JPS6246450A - Photomagnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To increase vertical components in a magnetic field and to reduce the variation of the magnetic field due to a distance by constituting the titled device so that an outside york is arranged so as to surround an exciting coil in a center york adjacently to the tip of the center york. CONSTITUTION:The center york 5 in a magnetic circuit 4 has the length of an access area of an optical head and the exciting coil is wound around the center york 5. On the other hand, the outside york 7 is arranged so as to surround the exciting coil 6 adjacently to the leading end of the center york. When a current is made to flow into the coil 6 under said shape, magnetic flux is concentrated near the tip of the center york and a magnetic field increasing its vertical component to a recording medium 1 by about 60% as compared to an ordinary device. Even if the distance between the york 5 and the medium 1 is changed, the vertical component of the magnetic field can be held and the change of the magnetic field due to the distance can be reduced.

Description

[Detailed description of the invention] Industrial applications The present invention records information on a disk-shaped magneto-optical medium.

The present invention relates to a magneto-optical recording and reproducing device that performs reproduction and erasing.

Conventional technology In recent years, there has been a remarkable increase in the capacity of optical disc recording and reproducing devices and technological innovations in high-speed access.In particular, magneto-optical media are capable of recording, reproducing, and erasing, so their use in optical discs has become important. Ta. Magneto-optical media is a medium in which a superimposed magnetic field is not applied to the medium, and a laser beam is irradiated with a finely focused laser beam to erase records due to the thermomagnetic effect, and a device that applies a magnetic field, that is, a magnetic bias application device, is important. Ta.

A conventional magneto-optical recording/reproducing device will be described below with reference to the drawings.

FIG. 6 shows a configuration diagram of a conventional magneto-optical reproducing device, and FIG. 7 is a sectional view of FIG. 6. In Figure 7,
11 is a recording medium, and 24 is a magnetic circuit for applying a perpendicular magnetic field to the recording medium 11 for recording and erasing information. The magnetic circuit 24 is disposed at a position facing the optical head 12 while sandwiching the recording medium 11, and is formed of a bar having a length corresponding to the scanning area of the optical head 12 along the access direction A of the optical head 12. It is composed of a shaped center yoke 26, an excitation coil 26 wound around the center yoke 25, and a channel-shaped outer yoke 27 sandwiching the center yoke 26. Center yoke 2so Tip end 25 facing recording medium 11
a is formed into a wedge shape, and its tip surface and the medium-facing tip surface of the outer yoke are on the same horizontal plane and are opposed in parallel to the recording medium 11 with a distance St-separated from them.

The operation of the magneto-optical recording and reproducing apparatus configured as described above will be explained below. When the excitation coil 26 is energized, zero magnetic flux flows through the magnetic path consisting of the center yoke 26 and the outer yoke 27 as shown in FIG. 7, and the zero magnetic flux cuts the recording medium 11 as shown. Here, if the distance S between the center yoke 26 and the recording medium 11 is made sufficiently small,
A magnetic field in a perpendicular direction can be applied to the recording medium 11 facing the tip of the center yoke 26. Furthermore, the strength of the magnetic field at this time can be increased by forming the tip 25a of the center yoke 25 into a wedge shape, and by providing the external yoke 27, the excitation current can also be reduced. (for example,
(Japanese Unexamined Patent Publication No. 59-119507) Problems to be Solved by the Invention However, the above configuration works well when the distance between the center yoke and the medium is small, but it is difficult to use when the distance between the center yoke and the medium is small. When using a double-sided disk made by bonding two sheets together, it is necessary to increase the distance between the center yoke and the medium, which has the problem of making it difficult to obtain a perpendicular magnetic field and reducing efficiency. .

If the perpendicularity of the magnetic field is poor, a tilted magnetic field will act on the recording medium, which will adversely affect recording and erasing characteristics.

If the efficiency deteriorates, an excessive current must be passed through the excitation coil, which causes problems such as heat generation in the magnetic bias applying device and a large-capacity power supply, and also makes it difficult to miniaturize as a recording/reproducing device. had.

In view of the above-mentioned problems, the present invention provides a magneto-optical recording and reproducing device that can provide a highly perpendicular magnetic field even when the distance between the magnetic bias yoke and the recording medium is separated, and furthermore, the magnetic field changes less due to changes in distance. It provides:

Means for Solving the Problems In order to solve the above problems, the magneto-optical recording and reproducing apparatus of the present invention includes a center yoke having a length that sandwiches a magneto-optical recording medium and covers the running range of the optical head, and the center yoke. An excitation coil is wound around the center yoke, and an outer yoke is arranged to surround the excitation coil up to a point close to the tip of the center yoke.

For production use.

With this configuration, when current flows through the excitation coil, the magnetic flux coming out of the center yoke has a small magnetic resistance because the distance between the center yoke and the outer yoke is small, and the total magnetic flux increases. At this time, the horizontal component is much larger, but
In terms of absolute numbers, the vertical component increases and the magnetic field becomes stronger than in the conventional shape. However, at this time, since the change in the vertical component of the magnetic flux is large, the change in the magnetic field is large when the distance S between the recording medium and the center yoke changes, so by increasing the width of the tip of the center yoke, The change is smaller compared to the one that does not increase the size of the area.

EXAMPLE Hereinafter, a magneto-optical recording and reproducing apparatus according to an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a perspective view of a magneto-optical recording and reproducing apparatus in a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a recording medium, and two disks are pasted together. 1a and 1b are the recording medium surfaces. When the disc is set as shown in Figure 1, the recording medium surface 1a on the optical head side is the recording surface, and the recording medium surface 1b is the recording surface when the disc is inserted upside down. be. 2 is an optical head,
The laser beam irradiated from the objective lens 3 is directed to the recording medium surface 1a.
The light is focused on the recording, reproducing, and erasing operations. Further, the optical head 2 is accessed at high speed in the direction of arrow A. Reference numeral 4 denotes a magnetic circuit for recording and erasing information on the recording medium 1, and a center yoke having a length sufficient to cover the access area of the optical head 2, which is placed at a position facing the optical head 2 while sandwiching the recording medium 1. 6, an outer yoke 7 disposed close to the tip of the center yoke 6, and an outer yoke 7 surrounding the excitation coil 6 wound around the center yoke 6.

The tip end 5a of the center yoke 6 facing the recording medium 1 has a wide cross section that is approximately in the shape of an inverted T.

However, although not shown, the center yoke may have a cross section with a constant width, and the center yoke 5 and the outer yoke 7 are opposed in parallel to the recording medium 1 at a distance S. .

The operation of the magneto-optical recording and reproducing apparatus configured as described above will be explained below with reference to FIGS. 1 and 2.

When a current is applied to the excitation coil 6, as shown in FIG. 2, the excitation coil 6 wound around the center yoke 5 and the outer yoke 7 and the tip of the center yoke 5 are excited up to a distance of 0.5 to 3 m, for example. It is composed of an outer yoke 7 arranged to surround a coil 6, and a center yoke 6.
Since the distance between the center yoke 5 and the outer yoke is small, the magnetic flux emitted from the magnetic flux has a smaller magnetic resistance than the conventional example, and the total magnetic flux increases. At this time, the horizontal component is much larger, but
The vertical component also increases and the magnetic field becomes stronger.The results of simulating these using an actual computer are shown in the third section.
As shown in the figure. The curve Z is the analysis result of the conventional example, the curve X is the analysis result of the present embodiment, and the curve Y is the analysis result of the cross section of the center yoke 6 having a constant width in the present embodiment.

The horizontal axis is the position perpendicular to the center yoke, and the vertical axis is the strength of the vertical magnetic field. Even if analyzed quantitatively as in the qualitative theory, if the outer yoke 7 is arranged so as to surround the excitation coil 6 close to the tip of the center yoke 5, the distance between the center yoke 6 and the outer yoke 7 will be Since it is smaller than the target, the magnetic resistance becomes smaller, and the magnetic field strength of the vertical component increases by about 60% at the same power. but,
When the cross section of the center yoke shown by the curve Y in FIG. 3 has a constant width, the magnetic field changes greatly when the distance S changes due to surface runout or the like.

By widening the width of the tip of the center yoke 5, a curve X is formed, and the change in the magnetic field is reduced by about 15% compared to a case where the width is not widened. As a result, a strong vertical magnetic field can be stably applied even if the distance varies due to surface wobbling or the like. In addition, in this simulation, 2.
The shape under the condition that the recording medium is installed at 8M was determined.

As described above, according to this embodiment, the cross-sectional shape of the center yoke is approximately inverted T-shape, and the tip of the outer yoke is placed close to the center yoke, so that the magnetic flux is concentrated and the area molten from the yoke is However, a strong vertical magnetic field is stably applied. Therefore, the magneto-optical recording and reproducing apparatus of the present invention can be used even in cases where the distance between the magnetic bias and the recording medium must be increased, such as in the case of double-sided discs in which two discs are glued together, discs with large surface runout, or discs with large surface runout. In addition, since the magnetic flux is concentrated, efficiency is improved, the current flowing through the excitation coil 9 generates less heat, the power supply capacity is reduced, and the device can be made more compact. .

FIG. 4 is a perspective view of a magneto-optical recording/reproducing apparatus according to a second embodiment of the present invention, and FIG. 5 is a sectional view of a main part thereof.

In FIGS. 4 and 6, 1 is a recording medium, 2 is an optical head, and 3 is an objective lens. Reference numeral 14 denotes a magnetic circuit for recording and erasing information on the recording medium 1, which is disposed at a position facing the optical head 2 while sandwiching the recording medium 1, and the optical head 2 is accessed at high speed in the direction of arrow A by another means. Due to the angle 8, the magnetic circuit 14 is always movable together with the optical head 2, and is brought close to the tip of the center yoke 15 so as to surround the center yoke 16 that applies a magnetic field to one point and the excitation coil 16 wound around the center yoke 16. This is because it consists of an outer yoke 17 arranged up to the point.

The leading end 11 of the center yoke 15 faces the recording medium 1
5a has a substantially inverted T-shaped cross section and is wider than the others. Further, the center yoke 16 and the outer yoke 17 are opposed in parallel to the recording medium with a distance S between them.

The operation of the magneto-optical recording and reproducing apparatus configured as described above is exactly the same as that of the first embodiment of the present invention, and the magnetic flux is concentrated, and a strong perpendicular magnetic field is stably provided even in the melted area from the yoke. This improves efficiency and reduces the amount of heat generated by the current flowing through the excitation coil.

The power supply capacity is small, and the device can be made smaller.

Effects of the Invention The present invention has a magneto-optical recording medium at a position opposite to the optical head, which increases the running range of the optical head by 7"-6 length 2.E'-"to optical'1'2 interlocking 21.・−
The tip facing the recording medium has a diameter that provides a magnetic field at one point.
The width of the tip part is wider on the cross section of 1.
□-, the excitation coil wound around the center yoke, and the area close to the tip of the center yoke.
By providing the outer yoke arranged to surround the excitation coil, the magnetic flux is concentrated near the center of the tip of the center yoke, and a magnetic field with many vertical components can be formed on the recording medium. Even if the distance between the yoke and the recording medium is large, the perpendicularity of the magnetic field can be maintained well, reducing the current flowing through the excitation coil, suppressing the heat generation of the magnetic bias applying device, and further achieving miniaturization of the magneto-optical recording and reproducing device. be able to.

Further, by widening the width of the tip on the cross section of the tip facing the old record, it is possible to suppress fluctuations in the magnetic field even when the distance between the recording medium and the magnetic bias yoke changes.

Therefore, it is possible to generate a magnetic field of uniform strength over the entire scanning range of the optical helad on the recording medium, and it is possible to stably record and erase information. It is possible to realize many excellent magneto-optical recording and reproducing devices, such as further miniaturization of magnetic recording and reproducing devices.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a magneto-optical recording and reproducing apparatus according to a first embodiment of the present invention, FIG. 2 is an enlarged sectional view of the main part of FIG. 1, and FIG.
The figure is a magnetic field strength distribution diagram showing the strength of the magnetic field with respect to the distance between the recording medium and the tip of the center yoke. Figure 4 is a perspective view of a magneto-optical recording and reproducing device according to the second embodiment of the present invention. Figure 5 4 is an enlarged sectional view of the main part of FIG. 4, FIG. 6 is a perspective view of a conventional magneto-optical recording/reproducing apparatus, and FIG. 7 is an enlarged sectional view of the main part of FIG. 6. 1...recording medium, 2.curve, optical head, 3.objective lens, 4.14.mark/magnetic circuit, 5.15
...Center yoke, 6,16...Excitation coil, 7゜17...Outer yoke, 8...
···angle. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 3 Figure 5 Katasu lens

Claims (4)

[Claims] (1) A center yoke that is located at a position facing the optical head while sandwiching the magneto-optical recording medium and has a length that covers the travel range of the optical head, an excitation coil wound around the center yoke, and the center yoke. A magneto-optical recording/reproducing device comprising: an outer yoke surrounding the excitation coil up to a point close to the excitation coil. (2) The magneto-optical recording according to claim 1, wherein the center yoke has a cross-sectional shape that is substantially inverted T-shaped by widening the width of the tip portion close to the recording medium in a direction horizontal to the surface of the recording medium. playback device. (3) an axially symmetrical center yoke located opposite to the optical head, sandwiching the magneto-optical recording medium and close to a portion of the optical head that is hit by a light spot; and an excitation coil wound around the center yoke; A magneto-optical recording and reproducing device comprising an outer yoke arranged to surround the excitation coil up to a point close to the tip of the center yoke, and configured such that the center yoke and the outer yoke are movable together with the optical head. . (4) The center yoke is magneto-optical according to claim 3, in which the width of the tip portion close to the recording medium is widened in a direction horizontal to the surface of the recording medium so that the cross-sectional shape is approximately inverted T-shape. Recording and playback device.