JPH03224148A - Bias magnetic field applying device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a bias magnetic field applying device used in a magneto-optical disk device or the like.

[Prior Art] Normally, magneto-optical recording is performed by first continuously irradiating a magneto-optical disk with a laser beam of recording power, and applying an erase magnetic field to align the magnetization direction in one direction. While applying a recording magnetic field in the opposite direction, a laser beam with a recording power modulated according to the recorded information is irradiated. The above two steps are required to record information. Therefore, in order to shorten the information recording time, it is necessary to shorten the switching time between the erasing magnetic field and the recording magnetic field as quickly as possible.

Conventionally, as a method to shorten the switching time, a rectangular magnet placed parallel to the magneto-optical disk was rotated during recording and erasing, and the magnet was rotated in the S and N directions facing the magneto-optical disk. A method to change this is proposed.

FIG. 10 shows a cross-sectional view of a magnetic field application device disclosed in Utility Model Application Publication No. 64-42503, which is one of these methods. Rotatably supported at the center. A first coil A and a second coil B to which a cantering current for controlling the rotation of the magnet 51 is supplied are arranged in parallel at symmetrical positions with respect to the rotation center axis C of the magnet 51.

When rotating the magneto-optical disk 50 from a state in which the north pole (or south pole) faces the surface of the magnet by 18 degrees to a state in which the south pole (or north pole) faces the magneto-optical disk 50, the first coil and the second By passing a constant current through the coil while the magnet rotates 180°, rotational force is generated in the first 90', stopping force is generated in the latter 90', and the rotational speed is zero at the 180° rotated position. Note that the rotation angle of the magnet is detected by a Hall element.

Next, the force exerted on the magnet 51 by the current flowing through the coil arranged around the magnet 51 will be explained with reference to FIG. When a current flows from the front to the back perpendicular to the plane of the paper at a position a facing the N pole of the magnet 51, the current flowing at a position a receives a rightward force fa in Figure 11 due to Fleming's left hand rule. . The magnet 51 receives a torque Ta around the axis C as a reaction. Similarly, the current flowing in the opposite side of the magnet is subjected to a leftward force fb. Since this direction fb is directed toward the rotation axis C of the magnet 51, the magnet is not subjected to torque around the axis C due to reaction.

Therefore, when the state shown in FIG. 5 is set to θ=0°, the relationship between the rotation angle θ and the torque received by the magnet when the magnet is rotated counterclockwise is as shown in FIG. 12.

Oo and 180' where the magnetic pole face faces the current flowing at position a
The torques Ta and Ta' reach their peaks at 90°, where the sides face each other, and the torques become zero. Also, the torque T a ' due to the current flowing at a position a' away from the magnet is f
Since a' is small, it is smaller than Ta.

[Problems to be Solved by the Invention] Again in the conventional example shown in FIG. 10, the relationship between the torque acting on the magnet 51 and the rotation angle is shown in FIG. 13 based on the above idea.

Figure 13 (a) shows the torque due to coil A,
The broken line is the torque due to parts a and a', and the dashed line is the coil A.
is the torque (total of parts a and a'). The figure (b) shows the torque due to the coil B, and the figure (c) shows the combined torque of the coils A and B. The combined torque of coil A and coil B is positive (counterclockwise) at θ=o°
peak, negative (clockwise) peak at 180°, 90°
It becomes zero at 90° in the first half (θ=o° to 90°), is accelerated by counterclockwise rotational force, and is accelerated at 90° in the second half (θ=o° to 90°).
90° to 180°), negative torque acts as a stopping force,
It is decelerated and the rotational speed becomes zero at θ=180'.

However, here, the torque due to parts a' and b'1 acts in a direction that prevents rotation when rotation starts, and acts in a direction that tries to rotate when stopped, which means that the current flowing through the coil is not used effectively. I understand. Therefore, the magnet is 18
The disadvantage is that the time required to rotate 0° is long, and switching between the erasing magnetic field and the recording magnetic field on the magneto-optical recording surface cannot be performed quickly.

SUMMARY OF THE INVENTION In view of the above-mentioned problems in the technology, it is an object of the present invention to provide a bias magnetic field applying device that rotates a magnetic field by 18 degrees at high speed and reduces the time required to switch between a recording magnetic field and an erasing magnetic field.

[Means for Solving the Problems] As shown in FIG. 1, the invention according to claim 1 is a magneto-optical disk that is rotatably supported around an axis C that is parallel to one surface of the disk, and whose magnetization direction is aligned with the axis C. In a bias magnetic field applying device comprising a magnet 2 which is perpendicular to the axis C, and a coil through which a driving current is passed to control the rotation of the magnet 2, the coil is parallel to the axis C, sandwiching the magnet 2, and applying light. A wire rod 4a located on the opposite side to the magnetic disk, a wire rod portion 4b placed on the side surface of the magnet 2 at a position parallel to the axis C and closer to the magneto-optical disk 1 than the axis C, Wire rod part 4a
, 4b.

4d, and a second coil 5 that is provided approximately symmetrically to the first coil with respect to a plane P that includes the axis C and is perpendicular to the surface of the magneto-optical disk. As shown in FIG. 4, the invention according to claim 2 is such that the magneto-optical disk is rotatably supported around an axis C parallel to one surface of the disk, and
A magnet 12 whose magnetization direction is perpendicular to the axis C, and a coil 14 through which a driving current for controlling the rotation of the magnet is passed.
In the bias magnetic field applying device, the coil is parallel to the axis C, and the wire portion 14a is located on the opposite side of the magneto-optical disk 1, sandwiching the magnet; It is characterized by consisting of a wire rod portion 14b located between the magnetic disk 1 and wire rod portions 14c and 14d that connect both ends of the two wire rod portions 14a and 14b.

Further, the invention according to claim 3 is the bias magnetic field applying device according to claim 2, wherein the bias magnetic field applying device is parallel to the axis C, and the magnet 2 is parallel to the axis C.
When the magnetic pole faces of the magneto-optical disk 1 are located at positions facing each other, the wire portion 1 is disposed at a position facing the side surface of the magnet.
It is characterized in that it includes an auxiliary coil 15 having a diameter of 5a.

[Function] According to the invention described in claim 1, the wire portion 4a parallel to the axis C
In addition to the section and section 58, there is also a wire section 4 provided next to the magnet.
Since the current flowing through portions b and 5b is also effectively used to rotate the magnet 2, a large torque is generated when starting and stopping, and the magnet can be rotated 180 inches at high speed.

According to the invention as claimed in claim 2, since the current flowing through the wire portions 148 and 14b parallel to the axis C in a state extremely close to the magnet 12 is used for rotating the magnet 12, the , generates sufficient torque when stopped, and at high speeds 18
It can be rotated by 0°.

Furthermore, according to the invention as claimed in claim 3, by arranging the auxiliary coil 15 having the wire portion 15a at the above-mentioned position, the torque acting on the magnet normally becomes zero at the 90° position, but in the present invention, the torque acting on the magnet becomes zero at the 90° position. In this case, it does not become zero and a rotational force acts.

[Embodiment] In FIG. 1 showing a first embodiment of the present invention, a magnet 2 is rotatably supported about an axis C parallel to a magneto-optical disk 1. As shown in FIG. Note that the axis C is normally taken in the radial direction of the magneto-optical disk 1. The optical pickup 3 can move in the radial direction of the magneto-optical disk 1 to access any desired track. The axis C is aligned with the moving direction of the optical pickup 3, and the length of the magnet 2 is made longer than the recordable range of the magneto-optical disk 1, so that the magnetic field is applied over the entire recordable area by the optical pickup 3. can be applied.

Parts 4a and 5a of the coils 4 and 5 are located on the opposite side of the magneto-optical disk 1 with the magnet 2 in between, and are parallel to the axis C. The 48th part and the 5a part are connected to the bent 40th part, 4d part, and 50th part and 5d part, respectively.

The coils 4 and 5 are arranged symmetrically with respect to a plane P that includes an axis C and is perpendicular to the magneto-optical disk 1, and are fixed to a box 6 (indicated by a dashed line).

The rotation of the magnet 2 can be detected by magnetic field detection means 7 and 8 symmetrically attached to the box body 6.

FIG. 2 is a schematic diagram seen from the direction of axis C, and the operation will be explained with reference to this diagram.

In the state shown in FIG. 2(A), the S pole of the magnet 2 faces the magneto-optical disk 1, and an upward magnetic field is applied to the magneto-optical disk 1. The optical pickup 3 continuously irradiates the magneto-optical disk 1 with laser light of sufficient power to reverse the magnetization direction, thereby aligning the magnetization direction upward.

Next, as shown in FIG.
By passing a current in the direction from the front to the back of the paper to the section 5a, and in the direction from the front to the front of the paper to the sections 4a and 5b,
FIG. 3 shows the change in torque while the magnet 2 rotates 180 degrees. Figure 3 (a) shows the torque applied to coil 4, and the broken line is 48
The torque due to portions 4a and 4a, and the dashed dotted line are the torque due to the entire coil 4.

Similarly, FIG. 3(b) shows the torque due to parts 5a, 5b, and the entire coil 5, and FIG. 3(c) shows the total torque of the coil 4 and coil 5. It is accelerated counterclockwise at the full 90°, decelerated by clockwise torque at the latter 90°, and when it has rotated 180', the rotational speed becomes zero.

At the Oo position and the 180° position, the outputs of the symmetrically provided magnetic field detection means 7 and 8 are equal, so that the 180° position can be detected. When 180° is detected, coil 4
, 5, the magnet 2 can be stopped at the 180° position.

In the case of the present invention, not only 48 parts and 5a parts, but also 4a parts, 5 parts
Since the current flowing through part b is also used effectively, large torque is generated at startup and stop, and it is possible to rotate 180 degrees at high speed.

As shown in FIG. 2(C), a downward magnetic field is applied while the N pole remains at a position facing the magneto-optical disk 1. Here, by irradiating a light beam modulated according to the recording signal, a downwardly magnetized region is created.

Through the above process, recording is completed. Since the time required to rotate the magnet 180 degrees is short, the time required for recording is also shortened.

FIG. 4 shows a second embodiment of the invention. In the same figure,
A magnet 12 is rotatably supported around an axis C parallel to the magneto-optical disk 1 . Note that the axis C is normally taken in the radial direction of the magneto-optical disk 1. The optical pickup 3 can move in the radial direction of the magneto-optical disk 1 to access any desired track. The axis C is aligned with the moving direction of the optical pickup 3, and the length of the magnet 12 is made longer than the recordable range of the magneto-optical disk 1, so that the magnetic field is applied over the entire recordable area by the optical pickup 3. can be applied. A portion 14a of the coil 14 is located on the opposite side of the magneto-optical disk 1 across the magnet 12, and is parallel to the axis C. The section 14a is located between the magnet 12 and the magneto-optical disk 1, and is arranged parallel to the axis C. 14a
The parts 14a and 14a are connected to each other by parts 14a and 14a, and are fixed to a box 16 (indicated by a dashed line) so as to surround the magnet 12.

The rotation of the magnet 12 can be detected by magnetic field detection means 17 , 18 symmetrically mounted on the box 16 .

FIG. 5 is a schematic view seen from the direction of axis C, and the operation will be explained with reference to this figure.

In the state shown in FIG. 5(a), the magnet 12 is attached to the magneto-optical disk 1.
The S poles of the two are facing each other and an upward magnetic field is applied thereto. The optical pickup 3 continuously irradiates the magneto-optical disk 1 with laser light of sufficient power to reverse the magnetization direction, thereby aligning the magnetization direction upward.

Next, as shown in Fig. 5 (b), 1 of the coil 14 (Fig. 4)
The magnet 12 is rotated by 180 degrees by passing a current in the direction from the front to the back of the paper through the section 4a and in the direction from the front to the front of the paper through the section 14a.

180' counterclockwise, assuming the state in figure (b) as 0°.
Figure 6 shows the change in torque during rotation.

In the same figure, the dashed-dotted line indicates the torque due to only portions 14a and 14b, and the solid line indicates the torque due to the entire coil 5, respectively. The first half is accelerated counterclockwise at 90 degrees, and the second half is accelerated at 90 degrees.
When the rotation speed is reduced by clockwise torque and rotated 180 degrees, the rotation speed becomes zero. Oo position and 180'
At the position, the magnetic field detection means 17 and 18 provided symmetrically have the same output direction, so the 180° position can be detected by detecting that the difference between the two outputs becomes zero.

When 180° is detected, the current in the coil 14 is cut off to stop the magnet 12 at the 180° position. In the case of this embodiment, since the current flowing through the parts 14a and 14b is effectively used, a large torque is generated at the time of starting and stopping, and it is possible to rotate the motor 180 degrees at high speed.

Next, as shown in FIG. 5(c), the north pole
A downward magnetic field is applied while the object is stopped at a position opposite to . Here, by irradiating a light beam modulated according to the recording signal, a downwardly magnetized region is created. Through the above process, recording is completed. 18 magnets
Since the time required for 0° rotation is short, the time required for recording is also shortened.

Next, an example in which an auxiliary coil is provided will be described. As can be seen from FIG. 6, the torque due to the coil 14 is 90
Since it is O at °, the magnet is at the 90' position,
If the magnet 12 stops at the 90° position due to disturbance or the like, there is a possibility that the magnet 12 will not rotate even if current is passed through the coil 14.

FIG. 7(a) shows when the magnetic pole surface of the magnet 12 is facing the magneto-optical disk 1 (at Oo or 180 degrees, the wire portions 15a and 15b are positioned facing the side surface of the magnet 12. FIG. 7 is a view of an embodiment in which a coil 15 is fixed to the side surface of a 16th box so as to surround a magnet 12, as seen from above perpendicularly to the disk.

FIG. 8(A) is a view of the embodiment according to FIG. 7(A) from the direction of axis C, and when the magnet 2 is rotated 90', 15a
The portions 15b and 15b are N poles, respectively.

Opposing the S pole. FIG. 9(A) shows the relationship between the rotation angle of the magnet 12 and the torque generated by the coil 15 in the embodiments shown in FIGS. 7(A) and 8(A).

In FIG. 7(B), when the magnet 12 is at the 0° or 180° position, the section 15a is placed on the side of the magnet 12.
An axis C' parallel to the magneto-optical disk surface and perpendicular to axis C
2 is a view of an embodiment in which a coil 15 wound around the magnet 12 is fixed to the side surface of the box body 16 as seen from the side surface of the magnet 12. FIG. Similarly, FIG. 8(B) is a view of the embodiment according to FIG. 7(B) from the direction of axis C, and when the magnet 12 is rotated by 90 degrees, 15a
The part faces the north pole. Figure 7 (b) and Figure 8 (b)
The relationship between the rotation angle of the magnet 12 and the torque caused by the coil 15 in this embodiment is shown in FIG. 9(b).

In FIG. 7(C), when the magnet 12 is at the 0° or 180° position, the magnet 12 is rotated around the axis CI+ perpendicular to the magneto-optical disk surface so that the section 15a is located at a position facing the side surface of the magnet 12. FIG. 3 is a view of an embodiment in which a wound coil 15 is fixed to a side surface of a box body 16, as viewed from above in a direction perpendicular to the disk. Similarly, FIG. 8(C) and FIG. 9(C) correspond to FIG. 7(C).

In the embodiment shown in FIG. 7(a), both portions 15a and 15b apply torque to the magnet 12, and in the embodiments shown in FIGS. 7(b) and 7(c), portion 15a faces the magnetic pole and exerts torque on the magnet 12. Therefore, as can be seen from FIGS. 9(a), (b), and (c), in each embodiment, torque is generated at 90', so the deadlock caused by the coil 14 causes the magnet 12 to rotate. It will never go away.

[Effect of the invention] As explained above, according to the invention of claim 1,
A coil for applying a current to control the rotation of the magnet that applies a magnetic field to the magneto-optical disk is connected to a part parallel to the rotation axis of the magnet and located on the opposite side of the magneto-optical disk across the magnet, and a part parallel to the rotation axis. A coil consisting of a part in which magnets are arranged side by side at a position closer to the magneto-optical disk than the rotating shaft, and a part connecting both ends of the above two parts, and a magneto-optical disk including this coil and the rotating shaft. Since the coils are arranged symmetrically with respect to a vertical plane, the current flowing through the coils can be used effectively, and the magnet can be rotated at high speed.

Further, since the coils 4 and 5 are arranged close to each side of the magnet 2, there is an effect that the magnetic field application device can be made compact.

In the invention as claimed in claim 2, the coil that flows a current that controls the rotation of the magnet that applies a magnetic field to the magneto-optical disk,
The part that is parallel to the magnet's rotation axis and is located on the opposite side of the magneto-optical disk.

It consists of a part that is parallel to the rotation axis and located between the magnet and the magneto-optical disk, and a part that connects both ends of the above two parts, so the current flowing through the coil can be used effectively and the magnet Can rotate at high speed.

Further, since the coils are arranged close to the upper and lower surfaces of the magnet, there is an advantage that the magnetic field application device can be made compact.

According to the invention as claimed in claim 3, when the magnetic pole face of the magnet is in a position parallel to the rotation axis of the magnet and facing the optical disk, the auxiliary member has a wire portion disposed at a position facing the side surface of the magnet. Since the coil is provided, deadlock of the device can be prevented.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a bias magnetic field applying device showing a first embodiment of the present invention, and FIGS. 2(a) and 2(b). (C) is a cross-sectional view showing the operation of the bias magnetic field applying device of the present invention, and FIGS. 4 is a perspective view of a bias magnetic field applying device showing a second embodiment of the present invention, and FIGS. 5(a), 5(b),
(c) is a cross-sectional view showing the operation of the bias magnetic field applying device shown in FIG. 4, FIG. 6 is a diagram showing changes in torque of the bias magnetic field applying device, and FIGS. 7 (a) and (b). ,(
C) is a diagram showing the configuration of a bias magnetic field applying device having an auxiliary coil, and FIGS. 8(A), (B), and (C) are respectively shown in FIGS. 9 (a), (b), and (c) are cross-sectional views of the bias magnetic field applying device shown in the bias magnetic field applying device shown in FIG. Figure 10 is a diagram showing the change in torque of a conventional bias magnetic field applying device, and Figure 11 is a diagram showing the relationship between the rotation angle and torque of the magnet, and Figure 11 is a diagram showing the relationship between the rotation angle and torque of the magnet. Diagrams for explaining the force exerted, Figures 12 and 13 (a),
(B) and (C) are diagrams showing changes in torque of the conventional bias magnetic field applying device, respectively. 1... Magneto-optical disk, 2, 12... Magnet, 3...
・Optical pickup, 4.14...Coil, 15...
Auxiliary coils, 4a to 4d, 14a to l
4d, 5a-5d. 15a to 15d... Wire portion of coil, 6, 16...
- Box body, 7゜17゜8゜18...Magnetic field detection means. No. 2 (Fig. 2) Fig. 5 (A) 4 parts) (C) Fig. 2 (A) 11=Deki 9 Figure 5

Claims (1)

[Claims] 1. A magnet that is rotatably supported around an axis C that is parallel to the magneto-optical disk surface and whose magnetization direction is perpendicular to the axis C, and a drive that controls the rotation of the magnet. In a bias magnetic field applying device comprising a coil through which a current is passed, the coil is parallel to the axis C, and a wire portion 4a located on the opposite side of the magneto-optical disk with the magnet in between; a wire portion 4b disposed on the side surface of the magnet 2 at a position closer to the magneto-optical disk than the axis C, and a wire portion 4c connecting both ends of the two wire portions 4a and 4b;
4d; and a second coil 5, which is provided approximately symmetrically to the first coil with respect to a plane P that includes the axis C and is perpendicular to the surface of the magneto-optical disk. Bias magnetic field application device. 2. A magnet that is rotatably supported around an axis parallel to the magneto-optical disk surface and whose magnetization direction is perpendicular to the axis, and a coil through which a driving current is passed to control the rotation of the magnet. In the bias magnetic field applying device, the coil has a wire portion 14a that is parallel to the axis and is located on the opposite side of the magneto-optical disk while sandwiching the magnet; and the two wire rod portions 14a, 14b.
A bias magnetic field applying device characterized by comprising wire portions 14c and 14d connecting both ends of the bias magnetic field applying device. 3. In the bias magnetic field applying device according to claim 2, the wire rod is parallel to the axis and is disposed at a position facing a side surface of the magnet when the magnetic pole face of the magnet is located at a position facing the magneto-optical disk. A bias magnetic field applying device characterized by comprising an auxiliary coil having a portion 15a.