JPS634401A - Magnetic bias generating device - Google Patents

Abstract

PURPOSE:To attain a prescribed data processing by using a cylindrical permanent magnet magnetized as multi-pole on a circumference and whose length corresponds to the size of all track width of a magnetic disk and a couple of magnetic pole pieces connected by a magnetic yoke and arranged in axis symmetry so as to have only to give a signal. CONSTITUTION:With the peripheral of the permanent magnet 3 near both magnetic pole pieces 1-1, 1-1' given as an S pole respectively, a stator winding 2 wound on a magnetic yoke 1-2 is excited so as to make both the magnetic pole pieces 1-1, 1-1' connected by the magnetic yoke 1-2 as the S pole. The S pole of the magnetic pole pieces 1-1, 1-1' and the S pole at the peripheral of the permanent magnet 3 opposing to it are repulsed with each other and the permanent magnet 3 supported freely turnably is turned counterclockwise (CCW) shown in solid line arrow or clockwise (CW) shown in broken line arrow. The polarity of the bias magnetic flux phi is inverted by having only to reverse the exciting polarity of the stator winding 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Field of Industrial Application) The present invention relates to a magnetic bias generator used in a writing device for a magneto-optical disk storage device.

(Conventional technology) Problems in the prior art will be explained with reference to FIG.

Figure 3 is a conceptual diagram of a conventional magneto-optical disk storage device.The basic function of the magneto-optical disk storage device is the same as that of other magnetic disk storage devices, and the surface of the rotating disk is made of magnetic material. A magnetic disk on which a thin film is formed is rotated at a constant speed, and a magnetic head disposed close to the magnetic disk magnetizes the magnetic thin film on the magnetic disk to store data. Data is read by detecting the voltage of the magnetic head induced by changes in the magnetic flux of a magnetized thin film of magnetic material.

In the magnetic thin film 100 formed on the surface of the magnetic disk 101 as a storage medium, the area for storing data has a width corresponding to the thickness of a magnetic head (not shown), and extends from the center of rotation of the magnetic disk 101 to the magnetic head. It forms an annular shape whose radius is the distance to the stopping position of
It is well known that a large amount of data can be stored by forming a large number of concentric tracks in the annular area.

In conventional magnetic disk storage devices, one way to increase storage capacity is to reduce the thickness of the magnetic head to narrow the track width and increase the number of tracks on the surface of the magnetic thin film 100. However, there is a problem in that reducing the thickness of the magnetic head results in a decrease in sensitivity.

Magneto-optical disk storage devices were devised to solve this problem and increase track density.

In FIG. 3(c), a magnetic bias generating bag @
Magnetic flux 115 from 105 acts almost perpendicularly to form magnetic domains 111 indicating magnetic poles on the front and back sides of the magnetic thin film 100.

The polarity of the magnetic domain 111 follows the bias magnetic flux 115 from the magnetic bias generator.

Further, a light beam 114 from the light beam generator 104 is irradiated so as to be focused on the magnetic thin film 100, and the magnetic thin film 100 irradiated with this light beam 114 is
The extremely narrow "plane" of the surface is instantaneously heated by the thermal energy of the irradiated light.

This heating causes the magnetic material used in the magnetic disk 101 to exceed its Curie point, causing the existing magnetic poles to disappear and become ready for new magnetization, that is, for storing new data. The magnetic domain 111 is the “plane” where this magnetic pole disappears.
is the magnetic flux 115 from the magnetic bias generating bag GL 105
By forming new magnetic poles, data is stored. The configuration using the light beam 114 allows heating during irradiation of the focused light to be much smaller than the critical dimension regulated by the thickness of conventional magnetic heads. The width of the 'plane' where magnetism disappears, that is, the magnetic domain 111, is small, and therefore the storage capacity can be increased to a greater extent than that of conventional magnetic disks.

However, despite the above-mentioned performance improvements, the magneto-optical disk storage devices in practical use require a linear motor 106 to move the magnetic bias generator 105 to the track position where predetermined data processing is performed. There have been problems, such as the size of the coil of the magnetic bias generator 105 for generating bias magnetic flux, which hinders miniaturization of the entire device.

(Problems to be Solved by the Invention) The present invention provides a magnetic bias generating device that does not impair storage capacity and can realize a magneto-optical disk storage device with a simple configuration.

(2) Structure of the Invention (Means for Solving the Problems) The magnetic bias generating device of the present invention is rotatably supported on a shaft and has multi-pole magnetization on its circumference, and at least its length is A cylindrical permanent magnet corresponding to the total track width of the disk is connected by a magnetic yoke, and arranged axially symmetrically with respect to the permanent magnet through a gap formed so that the size changes in the direction of rotation of the permanent magnet. The magnetic yoke is composed of a pair of magnetic pole pieces and a stator winding wound around the magnetic yoke.

(Function) In the above-mentioned configuration, a linear motor is not required to move to a predetermined track position, and predetermined data processing can be performed only by applying a signal to a fixed magnetic bias generator. In addition, it brings about other effects such as making it possible to realize miniaturization of the entire device.

(Example) The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a plan view for explaining the configuration of an embodiment of a magnetic bias generator according to the present invention and its operational steps. In this embodiment, 4 magnets are placed on the outer periphery of the permanent magnet 3 forming the rotor.
This is an example of pole magnetization, as shown in figure (a), both pole pieces 1
-1.1-1', when the outer peripheries of the permanent magnets 3 are S poles, the two magnetic pole pieces 1-1.1-1' connected by the magnetic yoke 1-2 are S poles :S''), when the stator winding 2 wound around the magnetic yoke 1-2 is excited, the S pole of the magnetic pole piece 1-1.1-1' (display: S
') and the S pole (
81 and 82) repel each other, and the rotatably supported permanent magnet 3 moves as shown by the solid arrow in the same figure.
Or, it turns CW as shown by the dashed arrow. In the example of the CCW operation indicated by the solid line arrow, the rotation operation is performed at the N pole on the outer periphery of the permanent magnet 3 located between the two magnetic pole pieces 1-1, 1-1' in FIG. ) as shown in the same figure (b).
The magnetic head (not shown, located at the top of the figure) in the vicinity of the pole (displayed at 82) is irradiated with a bias as shown in reverse by the arrows in each figure. Magnetic flux: The polarity of Φ will be reversed. Figure 1 (b
) Permanent magnet 3 in the middle position between both magnetic pole pieces 1-1゜1-1'
In order to reconvert the S pole (display: S, :S2) on the outer periphery of the stator winding 2 to the N pole, it is sufficient to reverse the polarity of the excitation current of the stator winding 2. Reversal is both pole pieces 1-1
．． 1-1' is converted to the N pole, and the result, as shown in FIG. 5(c), matches the initial state shown in FIG. 1(a).

That is, the length is such that the excitation polarity of the stator winding 2 can be changed, and the polarity of the bias magnetic flux: Φ can be changed.

Furthermore, as described above, in the above configuration, the rotation direction of the permanent magnet 3, which is a rotating body, is not stable and arbitrary when the excitation polarity of the stator winding 2 is changed, so there is a means for improving this and stabilizing the rotation direction. As illustrated in FIG. 2, both magnetic pole pieces 1-1.
1-1' are shifted in opposite directions with respect to the center of the permanent magnet 3, which is a rotating body (a), or both magnetic pole pieces 1-1.
By forming the tip of 1-1' so as to face the permanent magnet 3 with a slope (b), etc., it is possible to change the size of the air gap gll, g12 in the direction of rotation formed by both magnetic pole pieces. It may also be a configuration.

Furthermore, by making the length of the permanent magnet 3 equal to or more than the total track width of the magnetic disk, the permanent magnet 3 can be simply rotated without moving the position of the magnetic bias generator for all tracks. The structure is such that any magnetization process can be performed just by operation.

(3) Effects of the Invention Since the magnetic bias generating device of the present invention has the above-described configuration, the current direction of the winding of the yoke that connects the two magnetic pole pieces facing the permanent magnet rotor through the air gap is alternately applied. By simply switching to , it is possible to obtain a bias magnetic flux of any polarity for the entire track width of the magnetic disk, and since the only moving part is the rotor, which has a small mass, the response is fast and the configuration is only N, making it compact. It has the advantage of being lightweight.

[Brief explanation of the drawing]

FIG. 1 is a plan view for explaining an embodiment of the magnetic bias generating device according to the present invention and its operation steps, showing an initial state (a), a bias magnetic flux reversal state (b) due to the magnetization of both magnetic pole pieces, and FIG.
) and the state (C) of re-inversion of the bias magnetic flux due to reversal of the polarity of the magnetic pole, Fig. 2 is a plan view of an example of stabilizing the rotation direction of a permanent magnet according to the present invention, and Fig. 3 is a state of reversal of the bias magnetic flux due to polarity reversal of the magnetic pole. FIG. 1 is a conceptual diagram of a magnetic disk storage device, including a plan view (a), a front view (b), and an enlarged view of main parts (C). Explanation of symbols 1... Stator, 1-1.1-1'... Magnetic pole piece, 2... Stator winding, 3... Permanent magnet, 100... Magnetic thin film, 1
01...Magnetic disk, 102...Disk drive motor, 103...One plate of the entire device, 104...Light beam generator, 105...Magnetic bias generator, 106...
・Linear motor for moving magnetic bias generator, 111
...Magnetic domain, 114...Light beam, 115...Bias magnetic flux. Patent applicant Nippon Servo Co., Ltd. (a) (b) Figure 1 (a) (b) Figure 2

Claims (3)

[Claims] (1) A cylindrical permanent magnet that is rotatably supported and magnetized with multiple poles on its circumference, and a pair of magnetic poles that are connected by a magnetic yoke and arranged symmetrically about the axis with an air gap between them and the permanent magnet. and a stator winding wound around the magnetic yoke. (2) The magnetic bias according to claim 1, wherein the length of the cylindrical permanent magnet corresponds to at least the total track width of the magneto-optical disk of the storage device. Generator. (3) Claims 1 and 2 are characterized in that the length of the gap formed by the pair of magnetic pole pieces and the cylindrical permanent magnet is changed in accordance with the direction of rotation. The magnetic bias generator described in Section 1.