JPH09149586A - Spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce vibrations and noise by magnetically attracting a rotating body to a fixing part in the thrust direction by a magnetic attraction device provided in the rotating body and the fixing part. SOLUTION: The magnetic centers of a driving field magnet 13 and a yoke 4 are made to accord with each other, and an attracting magnet 18a is fixed to an open end located on the base 2 side of a sleeve near to the rotation center of the driving field magnet 13, and on the other hand, an attracting magnet 18b with the magnetic pole of a single pole for attracting each other in opposite to the attracting magnet 18a being magnetized is buried in an annular recessed part formed on the base 2. A rotor (hub assembly) is attracted on the base 2 side by the attraction of the attracting magnet 18a and the attracting magnet 18b without using the self-attracting action of the driving field magnet 13. Also, since the force of action in the thrust direction is located in the position near to the rotation center, a moment for moving the hub assembly vertically is reduced, thereby being able to reduce vibrations and noise.

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 DD, an optical disk drive device, or the like.

[0002]

2. Description of the Related Art A hard disk drive (HDD) device is built in as a storage device for a personal computer or the like.
In order to achieve high density of recorded information, low vibration, and low noise, it is necessary to dramatically improve the accuracy of the rotating main shaft part as a storage device of a child type. There is a tendency to adopt fluid bearings.

12 and 13 show a magnetic disk drive device as a spindle motor having a conventional structure. That is, in the spindle motor shown in FIG. 12, the fixed shaft 1 is fixed on the disk-shaped base 2, and the winding 3 is formed on the upper surface thereof.
The printed circuit board on which the core 4 wound with the coil and drive circuit components and the like are mounted is fixed. Radial dynamic pressure generating grooves (herringbone grooves) 1a and 1b are formed on the outer peripheral surface of the fixed shaft 1 at predetermined intervals in the axial direction.

A hub assembly 5 is composed of a cylindrical hub 6 which is a disk fixing portion made of aluminum, and a bronze sleeve 7 fixed to the inner peripheral portion thereof by a fixing means such as shrink fitting. This sleeve 7 is fixed shaft 1
The hub assembly 5 is rotatable around the fixed shaft 1 by being inserted into the. The sleeve 7 has an oil reservoir 7a formed on the surface corresponding to the interval between the radial dynamic pressure generating grooves 1a and 1b. The radial direction dynamic pressure generating grooves 1a, 1b may be formed on at least one of the fixed shaft 1 and the sleeve 7.

A plurality of aluminum disks 8 are arranged on the outer periphery of the hub 6 with a spacer 9 interposed therebetween.
The hub 6 is fixed with screws 11 via a fixing plate 10.
A bowl-shaped rotor yoke 12 fixed to the lower portion of the hub 6
Are arranged at a predetermined interval so as to be surrounded by an annular recess 2a formed in the base 2, while the rotor yoke 1
A magnetic field is formed by fixing a driving field magnet 13 having a predetermined distance to the core 4 on the inner surface thereof. By shifting the magnetic center P of the driving field magnet 13 and the magnetic center of the core 4 by δ, the driving field magnet 13 receives an attractive force (Pz) on the core 4 side which is a magnetic body. The hub assembly 5 is always pulled toward the base 2 side.

Further, a disk-shaped flange 14 bulging from the shaft diameter is fixed to the upper end of the fixed shaft 1 by screwing, press-fitting or the like to form the flange 14 and the sleeve 7 and the hub 6. Oil collecting space 7 between the cutout
b is formed. Then, by disposing the thrust plate 15 as a sealing body on the flange 14, the shaft portion is sealed. The bearing portion configured in this manner includes a thrust direction dynamic pressure generating groove 15a such as a spiral groove or a herringbone groove formed on the lower surface of the thrust plate 15, an oil collecting space 7
b, the thrust direction dynamic pressure generating grooves 15a, the upper oil reservoir space 17, and the radial direction dynamic pressure generating grooves 1
The bearing portion can be lubricated by filling and applying a lubricant 16 such as oil or grease in a and 1b.

The driving field magnet 13 and the core 4
In a configuration in which the magnetic centers of the base 2 and the base 2 are the same, as another method of pulling the hub assembly 5 toward the base 2 side at all times, as shown in FIG. It is also conceivable to arrange the yoke piece 17 made of a magnetic material on the surface facing the field magnet 13.

In the spindle motor using the hydrodynamic bearing constructed as described above, the driving field magnet 13 rotates the hub 6 by energizing the winding 3.
When the rotation starts, the sleeve 7 is centered and floated with respect to the fixed shaft 1 by the pumping force of the radial dynamic pressure groove, and the flange 14 floats with respect to the thrust plate 15 by the pumping force of the thrust dynamic pressure generating groove 15a. The hub 6 rotates without contacting the fixed shaft 1.

[0009]

The above-mentioned FIG.
In the motor shown in (1), since the magnetic centers of the driving field magnet 13 and the core 4 are positively shifted by δ, the effective magnetic flux for driving the motor is reduced and the desired driving torque is obtained. A problem occurs that cannot be done.

On the other hand, the driving field magnet 13 and the core 4
The magnetic center of the and the
The configuration of FIG. 13 that pulls toward the side has a problem that the magnetic field of the driving field magnet 13 causes an eddy current loss in the yoke piece 17 due to the rotation of the rotor and increases the motor current. Further, since the driving field magnet 13 is located outside of the center of rotation, the moment in which the rotor moves up and down due to the thrust direction force becomes large, which causes an increase in peer tone and a large noise reduction characteristic of the fluid bearing. There was a problem that could not show its characteristics.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is a rotary body for holding a disc which is rotatably supported by a fixed portion via a dynamic pressure bearing portion, and the rotary body. A driving field magnet disposed in the driving field magnet, a yoke having a winding disposed in the fixed portion with a predetermined gap from the driving field magnet, and a driving field magnet disposed inside the driving field magnet. The present invention provides a spindle motor that magnetically attracts the rotating body to the fixed portion in the thrust direction by magnetic attraction means provided on the rotating body and the fixed portion.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a spindle motor according to the present invention will be described below in detail with reference to FIGS. For convenience of explanation, the same components as those shown above are designated by the same reference numerals, and a detailed description of the operation is omitted.

FIG. 1 shows a first embodiment of the present invention. In this embodiment, the magnetic centers of the driving field magnet 13 and the yoke 4 are made to coincide with each other, and the driving field magnet is shown. At the open end located on the base 2 side of the sleeve 7 near the center of rotation of 13, the attraction magnet 18 for attracting the N-pole or S-pole single-pole magnetic pole in the magnetized thrust direction is fixed, while the attraction An attracting magnet 18b magnetized with a single-pole magnetic pole facing each other for attracting each other is embedded in an annular recess 2b formed on the base 2. In order to apply a thrust force to the rotor, it goes without saying that one may be a magnet for attraction and the other a magnet.

As a result, the rotor (hub assembly) does not use the self-attracting action of the driving field magnet 13, but the attracting magnet 18a and the attracting magnet 18b.
Is attracted to the base 2 side by the suction force of. Therefore, the motor can effectively utilize the magnetic flux of the driving field magnet 13 and does not cause a decrease in torque. Further, since the acting force in the thrust direction is close to the center of rotation, the moment for moving the hub assembly 5 up and down becomes small, and vibration and noise can be reduced.

2 to 8 show another embodiment of the present invention in which the magnetic field centers of the driving field magnet 13 and the yoke 4 are made coincident with each other. The second embodiment shown in FIG. That is, a single-pole magnetized cylindrical magnet 18a for attraction is fixed in the vertical direction (axial direction) to the inner peripheral surface of the recess 6a of the hub 6 facing the sleeve 7, while being concentric with the magnet for attraction 18a. The hub assembly 5 is magnetically attracted to the base 2 side by fixing a single-pole-magnetized cylindrical attraction magnet 18b having a magnetic center shifted by δ on the base 2.

In the third embodiment shown in FIG. 3, a cylindrical magnet 18b having a single-pole magnetization in the vertical direction is fixed on the base 2 on the sleeve 7 side, and the magnet 18 is attracted.
b, a yoke piece (or a magnet for attraction) 19 for magnetic attraction is fixed in the recess 6a of the hub 6 outside the attraction magnet 18b and so as to cover a part of the upper surface and side surfaces, and the magnetic center is displaced. It is a form.

The fourth embodiment shown in FIG. 4 is a single-pole-magnetized cylindrical magnet 18b for attraction as in the embodiment of FIG.
Is fixed to the base 2 close to the sleeve 7 side, and the other end 12 of the rotor yoke 12 opposite to the driving field magnet 13 is fixed.
This is a form in which a is opposed to a part of the attraction magnet 18b in the recess 6a and the magnetic center is displaced.

In the fifth embodiment shown in FIG. 5, the attraction magnet 18b is fixed in the recess 2b formed on the fixed shaft 1 side of the base 2, while the other end 12 of the rotor yoke 12 is fixed.
In this configuration, a is made to face a part of the attraction magnet 18b and the magnetic center is shifted.

Further, in the sixth embodiment shown in FIG. 6, a single pole disk-shaped magnet for attraction 18c is fixed to the upper surface of the base 2 near the sleeve 7 side, and the other end 12a of the rotor yoke 12 is fixed.
Is entirely opposed to the attraction magnet 18c in the axial direction, and the rotor yoke 12 (hub assembly 5) is magnetically attracted in the axial direction.

Further, a seventh embodiment shown in FIG. 7 is a hub 6
A cylindrical magnet for suction 18a on the outer peripheral surface of the recess 6a
Is fixed, and the attraction magnet 18a is opposed in a recess 2c formed in the base 2 so that a part of the mounting end surface of the yoke 4 with respect to the base 2 is exposed to shift the magnetic center.

In the eighth embodiment shown in FIG. 8, a part of the yoke 4 on the base 2 on the side of the fixed shaft 1 is extended, and the attraction magnet 1 is attached to the lower surface of the hub 6 facing the extended part.
By fixing 8d, the (hub assembly 5) is magnetically attracted in the axial direction.

In the above-described embodiment, when the hub assembly is pulled toward the base side, various forms such as a combination between the attraction magnets and a combination of the attraction magnet and the magnetic piece are conceivable. The present invention is not limited to the embodiment described above.

Based on the configuration described above, FIG.
A general comparison between the concept of the configuration of the present invention and the conventional spindle motor in which the magnetic centers of the driving field magnet 13 and the core 4 are deviated as shown in FIG. In order to obtain the attraction force FZ in the thrust direction, the magnetic attraction force on the fixed shaft 1 side is inside the driving field magnet 13 with respect to the distance R on which the magnetic attraction force by the driving field magnet 13 acts. With the configuration of the present invention in which the acting distance r is set, the moment for moving the hub up and down is reduced, and vibration and noise can be reduced.

Further, by magnetizing the attracting magnet with a single pole, the magnetic flux in the yoke does not change even when the rotor rotates, so that the eddy current loss becomes small and the steady current can be reduced. Furthermore, since the magnetic flux of the driving field magnet can be effectively used for driving, the counter electromotive voltage increases,
Alternatively, the driving field magnet can be made smaller, which can contribute to downsizing of the motor.

FIGS. 10 and 11 show data obtained by measuring the level of the frequency component of noise in the structure of the present invention and the conventional structure. It is necessary to make the frequency component protruding from the envelope level as close to the envelope as possible. In this embodiment, the rotation speed is 5200 rpm, the number of poles of the driving field magnet is 8, and the slot 12 of the yoke is a three-phase driving motor. Therefore, in the conventional configuration shown in FIG. 11, the switching frequency component of the carp has a coil switching frequency component of 2080 Hz of 3
Although it projects at 6 dB, the present invention provides a noise reduction effect improved by 10 dB or more as shown in FIG.

[0026]

According to the spindle motor according to the present invention described in detail above, there is no change in the magnetic flux in the yoke due to the rotation of the rotor, the eddy current loss becomes small, and the steady current can be reduced. Furthermore, since the magnetic flux of the driving field magnet can be effectively used for driving, the counter electromotive voltage increases,
Alternatively, it is possible to reduce the size of the driving field magnet, contribute to downsizing of the motor, and reduce noise.

[Brief description of the drawings]

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

FIG. 2 is a half sectional view showing a second embodiment of the spindle motor of the present invention.

FIG. 3 is a half sectional view showing a third embodiment of the spindle motor of the present invention.

FIG. 4 is a half sectional view showing a fourth embodiment of the spindle motor of the present invention.

FIG. 5 is a half sectional view showing a fifth embodiment of the spindle motor of the present invention.

FIG. 6 is a half sectional view showing a sixth embodiment of the spindle motor of the present invention.

FIG. 7 is a half sectional view showing a seventh embodiment of the spindle motor of the present invention.

FIG. 8 is a half cross-sectional view showing an eighth embodiment of the spindle motor of the present invention.

FIG. 9 is a half cross-sectional view of a spindle motor for comparing the configuration of the present invention and the conventional configuration.

FIG. 10 is data obtained by measuring the level of a frequency component of noise in an example of the present invention.

FIG. 11 is data obtained by measuring the level of noise frequency components in a conventional spindle motor.

FIG. 12 is a half sectional view showing an example of a conventional spindle motor.

FIG. 13 is a half sectional view showing another example of a conventional spindle motor.

[Explanation of symbols]

1 ... Fixed shaft, 2 ... Base, 4 ... Yoke, 5 ... Hub assembly, 6 ... Hub, 7 ... Sleep, 12 ... Rotor yoke, 1
3 ... driving field magnets, 18a, 18b ... attraction magnets.

Claims (4)

[Claims] 1. A rotating body for holding a disk rotatably supported by a fixed portion via a dynamic pressure bearing portion, a driving field magnet arranged on the rotating body, and the driving field magnet. A yoke having a winding wire disposed in the fixed portion with a predetermined gap, and a magnetic attraction means disposed inside the driving field magnet and provided in the rotating body and the fixed portion. A spindle motor that magnetically attracts the rotating body to the fixed portion in a thrust direction. 2. The magnetic attraction means comprises a yoke or another attraction magnet facing the attraction magnet provided on one of the rotating body and the fixed portion.
The spindle motor as described. 3. The spindle motor according to claim 1, wherein the magnetic attraction means shifts the magnetic center in the thrust direction to apply a magnetic attraction force in the thrust direction to the hub. 4. The magnetic attraction means comprises a part of a rotor yoke for holding the driving field magnet, and is composed of an attraction magnet arranged in the fixed portion.
The spindle motor described in 3.