JP2010144778A - Bearing device, spindle motor, and disk drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing device, a spindle motor, and a disk drive device capable of relatively rotating a sleeve and a shaft accurately by preventing an inner circumference surface of the sleeve from projecting out inward in the radial direction when a circumferential groove is formed on an end surface of a sleeve. <P>SOLUTION: This bearing device includes a shaft arranged in a vertical direction along an axis, a roughly cylindrical sleeve 343 including an inner circumference surface opposing to an outer circumference surface of the shaft and having lubricating oil impregnated in a porous body made of sintered metal. The sleeve includes a circumferential groove 343d formed on a circular arc shape or an annular shape about the axis on an upper surface thereof, and a chamfer part 343g formed on an inner circumference edge of the upper surface. Axial depth D1 of the circumferential groove is smaller than axial length D2 of the chamfer part. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a bearing device, a spindle motor including the bearing device, and a disk drive device including the spindle motor.

  A hard disk device or an optical disk device is equipped with a spindle motor for rotating the disk around its central axis. The spindle motor has a stationary part fixed to the housing of the apparatus and a rotating part that rotates while supporting the disk. The spindle motor generates torque about the central axis by the magnetic flux generated between the stationary part and the rotating part, and thereby rotates the rotating part with respect to the stationary part.

The stationary part and the rotating part of the spindle motor are connected via a bearing device. As a conventional bearing device, for example, a bearing device having a substantially cylindrical sleeve surrounding an outer peripheral surface of a shaft and a bearing housing for accommodating the sleeve is known. A conventional bearing device having a sleeve and a bearing housing, and a spindle motor including the bearing device are disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-176816.
JP 2004-176816 A

  In the conventional bearing device, the sleeve is fixed to the inner peripheral surface of the bearing housing with an adhesive. In the manufacturing process of such a bearing device, when the sleeve is inserted into the bearing housing in the axial direction, the adhesive may be squeezed out near the end face of the sleeve. For this reason, an annular groove may be formed on the end surface of the sleeve in order to secure a space for accommodating the squeezed adhesive near the end surface of the sleeve.

  However, when such an annular groove is formed on the end surface of the sleeve, for example, by press molding, there is a problem in that the inner peripheral surface of the sleeve protrudes radially inward in the vicinity of the end surface. In this case, since the interval between the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve is not uniform, it is difficult to rotate the shaft with respect to the sleeve with high accuracy.

  The present invention prevents the inner peripheral surface of the sleeve from projecting inward in the radial direction when forming the circumferential groove on the end surface of the sleeve, thereby enabling relative rotation between the sleeve and the shaft with high accuracy. An object of the present invention is to provide a bearing device, a spindle motor, and a disk drive device.

  In order to solve the above-mentioned problem, a first invention of the present application is a bearing device, which has a shaft disposed in a vertical direction along a central axis, and an inner peripheral surface facing the outer peripheral surface of the shaft, A substantially cylindrical sleeve formed by impregnating a porous body made of a binder metal with a lubricant, and the sleeve is formed in an arc shape or an annular shape around the central axis on an upper surface thereof. A circumferential groove and a chamfered portion formed on an inner peripheral edge of the upper surface, and an axial depth of the circumferential groove is smaller than an axial dimension of the chamfered portion.

  A second invention of the present application is a spindle motor, which has a stationary part and a support part that supports a disk, and is a rotary part that is rotatably supported by the stationary part via the bearing device of the first invention. And a torque generator that generates torque about the central axis between the stationary part and the rotating part.

  A third invention of the present application is a disk drive device, wherein the spindle motor of the second invention and an access for reading or writing information to or from the disk supported by the rotating part of the spindle motor. And a housing that houses the spindle motor and the access unit.

  According to the first invention of the present application, when the circumferential groove is formed in the sleeve, it is possible to prevent the inner circumferential surface of the sleeve from projecting radially inward. For this reason, the sleeve and the shaft can be relatively rotated with high accuracy.

  According to the second invention of the present application, the rotational accuracy of the spindle motor can be improved by improving the rotational accuracy of the bearing device mounted on the spindle motor.

  According to the third aspect of the present invention, it is possible to reduce errors in reading and writing information in the disk drive device by improving the rotation accuracy of the spindle motor mounted on the disk drive device.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the following description, the shape and positional relationship of each member will be described with the direction along the central axis A as the vertical direction, the rotation part 4 side as “upper” and the stationary part 3 side as “lower”. However, this is defined only in the vertical direction for convenience of explanation, and limits the installation posture when the bearing device, spindle motor, and disk drive device of the present invention are mounted on an actual device. It is not a thing.

<1. Configuration of disk drive>
FIG. 1 is a longitudinal sectional view of a disk drive device 2 according to an embodiment of the present invention. The disk drive device 2 is a hard disk device that reads information from and writes information to the magnetic disk 22 while rotating the magnetic disk 22. As shown in FIG. 1, the disk drive device 2 mainly includes a device housing 21, a magnetic disk (hereinafter simply referred to as “disk”) 22, an access unit 23, and a spindle motor 1.

  The device housing 21 is a housing that accommodates the magnetic disk 22, the access unit 23, and the spindle motor 1. The access unit 23 moves the head 231 along the recording surface of the disk 22 supported by the spindle motor 1 to read information from the disk 22 and write information to the disk 22. Note that the access unit 23 may perform only one of reading and writing of information with respect to the disk 22.

<2. Spindle motor configuration>
Next, a detailed configuration of the spindle motor 1 will be described. FIG. 2 is a longitudinal sectional view of the spindle motor 1. As shown in FIG. 2, the spindle motor 1 includes a stationary portion 3 fixed to the device housing 21 of the disk drive device 2, and a rotating portion 4 that rotates about the central axis A while supporting the disk 22. ing.

  First, the configuration of the stationary part 3 will be described. The stationary part 3 mainly includes a base member 31, a stator core 32, a coil 33, and a stationary bearing unit 34.

  The base member 31 is formed of a metal material such as an aluminum alloy, and is fixed to the device housing 21 of the disk drive device 2. The base member 31 is formed with a substantially cylindrical holder portion 311 that protrudes in the axial direction (a direction along the central axis A; the same applies hereinafter) around the central axis A. The holder member 311 has a radial direction (the central axis). The stationary bearing unit 34 is fixed inside the direction orthogonal to A. The same applies hereinafter. In the present embodiment, the base member 31 and the device housing 21 are separate bodies, but the base member 31 and the device housing 21 may be configured by a single member.

  The stator core 32 and the coil 33 function as a magnetic flux generator that generates a magnetic flux according to the drive current. The stator core 32 has an annular core back 321 fitted to the outer peripheral surface of the holder portion 311 of the base member 31 and a plurality of teeth portions 322 protruding outward from the core back 321 in the radial direction. ing. The stator core 32 is obtained, for example, by punching a laminated steel sheet in which electromagnetic steel sheets are laminated in the axial direction. Further, the coil 33 is constituted by a conductive wire wound around each tooth portion 322 of the stator core 32.

  The stationary bearing unit 34 is a mechanism for rotatably supporting the shaft 41 on the rotating unit 4 side. The static bearing unit 34 and the shaft 41 constitute a fluid dynamic bearing device 5 that connects the stationary part 3 and the rotating part 4 in a relatively rotatable state about the central axis A.

  FIG. 3 is an enlarged longitudinal sectional view of the fluid dynamic pressure bearing device 5. As shown in FIG. 3, the stationary bearing unit 34 mainly includes a bearing housing 341, a thrust member 342, and a sleeve 343.

  The bearing housing 341 is a member for housing the sleeve 343 and the lubricating oil 51 therein. The bearing housing 341 is made of a soft metal such as brass or a thermoplastic resin, and includes a substantially cylindrical side portion 341a and an annular lid portion 341b that protrudes radially inward from the upper end of the side portion 341a. Have. The bearing housing 341 is fixed inside the holder portion 311 of the base member 31 by press fitting, shrink fitting, or adhesion.

  A tapered space 52 is formed between the inner peripheral surface of the lid portion 341b of the bearing housing 341 and the outer peripheral surface of the shaft 41 so that the radial interval gradually increases upward. For this reason, the interface of the lubricating oil 51 located in the tapered space 52 is attracted downward by the surface tension (capillary force), thereby preventing the lubricating oil 51 from leaking outside the bearing housing 341. .

  The thrust member 342 is a member for sealing the lower opening of the bearing housing 341 and supporting the shaft 41 in the axial direction. The thrust member 342 is a substantially disk-shaped member made of, for example, a metal such as brass, and is fixed to the inside of the lower end portion of the side portion 341a of the bearing housing 341. A thrust dynamic pressure groove array (not shown) is formed on the upper surface of the thrust member 342 for generating fluid dynamic pressure in the lubricating oil 51 interposed between the upper surface of the thrust member 342 and the lower surface of the flange member 411 described later. Has been.

  The sleeve 343 is a substantially cylindrical member having an inner peripheral surface facing the outer peripheral surface of the shaft 41. The sleeve 343 is fixed to the inner peripheral surface of the side portion 341a of the bearing housing 341 via an adhesive 344 (see FIG. 7). The sleeve 343 functions as a radial bearing that allows the shaft 41 to rotate around the central axis A while supporting the shaft 41 disposed radially inward and restricting the movement of the shaft 41 in the radial direction. The inner peripheral surface of the sleeve 343 and the outer peripheral surface of the shaft 41 are opposed to each other through a minute gap (for example, about several μm), and the gap is filled with lubricating oil 51.

  The sleeve 343 is made of sintered metal obtained by bonding and solidifying metal powder while heating. Since the sintered metal is a porous body having a large number of cavities when viewed microscopically, the surface of the sleeve 343 is impregnated with a part of the lubricating oil 51. For this reason, the shaft 41 can rotate smoothly with respect to the sleeve 343.

  A more detailed shape and the like of the sleeve 343 will be described later.

  Next, the configuration of the rotating unit 4 of the spindle motor 1 will be described. The rotating unit 4 mainly includes a shaft 41, a hub 42, and a rotor magnet 43.

  The shaft 41 is a substantially cylindrical member disposed in the vertical direction along the central axis A. The shaft 41 is made of, for example, stainless steel. The shaft 41 is rotatably supported with respect to the stationary bearing unit 34 while being inserted into the inside (bearing hole) of the sleeve 343.

  A flange member 411 for preventing the shaft 41 from coming out of the stationary bearing unit 34 is fixed to the lower end portion of the shaft 41. The flange member 411 forms a protruding portion that protrudes in the radial direction from the outer peripheral surface of the shaft 41, and the upper surface of the flange member 411 faces the lower surface of the sleeve 343 in the axial direction. When an upward force is applied to the shaft 41, the upper surface of the flange member 411 contacts the lower surface of the sleeve 343, or the lubricating oil 51 interposed between the lower surface of the sleeve 343 and the upper surface of the flange member 411 The upward force of the member 411 is attenuated, thereby preventing the stationary bearing unit 34 and the shaft 41 from being separated. Note that the shaft 41 and the flange member 411 may be formed of a single member.

  Returning to FIG. The hub 42 is a member that is fixed to the shaft 41 and rotates together with the shaft 41. The hub 42 includes a joint portion 421 that is joined to the upper end portion of the shaft 41 by press-fitting or shrink fitting, and a body portion 422 that expands radially outward and downward from the joint portion 421. The body 422 is in contact with the lower surface of the disk 22 to restrict the movement of the disk 22 in the axial direction, and the body 422 is in contact with the inner periphery of the disk 22 to restrict the movement of the disk 22 in the radial direction. A second support surface 422b is formed. The hub 42 is formed of a metal such as aluminum, magnetic SUS (stainless steel), cold rolled steel plate (SPCC, SPCD, SPCE), for example.

  The rotor magnet 43 is attached to the body 422 of the hub 42 via a back yoke 431. The rotor magnet 43 has an annular shape centered on the central axis A, and the inner peripheral surface thereof opposes the outer peripheral surfaces of the plurality of teeth portions 322 of the stator core 32 in the radial direction. The inner peripheral surface of the rotor magnet 43 is a magnetic pole surface in which N poles and S poles are alternately arranged.

  In such a spindle motor 1, when a drive current is applied to the coil 33 of the stationary portion 3, a radial magnetic flux is generated in the plurality of teeth portions 322 of the stator core 32. Then, circumferential torque is generated by the action of magnetic flux between the teeth portion 322 and the rotor magnet 43, and the rotating portion 4 rotates about the central axis A with respect to the stationary portion 3. The disk 22 supported by the hub 42 rotates around the central axis A together with the shaft 41 and the hub 42.

<3. Detailed shape of sleeve>
Next, a more detailed shape and the like of the sleeve 343 will be described.

  FIG. 4 is a longitudinal sectional view of the sleeve 343. As shown in FIG. 4, on the inner peripheral surface of the sleeve 343, a radial dynamic pressure for generating fluid dynamic pressure in the lubricating oil 51 interposed between the inner peripheral surface of the sleeve 343 and the outer peripheral surface of the shaft 41 is provided. Groove rows 343a and 343b are formed. The radial dynamic pressure groove array 343a and the radial dynamic pressure groove array 343b are arranged vertically, and each form a so-called “herringbone” groove array in which a plurality of obliquely extending grooves are arranged in the circumferential direction. When the shaft 41 rotates, the lubricating oil 51 is pressurized by the radial dynamic pressure groove rows 343a and 343b, and the shaft 41 rotates while being supported in the radial direction by the fluid dynamic pressure generated in the lubricating oil 51.

  FIG. 5 is a bottom view of the sleeve 343. As shown in FIG. 5, on the lower surface of the sleeve 343, a thrust dynamic pressure groove array for generating fluid dynamic pressure in the lubricating oil 51 interposed between the lower surface of the sleeve 343 and the upper surface of the flange member 411 described later. 343c is formed. The thrust dynamic pressure groove array 343c is composed of a plurality of spiral grooves centered on the central axis A. When the shaft 41 rotates, the lubricating oil 51 is placed above and below the flange member 411 by the thrust dynamic pressure groove array 343c formed on the lower surface of the sleeve 343 and the thrust dynamic pressure groove array formed on the upper surface of the thrust member 342. The shaft 41 is rotated by the fluid dynamic pressure generated in the lubricating oil 51 while being supported in the axial direction.

  FIG. 6 is a top view of the sleeve 343. 4 corresponds to a longitudinal sectional view of the sleeve 343 taken along the line IV-IV shown in FIG. FIG. 7 is an enlarged longitudinal sectional view of the vicinity of the upper end portions of the bearing housing 341 and the sleeve 343. 6 and 7, the upper surface of the sleeve 343 includes a circumferential groove 343d formed in an annular shape around the central axis A, and a first upper surface located radially inward of the circumferential groove 343d. 343e and a second upper surface 343f located radially outside the circumferential groove 343d.

  On the other hand, the lower surface of the lid portion 341b of the bearing housing 341 is relatively higher than the first lower surface 341c on the radial outer side of the first lower surface 341c and the horizontal first lower surface 341c contacting the first upper surface 343e of the sleeve 343. And a second lower surface 341d.

  Therefore, the second lower surface 341d of the bearing housing 341, the circumferential groove 343d and the second upper surface 343f of the sleeve 343 are not in contact with each other, and a space 345 is formed therebetween. This space 345 is a preliminary for accommodating the adhesive 344 squeezed out above the sleeve 343 when the sleeve 343 is inserted from below the bearing housing 341 in the manufacturing process of the fluid dynamic bearing device 5. It becomes space.

  A chamfered portion 343 g is formed on the inner peripheral edge of the upper surface of the sleeve 343. The chamfered portion 343g is a tapered surface whose inner diameter gradually increases upward. Further, on the first upper surface 343e of the sleeve 343, three radial grooves 343h are formed as a flow path of the lubricating oil 51 that connects the circumferential groove 343d and the chamfered portion 343g. Further, three axial grooves 343 i extending up and down are formed on the outer peripheral surface of the sleeve 343 as flow paths for circulating the lubricating oil 51.

  FIG. 8 is a flowchart showing a procedure for manufacturing such a sleeve 343. When creating the sleeve 343, first, the metal powder as a material is filled in a mold and molded (step S1). Next, the metal powder is bonded and solidified by heating the mold and the metal powder in the mold (step S2). In Steps S1 and S2, the substantially cylindrical shape of the sleeve 343 and the chamfered portion 343g are formed by a mold. The radial dynamic pressure groove rows 343a and 343b, the thrust dynamic pressure groove row 343c, the circumferential groove 343d, the radial groove 343h, and the axial groove 343i are not formed at this time.

  Subsequently, the member taken out from the mold is subjected to a process of adjusting dimensions by polishing the inner peripheral surface, the upper surface, and the lower surface, that is, sizing (step S3). Then, the radial dynamic pressure groove rows 343a and 343b and the thrust dynamic pressure groove rows are formed by performing press molding using a mold on the inner peripheral surface, the lower surface, the upper surface, and the outer peripheral surface of the sized member. 343c, a circumferential groove 343d, a radial groove 343h, and an axial groove 343i are formed (step S4).

  In the present embodiment, as shown in FIG. 7, the depth D1 of the circumferential groove 343d formed on the upper surface of the sleeve 343 is smaller than the axial length D2 of the chamfered portion 343g. In the above step S4, when the circumferential groove 343d is formed, the sintered material existing on the radially inner side of the circumferential groove 343d is pushed into the inner circumferential surface side, but inside the pushed portion. The chamfered portion 343g having a relatively large inner diameter is formed in advance. For this reason, when the circumferential groove 343d is formed, it is possible to prevent the inner circumferential surface of the sleeve 343 from projecting radially inward. As a result, the sleeve 343 and the shaft 41 can be relatively rotated with high accuracy.

  In particular, in the present embodiment, the radial width W1 of the circumferential groove 343d is smaller than three times the radial length W2 of the chamfered portion 343g. For this reason, when the circumferential groove 343d is formed in step S4, it is possible to more appropriately prevent the inner circumferential surface of the sleeve 343 from projecting radially inward. More preferably, the radial width W1 of the circumferential groove 343d is set smaller than twice the radial length W2 of the chamfered portion 343g. In this way, the amount of movement of the sintered material pushed into the inner peripheral surface side can be made sufficiently smaller than the radial length W2 of the chamfered portion 343g.

  In the present embodiment, the volume V1 of the sleeve 343 reduced by the circumferential groove 343d is smaller than three times the volume V2 of the sleeve 343 reduced by the chamfered portion 343g. For this reason, when the circumferential groove 343d is formed in step S4, it is possible to more appropriately prevent the inner circumferential surface of the sleeve 343 from projecting radially inward. The volume V1 of the sleeve 343 that is reduced by the circumferential groove 343d is more preferably set to be smaller than twice the volume V2 of the sleeve 343 that is reduced by the chamfered portion 343g. If it does in this way, the volume of the sintered material pushed into the inner peripheral surface side can be set to a volume within a range that can be sufficiently absorbed by the chamfered portion 343g.

  In the present embodiment, the axial depth D3 of the radial groove 343h is smaller than the axial length D2 of the chamfered portion 343g. In step S4, when the radial groove 343h is formed in the sleeve 343, a part of the sintered material around the radial groove 343h is pushed inward in the radial direction. On the inner side, a chamfered portion 343g having a relatively large inner diameter is formed in advance. For this reason, when forming the radial groove 343h, it is possible to prevent the inner peripheral surface of the sleeve 343 from projecting radially inward. As a result, the sleeve 343 and the shaft 41 can be relatively rotated with high accuracy.

  In the present embodiment, the axial depth of the radial groove 343h is smaller than the axial depth of the circumferential groove 343d. For this reason, when forming the radial groove 343h in the above step S4, the sintered material around the radial groove 343h can be released not only to the chamfered portion 343g side but also to the circumferential groove 343d side. Thereby, the moving amount of the sintered material to the chamfered portion 343g side can be reduced, and the inner peripheral surface of the sleeve 343 can be more appropriately prevented from projecting radially inward.

<4. Modification>
Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.

  In the above embodiment, the chamfered portion 343g of the sleeve 343 has a tapered surface without unevenness. However, as shown in FIG. 9, the chamfered inner groove 343j is formed in the chamfered portion 343g of the sleeve 343. Good. The chamfered inner groove 343j may be formed together with the chamfered portion 343g in, for example, the above steps S1 to S2. In this way, when forming the circumferential groove 343d or the radial groove 343h in the above step S4, the sintered material pushed into the inner circumferential surface side can be absorbed by the chamfered inner groove 343j. Therefore, it is possible to further prevent the inner peripheral surface of the sleeve 343 from protruding radially inward.

  In the above embodiment, the circumferential groove 343d of the sleeve 343 has an annular shape, but the circumferential groove 343d does not necessarily have an annular shape. For example, the circumferential groove 343d may be an arc-shaped groove partially formed around the central axis A on the upper surface of the sleeve 343. In the above embodiment, the sleeve 343 is a V-shaped groove in a cross-sectional view, but may have another shape such as a U-shape.

  In the above embodiment, the second upper surface 343f of the sleeve 343 is formed on the outer side in the radial direction of the circumferential groove 343d. However, as shown in FIG. 10, there is no second upper surface 343f, and the circumferential groove 343d. May extend to the outer peripheral edge of the sleeve 343.

  Further, in the above embodiment, the circumferential groove 343 d is for securing the space 345 for accommodating the adhesive 344, but the circumferential groove of the present invention is used to circulate the lubricating oil 51 or the like. It may be formed for other purposes.

  In the above embodiment, the spindle motor 1 for rotating the magnetic disk 22 and the fluid dynamic pressure bearing device 5 used for the spindle motor 1 have been described. However, the present invention rotates other disks such as an optical disk. Therefore, the present invention can also be applied to a spindle motor and a bearing device used therefor. However, since the spindle motor for the magnetic disk is required to have particularly high rotational accuracy, the technical significance of applying the present invention is great.

It is a longitudinal cross-sectional view of a disk drive device. It is a longitudinal cross-sectional view of a spindle motor. It is a longitudinal cross-sectional view of a fluid dynamic pressure bearing device. It is a longitudinal cross-sectional view of a sleeve. It is a bottom view of a sleeve. It is a top view of a sleeve. It is an enlarged vertical sectional view near the upper end portion of the bearing housing and the sleeve. It is the flowchart which showed the manufacturing procedure of a sleeve. It is an enlarged longitudinal cross-sectional view of the vicinity of the upper end part of the bearing housing and sleeve which concern on a modification. It is an enlarged longitudinal cross-sectional view of the vicinity of the upper end part of the bearing housing and sleeve which concern on a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Spindle motor 2 Disk drive device 3 Static part 4 Rotating part 5 Fluid dynamic pressure bearing apparatus 21 Apparatus housing 22 Disk 23 Access part 31 Base member 32 Stator core 33 Coil 34 Stationary bearing unit 41 Shaft 42 Hub 43 Rotor magnet 51 Lubricating oil 341 Bearing Housing 341b Lid 342 Thrust member 343 Sleeve 343d Circumferential groove 343g Chamfered portion 343h Radial groove 343j Chamfered inner groove 344 Adhesive A Central shaft

Claims (9)

A shaft arranged vertically along the central axis;
A substantially cylindrical sleeve having an inner peripheral surface opposed to the outer peripheral surface of the shaft and configured by impregnating a porous body made of sintered metal with a lubricant;
With
The sleeve is
A circumferential groove formed in an arc shape or an annular shape around the central axis on the upper surface;
A chamfered portion formed on the inner periphery of the upper surface;
Have
A bearing device in which an axial depth of the circumferential groove is smaller than an axial length of the chamfered portion. The bearing device according to claim 1,
A bearing housing that houses the sleeve;
An adhesive interposed between the outer peripheral surface of the sleeve and the inner peripheral surface of the bearing housing to fix the sleeve and the bearing housing;
Further comprising
The bearing device has a lid portion facing the upper surface of the sleeve. In the bearing device according to claim 1 or 2,
The sleeve further includes a radial groove formed radially inward of the circumferential groove on the upper surface,
A bearing device in which an axial depth of the radial groove is smaller than an axial length of the chamfered portion. The bearing device according to claim 3,
A bearing device in which an axial depth of the radial groove is smaller than an axial depth of the circumferential groove. In the bearing device according to any one of claims 1 to 4,
A bearing device in which a radial width of the circumferential groove is smaller than three times a radial length of the chamfered portion. In the bearing apparatus in any one of Claim 1- Claim 5,
A bearing device in which the volume of the sleeve reduced by the circumferential groove is smaller than three times the volume of the sleeve reduced by the chamfered portion. In the bearing apparatus in any one of Claim 1- Claim 6,
The sleeve is a bearing device further having a chamfered inner groove formed in the chamfered portion. A stationary part;
A rotating part that has a support part that supports the disk, and is rotatably supported with respect to the stationary part via the bearing device according to any one of claims 1 to 7,
A torque generator that generates a torque about the central axis between the stationary part and the rotating part;
With spindle motor. A spindle motor according to claim 8;
An access unit for performing one or both of reading and writing of information with respect to the disk supported by the rotating unit of the spindle motor;
A housing for housing the spindle motor and the access unit;
A disk drive device comprising:

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