JPH0973711A - Magnetic disk type memory device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the height over the entire part smaller by providing the magnetic fluid sealing part of the rotor and stator of a magnetic disk type recorder with a difference in level in a radial direction at one of a pair of upper and lower pole pieces. SOLUTION: A magnetic fluid sealing body 17 is formed of a spacer 14, a pair of the pole pieces 15 consisting of the upper and lower pole pieces 15A, 15B, a magnet 16, a cover 18, magnetic fluid L, etc. The pole piece 15A is provided with the difference in level 15A1 toward the thickness direction of the magnet 20 in the radial direction to flatten the cover 18, by which the height over the entire part of the sealing body 17 is made smaller and the bearing span length is made longer. Then, the number of the disks to be mounted is increased and the influence of the resonance frequency is suppressed by increasing the resonance frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk type storage device arranged in an enclosure, and more particularly to a seal structure for a rotor portion and a stator portion.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 5, a magnetic disk type storage device is arranged in an enclosed clean space S called an enclosure 1 and is mounted on an outer peripheral surface of a cylindrical aluminum hub 2 which is rotationally driven. At least one disc 3
The discs 3 (three in the drawing) are alternately inserted and laminated via the spacers 4, and the discs 3 are fixed to the hub 2 by tightening the disc clamper 5 from the upper surface of the hub 2 with screws 6. A rotor yoke 7 and a magnet 8 which are magnetic materials are attached to the inside of the bulged outer diameter portion 2a located below the disk 3 of the hub 2, and these constitute a rotor of the motor.

On the other hand, a stator core 10 in which a coil 9 is wound so as to face the magnet 8 with a gap interposed therebetween is fixed to a motor base 11 formed integrally with a shaft 11A to form a stator.

The hub 2 is rotatably coupled between its inner diameter and the outer diameter of the shaft 11A by ball bearings 12A and 12B which are vertically spaced. A coil spring C is urged between the bearings to the outer rings to absorb the play between the inner and outer rings. Also, on the upper end surface of the upper bearing 12A,
By inserting and fixing the magnetic sleeve 13 on the shaft 11A, movement of the end portion of the inner ring of the bearing 12A is prevented.

Further, as also shown in FIG. 6, a spacer 14 is provided on the outer ring of the ball bearing 12A on the hub 2 side.
The magnetic fluid seal main body 17 in which the magnet 16 is disposed between the two pole pieces 15A and 15B is fitted on the spacer 4, and the magnetic fluid seal main body 1
The magnetic fluid L is injected into the gap formed between the sleeve 7 and the sleeve 13. And the magnetic fluid seal 1
A cover 18 is attached to the upper surface of the main body 7 to prevent foreign matter from entering the magnetic fluid. This cover 18
In consideration of the height of the meniscus, the base is fixed to the upper pole piece 15A so as to be separated from the upper pole piece 15A so that a constant gap is formed between the upper pole piece and the pole piece on the upper surface, particularly near the magnetic fluid. It has a stepped shape.

[0006]

The device constructed as described above has the following problems. (1) With the thinning of the magnetic disk device, the space for arranging the magnetic fluid seal has disappeared. In other words, in the conventional method, a spacer of about 0.5 mm, a magnetic fluid seal body of about 1 mm, and a cover of about 0.8 mm were required to place the magnetic fluid seal, and a total of 2.3 mm was required. However, in order to achieve a thinner motor, it is necessary to further reduce the thickness of the magnetic fluid seal portion. (2) As the capacity of the magnetic disk drive increases, the number of disks that can be stored in the same height is increasing. If one disk is added, the resonance frequency of the motor will drop by about 100Hz, and the resonance frequency will be low. In that case, the head also resonates and there is a problem that the servo write cannot be performed. In order to increase the resonance frequency, it is effective to increase the span of the ball bearing, and it was necessary to further reduce the thickness of the magnetic fluid seal portion. (3) In the conventional method, the magnetic fluid seal portion has a sleeve,
Four parts were required: the spacer, the magnetic fluid seal body, and the cover.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is a magnetic disk type storage device disposed in an enclosure, in which at least one disk center hole is mounted. And a rotor part supported by the stator part via a bearing, and a pair of pole pieces with a magnet interposed between the stator part and the rotor part. A magnetic fluid seal is provided, and at a seal portion having a diameter smaller than the inner diameter of the magnet of the magnetic fluid seal, a step is formed on one pole piece in the radial direction so that the inner diameter portions of the upper and lower pole pieces are smaller than the thickness of the magnet. The present invention provides a magnetic disk type storage device characterized by having.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a magnetic disk type storage device according to the present invention will be described in detail below with reference to FIGS.

For the sake of convenience of explanation, the same components as those shown above are designated by the same reference numerals, and the description of the overlapping components will be omitted.

As the structure of the seal in the disk type storage device of the present invention, the thickness of the spacer 14 is the same as in the conventional case.
Assuming that the thickness of the magnetic fluid seal main body 17 is 1 mm and the thickness of the cover 18 is 0.1 mm, the total thickness of the seal portion is 1.
By realizing 6 mm, it is possible to make it 0.7 mm thinner than the conventional device.

[0011]

[Embodiment] That is, in the first embodiment shown in FIG. 1, the upper pole piece 15A is opposed to the lower pole piece 15B.
Is formed close to the lower pole piece 15B by forming the step portion 15A ₁ in the thickness direction of the magnet 16 so that the inner circumferential portion in the radial direction in which the magnetic fluid is arranged is smaller than the inner diameter of the magnet 16. As a result, the cover 18 can cover the upper pole piece 15A in a flat state without forming a step portion as in the conventional case, and the magnetic fluid L
It is possible to form a constant gap between the upper pole piece 15A and the vicinity of the magnetic fluid in consideration of the meniscus height.

In the second embodiment shown in FIG. 2, the upper pole piece 15A is the same as the above embodiment, but the lower pole piece 15B has a step portion corresponding to the spacer thickness on the lower surface on which the magnet 16 is located. By forming 15B ₁ , a constant gap is formed between the ball bearing 12A and the ball bearing 12A in consideration of the meniscus height of the magnetic fluid L, and a spacer as a component can be omitted.

FIG. 3 shows a third embodiment. As in the case of FIG. 2, the lower pole piece 15B is provided with a protrusion (a dowel) on the circumference below the magnet 16 instead of forming a stepped portion as a substitute for the spacer. ) It is achieved by forming multiple protrusions of 15B ₂ . In these examples, each pole piece can be easily formed by press molding.

Since the disc-shaped cover 18 can be a flat cover, it is only necessary to attach a thin seal.

FIG. 4 shows the relationship between the number of DISKs and the resonance frequency. With the conventional structure, servo writing was possible with two DISKs, but with three DISKs, the resonance frequency was 460Hz, which is the lower limit frequency for servo writing. Servo writing was not possible because the frequency was below 470Hz. However, according to the present invention, the axial span between the ball bearings can be lengthened by an amount corresponding to the reduced thickness of the magnetic fluid seal portion.
Even with one disc, the frequency is 500Hz, and even with three discs, servo writing is possible and the storage capacity of the magnetic disk type storage device can be increased.

[0016]

According to the magnetic disk drive device of the present invention described in detail above, the height of the entire seal can be reduced while considering the meniscus height of the magnetic fluid seal, and the bearing span can be lengthened. Therefore, the number of disks to be mounted can be increased, and the effect of the resonance frequency can be suppressed low.

[Brief description of drawings]

FIG. 1 is a half-enlarged cross-sectional view of a seal portion showing an embodiment of a magnetic disk type storage device of the present invention.

FIG. 2 is a half-part enlarged cross-sectional view showing a second embodiment of the seal part.

FIG. 3 is a half-part enlarged cross-sectional view showing a third embodiment of the seal part.

FIG. 4 is a diagram showing a relationship between the number of mounted disks and a resonance frequency.

FIG. 5 is a half sectional view showing a conventional magnetic disk type storage device.

FIG. 6 is a half-part enlarged cross-sectional view showing a conventional seal part.

[Explanation of symbols]

13 ... Sleeve, 15A ... Upper pole piece, 15B ...
Lower pole piece, 17 ... Magnetic fluid seal body, L ... Magnetic fluid.

Claims (3)

[Claims] 1. A magnetic disk type storage device disposed in an enclosure, comprising a hub into which a central hole of at least one disk is mounted, and a stator part for driving the disk and the stator part. A magnetic fluid seal having a pair of pole pieces with a magnet interposed between the stator and the rotor, the magnetic fluid seal having a rotor portion supported by a bearing. A magnetic disk type storage device characterized in that, in a seal portion having a small diameter, one pole piece has a step in the radial direction so that the inner diameter portions of the upper and lower pole pieces are smaller than the thickness of the magnet. 2. The magnetic disk type storage device according to claim 1, wherein a protrusion for separating the pole piece from the outer ring of the bearing is formed on the other pole piece of the pair of pole pieces. 3. A disc-shaped cover or disc-shaped seal is disposed on the upper surface of the one pole piece.
Alternatively, the magnetic disk type storage device described in 2.