JPH04103076A - Spindle motor - Google Patents

Abstract

PURPOSE:To enable to obtain a bearing rigidity equivalent to that of a ball bearing while keeping a high rotation accuracy by forming a slip surface for noncontact bearing between a coil and a magnet. CONSTITUTION:A stator 2 wound with the coil is mounted in the central part of a housing 1 and the outside is covered with a sleeve 4. The magnet 6 is mounted inside of a spindle hub 5 and the inner face is covered with a sleeve 7. The outside of sleeve 4 and the inner face of sleeve 7 are machined respectively so that the gap in the radial direction is made to several microns. Consequently, the magnet 6 and spindle hub 5 are rotated in one body by supplying power to the coil of stator 2, then an air film is formed in the gap between the sleeve 4 and sleeve 7 by this rotation to get a function as the noncontact bearing. The rotation accuracy is thereby made higher than that in the case the ball bearing is used, and also the bearing rigidity can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a spindle motor, and particularly to a spindle motor used in a magnetic disk drive.

BACKGROUND OF THE INVENTION Generally, in a magnetic disk drive, a magnetic head flies at a height of submicrons over a magnetic disk medium rotating at high speed, and this magnetic head is positioned with an accuracy of several microns. For this reason, a spindle motor that rotates a magnetic disk medium is required to have high precision.

A conventional spindle motor used in a magnetic disk drive uses a high-precision ball bearing to hold a rotating spindle hub, as shown in FIG. 2(a). That is, the ball ring 8
As a result, a bearing is formed between the rotating shaft 3 that rotates integrally with the spindle hub 5 and the housing 1, and a coil (not shown) wound around the stator 2 and a magnet 6 provided opposite thereto are formed. Rotational motion was caused by magnetic repulsion.

However, with the recent increase in the capacity and recording density of magnetic disk drives, the demand for rotational accuracy of spindle motors has been increasing year by year. For this reason, the rolling bearing using the ball hair ring shown in FIG. 2(a) has a limit in achieving high rotation accuracy. Therefore, instead of rolling ball bearings, non-contact bearings that do not use ball hair rings have come to be used, as shown in FIG. 2(b).

That is, the rotating shaft 3 and the housing 1 form a non-contact bearing that uses air as a fluid film.

Therefore, in recent spindle motors for magnetic disk drives, the hydrodynamic bearing shown in FIG. 2(b), which has a simple structure and uses air as a fluid film, has been most commonly used.

However, as shown in Figure 2 (b), high rotational precision is possible with hydrodynamic bearings that utilize the space of ball bearings as they are, but because they use air as a fluid film, the ball The drawback was that it was not possible to obtain the same bearing rigidity as a hair ring.

OBJECTS OF THE INVENTION The present invention has been made to solve the above-mentioned conventional drawbacks, and its purpose is to provide a spindle motor that can obtain bearing rigidity equivalent to that of a ball hair ring while maintaining high rotational accuracy. That's true.

Structure of the Invention A spindle motor according to the present invention includes a rotational drive coil and a magnet provided opposite to the coil, and has a non-contact bearing between the coil and the magnet. It is characterized by forming a surface.

Example Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view of an embodiment of a spindle motor according to the present invention, and parts equivalent to those in FIG. 2 are designated by the same reference numerals. The figure shows a spindle motor using a dynamic pressure group bearing for a magnetic disk drive.

In the figure, a stator 2, which is wound with a coil (not shown), is attached to the central part of the hounging motor. The outside of the stator 2 is covered with a sleeve 4. A magnet 6 is attached to the inside of the spindle hub 5. The inner surface of the magnet 6 is covered with a sleeve 7.

The outside of the sleeve 4 and the inside of the sleeve 7 are machined so that there is a gap of several microns in the radial direction.

Furthermore, the sleeves 4 and 7 are made of a material that does not block the magnetic field generated by the coil and magnet. Further, the outer surface of the sleeve 4 is carved with spiral or stepped grooves (groups) for generating pressure.

In such a configuration, by energizing the fill (not shown) of the stator 2, the magnet 6 and the spindle hub 5
rotate together, and this rotation forms an air film in the gap between the sleeves 4 and 7, functioning as a non-contact bearing. This allows for higher rotation accuracy and higher bearing rigidity than when using a ball hair ring.

Note that the sleeves 4 and 7 are installed to form sliding surfaces of the non-contact bearing, and if the surfaces of the magnet and stator are processed in the same way, the sleeves 4 and 7
can be deleted. Further, the positions of the magnet and the stator may be exchanged.

As described above, the gap between the sleeve 4 and the sleeve 7 functions as an air gap between the stator and the magnet and as a sliding surface for the non-contact bearing.

DETAILED DESCRIPTION OF THE INVENTION As described in detail, the present invention forms a non-contact bearing in the air gap between the stator and magnet of a spindle motor, thereby making it possible to increase the diameter of the bearing. This increases the pressure exerted by the bearing, which has the effect of increasing the shaft rigidity and load capacity, which were problems with conventional air dynamic pressure bearings. Additionally, the bearing portion, which occupies a large space inside the motor, can be made smaller, and by enlarging the drive portion, the torque generated by the motor can be increased.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a spindle motor according to an embodiment of the present invention, Fig. 2(a) is a sectional view of a conventional speartle motor using a ball l-bearing, and Fig. 2(b) is a sectional view of a conventional speartle motor using a non-contact bearing. It is a sectional view of the conventional spindle motor used. Explanation of symbols of main parts 1... Housing 2... Stator 7... Sleeve 5... Spindle hub 6... Magnet

Claims (1)

[Claims] (1) A spindle motor including a rotational drive coil and a magnet provided opposite to this coil, characterized in that a sliding surface of a non-contact bearing is formed between these coils and the magnet. spindle motor.