JPS61250801A - Device of reversing external magnetic field for optomagnetic disc device - Google Patents

Abstract

PURPOSE:To attain low cost and miniaturization and to improve the reliability by giving a half turn to a permanent magnet in a desired direction with a torque exerted to the permanent magnet generated from a repulsing force caused by an external magnetic field formed by the permanent magnet and by a magnetic field by flowing a current to a coil. CONSTITUTION:The coil 25 is arranged around the permanent magnet 5 provided freely turnably and a torque in a desired direction is given to the permanent magnet 5 by a repulsive force between the magnetic field of the permanent magnet 5 and the magnet generated by flowing a current to the coil 25. In order to give the torque in the desired direction to the permanent magnet 5, for example, the turning center Lm of the permanent magnet 5 is shifted by a prescribed interval DELTAL in parallel with the coil center Lc along the length-wise direction of the permanent magnet 5. Since the repulsive force between the magnetic field caused by flowing a current to the coil 25 and the magnetic field by the permanent magnet 5 itself differs from the right and left side of the turning center Lm of the permanent magnet 5, the permanent magnet 5 is turned in the desired direction through the difference in the repulsive forces.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an external magnetic field reversal device used in a magneto-optical disk device.

(Summary of the Invention) The present invention relates to an external magnetic field reversal device used in a magneto-optical disk device, and in particular uses a permanent magnet as an external magnetic field forming means, and a coil is arranged to surround the permanent magnet. The permanent magnet can be rotated half a turn in a desired direction by the rotational force applied to the permanent magnet due to the repulsion between the external magnetic field formed by the magnet and the magnetic field generated by passing a current through the coil. This makes it possible to obtain an external magnetic field reversal device that is inexpensive, highly reliable, and can be downsized.

[Conventional technology]

Magneto-optical disk devices capable of recording and reproducing data using magneto-optical disks are already known (Japanese Patent Application Laid-Open Nos. 58-14306 and 1982-133537).
Publications, etc.).

The basic concept of this magneto-optical disk device is shown in Figures 11 and 1.
To explain using Figure 2, in Figure 11, ■ is a magneto-optical disk, which is magnetized uniformly in one direction (downward) in data recording, for example, as shown in the figure. shall be taken as a thing. An optical pink amplifier device 2 for recording data on the disk surface and for reproducing the data from the disk surface is arranged opposite to one surface of the disk 1. As is well known, the optical pickup device 2 uses a laser (semiconductor laser, etc.) for recording and reproducing data, and this laser is focused by an objective lens 3 onto the disk surface along an optical path l.

On the disk surface opposite to the optical pickup device 2, an electromagnet 5 serving as an external magnetic field forming means is arranged so as to face the optical pickup device 2, and this electromagnet 5 generates an external magnetic field H perpendicular to the disk surface as shown in the figure. is formed.

When the optical pink-up device 2 is moved to a predetermined disk surface and a laser beam is irradiated from it to heat the disk surface to a temperature of one Curie point or higher (400°C), the magnetic domains in the heated area become irregular. .

In this state, when a predetermined current is applied to the electromagnet 5 so that an external magnetic field H (FIG. 12) in the opposite direction to the external magnetic field H shown in FIG. As shown, the direction is the same as that of the external magnetic field H, so if laser irradiation is stopped in that state, the internal magnetic field remains in the state shown by the broken line. In order to further reverse the direction of this internal magnetic field, the external magnetic field H may be reversed as shown in FIG. 11 and the above-described operation may be performed. And the 11th
By setting the magnetization direction shown in the figure as, for example, "0" and the magnetization direction indicated by the broken line in FIG. Data of "0" and "1" can be recorded (including re-recording) in the circumferential direction.

In addition to electromagnets, permanent magnets can also be used as the external magnetic field forming means. FIG. 13 is a configuration diagram of an external magnetic field reversal device 20 showing an example of a case where a permanent magnet is used as the external magnetic field forming means 5. 5 is disposed opposite to the disk 1 and is rotatably attached, and its rotating shaft 6 is connected to the rotating shaft of the stamping motor via a connecting means 8.

The motor 7 is controlled based on a drive signal from a system controller (not shown), and the permanent magnet 5 is rotated by half a rotation based on the drive of the motor 7, and the half-rotation state is detected by a pair of switches 11 and 12 shown in FIG. be done.

Therefore, the holder 13 to which the permanent magnet 5 is attached is provided with a protruding piece 13A as shown in FIG. switch 11.12
The signal obtained when the protruding piece 13A comes into contact with the motor 7
The supply of drive signals to is stopped. This stabilizes the half-rotation state of the permanent magnet 5.

[Problem that the invention seeks to solve]

As described above, when the external magnetic field reversal device 10 is constructed using permanent magnets instead of electromagnets, the following problems occur.

First, since this external magnetic field reversal device IO uses the stamping motor 7 as a reversal drive source for the permanent magnet 5, it requires circuits such as a driver in addition to the motor 7, and has the drawback of increasing the overall cost. In addition, since the device is constructed using consumable parts such as the motor 7 and the pair of switches 1L12, the device has a short lifespan and lacks reliability, and is an obstacle to miniaturizing the device due to the attachment of the motor etc. .

Therefore, this invention solves these conventional problems.
This invention solves the problem □, and proposes an external magnetic field reversal device for a magneto-optical disk device that is inexpensive, highly reliable, and can be miniaturized.

[Means for solving problems]

In order to solve the above-mentioned problems, in the present invention, as shown in FIG. A rotational force in a desired direction is applied to the permanent magnet 5 by the repulsive force between the magnetic field and the magnetic field generated by passing a current through the coil 25.

Various means can be used to apply a rotational force in a desired direction to the permanent magnet 5, and in the embodiment shown in FIG. The rotation center Lm is slightly shifted in parallel with the coil center Lc by a predetermined distance Δ■-.

[Effect]

According to this configuration, since the repulsive force between the magnetic field generated by passing a current through the coil 25 and the magnetic field of the permanent magnet 5 itself is different between the left side and the right side of the rotation center Lm of the permanent magnet 5, this repulsive force is different. The permanent magnet 5 rotates in a desired direction (clockwise or counterclockwise). In this case, if the coil 25 is kept energized, the permanent magnet 5 is stabilized in a half-rotation state. This is because the magnetic field of the permanent magnet 5 and the magnetic field of the coil 25 are oriented in the opposite direction, and the repulsive force applied to the permanent magnet 5 disappears.

As a result, the direction of the external magnetic field H passing through the disk 1 is reversed, and in order to further reverse the direction of the external magnetic field H, if a current is passed through the coil 25 in the opposite direction to that of the double series, the above-mentioned method can be achieved. Based on the same reason, the permanent magnet 5 rotates another half turn and becomes stable in that state.

In this way, if the magnetic field of the permanent magnet 5 is actively used and the magnetic field generated by the coil 25 is generated only when necessary,
The opposing polarity of the permanent magnet 5 with respect to the disk surface can be freely changed.

According to the configuration of the present invention in which the magnetic field of the permanent magnet 5 and the magnetic field of the coil 25 form a rotational force on the permanent magnet 5, effects such as miniaturization of the device and reliability of the device can be obtained.

〔Example〕

An example of an external magnetic field reversal device 20 according to the present invention will be described in detail with reference to FIG. 1 and the following figures.

The permanent magnets used in this device are as shown in Figure 4.
It forms a flat rectangular parallelepiped and is magnetized so that one of the flat surfaces becomes an S pole and the other becomes an N pole. The permanent magnet 5 is shown in FIGS. 1 and 2.
The boulder 21 is attached to the holder 21 shown in the figure, and the boulder 21 is provided with rotating shafts 22 at both left and right ends thereof, which are attached to a pair of mounting pieces 24 formed on the main mounting plate 23. A and 24B are rotatably supported.

As shown in FIG. 1, a coil 2 with a predetermined number of turns surrounds the permanent magnet 5.
5 is provided. In this case, the rotation center L of the permanent magnet 5
m and the center Lc of the coil 25 in the direction of the rotation axis 22 are shifted by ΔL, and in this example, the rotation center Lm is located below the center Twc of the coil 25 by ΔL, as shown in the figure. The location of the installation is selected.

26 and 27 are locking pieces provided to specify the surrounding position of the coil 25, and these are both fixed to the main mounting plate 23.

Here, the main part of the longitudinal section of FIG. 1 is shown in FIG. 3. For convenience of explanation, the polarity of the permanent magnet 5 is N pole at the top and S pole at the bottom, and in this state, the coil 25
Suppose that a predetermined current is applied to the coil to generate a downward coil magnetic field Hc. At this time, the magnetic field Hc is maximum at the coil center Lc, so the strength of the magnetic field Hc on the right side of the rotating shaft 22 of the permanent magnet 5 placed within this magnetic field Hc, and the magnetic field Hc' on the left side thereof are The relationship is Hc >Hc'.

On the other hand, the magnetic field Hm of the permanent magnet 5 is equal on both sides of the rotating shaft 22, and in the polarity shown in FIG. 3, the magnetic field Hm is directed upward.
A repulsive force is generated between m and m.

In addition, the coil magnetic fields Hc, Hc' and the magnetic field Hm of the permanent magnet 5
The relationship with Hc, I(c'<<Hm) is selected.

For this reason, in the case shown in the figure, Hc>Hc'
Therefore, the repulsive force is greater on the right side of the rotating shaft 22 than on the left side, so the permanent magnet 5 rotates counterclockwise.

When the permanent magnet 5 rotates half a rotation, the polarity of the permanent magnet 5 becomes opposite to that shown in the figure, so the magnetic field Hm also becomes downward, and in this case, no repulsive force is generated.

A current is kept flowing through the coil 25 even after the permanent magnet 5 has rotated half a rotation. In this way, the rotational position of the permanent magnet 5 will not change even due to disturbances, and the rotational state will be stabilized.

To return the permanent magnet 5 to its original rotational state, the coil 2
5, a current is applied in the opposite direction to that described above.

Then, at this time, the upward coil magnetic field Hc.

This is because Hc' is generated, and a repulsive force is generated between the magnetic fields Hc, Hc' and the magnetic field Hm of the permanent magnet 5, causing the permanent magnet 5 to rotate in the same direction as described above.

As shown in FIG. 5, the external magnetic field reversal device 20 that operates in this manner has its main mounting plate 23 attached to a rotating plate 35, and the rotating plate 35 rotates about a fulcrum 36 in the direction of arrow a. move. Therefore, when the disk 1 is installed, the external magnetic field reversal device 20 is rotated as shown by the two-dot chain line to facilitate the disk installation, and after the disk is installed, it is rotated as shown by the solid line and permanently attached to the disk 1. Magnets 5 are opposed as shown.

Data recording and playback are executed in this state, for example,
When recording predetermined data (“0” or “1”) on the disk surface, move the optical pink-up device 2 to the recording position and irradiate the disk surface with a laser in that state, and a permanent magnet will be generated. Data can be recorded according to the direction of the external magnetic field Hm generated by the magnetic field Hm. In addition, when recording data different from that described above, the polarity of the permanent magnet 5 facing the disk surface may be reversed by energizing the coil 25, and the laser beam may be irradiated in this state.

In this way, in this invention, the magnetic field Hm of the permanent magnet 5 itself
By applying a coil magnetic field Hc from the outside, a rotational force is applied to the permanent magnet 5.
The means for applying rotational force to the permanent magnet 5 is not limited to the embodiment shown in FIG.

An example of other means will be explained with reference to FIG. 6 and subsequent figures.

In the example shown in FIG. 6, the rotating shaft 22 attached to the holder 21 of the permanent magnet 5 is mounted eccentrically by ΔL from the center Lm of the permanent magnet 5, so that the rotating shaft 22 is located at the center of the coil 25. It is attached to match Lc.

Even with this configuration, the strength of the magnetic field is different on the right side and the left side of the rotation axis 22 of the permanent magnet 5, so a repulsive force similar to that described above is generated, and the permanent magnet 5 is moved in the desired direction. It can be rotated to

The embodiment shown in FIG. 7 is a permanent magnet 5 having the structure shown in FIG.
As shown in FIG. 8, the relative positional relationship is selected so that both centers Lc and Lm coincide, and the bearing of one rotating shaft 22 is placed on the side. A hollow-shaped iron piece 30 is attached and fixed in a state of being inclined at a predetermined angle θ with respect to the axial load line.

With this iron piece 30, a magnetic path is formed in which the magnetic flux of the coil 25 passes through the iron piece 30, so that the coil magnetic field He is inclined by θ with respect to the magnetic field Hm of the permanent magnet 5. As a result, a rotational force is generated on the permanent magnet 5 due to the combined magnetic field, and the permanent magnet 5 is rotated in a predetermined direction in the same manner as described above.

The embodiment shown in FIG. 9 is a case where a short circuit coil 33 is provided in place of the iron piece 30 shown in FIG. 7, and as shown in the figure, a permanent magnet 5 similar to that in FIG. is arranged, and the shorting coil 33 is arranged so as to face one side of the permanent magnet 5.

That is, as shown in FIG. 10, in this example, it is arranged at a predetermined distance from the permanent magnet 5 so as to be located on the upper surface side of the permanent magnet 5 and on the left side of the rotation axis 22 thereof.

When configured in this way, a part of the magnetic flux of the coil 25 intersects with the short circuit coil 33, and an electromotive force is generated therein.
Based on this, a predetermined magnetic field is generated in the short circuit coil 33. Due to this magnetic field and the magnetic field of the coil 25, the combined magnetic field is tilted by a predetermined angle, for example, θ. As a result, the same rotational force as shown in FIG. 7 is applied to the permanent magnet 5, and the permanent magnet 5 can be rotated.

In the embodiment shown in FIG. 1 and below, the length of the permanent magnet 5 can be recorded on the disk 1 as shown in FIG. - When data is to be recorded on a predetermined (2) l rank, which is selected to be approximately equal to the length of the number of racks, the optical pickup device 2 is moved to that track. - Just an example.

In order to determine whether or not the permanent magnet 5 has been correctly reversed, a magnetic field reversal detecting means, e.g. , a Hall element 38 is attached. The external magnetic field Hrn from this permanent magnet 5 depends on whether the polarity of the permanent magnet 5 facing the pole element 38 is N or S.
Since the polarity and detection level of the detection output of the Hall element 38 differ depending on whether or not it passes vertically through the pole element 38, it is possible to determine whether the permanent magnet 5 is correctly reversed or not based on this detection output. Its polarity can be detected.

Detection output - Supplied to the system controller, and the presence or absence of laser irradiation is controlled based on the detection output.

The shape and length of the permanent magnet 5 shown in FIG. 1 and below are merely examples, and the invention can be applied to other shapes and lengths.

〔Effect of the invention〕

As explained above, in this invention, the permanent magnet 5 is used as an external magnetic field forming means, and the coil 25 is arranged to surround the permanent magnet 5, which is rotatably arranged.
is arranged, and a rotational force in a desired direction is applied to the permanent magnet 5 by using the magnetic field of the permanent magnet 5 and the repulsive force of the magnetic field generated by passing a current through the coil 25. That is, according to this configuration, since the repulsive force between the magnetic field generated by passing a current through the coil 25 and the magnetic field of the permanent magnet 5 itself is different between the left side and the right side of the rotation center Lm of the permanent magnet 5, this repulsive force The permanent magnet 5 moves in the desired direction (
The direction of rotation differs depending on which direction the magnet center Lm is shifted by ΔL with respect to the coil center Ic. ).

As a result, the direction of the external magnetic field Hm passing through the disk 1 is reversed, and if the direction of the external magnetic field Hm is to be further reversed, a current in the opposite direction to that of the two series can be passed through the coil 25, and the above-mentioned method can be achieved. Based on the same reason, the permanent magnet 5 rotates another half turn and becomes stable in that state. With this configuration, the present invention can achieve at least the following effects compared to the prior art.

First, a permanent magnet 5 and a coil 25 are used, and the permanent magnet 5
Since the permanent magnet 5 can be rotationally driven by skillfully utilizing the magnetic field, it is possible to realize an external magnetic field reversal device at a lower cost than the conventional one.

Second, most of the rotational force on the permanent magnet 5 is caused by the permanent magnet 5
Because it relies on its own magnetic flux, only a small amount of current needs to be passed through the coil 25 to obtain the rotational force, so the device 20 according to the present invention can significantly reduce power consumption.

Thirdly, since consumable parts such as motors are not used as components compared to the past, the life of the device is extended and a highly reliable device can be provided.

Fourthly, since only the coil 25 is provided in place of the motor 7, the device can be made smaller.

Fifth, the optical pink-up device 2 is an external magnetic field reversal device 20.
Since it is constructed separately from the main unit, maintenance and inspection are easy. For example, in the configuration disclosed in JP-A-57-133537, the optical pink-up device and the external magnetic field reversal device are integrated, so even if only the optical pink amplifier device fails, This is because the entire structure needs to be replaced or inspected.

Sixthly, as shown in FIG. 2, if a magnetic field reversal detecting means is attached, it is possible to confirm the polarity reversal of the permanent magnet 5, so that the laser irradiation state can be accurately controlled.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an example of an external magnetic field reversal device according to the present invention, FIG. 2 is a cross-sectional view thereof, FIG. 3 is a longitudinal cross-sectional view thereof, and FIG. 4 is a perspective view showing an example of a permanent magnet. FIG. 5 is a partial sectional view showing an example of a magneto-optical disk device equipped with this external magnetic field reversal device, and FIGS. 6, 7, and 9 are plan views showing other examples of the present invention, respectively. The sectional views, FIGS. 8 and 10, are the longitudinal sectional views of FIGS. 7 and 9, and 11
12 and 12 are conceptual explanatory diagrams of magneto-optical recording, FIG. 13 is a configuration diagram showing an example of a conventional external magnetic field reversal device, and FIG.
The figure is a partial diagram showing its operating state. 1 is a magneto-optical disk, 2 is an optical pickup device, 20 is an external magnetic field reversal device, 5 is a permanent magnet serving as an external magnetic field forming means, 22 is its rotating shaft, 25 is a coil, 30 is an iron piece, 33
is the short-circuited coil, Lc is the center of the coil, and Lm is the permanent magnet 5.
is the center of 7゜i′ Kaibeku Kidori Keizuka Bo Uta 7” y (L + force 2 尤 る fin SKh 人ふけ - 1 stone k (E hLk'1 '3 ''R7 Fig. 11 1 momme m1 conversion ikW 8 Figure 12 External details I Honjo 11 Figure 13 q Reversal of the outer world is prohibited l! f1 Tanuki' 1st view Figure 14

Claims (1)

[Scope of Claims] A rotatable permanent magnet that is disposed facing the magneto-optical disk surface at a predetermined distance and that receives an external magnetic field that passes perpendicularly to the disk surface, and a coil that surrounds the permanent magnet. is arranged, and by rotating this permanent magnet by half a rotation with the rotational force applied to the permanent magnet generated by the repulsion between the magnetic field generated by energizing this coil and the magnetic field of the permanent magnet, the external magnetic field due to the permanent magnet is reduced. An external magnetic field reversal device for a magneto-optical disk device that reverses the direction.