JPH03280203A - Bias magnetic field generation mechanism - Google Patents

Abstract

PURPOSE:To reduce the size and thickness of a magneto-optical recording/ reproducing device and to increase its operation speed by holding two rod-like permanent magnets magnetized in the thickness direction and a york by a magnet holder so as to linearly guide them and driving the holder by a flatly wound coil. CONSTITUTION:The length of the two rod-like permanent magnets A201, B202 is matched with the width of a recording area and these magnets A201, B202 are stuck and fixed to the magnetic holder 203 in parallel. The width and thickness of the magnets and the interval between the two magnets are set up so that magnetic flux generated as shown by the arrow 107 forms a vertical magnetic field with necessary strength on a laser focus 109. The magnetic holder 203 is used also as a york connecting the N and S magnetic poles of the magnets. In addition, bearings A206, B207 formed by perforating guide holes are fixed on both the ends of the holder 203 and engaged with guide spindles A208, B209 to support the holder 203 so as to linearly move it. The flatly wound driving coil 205 is arranged in the vicinity of the magnets A201, B202 and the holder 203 can be moved by energizing to the coil 205.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a bias magnetic field generating mechanism which is a means for generating a magnetic field on the surface of a recording medium when recording or erasing information in a magneto-optical recording/reproducing device.

[Prior Art] In a magneto-optical recording/reproducing device, when recording and erasing information, it is necessary to create a magnetic field of several hundred oersteds at the focal point of a laser beam on a recording medium.

This magnetic field during recording and erasing is called a bias magnetic field or the like. Methods for generating this bias magnetic field include a method using an electromagnet and a method using a permanent magnet.

Examples of conventional methods are given for each.

FIG. 3 is an example in which a bias magnetic field is generated using an electromagnet. In the figure, 303 is an optical head, 302 is an optical disk (
magneto-optical recording medium). Electromagnet 301 is connected to optical disk 3
It is placed on the opposite side of the optical head 303 across the optical head 303 and generates a bias magnetic field. By changing the direction of the current flowing through the electromagnet, the magnetic field for recording and erasing can be switched.

FIG. 4 is an example using a permanent magnet. Permanent magnet 401
is placed close to the optical disk 404, and the rotating shaft 402
It is supported so that it can rotate. This permanent magnet is driven by a coaxially connected motor 403, and N
It has a structure that allows the pole and south pole to be reversed.

Another method is to mount a small electromagnet or permanent magnet on the light source and create a noisy magnetic field only at the laser irradiation point.

[Problems and Objectives to be Solved by the Invention] Among the conventional methods, in the method in which a small device that creates a magnetic field only at the laser irradiation point is moved together with the head, the mass of the moving part due to access becomes large, and the high speed Difficult to access.

Further, the following problem also exists in a method in which a bias magnetic field generating mechanism of a size that can generate a magnetic field over the entire recording area is fixed to the head and the front.

First of all, with the method using electromagnets as shown in Figure 3, the current consumption increases, and as a result, heat generation increases (
It was a serious problem.

Next, in the method using permanent magnets as in the example in Figure 4,
Since the magnet is rotated to reverse the magnetic field, even if the magnet is made thinner, a gap must be provided for rotation, making it difficult to reduce the thickness of the device.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a bias magnetic field generation mechanism suitable for a magneto-optical recording and reproducing device that is small and thin and aims at high-speed access.

[Means for Solving the Problems] The bias magnetic field generation mechanism of the present invention is provided in a magneto-optical recording/reproducing device, and includes: (a) two rod-shaped permanent magnets magnetized in the thickness direction;
) a yoke that connects the N magnetic pole of one of the two permanent magnets and the S magnetic pole of the other; (c) a magnet holder that holds the permanent magnet and the yoke and has a bearing; (d) that engages with the bearing of the magnet holder; and (e) a flat-wound drive coil.

[Effect] The operating principle of the present invention will be explained with reference to FIGS. 1(a) and 1(b).

The figure depicts a cross section taken along a plane perpendicular to the longitudinal direction of a rod-shaped permanent magnet. 2 permanent magnets, magnet A101
, the magnet B102 and the yoke 103 move together and can be moved to two positions as shown in FIG. 1(a) and FIG. 1(b). It is also assumed that the permanent magnets are magnetized as indicated by the letters NSS in the figure.

Since the magnetic field created by the two permanent magnets is oriented as shown by the arrow 107, the direction of the magnetic field at the focal point 109 of the laser emitted from the objective lens 108 of the optical head is two directions in FIG. 1(a). In FIG. 1(b), the direction is -2.

When the permanent magnet is in the position shown in Fig. 1(a), when a current is passed through the drive coil 104 counterclockwise on two axes (the coil cross section 105 is facing straight in the paper), the electromagnet is moved in the -X direction by the magnetic field created by the permanent magnet. receive the power of At this time, since the electromagnet is fixed and the permanent magnet is movable, the permanent magnet receives a force in the X direction due to a reaction and moves to the position shown in FIG. 1(b).

On the other hand, if a current is applied to the electromagnet in the Z-axis direction, the permanent magnet receives a force in the -X direction and moves from the position shown in FIG. 1(b) to the position shown in FIG. 1(a).

By passing current in different directions through the electromagnet in this manner, the permanent magnet can be moved to two positions as shown in the figure.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIGS. 2(a), (b), (c), and (d) are diagrams showing the main components in the embodiment, and the case is omitted for clarity. Figure 2 (a) is a plan view, Figure 2 (b) is a second
FIG. 2(c) is a sectional view along line AA in FIG. 2(a), and FIG. 2(c) is a sectional view along line BB in FIG. 2(a). FIG. 2(d) is a plan view showing a state in which the magnet holder in FIG. 2(a) is moved.

The two rod-shaped permanent magnets (magnet A201, magnet B202) have a length that matches the width of the recording area (about 35 mm for a 5-inch disk). These are adhesively fixed to the magnet holder 203 in parallel. The width and thickness of the magnets and the spacing between the two magnets are such that the magnetic flux generated as shown by the arrow 107 in FIG. For example, it is set appropriately to produce 200 to 400 oersted, depending on the Moreover, this magnet holder 203 is made of a soft magnetic material, and also functions as a yoke that connects the N magnetic pole and the S magnetic pole of the two magnets.

In addition, at both ends of this magnet holder, bearings A206 and B2 are made by drilling guide holes in a material with a small coefficient of friction.
07 is fixed. These two bearings support the magnet holder 203 so that it can move linearly along the guide shaft by engaging with the guide shaft A208 and the guide shaft B209, respectively. Furthermore, magnet A201
．． A flat-wound drive coil 205 is placed close to the magnet B2O2. These components are housed in a case (not shown in the figure) to house the whole thing.
At this time, the guide shafts A, B and the drive coil are fixed to this case, and the magnet holder to which the magnet AS B is fixed is movable. It has already been mentioned that the magnet holder or magnet can be moved by energizing the electromagnet.

This moves the magnet holder to the position shown in Figure 2(a) and to the second position.
It can be moved to the position shown in Figure (d) at will.

In the embodiment described above, the magnet holder is guided by a sliding bearing and a rod-shaped guide. Alternatively, a rolling bearing may be used as the bearing and a groove may be used as the guide.

By using this method, the reversal time can be shortened because the resistance is reduced.

[Effects of the Invention] The bias magnetic field generating mechanism of the present invention has the following special effects.

First, since permanent magnets are used, current consumption is low. Furthermore, since the method applies a magnetic field to the entire recording area, it does not interfere with high-speed access by the head, and the structure is extremely simple. Furthermore, since the present invention adopts a method in which the magnets are moved in parallel, it has become possible to construct the entire mechanism extremely thinly.Also, by driving it with a single simple coil, the structure is simple, making it possible to This makes it possible to reduce the size and weight compared to the previous method.

[Brief explanation of the drawing]

FIGS. 1(Ei) and 1(b) are cross-sectional views showing the operating principle of an embodiment of the present invention. FIG. 2(a) is a plan view of an embodiment of the present invention. Figure 2(b)
is its AA sectional view. FIG. 2(c) is the BB sectional view. Fig. 2(d) is a plan view when the magnet boulder moves in Fig. 2 (a>). Fig. 3 is a perspective view of a conventional example using an electromagnet. Fig. 4 is a conventional example using a permanent magnet. A perspective view of 101, 102, 201, 202, 401...
Magnet 104.205... Drive coil 106.302
．． 404・-Optical Tisph 203・・・・Magnet Boulder 103, 204・・・Yoke 206.207・・・・Bearing 208.209・・・・・・Guide shaft that's all

Claims (1)

[Claims] In a magneto-optical recording and reproducing device, (a) two bar-shaped permanent magnets magnetized in the thickness direction; (b) of the two permanent magnets, one of the N magnetic poles and the other of the S magnetic poles. (c) a magnet holder that holds the permanent magnet and the yoke and has a bearing; (d) a guide that engages with the bearing of the magnet holder and guides the magnet holder linearly; (e) a flat A bias magnetic field generation mechanism comprising a wound drive coil.