JPS63124201A - Bias magnetic field generator - Google Patents

Abstract

PURPOSE:To improve the efficiency of the titled device and to shorten the rising time of a magnetic field by minimizing field gap width constituted between an outside york and a center york through a magneto-optical recording medium at a face opposed to the medium and expanding it in accordance with its separation from the recording face of the medium in the normal direction. CONSTITUTION:A chamber part 60 is formed on the back of one face of the outside york opposed to the medium 1 and the magnetic gap width formed between the center york 5 and the outside york 6 is set up so that the magnetic gap width S' formed on the opposite side to the face opposed to the medium 1 is larger than the magnetic gap width S formed on the face opposed to the medium 1. Since magnetic flux passing the opposite side to the face opposed to the medium 1 is reduced and magnetic flux passing near a recording point on the medium 1 is increased in accordance with the decrease, the efficiency can be improved. Thus, the rising time of the magnetic field can be shortened by expanding the magnetic gap width on the side separated from the face of the bias magnetic field generator 4 opposed to the medium 1, reducing magnetic coupling degree between the center york 5 and the outside york 6 and reducing self-inductance.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a bias magnetic field generating device used in a magneto-optical recording and reproducing device used in an external storage device of an electronic computer, a recording and reproducing device for music and video signals, and other information. It is related to.

BACKGROUND OF THE INVENTION In recent years, with the development of electronic computers and means of high-speed mass transmission of information, there has been a demand for low-cost, high-density, large-capacity, non-volatile storage devices with high-speed transfer capabilities, and magnetic disk devices are often used. However, there are problems such as low recording density, high price per unit of information, and especially in fixed magnetic disk drives, it is difficult to exchange the medium. Optical recording is currently in the spotlight as a technology that can solve these problems, and rewritable magneto-optical recording in particular has high expectations in many fields.

A conventional bias magnetic field generating device is placed opposite an optical head with a magneto-optical recording medium sandwiched therebetween, and the width of the magnetic gap is constant regardless of the distance from the medium.

Hereinafter, a conventional bias magnetic field generating device as described above will be explained with reference to the drawings.

Figures 4 and 6 show a conventional bias magnetic field generator. Figure 4 shows the arrangement within a magneto-optical recording device, and Figure 5 shows the structure and flow of magnetic flux generated by the bias magnetic field generator. . In FIG. 4, 1 is a magneto-optical recording medium, and 2 is an optical head, which is accessed in the direction of the arrow mark in FIG. An objective lens actuator for controlling the focus on the surface, a laser light source necessary for emitting the light spot, and an optical system for guiding this laser light to the objective lens 3 are built in. A bias magnetic field generating device 14 for applying a perpendicular magnetic field necessary for recording and erasing information on the magneto-optical recording medium 1 is disposed at a position facing the optical head 2 with the magneto-optical recording medium 1 in between. The center has a length sufficient to cover the access area of the optical head 2 along the access direction of It consists of a yoke 15, an excitation coil 17 wound around the center yoke 15, and a channel-shaped outer yoke 16 surrounding the center yoke 15. The magnetic gap width S formed by the center yoke 15 and the outer yoke 16 is constant with respect to the normal direction of the magneto-optical recording medium 1, and the tip surface of the center yoke 15 and the medium facing surface of the outer yoke 16 are on the same plane. It is located above the magneto-optical recording medium 1 and faces parallel to the magneto-optical recording medium 1 at a distance d.

The operation of the bias magnetic field generating device configured as described above will be explained below.

First, when the excitation coil 17 is energized, a magnetic flux φ flows through a magnetic path consisting of the center yoke 16 and the outer yoke 16 as shown in FIG. 5, and passes through the magneto-optical recording medium 1 as shown in the figure. At this time, if the distance d is made sufficiently small, a sufficient magnetic field with a component perpendicular to the magneto-optical recording medium 1 can be applied. In this state, information is recorded by applying a light spot from the optical head 2 to the magneto-optical recording medium 1 through the objective lens 3 in accordance with the information. In the case of erasing, the direction of the magnetic field is reversed to provide a light spot.

Since the center yoke 16 of the bias magnetic field generator has a length sufficient to cover the access range of the optical head 2, recording and erasing can be performed no matter which position the optical head 2 accesses in the direction of the arrow in FIG. A sufficiently strong magnetic field can be obtained.

Problems to be Solved by the Invention However, the above configuration has the following problems.

When the magnetic gap width of the bias magnetic field generating device is constant as in the conventional example shown in FIG. The magnetic flux passing through the point hit by the light spot above is only a small portion of the total magnetic flux. Therefore, the efficiency is very low and the power consumption must be large.

Furthermore, in order to improve the efficiency even a little, it is necessary to make the magnetic gap width sufficiently narrow. However, when the magnetic gap width is narrowed, the degree of magnetic coupling between the outer yoke and the center yoke increases, and the self-inductance of the bias magnetic field generator increases. A bias magnetic field generating device with such a large self-inductance requires a long time for the magnetic field to rise from zero to a strength sufficient for recording or erasing.

Normally, magneto-optical recording does not perform override, so when recording information, the corresponding area on the medium is erased first, but information is recorded using a bias magnetic field generator with a long magnetic field rise time. In this case, first wait until the magnetic field rises to the strength required for erasing, then start erasing, and even after erasing is completed, recording cannot be performed immediately.
It is necessary to wait until the magnetic field rises to the size necessary for recording before recording. Even if overrides were possible, some waiting time would still be required. That is, a large amount of overhead time occurs even when recording a small amount of information, and the actual operating rate of the magneto-optical recording/reproducing apparatus is greatly reduced.

In view of the above problems, the present invention provides a bias magnetic field generating device that is highly efficient and has a short magnetic field rise time.

Means for Solving the Problems To achieve this object, the bias magnetic field generating device of the present invention provides a magneto-optical recording medium at a position opposite to an optical head that provides a light spot for recording, reproducing and erasing on the magneto-optical recording medium. n, the width of the magnetic gap formed by the outer yoke and the center yoke is at least minimum on the medium facing surface and increases as it moves away from the medium facing surface in the normal direction of the recording surface of the magneto-optical recording medium. is configured to do so.

Effect: With this configuration, the magnetic gap width is widened on the side away from the medium facing surface of the bias magnetic field generating device, and the degree of magnetic coupling between the center yoke and the outer yoke is reduced, and the self-inductance is lowered, thereby increasing the magnetic field. The rise time can be shortened.

Furthermore, even if the width of the magnetic gap at the medium facing surface is narrowed sufficiently to increase efficiency, the self-inductance does not increase, and furthermore, the magnetic resistance of the magnetic gap on the side away from the medium facing surface increases. The amount of magnetic flux passing through the medium decreases, and this decrease results in an increase in the magnetic flux passing through the point on the medium where the light spot strikes. That is, improved efficiency is achieved without adversely affecting rise time.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIGS. 1 and 2 are diagrams showing a bias magnetic field generating device in one embodiment of the present invention. FIG. 1 shows the arrangement within the magneto-optical recording device, and FIG. 2 shows the configuration and the flow of magnetic flux generated by the bias magnetic field generating device.

In FIG. 1, 1 is a magneto-optical recording medium, 2 is an optical head, and 3 is an objective lens, which are the same as the conventional example. Reference numeral 4 denotes a bias magnetic field generator, which is disposed at a position facing the optical head 2 while sandwiching the magneto-optical recording medium 1, and is long enough to cover the access area of the optical head 2 along the access direction of the optical head 2. A center yoke 6 with a T-shaped cross section corresponding to
, an excitation coil 7 wound around the center yoke 5 , and a channel-shaped outer yoke 6 surrounding the center yoke 6 .

As shown in FIG. 2, a chamfered portion 61L is provided on the back side of the medium facing surface of the outer yoke 6, so that the magnetic gap width formed by the center yoke 5 and the outer yoke 6 is The magnetic gap S' on the opposite side of the medium facing surface is wider than the magnetic gap width S. Furthermore, the tip surface of the center yoke 6 and the medium facing surface of the outer yoke 6 are on the same plane, and the distance d is They are spaced apart and facing parallel to the magneto-optical recording medium 1.

The operation of the bias magnetic field generating device configured as described above will be explained below. First, when performing a recording operation, when the excitation coil 7 is energized, a magnetic flux φ
flows through the magneto-optical recording medium 1 as shown in the figure. At this time, since the magnetic gap width is sufficiently narrow on the medium facing surface and wide on the opposite side of the medium facing surface, the magnetic flux passing through the opposite side of the medium facing surface is reduced compared to the conventional example, and The magnetic flux passing near the recording point increases, improving efficiency.

In this state, if a light spot corresponding to the information is applied from the optical head 2 to the magneto-optical recording medium 1 through the objective lens 3, information is recorded. In the case of erasing, the direction of the magnetic field is reversed to provide a light spot.

In addition, since the magnetic gap width is expanded isometrically, the self-inductance of the bias magnetic field generator 4 is reduced.
Because the rise time of the magnetic field is shortened, it is possible to record information,
Erasure can be processed in a short time.

As described above, according to this embodiment, the magnetic gap width is widened on the side remote from the medium facing surface of the bias magnetic field generating device 4, the degree of magnetic coupling between the center yoke 5 and the outer yoke 6 is reduced, and the By lowering the inductance, the rise time of the magnetic field can be shortened. Furthermore, even if the width of the magnetic gap at the medium facing surface is sufficiently narrowed to increase efficiency, the self-inductance does not increase, and furthermore, the magnetic resistance of the magnetic gap on the side away from the medium facing surface increases, so the magnetic gap The amount of magnetic flux that passes through the medium decreases, and this decrease results in an increase in the magnetic flux that passes through the point on the medium that is hit by the light spot. That is, improved efficiency is achieved without adversely affecting rise time.

Other embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 shows a cross section of another embodiment of the bias magnetic field generating device of the present invention. In FIG. 3, the center yoke 6 has the same height, length in the direction perpendicular to the plane of the paper, arrangement within the magneto-optical recording/reproducing apparatus, etc. as in the first embodiment, but has a chamfer on the side opposite to the medium facing surface. Part 5! The difference is that it has L. Reference numeral 7 denotes an excitation coil, which is the same as in the first embodiment.

The outer yoke 6 is composed of the center yoke 6 and the center yoke 5.
It is a channel-shaped member that surrounds the excitation coil wound around the excitation coil. The method of use is the same as in the first embodiment.

This embodiment has the same effect as the second embodiment, but the structure of the outer yoke 6 is simpler than that of the first embodiment, and the chamfered shape of the center yoke 50 is relatively easy to form.
Manufacturing becomes easier.

Note that in this example, a method of chamfering was used as a means to reduce the degree of magnetic coupling of the magnetic air gap without reducing the efficiency of the bias magnetic field generator, but the shape of this part was There is no need to be limited to this, and an appropriate curved shape such as a cylindrical surface may be used as long as the magnetic gap width on the side opposite to the medium facing surface is wider than the magnetic gap width on the medium facing surface.

1fc, as a means to obtain the above effect, chamfering is applied to the inner surface of the outer yoke 6 or the inner surface of the center yoke 6, but chamfering may be applied to both the inner surfaces of the center yoke 5 and the outer yoke 6 if necessary. .

In this case, it is effective as a means to further reduce the self-inductance of the bias magnetic field generator.

For example, if the same level of low inductance is to be obtained only by molding the inner surface of the outer yoke 6, the thickness of the material in the vicinity of the magnetic gap must be made considerably thinner, resulting in a decrease in mechanical strength. That is, according to this method, it is possible to reduce the self-inductance without impairing the mechanical strength.

Furthermore, in this example, only the application to a bias magnetic field generator that simultaneously applies a bias magnetic field over the entire access range of an optical head is described, but the efficiency improvement and inductance reduction by the above method can be achieved by moving the optical spot along with the movement of the optical head. It is also applicable to a bias magnetic field generating device having a structure of

Effects of the Invention The present invention provides a bias magnetic field generating device that is placed between the magneto-optical recording medium at a position facing an optical head that provides a light spot for recording, reproducing and erasing on the magneto-optical recording medium, and that The medium of the bias magnetic field generating device is constructed such that the magnetic gap width is at least minimum at the medium facing surface and increases as it moves away from the medium facing surface in the direction normal to the recording surface of the magneto-optical recording medium. The width of the magnetic gap on the side away from the opposing surface becomes wider, reducing the degree of magnetic coupling between the center yoke and the outer yokes, reducing self-inductance, and shortening the rise time of the magnetic field. . Please note that even if the width of the magnetic gap at the medium facing surface is sufficiently narrowed to increase efficiency, the self-inductance does not increase, and the magnetic resistance of the magnetic gap on the side away from the medium facing surface increases, so the magnetic The amount of magnetic flux that passes through the air gap decreases, and this decrease results in an increase in the magnetic flux that passes through the point on the medium that is hit by the light spot. That is, improved efficiency is achieved without adversely affecting rise time. In addition, because unnecessary power consumption can be reduced, the temperature rise inside the magneto-optical recording/reproducing device can be minimized, and optical heads, which are relatively sensitive to temperature changes, can operate stably. Accordingly, it is possible to realize a bias magnetic field generating device that can generate a bias magnetic field.

[Brief explanation of the drawing]

FIG. 1 is a layout diagram of a bias magnetic field generating device in an embodiment of the present invention in a magneto-optical recording/reproducing device, FIG. 2 is a sectional view showing the flow of magnetic flux in the bias magnetic field generating device of FIG. 1, and FIG. The figure is a sectional view of a bias magnetic field generating device according to another embodiment of the present invention, FIG. 4 is a layout diagram of a conventional bias magnetic field generating device in a magneto-optical recording and reproducing device, and FIG. 5 is a bias magnetic field generating device of a conventional example. It is a sectional view showing the flow of magnetic flux of a magnetic field generating device. DESCRIPTION OF SYMBOLS 1... Magneto-optical recording medium, 2... Optical head, 3... Objective lens, 4... Bias magnetic field generator, 5...・Center York, S&
... Chamfered part, 6 ... Outer yoke, 6
G... Chamfered portion, 7... Excitation coil. Name of agent: Patent attorney Toshio Nakao and 1 other person1-
-Ikkou kalden 4---) Perfection 1 5---'C N yoke 6--Ichitato Ren N yoke 4--Rishi sword sobe 粁hii snake [5---' Hunta York 6-11 Outer I York 5-11 Se> Ta York No. 3. 5 years
--Moetori Fresh 6---Tad Seki I York 7---j Kogyoku Nigi Coil Figure 4 Figure 5

Claims (1)

[Scope of Claims] (1) The magneto-optical recording medium is arranged narrowly in a position facing an optical head that provides a light spot for recording, reproducing and erasing on the magneto-optical recording medium, and is composed of an outer yoke and a center yoke. A bias magnetic field generating device characterized in that a magnetic gap width is narrowest at a medium facing surface and increases as it moves away from the medium facing surface in a direction normal to a recording surface of the magneto-optical recording medium. (2) The magnetic gap width is narrowest at the medium facing surface and increases as the distance from the medium facing surface increases in the direction normal to the recording surface of the magneto-optical recording medium, so that the magnetic gap width is narrowest at the medium facing surface of the member forming the magnetic gap width. The bias magnetic field generating device according to claim 1, characterized in that the back side of the surface is chamfered. (3) The shape of the back side of the medium facing surface of the outer yoke is such that the magnetic gap width is narrowest at the medium facing surface and increases as it moves away from the medium facing surface in the direction normal to the recording surface of the magneto-optical recording medium. The first claim characterized in that
The bias magnetic field generator described in Section 1. (4) The cross-sectional shape perpendicular to the access direction of the optical head is such that the magnetic gap width is narrowest at the medium facing surface and increases as it moves away from the medium facing surface in the direction normal to the recording surface of the magneto-optical recording medium. 2. The bias magnetic field generating device according to claim 1, wherein the back side of the medium facing surface of the center yoke is T-shaped. (6) The magnetic gap width is narrowest at the medium facing surface and increases as the distance from the medium facing surface increases in the direction normal to the recording surface of the magneto-optical recording medium. 2. The bias magnetic field generating device according to claim 1, wherein the center yoke has a T-shaped cross section perpendicular to the access direction and forms a shape with the back side of the medium facing surface of the center yoke.