JPH06101082B2 - External magnetic field reversing device for magneto-optical disk device - Google Patents

Description

The present invention relates to an external magnetic field reversal device used in a magneto-optical disk device.

[Outline of Invention]

The present invention relates to an external magnetic field reversal device used in a magneto-optical disk device, and in particular, a permanent magnet is used as an external magnetic field forming means, a coil is arranged so as to surround the permanent magnet, and a current is passed through the coil. This allows the permanent magnet to be half-turned in the desired direction by the repulsive force generated by the magnetic field generated by this and the magnetic field of the permanent magnet, which makes it inexpensive, highly reliable, and compact. The external magnetic field reversal device which can be realized is obtained.

[Conventional technology]

A magneto-optical disk device capable of recording / reproducing data by using the magneto-optical disk has already been known (Japanese Patent Laid-Open No. S60-18753).
58-14306 and JP-A-57-133537).

The basic concept of this magneto-optical disk device will be described with reference to FIGS. 5 and 6. In FIG. 5, (21) is a magneto-optical disk, which is shown in FIG. It is assumed that the magnet is uniformly magnetized in the direction (downward). On one surface of the disk (21), an optical pickup device (22) for recording data on the disk surface and reproducing the data therefrom is arranged oppositely.
As is well known, the optical pickup device (22) uses a laser (semiconductor laser or the like) for recording / reproducing data, and this laser is focused by the objective lens (23) on the disk surface as an optical path l.

An electromagnet (25), which is an external magnetic field forming means, is arranged on the disk surface opposite to the optical pickup device (22) so as to face the optical pickup device (22).
Therefore, the external magnetic field H perpendicular to the disk surface as shown in FIG.
Is formed. (25a) and (25b) are the power supply terminals.

When the optical pickup device (22) is moved to the specified disk surface and the laser is irradiated from this, and the temperature of the disk surface is heated to a temperature above the Curie point (400 ° C), the magnetic domains in the heated portion become uneven. . In this state, when a predetermined current of the electromagnet (25) is applied so that an external magnetic field H (FIG. 6) opposite to the external magnetic field H shown in FIG. Since the magnetization direction is in the same direction as the external magnetic field H as shown by the broken line, when the laser irradiation is stopped in that state, the internal magnetic field remains as shown by the broken line. In order to further reverse the direction of the internal magnetic field, the external magnetic field H may be reversed as shown in FIG. 5 and the above operation may be executed. The magnetization direction shown in FIG. 5 is, for example, “0”, and the magnetization direction shown by the broken line in FIG. 6 is “1”.
Therefore, if the above-mentioned magnetization operation is sequentially performed in the circumferential direction of the disk (21) with a predetermined pitch, data "0" and "1" are recorded in the circumferential direction (including re-recording). )
can do.

As an external magnetic field forming means, the present applicant has previously described FIGS.
We proposed the device shown in the figure. Briefly explaining this, (1) is a frame made of a non-magnetic material such as aluminum, which has a long shape, and a pair of bearing pieces (2a) and (2b) face each other. It is cut and raised from the frame (1). (3) is a rectangular parallelepiped permanent magnet that is magnetized in the thickness direction of Y, and both ends in the longitudinal direction of the magnet (3) are magnet mounting brackets (4a) and (4b). It is rotatably attached to the above-mentioned bearing pieces (2a) and (2b) via the rotating shafts (5a) and (5b). (6) is the axis of rotation of the magnet (3).

A coil (8) is arranged so as to surround the magnet (3) described above, and the coil bobbin (7) is fixed on the frame (1). Of course, this bobbin (7) is also made of a non-magnetic material. In FIG. 9, (9) is a central axis of the coil (8), (3a) is an axis orthogonal to the rotation axis (6) and extending in the magnetizing direction of the magnet (3). The axis of the magnet (3). In FIG. 9, the two axes (9) and (3a) coincide with each other.

Further, one side is provided with a U-shaped iron piece (10) outside the bearing piece (2b) of the rotating shaft (5b), which is inclined by an angle θ with respect to the central axis (9) of the coil (8). ,
Both ends of the iron piece (10) are extended so as to approach the magnet (3).

In such a structure, the U-shaped iron piece (10) is now formed.
When there is not, since the magnetic state around the magnet (3) with respect to the magnetic flux from the magnet (3) is almost balanced left and right around the central axis (9), the coil (8) The magnet (3) is in the rotational position shown by the solid line regardless of whether the magnet is energized or not energized.

By arranging the U-shaped iron piece (10) in such a state, the magnetic state around the magnet (3) becomes unbalanced with respect to the left and right of the central axis (9), that is, the magnet (3). The magnetic flux generated thereby tends to flow toward the iron piece (10), so that when the coil (8) is not energized, the magnet (3) is inclined as shown by the dotted line in FIG. It will be stationary.

In this state, when a direct current is supplied to the coil (8), the magnet (3) is rotated along the axis of rotation so that the direction of the magnetic field generated thereby and the direction of the magnetic field generated by the magnet (3) match. It rotates about (6), that is, the ninth
The position indicated by the solid line in the figure is rotated. Also, by changing the direction of the current to the coil (8), the magnet (3) is rotated (reversed) by 180 ° from the above-mentioned state and is similarly positioned.
That is, by reversing the direction of the current to the coil (8), the magnet (3) is reversed and the coil (2) described in FIG.
The same magnetic field as in the case of 5) will be formed.

As described above, since the U-shaped iron piece (10) is provided, at the time of switching from the energized state in one direction to the energized state in the other direction (reverse direction), energization in one direction is performed. The moment the state is cut off, the magnet (3) starts rotating from the position shown by the solid line toward the position shown by the dotted line, and the reversal of this magnet (3) is surely and quickly when the energization in the other direction starts. Become.

In other words, if the iron piece (10) is not present, the magnet (3) is always in the state shown by the solid line, so even if a current for reversing this is supplied to the coil (8) in this state,
In some cases, the magnet (3) hits the dead point and cannot be inverted. The iron piece (10) ensures that this can be reversed.

[Problems to be Solved by the Invention] In the above-mentioned configuration, since the iron piece (10) is arranged in the longitudinal direction of the magnet (3), there is a problem that the entire device becomes long and large.

In particular, the disk (21) is rotatably accommodated in a cartridge (not shown), and a long window hole extending in the radial direction of the disk is formed in a part of the cartridge, and the external magnetic field reversal described above is performed through the window hole. In the case where the devices are opposed to each other, there is a problem that the magnet (3) does not enter the window hole when the length (size) of the window hole of the cattle ridge is regulated.

[Means for solving problems]

The present invention solves the above-mentioned problems and removes the iron piece (10) described above. An external magnetic field reversing device for a magneto-optical disk device according to the present invention is, for example, as shown in FIGS. 1 to 4, arranged so as to face a magneto-optical disk surface with a predetermined distance therebetween, and passes vertically through the disk surface. A rotatable permanent magnet (3) for obtaining an external magnetic field and a coil (8) surrounding the permanent magnet are arranged, and generated by the repulsive force of the magnetic field generated by energizing the coil and the magnetic field of the permanent magnet. An external magnetic field reversing device for a magneto-optical disk device, wherein the direction of an external magnetic field generated by the permanent magnet is reversed by rotating the permanent magnet halfway by a rotational force applied to the permanent magnet. In the plane perpendicular to the axis (6), the first axis is defined when the central axis (9) of the coil is the X axis and the line (11) orthogonal to the axis and passing through the rotation axis is the Y axis. Limited to the fourth quadrant I, II, III, characterized in that a IV magnetic piece in at least one quadrant of the (shown. In FIG. 4) (12).

[Action]

In this way, the magnetic piece (12) is placed in any of the first to fourth quadrants.
By arranging, the magnetic state around the magnet (3) is not what is called balanced centering around the X-axis, which causes the magnet (3) to move along the X-axis as shown by the dotted line in FIG. And becomes the same as the above-mentioned example.

〔Example〕

With reference to FIGS. 1 to 4 of the drawings, an example of the device according to the present invention will be described. In the parts corresponding to FIGS. 7 to 9,
The same reference numerals are given. Therefore, (1) is a frame made of non-magnetic material, (2a) and (2b) are bearing pieces formed by cutting and raising a part of them, (3) is a permanent magnet, and (4a) and (4b) are Bracket, (5a) and (5b) are rotating shafts,
(8) is a coil, and (7) is its bobbin. The structure is almost the same as the above example, but the above-mentioned U-shaped iron piece (10) does not exist.

And in the present invention, the rotation axis (6) of the magnet (3)
Center plane of the coil (8) (9) (X
Axis) and the magnetic piece (12) arranged in the third quadrant III defined by the axis (11) (Y axis) orthogonal to the axis,
The magnetic piece (12) is attached to the lower surface of the frame (1) so as to extend in the extension direction of the magnet (3).

According to such a configuration, when the coil (8) is not energized, the magnet (3) is inclined as shown by the dotted line, and when the coil (8) is energized, the axis (3a) of the magnet (3) is. Is brought to a position corresponding to the central axis (9) as shown by the solid line. Of course, when the direction of the current is changed, this magnet (3) is inverted at the position shown by the solid line.

The above is the case where the magnetic piece (12) is arranged in the third quadrant, or it may be arranged in the first quadrant I as shown by reference numeral (12 ′) in FIG. 4, or by the reference numeral (12 ″). It may be arranged in the second quadrant II as shown, in which case it can be mounted on the bobbin (7), and of course in the fourth quadrant IV as indicated by the reference numeral (12).

Further, magnetic pieces may be arranged in the quadrants having a symmetrical relationship with respect to the rotation axis (6), that is, in the first quadrant I and the third quadrant III, respectively, and in the second quadrant II and the fourth quadrant IV, respectively. You may arrange.

〔The invention's effect〕

According to the present invention described above, since the magnetic state around the magnet is unbalanced with respect to the central axis (9), the magnet (3) is not energized to the coil (8).
Always tries to rotate the state shown by the dotted line, and therefore, when the magnetic piece (12) does not exist, that is, when the magnetic state is balanced, the magnet (3) should be supplied with an electric current for reversing. However, it is possible to avoid the problem that the magnet cannot be reversed at the dead point, that is, to perform a reliable reversing operation. Of course, as shown in FIG. 7, there is no iron piece in the longitudinal direction of the magnet. Therefore, there is a feature that the length can be increased and the whole can be shortened, that is, the size can be reduced.

[Brief description of drawings]

1 is a plan view showing an example of an external magnetic field reversal device according to the present invention, FIG. 2 is a bottom view thereof, FIG. 3 is a sectional view taken along the line AA of FIG. 1, and FIG. 4 is for showing another example. 3 is a schematic cross-sectional view corresponding to FIG. 3, FIGS. 5 and 6 are explanatory views of magnetization reversal, respectively, and FIG. 7 is a plan view of an external magnetic field reversal device previously proposed by the applicant of the present invention, and FIG. The figure is a side view thereof, and FIG. 9 is a sectional view taken along line BB of FIG. (1) is a frame, (3) is a permanent magnet, (8) is a coil, and (12) is a magnetic piece.

Claims (1)

[Claims] 1. A rotatable permanent magnet, which is arranged to face the surface of a magneto-optical disk with a predetermined distance therebetween and obtains an external magnetic field passing perpendicularly to the surface of the disk, and a coil surrounding the permanent magnet. The direction of the external magnetic field generated by the permanent magnets is half-rotated by the rotational force applied to the permanent magnets, which is generated by the repulsive force generated by the magnetic field generated by energizing the coil and the magnetic field of the permanent magnets. In an external magnetic field reversing device for a magneto-optical disk device, the central axis of the coil is defined as the X axis in a plane perpendicular to the rotation axis of the permanent magnet, and a line orthogonal to and passing through the rotation axis. A magneto-optical disk characterized in that a magnetic piece is arranged in at least one of the first to fourth quadrants I, II, III and IV defined when the Y axis is defined as An external magnetic field reversing device.