JP2008138846A

JP2008138846A - Fluid bearing device

Info

Publication number: JP2008138846A
Application number: JP2006328468A
Authority: JP
Inventors: Isao Komori; 功古森; Yasuhiro Yamamoto; 康裕山本
Original assignee: NTN Corp; NTN Toyo Bearing Co Ltd
Current assignee: NTN Corp
Priority date: 2006-12-05
Filing date: 2006-12-05
Publication date: 2008-06-19

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid bearing device capable of avoiding inconvenience on the bearing function caused by a temperature change in use, while reducing torque. <P>SOLUTION: A shaft part 2 is composed of a large diameter part 2a and a small diameter part 2b, and the small diameter part 2b is formed between the large diameter parts 2a and 2a separately formed in the axial direction. The small diameter part 2b is composed of a small diameter part body 11 integrally formed with the large diameter part 2a of the shaft part 2, and a different material part 12 formed around the small diameter part body 11 and including an outer peripheral surface 2b1. Here, the different material part 12 is made of a material different in a linear expansion coefficient from the large diameter part 2a, and the outer peripheral surface 2b1 of the small diameter part 2b is opposed to an area between a dynamic pressure groove 8a1-forming area and a dynamic pressure groove 8a2-forming area of a sleeve part 8. In this embodiment, the different material part 12 is formed over the whole periphery out of a material (such as a resin material) having a linear expansion coefficient higher than the large diameter part 2a. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、流体軸受装置に関する。 The present invention relates to a hydrodynamic bearing device.

流体軸受装置は、軸受隙間に生じる潤滑流体の流体膜で軸を相対回転自在に支持するものである。この種の軸受装置は、特に高速回転時における回転精度、静粛性等に優れており、情報機器をはじめ種々の電気機器に搭載されるモータ用の軸受装置として好適に使用される。具体的には、ＨＤＤ等の磁気ディスク装置、ＣＤ−ＲＯＭ、ＣＤ−Ｒ／ＲＷ、ＤＶＤ−ＲＯＭ／ＲＡＭ等の光ディスク装置、ＭＤ、ＭＯ等の光磁気ディスク装置等におけるスピンドルモータ用の軸受装置として、あるいはレーザビームプリンタ（ＬＢＰ）のポリゴンスキャナモータ、プロジェクタのカラーホイールモータ、ファンモータなどのモータ用軸受装置として好適に使用される。 The hydrodynamic bearing device supports a shaft so as to be relatively rotatable with a fluid film of a lubricating fluid generated in a bearing gap. This type of bearing device is particularly excellent in rotational accuracy, quietness, etc. during high-speed rotation, and is suitably used as a bearing device for motors mounted on various electrical devices including information devices. Specifically, as a bearing device for a spindle motor in magnetic disk devices such as HDD, optical disk devices such as CD-ROM, CD-R / RW, DVD-ROM / RAM, magneto-optical disk devices such as MD and MO, etc. Alternatively, it is preferably used as a bearing device for a motor such as a polygon scanner motor of a laser beam printer (LBP), a color wheel motor of a projector, or a fan motor.

最近では、情報機器の更なる高速回転化に対応すべく、これらに組み込まれて使用される流体軸受装置にも、より一層の高回転精度が求められている。また、上記情報機器用のモータの消費電力を低減する目的、あるいはモータの立ち上がり時間の短縮化を図る目的から、回転精度の向上と共に駆動時の更なるトルク低減が要求されている。 Recently, in order to cope with further high-speed rotation of information equipment, even higher rotational accuracy is required for the hydrodynamic bearing device incorporated and used therein. Further, for the purpose of reducing the power consumption of the motor for information equipment or for the purpose of shortening the rise time of the motor, there is a demand for further reduction of torque during driving as well as improvement of rotation accuracy.

トルク低減のための手段としては、例えば、軸部材の外周面のうち、ラジアル軸受隙間と向かい合う領域以外に小径部、いわゆるヌスミ部を設けた構成が知られている（例えば、特許文献１を参照）。かかる構成とすることで、ヌスミ部とこれに向かい合う軸受スリーブとの半径方向隙間をラジアル軸受隙間より大きくとることができ、その分のロストルクの低減化を図っている。
特開２００２−３１０１５９号公報 As means for reducing torque, for example, a configuration is known in which a small diameter portion, a so-called Nusumi portion, is provided in addition to a region facing the radial bearing gap on the outer peripheral surface of the shaft member (see, for example, Patent Document 1). ). By adopting such a configuration, the radial gap between the Nusumi portion and the bearing sleeve facing it can be made larger than the radial bearing gap, and the loss torque is reduced accordingly.
JP 2002-310159 A

このように、低トルク化を目的としてヌスミ部は設けられるが、このヌスミ部を設けたが故に顕著となる問題もある。例えば、ヌスミ部を設けていない構成であれば、ロストルクは大きいものの、その分、高温時における潤滑油の粘度低下に対しても軸受剛性を確保することができる。これに対して、ヌスミ部を設けた構成では、その半径方向隙間が拡がるために、高温時、十分な大きさの軸受剛性を維持できなくなる可能性がある。このように、ロストルクと軸受剛性とは本来的に相反する関係にあるため、単にヌスミ部を設けただけでは双方の特性を満足することは難しい。 As described above, the nuisance portion is provided for the purpose of reducing the torque, but there is also a problem that becomes noticeable because the nuisance portion is provided. For example, if the structure is not provided, the loss torque is large, but the bearing rigidity can be ensured against the decrease in the viscosity of the lubricating oil at a high temperature. On the other hand, in the configuration provided with the Nusumi portion, since the radial gap is widened, there is a possibility that a sufficiently large bearing rigidity cannot be maintained at a high temperature. As described above, since the loss torque and the bearing rigidity are inherently contradictory to each other, it is difficult to satisfy both characteristics simply by providing a crushed portion.

あるいは、ヌスミ部を設けることで、軸受内部に保持される潤滑油の油量が増加することも新たな問題の温床となり得る。すなわち、この種の流体軸受装置では、非常に少量の潤滑油を精密に充填するようにしているため、潤滑油の充填空間となる軸受内部空間が僅かでも増加すると、その増加分に応じて高温時の膨張量が増す。そのため、所定のバッファ容量を超えて潤滑油が膨張することで油漏れを生じる恐れがある。 Alternatively, the provision of the Nusumi portion can increase the amount of lubricating oil retained inside the bearing, which can be a new problem hotbed. In other words, in this type of hydrodynamic bearing device, a very small amount of lubricating oil is precisely filled. Therefore, if the bearing internal space that becomes the lubricating oil filling space increases even slightly, the temperature increases according to the increase. The amount of expansion at the time increases. Therefore, there is a possibility that oil leakage may occur due to the expansion of the lubricating oil exceeding a predetermined buffer capacity.

以上の事情に鑑み、本発明では、低トルク化を図りつつも、使用時の温度変化に起因する軸受機能上の不具合を回避し得る流体軸受装置を提供することを技術的課題とする。 In view of the above circumstances, an object of the present invention is to provide a hydrodynamic bearing device capable of avoiding problems in bearing function due to temperature change during use while reducing torque.

前記課題を解決するため、本発明は、互いに外径寸法の異なる大径部と小径部とを有する軸部と、大径部の外周面とこの外周面に向かい合う面との間に形成される軸受隙間と、軸受隙間を満たすと共に小径部と接する潤滑流体とを備え、軸受隙間に形成される潤滑流体の流体膜を介して軸部を相対回転自在に支持する流体軸受装置において、小径部の外周面を含む領域を、大径部とは線膨張係数の異なる材料で形成したことを特徴とする流体軸受装置を提供する。 In order to solve the above problems, the present invention is formed between a shaft portion having a large diameter portion and a small diameter portion having different outer diameter dimensions, and an outer peripheral surface of the large diameter portion and a surface facing the outer peripheral surface. In a hydrodynamic bearing device that includes a bearing gap and a lubricating fluid that fills the bearing gap and is in contact with the small diameter portion, and supports the shaft portion in a relatively rotatable manner through a fluid film of the lubricating fluid formed in the bearing gap. A hydrodynamic bearing device is provided in which a region including an outer peripheral surface is formed of a material having a linear expansion coefficient different from that of a large diameter portion.

上述のように、本発明では、軸部のうち、軸受隙間を形成する箇所（大径部）とは別に、軸受隙間を満たす潤滑流体と接する小径部を設けることで、この小径部の外周面と向かい合う面との間の半径方向隙間を軸受隙間より大きくとるようにした。これにより、小径部が面する半径方向隙間におけるロストルクを減じ、装置全体としての低トルク化を可能とした。併せて、本発明では、小径部の外周面を含む領域を大径部とは線膨張係数の異なる材料で形成することで、小径部が面する半径方向隙間の温度変動量（温度変化に応じて変動する量）を、軸受隙間の温度変動量とは異ならせた。これにより、例えば（１）小径部の外周面を含む領域を、大径部よりも線膨張係数の高い材料で形成した場合、高温時には、小径部の外周面は、大径部の外周面に比べて大きく外側に拡がる（膨張する）ことで、軸受隙間に比べて、小径部が面する半径方向隙間をより大きく詰めることができる。従って、上述の構成によれば、ロストルクを低減しつつも、軸受剛性の低下を極力小さく抑えることができる。また、低温時には、小径部が面する半径方向隙間の増大量が軸受隙間のそれに比べて大きくなるため、潤滑流体の粘度上昇に伴うロストルクの増加を抑制することが可能となる。 As described above, in the present invention, the outer peripheral surface of the small-diameter portion is provided by providing a small-diameter portion in contact with the lubricating fluid that fills the bearing clearance separately from the portion (large-diameter portion) that forms the bearing clearance in the shaft portion. The gap in the radial direction between the face and the face is set larger than the bearing gap. As a result, the loss torque in the radial gap facing the small diameter portion is reduced, and the torque of the entire apparatus can be reduced. In addition, in the present invention, the region including the outer peripheral surface of the small-diameter portion is formed of a material having a linear expansion coefficient different from that of the large-diameter portion, so that the temperature fluctuation amount of the radial gap that the small-diameter portion faces (according to the temperature change). The amount of fluctuation in temperature) was made different from the amount of temperature fluctuation in the bearing gap. Thus, for example, (1) when the region including the outer peripheral surface of the small diameter portion is formed of a material having a higher linear expansion coefficient than that of the large diameter portion, the outer peripheral surface of the small diameter portion becomes the outer peripheral surface of the large diameter portion at high temperatures. Compared to the bearing gap, the radial gap facing the small diameter portion can be made larger than that by expanding (expanding) to the outside. Therefore, according to the above-described configuration, it is possible to suppress the decrease in bearing rigidity as much as possible while reducing the loss torque. Further, at the time of low temperature, the increase amount of the radial clearance that the small diameter portion faces becomes larger than that of the bearing clearance, so that it is possible to suppress an increase in loss torque accompanying an increase in the viscosity of the lubricating fluid.

また、（２）小径部の外周面を含む領域を、大径部よりも線膨張係数の低い材料で形成した場合、高温時には、小径部の外周面は、大径部の外周面に比べて外側に拡がる（膨張する）量が小さい。そのため、小径部とこれに向かい合う面との間に形成される半径方向隙間をなるべく確保して、軸受内部空間に充填された潤滑流体の膨張をこの隙間で吸収（言い換えると、膨張分のスペースを確保）することができる。従って、バッファ容量の増大化を図ることなく、高温時の油漏れを可及的に回避することができる。 (2) When the region including the outer peripheral surface of the small diameter portion is formed of a material having a lower linear expansion coefficient than that of the large diameter portion, the outer peripheral surface of the small diameter portion is higher than the outer peripheral surface of the large diameter portion at high temperatures. The amount of outward expansion (expansion) is small. For this reason, a radial clearance formed between the small diameter portion and the surface facing this is ensured as much as possible, and the expansion of the lubricating fluid filled in the bearing internal space is absorbed by this clearance (in other words, the space for expansion is reduced). Secure). Therefore, oil leakage at high temperatures can be avoided as much as possible without increasing the buffer capacity.

また、情報機器の最近の小型化を受けて、これら情報機器に組み込む流体軸受装置にも小型化の要請が強まる中、バッファ容積の増加に伴う流体軸受装置の大型化は当然に回避すべき課題となるところ、本発明によれば、バッファ容量の増大を狙ってシール空間（を形成するシール部）の軸方向寸法を大きく取らずに済む。そのため、流体軸受装置の大型化、特に長尺化を回避することができ、これを組み込むべき情報機器の小型化にも対応することが可能となる。 In addition, with the recent downsizing of information equipment, the demand for downsizing of hydrodynamic bearing devices incorporated in these information equipment has increased, and naturally, the increase in size of hydrodynamic bearing devices due to the increase in buffer volume is a problem to be avoided. Thus, according to the present invention, it is not necessary to increase the axial dimension of the seal space (the seal portion forming the seal space) in order to increase the buffer capacity. For this reason, it is possible to avoid an increase in size of the hydrodynamic bearing device, in particular, an increase in length, and it is possible to cope with a reduction in size of an information device into which this is to be incorporated.

上記構成の小径部は、例えば、軸受隙間が軸方向に離隔して形成される構成において、各々の軸受隙間を形成する複数の大径部の間に形成することができる。このように、複数の軸受隙間を軸方向に離隔して形成することで、更なる軸受剛性の向上、特にモーメント荷重に対する軸受剛性の向上が図られると共に、必然的に生じる軸受隙間の間のスペースを、ロストルク低減のためのスペースとして有効に利用することができる。 The small-diameter portion having the above configuration can be formed, for example, between a plurality of large-diameter portions that form the respective bearing gaps in a configuration in which the bearing gaps are formed apart in the axial direction. Thus, by forming a plurality of bearing gaps apart in the axial direction, the bearing rigidity can be further improved, especially the bearing rigidity against moment load, and the space between the bearing gaps that is inevitably generated. Can be effectively used as a space for loss torque reduction.

小径部の外周面を含む領域は、大径部とは線膨張係数の異なる材料で形成されていればよく、目的に応じて、小径部および大径部の材料の組み合わせが任意に可能である。例えば、大径部を含む軸部本体を機械的強度、耐食性に比較的優れた金属材料で形成する場合、小径部の外周面を含む領域を樹脂で形成することが可能である。この場合、小径部の外周面を含む領域を、この領域を除く軸部本体をインサート部品とする樹脂の射出成形で形成すれば、双方の部分をそれぞれ別体に形成して一体化する場合と比べて工程数の削減につながるため好ましい。また、小径部の外径寸法と大径部の外径寸法との差を、樹脂の成形収縮でもって得るようにすれば、成形金型をシンプルな形状（例えば軸部を収容するキャビティは径一定のストレートな形状）とすることができ、コストの低減化につながる。また、この場合、軸部に予め設けておいた窪み（小径部よりも外径寸法は小さい）を樹脂で埋めるだけでよいので、小径部の軸方向の位置決めも効率よく行うことができる。 The region including the outer peripheral surface of the small diameter portion only needs to be formed of a material having a linear expansion coefficient different from that of the large diameter portion, and any combination of materials of the small diameter portion and the large diameter portion is possible depending on the purpose. . For example, when the shaft portion main body including the large diameter portion is formed of a metal material having relatively excellent mechanical strength and corrosion resistance, the region including the outer peripheral surface of the small diameter portion can be formed of resin. In this case, if the region including the outer peripheral surface of the small-diameter portion is formed by resin injection molding using the shaft main body excluding this region as an insert part, both portions are formed separately and integrated. This is preferable because it leads to a reduction in the number of processes. In addition, if the difference between the outer diameter of the small diameter part and the outer diameter of the large diameter part is obtained by molding shrinkage of the resin, the molding die can have a simple shape (for example, the cavity that accommodates the shaft part has a diameter). A certain straight shape), leading to cost reduction. Further, in this case, it is only necessary to fill a recess (an outer diameter smaller than that of the small diameter portion) provided in advance in the shaft portion with resin, so that the small diameter portion can be positioned in the axial direction efficiently.

以上のように、本発明によれば、低トルク化を図りつつも、使用時の温度変化に起因する軸受機能上の不具合を回避し得る流体軸受装置を提供することができる。 As described above, according to the present invention, it is possible to provide a hydrodynamic bearing device capable of avoiding problems in bearing function due to temperature change during use while reducing torque.

以下、本発明の第１実施形態を図１〜図４に基づいて説明する。 Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

図１は、本発明の一実施形態に係る流体軸受装置（動圧軸受装置）１を組込んだ情報機器用スピンドルモータの一構成例を概念的に示している。このスピンドルモータは、例えばＨＤＤ等のディスク駆動装置に用いられるもので、軸部２を回転自在に支持する流体軸受装置１と、軸部２に固定されたハブ３と、例えば半径方向のギャップを介して対向させたステータコイル４ａおよびロータマグネット４ｂとからなる駆動部４と、ブラケット５とを備えている。ステータコイル４ａはブラケット５の側に取付けられ、ロータマグネット４ｂはハブ３の側に取付けられる。流体軸受装置１はブラケット５の内側に固定される。ハブ３には、情報記憶媒体としてのディスクＤが１又は複数枚（図１では２枚）保持される。上述のように構成されたスピンドルモータにおいて、ステータコイル４ａに通電すると、ステータコイル４ａとロータマグネット４ｂとの間に発生する励磁力でロータマグネット４ｂが回転し、それによってハブ３と、ハブ３に保持されたディスクＤとが軸部２と一体に回転する。 FIG. 1 conceptually shows one configuration example of a spindle motor for information equipment incorporating a fluid dynamic bearing device (dynamic pressure bearing device) 1 according to an embodiment of the present invention. This spindle motor is used in a disk drive device such as an HDD, for example, and has a hydrodynamic bearing device 1 that rotatably supports the shaft portion 2, a hub 3 fixed to the shaft portion 2, and a gap in the radial direction, for example. A drive unit 4 including a stator coil 4a and a rotor magnet 4b opposed to each other and a bracket 5 are provided. The stator coil 4a is attached to the bracket 5 side, and the rotor magnet 4b is attached to the hub 3 side. The hydrodynamic bearing device 1 is fixed inside the bracket 5. The hub 3 holds one or a plurality (two in FIG. 1) of disks D as information storage media. In the spindle motor configured as described above, when the stator coil 4a is energized, the rotor magnet 4b is rotated by the exciting force generated between the stator coil 4a and the rotor magnet 4b, thereby causing the hub 3 and the hub 3 to rotate. The held disk D rotates integrally with the shaft portion 2.

図２は、流体軸受装置１を示している。この流体軸受装置１は、軸受部材６と、軸受部材６の内周に位置し、軸受部材６に対して相対回転する軸部２と、軸受部材６を一部挟む形で軸部２の両端側に固定され、軸受部材６の双方の端面との間にそれぞれスラスト軸受隙間を形成するフランジ部９、１０とを備える。なお、以下の説明では、便宜上、流体軸受装置１から軸部２のハブ３側に突出する側を上側、軸部２の突出側と反対の側を下側としているが、これにより、モータや流体軸受装置の設置方向や使用態様等が特定されるわけではない。 FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 includes a bearing member 6, a shaft portion 2 that is positioned on the inner periphery of the bearing member 6, and that rotates relative to the bearing member 6, and both ends of the shaft portion 2 with a part of the bearing member 6 interposed therebetween. Flange portions 9 and 10 that are fixed to the side and that form thrust bearing gaps between both end surfaces of the bearing member 6. In the following description, for the sake of convenience, the side projecting from the hydrodynamic bearing device 1 to the hub 3 side of the shaft portion 2 is the upper side, and the side opposite to the projecting side of the shaft portion 2 is the lower side. The installation direction, usage mode, and the like of the hydrodynamic bearing device are not specified.

軸受部材６は、ハウジング部７と、ハウジング部７の内周に一体又は別体に配設されるスリーブ部８とで構成される。 The bearing member 6 includes a housing portion 7 and a sleeve portion 8 that is disposed integrally or separately on the inner periphery of the housing portion 7.

ハウジング部７は両端開口の筒状をなし、例えば真ちゅう等の金属で、あるいはＬＣＰ、ＰＰＳ、ＰＥＥＫ等の結晶性樹脂をベースとする樹脂組成物の射出成形で形成される。もちろん、ハウジング部７の内部に充填される潤滑油に対して十分な耐浸透性（耐油性）を有するのであれば、ＰＰＳＵ、ＰＥＳ、ＰＥＩ等の非晶性樹脂をベースとする樹脂組成物を射出成形することでハウジング部７を形成することもできる。この実施形態では、ハウジング部７の内周面７ａは径一定の円筒面形状をなし、その軸方向中間位置にスリーブ部８を固定している。 The housing part 7 has a cylindrical shape with openings at both ends, and is formed by injection molding of a resin composition based on a metal such as brass or a crystalline resin such as LCP, PPS, or PEEK. Of course, a resin composition based on an amorphous resin such as PPSU, PES, PEI, etc., if it has sufficient penetration resistance (oil resistance) to the lubricating oil filled in the housing part 7. The housing part 7 can also be formed by injection molding. In this embodiment, the inner peripheral surface 7a of the housing portion 7 has a cylindrical surface shape with a constant diameter, and the sleeve portion 8 is fixed at an intermediate position in the axial direction.

スリーブ部８は、例えば金属製の非孔質体あるいは焼結金属からなる多孔質体で円筒状に形成される。この実施形態では、スリーブ部８は、Ｃｕを主成分とする焼結金属の多孔質体で円筒状に形成され、ハウジング部７の内周面７ａに、例えば接着（ルーズ接着を含む）、圧入（圧入接着を含む）、溶着（超音波溶着を含む）等、適宜の手段で固定される。もちろん、スリーブ部８を樹脂やセラミック等、金属以外の材料で形成することも可能である。また、焼結金属等の多孔質体以外にも、内部空孔を持たない、あるいは潤滑油の出入りができない程度の大きさの空孔を有する構造の材料で形成することもできる。 The sleeve portion 8 is formed in a cylindrical shape with a porous body made of, for example, a metal non-porous body or sintered metal. In this embodiment, the sleeve portion 8 is made of a sintered metal porous body mainly composed of Cu and is formed into a cylindrical shape. For example, the sleeve portion 8 is bonded to the inner peripheral surface 7a of the housing portion 7 (including loose bonding) or press-fitted. It is fixed by appropriate means such as (including press-fit adhesion) and welding (including ultrasonic welding). Of course, the sleeve portion 8 can be formed of a material other than metal, such as resin or ceramic. In addition to a porous body such as a sintered metal, it can be formed of a material having a structure that does not have internal pores or that has pores of a size that does not allow the lubricating oil to enter and exit.

スリーブ部８の内周面８ａの全面又は一部領域には、ラジアル動圧発生部として複数の動圧溝を配列した領域が形成される。この実施形態では、例えば図３（ａ）に示すように、複数の動圧溝８ａ１、８ａ２をヘリングボーン形状に配列した領域が軸方向に離隔して２箇所形成される。これら動圧溝８ａ１、８ａ２の形成領域はそれぞれラジアル軸受面として軸部２の大径部２ａと対向し、軸部２の回転時には、大径部２ａとの間に後述する第１、第２ラジアル軸受部Ｒ１、Ｒ２のラジアル軸受隙間をそれぞれ形成する（図２を参照）。 A region where a plurality of dynamic pressure grooves are arranged as a radial dynamic pressure generating portion is formed on the entire or partial region of the inner peripheral surface 8 a of the sleeve portion 8. In this embodiment, for example, as shown in FIG. 3A, two regions having a plurality of dynamic pressure grooves 8a1 and 8a2 arranged in a herringbone shape are formed apart from each other in the axial direction. The formation regions of these dynamic pressure grooves 8a1 and 8a2 are opposed to the large diameter portion 2a of the shaft portion 2 as radial bearing surfaces, respectively, and when the shaft portion 2 is rotated, first and second described later between the large diameter portion 2a. Radial bearing gaps of the radial bearing portions R1 and R2 are formed (see FIG. 2).

スリーブ部８の上端面８ｂの全面又は一部領域には、スラスト動圧発生部として、例えば図３（ｂ）に示すように、複数の動圧溝８ｂ１をスパイラル形状に配列した領域が形成される。この動圧溝８ｂ１形成領域はスラスト軸受面として、第１フランジ部９の下端面９ａと対向し、軸部２の回転時には、下端面９ａとの間に後述する第１スラスト軸受部Ｔ１のスラスト軸受隙間を形成する（図２を参照）。 As shown in FIG. 3B, for example, as shown in FIG. 3B, a region where a plurality of dynamic pressure grooves 8b1 are arranged in a spiral shape is formed on the entire upper surface 8b of the sleeve portion 8 or a partial region. The This dynamic pressure groove 8b1 formation region is opposed to the lower end surface 9a of the first flange portion 9 as a thrust bearing surface, and a thrust of a first thrust bearing portion T1, which will be described later, between the lower end surface 9a when the shaft portion 2 rotates. A bearing gap is formed (see FIG. 2).

スリーブ部８の下端面８ｃの全面又は一部領域には、スラスト動圧発生部として、例えば図３（ｃ）に示すように、複数の動圧溝８ｃ１をスパイラル状に配列した領域が形成される。この動圧溝８ｃ１形成領域はスラスト軸受面として、第２フランジ部１０の上端面１０ａと対向し、軸部２の回転時には、上端面１０ａとの間に後述する第２スラスト軸受部Ｔ２のスラスト軸受隙間を形成する（図２を参照）。 As shown in FIG. 3C, for example, as shown in FIG. 3C, a region where a plurality of dynamic pressure grooves 8c1 are arranged in a spiral shape is formed on the entire lower surface 8c of the sleeve portion 8 or a partial region. The This dynamic pressure groove 8c1 formation region is opposed to the upper end surface 10a of the second flange portion 10 as a thrust bearing surface, and a thrust of a second thrust bearing portion T2, which will be described later, between the upper end surface 10a when the shaft portion 2 rotates. A bearing gap is formed (see FIG. 2).

軸部２は、例えばＳＵＳ鋼等の金属材料で形成され、スリーブ部８の内周に挿入される。軸部２は主に大径部２ａと小径部２ｂとからなる。この実施形態では、大径部２ａは軸方向に離隔して形成されると共に、各大径部２ａ、２ａの間に小径部２ｂが形成されている。 The shaft portion 2 is formed of a metal material such as SUS steel and is inserted into the inner periphery of the sleeve portion 8. The shaft portion 2 mainly includes a large diameter portion 2a and a small diameter portion 2b. In this embodiment, the large diameter portion 2a is formed so as to be separated in the axial direction, and the small diameter portion 2b is formed between the large diameter portions 2a and 2a.

上側の大径部２ａの外周面２ａ１は、この実施形態では、部分的にスリーブ部８の動圧溝８ａ１形成領域とラジアル方向に対向し、これら対向面間に、後述する第１ラジアル軸受部Ｒ１のラジアル軸受隙間を形成する（後述の図４を参照）。同様に、下側の大径部２ａの外周面２ａ１は、部分的にスリーブ部８の動圧溝８ａ２形成領域とラジアル方向に対向し、これら対向面間に、後述する第２ラジアル軸受部Ｒ２のラジアル軸受隙間を形成する。これら外周面２ａ１、２ａ１のうち、スリーブ部８の内周面８ａとの間にラジアル軸受隙間を形成しない箇所には第１フランジ部９および第２フランジ部１０が固定される。 In this embodiment, the outer peripheral surface 2a1 of the upper large-diameter portion 2a partially opposes the dynamic pressure groove 8a1 formation region of the sleeve portion 8 in the radial direction, and a first radial bearing portion, which will be described later, is interposed between these opposing surfaces. A radial bearing gap of R1 is formed (see FIG. 4 described later). Similarly, the outer peripheral surface 2a1 of the lower large-diameter portion 2a partially opposes the formation region of the dynamic pressure groove 8a2 of the sleeve portion 8 in the radial direction, and a second radial bearing portion R2 described later is provided between these opposing surfaces. The radial bearing gap is formed. The first flange portion 9 and the second flange portion 10 are fixed to portions of the outer peripheral surfaces 2a1 and 2a1 that do not form a radial bearing gap with the inner peripheral surface 8a of the sleeve portion 8.

小径部２ｂは、図２に示すように、軸部２の大径部２ａと一体に形成される小径部本体１１と、小径部本体１１の周囲に形成され、外周面２ｂ１を含む異材部１２とからなる。ここで、異材部１２は、大径部２ａとは線膨張係数の異なる材料で形成されており、小径部２ｂの外周面２ｂ１は、スリーブ部８の動圧溝８ａ１形成領域と動圧溝８ａ２形成領域との間の領域と向かい合うようになっている。この実施形態では、異材部１２は、大径部２ａに比べて線膨張係数の高い材料（樹脂材料など）で全周にわたって形成される。一例として、軸部２本体にＳＵＳ鋼（線膨張係数：１０．４×１０^−６）、小径部２ｂの外周面２ｂ１を形成する異材部１２にＬＣＰ（線膨張係数：３×１０^−５）をそれぞれ使用する組み合わせを挙げることができる。 As shown in FIG. 2, the small-diameter portion 2b includes a small-diameter portion main body 11 formed integrally with the large-diameter portion 2a of the shaft portion 2, and a dissimilar material portion 12 formed around the small-diameter portion main body 11 and including the outer peripheral surface 2b1. It consists of. Here, the dissimilar material portion 12 is formed of a material having a linear expansion coefficient different from that of the large diameter portion 2a, and the outer peripheral surface 2b1 of the small diameter portion 2b is formed in the dynamic pressure groove 8a1 formation region and the dynamic pressure groove 8a2 of the sleeve portion 8. It faces the area between the formation area. In this embodiment, the dissimilar material portion 12 is formed over the entire circumference with a material (resin material or the like) having a higher linear expansion coefficient than that of the large diameter portion 2a. As an example, SUS steel (linear expansion coefficient: 10.4 × 10 ⁻⁶ ) is used for the shaft 2 body, and LCP (linear expansion coefficient: 3 × 10 ⁻⁵ ) is used for the dissimilar material portion 12 that forms the outer peripheral surface 2b1 of the small diameter portion 2b. The combination which uses each can be mentioned.

異材部１２は、例えば異材部１２を除く軸部２本体（大径部２ａや小径部本体１１を含む）をインサート部品とする樹脂の射出成形で形成することができる。この場合、異材部１２の半径方向厚みは、所望する温度変動量に応じて設定すればよい。また、異材部１２の半径方向厚みや材料によって小径部２ｂの外周面２ｂ１の内側への成形収縮量が異なるので、逆にこのことを利用して小径部２ｂの外径寸法（大径部２ａの外径寸法から小径部２ｂの外径寸法を引いた値）を所望の値に設定することもできる。 The dissimilar material part 12 can be formed, for example, by resin injection molding using the shaft part 2 main body (including the large diameter part 2a and the small diameter part main body 11) excluding the dissimilar material part 12 as an insert part. In this case, the radial thickness of the dissimilar material portion 12 may be set according to the desired amount of temperature fluctuation. Further, since the amount of molding shrinkage to the inside of the outer peripheral surface 2b1 of the small diameter portion 2b varies depending on the radial thickness and material of the different material portion 12, the outer diameter dimension of the small diameter portion 2b (large diameter portion 2a) is reversed by utilizing this fact. The value obtained by subtracting the outer diameter dimension of the small-diameter portion 2b from the outer diameter dimension) can be set to a desired value.

第１フランジ部９および第２フランジ部１０は共に環状をなすもので、例えば何れも真ちゅう等の金属材料や樹脂材料で形成される。第１フランジ部９は、その下端面９ａをスリーブ部８の上端面８ｂと対向させた状態で軸部２の大径部２ａ外周に固定される。同様に、第２フランジ部１０は、その上端面１０ａをスリーブ部８の下端面８ｃと対向させた状態で軸部２の大径部２ａ外周に固定される。なお、この実施形態では、双方のフランジ部９、１０と軸部２（大径部２ａ）との接着強度向上を図るため、接着剤溜りとしての環状溝２ｃ、２ｃがそれぞれ大径部２ａ、２ａの接着固定領域中に形成されている。 Both the first flange portion 9 and the second flange portion 10 have an annular shape, and for example, both are formed of a metal material such as brass or a resin material. The first flange portion 9 is fixed to the outer periphery of the large-diameter portion 2a of the shaft portion 2 with its lower end surface 9a facing the upper end surface 8b of the sleeve portion 8. Similarly, the second flange portion 10 is fixed to the outer periphery of the large-diameter portion 2a of the shaft portion 2 with the upper end surface 10a facing the lower end surface 8c of the sleeve portion 8. In this embodiment, in order to improve the adhesive strength between the flange portions 9 and 10 and the shaft portion 2 (large-diameter portion 2a), the annular grooves 2c and 2c serving as adhesive reservoirs are respectively provided with the large-diameter portion 2a, It is formed in the adhesive fixing area 2a.

第１フランジ部９の外周面９ｂは、上方（スリーブ部８から離れる向き）に向けて漸次縮径するテーパ形状をなす。従い、第１フランジ部９を軸部２に固定した状態では、外周面９ｂと、外周面９ｂに向かい合うハウジング部７の上端内周面７ａ１との間に、半径方向寸法が下方に向けて漸次縮小するテーパ状の第１シール空間Ｓ１が形成される。 The outer peripheral surface 9b of the first flange portion 9 has a tapered shape that gradually decreases in diameter toward the upper side (in the direction away from the sleeve portion 8). Therefore, in a state where the first flange portion 9 is fixed to the shaft portion 2, the radial dimension gradually decreases downward between the outer peripheral surface 9b and the upper end inner peripheral surface 7a1 of the housing portion 7 facing the outer peripheral surface 9b. A tapered first seal space S1 is formed.

同様に、第２フランジ部１０の外周面１０ｂは、下方（スリーブ部８から離れる向き）に向けて漸次縮径するテーパ形状をなす。従い、第２フランジ部１０を軸部２に固定した状態では、外周面１０ｂと、外周面１０ｂに向かい合うハウジング部７の下端内周面７ａ２との間に、半径方向寸法が上方に向けて漸次縮小するテーパ状の第２シール空間Ｓ２が形成される。 Similarly, the outer peripheral surface 10b of the second flange portion 10 has a tapered shape that gradually decreases in diameter downward (in a direction away from the sleeve portion 8). Therefore, in the state where the second flange portion 10 is fixed to the shaft portion 2, the radial dimension gradually increases upward between the outer peripheral surface 10b and the lower end inner peripheral surface 7a2 of the housing portion 7 facing the outer peripheral surface 10b. A tapered second seal space S2 is formed.

上記構成の流体軸受装置１において、軸部２の回転時、スリーブ部８の内周面８ａのラジアル軸受面となる領域（上下２箇所の動圧溝８ａ１、８ａ２形成領域）は、軸部２の大径部２ａの外周面２ａ１とラジアル軸受隙間を介して向かい合う。そして、軸部２の回転に伴い、上記ラジアル軸受隙間の潤滑油が動圧溝８ａ１、８ａ２の軸方向中心側に押し込まれ、その圧力が上昇する。このような動圧溝８ａ１、８ａ２の動圧作用によって、軸部２を回転自在にラジアル方向に非接触支持する第１ラジアル軸受部Ｒ１と第２ラジアル軸受部Ｒ２とがそれぞれ構成される。 In the hydrodynamic bearing device 1 having the above-described configuration, when the shaft portion 2 rotates, the region that forms the radial bearing surface of the inner peripheral surface 8a of the sleeve portion 8 (the two dynamic pressure grooves 8a1 and 8a2 forming regions) is the shaft portion 2. The large-diameter portion 2a faces the outer peripheral surface 2a1 through a radial bearing gap. As the shaft portion 2 rotates, the lubricating oil in the radial bearing gap is pushed toward the axial center of the dynamic pressure grooves 8a1 and 8a2, and the pressure rises. Due to the dynamic pressure action of the dynamic pressure grooves 8a1 and 8a2, the first radial bearing portion R1 and the second radial bearing portion R2 that rotatably support the shaft portion 2 in the radial direction are configured.

これと同時に、スリーブ部８の上端面８ｂ（動圧溝８ｂ１形成領域）とこれに向かい合う第１フランジ部９の下端面９ａとの間のスラスト軸受隙間、およびスリーブ部８の下端面８ｃ（動圧溝８ｃ１形成領域）とこれに向かい合う第２フランジ部１０の上端面１０ａとの間のスラスト軸受隙間に、動圧溝８ｂ１、８ｃ２の動圧作用により潤滑油の油膜がそれぞれ形成される。そして、これら油膜の圧力によって、軸部２をスラスト方向に非接触支持する第１スラスト軸受部Ｔ１と第２スラスト軸受部Ｔ２とがそれぞれ構成される。 At the same time, the thrust bearing gap between the upper end surface 8b (dynamic pressure groove 8b1 formation region) of the sleeve portion 8 and the lower end surface 9a of the first flange portion 9 facing the upper end surface 8b, and the lower end surface 8c of the sleeve portion 8 (dynamic An oil film of lubricating oil is formed in the thrust bearing gap between the pressure groove 8c1 formation region) and the upper end surface 10a of the second flange portion 10 facing this by the dynamic pressure action of the dynamic pressure grooves 8b1 and 8c2. The first thrust bearing portion T1 and the second thrust bearing portion T2 that support the shaft portion 2 in the thrust direction in a non-contact manner are constituted by the pressure of these oil films.

ここで、図４に示すように、小径部２ｂの外周面２ｂ１と、外周面２ｂ１に向かい合うスリーブ部８の内周面８ａとの間の第１環状隙間の半径隙間寸法Ｇ１は、大径部２ａの外周面２ａ１と内周面８ａとの間のラジアル軸受隙間（第２環状隙間）の半径隙間寸法Ｇ２よりも大きく設定されている。そのため、軸部２の回転時、第１環状隙間の隙間寸法Ｇ１から第２環状隙間の隙間寸法Ｇ２を減じた分、ロストルクの低減化が可能となる。 Here, as shown in FIG. 4, the radial gap dimension G1 of the first annular gap between the outer peripheral surface 2b1 of the small diameter portion 2b and the inner peripheral surface 8a of the sleeve portion 8 facing the outer peripheral surface 2b1 is the large diameter portion. It is set larger than the radial gap dimension G2 of the radial bearing gap (second annular gap) between the outer peripheral surface 2a1 and the inner peripheral surface 8a of 2a. Therefore, when the shaft portion 2 rotates, the loss torque can be reduced by the amount obtained by subtracting the gap dimension G2 of the second annular gap from the gap dimension G1 of the first annular gap.

併せて、小径部２ｂの外周面２ｂ１を含む領域を大径部２ａよりも線膨張係数の高い材料で形成することで、小径部２ｂが面する第１環状隙間の温度変動量を、ラジアル軸受隙間の温度変動量より大きくした。これにより、例えば高温時、小径部２ｂの外周面２ｂ１を大きく外側に変位させて、第１環状隙間の隙間寸法Ｇ１をラジアル軸受隙間の隙間寸法Ｇ２に比べて大きく詰めることができる。従って、ロストルクの低減化を図りつつも、高温時、流体軸受装置１全体での軸受剛性を極力確保することができる。また、低温時には、小径部２ｂの外周面２ｂ１を大きく内側に変位させて、ラジアル軸受隙間の隙間寸法Ｇ２に比べて第１環状隙間の隙間寸法Ｇ１を大きく拡げることができる。そのため、潤滑油の粘度上昇に伴うロストルクの増加を抑えて、小径部２ｂを設けたことによるメリット（ロストルクの低減作用）をより生かすことができる。 In addition, by forming the region including the outer peripheral surface 2b1 of the small diameter portion 2b with a material having a higher linear expansion coefficient than that of the large diameter portion 2a, the temperature fluctuation amount of the first annular gap facing the small diameter portion 2b can be reduced. It was larger than the temperature variation of the gap. As a result, for example, when the temperature is high, the outer peripheral surface 2b1 of the small diameter portion 2b can be displaced greatly outward so that the gap dimension G1 of the first annular gap can be made larger than the gap dimension G2 of the radial bearing gap. Therefore, the bearing rigidity of the entire hydrodynamic bearing device 1 can be ensured as much as possible at high temperatures while reducing the loss torque. Further, when the temperature is low, the outer peripheral surface 2b1 of the small diameter portion 2b can be displaced largely inward so that the gap dimension G1 of the first annular gap can be greatly increased compared to the gap dimension G2 of the radial bearing gap. Therefore, an increase in loss torque accompanying an increase in the viscosity of the lubricating oil can be suppressed, and the merit (loss torque reducing action) of providing the small diameter portion 2b can be further utilized.

また、この実施形態のように、焼結金属製のスリーブ部８の内周面８ａに動圧溝８ａ１、８ａ２を形成する場合には、軸部２の側に小径部２ｂを設け、かつ小径部２ｂの外周部を異材部１２で形成することで、隙間寸法Ｇ１の調整を行うようにするのが望ましい。焼結金属製のスリーブ部８であれば、通常、動圧溝サイジングと呼ばれる方法で動圧溝８ａ１、８ａ２を圧迫成形することが可能だが、この際、動圧溝８ａ１、８ａ２の成形性を確保するためには、溝成形前のスリーブ部８の内周面８ａはなるべく径一定の円筒面形状であることが望ましいためである。 Further, when the dynamic pressure grooves 8a1 and 8a2 are formed in the inner peripheral surface 8a of the sintered metal sleeve portion 8 as in this embodiment, the small diameter portion 2b is provided on the shaft portion 2 side, and the small diameter portion is formed. It is desirable to adjust the gap dimension G1 by forming the outer peripheral portion of the portion 2b with the dissimilar material portion 12. In the case of the sleeve portion 8 made of sintered metal, the dynamic pressure grooves 8a1 and 8a2 can be usually compression-molded by a method called dynamic pressure groove sizing. In this case, the formability of the dynamic pressure grooves 8a1 and 8a2 is improved. This is because the inner peripheral surface 8a of the sleeve portion 8 before the groove formation is desirably a cylindrical surface shape having a constant diameter as much as possible.

また、この実施形態のように、ラジアル軸受部Ｒ１、Ｒ２が軸方向に離隔して形成される場合には、必然的に軸方向中間部に、ラジアル軸受部Ｒ１、Ｒ２に直接関与しない領域が形成される。そのため、かかる領域をロストルク低減のためのスペースとして有効に利用しつつも、ラジアル軸受部Ｒ１、Ｒ２を軸方向に離隔して設けることで、更なる軸受剛性の向上、特にモーメント荷重に対する軸受剛性の向上を図ることができる。特に、この実施形態のように、へリングボーン形状に配列された動圧溝８ａ１、８ａ２形成領域を軸方向に離隔して形成する場合、小径部２ｂが面する第１環状隙間は、油を軸方向両側に引き込むための油の貯留部として機能する。そのため、隙間寸法Ｇ１の温度変化に伴う変動量を大きくとることは、特に低温時、油不足を招くことなく動圧溝８ａ１、８ａ２による動圧作用を安定して発揮させるのに非常に有効に作用する。なお、内周面８ａのうちラジアル軸受部Ｒ１、Ｒ２に直接関与しない領域の内径寸法を、ラジアル軸受部Ｒ１、Ｒ２に関与する領域よりもわずかに大きく形成することにより、さらにこの効果を高めることもできる。例えば、この実施形態のように、各動圧溝８ａ１、８ａ２間を区分する領域（図３中クロスハッチングで示す領域）が実質的に軸受面として機能し、かつ、この軸受面として機能する領域と、この領域を除く内周面８ａとの間に動圧溝８ａ１、８ａ２の溝深さ分の径差を設けた構成は、上述の『わずかに大きく形成する』構成に含まれる。 Further, when the radial bearing portions R1 and R2 are formed apart from each other in the axial direction as in this embodiment, an area that is not directly related to the radial bearing portions R1 and R2 is necessarily formed in the axially intermediate portion. It is formed. Therefore, while effectively using such a region as a space for reducing the loss torque, the radial bearing portions R1 and R2 are provided apart from each other in the axial direction, thereby further improving the bearing rigidity, particularly the bearing rigidity against moment load. Improvements can be made. In particular, when the dynamic pressure grooves 8a1 and 8a2 forming regions arranged in a herringbone shape are formed apart in the axial direction as in this embodiment, the first annular gap facing the small diameter portion 2b It functions as an oil reservoir for drawing in both axial sides. Therefore, taking a large amount of fluctuation accompanying the temperature change of the gap dimension G1 is very effective for stably exerting the dynamic pressure action by the dynamic pressure grooves 8a1 and 8a2 without causing oil shortage especially at low temperatures. Works. In addition, this effect is further enhanced by forming the inner diameter dimension of the inner peripheral surface 8a that is not directly related to the radial bearing portions R1 and R2 slightly larger than the region related to the radial bearing portions R1 and R2. You can also. For example, as in this embodiment, a region (region indicated by cross-hatching in FIG. 3) that divides each of the dynamic pressure grooves 8a1 and 8a2 substantially functions as a bearing surface and functions as this bearing surface. And a configuration in which a diameter difference corresponding to the groove depth of the dynamic pressure grooves 8a1 and 8a2 is provided between the inner peripheral surface 8a excluding this region is included in the above-described “slightly large” configuration.

また、この実施形態のように、小径部２ｂの外周面２ｂ１を含む領域（異材部１２）を、この領域を除く軸部２本体をインサート部品とする樹脂の射出成形で形成すれば、双方の部材をそれぞれ別体に形成して一体化する場合と比べて工程数の削減につながるため好ましい。特に、この実施形態のように、複数の大径部２ａを軸方向に離隔して形成し、その間に小径部２ｂ、およびその外周部に異材部１２を設ける場合には、異材部１２を軸部２本体と別体に形成し、一体化する（組み込む）ことは困難であるので、上述のインサート成形は有効である。また、この際、大径部２ａの外径寸法から小径部２ｂの外径寸法を減じた値（外周面２ｂ１の、外周面２ａ１からの内側への後退量）を、樹脂の成形収縮で得るようにすれば、成形金型をシンプルな形状（軸部２を収容するキャビティは径一定のストレートな形状）とすることができ、金型を低コストに製作可能となる。 Further, as in this embodiment, if the region including the outer peripheral surface 2b1 of the small-diameter portion 2b (the dissimilar material portion 12) is formed by resin injection molding using the shaft portion 2 main body excluding this region as an insert part, both This is preferable because the number of steps can be reduced as compared with the case where the members are separately formed and integrated. In particular, when a plurality of large-diameter portions 2a are formed apart from each other in the axial direction as in this embodiment, and the dissimilar material portion 12 is provided between the small-diameter portions 2b and the outer periphery thereof, the dissimilar material portion 12 is pivoted. The above-described insert molding is effective because it is difficult to form and integrate (incorporate) the part 2 body separately. At this time, a value obtained by subtracting the outer diameter size of the small diameter portion 2b from the outer diameter size of the large diameter portion 2a (retraction amount of the outer peripheral surface 2b1 to the inner side from the outer peripheral surface 2a1) is obtained by molding shrinkage of the resin. By doing so, the molding die can be made into a simple shape (the cavity accommodating the shaft portion 2 is a straight shape with a constant diameter), and the die can be manufactured at low cost.

以上、本発明の第１実施形態を説明したが、本発明は、この実施形態に限定されるものではない。以下、本発明に係る他の実施形態を説明する。ここで、既述の構成要素と同一の構成、作用を有するものについては、同一の符号を付して当該要素に係る説明を省略する。 The first embodiment of the present invention has been described above, but the present invention is not limited to this embodiment. Hereinafter, other embodiments according to the present invention will be described. Here, components having the same configuration and function as the above-described components are denoted by the same reference numerals, and description of the components is omitted.

図５は、本発明の第２実施形態に係る流体軸受装置２１を示している。この実施形態では、ハウジング部７の上端内周にシール部２５が固定され、その内周面２５ａと、内周面２５ａに向かい合う軸部２２のテーパ面２２ｃとの間に、シール空間Ｓ３が形成されている。ハウジング部７の下端内周には蓋部材２６が固定され、これによりハウジング部７の下端側を閉塞している。また、軸部２２の下端には別体に設けたフランジ部２７が固定され、その上端面２７ａと、この面に向かい合うスリーブ部８の下端面８ｃとの間に第１スラスト軸受部Ｔ１１のスラスト軸受隙間が形成される。また、フランジ部２７の下端面２７ｂと、この面に向かい合う蓋部材２６の上端面２６ａとの間に第２スラスト軸受部Ｔ１２のスラスト軸受隙間が形成されている。 FIG. 5 shows a hydrodynamic bearing device 21 according to a second embodiment of the present invention. In this embodiment, the seal portion 25 is fixed to the inner periphery of the upper end of the housing portion 7, and a seal space S3 is formed between the inner peripheral surface 25a and the tapered surface 22c of the shaft portion 22 facing the inner peripheral surface 25a. Has been. A lid member 26 is fixed to the inner periphery of the lower end of the housing part 7, thereby closing the lower end side of the housing part 7. Further, a flange portion 27 provided separately is fixed to the lower end of the shaft portion 22, and the thrust of the first thrust bearing portion T11 is provided between the upper end surface 27a and the lower end surface 8c of the sleeve portion 8 facing this surface. A bearing gap is formed. Further, a thrust bearing gap of the second thrust bearing portion T12 is formed between the lower end surface 27b of the flange portion 27 and the upper end surface 26a of the lid member 26 facing this surface.

軸部２２は、大径部２２ａと小径部２２ｂ、およびシール部２２ｃとを主として構成される。大径部２２ａは軸方向に離隔して形成されると共に、各大径部２２ａ、２２ａの間に小径部２２ｂが形成されている。このうち、小径部２２ｂは、図５に示すように、軸部２２の大径部２２ａと一体に形成される小径部本体２３と、小径部本体２３の周囲に形成され、外周面２２ｂ１を含む異材部２４とからなる。ここで、異材部２４は、大径部２２ａに比べて線膨張係数の高い材料で全周にわたって形成されており、小径部２２ｂの外周面２２ｂ１は、スリーブ部８の動圧溝８ａ１形成領域と動圧溝８ａ２形成領域との間の領域と向かい合うようになっている。なお、図５中、ラジアル軸受部Ｒ１１、Ｒ１２はそれぞれ第１実施形態におけるラジアル軸受部Ｒ１、Ｒ２に対応している。これ以外の構成は、第１実施形態に準じるので説明を省略する。 The shaft portion 22 mainly includes a large diameter portion 22a, a small diameter portion 22b, and a seal portion 22c. The large diameter portion 22a is formed to be separated in the axial direction, and a small diameter portion 22b is formed between the large diameter portions 22a and 22a. Among these, as shown in FIG. 5, the small diameter portion 22b is formed around the small diameter portion main body 23 and the small diameter portion main body 23 formed integrally with the large diameter portion 22a of the shaft portion 22, and includes an outer peripheral surface 22b1. It consists of a different material portion 24. Here, the dissimilar material portion 24 is formed over the entire circumference with a material having a higher linear expansion coefficient than the large diameter portion 22a, and the outer peripheral surface 22b1 of the small diameter portion 22b is a region where the dynamic pressure groove 8a1 of the sleeve portion 8 is formed. It faces the region between the dynamic pressure groove 8a2 formation region. In FIG. 5, radial bearing portions R11 and R12 correspond to the radial bearing portions R1 and R2 in the first embodiment, respectively. Since the other configuration conforms to the first embodiment, the description thereof is omitted.

この実施形態においても、（１）軸部２２に、向かい合うスリーブ部８との間にラジアル軸受隙間を形成する大径部２２ａと、大径部２２ａに比べて外径寸法を小さくした小径部２２ｂとを設け、小径部２２ｂとスリーブ部８との間の第１環状隙間をラジアル軸受隙間（第２環状隙間）より大きく設定した。また、併せて、（２）小径部２２ｂの外周面２２ｂ１を含む領域を大径部２２ａよりも線膨張係数の高い材料で形成することで、小径部２２ｂが面する第１環状隙間の温度変動量を、ラジアル軸受隙間の変動量より大きくした。従い、前者の構成（１）によれば、軸部２２の回転時、第１環状隙間の隙間寸法からラジアル軸受隙間の隙間寸法を減じた分、ロストルクの低減化が可能となる。また、後者の構成（２）によれば、例えば高温時、異材部２４をなるべく大きく外側に変位させて第１環状隙間を減少させることにより、流体軸受装置２１全体での軸受剛性を高めることができる。また、低温時には、小径部２２ｂの外周面２２ｂ１をなるべく大きく内側に変位させて、ラジアル軸受隙間の隙間寸法に比べて第１環状隙間の隙間寸法を大きく拡げることができる。そのため、潤滑油の粘度上昇に伴うロストルクの増加を抑えることができる。 Also in this embodiment, (1) a large-diameter portion 22a that forms a radial bearing gap between the shaft portion 22 and the facing sleeve portion 8, and a small-diameter portion 22b that has a smaller outer diameter than the large-diameter portion 22a. And the first annular gap between the small diameter portion 22b and the sleeve portion 8 is set larger than the radial bearing gap (second annular gap). In addition, (2) by forming the region including the outer peripheral surface 22b1 of the small diameter portion 22b with a material having a higher linear expansion coefficient than that of the large diameter portion 22a, the temperature variation of the first annular gap facing the small diameter portion 22b. The amount was larger than the amount of variation in the radial bearing clearance. Therefore, according to the former configuration (1), when the shaft portion 22 is rotated, the loss torque can be reduced by subtracting the clearance dimension of the radial bearing clearance from the clearance dimension of the first annular clearance. Further, according to the latter configuration (2), for example, at high temperatures, the dissimilar material portion 24 is displaced as much as possible outside to reduce the first annular gap, thereby increasing the bearing rigidity of the entire hydrodynamic bearing device 21. it can. Further, at the time of low temperature, the outer peripheral surface 22b1 of the small diameter portion 22b can be displaced inward as much as possible, so that the gap dimension of the first annular gap can be greatly expanded compared to the gap dimension of the radial bearing gap. Therefore, an increase in loss torque accompanying an increase in the viscosity of the lubricating oil can be suppressed.

図６は、本発明の第３実施形態に係る流体軸受装置３１を示している。この実施形態において、軸部３２の上端（フランジ部３７とは反対側）にはハブ部３５が一体あるいは別体に設けられる。ここで、ハブ部３５は、ハウジング部７の開口側（上側）を覆う円盤部３５ａと、円盤部３５ａの外周部から軸方向下方に延びた筒状部３５ｂとを主に有する。また、この実施形態では、ハウジング部７の上端に、例えば図３（ｂ）に示す配列態様をなす動圧溝形成領域７ｂが設けられ、スラスト方向に向かい合うハブ部３５の円盤部３５ａの下端面３５ａ１との間に第１スラスト軸受部Ｔ２１のスラスト軸受隙間を形成する。また、ハウジング部７の外周には、上方に向かって漸次拡径するテーパ状のシール面７ｃが形成される。このテーパ状のシール面７ｃは、筒状部３５ｂの内周面３５ｂ１との間に、ハウジング部７の閉塞側（下方）から開口側（上方）に向けて半径方向寸法が漸次縮小した環状のシール空間Ｓ４を形成する。 FIG. 6 shows a hydrodynamic bearing device 31 according to a third embodiment of the present invention. In this embodiment, the hub portion 35 is provided integrally or separately at the upper end of the shaft portion 32 (on the side opposite to the flange portion 37). Here, the hub part 35 mainly has a disk part 35a that covers the opening side (upper side) of the housing part 7 and a cylindrical part 35b that extends downward in the axial direction from the outer peripheral part of the disk part 35a. In this embodiment, a dynamic pressure groove forming region 7b having an arrangement shown in FIG. 3B, for example, is provided at the upper end of the housing portion 7, and the lower end surface of the disc portion 35a of the hub portion 35 facing the thrust direction. A thrust bearing gap of the first thrust bearing portion T21 is formed between the bearing 35a1. In addition, a tapered seal surface 7 c that gradually increases in diameter upward is formed on the outer periphery of the housing portion 7. This taper-shaped sealing surface 7c has an annular shape between the inner peripheral surface 35b1 of the cylindrical portion 35b and whose radial dimension is gradually reduced from the closing side (downward) to the opening side (upward) of the housing portion 7. A seal space S4 is formed.

軸部３２は、大径部３２ａと小径部３２ｂとを有し、その下端に大径部３２ａおよび小径部３２ｂとは別体に形成したフランジ部３７をねじ止め等で固定してなる。大径部３２ａは軸方向に離隔して形成されると共に、各大径部３２ａ、３２ａの間に小径部３２ｂが形成されている。このうち、小径部３２ｂは、図６に示すように、軸部３２の大径部３２ａと一体に形成される小径部本体３３と、小径部本体３３の周囲に形成され、外周面３２ｂ１を含む異材部３４とからなる。ここで、異材部３４は、大径部３２ａに比べて線膨張係数の高い材料（樹脂材料）で全周にわたって形成されており、小径部３２ｂの外周面３２ｂ１は、スリーブ部８の動圧溝８ａ１形成領域と動圧溝８ａ２形成領域との間の領域と向かい合うようになっている。また、蓋部材３６とフランジ部３７との間には、スリーブ部８とフランジ部３７との間に比べて十分な大きさの軸方向隙間が設けられている。なお、図６中、ラジアル軸受部Ｒ２１、Ｒ２２、第２スラスト軸受部Ｔ２２、フランジ部３７はそれぞれ第２実施形態におけるラジアル軸受部Ｒ１１、Ｒ１２、第１スラスト軸受部Ｔ１１に対応している。これ以外の構成は、第１、第２実施形態に準じるので説明を省略する。 The shaft portion 32 has a large-diameter portion 32a and a small-diameter portion 32b, and a flange portion 37 formed separately from the large-diameter portion 32a and the small-diameter portion 32b at the lower end thereof is fixed by screwing or the like. The large diameter portion 32a is formed to be separated in the axial direction, and a small diameter portion 32b is formed between the large diameter portions 32a and 32a. Among these, the small diameter part 32b is formed around the small diameter part main body 33 and the small diameter part main body 33 formed integrally with the large diameter part 32a of the shaft part 32 as shown in FIG. 6, and includes an outer peripheral surface 32b1. It consists of a different material part 34. Here, the dissimilar material portion 34 is formed over the entire circumference with a material (resin material) having a higher linear expansion coefficient than the large diameter portion 32 a, and the outer peripheral surface 32 b 1 of the small diameter portion 32 b is a dynamic pressure groove of the sleeve portion 8. It faces a region between the 8a1 formation region and the dynamic pressure groove 8a2 formation region. Further, an axial gap having a sufficiently large size is provided between the lid member 36 and the flange portion 37 as compared with the sleeve portion 8 and the flange portion 37. In FIG. 6, the radial bearing portions R21 and R22, the second thrust bearing portion T22, and the flange portion 37 correspond to the radial bearing portions R11 and R12 and the first thrust bearing portion T11 in the second embodiment, respectively. Since the other configuration conforms to the first and second embodiments, the description thereof is omitted.

この実施形態においても、（１）軸部３２に、向かい合うスリーブ部８との間にラジアル軸受隙間を形成する大径部３２ａと、大径部３２ａに比べて外径寸法を小さくした小径部３２ｂとを設け、小径部３２ｂとスリーブ部８との間の第１環状隙間をラジアル軸受隙間（第２環状隙間）より大きく設定した。また、併せて、（２）小径部３２ｂの外周面３２ｂ１を含む領域を大径部３２ａよりも線膨張係数の高い材料で形成することで、小径部３２ｂが面する第１環状隙間の温度変動量を、ラジアル軸受隙間の変動量より大きくした。従い、前者の構成（１）によれば、軸部３２の回転時、第１環状隙間の隙間寸法からラジアル軸受隙間の隙間寸法を減じた分、ロストルクの低減化が可能となる。また、後者の構成（２）によれば、例えば高温時、異材部３４を大きく外側に変位させて第１環状隙間を減少させることにより、流体軸受装置３１全体での軸受剛性を高めることができる。また、低温時には、小径部３２ｂの外周面３２ｂ１を大きく内側に変位させて、ラジアル軸受隙間の隙間寸法に比べて第１環状隙間の隙間寸法を大きく拡げることができる。そのため、潤滑油の粘度上昇に伴うロストルクの増加を抑えることができる。 Also in this embodiment, (1) a large diameter portion 32a that forms a radial bearing gap between the shaft portion 32 and the facing sleeve portion 8, and a small diameter portion 32b that has a smaller outer diameter than the large diameter portion 32a. The first annular gap between the small diameter portion 32b and the sleeve portion 8 is set larger than the radial bearing gap (second annular gap). In addition, (2) the temperature variation of the first annular gap facing the small diameter portion 32b is formed by forming the region including the outer peripheral surface 32b1 of the small diameter portion 32b with a material having a higher linear expansion coefficient than the large diameter portion 32a. The amount was larger than the amount of variation in the radial bearing clearance. Therefore, according to the former configuration (1), when the shaft portion 32 is rotated, the loss torque can be reduced by the amount obtained by subtracting the gap dimension of the radial bearing gap from the gap dimension of the first annular gap. Further, according to the latter configuration (2), for example, at high temperatures, the dissimilar material portion 34 is largely displaced outwardly to reduce the first annular gap, whereby the bearing rigidity of the entire hydrodynamic bearing device 31 can be increased. . Further, at the time of low temperature, the outer peripheral surface 32b1 of the small diameter portion 32b can be greatly displaced inward, so that the gap dimension of the first annular gap can be greatly expanded compared to the gap dimension of the radial bearing gap. Therefore, an increase in loss torque accompanying an increase in the viscosity of the lubricating oil can be suppressed.

なお、第３実施形態では、ハウジング部７の上端面に複数の動圧溝を配列した領域７ｂを設けると共に、スリーブ部８の下端面８ｃに複数の動圧溝８ｃ１を配列した領域を設けた場合を説明したが、本発明は、同実施形態に係る構成において第１スラスト軸受部Ｔ１のみを設けた流体軸受装置にも同様に適用することができる。この場合、軸部３２を、フランジ部３７を有しない形状とし、かつハウジング部７を、蓋部材３６を底部として一体に形成することで有底円筒形とした形状にすることができる。 In the third embodiment, a region 7b in which a plurality of dynamic pressure grooves are arranged is provided on the upper end surface of the housing portion 7, and a region in which a plurality of dynamic pressure grooves 8c1 are arranged is provided in the lower end surface 8c of the sleeve portion 8. Although the case has been described, the present invention can be similarly applied to a hydrodynamic bearing device in which only the first thrust bearing portion T1 is provided in the configuration according to the embodiment. In this case, the shaft portion 32 can be formed into a shape without the flange portion 37 and the housing portion 7 can be formed into a bottomed cylindrical shape by integrally forming the lid member 36 as the bottom portion.

また、第２、第３実施形態では、軸部２２、３２とフランジ部２７、３７とをそれぞれ別体に形成した後、一体化（固定）する構成を採っていたが、最初からフランジ部２７、３７を軸部２２、３２と一体に形成したものに対して本発明を適用しても構わない（第３実施形態においては、ハブ部３５が、フランジ部３７および軸部３２と別体構造になる）。また、異材部１２、２４、３４を射出成形可能な材料（例えば樹脂）で形成するのであれば、一部を金属で、異材部１２、２４、３４を含む残部を樹脂で形成してなる軸部を形成することも可能である。 In the second and third embodiments, the shaft portions 22 and 32 and the flange portions 27 and 37 are formed separately and then integrated (fixed). , 37 may be integrally formed with the shaft portions 22 and 32 (in the third embodiment, the hub portion 35 has a separate structure from the flange portion 37 and the shaft portion 32). become). Further, if the dissimilar material parts 12, 24, 34 are formed of a material (for example, resin) that can be injection-molded, a part is made of metal and the remaining part including the dissimilar material parts 12, 24, 34 is formed of resin. It is also possible to form a part.

図７はその一例を示すもので、軸部の外周を構成する筒部４２と、筒部４２の一端から半径方向に延び、筒部４２と一体に形成される鍔部４３とからなる金属部４１をインサート部品として、フランジ部および異材部を一体に備えた軸部を射出成形する工程を概念的に示している。ここで、筒部４２の外周には環状の凹部４４が設けられ、この凹部４４と筒部４２の内周とを連通する連通孔４５が円周方向等間隔に複数設けられている。この場合、上記構成をなす金属部４１を例えば図７に示すように完成品に倣った形状のキャビティ４６を有する金型４７、４８内に供給配置する。そして、例えば金型４８のフランジ部底面中央に対応する位置に設けたゲート４９より溶融樹脂をキャビティ４６内に充填し、これを固化することで、樹脂製の異材部を一体に有し、かつ鞘部を金属、芯部を樹脂とするハイブリッド構造の軸部を容易に形成することができる。この場合、ゲート４９より供給された溶融樹脂は連通孔４５を介して環状凹部４４に供給されることで、ピンゲートのような単純な機構で異材部への樹脂の充填を容易に行うことができる。もちろん、樹脂の成形態様はこれに限定されず、完成品としての大径部２ａよりも外側に突出しなければ、（異材部１２形成箇所となる）凹部４４の外側に１もしくは複数の点ゲートを設ける構成、あるいは点以外の任意形状のゲートを設ける構成を採ることもできる。 FIG. 7 shows an example of this, and a metal part comprising a cylindrical part 42 that forms the outer periphery of the shaft part, and a flange part 43 that extends radially from one end of the cylindrical part 42 and is formed integrally with the cylindrical part 42. The process of carrying out the injection molding of the shaft part which integrally provided the flange part and the dissimilar material part by using 41 as an insert part is shown conceptually. Here, an annular concave portion 44 is provided on the outer periphery of the cylindrical portion 42, and a plurality of communication holes 45 communicating the concave portion 44 and the inner periphery of the cylindrical portion 42 are provided at equal intervals in the circumferential direction. In this case, the metal part 41 having the above-described configuration is supplied and arranged in dies 47 and 48 having a cavity 46 shaped like a finished product as shown in FIG. Then, for example, molten resin is filled into the cavity 46 from a gate 49 provided at a position corresponding to the center of the bottom surface of the flange portion of the mold 48 and solidified, thereby integrally having a different material portion made of resin, and The shaft portion of the hybrid structure in which the sheath portion is made of metal and the core portion is made of resin can be easily formed. In this case, the molten resin supplied from the gate 49 is supplied to the annular recess 44 through the communication hole 45, so that the resin can be easily filled into the different material portion by a simple mechanism such as a pin gate. . Of course, the resin molding mode is not limited to this, and one or a plurality of point gates are provided outside the recess 44 (where the dissimilar material portion 12 is formed) as long as it does not protrude outward from the large-diameter portion 2a as a finished product. It is also possible to adopt a configuration in which a gate having an arbitrary shape other than a point is provided.

また、以上の実施形態（第１〜第３実施形態）では、軸受部材６を構成するハウジング部７とスリーブ部８とを別体に形成した場合を説明したが、これに限る必要はなく、ハウジング部７とスリーブ部８とを樹脂又は金属で一体に形成することも可能である。あるいは、ハウジング部７とスリーブ部８との一体化に限らず、ハウジング部７とシール部２５、ハウジング部７と蓋部材２６など、既述の構成部品同士を一体化（同一材料で一体に形成）することも可能である。 Moreover, although the above embodiment (1st-3rd embodiment) demonstrated the case where the housing part 7 and the sleeve part 8 which comprise the bearing member 6 were formed in the different body, it is not necessary to restrict to this, It is also possible to integrally form the housing portion 7 and the sleeve portion 8 with resin or metal. Alternatively, not only the integration of the housing part 7 and the sleeve part 8, but also the above-described components such as the housing part 7 and the seal part 25, the housing part 7 and the lid member 26 are integrated (formed integrally with the same material). ) Is also possible.

また、第１実施形態では、大径部２ａをＳＵＳ鋼等の金属製とし、小径部２ｂの外周面２ｂ１を含む異材部１２をＬＣＰ等の樹脂製とした場合を例示したが、もちろんこれに限る必要はない。異材部１２が、大径部２ａよりも線膨張係数の高い材料で形成されている限り、種々の材料およびその組み合わせが選択可能である（第２、第３実施形態についても同様）。例えば、異材部１２を、樹脂に代えてＣｕなどの金属材料などで形成することもできる。また、形成方法についてもめっき（Ｃｕ、Ｎｉなど）、インクジェット方式など任意の方法が選択できる。また、樹脂等に添加する添加剤の種類、添加量によっても膨張・収縮量（あるいは成形収縮量など）を調整することが可能である。 In the first embodiment, the case where the large-diameter portion 2a is made of a metal such as SUS steel and the dissimilar material portion 12 including the outer peripheral surface 2b1 of the small-diameter portion 2b is made of a resin such as LCP. There is no need to limit. As long as the dissimilar material portion 12 is formed of a material having a higher linear expansion coefficient than the large diameter portion 2a, various materials and combinations thereof can be selected (the same applies to the second and third embodiments). For example, the dissimilar material portion 12 can be formed of a metal material such as Cu instead of the resin. As a forming method, any method such as plating (Cu, Ni, etc.) or an ink jet method can be selected. Further, the amount of expansion / shrinkage (or the amount of molding shrinkage, etc.) can be adjusted by the type and amount of additive added to the resin.

また、第１実施形態では、小径部２ｂの外周面２ｂ１を含む領域を大径部２ａよりも線膨張係数の高い材料で形成した場合を説明したが、逆に、小径部２ｂの外周面２ｂ１を含む領域を大径部２ａよりも線膨張係数の低い材料で形成することによっても、低トルク化を図りつつ、使用時の温度変化に起因する軸受機能上の不具合を回避することが可能である。すなわち、小径部２ｂの外周面２ｂ１を含む領域を、大径部２ａよりも線膨張係数の低い材料で形成した場合、高温時には、大径部２ａの外周面２ａ１の外側への変位量が、小径部２ｂの外周面２ｂ１のそれに比べて大きくなる。そのため、小径部２ｂの外周面２ｂ１と、外周面２ｂ１に向かい合う内周面８ａとの間に形成される第１環状隙間の隙間寸法Ｇ１が大きくなり、潤滑油の膨張を第１環状隙間に形成される空間で吸収することができる。従って、シール空間におけるバッファ容量の増大化を抑え、高温時の油漏れを可及的に回避することができる。第２、第３実施形態についても同様のことがいえる。例えば大径部２ａ等にＳＵＳ鋼などの金属材料を、異材部１２にセラミックスなどを適用すればこの構成を採ることができる。なお、形成方法としては溶射など任意の方法が適用可能である。 Moreover, although 1st Embodiment demonstrated the case where the area | region containing the outer peripheral surface 2b1 of the small diameter part 2b was formed with the material whose linear expansion coefficient is higher than the large diameter part 2a, conversely, the outer peripheral surface 2b1 of the small diameter part 2b It is possible to avoid problems on the bearing function due to temperature changes during use, while reducing torque, by forming the region including the material with a material having a lower linear expansion coefficient than that of the large-diameter portion 2a. is there. That is, when the region including the outer peripheral surface 2b1 of the small-diameter portion 2b is formed of a material having a lower linear expansion coefficient than the large-diameter portion 2a, the amount of displacement of the large-diameter portion 2a to the outside of the outer peripheral surface 2a1 is It becomes larger than that of the outer peripheral surface 2b1 of the small diameter portion 2b. Therefore, the gap dimension G1 of the first annular gap formed between the outer peripheral surface 2b1 of the small diameter portion 2b and the inner peripheral surface 8a facing the outer peripheral surface 2b1 is increased, and the expansion of the lubricating oil is formed in the first annular gap. Can be absorbed in space. Therefore, an increase in the buffer capacity in the seal space can be suppressed, and oil leakage at a high temperature can be avoided as much as possible. The same can be said for the second and third embodiments. For example, this configuration can be adopted if a metal material such as SUS steel is applied to the large diameter portion 2a and the like, and ceramics or the like is applied to the dissimilar material portion 12. As a forming method, any method such as thermal spraying can be applied.

特に、第１、第２実施形態に係る流体軸受装置１、２１であれば、バッファ容量の増大を狙ってシール空間Ｓ１〜Ｓ３（を形成するフランジ部９、１０、およびシール部２５）の軸方向寸法を大きく取らずに済む。そのため、流体軸受装置１、２１の大型化、特に厚肉化を回避することができ、これを組み込むべき情報機器の小型化にも対応することができる。 In particular, in the hydrodynamic bearing devices 1 and 21 according to the first and second embodiments, the shafts of the seal spaces S1 to S3 (the flange portions 9 and 10 and the seal portion 25 that form the seal space) aiming at an increase in the buffer capacity. It is not necessary to take a large dimensional dimension. Therefore, it is possible to avoid an increase in size, particularly a thickness, of the hydrodynamic bearing devices 1 and 21, and it is possible to cope with a reduction in the size of an information device into which the fluid bearing devices 1 and 21 are to be incorporated.

また、以上の実施形態では、ラジアル軸受部Ｒ１〜Ｒ２２およびスラスト軸受部Ｔ１〜Ｔ２２として、へリングボーン形状やスパイラル形状の動圧溝により流体の動圧作用を発生させる構成を例示しているが、本発明はこれに限定されるものではない。 Moreover, in the above embodiment, although the radial bearing part R1-R22 and the thrust bearing part T1-T22 have illustrated the structure which generate | occur | produces the dynamic pressure action of the fluid by a herringbone shape or a spiral-shaped dynamic pressure groove. However, the present invention is not limited to this.

例えば、ラジアル軸受部Ｒ１、Ｒ２として、図示は省略するが、軸方向の溝を円周方向の複数箇所に形成した、いわゆるステップ状の動圧発生部、あるいは、円周方向に複数の円弧面を配列し、向かい合う軸部２の大径部２ａとの間に、くさび状の径方向隙間（軸受隙間）を形成した、いわゆる多円弧軸受を採用してもよい。 For example, although not shown as radial bearing portions R1 and R2, a so-called step-like dynamic pressure generating portion in which axial grooves are formed at a plurality of locations in the circumferential direction, or a plurality of circular arc surfaces in the circumferential direction. A so-called multi-arc bearing in which a wedge-shaped radial clearance (bearing clearance) is formed between the shaft portion 2 and the large-diameter portion 2a of the opposite shaft portion 2 may be employed.

あるいは、ラジアル軸受面となるスリーブ部８の内周面８ａを、動圧発生部としての動圧溝や円弧面等を設けない真円状内周面とし、この内周面と向かい合う大径部２ａの真円状外周面２ａ１とで、いわゆる真円軸受を構成することができる。もちろん、同様の構成は、他の実施形態に係るラジアル軸受部Ｒ１１、Ｒ１２、Ｒ２１、Ｒ２２にも採用可能である。 Alternatively, the inner peripheral surface 8a of the sleeve portion 8 serving as a radial bearing surface is a perfectly circular inner peripheral surface not provided with a dynamic pressure groove or arc surface as a dynamic pressure generating portion, and a large diameter portion facing the inner peripheral surface A so-called perfect circle bearing can be constituted by the perfect circular outer peripheral surface 2a1 of 2a. Of course, the same configuration can also be adopted for the radial bearing portions R11, R12, R21, and R22 according to other embodiments.

また、スラスト軸受部Ｔ１、Ｔ２の一方又は双方は、同じく図示は省略するが、スラスト軸受面となる領域に、複数の半径方向溝形状の動圧溝を円周方向所定間隔に設けた、いわゆるステップ軸受、あるいは波型軸受（端面が調和波形などの波型になったもの）等で構成することもできる。もちろん、他のスラスト軸受部Ｔ１１〜Ｔ２２についても同様に構成することができる。 One or both of the thrust bearing portions T1 and T2 are also not shown in the figure, but a plurality of radial groove-shaped dynamic pressure grooves are provided at predetermined intervals in the circumferential direction in a region that becomes a thrust bearing surface. It can also be configured by a step bearing or a corrugated bearing (having a corrugated waveform such as an end face). Of course, the other thrust bearing portions T11 to T22 can be similarly configured.

また、以上の説明では、動圧発生部を何れも固定体（ハウジング部７やスリーブ部８など）の側に設けた場合を説明したが、その一部あるいは全てを回転体（軸部２やフランジ部９、１０など）の側に設けることも可能である。 In the above description, the case where all of the dynamic pressure generating portions are provided on the side of the fixed body (such as the housing portion 7 and the sleeve portion 8) has been described. It can also be provided on the side of the flange portions 9, 10, etc.

また、以上の説明では、流体軸受装置１、２１、３１の内部に充満し、ラジアル軸受隙間に流体膜を形成可能な潤滑流体として潤滑油を例示したが、それ以外にも当該軸受隙間に流体膜を発生可能な潤滑流体、例えば空気等の気体や、液体、磁性流体等の流動性を有する潤滑剤、あるいは潤滑グリース等を使用することもできる。 In the above description, the lubricating oil is exemplified as the lubricating fluid that fills the fluid bearing devices 1, 21, and 31 and can form a fluid film in the radial bearing gap. A lubricating fluid capable of generating a film, for example, a gas such as air, a fluid lubricant such as a liquid or a magnetic fluid, or a lubricating grease may be used.

本発明の第１実施形態に係る流体軸受装置を組込んだスピンドルモータの断面図である。It is sectional drawing of the spindle motor incorporating the hydrodynamic bearing apparatus which concerns on 1st Embodiment of this invention. 第１実施形態に係る流体軸受装置の断面図である。It is sectional drawing of the hydrodynamic bearing apparatus which concerns on 1st Embodiment. （ａ）はスリーブ部の断面図、（ｂ）はスリーブ部を矢印ａの方向から見た平面図、（ｃ）はスリーブ部の矢印ｂの方向から見た平面図である。(A) is sectional drawing of a sleeve part, (b) is the top view which looked at the sleeve part from the direction of arrow a, (c) is the top view which looked at the direction of arrow b of the sleeve part. 大径部と小径部との境界周辺を拡大した一部断面図である。It is the partial cross section figure which expanded the boundary periphery of a large diameter part and a small diameter part. 本発明の第２実施形態に係る流体軸受装置の断面図である。It is sectional drawing of the hydrodynamic bearing apparatus which concerns on 2nd Embodiment of this invention. 本発明の第３実施形態に係る流体軸受装置の断面図である。It is sectional drawing of the hydrodynamic bearing apparatus which concerns on 3rd Embodiment of this invention. 他の構成例に係る軸部のインサート成形工程を概念的に示す図である。It is a figure which shows notionally the insert molding process of the axial part which concerns on the other structural example.

Explanation of symbols

１、２１、３１流体軸受装置
２、２２、３２軸部
２ａ、２２ａ、３２ａ大径部
２ｂ、２２ｂ、３２ｂ小径部
２ｂ１、２２ｂ１、３２ｂ１外周面
８スリーブ部
８ａ内周面
８ａ１、８ａ２動圧溝
１１、２３、３３小径部本体
１２、２４、３４異材部
Ｇ１半径隙間寸法
Ｇ２半径隙間寸法
Ｒ１、Ｒ２、Ｒ１１、Ｒ１２、Ｒ２１、Ｒ２２ラジアル軸受部
Ｔ１、Ｔ２、Ｔ１１、Ｔ１２、Ｔ２１、Ｔ２２スラスト軸受部
Ｓ１、Ｓ２、Ｓ３、Ｓ４シール空間 1, 21, 31 Hydrodynamic bearing devices 2, 22, 32 Shaft portions 2a, 22a, 32a Large diameter portions 2b, 22b, 32b Small diameter portions 2b1, 22b1, 32b1 Outer surface 8 Sleeve portion 8a Inner surfaces 8a1, 8a2 Dynamic pressure grooves 11, 23, 33 Small-diameter portion main body 12, 24, 34 Dissimilar material portion G1 Radial gap size G2 Radial gap size R1, R2, R11, R12, R21, R22 Radial bearing portions T1, T2, T11, T12, T21, T22 Thrust bearing Part S1, S2, S3, S4 Seal space

Claims

A shaft portion having a large diameter portion and a small diameter portion having different outer diameter dimensions, and
A bearing gap formed between the outer peripheral surface of the large-diameter portion and the surface facing the outer peripheral surface;
In a hydrodynamic bearing device that includes a lubricating fluid that fills the bearing gap and is in contact with the small diameter portion, and that supports the shaft portion so as to be relatively rotatable via a fluid film of the lubricating fluid formed in the bearing gap.
A hydrodynamic bearing device characterized in that a region including an outer peripheral surface of a small diameter portion is formed of a material having a linear expansion coefficient different from that of a large diameter portion.

2. The hydrodynamic bearing device according to claim 1, wherein the region including the outer peripheral surface of the small diameter portion is formed of a material having a higher linear expansion coefficient than that of the large diameter portion.

The hydrodynamic bearing device according to claim 1, wherein the bearing gap is formed apart in the axial direction, and a small diameter portion is provided between a plurality of large diameter portions forming each bearing gap.

2. The hydrodynamic bearing device according to claim 1, wherein the region including the outer peripheral surface of the small diameter portion is formed by resin injection molding using the shaft portion main body excluding this region as an insert part.