JPH05347066A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To prevent data on a magnetic head from being destroyed, which are caused by that a static electricity generated due to friction with an air during the rotation of a magnetic disk is charged on the magnetic disk and discharged the potential difference with the magnetic head. CONSTITUTION:A conductive magnetic fluid 15 is used as an operating fluid for the bearing of a spindle motor using a dynamic pressure bearing to facilitate the conduction between a shaft 13 and a housing 11. Thus, the magnetic disk 2 is prevented from being charged by the static electricity, and the data are prevented from being destroyed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device, and more particularly to a magnetic disk device using a dynamic pressure bearing as a bearing of a spindle motor.

[0002]

2. Description of the Related Art As shown in FIG. 2, a conventional magnetic disk apparatus is provided with a magnetic disk 2 which is rotated by driving a spindle motor 1 and a magnetic disk 2 which is opposed to the magnetic disk 2. A magnetic head 3 for writing / reading information to / from a magnetic disk with a flying height of submicron, a carriage 4 for moving the magnetic head 3 in the radial direction of the magnetic disk 2, a base plate 6 for mounting the carriage 4, and a cover. And a bed disk assembly constituted by

A head disk assembly using a dynamic pressure bearing for the shaft 13 of the spindle motor 1 has a cylindrical projecting portion at the center of the housing 11 of the spindle motor 1, and the inner surface of this cylindrical portion is Shaft 1
Holds 3. Further, a stator 14 in which a coil is wound around a laminated iron core is concentrically attached to the outer surface of the cylindrical portion, and a cylindrical hub 12 having a hollow portion in the lower inside is attached to the upper end of the shaft 13. Is fixed at the center of its upper plate so as to cover the stator 14.

On the inner peripheral surface of the cylindrical portion of the hub 12, a cylindrical driving permanent magnet 17 is fixed at a position facing the stator 14 with a slight gap. Grooves are provided so that pressure is generated when the shaft 13 rotates. Then, the shaft 13 passes through the oil 16 filled in the gap between the shaft 13 and the inner peripheral surface of the cylindrical portion of the housing 11,
It rotates without contacting the inner surface of the cylindrical portion of the housing 11.

Further, a conductive metal (for example, aluminum alloy, iron, etc.) is used as a material for each structural body, and a method such as fastening, pressure welding or fitting is used for joining each structural body.

[0006]

In the conventional magnetic disk drive as described above, the shaft of the spindle motor and the housing are insulated from each other by oil, and the magnetic disk is insulated from the magnetic head. Due to the friction between the magnetic disk and the air, static electricity is charged on the magnetic disk, and a potential difference occurs between the magnetic disk and the magnetic head. Then, this potential difference causes a discharge phenomenon between the magnetic disk and the magnetic head, and there is a drawback that the information written on the magnetic disk is destroyed.

[0007]

SUMMARY OF THE INVENTION The present invention comprises a spindle motor having a dynamic pressure bearing, a magnetic disk driven and rotated by the spindle motor, and a magnetic head for writing / reading information to / from this magnetic disk. In the magnetic disk device provided, a conductive magnetic fluid is used as a working fluid of the dynamic pressure bearing of the spindle motor.

[0008]

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

FIG. 1 is a sectional view showing an embodiment of the present invention. As shown in FIG. 1, the magnetic disk device of the present embodiment is provided with a magnetic disk 2 which is rotated by the drive of a spindle motor 1, and a magnetic disk 2 which faces the magnetic disk 2.
While the magnetic disk 2 is rotating, a magnetic head 3 for writing / reading information to / from the magnetic disk with a flying height of submicron, a carriage 4 for moving the magnetic head 3 in the radial direction of the magnetic disk 2, and a carriage 4 are provided. The head disk assembly including the base plate 6 to be mounted and the cover 5 is provided and has the same configuration as the conventional example.

Further, the shaft 13 of the spindle motor 1
The structure of the dynamic pressure bearing is similar, but in the magnetic disk device of the present invention, the oil 16 (see FIG. 2) of the conventional example is used in the gap between the shaft 13 and the inner peripheral surface of the cylindrical portion of the housing 11. A conductive magnetic fluid 15 is filled as a working fluid. Then, the shaft 13 has the conductive magnetic fluid 15
The shaft 13 and the housing 11 are electrically connected to each other by rotating without contacting with the inner peripheral surface of the cylindrical portion of the housing 11 through.

[0011]

As described above, the magnetic disk device of the present invention uses the conductive magnetic fluid as the working fluid of the dynamic pressure bearing of the shaft of the spindle motor to establish the electrical conduction between the shaft and the housing. As a result, the static electricity charged on the magnetic disk during the rotation of the magnetic disk is bypassed to the ground, and there is no potential difference between the magnetic disk and the magnetic head. Therefore, there is an effect that it is possible to prevent the information written on the magnetic disk from being destroyed by the discharge.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an example of a conventional magnetic disk device.

[Explanation of symbols]

 1 Spindle Motor 2 Magnetic Disk 3 Magnetic Head 4 Carriage 5 Cover 6 Base Plate 11 Housing 12 Hub 13 Shaft 14 Stator 15 Conductive Magnetic Fluid 16 Oil 17 Permanent Magnet

Claims (1)

[Claims] 1. A spindle motor having an axial pressure bearing,
In a magnetic disk device including a magnetic disk driven by the spindle motor to rotate and a magnetic head for writing and reading information to and from the magnetic disk, a conductive magnetic fluid is used as a working fluid of the dynamic pressure bearing of the spindle motor. A magnetic disk device characterized by using.