JPH11288551A - Spindle motor - Google Patents

Abstract

The present invention relates to a spindle motor for rotating and driving a magnetic disk, and provides a specific configuration for reducing and eliminating thermal deformation, noise and vibration of a motor hub. SOLUTION: A stator core 3 arranged annularly around a shaft 1 and a magnetic disk 6 is held on an outer periphery near a lower end portion, and an upper end portion is rotatably supported by the shaft 1 and has a cylindrical shape with a lower opening. Motor yoke 4 and a cylindrical back yoke 7 adhesively fixed inside the motor hub 4
And a cylindrical rotor magnet 8 fixed through the motor hub 4 to the back yoke bonding surface of the motor hub 4 at least from a lower end thereof to a position above a position where the magnetic disk 6 is fixed. By forming the cut 9, the motor hub 4 is formed.
A gap is provided between the motor hub 4 and the back yoke 7 to prevent thermal deformation of the motor hub 4 due to a difference in thermal expansion coefficient between the motor hub 4 and the back yoke 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor hub having a plurality of stator cores arranged annularly around a shaft provided on a motor base, a motor hub holding a magnetic disk on the outer periphery and rotatably supported by the shaft. A spindle motor having a cylindrical rotor magnet fixed via a cylindrical back yoke adhered and fixed to the inside of the motor hub so as to face the stator core with a predetermined gap therebetween, The present invention is characterized in that the means for reducing and removing the deformation of the motor hub due to the stress generated by the difference in the coefficient of thermal expansion between the motor hub and the back yoke.

[0002]

2. Description of the Related Art FIG. 3 shows a configuration of a spindle motor for driving a magnetic disk to rotate. FIG. 3 is a sectional view of a conventional spindle motor.
Reference numeral 1 denotes a shaft implanted in the motor base 2, and reference numeral 3 denotes a stator core which is annularly arranged around the shaft 1 at equal intervals around the shaft 1. Reference numeral 4 denotes a cylindrical motor hub made of aluminum and having a lower opening, the upper end of which is
A magnetic disk 6 is fixed to the shaft 1 so as to be rotatable by bearings 5 around the lower end of the motor hub 4.

[0003] Reference numeral 7 denotes a cylindrical back yoke made of an iron material, the entire outer peripheral surface of which is bonded and fixed to the inner peripheral surface near the lower end of the motor hub 4 with an adhesive. Further, a cylindrical rotor magnet 8 is fixed to the inner peripheral surface of the back yoke 7 with an adhesive.

[0004]

However, in the above-described conventional configuration, thermal stress is generated in the axial direction due to a difference in thermal expansion coefficient between the motor hub 4 and the back yoke 7 due to a rise in temperature due to driving or a rise in environmental temperature. Thus, there is a problem that the motor hub 4 is thermally deformed and stable rotation of the magnetic disk cannot be expected.

An object of the present invention is to reduce and eliminate the thermal deformation of a motor hub due to an increase in the temperature of the motor or the environmental temperature.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a plurality of stator cores arranged annularly around a shaft provided on a motor base, and a magnetic disk held on an outer periphery near a lower end. A cylindrical motor hub having an upper end rotatably supported by the shaft and having a downwardly open cylindrical motor hub and a cylindrical core bonded and fixed inside the motor hub so as to face each other with a predetermined gap therebetween. And a cylindrical rotor magnet fixed via the back yoke of the spindle motor, the motor hub continues to the back yoke bonding surface of the motor hub at least from a lower end thereof to a position above a position where the magnetic disk is fixed. A gap is provided between the motor hub and the back yoke by forming a notch.

[0007] According to this configuration, at the lower end of the cylindrical motor hub that is open at the bottom, where a deformable lower end is formed, a gap is formed between the motor hub and the back yoke.
The lower end of the motor hub can be prevented from being deformed due to the thermal stress caused by the difference in the coefficient of thermal expansion between the motor hub and the back yoke.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment) The first and second embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a sectional view of a spindle motor according to an embodiment of the present invention. Functional components similar to those of the conventional configuration shown in FIG. 3 are denoted by the same reference numerals.

The difference between the present embodiment and the conventional structure shown in FIG. 3 is that the motor hub 4 has a depth of 25 to 50 μm which extends from the lower end to at least a position where the magnetic disk 6 is fixed. The point is that the notch 9 is formed. That is, by forming the cut 9, when the back yoke 7 is joined to the inner peripheral surface of the motor hub 4, a gap is formed only in the section of the cut 9 between the inner peripheral surface of the motor hub 4 and the back yoke 7. It is configured as follows.

As described above, compared to the case where the entire surface of the back yoke 7 is joined to the inner peripheral surface of the motor hub 4,
Even if there is a difference in the coefficient of thermal expansion between the motor hub 4 and the back yoke 7, thermal deformation of the motor hub 4 can be prevented due to the gap.

FIG. 2 is an enlarged sectional view of a main part showing another embodiment of the present invention. The difference from the above embodiment is that the gap 9 formed by the cut 9 is made of, for example, an acrylic resin adhesive material. The point is that the resin material 10 is filled. According to this configuration, since the resin material 10 having a higher elastic deformation rate than the metal forming the motor hub 4 and the back yoke 7 is filled in the gap, the deformation of the resin material 10 causes the motor hub 4 and the back yoke 7 to be filled. The thermal stress generated due to the difference in the coefficient of thermal expansion is absorbed, and deformation of the motor hub 4 is avoided.
Further, by filling the gap with the resin, the vibration of the motor hub 4 and the back yoke 7, which may be caused by the formation of the gap, can be absorbed, and noise and vibration can be prevented.

[0012]

As described above, according to the spindle motor of the present invention, by forming a gap between the motor hub and the back yoke, thermal stress between the members can be avoided and thermal deformation of the motor hub can be prevented. Further, by filling the gap with a resin, vibration of the member can be absorbed and noise and vibration can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a spindle motor according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of a spindle motor according to another embodiment of the present invention.

FIG. 3 is a sectional view of a conventional spindle motor.

[Explanation of symbols]

 Reference Signs List 1 shaft 2 motor base 3 stator core 4 motor hub 5 bearing 6 magnetic disk 7 back yoke 8 rotor magnet 9 cut 10 resin

Claims (2)

[Claims] 1. A plurality of stator cores arranged annularly around a shaft provided on a motor base, and a magnetic disk held on an outer periphery near a lower end, and an upper end rotatably supported by the shaft. And a cylindrical rotor magnet fixed via a cylindrical back yoke adhesively fixed inside the motor hub so as to face through a predetermined gap between the motor hub and the stator core. A spindle motor having a notch formed on the back yoke bonding surface of the motor hub from a lower end thereof to at least a position above a position at which the magnetic disk is fixed, so that the notch is provided between the motor hub and the back yoke. A spindle motor having a gap. 2. The spindle motor according to claim 1, wherein the gap is filled with a resin having a larger elastic coefficient than the motor hub.