【０００１】
【発明の属する技術分野】
この発明に係る回転支持装置及び回転機械装置は、例えばハードディスクドライブ装置（ＨＤＤ）、フレキシブルディスクドライブ装置（ＦＤＤ）、デジタルビデオディスク（ＤＶＤ）、ミニディスク（ＭＤ）等の磁気、光、光磁気のディスクドライブ装置に組み込むスピンドルモータを構成する部材を回転自在に支持する構造の改良に関する。
【０００２】
【従来の技術】
例えば、コンピュータの記憶装置等として使用されるＨＤＤは、フレーム等に固定されるハウジングに固定した内側部材である、支持軸の周囲に、軸受装置を介して、外側部材であるハブを、回転自在に支持している。円輪状に形成した１乃至複数枚のハードディスクは、上記ハブの一部に結合支持して、このハブと共に回転する。
【０００３】
上記ハードディスクにデータを記録するトラックの幅は極く狭い為、上記ハブは上記支持軸に、ぶれが生じない状態で、回転自在に支持する必要がある。この為従来から、上記支持軸の外周面とハブの内周面との間に設ける軸受装置として、１対の玉軸受を組み合わせ、それぞれの玉軸受を構成する各玉に予圧を付与する事で軸受剛性を確保したものを、広く使用している。
【０００４】
又、近年、ＨＤＤに組み込むスピンドルモータの薄型化を図る為に、ハウジングに固定した、外側部材である固定部材の内側に、内側部材であるハブを、軸受装置を介して回転自在に支持する事も行なわれている。図３は、この様に従来から使用している、軸方向長さが極く小さいスピンドルモータの１例を示している。このスピンドルモータ１は、外側部材である固定部材（ハウジング）２の内周面と、内側部材であるハブ３の中心部に設けた軸部４の外周面との間に、１対の玉軸受５、５を設けている。これら各玉軸受５、５は、外周面に内輪軌道６を有する内輪７と、内周面に外輪軌道８を有する外輪９と、上記内輪軌道６と外輪軌道８との間にそれぞれ複数個ずつ転動自在に設けた、それぞれが転動体である玉１０、１０とを備える。これら各玉１０、１０は、図示しない保持器により転動自在に保持している。又、複数枚のハードディスク１２、１２の内周縁部は、上記ハブ３の外径側に設けた円筒部１１に支持している。
【０００５】
そして、上記各内輪７、７を上記軸部４の外周面の軸方向に離隔した２個所位置に、接着或は締り嵌めにより外嵌固定している。又、上記各内輪７、７の軸方向端面同士を、これら軸方向両端面同士の間に隙間１３を設けた状態で対向させている。これに対して、上記各外輪９、９は、互いに対向する軸方向端面同士の間に間座１４を挟持した状態で、上記固定部材２の内周面に、それぞれ接着或は締り嵌めにより内嵌固定している。尚、上記ハブ３の円筒部１１の内周面にロータ１５を固定し、このロータ１５と上記固定部材２の外周面に固定したステータ１６とを対向させている。
【０００６】
上述の様に構成するスピンドルモータ１は、上記各内輪６、６を、互いに対向する軸方向端面同士の間に隙間１３を介在させた状態のまま互いに近づき合う方向に押圧しつつ、上記ハブ３に外嵌固定する事により、上記各玉１０、１０に所望の予圧を付与している。そして、この様に予圧を付与した状態で、上記ハブ３は、上記固定部材２の内側に、がたつきなく回転自在に支持される。又、上記スピンドルモータ１の使用時には、上記ステータ１６を構成するコイル１８、１８の導線に通電する事により、上記ハブ３を上記固定部材２に対し相対回転させる事ができる。
【０００７】
【発明が解決しようとする課題】
上述した様な従来のスピンドルモータ１に組み込んで、ハブ３を回転自在に支持する回転支持装置の場合、円筒部１１と軸部４とを連結する円輪部１７を、図３の上端部に設けている為、ハブ３及びこのハブ３に固定したハードディスク１２、１２から成る回転部材の重心Ｇは、同図の上端寄りに位置する。又、上記回転支持装置の場合には、軸方向長さを極く小さくする為に、１対の玉軸受５、５を、図３の下端寄りに設けている。従って、上記重心Ｇと、上記１対の玉軸受５、５同士の間の軸方向中心Ｍとは、回転支持装置の軸方向に関して互いにずれている。又、従来構造の場合には、上記１対の玉軸受５、５の諸元（内輪７の内径、外輪９の外径、負の内部隙間等）を、互いに同じとしている。
【０００８】
一方、スピンドルモータ１の使用時には、このスピンドルモータ１の固有振動数と、このスピンドルモータ１に組み込んだ玉軸受５、５の軌道面のうねり等に基づく、これら各玉軸受５、５の固有振動数とにより、上記スピンドルモータ１が特定の周波数で共振し、固定部材２に対してハブ３が振れ回り運動する可能性がある。この場合、スピンドルモータに組み込んだ１対の玉軸受５、５の間の軸方向中心Ｍの位置と、上記重心Ｇの位置とが軸方向に関して一致していれば、振れ回りにより上記各玉軸受５、５に加わる荷重を、これら各玉軸受５、５同士で均等にする事ができ、しかも上記ハブ３にモーメントが加わらない為、これら各玉軸受５、５が（弾性）変形する量を極く小さくできる。従って、この場合には、上記ハブ３が振れ回りする量（使用時にハブ３の中心軸が固定部材２の中心軸に対し傾斜する角度）を極く小さくできて、特に問題を生じる事はない。
【０００９】
これに対して、上述の図３に示した従来のスピンドルモータ１の様に、１対の玉軸受５、５の間の軸方向中心Ｍの位置と、上記重心Ｇの位置とが軸方向に関して互いにずれている場合には、上記１対の玉軸受５、５のうち、上記重心Ｇからの距離が大きい位置に設けた、一方（図３の下方）の玉軸受５に、上記１対の玉軸受５、５のうち、上記重心Ｇからの距離が近い位置に設けた、他方（図３の上方）の玉軸受５よりも大きな荷重が加わる。これに対して従来構造の場合には、上記１対の玉軸受５、５の諸元を互いに同じとしており、これら１対の玉軸受５、５の剛性が互いに同じである為、上記一方の玉軸受５の（弾性）変形量が大きくなり、上記ハブ３が振れ回りする量が大きくなる可能性がある。この様にハブ３が振れ回りする量が大きくなった場合には、このハブ３に固定したハードディスク１２、１２のぶれが大きくなり、スピンドルモータ１を組み込んだＨＤＤの性能が悪化する。
本発明は、この様な事情に鑑みて、使用時に回転する部材の重心と、１対の転がり軸受同士の間の軸方向中心とが軸方向に関して互いにずれている構造で、使用時に回転する部材が振れ回りする量を抑えるべく発明したものである。
【００１０】
【課題を解決するための手段】
本発明の回転支持装置は、前述の図３に示した従来構造と同様に、外側部材の内周面と内側部材の外周面との間に設けた１対の転がり軸受を備え、使用時に上記外側部材又は内側部材に対し回転する部材の重心位置と、上記１対の転がり軸受同士の間の軸方向中心位置とが、軸方向に関して互いにずれている。
特に、本発明の回転支持装置に於いては、上記１対の転がり軸受のうち、上記重心からの距離が大きい位置に設けた一方の転がり軸受の剛性を、上記１対の転がり軸受のうち、上記重心からの距離が小さい位置に設けた他方の転がり軸受の剛性よりも大きくしている。
又、本発明の回転機械装置は、上記回転支持装置を組み込んでおり、使用時に、内側部材を外側部材に対し相対回転させる。
【００１１】
【作用】
上述の様に構成する本発明の回転支持装置によれば、使用時に回転する部材の重心位置と、１対の転がり軸受同士の間の軸方向中心位置とが軸方向に関して互いにずれている構造で、これら１対の転がり軸受のうち、使用時に大きな荷重が作用する、一方の転がり軸受の変形量を小さくできる。この為、使用時に回転する部材が振れ回りする量を小さくできて、本発明の回転支持装置を組み込んだ各種回転機械装置の性能向上を図れる。しかも本発明の場合には、回転支持装置の回転抵抗を大きくする等の不都合を生じる事がない。
【００１２】
【発明の実施の形態】
図１は、本発明の実施の形態の第１例として、本発明をスピンドルモータに適用した場合で、このスピンドルモータの固有振動数モードで、ハブ３が振れ回りする状態を、模式的に表している。尚、本発明の特徴は、使用時に回転する部材の重心位置と、１対の転がり軸受同士の間の軸方向中心位置とが軸方向に関して互いにずれている構造で、使用時に回転する部材が振れ回りする量を小さく抑えるべく、１対の転がり軸受同士の剛性を異ならせた点にある。その他の部分の構成及び作用は、前述の図３に示した従来構造の場合と同様である為、重複する説明は省略し、以下、本発明の特徴部分を中心に説明する。
【００１３】
又、図１では、内側部材であるハブ３に設けた軸部４の外周面と、外側部材である固定部材２の内周面との間に設ける、１対の玉軸受５、５ａを、ばねにより表している。尚、本例の場合には、これら各玉軸受５、５ａを構成する内輪７（図３）の内径を４ｍｍ、外輪９（図３）の外径を９ｍｍ、これら内輪７及び外輪９の幅を２．６ｍｍ、各玉１０、１０（図３）の外径を１．５８８ｍｍ、上記各玉軸受５、５ａに組み込む玉１０、１０の数を、それぞれ７個ずつとしている。
【００１４】
特に、本発明の回転支持装置と、本発明の回転機械装置であるスピンドルモータとの場合には、上記１対の玉軸受５、５ａのうち、ハブ３及びこのハブ３に固定したハードディスク１２、１２とから成る回転部材の重心Ｇ（図３）からの距離が大きい位置に設けた、一方（図１の下方）の玉軸受５ａの、回転支持装置への組み付け前でのラジアル方向の内部隙間を０．０１６ｍｍとし、上記１対の玉軸受５、５ａのうち、上記重心Ｇからの距離が小さい位置に設けた、他方（図１の上方）の玉軸受５の、同じく組み付け前でのラジアル方向の内部隙間を０．０１０ｍｍとしている。従って、本発明の場合には、これら１対の玉軸受５、５ａを回転支持装置に組み付けた状態で、一方の玉軸受５ａのモーメント剛性が、他方の玉軸受５のモーメント剛性よりも大きくなっている。
【００１５】
上述の様に本発明の回転支持装置の場合には、１対の玉軸受５、５ａのうち、上記回転部材の重心Ｇからの距離が大きい位置に設けた、一方の玉軸受５ａの剛性を、上記１対の玉軸受５、５ａのうち、上記重心Ｇからの距離が小さい位置に設けた、他方の玉軸受５の剛性よりも大きくしている。この為、上記重心Ｇの位置と、１対の玉軸受５、５ａ同士の間の軸方向中心Ｍの位置とが軸方向に関して互いにずれている構造で、上記１対の玉軸受５、５ａのうち、使用時に大きな荷重が作用する、一方の玉軸受５ａの変形量を小さくできる。この為、本発明によれば、使用時にハブ３が振れ回りする量を小さく抑える事ができて、本発明の回転支持装置を組み込んだ、スピンドルモータの性能向上を図れる。
【００１６】
一方、本発明の場合と異なり、スピンドルモータに組み込む１対の玉軸受のうち、上記重心Ｇからの距離が小さい位置に設けた、他方の玉軸受の剛性を大きくしたり、上記１対の玉軸受の両方の剛性を大きくする事により、上記ハブ３が振れ回りする量を小さく抑える事も考えられる。但し、振れ回りにより小さい荷重が加わる、他方の玉軸受の剛性のみを大きくする事により、ハブ３の振れ回りを抑えられる効果は小さい。又、上記１対の玉軸受の両方の剛性を大きくした場合には、回転支持装置の回転抵抗が大きくなる等の不都合を生じる可能性がある。これに対して、本発明の場合には、この様な不都合の発生を抑えつつ、上記ハブ３が振れ回りする量を、有効に抑える事ができる。
【００１７】
尚、図２は、前述した従来構造と同様に、ハブ３に設ける軸部４の外周面と、固定部材２の内周面との間に設ける１対の玉軸受５、５の剛性を互いに同じとした構造で、スピンドルモータの固有振動数モードで、ハブ３が振れ回りする状態を、模式的に表している。この図２に示した従来構造の場合、上記１対の玉軸受５、５の、回転支持装置への組み付け前でのラジアル方向の内部隙間を、何れも０．０１０ｍｍとし、他の諸元も同じとする事により、これら両玉軸受５、５の剛性を互いに同じとしている。この様な図２に示した従来構造の場合には、上記１対の玉軸受５、５のうち、上記ハブ３とこのハブ３に固定したハードディスク１２、１２とから成る回転部材の重心Ｇ（図３）からの距離が大きい位置に設けた、一方の玉軸受５の変形量δが、前述の図１に示した、本発明の場合の変形量δ´よりも大きくなる。この為、この場合には、上記ハブ３が振れ回りする量が、本発明の場合に比較して大きくなる。
【００１８】
又、本例の場合には、１対の玉軸受５、５ａのうち、一方の玉軸受５ａの、回転支持装置への組み付け前でのラジアル方向の内部隙間を大きくする事により、この一方の玉軸受５ａのモーメント剛性を、他方の玉軸受５のモーメント剛性よりも大きくしている。この様に１対の玉軸受５、５ａの内部隙間を互いに異ならせるには、上記各玉軸受５、５ａの内部寸法の諸元を変える。例えば、これら両玉軸受５、５ａの接触角を変えて、これら各玉軸受５、５ａを回転支持装置へ組み付ける前の状態での、これら各玉軸受５、５ａのラジアル方向の内部隙間を互いに異ならせれば、これら両玉軸受５、５ａへの予圧付与を同時に行ない、しかも互いのモーメント剛性を異ならせる事ができる。但し、本発明は、この様にして剛性を大きくする場合に限定するものではない。即ち、本発明では、上記各玉軸受５、５ａの玉の直径や個数、外輪軌道や内輪軌道の曲率半径、複数の玉のピッチ円直径（ＰＣＤ）、内輪の内径、外輪の外径、玉の直径等の諸元を、上記一方の玉軸受５ａと上記他方の玉軸受５とで異ならせる事により、この一方の玉軸受５ａの剛性をこの他方の玉軸受５の剛性よりも大きくする事もできる。
【００１９】
【発明の効果】
本発明の回転支持装置及び回転機械装置は、以上に述べた通り構成され作用するので使用時に回転する部材が振れ回りする量を、有効に抑える事ができて、ＨＤＤ等の性能向上に寄与できる。
【図面の簡単な説明】
【図１】本発明の実施の形態の１例に於いて、スピンドルモータの固有振動数モードで、ハブが振れ回りする状態を模式的に表した図。
【図２】従来構造の１例に於いて、スピンドルモータの固有振動数モードで、ハブが振れ回りする状態を模式的に表した図。
【図３】従来から使用している、薄型のスピンドルモータの１例を示す断面図。
【符号の説明】
１ スピンドルモータ
２ 固定部材
３ ハブ
４ 軸部
５、５ａ 玉軸受
６ 内輪軌道
７ 内輪
８ 外輪軌道
９ 外輪
１０ 玉
１１ 円筒部
１２ ハードディスク
１３ 隙間
１４ 間座
１５ ロータ
１６ ステータ
１７ 円輪部
１８ コイル[0001]
TECHNICAL FIELD OF THE INVENTION
The rotating support device and the rotating mechanical device according to the present invention are, for example, magnetic, optical, magneto-optical such as a hard disk drive (HDD), a flexible disk drive (FDD), a digital video disk (DVD), and a mini disk (MD). The present invention relates to an improvement in a structure for rotatably supporting a member constituting a spindle motor incorporated in a disk drive device.
[0002]
[Prior art]
For example, an HDD used as a storage device of a computer or the like is configured such that a hub serving as an outer member is rotatable around a support shaft, which is an inner member fixed to a housing fixed to a frame or the like, via a bearing device. I support it. One or more hard disks formed in a ring shape are connected to and supported by a part of the hub, and rotate together with the hub.
[0003]
Since the width of a track for recording data on the hard disk is extremely narrow, the hub needs to be rotatably supported on the support shaft without causing blurring. For this reason, conventionally, as a bearing device provided between the outer peripheral surface of the support shaft and the inner peripheral surface of the hub, a pair of ball bearings is combined and a preload is applied to each ball constituting each ball bearing. Widely used bearing stiffness.
[0004]
In recent years, in order to reduce the thickness of a spindle motor incorporated in an HDD, a hub as an inner member is rotatably supported via a bearing device inside a fixed member as an outer member fixed to a housing. Has also been done. FIG. 3 shows an example of a spindle motor which is conventionally used and has a very small axial length. The spindle motor 1 has a pair of ball bearings between an inner peripheral surface of a fixed member (housing) 2 which is an outer member and an outer peripheral surface of a shaft portion 4 provided at the center of a hub 3 which is an inner member. 5 and 5 are provided. Each of these ball bearings 5, 5 has an inner ring 7 having an inner ring raceway 6 on the outer peripheral surface, an outer ring 9 having an outer raceway 8 on the inner peripheral surface, and a plurality of each between the inner raceway 6 and the outer raceway 8. Balls 10 and 10, each of which is a rolling element, are provided so as to freely roll. Each of the balls 10, 10 is rotatably held by a retainer (not shown). The inner peripheral edges of the plurality of hard disks 12 are supported by a cylindrical portion 11 provided on the outer diameter side of the hub 3.
[0005]
The inner rings 7, 7 are externally fixed to each other at two axially spaced positions on the outer peripheral surface of the shaft portion 4 by bonding or interference fitting. Also, the axial end faces of the inner rings 7, 7 are opposed to each other with a gap 13 provided between the axial end faces. On the other hand, the outer races 9 and 9 are bonded to each other on the inner peripheral surface of the fixing member 2 by bonding or interference fitting in a state where the spacer 14 is sandwiched between the axial end surfaces facing each other. It is fitted and fixed. The rotor 15 is fixed to the inner peripheral surface of the cylindrical portion 11 of the hub 3, and the rotor 15 faces the stator 16 fixed to the outer peripheral surface of the fixing member 2.
[0006]
The spindle motor 1 configured as described above presses each of the inner races 6, 6 in a direction approaching each other with a gap 13 interposed between the axial end faces facing each other, and A desired preload is applied to each of the balls 10 and 10 by external fitting and fixing. The hub 3 is rotatably supported inside the fixed member 2 without play in a state where the preload is applied in this manner. When the spindle motor 1 is used, the hub 3 can be relatively rotated with respect to the fixed member 2 by supplying electricity to the conductive wires of the coils 18 constituting the stator 16.
[0007]
[Problems to be solved by the invention]
In the case of a rotation supporting device which rotatably supports the hub 3 by being incorporated in the conventional spindle motor 1 as described above, a circular ring portion 17 connecting the cylindrical portion 11 and the shaft portion 4 is provided at the upper end portion in FIG. The center of gravity G of the hub 3 and the rotating member composed of the hard disks 12 fixed to the hub 3 is located near the upper end in FIG. Further, in the case of the rotation support device, a pair of ball bearings 5, 5 are provided near the lower end in FIG. 3 in order to minimize the axial length. Therefore, the center of gravity G and the axial center M between the pair of ball bearings 5, 5 are shifted from each other in the axial direction of the rotation support device. In the case of the conventional structure, the specifications (the inner diameter of the inner ring 7, the outer diameter of the outer ring 9, the negative internal clearance, and the like) of the pair of ball bearings 5, 5 are the same.
[0008]
On the other hand, when the spindle motor 1 is used, the natural frequency of each of the ball bearings 5, 5 based on the natural frequency of the spindle motor 1 and the waviness of the raceway surfaces of the ball bearings 5, 5 incorporated in the spindle motor 1. Depending on the number, there is a possibility that the spindle motor 1 resonates at a specific frequency, and the hub 3 oscillates with respect to the fixed member 2. In this case, if the position of the center M in the axial direction between the pair of ball bearings 5 and 5 incorporated in the spindle motor and the position of the center of gravity G coincide with each other in the axial direction, each of the ball bearings is swung due to whirling. Since the loads applied to the ball bearings 5 and 5 can be equalized between the ball bearings 5 and 5 and no moment is applied to the hub 3, the amount of deformation (elasticity) of the ball bearings 5 and 5 is reduced. It can be extremely small. Therefore, in this case, the amount by which the hub 3 whirls (the angle at which the center axis of the hub 3 is inclined with respect to the center axis of the fixing member 2 during use) can be made extremely small, and there is no particular problem. .
[0009]
On the other hand, as in the conventional spindle motor 1 shown in FIG. 3 described above, the position of the center M in the axial direction between the pair of ball bearings 5, 5 and the position of the center of gravity G are in the axial direction. If they are shifted from each other, one of the pair of ball bearings 5 (5, 5) provided at a position where the distance from the center of gravity G is large, and Among the ball bearings 5, 5, a larger load is applied than the other (upper in FIG. 3) ball bearing 5 provided at a position closer to the center of gravity G. On the other hand, in the case of the conventional structure, the specifications of the pair of ball bearings 5 and 5 are the same, and the rigidity of the pair of ball bearings 5 and 5 is the same. The amount of (elastic) deformation of the ball bearing 5 may increase, and the amount of the hub 3 whirling may increase. When the amount of whirling of the hub 3 increases in this manner, the hard disks 12, 12 fixed to the hub 3 move more, and the performance of the HDD incorporating the spindle motor 1 deteriorates.
In view of such circumstances, the present invention has a structure in which the center of gravity of a member that rotates during use and the axial center between a pair of rolling bearings are displaced from each other in the axial direction. Has been invented to suppress the amount of whirling.
[0010]
[Means for Solving the Problems]
The rotation support device of the present invention includes a pair of rolling bearings provided between the inner peripheral surface of the outer member and the outer peripheral surface of the inner member, similarly to the conventional structure shown in FIG. The position of the center of gravity of the member rotating with respect to the outer member or the inner member and the axial center position between the pair of rolling bearings are shifted from each other in the axial direction.
In particular, in the rotation support device of the present invention, the rigidity of one of the pair of rolling bearings, which is provided at a position where the distance from the center of gravity is large, of the pair of rolling bearings, The rigidity of the other rolling bearing provided at a position where the distance from the center of gravity is small is larger than the rigidity of the other rolling bearing.
In addition, the rotary mechanical device of the present invention incorporates the rotation support device described above, and rotates the inner member relative to the outer member during use.
[0011]
[Action]
ADVANTAGE OF THE INVENTION According to the rotation supporting apparatus of this invention comprised as mentioned above, the position of the center of gravity of the member which rotates at the time of use, and the axial center position between a pair of rolling bearings are mutually shifted with respect to an axial direction. Of the pair of rolling bearings, a large load acts during use, and the amount of deformation of one of the rolling bearings can be reduced. Therefore, the amount of whirling of the rotating member during use can be reduced, and the performance of various rotating machinery incorporating the rotation supporting device of the present invention can be improved. Moreover, in the case of the present invention, there is no inconvenience such as increasing the rotation resistance of the rotation support device.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 schematically shows, as a first example of the embodiment of the present invention, a case where the present invention is applied to a spindle motor, in which the hub 3 whirls in a natural frequency mode of the spindle motor. ing. The feature of the present invention is a structure in which the position of the center of gravity of the member that rotates during use and the axial center position between the pair of rolling bearings are shifted from each other in the axial direction. The point is that the rigidity of the pair of rolling bearings is made different to suppress the amount of rotation. The configuration and operation of the other parts are the same as in the case of the conventional structure shown in FIG. 3 described above, and thus redundant description will be omitted, and the following description will focus on features of the present invention.
[0013]
In FIG. 1, a pair of ball bearings 5 and 5a provided between the outer peripheral surface of the shaft portion 4 provided on the hub 3 serving as the inner member and the inner peripheral surface of the fixed member 2 serving as the outer member are provided. It is represented by a spring. In the case of this example, the inner diameter of the inner race 7 (FIG. 3) constituting each of the ball bearings 5 and 5a is 4 mm, the outer diameter of the outer race 9 (FIG. 3) is 9 mm, and the width of the inner race 7 and the outer race 9 is shown. Is 2.6 mm, the outer diameter of each ball 10, 10 (FIG. 3) is 1.588 mm, and the number of balls 10, 10 to be incorporated in each of the ball bearings 5, 5a is seven.
[0014]
In particular, in the case of the rotation support device of the present invention and the spindle motor which is the rotary mechanical device of the present invention, of the pair of ball bearings 5 and 5a, the hub 3 and the hard disk 12 fixed to the hub 3, 12 is provided at a position where the distance from the center of gravity G (FIG. 3) of the rotating member is large, and the one (lower in FIG. 1) ball bearing 5a has a radial internal clearance before being assembled to the rotation supporting device. Is set to 0.016 mm, and the other (upper in FIG. 1) ball bearing 5 of the pair of ball bearings 5 and 5a is provided at a position where the distance from the center of gravity G is smaller, and is the same as before the assembly. The internal gap in the direction is 0.010 mm. Therefore, in the case of the present invention, the moment rigidity of one of the ball bearings 5a becomes larger than the moment rigidity of the other ball bearing 5 in a state where the pair of ball bearings 5 and 5a are assembled to the rotation support device. ing.
[0015]
As described above, in the case of the rotation supporting device of the present invention, the rigidity of one of the ball bearings 5 and 5a provided at a position where the distance from the center of gravity G of the rotating member is large is reduced. Of the pair of ball bearings 5, 5a, the rigidity of the other ball bearing 5, which is provided at a position where the distance from the center of gravity G is small, is larger. Therefore, the position of the center of gravity G and the position of the axial center M between the pair of ball bearings 5 and 5a are shifted from each other in the axial direction. Among them, the amount of deformation of one of the ball bearings 5a on which a large load acts during use can be reduced. Therefore, according to the present invention, the amount of whirling of the hub 3 during use can be reduced, and the performance of the spindle motor incorporating the rotation support device of the present invention can be improved.
[0016]
On the other hand, unlike the case of the present invention, of the pair of ball bearings incorporated in the spindle motor, the rigidity of the other ball bearing provided at a position where the distance from the center of gravity G is small is increased, or the pair of ball bearings is increased. By increasing the rigidity of both of the bearings, it is conceivable to reduce the amount of whirling of the hub 3. However, the effect of suppressing the whirling of the hub 3 is small by increasing only the rigidity of the other ball bearing where a smaller load is applied to the whirling. In addition, when the rigidity of both of the pair of ball bearings is increased, there is a possibility that inconveniences such as an increase in rotational resistance of the rotation support device may occur. On the other hand, in the case of the present invention, the amount of the hub 3 whirling can be effectively suppressed while suppressing the occurrence of such inconvenience.
[0017]
FIG. 2 shows that the rigidity of a pair of ball bearings 5 provided between the outer peripheral surface of the shaft portion 4 provided on the hub 3 and the inner peripheral surface of the fixing member 2 is the same as in the conventional structure described above. FIG. 3 schematically shows a state in which the hub 3 whirls in the natural frequency mode of the spindle motor with the same structure. In the case of the conventional structure shown in FIG. 2, the radial internal gap of the pair of ball bearings 5 and 5 before assembly to the rotation support device is set to 0.010 mm, and other specifications are also omitted. By making them the same, the rigidity of these two ball bearings 5, 5 is made equal to each other. In the case of such a conventional structure shown in FIG. 2, the center of gravity G (of the rotating member composed of the hub 3 and the hard disks 12, 12 fixed to the hub 3) of the pair of ball bearings 5, 5 ( The deformation amount δ of one of the ball bearings 5 provided at a position at a large distance from FIG. 3) is larger than the deformation amount δ ′ of the present invention shown in FIG. 1 described above. Therefore, in this case, the amount of the whirling of the hub 3 is larger than in the case of the present invention.
[0018]
Further, in the case of the present example, by increasing the radial internal gap of one of the pair of ball bearings 5 and 5a before assembling it to the rotation support device, one of the ball bearings 5a and 5a is made larger. The moment rigidity of the ball bearing 5a is set larger than the moment rigidity of the other ball bearing 5. In order to make the internal clearances of the pair of ball bearings 5 and 5a different from each other, the specifications of the internal dimensions of the ball bearings 5 and 5a are changed. For example, by changing the contact angles of the two ball bearings 5 and 5a, the radial internal gaps between the ball bearings 5 and 5a in a state before the respective ball bearings 5 and 5a are assembled to the rotation support device are mutually set. If different, it is possible to simultaneously apply preload to these two ball bearings 5 and 5a, and to make the moment rigidities different from each other. However, the present invention is not limited to the case where the rigidity is increased in this way. That is, in the present invention, the diameter and number of the balls of each of the ball bearings 5 and 5a, the radius of curvature of the outer raceway and the inner raceway, the pitch circle diameter (PCD) of a plurality of balls, the inner diameter of the inner race, the outer diameter of the outer race, The rigidity of the one ball bearing 5a is made larger than the rigidity of the other ball bearing 5 by making the specifications such as the diameter of the one ball bearing 5a and the other ball bearing 5 different from each other. You can also.
[0019]
【The invention's effect】
Since the rotation support device and the rotation mechanical device of the present invention are configured and operated as described above, the amount of whirling of the rotating member during use can be effectively suppressed, and can contribute to the improvement of the performance of the HDD and the like. .
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a state in which a hub whirls in a natural frequency mode of a spindle motor in one example of an embodiment of the present invention.
FIG. 2 is a diagram schematically showing a state in which a hub whirls in a natural frequency mode of a spindle motor in one example of a conventional structure.
FIG. 3 is a sectional view showing an example of a thin spindle motor conventionally used.
[Explanation of symbols]
Reference Signs List 1 spindle motor 2 fixing member 3 hub 4 shaft portion 5, 5a ball bearing 6 inner ring raceway 7 inner ring 8 outer ring raceway 9 outer ring 10 ball 11 cylindrical portion 12 hard disk 13 gap 14 spacer 15 rotor 16 stator 17 circular ring portion 18 coil
