JP3736250B2 - Method and apparatus for measuring radial resonance frequency of rolling bearing unit - Google Patents

Method and apparatus for measuring radial resonance frequency of rolling bearing unit Download PDF

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JP3736250B2
JP3736250B2 JP2000004454A JP2000004454A JP3736250B2 JP 3736250 B2 JP3736250 B2 JP 3736250B2 JP 2000004454 A JP2000004454 A JP 2000004454A JP 2000004454 A JP2000004454 A JP 2000004454A JP 3736250 B2 JP3736250 B2 JP 3736250B2
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bearing unit
rolling bearing
resonance frequency
rigidity
radial
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JP2001194223A (en
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佳宏朗 佐藤
真一郎 淺枝
博 石和田
達信 桃野
泰之 武藤
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NSK Ltd
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Description

【０００１】
【発明の属する技術分野】
この発明は、例えば、ハードディスクドライブ装置（ＨＤＤ）等の磁気ディスクドライブ装置を構成するスイングアームを揺動変位自在に支持する為の転がり軸受ユニット等、各種精密回転部分に組み込む転がり軸受ユニットのラジアル方向の共振周波数を測定する為に利用する。
【０００２】
【従来の技術】
コンピュータ等の記憶装置として使用するＨＤＤは、例えば特開平７−１１１０５３号公報に記載されている様に、図１に示す様な構造を有する。ＨＤＤの使用時にハードディスク１は、ダイレクトドライブ型の電動モータにより高速で回転する。又、先端部にヘッド２を設けたスイングアーム３の基端部は、図２に示す様な転がり軸受ユニット４により、基板５上に固定した、上記ハードディスク１の回転軸と平行な支持軸６に対し、揺動変位自在に支持している。
【０００３】
上記転がり軸受ユニット４は、内側部材である内筒７の外周面と外側部材である外筒８の内周面との間に、１対の玉軸受９、９を設けて成る。これら各玉軸受９、９はそれぞれ、外周面に深溝型若しくはアンギュラ型の内輪軌道１０を有する内輪１１と、内周面に深溝型若しくはアンギュラ型の外輪軌道１２を有する外輪１３と、上記内輪軌道１０と外輪軌道１２との間に転動自在に設けた、それぞれが転動体である複数個の玉１４、１４とから成る。これら各玉１４、１４は、図示を省略した保持器により転動自在に保持している。又、上記外輪１３の両端部内周面には、それぞれシールド板１５、１５の外周縁を係止して、上記複数個の玉１４、１４を設置した空間内のグリースの漏洩防止を図ると共に、周囲に浮遊する塵芥等の異物がこの空間内に入り込む事の防止を図っている。
【０００４】
上述の様な玉軸受９、９のうち、内輪１１、１１は、上記内筒７の両端部に締まり嵌めにより外嵌固定している。又、外輪１３、１３は、上記外筒８に内嵌すると共に、互いに対向する端面を、上記外筒８の中間部内周面に形成した段部１６、１６に突き当てている。従って、上記１対の外輪１３、１３は、図示の状態よりも近づき合う事はない。又、上記１対の内輪１１、１１は、互いに近づき合う方向に押圧した状態で、上記内筒７の両端部に外嵌固定している。従って、上記１対の玉軸受９、９には、所定の予圧が付与された状態となり、上記内筒７の周囲に外筒８を、回転自在に支持している。即ち、図２に示した様に組み立てられた、上記転がり軸受ユニット４のうち、上記各玉軸受９、９の剛性Ｋ9 及び互いに並列に組み合わされたこれら両玉軸受９、９の剛性は、設計により定められた、既知の値となる。尚、上記内筒７に対する上記各内輪１１、１１の嵌合状態を隙間嵌めとし、これら各内輪１１、１１の内周面と上記内筒７の外周面とを接着する場合もある。勿論、この様な場合でも、上記各玉軸受９、９の剛性Ｋ9 及び互いに並列に組み合わされたこれら両玉軸受９、９の剛性の値は既知となる。
【０００５】
上述の様な転がり軸受ユニット４により、例えば前記スイングアーム３（図１）の基端部を、前記支持軸６に対して揺動自在に支持するには、この支持軸６の周囲に上記内筒７を配置すると共に、この内筒７を、上記支持軸６の基端部に設けた段部１７と、上記支持軸６の先端面にねじ１８により結合固定した抑え板１９との間で挟持する。又、上記スイングアーム３の基端部を、上記外筒８に結合する。この様に組み立てた状態で、上記スイングアーム３の先端部に支持した前記ヘッド２（図１）は、上記スイングアーム３の揺動に伴って、前記ハードディスク１（図１）の表面に近接した状態のまま、この表面を倣う様に移動しつつ、信号の読み取り並びに書き込みを行なう。
【０００６】
上述の様にしてその基端部を上記転がり軸受ユニット４により揺動自在に支持した、上記スイングアーム３の揺動変位に伴う位置決め精度等を十分に確保し、上記ヘッド２による信号の読み取り並びに書き込みのエラーを防止する為には、上記転がり軸受ユニット４全体としての剛性（この転がり軸受ユニット４による上記スイングアーム３の支持剛性）を適正範囲内に収める必要がある。一方、上記転がり軸受ユニット４全体としての剛性と、この転がり軸受ユニット４全体としての共振周波数との間には、後述する様に、密接な関係がある事が知られている。従って、上記転がり軸受ユニット４全体としての共振周波数を管理（適正範囲内に規制）すれば、この転がり軸受ユニット４全体としての剛性を適正範囲内に収める事ができる。この様な事情に鑑みて、この転がり軸受ユニット４全体としての共振周波数を管理すべく、上記共振周波数を測定する為に従来から、図３に示す様な測定装置２０により、上記転がり軸受ユニット４全体としてのアキシアル方向の共振周波数を測定している。
【０００７】
この測定装置２０は、支持軸２１と、加振器２２と、重錘２３と、振動検出器２４とから成る。上記転がり軸受ユニット４は、鉛直方向に配置した上記支持軸２１（支持部材）の中間部に外嵌支持している。即ち、この転がり軸受ユニット４を構成する内筒７は、上記支持軸２１に隙間嵌めにより外嵌すると共に、この支持軸２１の下端寄り部に形成した段部２５と、この支持軸２１の上端部に外嵌固定した円輪状の固定具２６との間で挟持する事により、上記支持軸２１に支持固定している。又、この支持軸２１の下端面は上記加振器２２の上面に突き当てて、この支持軸２１に支持した上記転がり軸受ユニット４全体を、アキシアル方向（図３の上下方向）に加振自在としている。又、上記重錘２３は、使用時に於いて上記転がり軸受ユニット４を構成する外筒８に外嵌する部材と同等の質量を具えたもので、この外筒８に外嵌固定している。又、上記重錘２３の上端面には、上記振動検出器２４の測定端子２７を当接若しくは近接対向させて、上記加振器２２により加振された上記転がり軸受ユニット４の外筒８のアキシアル方向の振動を検出自在としている。
【０００８】
上述の様に構成する測定装置２０により、上記転がり軸受ユニット４のアキシアル方向の共振周波数を求める場合には、上記加振器２２により上記転がり軸受ユニット４をアキシアル方向に加振しつつ、上記振動検出器２４を構成する測定端子２７により、上記外筒８のアキシアル方向の振動を検出する。そして、この振動の検出値を、上記振動検出器２４を構成する周波数分析器により周波数分析する。上記転がり軸受ユニット４全体としてのアキシアル方向の共振周波数は、上記周波数分析の結果に、周波数成分のピーク値として現われる。この為、この周波数分析の結果から、上記アキシアル方向の共振周波数を求める事ができる。
【０００９】
尚、上記転がり軸受ユニット４全体としてのアキシアル方向の剛性Ｋ4aは、上述の様に測定したアキシアル方向の共振周波数から、次の様にして求める事ができる。即ち、上記転がり軸受ユニット４を１自由度系の振動モデルに置き換えると、この転がり軸受ユニット４の共振周波数（固有振動数）ｆn と、この転がり軸受ユニット４の剛性Ｋと、この転がり軸受ユニット４の浮動質量（前記外輪１３、１３と前記外筒８と前記重錘２３との合計質量）Ｍとの間には、
【数１】

Figure 0003736250
なる関係式が成立する。そこで、上記（１）式に、上述の様にして測定した転がり軸受ユニット４のアキシアル方向の共振周波数ｆnaと、上記浮動質量Ｍとを代入すれば、上記転がり軸受ユニット４全体としてのアキシアル方向の剛性Ｋ4aを求める事ができる。この様に、転がり軸受ユニット４全体としての剛性と共振周波数との間には一定の関係があるので、この転がり軸受ユニット４全体としてのアキシアル方向の共振周波数を管理すれば、この転がり軸受ユニット４全体としてのアキシアル方向の剛性を適正範囲内に収める事ができる。
【００１０】
【発明が解決しようとする課題】
上述の様に、従来、転がり軸受ユニット４全体としてのアキシアル方向の剛性を適正範囲内に収める管理を行なってはいたが、この転がり軸受ユニット４全体としてのラジアル方向の剛性を所定範囲内に収める管理は行なっていなかった。ところが、近年、ＨＤＤ等の記憶装置の高密度化が進み、ハードディスク１やフレキシブルディスクに信号を記録するトラックの幅が益々狭くなっている。又、磁気記録の読み取り並びに書き込みの高速化も図られている。そして、この様に極端に幅が狭くなっているトラックを、ヘッド２により忠実に、しかも高速でトレースする必要上、上記スイングアーム３の揺動変位に伴う位置決め精度並びに揺動速度の更なる向上が求められている。そして、この様な要求に応じるべく、上記転がり軸受ユニット４全体としてのラジアル方向の剛性に就いても、所定範囲内に収める管理を行なう事が求められている。
【００１１】
上記転がり軸受ユニット４全体としてのラジアル方向の剛性を所定範囲内に収めるべく、この転がり軸受ユニット４全体としてのラジアル方向の共振周波数の管理（調節）を行なう為には、やはり、このラジアル方向の共振周波数を測定する事が考えられる。この為に、本発明者は先ず、前述の図３に示した測定装置２０を利用し、加振方向と測定方向とをアキシアル方向からラジアル方向に変える以外は、前述のアキシアル方向の共振周波数の測定方法と同様の測定方法により、上記転がり軸受ユニット４全体としてのラジアル方向の共振周波数の測定を行なった。即ち、前記加振器２２により上記転がり軸受ユニット４全体をラジアル方向（例えば、図３の左右或は表裏方向）に加振した状態で、この転がり軸受ユニット４を構成する外筒８のラジアル方向の振動を、前記重錘２３の中間部外周面に当接若しくは近接対向させた測定端子２７により検出し、更に、この検出値を周波数分析して、図４に示す様な分析結果を得た。
【００１２】
そして、この分析結果から、上記検出値にノイズが含まれている事が分かった。即ち、本発明者が上述の様なラジアル方向の共振周波数の測定を、同一条件で繰り返し行なった所、測定を繰り返す毎に共振周波数の値が少しずつ異なる（上記ピーク値として現われる周波数成分の位置がばらつく）事が分かった。これらの事から、前述のアキシアル方向の共振周波数の場合と同様の測定方法では、上記ラジアル方向の共振周波数を正確に測定できない事が分かった。この為、このラジアル方向の共振周波数を正確に測定できる、新たな測定方法及び装置を開発する必要が生じた。
本発明の転がり軸受ユニットのラジアル共振周波数の測定方法及び測定装置は、この様な事情に鑑みて、内側部材と外側部材との間に１対の転がり軸受を組み込んで成る転がり軸受ユニット全体としての、ラジアル方向の共振周波数（ラジアル共振周波数）を正確に測定自在とすべく発明したものである。
【００１３】
【課題を解決するための手段】
本発明の転がり軸受ユニットのラジアル共振周波数の測定方法及び測定装置の対象となる転がり軸受ユニットは、内側部材の外周面に軸方向に互いに離隔した状態で設けた１対の内輪軌道と外側部材の内周面に軸方向に互いに離隔した状態で設けた１対の外輪軌道との間に複数の転動体を、予圧を付与した状態で設けて成る。
【００１４】
上述の様な転がり軸受ユニット全体としてのラジアル共振周波数を測定する、本発明の転がり軸受ユニットのラジアル共振周波数の測定方法では、上記内側部材と上記外側部材とのうちの一方の部材を支持部材により支持しつつ、これら内側部材と外側部材とのうちの他方の部材をラジアル方向に加振する。そして、この他方の部材のラジアル方向の振動を検出して、上記転がり軸受ユニットのラジアル共振周波数を測定する。
特に、本発明の転がり軸受ユニットのラジアル共振周波数の測定方法では、上記支持部材から上記一方の部材に付与する荷重に基づく、これら支持部材及び一方の部材に関する剛性（支持剛性）の値が、上記転がり軸受ユニットの剛性（互いに並列に配置された、複列の転動体により構成される１対の転がり軸受の剛性を合成して得られる軸受剛性）の値よりも大きくなる状態で、上記測定作業を行なう。
好ましくは、上記支持剛性の値を、上記軸受剛性の値を越えて１００倍以下（より好ましくは２〜２０倍程度）に設定する。
更に、本発明の転がり軸受ユニットのラジアル共振周波数の測定装置は、上記転がり軸受ユニットを構成する内側部材を、軸方向両側から挟持した状態で支持する１対の支持部材と、上記転がり軸受ユニットを構成する外側部材に外嵌固定した重錘を、ラジアル方向に加振自在な加振器と、上記外側部材のラジアル方向の振動を検出自在な振動検出器とを具える。そして、上記両支持部材により上記内側部材を挟持する力を調節する事により、これら両支持部材による上記内側部材の支持剛性を調節自在としている。
【００１５】
【作用】
上述の様に構成する転がり軸受ユニットのラジアル共振周波数の測定方法及び測定装置によれば、転がり軸受ユニットを構成する内側部材と外側部材とのうちの一方の部材と、支持部材との係合部の接触剛性、並びにこれら一方の部材及び支持部材の曲げ剛性等の影響をなくすか少なくして、検出値に含まれるノイズをなくすか少なくできる。従って、上記転がり軸受ユニットのラジアル方向の振動のみを取り出して、この転がり軸受ユニットのラジアル共振周波数を正確に測定できる。
特に、支持剛性の値を軸受剛性の値を越えて１００倍以下（より好ましくは２〜２０倍程度）に設定すれば、上記一方の部材や支持部材を損傷する事なく、上記転がり軸受ユニットのラジアル共振周波数を正確に測定できる
【００１６】
【発明の実施の形態】
本発明を完成するに至る過程を説明しつつ、本発明の実施の形態に就いて説明する。
先ず、本発明者は、前述した様に、ラジアル方向の共振周波数を測定するのに、アキシアル方向の振動周波数の場合と同様の測定作業を行なうと、アキシアル方向の共振周波数の測定の場合と異なり、測定を繰り返す毎に共振周波数の値が変化する（安定しない）理由を、次の様に考えた。
【００１７】
即ち、前述したアキシアル方向の共振周波数の測定の場合には、前記支持軸２１及び固定具２６により転がり軸受ユニット４を支持しているアキシアル方向の支持剛性と、これら支持軸２１及び固定具２６のアキシアル方向の剛性とを足し合わせた（合成した）、アキシアル方向の等価剛性が、上記転がり軸受ユニット４全体としてのアキシアル方向の剛性（アキシアル軸受剛性）よりも十分に大きい（アキシアル等価剛性≫アキシアル軸受剛性）。従って、上記支持軸２１及び固定具２６と上記転がり軸受ユニット４との接触部、上記支持軸２１及び固定具２６の弾性変形は十分に小さく、無視できる。従って、アキシアル方向の共振周波数を測定する場合に、上記アキシアル方向の等価剛性を無視できる。
【００１８】
これに対して、本発明の対象となるラジアル方向の共振周波数の測定の場合には、上記支持軸２１及び固定具２６による転がり軸受ユニット４のラジアル方向の支持剛性と、これら支持軸２１及び固定具２６のラジアル方向の剛性とを足し合わせた、ラジアル方向の等価剛性が、上記転がり軸受ユニット４全体としてのラジアル方向の剛性（ラジアル軸受剛性）と同程度若しくはこれよりも小さな値となる（ラジアル等価剛性≦ラジアル軸受剛性）。この為、測定する毎に共振周波数の値を変化させる原因となる。
【００１９】
この様な事を前提として本発明者は、ラジアル方向に振動する上記転がり軸受ユニット４及び上記支持軸２１及び固定具２６に関する振動を、図７に示す様な、２自由度系の振動モデルに置き換える事ができると考えた。この２自由度系の振動モデルは、その基端部を固定の壁面３４に結合固定した第二のばね３２（剛性Ｋ2 ）と、この第二のばね３２の先端部に結合固定した第二の浮動質量３３（質量Ｍ2 ）と、その基端部を第二の浮動質量３３の先端面に結合固定した第一のばね３０（剛性Ｋ1 ）と、この第一のばね３０の先端部に結合固定した第一の浮動質量３１（質量Ｍ1 ）とから成る。この２自由度系の振動モデルのうち、上記第一の浮動質量３１が、前述した、本発明方法による振動周波数の測定対象となる転がり軸受ユニット４を構成する、外輪１３、１３と外筒８と重錘２３とに相当する。又、上記第一のばね３０の剛性Ｋ1 が、上記転がり軸受ユニット４のラジアル方向の剛性に相当する。更に、上記第二の浮動質量３３が、上記転がり軸受ユニット４を構成する内筒７及び内輪１１、１１に相当する。更に、上記第二のばね３２の剛性Ｋ2 が、上記支持軸２１及び固定具２６による転がり軸受ユニット４のラジアル方向の支持剛性（ラジアル方向の等価剛性）に相当する。
【００２０】
又、本発明者は、上述の様な考えを基に、上記ラジアル方向の等価剛性（支持剛性）を上記転がり軸受ユニット４を構成する１対の玉軸受９、９のラジアル方向の剛性よりも十分に大きくすれば、これら各玉軸受９、９を含んで構成する転がり軸受ユニット４で発生する振動のみを精度良く検出できると考えた。何となれば、図７でＫ2 を大きくし、このＫ2 及びＭ2 部分が振動しにくくすれば、残りのＭ1 、Ｋ1 部分の振動を取り出せる（検出できる）が、これらＭ1 、Ｋ1 部分の振動は、求めようとする上記転がり軸受ユニット４の振動そのものである為である。この為に本発明者は、上記ラジアル方向の等価剛性を大きくすべく、支持部材による転がり軸受ユニット４の支持剛性を大きくできる手段を採用し、上記ラジアル方向の等価剛性と上記転がり軸受ユニット４のラジアル方向の共振周波数との関係を求めた。図５は、この関係を求める為に使用した測定装置３５を示している。
【００２１】
この測定装置３５は、本発明の転がり軸受ユニットのラジアル共振周波数の測定方法を実施する場合に使用する測定装置（実施の形態の第１例）ともなるものである。この様な測定装置３５は、上記転がり軸受ユニット４を構成する内筒７を、軸方向（図５の左右方向）両側から挟持した状態で支持する１対の支持部材３６、３６と、上記転がり軸受ユニット４を構成する外筒８に外嵌固定した重錘２３を、ラジアル方向（図５の上下方向）に加振自在な加振器２２と、上記外筒８のラジアル方向の振動を検出自在な振動検出器２４とを具える。上記１対の支持部材３６、３６は、それぞれの先端部に設けた円柱状の凸部３７、３７を、それぞれ上記内筒７の軸方向両端開口部にがたつきなく挿入した状態で、この内筒７の軸方向両端面を挟持している。そして、上記両支持部材３６、３６により上記内筒７を挟持する力、即ち、これら両支持部材３６、３６がこの内筒７の軸方向端面を押圧する力Ｆを調節する事により、これら両支持部材３６、３６による上記内筒７の支持剛性を調節自在としている。この場合に、上記押圧する力Ｆとこの支持剛性とは、比例関係にある。又、上記振動検出器２４を構成する測定端子２７は、上記重錘２３の軸方向中央部外周面に、当接若しくは近接対向している。
【００２２】
そして、本発明者は、上述の様な構成を有する測定装置３５により、上記両支持部材３６、３６による上記内筒７の支持剛性の大きさと、上記振動検出器２４により測定される、上記転がり軸受ユニット４全体としてのラジアル方向の共振周波数との関係を調べた。その結果を図６に示す。
【００２３】
一方、前述の図７に示した、２自由度の振動モデルに於ける転がり軸受ユニット４に関して、ラジアル剛性（Ｋ1 ）が支配的である、共振周波数（固有振動数）ｆn は、
【数２】
Figure 0003736250
で表わされる。この（２）式から明らかな通り、第二のばね３２の剛性値Ｋ2 と共振周波数ｆn との関係は、図８に示す曲線の様になる。尚、この図８の横軸は、支持剛性に対応する上記第二のばね３２の剛性値Ｋ2 を、軸受剛性に対応する第一のばね３０の剛性値Ｋ1 により除した（Ｋ2 ／Ｋ1 ）、無次元数である。
【００２４】
上記図８に示した理論曲線と、上記図６に示した測定結果とを比較すると、両者の特性がほぼ一致している事が分かる。これにより、本発明者は、前述の様にラジアル方向に振動する転がり軸受ユニット４及び支持部材を、図７に示す様な、２自由度系の振動モデルに置き換える仮定が正しい事を確認した。
【００２５】
ところで、上記図６の測定結果から、支持剛性が低いＡ範囲と、支持剛性が高いＣ範囲とで、ラジアル共振周波数の測定値がばらついており、支持剛性の値が中間であるＢ範囲で、共振周波数の測定値が安定している事が分かる。尚、上記支持剛性が低い上記Ａ範囲で測定値がばらついているのは、１対の支持部材３６、３６による転がり軸受ユニット４のラジアル方向の支持部やこれら各支持部材３６、３６で生じるラジアル方向の振動の大きさが、上記転がり軸受ユニット４全体としての振動の大きさに近くなったり、この振動の大きさを上回る事による。この理由は、支持剛性が安定しない為に、非線形な振動が起こり易い為である。これに対して、上記支持剛性が大きい、Ｃ範囲でのばらつきの原因は、前記支持部材３６、３６による前記転がり軸受ユニット４を構成する内筒７の挟持力が大きくなり過ぎて、これら各支持部材３６、３６や内筒７が変形し、玉軸受９、９のラジアル剛性が支配する、前記剛性Ｋ1 が変化する為と考えられる。
【００２６】
これらの事を考慮した場合、中間のＢ範囲となる様な支持剛性により、上記転がり軸受ユニット４を構成する内筒７を１対の支持部材３６、３６の間に挟持した状態で、この転がり軸受ユニット４全体としてのラジアル共振周波数を測定すれば、このラジアル共振周波数を正確に測定できる事が分かる。
そこで、上記図６から、ラジアル共振周波数を安定して測定できる上記Ｂ範囲での共振周波数の範囲を求め、図８でこの共振周波数の範囲に対応する剛性（Ｋ2 ／Ｋ1 ）の範囲を調べた所、１＜Ｋ2 ／Ｋ1 ≦１００となる事が分かった。そこで、上記１対の支持部材３６、３６による上記内筒７の支持剛性の値を、上記転がり軸受ユニット４を構成する１対の玉軸受９、９の軸受剛性の値（１対の玉軸受９、９の軸受剛性の合成値）を越えて１００倍以下（より好ましくは２〜２０倍）に設定した状態で、上記転がり軸受ユニット４全体としてのラジアル共振周波数を測定する。
【００２７】
尚、上述の説明では、転がり軸受ユニット４全体としてのラジアル共振周波数の測定を行なう際に、加振器２２により重錘２３をラジアル方向に加振している。但し、本発明の転がり軸受ユニットのラジアル共振周波数の測定方法を実施する場合に於ける加振方法は、必ずしもこの様な方法によらなくても良い。例えば、図９に示す様に、独立した加振器を省略し、内筒７を軸方向両側から挟持した１対の支持部材３６、３６をラジアル方向に振動させる事で、転がり軸受ユニット４にラジアル方向の振動を付与する事もできる。又、打撃による加振、ボール落下による加振、振り子による加振等を採用する事もできる。
【００２８】
又、上述した本発明の測定方法によりラジアル方向の共振周波数を測定した転がり軸受ユニット４を、例えば前述の図２に示した様にしてＨＤＤに組み付ける場合、段部１７と抑え板１９とによる上記内筒７の挟持力を、上記図６に示したＢ範囲に規制すれば、上記転がり軸受ユニット４のラジアル方向の共振周波数を、上述した測定値通りに維持できる。これにより、上記転がり軸受ユニット４全体としてのラジアル方向の剛性を管理して、前記スイングアーム３（図１）の揺動変位に伴う位置決め精度等を十分に確保できる。
【００２９】
尚、図示の例では、内筒７の外周面と外筒８の内周面との間に、それぞれ独立した玉軸受９、９を１対組み付けて、転がり軸受ユニット４を構成した場合に就いて説明した。但し、本発明は、この様な構造の転がり軸受ユニット４に限らず、例えば内筒の外周面に直接内輪軌道を形成した構造、或は外筒の内周面に直接外輪軌道を形成した構造、更にはこれらを併せ持つ構造でも実施できる。要は、複列に配置した転動体に予圧を付与した複列転がり軸受ユニットであれば、本発明の方法によりラジアル共振周波数を測定する対象となる。
【００３０】
【発明の効果】
本発明の転がり軸受ユニットのラジアル共振周波数の測定方法及び測定装置は、以上に述べた通り構成され作用するので、従来は難しかった転がり軸受ユニット全体としてのラジアル共振周波数の測定を、正確に行なう事ができる。
【図面の簡単な説明】
【図１】本発明による測定の対象となる転がり軸受ユニットを組み込んだハードディスクドライブ装置の斜視図。
【図２】本発明による測定の対象となる転がり軸受ユニットの１例を示す拡大断面図。
【図３】従来から行なわれている、アキシアル共振周波数の測定方法を示す断面図。
【図４】図３に示した方法により転がり軸受ユニットのラジアル共振周波数を測定した場合の測定結果を示す線図。
【図５】本発明の方法により転がり軸受ユニットのラジアル共振周波数を測定する状態の第１例を示す断面図。
【図６】図５に示した方法により転がり軸受ユニットのラジアル共振周波数を測定した場合の測定結果を示す線図。
【図７】転がり軸受ユニットの支持剛性がこの転がり軸受ユニットの共振周波数の測定に及ぼす影響を説明する為の模式図。
【図８】転がり軸受ユニットの支持剛性がこの転がり軸受ユニットの共振周波数の測定に及ぼす影響の理論値を示す線図。
【図９】本発明の方法により転がり軸受ユニットのラジアル共振周波数を測定する状態の第２例を示す断面図。
【符号の説明】
１ ハードディスク
２ ヘッド
３ スイングアーム
４ 転がり軸受ユニット
５ 基板
６ 支持軸
７ 内筒
８ 外筒
９ 玉軸受
１０ 内輪軌道
１１ 内輪
１２ 外輪軌道
１３ 外輪
１４ 玉
１５ シールド板
１６ 段部
１７ 段部
１８ ねじ
１９ 抑え板
２０ 測定装置
２１ 支持軸
２２ 加振器
２３ 重錘
２４ 振動検出器
２５ 段部
２６ 固定具
２７ 測定端子
３０ 第一のばね
３１ 第一の浮動質量
３２ 第二のばね
３３ 第二の浮動質量
３４ 壁面
３５ 測定装置
３６ 支持部材
３７ 凸部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radial direction of a rolling bearing unit incorporated in various precision rotating parts, such as a rolling bearing unit for swingably supporting a swing arm constituting a magnetic disk drive device such as a hard disk drive device (HDD). This is used to measure the resonance frequency.
[0002]
[Prior art]
An HDD used as a storage device such as a computer has a structure as shown in FIG. 1 as described in, for example, JP-A-7-111053. When the HDD is used, the hard disk 1 is rotated at a high speed by a direct drive type electric motor. Further, the base end portion of the swing arm 3 provided with the head 2 at the distal end portion is supported on a substrate 5 by a rolling bearing unit 4 as shown in FIG. On the other hand, it is swingably supported.
[0003]
The rolling bearing unit 4 includes a pair of ball bearings 9 and 9 provided between an outer peripheral surface of an inner cylinder 7 as an inner member and an inner peripheral surface of an outer cylinder 8 as an outer member. Each of these ball bearings 9 and 9 includes an inner ring 11 having a deep groove or angular inner ring raceway 10 on an outer peripheral surface, an outer ring 13 having a deep groove type or angular outer ring raceway 12 on an inner peripheral surface, and the inner ring raceway. 10 and an outer ring raceway 12 are provided between a plurality of balls 14 and 14 which are provided so as to be freely rollable, each being a rolling element. Each of these balls 14 and 14 is held so as to roll freely by a cage not shown. In addition, the outer peripheral edges of the outer ring 13 are engaged with the outer peripheral edges of the shield plates 15 and 15, respectively, to prevent leakage of grease in the space where the plurality of balls 14 and 14 are installed, and It is intended to prevent foreign matter such as dust floating around from entering this space.
[0004]
  Of the ball bearings 9 and 9 as described above, the inner rings 11 and 11 are externally fixed to both ends of the inner cylinder 7 by an interference fit. Further, the outer rings 13, 13 are fitted into the outer cylinder 8, and end surfaces facing each other are abutted against stepped parts 16, 16 formed on the inner peripheral surface of the intermediate part of the outer cylinder 8. Accordingly, the pair of outer rings 13 and 13 do not approach each other than the illustrated state. Further, the pair of inner rings 11 and 11 are externally fitted and fixed to both end portions of the inner cylinder 7 in a state where the inner rings 11 and 11 are pressed toward each other. Accordingly, a predetermined preload is applied to the pair of ball bearings 9, 9, and the outer cylinder 8 is rotatably supported around the inner cylinder 7. That is, the rolling bearing unit assembled as shown in FIG.4Among these, the rigidity K of each of the ball bearings 9 and 99 And the rigidity of these ball bearings 9, 9 combined in parallel with each other is a known value determined by the design. In addition, the fitting state of the inner rings 11, 11 with respect to the inner cylinder 7 may be a clearance fit, and the inner peripheral surface of the inner rings 11, 11 and the outer peripheral surface of the inner cylinder 7 may be bonded. Of course, even in such a case, the rigidity K of each of the ball bearings 9 and 9 will be described.9 The stiffness values of these ball bearings 9, 9 combined in parallel with each other are known.
[0005]
In order to support, for example, the base end portion of the swing arm 3 (FIG. 1) with respect to the support shaft 6 by the rolling bearing unit 4 as described above, The cylinder 7 is disposed, and the inner cylinder 7 is disposed between a stepped portion 17 provided at the base end portion of the support shaft 6 and a holding plate 19 that is coupled and fixed to the distal end surface of the support shaft 6 by screws 18. Hold it. Further, the base end portion of the swing arm 3 is coupled to the outer cylinder 8. In this assembled state, the head 2 (FIG. 1) supported on the tip of the swing arm 3 comes close to the surface of the hard disk 1 (FIG. 1) as the swing arm 3 swings. The signal is read and written while moving so as to follow the surface in the state.
[0006]
As described above, the base end portion of the swing arm 3 is swingably supported by the rolling bearing unit 4 so that the positioning accuracy associated with the swing displacement of the swing arm 3 is sufficiently secured. In order to prevent writing errors, it is necessary to keep the rigidity of the entire rolling bearing unit 4 (support rigidity of the swing arm 3 by the rolling bearing unit 4) within an appropriate range. On the other hand, it is known that there is a close relationship between the rigidity of the entire rolling bearing unit 4 and the resonance frequency of the entire rolling bearing unit 4 as described later. Therefore, if the resonance frequency of the entire rolling bearing unit 4 is managed (restricted within an appropriate range), the rigidity of the entire rolling bearing unit 4 can be kept within the appropriate range. In view of such circumstances, in order to manage the resonance frequency of the entire rolling bearing unit 4 in order to measure the resonance frequency, a measuring device 20 as shown in FIG. The resonance frequency in the axial direction as a whole is measured.
[0007]
The measuring device 20 includes a support shaft 21, a vibrator 22, a weight 23, and a vibration detector 24. The rolling bearing unit 4 is externally fitted and supported at an intermediate portion of the support shaft 21 (support member) arranged in the vertical direction. That is, the inner cylinder 7 constituting the rolling bearing unit 4 is externally fitted to the support shaft 21 by a clearance fit, and a step portion 25 formed near the lower end of the support shaft 21 and the upper end of the support shaft 21. It is supported and fixed to the support shaft 21 by being sandwiched between an annular fixing tool 26 which is externally fitted and fixed to the portion. Further, the lower end surface of the support shaft 21 abuts against the upper surface of the vibrator 22 so that the entire rolling bearing unit 4 supported by the support shaft 21 can be vibrated in the axial direction (vertical direction in FIG. 3). It is said. The weight 23 has a mass equivalent to that of a member fitted to the outer cylinder 8 constituting the rolling bearing unit 4 in use, and is fitted and fixed to the outer cylinder 8. In addition, the measurement terminal 27 of the vibration detector 24 is brought into contact with or in close proximity to the upper end surface of the weight 23, and the outer cylinder 8 of the rolling bearing unit 4 vibrated by the vibration exciter 22. The vibration in the axial direction can be detected.
[0008]
When the resonance device in the axial direction of the rolling bearing unit 4 is obtained by the measuring device 20 configured as described above, the vibration is generated while the rolling bearing unit 4 is vibrated in the axial direction by the vibrator 22. The measurement terminal 27 constituting the detector 24 detects the vibration in the axial direction of the outer cylinder 8. The vibration detection value is subjected to frequency analysis by a frequency analyzer constituting the vibration detector 24. The axial resonance frequency of the rolling bearing unit 4 as a whole appears as a peak value of the frequency component in the result of the frequency analysis. Therefore, the resonance frequency in the axial direction can be obtained from the result of the frequency analysis.
[0009]
The axial stiffness of the rolling bearing unit 4 as a whole is K.4aCan be obtained as follows from the resonance frequency in the axial direction measured as described above. That is, when the rolling bearing unit 4 is replaced with a one-degree-of-freedom vibration model, the resonance frequency (natural frequency) f of the rolling bearing unit 4 is calculated.n And between the rigidity K of the rolling bearing unit 4 and the floating mass M of the rolling bearing unit 4 (the total mass of the outer rings 13, 13, the outer cylinder 8, and the weight 23),
[Expression 1]
Figure 0003736250
The following relational expression holds. Therefore, the resonance frequency f in the axial direction of the rolling bearing unit 4 measured as described above is expressed by the above equation (1).naAnd the above-mentioned floating mass M, the rigidity K in the axial direction of the entire rolling bearing unit 4 is obtained.4aCan be requested. Thus, since there is a certain relationship between the rigidity and the resonance frequency of the entire rolling bearing unit 4, if the axial resonance frequency of the rolling bearing unit 4 is managed, this rolling bearing unit 4. The rigidity in the axial direction as a whole can be kept within an appropriate range.
[0010]
[Problems to be solved by the invention]
As described above, conventionally, management has been performed in which the axial rigidity of the rolling bearing unit 4 as a whole falls within an appropriate range, but the radial rigidity of the rolling bearing unit 4 as a whole falls within a predetermined range. It was not managed. However, in recent years, the density of storage devices such as HDDs has increased, and the width of tracks for recording signals on the hard disk 1 and flexible disks has become increasingly narrow. In addition, the speed of reading and writing of magnetic recording has been increased. Further, it is necessary to trace the track having such an extremely narrow width more faithfully and at a high speed by the head 2, and further improve the positioning accuracy and the swing speed associated with the swing displacement of the swing arm 3. Is required. In order to meet such demands, it is required to manage the rolling bearing unit 4 so as to be within a predetermined range even in the radial rigidity of the entire rolling bearing unit 4.
[0011]
In order to manage (adjust) the radial resonance frequency of the rolling bearing unit 4 as a whole in order to keep the radial rigidity of the rolling bearing unit 4 as a whole within a predetermined range, the radial direction of the rolling bearing unit 4 as a whole is also adjusted. It is conceivable to measure the resonance frequency. For this purpose, the present inventor first uses the measuring apparatus 20 shown in FIG. 3 to change the excitation direction and the measurement direction from the axial direction to the radial direction, and to change the resonance frequency in the axial direction described above. The resonance frequency in the radial direction of the rolling bearing unit 4 as a whole was measured by a measurement method similar to the measurement method. That is, the radial direction of the outer cylinder 8 constituting the rolling bearing unit 4 in a state where the entire rolling bearing unit 4 is vibrated in the radial direction (for example, left and right or front and back in FIG. 3) by the vibrator 22. 4 is detected by a measurement terminal 27 in contact with or in close proximity to the outer peripheral surface of the intermediate portion of the weight 23, and the detected value is subjected to frequency analysis to obtain an analysis result as shown in FIG. .
[0012]
  From this analysis result, it was found that the detection value contained noise. That is, when the inventor repeatedly measured the resonance frequency in the radial direction as described above under the same conditions, the value of the resonance frequency slightly changed each time the measurement was repeated (the position of the frequency component appearing as the peak value). I found out that it fluctuated. From these facts, it was found that the resonance frequency in the radial direction cannot be accurately measured by the same measurement method as that in the case of the resonance frequency in the axial direction. Therefore, a new measurement method that can accurately measure the resonance frequency in the radial direction.And equipmentIt became necessary to develop.
  Method for measuring radial resonance frequency of rolling bearing unit of the present inventionAnd measuring deviceIn view of such circumstances, the radial resonance frequency (radial resonance frequency) of the entire rolling bearing unit in which a pair of rolling bearings is incorporated between the inner member and the outer member can be accurately measured. Invented to do so.
[0013]
[Means for Solving the Problems]
  Method for measuring radial resonance frequency of rolling bearing unit of the present inventionAnd measuring deviceThe rolling bearing unit that is the target of the pair of inner ring raceways provided in the axially spaced state on the outer peripheral surface of the inner member and the pair provided in the axially spaced state on the inner peripheral surface of the outer member A plurality of rolling elements are provided with a preload applied between the outer ring raceway and the outer ring raceway.
[0014]
  In the method for measuring the radial resonance frequency of the rolling bearing unit of the present invention for measuring the radial resonance frequency of the entire rolling bearing unit as described above, one member of the inner member and the outer member is supported by a support member. While supporting, the other member of the inner member and the outer member is vibrated in the radial direction. Then, the radial vibration of the other member is detected, and the radial resonance frequency of the rolling bearing unit is measured.
  In particular, in the method for measuring the radial resonance frequency of the rolling bearing unit according to the present invention, the value of the rigidity (support rigidity) of the support member and the one member based on the load applied from the support member to the one member is the above. The above measurement work in a state where it is larger than the value of the rigidity of the rolling bearing unit (the bearing rigidity obtained by combining the rigidity of a pair of rolling bearings arranged in parallel with each other and composed of double row rolling elements) To do.
  Preferably, the value of the support rigidity is set to 100 times or less (more preferably about 2 to 20 times) exceeding the value of the bearing rigidity.
  Furthermore, the radial resonance frequency measuring apparatus for a rolling bearing unit according to the present invention includes a pair of supporting members that support the inner member constituting the rolling bearing unit in a state of being sandwiched from both sides in the axial direction, and the rolling bearing unit. A weight that is externally fitted and fixed to the constituting outer member is provided with a vibrator capable of vibrating in the radial direction and a vibration detector capable of detecting vibration in the radial direction of the outer member. And by adjusting the force which clamps the said inner member by the said both supporting members, the support rigidity of the said inner member by these both supporting members is made adjustable.
[0015]
[Action]
  Measuring method of radial resonance frequency of rolling bearing unit configured as described aboveAnd measuring deviceAccording to the above, the influence of the contact rigidity of the engagement portion between one member of the inner member and the outer member constituting the rolling bearing unit and the support member, the bending rigidity of the one member and the support member, and the like. It is possible to eliminate or reduce the noise included in the detection value by eliminating or reducing it. Therefore, it is possible to accurately measure the radial resonance frequency of the rolling bearing unit by extracting only the radial vibration of the rolling bearing unit.
  In particular, if the value of the support stiffness is set to 100 times or less (more preferably about 2 to 20 times) exceeding the value of the bearing stiffness, the rolling bearing unit of the rolling bearing unit is not damaged without damaging the one member or the support member. The radial resonance frequency can be measured accurately
[0016]
DETAILED DESCRIPTION OF THE INVENTION
While explaining the process leading to the completion of the present invention, an embodiment of the present invention will be described.
First, as described above, the present inventor performs the same measurement work as that in the case of the vibration frequency in the axial direction to measure the resonance frequency in the radial direction, which is different from the case of measurement of the resonance frequency in the axial direction. The reason why the value of the resonance frequency changes (is not stable) every time the measurement is repeated was considered as follows.
[0017]
  That is, in the case of the measurement of the resonance frequency in the axial direction described above, the support rigidity in the axial direction in which the rolling bearing unit 4 is supported by the support shaft 21 and the fixture 26, and the support shaft 21 and the fixture 26. The axial stiffness is the sum of the stiffness in the axial direction (synthesized), and the equivalent stiffness in the axial direction is the stiffness in the axial direction of the rolling bearing unit 4 as a whole (AxialIt is sufficiently larger than (bearing rigidity) (axial equivalent rigidity >> axial bearing rigidity). Therefore, the elastic deformation of the contact portion between the support shaft 21 and the fixture 26 and the rolling bearing unit 4 and the support shaft 21 and the fixture 26 is sufficiently small and can be ignored. Therefore, when measuring the resonance frequency in the axial direction, the equivalent rigidity in the axial direction can be ignored.
[0018]
On the other hand, in the case of measurement of the resonance frequency in the radial direction, which is an object of the present invention, the support rigidity in the radial direction of the rolling bearing unit 4 by the support shaft 21 and the fixture 26, and the support shaft 21 and the fixed The radial equivalent rigidity obtained by adding the radial rigidity of the tool 26 is equal to or smaller than the radial rigidity (radial bearing rigidity) of the entire rolling bearing unit 4 (radial bearing). Equivalent rigidity ≤ radial bearing rigidity). This causes a change in the value of the resonance frequency each time measurement is performed.
[0019]
Based on such a premise, the present inventor converts the vibration related to the rolling bearing unit 4, the support shaft 21 and the fixture 26 oscillating in the radial direction into a vibration model of a two-degree-of-freedom system as shown in FIG. I thought it could be replaced. This two-degree-of-freedom vibration model includes a second spring 32 (rigidity K) whose base end is coupled and fixed to a fixed wall surface 34.2 ) And a second floating mass 33 (mass M) coupled and fixed to the tip of the second spring 322 ), And a first spring 30 (rigidity K) whose base end portion is coupled and fixed to the distal end surface of the second floating mass 33.1 ) And a first floating mass 31 (mass M) coupled and fixed to the tip of the first spring 301 ). Of the two-degree-of-freedom vibration model, the first floating mass 31 constitutes the outer bearings 13 and 13 and the outer cylinder 8 constituting the rolling bearing unit 4 to be measured for the vibration frequency according to the method of the present invention described above. And the weight 23. Also, the rigidity K of the first spring 301 This corresponds to the rigidity of the rolling bearing unit 4 in the radial direction. Further, the second floating mass 33 corresponds to the inner cylinder 7 and the inner rings 11, 11 constituting the rolling bearing unit 4. Furthermore, the rigidity K of the second spring 322 This corresponds to the radial support rigidity (equivalent rigidity in the radial direction) of the rolling bearing unit 4 by the support shaft 21 and the fixture 26.
[0020]
Further, based on the above-mentioned idea, the present inventor sets the radial equivalent rigidity (support rigidity) to be greater than the radial rigidity of the pair of ball bearings 9 and 9 constituting the rolling bearing unit 4. It was considered that if it was made sufficiently large, only vibrations generated in the rolling bearing unit 4 including these ball bearings 9 and 9 could be detected with high accuracy. What is K2 To increase this K2 And M2 If the part is hard to vibrate, the remaining M1 , K1 The vibration of the part can be taken out (detected), but these M1 , K1 This is because the vibration of the portion is the vibration itself of the rolling bearing unit 4 to be obtained. For this purpose, the present inventor adopts means that can increase the supporting rigidity of the rolling bearing unit 4 by the support member in order to increase the equivalent radial rigidity, and the radial equivalent rigidity and the rolling bearing unit 4 can be increased. The relationship with the resonance frequency in the radial direction was obtained. FIG. 5 shows the measuring device 35 used to obtain this relationship.
[0021]
  This measuring device 35 also serves as a measuring device (first example of the embodiment) used when carrying out the method for measuring the radial resonance frequency of the rolling bearing unit of the present invention. Such a measuring device 35 includes a pair of support members 36 and 36 that support the inner cylinder 7 constituting the rolling bearing unit 4 from both sides in the axial direction (left and right direction in FIG. 5), and the rolling member. An exciter 22 that can freely vibrate a weight 23 fitted and fixed to an outer cylinder 8 constituting the bearing unit 4 in a radial direction (vertical direction in FIG. 5), and the outer cylinder.8And a vibration detector 24 that can detect vibrations in the radial direction. The pair of support members 36, 36 are arranged in such a state that the columnar convex portions 37, 37 provided at the respective tip portions are respectively inserted into the opening portions in the axial direction of the inner cylinder 7 without rattling. Both end surfaces in the axial direction of the inner cylinder 7 are sandwiched. Then, by adjusting the force for holding the inner cylinder 7 by the both support members 36, 36, that is, the force F by which the both support members 36, 36 press the axial end surface of the inner cylinder 7, The support rigidity of the inner cylinder 7 by the support members 36, 36 is adjustable. In this case, the pressing force F and the support rigidity are in a proportional relationship. The measurement terminal 27 constituting the vibration detector 24 is in contact with or close to the outer peripheral surface of the central portion in the axial direction of the weight 23.
[0022]
Then, the inventor uses the measuring device 35 having the above-described configuration to measure the degree of support rigidity of the inner cylinder 7 by the support members 36 and 36 and the rolling detector 24 measured by the vibration detector 24. The relationship with the radial resonance frequency of the entire bearing unit 4 was examined. The result is shown in FIG.
[0023]
On the other hand, regarding the rolling bearing unit 4 in the two-degree-of-freedom vibration model shown in FIG.1 ) Is dominant, the resonance frequency (natural frequency) fn Is
[Expression 2]
Figure 0003736250
It is represented by As is apparent from the equation (2), the stiffness value K of the second spring 322 And resonance frequency fn Is a curve as shown in FIG. The horizontal axis in FIG. 8 indicates the stiffness value K of the second spring 32 corresponding to the support stiffness.2 Is the stiffness value K of the first spring 30 corresponding to the bearing stiffness.1 Divided by (K2 / K1 ), Dimensionless number.
[0024]
When the theoretical curve shown in FIG. 8 is compared with the measurement result shown in FIG. 6, it can be seen that the characteristics of the two are almost the same. As a result, the present inventor confirmed that the assumption that the rolling bearing unit 4 and the support member that vibrate in the radial direction as described above are replaced with a two-degree-of-freedom vibration model as shown in FIG. 7 is correct.
[0025]
By the way, from the measurement result of FIG. 6, the measured value of the radial resonance frequency varies between the A range where the support stiffness is low and the C range where the support stiffness is high, and the B range where the support stiffness value is intermediate, It can be seen that the measured value of the resonance frequency is stable. Note that the measurement values vary in the range A where the support rigidity is low. The radial support portions of the rolling bearing unit 4 by the pair of support members 36 and 36 and the radials generated by the support members 36 and 36. This is because the magnitude of the vibration in the direction becomes close to or exceeds the magnitude of the vibration of the rolling bearing unit 4 as a whole. This is because nonlinear vibration is likely to occur because the support rigidity is not stable. On the other hand, the cause of the variation in the C range where the support rigidity is large is that the holding force of the inner cylinder 7 constituting the rolling bearing unit 4 by the support members 36, 36 becomes too large, and each of these supports. The rigidity K, in which the members 36, 36 and the inner cylinder 7 are deformed and the radial rigidity of the ball bearings 9, 9 dominates.1 Is considered to change.
[0026]
In consideration of these matters, the rolling is performed in a state where the inner cylinder 7 constituting the rolling bearing unit 4 is sandwiched between a pair of supporting members 36 and 36 due to the supporting rigidity so as to be in the middle B range. If the radial resonance frequency of the entire bearing unit 4 is measured, it can be seen that this radial resonance frequency can be measured accurately.
Therefore, from FIG. 6, the range of the resonance frequency in the above-mentioned B range where the radial resonance frequency can be stably measured is obtained, and the stiffness (K) corresponding to this resonance frequency range is obtained in FIG.2 / K1 ), 1 <K2 / K1 It was found that ≦ 100. Therefore, the value of the support rigidity of the inner cylinder 7 by the pair of support members 36, 36 is set to the value of the bearing rigidity of the pair of ball bearings 9, 9 constituting the rolling bearing unit 4 (one pair of ball bearings). The radial resonance frequency of the rolling bearing unit 4 as a whole is measured in a state where it is set to 100 times or less (more preferably 2 to 20 times) exceeding the combined value of the bearing stiffness of 9 and 9.
[0027]
In the above description, when measuring the radial resonance frequency of the entire rolling bearing unit 4, the weight 23 is vibrated in the radial direction by the vibrator 22. However, the excitation method in the case of carrying out the method for measuring the radial resonance frequency of the rolling bearing unit of the present invention does not necessarily need to be based on such a method. For example, as shown in FIG. 9, an independent vibrator is omitted, and a pair of support members 36 and 36 holding the inner cylinder 7 from both sides in the axial direction are vibrated in the radial direction so that the rolling bearing unit 4 Radial vibration can also be applied. Further, it is possible to employ vibration by striking, vibration by dropping a ball, vibration by a pendulum, or the like.
[0028]
Further, when the rolling bearing unit 4 whose radial resonance frequency is measured by the above-described measuring method of the present invention is assembled to an HDD as shown in FIG. If the clamping force of the inner cylinder 7 is restricted within the range B shown in FIG. 6, the radial resonance frequency of the rolling bearing unit 4 can be maintained as described above. As a result, the radial rigidity of the rolling bearing unit 4 as a whole can be managed to sufficiently ensure the positioning accuracy associated with the swing displacement of the swing arm 3 (FIG. 1).
[0029]
In the illustrated example, the rolling bearing unit 4 is configured by assembling a pair of independent ball bearings 9 and 9 between the outer peripheral surface of the inner cylinder 7 and the inner peripheral surface of the outer cylinder 8. Explained. However, the present invention is not limited to the rolling bearing unit 4 having such a structure, for example, a structure in which the inner ring raceway is directly formed on the outer peripheral surface of the inner cylinder, or a structure in which the outer ring raceway is directly formed on the inner peripheral surface of the outer cylinder. Furthermore, it can be implemented by a structure having both of them. In short, in the case of a double row rolling bearing unit in which a preload is applied to the rolling elements arranged in a double row, the radial resonance frequency is measured by the method of the present invention.
[0030]
【The invention's effect】
  Method for measuring radial resonance frequency of rolling bearing unit of the present inventionAnd measuring deviceSince it is configured and operates as described above, it is possible to accurately measure the radial resonance frequency of the entire rolling bearing unit, which has been difficult in the past.
[Brief description of the drawings]
FIG. 1 is a perspective view of a hard disk drive device incorporating a rolling bearing unit to be measured according to the present invention.
FIG. 2 is an enlarged sectional view showing an example of a rolling bearing unit to be measured according to the present invention.
FIG. 3 is a cross-sectional view showing a conventional method for measuring an axial resonance frequency.
4 is a diagram showing a measurement result when a radial resonance frequency of a rolling bearing unit is measured by the method shown in FIG. 3;
FIG. 5 is a cross-sectional view showing a first example of a state in which a radial resonance frequency of a rolling bearing unit is measured by the method of the present invention.
6 is a diagram showing a measurement result when a radial resonance frequency of a rolling bearing unit is measured by the method shown in FIG.
FIG. 7 is a schematic diagram for explaining the influence of the support rigidity of the rolling bearing unit on the measurement of the resonance frequency of the rolling bearing unit.
FIG. 8 is a diagram showing the theoretical value of the influence of the support rigidity of the rolling bearing unit on the measurement of the resonance frequency of the rolling bearing unit.
FIG. 9 is a sectional view showing a second example of a state in which the radial resonance frequency of the rolling bearing unit is measured by the method of the present invention.
[Explanation of symbols]
    1 Hard disk
    2 heads
    3 Swing arm
    4 Rolling bearing unit
    5 Substrate
    6 Support shaft
    7 inner cylinder
    8 outer cylinder
    9 Ball bearing
  10 Inner ring raceway
  11 Inner ring
  12 Outer ring raceway
  13 Outer ring
  14 balls
  15 Shield plate
  16 steps
  17 steps
  18 screws
  19 Retaining plate
  20 Measuring device
  21 Support shaft
  22Exciter
  23 weight
  24 Vibration detector
  25 steps
  26 Fixing tool
  27 Measuring terminal
  30 First spring
  31 First floating mass
  32 Second spring
  33 Second floating mass
  34 Wall
  35 Measuring device
  36 Support members
  37 Convex

Claims (3)

内側部材の外周面に軸方向に互いに離隔した状態で設けた１対の内輪軌道と外側部材の内周面に軸方向に互いに離隔した状態で設けた１対の外輪軌道との間に複数の転動体を、予圧を付与した状態で設けて成る転がり軸受ユニットの、ラジアル方向の共振周波数の測定方法であって、上記内側部材と上記外側部材とのうちの一方の部材を支持部材により、この支持部材からこの一方の部材に付与する荷重に基づくこれら支持部材及び一方の部材に関する剛性の値が、上記転がり軸受ユニットの剛性の値よりも大きくなる状態で支持しつつ、これら内側部材と外側部材とのうちの他方の部材をラジアル方向に加振し、この他方の部材のラジアル方向の振動を検出して上記転がり軸受ユニットのラジアル共振周波数を測定する、転がり軸受ユニットのラジアル共振周波数の測定方法。  A plurality of inner ring raceways provided on the outer peripheral surface of the inner member in the axially spaced state and a pair of outer ring raceways provided on the inner peripheral surface of the outer member in the axially spaced state are provided. A method of measuring a radial resonance frequency of a rolling bearing unit in which a rolling element is provided with a preload applied thereto, wherein one member of the inner member and the outer member is supported by a support member. The inner member and the outer member are supported while the rigidity value of the supporting member and the one member based on the load applied to the one member from the supporting member is larger than the rigidity value of the rolling bearing unit. The rolling bearing unit is configured to vibrate the other member in the radial direction and detect the radial vibration of the other member to measure the radial resonance frequency of the rolling bearing unit. Method of measuring the radial resonance frequency. 支持部材による一方の部材の支持剛性の値を、軸受ユニットの軸受剛性の値を越えて１００倍以下とする、請求項１に記載した転がり軸受ユニットのラジアル共振周波数の測定方法。The method for measuring a radial resonance frequency of a rolling bearing unit according to claim 1, wherein the value of the support rigidity of one member by the support member is set to 100 times or less exceeding the value of the bearing rigidity of the bearing unit. 内側部材の外周面に軸方向に互いに離隔した状態で設けた１対の内輪軌道と外側部材の内周面に軸方向に互いに離隔した状態で設けた１対の外輪軌道との間に複数の転動体を、予圧を付与した状態で設けて成る転がり軸受ユニットを構成する内側部材を、軸方向両側から挟持した状態で支持する１対の支持部材と、上記転がり軸受ユニットを構成する外側部材に外嵌固定した重錘を、ラジアル方向に加振自在な加振器と、上記外側部材のラジアル方向の振動を検出自在な振動検出器とを具え、上記両支持部材により上記内側部材を挟持する力を調節する事により、これら両支持部材による上記内側部材の支持剛性を調節自在とした、転がり軸受ユニットのラジアル共振周波数の測定装置。A plurality of inner ring raceways provided on the outer peripheral surface of the inner member in the axially spaced state and a pair of outer ring raceways provided on the inner peripheral surface of the outer member in the axially spaced state are provided. A pair of support members that support an inner member that constitutes a rolling bearing unit in which a rolling element is provided in a state where a preload is applied, sandwiched from both axial sides, and an outer member that constitutes the rolling bearing unit. An externally fitted weight is provided with a vibrator capable of vibrating in the radial direction and a vibration detector capable of detecting vibration in the radial direction of the outer member, and the inner member is sandwiched between the support members. A device for measuring the radial resonance frequency of a rolling bearing unit, wherein the support rigidity of the inner member by these two support members can be adjusted by adjusting the force.
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KR20170009021A (en) * 2015-07-15 2017-01-25 한국기계연구원 Device and Method for Measuring the Characteristics of Axial Bearing

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KR101713892B1 (en) 2015-07-15 2017-03-09 한국기계연구원 Device and Method for Measuring the Characteristics of Axial Bearing

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