JP2015096771A - Spindle motor for hard disk drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spindle motor small in deflection of a shaft and having a long service life even with a thin thickness.SOLUTION: A spindle motor for a hard disk drive, which is equipped with a dynamic bearing, comprises: a core having an annular part and salient poles; coils formed at the salient poles; a base having a bottom; a sleeve outserted on a shaft and rotatably supported by the shaft; a hub rotating integrally with the sleeve; a magnet fixed to the hub; a radial dynamic bearing part formed between the shaft and the sleeve; a seal part which extends axially with the liquid level of a lubricant situated in the middle and prevents leakage of the lubricant; and a seal incorporated annular projection part provided with the seal part on the inner peripheral surface. The seal part is arranged at a position surrounding the radial dynamic bearing part and being surrounded by the annular part. The hub has a hub annular projection part which annularly projects toward the seal incorporated annular projection part on the base side, and the seal incorporated annular projection part forms an axial gap with the hub annular projection part.

Description

  The present invention relates to a spindle motor provided with a dynamic pressure bearing, and can be suitably used particularly for a thin disk device or a driving spindle motor mounted on a laser beam printer.

Spindle motors are required to be stable at high speeds and have excellent durability. In order to meet these requirements, spindle motors equipped with a hydrodynamic bearing device using a fluid lubricant are generally used. It has become.
On the other hand, disk devices such as hard disk drives and laser beam printer devices are required to be thinned, and a driving spindle motor equipped with a hydrodynamic bearing device used in these devices must be made as thin as possible. .
Therefore, a spindle motor has been proposed in which a thrust bearing portion that has been conventionally arranged on the shaft end portion side of the shaft is arranged on the outer peripheral side of the sleeve, which is outside the radial bearing portion, to reduce the thickness (Patent Document). 1).
JP 2001-65552 A

By the way, in this conventional spindle motor, a radial bearing portion is provided on the inner peripheral surface of the sleeve, and the axial both surfaces of the protruding portion protruding in a flange shape in the radial direction form a pair of thrust bearing portions. Needless to say, the surfaces of these bearing portions need to be formed with extremely high accuracy.
However, in this spindle motor, it is necessary to form two thrust bearing surfaces in a direction perpendicular to the radial bearing surface on the sleeve having the radial bearing surface.
Therefore, deformation may occur in one thrust bearing surface or the radial bearing surface due to a processing load applied when one thrust bearing surface is formed and then the other thrust bearing surface is formed.

  If this deformation occurs, the verticality and horizontality between the bearing surfaces will deteriorate, and the shaft will run out during rotation. In some cases, the rotor and stator will come into contact with each other, making rotation impossible and impairing reliability. In addition, the bearing life may be shortened due to non-uniform dynamic pressure. Further, when such a motor is used for driving in a disk device, an error may occur in recording / reproducing information on a recording disk, and high-density recording / reproducing may become difficult.

  Accordingly, the problem to be solved by the present invention is to provide a spindle motor that has a small shaft runout, a long life, and high reliability even when the thickness is reduced using a hydrodynamic bearing.

  In order to solve the above problems, a spindle motor for a hard disk device according to an aspect of the present invention is a spindle motor for a hard disk device including a dynamic pressure bearing, and includes an annular portion and a plurality of salient poles protruding from the annular portion. , A coil formed by being wound around each of a plurality of salient poles, a base having a bottom portion facing the coil in the axial direction, a shaft, an extrapolated shaft, and rotatable about the shaft Formed between a shaft and a sleeve, a sleeve to be supported, a hub that rotates integrally with the sleeve, a ring-shaped magnet that is fixed to the hub and has an inner peripheral surface facing the outer peripheral surface of the plurality of salient poles The radial dynamic pressure bearing portion and the rotational surface of the hub extending in the direction of the rotation axis, and at least the liquid level of the lubricant charged in the radial dynamic pressure bearing portion is located in the middle, and lubrication from the lubricant filling portion To prevent agent leakage And a seal-incorporated annular projecting portion projecting so as to surround the sleeve and having a seal portion provided on the inner peripheral surface thereof, and the seal portion surrounds the radial dynamic pressure bearing portion and is connected to the annular portion. The hub is disposed at an enclosed position, and the hub includes a hub annular protrusion that is provided integrally with the hub and projects annularly toward the base-side seal-internal annular protrusion. An annular protrusion and an axial gap are formed.

  According to the present invention, there is an effect that the shaft runout is small, high reliability is obtained, and the life is extended.

It is sectional drawing which shows Example 1 of the spindle motor of this invention. It is sectional drawing explaining Example 1 of the spindle motor of this invention. It is an expanded sectional view of the principal part in Example 1 of the spindle motor of the present invention. It is sectional drawing which shows Example 2 of the spindle motor of this invention. It is sectional drawing which shows Example 3 of the spindle motor of this invention.

<Example 1>
First, Example 1 will be described with reference to FIGS.
The spindle motor 50 according to the first embodiment is a so-called inner rotor type for a hard disk device, and includes a stator portion 50S and a rotor portion 50R that rotates with respect to the stator portion 50S.

The rotor portion 50 </ b> R includes a hub 7 having a cylindrical shaft portion 1 as a core formed integrally, and a cylindrical outer tube portion 13 fitted to the outer peripheral portion of the shaft portion 1. In FIG. 3, the outer cylinder portion 13 is indicated by dotted hatching for easy understanding.
A hub flange portion 7 a that is a wall portion protruding so as to surround the shaft portion 1 is formed on the outer peripheral side of the hub 7. An annular magnet 11 in which N poles and S poles are alternately magnetized in multiple poles is mounted on the outer peripheral surface of the hub flange portion 7a. A ring-shaped thrust ring 3 is fixed to the inner peripheral surface of the hub flange portion 7a by press-fitting or bonding.

On the other hand, the stator portion 50 </ b> S includes a base 8 and a sleeve 4 that is erected and fixed to the base 8.
An annular core 9 having a plurality of salient poles (not shown) is fixed to the base 8. A coil 10 is wound around each salient pole. Further, the annular core 9 is arranged so that its inner peripheral surface faces the outer peripheral surface of the magnet 11 with a predetermined gap.
The sleeve 4 has a substantially annular shape having a through hole 4b, and the outer cylinder portion 13 is inserted with a minute gap.
Further, a flange portion 4a protruding in the radial direction is provided on one end portion side of the sleeve 4, and an end plate 5 for closing the through hole 4b is fixed on the other end portion side.
Further, an annular seal plate 17 is press-fitted and fixed to the outer peripheral portion of the sleeve 4 so as to sandwich the thrust ring 3 with the flange portion 4a with a minute gap.

In this configuration, the inner peripheral surface 4c of the through-hole 4b of the sleeve 4, the outer peripheral surface 13c of the outer cylindrical portion 13, the radial dynamic pressure groove (not shown) formed in at least one of the two, and the gap between them A radial dynamic pressure bearing RB is constituted by the filled lubricating fluid (hereinafter referred to as a lubricant) 20. This radial dynamic pressure bearing RB is provided at one place or two places at a distance in the axial direction.
Also, the axial end surfaces 3a and 3b of the thrust ring 3 and the axial end surface 4a1 of the flange portion 4a and the axial end surface 17a of the seal plate facing the both end surfaces 3a and 3b with a small gap therebetween. In each opposing surface, a thrust dynamic pressure bearing is constituted by a thrust dynamic pressure groove (not shown) formed in at least one of them and a lubricant 20 filled in a gap between the two.
In other words, the spindle motor of the embodiment forms a first thrust dynamic pressure bearing (SB1) between the end surface 3a of the thrust ring 3 and the axial end surface 4a1 of the flange portion 4a, and the end surface 3b of the thrust ring 3 And a second thrust dynamic pressure bearing (SB2) between the seal plate and the axial end surface 17a of the seal plate.
Then, due to the dynamic pressure generated by the first thrust dynamic pressure bearing and the second thrust dynamic pressure bearing, the sleeve 4 is in a state of being neutrally floated in the axial direction, and the rotor portion 50R does not come into contact with other members. It can be turned.

Further, the lubricant 20 includes a gap between the end plate 5 and the shaft portion 1 and the outer cylinder portion 13, a gap between the outer cylinder portion 13 and the sleeve 4, a gap between the sleeve 4 and the hub 7, a sleeve 4 and a thrust. The lubricant filling portion is filled with a gap with the ring 3, a gap between the thrust ring 3 and the seal plate 17, and a gap between the seal plate 17 and the hub flange portion 7a.
In addition, the gap between the seal plate 17 serving as the open end of the lubricant filling portion and the hub flange portion 7a is a tapered seal portion 6 that increases in width toward the open end side, thereby preventing leakage of the lubricant 20. ing. The amount of the lubricant 20 is adjusted and filled so that the liquid level is located in the middle of the taper seal portion 6.

As described above, this spindle motor is for a hard disk, and is an example of a motor for mounting a hard disk having a particularly small inner diameter. On the center line of the hub 7, a female screw 2 for fixing the hard disk is formed. Yes.
In the hub manufacturing process, the internal thread 2 is cleaned after being processed. In order to sufficiently remove foreign matter contained in the cutting powder and cleaning liquid generated in the processing, the internal thread 2 is used as a part of the through hole 2a. It is formed.
After assembly, in order to prevent the lubricant 20 from leaking from the through hole 2a, a sealing material 16 for sealing the lubricant 20 is fixed to the through hole 2a with an adhesive. As this sealing material 16, an elastic body, for example, a rubber ball having a diameter larger than the inner diameter of the through hole 2a can be used, and this is fixedly sealed into the through hole 2a by press-fitting or bonding.

Further, the shaft portion 1 and the hub 7 are integrally formed, and thereby the squareness accuracy of the thrust bearing portion with respect to the radial bearing portion can be further improved.
As a result, the clearance between the radial bearing portion and the thrust bearing portion becomes more uniform, and no load is generated during rotation and no contact with the rotating member occurs, so that higher reliability is obtained.

  The outer peripheral surface of the outer cylinder portion 13 is polished. Further, in this outer peripheral surface, the range in which the radial dynamic pressure groove is formed, or the region facing the dynamic pressure groove when the dynamic pressure groove is formed on the sleeve 4 side, particularly reduces the surface roughness. Polished with high precision.

The outer cylinder portion 13 is press-fitted into the shaft portion 1 to be fitted, but a plurality of axially extending outer peripheral portions of the shaft portion 1 extend in the axial direction so as to reduce the pressure input and enable smooth press-fitting without distortion. Groove 1a is formed (see FIG. 2). In FIG. 2, three grooves 1a are formed at equal intervals in the circumferential direction.
When the number of the grooves 1a is two or less, the effect of reducing the pressure input cannot be sufficiently obtained, and the cylindricity accuracy of the outer peripheral surface of the outer cylinder portion 13 is lowered by the press-fitting.
On the other hand, if the number is increased, the number of processing steps increases and the processing apparatus becomes complicated, so three is most preferable.
Further, at the time of the processing, it is desirable to process three grooves 1a at the same time so that a uniform processing pressure is applied to the shaft portion 1 in order to prevent the shaft from collapsing as much as possible.
By providing this groove 1a, both end sides of the lubricant filling portion in the radial bearing portion are connected. Therefore, the effect of adjusting the pressure balance of the dynamic pressure is exhibited, and for example, it is possible to prevent the occurrence of a problem that a negative pressure occurs or an excessive levitation occurs.

Here, the detailed configuration of the taper seal portion 6 will be described with reference to FIG.
In the taper seal portion 6, the inner peripheral surface 7 a 1 of the flange portion 7 a of the hub 7 is formed as an inclined surface whose inner diameter becomes smaller toward the open end 18 (lower side in FIG. 3) of the lubricant filling portion. .
On the other hand, the outer peripheral surface 17 b of the seal plate 17 is formed as an inclined surface in a direction in which the outer diameter becomes smaller toward the open end 18.
Since the inclination angle of the outer peripheral surface 17b of the seal plate 17 with respect to the rotation axis C is formed to be larger than the inclination angle of the inner peripheral surface 7a1 of the flange portion 7a with respect to the rotation axis C, the gap between the two is opened. It becomes wider toward the end 18.

In such a taper seal portion 6, the centrifugal force applied to the lubricant 20 during rotation acts so as to move it to the inside of the lubricant filling portion. Therefore, the seal portion 6 can more effectively prevent leakage of the lubricant 20 from the lubricant filling portion, and is a highly reliable seal portion.
Moreover, since this taper seal part 6 is arrange | positioned at the outermost diameter part of the lubricant filling part, the capacity | capacitance in the seal part 6 is increased in proportion to the diameter.
Therefore, the change in the liquid level of the lubricant 20 in the seal portion 6 accompanying the change in temperature is very small, and the hydrodynamic bearing used in this embodiment is a highly reliable bearing.

<Example 2>
Next, the spindle motor 51 of the second embodiment will be described with reference to FIG.
The spindle motor 51 is a so-called outer rotor type for a hard disk device, and is the same as that of the first embodiment except for the configuration of the outer rotor and the configuration described below.
The spindle motor 51 of this embodiment is a so-called shaft rotation type similar to that of the first embodiment, and is an example applied when the inner diameter of the hard disk is large.
Therefore, since the hard disk is fixed by the plurality of female screws 2 provided on the hub 7, no female screw is formed on the shaft portion 1 (hereinafter also referred to as the shaft 1).
Further, in this example, the shaft 1 and the hub 7 are separated from each other, whereby the outer peripheral surface of the shaft 1 can be polished with high accuracy, and the outer cylinder portion 13 used in the first embodiment is not required. It has become.

The shaft 1 and the through-hole 7b of the hub 7 are press-fitted, but in order to improve the strength of this fitting and the deflection accuracy of the shaft 1, a range of the range in which the shaft 1 is fitted to the through-hole 7b. A small-diameter portion 1b having a slightly small diameter is provided, and the through-hole 7b side is configured to be press-fitted as a small-diameter portion 7c in a range where the small-diameter portion 1b of the shaft 1 is fitted.
The diameters of the small diameter portions 1b and 7c are set to 5 to 10 μm, and the diameters of the other portions are set to 5 to 20 μm.

  In the configuration of the second embodiment, the outer peripheral surface 1c of the shaft 1, the inner peripheral surface 4c of the through hole of the sleeve 4, the radial dynamic pressure groove (not shown) formed in at least one of the two, and the gap between the two A radial dynamic pressure bearing RB is constituted by the filled lubricant 20.

On the other hand, both end surfaces 3a, 3b in the axial direction of the thrust ring 3 fixed to the inner peripheral surface of the hub flange portion 7a and the shaft of the flange portion 4a opposed to the both end surfaces 3a, 3b with a minute gap. The axial end surface 17a of the annular seal plate 17 fixed to the outer peripheral portion of the directional end surface 4a1 and the sleeve 4, a thrust dynamic pressure groove (not shown) formed on at least one of the opposing surfaces, A thrust dynamic pressure bearing is constituted by the lubricant 20 filled in the gap. Schematically, the thrust ring 3 is sandwiched between the seal plate 17 and the flange portion 4a.
Also in this embodiment, the first thrust dynamic pressure bearing SB1 is formed between the end face 3a of the thrust ring 3 and the axial end face 4a1 of the flange portion 4a, and the end face 3b of the thrust ring 3 and the axial end face of the seal plate are formed. The second thrust dynamic pressure bearing SB2 is formed between the first thrust bearing 17a and the second thrust dynamic pressure bearing SB2.
Then, due to the dynamic pressure generated by the first thrust dynamic pressure bearing SB1 and the second thrust dynamic pressure bearing SB2, the sleeve 4 is in a state of floating neutrally in the axial direction, and the rotor portion 51R comes into contact with other members. It becomes possible to rotate without.

Further, the lubricant 20 includes a gap between the end plate 5 and the shaft 1 fixed to the sleeve 4 so as to close the through hole 4b on one end side, a gap between the shaft 1 and the sleeve 4, a sleeve 4 Lubricant filling comprising a gap with the hub 7, a gap between the sleeve 4 and the thrust ring 3, a gap between the thrust ring 3 and the seal plate 17, and a gap between the seal plate 17 and the hub flange portion 7 a of the hub 7. The part is filled.
Further, the gap between the seal plate 17 serving as the open end of the lubricant filling portion and the flange portion 7a of the hub 7 is a tapered seal portion 6 in which the gap becomes wider toward the open end, and leakage of the lubricant 20 occurs. Is preventing. The amount of the lubricant 20 is adjusted and filled so that the liquid level is located in the middle of the taper seal portion 6.

  The detailed configuration of the taper seal portion 6 is the same as that of the first embodiment, and the centrifugal force applied to the lubricant 20 during rotation acts to move it to the inside of the lubricant filling portion. It is a highly reliable seal part that can prevent the above effectively.

<Example 3>
FIG. 5 shows a cross-sectional view of the spindle motor 52 of the third embodiment. This spindle motor is a fixed shaft type with respect to the spindle motor 51 of the second embodiment.
In the configuration of the third embodiment, the shaft 1 is press-fitted and fixed to the base 8.
The annular thrust ring 3 is fixed to the inner peripheral surface of the annular protrusion 8a of the base 8 and is on the stator 52S side.
On the other hand, the sleeve 4 is press-fitted and fixed in the through hole 7d of the hub 7, and the through hole is extrapolated to the shaft 1 to form the rotor side 52R.
The seal plate 17 is fixed to the outer peripheral portion of the sleeve 4.
Accordingly, the outer peripheral surface 1c of the shaft 1, the inner peripheral surface 4c of the through hole 4b of the sleeve 4, the radial dynamic pressure groove (not shown) formed in at least one of the two, and the lubricant filled in the gap between the two. 20 constitutes a radial dynamic pressure bearing RB.
Also in the third embodiment, the first thrust dynamic pressure bearing SB1 is formed between the end face 3a of the thrust ring 3 and the axial end face 4a1 of the flange portion 4a, and the end face 3b of the thrust ring 3 and the axial direction of the seal plate are formed. A second thrust dynamic pressure bearing SB2 is formed between the end surface 17a.
Then, due to the dynamic pressure generated by the first thrust dynamic pressure bearing SB1 and the second thrust dynamic pressure bearing SB2, the sleeve 4 is in a state of being neutrally floated in the axial direction, and the rotor portion 52R comes into contact with other members. It becomes possible to rotate without.

  Further, both end surfaces 3a and 3b in the axial direction of the thrust ring 3 fixed to the inner peripheral surface of the annular projecting portion 8a of the base 8 are opposed to the both end surfaces 3a and 3b with a minute gap therebetween. An axial end surface 17a of an annular seal plate 17 that is fixed to the outer peripheral portion of the sleeve 4 and has a minute gap between the axial end surface 4a1 of 4a and the flange portion 4a, and sandwiches the thrust ring 3; A thrust dynamic pressure bearing is constituted by a thrust dynamic pressure groove (not shown) formed in at least one of the grooves and a lubricant 20 filled in a gap therebetween.

Further, the lubricant 20 is attached to the sleeve 4 so as to close the through hole 4b on one end side, the gap between the end plate 5 and the shaft 1, the gap between the shaft 1 and the sleeve 4, and the sleeve 4 And the base 8, the gap between the sleeve 4 and the thrust ring 3, the gap between the thrust ring 3 and the seal plate 17, and the gap between the seal plate 17 and the annular protrusion 8 a of the base 8. The filling part is filled.
Further, the gap between the seal plate 17 serving as the open end of the lubricant filling portion and the annular protruding portion 8a of the base 8 is a tapered seal portion 6 whose gap becomes wider toward the open end 18 side. Leakage of the lubricant 20 filled in the portion is prevented. The amount of the lubricant 20 is adjusted and filled so that the liquid level is located in the middle of the taper seal portion 6.

Here, a detailed configuration of the taper seal portion 6 will be described with reference to FIG.
In the taper seal portion 6, the inner peripheral surface 8 a 1 of the annular projecting portion 8 a of the base 8 is formed as an inclined surface whose inner diameter becomes smaller toward the open end 18 (upper side in FIG. 5) of the lubricant filling portion. Yes.
On the other hand, the outer peripheral surface 17 b of the seal plate 17 is formed as an inclined surface in a direction in which the outer diameter becomes smaller toward the open end 18.
Since the inclination angle of the outer peripheral surface 17b of the seal plate 17 with respect to the rotation axis C is formed to be larger than the inclination angle of the inner peripheral surface 8a1 of the annular protrusion 8a with respect to the rotation axis C, the gap between the two is It becomes wider toward the open end 18.

In such a taper seal portion 6, the centrifugal force applied to the lubricant 20 during rotation acts so as to move it to the inside of the lubricant filling portion. Therefore, the seal portion 6 can more effectively prevent leakage of the lubricant 20 from the lubricant filling portion, and is a highly reliable seal portion.
Moreover, since this taper seal part 6 is arrange | positioned at the outermost diameter part of the lubricant filling part, the capacity | capacitance (annular capacity | capacitance) in the seal part 6 is very large.
Therefore, the change in the liquid level of the lubricant 20 in the seal portion 6 accompanying the change in temperature is very small, and the hydrodynamic bearing used in this embodiment is a highly reliable bearing.

  According to each of the above-described embodiments, the sleeve 4 having the radial bearing surface further has only one thrust bearing surface, and the sleeve 4 is not provided with a plurality of thrust bearing surfaces. The perpendicularity between the surfaces can be obtained with extremely high accuracy, and the shaft runout is reduced. Further, the clearance between the radial bearing portion and the thrust bearing portion becomes more uniform, and a load is generated or a rotating member hits during rotation, so that high reliability is obtained and a long life is achieved.

  The embodiment of the present invention is not limited to the configuration and procedure described above, and it goes without saying that modifications may be made without departing from the scope of the present invention.

  1 Shaft (shaft), 1a groove, 1b small diameter part, 1c outer peripheral surface, 2 female screw, 2a through hole, 3 thrust ring, 3a, 3b (axial) end face, 4 sleeve, 4a flange, 4a1 axial end face 4b through hole, 4c inner peripheral surface, 5 end plate, 6 taper seal portion, 7 hub, 7a hub flange portion, 7a1 inner peripheral surface, 7c small diameter portion, 8 base, 8a annular projecting portion, 8a1 inner peripheral surface, 9 Core, 10 Coil, 11 Magnet, 13 Outer cylinder, 13c Outer peripheral surface, 16 Sealing material, 17 Seal plate, 17a Axial end surface, 17b Outer peripheral surface, 18 Open end, 20 Lubricant (lubricating fluid), 50- 52 Spindle motor, C rotating shaft, RB radial dynamic pressure bearing portion, SB1, SB2 first and second thrust dynamic pressure bearing portions.

Claims (6)

A spindle motor for a hard disk drive equipped with a hydrodynamic bearing,
A core having an annular portion and a plurality of salient poles protruding from the annular portion;
A coil formed by being wound around each of the plurality of salient poles;
A base having a bottom portion facing the coil in the axial direction;
The axis,
A sleeve that is extrapolated to the shaft and rotatably supported on the shaft;
A hub that rotates integrally with the sleeve;
A ring-shaped magnet fixed to the hub and having an inner peripheral surface facing an outer peripheral surface of the plurality of salient poles;
A radial dynamic pressure bearing portion formed between the shaft and the sleeve;
Extending in the direction of the rotation axis of the hub, at least the liquid level of the lubricant filled in the radial dynamic pressure bearing portion is located in the middle thereof, preventing leakage of the lubricant from the lubricant filling portion. Sealing part to be
A seal-incorporated annular projecting portion projecting so as to surround the sleeve and having the seal portion provided on the inner peripheral surface thereof,
The seal portion is disposed at a position surrounding the radial dynamic pressure bearing portion and surrounded by the annular portion,
The hub includes a hub annular protrusion that is provided integrally with the hub and protrudes annularly toward the seal-internal annular protrusion on the base side,
The spindle motor for a hard disk device, wherein the annular protrusion in the seal forms an axial gap with the hub annular protrusion. The hub has a cylindrical disk magnet interposition wall portion that protrudes toward the base and should be interposed in a radial gap between the inner peripheral surface of the hard disk and the outer peripheral surface of the magnet.
The disk magnet interposition wall portion surrounds the radial dynamic pressure bearing portion, the seal-incorporated annular projecting portion, and the core, and has a portion that overlaps each of the surrounding portions in the axial direction. The spindle motor for hard disk drives according to claim 1. The hub has a flange extending radially outward from a side close to the base of the disk magnet intervening wall,
3. The spindle motor for a hard disk device according to claim 2, wherein the base has a concave portion into which a part of the flange portion is inserted so as to face the outer peripheral surface of the flange portion in the radial direction only through a gap.   4. The spindle motor for a hard disk device according to claim 1, wherein the seal portion is a taper seal portion whose interval becomes wider toward the hub annular projecting portion. 5.   5. The spindle motor for a hard disk device according to claim 4, wherein an inner peripheral surface of the annular protrusion provided in the seal is formed as an inclined surface having an inner diameter that decreases toward the hub annular protrusion.   6. The spindle motor for a hard disk device according to claim 1, wherein the annular protrusion provided in the seal is provided integrally with the base.

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