JPH1127895A - Spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spindle motor having the small deflection of an irrotational synchronous constituent, is usable in an inverted position and has superior impact resistance. SOLUTION: In this motor, a cylindrical radial-receiving surface provided on a shaft member faces a radial bearing surface provided on a bearing member, via the radial bearing gap of a radial kinetic pressure bearing. A thrust-receiving surface provided on the shaft member faces a thrust-bearing surface provided on the bearing member to constitute a thrust bearing. A rotor fixed to one of the shaft members or bearing member faces a stator fixed to the other. In this case, the shaft member has a flange 3 positioned outside in a radial direction from the radial-receiving surface 1b. The end surfaces of the far side of the flange 3 from the thrush-bearing face each other via the bearing member and a gap in a shaft direction. A gap in a radial direction between the outside circumferential surface of the flange 3, and bearing member is larger than the radial bearing gap and equal to 0.5 mm or smaller. An axial load is applied to the thrust bearing by a magnetic attraction in an axial direction of the tare or larger of rotational members, provided with either one of the shaft member and bearing member and a rotor 10 and equal to 30N or smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor for information equipment and video equipment, and more particularly to a spindle motor most suitable for a disk drive such as a magnetic disk drive or an optical disk drive.

[0002]

2. Description of the Related Art Conventionally, a disk spindle motor has a structure as shown in FIG. That is, a hub 42 on which a disk can be mounted is rotatably supported on the shaft 41 via two ball bearings 43, and the lower end of the shaft 41 is
It is fixed to. The hub 42 and a disk (not shown) mounted on the hub 42 are rotationally driven by a motor M2 inserted between the base 47 and the hub 42. Motor M
2 has a rotor 40 fixed to the hub 42 and a stator 45 fixed to the base 47.

[0003]

In the magnetic disk drive, high-density recording has been developed, and a spindle motor used therefor is required to have a small non-rotational synchronous component swing.

A ball bearing 43 as shown in FIG. 4 has been used in a conventional spindle motor. The ball bearing 43 is
It is required that the swing of the non-rotational synchronous component be small. However, the ball bearing 43 has ball passing vibration and vibration caused by a shape error of the bearing component, and it is difficult to reduce the runout of the non-rotational synchronous component to a predetermined value or less even if the processing accuracy is improved. .

On the other hand, a spindle motor having a structure as shown in FIG. 5 in which a dynamic pressure bearing having a small runout of a non-rotational synchronous component is used for both a radial bearing and a thrust bearing instead of the ball bearing 43 is being studied. In this example, a radial dynamic pressure bearing is formed by a radial bearing surface 56 a provided on the inner diameter surface of the cylindrical hole of the sleeve 56 fitted to the base 57 and the outer diameter surface of the shaft 51. The end face 51a and the upper face 58a of the thrust receiver 58 constitute a thrust dynamic pressure bearing to support a thrust load.

Further, the rotor 50 fixed to the inner diameter surface of the rotating hub 52 and the stator 55 fixed to the base 57 are opposed to each other in the radial direction to form a motor M2, and the hub 52 is driven. Note that the rotor 50 and the stator 55 of the motor M2 are provided at substantially the same position in the axial direction.

However, when the bearing is a dynamic pressure bearing, the non-rotational synchronous component of the spindle is reduced in runout, but the shaft 51 comes out of the sleeve 56 when an impact is applied in an inverted state or in a direction in which the shaft comes off from the outside. There were drawbacks. Therefore, as shown in FIG.
However, it is difficult to attach the stopper 60 with such a structure, and the stopper 60 and the flange portion 56b of the sleeve axially facing the stopper 60 due to an impact during transportation or the like. There is a problem that abrasion powder is likely to be generated when the contact is frequently made.

The present invention focuses on the above-described problem, and has a small non-rotational synchronous component swing, and can be used even in an inverted state.
Moreover, it is an object of the present invention to provide a spindle motor having excellent impact resistance.

[0009]

In order to achieve the above object, a spindle motor according to the present invention has a radial bearing gap between a cylindrical radial receiving surface provided on a shaft member and a radial bearing surface provided on a bearing member. A radial dynamic pressure bearing is opposed to the shaft member, and a thrust bearing surface provided on the shaft member and a thrust bearing surface provided on the bearing member face each other to constitute a thrust bearing. The rotor fixed to one of them faces the stator fixed to the other.

Further, in the spindle motor according to the present invention, the shaft member has a flange located radially outward from the radial receiving surface, and an end surface of the flange farther from the thrust bearing is provided with an axial clearance with the bearing member. The radial gap between the outer diameter surface of the flange and the bearing member is larger than the radial bearing gap and 0.5 mm or less,
An axial load is applied to the thrust bearing by a magnetic attraction force in the axial direction that is equal to or more than its own weight and equal to or less than 30 N, of the rotating member including the shaft member and the member to which the rotor is fixed, of the bearing member. It is characterized by.

According to the present invention, since the rotating member is supported by the radial dynamic pressure bearing and the thrust bearing, the fluctuation of the non-rotation synchronous component is small. Further, since a predetermined magnetic attraction force is applied in the axial direction, there is no restriction on the use posture.
Moreover, the end surface of the flange farther from the thrust bearing faces the bearing member via the axial gap, so that the shaft member does not come off from the bearing member.

Further, the radial gap between the outer diameter surface of the flange and the inner diameter surface of the bearing member opposed thereto is larger than the radial bearing clearance and 0.5 mm or less.
Even if an external impact acts in the direction in which the shaft member comes out of the bearing member, when the lubricating fluid flows from one axial side of the flange to the other through the gap, the gap acts as a throttle for the lubricating fluid. The resistance of the lubricating fluid to flow,
The shaft member is prevented from being axially displaced with respect to the bearing member.
As a result, tens of milliseconds (for example, 0.05 to 0.0
With a short impact of about 6 seconds or less, the shaft member hardly moves relative to the bearing member.

[0013]

Examples of the present invention will be described below. FIG. 1 is a schematic longitudinal sectional view of a first embodiment of a spindle motor according to the present invention, in which a bearing member is fitted on a sleeve 6 on which the shaft 1 is fitted, and on an outer peripheral surface of a lower end of the sleeve 6. There is provided a base 7 to be fixed, and a thrust plate 8 fixed to the base 7 by covering a cylindrical hole of the sleeve 6. The shaft member includes a shaft 1, an annular flange 3 fixed near one shaft end of the shaft 1, and a hub 2 fixed to the other end of the shaft 1. It can be installed. A rotor 10 is fixed to the hub 2.
Reference numeral 0 denotes a back yoke fixed to the hub 2 and a magnet 12 fixed to the back yoke 11, and the rotating member includes a shaft member and a rotor 10 fixed to the shaft member.
The rotor 10 fixed to the shaft member radially faces the stator 15 fixed to the bearing member to constitute a motor M.

A cylindrical radial receiving surface 1b provided at two places on the shaft member with an axial space therebetween is opposed to a radial bearing surface 6a provided on the bearing member via a radial bearing gap to form a radial dynamic pressure bearing. In the embodiment shown, at least one of the radial receiving surface 1b and the radial bearing surface 6a which are respectively opposed to each other is provided with a herringbone-shaped groove 6b for generating dynamic pressure in the radial bearing surface 6a. A flat thrust receiving surface 1a provided on the shaft end of the shaft 1 and a thrust bearing surface 8a provided on the thrust plate 8 face each other to constitute a thrust dynamic pressure bearing. In the illustrated embodiment, at least one of the thrust receiving surface 1a and the thrust bearing surface 8a facing each other is provided with a spiral dynamic pressure generating groove 8b in the thrust bearing surface 8a. A flange 3 is fixed to the shaft 1 by press-fitting or bonding, and the shaft member has the flange 3 located radially outward from the radial receiving surface 1b.

If the thrust plate 8 is manufactured by injection molding of plastic, the grooves 8b for generating dynamic pressure can be formed by molding, so that the manufacturing cost can be reduced. In particular, if PPS (polyphenylene sulfide resin) is used as a base and manufactured by injection molding with a plastic to which carbon fiber and Teflon (registered trademark: polytetrafluoroethylene) are added, slidability,
Excellent in strength and moldability, preferred.

Further, when the axial load is large, the thrust plate 8 may be sandwiched between the holding of the steel plate and the base 7 in order to reinforce the plastic thrust plate 8. In addition, the groove 8b for generating dynamic pressure is omitted, and at least one of the thrust receiving surface 1a and the thrust bearing surface 8a is formed as a convex spherical surface, and the thrust receiving surface 1a and the thrust bearing surface 8a are formed.
A so-called pivot bearing that makes point contact with the bearing may be used.

On the other hand, a sleeve 6 made of a copper-based material is used for the radial dynamic pressure bearing, so that a groove 6b for generating dynamic pressure is easily formed on the radial bearing surface 6a of the sleeve 6. . By manufacturing the sleeve 6 using a copper-based material, the slidability between the radial bearing surface 6a and the radial receiving surface 1b of the stainless steel shaft 1 is improved, and the start / stop durability is improved. Since the sleeve 6 and the thrust plate 8 are directly fixed to the base 7, the assembling is easy and the reliability is excellent.

In this embodiment, the axial center of the rotor 10 constituting the motor M is shifted in the axial direction with respect to the axial center of the stator 15, so that the rotor 10 and the stator 15 A magnetic attraction force acts, and an axial load is applied to the thrust bearing by an axial magnetic attraction force equal to or more than its own weight of the rotating member and equal to or less than 30N. By fixing a magnet to one of the shaft member and the bearing member, and fixing a magnet or a magnetic body to the other, the thrust bearing is actuated by an axial magnetic attraction applied to the shaft member and the bearing member. May be given an axial load.

The magnitude of the magnetic attraction in the axial direction in which the axial load is applied to the thrust bearing is not less than the own weight of the rotating member and not more than 30 N, more preferably more than twice the own weight of the rotating member and 10 N. The following is good. If the magnetic attraction in the axial direction is smaller than the own weight of the rotating member, when the rotating member is used in the inverted position, the thrust receiving surface 1a of the shaft member and the thrust bearing surface 8a of the bearing member do not come into contact with each other. Contact in the axial direction. If it is larger than 30 N, the axial load applied to the thrust bearing is large, the starting torque becomes large, and wear at the time of starting and stopping becomes a problem.
When the magnetic attraction in the axial direction is twice or more the own weight of the rotating member, the contact between the thrust bearing surface 8a and the thrust receiving surface 1a is maintained even if some external impact is applied. When the thickness is set to 10 N or less, the axial load applied to the thrust bearing is reduced, so that it is not necessary to use an expensive material such as ceramic for the thrust bearing surface 8a of the thrust plate 8, and the cost can be reduced.

The flange 3 is preferably integral with the shaft 1 made of stainless steel. When the flange 3 is separate from the shaft 1, a material such as an aluminum alloy, stainless steel, or plastic is used. However, a material having the same linear expansion coefficient as that of the shaft 1 is preferable because it does not loosen when the temperature changes. The flange 3 is connected to the shaft 1
It is desirable to use the same stainless steel because the sliding property of the bearing member with the copper-based sleeve 6 is good. Further, a disk-shaped flange may be attached to the end face of the shaft 1 by screwing or the like. In this case, the lower end surface of the disc-shaped flange serves as the thrust receiving surface of the thrust bearing.

An inner circumferential groove 2a is provided on the surface of the hub 2 facing the bearing member at the boundary between the inner diameter surface and the bottom surface, that is, the upper surface. Even if the lubricating fluid in the radial bearing gap is scattered by the rotation from the outer peripheral surface of the shaft 1 due to the inner circumferential groove 2a, the inner circumferential groove 2a is formed by the surface tension of the lubricating fluid.
As a result, the lubricating oil of the lubricating fluid can be prevented from scattering to the surface of the disk 20.

FIG. 2 is an enlarged view around the flange 3 at the shaft end. The radial gap R between the outer diameter surface 3a of the flange and the inner diameter surface 6d of the inner peripheral groove provided in the bearing member for accommodating the flange is defined by the radial bearing surface 6a and the radial receiving surface 1b.
And larger than the radial bearing gap r between
mm or less. Note that the radial gap R is 0.5 m
If it is larger than m, the resistance of the lubricating fluid to flow through the gap R is low, and if the radial gap R is less than or equal to the value of the radial bearing gap, the outer diameter surface 3a of the flange may come into contact with the bearing member.

Since r <R ≦ 0.5 mm, even if an external impact acts in the direction in which the shaft member comes out of the bearing member, the radial gap R acts as a throttle for lubricating fluid such as oil and grease. Flow resistance of the lubricating fluid flowing through
The shaft member is prevented from moving in the direction in which it comes off from the bearing member. As a result, the shaft member hardly moves with respect to the bearing member if the impact is for a short time of about several tens of milliseconds or less. The tolerance that is practical in terms of mass productivity and processing cost is that the coaxiality between the outer diameter surface 3a of the flange and the radial receiving surface 1b is 0.005 mm, the radial bearing surface 6a and the inner diameter surface 6d of the inner circumferential groove. Is 0.005 mm, and the outer diameter dimension tolerance of the outer diameter surface 3a of the flange is 0.01 m.
m, and the inner diameter tolerance of the inner diameter surface 6d of the inner circumferential groove is 0.0
1 mm. Therefore, considering these accumulated tolerances, the radial gap R is preferably larger than 0.03 mm in order to prevent the contact between the outer diameter surface 3a of the flange and the bearing member. In addition, since it is not good to make the viscosity of the lubricating fluid too high in terms of bearing performance, in order to obtain the flow resistance of the lubricating fluid, the value of the radial gap R is preferably 0.2 mm or less.

The end face 3b of the flange farther from the thrust bearing is connected to the opposed lower surface 6c of the sleeve 6 of the bearing member.
And an axial gap h, and the axial gap h is set to 0.01 mm or more and 0.5 mm or less, so that a very large external impact causes the shaft member to move in a direction to come off from the bearing member. However, it does not move more than 0.5 mm. In consideration of preventing damage to the head facing the magnetic disk attached to the hub 2, the axial gap h is preferably 0.1 mm or less.

Further, a groove for generating dynamic pressure may be formed in the upper end face 3b of the flange, and the upper end face 3b of the flange and the lower surface 6c of the sleeve facing each other may constitute a thrust dynamic pressure bearing. In this case, even when the shaft member moves in the axial direction with respect to the bearing member due to an extremely large impact, the thrust dynamic pressure bearing supports the impact, so that contact between the flange 3 and the bearing member can be prevented.

FIG. 3 shows a second embodiment. Note that the same reference numerals are used for components having the same functions as in the first embodiment. In this embodiment, an annular plate 16 of a magnetic material for suction is fixed to the base 7 at a position facing the rotor 10 in the axial direction, and the rotor 10 and the annular plate 16 facing each other via the axial gap are fixed. A magnetic attraction in the axial direction is given between them. This magnetic attraction applies an axial load to the thrust bearing.

The magnetization pattern of the rotor 10 may be the same as that of a general motor. However, when a magnetizing pattern for attraction is added to the lower end surface of the magnet 12 of a general motor rotor, an axial magnetic attraction is generated between the rotor magnet 12 and the annular plate 16. In this case, the lower end face of the magnet 12 of the rotor has N
It is more preferable that the other pole is the south pole because the eddy current generated in the annular plate 16 made of the magnetic material can be reduced and the loss of the motor M can be reduced.

In the first and second embodiments,
Since there is no air vent hole between the thrust bearing and the radial dynamic pressure bearing, which communicates the inner surface and the outer surface of the bearing member, the gap between the bearing member and the shaft member is in a sealed state, which is excellent in retaining lubricating fluid. Therefore, reliability is improved even for long-term use, which is preferable. In the present embodiment, the case where the shaft member rotates is described. However, the stator is fixed to the shaft member, the rotor facing the stator is fixed to the bearing member, and the rotating member including the bearing member and the rotor rotates. The structure may be used. For the motor, the rotor 10 and the stator 1
5 may be used instead of the circumferentially opposed motor, and the thrust bearing may be provided with a groove for generating dynamic pressure on the thrust receiving surface 1a.

In fixing the thrust plate 8 to the base 7 or the sleeve 6, instead of screwing, the thrust plate 8 may be adhered to the base 7 or the sleeve 6 to prevent leakage of the lubricating fluid. Further, as the lubricating fluid used in the gap defined between the shaft member and the bearing member, a fluorine oil excellent in temperature viscosity characteristics, that is, a fluorine oil having a small change in viscosity with respect to a temperature change, for example, a fluorine oil having a high viscosity index is used. preferable. In particular, in order to improve the slidability and the retention property of the lubricating fluid, a fluoro oil to which a perfluoroalkyl polyether having a carboxylic acid at a terminal is added is preferable.

[0030]

According to the present invention, since the rotating member is supported by the radial dynamic pressure bearing and the thrust bearing, a spindle motor having a small non-rotational synchronous component runout can be obtained. Further, the spindle motor according to the present invention exerts a predetermined magnetic attraction force in the axial direction, so that there is no restriction on the use posture. Furthermore, by providing a flange on the shaft member, the axial displacement of the bearing member with respect to the shaft member is reduced, and the flow resistance of the lubricating fluid in the radial gap between the flange and the bearing member is increased, so that the impact resistance is improved. Are better.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a spindle motor according to a first embodiment of the present invention.

FIG. 2 is an enlarged view around a shaft end of the spindle motor shown in FIG. 1;

FIG. 3 is a schematic longitudinal sectional view of a spindle motor according to a second embodiment of the present invention.

FIG. 4 is a schematic longitudinal sectional view of a spindle motor using a ball bearing according to the prior art.

FIG. 5 is a schematic longitudinal sectional view of a spindle motor using a dynamic pressure bearing according to the related art.

[Explanation of symbols]

 Reference numerals 1, 41, 51 Shafts 1a, 51a Thrust receiving surface 1b Radial receiving surface 2, 42, 52 Hub 2a Inner circumferential groove 3 Flange 3a Flange outer diameter surface 3b Flange end surface 6, 56 Sleeve 6a, 56a Radial bearing surface 6d Inner circumferential groove inner diameter surface 56b Flange portion 6c Lower surface 7, 47, 57 Base 8 Thrust plate 8a Thrust bearing surface 10, 50 Rotor 11 Back yoke 12 Magnet 15, 55 Stator 16 Ring plate 20 Disk 43 Ball bearing 60 Stopper M, M2 Motor h Axial gap R Radial gap r Radial bearing gap

Claims (1)

[Claims] A radial bearing surface provided on a shaft member and a radial bearing surface provided on a bearing member opposing each other via a radial bearing gap to constitute a radial dynamic pressure bearing; The provided thrust receiving surface and the thrust bearing surface provided on the bearing member face each other to constitute a thrust bearing, and the rotor fixed to one of the shaft member and the bearing member is a stator fixed to the other. In the opposed spindle motor, the shaft member has a flange located radially outward from the radial receiving surface, and an end surface of the flange farther from the thrust bearing is separated from the bearing member by an axial gap. The opposed radial gap between the outer diameter surface of the flange and the bearing member is greater than the radial bearing gap and is equal to 0.1 mm.
5 mm or less, and the thrust bearing has a weight equal to or greater than the weight of a rotating member including the shaft member and the bearing member to which the rotor is fixed and the rotor.
A spindle motor, wherein an axial load is applied by a magnetic attraction force in an axial direction of N or less.