JPH0562335A - Spindle motor for magnetic disk device - Google Patents

Abstract

PURPOSE:To eliminate the amount of the inherent unbalance of the spindle motor and the amount of unbalance caused by a difference between the centroid of the magnetic disk medium and the rotary center of the spindle motor as finely as possible under a clean condition. CONSTITUTION:An annular void 6 is provided on the shoulder part 10 of a spindle hub 3 and a magnetic fluid 8 is enclosed in it. A balancing magnet is attached to a balancing magnet attaching yoke 7 in a unbalance direction concentrating the magnetic fluid 8 on the position of the unbalance and thus, a fine balancing is operated.

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 a magnetic disk device.

[0002]

2. Description of the Related Art Conventionally, a spindle motor used in a magnetic disk device has a shaft 1 and a shaft 1 as shown in FIG.
A stator 5 fixed to the shaft 1 and two sets of bearings 2, and a spindle hub 3 in which a magnetic disk medium is mounted, which is rotatably supported by the bearings 2, and a magnet yoke 4 is arranged at a position facing the stator 5. It consists of Of these, the spindle hub 3
The shoulder 9 is generally solid and made of a non-magnetic material.

[0003]

In the above-described conventional magnetic disk device equipped with a spindle motor, a magnetic disk medium and a spacer for positioning the magnetic disk medium are laminated, and a magnetic disk laminated structure in which a spacer is pressed by a clamper is formed. There is. In this magnetic disk laminated structure, an unbalance amount that the spindle motor has and an unbalance amount that is caused by a deviation between the rotation center of the spindle motor and the center of gravity of the magnetic disk medium when assembling the magnetic disk medium remain.

In general, the magnetic disk device is required to be under a clean condition, so that it is impossible to perform balancing adjustment which causes dust such as cutting, and the only method for balancing adjustment is to attach a weight. However, it is difficult to eliminate a minute amount of imbalance simply by attaching a weight.

An object of the present invention is to provide a spindle motor for a magnetic disk device, which can remove this fine unbalanced amount under cleaning.

[0006]

A spindle motor for a magnetic disk device according to the present invention comprises a spindle hub for rotating and holding a magnetic disk medium for storing information, and two sets of outer rings fixed above and below the spindle hub. And a spindle fixed to the bearing inner ring, the spindle motor for a magnetic disk device,
At least one of the shoulders of the spindle hub has an annular cavity, and a plurality of yokes for enclosing a magnetic fluid in the cavity and for attaching magnets to the bottom surface of the shoulder are provided at substantially equal intervals.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a drawing showing an embodiment of the present invention, where FIG. 1A is a sectional view and FIG. 1B is a bottom view.

The spindle motor for a magnetic disk device shown in FIG. 1 has a shaft 1, two sets of bearings 2 fixed to the upper and lower parts thereof, a spindle hub 3 rotatably supported by these bearings 2, and a shaft 1. And a magnet yoke 4 arranged at a position facing the stator 5 inside the spindle hub 3, and these configurations are similar to those in the conventional spindle motor for a magnetic disk device. ..

In the embodiment of FIG. 1, in addition to the above-mentioned structure, the shoulder portion 10 of the spindle hub 3 is provided with a cavity 6 which can be hermetically sealed. The magnetic fluid 8 is enclosed in the annular cavity 6. The magnetic fluid 8 is free of the annular cavity 6
You can move inside. On the bottom, as shown in FIG.
The yokes 7 facing the annular cavity 6 and to which the housing magnets can be attached are arranged in a uniform distribution.

In the spindle motor for a magnetic disk device having the above-described structure, the magnetic disk medium and the spacer for positioning the magnetic disk medium are laminated, and in the state of the magnetic disk laminated structure in which the spacer is fixed by the clamper, the spindle motor is formed. The vector sum of the unbalance amount of the motor and the unbalance amount due to the difference in position between the center of gravity of the medium and the rotation center of the spindle motor remains. This unbalance amount is
The fluctuation of the magnetic disk medium, that is, the fluctuation of the data waveform, causes off-track. Therefore, it is necessary to suppress this unbalance amount to a fine level.

Therefore, in the spindle motor for a magnetic disk device shown in FIG. 1, the magnetic fluid 8 is moved to an unbalanced position by appropriately attaching a magnet to the balancing magnet attaching yoke 7, and the magnetic fluid is placed in the annular cavity 6. By forming a distribution of the presence or absence of 8 and the self weight of the magnetic fluid 8, it becomes possible to make a finer balance than a weight. Further, for a large amount of unbalance, since the size of the magnet is changed and the magnet is attached to the balancing magnet mounting yoke 7, it does not come off when the motor is rotating, which is safe. By the way, in general, the balancing adjustment is performed by the two-sided correction. Therefore, in addition to the bottom surface described above, for example, it is desirable to provide the same balancing adjustment structure on a clamper that fixes the magnetic disk medium.

[0013]

As described above, according to the present invention, there is an effect that fine imbalance can be removed under a clean condition without generation of dust due to cutting and in a state where the disk media are stacked on the spindle motor.

[Brief description of drawings]

1A and 1B are drawings showing an embodiment of the present invention, where FIG. 1A is a sectional view and FIG. 1B is a bottom view.

FIG. 2 is a sectional view showing a conventional spindle motor for a magnetic disk device.

[Explanation of symbols]

 1 Shaft 2 Bearing 3 Spindle Hub 4 Magnet / Yoke 5 Stator 6 Annular Cavity 7 Magnet Mounting Yoke for Balancing 8 Magnetic Fluid

Claims (1)

[Claims] 1. A spindle hub for rotating and holding a magnetic disk medium for storing information, and an upper part of the spindle hub.
A spindle motor for a magnetic disk device, comprising a pair of bearings fixed to an outer ring at a lower portion and a shaft fixed to the bearing inner ring, and having an annular cavity in at least one shoulder portion of the spindle hub. Then
A spindle motor for a magnetic disk device, characterized in that a magnetic fluid is enclosed in the cavity, and a plurality of yokes for attaching magnets are attached to the bottom surface of the shoulder portion at substantially equal intervals.