When the amount of retained austenite is reduced to 6% by mass or less, the surface shape of each of the inner and outer raceways 13, 11 can be prevented from deteriorating with time. That is, if the amount of retained austenite present in each of the raceways 13, 11 is large, the residual austenite is decomposed due to the rolling stress that is repeatedly applied to each of the raceways 13, 11 with use of each of the ball bearings 8, 8. Then, the surface shape of each of the tracks 13 and 11 deteriorates with the disassembly. On the other hand, when the amount of retained austenite is reduced to 6% by mass or less by the above-described heat treatment, it is possible to suppress deterioration with time of the surface shape due to decomposition of the retained austenite. In particular, when the amount of retained austenite is suppressed to 4% by mass or less, the above-mentioned deterioration with time can be further suppressed. When the amount of retained austenite is suppressed to 2% by mass or less, the deterioration with time can be almost eliminated.
[0039]
In addition, when the amount of retained austenite is reduced to 6% by mass or less, even when the surroundings become high in temperature, the temporal deformation of the inner ring 14 and the outer ring 12 can be suppressed, and the displacement of the ball bearing 8 and the displacement of the ball bearing 8, Wear and vibration between the rotating shaft 2 and the inner ring 14 can also be suppressed. That is, in an electric motor for a vehicle, the ball bearing 8 incorporated therein may be used in a state where the temperature of the surroundings becomes high. In this case, when the conventional heat treatment is performed, the amount of retained austenite in the inner ring is large, and the retained austenite is decomposed and changes to martensite, thereby increasing the inner diameter of the inner ring (expansion). Do). Therefore, when the ball bearing 8 is positioned by fixing the inner ring to the rotating shaft 2 by interference fit, the position of the inner ring with respect to the rotating shaft 2 is shifted or the inner peripheral surface of the inner ring is fixed. And the outer peripheral surface of the rotating shaft 2 causes slippage, causing wear and vibration. On the other hand, when the amount of retained austenite is reduced as described above, temporal deformation of the inner ring 14 due to high temperature can be suppressed, and the displacement of the inner ring 14 with respect to the rotating shaft 2 and the rotation of the rotating shaft 2 and the Wear and vibration between the inner ring 14 and the inner ring 14 can be suppressed.
[0040]
Next, by reducing the amount of retained austenite in the inner ring 14 as described above, the effect of being able to suppress the temporal deformation of the inner ring 14 can be obtained even when the surroundings become hot. A second experiment performed to confirm this will be described. In this second experiment, the inner rings constituting the conventional product and the product of the present invention used in the first experiment were used. Then, after leaving each of these inner rings in a constant temperature bath having an ambient temperature of 180 ° C., they were taken out at predetermined time intervals, the inner diameter was measured at room temperature, and the dimensional change rate with respect to the initial dimensions was obtained. FIG. 5 shows the results of the second experiment performed in this manner. In FIG. 5, the solid line represents the product of the present invention, and the broken line represents the conventional product. As is clear from the experimental results shown in FIG. 5, in the case of the conventional product, the inner diameter of the inner ring changes over time, and after 1000 hours, the dimensional change rate becomes 0.08% or more. Was. On the other hand, in the case of the product of the present invention, no dimensional change in the inner diameter of the inner ring 14 was observed at all even after the elapse of 1000 hours. From the results of such experiments, it was found that the product of the present invention subjected to the predetermined heat treatment as described above and having the hardness, the amount of retained austenite, and the elastic limit within the predetermined ranges was subjected to the temporal deformation of the inner ring 14 in a high temperature environment. (Expansion) can be suppressed. In Table 1 described above, the circles are marked in the columns of the indentation resistance and the high-temperature dimensional stability of the product of the present invention. This indicates that the product of the present invention has better performance than the conventional product. It indicates that excellent results were obtained.
[0041]
In addition, as a heat treatment performed on the surface of each of the balls 15, 15 to suppress the deterioration of the surface shape with time, for example, a normal quenching process is performed on the surface of each of the balls 15, 15 processed into a predetermined shape, Next, there is a heat treatment of performing a surface hardening treatment and then performing a tempering treatment. This tempering process is performed, for example, at 160 ° C. for 120 minutes. In such a heat treatment, a preliminary tempering treatment can be performed after the quenching treatment and before the surface hardening treatment. This preliminary tempering is performed, for example, at 125 ° C. for 120 minutes. As the surface hardening treatment applied to the balls 15, various methods conventionally known, such as the method described in Patent Document 4, can be used.
[0042]
Further, the upper and lower limits of the tempering temperature in the tempering process are preferably regulated by the following (a) to (f).
(A) When the tempering time is 10 to 120 minutes, the upper limit of the tempering temperature is 200 ° C.
(B) When the tempering time exceeds 120 minutes, the upper limit of the tempering temperature, the tempering temperature is indicated on one axis of the orthogonal coordinates, and the tempering time is expressed on a logarithmic scale on the other axis. Is obtained in correspondence with the tempering time.
(C) The line (b) starts at a point of 120 minutes at 200 ° C. and passes through a point of 1000 minutes at 175 ° C. and 4000 minutes at 160 ° C.
(D) When the tempering time is 10 to 120 minutes, the lower limit of the tempering temperature is 150 ° C.
(E) When the tempering time exceeds 120 minutes, the lower limit of the tempering temperature, the tempering temperature is represented on one axis of the orthogonal coordinates, and the tempering time is represented on a logarithmic scale on the other axis. Is obtained in correspondence with the tempering time.
(F) The line (e) starts at a point of 120 minutes at 150 ° C. and passes through a point of 300 minutes at 140 ° C., a point of 1000 minutes at 130 ° C., and a point of 6000 minutes at 120 ° C.
[0043]
The preferable temperature conditions of the tempering treatment performed after the surface hardening treatment of the balls 15 will be described in more detail with reference to FIG. FIG. 6 shows the relationship between the tempering time t and the upper limit value and the lower limit value of the tempering temperature T among the tempering conditions in performing this tempering process. In FIG. 6, the vertical axis represents the tempering temperature T, and the horizontal axis represents the tempering time t on a logarithmic scale.
[0044]
The solid line a in FIG. 6 represents the relationship between the upper limit value of the tempering temperature T and the tempering time t. The solid line a represents a straight line portion a representing a constant value of 200 ° C. when the tempering time t is between 10 and 120 minutes. ₁ In a portion where the tempering time t exceeds 120 minutes, the curve portion a indicates that the upper limit value of the tempering temperature T gradually decreases as the tempering time t increases. ₂ It has become. And this curved part a ₂ Starts at a point of 120 minutes at 200 ° C. and passes through a point of 1000 minutes at 175 ° C. and 4000 minutes at 160 ° C.
[0045]
Further, the solid line b in FIG. 6 represents the relationship between the lower limit value of the tempering temperature T and the tempering time t. The solid line b represents a straight line part b representing a constant value of 150 ° C. when the tempering time t is between 10 and 120 minutes. ₁ In the portion where the tempering time t exceeds 120 minutes, the lower limit of the tempering temperature T gradually decreases as the tempering time t increases. ₂ It has become. And this curved part b ₂ Starts at a point of 120 minutes at 150 ° C. and passes through a point of 300 minutes at 140 ° C., a point of 1000 minutes at 130 ° C., and a point of 6000 minutes at 120 ° C.
Therefore, it is preferable that the tempering process after the surface hardening process is performed in the shaded area in FIG.
[0046]
Further, it is preferable that the preliminary tempering process is performed under conditions satisfying the following (g) to (i).
(G) When the tempering time is 10 to 120 minutes, the upper limit of the tempering temperature is 140 ° C.
(H) When the tempering time exceeds 120 minutes, the upper limit of the tempering temperature, the tempering temperature is represented on one axis of the orthogonal coordinates, and the tempering time is represented on the other axis on a logarithmic scale. Is obtained in correspondence with the tempering time.
(I) The line (h) starts at a point of 120 minutes at 140 ° C. and passes through a point of 300 minutes at 130 ° C., a point of 1000 minutes at 120 ° C., and a point of 6000 minutes at 110 ° C.
[0047]
Preferred temperature conditions for such preliminary tempering will be described in more detail with reference to FIG. FIG. 7 shows the relationship between the tempering time t and the upper limit value of the tempering temperature T in the tempering conditions when the preliminary tempering is performed after the quenching and before the surface hardening. Represents. In FIG. 7, the vertical axis represents the tempering temperature T, and the horizontal axis represents the tempering time t on a logarithmic scale.
[0048]
The solid line c representing the upper limit of the tempering temperature described in FIG. 7 is a straight line portion c representing a constant value of 140 ° C. when the tempering time is 10 to 120 minutes. ₁ In a portion where the tempering time exceeds 120 minutes, the curve portion c indicates that the upper limit value of the tempering temperature T gradually decreases as the tempering time t increases. ₂ It has become. And this curved part c ₂ Starts at 140 ° C. for 120 minutes, passes at 130 ° C. for 300 minutes, 120 ° C. for 1000 minutes, and 110 ° C. for 6000 minutes.
Therefore, it is preferable that the preliminary tempering process be performed in the shaded area in FIG.
[0049]
As described above, when the tempering treatment is performed after the surface hardening treatment of each of the balls 15, 15, the surface shape of each of the balls 15, 15 does not deteriorate with time. That is, by performing the tempering treatment after the surface hardening treatment, the residual stress generated inside each of the balls 15, 15 due to the surface hardening treatment can be eliminated, and the surface shape does not deteriorate with time.
[0050]
When the upper limit and the lower limit of the tempering temperature in the case of performing the tempering treatment after the surface hardening treatment are regulated as described above, the surface hardness of each ball 15 can be increased. The surface of the balls 15, 15 can be hardly damaged. In addition, it is possible to easily eliminate the residual stress generated inside each of the balls 15, 15 due to the surface hardening treatment of each of the balls 15, 15.
[0051]
Further, when the upper limit of the tempering temperature in performing the preliminary tempering treatment is regulated as described above, the surface hardness of each ball 15, 15 can be increased, and the surface of each ball 15, 15 can be increased. Can be hardly damaged. The preliminary tempering process is performed in order to prevent the surface of each of the balls 15, 15 from being damaged, such as cracks, during the subsequent surface hardening process. Therefore, if the occurrence of the loss can be prevented separately, the preliminary tempering process can be omitted.
[0052]
Furthermore, in the case of this example, the radius of curvature of the cross-sectional shape of the inner raceway 13 with respect to a virtual plane including the center axis of the inner raceway 13 is set to 51 to 54% of the diameter of each of the balls 15, 15 (more preferably, 51 to 52.5%), and the radius of curvature of the cross-sectional shape of the outer raceway 11 with respect to an imaginary plane including the central axis of the outer raceway 11 is 52 to 57% (more (Preferably 52.5 to 57%). Further, when a radial load of 0.02 times the dynamic load rating is applied to each of the ball bearings 8, 8, the area of the contact portion between the rolling surface of each of the balls 15, 15 and the inner ring raceway 13. The sum of ₁ The sum of the areas of the contact portions between the rolling surfaces of these balls 15 and 15 and the outer raceway 11 is S ₂ , S ₁ > S ₂ And Furthermore, (S ₁ + S ₂ ) Is smaller than the case where the radius of curvature of the cross-sectional shape of the inner raceway 13 and the outer raceway 11 is 52% of the diameter of each of the balls 15, 15.
[0053]
ADVANTAGE OF THE INVENTION According to the ball bearing for electric motors for vehicles of this invention comprised as mentioned above, and the electric motor for vehicles incorporating this, while improving the rotational torque of an electric motor for vehicles, sound characteristics can be improved. it can. That is, in the case of the electric motor for an automobile of the present invention, the ball bearings 8, 8 in which the contact portions of the respective components are in rolling contact with each other, are used for the rotation support portion of the rotating shaft 2. For this reason, the rotational torque can be reduced to about 1/2 as compared with the case of the conventional structure using the slide bearing in which the contact portion of each component is in a sliding contact state. In addition, in the case of the present invention using the ball bearings 8 and 8, the generation of abnormal noise at the time of starting at a low temperature can be reduced to a negligible level.
[0054]
In the case of this example, the rolling surfaces of the balls 15, 15 and the inner and outer raceways 13, 11 are subjected to a heat treatment for suppressing the deterioration of the surface shape with time. The deterioration of the acoustic characteristics due to the deterioration with time can be suppressed. Further, since grease for ensuring excellent acoustic characteristics is sealed in each of the ball bearings 8, deterioration of acoustic characteristics due to the use of grease can be suppressed. Further, since the cage 16 incorporated in each of the ball bearings 8, 8 is made of synthetic resin, even when the cage 16 collides with the balls 15, 15, generation of abnormal noise due to the collision is suppressed. Can do things. As a result, according to the present invention, it is possible to improve the acoustic characteristics while reducing power consumption by reducing the rotational torque of the electric motor for a vehicle.
[0055]
Also, in the case of the electric motor for an automobile according to the present invention, since the ball bearings 8 and 8 are used for the rotation supporting portion of the rotating shaft 2, unlike the conventional structure using the sliding bearing for the rotation supporting portion. Therefore, it is not necessary to separately provide a structure for receiving the thrust load. When the seal rings 17 are provided on the ball bearings 8 as in the present embodiment, a structure for preventing foreign matter from entering the electric motor for automobiles is provided with a structure for preventing the intrusion of foreign matters into these motors. There is no need to provide the bearings 8 and 8 separately. Thus, in the case of the present invention, it is easy to reduce the cost by facilitating the assembling work.
[0056]
In the case of this example, it is the sum of the contact areas between the inner ring and outer ring raceways 13 and 11 and the rolling surfaces of the balls 15 and 15 (S ₁ + S ₂ ) Is smaller than that of the conventional structure in which the radius of curvature of the cross-sectional shape of the inner raceway 13 and the outer raceway 11 is 52% of the diameter of each of the balls 15, 15. Therefore, the rotational torque of the electric motor for a vehicle can be further reduced. That is, the rotational torque of each of the ball bearings 8, 8 is (S ₁ + S ₂ ) Is approximately proportional to ₁ + S ₂ ) Is smaller, the rotational torque can be smaller. Therefore, (S ₁ + S ₂ In the case of the present invention, which is smaller than that of the conventional structure, the rotational torque of each of the ball bearings 8 can be reduced, and the rotational torque of the electric motor can be further reduced.
[0057]
Also, in general, in a ball bearing, one of the inner ring and the outer ring is mainly used to make each ball rotate and revolve, but in this case, the main race is made up of each ball. This is the raceway on the side where the contact area between the rolling surface and the inner raceway or the outer raceway becomes larger. When the main bearing ring is a rotating ring that rotates during use, each ball can more stably rotate and revolve. In the case of this example, the inner race 14 is a rotating wheel, and the area S of the contact portion between the inner raceway 13 provided on the inner race 14 and the rolling surfaces of the balls 15, 15 is provided. ₁ Is the area S of the contact portion between the outer raceway 11 provided on the outer race 12, which is a stationary wheel, and the rolling surfaces of the balls 15, 15. ₂ (S ₁ > S ₂ ). Therefore, the balls 15 can be more stably rotated and revolved, and the rotation of the electric motor for a vehicle can be smoothly performed.
[0058]
The ball bearing for an electric motor for an automobile, which is an object of the present invention, is used in a state where a radial load having a large range of 0.005 to 0.3 times the dynamic rated load is applied. It is used in a state where a radial load of about 0.008 to 0.05 times the rated load is applied. In addition, the present inventor has used various types of ball bearings in which the curvature radii of the cross-sectional shapes of the inner ring and outer ring raceways 13 and 11 are variously varied, and the ball under conditions where the magnitude of the radial load applied is different. When the contact state between the ball 15 of the bearing 8 and the races 13 and 11 of the inner ring and the outer ring was examined, the S in the case where a radial load of 0.005 to 0.3 times the dynamic rated load was applied. ₁ , S ₂ , S ₁ + S ₂ Is S when the radial load of 0.02 times the dynamic load rating is applied. ₁ , S ₂ , S ₁ + S ₂ It turned out to be the same as the relationship described above. Therefore, when a radial load of 0.02 times the dynamic load rating, which is a representative value of the above range, is applied, S ₁ , S ₂ , S ₁ + S ₂ Is regulated as described above, even when the radial load applied to the ball bearing for the electric motor for an automobile is other than 0.02 times the dynamic rated load, the rotational torque of the electric motor for the automobile can be further reduced. In addition, smooth rotation can be achieved.
[0059]
In addition, the ball bearing for an electric motor of a vehicle according to the present invention is incorporated in an electric motor for a vehicle that may not rotate when the vehicle is running. However, vibration is applied as the vehicle runs without rotating. According to the present invention, even in this case, occurrence of fretting can be suppressed, and generation of abnormal noise due to surface roughness of the inner ring and outer ring raceways 13 and 11 can be suppressed. The reasons for this are as follows: (1) heat treatment was applied to each of the tracks 13 and 11 to suppress the deterioration of the surface shape with time; (2) grease was added to ensure excellent acoustic characteristics; 3 ▼ Area S of contact portion between inner ring track 13 and outer ring track 11 and rolling surface of each ball 15 ₁ , S ₂ , S ₁ + S ₂ The reason for this is that the proper control of flaws effectively worked as an effect for suppressing fretting and as a synergistic effect of these.
[0060]
In the case of this example, the inner peripheral edges of the seal rings 17, 17 provided at both ends of the ball bearings 8, 8 are brought into sliding contact with both ends of the outer peripheral surface of the inner ring 14, and The seal rings 17, 17 are contact seals. For this reason, abnormal noises generated by the rolling of the balls 15 on the inner race and outer race tracks 13 are less likely to leak to the outside of the ball bearings 8. Therefore, in the case of the present example, the acoustic characteristics can be further improved.
[0061]
Further, since the seal rings 17, 17 are contact seals, the grease sealed in the ball bearings 8, 8 enters the space where the rotor 4 and the stators 5, 5 exist inside the electric motor. Can be more effectively prevented. In particular, in the case where the electric motor has a structure having brushes 6, 6, when foreign matter such as grease enters between the brushes 6, 6 and the commutator 7, conduction between the brushes 6, 6 and the commutator 7 becomes possible. May be hindered and the normal function of the electric motor may not be exhibited. On the other hand, in the case of the present example, foreign substances such as grease can be more effectively prevented from entering the above-mentioned space, so that the normal function of the electric motor can be exhibited for a long period of time. In the case of the structure provided with the brushes 6, 6, there is a possibility that abrasion powder generated by the contact between the brushes 6, 6 and the commutator 7 may enter the inside of the ball bearings 8, 8. There is. When the abrasion powder enters the ball bearings 8 in this way, the grease present in each of the ball bearings 8 tends to deteriorate early. On the other hand, in the case of this example, since the seal rings 17 provided on the respective ball bearings 8 are used as contact seals, the grease is applied even when the electric motor has the brushes 6. It is possible to improve the durability by making it hard to deteriorate.
[0062]
Unlike the case of this example, as shown in FIG. 8, the inner peripheral edges of the pair of seal rings 17 a, 17 a locked on the inner peripheral surfaces of both ends of the outer ring 12 are recessed on the outer peripheral surface of the inner ring 14. The present invention can also be implemented with a structure provided with a so-called non-contact seal that does not slide on the side surfaces and the bottom surface of 25, but faces the side surfaces and the bottom surface with a small gap all around. In the case where the non-contact seal is provided in this manner, abnormal noise caused by rolling of the balls 15, 15 on the inner ring and outer ring raceways 13, 11 in each of the ball bearings 8 is generated in the case of this example. It becomes easier to leak out. In this case, the grease easily enters the space where the rotor 4 and the stator 5 (see FIG. 1) exist inside the electric motor for the vehicle. However, as described above, when the pair of seal rings 17a, 17a is a non-contact seal, the rotational torque of the electric motor for automobile can be further reduced, and the power consumption of the electric motor for automobile can be reduced. It can be suppressed more.
[0063]
In the structure shown in FIG. 8 described above, seal rings 17a, 17a are formed by connecting an elastic material 27 made of rubber, elastomer, or the like to a metal core 26 made of a metal plate and having an L-shaped cross section. . However, as shown in FIG. 9, the present invention can also be implemented with a structure in which the seal rings 17b, 17b are formed only by subjecting a metal plate to plastic working. In the case of the seal rings 17a, 17a shown in FIG. 8, since the elastic members 27 are joined, the degree of freedom in molding can be made larger than that of the seal rings 17b, 17b shown in FIG. The path length of the gap between the concave portions 25, 25 provided on the outer peripheral surface and the inner peripheral edges of the seal rings 17a, 17a can be increased. For this reason, higher dust resistance and grease leakage resistance can be ensured. However, since the seal rings 17a, 17a are made of the elastic material 27 whose use temperature is relatively limited, it is generally necessary to select an appropriate material according to the use temperature. On the other hand, in the case of the seal rings 17b, 17b shown in FIG. 9, they can be manufactured inexpensively and can be used in a wide temperature range from a low temperature to a high temperature without the trouble of selecting an appropriate material. .
[0064]
Unlike the structure shown in FIGS. 2, 8, and 9, the inner peripheral edge of one of the pair of seal rings provided on both ends of the ball bearing is slidably contacted with the outer peripheral surface of the inner ring. At the same time, the inner peripheral edge of the other seal ring may be separated from the outer peripheral surface of the inner ring.
[0065]
Further, the electric motor for a vehicle according to the present invention is different from the structure shown in FIG. Thus, a so-called brushless structure including a control unit for switching the direction of a current flowing through a coil provided on a stator fixed to the inner surface of the casing may be employed. In the case where the present invention is implemented with the electric motor for a vehicle having a brushless structure as described above, it is not necessary to take into consideration the prevention of the abrasion powder of the brush from entering the inside of each ball bearing 8. Therefore, for example, even when the non-contact type seal rings 17a and 17b as shown in FIGS. It can be prevented from being mixed in, and the reduction of the rotational torque and the improvement of the durability can be highly compatible.
[0066]
【The invention's effect】
Since the present invention is configured and operates as described above, it is possible to improve acoustic characteristics while suppressing power consumption by reducing the rotational torque of the electric motor for a vehicle.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an example of an electric motor for a vehicle according to the present invention.
FIG. 2 is a half sectional view showing only a ball bearing taken out from FIG. 1;
FIG. 3 is a perspective view showing a retainer incorporated in a ball bearing.
FIG. 4 is a diagram showing the results of a first experiment performed to confirm the indentation resistance of a ball bearing using an inner ring and an outer ring in which the amount of retained austenite was reduced by performing a predetermined heat treatment.
FIG. 5 is a diagram showing the results of a second experiment in which the amount of retained austenite was reduced by performing a predetermined heat treatment and the dimensional stability of the inner ring at a high temperature was confirmed.
FIG. 6 is a diagram showing a relationship between temperature and time of a tempering process performed after a surface hardening process.
FIG. 7 is a diagram showing a relationship between temperature and time of a preliminary tempering process.
FIG. 8 is a view similar to FIG. 2, showing a first example of another structure of the ball bearing.
FIG. 9 is a view similar to FIG. 2, showing a second example.
FIG. 10 is a sectional view showing a first example of an electric motor for a vehicle having a conventional structure.
FIG. 11 is a sectional view showing an electric motor for a vehicle of the second example.
[Explanation of symbols]
1, 1a casing
2 Rotation axis
3 Slide bearing
4 Rotor
5 Stator
6 brushes
7 commutator
8 Ball bearing
9 Casing body
10 End member
11 Outer ring track
12 Outer ring
13 Inner ring track
14 Inner ring
15 balls
16 cage
17, 17a, 17b Seal ring
18 Seal groove
19 Side wall surface
20 main part
21 pockets
22 Elastic piece
23 Concave surface
24 Space
25 recess
26 core metal
27 Elastic material

Claims (5)

An outer ring having an outer raceway on an inner peripheral surface, an inner racer having an inner raceway on an outer peripheral surface, a plurality of balls rotatably provided between the outer raceway and the inner raceway, and holding these balls; A retainer, wherein the outer ring is internally fitted and fixed to a part of a casing of an electric motor for a vehicle, and the inner shaft is externally fitted to a rotating shaft of the electric motor, and the rotating shaft is fixed inside the casing. A ball bearing for an electric motor for an automobile that is rotatably supported on the vehicle, wherein the retainer is made of synthetic resin, and the balls are installed between an inner peripheral surface of the outer ring and an outer peripheral surface of the inner ring. Grease for ensuring excellent acoustic characteristics is enclosed in the space defined, and at least one of the inner ring raceway, the outer ring raceway, and the rolling surface of each ball suppresses deterioration with time of the surface shape. Motors for automobiles that have undergone heat treatment for Ball bearings. The radius of curvature of the cross-sectional shape of the inner raceway with respect to the virtual plane including the center axis of the inner raceway is set to 51 to 54% of the diameter of each ball, and the cross-sectional shape of the outer raceway with respect to the virtual plane including the center axis of the outer raceway. Is 52-57% of the diameter of each of these balls, and when a radial load of 0.02 times the dynamic rated load is applied, the rolling surface of each of the balls and the inner ring raceway are moved. the total area of the contact portion and S _1, the total area of the contact portion between the rolling surface and the outer ring raceway of the balls when the S _2, a S _1> S _2, and, (S ₁ + S ₂ ) is smaller than the radius of curvature of the cross-sectional shape of each of the inner ring and outer ring raceways with respect to a virtual plane including the center axis of the inner ring raceway and the outer ring raceway, each being 52% of the diameter of each ball. Item 1. Electric motors for automobiles described in item 1. Bearing. The ball bearing for an electric motor for an automobile according to claim 1 or 2, wherein an end of a space where each ball is installed is closed by a non-contact seal between an outer peripheral surface of the inner ring and an inner peripheral surface of the outer ring. . In an electric motor for automobiles, a rotating shaft is rotatably supported by a pair of bearings inside a casing, and a rotor is provided between the pair of bearings at an intermediate portion of the rotating shaft. An electric motor for an automobile, wherein at least one of the pair of bearings is the ball bearing for an electric motor for an automobile according to any one of claims 1 to 3. A sensor provided on the outer peripheral surface of the rotating shaft for detecting the phase of the rotor, and a control unit for switching the direction of a current flowing through a coil provided on a stator fixed on the inner surface of the casing based on a signal generated from the sensor. The electric motor for a vehicle according to claim 4, comprising:

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