JPH06335219A - Electric motor for floppy disk drive - Google Patents

Abstract

PURPOSE:To prevent leakage flux by providing a yoke member for passing flux from both magnets between a plurality of permanent magnets provided at a rotor. CONSTITUTION:A ring-shaped magnetic shield plate 30 is engaged to the outside of a rotating magnetic pole 9 and driving current is applied from an electric motor drive circuit provided on a substrate 1 to a stator coil winding 22 to generate a rotating magnetic field at a stator magnetic pole 21, thus rotating a rotating disc 7 by the mutual operation with the exciting flux from the rotating magnetic pole 9. Then, the exciting flux from a permanent magnet reaches an S pole of the other permanent magnet through the magnetic shield plate 30 provided inside the circumferential part of the rotar from the N magnetic pole. Then, it passes through the opposing stator magnetic pole 21 via a gap from the N pole of the permanent magnet, passes through a yoke part 31 at a root and the stator magnetic pole 21 opposing the permanent magnet, and then returns to the S pole via the gap, thus drastically reducing the magnetic reluctance of a flux passage route and at the same time reducing leakage flux.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric motor for a floppy disk drive, and more particularly to a mechanism of the electric motor for the floppy disk drive which is suitable for application to a thin floppy disk drive.

[0002]

2. Description of the Related Art A floppy disk drive is widely used as an external storage device for a computer because the floppy disk can be freely exchanged and handled easily. Recent computers are in a tendency of downsizing, and a floppy disk drive device incorporated in a microcomputer is forced to follow this tendency. In particular, the downsizing requirement in the thickness direction is strict, and in particular, an electric motor for rotating a floppy disk is allowed to have a thickness of only a few millimeters.

By the way, in the electric motor for rotating the above-mentioned floppy disk, a thin stator magnetic pole having a plurality of convex poles is attached from the center to the outside on the substrate of the floppy disk drive, and the stator is attached. A ring-shaped permanent magnet provided inside the outer peripheral edge of a thin dish-shaped disk rotatably supported at the center of the magnetic pole constitutes the rotor desired at the tip of the salient pole constituting the stator magnetic pole. The rotating magnetic field is generated in the plurality of convex poles to rotate the rotor.

[0004]

Although the above-mentioned conventional floppy disk drive device is extremely thin and small in size as described above, the electric motor used therein also generates the necessary rotational drive torque. As a matter of necessity, the ring-shaped permanent magnet provided on the rotor is a fairly strong one. On the other hand, the rotor is formed in a thin dish shape as described above, and the magnetic path of the permanent magnet moves from the N magnetic pole of the permanent magnet to the peripheral portion of the dish type rotor, and from here, the other permanent magnets. It reaches the S pole, passes from the N pole of this permanent magnet through the gap, through the stator magnetic pole wound with the stator coil facing it, and passes through the yoke portion at the base of the stator magnetic pole to face the permanent magnet. It passes through the stator magnetic pole that is wound the stator coil and returns to the S pole of the permanent magnet through the gap, but there is some gap between the permanent magnet and the dish type rotor, When a magnetic flux flows from one magnetic pole of the permanent magnet to the rotor, a large magnetic flux leakage occurs. This leakage of magnetic flux reduces the rotational torque of the electric motor, and this leakage magnetic flux extends to the magnetic medium mounted in the floppy disk drive, obstructs reading and writing of information, and may damage the recorded contents. is there.

The present invention is intended to improve the above-mentioned conventional drawbacks, and an object of the present invention is to provide a motor for a floppy disk driving device, which is a motor for a powerful floppy disk driving device which does not generate a magnetic flux leakage. To provide.

[0006]

In order to achieve the above object of the present invention, the present invention provides a plurality of permanent magnets for generating magnetic flux with respect to a stator fixed to a substrate of a floppy disk drive. In a motor of a floppy disk device including a rotating disk that is a rotatably provided rotor, between a plurality of permanent magnets provided on the rotor,
The present invention provides an electric motor for a floppy disk drive device, which comprises a yoke member that allows the magnetic flux generated from both permanent magnets to pass through.

[0008]

The exciting magnetic flux generated from the permanent magnet constituting the rotating magnetic pole passes from the N magnetic pole of the permanent magnet through the magnetic shield plate provided inside the peripheral portion of the dish-shaped rotor, and from there, the S pole of another permanent magnet. To the permanent magnet through the gap between the N pole of the permanent magnet, the stator pole wound with the stator winding facing the pole, and the yoke portion at the base of the stator pole. It passes through the stator magnetic pole wound around the existing stator winding and returns to the S pole of the permanent magnet through the gap.

[0009]

An embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a thin electric motor of a floppy disk drive device according to the present invention. The thin electric motor also includes a floppy disk chucking mechanism. In the figure, reference numeral 1 is a substrate which constitutes a floppy disk drive and is made of a ferromagnetic material such as iron. A circular hole 2 is formed in the substrate 1, and a bearing base 3 is fitted in the circular hole 2 and fixed to the substrate 1 with a screw 4. The bearing base 3 has two ball bearings 5, 6
Is stuck. Reference numeral 7 denotes a rotating disk which constitutes a rotor and rotates a floppy disk, and has a thin circular dish shape. A rotating magnetic pole 9 made of a ring-shaped permanent magnet is fixed inside the outer periphery 8 of the rotating disk 7. A speed detecting permanent magnet 10 for detecting the rotation speed of the rotating disk 7 is fixed to the lower portion of the outer circumference 8. The rotating magnetic pole 9 composed of the permanent magnet is made of a rare earth and has a ring shape as shown in FIG. A magnetic shield plate 30 made of soft iron and also formed in a ring shape is fitted on the outer side of the rotating magnetic pole. A plurality of permanent magnets are formed on the rotating magnetic pole 9 by magnetization. These permanent magnets are magnetized in the diameter direction of the rotating magnetic pole 9, and the magnetic pole directions of these permanent magnets are reversed adjacent to each other.

A brass rotary shaft mounting plate 11 is fixed to the center of the rotary disk 7, and a rotary shaft 12 is fixed to the center of the rotary shaft mounting plate 11. The rotary shaft 12 is rotatably attached to the ball bearings 1 and 6. A hole 13 is formed in the rotary disk 7, and a drive pin 14 projects from the hole 13 as shown in FIG. As shown in FIG. 4, the drive pin 14 is fixed to the other end of a spring plate 15 whose one end is fixed to the back surface of the rotary disc 7. The spring plate 15 has a mounting base portion 16, an arm portion 17 following the mounting base portion 16 and a U-shaped drive pin mounting portion 18 at the tip thereof.
A drive pin 14 is crimped onto the drive pin 8. The mounting base 15 is fixed to the back surface of the rotating disc 7 by rivets 19. In FIG. 1, 21 is a stator magnetic pole, 22 is a stator winding, and 23 is a synthetic resin stator frame. An attraction magnet 24 is attached to the surface of the rotating disk 7 about the rotating shaft 12. In FIG. 1, reference numeral 25 denotes a terminal fitted in a recess opened in the surface of the bearing base 3. Although not shown in the drawing, the conductive wire drawn from the stator winding 22 penetrates the inside of the stator frame 23 and is wound around the terminal 25, and the terminal 25 is a printed wiring formed on the surface of the substrate 1. Connected with.

Next, the operation of the present invention will be described. Figure 4
In, the dotted lines indicate the stator magnetic poles 21 and the stator windings 22. Although not shown in FIG. 1, a drive current is applied to the stator winding 22 from an electric motor drive circuit provided on the substrate 1 to generate a rotating magnetic field in the stator magnetic pole 21. Then, the rotating disk 7 constituting the rotor rotates due to the interaction with the exciting magnetic flux generated from the rotating magnetic pole 9. Then, as shown by the dotted line, the exciting magnetic flux generated from the permanent magnets constituting the rotating magnetic pole 9 passes from the N magnetic poles of the permanent magnets through the magnetic shield plate 30 provided inside the peripheral portion of the dish-shaped rotor, and from here. The stator winding 22 that reaches the S pole of another permanent magnet and faces the S pole of this permanent magnet through a gap from the stator.
Passing through the stator magnetic pole 21 wound around, passing through the yoke portion 31 at the base of the stator magnetic pole 21, passing through the stator magnetic pole 21 around which the stator winding is wound, and passing through a gap. Return to the S pole of the permanent magnet. Since the magnetic shield plate 30 is interposed in such a magnetic flux passage route, the magnetic resistance of the magnetic flux passage route is significantly reduced, and the magnetic flux extending between the permanent magnets constituting the rotating magnetic pole 9 passes through the magnetic shield plate 30. Therefore, the leakage magnetic flux is extremely small.

[0012]

As described in detail above, the present invention is
Rotation in a motor of a floppy disk drive having a rotating disk that is a rotatably provided rotor having a plurality of permanent magnets for generating magnetic flux with respect to a stator fixed to a substrate of the floppy disk drive. Since a yoke member that allows the magnetic flux generated from both permanent magnets to pass through is provided between the plurality of permanent magnets provided on the child, the magnetic resistance of the magnetic flux passage route is greatly reduced, and the drive torque of the electric motor is also increased. Moreover, since the magnetic flux passing between the permanent magnets constituting the rotating magnetic pole passes through the magnetic shield plate, the leakage magnetic flux is extremely small and does not reach the magnetic medium mounted in the floppy disk drive device. It does not interfere with reading and writing and does not destroy the recorded contents.

[Brief description of drawings]

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

FIG. 2 is a perspective view of a rotating magnetic pole and a magnetic shield plate.

FIG. 3 is a perspective view of a rotating disk.

[Figure 4] Rear view of rotating disk

[Explanation of symbols]

 1 ... Substrate 2 ... Circular hole 3 ... Bearing base 4 ... Screw 5,6 ... Ball bearing 7 ... Rotating disk 8 ... ... Outer circumference 9 ... Rotating magnetic pole 10 ... Position detecting permanent magnet 11 ... Rotating shaft mounting plate 12 ... Rotating shaft 13 ... Hole 14・ ・ ・ ・ Drive pin 15 ・ ・ ・ Spring plate 16 ・ ・ ・ Mounting base 17 ・ ・ ・ Arm 18 ・ Drive pin mounting 19 ・ Rivets 20 ・ ・・ ・ ・ Folded portion 21 ・ ・ ・ Stator magnetic pole 22 ・ ・ ・ Stator winding 23 ・ ・ ・ Stator frame 24 ・ ・ ・ Suction magnet 25 ・ ・ ・ Terminal 30 ・ ・... Magnetic shield plate 31 ... Yoke part

Claims (4)

[Claims] 1. A floppy disk device comprising a rotating disk provided as a rotor rotatably provided with a plurality of permanent magnets for generating magnetic flux with respect to a stator fixed to a substrate of a floppy disk driving device. The electric motor of the floppy disk drive device according to claim 1, wherein a magnetic shield plate that allows the magnetic flux generated from both permanent magnets to pass through is formed between a plurality of permanent magnets provided on the rotor. 2. The electric motor for a floppy disk drive according to claim 1, wherein the rotating disk is a thin dish type. 3. A plurality of permanent magnets provided on the rotating disk serving as the rotor are provided inside the outer edge of the rotating disk, and are ferrite-made permanent magnets having a ring shape. The electric motor of the floppy disk drive device described in 1. 4. The electric motor for a floppy disk drive according to claim 1, wherein the magnetic shield plate is made of a ferromagnetic metal and is closely arranged on the outer circumference of the permanent magnet.