JPH052792A - Bias magnetic field generator for optical magnetic recording - Google Patents

Abstract

PURPOSE:To improve a rotating speed by controlling a damping in the case of the driving of intermittent rotation of a cylindrical permanent magnet. CONSTITUTION:A bias magnetic field generator is constituted of a bias means 1, driving means 2, and control means 3. The bias means 1 is constituted by a cylindrical permanent magnet 4 for a bias faced with a recording medium 5, mounted so as to be rotatable, and multipole-polarized along the direction of rotation. The driving means 2 is constituted by a stepping motor connected with a rotary shaft 6 of the permanent magnet 4, the bias means 1 is intermittently driven so as to rotated, and the polarity of a bias magnetic field is alternately switched synchronously with the erasure of information for the recording medium 5. The control means 3 magnetically acts on the bias means 1, controls the damping of the bias means 1 accompanied with the driving of the intermittent rotation, and shortens a static determination, The control means 3 is a closed magnetic flux circuit constituted of both the mutipole-polarized cylindrical magnet 10 for a brake fixed to the rotary shaft 6, and a yoke 11 for a brake arranged at the position surrounding it, and a detent torque which is effective to the suppression of the damping is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bias magnetic field generator for magneto-optical recording, and more particularly to a magnetic circuit structure for braking of a bias magnetic field generator using a cylindrical rotating permanent magnet with multipole magnetization.

[0002]

2. Description of the Related Art In so-called magneto-optical recording, information is recorded according to the direction of magnetization of a magnetic film. The coercive force required to reverse the magnetization of the magnetic film becomes smaller as the temperature rises. By utilizing this phenomenon, the laser beam is focused on the magnetic film to reverse the magnetization and record information. The direction of the magnetization is determined by the direction of the bias magnetic field applied from the outside, and the direction of the bias magnetic field is opposite in the erasing and recording of information. At the time of erasing, a bias magnetic field in one direction is applied to the magnetic film and the laser beam is continuously irradiated at the same time to raise the temperature of the magnetic film to the Curie point or higher, and the magnetic pole is moved in one direction along the information recording track of the magnetic film. Align. During recording, magnetization reversal is performed by applying a bias magnetic field in the other direction and simultaneously irradiating a laser beam intermittently. Since this erasing and recording are performed continuously, it is necessary to switch the bias magnetic field at high speed. The switching time is within 1 ms.

Conventionally, electromagnets or permanent magnets have been used to generate a bias magnetic field. Recently, permanent magnets are more frequently used than electromagnets because electromagnets have the disadvantage that they generate heat due to continuous power feeding for a long time and also have the disadvantage that they require a large amount of power consumption. The bias magnetic field is reversed by switching and moving the S pole and the N pole of the permanent magnet arranged so as to face the magnetic film. For this reason, the parallel movement method has been conventionally used. In this parallel movement method, a permanent magnet member having an adjacent S pole and N pole is reciprocally moved in parallel at a high speed in a state of being close to a magnetic film.

[0004]

As described above, the magneto-optical recording apparatus has become the mainstream of the optical recording apparatus because it can rewrite information and has a relatively long erasing and recording life and is stable. For this reason, the field of use is expanding year by year, and it is being installed in various information devices as a large-capacity memory. Improving the internal data transfer rate is indispensable in order to increase the processing capacity of information equipment, and there is a strong demand for a higher operating speed of the magneto-optical recording apparatus. Along with this, there is a demand for further shortening of the magnetic pole switching time of the bias magnetic field generator. In this regard,
In the parallel movement method described above, since the inertia of the permanent magnet member is relatively large, there is a physical limit to the speed of the reciprocal parallel movement.

In order to solve this problem, the applicant has proposed a rotational movement system of a biasing permanent magnet in a prior related application. In this method, a multi-pole magnetized cylindrical permanent magnet member is rotated at high speed in a state of being close to a magnetic film. The rotational movement method maintains the weight balance of the permanent magnet members, so it is not affected by the installation posture, is stable against external vibration, and has a small rotation inertia, which allows faster magnetic pole switching. I can do it.

When a cylindrical permanent magnet is driven to rotate intermittently by a stepping motor or the like, the higher the rotational speed, the more pronounced the damping vibration or damping near the stop position. Therefore, there is a problem that it becomes more difficult to stably reverse the bias magnetic field at higher speeds. or,
When the damped vibration becomes noticeable, there is a problem that the settling time until the rotating permanent magnet reaches the stopped state becomes longer and the speedup is hindered.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the rotary movement system, an object of the present invention is to suppress damped vibration of a permanent magnet that is driven to rotate intermittently. Hereinafter, means for solving the above-mentioned problems will be described with reference to FIG. The illustrated magneto-optical recording bias magnetic field generating device includes a bias means 1, a driving means 2 and a suppressing means 3.
The biasing means 1 is composed of a biasing cylindrical permanent magnet 4. The permanent magnet 4 is mounted rotatably so as to face the medium 5 for magneto-optical recording, and is magnetized in multiple poles along the rotation direction. In the illustrated example, the cylindrical permanent magnet 4 has a 4-pole magnetized structure in which N poles and S poles are alternately formed at equal intervals of 90 degrees. However, the number of magnetic poles is not limited to this, and may be, for example, two-pole magnetized. The permanent magnet 4 is fixed to the rotation shaft 6. Rotation axis 6
Both ends of each are supported by side walls of the hollow frame 8 via bearings 7.

The driving means 2 is connected to one end of a rotation shaft 6 and drives the bias means 1 to rotate intermittently to alternate the polarities of the bias magnetic fields in synchronization with the erasing / recording cycle of information on the medium 5 made of an optical disk. Switch. In the illustrated example, the driving means 2 comprises a multi-pole magnetized cylindrical permanent magnet 9 for a rotor fixed to one end of a rotation shaft 6, and a stator yoke (not shown) arranged and wound around the cylindrical permanent magnet 9. It is composed of a stepping motor consisting of a combination of. However, the driving means is not limited to this, and may be configured using, for example, an electromagnetic coil arranged around the cylindrical permanent magnet 4 for bias.

On the other hand, the suppressing means 3 is arranged on the other end side of the rotation shaft 6. The suppressing means 3 is for magnetically acting on the bias means 1 to suppress the damping vibration or damping of the bias means 1 associated with the intermittent rotation drive, and to shorten the settling time to reach the stopped state. In the example shown in the figure, the suppressing means 3 is composed of a combination of a cylindrical cylindrical permanent magnet 10 for braking fixed to the rotating shaft 6 of the biasing means and a yoke 11 for braking arranged around the permanent magnet. The permanent magnet 10 and the yoke 11 form a closed magnetic flux circuit and generate detent torque effective in suppressing damping. In the illustrated example, the brake cylinder permanent magnet 10 is separate from the bias cylinder permanent magnet 4, but the brake cylinder permanent magnet 10 is not limited to this. For example, the extension of the cylindrical permanent magnet for bias can be used for the brake.

[0010]

2 is a sectional view of the structure shown in FIG. 1 taken along the line AA. The bias magnetic field generator including the cylindrical permanent magnet 4 for bias is housed in a frame 8 made of a non-magnetic material. The frame 8 is mounted on the upper surface of the housing 12 of the magneto-optical recording device. The frame 8 is fixed to the housing 12 via screws 13. Below the housing 12, a medium 5 for magneto-optical recording housed in a cassette 14, for example, a magneto-optical disk is inserted. A head 16 is arranged below the inserted medium 5 and irradiates a laser beam spot for erasing, recording and reproducing information on the medium 5.

In the illustrated example, the four-pole magnetized cylindrical permanent magnet 4 for bias is in a stopped state, and the N pole faces the medium 5. Information is erased in this state. That is, a bias magnetic field 17 in one direction is applied to the medium 5 and at the same time the head 1 is
By driving 6 to continuously irradiate a laser beam, the medium temperature is raised above the Curie point, and the magnetic poles are aligned in one direction along a predetermined information recording track of the rotating medium 5.

At the time of recording, a driving means (not shown) is operated to rotate the bias permanent magnet 4 stepwise by 90 degrees as shown by an arrow to reverse the direction of the bias magnetic field 17. When the permanent magnet 4 is stationary, the head 16 is driven again to intermittently irradiate the laser beam, thereby selectively reversing the magnetization of the information recording track in the erased state to form a pit. Since this erasing and recording are performed continuously, the bias magnetic field 17 is switched at high speed. That is, the cylindrical permanent magnet 4 for bias rotates at high speed intermittently around the rotation axis 6. At this time, the damping vibration near the stop position becomes more prominent as the rotation speed is increased. In the present invention, the suppressing means (not shown) acts so as to suppress this damped vibration or damping. Therefore, the settling time from the intermittent start up to the stopped state can be shortened, and high-speed bias magnetic field reversal is possible.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 3 is a schematic perspective view showing an embodiment of the magneto-optical recording bias magnetic field generator according to the present invention. In this example, the bias means 1, the driving means 2 and the suppressing means 3 have a separate structure arranged along the common rotation axis 6. The bias means 1 is composed of a quadrupole magnetized cylindrical permanent magnet 4 for bias.

The driving means 2 is composed of a 4-pole stepping motor and drives the bias means 1 intermittently at regular intervals of 90 degrees. The stepping motor is composed of a combination of a four-pole magnetized cylindrical permanent magnet 9 for a rotor, which is fixed to one end side of the rotation shaft 6, and a stator yoke 18 which is arranged and wound around the rotor. A drive circuit 19 is connected to the terminals of the winding, and energization control for the winding is performed in synchronization with the information erasing / recording cycle for the medium. The phase of the rotor cylindrical permanent magnet 9 is shifted from the phase of the bias cylindrical permanent magnet 4 by a predetermined angle. This is so that the magnetic poles of the biasing permanent magnet 4 can properly face the medium in accordance with the stop position of the stepping motor.

Finally, the suppressing means 3 is composed of a combination of a four-pole magnetized cylindrical permanent magnet 10 for braking fixed to the other end side of the rotating shaft 6 and a brake yoke 11 arranged around the permanent magnet 10. There is. The yoke 11 is made of a ferromagnetic material and has four standing bent portions 20 corresponding to the four magnetic poles of the brake permanent magnet 10. The standing bending portion 20 is arranged so as to be aligned with each magnetic pole of the brake permanent magnet 10 in a stopped state. Therefore, the closed magnetic flux circuit 21 is configured to generate detent torque effective for suppressing damping.

FIG. 4 is a schematic perspective view showing another embodiment of the bias magnetic field generator for magneto-optical recording according to the present invention. In this example, the bias means 1, the driving means 2 and the suppressing means 3 are configured by using a common cylindrical permanent magnet having four poles magnetized. The biasing means 1 is composed of a biasing cylindrical permanent magnet 4. The driving means 2 is composed of a pair of electromagnetic coils 2 arranged around the permanent magnet 4 and a driving circuit 19 connected to the coil terminals. The drive circuit 19 controls the energization timing for the pair of electromagnetic coils 22 in synchronization with the information erasing / recording cycle. As a result, the electromagnetic coil 22 intermittently exerts a repulsive attraction action on the permanent magnet 4 and drives the bias means 1 intermittently by the same principle as the stepping motor. Finally, the restraining means 3 is composed of a cylindrical yoke 11 having four standing bends 20. The cylindrical yoke 11 is arranged so as to house the brake permanent magnet 10, which is an extension of the bias permanent magnet 4. In the stopped state shown in the drawing, each of the bent portions 20 is adapted to match with each magnetic pole of the permanent magnet, and generates a detent torque effective for suppressing damping.

In this embodiment, one cylindrical permanent magnet serves as a bias, a brake, and a rotor of a stepping motor, so that the structure is simplified as compared with the embodiment shown in FIG. Is also good. In addition,
In order to perform smooth and high-speed intermittent rotation drive, drive means 2
It is preferable to appropriately balance the drive torque generated by the above-mentioned torque and the detent torque generated by the suppressing means 3.

[0018]

FIG. 5 shows a sectional structure obtained by cutting the suppressing means 3 shown in FIG. 3 or 4 at a right angle to the rotation axis. In the illustrated state, the brake cylinder permanent magnet 10 is held at a stop position or a stable position. In this state, the four bent portions 20 of the cylindrical brake yoke 11 are aligned and face the four magnetic poles of the brake permanent magnet 10 with a predetermined gap therebetween. That is, the N pole and the S pole which are adjacent to each other form a closed magnetic flux circuit 21 or a closed magnetic flux loop via the yoke 20. In this state, the magnetic potential of the system becomes the lowest and a stable state is realized. In other words, detent torque is generated so as to maintain this stable state. Therefore, the damping vibration or damping of the permanent magnet 10 that occurs between the intermittent start and the stop position is extremely effectively suppressed by the detent torque, and the permanent magnet 10 is pulled into a stable state in a short time.

Finally, FIG. 6 is a graph showing the rotational displacement of the cylindrical permanent magnet. For comparison, the solid curve shows the case where the suppressing means is adopted, and the dotted curve shows the case where the suppressing means is not adopted. As is clear from the graph, when the suppression means is adopted, after starting the stepping motor,
The permanent magnet quickly rotates 90 degrees and reaches the next stop position.
On the other hand, when the suppression means is not adopted, after the stepping motor is started, the target next stop position is largely overshooted, and subsequently, the overshoot is again made in the reverse rotation direction. Since the damping stop is repeated to reach the next stop position, the settling time becomes long. As described above, by using the suppressing means, the settling time in the intermittent rotation drive of the permanent magnet can be remarkably shortened, so that the faster bias magnetic field reversal becomes possible and the information erasing / recording speed of the magneto-optical recording apparatus can be improved. There is an effect that can be. Further, according to the present invention, the damping is effectively suppressed by the magnetic means using the yoke member made of a magnetic material instead of the mechanical or electrical means. There is an effect that the speeding up of can be achieved.

[Brief description of drawings]

FIG. 1 is a plan view showing a basic configuration of a bias magnetic field generator for magneto-optical recording according to the present invention.

FIG. 2 is a schematic cross-sectional view of the structure shown in FIG. 1 taken along line AA.

FIG. 3 is a schematic perspective view showing an embodiment of a bias magnetic field generator according to the present invention.

FIG. 4 is a schematic perspective view showing another embodiment of the bias magnetic field generator according to the present invention.

FIG. 5 is a schematic cross-sectional view of a suppressing unit that constitutes a main part of the bias magnetic field generator according to the present invention.

FIG. 6 is a graph showing the time course of rotational displacement of a cylindrical permanent magnet used in the bias magnetic field generator according to the present invention.

[Explanation of symbols]

1 Biasing means 2 drive means 3 suppression means 4 Cylindrical permanent magnet for bias 5 medium 6 rotation axis 9 Cylindrical permanent magnet for rotor 10 Cylindrical permanent magnet for brake 11 Brake yoke 17 Bias magnetic field 18 Stator yoke 19 Drive circuit 20 Bending part of yoke for brake 21 Closed magnetic flux circuit 22 Electromagnetic coil

Claims (5)

[Claims] 1. A biasing magnetic field is applied to a medium, which comprises a biasing cylindrical permanent magnet which is rotatably mounted so as to face a medium for magneto-optical recording and which is magnetized in multiple poles along the rotation direction. Bias means, driving means for intermittently rotating the bias means to alternately switch the polarity of the bias magnetic field in synchronization with information erasing recording on the medium, and intermittent rotation driving magnetically acting on the bias means. A bias magnetic field generator for magneto-optical recording, comprising: a damping means for suppressing damping vibration of the bias means and shortening the settling time. 2. The closing means is a closed magnetic flux circuit comprising a combination of a multi-pole magnetized cylindrical permanent magnet for a brake fixed to the rotation axis of the bias means and a brake yoke arranged around the permanent magnet. The bias magnetic field generator for magneto-optical recording according to claim 1. 3. The bias magnetic field generator for magneto-optical recording according to claim 2, wherein the cylindrical permanent magnet for braking is an extension of the cylindrical permanent magnet for bias. 4. The stepping means, wherein the driving means is a combination of a multi-pole magnetized cylindrical permanent magnet for a rotor fixed to a rotation shaft of a bias means and a stator yoke arranged and wound around the rotor. The bias magnetic field generator for magneto-optical recording according to claim 1, which is a motor. 5. The bias magnetic field generator for magneto-optical recording according to claim 1, wherein said driving means is composed of an electromagnetic coil arranged around a cylindrical permanent magnet for bias.