JP3463050B2 - Disk drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus using a disk, and more particularly to a disk drive of an apparatus using a magneto-optical disk. 2. Description of the Related Art In recent years, the miniaturization of equipment using a disk has been advanced, the size and weight of a magnetic disk have been increased, and the capacity of a magnetic disk has been advanced. In response to the above demand, it is necessary to reduce the size and thickness of a magnetic disk drive used for a magneto-optical disk. In this case, if the magnetic disk drive is downsized, it is difficult to maintain the chucking force of the downsized magnet for chucking the magneto-optical disk, and the leakage of the magnetic field lines from the chucking magnet causes various characteristics of the spindle motor. The adverse effect of this occurs. A conventional example of a magnetic disk drive will be described with reference to FIGS. In FIG. 8, reference numeral 201 denotes a magneto-optical disk,
202 is a disk hub, 203 is a shaft, 204 is a ball bearing, 206 is a chucking magnet, 207 is a shaft fastening part, 208 is a rotor hub, 209 is a magnetic yoke, 210 is a field magnet, 211 is a stator core, 213 is a printed board, 214 is a housing. The rotor section is assembled as follows. A rotor hub 208 for mounting and positioning the magneto-optical disk 201 is fastened to the shaft 203 via a shaft fastening portion 207. At the center of the lower surface of the magneto-optical disk 201 mounted on the rotor hub 208, there is provided a disk hub 202 formed of a soft magnetic material. The disk hub 202 is magnetically attracted to move the magneto-optical disk 201 to the rotor hub 208. Is fixed to the rotor hub 208.
A substantially cylindrical magnetic path yoke (also referred to as a rotor frame) 209 is coaxially attached to the outer periphery of the rotor hub 208, and the inner surface of the magnetic path yoke 209 has a hollow cylindrical shape and is attached to multiple poles. A field magnet 210 which is magnetized and has 12 poles is attached. The stator is assembled as follows. The shaft 203 of the rotor section is connected to the ball bearing 20.
Housing 21 rotatably supported via 4, 204
A 9-slot stator core 211 around which a coil 212 is wound is fixed to the outside of the cylindrical portion 4. A printed circuit board 213 on which elements such as an IC for driving a driving device are mounted is mounted on an upper surface of a disk portion following the base of the cylindrical portion of the housing 214. The configuration of the conventional driving unit is a brushless spindle motor having a 9-slot stator core 211 and a 12-pole field magnet 210. The chucking magnet 206 is magnetized in a four-pole magnetized pattern, as shown in FIG. Since the rotor hub 208 is made of a non-magnetic material, and there is no member of the magnetic path yoke 209 at the center of the rotor hub 208, the magnetic flux of the chucking magnet 206 reaches the inside of the motor. That is, as shown in FIG. 9, when the number of poles is four, the mechanical angle of one pole becomes 90 °, which is more than twice the mechanical angle of the stator core 211 having nine slots. If the distance between the chucking magnet 206 and the stator core 211 of the motor is shortened to reduce the height of the motor, the lines of magnetic force of the chucking magnet 206 can easily enter the magnetic circuit of the motor. Accordingly, in the above-described conventional configuration, the magnetic lines of force of the chucking magnet 206 attached to the rotor hub 208 are fixed to the stator core 211.
, And affects the magnetic field lines of the coil 212. That is, vibration occurs at a frequency that is an integral multiple and half of the number of poles of the chucking magnet 206, and causes rotation of the motor during reading and writing during use. An object of the present invention is to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a thin disk drive which is less susceptible to leakage of magnetic field lines of a chucking magnet. In order to solve the above-mentioned problems, a disk drive device according to the present invention is provided with a disk-shaped disk mounted on a magneto-optical disk having a disk hub on a lower surface and mounted on an upper surface. A substantially disk-shaped rotor hub for fixing the magneto-optical disk by a magnetic attraction between the chucking magnet and the disk hub, a cylindrical magnetic path yoke attached to the outer periphery of the rotor hub, and an inner side of the magnetic path yoke. , A rotor portion comprising a shaft having one end fastened to the center of the rotor hub, a housing rotatably supporting the shaft, and the housing facing the field magnet. In the disk drive device having a stator portion and a stator portion including a coil attached to the chucking magnet, This has a magnetic pole part which is divided radially and magnetized,
The number of poles of the magnetic pole portion is k, and the number of poles of the field magnet is p.
In this case, k ≠ p and k> p / 2. As a result of various studies, the influence of the magnetic field lines of the chucking magnet on the stator core has been found to occur when two or more poles of the field magnet enter the closed loop of the magnetic field lines. Therefore, the relationship between the number of poles p of the field magnet and the number k of poles of the chucking magnet is k ≠ p, k> p.
/ 2, the magnetic field line MR of the chucking magnet
Is as shown in FIG. 3 and does not affect the characteristics of the motor. Hereinafter, a reference example and an embodiment of the present invention will be described. In the first reference example shown in FIG. 1, the main body of the disk drive device is the same as the conventional example shown in FIG. 8, but the chucking magnet 206 of the conventional example shown in FIG. One feature is that the chucking magnet 6 of the reference example is changed. In FIG. 1, the chucking magnet 6
Has N poles 21 and 21 and S poles 22 and 22 arranged in parallel with each other. Compared to the conventional example shown in FIG. 9, in the conventional example shown in FIG. 9, the chucking magnet 206 having the diameter D is radially divided into four poles. The width a increases as a = πD / 4 (1), and the height of the magnetic field line from the N pole to the S pole increases. Is getting higher. On the other hand, in the first reference example of FIG. 1, the chucking magnet 6 having the diameter D is divided into four poles in parallel, so that the width a of each pole is a = D / 4. (2), which is 1 / π as compared with the conventional example. That is, the conventional chucking magnet 2
The passing path of the magnetic field line MR of No. 06 becomes higher in proportion to a = πD / 4, but the passing path of the magnetic field line MP of the chucking magnet 6 of the first reference example becomes lower in proportion to a = D / 4, and The influence of the line of magnetic force MP of the king magnet 6 on the stator core 11 is reduced. An embodiment of the present invention will be described with reference to FIGS. In FIG. 2 which is a sectional view of a disk drive device using the dynamic pressure bearing 3, and FIG. 3 which is a perspective view of a chucking magnet 6 which is radially divided into a large number of magnetic poles, 1 is a magneto-optical disk, 2 is a disk hub, 3 is a shaft, 4 is a sleeve part, 5 is a bottom plate, 6 is a chucking magnet, 8 is a rotor hub, 9 is a magnetic yoke, 10 is a field magnet, 11 is a stator core, 12 is a coil, 1
Reference numeral 3 denotes a printed board, 14 denotes a housing, and 15 denotes a shaft fastening portion of the rotor hub 8. The rotor section is assembled as follows.
Rotor hub 8 for mounting and positioning magneto-optical disk 1
Are fastened to the shaft 3 via the shaft fastening portion 15. Magneto-optical disk 1 mounted on rotor hub 8
A disk hub 2 made of a soft magnetic material is provided
A chucking magnet 6 radially divided into multiple poles serving to fix the magneto-optical disk 1 to the rotor hub 8 by magnetically attracting the disk hub 2 is fixed to the upper surface of the rotor hub 8. I have. A substantially cylindrical magnetic path yoke (also referred to as a rotor frame) 9 is coaxially mounted on the outer periphery of the rotor hub 8, and a p pole (p is a multiple of 2) is provided on the inner surface of the magnetic path yoke 9. ) Is attached to the magnetized cylindrical field magnet 10. The stator is assembled as follows. Inserting the shaft 3 of the rotor portion into the cylindrical inner surface of the sleeve portion 4 having a cylindrical inner surface formed with a herringbone groove for generating dynamic pressure via oil and causing the shaft 3 to float and rotate in a non-contact manner; A rotor hub 8 of the rotor portion is fixed to a predetermined position on an upper portion of the shaft 3, and a lower end of the shaft 3 slides on a bottom plate 5 provided on a bottom portion of the sleeve portion 4. Outside the cylindrical portion of the housing 14 that rotatably supports the shaft 3 via the sleeve portion 4,
The stator core 11 having m slots (m is a multiple of 3) around which the coil 12 is wound is fixed. The housing 1
4 is a printed circuit board 1 on which elements such as an IC for driving a driving device are mounted
3 is attached. The operation of this embodiment will be described with reference to FIGS. In FIG. 3, since the magnetic field lines MR of the chucking magnet 6 divided into multiple poles are the south pole on the back side of the north pole, the magnetic field line MR on the front side and the magnetic field line MR on the back side are formed.
Form a closed loop. The height of the closed loop of the line of magnetic force MR is also determined by the strength of the magnetic pole, but the magnetic pole a = πD / 4 at the outer periphery of the chucking magnet 6 shown in equation (1). (1) It is also determined by the width a. However, the influence of the magnetic field lines MR of the chucking magnets 6 on the stator core 11 has been examined in various ways, and as a result, the stator core 11 is included in the closed loop of the magnetic lines MR.
Has been found to occur when more than one pole enters. Accordingly, the relationship between the number of poles p of the field magnet 10 and the number k of poles of the chucking magnet 6 is given by the following equation (3).
If there is a relationship shown in the following, k ≠ p, k> p / 2 (3) The magnetic force line MR of the chucking magnet 6 is Does not affect the characteristics of The degree of the effect on the stator core 11 and the field magnet 10 is determined by the distance between the chucking magnet 6. In the structure shown in FIG. 2, the influence on the stator core 11 is greater. A second reference example will be described with reference to FIGS. The feature of this embodiment lies in the shape of the chucking magnet 6 shown in FIGS. The basic feature is that, as shown in FIGS. 4 and 5, the chucking magnet 6 is concentrically divided and magnetized. FIG. 4 shows that the chucking magnet 6 is only magnetized concentrically inside and outside.
In the one shown in FIG. 5, a part of the internal magnetic pole communicates with the outside, and the boundary between the N pole and the S pole is connected on both sides through the outer peripheral side surface, which is a one-stroke in general. The patterns of FIGS. 4 and 5 make it easy to attach a magnetized electric wire to the magnetized yoke when magnetizing with the magnetized yoke. In the case of the above-mentioned concentric magnetic poles, since the magnetic field lines MC are in the radial direction, they do not pass through the electrodes of two or more stator cores 11 or the electrodes of two or more field magnets 10. The lines of magnetic force MC of the chucking magnet 6 do not affect the magnetic circuit of the motor. A third reference example will be described with reference to FIG. Referring to FIG. 6, a feature of the third embodiment is that a stepped portion 6 a is provided on the outer peripheral portion of the chucking magnet 6 in a direction approaching the disk hub 2. In the third reference example, the rotor hub 8 is also provided with a step 8a corresponding to the step 6a. By providing the stepped portion 6a, the distance between the chucking magnet 6 and the disk hub 2 is reduced in the portion of the stepped portion 6a, thereby increasing the magnetic attraction between the chucking magnet 6 and the disk hub 2. Is more stable than in the conventional example. Further, since the distance between the chucking magnet 6 and the stator core 11 is large in the step 6a, the amount of magnetic force lines of the chucking magnet 6 leaking to the stator core 11 is reduced. A fourth reference example will be described with reference to FIG. Referring to FIG. 7, a feature of the fourth embodiment is that a chucking yoke plate 6b made of an iron-based material is provided between the chucking magnet 6 and the rotor hub 8 made of a nonmagnetic material. In this manner, in the conventional example, since the rotor hub 8 is made of a non-magnetic material, the lines of magnetic force of the chucking magnet 6 pass through the rotor hub 8 and the stator core 11
In the fourth embodiment, the chucking yoke plate 6b made of an iron-based material has the effect of shielding the magnetic lines of force of the chucking magnet 6. According to the present invention, since the magnetic lines of force of the chucking magnet do not affect the characteristics of the motor, it is possible to provide a thin disk drive having less adverse effects of leakage of the magnetic lines of force of the chucking magnet.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a chucking magnet of a first reference example. FIG. 2 is a sectional view of an embodiment of the present invention. FIG. 3 is a perspective view of a chucking magnet according to the embodiment of the present invention. FIG. 4 is a perspective view of a chucking magnet of a second reference example. FIG. 5 is a perspective view of a chucking magnet of a modification of the second reference example. FIG. 6 is a sectional view of a third reference example. FIG. 7 is a sectional view of a fourth reference example. FIG. 8 is a sectional view of a conventional example. FIG. 9 is a perspective view of a conventional chucking magnet. [Description of Signs] 1 magneto-optical disk 2 disk hub 3 shaft 6 chucking magnet 8 rotor hub 9 magnetic path yoke 10 field magnet 11 stator core 12 coil 14 housing

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-144168 (JP, A) JP-A-7-29297 (JP, A) JP 6-68139 (JP, U) JP 6-139 11164 (JP, U) Japanese Utility Model Hei 6-43863 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 17/022-17/035 G11B 19/20 H02K 21/22

Claims (1)

(57) Claims 1. A magneto-optical disk having a disk hub on a lower surface is mounted thereon, and the light is generated by a magnetic attractive force between a disk-shaped chucking magnet provided on an upper surface and the disk hub. A substantially disk-shaped rotor hub for fixing a magnetic disk, a cylindrical magnetic path yoke mounted on the outer periphery of the rotor hub, a field magnet mounted inside the magnetic path yoke, and a central portion of the rotor hub. It has a rotor portion including a shaft with one end fastened, a housing rotatably supporting the shaft, and a stator portion including a stator core and a coil attached to the housing so as to face the field magnet. In the disk drive device, the chucking magnet has a magnetic pole portion which is radially divided and magnetized, and the number of poles of the magnetic pole portion is reduced. , The number of poles of the field magnet in the case of a p, k ≠
A disk drive device, wherein p, k> p / 2.