JPH0116364Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a brushless motor that rotationally drives a magnetic disk.

BACKGROUND ART Conventionally, brushless motors of this type used in electronic computers and the like have been constructed so that the entire motor is shielded with a large steel plate having a thickness of 1 mm or more in order to prevent magnetic noise and flux. However, with such a structure, there were problems in making it lighter, thinner, and smaller. In particular, the shaft, which is rotatably held by a bearing, is inserted into the motor housing along the axis of the cylindrical part, and when the shaft rotates, grease from the bearing is scattered in a mist and becomes magnetic. A magnetic fluid seal is attached to the inner peripheral surface of the upper end of the cylindrical part in order to prevent fine dirt and dust in the air from entering the magnetic disk mounting side. Due to the influence of this magnetic fluid seal, magnetic noise and flux are generated in the magnetic disk device, causing problems.

The present invention solves these conventional problems, reliably prevents magnetic noise and flux in magnetic disk drives, and also reliably prevents fine dirt and dust from entering and leaving the shaft insertion part. The purpose is to make the entire motor lighter, thinner, and smaller so that it does not become an obstacle and can be manufactured at low cost. Therefore, the features of the present invention include, in a brushless motor that rotationally drives a magnetic disk, a magnetic liquid seal attached to the inner peripheral surface of the upper end of the cylindrical portion of the housing into which the rotary shaft is inserted; A magnetic shield cover material made of a high magnetic permeability material is provided between the magnetic disk mounting plate fixed to the upper end.

Hereinafter, the present invention will be explained in detail based on the illustrated embodiments.

In FIG. 1, reference numeral 1 denotes a brushless motor that rotationally drives magnetic disks 2, and is equipped with a housing 3 made of a non-magnetic material such as aluminum, into which bearings 4, 4 are fitted. It consists of a cylindrical portion 5 and a housing flange 6 that protrudes largely from the outer peripheral surface of the cylindrical portion 5 in the shape of an outer flange. The outer peripheral edge of the flange 6 is provided with mounting holes (not shown) at a suitable number of locations, and a pilot protrusion 7 is provided on the back surface (bottom surface in the figure), which is indicated by the imaginary line. The housing 3 is fitted into the hole 9 of the other member 8 (as shown), and the housing 3 is fixed to the other member 8 by inserting screws, bolts, etc. into the mounting hole.

Reference numeral 10 denotes a stator attached to the outer peripheral surface of the lower end of the cylindrical portion 5 of the housing 3. Reference numeral 11 denotes a rotary shaft, which is rotatably held by the bearings 4, 4, and is inserted through the cylindrical portion 5 along its axis, and has a shallow dish-shaped rotor 12 fixed to the lower end of the figure. Ru. Magnetic poles 13 made of permanent magnets are attached to the inner surface of the rotor 12, and a rotor position detector made of a Hall element (not shown) detects the stator 10...
control the magnetic poles of the

14 is a magnetic liquid seal attached to the inner peripheral surface of the upper end of the cylindrical portion 5 of the housing 3, and includes a magnet body 17 in which a permanent magnet 15 is sandwiched between two iron plates 16, 16, and the magnet body. 17 and a magnetic fluid 18 (for example, manufactured by Nippon Ferrofluidics Co., Ltd.) injected and held in a small gap between the shaft 11 and the magnetic fluid 18 (trade name: Ferrofluidics Seal, manufactured by Nippon Ferrofluidics Co., Ltd.). That is, as shown in FIG. 2, the magnetic fluid 18 is held in the small gap by the dispersed fine powder magnetic material 19 being attracted to the magnet 17, and the magnetic fluid 18 is held in the cylindrical portion 5.
The top opening of is sealed. Then, when the shaft rotates, grease and the like from the bearing 4 is prevented from entering the magnetic disk mounting side in the form of mist, and minute dirt and dust in the air is prevented from entering the magnetic disk mounting side.

Reference numeral 20 denotes a magnetic disk 2 mounting plate fixed to the upper end of the shaft 11. The mounting plate 20 has a fitting hole 21 in the center, fixes the shaft 11 in a fitting shape, and has a disk-shaped upper wall portion. 22 is provided with screw holes 24 for attaching the presser plate 23, and furthermore, a cylindrical portion 25 is suspended from the outer peripheral edge of the disc-shaped upper wall portion 22, and an outer flange-shaped receiving portion 26 is provided at the lower end of the cylindrical portion 25. is installed protrudingly. Further, a plurality of holes 27 are provided through the cylindrical portion 25 in the radial direction.

FIG. 1 illustrates a case where three magnetic disks 2... are attached to the cylindrical part 25 of the mounting board 20 via spacers 28, 28, but of course the number of magnetic disks 2... is limited to three. It can be increased or decreased freely. Specifically, the lowermost magnetic disk 2 is received by the outer flange-shaped receiver 26, and the spacer 28 is stacked on top of this, followed by the magnetic disk 2, and then clamped with the holding plate 23. can be installed.

29 is an access arm, and 30... is a magnetic head attached to the tip of this access arm 29, which moves in the radial direction of the magnetic disk 2... from a stationary part, that is, a predetermined position on the other member 8 and the housing 3. . Then, information is written to and read from the magnetic disk 2.

Reference numeral 31 denotes a magnetic shield thin plate made of a high magnetic permeability material and attached to the back surface 6a of the housing flange 6 with an adhesive or the like. This magnetic shield thin plate 31
is formed in an annular shape and is coaxially attached to almost the entire surface of the back surface 6a of the flange 6. Further, as the magnetic shielding thin plate 31, any material with high magnetic permeability is sufficient, and for example, materials such as permalloy, supermalloy, permendile, silicon steel plate, iron plate, etc. can be used.

That is, as shown by arrow G in FIG.
The influence of the magnetic field near zero can be effectively blocked.

32 is a magnetic liquid seal 14 attached to the inner peripheral surface of the upper end of the cylindrical portion 5 of the housing 3;
This is a magnetic shield cover material provided between the magnetic disk mounting board 20 and the same material as the magnetic shield thin plate 31 is used.

Specifically, the magnetic shield cover material 32 is attached to the upper end of the cylindrical portion 5 of the housing 3 via an adhesive, and the upper end opening of the cylindrical portion 5 is closed to seal the magnetic liquid seal 14 into the cylinder. It is sealed in part 5.

That is, as shown in the enlarged view of FIG. 2, by allowing the magnetic flux to pass through the magnetic shield cover material 32, the influence of the magnetic field on the magnetic disk 2 and the magnetic head 30 can be effectively blocked, and the magnetic disk mounting board 20 can be effectively blocked. Holes 27 provided through the holes 27 and the receiving portions 2
The magnetic shield cover material 32 prevents external fine dirt and dust from entering the housing 3 through the gap between the lower end or inner peripheral side of the housing 3 and the housing 3.

The one shown in FIG. 3 is another embodiment, in which the housing 3 has a shape in which a flange 6 is protruded from the outer peripheral surface of the upper end of a cylindrical portion 5, and a magnetic shielding cover material 32
, the entire surface 6b of the flange 6 and the cylindrical portion 5
the cylindrical part 5.
The opening at the top end is sealed tightly.

Note that the present invention is not limited to the illustrated embodiment; for example, it is preferable to provide the magnetic shielding thin plate 31 attached to the back surface 6a of the flange 6 on the entire front surface 6b of the flange 6 in FIG. It is also preferable that the magnetic shielding thin plate 31 is made into a rectangular or fan-shaped shape and attached only to a portion of the front surface 6b of the flange 6 in the circumferential direction corresponding to the magnetic head 30. In this case, it is generally used for computers, etc. In this magnetic disk device, the position of the magnetic head 30 is determined depending on the model, so in order to correspond to this position, the magnetic shield thin plate 31 is installed in advance as a single brushless motor 1.
be attached to a designated location. and,
If magnetic noise cannot be sufficiently prevented by the internal magnetic circuit of the motor alone, countermeasures can be easily taken from the outside (front surface) of the motor.

According to the effect of the embodiment of the present invention, as shown in FIG. Together with the magnetic shield cover material 32, the influence of the magnetic field on the magnetic disk 2 and the magnetic head 30 can be completely blocked, and a sufficient magnetic noise prevention effect can be obtained. Further, as shown in FIG. 3, a single magnetic shield cover material 32 is attached so as to cover the entire surface 6b of the flange 6 of the housing 3 and the upper end opening of the cylindrical portion 5. It has a simple structure that also serves as the magnetic shield thin plate 31 in the process, and is extremely easy to manufacture.

The present invention has effectively achieved the intended purpose with the configuration detailed above. In particular, since the magnetic shield cover material 32 made of a high magnetic permeability material is provided between the magnetic liquid seal 14 attached to the inner peripheral surface of the upper end of the cylindrical portion 5 of the housing 3 and the magnetic disk mounting board 20,
The structure is simple, the volume is not increased at all, the motor can be made compact, and a lightweight and thin motor can be easily obtained. Of course, it can be manufactured at low cost and is extremely easy to manufacture.

In particular, when the magnetic noise from the drive motor of a magnetic disk device is large, information writing and
Although reading errors may occur and cause serious trouble, the above-described configuration can reliably block magnetic noise and flux. Furthermore, it prevents minute external dirt and dust from entering the housing 3 through the holes 27 formed through the magnetic disk mounting board 20, making it possible to withstand long-term use with extremely few breakdowns. .

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing one embodiment of the present invention;
The figure is an enlarged sectional view of a main part, and FIG. 3 is a half-cut sectional view of another embodiment. 2...Magnetic disk, 3...Housing, 5...
...Cylindrical part, 11...Shaft, 14...Magnetic liquid seal, 20...Magnetic disk mounting board, 32...
Magnetic shield cover material.

Claims (1)

[Scope of utility model registration request] In the brushless motor that rotationally drives the magnetic disks 2..., a magnetic liquid seal 14 is attached to the inner circumferential surface of the upper end of the cylindrical portion 5 of the housing 3 through which the rotating shaft 11 is inserted, and A brushless motor characterized in that a magnetic shield cover material 32 made of a high magnetic permeability material is provided between the magnetic disk mounting board 20 and the magnetic disk mounting board 20.