JPH0512792A - Spindle motor for magnetic disk drive - Google Patents

Abstract

(57) [Summary] [Purpose] To maintain the irregular surface runout accuracy of the magnetic disk mounting surface and to make the total length of the spindle motor ultra-thin. [Structure] A spindle motor for driving a magnetic disk comprises a stator 2 fixed to a bracket 1, a rotor 3 arranged on the outer circumference of the stator 2 with a gap, and an inner circumference of the bracket 1. A rotating shaft 5 rotatably supported by a bearing 4 attached, and a rotor 3 fixed to the rotating shaft 5.
And a hub 6 for mounting a magnetic disk. The bearing 4 is made ultra thin using one radial ball bearing capable of bearing an axial load, and a pre-load is axially applied to the center of the rotating shaft 5 by a leaf spring 7 attached to the bracket 1. The ball is pressed against the rolling surface inside the radial ball bearing 4 that can bear the axial load, and the balls rotate while the axial centers of the inner and outer rings of the bearing are aligned. It

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 driving a magnetic disk used in a magnetic recording device or the like.

[0002]

2. Description of the Related Art As a conventional technique of a spindle motor for driving a magnetic disk, for example, an actual flat head 1-105373 is available.
The one shown in Japanese Patent Publication is known. This is also called an in-hub shaft rotating type, and has a structure in which a motor is configured inside a hub for mounting a magnetic disk, and only the outer periphery of a bracket is exposed to the outside of the hub for mounting, and the shaft rotates.
The structure includes a stator fixed to the bracket, a rotor arranged on the outer circumference of the stator with a gap, and a rotary shaft rotatably supported by a bearing mounted on the inner circumference of the bracket. It comprises a hub fixed to this rotary shaft to support the rotor and to mount a magnetic disk, and uses two of the bearings.

Apart from this, the in-hub shaft fixed type is also well known, and its constitution is a stator fixed to a bracket,
A rotor arranged around the outer periphery of this stator with a gap,
It comprises a fixed shaft fixed to the inner circumference of the bracket, and a hub rotatably supported by a bearing on the fixed shaft to support the rotor and mount a magnetic disk, and uses two of the bearings. is there.

[0004]

In a spindle motor for driving a magnetic disk, it is necessary to suppress irregular surface runout accuracy of the magnetic disk mounting surface called "non-repetitive runout" to 0.5 .mu.m or less. The two ball bearings have been used to stabilize the rotation accuracy. However, when the magnetic disk is downsized from 3.5 inches to 2.5 inches and further downsized to 1.8 inches, the total length of the spindle motor for driving the magnetic disk is only 8 inches.
Ultra thinning of less than mm has become a target, and the non-repetitive runout must be maintained.

An object of the present invention is to provide a spindle motor for driving a magnetic disk, which can make the total length of the spindle motor ultra thin while maintaining the irregular surface runout accuracy of the magnetic disk mounting surface. It is in.

[0006]

A spindle motor for driving a magnetic disk according to the first aspect of the present invention is a so-called in-hub shaft rotating type, and referring to FIG. 1, a stator 2 fixed to a bracket 1 and this fixing A rotor 3 arranged on the outer circumference of the child 2 with a gap, a rotary shaft 5 rotatably supported by a bearing 4 mounted on the inner circumference of the bracket 1, and the rotor fixed to the rotary shaft 5 3 which comprises a hub 6 for supporting 3 and mounting a magnetic disk, one of the radial ball bearings capable of bearing an axial load is used for the bearing 4 and is mounted on the bracket 1 at the center of the rotary shaft 5. The leaf spring 7 applies a preload in the axial direction.

A spindle motor for driving a magnetic disk according to a second aspect of the invention is of a so-called in-hub shaft fixed type, and referring to FIG. 3, a stator 2 fixed to a bracket 11 and a gap around the outer periphery of the stator 2. Rotor 3 arranged via
And a fixed shaft 15 fixed to the inner circumference of the bracket 11.
And a hub 16 which is rotatably supported by a bearing 4 on the fixed shaft 15 to support the rotor 3 and to mount a magnetic disk, which is a radial ball bearing capable of bearing an axial load on the bearing 4. Use pieces,
A plate spring 17 attached to the hub 16 applies a preload to the center of the fixed shaft 15 in the axial direction.

A third aspect of the present invention is the same as the first or second aspect, wherein a hard ball 7b is fitted in the center of the rotary shaft 5 or the fixed shaft 15,
The hard spring presses the leaf spring.

[0009]

In the invention 1 or 2, if the center of the rotary shaft 5 or the fixed shaft 15 is pushed in the axial direction by the leaf springs 7 or 17, the balls are formed on the rolling surface inside the radial ball bearing 4 capable of bearing the axial load. The bearing is pressed and rotates with the inner and outer rings of the bearing aligned with each other, so that the surface wobbling accuracy of the magnetic disk mounting surface is properly secured. At this time, if the hard sphere 7b is used as in the invention 3, the hard sphere 7b and the leaf spring 7 or 17 are used.
The contact point with can be located at the correct center, and the peripheral velocity at the contact point can be minimized to minimize friction torque and wear.

[0010]

EXAMPLE FIG. 1 is a longitudinal sectional view showing only one side except the axis of Example 1, FIG. 2 is a longitudinal sectional view showing only one side except the axis of Example 2, and FIG. 3 is other than the axis of Example 3. FIG. 4 is a vertical cross-sectional view showing only one side, and FIG. 4 is a vertical cross-sectional view showing only one side except for the shaft of the fourth embodiment. In each figure, components having the same reference numerals have approximately the same function, and duplicate explanation may be omitted. 1 and 2 show an in-hub shaft rotating type, and FIGS. 3 and 4 show an in-hub shaft fixed type.

In FIG. 1, a spindle motor for driving a magnetic disk comprises a stator 2 fixed to a bracket 1.
A rotor 3 arranged on the outer circumference of the stator 2 with a gap therebetween, and a bearing 4 mounted on the inner circumference of the bracket 1.
And a rotary shaft 5 rotatably supported by the rotary shaft 5.
The hub 6 is fixed to the hub 6 to support the rotor 3 and to which a magnetic disk (not shown) is attached. This point is basically the same as that described in the section of the prior art.

As a characteristic structure of the embodiment, the bearing 4
Is a radial ball bearing 4, which can bear an axial load,
For example, only one deep groove ball bearing is used. Then, a pre-load is axially applied to the center of the rotating shaft 5 by a leaf spring 7 attached to the bracket 1 with a rivet 7a. It is well known that the radial ball bearing 4 capable of bearing the axial load includes a double-row deep groove ball bearing, a double row deep groove ball bearing, and an angular ball bearing. The second embodiment shown in FIG. 2 is different from FIG. 1 in that a preload is applied in the axial direction by a leaf spring 7 via a hard ball 7b mounted in a hole provided at the center of the rotary shaft 5.

In a third embodiment shown in FIG. 3, a spindle motor for driving a magnetic disk comprises a stator 2 fixed to a bracket 11 and a rotor 3 arranged on the outer periphery of the stator 2 with a gap therebetween. The embodiment comprises a fixed shaft 15 fixed to the inner circumference of the bracket 11, and a hub 16 rotatably supported by a bearing 4 on the fixed shaft 15 for supporting the rotor 3 and mounting a magnetic disk. As a characteristic structure of the above, as the bearing 4, only one radial ball bearing 4 capable of bearing an axial load, for example, a deep groove ball bearing is used. Then, a pre-load is applied in the axial direction by a leaf spring 17 press-fitted and attached to the hub 16 at the center of the fixed shaft 15. The embodiment 4 shown in FIG. 4 is different from that of FIG. 3 in that a pre-load is applied in the axial direction by a leaf spring 17 via a hard ball 7b mounted in a hole provided at the center of the fixed shaft 15.

In the first or third embodiment, if the center of the rotary shaft 5 or the fixed shaft 15 is pushed in the axial direction by the leaf springs 7 or 17, the ball is attached to the rolling surface inside the radial ball bearing 4 which can bear the axial load. Is pressed and the bearings rotate while the inner and outer rings of the bearing are aligned with each other, and the surface runout accuracy of the magnetic disk mounting surface is properly secured. At this time, if the hard sphere 7b is used as in Example 2 or 4, the contact point between the hard sphere 7b and the leaf spring 7 or 17 can be positioned at the correct center, and the peripheral velocity at the contact point can be minimized. Minimize friction torque and wear.

[0015]

The spindle motor for driving a magnetic disk according to the present invention 1 or 2 is of a so-called in-hub shaft rotating type or in-hub shaft fixed type, and uses only one radial ball bearing capable of bearing an axial load. However, since a preload is applied to the center of the rotating shaft or the fixed shaft in the axial direction with a leaf spring, the balls are pressed against the rolling surface inside the ball bearing, and the axial center of the inner and outer rings of the bearing match Since it will rotate, the surface runout accuracy of the magnetic disk mounting surface will be ensured correctly, and only one bearing will be required instead of two.
There is an effect that the total length of the spindle motor can be made extremely thin. According to the invention 3, the contact point between the hard ball and the leaf spring can be located at the correct center, and the peripheral velocity at the contact point can be minimized to minimize friction torque and wear. effective.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing only one side except the shaft of the first embodiment.

FIG. 2 is a vertical cross-sectional view showing only one side except the shaft of the second embodiment.

FIG. 3 is a vertical cross-sectional view showing only one side except the shaft of the third embodiment.

FIG. 4 is a vertical cross-sectional view showing only one side except the axis of the fourth embodiment.

[Explanation of symbols]

1 bracket 2 stator 3 rotor 4 bearings 5 rotation axes 6 hubs 7 leaf spring 7b hard ball 11 bracket 15 fixed axis 16 hubs 17 leaf spring

Claims (3)

[Claims] 1. A stator fixed to a bracket, a rotor arranged on the outer periphery of the stator with a gap, and a rotary shaft rotatably supported by a bearing mounted on the inner periphery of the bracket. A radial ball bearing capable of bearing an axial load on the bearing in a spindle motor for driving a magnetic disk, the spindle motor being fixed to the rotary shaft and supporting the rotor and a hub for mounting a magnetic disk
A spindle motor for driving a magnetic disk, characterized in that a single piece is used and a pre-load is axially applied to the center of the rotary shaft by a leaf spring attached to the bracket. 2. A stator fixed to the bracket, a rotor arranged on the outer circumference of the stator with a gap, a fixed shaft fixed to the inner circumference of the bracket, and a bearing on the fixed shaft. In a spindle motor for driving a magnetic disk, which is rotatably supported and supports the rotor, and a hub for mounting a magnetic disk, one of the radial ball bearings capable of bearing an axial load is used for the bearing,
A spindle motor for driving a magnetic disk, characterized in that a leaf spring attached to the hub applies axial preload to the center of the fixed shaft. 3. A spindle motor for driving a magnetic disk according to claim 1 or 2, wherein a hard ball is fitted to the center of the rotary shaft or the fixed shaft, and the hard spring presses the leaf spring. Spindle motor for driving magnetic disks.