JP2001339899A - Spindle motor - Google Patents

Abstract

(57) [Summary] To provide a spindle motor capable of preventing shaft runout which is important for improving the reliability of a magnetic disk drive or the like. A rotating shaft (2) inserted through a sleeve (9) and rotating around an axis, a rotor (1) fixed to one end of the rotating shaft (2) and rotating integrally with the rotating shaft, and an inner periphery of the sleeve (9) First and second radial bearing portions 10 and 11 which are sequentially provided along the longitudinal direction of the rotating shaft 2 between the cylindrical surface and the outer peripheral cylindrical surface of the rotating shaft 2 to support the rotating shaft 2 in the radial direction.
And a thrust plate 12 that abuts against the end surface of the other end of the rotating shaft 2 and supports the rotating shaft 2 in the thrust direction, in the vicinity of the other end of the rotating shaft 2 supported by the thrust plate 12. The second radial bearing portion 11 further increases the bearing rigidity for pressing the rotating shaft 2 in the radial direction toward the axis of the sleeve 9. This allows
The rotating shaft 2 swings with the second radial bearing portion 11 closer to the other end as a fulcrum, and the swing amount decreases.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor suitable for mounting on information / video equipment and the like.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for higher recording density / high-speed data transfer in information / video equipment. For this purpose, a spindle motor capable of simultaneously satisfying the rotational accuracy and high-speed rotation of a motor has been developed. Is coming.

A spindle motor for a magnetic disk drive using a fluid bearing as a radial bearing will be described as an example.
As shown in FIG. 3A, a hub 101 on which a magnetic disk (not shown) is mounted has a rotating shaft 10 press-fitted at the center.
The yoke 103 rotates in one direction integrally with the yoke 2, and a yoke 103 made of a soft magnetic material and a magnet 104 are mounted on the inner peripheral side to form a rotor. The inner peripheral cylindrical surface of the magnet 104 is magnetized with a plurality of poles. A stator core 108 around which a plurality of phases of stator coils 107 are wound is attached to an outer peripheral surface of a cylindrical portion 106 rising from the base 105 so as to face the magnet 104.

A sleeve 109 for supporting the rotating shaft 102 is fixed inside the cylindrical portion 106 by bonding or the like, and a predetermined space is provided between the rotating shaft 102 and radial bearings 110 and 111 formed on the inner peripheral surface thereof. A gap (several μm order) is formed. As shown in FIG. 3B, these radial bearing portions 110 and 111 are wedge-shaped dynamic pressure generating grooves 110a and 111 formed by processing means such as rolling.
a, and a lubricant L
Are injected to form a radial bearing. Upper radial bearing 1 along the longitudinal direction of rotating shaft 102
10 and the groove width D of the lower radial bearing portion 111.
2 is designed to be equal or D1 to be larger than D2 from the relationship between the center of gravity of the rotor and the radial suction force of the motor. A thrust plate 112 for closing the lower end opening of the sleeve 109 is provided between the thrust plate 112 and an inwardly protruding portion 106 a formed on the cylindrical portion 106, and has a convex arcuate surface 102 formed on the lower end of the rotating shaft 102.
a to form a thrust bearing.

In such a spindle motor, when a plurality of phases of the stator coil 107 are sequentially energized according to the rotation phase of the rotor, torque is generated between the stator coil 107 and the magnet 104 by the Fleming's left-hand rule. As a result, the magnet 104, the yoke 103, the hub 101, and the rotating shaft 102 start rotating integrally. Accordingly, the dynamic pressure generating groove 11
At 0a and 111a, a pumping action based on the wedge shape works, and the pressure of the lubricant L increases at the central bent portion of the wedge shape, so that the rotating shaft 102 is pressed in the radial direction and the rotating shaft 1
02 and sleeve 109 (radial bearings 110, 11)
1) is kept non-contact. On the other hand, in the thrust bearing part,
A low-friction plain bearing is realized between the convex arc surface 102 a at the lower end of the rotating shaft 102 and the thrust plate 112.

[0006]

However, as the spindle motor becomes smaller and thinner, the bearing span of the radial bearing portions 110 and 111 cannot be sufficiently secured as described above. Part 11
One groove width D2 must be made extremely small, so that the bearing rigidity is reduced and the rotation of the rotary shaft 102 is increased as compared with the case where a sufficient bearing span can be obtained. This hinders the increase in recording density in the disk device, and leads to a decrease in printing performance in the laser beam printer. When the above-described slide bearing is employed as the thrust bearing, an in-plane directional force (radial force) is generated according to the state of the sliding surface, which causes the rotation of the rotating shaft 102. Therefore, it was a particularly serious problem.

On the other hand, downsizing of the spindle motor,
As the rotor becomes lighter and the motor's radial suction force becomes smaller due to its thinner design, the spindle motor, which has become smaller and thinner, takes into account the rotor's center of gravity and the motor's radial suction force as described above. With such a radial bearing stiffness, it has become impossible to sufficiently suppress the runout of the rotating shaft.

SUMMARY OF THE INVENTION An object of the present invention is to provide a spindle motor which can solve the above-mentioned problem and can prevent the rotation of a rotating shaft which is important for improving the reliability of a magnetic disk drive or the like.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a radial bearing closer to the thrust bearing, having a higher bearing rigidity to reduce the run-out of the rotary shaft and to reduce the radial bearing closer to the thrust bearing. The means was used as a fulcrum, and the amount of shake was reduced.

[0010]

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, there is provided a rotating shaft which is inserted through a sleeve member and rotates around an axis, and a rotor which is fixed to one end of the rotating shaft and rotates integrally with the rotating shaft. Radial bearing means provided between the inner peripheral cylindrical surface of the sleeve member and the outer peripheral cylindrical surface of the rotary shaft in a plurality of stages along the longitudinal direction of the rotary shaft to support the rotary shaft in the radial direction; A thrust bearing means for abutting against the end face of the other end of the rotary shaft and supporting the rotary shaft in the thrust direction, wherein the rotary shaft is located closer to the other end of the rotary shaft supported by the thrust bearing means. Radial bearing means for urging the bearing member in the radial direction toward the axis of the sleeve member and having higher bearing rigidity is arranged.

With this configuration, the rotating shaft swings around the radial bearing means near the thrust bearing means having higher bearing rigidity, and the end face of the other end of the rotating shaft supported by the thrust bearing means in the radial direction. Even when a force is applied, the amount of shaft runout can be kept small.

According to a second aspect of the present invention, in the spindle motor according to the first aspect, the radial bearing means is first and second fluid bearings having a dynamic pressure generating groove, and is closer to the thrust bearing means. The dynamic pressure generating groove of the second fluid bearing has a groove width in the longitudinal direction of the rotating shaft which is wider than the dynamic pressure generating groove of the first fluid bearing in the rotating shaft longitudinal direction.

According to this configuration, the first fluid bearing uses the first fluid bearing.
A higher dynamic pressure is generated than that of the hydrodynamic bearing, so that a radial bearing means closer to the thrust bearing means can easily realize a configuration having higher bearing rigidity.

According to a third aspect of the present invention, in the spindle motor according to any one of the first and second aspects, the other end of the rotating shaft and one of the thrust bearing means, It is characterized in that a convex arc surface that makes point contact is formed.

According to this configuration, the rotating shaft rotates with low friction by being brought into point contact with the thrust bearing means. At this time, the radial direction which is easily generated at the lower end portion of the rotating shaft by such a sliding bearing is used. Even if the above-mentioned force acts and the rotary shaft oscillates, the amount of shaft sway is suppressed as described above, so that the reliability can be improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) FIGS. 1A and 1B show a spindle motor for a magnetic disk according to Embodiment 1 of the present invention. FIG. 1A is a cross-sectional view of the spindle motor, and FIG. FIG.

In FIG. 1, a magnetic disk (not shown)
Is mounted so that the upper end of the rotating shaft 2 in the vertical direction is press-fitted and fixed and rotates integrally with the rotating shaft 2, and constitutes a rotor together with the magnet 4 mounted on the outer peripheral surface. I have. The magnet 4 is magnetized with a plurality of poles. A stator core 8 having a plurality of stator coils 7 wound thereon is fixed to the base 5 on the outer peripheral side of the magnet 4.

The sleeve 9 for supporting the rotating shaft 2 is connected to the hub 1.
Is fixed to the cylindrical portion 6 rising from the base 5 by adhesion or the like. On the inner peripheral surface of the sleeve 9,
1st radial bearing part 10, 2nd radial bearing part 11
Are provided in this order from above, and the radial bearing 1
A predetermined gap (on the order of several μm) is formed between 0 and 11 and the rotating shaft 2.

First and second radial bearing portions 10, 1
Reference numeral 1 denotes a herringbone-shaped dynamic pressure generating groove (a plurality of wedge-shaped grooves) 10a, which is formed by bending a line perpendicular to the axis of the sleeve 9 by machining means such as rolling.
1a, and a lubricant L is injected into a gap between the rotary shaft 2 and the rotary shaft 2 to form a radial bearing. However, the groove in the rotation axis direction of the dynamic pressure generation groove 11a of the second lower radial bearing 11 is smaller than the groove width B1 of the dynamic pressure generation groove 10a of the upper first radial bearing 10 in the rotation axis direction. The width B2 is formed wide. The thrust plate 12 fixed to the cylindrical portion 6 so as to close the opening of the sleeve 9 constitutes a thrust bearing that receives the convex arc surface 2 a formed at the lower end of the rotating shaft 2. 13 is a suction plate.

In such a spindle motor, when power is supplied to each phase of the stator coil 7 in accordance with the phase of the rotor, the magnet 4, the hub 1, and the rotating shaft 2 start rotating integrally.
For example, the vehicle accelerates until it reaches a steady rotation speed such as 4500 revolutions per minute.

At this time, with the rotation of the rotating shaft 2, the first
The lubricant L flows into the bent portions of the dynamic pressure generating grooves 10a, 11a of the second radial bearings 10, 11, and the rotating shaft 2 is radially moved toward the axis of the sleeve 9 by the generated dynamic pressure. Direction, the rotating shaft 2 and the sleeve 9 (radial bearings 10 and 11) are kept in non-contact. In addition, the convex arc surface 2a at the lower end of the rotating shaft 2 slides on a substantially circular surface having a diameter of several tens of μm at a substantially central portion of the thrust plate 12, thereby supporting a thrust load.

However, the convex arc surface 2 at the lower end of the rotating shaft 2
a and the thrust plate 12 are in contact with each other on such an extremely narrow surface, so that even a slight change in the interface changes the sliding state. The sliding state changes due to indentation or the like. As a result, a force is generated not only in the axial direction but also in the radial direction at the lower end of the rotating shaft 2 sliding with the thrust plate 12, and as shown in FIG. 2, the lower end of the rotating shaft 2 is moved in the radial direction. Try to move.

However, as described above, in the lower second radial bearing portion 11 formed with a wider groove width B2, the amount of the lubricant L flowing into the wedge-shaped bent portion is increased by the upper first radial bearing portion. As the dynamic pressure increases, the bearing rigidity increases. For this reason, the rotating shaft 2 swings around the lower second radial bearing portion 11 as a fulcrum, and the swing amount can be suppressed to a small amount. Since the groove width B2 is large, no lubricant leakage occurs.

Therefore, the reliability of the magnetic disk drive equipped with the spindle motor can be improved, and a higher recording density can be realized. In the first embodiment, in order to make the bearing rigidity of the lower second radial bearing portion 11 larger than that of the upper first radial bearing portion 10, the groove width of the wedge-shaped groove is Although the second radial bearing portion 11 is larger than the first radial bearing portion 10 in the configuration, the bearing rigidity of the radial bearing portion on the lower side, that is, the thrust bearing side is higher than the bearing rigidity of the upper radial bearing portion. If so, the same effect as in the first embodiment can be obtained.

For example, the number of wedge-shaped grooves is smaller than that of the upper first radial bearing portion 10 in the second radial bearing portion 1.
1 and the upper first radial bearing portion 10
A configuration in which the lower second radial bearing portion 11 is filled with a lubricant having a higher viscosity, and a configuration in which the second radial bearing portion 1 below the bearing gap of the upper first radial bearing portion 10 is used.
1, a configuration in which the bearing gap is reduced, and the like are possible.

Furthermore, although the configuration in which the thrust bearing is a slide bearing is illustrated here, even if the thrust bearing is also a fluid bearing, a radial force is applied to the lower end of the rotary shaft due to machining accuracy and the like. Is assumed, the lower second radial bearing portion 1 as described above is used.
A configuration in which the bearing stiffness of the first radial bearing portion 10 is greater than the bearing stiffness of the upper first radial bearing portion 10 is effective.

[0027]

As described above, according to the spindle motor of the present invention, since the rigidity of the radial bearing closer to the thrust bearing is increased, even if the radial bearing span is short, the rotation of the rotary shaft can be sufficiently reduced. It can be kept small. Therefore, when the spindle motor of the present invention is used in a disk drive, it is possible to achieve high recording density, and when mounted in a laser beam printer, it is possible to achieve high printing accuracy. Become.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram of a shaft runout suppressing effect in the spindle motor shown in FIG. 1;

FIG. 3 is a sectional view showing a schematic configuration of a conventional spindle motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hub 2 Rotating shaft 2a Convex arc surface 4 Magnet 7 Stator coil 8 Stator core 9 Sleeve 10 First radial bearing portion 10a Dynamic pressure generating groove 11 Second radial bearing portion 11a Dynamic pressure generating groove 12 Thrust plate L Lubricant

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat 参考 (Reference) H02K 7/08 H02K 7/08 A (72) Inventor Kaoru Matsuoka 1006 Kazuma Kazuma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial In-house F term (reference) 3J011 AA07 AA11 BA04 BA10 CA03 JA02 KA02 KA03 MA07 5D109 BB05 BB12 BB18 BB21 BB23 BB27 5H605 AA04 AA05 BB05 BB15 CC04 CC05 DD09 EB06 5H607 AA04 BB01 BB07 BB14 CC01 DD03

Claims (3)

[Claims] A rotating shaft that is inserted through a sleeve member and rotates around an axis; a rotor that is fixed to one end of the rotating shaft and rotates integrally with the rotating shaft; and an inner cylindrical surface of the sleeve member. Radial bearing means provided in a plurality of stages along the longitudinal direction of the rotating shaft between the outer peripheral cylindrical surface of the rotating shaft and supporting the rotating shaft in the radial direction, and contacting the rotating shaft with the other end of the rotating shaft. A spindle motor having thrust bearing means for supporting in the thrust direction, wherein at a position closer to the other end of the rotating shaft supported by the thrust bearing means, the rotating shaft is radially directed toward the axis of the sleeve member. A spindle motor characterized by arranging radial bearing means having a higher bearing rigidity for urging in a direction. 2. The radial bearing means is a first and a second fluid bearing having a dynamic pressure generating groove, and the dynamic pressure generating groove of the second fluid bearing closer to the thrust bearing means in the rotation axis longitudinal direction. 2. The spindle motor according to claim 1, wherein a groove width of the dynamic pressure generating groove of the first fluid bearing is wider than a groove width in a longitudinal direction of the rotating shaft. 3. A method according to claim 1, wherein one of the other end of the rotating shaft and the thrust bearing means is formed with a convex arc surface which makes point contact with the opposing surface. A spindle motor according to any one of the above.