JPH02123502A - Bias magnetic field impressing device - Google Patents

Abstract

PURPOSE:To thin a device by switching the impressed current to an electromagnet, changing the polarity of the electromagnet and rotating a permanent magnet. CONSTITUTION:When the S pole of a permanent magnet 1 is faced to a disk medium 9 and the magnetic field of the magnetizing direction in the upper direction is impressed to the medium 9, a second electromagnet 4a is made into an N pole, 4b is made into an S pole, and by facing the S and N poles of a permanent magnet 2 for rotation to electromagnets 4a and 4b, respectively, the impressing position is held. When the magnetic field in the reverse direction is impressed to the medium 9, the impressing direction of the current to respective electromagnets 3a, 3b, 4a and 4b is switched, the electromagnet 4a is made into the S pole, 4b is made into the N pole, an electromagnet 3a is made into the N pole, 3b is made into the S pole, the magnet 2 and the electromagnets 4a and 4b are mutually made repulsive to each other, the magnet 1 and electromagnets 3a and 3b are attracted and a turning shaft 7 is rotated in the clockwise direction like an arrow. When the magnet 1 attains the horizontal direction, the electromagnet 3a is switched into the S pole, 3b is switched into the N pole, further, rotated in the clockwise direction of the arrow mark, the turning shaft is rotated by 180 deg., the N pole of the magnet 1 is made into the lower direction and face to the medium 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a bias magnetic field applying device for a magneto-optical disk device, and more specifically, to a bias magnetic field applying device with improved rotating means for a permanent magnet. .

[Conventional technology]

Conventionally, as this type of bias magnetic field applying device,
As shown in Japanese Patent No. 1-261802, an apparatus has been proposed in which a permanent magnet is used as a magnetic field generation source and the polarity of the bias magnetic field is changed by reversing the permanent magnet using an independent driving means such as a morph.

FIG. 5 is a schematic diagram showing a conventional bias magnetic field applying device, a disk medium, and an optical system having a permanent magnet and an independent driving means for reversing the permanent magnet. In the figure, the bias magnetic field applying device has a permanent magnet 1 provided with a rotating shaft 7, and this rotating shaft 7 is connected to a motor 12 which is an independent drive means.

The disk medium 9 consists of a magnetic layer 91 and a substrate 92, and the direction of magnetization of the magnetic layer 91 is made variable by a bias magnetic field generated by reversal of the permanent magnet 1. Further, the objective lens 10 for light focusing focuses the laser light from the laser light source 11 onto the magnetic layer 91 of the disk medium 9 .

Next, the operation will be explained.

Magneto-optical recording methods can be roughly divided into Curie temperature recording and compensation point temperature recording. In both cases, a laser beam is generated from a laser light source 11 in response to a recording signal, and is passed through an objective lens 10 for converging the light. , magnetic layer 91 of disk medium 9
Then, recording is performed by narrowing down the spot to a minute spot with a diameter of 1 to 2 μm, raising the medium temperature, and simultaneously applying a bias magnetic field in the opposite direction to the medium magnetization in the erased or unrecorded area to form reversed magnetic domains. The bias magnetic field is generated by a permanent magnet or an electromagnet, but from a practical point of view, the permanent magnet 1 is used, which does not require power supply and does not have the problem of heat generation when generating the magnetic field.

Note that Curie temperature recording refers to raising the magnetic JI91 to a temperature higher than the Curie temperature and applying a bias magnetic field or magnetic layer 91.
Compensation point temperature recording is a method in which a reversal magnetic domain is formed by a demagnetizing field of
This method utilizes a decrease in coercive force to form reversed magnetic domains using a bias magnetic field.

On the other hand, for erasing, a bias magnetic field in the opposite direction to that during recording is applied, and at the same time, a laser beam is continuously applied to the medium, thereby eliminating the reversed magnetic domain in the recording area and aligning the magnetization in the direction of the erasing bias magnetic field. will be held.

As described above, in order to perform recording and erasing using the bias magnetic field generated from the permanent magnet 1, the polarity of the bias magnetic field is changed by reversing the permanent magnet 1 using an independent drive unit such as the motor 12. It is.

Further, Japanese Patent Application Laid-Open No. 62-283402 discloses a device for rotating a permanent magnet using an electromagnet.

This supports a permanent magnet rotatably, and an electromagnet is provided above the rotating shaft at a position opposite to the position where a bias magnetic field is applied to the optical disk. is rotated in accordance with recording or erasing information.

[Problem to be solved by the invention]

However, in the former prior art, since the permanent magnet is rotated by a motor, the height of the device is restricted by the size of the motor, making it difficult to reduce the thickness of the device.

Furthermore, in the latter case where an electromagnet is used, it is difficult to place the electromagnet above the permanent magnet, that is, to reduce the thickness of the device.

This invention was made in view of the above circumstances, and includes a rotating permanent magnet that is provided coaxially with the permanent magnet in a direction that intersects it, and a rotating permanent magnet that is provided in a horizontal direction corresponding to the permanent magnet and the rotating permanent magnet. Separate electromagnets are provided at appropriate lengths apart, the polarity of the electromagnets is changed by switching the current applied to the electromagnets, and the permanent magnets are rotated, thereby making the rotating means of the permanent magnets simple and thin. The purpose is to

[Means to solve the problem]

The bias magnetic field applying device according to the present invention is provided with a rotating permanent magnet coaxially with the rotation axis of the permanent magnet, with its magnetic pole direction intersecting the direction of the permanent magnet, and with the rotation axis being the center of symmetry. The rotational direction of the rotating permanent magnet is symmetrical about the rotational axis and a pair of first electromagnets provided facing the permanent magnet and separated by a distance # greater than the length of the permanent magnet in the rotational direction. A pair of second electromagnets are provided facing the rotating permanent magnet and separated from each other by a distance longer than the length thereof.

[Effect]

In this invention, by sequentially changing the polarity of the first and second electromagnets, attractive and repulsive forces are generated between the permanent magnets and rotating permanent magnets and the first and second permanent magnets, thereby creating a permanent magnet. The magnet rotates and is held in any position.

〔Example〕

The present invention will be explained below based on the drawings showing one embodiment thereof.

FIG. 1 is a plan view showing the configuration of a bias magnetic field applying device according to the present invention, and FIG. 2 is a sectional view taken along line nn in FIG. 1. In the figure, reference numeral 9 denotes a disc-shaped disk medium including a substrate 92 and a magnetic layer 91 laminated thereon, and a rectangular frame-shaped frame 8 is disposed above the disk medium 9. A rotation shaft 7 for rotating a permanent magnet 1 for applying a bias magnetic field is rotatably supported at the center of the frame 8 in the width direction, with the longitudinal direction being the radial direction of the disk medium 9. The rotating shaft 7 has a rotating permanent magnet 2. Three permanent magnets, a permanent magnet 1 and a magnetic detection magnet 5, are attached in this order. The permanent magnet 1 is in the shape of a flat bar, and its length in the longitudinal direction is slightly longer than the trunk width of the disk medium 9 facing downward. A magnetic field is applied to the magnetic layer 91 formed on the substrate 92 (see FIG. 2). The rotating permanent magnet 2 has an N pole in a direction crossing the magnetic pole direction of the permanent magnet 1.

It is attached to the rotating shaft 7 at an appropriate distance from the permanent magnet 1 so that the magnetic pole direction of the S pole faces, and the magnet 5 for detecting the magnetism of the permanent magnet 1 has the same magnetic pole direction as the permanent magnet 1. It is attached on the opposite side of the rotating permanent magnet 2 with the magnet 1 in between and separated from the permanent magnet 1 by an appropriate length. At positions facing the longitudinal center of the permanent magnet l of the frame 8, first electromagnets 3a and 3b are erected with their tips facing each other and separated from each other by the length of the permanent magnet 1 in the rotational direction.

Further, at a position facing the rotating permanent magnet 2 of the frame 8, second electromagnets 4a and 4b are erected at a corner slightly apart from the length of the rotating permanent magnet 2 in the rotational direction, with their tips facing each other.

Further, a magnetic detector 6 is provided facing above the magnetic detection magnet 5, and this detects the magnetic pole direction of the permanent magnet 1, that is, N, S.
Detect the direction of the poles.

Next, the operation of the inventive device configured as above will be explained.

FIG. 3 is a sectional view taken along the line I'ff-TII in FIG. 1 showing the relationship between the magnetic pole directions of the rotating permanent magnet and the second electromagnet;
FIG. 4 is a sectional view taken along the line IV-IV in FIG. 1 showing the relationship between the magnetic poles of the permanent magnet and the first electromagnet, and FIG.
4(d) and FIGS. 4(a) to 4(d) show the same timing, respectively.

First, for example, when the S pole of the permanent magnet 1 is opposed to the disk medium 9 as shown in FIG. 4(a) and a magnetic field in the upward magnetization direction is applied to the disk medium 9, as shown in FIG. 3(a).
As shown in FIG.
, 4b, the application position is maintained. When applying a magnetic field in the opposite direction (N pole in this case) to the disk medium 9, each electromagnet 3a, 3b+
Switch the direction of current application to 4a and 4b, and
b) As shown in FIG. 4(b), the second electromagnet 4a is the S pole, the second electromagnet 4b is the N pole, the first electromagnet 3a is the N pole, and the first electromagnet 3b is the S pole, and the rotating permanent magnet 2 By causing the permanent magnet 1 and the second electromagnets 4a, 4b to repel each other and attracting the permanent magnet 1 and the first electromagnets 3a, 3b, the rotating shaft 7 is rotated clockwise as shown by the arrow. When the permanent magnet 1 becomes horizontal as shown in FIG. 4(C), the first
Switch the electromagnet 3a to the S pole and the electromagnet 3b to the N pole, and then rotate the electromagnet 3a clockwise as shown by the arrow to rotate the rotation axis 1806 times as shown in FIGS. 3(d) and 4(d). The N pole of the permanent magnet 1 is directed downward and is opposed to the disk medium 9.

The direction of the magnetic pole of the permanent magnet 1 is detected by the magnetic detector 5, and when no magnetic field is applied, the direction of the magnetic pole of the permanent magnet 1 is detected as shown in Fig. 4 (C1
The second electromagnets 4a and 4b are held at the position shown in FIG.
Therefore, no magnetic field is formed in these either.

In this way, in this embodiment, the electromagnets are erected in a horizontal direction parallel to the surface of the disk medium, making it possible to make the device thinner, and by switching and cutting off the flow to the electromagnets, the rotational position of the permanent magnets can be adjusted. and the direction can be freely selected.

In this embodiment, the permanent magnet was constructed with two poles, N and S. However, the present invention is not limited to this, and the number of poles may be any even number, and the poles of the rotating permanent magnet may be The number may be any number as long as it is the same number as the number of permanent magnets.

〔Effect of the invention〕

As explained above, in this invention, a rotating permanent magnet is provided concentrically with the permanent magnet and its magnetic pole directions cross each other, and the permanent magnet and the rotating permanent magnet are each provided with appropriate lengths in the horizontal direction corresponding to the permanent magnet and the rotating permanent magnet. Separate electromagnets are installed separately,
By changing the polarity of the electromagnet by switching the current applied to the electromagnet and rotating the permanent magnet, an equivalent effect can be achieved that allows the device to be made thinner with a simple structure.

[Brief explanation of drawings]

FIG. 1 is a plan view showing the configuration of a bias magnetic field applying device according to the present invention, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, and FIGS. 3 and 4 are for explaining the operation. I in Figure 1
II-I
The figure is a schematic perspective view showing the configuration of a conventional bias magnetic field applying device. 1... Permanent magnet 2... Rotating permanent magnet 3a
, 3b... First electromagnet 4a, 4b... Second electromagnet 7... Rotating shaft 9... Disk medium
91...Magnetic layer In the drawings, the same reference numerals indicate the same or corresponding parts. Funeral map of agent Masuo Oiwa Funeral map

Claims (1)

[Scope of Claims] 1. According to the recording of data on the magneto-optical recording medium and the erasure of data therefrom, a rod-shaped permanent magnet that is rotatable around its longitudinal axis is rotated, and the In a bias magnetic field applying device that applies a predetermined bias magnetic field to a magnetic layer of a magnetic recording medium, the direction of the opposing magnetic pole is coaxial with the rotation axis of the permanent magnet in a direction that intersects the direction of the magnetic pole of the permanent magnet. A pair of first magnets are provided facing the permanent magnet and are spaced apart from each other by a distance longer than the length of the permanent magnet in the rotational direction, with the rotation axis as the center of symmetry. an electromagnet; and a pair of second electromagnets provided facing the rotating permanent magnet and separated from each other by a suitable distance longer than the rotational direction length of the rotating permanent magnet, with the rotating axis as a center of symmetry. A bias magnetic field applying device characterized by: