JP3814890B2

JP3814890B2 - Low friction torque thrust ball bearing

Info

Publication number: JP3814890B2
Application number: JP27400196A
Authority: JP
Inventors: 秀雄大越
Original assignee: NSK Ltd
Current assignee: NSK Ltd
Priority date: 1996-09-26
Filing date: 1996-09-26
Publication date: 2006-08-30
Anticipated expiration: 2016-09-26
Also published as: JPH10103348A

Description

【０００１】
【発明の属する技術分野】
本発明は低摩擦トルクスラスト玉軸受に関する。特に、本発明はトラクション・ドライブ無段変速機の伝動ローラや入力部材の支持軸受、工作機械など、大きなアキシャル荷重を受けて高速回転し、低摩擦を要求される用途に適した低摩擦トルクスラスト玉軸受に関する。
【０００２】
【従来の技術】
スラスト玉軸受は、玉と軌道輪の軌道面との接触点におけるスピンが大きい。そのため、特に大きなアキシャル荷重を受けるときの軸受の摩擦トルクが大きく、この種の軸受を伝動ローラや入出力部材の支持軸受として用いるトロイダル型無段変速機の場合、軸受の摩擦トルクが変速機の動力伝達効率を低下させる大きな要因になる。
【０００３】
このようにスラスト玉軸受の摩擦トルクが大きいという欠点を改めるために、次の２つの方法が提案されている。
【０００４】
その第１のタイプのものはスラスト玉軸受の玉を軸受中心軸に向かって偏倚させ、玉と２つの軌道輪の軌道面との接触点における転動を純転がりに近づけるように、玉の外周側に補助軌道輪（Ｃｏｌｌａｒ）を設けたスラスト玉軸受である。
【０００５】
この第１のタイプのスラスト玉軸受においては軌道面での玉のスピンによる摩擦損失を除くため、玉の外周に補助軌道輪を嵌めて玉をピッチ円の内側に寄せ、２つの軌道輪の軌道面と玉との接点を通り軌道面に引いた接線の交点（コーンセンタ）が玉の中心を含む平面上にあり、かつ軸受中心軸線上に来るようにして、玉と軌道面との接触点における転動を純転がりにしたものである。
【０００６】
この結果、この第１のタイプのスラスト玉軸受において、補助軌道輪の軌道面と玉とは、軸受中心軸線に直角で玉の中心を含む平面上で接触することになり、玉の自転軸も玉の中心を含む平面上にあるため、補助軌道輪の軌道面と玉との接点と玉の自転中心とが一致する。従って、軌道面における玉のスピンによる摩擦損失はなくなり、かつ、補助軌道輪の軌道面と玉との接点における運動は滑り速度の遅いスピン運動だけで、摩擦損失が小さくなり、通常のスラスト軸受に比べて摩擦トルクが大幅に低減される。
【０００７】
また、従来のスラスト玉軸受の第２のタイプのものは、上記第１のタイプのものにアンギュラ玉軸受の要素を加味して、２つの軌道輪の軌道面における接触角に差を与え、該第１のタイプのスラスト玉軸受におけるコーンセンタを、玉の中心を含む平面から軸受の軸方向に偏倚することによって、玉の中心を含む平面上にある補助軌道輪と玉との接触点を玉の自転軸中心と別の位置にすることにより、補助軌道輪と玉との接触点における相対運動を、スピン運動に転がり運動を加えたものにしている（米国特許１，４２３，６６６号参照）。
【０００８】
【発明が解決しようとする課題】
従来技術における上記第１のタイプのスラスト玉軸受では、補助軌道輪の軌道面と玉との接触点では純スピン運動を行うので、接触面の中に潤滑剤が補給されず、軸受の荷重が極く小さいときを除き、接触点にかじりや磨耗を生ずる（図１０参照）。このことは上記従来技術の第２のタイプのものについての米国特許１，４２３，６６６号の第１頁６１〜７２行に述べられている。
【０００９】
上記従来技術の第２のタイプのものは第１のタイプのものの上記の欠点を解決するためのもので、補助軌道輪と玉との接触点における相対運動を、スピン運動に転がり運動を加わったものにすることによって、接触面への潤滑剤の補給を図ったものである。この方法により、荷重が大きいときにも接触点のかじりや磨耗を防ぐ効果が得られる。
【００１０】
この軸受について試験した結果、この方法による軸受の摩擦トルク低減の効果が明らかになった（図１１参照）が、この軸受でも、玉の自転軸が軸受中心軸線に直角方向に近い（上記第１のタイプのものに近い）場合、玉の自転軸中心が補助軌道輪の軌道面と玉との接触楕円の中にあると、補助軌道輪の軌道面にかじりや摩耗が生じ、また、玉の自転軸中心が接触楕円を多少外れていても、一旦僅かでもかじりを生ずると力のバランスが崩れ、軸方向の支持のない補助軌道輪は軸方向に振動を生じ、かじりが急速に広がって（図１２参照）軸受の運転を継続することが困難になることが明らかになった。従って、玉の自転軸中心は補助軌道輪の軌道面と玉との接触楕円から外れていなければならない。
【００１１】
更に、通常の使用条件においては純アキシャル荷重ばかりでなく、ラジアル荷重や偏心荷重が加わるほか、取付誤差によっても回転軸と固定軸との軸心の不一致を生じ、玉の自転軸が変動するので、玉の自転軸は常に軸受の設計時に定めた方向にあるとは限らない。従って、純アキシャル荷重のときの玉の自転軸中心が、補助軌道輪の軌道面と玉との接触楕円からある程度の余裕を持って離れていることが必要である。
【００１２】
しかし、玉の自転軸中心が補助軌道輪の軌道面と玉との接触楕円からある程度の余裕を持って離れていると言うことは、スラスト玉軸受（接触角９０°）からアンギュラ玉軸受に近づけることであり、その結果、アキシャル荷重による玉の垂直力が大きくなり、かつ軌道面の転がり方向曲率半径がスラスト玉軸受の場合の∞より小さく（凸面に）なるため、軌道面の接触面圧が増大して、軸受の寿命を無視し得ない程低下させる。また、アンギュラ玉軸受の摩擦トルクはスラスト玉軸受の場合よりも補助軌道輪による軸受の摩擦トルク低減効果が小さい（図１３参照）。
【００１３】
従って、大きなアキシャル荷重を受ける玉軸受において、軸受寿命の低下を防ぎながら軸受摩擦トルクの大幅な低減を実現することは難しいと言う欠点があった。
【００１４】
この発明は、従来技術におけるこれらの欠点を解決することを目的とする。
【００１５】
【課題を解決する手段】
本発明の第１の態様では、それぞれ軸方向に互いに向かい合う円弧状断面を含む軌道面を有する２つの軌道輪と、それら軌道面に接触して該軌道輪間に介装された複数個の玉と、内周側に円弧状断面を含む軌道面を有し、該内周側軌道面がこれらの玉に外周側から接触して該玉を軸受中心軸線に向かって偏倚させて、前記２つの軌道輪の軌道面と玉との接点を通り軌道面に引いた接線の交点を、玉の中心を含む平面上でかつ軸受中心軸線上の位置に近づけることにより、玉と軌道面との接触点における転動を純転がりに近づけるようにして軌道輪間に保持するための補助軌道輪とからなり、これら２つの軌道輪の軌道面における接触角が相違するスラスト玉軸受において、
該玉軸受にかかるスラスト荷重に対し、該補助軌道輪の該内周側軌道面には、該補助軌道輪を前記接触角の大きい方の軌道輪の方向に向かわせるような軸方向分力が発生するように構成し、
前記接触角の大きい方の軌道輪の、軌道外側の肩部と、該肩部に対向する補助軌道輪の平面部とに互いに接触する案内面を設けたことを特徴とする低摩擦トルクスラスト玉軸受を提供する。
本発明の第１の態様による低摩擦トルクスラスト玉軸受において、前記案内面は案内面間の摩擦を少なくし軸受摩擦トルクを低減する構造とされていることが好ましい。
本発明の第２の態様では、それぞれ軸方向に互いに向かい合う円弧状断面を含む軌道面を有する２つの軌道輪と、それら軌道面に接触して該軌道輪間に介装された複数個の玉と、内周側に円弧状断面を含む軌道面を有し、該内周側軌道面がこれらの玉に外周側から接触して該玉を軸受中心軸線に向かって偏倚させて、前記２つの軌道輪の軌道面と玉との接点を通り軌道面に引いた接線の交点を、玉の中心を含む平面上でかつ軸受中心軸線上の位置に近づけることにより、玉と軌道面との接触点における転動を純転がりに近づけるようにして軌道輪間に保持するための補助軌道輪とからなり、これら２つの軌道輪の軌道面における接触角が相違するスラスト玉軸受において、
該玉軸受にかかるスラスト荷重に対し、該補助軌道輪の該内周側軌道面には、該補助軌道輪を前記接触角の大きい方の軌道輪の方向に向かわせるような軸方向分力が発生するよう構成し、
前記補助軌道輪の軌道面の円弧状断面の曲率半径中心は玉の中心を含む平面よりも接触角の小さい方の軌道輪に近い側にあることを特徴とする低摩擦トルクスラスト玉軸受を提供する。
本発明の第３の態様では、それぞれ軸方向に互いに向かい合う円弧状断面を含む軌道面を有する２つの軌道輪と、それら軌道面に接触して該軌道輪間に介装された複数個の玉と、内周側に円弧状断面を含む軌道面を有し、該内周側軌道面がこれらの玉に外周側から接触して該玉を軸受中心軸線に向かって偏倚させて、前記２つの軌道輪の軌道面と玉との接点を通り軌道面に引いた接線の交点を、玉の中心を含む平面上でかつ軸受中心軸線上の位置に近づけることにより、玉と軌道面との接触点における転動を純転がりに近づけるようにして軌道輪間に保持するための補助軌道輪とからなり、これら２つの軌道輪の軌道面における接触角が相違するスラスト玉軸受において、
該玉軸受にかかるスラスト荷重に対し、該補助軌道輪の該内周側軌道面には、該補助軌道輪を前記接触角の大きい方の軌道輪の方向に向かわせるような軸方向分力が発生するよう構成し、
前記２つの軌道輪の軌道面にそれぞれ引いた接線の交点は、ほぼ軸受中心軸線上でかつ前記平面よりも前記接触角の大きい方にあり、
前記交点と各玉の中心を結ぶ直線は玉のピッチ円外側では前記平面よりも前記接触角の小さい軌道輪の近くにあるように構成されたことを特徴とする低摩擦トルクスラスト玉軸受を提供する。
【００１６】
【実施の形態】
以下図を参照して本発明の実施の形態について説明する。
【００１７】
図１に示す第１の実施の形態において、軌道輪１と軌道輪２とは互いに軸方向に対向しており、軌道輪１は円弧状断面の軌道面１１を有し、また軌道輪２は円弧状断面の軌道面２１を有しており、軌道面１１と２１とは軸方向に向かい合ってその間に介装された複数個の玉４にそれぞれ接触している。
【００１８】
軌道輪１と２との間で玉の外周側には補助軌道輪３が嵌めてあり、補助軌道輪３は円弧状断面の軌道面３１を有しており、該軌道面３１が玉４に軸受外周側から接触して玉４を軌道輪１と２との間に保持している。
【００１９】
軌道輪２は径方向外向きに延びる肩部を有し、該肩部の補助軌道輪３に面する側に径方向に延びる案内面２３を有しており、そして補助軌道輪３にはこの案内面２３と軸方向に向かい合って案内面３３が設けてあり、案内面２３と３３とは互いに接触している。
【００２０】
補助軌道輪３の軌道面３１の断面の曲率半径中心３４は、軸受中心軸線Ｘ−Ｘに直角で玉４の中心４１を通る平面Ｙ−Ｙよりも軌道輪１に近い側にある。
【００２１】
玉４は、軌道輪１の軌道面１１とは接点１２で、軌道輪２の軌道面２１とは接点２２で、補助軌道輪３の軌道面３１とは接点３２で接触している。
【００２２】
接点１２および接点２２を通り軌道面に引いた接線１３および２４の交点Ｃ（コーンセンタ）はほぼ軸受中心軸線Ｘ−Ｘ上で、かつ上記平面Ｙ−Ｙよりも軌道輪２の側にあり、交点Ｃと各玉の中心４１とを結ぶ直線すなわち玉の自転軸は、玉のピッチ円の外側では平面Ｙ−Ｙよりも軌道輪１に近い自転軸中心点４２を通る。従って、軌道輪２の接触角の方が軌道輪１の接触角より大きい。
【００２３】
この軸受に第２図のようにアキシャル荷重Ｌａが加わると、軌道輪１と玉４との接点１２および軌道輪２と玉４との接点２２にはそれぞれアキシャル方向の分力Ｆａ１およびＦａ２と、それぞれラジアル方向の分力Ｆｒ１およびＦｒ２が発生する。
【００２４】
ラジアル方向分力Ｆｒ１とＦｒ２との反力の和Ｆｒ３は、補助軌道輪３を押し拡げるように軌道面３１と玉４との接点３２に作用する。軌道面３１の曲率半径中心３４が平面Ｙ−Ｙよりも軌道輪１に近い側にあるため、接点３２は平面Ｙ−Ｙよりも案内面を有する軌道輪２に近い側にある。従って軌道面３１にはＦｒ３と、補助軌道輪３を軌道輪２の方向に向かわせるような軸方向分力Ｆａ３が発生し、案内面３３と案内面２３とは軸方向分力Ｆａ３で押付けられる。そのため、何等かの原因で補助軌道輪３を軸方向に移動しようとする力が作用しても案内面２３と案内面３３とが離れず、補助軌道輪３が軸方向に安定に支持されることになり、軸方向の振動が抑えられて安定して回転することができる。
【００２５】
また、玉４と補助軌道輪３の軌道面３１との接点３２は、玉４の中心を含む平面Ｙ−Ｙよりも軌道輪２に近い側にあり、平面Ｙ−Ｙよりも軌道輪１に近い位置にある玉の自転軸中心点４２から遠くなる。従って図３に示すように、補助軌道輪３の軌道面３１と玉４との接触楕円ａの端から玉の自転軸中心点４２までの間の余裕ｓが大きくなり、補助軌道輪３の軌道面３１のかじりや焼き付きを防止できる。
【００２６】
しかし、図１に示す第１の実施の形態において、補助軌道輪３は玉４による軸方向分力Ｆａ３を受けながら案内面が摺動するので、案内面３３には軌道輪２の案内面２３との間に摩擦力が働き、この摩擦力が軸受の摩擦トルクを増加させ、また、案内面の潤滑が悪い場合には、案内面のかじりや焼き付きを生ずる危険もある。そこで、以下に示す実施の形態においては、案内面間の摩擦を少なくし軸受摩擦トルクを低減する構造とされている。
【００２７】
図４に示す第２の実施の形態は、補助軌道輪３の案内面に油溝３５を設けたもので、この結果、案内面の潤滑を良好に保つことができ、案内面の摩擦による軸受の摩擦トルクの増加と案内面のかじりや焼き付きを防ぐ効果が得られる。油溝は軌道輪２の肩部案内面に設けてもよい。
【００２８】
図５に示す第３の実施の形態は、補助軌道輪の案内面にＶ字形状の油溝３６を設けたもので、案内面において動圧流体軸受を形成するので、図４の第２の実施の形態より一層案内面の摩擦を低減し、軸受の摩擦トルクの増加と案内面のかじりや焼き付きを防ぐ効果を期待できる。この油溝も軌道輪２の案内面に設けてもよい。
【００２９】
図６に示す第４の実施の形態は、軌道輪２に油路３７、絞り３８、油室３９を設け、案内面に圧油を供給することによって、案内面において静圧軸受を形成するようにしたもので、図５の第３の実施の形態より更に一層軸受摩擦トルクを低減する効果がある。
【００３０】
一般に軌道輪と補助軌道輪とは同じ材質で構成されているので、このような場合には特に案内面にかじりや焼き付きを生じ易い。
【００３１】
図７に示す第５の実施の形態は、軌道輪肩部と補助軌道輪との案内面の少なくとも一方に潤滑を良好にする表面被膜処理や、軌道輪と異なる金属その他の溶射や焼き付けなどを施した被膜層５を設けたもので、案内面にかじりや焼き付きを生じにくくする効果が得られる。
【００３２】
図８に示す第６の実施の形態は、軌道輪の肩部と補助軌道輪の平面部との間に軌道輪と異なる材質の滑り部材６を挿入したもので、図７の第５の実施の形態と同様に、案内面のかじりや焼き付きを防ぐ効果が得られる。
【００３３】
図９に示す第７の実施の形態は、軌道輪の肩部と補助軌道輪の平面部とに玉軸受の溝をそれぞれ形成し、転がり部材７を挿入して案内面を転がり接触としたもので、摩擦の低減とかじりや焼き付きの防止に一層の効果が得られる。
【００３４】
【発明の効果】
本発明によれば、補助軌道輪が軸方向に安定に支持されるため、補助軌道輪の軸方向の振動の発生を防いで軸受が安定に回転する。また、本発明によれば、補助軌道輪の軌道面と玉との接触楕円から玉の自転軸中心点までの間の余裕が大きくなるため、ラジアル荷重や取付け誤差などによって２つの軌道輪の間に軸心の不一致が生じても、補助軌道輪の軌道面のかじりや焼き付きを防止し、案内面の潤滑を良好に保ち摩擦を低減する手段により、補助軌道輪の案内面の摩擦による軸受トルクの増加と案内面のかじりや焼き付きを防いで、低摩擦トルクで長寿命のスラスト玉軸受を実現することができる。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態の軸方向断面図である。
【図２】第１の実施の形態における力の関係を示す図である。
【図３】第１の実施の形態における補助軌道輪の軌道面と玉との接触楕円と玉の自転軸との関係を示す図である。
【図４】この発明の第２の実施の形態の案内面の例を示す図である。
【図５】この発明の第３の実施の形態の案内面の例を示す図である。
【図６】この発明の第４の実施の形態の軸方向部分断面図である。
【図７】この発明の第５の実施の形態の軸方向部分断面図である。
【図８】この発明の第６の実施の形態の軸方向部分断面図である。
【図９】この発明の第７の実施の形態の軸方向部分断面図である。
【図１０】従来技術の第１のタイプのスラスト玉軸受におけるかじりの例を示す図である。
【図１１】従来技術の第２のタイプのスラスト玉軸受におけるトルク低減効果の例を示す図である。
【図１２】従来技術の第２のタイプのスラスト玉軸受におけるかじりの例を示す図である。
【図１３】従来技術の第２のタイプのスラスト玉軸受をアンギュラ玉軸受に適用した場合のトルク低減効果の例を示す図である。
【符号の説明】
１、２軌道輪
３補助軌道輪
１１、２１、３１軌道面
１２、２２、３２軌道面と玉との接点
２３、３３案内面
３４補助軌道輪軌道面の円弧中心
４玉
４１玉の中心
４２玉の自転軸中心点
Ｘ−Ｘ軸受中心軸線[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a low friction torque thrust ball bearing. In particular, the present invention is a low-friction torque thrust suitable for applications requiring low friction, such as transmission rollers for traction drive continuously variable transmissions, support bearings for input members, machine tools, etc. Related to ball bearings.
[0002]
[Prior art]
The thrust ball bearing has a high spin at the contact point between the ball and the raceway surface of the raceway. Therefore, the friction torque of the bearing is particularly large when receiving a large axial load. In the case of a toroidal continuously variable transmission that uses this type of bearing as a support bearing for a transmission roller or an input / output member, the friction torque of the bearing This is a major factor that reduces power transmission efficiency.
[0003]
In order to correct the disadvantage that the friction torque of the thrust ball bearing is large as described above, the following two methods have been proposed.
[0004]
In the first type, the ball of the thrust ball bearing is biased toward the center axis of the bearing so that the rolling at the contact point between the ball and the raceway surface of the two race rings is close to the pure rolling. A thrust ball bearing provided with an auxiliary bearing ring (Collar) on the side.
[0005]
In this first type of thrust ball bearing, in order to eliminate friction loss due to ball spin on the raceway surface, an auxiliary raceway is fitted on the outer periphery of the ball, and the ball is brought inside the pitch circle so that the raceway of the two raceways The contact point between the ball and the raceway surface so that the intersection (cone center) of the tangent line that passes through the contact point between the surface and the ball and is drawn on the raceway surface is on the plane including the center of the ball and on the bearing center axis. The rolling in is a pure rolling.
[0006]
As a result, in this first type of thrust ball bearing, the raceway surface of the auxiliary raceway ring and the ball come into contact with each other on a plane that is perpendicular to the bearing center axis and includes the center of the ball. Since it lies on a plane including the center of the ball, the contact point between the raceway surface of the auxiliary race and the ball and the center of rotation of the ball coincide. Therefore, the friction loss due to the spin of the ball on the raceway surface is eliminated, and the motion at the contact point between the raceway surface and the ball of the auxiliary raceway is only a spin motion with a low sliding speed, and the friction loss is reduced, so that it becomes a normal thrust bearing. In comparison, the friction torque is greatly reduced.
[0007]
In addition, the second type of conventional thrust ball bearing adds an angular ball bearing element to the first type to give a difference in the contact angle on the raceway surfaces of the two race rings. By deviating the cone center in the first type of thrust ball bearing from the plane including the center of the ball in the axial direction of the bearing, the contact point between the auxiliary ring and the ball on the plane including the center of the ball is By making the position different from the center of the rotation axis, the relative motion at the contact point between the auxiliary ring and the ball is the spin motion plus the rolling motion (see US Pat. No. 1,423,666). .
[0008]
[Problems to be solved by the invention]
In the thrust ball bearing of the first type in the prior art, since the pure spin motion is performed at the contact point between the raceway surface of the auxiliary race and the ball, the lubricant is not replenished in the contact surface, and the load of the bearing is reduced. Except when it is extremely small, the contact point is galled and worn (see FIG. 10). This is described on page 1, lines 61-72 of U.S. Pat. No. 1,423,666 for the second type of prior art described above.
[0009]
The second type of the above prior art is for solving the above-mentioned drawbacks of the first type, and the relative motion at the contact point between the auxiliary track ring and the ball is added to the spin motion by rolling motion. In this way, the lubricant is supplied to the contact surface. By this method, even when the load is large, the effect of preventing galling and wear of the contact point can be obtained.
[0010]
As a result of testing this bearing, the effect of reducing the friction torque of the bearing by this method was clarified (see FIG. 11). However, also in this bearing, the rotation axis of the ball is close to a direction perpendicular to the bearing center axis (the above-mentioned first If the center of rotation of the ball is in the contact ellipse between the raceway surface of the auxiliary raceway and the ball, the raceway surface of the auxiliary raceway will be galled or worn, Even if the rotation axis center is slightly out of the contact ellipse, once a slight galling occurs, the balance of force will be lost, and the auxiliary bearing ring without axial support will vibrate in the axial direction and the galling will spread rapidly ( It became clear that it was difficult to continue the operation of the bearing. Accordingly, the center of rotation of the ball must be out of contact ellipse between the raceway surface of the auxiliary raceway and the ball.
[0011]
In addition, under normal operating conditions, not only pure axial load, but also radial load and eccentric load are applied, and due to mounting error, the axis of rotation and the fixed shaft will not match, and the rotation axis of the ball will fluctuate. The rotation axis of the ball is not always in the direction determined when designing the bearing. Therefore, it is necessary that the center of rotation of the ball in the case of a pure axial load be separated from the contact ellipse between the raceway surface of the auxiliary raceway and the ball with a certain margin.
[0012]
However, the fact that the center of rotation of the ball is separated from the contact ellipse between the raceway surface of the auxiliary raceway and the ball with a certain margin means that the thrust ball bearing (contact angle 90 °) approaches the angular ball bearing. As a result, the vertical force of the ball due to the axial load increases, and the radius of curvature of the raceway surface in the rolling direction is smaller than ∞ in the case of a thrust ball bearing (convex surface), so the contact surface pressure of the raceway surface is It increases, and the life of the bearing is reduced to a degree that cannot be ignored. In addition, the friction torque of the angular ball bearing has a smaller effect of reducing the friction torque of the bearing by the auxiliary raceway than in the case of the thrust ball bearing (see FIG. 13).
[0013]
Therefore, in a ball bearing that receives a large axial load, it is difficult to achieve a significant reduction in bearing friction torque while preventing a decrease in bearing life.
[0014]
The present invention is directed to overcoming these deficiencies in the prior art.
[0015]
[Means for solving the problems]
In the first aspect of the present invention , two race rings having raceway surfaces each including an arcuate cross section facing each other in the axial direction, and a plurality of balls that are in contact with the raceway surfaces and interposed between the raceways A raceway surface including an arc-shaped cross section on the inner circumference side, the inner circumference raceway surface comes into contact with these balls from the outer circumference side to bias the balls toward the bearing center axis , The point of contact between the ball and the raceway surface by bringing the intersection of the tangent line drawn through the contact surface between the raceway surface of the raceway and the ball to the raceway surface to a position on the plane including the center of the ball and on the bearing center axis. In a thrust ball bearing comprising a bearing ring for holding between the race rings so that the rolling in the ring approaches a pure rolling, the contact angles on the raceway surfaces of these two race rings are different.
With respect to the thrust load applied to the ball bearing, the inner raceway surface of the auxiliary raceway has an axial component force that directs the auxiliary raceway toward the raceway having the larger contact angle. Configured to occur ,
A low-friction torque thrust ball characterized in that a guide surface that contacts each other is provided on a shoulder portion on the outer side of the raceway of the raceway having the larger contact angle and a flat portion of the auxiliary raceway ring facing the shoulder portion. Provide bearings.
In the low friction torque thrust ball bearing according to the first aspect of the present invention, it is preferable that the guide surface has a structure that reduces friction between the guide surfaces and reduces the bearing friction torque.
In the second aspect of the present invention, two raceways having raceway surfaces each including an arcuate cross section facing each other in the axial direction, and a plurality of balls that are in contact with the raceway surfaces and interposed between the raceways A raceway surface including an arc-shaped cross section on the inner circumference side, the inner circumference raceway surface comes into contact with these balls from the outer circumference side to bias the balls toward the bearing center axis, The point of contact between the ball and the raceway surface by bringing the intersection of the tangent line drawn through the contact surface between the raceway surface of the raceway and the ball to the raceway surface to a position on the plane including the center of the ball and on the bearing center axis. In a thrust ball bearing comprising a bearing ring for holding between the race rings so that the rolling in the ring approaches a pure rolling, the contact angles on the raceway surfaces of these two race rings are different.
With respect to the thrust load applied to the ball bearing, the inner raceway surface of the auxiliary raceway has an axial component force that directs the auxiliary raceway toward the raceway having the larger contact angle. Configured to occur,
Provided is a low-friction torque thrust ball bearing characterized in that the center of curvature radius of the arc-shaped cross section of the raceway surface of the auxiliary raceway is closer to the raceway having a smaller contact angle than the plane including the center of the ball To do.
In the third aspect of the present invention, two race rings having raceway surfaces each including an arcuate cross section facing each other in the axial direction, and a plurality of balls that are in contact with the raceway surfaces and interposed between the raceways A raceway surface including an arc-shaped cross section on the inner circumference side, the inner circumference raceway surface comes into contact with these balls from the outer circumference side to bias the balls toward the bearing center axis, The point of contact between the ball and the raceway surface by bringing the intersection of the tangent line drawn through the contact surface between the raceway surface of the raceway and the ball to the raceway surface to a position on the plane including the center of the ball and on the bearing center axis. In a thrust ball bearing comprising a bearing ring for holding between the race rings so that the rolling in the ring approaches a pure rolling, the contact angles on the raceway surfaces of these two race rings are different.
With respect to the thrust load applied to the ball bearing, the inner raceway surface of the auxiliary raceway has an axial component force that directs the auxiliary raceway toward the raceway having the larger contact angle. Configured to occur,
The intersection of the tangent lines drawn on the raceway surfaces of the two race rings is substantially on the bearing center axis and on the larger contact angle than the plane,
Provided is a low-friction torque thrust ball bearing characterized in that a straight line connecting the intersection and the center of each ball is located near the raceway having a smaller contact angle than the plane outside the ball pitch circle. To do.
[0016]
Embodiment
Embodiments of the present invention will be described below with reference to the drawings.
[0017]
In the first embodiment shown in FIG. 1, the bearing ring 1 and the bearing ring 2 face each other in the axial direction, the bearing ring 1 has a raceway surface 11 having an arc-shaped cross section, and the bearing ring 2 is The raceway surface 21 has an arc-shaped cross section, and the raceway surfaces 11 and 21 face each other in a plurality of balls 4 that face each other in the axial direction and are interposed therebetween.
[0018]
An auxiliary raceway ring 3 is fitted between the raceway rings 1 and 2 on the outer peripheral side of the ball, and the auxiliary raceway ring 3 has a raceway surface 31 having an arcuate cross section. The ball 4 is held between the bearing rings 1 and 2 in contact with the outer peripheral side of the bearing.
[0019]
The track ring 2 has a shoulder portion extending radially outward, and has a guide surface 23 extending in the radial direction on the side of the shoulder portion facing the auxiliary track ring 3. A guide surface 33 is provided facing the guide surface 23 in the axial direction, and the guide surfaces 23 and 33 are in contact with each other.
[0020]
The center of curvature radius 34 of the cross section of the raceway surface 31 of the auxiliary raceway ring 3 is closer to the raceway ring 1 than the plane YY perpendicular to the bearing center axis line XX and passing through the center 41 of the ball 4.
[0021]
The ball 4 is in contact with the raceway surface 11 of the raceway ring 1 at the contact point 12, the raceway surface 21 of the raceway ring 2 at the contact point 22, and the contact raceway 31 of the auxiliary raceway ring 3 at the contact point 32.
[0022]
The intersection C (cone center) of the tangents 13 and 24 drawn through the contact points 12 and 22 to the raceway surface is substantially on the bearing center axis line XX and closer to the raceway ring 2 than the plane YY. A straight line connecting the intersection C and the center 41 of each ball, that is, the rotation axis of the ball passes through a rotation axis center point 42 closer to the raceway 1 than the plane YY outside the pitch circle of the ball. Therefore, the contact angle of the track ring 2 is larger than the contact angle of the track ring 1.
[0023]
When axial load La as in the second diagram the bearing is applied, the bearing ring 1 and the contact point 12 and the bearing ring 2 and each of the contacts 22 minute force of the axial direction of the balls 4 Fa1 and Fa2 the balls 4, Radial component forces Fr1 and Fr2 are generated, respectively.
[0024]
The sum Fr3 of the reaction force of the radial component forces Fr1 and Fr2 acts on the contact 32 between the raceway surface 31 and the ball 4 so as to expand the auxiliary raceway ring 3. Since the radius of curvature center 34 of the raceway surface 31 is closer to the raceway 1 than the plane YY, the contact 32 is closer to the raceway 2 having the guide surface than the plane YY. Therefore, Fr3 and an axial component force Fa3 that causes the auxiliary raceway ring 3 to be directed in the direction of the raceway ring 2 are generated on the raceway surface 31, and the guide surface 33 and the guide surface 23 are pressed by the axial component force Fa3. . Therefore, even if a force for moving the auxiliary track ring 3 in the axial direction is applied for some reason, the guide surface 23 and the guide surface 33 are not separated from each other, and the auxiliary track ring 3 is stably supported in the axial direction. That is, the vibration in the axial direction is suppressed and the rotation can be stably performed.
[0025]
The contact point 32 between the ball 4 and the raceway surface 31 of the auxiliary raceway ring 3 is closer to the raceway ring 2 than the plane YY including the center of the ball 4 and is closer to the raceway ring 1 than the plane YY. It is far from the rotation axis center point 42 of the ball at a close position. Therefore, as shown in FIG. 3, the margin s from the end of the contact ellipse a between the raceway surface 31 of the auxiliary raceway 3 and the ball 4 to the center axis 42 of the ball's rotation axis is increased, and the track of the auxiliary raceway 3 is increased. It is possible to prevent the surface 31 from galling and seizing.
[0026]
However, in the first embodiment shown in FIG. 1, the guide raceway slides while the auxiliary raceway ring 3 receives the axial component force Fa <b> 3 by the balls 4, so that the guide surface 33 has the guide surface 23 of the raceway ring 2. A frictional force acts between the two, and this frictional force increases the frictional torque of the bearing, and when the guide surface is poorly lubricated, there is a risk that the guide surface will be galled or seized. Therefore, in the following embodiment, the structure is such that the friction between the guide surfaces is reduced and the bearing friction torque is reduced.
[0027]
In the second embodiment shown in FIG. 4, an oil groove 35 is provided on the guide surface of the auxiliary raceway ring 3. As a result, the guide surface can be kept in good lubrication, and the bearing caused by friction of the guide surface can be maintained. The effect of preventing the friction torque from increasing and rubbing and seizing of the guide surface can be obtained. The oil groove may be provided on the shoulder guide surface of the raceway ring 2.
[0028]
In the third embodiment shown in FIG. 5, a V-shaped oil groove 36 is provided on the guide surface of the auxiliary raceway, and a hydrodynamic bearing is formed on the guide surface. Therefore, the second embodiment shown in FIG. The effect of reducing the friction of the guide surface more than that of the embodiment and preventing the bearing friction torque from increasing and the guide surface from galling or seizing can be expected. This oil groove may also be provided on the guide surface of the raceway ring 2.
[0029]
In the fourth embodiment shown in FIG. 6, an oil passage 37, a throttle 38, and an oil chamber 39 are provided in the raceway ring 2, and a hydrostatic bearing is formed on the guide surface by supplying pressure oil to the guide surface. Thus, the bearing friction torque can be further reduced as compared with the third embodiment shown in FIG.
[0030]
In general, since the raceway ring and the auxiliary raceway ring are made of the same material, in such a case, the guide surface is particularly likely to be galled or seized.
[0031]
In the fifth embodiment shown in FIG. 7, the surface coating treatment for improving the lubrication on at least one of the guide surfaces of the bearing ring shoulder portion and the auxiliary raceway ring, the thermal spraying or baking of metal other than the raceway ring, etc. By providing the applied coating layer 5, an effect of making it difficult to cause galling or seizure on the guide surface is obtained.
[0032]
In the sixth embodiment shown in FIG. 8, a sliding member 6 made of a material different from that of the raceway ring is inserted between the shoulder portion of the raceway ring and the flat portion of the auxiliary raceway ring. As in the case of, the effect of preventing the guide surface from galling and seizing can be obtained.
[0033]
In the seventh embodiment shown in FIG. 9, ball bearing grooves are respectively formed in the shoulder portion of the raceway ring and the flat portion of the auxiliary raceway ring, and the rolling member 7 is inserted to make the guide surface in rolling contact. Thus, further effects can be obtained in reducing friction and preventing galling and seizure.
[0034]
【The invention's effect】
According to the present invention, since the auxiliary track ring is stably supported in the axial direction, generation of vibration in the axial direction of the auxiliary track ring is prevented and the bearing rotates stably. In addition, according to the present invention, the margin between the contact ellipse between the raceway surface of the auxiliary raceway and the ball and the center point of the ball's rotation axis is increased. Even if there is a discrepancy in the shaft center, the bearing torque due to friction on the guide surface of the auxiliary raceway is reduced by means of preventing scuffing and seizure of the raceway surface of the auxiliary raceway, maintaining good lubrication of the guide surface and reducing friction. The thrust ball bearing can be realized with a low friction torque and a long service life.
[Brief description of the drawings]
FIG. 1 is an axial sectional view of a first embodiment of the present invention.
FIG. 2 is a diagram showing a force relationship in the first embodiment.
FIG. 3 is a diagram showing a relationship between a contact ellipse between a raceway surface of an auxiliary race and a ball and a rotation axis of the ball in the first embodiment.
FIG. 4 is a diagram showing an example of a guide surface according to a second embodiment of the present invention.
FIG. 5 is a diagram showing an example of a guide surface according to a third embodiment of the present invention.
FIG. 6 is a partial axial sectional view of a fourth embodiment of the present invention.
FIG. 7 is a partial axial sectional view of a fifth embodiment of the present invention.
FIG. 8 is a partial axial sectional view of a sixth embodiment of the present invention.
FIG. 9 is a partial axial sectional view of a seventh embodiment of the present invention.
FIG. 10 is a diagram showing an example of galling in a first type thrust ball bearing of the prior art.
FIG. 11 is a diagram showing an example of a torque reduction effect in a second type thrust ball bearing of the prior art.
FIG. 12 is a view showing an example of scoring in a second type thrust ball bearing of the prior art.
FIG. 13 is a diagram showing an example of a torque reduction effect when a second type of thrust ball bearing of the prior art is applied to an angular ball bearing.
[Explanation of symbols]
1, 2, raceway 3, auxiliary raceway 11, 21, 31 raceway surface 12, 22, 32 contact point 23, 33 guide surface 34, guide surface 34 arc center of auxiliary raceway raceway surface 4 ball 41 center of ball 42 ball Rotation shaft center point XX Bearing center axis

Claims

Two race rings each having a raceway surface including an arcuate cross section facing each other in the axial direction;
A plurality of balls that are in contact with the raceway surfaces and interposed between the raceways,
The two race rings have a raceway surface including an arcuate cross section on the inner circumference side, the inner circumference raceway surface comes into contact with these balls from the outer circumference side, and the balls are biased toward the bearing center axis. The contact point between the ball and the raceway surface is brought closer to the position on the plane that includes the center of the ball and on the bearing center axis by bringing the intersection point of the tangent line that passes through the contact point between the raceway surface and the ball into the raceway surface. It consists of an auxiliary track ring for holding the movement between the track rings so that the movement approaches a pure rolling,
In thrust ball bearings with different contact angles on the raceway surfaces of these two race rings,
Against the thrust load applied to the該玉bearing, the inner peripheral raceway surface of the auxiliary bearing ring, the axial component of force that directs the direction of the larger bearing ring of the auxiliary bearing ring wherein the contact angle Configured to occur ,
A low-friction torque thrust ball characterized in that a guide surface that contacts each other is provided on a shoulder portion on the outer side of the raceway of the raceway having the larger contact angle and a flat portion of the auxiliary raceway ring facing the shoulder portion. bearing.

Two race rings each having a raceway surface including an arcuate cross section facing each other in the axial direction;
A plurality of balls that are in contact with the raceway surfaces and interposed between the raceways,
The two race rings have a raceway surface including an arcuate cross section on the inner circumference side, the inner circumference raceway surface comes into contact with these balls from the outer circumference side, and the balls are biased toward the bearing center axis. The contact point between the ball and the raceway surface is brought closer to the position on the plane that includes the center of the ball and on the bearing center axis by bringing the intersection point of the tangent line that passes through the contact point between the raceway surface and the ball into the raceway surface. It consists of an auxiliary track ring for holding the movement between the track rings so that the movement approaches a pure rolling,
In thrust ball bearings with different contact angles on the raceway surfaces of these two race rings,
With respect to the thrust load applied to the ball bearing, the inner raceway surface of the auxiliary raceway has an axial component force that directs the auxiliary raceway toward the raceway having the larger contact angle. Configured to occur,
A low-friction torque thrust ball bearing, characterized in that the center of curvature radius of the arc-shaped cross section of the raceway surface of the auxiliary raceway is closer to the raceway having a smaller contact angle than the plane including the center of the ball.

Two race rings each having a raceway surface including an arcuate cross section facing each other in the axial direction;
A plurality of balls that are in contact with the raceway surfaces and interposed between the raceways,
The two race rings have a raceway surface including an arcuate cross section on the inner circumference side, the inner circumference raceway surface comes into contact with these balls from the outer circumference side, and the balls are biased toward the bearing center axis. The contact point between the ball and the raceway surface is brought closer to the position on the plane that includes the center of the ball and on the bearing center axis by bringing the intersection point of the tangent line that passes through the contact point between the raceway surface and the ball into the raceway surface. It consists of an auxiliary track ring for holding the movement between the track rings so that the movement approaches a pure rolling,
In thrust ball bearings with different contact angles on the raceway surfaces of these two race rings,
With respect to the thrust load applied to the ball bearing, the inner raceway surface of the auxiliary raceway has an axial component force that directs the auxiliary raceway toward the raceway having the larger contact angle. Configured to occur,
The intersection of the tangents is approximately on the bearing center axis and on the larger contact angle than the plane,
A low friction torque thrust ball bearing, characterized in that a straight line connecting the intersection and the center of each ball is located near the raceway having a smaller contact angle than the plane outside the ball pitch circle.

The low friction torque thrust ball bearing according to claim 1, wherein the guide surface has a structure that reduces friction between the guide surfaces and reduces bearing friction torque.