JP2652990B2 - Spindle motor - Google Patents

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 rotating a magnetic disk of a magnetic disk drive at a high speed.

[0002]

2. Description of the Related Art In a magnetic disk drive, a plurality of magnetic disks are rotated at a high speed to read and write data by a head. The head is positioned in the radial direction of the magnetic disk to read and write desired data. Positioning is performed based on positioning information recorded in advance on a magnetic disk surface facing a servo head dedicated to positioning. Therefore,
The relative position error between the servo head and the data head and the relative position error between the servo disk and the data head become a deviation amount from a position to be originally positioned, that is, an off-track. The smaller the off-track, the higher the positioning accuracy.

[0003] However, in practice, off-track exceeding the allowable amount may occur due to various factors. Of these, off-track caused by a change in the temperature of the magnetic disk drive or a change in environmental temperature is called a thermal off-track and is a major one of the off-tracks, and thermal expansion of mechanical components of each part constituting the magnetic disk drive. The difference in the coefficients is the main cause. This will be described with reference to the drawings.

FIG. 2 is a sectional view of a conventional spindle motor,
FIG. 3 is a side view of a main part of a magnetic disk drive to which a conventional spindle motor is applied. In these figures, what is indicated by reference numeral 2 is a fixed base, on which a winding coil 3 is mounted. Reference numeral 5 denotes a rotating shaft which is rotatably supported by a pair of upper and lower bearings 6. A hub 21 having a substantially bell-shaped cross section is attached to the upper portion of the rotating shaft 5, and is configured to rotate integrally with the rotating shaft 5. A yoke 22 containing the magnet 9 facing the winding coil 3 with a fixed gap is attached to the inner wall surface of the hub 21.

[0005] The spindle motor 2 thus configured
Magnetic disks 25 and 26 are mounted on the hub 21 at a constant interval. Data is written on the magnetic disk 25 by a data disk, and position information is written on the magnetic disk 26 by a servo disk in advance. A data head 27 floats on the surface of the magnetic disk 25, and a servo head 28 faces the magnetic disk 26. A positioning mechanism 29 positions the head 27 based on the position information of the servo disk 26.

[0006]

In the above-described conventional spindle motor, since the entire outer wall surface of the yoke is attached to the inner wall surface of the hub on which the magnetic disk is mounted, the magnetic disk drive is mounted. When the temperature of the hub changes and the temperature of the environment changes, distortion occurs in the hub due to the difference in linear expansion coefficient between the hub and the yoke. As a result, a relative position error occurs between the magnetic disks mounted on the hub, which causes a thermal off-track and causes a data reading error. SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a spindle motor suitable for a magnetic disk which prevents thermal off-track and has no data reading error.

[0007]

In order to achieve the above-mentioned object, a spindle motor according to the present invention comprises a rotary shaft, a hub integrally mounted on the rotary shaft, and a magnetic member mounted on the hub. And a coil winding portion that is disposed opposite to and fixed to the magnetic member at a constant distance from the magnetic member, and a gap is provided between one end of the yoke and the hub over the entire circumference. .

[0008]

In the spindle motor according to the present invention, a gap is provided between one end of the yoke and the hub. When a temperature change of the magnetic disk device and a temperature change of the environment occur, the yoke and the hub are heated. Although the amount of deformation due to expansion is different, the deformation of the yoke does not reach the hub and the hub is not distorted because of the independent configurations.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in the drawings. FIG. 1 is a sectional view of the spindle motor according to the present invention. In the figure, components denoted by the same reference numerals as those of the prior art indicate the same configuration, and detailed description is omitted. A feature of the present invention is that a gap 10 is provided between the inner wall surface of the hub 7 and one end of the yoke 8. With this configuration, the hub 7 and the yoke 8 expand and contract due to the temperature change of the magnetic disk device and the temperature of the environment.
, And the hub 7 expands and contracts independently, so that distortion that causes uneven deformation does not occur. Therefore, the relative position between the magnetic disks does not change due to the deformation of the hub 7, and no thermal off-track occurs.

[0010]

According to the present invention, a gap is provided over the entire circumference between the hub on which the magnetic disk is mounted and the yoke having a different coefficient of thermal expansion. When the yoke does not occur, the deformation of the yoke does not reach the hub, so that the relative position between the magnetic disks does not change. As a result, thermal off-track can be prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view of a spindle motor according to the present invention.

FIG. 2 is a sectional view of a conventional spindle motor.

FIG. 3 is a side view of a main part of a magnetic disk drive employing a conventional spindle motor.

[Explanation of symbols]

 7 Hub 8 Yoke 10 Clearance

Claims (1)

(57) [Claims] 1. A rotating shaft, a hub integrally attached to the rotating shaft, a yoke attached to the hub and enclosing a magnetic member, and opposed to and fixed to the magnetic member at a fixed distance from the magnetic member. A spindle motor comprising: a coil winding portion provided with a gap provided over the entire circumference between one end of the yoke and the hub.