JPH0573807A - Magnetic field impressing mechanism for magneto-optical disk - Google Patents

Abstract

PURPOSE:To reduce a thickness, to speed-up the magnetic field inverting and moreover reduce the power consumption of the magnetic field impressing mechanism for the magneto-optical disk, capable of obtaining good efficiency of an outer magnetic field which is vertical to a medium surface required for recording and erasing information in magneto-optical recording. CONSTITUTION:The mechanism is constituted in such a way that it has a length to cover a recording area in the radius direction, and one of side surfaces where the magnetic poles of a permanent magnet 6 in a slender shape having the magnetic poles N and S on both side surfaces are not formed is disposed freely oscillatably in the orthogonal direction to the area in the radius direction of the recording medium 3 keeping a constant gap with the medium surface, and one pair of electromagnets 13 and 14 fixed with nonmagnetic spacers 11 and 12 respectively on their tips opposite to both side surfaces having the magnetic poles of the permanent magnet 6 are disposed, and hence the permanent magnet 6 is positioned by selecting a polarity of an exciting current to be impressed upon exciting coils 15 and 16 wound around the electromagnets 13 and 14 respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field applying mechanism for a magneto-optical disk which can efficiently obtain an external magnetic field perpendicular to the medium surface necessary for recording and erasing information in magneto-optical recording.

In a magneto-optical recording device such as a magneto-optical disk, a constant magnetic field is applied to a medium, the medium is irradiated with a laser beam or the like, and partially heated above the Curie point to remain in the medium. Information is recorded or erased by directing the direction of the existing magnetization to the direction of the applied magnetic field. When recording and erasing this information,
A magnetic field applying mechanism is required to place the vicinity of the light spot formed on the medium in a constant magnetic field in opposite directions during recording and erasing.

[0003]

2. Description of the Related Art FIG. 5 is a perspective view illustrating a magnetic field applying mechanism of a conventional magneto-optical disk. In addition, in order to make the description of the configuration and the operation easy to understand, the same reference numerals are given to the same portions throughout the drawings, and the duplicated description will be omitted.

In the figure, 1 is an objective lens for focusing, and 2 is an optical head, which has a focusing function and always irradiates a laser beam so that the surface of the recording medium 3 is always focused.
Further, the optical head 2 moves in the direction of arrow A, and the recording medium 3
Recording, reproducing, and erasing information at any place in

Reference numerals 4 and 5 are magnetic poles arranged so as to face the optical head 2, and are made of yoke iron having a small magnetic resistance.
In order to concentrate the magnetic field on the facing surface of the recording medium 3, the taper is formed in a tapered shape, and has a length sufficient to cover the entire moving range of the optical head 2 in the moving direction.

The magnetic poles 4 and 5 together with the permanent magnet 6 sandwiched therebetween form a U-shaped magnetic circuit and form a magnetic path as shown by the broken line in the figure. Reference numeral 7 denotes a drive device (solenoid or the like) for moving the entire magnetic circuit in the direction of arrow B, which constitutes a magnetic field applying mechanism together with the magnetic circuit.

FIG. 6 is a diagram for explaining the reversal of the direction of the external magnetic field at the time of conventional recording and erasing, in which (a) shows a downward magnetic field and (b) shows an upward magnetic field. Figure 6 below
The operation of FIG. 5 will be described with reference to FIG.

When information is recorded on the recording medium 3, the optical head 2 is moved to a predetermined position in the radial direction of the recording medium 3, and the driving device 7 drives the entire magnetic circuit (the magnetic poles 4, 5).
Then, the permanent magnet 6) is moved to, for example, the state shown in FIG. 6A, and downward magnetization is performed at a position opposite to the recording medium 3 corresponding to the irradiation point of the laser light.

Next, when the information on the recording medium 3 is erased, the optical head 2 is moved to a predetermined position in the radial direction of the recording medium 3 and the drive device 7 drives the entire magnetic circuit (the magnetic poles 4, 5 and the permanent magnets). 6) is moved to, for example, the state shown in FIG. 6B, and the recording medium 3 corresponding to the irradiation point of the laser light is moved.
Magnetize upward to the opposite position. If the magnetic poles N and S of the permanent magnet 6 are arranged oppositely, the upward and downward magnetizations corresponding to the objective lens 1 are naturally opposite.

Information can be recorded on and erased from the recording medium 3 as described above, but at this time, the movement of the entire magnetic circuit in the direction of arrow B by the driving device 7 for reversing the magnetization is extremely small (embodiment). In the case of 2 to 5 mm, the direction of the magnetic field is reversed in a short time.

[0011]

In the above-mentioned magnetic field applying mechanism of the magneto-optical disk, since the U-shaped magnetic circuit is formed, the height in the direction perpendicular to the surface of the recording medium 3 is made low and the size is reduced. Difficult to convert. In addition, since the U-shaped magnetic circuit has a large mass and is heavy, the driving device 7 including a motor for moving the U-shaped magnetic circuit also requires a large space,
Power consumption corresponding to this is required, and movement of the U-shaped magnetic circuit takes time.

The present invention has been made in view of the above-mentioned conventional drawbacks, and an object of the present invention is to reduce the thickness of a magnetic field applying mechanism of an optical disk, speed up the magnetic field reversal time, and reduce power consumption.

[0013]

In order to achieve the above object, the present invention, as shown in FIG. 1, applies a constant magnetic field onto a region provided in the radial direction of one surface of a recording medium 3 and the region concerned. In a magnetic field applying mechanism of a magneto-optical disc that irradiates a laser spot on the opposite surface of the objective lens 1 with the objective lens 1 and records or erases information by thermomagnetic action, has a length that covers the recording area in the radial direction, In addition, one of the side surfaces of the elongated permanent magnet 6 having the magnetic poles N and S on both side surfaces on which the magnetic poles are not formed is orthogonal to the radial area of the recording medium 3 while maintaining a constant gap with the medium surface. A pair of electromagnets 13 and 14 having non-magnetic spacers 11 and 12 fixed to the ends thereof are disposed so as to be swingable so as to face both side surfaces having the magnetic poles of the permanent magnet 6, and the electromagnet 13 is disposed. Excitations wound around 14 and 14, respectively Configured to position the permanent magnet 6 by selecting the polarity of the exciting current applied to the yl 15,16.

[0014]

In the present invention, the recording area of the recording medium 3 is covered in the radial direction, and both side surfaces are magnetic poles N and S.
The prismatic elongated permanent magnet 6 formed in the above is disposed so as to be swingable in a direction orthogonal to the radial direction of the recording medium 3 with a constant gap from the surface of the medium. One of the opposite magnetic fields leaking in the direction perpendicular to the recording medium 3 is used as the applied magnetic field.

The method of selecting both magnetic fields is to select the polarities of the exciting currents for the exciting coils 15 and 16 wound around the electromagnets 13 and 14, respectively, and to select N for the opposing magnetic poles of the electromagnets 13 and 14.
Alternatively, the magnetizing direction of S having the same polarity is applied, and the desired magnetic field application direction of the permanent magnet 6 to the recording medium 3 is caused by the attraction and repulsion of the polarity of the permanent magnet 6 and the polarities of the electromagnets 13 and 14 opposite thereto. The movement is controlled so as to face with. With this configuration, the magnetic field applying device can be downsized.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic view of the essential parts of an embodiment of the present invention.
(A) is a plan view of a main part, (b) is a sectional view taken along line CC 'of FIG. 2 (a), FIG. 2 is a sectional view taken along line DD' of FIG. 1 (a), and FIG. Figure 3 shows an exploded perspective view of the invention. 1 will be described below with reference to FIGS. 2 and 3. These figures show the cartridge that contains the recording medium 3 and the cartridge holder that is equipped with the magnetic field applying mechanism of the present invention.

In each drawing, 20 is a cartridge for accommodating the recording medium 3, 21 is a window of the cartridge in a state where a shutter (not shown) attached to the cartridge 20 is opened, and 30 is an assembly of each component of the magnetic field applying mechanism of the present invention. It shows a cartridge holder that serves as a frame for holding the cartridge 20 in a predetermined position as a guide.

Reference numeral 6 denotes a permanent magnet, which is an elongated prism having a length that covers the recording area 3a in a predetermined radial direction (moving range of the objective lens 1) and has magnetic poles N and S on both side surfaces. It is a magnet. Then, one of the side surfaces on which the magnetic poles N and S are not formed is arranged so as to be swingable in a direction orthogonal to the radial direction of the recording medium 3 (moving direction of the objective lens 1) while maintaining a constant gap with the medium surface of the recording medium 3. It is set up.

The arrangement method is as follows. First, the support plate 8 fixed to the side surface of the permanent magnet 6 opposite to the side facing the recording medium 3.
Guide holes 9 each having a long hole for guiding at both ends of
Provide 10.

On the other hand, as shown in FIGS. 2 and 3, stud pins 33 and 34 are planted in the magnetic field applying mechanism mounting portions 31 and 32 of the cartridge holder 30, respectively.
After inserting the above-mentioned guide holes 9 and 10 into 33 and 34 in a guideable manner,
Caps are provided at the ends of each stud pin 33 and 34 to prevent them from falling off.
35 and 36 are fitted. With this structure, the permanent magnet 6 can be swingably moved in a direction orthogonal to the moving direction of the objective lens 1.

Reference numerals 11 and 12 denote non-magnetic spacers which are arranged at a required interval so as to face the side surfaces of the permanent magnet 6 near the central portion in the longitudinal direction, where the magnetic poles N and S are formed, respectively. The permanent magnet 6 is oscillated so that the magnetic pole surface of the permanent magnet 6 contacts one of the spacers 11 and 12.
Reference numerals 13 and 14 are electromagnets connected to the spacers 11 and 12, respectively, and excitation coils 15 and 16 are wound around the electromagnets 13 and 14, respectively.

Reference numerals 17 and 18 are yokes formed integrally with the electromagnets 13 and 14, respectively, which also serve as mounting fittings.
Each of the yokes 3 and 14 is formed in a T shape, and the ends of the yokes in the longitudinal direction are fixed to the magnetic field applying mechanism mounting portions 31 and 32 by mounting screws 37 to 40. Excitation coil 1
The reference numerals 5 and 16 and the yokes 17 and 18 are arranged without contacting the window 21 of the cartridge 20 and the recording medium 3.

With this structure, when the cartridge 20 shown in FIG. 3 is inserted into the cartridge holder 30, the permanent magnet 6 is swingably positioned with respect to the recording area 3a of the recording medium 3.

FIG. 4 is a diagram for explaining the magnetic field reversal control action of the present invention, in which (1) to (2) show the control sequence. In the first state, the permanent magnet 6 is magnetized such that the magnetic poles N and S are arranged as shown by arrow E. Spacers 11 and 12 are arranged with the permanent magnet 6 sandwiched between them, and electromagnets 13 and 14 each having excitation coils 15 and 16 wound around magnetic cores made of a magnetic material are arranged on the outside of the yokes 17 and 18, respectively. The yokes 17 and 18 are connected to the magnetic field applying mechanism mounting portions 31 and 32 shown in FIG. 1 by screws or the like. It is assumed that no current flows in the exciting coils 15 and 16 in this state.

In the initial state, the permanent magnet 6 has the spacer 12
, The attractive force of the permanent magnet 6 acts more strongly on the magnetic core of the electromagnet 14 with the spacer 12 sandwiched between it and the electromagnet 13 on the opposite side.
It is self-held at the position where it touches 12.

The exciting coils 15 and 16 are connected in series, for example, so that when a current is passed through them, the opposite poles of the electromagnets 13 and 14 have the same polarity (for example, the S polarity is generated as shown in the above state). The direction in which the coil is wound is determined, so that the N polarities are opposed when the directions of the exciting currents are reversed.

[0027] indicates the moment when the exciting current starts to flow in one direction. In this case, since the permanent magnets 6 and the electromagnets 14 have opposite S polarities having the same magnetic polarities, a repulsive force acts. On the contrary, since the permanent magnets 6 and the electromagnets 13 have different magnetic polarities facing each other, the attraction force acts, and as a result, the permanent magnets 6 are
A force acts in the direction of moving to the 13 side.

If the spacers 11 and 12 are not provided, the attractive force of the permanent magnet 6 with respect to the electromagnets 13 and 14 is large. Therefore, the spacers 11 and 12 having an appropriate thickness for facilitating the separation with a small exciting current. Twelve are provided.

The state (1) shows the case where the exciting current is cut off, and the magnetic pole property of the electromagnet 13 disappears, but contrary to the case (3), the electromagnet whose N-polar attractive force of the permanent magnet 6 disappears.
The magnetic core of 13 acts more strongly on the electromagnet 14 on the opposite side and is self-held.

The state (1) shows the relationship between the flow of the magnetic field generated by the permanent magnet 6 and the recording medium 3 and the objective lens 1 in the state (2). The upward flow of the magnetic field returning to the S magnetic pole of the permanent magnet 6 is shown. It is applied to the recording medium 3, and the laser spot is irradiated from the objective lens 1 to the application point. This allows the upward magnetic field to be recorded or erased.

By applying an exciting current in the opposite direction from this state, the permanent magnet 6 has an action which is completely opposite to the action of.
Moves so as to abut the spacer 12. Moreover, the moving distance may be at most about 2 to 5 mm as described in the conventional example, so that the thickness direction can be made extremely small as a whole. Since only the permanent magnet 6 and the support plate 8 move, the weight of the movable part can be reduced. Realization of this thinning and weight saving promotes reduction of magnetic field reversal time and reduction of power consumption.

Although the permanent magnet 6 has a prismatic elongated shape having the magnetic poles N and S on both side surfaces, the permanent magnet 6 is not limited to this, and in order to efficiently concentrate the leakage magnetic flux in the perpendicular direction to the recording medium 1. In addition, it is more preferable to form the magnetic pole shape into a deformed magnetic pole as shown by the broken line while maintaining the non-contact positional relationship with the recording medium 1.

[0033]

As is apparent from the above description, according to the present invention, it is possible to realize a thin magnetic field applying mechanism for an optical disc,
This has the effect of shortening the magnetic field reversal time and reducing power consumption.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a main part of an embodiment of the present invention.

FIG. 2 is a sectional view taken along line D-D ′ of FIG.

FIG. 3 is an exploded perspective view of the present invention.

FIG. 4 is a diagram for explaining the magnetic field reversal control action of the present invention.

FIG. 5 is a perspective view illustrating a magnetic field applying mechanism of a conventional magneto-optical disk.

FIG. 6 is a diagram for explaining reversal of the direction of an external magnetic field for conventional recording and erasing.

[Explanation of symbols]

 1 Objective lens 3 Recording medium 3a Recording area 6 Permanent magnet 11,12 Spacer 13,14 Electromagnet 15,16 Excitation coil

Claims (1)

[Claims] 1. A constant magnetic field is applied to an area provided in the radial direction of one surface of a recording medium (3), a laser spot is irradiated by an objective lens 1 on the opposite surface of the area, and information is generated by thermomagnetic action. In a magnetic field applying mechanism of a magneto-optical disk for recording or erasing, a length that covers the recording area in the radial direction,
Also, an elongated permanent magnet having magnetic poles N and S on both sides (6)
One of the side surfaces on which the magnetic pole is not formed is swingably arranged in a direction orthogonal to the radial area of the recording medium (3) while maintaining a constant gap with the medium surface. A pair of electromagnets (13, 14) with non-magnetic spacers (11, 12) fixed to the ends so as to face both sides having magnetic poles are wound around the electromagnets (13, 14) respectively. Exciting coil (1
A magnetic field applying mechanism for a magneto-optical disk, characterized in that the permanent magnet (6) is positioned by selecting the polarity of the exciting current applied to the magnetic field.