JPH04358350A - Spindle motor - Google Patents

Abstract

PURPOSE:To prevent the fall-off of a shaft out of a housing when the posture of the spindle motor is vertically turned over. CONSTITUTION:Magnets 6 are provided on the upper end face of the supporting part 4a of the housing 4 and the positions facing the front surface plate and rear surface of a hub 2, respectively. These magnets are so mounted as to generate attraction forces to each other.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor used in a magnetic disk drive, and more particularly to a spindle motor having a hydrodynamic bearing.

0002

2. Description of the Related Art FIG. 2 is a sectional view showing an example of a conventional spindle motor.

A conventional spindle motor having a hydrodynamic bearing used in a magnetic disk drive has a configuration as shown in FIG. That is, a housing 14 having a cylindrical support part 14a projecting upward at the center of the upper surface, a stator 15 consisting of an iron core and a coil fixed to the outer periphery of the support part 14a of the housing 14, and a support part 14a of the housing 14. A shaft 11 is rotatably held within the shaft 11, and a magnetic disk holding portion 1 having a cylindrical shape with the center of the top plate fixed to the upper end of the shaft 11 and surrounding the support portion 14a.
2a, and a permanent magnet 13 fixed at a position facing the stator 15 on the inner surface of the magnetic disk holding portion 12a of the hub 12, and a magnetic field is generated by energizing the coil of the stator 15. occurs,
When this magnetic field and the magnetic field of the magnet 13 repel each other, the hub 12, which is integrated with the magnet 13, rotates. The diameter of the shaft 11 is slightly smaller than the inner diameter of the support portion 14a, and grooves 11a and 11b are provided on the outer periphery of the center and lower end portions of the shaft 11. The shaft 11 is inserted into the support part 14a of this housing 14, and the shaft 11 and the support part 1
A lubricant 18 is filled in the gap with 4a. The grooves 11a and 11b provided in the shaft 11
When rotated, a fluid film is formed between the support portion 14a of the housing 14 and the inner surface of the support portion 14a, thereby functioning as a non-contact bearing.

0004

[Problems to be Solved by the Invention] In the conventional spindle motor as described above, when the position of the spindle motor is turned upside down, no force is applied to hold the shaft. It has the disadvantage of causing omissions.

[0005]

[Means for Solving the Problems] A spindle motor of the present invention includes a housing having a cylindrical support portion projecting upward at the center of the upper surface, a stator fixed to the outer periphery of the support portion of the housing, and a stator fixed to the outer periphery of the support portion of the housing. a hub having a shaft rotatably held in the support portion of the housing; a cylindrical magnetic disk holding portion having a center of a top plate fixed to the upper end of the shaft and surrounding the support portion of the housing; a first magnet fixed on the inner surface of the magnetic disk holding portion of the hub at a position facing the stator, and dynamic pressure between the shaft and the inner surface of the supporting portion of the housing generated by rotation of the shaft; In a spindle motor having a hydrodynamic bearing function to support the shaft, a second magnet provided on an upper end surface of the support portion of the housing and a second magnet provided on a lower surface of the upper surface plate of the housing are opposed to each other. and a third magnet that generates an attractive force with each other.

[0006]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

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

Housing 4 and stator 5 of the embodiment of FIG.
The basic structure and operation of the shaft 1, hub 2, and permanent magnet 3 are the same as in the conventional example shown in FIG. That is, a housing 4 having a cylindrical support part 4a projecting upward at the center of the upper surface, a stator 5 consisting of an iron core and a coil fixed to the outer periphery of the support part 4a of the housing 4, and a support part 4a of the housing 4. a hub 2 having a cylindrical magnetic disk holding part 2a surrounding a support part 4a, the center of the top plate being fixed to the upper end of the shaft 1; A magnet 3 is fixed at a position facing the stator 5 on the inner surface of the magnetic disk holding part 2a, and a magnetic field is generated by energizing the coil of the stator 5, and this magnetic field and the magnetic field of the magnet 3 are opposite to each other. The hub 2, which is integrated with the magnet 3, rotates by squeezing each other. shaft 1
The diameter of the shaft 1 is slightly smaller than the inner diameter of the support portion 4a, and grooves 1a and 1b are provided on the outer periphery of the center and lower end portions of the shaft 1. Shaft 1 is
The shaft 1 is inserted into the support portion 4a of the housing 4, and a lubricant 8 is filled in the gap between the shaft 1 and the support portion 4a. When the shaft 1 rotates, the grooves 1a and 1b formed in the shaft 1 form a fluid film with the inner surface of the support portion 4a of the housing 4, thereby functioning as a non-contact bearing.

Permanent magnets 6a and 6 are located on the upper end surface of the support portion 4a of the housing 4 and at positions facing the upper end surface of the support portion 4a on the lower surface of the upper surface plate of the hub 2, respectively.
b, and these magnets are attached to each other so as to generate an attractive force.

In the spindle motor configured as described above, when the shaft 1 rotates, a pressure in the opposite direction to the attraction force of the magnets 6a and 6b is generated on the lower end surface of the shaft 1, and the shaft 1 rises above the surface of the housing 4. Rotate. When the rotation of the shaft 1 is stopped, the hub 2 is attracted to the housing 4 by the attraction force of the magnets 6a and 6b, so even if the spindle motor is turned upside down, the shaft 1 is held by the housing 4 and the shaft does not come off. does not occur.

[0011]

[Effects of the Invention] As explained above, the spindle motor of the present invention has magnets provided on the upper end surface of the support portion of the housing and at opposing positions on the lower surface of the upper surface plate of the hub. By mounting the shaft so as to generate a suction force, it is possible to prevent the shaft from coming out of the housing when the spindle motor is turned upside down.

[Brief explanation of drawings]

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

FIG. 2 is a sectional view showing an example of a conventional spindle motor.

[Explanation of symbols]

1 Shaft 1a Groove 1b Groove 2. Hub 2a Magnetic disk holding part 3 Magnet 4 Housing 4a Support part 5 Stator 6a Magnet 6b Magnet 8 Lubricant 11 Shaft 11a Groove 11b Groove 12 Hub 12a Magnetic disk holding part 13 Magnet 14 Housing 14a Support part 15 Stator 18 Lubricant

Claims (1)

[Claims] Claims: 1. A housing having a cylindrical support part protruding upward at the center of the upper surface, a stator fixed to the outer periphery of the support part of the housing, and a stator rotatable within the support part of the housing. a hub having a cylindrical magnetic disk holder whose top plate has a center fixed to the upper end of the shaft and which surrounds the support portion of the housing; a first magnet fixed at a position facing the stator, and has a dynamic pressure bearing function of supporting the shaft by dynamic pressure between the shaft and the inner surface of the support portion of the housing generated by rotation of the shaft. In the spindle motor, a second magnet provided on the upper end surface of the support part of the housing and a second magnet provided on the lower surface of the upper surface plate of the housing at a position opposite to the second magnet generate an attractive force with each other. A spindle motor characterized by comprising a third magnet.