JP3023752B2 - Disk drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor mounted on a disk drive and used for rotating a disk, and more particularly to a drive magnet.

[0002]

2. Description of the Related Art Conventionally, there has been a disk drive of this type as shown in FIG. That is, the device disclosed in Japanese Patent Publication No. Hei 4-22297 shown in FIG.
In a magnetic disk motor having a shaft 6 whose both ends are supported by at least a pair of bearings 5a and 5b in a cylindrical hub 1 for supporting a magnetic disk, a cover 11 is provided outside one bearing 5a and the other is provided. Outside the bearing 5b, there is a dust-proof seal structure of a magnetic disk motor constituted by providing a washer 13 covering at least a part of the shield 12 of the bearing 5b.

In the above-described disk drive device, the drive magnet 2 of the magnetic disk motor is generally made of Nd-Fe-B-based magnetic powder by compression molding. Here, Nd used rare earth neodymium, Fe used transition metal iron, and B used boron-based boron. However, according to this compression molding method, the drive magnet 2 can be manufactured only in a simple annular shape, and dust such as oil mist generated from the inside of the bearing 5b is shielded by connecting the washer 13 to the lower shield 5b. 12 and a structure that covers the shield 12. However, there is a slight gap S between the shield 12 and the washer 13,
Dust from inside the bearing 5b may leak through the gap S, and the dust cannot be completely shut off.

In the drive magnet 2 formed by compression molding, a metal which is easily oxidized is exposed on the surface, and in general, coating with an epoxy resin or the like is indispensable as a surface treatment for rust prevention. That is, as shown in FIG. 6, the outer peripheral surface of the stator core 7 fixed to the shaft 6 is coated with an insulating resin 14, and the outer peripheral surface of the drive magnet 2 fixed to the hub 1 is coated with a rust prevention resin. 15 are painted. here,
The closer the magnetic surface facing between the outer circumference of the stator core 7 and the inner circumference of the drive magnet 2 is, the higher the torque of the motor can be obtained. However, due to the thickness of the coating of the rust-preventive resin 15, the effective gap d, which is the gap between the opposing magnetic surfaces between the outer periphery of the stator core 7 and the inner periphery of the drive magnet 2, is widened, which increases the cost, There is also a problem that the torque constant decreases.

[0005]

Therefore, in the above-mentioned prior art, dust such as oil mist generated inside the bearing leaks from the minute gap between the shield and the washer to the outside of the motor, and adheres to the magnetic disk or the magnetic head. Or damage to the disk drive. Also, due to the thickness of the rust prevention coating on the drive magnet,
There is also a problem that the effective gap between the outer circumference of the stator core and the inner circumference of the drive magnet is widened and the torque constant of the motor is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and it is an object of the present invention to reduce the leakage of dust to the outside of a motor and to reduce the effective gap between the outer circumference of a stator core and the inner circumference of a driving magnet. Accordingly, an object of the present invention is to provide a highly reliable disk drive device by suppressing a decrease in the torque constant of the motor.

[0007]

In order to achieve the above object, the present invention provides a hub on which a disk is mounted, an annular drive magnet which is driven to rotate integrally with the hub, and a radial drive magnet which is connected to the hub. A stator core disposed opposite to the direction, a frame supporting the stator core, a shaft provided at the center of the frame, and a bearing fitted to the shaft and rotatably supporting the hub. In a disk drive device in which the hub is driven to rotate by the magnetic action of the drive magnet and the stator core, the magnet is a resin-bonded magnet containing a rare earth-transition metal-boron-based magnetic powder and a polyamide-based binder. And a plurality of groove groups for controlling the flow of air in the inner circumferential direction are formed on the end face facing the bottom of the frame. And it features. The drive magnet has six or more magnetic poles, has a residual magnetic flux density of 4,000 to 6,200 Gauss or less, and has a magnetic powder content of 48 to 73% by volume. It is characterized by the following. Further, the drive magnet is formed by injection molding, and at least an inner peripheral surface and an end surface on the frame side have a molding surface exposed.

[0008]

According to the structure of the present invention, the drive magnet is formed with a plurality of groove groups on the end face facing the bottom of the frame, so that the flow of air can be controlled in the inner circumferential direction. Leakage of dust generated inside to the outside of the motor can be reduced. Further, the drive magnet has six or more magnetic poles, and the residual magnetic flux density is 4,000 to
When the content is within 6,200 Gauss and the content ratio of the magnetic powder is 48 to 73% by volume, the cost of the motor can be suppressed and a high torque can be obtained. Furthermore, by forming the drive magnet by injection molding,
No surface treatment is required, the effective gap between the outer circumference of the stator core and the inner circumference of the drive magnet can be reduced, and a decrease in the torque constant of the motor can be suppressed.

[0009]

1 to 4 show an embodiment of the present invention. Elements having the same functions and functions as those of the prior art shown in FIGS. 5 and 6 will be described with the same reference numerals. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

A disk drive device according to the present invention shown in FIG. 1 has a hub 1 on which a disk is mounted, a rotor yoke 3 made of a magnetic material fixed to the hub 1, and a rotor yoke 3 fixed to the rotor yoke 3. Toroidal drive magnet 2
A stator core 7 radially opposed to the drive magnet 2, a frame 4 supporting the stator core 7, a shaft 6 provided at the center of the frame 4, and fitted to the shaft 6. Bearings 5a and 5b for rotatably supporting the hub 1 and the hub 1 is rotationally driven by the magnetic action of the drive magnet 2 and the stator core 7. In addition,
The cap 9 covers the ball bearing 5 a and the shaft 6.
Is fixed.

In the disk drive device as described above, wherein the maximum outer diameter of the frame 4 is larger than the inner diameter of the drive magnet 2, the drive magnet 2 is made of a magnetic powder made of a magnetic material, It is a resin-bonded magnet in which a binder made of resin and a coupling agent are mixed, and is formed of a plastic magnet.

As the magnetic material used in the plastic magnet, an R-Fe-B system is used. Here, R is a rare earth element such as lanthanum-cerium, cerium, neodymium, neodymium-praseodymium, or samarium, Fe is iron as a transition metal, and B is boron-based boron. The non-magnetic portion used as a binder other than the magnetic material used in the plastic magnet is filled with a resin.
This resin includes polyamide, phenol, epoxy,
Urethane, polybutylene terephthalate, polyphenylene sulfide, polyolefin resin, or the above 2
A combination of more than one type. Further, in the plastic magnet, a titanate-based or silane-based coupling agent is used between the magnetic powder and the resin used as the binder.

As for the magnetic properties of the plastic magnet, the residual magnetic flux density is 4,000 to 6,200 G
auss range. The lower limit is 4,000 Ga
The value of uss is limited by the size of the motor for a small hard disk motor because of the size of the motor.
The reason why the upper limit is set to 6,200 Gauss is that if the value is more than this value, the cost increases. The magnetic powder content of the plastic magnet is 48 to 7 in volume ratio.
3% is desirable. This is because the residual magnetic flux density is 4,000
This is a ratio for setting the range of 0 to 6,200 Gauss.

The drive magnet 2 can be injection-molded by using the plastic magnet, and a complicated shape can be accurately formed by injection molding. Therefore, as shown in FIG. 2, it can be manufactured in an annular shape having a step on the outer peripheral side. Further, unlike the compression-molded magnet, the injection-molded plastic magnet does not have a readily oxidizable metal exposed on the surface, and thus is not subjected to rust-preventive surface treatment.

As shown in FIGS. 3 and 4, the drive magnet 2 formed of the plastic magnet has a plurality of groove groups formed on a lower end surface 10 thereof facing the frame bottom of the drive magnet 2. In the figure, the groove 8 has an angle θ of less than 90 ° with respect to a tangent line forming the outer peripheral surface of the lower end surface of the driving magnet 2, and has a quadrangular shape in a direction opposite to the center line, and is formed inside the outer peripheral surface. It is configured in a shape penetrating toward the peripheral surface direction. The direction penetrating from the outer peripheral surface toward the inner peripheral surface is opposite to the rotational direction. Therefore, the plurality of grooves 8 form a spiral groove group for controlling the flow of air in the inner circumferential direction. The depth of each groove 8 of the groove group is preferably about 0.03 to 0.5 mm.

As shown in FIG. 2, the driving magnet is magnetized with a predetermined number of poles of 6 or more. Here, the driving magnet 2 is multipolar magnetized so that a total of six magnetic poles, three each of three north and south poles, are alternately different in the circumferential direction. Here, the number of magnetized poles will be described here. As the number of magnetized poles increases, there is an advantage that a high torque can be easily obtained even with a small motor, but conversely, the switching frequency, which is the phase switching frequency, increases, so that iron loss is reduced. Increase,
There is a disadvantage that the current consumption of the motor increases. The iron loss is determined by the product of the magnetic flux density of the magnet and the switching frequency. Therefore, in order to avoid the above drawbacks and take advantage of the above advantages, it is only necessary to slightly reduce the magnetic flux density and increase the number of magnetized poles. In other words, when the plastic magnet according to the present invention is used for the motor for a small hard disk, the number of magnetized poles is increased to increase the torque constant, and the magnetic flux density is compared with that of a conventional Nd-Fe-B-based compression molded product Therefore, the current consumption of the motor does not increase. From the above description, the number of magnetized poles is set to 6 or more.

Next, the flow of air on the lower end face 10 of the drive magnet 2 will be described. In FIG. 1, when the hub 1 rotates, air moves in the minute gap c between the lower end face 10 of the drive magnet 2 and the frame 4 facing the hub. The air in the minute gap c is generated by the lower end face 10 of the drive magnet 2.
Alternatively, if there are slight irregularities in the opposing frame 4, turbulent air flow occurs. However, when the irregularities are regulated in a specific direction, the turbulent flow becomes a constant flow.

Then, by rotating the driving magnet 2 configured as described above, the air on the lower end face 10 of the driving magnet 2 becomes, as shown in FIG.
The flow of air in the inner circumferential direction is generated as shown in (2), and this flow acts as a force for moving the air in the small gap c toward the center of the shaft 6, so that dust generated inside the bearings 5a and 5b is small. Leakage to the outside through c can be prevented.

Although the present invention has been described in detail with reference to the embodiment, the present invention is not limited to the above embodiment.
Various changes can be made without departing from the spirit of the invention. For example, if the shape of the groove is provided, the shape is a quadrilateral in the above embodiment. However, the shape is not limited to this, and the inner peripheral surface side may be a triangular shape. In the above embodiment, the motor for a small hard disk is used. However, any motor can be used as long as the disk drive motor has a maximum outer shape of the frame larger than the inner diameter of the drive magnet.

[0020]

As described above, according to the motor of the present invention, since the groove group is provided on the lower end face of the drive magnet, dust generated from inside the motor is forcibly trapped in the motor and leaks to the outside of the motor. Thus, a highly reliable disk drive can be realized. Further, according to the motor of the present invention, since the drive magnet can be manufactured by injection molding, no magnetic powder is exposed on the surface of the drive magnet after molding, so that surface treatment for rust prevention becomes unnecessary, and the outer periphery of the stator core is eliminated. And the effective gap between the drive magnet and the inner circumference of the drive magnet can be reduced, and a decrease in torque constant can be suppressed even in a small motor. Further, since complicated painting can be omitted, motors can be supplied inexpensively and in large quantities.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a disk drive device showing an embodiment of the present invention.

FIG. 2 is a perspective view of a drive magnet according to the embodiment of the present invention.

FIG. 3 is an explanatory view of a lower end portion of a driving magnet according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing the flow of air at the lower end surface of the drive magnet according to the embodiment of the present invention.

FIG. 5 is a sectional view of a main part of a disk drive device showing a conventional embodiment.

FIG. 6 is a cross-sectional view of a main part of a drive magnet section showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hub 2 Drive magnet 4 Frame 5a, 5b Bearing 6 Shaft 7 Stator core 8 Groove 10 End face

Continuation of front page (56) References JP-A-53-55105 (JP, A) JP-A-4-67357 (JP, A) JP-A-4-222432 (JP, A) JP-A-4-93468 (JP) , U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 19/20 H02K 1/27, 21/22

Claims (3)

(57) [Claims] 1. A hub on which a disk is mounted, an annular drive magnet that rotates integrally with the hub, a stator core radially opposed to the drive magnet, and supports the stator core. A frame provided at the center of the frame; and a bearing fitted to the shaft to rotatably support the hub. The hub is driven to rotate by the magnetic action of the drive magnet and the stator core. In the disk drive device, the magnet is a resin-bonded magnet including a rare earth-transition metal-boron-based magnetic powder and a polyamide-based binder, and on an end face facing the bottom of the frame,
A disk drive device comprising a plurality of groove groups for controlling an air flow in an inner circumferential direction. 2. The driving magnet has six or more magnetic poles and has a residual magnetic flux density of 4,000 to 6,200.
2. The disk drive according to claim 1, wherein the content is within Gauss and the content ratio of the magnetic powder is 48 to 73% by volume. 3. The disk drive device according to claim 1, wherein the drive magnet is formed by injection molding, and at least an inner peripheral surface and an end surface on a frame side have exposed molding surfaces.