JPH11262214A - Spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spindle motor which shows small fluctuations of an asynchronous rotary component, needs a small starting torque, can be used in an inverted state, and further, more has superior impact resistance. SOLUTION: The rotary unit of a spindle motor 1 is supported by a housing 3 via a radial dynamic pressure bearing and a thrust bearing and driven to rotate by a motor. A magnetic attraction force is generated between a the part of a motor magnet yoke 35 and a magnet 45 which is attached to the housing 3, so as to face the part of the motor magnet yoke 35 for applying an axial load larger than the self-weight of the rotary unit to the thrust bearing.

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 audio / 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 High recording densities have been developed in magnetic disk drives, and it is required that spindle motors used therein have small fluctuations in non-rotational synchronous components. FIG.
As shown in FIG. 1, in the conventional spindle motor 61, a ball bearing has been used to rotatably support the hub on a fixed shaft. That is, a fixed shaft 71 is provided upright on the housing 63, and a hub 69 for mounting a disk (not shown)
It is rotatably supported by a shaft 71 via two ball bearings 64 arranged in series. A stator 91 provided in the housing 63 and a hub 69 facing the stator 91
A motor is constituted by a magnet 97 provided on the inner diameter surface of the hub, and the hub 69 is driven to rotate by this motor.

As described above, a spindle motor is required to have a small non-rotational synchronous component swing. However, although the ball bearing 64 is excellent in preventing the hub 69 from dropping off the shaft 71, it has ball passing vibration and vibration caused by a shape error of a bearing component. It is difficult to reduce the swing of the rotation synchronization component to a value equal to or less than a predetermined value.

[0004]

For this purpose, instead of a ball bearing, a spindle motor 101 having a structure as shown in FIG. 4 in which a dynamic pressure bearing having small runout of a non-rotational synchronous component is used for both a radial bearing and a thrust bearing. It has been known.

In this example, a thrust plate 105 and a sleeve 107 are provided on a housing 103, and a lower end surface of a rotating shaft 111 fixed to a hub 109 and an upper surface of the thrust plate 105 constitute a thrust dynamic pressure bearing to form a thrust load. I support. Also, the thrust plate 10 of the housing 103
Above 5, a sleeve 107 having a groove 117 for generating dynamic pressure on the inner diameter surface is provided, and a radial dynamic pressure bearing is constituted by the outer peripheral surface of the rotating shaft 111 fixed to the hub 109. On the other hand, the stator 131 provided in the housing 103
And a magnet 137 provided on the inner diameter surface of the hub 109 so as to face the stator 131 so as to be substantially at the same position in the axial direction as the stator 131.
The hub 109 is driven to rotate by this motor.

[0006] However, when the radial and thrust bearings are dynamic pressure bearings as described above, the run-out of the non-rotational synchronous component of the spindle is reduced, but there is a disadvantage that the shaft comes off when it is in an inverted state or when an external impact acts. In order to solve this drawback, a stopper 121 (a stopper attached to the flange at the upper end of the rotating shaft and the hub) is provided as shown in FIG. However, with such a structure, it is difficult to attach the stopper 121, and there is a problem that abrasion powder is likely to be generated due to repeated contact between the stopper 121 and the sleeve 107 due to an impact applied during transportation or the like. Was.

Therefore, the present invention focuses on the above problems, and provides a spindle motor which has a small non-rotational synchronous component swing, a small starting torque, can be used even in an inverted state, and has excellent impact resistance. It is intended to be.

[0008]

In order to solve the above problems, a disk spindle motor according to the present invention comprises:
The rotating body is supported by a radial dynamic pressure bearing and a thrust bearing provided at the shaft end of the rotating shaft, and a part of a yoke for a motor magnet of a spindle motor and a magnet attached to a stationary member opposed to this part are supported. A thrust bearing is applied with an axial load of a predetermined value or more.

[0009]

According to the present invention, since the rotating body is supported by the radial dynamic pressure bearing and the thrust bearing provided at the shaft end of the rotating shaft, the non-rotational synchronous component has a small swing and the starting torque is small. Further, since a predetermined suction force is applied in the axial direction, there is no restriction on the use posture. Further, since the stopper is provided between the rotating body and the housing, the rotating shaft and the hub do not come off even if a large force greater than the suction force acts. In addition, since the attraction member for generating the magnetic attraction uses a part of the yoke for the motor magnet, it is not necessary to separately provide a magnetic material for attraction, so that the number of parts can be reduced and the number of assembling steps can be reduced. The cost can be reduced and the cost can be reduced.

[0010]

FIG. 1 shows a first embodiment. The spindle motor 1 includes a housing 3, a thrust plate 5, a sleeve 7,
The hub 9 and the shaft 11 are included.

At the center of the housing 3, a circular thrust plate 5 is provided. The thrust plate 5 has a groove 13 for generating dynamic pressure on its upper surface, and forms a thrust dynamic pressure bearing together with the lower end surface 15 of the rotating shaft 11 (shaft diameter is φ1 to φ6) whose upper end is fixed to the hub 9. , Support thrust load. The thrust plate 5 is made by injection molding of plastic, and the groove 13 for generating dynamic pressure can be processed by molding, so that the cost is low.

Further, above the thrust plate 5, a cylindrical sleeve 7 having a groove 17 for generating dynamic pressure on the inner diameter surface is provided with its outer peripheral surface held by a holding portion 19, and is fixed to the hub 9. The outer peripheral surface of the rotating shaft 11 constitutes a radial dynamic pressure bearing. Since the shaft 11 is made of stainless steel and the sleeve 7 is made of a copper-based material, the slidability between the shaft 11 and the sleeve 7 is good, and the starting and stopping durability is excellent.
As the lubricant to be supplied to the radial dynamic pressure bearing and the thrust dynamic pressure bearing, fluorine oil (fluorine oil having a high viscosity index) having excellent temperature-viscosity characteristics, that is, having a small change in viscosity with respect to a temperature change is used. In addition, since there is no air vent hole between the thrust bearing and the radial bearing, the shaft end is in a sealed state and the lubricant retention is excellent, so reliability is improved even for long-term use. . With the above-described configuration, it is possible to provide a spindle motor in which the swing of the non-rotational synchronous component is small and the starting torque is small.

An annular stopper 21 is fixed to the outer peripheral surface of the lower end of the rotating shaft 11 integrally with the rotating shaft 11 by press-fitting or bonding so as to be located between the thrust plate 5 and the sleeve 7. It is. As a result, even if a large force acts on the hub 9, the housing 3, etc., the shaft 11 and the hub 9 do not come off because the stopper 21 contacts the sleeve 7. Further, since the sleeve 7 and the thrust plate 5 are directly fixed to the housing 3, the hub 9, the rotating shaft 11 and the stopper 21 can be easily assembled with the sleeve 7 and the housing 3 to which the thrust plate 5 is fixed. Moreover, it has excellent reliability. Since the stopper 21 is made of the same stainless steel as the shaft 11, it has good slidability with the copper sleeve 7.

Here, the gap 23 between the outer diameter surface of the retaining member 21 provided on the shaft 11 and the inner diameter surface of the holding portion 19 facing the radial direction is defined as the bearing radial clearance (the distance between the shaft 11 and the sleeve 7). ) And 0.5 mm or less. Therefore, even if an external impact acts in the direction in which the rotating shaft 11 comes off, the clearance acts as an oil restrictor, and the oil above the retaining 21 becomes a resistance to flow out, so that the shaft 11 moves in the direction in which the shaft 11 comes out. Hinder As a result, the shaft 11 hardly moves if the impact is for a short time of about several tens of milliseconds or less. The gap 25 between the upper surface of the retaining member 21 and the lower surface of the sleeve 7 is set to 0.01 mm or more and 0.5 mm or less. Therefore, even if the shaft 11 moves in a direction in which the shaft 11 comes off due to an external impact, it does not move more than 0.5 mm.

A peripheral groove 27 for oil supplement is provided on the inner peripheral surface of the hub 9 corresponding to the upper end surface in the axial direction of the sleeve 7. Even if the lubricant is scattered from the outer periphery of the shaft 11 by rotation due to the circumferential groove 27, the lubricant is captured by the circumferential groove due to its surface tension, so that the lubricant scatters to the disk surface (not shown). Can be prevented. A circumferential groove 29 for correcting imbalance is provided on the upper surface in the axial direction of the hub 9.
With this circumferential groove, the imbalance of the upper part of the spindle motor can be corrected.

The holding portion 19 of the housing 3 is provided with a stator 31 on a radially outer side. The inner diameter surface of the cylindrical portion 33 of the hub 9 is axially opposed to the stator 31 so as to face the stator 31 in the radial direction. A magnet 37 is provided at substantially the same position via a yoke 35. A motor is constituted by the stator 31 and the magnet 37, and the hub 9 is driven to rotate by the motor.

The yoke 35 is made of a magnetic material,
The magnet 37 is attached to the main body 39 and extends radially outward of the shaft 11 along the lower surface of the cylindrical portion 33 of the hub 9. The housing 3 is provided with an attraction magnet 45 in an annular recess 43 formed in a portion of the yoke 35 facing the overhanging portion 41. With this configuration, the magnetic attraction between the overhanging portion 41 of the yoke and the attraction magnet 45 on the housing 3 causes the hub 9 and the housing 3 to move in the axial direction.
A suction force acts on the thrust plate 5 from the rotating shaft 11. In the present embodiment, the suction force is set to be equal to or more than the own weight of the rotating portion (the rotating shaft 11 and the hub 9) and equal to or less than 30N. The magnitude of the suction force is more than twice the own weight of the rotating part and 10N.
The following are more preferred.

The attraction magnet 45 is magnetized so that one surface (upper surface) is N-pole and the other surface (lower surface) is S-pole, so that the attraction force is increased and the attraction magnetic body 41 is formed. The generated eddy current can be reduced, and the loss of the entire motor can be reduced. With the above configuration, a predetermined suction force can be applied in the axial direction of the rotating shaft 11, so that a spindle motor that can be used even in an inverted state and has excellent impact resistance can be provided. .

Further, since the back yoke 47 is attached to the outside of the attraction magnet 45 in the axial direction, compared with the case where it is not attached, there is no leakage magnetic flux, so that the attraction force is increased.

The suction force is selected as described above for the following reason. (1) When the suction force is equal to or less than the own weight of the rotating part, when the spindle motor 1 is used in the inverted position, the suction force is smaller than the own weight of the rotating body, so that the shaft 11 does not come into contact with the thrust bearing. Since the sleeve 7 comes into contact with the sleeve 7, the weight is set to be equal to or more than its own weight. (2) When the suction force is 30 N or more, the axial load applied to the thrust bearing increases, the starting torque increases, and the abrasion of the thrust bearing when starting and stopping increases. (3) When the suction force is more than twice the own weight of the rotating part, the contact between the rotating shaft 11 and the thrust bearing is maintained even if some external impact is applied. I have. (4) When the suction force is 10 N or less, the axial load applied to the thrust plate 5 is reduced, and wear of the thrust plate 5 is reduced. Therefore, it is not necessary to use an expensive material such as ceramic for the thrust plate 5. Since the cost can be reduced, it is set to 10N or less.

With the above configuration, it is possible to provide a spindle motor which has a small non-rotational synchronous component swing, a small starting torque, can be used even in an inverted state, and has excellent shock resistance.

Further, since a part of the yoke 35 for the motor magnet is used as an attraction member for generating a magnetic attraction force, it is not necessary to separately provide a magnetic material for attraction, and the number of parts can be reduced. At the same time, the number of assembling steps is reduced, so that the cost can be reduced.

In the above embodiment, the following modifications are possible. In the above embodiment, the back yoke 47 is attached to the outside of the attraction magnet 45. If a large attraction force is not required, the attraction force is weakened by eliminating the back yoke 47 and using only the magnet 45. Is reduced by one, so that the cost can be reduced.

The thrust plate 5 is made by injection molding of plastic. In particular, when the thrust plate 5 is made of PPS (polyphenylene sulfide resin) as a base and is made of plastic to which carbon fiber and Teflon are added, slidability and strength are obtained. Excellent in moldability and preferable. When the axial load is large, a steel plate may be added to reinforce the plastic thrust plate 5. Further, a so-called pivot support bearing in which at least one of the thrust plate 5 and the shaft end 15 is supported as a convex spherical surface in point contact by omitting the groove 17 for generating dynamic pressure may be used. At this time,
When a conductive plastic such as a plastic containing carbon fiber is used, static electricity accumulated in the rotating body can be supplied to the housing, so that the GMR head and the like are not broken. In addition, it is not necessary to provide a separate ground, and the cost can be reduced.

The retainer 21 is integrated with the stainless steel rotary shaft 11.
In the case where the shaft and the shaft are separated from each other, a material such as an aluminum alloy, stainless steel, or plastic having the same linear expansion coefficient as that of the shaft is preferable because the material does not become loose when the temperature changes. Further, a disk-shaped stopper may be attached to the shaft end face by screwing or the like. In this case, the lower end surface of the disc-shaped retainer serves as a thrust bearing. Also, the stopper and the shaft may be integrated.

In the above-described embodiment, the clearance between the outer diameter surface of the stopper provided on the shaft 11 and the inner diameter surface of the holding portion facing the same is larger than the bearing radial clearance (the distance between the shaft 11 and the sleeve 7). Although it is set to 0.5 mm or less, when the viscosity of the oil is low, it is preferable to set the gap R to 0.2 mm or less since the oil squeezing effect becomes large.

Although the gap between the upper surface of the stopper 21 and the lower surface of the sleeve 7 is set to be 0.01 mm or more and 0.5 mm or less, in order to prevent damage to the head of the magnetic disk, the gap in the axial direction is required. h is preferably 0.1 mm or less. Further, a thrust bearing can be formed between the sleeve 7 and the sleeve 7 by forming a groove for generating dynamic pressure on the axially upper surface of the retaining 21. In this case, even if the shaft 11 is moved by an extremely large impact, the retaining force can be supported by the dynamic pressure generating groove above the retaining 21, so that the retaining 21 does not contact the sleeve 7. .

In the above embodiment, no air vent hole is provided between the thrust bearing and the radial bearing, but an air hole may be provided if necessary. The shaft 11 is fixed,
A structure in which the sleeve 7 rotates may be used. The motor is not limited to the circumferentially opposed motor in which the stator 31 and the magnet 37 are opposed in the radial direction, but may be a planar opposed motor in which the stator 31 and the magnet 37 are opposed in the axial direction.

In the above embodiment, the thrust bearing is formed by providing grooves for generating dynamic pressure on the thrust plate, but grooves for generating dynamic pressure may be provided at the shaft end. Instead of screwing, the thrust plate 5 may be glued to the sleeve 7 after being caulked to the sleeve 7 to prevent leakage of the lubricant.

In the above embodiment, fluorine oil (fluorine oil having a high viscosity index) is used as the lubricant. However, in order to improve the sliding property and the holding property of the lubricant, the lubricant having a carboxylic acid at the terminal is used. Fluorinated oils to which fluoroalkyl porethers have been added are preferred. Note that, depending on the use conditions, the lubricant need not be a fluoro oil having excellent temperature viscosity characteristics, but may be a synthetic oil such as a hydrocarbon oil or a mineral oil. Alternatively, a conductive lubricant may be used if necessary. In the above embodiment, the circumferential groove 29 for correcting imbalance is provided on the upper surface in the axial direction of the hub 9, but the imbalance of the spindle can be corrected in the space below the motor magnet.
In addition to the circumferential groove for correcting imbalance on the upper surface, two-surface correction can be performed.

Further, the magnetic attraction between the projecting portion 41 of the yoke and the attraction magnet 45 exerts an attraction between the hub 9 and the housing 3 in the axial direction. It is also possible.

FIG. 2 shows a second embodiment. In this example,
The yoke 35 of the motor magnet has an annular L-shaped cross section, and is bent radially inward along the lower surface of the main body 49 of the hub 9. The holding portion 19 of the housing 3 includes
An attraction magnet 53 is provided so as to face the bent portion 51 of the yoke 35 in the axial direction, and gives an axial attraction force to the thrust bearing by magnetic attraction between the yoke 35 and the attraction magnet 53. ing. Other configurations and effects are the same as those of the first embodiment.

[0033]

According to the present invention, the swing of the non-rotational synchronous component is small, and the starting torque is small. Further, it is possible to provide a spindle motor which is not restricted in use posture, has excellent impact resistance, and has a small number of parts and a small number of assembly steps.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a conventional example.

FIG. 4 is a diagram showing a configuration of a conventional example.

[Explanation of symbols]

 Reference Signs List 1 spindle motor 3 housing 5 thrust plate 7 sleeve 9 hub 11 shaft 13 groove 17 groove 21 retainer 31 stator 35 yoke 37 magnet 45 magnet

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Katsuumi Nakamura, Inventor 13-20, Kamihosakaemachi, Komagane-shi, Nagano (72) Inventor Mutsumiaki Seki, 13-20 Kamihosakae-cho, Komagane-shi, Nagano

Claims (1)

[Claims] 1. A yoke for a motor magnet provided on a rotary body of a spindle motor which is driven by a motor to rotate a rotary body supported by a housing via a radial dynamic pressure bearing and a thrust bearing. A magnetic attractive force is generated between a part of the rotor and a magnet attached to the housing so as to face the part, and an axial load equal to or more than the own weight of the rotating body is applied to the thrust bearing. Spindle motor.