JPH0678483A - Spindle motor for magnetic disk - Google Patents

Abstract

PURPOSE:To prevent discharge of volatile component of adhesive for fixing a magnet to a yoke. CONSTITUTION:A stator 2 is mounted on a bracket 1, a hub 6 is fixed to a shaft 5 to be supported by a bearing 4, and a cylindrical magnet 8 is fixed to a cylindrical yoke 17 mounted on the hub 6 with adhesive. A flange 17a directed inside is formed at the yoke 17, brought into contact with the magnet 8, and an annular groove 17b is formed at the periphery of the flange 17a. When the inner periphery of the yoke 17 is coated with a suitable amount of adhesive and the magnet 8 is press-fitted, a slightly excess adhesive is scraped by a corner of the magnet 8 to be retained in the groove 17b. The magnet 8 is brought into axial contact with the flange 17a to seal the slightly excess adhesive in the groove 17b.

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 a magnetic disk, and more particularly to a technique for fixing a yoke and a magnet.

[0002]

2. Description of the Related Art FIG. 3 is a half sectional view of a conventional example. In the figure, the structure of this spindle motor for magnetic disk is
A stator 2 having a winding 3 is attached to the outer circumference of a bearing box 1a on one side of the bracket 1, and a hub 6 is fixed to one side of a shaft 5 supported by a bearing 4 attached to the bearing box 1a. A cylindrical magnet 8 is fixed to the inner periphery of a cylindrical yoke 7 which is attached to the other side of the bracket 1 and has a gap in the axial direction, and the inside of the magnet 8 is opposed to the stator 2 through the gap. The yoke 7 and the magnet 8 are fixed with an adhesive. This is also called an in-hub motor and is a kind of three-phase brushless DC motor.

[0003]

The discharge of volatile components in the bearing grease can be solved by improving the bearing sealing technique without using a magnetic fluid seal as in the conventional case. However, the curing treatment of an adhesive such as an anaerobic adhesive that fixes the yoke 7 and the magnet 8 is harmful because the volatile component is still discharged even when the ultraviolet irradiation adhesive is used.

An object of the present invention is to provide a spindle motor for a magnetic disk, which can prevent discharge of volatile components of an adhesive for fixing a yoke and a magnet.

[0005]

In a spindle motor for a magnetic disk according to a first aspect of the invention, a stator is attached to the outer periphery of a bearing box on one side of a bracket, and one side of a shaft supported by a bearing attached to the bearing box is attached to the shaft. A hub is fixed, a cylindrical magnet is fixed to the inner circumference of a cylindrical yoke attached to the other side of the hub and having a gap in the axial direction with the bracket, and the inside of the magnet is fixed through the gap. In a spindle motor for a magnetic disk in which the yoke and the magnet are fixed to each other with an adhesive, facing the child, a flange facing inward is formed on the other side of the yoke to abut the other side of the magnet, An annular groove is formed at a corner of the flange or an outer peripheral corner of the magnet.

In the spindle motor for a magnetic disk according to the invention 2, a stator is attached to the outer periphery of the bearing box on one side of the bracket, and a hub is fixed to one side of the shaft supported by the bearing attached to the bearing box. A cylindrical magnet is fixed to the inner circumference of a cylindrical yoke attached to the other side of the hub and having a gap in the axial direction with the bracket, and the inside of the magnet is opposed to the stator through the gap, In a magnetic disk spindle motor in which a yoke and the magnet are fixed with an adhesive, the inner circumference of the yoke that contacts the hub is fixed to an axial projection provided on the hub, and the other side of the projection is fixed. An annular groove is formed at the outer peripheral corner or the outer peripheral corner on one side of the magnet.

[0007]

In the first aspect of the invention, reference is made to FIG. 1 or 2. Apply an appropriate amount of adhesive to the inner circumference of the yoke 17 to form the magnet 8 or 28.
By pressing in, a little excess adhesive is squeezed at the other corner of the magnet 8 or 28 and collected in the annular groove 17b or 28a. Then, the magnet 8 or 28 and the flange 17a come into contact with each other in the axial direction to seal a little excess adhesive in the groove 17b or 28a, so that the discharge of the volatile component of the adhesive can be prevented.

In the invention 2, when an appropriate amount of adhesive is applied to the inner circumference of the yoke and the magnet is press-fitted, a slight excess of adhesive is squeezed at one corner of the magnet to form an annular portion of the portion A. Collect in the groove. Then, since the magnet and the projection abut on each other in the axial direction to seal a little excess adhesive in the groove, it is possible to prevent discharge of the volatile component of the adhesive.

[0009]

FIG. 1 is a half sectional view of the first embodiment, and FIG. 2 is a sectional view of the essential parts of the second embodiment. In FIG. 1, first, a portion similar to the conventional example will be described. This magnetic disk spindle motor has a structure in which a stator 2 having a winding 3 is attached to the outer periphery of a bearing box 1a on one side of a bracket 1 and one side of a shaft 5 supported by a bearing 4 attached to the bearing box 1a. The hub 6 is fixed to the hub 6, the cylindrical magnet 8 is fixed to the inner periphery of the bracket 1 and the cylindrical yoke 17 that has a gap in the axial direction and is attached to the other side of the hub 6. The yoke 17 and the magnet 8 are fixed to each other with an adhesive so as to face the stator 2 with a gap.

As a characteristic structure of the first embodiment, a flange 17a facing inward is formed on the other side of the yoke 17 so as to abut against the other side of the magnet 8, and an annular groove 17b is formed at a corner of the flange 17a. Form. According to such a structure, the yoke 1
When a proper amount of adhesive is applied to the inner circumference of 7 and the magnet 8 is press-fitted, a slight excess of adhesive is squeezed at the other corner of the magnet 8 and collected in the annular groove 17b. Then, since the magnet 8 and the flange 17a come into axial contact with each other to seal a little excess adhesive in the groove 17b, it is possible to prevent discharge of the volatile component of the adhesive.

The second embodiment shown in FIG. 2 is the same in that a flange 17a facing inward is formed on the other side of the yoke 17 and is brought into contact with the other side of the magnet 28, but the outer periphery of the other side of the magnet 28 is the same. The difference is that an annular groove 28a is formed at the corner of the. According to such a structure, there are the same operational effects as those of the first embodiment. In either embodiment, the groove 17b or the groove 28a is
It can be formed in a press or in a mold.

When the structure of the first or second embodiment is adopted in the arrow A of FIG. 1, the inner circumference of the yoke 17 that abuts on the hub 6 is fixed to the axial projection provided on the hub 6. An annular groove is formed at the corner A of the outer circumference on the other side of the protrusion or the corner A of the outer circumference on one side of the magnet. Flange 17a is not required. According to such a structure, there are the same operational effects as those of the first or second embodiment.

[0013]

According to the spindle motor for a magnetic disk of the invention 1 or 2, since the adhesive squeezed by press-fitting the magnet into the yoke is accumulated in the annular groove and sealed, the yoke and the magnet are fixed. There is an effect that it is possible to prevent discharge of the volatile component of the adhesive.

[Brief description of drawings]

FIG. 1 is a half sectional view of a first embodiment.

FIG. 2 is a cross-sectional view of a main part of the second embodiment.

FIG. 3 is a half sectional view of a conventional example.

[Explanation of symbols]

 1 Bracket 2 Stator 6 Hub 7 Yoke 8 Magnet 17 Yoke 17a Flange 17b Groove 28 Yoke 28a Groove

Claims (2)

[Claims] 1. A bracket is mounted on the outer periphery of a bearing box on one side, a hub is fixed on one side of a shaft supported by a bearing mounted on the bearing box, and the hub is mounted on the other side of the hub. A cylindrical magnet is fixed to the inner circumference of a bracket-shaped cylindrical yoke having a gap in the axial direction, the inside of the magnet is opposed to the stator through the gap, and the yoke and the magnet are bonded by an adhesive. In the spindle motor for magnetic disk fixed by the above, a flange facing inward is formed on the other side of the yoke and brought into contact with the other side of the magnet, and an annular shape is formed at a corner of the flange or an outer peripheral corner of the magnet. A spindle motor for a magnetic disk, which is characterized by forming a groove. 2. A bracket is mounted on the outer circumference of a bearing box on one side of the bracket, a hub is fixed on one side of a shaft supported by a bearing mounted on the bearing box, and the hub is mounted on the other side of the hub. A cylindrical magnet is fixed to the inner circumference of a bracket-shaped cylindrical yoke having a gap in the axial direction, the inside of the magnet is opposed to the stator through the gap, and the yoke and the magnet are bonded by an adhesive. In the spindle motor for a magnetic disk, the inner circumference of the yoke that abuts the hub is fixed to an axial projection provided on the hub, and one of the corners of the outer circumference on the other side of the projection or the magnet. A spindle motor for a magnetic disk, wherein an annular groove is formed at a corner of a side outer circumference.