JP2790910B2 - Bias magnetic field applying device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bias magnetic field applying device used for a magneto-optical disk device or the like.

2. Description of the Related Art In magneto-optical recording, first, an erasing magnetic field is applied while continuously irradiating a laser beam of a recording power to a magneto-optical disk to align the magnetization direction in one direction, While applying a recording magnetic field in the opposite direction, a laser beam having a recording power modulated in accordance with recording information is irradiated. Recording information requires the above two steps. Therefore, it is necessary to make the switching time between the erasing magnetic field and the recording magnetic field as short as possible in order to reduce the information recording time.

Conventionally, as a method of shortening the switching time, a rectangular magnet arranged in a direction parallel to the magneto-optical disk is rotated by a recording magnet and an erasing magnet, and the S direction and the N direction of the magnet facing the magneto-optical disk are changed. A way to change it has been proposed.

FIG. 10 is a cross-sectional view of a magnetic field applying apparatus disclosed in Japanese Utility Model Application Laid-Open No. Sho 42-42503, which is one of the methods.

The magnet 51 for the magneto-optical disk 50
It is supported rotatably about an axis C parallel to 50. A first coil A and a second coil B, to which a drive current for controlling the rotation of the magnet 51 is supplied, are arranged in parallel at symmetrical positions about the rotation center axis of the magnet 51.

From the state where the N-pole (or S-pole) of the magnet faces the surface of the magneto-optical disk 50, rotate it by 180 ° to make the S-pole (or N-pole)
When the magnets are rotated by 180 ° in the first coil and the second coil when they face each other, a constant current is passed,
A rotational force is generated in the first 90 °, and a stop force is generated in the second 90 °, and the rotational speed becomes zero at a position rotated 180 °. The rotation angle of the magnet is detected by a Hall element.

Next, with reference to FIG. 11, the force exerted on the magnet 51 by the current flowing through the coil disposed around the magnet 51 will be described. When a current flows from the front to the back perpendicular to the plane of the drawing at the position a facing the N pole of the magnet 51, the current flowing to the position a receives a rightward force fa in FIG. 11 according to Fleming's left-hand rule. . As a reaction, the magnet 51 torques around the axis C6.
Receive Ta. The current that similarly flows to the position b facing the side surface of the magnet receives a leftward force fb. Since this force fb is directed to the rotation axis c of the magnet 51, the magnet does not receive torque around the axis C due to the reaction. From this, the state of FIG.
As ゜, the relationship between the rotation angle θ when the magnet is rotated counterclockwise and the torque received by the magnet is as shown in FIG.
Each of the torques Ta and Ta 'peaks at 0 ° and 180 ° where the pole face opposes the current flowing to the position a, and becomes zero at 90 ° where the side faces oppose. Further, the torque Ta 'due to the current flowing to the position a' remote from the magnet is smaller than Ta because fa 'is small.

[Problem to be Solved by the Invention] In the conventional example of FIG. 10 again, the relationship between the torque acting on the magnet 51 and the rotation angle is illustrated based on the above-described invention.
Figure 13 shows.

FIG. 13 (a) shows the torque by the coil A,
The broken line indicates the torque caused by the portions a and a ', and the dashed line indicates the coil A
(The sum of the portions a and a '). FIG. 2B shows the torque generated by the coil B, and FIG.
And the torque of the coil B together. Coil A
And the coil B have a positive (counterclockwise) peak at θ = 0 °, a negative (clockwise) peak at 180 °, zero at 90 °, and a first half 90 ° (θ = 0 ° to 90 °).゜), which is accelerated by the counterclockwise rotation force, and the latter half 90 後 半 (θ = 90 ゜ ~ 18
At 0 ゜), the negative torque acts as a stopping force, decelerates,
The rotation speed becomes zero at θ = 180 °. However, the torque generated by the portions a 'and b' works in a direction to hinder the rotation at the time of starting the rotation, and works in a direction to try to rotate at the time of the stop. Therefore, the current flowing through the coil is not used effectively. I understand. For this reason, there is a disadvantage that the time required for the magnet to rotate by 180 ° becomes longer, and the switching between the erasing magnetic field and the recording magnetic field on the magneto-optical recording surface is not performed quickly.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a bias magnetic field applying apparatus which rotates a magnetic field at a high speed of 180 ° at a high speed and requires a short time for switching between a recording magnetic field and an erasing magnetic field.

[Means for Solving the Problems] The invention according to claim 1 is rotatably supported about an axis C parallel to the surface of the magneto-optical disk 1, as shown in FIG.
In a bias magnetic field applying device including a magnet 2 whose magnetization direction is perpendicular to the axis C and a coil through which a drive current for controlling the rotation of the magnet 2 flows, the coil is parallel to the axis C, A wire rod 4a located on the opposite side of the magneto-optical disk with the magnet 2 interposed therebetween, and a wire rod arranged 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 Part 4b and the two wire parts 4a, 4b
Coil 4 consisting of wire parts 4c and 4d connecting both ends of
And a plane P including the axis C and perpendicular to the surface of the magneto-optical disk 1.
With respect to the second coil provided substantially symmetrically with the first coil.
And the coil 5.

As shown in FIG. 4, the magnet according to claim 2 is supported rotatably about an axis C parallel to the surface of the magneto-optical disk 1 and has a magnetization direction perpendicular to the axis C. 12
And a coil 14 through which a drive current for controlling the rotation of the magnet flows.
A coil portion parallel to the axis C, and a wire portion 14a located on the opposite side of the magneto-optical disk 1 with the magnet interposed therebetween; and a wire portion 14a parallel to the axis C and It is characterized by comprising a wire portion 14b positioned between the magnetic disk 1 and wire portions 14c and 14d connecting both ends of the two wire portions 14a and 14b.

According to a third aspect of the present invention, in the bias magnetic field applying apparatus according to the second aspect, when the magnetic pole surface of the magnet 2 is in a position facing the magneto-optical disk 1 parallel to the axis C, Wire section located at the position facing the side of the magnet
An auxiliary coil 15 having 15a is provided.

[Operation] According to the invention described in claim 1, the wire portion 4a parallel to the axis C is provided.
Section, 5a section, as well as the wire section 4b provided next to the magnet
Since the current flowing in the section 5b is also used effectively for the rotation of the magnet 2, a large torque is generated at the time of starting and stopping,
Can rotate 180 ° at high speed.

According to the invention described in claim 2, the current flowing through the wire portions 14a and 14b parallel to the axis C is used for rotating the magnet 12 in a state very close to the magnet 12, so When stopped, it generates sufficient torque and can rotate 180 ° at high speed.

According to the third aspect of the present invention, by arranging the auxiliary coil 15 having the wire portion 15a at the aforementioned position, the torque normally applied to the magnet becomes zero at the position of 90 °,
In the case of the present invention, the rotational force does not become zero but acts.

[Embodiment] In FIG. 1 showing a first embodiment of the present invention, a magnet 2 is supported rotatably about an axis C parallel to the magneto-optical disk 1. The axis C is usually set in the radial direction of the magneto-optical disk 1. The optical pickup 3 moves in the radial direction of the magneto-optical disk 1 and can access an arbitrary track. The axis C is aligned with the moving direction of the optical pickup 3, and the length of the magnet 2 is longer than the recordable range of the magneto-optical disk 1.
A magnetic field can be applied over the entire area where recording can be performed by using the above method.

The portions 4a and 5a of the coils 4, 5 are on the opposite side of the magneto-optical disk 1 with the magnet 2 interposed therebetween, and are parallel to the axis C. The portions 4a and 5a are connected to the bent portions 4c and 4d, respectively, and the portions 5c and 5d. The coils 4 and 5 include an axis C, are arranged perpendicularly to the magneto-optical disk 1 symmetrically with respect to a plane P, and are fixed to a box 6 (indicated by a dashed line).

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

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

In the state shown in FIG. 2A, the magnet 2 is
And an upward magnetic field is applied. By continuously irradiating a laser beam having a power sufficient to reverse the magnetization direction of the magneto-optical disk 1 by the optical pickup 3, the magnetization direction is aligned upward.

Next, as shown in FIG. 2 (b), currents are applied to the coils 4 and 5 in the directions of 4a and 5a in the direction from the front to the back of the paper, and in the 4a and 5b parts, currents in the direction of the back to the front are applied. As a result, the magnet 2 becomes 18
FIG. 3 shows the change in torque during the 0 ° rotation. FIG. 3 (a) shows the torque applied to the coil 4, the broken line represents the torque generated by the portions 4a and 4b, and the dashed line represents the torque generated by the entire coil 4.

FIG. 3 (b) shows the torque generated by the whole of the coils 5a and 5b and the coil 5, and FIG. 3 (c) shows the total torque of the coils 4 and 5 and the entire torque. It is accelerated in the counterclockwise direction at the full 90 °, decelerated by the clockwise torque at the second 90 °, and rotates 180 ° when it rotates 180 °. At the position of 0 ° and the position of 180 °, the outputs of the magnetic field detecting means 7, 8 provided symmetrically become equal, so that the position of 180 ° can be detected. When 180 ° is detected, the magnet 2 can be stopped at the 180 ° position by cutting off the current of the coils 4 and 5.

In the case of the present invention, not only the current flowing through the portions 4a and 5a but also the currents flowing through the portions 4b and 5b are effectively used, so that a large torque is generated at the time of starting and stopping, and the motor can be rotated 180 ° at high speed. .

As shown in FIG. 2 (c), a downward magnetic field is applied in a state where the N pole stops at a position facing the magneto-optical disk 1. Here, by irradiating a modulated light beam in accordance with the recording signal, a downward magnetized region is formed. Recording is completed by the above process. Since the time required to rotate the magnet by 180 ° is short, the time required for recording is also reduced.

FIG. 4 shows a second embodiment of the present invention. In FIG. 1, a magnet 12 is rotatably supported about an axis C parallel to the magneto-optical disk 1. The axis C is usually set in the radial direction of the magneto-optical disk 1. The optical pickup 3 moves in the radial direction of the magneto-optical disk 1 and can access an arbitrary track. Axis C is optical pickup 3
And the length of the magnet 12 is longer than the recordable range of the magneto-optical disk 1, so that a magnetic field can be applied over the entire recordable area of the optical pickup 3. 14a of coil 14 is magnet 12
Is located on the opposite side of the magneto-optical disk 1 and is parallel to the axis C. The portion 14b is located between the magnet 12 and the magneto-optical disk 1, and is arranged parallel to the axis C. Parts 14a and 14b are
The magnets 12 are connected to each other by a portion 14c and a portion 14d, 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 detecting means 17 and 18 symmetrically attached to the box 16.

FIG. 5 is a schematic diagram viewed from the axis C direction, and the operation will be described with reference to FIG.

In the state shown in FIG. 5A, the magnet is placed on the magneto-optical disk 1.
An upward magnetic field is applied with 12 south poles facing each other. By continuously irradiating a laser beam having a power sufficient to reverse the magnetization direction of the magneto-optical disk 1 by the optical pickup 3, the magnetization direction is aligned upward.

Next, as shown in FIG. 5 (b), the coil 14 (FIG. 4)
By passing a current in the direction a from the front to the back of the paper in part a, and flowing a current in a direction from the back to the front in the part 14b, the magnet 12 is
Rotated 0 °. FIG. 6 shows a change in torque during a 180 ° counterclockwise rotation with the state of FIG.

In the figure, the dashed line indicates the torque due to only the portions 14a and 14b, and the solid line indicates the torque due to the entire coil 5.
In the first half 90 °, it is accelerated counterclockwise, in the second half 90 °, it is decelerated by clockwise torque, and when it rotates 180 °, the rotation speed becomes zero. At 0 ° and 180 °,
Since the outputs of the symmetrically provided magnetic field detecting means 17 and 18 are equal, by detecting that the difference between the two outputs becomes zero,
180 ゜ position can be detected. After detecting 180 ゜,
By turning off the current of the coil 14, the magnet 12 can be stopped at a position of 180 °. In the case of this embodiment, 14a section, 14
Since the current flowing in section b is used effectively, a large torque is generated when starting and stopping, and the motor can be rotated 180 ° at high speed.

Next, as shown in FIG. 5C, a downward magnetic field is applied with the N pole stopped at a position facing the magneto-optical disk 1. Here, by irradiating a modulated light beam in accordance with the recording signal, a downward magnetized region is formed. Recording is completed by the above process. 18 magnets
Since the time required for the rotation by 0 ° is short, the time required for recording is also reduced.

Next, an embodiment in which an auxiliary coil is provided will be described.
As can be seen from FIG. 6, since the torque by the coil 14 is 0 at 90 °, when the magnet is at the 90 ° position or stops at the 90 ° position due to disturbance or the like, the coil 14
, There is a risk that the magnet 12 will not rotate.

FIG. 7A shows that when the magnetic pole surface of the magnet 12 faces the magneto-optical disk 1 (0 ° or 180 °, the wire portions 15a and 15b are positioned so as to face the side surface of the magnet 12). , Magnet 1
FIG. 14 is a view of the embodiment in which the coil 15 is fixed to the 16th side surface of the box so as to surround the disk 2 as viewed from above the disk vertically.

FIG. 8 (a) is a view of the embodiment according to FIG. 7 (a) from the axis C direction.
The portion 15b faces the north pole and the south pole, respectively. Fig. 7 (a)
FIG. 9A shows the relationship between the rotation angle of the magnet 12 and the torque by the coil 15 in the embodiment according to FIG. 8A.

FIG. 7 (b) shows an axis in a direction parallel to the magneto-optical disk surface and perpendicular to the axis C such that the portion 15a is on the side surface of the magnet 12 when the magnet 12 is at the 0 ° or 180 ° position. FIG. 9 is a view of the embodiment in which the coil 15 wound around C ′ is fixed to the side surface of the box body 16 as viewed from the side surface of the magnet 12. Similarly, FIG. 8 (b)
Is a view of the embodiment according to FIG. 7 (b) from the direction of the axis C,
When the magnet 12 is rotated by 90 °, the portion 15a faces the N pole. FIG. 9 (b) shows the relationship between the rotation angle of the magnet 12 and the torque by the coil 15 in the embodiment according to FIGS. 7 (b) and 8 (b).

FIG. 7 (c) shows a state in which, when the magnet 12 is at the position of 0 ° or 180 °, the portion 15a is located at a position facing the side surface of the magnet 12 around the axis C ″ perpendicular to the magneto-optical disk surface. 8 (a) and 9 (c) are views of the embodiment in which the coil 15 wound around is fixed to the side surface of the box body 16 when viewed from above in the disk vertical direction. Corresponds to c).

In the embodiment shown in FIG. 7 (a), both the portions 15a and 15b
In the embodiment shown in FIGS. 7 (b) and (c), a portion 15a opposes the magnetic pole and exerts a torque on the magnet 12. Therefore, FIG.
As can be seen from (b) and (c), in each of the embodiments, since torque is generated at 90 °, the magnet 12 does not stop rotating due to the deadlock by the coil 14 described above.

[Effects of the Invention] As described above, according to the first aspect of the present invention, the coil for flowing the current for controlling the rotation of the magnet for applying the magnetic field to the magneto-optical disk is provided in parallel with the rotation axis of the magnet, A portion located on the opposite side of the magneto-optical disk with the magnet interposed therebetween, a portion in which magnets are arranged in parallel with the rotation axis and closer to the magneto-optical disk than the rotation axis, and both ends of the two portions Since the coil consists of a part that connects the two, and the coil is provided symmetrically with respect to a plane perpendicular to the magneto-optical disk, including the coil and the rotation axis, the current flowing through the coil can be used effectively, and the magnet can be used. Can be rotated at high speed.

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

According to the second aspect of the present invention, a coil for flowing a current for controlling the rotation of a magnet for applying a magnetic field to the magneto-optical disk, and a coil parallel to the rotation axis of the magnet and opposite to the magneto-optical disk with the magnet interposed therebetween. Since it is composed of a part, a part parallel to the rotation axis and located between the magnet and the magneto-optical disk, and a part connecting both ends of the two parts, the current flowing through the coil can be used effectively. , Can rotate the magnet 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 applying device can be made compact.

According to the third aspect of the present invention, when the magnetic pole surface of the magnet is located at a position facing the optical disk in parallel with the rotation axis of the magnet, the auxiliary member having the wire portion disposed at the position facing the side surface of the magnet is provided. Since the coil is provided, deadlock of the device can be prevented.

[Brief description of the drawings]

FIG. 1 is a perspective view of a bias magnetic field applying device according to a first embodiment of the present invention, and FIGS. 2 (a), (b) and (c) show the operation of the bias magnetic field applying device of the present invention, respectively. 3 (a), 3 (b) and 3 (c) are diagrams showing a change in torque of the bias magnetic field applying device according to the present invention, respectively.
FIG. 4 is a perspective view of a bias magnetic field applying device showing a second embodiment of the present invention, and FIGS. 5 (a), (b) and (c) show the operation of the bias magnetic field applying device shown in FIG. FIG. 6 is a diagram showing a change in torque of the bias magnetic field applying device, and FIGS. 7 (a), (b) and (c) are configurations of a bias magnetic field applying device having an auxiliary coil. Figure showing
FIGS. 8 (a), (b) and (c) show the state where the magnet is rotated by 90 ° in the bias magnetic field applying device shown in FIGS. 7 (a), (b) and (c), respectively. 9, (a), (b), and (c) are views showing the relationship between the rotation angle of the magnet and the torque of the bias magnetic field applying device shown in FIG. 4, respectively, and FIG. FIG. 11 is a diagram showing a change in torque of the conventional bias magnetic field applying device. FIG. 11 is a diagram for explaining the force exerted on the magnet by the current flowing through the coil around the magnet. FIG. 12 and FIG. ), (B), (c)
It is a figure which shows the change of the torque of the conventional bias magnetic field application apparatus, respectively. 1 ... Magneto-optical disk, 2,12 ... Magnet, 3 ... Optical pickup, 4,14 ... Coil, 15 ... Auxiliary coil, 4a-4d, 1
4a ~ 14d, 5a ~ 5d, 15a ~ 15d ... Coil wire part, 6,16 ...
... box, 7, 17, 8, 18 ... magnetic field detecting means.

Claims (3)

(57) [Claims] 1. A magnet rotatably supported about an axis C parallel to the surface of a magneto-optical disk and having a magnetization direction perpendicular to the axis C, and a drive current for controlling the rotation of the magnet. A biasing magnetic field applying device comprising a coil, wherein the coil is parallel to the axis C, and a wire portion 4a located on the opposite side to the magneto-optical disk with the magnet interposed therebetween;
A wire rod portion 4b disposed on the side surface of the magnet 2 at a position parallel to the axis C and closer to the magneto-optical disk than the axis C;
A first coil 4 including wire portions 4c and 4d connecting both ends of the two wire portions 4a and 4b; and a substantially symmetrical shape with respect to a plane P including the axis C and perpendicular to the magneto-optical disk surface. And a second coil provided in the bias magnetic field applying device. 2. A magnet rotatably supported about an axis parallel to the surface of the magneto-optical disk and having a magnetization direction perpendicular to the axis, and a drive current for controlling the rotation of the magnet. A bias magnetic field applying device comprising a coil, wherein the coil is parallel to the axis, and a wire portion 14a located on the opposite side of the magneto-optical disk with the magnet interposed therebetween; A bias magnetic field applying apparatus comprising: a wire portion 14b located between the magnetic disk 1; and wire portions 14c and 14d connecting both ends of the two wire portions 14a and 14b. 3. The bias magnetic field applying apparatus according to claim 2, wherein the magnet is disposed at a position parallel to the axis and at a position facing a side surface of the magnet when a magnetic pole surface of the magnet is positioned at a position facing the magneto-optical disk. A bias magnetic field applying device, comprising: an auxiliary coil having a shaped wire portion 15a.