JPH05120605A - Bias magnetic field applying device for magneto-optical disk device - Google Patents

Abstract

PURPOSE:To provide a bias magnetic applying device with less heat generation, which can be obtained a strong magnetic field even with a small size, by bringing a positive or a negative pole of a permanent magnet close to a recording surface of a magneto-optical disk. CONSTITUTION:The permanent magnet 1a extending in the direction vertical to a magnetic axis between the positive pole and the negative pole is attached freely rotatably to a frame 6 so that it can rotate with a center of the magnetic axis as a rotary shaft. A magnetic coil 3a for rotation of the magnet surrounding the magnet 1a rotatably around the magnet 1a at the lower place of the frame 6, is provided, and a magnetic field for rotation in order to become vertical in the magnetic axis with respect to a magneto-optical surface is generated at the recording/reproducing time of the magneto-optical disk. By causing an electric current to flow to the coil 3a, the positive pole or the negative pole is independently brought close to the recording surface of the magneto- optical disk. Thus in spite of that the strong magnetic field can be obtained even with a small sized magnet, the bias magnetic field applying device with less heat generation is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bias magnetic field applying device used for recording / erasing on a magneto-optical disk.

[0002]

2. Description of the Related Art A magneto-optical disk device has a large storage capacity like a conventional write-once optical disk device.
It enables rewriting and erasing of information, which was not possible with the conventional write-once optical disc device. A magneto-optical disk device capable of rewriting and erasing this information will be briefly described. For example, a diameter of 130 mm (5.2
When a disk cartridge accommodating a 5 inch (5 inch) magneto-optical disk is inserted, the head window of the disk cartridge is opened, and the magneto-optical head accesses the magneto-optical disk through this head window. According to the ISO standard, the width of this head window is defined as a minimum of 40 mm.

The principle of recording / erasing utilizes the property that when a magnetic material is heated to a temperature above the Curie point to lose its magnetism and a magnetic field is applied from the outside, it is magnetized in the direction of the applied magnetic field. That is, the magnetic film formed on the disk surface is irradiated with laser light to raise the temperature, and a magnetic field is applied by a bias magnetic field applying device to change the direction of magnetization to record / erase data. is there.

Therefore, a bias magnetic field applying device for applying a bias magnetic field at the time of recording / erasing is provided above the magneto-optical disk at a position corresponding to the moving range of the actuator of the magneto-optical head. In the conventional bias magnetic field applying device, an electromagnet composed of a yoke and a coil is mainly used.

[0005]

However, in the bias magnetic field applying apparatus using the conventional electromagnet, when a strong magnetic field is to be generated, a large electromagnet has to be used. Therefore, there is a problem that the volume of the bias magnetic field applying device in the magneto-optical disk device becomes excessively large. There is also a problem that an increase in the amount of heat generated by a large electromagnet cannot be ignored.

Patent application by the same applicant as the present application (Heisei 2
In a magneto-optical disk device equipped with two magneto-optical heads proposed in Japanese Patent Application No. Hei 2-232147 filed on Aug. 31, 2012, the size of the head window of a standardized disk cartridge is within the range. Since two magneto-optical heads are driven by the above, it is necessary to provide a bias magnetic field applying device for each magneto-optical head. Therefore, it is necessary to limit the size of the bias magnetic field applying device, and a small bias magnetic field applying device is required, but it is difficult to reduce the size of the bias magnetic field applying device of the electromagnet composed of the yoke and the coil. was there.

It is an object of the present invention to provide a bias magnetic field applying device which can obtain a strong magnetic field even with a small size and generate a small amount of heat.

[0008]

SUMMARY OF THE INVENTION The above object is to provide a bias magnetic field applying device for applying a magnetic field to the recording surface of a magneto-optical disk when recording / erasing the magneto-optical disk. A permanent magnet that extends in the moving direction of the magnetic head and is rotatably supported about the center of a magnetic axis connecting the positive electrode and the negative electrode as a rotation axis; A permanent magnet rotating magnetic coil that generates a magnetic field that applies a couple to the permanent magnet so that it is substantially perpendicular to the recording surface of the disk, and the positive or negative electrode of the permanent magnet is connected to the magneto-optical disk. This is achieved by a bias magnetic field applying device characterized in that a predetermined magnetic field is applied to the recording surface of the magneto-optical disk in the vicinity of the recording surface.

[0009]

According to the present invention, since a permanent magnet is used, the amount of heat generation can be suppressed, and a bias magnetic field applying device capable of generating a strong magnetic field even with a small size can be realized, and the rotation of the permanent magnet can be assisted. With the rotation assist mechanism, the permanent magnet can be easily rotated.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A bias magnetic field applying apparatus according to an embodiment of the present invention will be described with reference to FIGS. The bias magnetic field applying device in this embodiment is an example applied to the proposed magneto-optical disk device using two magneto-optical heads. FIG. 1 is a sectional perspective view of a bias magnetic field applying apparatus according to an embodiment of the present invention. 2 (a) is a plan view of a bias magnetic field applying apparatus according to an embodiment of the present invention, FIG. 2 (b) is an AA end view, and FIG. 2 (c) is a bottom view.

Each end of rod-shaped (plate-shaped) permanent magnets 1a, 1b extending in a direction perpendicular to the magnetic axis between the positive electrode (N pole) and the negative electrode (S pole) is rotatably mounted on a frame by bearings or the like. It is attached side by side at the bottom of 6. The permanent magnets 1a and 1b can be rotated with the center of the magnetic axis as the center of rotation.
Semi-cylindrical permanent magnet rotary holders 2a and 2b are attached to both sides of the magnetic poles of the permanent magnets 1a and 1b. The weight of one of the two semi-cylindrical permanent magnet rotary holders 2a is made heavier than the weight of the other so that the balance between the center of rotation of the permanent magnet 1a and the center of gravity is lost, and the permanent magnet 1a is permanently exposed to an external magnetic field. The magnetic axis of the magnet 1a can be set to be substantially horizontal to the surface of the magneto-optical disk. As for the permanent magnet 1b as well, the balance between the two permanent magnet rotation holders 2b is disturbed so that the permanent magnet 1b is not applied to the permanent magnet 1b.
The magnetic axis of can be made substantially horizontal to the surface of the magneto-optical disk. By doing this, recording /
There is an advantage that a strong magnetic field is not applied to the magneto-optical disk surface except when erasing.

Around the permanent magnet 1a under the frame 6,
A permanent magnet rotating magnetic coil 3a is wound so as to rotatably surround the permanent magnet 1a. Similarly, a permanent magnet rotating magnetic coil 3b is wound around the permanent magnet 1b below the frame 6 so as to rotatably surround the permanent magnet 1b. These permanent magnet rotating magnetic coils 3a and 3b generate a magnetic field for rotating the permanent magnets 1a and 1b so that the magnetic axis becomes substantially perpendicular to the surface of the magneto-optical disk when recording / erasing the magneto-optical disk. Occur. By supplying currents to the permanent magnet rotating magnetic coils 3a and 3b, respectively, the positive and negative electrodes of the permanent magnets 1a and 1b are independently brought close to the recording surface side of the magneto-optical disk to record a predetermined magnetic field on the magneto-optical disk. Can be applied to the surface.

On the upper part of the frame 6, permanent magnets 1a, 1b are provided.
The yokes 5a and 5b are formed in parallel with the rotation axis of the above and have substantially the same length as the permanent magnets 1a and 1b. York 5a, 5
The position of the central axis of b is separated from the rotation axes of the permanent magnets 1a and 1b by a certain distance in the horizontal direction. York 5
Coils 4a and 4b are wound around a and 5b, respectively. The coil 4a and the yoke 5a, and the coil 4b and the yoke 5b form rotation auxiliary electromagnets 8a and 8b.

The coils 4a of the rotation assisting electromagnets 8a and 8b,
When a current is passed through 4b, a magnetic field that vertically penetrates the yokes 5a and 5b is generated, and this magnetic field causes the magnetic axes of the permanent magnets 1a and 1b to deviate from the position perpendicular to the magneto-optical disk surface. 1b can be rotated. At the time of recording / erasing on the magneto-optical disk, the permanent magnets 1a, 1b are driven by applying a current to the auxiliary rotation electromagnets 8a, 8b before applying a current to the permanent magnet rotating magnetic coils 3a, 3b.
b can be easily rotated. The timing of the voltage applied to the bias magnetic field applying apparatus according to the embodiment of the present invention will be described with reference to FIG.

At the time of reproduction, it is not necessary to apply a bias magnetic field, so the permanent magnet rotating magnetic coil 3a,
The voltage applied to 3b and the rotation assist electromagnets 8a and 8b is 0.
(FIG. 3 (a)). At the time of recording, a voltage for rotating the permanent magnets 1a, 1b is applied to the permanent magnet rotating magnetic coils 3a, 3b so that a predetermined polarity is directed to the disk surface (FIG. 3 (b)), and at the time of erasing, A voltage opposite to that at the time of recording is applied to the magnetic coils 3a and 3b for rotating the permanent magnets, and the permanent magnets 1a and 1b are rotated so that the polarity opposite to that at the time of recording is directed to the disk surface. (Fig. 3 (c)). In these cases, the voltage is applied to the rotation assisting electromagnets 8a and 8b for a short time before the voltage is applied to the permanent magnet rotating magnetic coils 3a and 3b. The voltage applied to the rotation assisting electromagnets 8a and 8b may have the same polarity during recording and erasing (FIGS. 3B and 3C).

By doing so, the permanent magnets 1a, 1b are
Since it can be rotated by a small angle by the rotation assisting electromagnets 8a and 8b, it can always easily rotate.
In particular, the permanent magnet 1a is located at a position such that the direction of the magnetic field generated by the permanent magnet rotating magnetic coils 3a and 3b and the direction of the magnetic field of the permanent magnets 1a and 1b are shifted by 180 degrees, and the couple becomes zero. When there is 1b, the rotation assist electromagnets 8a and 8b can give a trigger for rotation. Further, the application of the bias magnetic field is controlled by the permanent magnets 1a, 1b.
Therefore, compared with the case of using an electromagnet,
There is an advantage that a strong magnetic field can be obtained by significantly reducing the amount of heat generation, a small bias magnetic field applying device having a small width and height can be realized, and the device can be arranged in a narrow region.

FIGS. 4 and 5 show an example in which the bias magnetic field applying device according to the present embodiment is incorporated in a magneto-optical disk device having two magneto-optical heads mounted therein. The magneto-optical disk device of this embodiment will be described. A clamp table 14b is formed at the tip of the rotary shaft 14a of the spindle motor 14, and the hub 12a of the magneto-optical disk 12 housed in the disk cartridge 10 is attached to the clamp table 14b.
Clamped by.

Below the magneto-optical disk 12, a center rail 16 is provided in the center, and side rails 18 and 20 are provided on both sides thereof. The center rail 16 and the side rails 18 and 2 are provided.
Linear motors 22 and 24 are provided between 0, respectively. The linear motors 22 and 24 have a lower yoke 22.
upper yokes 22b and 24b are provided on a and 24a,
Plate-shaped magnets 22c and 24c are provided on the upper surfaces of the bottom portions of the lower yokes 22a and 24a to form a magnetic circuit.

Two carriages 26, 28 are provided corresponding to the two linear motors 22, 24. The carriage 26 is provided between the center rail 16 and the side rails 18 and is slidably supported by two sets of bearings 26 a each for the center rail 16, and two sets for the side rail 18 are one set. It is slidably supported by a bearing 26a. In the center of the carriage 26, a hole having a quadrangular cross section through which the upper yoke 22b of the linear motor 22 penetrates is formed, and the coil 26b is embedded along the inner surface of the hole.

The carriage 28 is provided between the center rail 16 and the side rail 20, slidably supported by two pairs of bearings 28a, two for the center rail 16, and two for the side rail 20. Are slidably supported by a pair of bearings 28a. In the center of the carriage 28, a hole having a quadrangular cross section is formed so that the upper yoke 26b of the linear motor 26 penetrates, and the coil 28b is embedded along the inner surface of the hole.

Actuators 34 and 36 for driving the objective lenses 30 and 32 are mounted on the carriages 26 and 28. These actuators 34 and 36 are used for the head window 10a of the disk cartridge 10 having a width of 40 mm.
It is mounted at a position near the center rail 16 so as to fit inside. Above the magneto-optical disk 12, the bias magnetic field applying devices 40 and 41 shown in this embodiment for applying a bias magnetic field to a position corresponding to the moving range of the actuators 34 and 36 are incorporated. The bias magnetic field applying device 40 is used for the magneto-optical head of the actuator 34,
The bias magnetic field applying device 41 is used for the magneto-optical head of the actuator 36. Bias magnetic field applying device 4
The frame 6 supporting 0 and 41 is also provided at a position near the center rail 16 so as to be accommodated in the head window 10a of the disk cartridge 10.

The light path on the actuator 32 side for recording / reproducing / erasing will be described. The laser light (two-dot chain line) from the optical system 44 is emitted from the hole 2 formed in the carriage 28.
After passing through 8c, it is guided to the objective lens 32 by the raising mirror 48 inside the carriage 28 and focused on the recording surface of the magneto-optical disk 12. Similarly, the laser beam reflected from the recording surface of the magneto-optical disk 12 is guided to the optical system 44 through the hole 28c by the raising mirror 48 via the objective lens 32. The same applies to the light path at the time of recording / reproducing / erasing on the actuator 30 side.

As described above, it is possible to realize a small bias magnetic field applying device corresponding to two magneto-optical heads driven within a narrow head window. The present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above embodiment, the present invention is applied to a magneto-optical disk having two magneto-optical heads, taking advantage of the fact that it can be arranged in a narrow head window. However, one ordinary magneto-optical head is mounted. It is of course possible to apply the present invention to a magneto-optical disk.

[0024]

As described above, according to the present invention, it is possible to realize a bias magnetic field applying apparatus which can obtain a strong magnetic field even with a small size and generate a small amount of heat.

[Brief description of drawings]

FIG. 1 is a cross-sectional perspective view of a bias magnetic field applying apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a bias magnetic field applying apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing timing of voltages applied to a bias magnetic field applying apparatus according to an embodiment of the present invention.

FIG. 4 is a front view of a magneto-optical disk device equipped with a bias magnetic field applying device according to an embodiment of the present invention.

FIG. 5 is a sectional view of a magneto-optical disk device equipped with a bias magnetic field applying device according to an embodiment of the present invention.

[Explanation of symbols]

 1a, 1b ... Permanent magnets 2a, 2b ... Permanent magnet rotation holders 3a, 3b ... Permanent magnet rotating magnetic coils 4a, 4b ... Coils 5a, 5b ... Yoke 6 ... Frames 8a, 8b ... Rotation auxiliary electromagnets 10 ... Disk cartridges 10a ... Head window 12 ... Magneto-optical disk 12a ... Hub 14 ... Spindle motor 14a ... Rotating shaft 14b ... Clamp table 16 ... Center rails 18, 20 ... Side rails 22, 24 ... Linear motors 22a, 24a ... Lower yoke 22b, 24b ... Upper yoke 22c, 24c ... Magnets 26, 28 ... Carriage 26a, 28a ... Bearings 26b, 28b ... Coils 26c, 28c ... Holes 30, 32 ... Objective lenses 34, 36 ... Actuators 40, 41 ... Bias magnetic field applying device 44 ... Optical system 48 ... Startup mirror

Claims (3)

[Claims] 1. A bias magnetic field applying device for applying a magnetic field to a recording surface of a magneto-optical disk at the time of recording / erasing on / from the magneto-optical disk, extending in a moving direction of a magneto-optical head for recording / erasing on the magneto-optical disk. A permanent magnet rotatably supported about a center of a magnetic axis connecting the positive electrode and the negative electrode as a rotation axis, and the magnetic axis is substantially aligned with the recording surface of the magneto-optical disk during recording / erasing on the magneto-optical disk. A permanent magnet rotating magnetic coil that generates a magnetic field that applies a couple to the permanent magnet so that it is perpendicular, and a positive or negative electrode of the permanent magnet is brought close to the recording surface of the magneto-optical disk to obtain a predetermined magnetic field. Is applied to the recording surface of the magneto-optical disk. 2. The bias magnetic field applying apparatus according to claim 1, wherein a magnetic field for rotating the permanent magnet is set so that the magnetic axis of the permanent magnet deviates from a position perpendicular to the recording surface of the magneto-optical disk. A rotation auxiliary electromagnet for generating is provided, and at the time of recording / erasing on the magneto-optical disk, a current is passed through the rotation auxiliary electromagnet before a current is passed through the permanent magnet rotating magnetic coil, thereby rotating the permanent magnet by a small angle. A bias magnetic field applying device characterized by: 3. The bias magnetic field applying apparatus according to claim 1, wherein the magnetic axis is substantially on the recording surface of the magneto-optical disk when no current is applied to the permanent magnet rotating magnetic coil. A bias magnetic field applying device, wherein the center of rotation and the center of gravity of the permanent magnet are displaced so as to be parallel to each other.