JPH10143990A - Magnetic disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure high rotary accuracy of a spindle motor and to enhance reliability in high recording densification by preventing a bearing set in the spindle motor from resonating which is apt to cause an off-track. SOLUTION: This magnetic disk device is set for revolving speed used for magnetic disks 20 and 21 to a range of 5200 to 5400 r.p.m., and is set for a 1st-order resonance point at the time of rotating the spindle motor under the actual load mounting state to become 460 to 500Hz, and then a ball bearing 8 used for this spindle motor 3 is specified as a ball diameter of 1.588mm, a revolution diameter of 8.9mm and 10 balls in number. By this method, the ball bearing is prevented from resonating with the spindle motor, and an off- track error caused by increasing runout is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a magnetic disk drive.

[0002]

2. Description of the Related Art Generally, a magnetic disk drive has a structure in which a magnetic disk is rotated by driving a spindle motor.
A magnetic head arranged opposite to the magnetic disk reads and writes data on the disk. The magnetic head is carried on a carriage and is movable in the radial direction of the magnetic disk. In a spindle motor, a hub rotates around bearings around bearings through bearings, and includes a stator, magnets, and the like formed by copper windings. Therefore, when a current is applied to the stator, a magnetic field is generated, and the hub is attracted to and repelled by the magnet and rotates, so that the magnetic disk rotates integrally with the hub.

[0003]

By the way, in a magnetic disk drive having such a structure, a so-called off-track error that causes a displacement between recorded data on a magnetic disk and a magnetic head is likely to be induced. One of the causes is that the spindle motor is in a run-out state, which causes an increase in vibration and generation of a beat. The runout is caused by the vibration generated by the rotation of the steel ball loaded in the bearing,
It is caused by vibrations generated by rebound. Above all, when the vibration component in the bearing resonates with the vibration of the spindle motor, the runout increases and off-track is easily induced.

Accordingly, an object of the present invention is to prevent the resonance of a bearing incorporated in a spindle motor, which is likely to cause off-track, to secure high rotational accuracy of the spindle motor and to improve reliability by increasing the recording density. To provide a magnetic disk device that achieves the above.

[0005]

According to the magnetic disk drive of the present invention, the number of rotations of the magnetic disk is set to 5200 to 5400.
rpm, and the primary resonance point when the spindle motor rotates in the actual load mounting state is 460-460.
Set to 500 Hz, and set the ball diameter of the ball bearing used for the spindle motor to 1.588 m.
m, the revolving diameter is 8.9 mm, and the number of balls is 10.

Thus, it is possible to prevent the vibration component of the ball bearing from resonating with the spindle motor.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a magnetic disk drive according to an embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, the magnetic disk drive of the present embodiment has a main body case formed in a housing shape by a base plate 1 and a cover 2, and the inside of the main body case is hermetically sealed to provide a high clean space. Are formed.

A spindle motor 3 is supported on the base plate 1 via a bracket 4 inside the main body case. The configuration of each part of the motor is such that a fixed shaft 5 is supported at its lower part by the bracket 4 and its upper end is locked by a fixing pin 6, and extends in the vertical and vertical directions in the figure. A cylindrical hub 7 is rotatably supported around the axis of the fixed shaft 5 via two radial bearings or the like ball bearings 8. A magnet 9 is attached along the inner peripheral surface of the hub 7, and a stator 10 made of copper winding is provided on a concentric axis inside the magnet 9 using a bracket 4. That is, the electric circuit 16 energizes the stator 10 to generate a magnetic field, and the magnet 9
Then, the hub 7 is rotated around the axis of the fixed shaft 4, and the magnetic disks 20 and 21 are driven to rotate integrally with the hub 7.

The disk-shaped magnetic disks 20 and 21 are connected to the motor-side hub 7 via a cylindrical boss 17 at the inner peripheral portion thereof by fitting or the like, and are rotated integrally with the hub 7.

A magnetic head 11 for writing and reading information is disposed in close proximity to the upper surfaces of the magnetic disks 20 and 21. The magnetic head 11 is the carriage 1
2 and is movable in the radial direction of the magnetic disks 20 and 21. The carriage 12 is mounted on the fixed shaft 1 via a ball bearing 13 such as a radial bearing.
4 rotatably supports a required angle range. The fixed shaft 14 has a lower end fixed to the base plate 1 and an upper end fixed vertically by a fixing pin 15 in the vertical direction in the figure.

FIG. 2 shows a ball bearing 8 of the spindle motor 3. The ball bearing 8 has an inner ring 8a and an outer ring 8b, and balls 8c made of steel balls or the like are arranged at equal intervals in an annular gap between the inner and outer rings. The frequency of such rotational vibration of the ball bearing 8 can be geometrically determined based on the number of balls 8c, the diameter of the balls, the orbital diameter indicated by the symbol D, the contact angle, and the rotational speed.

In a rotating body such as a combination of a disk such as the magnetic disks 20 and 21 and the spindle motor 3, the resonance point at rest and the rotation frequency are ω ₀ (Hz) and ω, respectively.
(Hz), the resonance point during rotation is approximately ω ₀ ± ω (H
z).

When ω ₀ −ω is a primary resonance point and ω ₀ + ω is a secondary resonance point, the resonance points of the spindle motor 3 according to the present embodiment when the magnetic disk or the like is mounted on an actual load are as follows. It is adjusted to. That is, the number of rotations used is 520
In the range of 0 rpm to 5400 rpm, the primary resonance point is adjusted to be in the range of 460 Hz to 500 Hz by the interval between the two ball bearings 8 and the amount of preload.

Therefore, 5200 rpm to 5400 r
The primary resonance point is 460 Hz for the rotational speed in the range of pm.
In the spindle motor 3 existing in the range of 500 Hz to 500 Hz, the ball diameter of the ball bearing 8 to be used is set to 1.5
88 mm, orbit diameter D is 8.9 mm, and the number of balls is 10. Thus, even if the variation in the resonance point due to manufacturing variations or temperature is taken into account, resonance of the ball bearing 8 with the spindle motor 3 can be prevented.

[0016]

As described above, in the magnetic disk drive according to the present invention, the number of rotations used is from 5200 rpm to 540 rpm.
Assuming that the rotation speed is 0 rpm, the primary resonance point when the spindle motor rotates in the actual load state of the magnetic disk or the like is 460 Hz to
500 Hz, the ball diameter of the ball bearing used for the spindle motor is 1.588 mm, and the revolution diameter is 8.9.
By setting the number of balls to 10 mm, it is possible to prevent ball bearings from resonating with the spindle motor, and to suppress the occurrence of off-track errors due to an increase in runout. Thereby, high rotation accuracy of the spindle motor can be secured, high recording density can be realized, and reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a magnetic disk drive according to an embodiment of the present invention.

FIG. 2 is a front view of a ball bearing used in the spindle motor of the embodiment.

[Explanation of symbols]

 1 Base Plate 2 Cover 3 Spindle Motor 4 Bracket 5 Fixed Shaft 7 Hub 8 Ball Bearing 8a Inner Ring 8b Outer Ring 8c Ball 9 Magnet 10 Stator 11 Magnetic Head 12 Carriage 20, 21 Magnetic Disk

Claims (1)

[Claims] 1. The method according to claim 1, wherein the number of rotations of the magnetic disk is from 5200 to 5
In the magnetic disk drive set in the range of 400 rpm, the primary resonance point when the spindle motor rotates in the actual load mounting state is set to 460 to 500 Hz, and the diameter of the ball of the ball bearing used for the spindle motor is set to 1. 588mm, orbit diameter 8.9mm, number of balls 10
A magnetic disk drive comprising: a plurality of ball bearings configured to prevent a vibration component of a ball bearing from resonating with a spindle motor.