JP2004036741A

JP2004036741A - Assembly of rolling bearing and shaft, and rolling bearing

Info

Publication number: JP2004036741A
Application number: JP2002194138A
Authority: JP
Inventors: Hideto Torisawa; 鳥澤　秀斗
Original assignee: NTN Corp; NTN Toyo Bearing Co Ltd
Current assignee: NTN Corp
Priority date: 2002-07-03
Filing date: 2002-07-03
Publication date: 2004-02-05
Anticipated expiration: 2022-07-03
Also published as: JP4334184B2

Abstract

<P>PROBLEM TO BE SOLVED: To prevent abnormal heating and premature peeling of a bearing by reducing a radial clearance between double-row raceways after fitting. <P>SOLUTION: This assembly comprises the double-row rolling bearing 1 in which the inner diameter surface 2c of an inner ring 2 is formed in a tapered surface and a shaft 6 having a tapered portion 6a fitted to the inner diameter surface 2c of the inner ring. A difference ▵α in taper angle between the tapered portion 6a of the shaft 6 and the inner diameter surface 2c of the inner ring is set within the range of -9 to +3 sec. when a bearing width is 37 mm or wider and within -15 to +9 sec. when the bearing width is 37 mm or narrower. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
この発明は、工作機械の主軸等に使用される、軸受内径面をテーパ面とした転がり軸受と軸との組立体、および転がり軸受に関する。
【０００２】
【従来の技術】
軸受に高速性および高精度を要求される工作機械の主軸等において、内輪内径面をテーパ面とした転がり軸受を使用したものがある。この様な用途では、軸受のラジアル隙間が過大の場合に、主軸精度の悪化の問題を、ラジアル隙間が過小の場合には軸受の異常発熱および早期剥離等の問題を発生することがあり、軸受のラジアル隙間調整が重要となっている。このため上記テーパ面の作用により、軸に嵌め合った内輪を膨張させ、その膨張量を軸方向の圧入の深さで調整することによって、ラジアル隙間を調整可能としている。
【０００３】
図４は、この種の従来の軸受の一例を示す。複列の軸受１は、内輪鍔付きの円筒ころ軸受であり、内輪２および外輪３に、軸方向に並ぶ２列の軌道面２ａ，２ｂ，３ａ，３ｂを有している。外輪３の軌道面３ａ，３ｂは連続した円筒面に形成されている。各列の転動体４ａ，４ｂは、保持器（図示せず）により保持されている。内輪２の内径面２ｃはテーパ面とされ、軸６のテーパ部分６ａの外周に嵌め合っている。軸受のラジアル内部隙間δは、上記のようにテーパ面を利用して軸６を圧入し、内輪２を膨張させることで、調整が可能である。
【０００４】
【発明が解決しようとする課題】
内輪２の内径面２ｃはテーパ形状であるため、各軌道面２ａ，２ｂで内輪内径面から軌道面２ａ，２ｂまでの肉厚ｔ１，ｔ２が異なる。嵌め合いによる軌道面２ａ，２ｂの膨張量は、肉厚の大小によって変化するため、図５に強調して示すように、２列の軌道面２ａ，２ｂ間でラジアル隙間の相互差δ_Ｓが出る。この相互差δ_Ｓは、各列間の膨張量差Ｓとなる。
この相互差δ_Ｓが大きい場合、ラジアル隙間が小さい列の転動体４ａに軸受荷重が集中するため、軸受の異常発熱および早期剥離が発生する恐れがある。また軸６と内輪２とのテーパ角度精度が悪く、軸６と内輪２とで極端に不均一な嵌め合いをする場合、上記発熱，早期剥離の不具合が発生する確率が高くなる。
【０００５】
この発明の目的は、嵌め合い後における複列の軌道面間のラジアル隙間の相互差が小さく、軸受の異常発熱および早期剥離を防止することのできる転がり軸受と軸との組立体を提供することである。
この発明の他の目的は、嵌め合い後における複列の軌道面間のラジアル隙間の相互差が小さくでき、軸受の異常発熱および早期剥離を防止することのできる転がり軸受を提供することである。
【０００６】
【課題を解決するための手段】
この発明における第１の発明の転がり軸受と軸との組立体は、内輪の内径面をテーパ面とした複列の転がり軸受と、上記内輪の内径面に締まり嵌め状態に嵌合するテーパ部分を有する軸とよりなり、上記軸のテーパ部分と内輪の内径面とのテーパ角度の差（軸のテーパ角度−内輪内径面のテーパ角度）を、
軸受幅が３７ｍｍより大きい場合は、−９秒〜＋３秒の範囲とし、
軸受幅が３７ｍｍ以下の場合は、−１５秒〜＋９秒の範囲、
としたことを特徴とする。
この構成によると、テーパ角度の差を上記の範囲に設定したため、軸と軸受とを嵌め合った後の２列の軌道面間で、ラジアル隙間の相互差が所定値よりも小さくなる。そのため、片方の転動体列への軸受荷重の集中がなく、軸受の異常発熱や早期剥離が防止される。
【０００７】
この発明における第２の発明の転がり軸受と軸との組立体は、内輪の内径面をテーパ面とした複列の転がり軸受と、上記内輪の内径面に締まり嵌め状態に嵌合するテーパ部を有する軸とよりなり、上記内輪の内径面を所望の基準テーパ角度を狙って製作し、かつ軸の上記テーパ部分のテーパ角度を上記基準テーパ角度に対して−３秒を狙って製作したときに、上記軸のテーパ部分および内輪内径面の狙い角度に対するテーパ角度の許容差を、
軸受幅が３７ｍｍより大きい場合は、軸、内輪共に、−３秒〜＋３秒の範囲とし、
軸受幅が３７ｍｍ以下の場合は、軸、内輪共に、−６秒〜＋６秒の範囲、
としたことを特徴とする。
この構成の場合、軸のテーパ部分および内輪内径面の狙い角度に対する加工後のテーパ角度の許容差を上記の範囲としたため、軸と軸受とを嵌め合った後の２列の軌道面間で、ラジアル隙間の相互差が所定値よりも小さくなる。そのため、片方の転動体列への軸受荷重の集中がなく、軸受の異常発熱や早期剥離が防止される。
【０００８】
この発明における第３の発明の転がり軸受は、内輪の内径面をテーパ面とした複列の転がり軸受において、内輪の軌道面、外輪の軌道面、およびこれら内外輪の軌道面間に介在した転動体によって定まる各列のラジアル隙間に相互差を持たせたことを特徴とする。
この構成の場合、軸受単体の状態で、各列のラジアル隙間に予め相互差を持たせているので、軸と軸受との嵌め合いの際、内輪内径面のテーパ面に基づく軌道面の各列間の膨張差を、予め設定した相互差で吸収させることができる。したがって、これにより嵌め合い後の各列のラジアル隙間の相互差を小さくすることができ、特定列への軸受荷重の集中がなく、軸受の異常発熱や早期剥離が防止される。なお、各例のラジアル隙間に相互差を与えるには、例えば各列で互いに転動体に外径の異なるものを用い、内輪および外輪の軌道面の径は両列で同じとしても良い。
【０００９】
【発明の実施の形態】
この発明の第１および第２の実施形態を図１と共に説明する。この転がり軸受と軸との組立体は、複列の転がり軸受１と軸６とよりなり、転がり軸受１の内輪２の内径面２ｃがテーパ面とされ、軸６が内輪２の内径面２ｃに嵌合するテーパ部分６ａを有するものである。軸６は、例えば工作機械における主軸である。
転がり軸受１の内輪２および外輪３は、軸方向に並ぶ２列の軌道面２ａ，２ｂ，３ａ，３ｂを有し、対向する軌道面間に、各列の転動体４ａ，４ｂが配置されている。各列の転動体４ａ，４ｂは、各列毎に設けられた保持器５に保持されている。この転がり軸受１は、円筒ころ軸受であって、転動体４はころからなる。内輪２は、両側および中央に鍔７，８を有し、外輪３は鍔無しのものとされて、２列の軌道面３ａ，３ｂは連続した円筒面に形成されている。
内輪２、外輪３、および転動体４ａ，４ｂの材質は、軸受鋼等の鋼製とされている。以上を基本構成とする。
【００１０】
第１の実施形態は上記基本構成において、軸６のテーパ部分６ａと内輪２の内径面２ｃとのテーパ角度の差（軸のテーパ角度−内輪内径面のテーパ角度）を、
軸受幅Ｂが３７ｍｍより大きい場合は、−９秒〜＋３秒の範囲とし、
軸受幅Ｂが３７ｍｍ以下の場合は、−１５秒〜＋９秒の範囲、
としたものである。
【００１１】
第２の実施形態は上記基本構成において、内輪２の内径面２ｃを所望の基準テーパ角度を狙って製作し、かつ軸６のテーパ部分６ａのテーパ角度を上記基準テーパ角度に対して−３秒を狙って製作する。この場合に、上記軸６のテーパ部分６ａおよび内輪内径面２ｃの狙い角度に対するテーパ角度の許容差を、
軸受幅Ｂが３７ｍｍより大きい場合は、軸６、内輪２共に、−３秒〜＋３秒の範囲とし、
軸受幅Ｂが３７ｍｍ以下の場合は、軸６、内輪２共に、−６秒〜＋６秒の範囲とする。
上記所望の基準テーパ角度は、例えば、通常に採用されているテーパ比である基準テーパ比１／１２または１／３０とする。
【００１２】
これら第１の実施形態および第２の実施形態の構成によると、いずれも、２列の軌道面２ａ，２ｂ間でラジアル隙間の相互差が小さくなり、転がり軸受１の異常発熱および早期剥離を防止することができる。以下にその理由を説明する。
【００１３】
軸６に嵌め合った内輪２の、２列の軌道面２ａ，２ｂの膨張量差は、
（１）　軸６のテーパ角度と内輪内径面２ｃのテーパ角度との角度差、および
（２）　内輪２の締代、
を基に計算され、以下の式で表されることがＦＥＭ（有限要素法）解析および実験検証を行った結果、判明した。
Ｓ＝ａ×Δα＋ｂ×Ｙ＋ｃ　　　　　　　　　　　　　　　　　　……（１）
ただし、
Ｓ：内輪の２列の軌道面の膨張量差（μｍ）、
（＝内輪内径面の大径側の軌道径膨張量−小径側の軌道径膨張量）、
Δα：軸テーパ角度と内輪内径面テーパ角度との角度差（秒）、
（＝軸テーパ角度−軸受内径面テーパ角度）、
Ｙ：内輪内径面小径側の軌道面の軸方向中心に与えられる内輪の締代（μｍ）
ａ，ｂ，ｃ：使用する軸と軸受の組合せ毎に設定される定数。
定数ａ，ｂ，ｃは、ＦＥＭ解析または実験によって決定される数値である。
【００１４】
工作機械の主軸として通常使用される内輪の締代Ｙの範囲において、２列の軌道面２ａ，２ｂの膨張量差Ｓが±１μｍ以下となる軸テーパ角度と内輪内径面テーパ角度との角度差Δαを、上記（１）式を用いて種々の型番の軸受について計算した結果、図２を得た。膨張量差Ｓを±１μｍ以下としたのは、これまでの経験から、軸受に異常発熱および早期剥離等の問題が生じないとわかる略最大の範囲として規定したものである。同図の縦軸には軸受幅Ｂをとっている。
【００１５】
図２より、軸受幅Ｂが３７ｍｍより大きい軸受では、角度差Δαを約−９秒から＋３秒（中央値−３秒）とし、軸受幅Ｂが３７ｍｍ以下の軸受では、角度差Δαを約−１５秒から＋９秒（中央値−３秒）とすれば、２列の軌道面２ａ，２ｂの膨張量差Ｓが±１μｍ以下となることがわかる。厳密に言えば、型番毎に角度差Δαの範囲が異なりその中央値も異なることが図２よりわかるが、型番毎に狙い値（中央値）を変更するのは製作の都合上不便である。したがって、上記の様に角度差Δαの範囲を決定した。
【００１６】
通常の軸受は、内輪内径面２ｃのテーパ面として基準テーパ比１／１２または１／３０が用いられ製作される。図２より角度差Δαは中央値−３秒とすれば良いことがわかっているため、軸のテーパ角度としては内輪内径面のテーパ基準角度−３秒で製作すれば良いことになる。
また、上記角度差Δαの範囲を軸受と軸のテーパ角度に許容差として振り当てると、軸受内径面のテーパ面を所望の基準角度を狙って製作し、軸のテーパ部分を、内輪内径面の基準角度−３秒を狙って製作したときに、軸受幅Ｂが３７ｍｍより大きい場合は、軸６、内輪２ともに±３秒となり、軸受幅Ｂが３７ｍｍ以下の場合、軸６、内輪２ともに±６秒となる。このようにして軸６と内輪２のテーパ角度を製作すると、内輪２と軸６とが嵌め合った後、２列の軌道面２ａ，２ｂ間でのラジアル隙間の相互差は±１μｍとなる。そのため、転がり軸受１の異常発熱および早期剥離を防止することができる。
【００１７】
つぎに、この発明の第３の実施形態を図３と共に説明する。この実施形態は、図１と共に説明した基本構成において、その転がり軸受１につき、計算によって内輪２の２列の軌道面２ａ，２ｂの膨張量差を見込み、その量を軸受単体時のラジアル隙間相互差（各列のラジアル隙間の差）として与えておくものである。
例えば、軸受組み込み時に内輪２のＡ列の軌道面２ａのラジアル隙間よりもＢ列の方が１μｍ大きく膨張することが計算される場合、軸受単体時ではＢ列の軌道面２ｂのラジアル隙間をＡ列よりも１μｍ小さくしておく。Ｂ列のラジアル隙間を小さくするには、例えばＢ列の転動体４ｂにＡ列の転動体４ａよりも大きなものを用いる。
この結果、転がり軸受１を軸６に組み込んだ時のラジアル隙間を各列の軌道面２ａ，２ｂで同一とすることができる。この方法は、内輪内径面のテーパ角度と同一角度に軸６のテーパ角度を現合加工する場合に特に有効である。軸６のテーパ角度を内輪内径面２ｃに現合加工する場合にこの方法を用いれば、角度差Δαにばらつきが無く、常に角度差Δα＝０となるため、より正確に膨張量差Ｓを小さくすることができる。また、軸６と内輪内径面２ｃのテーパ角度を測定したうえで、軸受単体時のラジアル隙間相互差を計算によって決定し、採用しても良い。
【００１８】
なお、上記各実施形態は円筒ころ軸受を例にして説明を行ったが、この発明は内輪内径面をテーパ面とした複列の転がり軸受と軸であれば、他の形式の軸受にも適用することができる。
【００１９】
【実施例】
（実施例１）
図１と共に説明した第１の実施形態において、転がり軸受１の各部の寸法を次の値とした。すなわち内輪２の内径Ｄ１＝１３０ｍｍ、外径Ｄ２＝２００ｍｍ、軸受幅Ｂ＝５２ｍｍとした。軸６は中空軸であり、内径ｄ_ｉは７８ｍｍである。
この寸法の転がり軸受１の場合、上記（１）式は下記（２）式となることがＦＥＭ解析によって求められた。
Ｓ＝０．１０６４×Δα＋０．００９２×Ｙ＋０．００４　　　……（２）
この時、軸６のテーパ部分６ａのテーパ角度を、基準角度＋９秒±３秒、内輪内径面２ｃのテーパ角度を基準角度＋１２秒±３秒で加工した。つまり、角度差Δα＝−９〜＋３となる。
【００２０】
この実施例の軸受１の場合、工作機械の主軸として通常使用される内輪２の締代Ｙの範囲は、２０〜７０μｍであり、角度差ΔαとＹを（２）式に代入すると、Ｓ＝−０．７７〜＋０．９７μｍとなる。したがって、軸６と内輪２との嵌め合いによる２列の軌道面２ａ，２ｂの膨張量差Ｓは１μｍ以下に抑えられる。そのため、軸受１に異常発熱および早期剥離が発生する可能性を低くすることができる。
【００２１】
（実施例２）
図３と共に説明した第３の実施形態において、実施例１と同じく、図１のように軸受内輪２の内径Ｄ１＝１３０ｍｍ、外径Ｄ２＝２００ｍｍ、軸受幅Ｂ＝５２ｍｍとした。軸６は中空軸であり、内径ｄ_ｉは７８ｍｍである。
この場合に、軸６のテーパ部分６ａのテーパ角度が基準角度＋６秒、内輪内径面２ｃのテーパ角度が基準角度＋１４秒となっていることが分かった。つまり、角度差Δα＝６−１４＝−８、である。
内輪２の締代Ｙの範囲は、２０〜７０μｍであるため、（２）式により軸６と内輪２との嵌め合いによる２列の軌道面２ａ，２ｃの膨張量差Ｓを計算すると、Ｓ＝−０．６６〜−０．２０μｍとなり、中央値は約−０．４μｍとなった。このとき、軸受単体時において、内輪内径面２ｃの小径側の軌道面２ｂに大径側軌道面２ａよりも径が０．２μｍ大きい転動体４ｂを入れれば、軸６と内輪２との嵌め合いによる２列の軌道面２ａ，２ｂの膨張量差Ｓは、Ｓ＝−０．２６〜＋０．２０μｍに抑えられる。そのため、転がり軸受１に異常発熱および早期剥離が発生する可能性を低くすることが可能になる。
【００２２】
【発明の効果】
この発明における第１の発明の転がり軸受と軸との組立体は、内輪の内径面をテーパ面とした複列の転がり軸受と、上記内輪の内径面に嵌合するテーパ部分を有する軸とよりなるものにおいて、上記軸のテーパ部分と内輪の内径面とのテーパ角度の差を所定の範囲としたため、嵌め合い後における複列の軌道面間のラジアル隙間の相互差が小さく、軸受の異常発熱および早期剥離を防止することができる。
この発明における第２の発明の転がり軸受と軸との組立体は、内輪の内径面をテーパ面とした複列の転がり軸受と、上記内輪の内径面に嵌合するテーパ部を有する軸とよりなるものにおいて、内輪の内径面を所望の基準テーパ角度を狙って製作し、かつ軸の上記テーパ部分のテーパ角度を上記基準テーパ角度に対して−３秒を狙って製作したときに、上記軸のテーパ部分および内輪内径面の狙い角度に対するテーパ角度の許容差を所定の範囲としたため、嵌め合い後における複列の軌道面間のラジアル隙間の相互差が小さく、軸受の異常発熱および早期剥離を防止することができる。
この発明の転がり軸受は、内輪の内径面をテーパ面とした複列の転がり軸受において、内輪の軌道面、外輪の軌道面、およびこれら内外輪の軌道面間に介在した転動体によって定まる各列のラジアル隙間につき、軸受単体の状態で、内輪内径面の小径側の列のラジアル隙間と大径側の列のラジアル隙間に相互差を持たせたため、嵌め合い後における複列の軌道面間のラジアル隙間の相互差が小さく、軸受の異常発熱および早期剥離を防止することができる。
【図面の簡単な説明】
【図１】この発明の第１の実施形態に係る転がり軸受と軸との組立体の断面図である。
【図２】同組立体において、膨張量差が所定値以下となる軸受幅とテーパ角度差との関係を示す図である。
【図３】この発明の第３の実施形態に係る転がり軸受と軸との組立体の断面図である。
【図４】従来例の断面図である。
【図５】同従来例の作用説明図である。
【符号の説明】
１…転がり軸受
２…内輪
２ａ，２ｂ…軌道面
２ｃ…内径面
３…外輪
４…転動体
６…軸
６ａ…テーパ部分[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an assembly of a rolling bearing and a shaft having a tapered inner diameter surface of a bearing and a rolling bearing used for a main shaft of a machine tool or the like.
[0002]
[Prior art]
2. Description of the Related Art Some machine tool spindles and the like that require high-speed and high-precision bearings use rolling bearings having a tapered inner ring inner surface. In such an application, if the radial clearance of the bearing is too large, there is a problem that the spindle accuracy is deteriorated.If the radial clearance is too small, problems such as abnormal heat generation and early peeling of the bearing may occur. The radial gap adjustment is important. Therefore, the radial gap can be adjusted by expanding the inner ring fitted to the shaft by the action of the tapered surface and adjusting the expansion amount by the depth of the press-fit in the axial direction.
[0003]
FIG. 4 shows an example of this type of conventional bearing. The double row bearing 1 is a cylindrical roller bearing with an inner ring flange, and has two rows of raceway surfaces 2a, 2b, 3a, 3b arranged in the axial direction on the inner ring 2 and the outer ring 3. The raceways 3a, 3b of the outer race 3 are formed as continuous cylindrical surfaces. The rolling elements 4a and 4b in each row are held by a holder (not shown). An inner diameter surface 2 c of the inner ring 2 is a tapered surface, and is fitted on the outer periphery of the tapered portion 6 a of the shaft 6. The radial internal gap δ of the bearing can be adjusted by press-fitting the shaft 6 using the tapered surface and expanding the inner ring 2 as described above.
[0004]
[Problems to be solved by the invention]
Since the inner diameter surface 2c of the inner ring 2 has a tapered shape, the thicknesses t1, t2 from the inner ring inner diameter surface to the raceway surfaces 2a, 2b are different between the raceway surfaces 2a, 2b. Since the amount of expansion of the raceway surfaces 2a and 2b due to the fitting varies depending on the thickness, the mutual difference δ _S of the radial gap between the two rows of raceway surfaces 2a and 2b is emphasized in FIG. Get out. The relative difference [delta] _S is a expansion amount difference S between each column.
If this relative difference [delta] _S is large, the bearing load on the rolling elements 4a column radial clearance is small is concentrated, there is a possibility that abnormal heating and premature flaking of the bearing occurs. In addition, when the taper angle accuracy between the shaft 6 and the inner ring 2 is poor and the shaft 6 and the inner ring 2 are extremely non-uniformly fitted with each other, there is a high probability that the above-described problems of heat generation and early peeling occur.
[0005]
SUMMARY OF THE INVENTION An object of the present invention is to provide an assembly of a rolling bearing and a shaft in which the mutual difference in radial gap between the double-row raceway surfaces after fitting is small and abnormal heat generation and early separation of the bearing can be prevented. It is.
Another object of the present invention is to provide a rolling bearing that can reduce the mutual difference of radial gaps between the double-row raceway surfaces after fitting, and can prevent abnormal heat generation and early peeling of the bearing.
[0006]
[Means for Solving the Problems]
An assembly of a rolling bearing and a shaft according to a first aspect of the present invention includes a double-row rolling bearing having a tapered inner surface of an inner ring, and a tapered portion fitted to the inner surface of the inner ring in a tight fit. The difference between the taper angle between the tapered portion of the shaft and the inner surface of the inner ring (the taper angle of the shaft−the taper angle of the inner surface of the inner ring)
When the bearing width is larger than 37 mm, the range is -9 seconds to +3 seconds,
When the bearing width is 37 mm or less, the range is -15 seconds to +9 seconds,
It is characterized by having.
According to this configuration, since the difference between the taper angles is set in the above range, the mutual difference in the radial gap between the two rows of raceway surfaces after the shaft and the bearing are fitted is smaller than a predetermined value. Therefore, the bearing load is not concentrated on one of the rolling element rows, and abnormal heat generation and early peeling of the bearing are prevented.
[0007]
An assembly of a rolling bearing and a shaft according to a second aspect of the present invention includes a double-row rolling bearing having a tapered inner diameter surface of an inner ring, and a tapered portion fitted to the inner diameter surface of the inner ring in a tightly fitted state. When the inner ring is manufactured with the inner diameter surface of the inner ring aimed at a desired reference taper angle, and the taper angle of the tapered portion of the shaft is aimed at -3 seconds with respect to the reference taper angle. The tolerance of the taper angle to the target angle of the tapered portion of the shaft and the inner ring inner diameter surface,
When the bearing width is larger than 37 mm, the shaft and inner ring are both in the range of -3 seconds to +3 seconds,
When the bearing width is 37mm or less, both shaft and inner ring range from -6 seconds to +6 seconds,
It is characterized by having.
In the case of this configuration, the tolerance of the taper angle after machining with respect to the target angle of the tapered portion of the shaft and the inner ring inner diameter surface is within the above range, so between the two rows of raceway surfaces after the shaft and the bearing are fitted, The mutual difference between the radial gaps becomes smaller than a predetermined value. Therefore, the bearing load is not concentrated on one of the rolling element rows, and abnormal heat generation and early peeling of the bearing are prevented.
[0008]
A rolling bearing according to a third aspect of the present invention is a double row rolling bearing having a tapered inner diameter surface of an inner ring in a raceway surface of an inner ring, a raceway surface of an outer ring, and a rolling surface interposed between the raceway surfaces of the inner and outer rings. It is characterized in that radial gaps of each row determined by the moving body have a mutual difference.
In the case of this configuration, the radial gap of each row is given a mutual difference in advance in the state of the bearing alone, so when fitting the shaft and the bearing, each row of the raceway surface based on the tapered surface of the inner ring inner diameter surface. The difference in expansion between them can be absorbed by a preset mutual difference. Therefore, the mutual difference between the radial gaps of each row after fitting can be reduced, and the bearing load does not concentrate on a specific row, and abnormal heat generation and early peeling of the bearing are prevented. In order to give a mutual difference to the radial gap in each example, for example, rolling elements having different outer diameters in each row may be used, and the diameters of the raceway surfaces of the inner ring and the outer ring may be the same in both rows.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
First and second embodiments of the present invention will be described with reference to FIG. The assembly of the rolling bearing and the shaft includes a double-row rolling bearing 1 and a shaft 6. The inner surface 2 c of the inner ring 2 of the rolling bearing 1 has a tapered surface, and the shaft 6 is formed on the inner surface 2 c of the inner ring 2. It has a fitted tapered portion 6a. The shaft 6 is, for example, a main shaft of a machine tool.
The inner ring 2 and the outer ring 3 of the rolling bearing 1 have two rows of raceways 2a, 2b, 3a, 3b arranged in the axial direction, and the rolling elements 4a, 4b of each row are arranged between opposing raceways. I have. The rolling elements 4a and 4b in each row are held by holders 5 provided for each row. The rolling bearing 1 is a cylindrical roller bearing, and the rolling elements 4 are composed of rollers. The inner ring 2 has flanges 7 and 8 on both sides and the center, the outer ring 3 has no flange, and two rows of raceway surfaces 3a and 3b are formed as continuous cylindrical surfaces.
The materials of the inner ring 2, the outer ring 3, and the rolling elements 4a and 4b are made of steel such as bearing steel. The above is the basic configuration.
[0010]
In the first embodiment, the difference in the taper angle between the tapered portion 6a of the shaft 6 and the inner diameter surface 2c of the inner ring 2 (the taper angle of the shaft−the taper angle of the inner ring inner diameter surface) in the above basic configuration is as follows:
When the bearing width B is larger than 37 mm, the range is from -9 seconds to +3 seconds,
When the bearing width B is 37 mm or less, the range is -15 seconds to +9 seconds,
It is what it was.
[0011]
In the second embodiment, in the above basic configuration, the inner diameter surface 2c of the inner ring 2 is manufactured by aiming at a desired reference taper angle, and the taper angle of the tapered portion 6a of the shaft 6 is set to -3 seconds with respect to the reference taper angle. It is produced aiming at. In this case, the tolerance of the taper angle with respect to the target angle of the tapered portion 6a of the shaft 6 and the inner ring inner diameter surface 2c is defined as:
When the bearing width B is larger than 37 mm, both the shaft 6 and the inner ring 2 have a range of -3 seconds to +3 seconds,
When the bearing width B is 37 mm or less, both the shaft 6 and the inner ring 2 have a range of -6 seconds to +6 seconds.
The desired reference taper angle is, for example, a standard taper ratio of 1/12 or 1/30, which is a commonly used taper ratio.
[0012]
According to the configurations of the first embodiment and the second embodiment, in both cases, the mutual difference in the radial gap between the two rows of raceway surfaces 2a and 2b is reduced, and abnormal heat generation and early peeling of the rolling bearing 1 are prevented. can do. The reason will be described below.
[0013]
The difference between the expansion amounts of the two rows of raceway surfaces 2a and 2b of the inner race 2 fitted to the shaft 6 is as follows:
(1) the angle difference between the taper angle of the shaft 6 and the taper angle of the inner ring inner diameter surface 2c, and (2) the interference of the inner ring 2,
As a result of FEM (finite element method) analysis and experimental verification, it was found that the calculated value was calculated based on the following equation.
S = a × Δα + b × Y + c (1)
However,
S: difference in expansion amount (μm) between two rows of raceways of the inner ring,
(= Raceway diameter expansion amount on the large diameter side of inner ring inner diameter surface-raceway diameter expansion amount on the small diameter side),
Δα: Angle difference (sec) between shaft taper angle and inner ring inner surface taper angle,
(= Shaft taper angle-bearing inner surface taper angle),
Y: Inner ring interference (μm) given to the axial center of the raceway surface on the inner ring inner diameter surface small diameter side
a, b, c: constants set for each combination of shaft and bearing used.
The constants a, b, and c are numerical values determined by FEM analysis or experiment.
[0014]
In the range of the interference Y of the inner ring normally used as the main shaft of the machine tool, the angle difference between the shaft taper angle at which the difference S in expansion amount between the two rows of raceway surfaces 2a and 2b is ± 1 μm or less and the taper angle of the inner ring inner surface. Δα was calculated for various types of bearings using the above equation (1), and as a result, FIG. 2 was obtained. The reason why the expansion amount difference S is set to ± 1 μm or less is defined as a substantially maximum range in which it is known from the experience so far that problems such as abnormal heat generation and early peeling do not occur. The vertical axis in the figure indicates the bearing width B.
[0015]
As shown in FIG. 2, the angle difference Δα is set to about −9 seconds to +3 seconds (median value −3 seconds) for a bearing having a bearing width B larger than 37 mm, and the angle difference Δα is set to about −9 seconds for a bearing having a bearing width B of 37 mm or less. From 15 seconds to +9 seconds (median value −3 seconds), it can be seen that the difference S in expansion amount between the two rows of track surfaces 2a and 2b is ± 1 μm or less. Strictly speaking, FIG. 2 shows that the range of the angle difference Δα is different for each model number and the median value is also different, but changing the target value (median value) for each model number is inconvenient for manufacturing reasons. Therefore, the range of the angle difference Δα was determined as described above.
[0016]
A normal bearing is manufactured using a reference taper ratio of 1/12 or 1/30 as the tapered surface of the inner ring inner diameter surface 2c. Since it is known from FIG. 2 that the angle difference Δα should be set to the median value of −3 seconds, the shaft taper angle can be manufactured at the taper reference angle of the inner ring inner surface of −3 seconds.
When the range of the above angle difference Δα is applied to the taper angle between the bearing and the shaft as an allowable difference, the tapered surface of the bearing inner diameter surface is manufactured at a desired reference angle, and the tapered portion of the shaft is formed at the inner ring inner diameter surface. When the bearing angle B is larger than 37 mm, the shaft 6 and the inner ring 2 are both ± 3 seconds when the bearing width B is larger than 37 mm, and when the bearing width B is 37 mm or less, both the shaft 6 and the inner ring 2 are ± 3 seconds. 6 seconds. When the taper angle between the shaft 6 and the inner ring 2 is manufactured in this manner, after the inner ring 2 and the shaft 6 are fitted with each other, the mutual difference of the radial gap between the two rows of raceway surfaces 2a and 2b becomes ± 1 μm. Therefore, abnormal heat generation and early peeling of the rolling bearing 1 can be prevented.
[0017]
Next, a third embodiment of the present invention will be described with reference to FIG. In this embodiment, in the basic configuration described with reference to FIG. 1, the difference in the amount of expansion between the two raceways 2a and 2b of the inner race 2 is estimated by calculation for the rolling bearing 1 and the amount is determined by the radial clearance between the bearings alone. This is given as a difference (difference between radial gaps of each row).
For example, when it is calculated that the radial gap of the row B expands by 1 μm larger than the radial gap of the raceway surface 2a of the row A of the inner ring 2 when the bearing is incorporated, the radial gap of the raceway surface 2b of the row B is set to A when the bearing alone is used. It is 1 μm smaller than the row. In order to reduce the radial gap in row B, for example, a rolling element 4b in row B that is larger than the rolling element 4a in row A is used.
As a result, the radial gap when the rolling bearing 1 is incorporated into the shaft 6 can be made the same between the raceway surfaces 2a and 2b in each row. This method is particularly effective when the taper angle of the shaft 6 is formed to the same angle as the taper angle of the inner ring inner diameter surface. If this method is used when the taper angle of the shaft 6 is currently formed on the inner ring inner diameter surface 2c, there is no variation in the angle difference Δα, and the angle difference Δα always becomes 0, so that the expansion amount difference S can be reduced more accurately. can do. Alternatively, after measuring the taper angle between the shaft 6 and the inner ring inner diameter surface 2c, the radial gap mutual difference of the bearing alone may be determined by calculation and adopted.
[0018]
Although the above embodiments have been described with reference to a cylindrical roller bearing as an example, the present invention is applicable to other types of bearings as long as a double-row rolling bearing and a shaft having a tapered inner ring inner surface. can do.
[0019]
【Example】
(Example 1)
In the first embodiment described with reference to FIG. 1, the dimensions of each part of the rolling bearing 1 are set to the following values. That is, the inner diameter D1 of the inner ring 2 was 130 mm, the outer diameter D2 was 200 mm, and the bearing width B was 52 mm. Shaft 6 is a hollow shaft, the inner diameter _{d i} is 78mm.
In the case of the rolling bearing 1 having such dimensions, it was determined by FEM analysis that the above equation (1) becomes the following equation (2).
S = 0.1064 × Δα + 0.0092 × Y + 0.004 (2)
At this time, the taper angle of the tapered portion 6a of the shaft 6 was processed at the reference angle + 9 seconds ± 3 seconds, and the taper angle of the inner ring inner diameter surface 2c was processed at the reference angle + 12 seconds ± 3 seconds. That is, the angle difference Δα = −9 to +3.
[0020]
In the case of the bearing 1 of this embodiment, the range of the interference Y of the inner ring 2 normally used as the main shaft of the machine tool is 20 to 70 μm, and when the angle difference Δα and Y are substituted into the equation (2), S = −0.77 to +0.97 μm. Therefore, the difference S in expansion amount between the two rows of raceway surfaces 2a and 2b due to the fitting of the shaft 6 and the inner ring 2 is suppressed to 1 μm or less. Therefore, the possibility that abnormal heat generation and early peeling occur in the bearing 1 can be reduced.
[0021]
(Example 2)
In the third embodiment described with reference to FIG. 3, the inner diameter D1 of the bearing inner ring 2 is 130 mm, the outer diameter D2 is 200 mm, and the bearing width B is 52 mm, as in FIG. Shaft 6 is a hollow shaft, the inner diameter _{d i} is 78mm.
In this case, it was found that the taper angle of the tapered portion 6a of the shaft 6 was the reference angle +6 seconds, and the taper angle of the inner ring inner surface 2c was the reference angle +14 seconds. That is, the angle difference Δα = 6−14 = −8.
Since the range of the interference Y of the inner race 2 is 20 to 70 μm, the difference S between the two rows of the raceway surfaces 2a and 2c due to the fitting of the shaft 6 and the inner race 2 is calculated by the equation (2). = −0.66 to −0.20 μm, and the median was about −0.4 μm. At this time, when the rolling element 4b having a diameter 0.2 μm larger than the large-diameter raceway surface 2a is inserted into the raceway surface 2b on the small-diameter side of the inner race inner diameter surface 2c when the bearing is alone, the shaft 6 and the inner race 2 are fitted. The expansion amount difference S between the two rows of raceway surfaces 2a and 2b is suppressed to S = −0.26 to +0.20 μm. Therefore, it is possible to reduce the possibility that abnormal heat generation and early peeling occur in the rolling bearing 1.
[0022]
【The invention's effect】
An assembly of a rolling bearing and a shaft according to a first aspect of the present invention includes a double-row rolling bearing having a tapered inner surface of an inner ring, and a shaft having a tapered portion fitted to the inner surface of the inner ring. Since the difference in the taper angle between the tapered portion of the shaft and the inner diameter surface of the inner ring is within a predetermined range, the mutual difference in the radial gap between the double-row raceway surfaces after fitting is small, resulting in abnormal heat generation of the bearing. And early peeling can be prevented.
An assembly of a rolling bearing and a shaft according to a second aspect of the present invention includes a double-row rolling bearing having a tapered inner surface of an inner ring, and a shaft having a tapered portion fitted to the inner surface of the inner ring. When the inner diameter surface of the inner ring is manufactured by aiming at a desired reference taper angle, and the taper angle of the tapered portion of the shaft is manufactured by aiming at -3 seconds with respect to the reference taper angle, the shaft is removed. The tolerance of the taper angle with respect to the target angle of the tapered portion of the inner ring and the inner ring inner diameter surface is within a predetermined range, so the mutual difference in the radial gap between the multiple rows of raceway surfaces after fitting is small, resulting in abnormal heat generation and early peeling of the bearing. Can be prevented.
The rolling bearing according to the present invention is a double-row rolling bearing having an inner ring having a tapered inner diameter surface, wherein each raceway is determined by a raceway surface of an inner race, a raceway surface of an outer race, and a rolling element interposed between the raceways of the inner and outer races. The radial gap of the inner ring has a mutual difference between the radial gap of the row on the small diameter side and the radial gap of the row on the large diameter side in the state of the bearing alone. The difference between the radial gaps is small, and abnormal heat generation and early peeling of the bearing can be prevented.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an assembly of a rolling bearing and a shaft according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a relationship between a bearing width and a taper angle difference in which a difference in expansion amount is equal to or less than a predetermined value in the assembly.
FIG. 3 is a sectional view of an assembly of a rolling bearing and a shaft according to a third embodiment of the present invention.
FIG. 4 is a sectional view of a conventional example.
FIG. 5 is an operation explanatory view of the conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Rolling bearing 2 ... Inner ring 2a, 2b ... Raceway surface 2c ... Inner diameter surface 3 ... Outer ring 4 ... Rolling element 6 ... Shaft 6a ... Tapered part

Claims

A double-row rolling bearing having an inner ring with a tapered inner surface, and a shaft having a tapered portion fitted in a tightly fitted state on the inner ring of the inner ring, wherein the tapered portion of the shaft and the inner ring of the inner ring are The difference in taper angle (taper angle of shaft-taper angle of inner ring inner diameter surface)
When the bearing width is larger than 37 mm, the range is -9 seconds to +3 seconds,
When the bearing width is 37 mm or less, the range is -15 seconds to +9 seconds,
An assembly of a rolling bearing and a shaft, characterized in that:

A double-row rolling bearing having a tapered inner diameter surface of the inner ring, and a shaft having a tapered portion that fits into the inner diameter surface of the inner ring in a tightly fitted state. The inner diameter surface of the inner ring has a desired reference taper angle. The tolerance of the taper angle with respect to the target angle of the taper portion of the shaft and the inner diameter of the inner ring when the target taper portion of the shaft is manufactured and the taper angle of the taper portion of the shaft is -3 seconds with respect to the reference taper angle. The difference
When the bearing width is larger than 37 mm, the shaft and inner ring are both in the range of -3 seconds to +3 seconds,
When the bearing width is 37mm or less, both shaft and inner ring range from -6 seconds to +6 seconds,
An assembly of a rolling bearing and a shaft, characterized in that:

In a double-row rolling bearing with a tapered inner diameter surface of the inner ring, the mutual difference between the raceway surface of the inner ring, the raceway surface of the outer ring, and the radial gap of each row determined by the rolling elements interposed between the raceways of the inner and outer rings. Rolling bearing characterized by having.