Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-10-01
2001-06-26
Mullins, Burton (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S049540, C310S089000, C310S06700R, C310S091000, C384S107000, C384S100000, C360S099080
Reexamination Certificate
active
06252322
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to spindle motors and, more particularly, to a spindle motor having unitized components so that faulty components can be replaced and modification can be made without replacing the entire spindle motor or discarding useable components.
2. Background Information
In the related-art spindle motors to be built into various apparatuses including hard disc drive apparatuses, there is known a structure having a rotor hub and sleeve that are combined by arranging a shaft on a motor frame or a structure having a rotor hub and shaft that are combined by attaching a sleeve onto a motor frame (e.g. Japanese Patent Laid-Open No. 245427/1994).
Also, there is adopted a structure for a spindle motor by directly assembling on an apparatus a ball bearing or bearing as a part of the motor.
In the former structure, however, there has been a problem that if the motor assembled upon manufacture becomes faulty, it must be scrapped entirely. There has arisen another problem that, where there are diversified specifications, the number of parts has to be increased on a model-by-model basis.
In the latter structure, on the other hand, the parts are directly assembled into the apparatus and hence some motor parts are integrated with the mating apparatus structure in order to reduce the apparatus size. However, when there occurs faulty in the apparatus, the apparatus as a whole has to be scrapped causing an increase in cost.
It is therefore an object of the present invention to provide a spindle motor which is capable of solving the problems as encountered in the related art.
SUMMARY OF THE INVENTION
In order to solve the foregoing problems in the conventional art, the present invention provides a spindle motor comprising a sleeve fixed in a base; a bearing section rotatably accommodated and held in the sleeve; a shaft section attached to the bearing section; a hub attached co the shaft; a rotor magnet mounted on the hub; a stator coil arranged close to the rotor magnet; and wherein at least one portion is included which is made as a unit formed by two and more of the constituent elements. This enables checking on a unit-by-unit basis during manufacture. It there is an unacceptable unit, it is satisfactory to merely scrap the sane unit. In a case that some parts require modification due to diversification of specifications, the unitized common parts can be still used without change, making it unnecessary to increase parts for each model.
Also, such unitization makes it possible to cope with an unacceptable unit by merely removing it. Thus, cost reduction is to be expected.
In this manner, parts can be made common for all the models, resulting in cost reduction. Furthermore, even where it is built in an apparatus and thereafter becomes poor, the apparatus and its parts can be reusable.
According to the invention, there is provided a spindle motor, further comprising: the base; a stator coil arranged in the base; a sleeve-and-bearing unit formed by attaching the bearing in the sleeve arranged in a center position of the base; and a rotor unit having a shaft section arranged in the bearing section and an inner peripheral surface mounted with the rotor magnet opposed to the stator coil.
The base may be exclusive one prepared for the spindle motor. Alternatively, it is possible to utilize as the base one part of a frame of an apparatus on which the spindle motor is to be mounted.
In the invention, an adhesive groove can be provided in an outer peripheral surface of the sleeve to hold an adhesive for fixing the sleeve to the base, and the sleeve at the outer peripheral surface being fixed to the base through the adhesive.
The shaft section may have a tip formed with a convex spherical surface, thereby reducing a frictional force to be applied to the shaft section at a start and stop of the motor.
The bearing section may have a linear expansion coefficient greater than that of the sleeve, thereby having less effects upon the shaft rigidity due to temperature change.
Due to this, the bearing section may be formed of a copper based metal material, and the sleeve being formed of a stainless based metal material.
The bearing section is formed by a fluid dynamic pressure bearing.
Also in this case, the shaft section has a tip formed by a convex spherical surface to thereby reduce a frictional force to be applied to the shaft section at a start and stop of the motor.
Furthermore, the bearing section may have a linear expansion coefficient greater than that of the sleeve, thereby having less effects upon the shaft rigidity due to temperature change.
Due to this, the bearing section may be formed of a copper based metal material, and the sleeve being formed of a stainless based metal material.
The bearing section may have a vertical circulatory groove provided in an inner peripheral surface thereof to enable a dynamic pressure producing liquid to be circulated around the bearing section.
A space may be formed by the shaft section, the bearing section and the sleeve to collect a dynamic pressure fluid, thereby smoothing the supply of a dynamic pressure fluid.
A radial dynamic pressure producing groove may be formed in an outer peripheral surface of the bearing section and a thrust dynamic pressure producing groove be formed in at least one side surface of the bearing section. With this structure, the dynamic pressure producing grooves may be satisfactorily formed only in the surface of the bearing section, thus facilitating forming and hence improving forming efficiency.
Also, a radial dynamic pressure groove may be formed in an outer peripheral surface of the bearing section and thrust dynamic pressure producing grooves may be formed in respective side surfaces.
The sleeve may be in a cap form, and the bearing section in the sleeve being rotatably held in the sleeve by an annular pressing member press-fitted in the sleeve.
In this case, the sleeve has an inner peripheral surface end edge projecting greater than the pressing member to thereby form an adhesive reservoir close to the inner peripheral surface end edge of the sleeve, preventing the adhesive from flowing to an outside.
The base and the rotor unit at an outer peripheral edge may form an opposed portion, and a labyrinth is formed in the opposed portion. In the event that dusts, such as magnetic particles or oil mist, accumulate at an inside portion, the above structure can prevent the magnetic particles and dusts from being discharged to an outside. This is very effective if applied for a hard disc drive apparatus.
A wide annular groove may be circumferentially formed in an outer peripheral surface of the sleeve, and the sleeve being press-fitted in a fitting hole opened correspondingly in the base to the sleeve thereby fixing the sleeve to the base. Fixing is possible without using an adhesive, improving operationality.
The annular groove may be also utilized as an adhesive groove, and the sleeve being fixed to the base using both press-fit and adhesion, thereby providing further firm fixing.
The annular groove may be formed in a corresponding position to the bearing section, thereby preventing a deforming stress to be applied to the bearing section upon press-fitting.
The shaft section may have a tip formed with a convex spherical surface, thereby reducing a frictional force to be applied to the shaft section at a start and stop of the motor.
The bearing section may have a linear expansion coefficient greater than that of the sleeve, thereby having less effects upon the shaft rigidity due to temperature change.
Due to this, the bearing section may be formed of a copper based metal material, and the sleeve may be formed of a stainless based metal material.
The bearing section may be formed by a fluid dynamic pressure bearing.
The shaft section may have a tip formed with a convex spherical surface, thereby reducing a friction force to be applied to the shaft section at a start or stop of the motor.
The bearing section may have a linear expansion coefficient greater than that of
Goto Hiromitsu
Iwaki Tadao
Kawawada Naoki
Suzuki Takahumi
Adams & Wilks
Mullins Burton
Seiko Instruments Inc.
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