JP3320121B2 - Magneto-optical disk drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk drive for applying a bias magnetic field to a recording medium when recording data on the recording medium or erasing the recorded data.
In particular, the present invention relates to a magneto-optical disk drive in which a bias magnetic field is applied using a permanent magnet.

[0002]

2. Description of the Related Art A bias magnetic field applying device of a magneto-optical disk device applies a magnetic field in a direction perpendicular to a recording medium in directions opposite to each other at the time of erasing and at the time of recording. In conjunction with the action of the light spot, data on the recording medium is erased or data is recorded on the data. The bias magnetic field applying device includes one using an electromagnet and one using a permanent magnet.

A conventional bias magnetic field applying device is provided so that a light spot is located on the center of the bias magnetic field applying device regardless of the electromagnet system or the permanent magnet system. JP-A-59-2032 discloses an example in which an electromagnet is arranged on the opposite side of an objective lens with respect to a recording medium.
Japanese Unexamined Patent Publication No. 57-27449 discloses a technique in which an electromagnet is disposed on the same side of a recording medium as an objective lens with respect to a recording medium. On the other hand, in the case of using a permanent magnet, a technique described in JP-A-57-24047 may be mentioned as an example in which a permanent magnet is arranged on the opposite side of the objective lens with respect to the recording medium. There is no idea to place a permanent magnet on the same side as the objective lens.

[0004]

The magneto-optical disk medium currently in practical use having a diameter of 130 mm is 18000 A / m for both erasing and recording.
As described above, erasing or recording is performed by changing the intensity of the light spot under an upward or downward bias magnetic field perpendicular to the recording medium of 48000 A / m or less. The bias magnetic field applying device needs to apply a magnetic field of the above-mentioned strength to the surface of the recording medium on which the light spot is to be formed. It is necessary to apply a magnetic field through the substrate. Therefore, in the electromagnet method, switching between erasing and recording only requires switching the direction of the current flowing through the magnet coil, but the electromagnet becomes large to obtain the required product of the number of turns of the electromagnetic coil and the current, that is, the required ampere-turn. It is very difficult to attach this to an objective lens. It is also conceivable to provide an electromagnet adjacent to the objective lens. However, the distance between the light spot convergence point and the electromagnet increases, and the required ampere-turn further increases. For example, a height of about 10 mm is required. Therefore, it was difficult to provide an electromagnet of a practical size on the objective lens side. Under such circumstances, conventionally, an electromagnet is generally provided on the opposite side of the recording medium from the objective lens.

On the other hand, in the permanent magnet system, there is an example of a bias magnetic field applying device for rotating a permanent magnet having a diameter equivalent to 3 to 4 mm, in which the magnet itself can be made smaller than the electromagnet. It is necessary to rotate the magnet, and the height of about 10 mm is also required including the height of the rotation support mechanism of the permanent magnet and the attached mechanism such as the drive coil, so it is difficult to incorporate it into the objective lens driving device. Therefore, conventionally, it has not been considered to provide a permanent magnet on the objective lens side.

As described above, in the prior art, since the bias magnetic field applying device is arranged on the opposite side of the objective lens with respect to the recording medium, the optical disk device includes the objective lens driving device, the optical disk and the bias magnetic field applying device. Only the sum of the heights of the persons was required, and there was a problem in making the device thinner.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to overcome the above-mentioned problems of the prior art and to use a permanent magnet type bias magnetic field applying device on the same side of an optical disk recording medium as an objective lens. Accordingly, it is an object of the present invention to provide a magneto-optical disk drive capable of reducing the size and thickness of the drive.

[0008]

In order to achieve the above object, a magneto-optical disk drive according to the present invention has an objective lens for forming a minute light spot on a recording film of the magneto-optical disk recording medium, facing the recording medium. A magneto-optical disk drive comprising: a movable head; and a bias magnetic field applying device for rotating a permanent magnet to invert the polarity of a bias magnetic field perpendicular to the recording film, wherein the bias magnetic field applying device comprises a single permanent magnet.
The movable head is mounted on the movable head so that the height is equal to or less than the height of the objective lens driving device on the same side as the objective lens with respect to the magneto-optical disk recording medium .
Set the strength of the magnetic field by the single permanent magnet to a predetermined value.
For this purpose, the rotation angle of the permanent magnet is controlled .

Here, the bias magnetic field applying device is provided on a side opposite to the objective lens driving device and the objective lens supporting means with respect to the objective lens in a direction parallel to the surface of the magneto-optical disk recording medium.

[0010] The permanent magnet of the bias magnetic field applying device and the rotating means of the permanent magnet can be housed in a closed container. In this case, a drive coil for driving the permanent magnet is integrally embedded and formed as a part of the container in a closed container containing the bias magnetic field.

Further, the permanent magnet of the bias magnetic field applying device is constituted by a rotating body itself, and is constituted so that a rotating force can be obtained by a magnetic field generated by the permanent magnet and a driving current flowing through a driving coil of the permanent magnet. . In this case, the permanent magnet is magnetized in the rotational diameter direction, and the driving coil of the permanent magnet is provided so as to have portions parallel to the rotation axis of the permanent magnet, facing the N pole and the S pole of the permanent magnet, respectively. can do.

In this case, the rotation axis of the permanent magnet is set in a direction parallel to the surface of the magneto-optical disk recording medium and on the side opposite to the objective lens driving device and the support means with respect to the objective lens. It can be arranged to face the radial direction of the medium.

[0013]

The operation based on the above configuration will be described.

As described above, when an electromagnet is used as the bias magnetic field applying device, the size of the electromagnet is increased in order to obtain a necessary ampere turn.
It is difficult to provide it adjacent to the objective lens.

On the other hand, the permanent magnet requires a rotation mechanism as described above, and it is difficult to incorporate the permanent magnet into the objective lens driving device. However, since a strong permanent magnet has been developed, When provided adjacent to the objective lens driving device on the same side as the objective lens, the diameter is several mm.
, It is possible to apply a magnetic field having a strength of 18000 A / m or more to the light spot convergence point.

According to the present invention, the movable head is configured such that the bias magnetic field applying device using such a permanent magnet is at the same side as the objective lens with respect to the recording medium and at the same height as the objective lens or the objective lens driving device. Since it is mounted on the top, the distance from the permanent magnet to the light spot convergence point on the recording medium can be made sufficiently short, and the vertical magnetic field of the strength required for erasing and recording can be reduced with a small bias magnetic field application device. It can be generated at the light spot convergence point, and the size and thickness of the magneto-optical disk device can be reduced.

Further, since a bias magnetic field applying device including a permanent magnet cannot be arranged immediately below the light spot,
In the present invention, the bias magnetic field applying device is provided on the side opposite to the objective lens driving device and the support means with respect to the objective lens in a direction parallel to the recording medium surface, thereby achieving a reduction in thickness. By setting the polarity of the permanent magnet so as to be inclined from the perpendicular direction of the recording medium, the magnetic field component in the direction perpendicular to the recording medium at the light spot convergence point can be further increased.

Since the permanent magnet and its rotating means are housed in a closed container, and a permanent magnet drive coil is integrally embedded in the closed container as a part of the container by molding or the like.
The bias magnetic field applying device can be further reduced in size and thickness.

Further, since the permanent magnet itself is a rotating body, and a rotating force is obtained by a magnetic field generated by the permanent magnet and a current flowing through the permanent magnet driving coil, a special mechanism for rotating the permanent magnet is provided. Need not be provided separately.

The bias magnetic field applying device including the permanent magnet is disposed on the movable head on the side opposite to the objective lens driving device and the supporting means with respect to the objective lens as described above. It is magnetized in the diameter direction, and its rotation axis is arranged in a direction parallel to the recording medium surface and in a radial direction of the recording medium. The magnetic field formed by the permanent magnet is symmetric with respect to the center of magnetization, and the magnetic field lines exit from the N pole of the permanent magnet, pass through the light spot convergence point on the way, rotate 360 ° and enter the S pole. Since the position of the permanent magnet is not directly below the light spot convergence point but slightly off from it, the angle of the magnetic field at the light spot convergence point is substantially determined according to this relative positional relationship. Therefore, by setting the rotation angle of the permanent magnet to a predetermined value, the strength of the magnetic field perpendicular to the recording medium at the light spot convergence point can be set to a predetermined range (preferably the maximum value). The set value of the rotation angle includes an angle position (reference angle) at which the maximum value of the vertical magnetic field component of one polarity is obtained at the light spot convergence point, and the other angle at the light spot convergence point is rotated 180 ° from this reference angle. There is an angular position that gives the maximum value of the (inverted) polarity vertical magnetic field component. One of the angular positions is a position at the time of erasing, and the other angular position is a position at the time of recording. Such a permanent magnet arrangement shortens the distance between the light spot convergence point and the permanent magnet,
A large magnetic field can be applied to the light spot convergence point.

In order to set the rotation angle of the permanent magnet to the above two angular positions, a rotation driving means and an angle setting means are required. In the present invention, a simple method is employed in which the permanent magnet itself is used as the rotating body as the rotating means as described above, and the drive coil as the fixed side is placed in the magnetic field generated by the permanent magnet. This drive coil is constituted by a pair of clad coils having portions parallel to the rotation axis of the permanent magnet, facing the north and south poles of the permanent magnet. The current flowing through the coil and the magnetic field generated by the permanent magnet With this function, a rotational force can be obtained.

As the angle setting means, a method using a mechanical stopper, or a method in which the rotation means is constituted by a pulse motor to electromagnetically set the angle may be considered.
Considering the reliability of operation and shortening of the time to rest after rotation, a rotation angle detection means is provided, and its output is fed back to the drive coil to rotate a small permanent magnet with a small radius of rotation and a low rotational moment. It was configured as follows. With this configuration, it is possible to perform 180 ° rotation angle control at high speed and stably and surely hold the permanent magnet rotating body at the two angular positions.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 9 is an external view showing an embodiment of a magneto-optical disk drive according to the present invention. This magneto-optical disk device has the same size as a half-height 5.25 inch magnetic disk device. The front panel 101 is provided with a cartridge insertion slot 102 and a cartridge ejection button 103 so that a cartridge containing a magneto-optical disc for recording and reproducing information can be manually inserted into or ejected from the apparatus. ing. A double door is provided in the cartridge insertion port 102,
At least one of the doors closes the insertion slot except when the cartridge is inserted or ejected, so that the intrusion of dust from the cartridge insertion slot 102 is suppressed as much as possible.

FIG. 10 is a mechanism diagram of the magneto-optical disk device shown in FIG. (A) is a front view, (b) is a side view, and only main parts are shown.

Circuit board 104 on which main circuit components are mounted
Is mounted on the lower surface of the apparatus with the component side outside to facilitate air cooling. A connector 105 for the SCSI interface is provided at the rear end of the circuit board 104 so that an interface cable can be pulled in and out from the rear of the device. When the present apparatus is used in a different housing, the position of the screw hole 120 for fixing the present apparatus to the housing is determined by the position of a 5.25 inch magnetic disk drive having the same external dimensions (half height). It is in the same position as the screw hole position.

The optical head for recording and reproducing signals is divided into two parts, a fixed part 106 and a movable part 107.
The movable part 107 includes one carriage case 25,
As shown in FIGS. 1 and 2, a pin-supporting rotary type two-dimensional actuator and a rotary magnet for recording and erasing are mounted on the carriage case 25. This carriage case 25
Is 13.5 mm, which is considerably thinner than a conventional optical head.
Conventionally, the recording / erasing magnet provided on the opposite side of the optical head with respect to the optical disk is configured to be on the same side as the optical head, so that a magnet or an electromagnetic coil is provided on the cartridge holder 108. No space is required, which greatly contributes to the thinning of this device.

Carriage case 2 shown in FIGS. 1 and 2
As shown in FIG. 6, coarse coils (drive coils) 23 are attached to both ends of the magnetic circuit 2.
With the help of 4, the movable part 107 is moved at high speed in the radial direction of the disk. Carriage case 2
5 is a ball bearing 2 along the guide shaft 21.
You will be guided to 2. The magnetic circuit 24 has a magnet 210 and a yoke 220 arranged so as to be parallel to the inserted disk surface. Therefore, the height of the magnetic circuit 24 can be considerably reduced to 9.5 mm.

Although the details of the fixing portion are not shown, a semiconductor laser is attached to the fixing portion 106 as a light source. A laser beam emitted from the semiconductor laser is converted into a parallel beam by a collimating lens, and further, the beam is shaped. The light is converted into a substantially circular parallel beam by the prism and guided to the movable unit 107. The laser beam from the movable section 107 is separated into a desired light beam by a beam splitter provided in the fixed section 106, received by a photodetector having a light receiving section of a desired shape, and has fine irregularities on a disk substrate. It is used for reproducing a preformat signal formed of pits, detecting control signals for focus servo and tracking servo, and reproducing a magneto-optical signal.

FIGS. 1 and 2 show a separation optical system in which only the peripheral portion of the objective lens according to an embodiment of the present invention moves in the radial direction of the recording medium, and most of the optical system is housed in a fixed portion. The main part of the movable head is shown. FIG. 2 is a plan view of a main part of the movable head, and FIG. 1 is a sectional view taken along line BB of FIG.

A carriage case 25 on which a two-dimensional actuator and a bias magnetic field applying device are mounted is opposed to the magneto-optical disk having the recording film 1 formed on the transparent substrate 2. As shown in FIG. 6, the carriage case 25 is guided by a ball bearing 22 along a guide shaft 21 fixed on a base (not shown), and is moved in the radial direction of the magneto-optical disk (perpendicular to the paper plane in FIGS. 1 and 6). Direction). Drive coils 23 are attached to both side surfaces of the carriage case 25, and the carriage case 25 is moved in the radial direction of the magneto-optical disk by an electromagnetic force acting between the carriage case 25 and a magnetic circuit 24 fixed on the base.

In the carriage case 25, as shown in FIGS. 1 and 2, the objective lens 3 is placed in an AF direction perpendicular to the surface of the magneto-optical disk (the direction perpendicular to the plane of FIG. 2).
A two-dimensional actuator that is driven in a TR (automatic tracking) direction, which is a (autofocus) direction and a radial direction (front-back direction in FIG. 2) of the magneto-optical disk, and a parallel light beam that enters the carriage case 25 from a fixed optical system. And a bias magnetic field applying device for applying a bias magnetic field perpendicular to the recording film 1 are mounted. The two-dimensional actuator includes a movable part to which the objective lens 3 is attached, a support shaft 5 that slides and supports the movable part, and a magnetic circuit.
The movable part includes a lens support 4 having an objective lens 3 attached to a tip thereof, and an AF fixed to both sides of a central portion of the lens support 4.
(Autofocus) coils 6a and 6b and TR (tracking) coils 7 fixed to both rear side surfaces of the lens support 4
a and 7b. The lens support 4 has a guide hole passing through the center of gravity of the movable part. The guide hole is fitted with the support shaft 5 to guide the movable portion so as to be able to move straight in the AF direction, and to guide the movable portion rotatably around the support shaft 5. In the magnetic circuit, magnets 8a, 9a and 8b, 9b having opposite polarities are fixed to the back yokes 10a, 10b (for example, assuming that the front side of the magnet 8a is N and the rear side is S in FIG. 2, the front side of the magnet 9a is S, N on the rear side), center yokes 11a, 11b are connected to the back yokes 10a, 10b on the bottom surface of the carriage case 25 in FIG.
The main part of 1b stands upright in the AF coils 6a and 6b. The AF coils 6a and 6b are partially formed of magnets 8a and 8b.
b and the center yokes 11a and 11b. The TR coils 7a and 7b have a magnet 8 at the side of the objective lens.
a, 8b and the center yokes 11a, 11b, and the opposite parts face the magnets 9a, 9b. Further, the extended portions of the back yokes 10a and 10b and the lens support 4 are connected by support springs 12a to 12d to perform reference positioning of the objective lens 3 in the direction perpendicular to the magneto-optical disk surface and in the radial direction of the magneto-optical disk. I have.

In FIG. 2, the magnetic flux passing between the center yokes 11a and 11b and the front sides of the magnets 8a and 8b
a, 6b, the front side of the magnets 9a, 9b and the magnet 8
A magnetic flux passing between the front sides of the coils 7a and 8b
To cross. When current flows through the AF coils 6a and 6b, the forces received by both coils are in the same direction (for example, when an upward force acts on the coil 6a, an upward force also acts on the coil 6b). When a current is applied to the coil 7b, the forces received by both coils are opposite (for example, when a rightward force acts on the coil 7a in FIG. 2, a leftward force acts on the coil 7b).

As shown in FIG. 2, an AF coil 6 (6a, 6b) and a TR coil (7a, 7b) as driving means are provided.
And all of the magnetic circuits 8 to 11, the support springs 12a to 12d as support means, and the fixing means are all provided in a direction (line BB in FIG. 2) connecting the objective lens 3 and the support pin 5.
Because all of them are on the support pin side from the tip of the objective lens (Fig. 1,
Since the bias magnetic field applying device described below is hardly obstructed (obstructed) by the two-dimensional actuator, which is the objective lens driving means, in terms of the mounting space thereof (because it is arranged on one side only on the left side of the objective lens in FIG. 2). Can be installed). As a result, the distance between the bias magnet and the light spot convergence point F (the focal point of the objective lens 3 on the recording film 1) can be reduced, and the strength of the bias magnetic field at the light spot convergence point can be ensured even when the size of the bias magnet is small. It becomes possible.

Next, the structure of the bias magnetic field applying device will be described with reference to FIGS. FIG. 3 is a perspective view showing a structure of a saddle coil for driving a bias magnet, and FIG. 4 is a sectional view of a bias magnetic field applying device. The bias magnet 13 magnetized in one direction perpendicular to the central axis is rotatable by a shaft 20 inserted into a through hole provided at the center and ball bearings 18a and 18b fitted to both ends of the shaft 20. Supported. The ball bearings 18a and 18b are inserted into and supported by the coil cover 14 molded into a cylindrical shape having one end closed. The coil cover 14 is formed by molding with saddle-shaped coils 15a and 15b integrally embedded therein. The opening side of the coil cover 14 is closed by a lid 19, and a fitting portion between the coil cover 14 and the lid 19 is adhesively fixed. Two Hall elements 17a, 1 are provided on the sensor support plate 16 in the coil attachment portion of the coil cover 14.
The sensor to which 7b is attached is fixed. As shown in FIG. 1, the coil cover 14 is supported by the bias magnet holder 26 such that a line L connecting a coil attachment portion to which two coils are attached is inclined by an angle A from a line perpendicular to the magneto-optical disk. I have.

The outputs of the Hall elements 17a and 17b change depending on the magnetic flux density penetrating the respective elements, and the difference between the outputs of the two Hall elements 17a and 17b is fed back to the saddle coil 15 by the control system shown in FIG. . The saddle coil 15 is formed by connecting two saddle coils 15a and 15b in series. The differential amplifier 27 shown in FIG. 5 outputs the difference between the outputs of the Hall elements 17a and 17b, and the differential output is connected to a switching circuit 29 through a phase lead compensation circuit 28. The switching circuit 29 includes a terminal having a constant output V _C according to a command from a separately provided controller, and a phase lead compensation circuit 28.
Select one of the inputs. The output of the switching circuit 29 is amplified by the driving circuit 30 and a current flows through the saddle coil 15.

Next, the basic operation of the bias magnetic field applying device will be described. The basic operation includes three operations of detecting the polarity of the bias magnetic field, detecting that the angle of the bias magnet has entered a normal range, and inverting the polarity to the required polarity. Before each operation, the Hall element 1 when the bias magnet 13 makes one rotation from the reference angle A (position of the line L) shown in FIG.
7a and 17b, their sum signal and difference signal, and changes in the magnetic field strength H perpendicular to the recording film 1 at the light spot convergence point F will be described with reference to FIG. The range of the rotation angle of the bias magnet 13 in which the strength H of the magnetic field becomes equal to or more than the strength required for
A range from a ₁ degree to a ₁ degree and from a ₄ degree to 360 degrees, and a range equal to or less than the strength required for recording (absolute value increases) are defined as a ₂ degrees to a ₃ degrees. The sum output value at each angle from a ₁ to a ₄ degrees is S
₁ to S ₄ , and the difference output values are D ₁ to D ₄ . As shown in FIG. 7, the magnetic field strength (magnetic field component perpendicular to the recording film 1) H at the light spot convergence point F of the recording film 1 and the Hall element 17
Since the outputs of a and 17b show a change similar to a sine wave, the fact that the bias magnetic field H is in a range suitable for erasing means that the sum output S
Is greater than or equal to the larger of S ₁ and S ₄ , and can be reliably detected by matching that the difference output D is between D ₄ and D ₁ . Similarly in the range of bias field H can be recorded, confirmed by the sum output S is smaller (larger absolute value) of S ₂ and S ₃ or less, further, a difference output D is the D ₂ it can be reliably detected by combining that value between the D _3.

The polarity of the bias magnetic field can be determined based on the value of the sum output since the sum output S shows the same change as the bias magnetic field H as shown in FIG. Sum output is S
₁ or confirmed to be erased side S ₄ or more, it is confirmed that the polarity of the recording side S ₃ or S ₂ or less.
However, it is easily understood that the polarity can be determined even if the value is closer to the center value of the sum output (even if the absolute value of the sum output is smaller) if only the polarity is determined.

It is determined whether the angle of the bias magnet is in the normal range by determining whether the difference output D is in the range from D ₄ to D ₁ or not.
₂ from may be determined in the range of D _3. It may determine that the need to consider the polarity between the D ₃ and larger D ₄ and D ₁ and smaller D ₂ are different output S. Difference output D
Becomes zero, the absolute value of the sum output S gives the maximum output.

The reversal of the bias polarity will be described with reference to FIG. The magnetic field applied to the saddle coil 15 changes sinusoidally according to the rotation angle of the bias magnet 13. Therefore, when a constant drive current i flows through the saddle-shaped coil 15,
The drive torque Tr applied to the bias magnet 13 changes similarly to the magnetic field applied to the saddle coil. Assuming that the magnetization direction of the bias magnet 13 starts to rotate from the direction of the mating portion of the saddle-shaped coil, the drive torque applied to the bias magnet changes to the deceleration direction at a rotation angle of 90 degrees or more. The speed becomes zero. If the same drive current is applied any longer, the rotation reverses and returns to the initial angle. Therefore, a time T at which the rotation speed becomes substantially zero from the first rotation is obtained in advance, and the switching circuit 2 is first switched by the control system shown in FIG.
9 in the constant input V _C side is rotated a bias magnet, the time to switch the phase compensation circuit 28 side input of the switching circuit 29 after the elapse of T, to the angle of the positioning control system. By switching to the angle positioning control system, the Hall element 1
The feedback control system operates so that the difference output between 7a and 17b becomes zero, and the magnet 13 is stably held at a predetermined rotation angle position. As described above, the inversion and holding of the bias magnetic field can be performed. In order to make the initial position of the angle of the bias magnet 13 constant, the switching circuit 29 in FIG.
Must be controlled so that the direction of magnetization comes to the joining portion of the saddle-shaped coil 15.

The magnetic field caused by the current flowing through the saddle-shaped coil 15 is considered to be small and has almost no effect on the bias magnetic field and the like. However, when the magnetic field is considerably large, the influence of the bias magnetic field applying device is taken into consideration. What is necessary is just to design.

In the above embodiment, the bias magnet 13
It has been described that the sum output S of the Hall elements 17a and 17b with respect to the rotation angle θ shows a sinusoidal change similar to the vertical magnetic field strength H at the light spot convergence point on the recording film 1 with respect to the rotation angle θ. Depending on the relationship between the angle position of the Hall element with respect to the bias magnet 13 and the angle position of the light spot convergence point, a sine wave of the same phase may not always be obtained. In this case, a sine wave of the same phase is obtained. It is necessary to adjust the mounting angle position of the Hall elements 17a and 17b or to adjust the output phase of the Hall elements 17a and 17b.

[0043]

As described above in detail, according to the magneto-optical disk device of the present invention, the bias magnetic field applying device is
On the same side as the objective lens with respect to the recording medium, and on the opposite side of the objective lens driving device and the support means with respect to the objective lens, since it is mounted on the movable head so as to be equal to or less than the height of the objective lens driving device, The bias magnetic field applying device can be provided without increasing the height of the mechanism, and the effect that the magneto-optical disk device can be reduced in size and thickness can be obtained.

Further, the objective lens driving device or the objective lens supporting means is provided only on one side as viewed from the objective lens, and a bias magnetic field applying device is provided on a vacant side on the opposite side. Since the height is less than the height of the objective lens driving device, the distance between the light spot convergence point (bias magnetic field application point) and the bias magnetic field application device can be shortened, and the diameter of the bias magnetic field application permanent magnet can be reduced. This reduces the rotational moment of inertia of the permanent magnet,
The effect of shortening the magnetic field reversal time for switching between erasing and recording can be obtained.

Further, the permanent magnet itself of the bias magnetic field applying device is constituted by a rotating body magnetized in the direction of the rotational diameter, and a rotating force is obtained by a generated magnetic field and a current flowing through a driving coil of the permanent magnet. As a result, the entire bias magnetic field applying device can be reduced in size, the distance between the light spot convergence point and the permanent magnet can be shortened, and a magnetic field perpendicular component effective for recording and erasing at the light spot convergence point can be obtained with sufficient strength. The effect is obtained.

Further, the rotation driving coil of the permanent magnet and the holding portion are constituted by a hermetically sealed container integrally molded,
Since the rotating magnet holding mechanism is sealed and held by this sealed container, dust is prevented from entering the permanent magnet from the surroundings, and conversely, the lubricant on the supporting portion of the rotating magnet is prevented from scattering around. Thus, the effect of improving the reliability of the magneto-optical disk device can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an embodiment of a movable head used in a magneto-optical disk device of the present invention.

FIG. 2 is a plan view of a main part of the embodiment of the movable head of FIG. 1;

FIG. 3 is a perspective view showing a structure of a saddle-shaped coil for driving a bias magnet.

FIG. 4 is a sectional view of a bias magnetic field applying device.

FIG. 5 is a configuration diagram of a control system of the bias magnetic field applying device.

FIG. 6 is a front view showing an outline of a movable head of the magneto-optical disk device.

FIG. 7 is a diagram showing a relationship between signals of various parts and a magnetic field when the bias magnet makes one rotation.

FIG. 8 is an explanatory diagram of the relationship between the drive current and the rotation of the magnet when reversing the bias magnetic field.

FIG. 9 is an external view showing an embodiment of a magneto-optical disk drive according to the present invention.

10 is a mechanism diagram of the magneto-optical disk device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Recording film 2 Transparent substrate 3 Objective lens 4 Lens support 5 Support axis of lens movable part 6a, 6b AF (automatic focusing) coil 7a, 7b TR (tracking) coil 8a, 8b, 9a, 9b Magnet 10a, 10b Back yoke 11a, 11b Center yokes 12a to 12d Support springs 13 Permanent magnets for applying a bias magnetic field 14 Coil covers 15a, 15b Saddle-shaped coils (permanent magnet drive coils) 16 Sensor support plates 17a, 17b Hall elements (rotation angle detecting means) 18a, 18b Ball bearing 19 Lid 20 Shaft 21 Guide shaft 22 Ball bearing 23 Carriage drive coil 24 Magnetic circuit 25 Carriage case 26 Start-up mirror 27 Operation amplifier 28 Phase lead compensation circuit 29 Switching circuit 30 Drive circuit 101 Front panel 102 cartridge slot 103 cartridge ejection button 104 circuit board 105 the connector 106 the optical head of the fixing unit 107 an optical head movable portion 108 cartridge holder 120 threaded hole 210 magnet 220 York

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 11/105 G11B 5/02

Claims (7)

(57) [Claims] 1. A movable head having an objective lens for forming a minute light spot on a recording film thereof facing a magneto-optical disk recording medium, and a polarity of a bias magnetic field perpendicular to the recording film by rotating a permanent magnet. A bias magnetic field applying device for inverting the magnetic field, wherein the bias magnetic field applying device includes a single permanent magnet and an objective lens driving device on the same side as the objective lens with respect to the magneto-optical disk recording medium. Is mounted on the movable head so that the height is equal to or less than the height of the single permanent magnet at the light spot convergence point.
Rotation of the permanent magnet to set the field strength to a predetermined value
A magneto-optical disk device characterized by performing angle control . 2. The apparatus according to claim 1, wherein the bias magnetic field applying device is provided on a side opposite to the objective lens driving device and the support means with respect to the objective lens in a direction parallel to the surface of the magneto-optical disk recording medium. 2. The magneto-optical disk drive according to claim 1, wherein: 3. The magneto-optical disk device according to claim 1, wherein the permanent magnet of the bias magnetic field applying device and the rotating means of the permanent magnet are housed in a closed container. 4. The magneto-optical disk drive according to claim 3, wherein a drive coil for driving the permanent magnet is integrally embedded as a part of the container in a closed container containing the bias magnetic field. 5. The permanent magnet of the bias magnetic field applying device is constituted by a rotating body itself, and is configured such that a rotating force can be obtained by a magnetic field generated by the permanent magnet and a driving current of a driving coil of the permanent magnet. 5. The magneto-optical disk drive according to claim 1, wherein: 6. A permanent magnet of the bias magnetic field applying device is magnetized in a rotational diameter direction, and a driving coil of the permanent magnet faces a north pole and a south pole of the permanent magnet, respectively. 6. The magneto-optical disk drive according to claim 5, further comprising a portion parallel to the rotation axis. 7. The permanent magnet of the bias magnetic field applying device has a rotation axis in a direction parallel to the surface of the magneto-optical disk recording medium on the side opposite to the objective lens driving device and the support means with respect to the objective lens. 7. The magneto-optical disk device according to claim 6, wherein the magneto-optical disk device is arranged in a radial direction of the magneto-optical disk recording medium.