JP2006275246A - Spindle motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reliable spindle motor capable of preventing leakage of lubricant. <P>SOLUTION: This spindle motor is provided with a radial dynamic pressure bearing RB and a thrust dynamic pressure bearing SB for rotatably supporting a rotor 54R in relation to a stator 54R by interposing the lubricant 16 between the rotor 54R and the stator 54R, a lubricant holding part 117 continuously provided to these bearing parts and filled with the lubricant 16 and extended in a direction along a shaft C and formed with an open end 117a opened on at least one end thereof and filled with the lubricant so that the liquid level 16a is positioned inside the open end, a capillary seal 18 continuously provided to the open end of the lubricant holding part, extending in a direction coming close to the shaft, and formed so that cross sectional area in the axial direction is gradually increased as it comes close to the shaft, and a lubricant flowing path 16b extended in a direction separating from the rotary shaft. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a spindle motor provided with a hydrodynamic bearing, and in particular, can be suitably used as a spindle motor for a disk device or a hard disk device (hereinafter referred to as HDD) that rotates a high-capacity optical disk or the like at high speed. Is.

A conventional spindle motor will be described with reference to FIGS.
This spindle motor is an outer rotor type spindle motor for HDD, FIG. 8 is a sectional view thereof, and FIG. 9 is an enlarged view of a portion A in FIG.
The spindle motor 50 includes a stator portion 50S and a rotor portion 50R that rotates with respect to the steering portion 50S via a dynamic pressure bearing.

The stator unit 50S has a base 15 and a shaft 1 fixed to the base.
A thrust plate 4 is press-fitted or shrink-fitted to both ends of the shaft 1 and fixed with an adhesive.
A female screw 8 is formed on the center line on one end side of the shaft 1, and this motor is used to fasten the screw to a cover (not shown) of the HDD using this female screw 8. The vibration during rotational driving is suppressed.
The base 15 is provided with an annular protruding wall 11a centering on the axis. An annular core 11 having a plurality of salient poles (not shown) is fixed to the outer peripheral surface of the protruding wall 11a, and a coil 12 is wound around each salient pole.

On the other hand, the rotor portion 50 </ b> R includes the hub 10, the outer sleeve 3, and the inner sleeve 2.
The outer sleeve 3 is fixed to the inner periphery of the hub 10 by press-fitting or bonding.
A hub flange 10 a that projects in the radial direction and supports the disk 20 in the axial direction is formed on the outer peripheral portion of the hub 10.
A rotor yoke 14 forming a magnetic circuit of the motor and an annular magnet 13 in which N poles and S poles are alternately magnetized in multiple poles are mounted on the inner peripheral surface of the hub flange 10a.
The magnet 13 is arranged so that its inner circumferential surface faces the outer circumferential surface of the core 11 on the stator 50S side with a predetermined gap.
The inner sleeve 2 is fixed to the inner peripheral portion of the outer sleeve 3 by press fitting.

Next, the hydrodynamic bearing will be described.
The radial dynamic pressure bearing includes a pair of radial dynamic pressure grooves 2 a and 2 b formed in at least one of the inner peripheral portion of the inner sleeve 2 and the outer peripheral portion of the shaft 1, and a lubricant 16 filled in a gap therebetween. And is constituted by.
The radial dynamic pressure grooves 2a and 2b are provided at two positions with a distance in the axial direction.

A pair of thrust dynamic pressure bearings are symmetrically arranged on both end sides of the shaft 1.
Specifically, both end surfaces 2d (see FIG. 8) in the axial direction of the inner sleeve 2 and the axial inner surface 4b facing the both end surfaces 2d of the inner sleeve 2 in the thrust plate 4 with a small gap. The thrust dynamic pressure groove 4a is formed in at least one of the lubricants 16 and the lubricant 16 filled in the gap between them.
With these dynamic pressure bearings, the spindle motor 50 causes the rotor portion 50R to move to the stator portion 50S by the dynamic pressure generated in the pair of thrust dynamic pressure grooves 4a and the radial dynamic pressure generated in the radial dynamic pressure grooves 2a and 2b. On the other hand, it can rotate without contacting other members.

Next, the through hole through which the lubricant flows will be described.
In the outer peripheral portion of the inner sleeve 2, when the inner sleeve 2 is coupled to the outer sleeve 3 by press-fitting, a groove 2c along the axial direction is 180 ° so that the press-fitting force can be reduced and smooth press-fitting can be performed. Two places are formed at intervals.
If the number of the grooves 2c is further increased, the number of processing steps increases more than necessary, and the coupling force after assembly may decrease excessively, so that the performance due to shock / vibration may change. It is as follows.

When the inner sleeve 2 is inserted into the outer sleeve 3, a through hole 7 is formed by the groove 2c.
Since the through holes 7 connect both end sides of the radial bearing portions 2a and 2b filled with the lubricant 16, the flow of the lubricant is obtained.
Therefore, the effect of adjusting the pressure balance of the dynamic pressure is exerted, and for example, it is possible to prevent the occurrence of a problem that a negative pressure is generated in the dynamic pressure or an excessive levitation occurs.

Next, the lubricant outflow prevention seal filled in the hydrodynamic bearing will be described with reference to FIG.
The hydrodynamic bearing and the seal are configured substantially symmetrically on both ends of the shaft.
The inner peripheral surface of the outer sleeve 3 is formed with a portion 3e having a small inner diameter that is substantially the same as the outer peripheral surface of the inner sleeve 2, and a portion 3f having a larger inner diameter.
An end cap 5 is arranged on the large inner diameter portion 3f so as to cover the thrust plate 4 projecting in the radial direction from the outside, and is fixed to the outer surface 3e1 of the small inner diameter portion 3e with an adhesive 21.

Further, the lubricant 16 is filled in the following gaps and the like.
That is, a gap between the inner circumferential surface of the inner sleeve 2 and the outer circumferential surface of the shaft 1, a gap between the end surface of the inner sleeve 2 and the opposed surface of the thrust plate 4 facing this, the inner circumferential surface of the outer sleeve 3 and the thrust plate 4. A gap between the outer circumferential surface of the thrust plate 4, a gap between the axially outer side surface of the thrust plate 4 and the opposing surface of the end cap 5, and the through hole 7.

The gap between the end cap 5 and the thrust plate 4 has a first taper portion 5a that gradually widens at an angle θ1 with respect to the end cap mounting surface 5b, and a first capillary seal 17 (taper seal utilizing capillary action). ) Is formed.
The filling amount is set so that the liquid surface 16 a of the lubricant 16 is located in the middle of the first capillary seal 17.
The lubricant 16 filled in this amount may leak to the outside from the first capillary seal 17 due to temperature change, vibration shock, or the like. In order to prevent this, a second taper portion 1a1 whose diameter gradually decreases at an angle θ2 toward the open end side is provided on the outer peripheral surface of the open end side of the shaft 1 in the gap between the end cap 5 and the shaft 1. The third taper portion 5c is formed on the inner peripheral surface of the end cap 5 so that the diameter gradually decreases at an angle θ3 toward the open end side.

By setting the angle between the second taper portion 1a1 and the third taper portion 5c to θ2> θ3, a second capillary seal 18 is formed in which the gap gradually increases toward the outside (open end side). Yes.
Even with such a seal structure, the viscosity of the lubricant is reduced to enable high-speed rotation of the HDD, and the operating temperature range is expanded and vibrations occur due to heat generation inside the equipment when incorporated in various equipment. Due to an increase in impact, there is a case where the leakage of the lubricant cannot be prevented and diffuses from the open end 9 to the outside.
In order to cope with this, Patent Document 1 provides the first to third taper seal portions along the lubricant flow path, and in particular, a motion in which a spiral groove is formed on the surface constituting the seal portion. A pressure type hydrodynamic bearing device is disclosed.
Table 01/001003

By the way, in the conventional spindle motor 50, in order to prevent the lubricant 16 from leaking, the end cap 5 is fixed to the outer sleeve 3 with the adhesive 21 and covered. Thereafter, a lubricant is injected.
However, when the mounting surface of the end cap 5 is processed, the accuracy of flatness is insufficient or the processing roughness becomes large, or an adhesive having a low viscosity or a long curing time is used. If selected, the adhesive 21 may flow out of a predetermined region and may enter the gap between the outer peripheral surface of the thrust plate 4 and the inner peripheral surface of the outer sleeve 3 or the fluid bearing.
In this case, the rotational load of the motor becomes large, or the motor does not rotate.
The attachment of the end cap 5 is a final assembly process in the motor manufacturing process, and the outflow of the adhesive and its state cannot be confirmed until the adhesive 21 is completely cured. Loss is greater when defects occur in the final process.

In addition, when the amount of lubricant filled is small, sufficient dynamic pressure cannot be obtained, leading to an increase in runout and rotation unevenness. In some cases, the bearing may come into contact with other members and the motor may stop.
On the other hand, when the amount of the filled lubricant is too large, leakage or scattering to the outside is likely to occur due to movement or impact application.
For example, the scattered lubricant adheres to the surface of the disk 20 mounted on the hub 10 of the rotor 50R and the optical head on the disk device side, and an error occurs in data recording / reproduction.
For this reason, in the manufacturing process, it is necessary to accurately control the amount of lubricant filling to prevent leakage.

However, since the position of the lubricant liquid surface 16a is in the middle of the first capillary seal 17 from the outside in the radial direction to the inside, it can be judged by visual observation or a laser displacement meter by being blocked by the end cap 5. It was not possible, and it was difficult to control the filling amount with high accuracy.
In addition, the lubricant is injected by inserting a thin nozzle. However, when the nozzle is pulled out after injection, the tip of the nozzle inevitably touches both surfaces 1a and 5c forming the second capillary seal 18. In some cases, the agent remains adhered, and the lubricant 16 inside leaks outside through the adhered lubricant.
We must try to prevent it.

On the other hand, Patent Document 1 discloses a technique for preventing a lubricant from leaking by providing a third seal and providing a spiral groove on a surface forming the second seal and the third seal. Although disclosed, there were various problems as follows.
That is, since the sleeve and the hub are press-fitted and fixed, the lubricant may leak from the gap. As a countermeasure, if an adhesive is used together for fixing, there is a concern that the protrusion of the adhesive may flow out to the seal part, and the rotation load increases due to the gap between the rotor side and the seal plate becoming narrower or in contact. There is a concern that a motor that cannot be rotated or that cannot be rotated will be manufactured.
We must try to prevent it.

Further, regarding the third seal, since the inclination is provided in the direction in which the cross-sectional area decreases from the inner side to the outer side of the bearing, there is an effect of preventing leakage of the lubricant during rotation, No effect can be expected against leakage due to temperature change or vibration / impact when rotation is stopped.
That is, the lubricant once attached so as to straddle the inner peripheral surface and the outer peripheral surface of the third seal portion moves in a direction in which the surface area is reduced by the action of the surface tension. As a result, there is a possibility that the lubricant collects at the tip end side of the third seal portion and leaks to the outside from the third seal portion when the rotor starts to rotate next time.
Therefore, the problem to be solved by the present invention is that there is no variation in the amount of lubricant to be injected, and it can be filled with high accuracy, the performance does not vary, and the lubricant does not leak out. It is an object of the present invention to provide a spindle motor that can be obtained.
It is another object of the present invention to provide a spindle motor which does not cause a failure because the sealing adhesive does not flow out to the seal portion.
It is another object of the present invention to provide a spindle motor that can obtain high resistance to disturbance without leakage of lubricant even when excessive temperature change or vibration shock is applied.

In order to solve the above problems, the present invention has the following configuration as means.
[1] That is, in the spindle motor, the lubricant (16) is interposed between the rotor part (54R) and the stator part (54R), and the rotor part (54R) is rotated with respect to the stator part (54R). A radial dynamic pressure bearing portion (RB) and a thrust dynamic pressure bearing portion (SB) that are freely supported are provided, connected to the radial dynamic pressure bearing portion (RB) and the thrust dynamic pressure bearing portion (SB), and a predetermined gap A lubricant holding portion that is filled with the lubricant (16) and extends in a direction along the rotation axis (C) and is open at least one side in the direction (117a). The lubricant holding portion (117) filled with the lubricant (16) so that the liquid level (16a) is located on the inner side of the open end portion (117a), and the lubricant holding portion The open end (11) of (117) a) connected to a), extending in a direction approaching the rotation axis (C), and formed so that a cross-sectional area in the direction of the rotation axis (C) gradually increases as approaching the rotation axis (C). A spindle motor (54) having a capillary seal (18) and a lubricant movement path (16b) extending in a direction away from the rotating shaft (C) is provided.
[2] Further, in the spindle motor according to [1], the lubricant holding portion (117) is at least on the open end portion (117a) side and toward the open end portion (117a), the rotating shaft (C ), And a capillary seal (17) formed so that the cross-sectional area in the direction orthogonal to the direction gradually increases.
[3] The spindle motor according to [1] or [2] is connected to the capillary seal (18), extends in a direction along the rotation axis (C), and extends from the capillary seal (18). The spindle motors (51, 52) were provided with another capillary seal (19) formed so that the cross-sectional area in the direction perpendicular to the rotation axis (C) gradually increased as the distance increased.
[4] Further, the rotating shaft in the portion of the capillary seal (18) connected to the open end portion of the lubricant holding portion (17, 117) of the spindle motor according to [1] or [2]. The spindle motor (51, 52) is configured such that the gap in the direction is smaller than the gap in the direction of the rotation axis at the portion of the lubricant moving path connected to the open end portion of the lubricant holding portion. .

According to the present invention, the lubricant is not leaked to the outside, and an effect of high reliability can be obtained.
Moreover, there is no outflow of the sealing adhesive to the seal portion, and an effect that no defect occurs is obtained.
Moreover, the effect that it has high tolerance with respect to a disturbance is acquired.

The preferred embodiments of the present invention will be described with reference to FIGS.
FIG. 1 is a partial cross-sectional view for explaining a first embodiment of a spindle motor of the present invention.
FIG. 2 is a partially enlarged cross-sectional view for explaining a main part in the first embodiment of the spindle motor of the present invention.
FIG. 3 is a partially enlarged sectional view for explaining a spindle motor according to a second embodiment of the present invention.
FIG. 4 is a partially enlarged cross-sectional view for explaining a main part of the spindle motor according to the second embodiment of the present invention.
FIG. 5 is a partial enlarged cross-sectional view for explaining a main part in the third embodiment of the spindle motor of the present invention.
FIG. 6 is a partially enlarged sectional view for explaining a spindle motor according to a fourth embodiment of the present invention.
FIG. 7 is a partial enlarged cross-sectional view for explaining a modification of each embodiment of the spindle motor of the present invention.

<Example 1>
The configuration of the spindle motor according to the first embodiment of the present invention will be described with reference to FIGS. The spindle motor 51 is a spindle motor for the hard disk drive (HDD) shown in FIG. 1, and FIG. 2 is an enlarged cross-sectional view of a main part A of FIG.
In FIG. 1, the spindle motor 51 is composed of a rotor portion 51R and a stator portion 51S.
The stator portion 51S has a base 15 and a shaft 1 fixed to the base.
A pair of thrust plates 4 are press-fitted or shrink-fitted to the shaft 1 in the axial direction and further fixed with an adhesive.
A female screw 8 is formed on the center line on one end side of the shaft 1, and this motor is used to fasten the screw to a cover (not shown) of the HDD using this female screw 8. The vibration during rotational driving is suppressed.
A core 11 formed by laminating thin sheets of annular electromagnetic steel plates having a plurality of salient poles (not shown) is fixed to the base 15, and a coil 12 is wound around each salient pole.

On the other hand, the rotor portion 51 </ b> R has an aluminum hub 10 and an inner sleeve 2.
The inner sleeve 2 is fixed to the inner peripheral surface of the hub 10 by press fitting.
A hub flange 10 a that protrudes in the radial direction and supports the disk 20 in the axial direction is formed on the outer peripheral portion of the hub 10.
On the inner peripheral surface 10a1 of the hub 10 corresponding to the hub flange 10a, an annular rotor yoke 14 forming a magnetic circuit of the motor, and an annular magnet in which N poles and S poles are alternately magnetized in multiple poles. 13 is mounted with the magnet 13 inside.
The magnet 13 is arranged such that its inner peripheral surface faces the outer peripheral surface of the core 11 on the stator 51S side with a predetermined gap.

Next, the hydrodynamic bearing will be described.
The radial dynamic pressure bearing portion RB includes a pair of radial dynamic pressure grooves 2a and 2b formed in at least one of the inner peripheral portion of the inner sleeve 2 and the outer peripheral portion of the shaft 1, and lubrication filled in the gap between the two. Agent 16.
The radial dynamic pressure grooves 2a and 2b are provided at two positions with a distance in the axial direction.

Further, a pair of thrust dynamic pressure bearings SB are disposed symmetrically on both end sides of the shaft 1.
Specifically, both end surfaces 2d (see FIG. 2) on both sides in the axial direction of the inner sleeve 2 and axial end surfaces 4b facing the end surface 2d of the inner sleeve 2 in the thrust plate 4 with a minute gap. The thrust dynamic pressure groove 4a is formed in at least one of the lubricants 16 and the lubricant 16 filled in the gap between them.
FIG. 2 shows a case where the dynamic pressure groove 4 a is formed on the end surface 2 d of the inner sleeve 2.

  The spindle motor 51 utilizes the dynamic pressure generated in the pair of thrust dynamic pressure grooves 4a and the radial dynamic pressure generated in the radial dynamic pressure grooves 2a and 2b in the dynamic pressure bearings RB and SB, and the rotor portion 51R. Can rotate without contacting other members with respect to the stator portion 51S.

Next, the through hole through which the lubricant 16 flows will be described.
In the outer peripheral portion of the inner sleeve 2, when the inner sleeve 2 is joined to the hub 10 by press-fitting, grooves 2 c along the axial direction are spaced at 180 ° intervals so that the press-fitting force can be reduced and the press-fitting can be smoothly performed. Two places are formed.
If the number of the grooves 2c is further increased, the number of processing steps increases more than necessary, and the coupling force after assembly may decrease excessively, so that the performance due to shock / vibration may change. The following is preferable.

When such an inner sleeve 2 is fitted to the hub 10, a through hole 7 is formed by the groove 2c.
Since the through hole 7 connects both ends of the pair of radial dynamic pressure grooves 2 a and 2 b filled with the lubricant 16, the flow of the lubricant 16 can be obtained through the through hole 16.
Therefore, the effect of adjusting the pressure balance between the thrust dynamic pressure and the radial dynamic pressure is exhibited. For example, it is possible to prevent the occurrence of a problem that negative pressure or excessive levitation occurs in these dynamic pressures.

In this configuration, the lubricant 16 is filled in the following gaps and the like.
That is, the clearance between the inner peripheral surface 2f of the inner sleeve 2 and the outer peripheral surface 1a of the shaft 1, the clearance between the end surface 2d of the inner sleeve 2 and the end surface 4b of the thrust plate 4 opposed thereto, and the outer peripheral surface 4c of the thrust plate 4 A gap with an inner peripheral surface 6k1 of a washer ring 6 to be described later, and a through hole 7.

  Next, the details of the thrust bearing portion SB will be described in detail with reference to FIG.

A first step portion 10e and a second step portion 10f having a larger diameter toward the end face side are provided in a stepped manner at the end portion of the inner peripheral portion of the hub 10 opposite to the base 15. Yes.
A washer ring 6 is attached to the first step portion 10e.
Specifically, as shown in detail in FIG. 2, the washer ring 6 is annular, and includes a base portion 6k extending along the axis and a protruding portion 6t protruding outward from one end side of the base portion 6k. The cross section becomes substantially L-shaped.
The inner peripheral surface 6k1 of the base portion 6k is opposed to the outer peripheral surface 4c of the thrust plate 4 with a space having a predetermined shape, and the outer peripheral surface 6t1 of the protruding portion 6t is orthogonal to the rotation axis C of the first step portion 10e. The washer ring 6 is fixed to the hub 10 by press-fitting the front end surface 6t2 of the protruding portion 6t into the inner peripheral surface 10e2 of the first stepped portion 10e of the hub 10 so as to abut against 10e1.
The washer ring 6 is formed of a stainless alloy, aluminum, or copper alloy.

The second stepped portion 10f faces the outer peripheral surface 1a of the shaft 1, the axial end surface 4m of the thrust plate 4 and the axial end surface 6k2 of the base portion 6k of the washer ring 6 with a predetermined gap. A thin annular end cap 5 is fixed.
Specifically, the outer peripheral side portion and the outer peripheral surface 5d of the end surface 5b of the end cap 5 are respectively bonded to the wall surface 10f1 orthogonal to the axis of the second step portion 10f and the inner peripheral surface 10f2 of the second step portion 10f. It adheres by.
Adhesive reservoirs 10f3 and 10f4 are formed on the second step portion 10f to enable stronger fixation.
The end cap 5 is fixed after a predetermined amount of the lubricant 16 is injected into the dynamic pressure bearing portion.
The end cap 5 is made of aluminum.

The inner peripheral surface 6k1 of the base 6k of the washer ring 6 fixed to the hub 10 has a diameter that gradually decreases at an angle θ1 from the inner side to the outer side (from the lower side to the upper side in FIG. 2) of the radial bearing portion RB. 1 taper portion 6a.
The outer peripheral surface 4c of the thrust plate 4 fixed to the shaft 1 is a second tapered portion 4e whose diameter gradually decreases at an angle θ2 from the inner side to the outer side of the radial bearing portion RB.
Further, since the angles are in a relation of θ1 <θ2, the first capillary seal 17 is formed between the inner peripheral surface 6k1 and the outer peripheral surface 4c facing each other, and the gap gradually increases as the gap goes outward.
Then, the filling amount of the lubricant 16 is managed so that the liquid level 16 a of the lubricant 16 filled in the hydrodynamic bearing is located in the middle of the first capillary seal 17.

In the configuration described above, the lubricant 16 tends to move in the first capillary seal 17 toward the open end 17a side by receiving stirring or the like by the thrust dynamic pressure groove 4a when the motor rotates.
At that time, the liquid surface 16a of the lubricant 16 gradually increases in surface area according to the angle difference between the angle θ2 and the angle θ4, but the surface area of the liquid surface 16a is reduced by the intermolecular force on the liquid surface 16a. Surface tension works.
Accordingly, the lubricant 16 receives a resistance force (also referred to as a sealing force) due to the capillary phenomenon and is pulled back toward the inside of the radial bearing RB, and is sealed so as not to move outward from a certain position.

Further, the lubricant 16 tends to move to a portion having a large diameter due to the centrifugal force generated with the rotation of the motor.
Here, the first capillary seal 17 is formed such that the inner peripheral surface 6k1 of the washer ring 6 that is the outer peripheral surface thereof becomes larger in diameter toward the inner side of the radial bearing portion RB.
Therefore, the lubricant 16 tries to move in the direction toward the inside of the filling portion, and leakage of the lubricant 16 to the outside can be prevented more reliably.

As the inclination angle θ1 of the inner peripheral surface 6k1 of the first capillary seal 17 is larger, the sealing effect of the lubricant due to the centrifugal force described above is exhibited. However, in the process of injecting the lubricant 16, the position of the liquid surface is grasped and measured. It is preferable that the angle θ1 is 10 ° or less so that the angle is easy.
As described above, the inclination angle θ2 is set to be slightly larger than θ1 because sealing is performed by capillary action.
Under such conditions, in the spindle motor of the first embodiment, the drive rotation speed of the spindle motor 51 is set to 1500 times / minute to 7200 times / minute, and the taper angles are set to θ1 = 2 ° and θ5 = 5 °, respectively.

Even in the configuration described above, the lubricant 16 may leak from the first capillary seal 17 due to expansion of the lubricant 16 due to excessive temperature change, excessive vibration or impact applied from the outside, and the like. Cannot be denied.
In order to further improve reliability, the market demands a structure that is not affected by these unexpected disturbances.

Therefore, in the spindle motor according to the first embodiment, the second capillary seal 18 connected to the open end 17a side of the first capillary seal 17 and extending in the radial direction toward the rotation axis C and outward. A lubricant conduction space 16b extending in the radial direction is provided (details of the second capillary seal 17 and the lubricant conduction space 16b will be described later).
That is, the outlet of the first capillary seal 17 is branched into the second capillary seal 18 and the lubricant conducting space 16b so as to be directed in the opposite radial directions.

For example, the lubricant 16 leaked from the first capillary seal 17 due to disturbance, for example, moves to one of the branched branches and flows out.
A third capillary seal 19 (described later) is provided further ahead of the second capillary seal 18, but since the tip is an external space, it is not connected to the outside in terms of leakage to the outside. It is preferable to move to the lubricant conduction space 16b.

If the rotor portion 51R is in a rotating state, most of the lubricant 16 is directed to the lubricant conduction space 16b by centrifugal force.
On the other hand, even in a stationary state, if the width W1 in the axial direction of the inlet to the second capillary seal 18 is narrower than the width W2 of the lubricant conducting space 16b, lubrication toward the lubricant conducting space 16b is performed. Since the agent 16 increases, it is more preferable.
Further, it is more preferable to apply an oil repellent agent to one side or both sides of each surface constituting the second capillary seal 18 because the movement of the lubricant 16 to the second capillary seal becomes more difficult.

Next, the second capillary seal 18 will be described in detail.
The second capillary seal 18 is constituted by an end face 4 m of the thrust plate 4 and an inner diameter side face 5 b 1 of the end face 5 b of the end cap 5.
The end surface 4m of the thrust plate 4 has a surface orthogonal to the rotation axis C, and the inner diameter side surface 5b1 of the end cap 5 extends from the vicinity of the open end portion 17a of the first capillary seal 17 toward the rotation axis in the radial direction. It is formed with an inclination angle of angle θ3 so that the distance with 4 m gradually increases.
That is, the second capillary seal 18 is a taper seal formed so that the distance between the opposing surfaces gradually increases from the outside in the radial direction toward the inside.
Thereby, like the first capillary seal 17 described above, leakage of the lubricant 16 can be prevented by capillary action.

In the first embodiment, a third capillary seal 19 is further provided at the tip of the second capillary seal 18. Hereinafter, the third capillary seal 19 will be described.
The third capillary seal 19 is formed by forming both the inner peripheral surface 5c of the end cap 5 and the opposing surface 1a1 of the outer peripheral surface 1a of the shaft 1 facing the end cap 5 as inclined surfaces.
Specifically, the inner peripheral surface 5c is an inclined surface having an angle θ5 that decreases in diameter toward the end of the shaft 1, and the outer surface 1a has an angle θ4 that decreases in diameter as it approaches the end of the shaft 1. And each angle is set to θ5 <θ4.

As a result, the outer peripheral surface 1a1 and the inner peripheral surface 5c that face each other form a third capillary seal 19 that gradually expands and inclines in the small diameter direction as the gap goes outward (toward the end of the shaft). .
The second and third capillary seals exhibit a sealing effect by capillary action and centrifugal force similar to the first capillary seals.

As described above, the first to third capillary seals are provided in three stages by sequentially changing the radial direction, the axial direction, and the radial direction, so that the axial thickness of the motor itself can be suppressed relatively. A taper seal having a long path length can be provided, and a more reliable sealing effect can be obtained even with a thin motor.
Further, since there is no passage through which the lubricant can jump out to the outside, the lubricant 16 does not leak to the outside with respect to impacts in all directions.

Next, the lubricant conduction space 16b will be described in detail.
The lubricant conducting space 16b branched and connected from the first capillary seal 17 is further connected to the space portion 6b ahead.
The space portion 6b is a ring-shaped space that is surrounded by the end cap 5, the washer ring 6 and the hub 10 and seals other than the lubricant conduction space 16b.
As described above, even if an excessive temperature change, excessive vibration or impact is applied and the lubricant 16 flows into the lubricant conducting space 16b, the lubricant 16 accumulates in the space 6b. 16 does not leak.

By the way, the fixing surface between the end cap 5 and the hub 10 may be sealed with a sealing adhesive 21 in order to further improve the sealing property of the space 6b.
FIG. 2 shows an example of the case where this sealing adhesive 21 is used. Since this adhesive 21 uses a low-viscosity adhesive in order to improve the sealing performance, a sufficient amount is used. The adhesive reservoirs 10f3 and 10f4 are provided so that they can be supplied and do not flow to unnecessary places until they are cured. The space 6b also has the function of the adhesive reservoir.

As described above, in the first embodiment described in detail, the outlets of the lubricant filling portions in the hydrodynamic bearing portions SB and RB are branched and are not connected to the outside with the three-stage seal portions 17 to 19 in which the extending directions are sequentially changed. Since the space 6b is connected, leakage of the lubricant 16 to the outside can be reliably prevented.
Further, since the liquid level 16a of the lubricant 16 is positioned on the first-stage seal portion 17 and the seal portion 17 extends at an angle close to parallel to the axis C, before the end cap 5 is fixed. When the lubricant 16 is injected, the liquid level 16a can be confirmed from the outside, and the sealing effect of centrifugal force is exhibited.
Accordingly, it is possible to manage the filling amount with high accuracy and to obtain the spindle motor 51 with extremely high reliability.

<Example 2>
Next, Example 2 will be described with reference to FIGS.
The first embodiment is a so-called shaft fixed type spindle motor, but the second embodiment is a spindle motor in which the first embodiment is a so-called shaft rotation type.
In the spindle motor 52, the shaft 1 is fixed to the center hole 10p of the hub 10 on the rotor portion 52R side, the outer sleeve 3 is fixed to the base 15 on the stator portion 52S side, and further, the inner periphery of the outer sleeve 3 is fixed. An HDD spindle configured such that the inner sleeve 2 is fixed and the shaft 1 is pivotally supported by the inner sleeve 2 so that the rotor portion 52R rotates with respect to the stator portion 52S via the hydrodynamic bearing portions RB and SB. This is a motor 52.

FIG. 4 shows an enlarged cross-sectional view of part A of FIG.
The configurations of the thrust dynamic pressure portion SB and the radial dynamic pressure portion RB in the second embodiment are the same as those of the first embodiment including the main configuration except for the shaft rotation type.
Referring to FIG. 4, the second embodiment is the same as the first embodiment except that the hub 10 is replaced with the outer sleeve 3 and the shaft 1 is fixed to the hub 10.
Therefore, the second embodiment can obtain the same effect as the first embodiment.

<Example 3>
The third embodiment is an example in which the number of parts is reduced by forming the washer ring 6 integrally with the hub 10 or the outer sleeve 3 with respect to the first embodiment or the second embodiment. Show.
That is, the hub 10 or the outer sleeve 3 has an annular protrusion 116 having a shape corresponding to the washer ring 6 in the first or second embodiment on the inner peripheral surface.
By integrating in this way, the number of parts is reduced, the number of man-hours is reduced, and a sealing adhesive for sealing the washer ring 6 is not required, so that the cost can be reduced.
Other configurations are the same as those of the first or second embodiment, and the same effects as those of the first or second embodiment are obtained.

<Example 4>
As shown in FIG. 6, the fourth embodiment is an enlarged cross-sectional view of the main portion, compared to the first and second embodiments. In this example, 4c is a cylindrical surface parallel to the rotation axis C of the shaft 1 and the inclination is eliminated.
That is, in this embodiment, the spindle motor 54 is the first capillary seal 17 which is a lubricant holding portion 117 excluding the sealing function.
In other words, in the first to third embodiments, the first capillary seal 17 is provided on at least the open end 117a side of the lubricant retaining portion 117 in the fourth embodiment.
In the fourth embodiment, as in the first and second embodiments, the capillary seal 18 extending in the direction of the rotation axis C and the rotation axis C are separated from the open end portion 117a of the lubricant holding portion 117. A lubricant conduction space 16b extending in the direction is provided.
The lubricant 17 is filled so that the liquid level 16a is positioned inside the open end 117a of the lubricant holding portion 117.
The surface on which the taper seal is formed is easier to process with a cylindrical surface having no inclination, and can be processed with high accuracy.
Therefore, it is not necessary to consider variation in the capacity of the seal portion having the inclined surface, and the volume of the lubricant when the position of the liquid surface 16a of the lubricant 16 is constant can be managed with higher accuracy.
This is for applications where vibrations and impacts are difficult to apply, and in applications where disturbances are difficult to apply and lubricants are difficult to leak out, because there is little variation in motor performance and higher reliability can be obtained. It is.

Even in this fourth embodiment, as described in the other embodiments, even if the lubricant leaks from the lubricant holding portion 117, most of the lubricant moves to the space portion 6b through the lubricant conduction space 16b. There is no leakage.
If there is little disturbance in the normal use state, even if it enters the second (corresponding to the first in this embodiment) capillary seal 18, the third (similarly second) capillary seal 19 Since it is sealed, there is almost no possibility of leakage from there into the external space.
Therefore, it is needless to say that in the fourth embodiment, a highly reliable spindle motor that does not adversely affect the outside can be obtained.

<Modification>
Each embodiment may be modified as described below.
In this modification, as shown in FIG. 7, an adhesive reservoir 10f3 is provided outside the space 6b in the same shape. As a result, even if the flow of the adhesive 21 is large, a stronger adhesive force can be exhibited without flowing out to other unnecessary portions, and a highly reliable motor can be provided.

As described above in detail, 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.
For example, in each of the embodiments, the spindle motor that supports both ends of the shaft and has two liquid levels on the upper and lower sides has been described to provide a similar seal structure on both liquid levels. If there is little, you may apply only to the other side.
Further, the above-described configuration may be applied to the sealing structure of the liquid surface of the spindle motor in which the shaft is pivotally supported by a bag-like sleeve and the liquid surface has only one side, and the same effect can be obtained.
Further, it is more preferable to provide each capillary seal portion with a spiral groove that becomes a pump-in by rotation or to apply an oil repellent agent to a necessary portion, since this further prevents leakage of the lubricant.

It is a fragmentary sectional view explaining Example 1 of the spindle motor of the present invention. It is a partial expanded sectional view explaining the principal part in Example 1 of the spindle motor of this invention. It is a partial expanded sectional view explaining Example 2 of the spindle motor of this invention. It is a partial expanded sectional view explaining the principal part in Example 2 of the spindle motor of this invention. It is a partial expanded sectional view explaining the principal part in Example 3 of the spindle motor of this invention. It is a partial expanded sectional view explaining Example 4 of the spindle motor of this invention. It is a partial expanded sectional view explaining the modification with respect to each Example of the spindle motor of this invention. It is a fragmentary sectional view explaining the conventional spindle motor. It is a partial expanded sectional view explaining the principal part of the conventional spindle motor.

Explanation of symbols

1 shaft 1a outer peripheral surface 2 inner sleeves 2a, 2b radial dynamic pressure groove 2c groove 2d end surface 2e outer peripheral surface 2f inner peripheral surface 3 outer sleeve 4 thrust plate 4a dynamic pressure groove 4b opposing surface 4c outer peripheral surface 4e second tapered portion 4m end surface 5 end cap 5b end surface 5b1 inner peripheral side surface 5c inner peripheral surface 5d outer peripheral surface 6 washer ring 6a first taper portion 6b space 6k base 6k1 inner peripheral surface 6k2 end surface 6t protrusion 6t1 outer peripheral surface 6t2 distal end surface 7 through hole 8 female Screw 10 Hub 10p Center hole 10a Hub flange portion 10a1 Inner peripheral surface 10e First step portion 10e1 Wall surface 10e2 Inner peripheral surface 10f Second step portion 10f1 Wall surface 10f2 Inner peripheral surfaces 10f3, 10f4 Adhesive reservoir 11 Core 12 Coil 13 Magnet 14 Rotor yoke 15 Base 16 Lubricant 16b Lubricant conduction space 16c Liquid level 7-19 First to third capillary seals 17a Open end 20 Disc 21 Adhesives 51, 52, 54 Spindle motors 51S, 52S Stator portions 51R, 52R Rotor portion 117 Lubricant holding portion 117a Open end portion C (Rotation) shaft SB Thrust bearing part RB Radial bearing part θ1-θ5 Inclination angle

Claims (4)

In a spindle motor provided with a radial dynamic pressure bearing portion and a thrust dynamic pressure bearing portion for interposing a lubricant between the rotor portion and the stator portion and rotatably supporting the rotor portion with respect to the stator portion,
A lubricant holding portion connected to the radial dynamic pressure bearing portion and the thrust dynamic pressure bearing portion and filled with the lubricant with a predetermined gap, and extending in a direction along the rotation axis A lubricant holding portion that is an open end that is open at least one side of the direction, and is filled with the lubricant such that the liquid level is located on the inner side of the open end; and
A capillary connected to the open end of the lubricant holding portion, extending in a direction approaching the rotation axis, and formed so that a cross-sectional area in the rotation axis direction gradually increases as the rotation axis is approached. A spindle motor comprising: a seal and a lubricant moving path extending in a direction away from the rotating shaft. The spindle motor according to claim 1,
The lubricant holding part includes at least the other end of the capillary seal formed so that a cross-sectional area in a direction orthogonal to the rotation axis gradually increases toward the open end. A spindle motor characterized by that. The spindle motor according to claim 1 or 2, wherein
Another capillary seal connected to the capillary seal, extending in a direction along the rotation axis, and formed so that a cross-sectional area in a direction perpendicular to the rotation axis gradually increases as the distance from the capillary seal increases. A spindle motor characterized by comprising:   The gap in the rotation axis direction at the portion of the capillary seal that is connected to the open end of the lubricant holding portion is the portion of the lubricant movement path that is connected to the open end of the lubricant holding portion. 2. The spindle motor according to claim 1, wherein the spindle motor is smaller than the gap in the rotation axis direction.

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