JPH06131608A - Device for generating bias magnetic field - Google Patents

Abstract

PURPOSE:To obtain a thin bias magnetic field generator with stable magnetic field by simple constitution. CONSTITUTION:Respective one side bent parts 10a, 11a of two pieces of U-shaped sheet metal members are made adjacent to be welded and fixed. A center yoke 1a is constituted of the bent parts 10a, 11a, and side yokes are constituted of respective the other bent parts 10b, 11b. An insulation sheet 2 and a wiring coil 3 are inserted into the center yoke 1a to be stuck and fixed.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bias magnetic field generator for a magneto-optical disk drive device.

2. Description of the Related Art A magneto-optical disk drive device used for a computer memory, a document file, etc. records and reproduces information by making a cartridge containing a disk-shaped magnetic recording medium replaceable. In this magneto-optical disk drive device, the recording and erasing of information is
By utilizing the property that the temperature of the recording medium rises and the coercive force decreases due to the laser light irradiation, the direction of the auxiliary magnetic field (bias magnetic field) applied from the outside is switched to distinguish between recording and erasing. That is, a disk-shaped magnetic recording medium (hereinafter referred to as a disk) used in a magneto-optical disk drive device has a magnetic film formed on the disk surface and is magnetized in one direction in a direction perpendicular to the disk surface. When the disk is irradiated with laser light while applying a magnetic field in the opposite direction, the direction of magnetization is reversed. Information is recorded by reversing the direction of magnetization according to the information. Further, by irradiating the laser beam while applying a magnetic field in the opposite direction (that is, the direction magnetized in advance), recorded information can be erased. To reproduce the recorded information, the disk is irradiated with laser light. The polarization plane of the reflected light or transmitted light from the magnetized disk is rotated by magnetic rotation. Since the rotation direction of this magnetic rotation changes by reversing the magnetization direction of the disk, information can be reproduced by detecting the rotation direction. An outline of the magneto-optical disk drive device will be described with reference to the drawings. In the magneto-optical disk drive device 50 shown in FIG. 13, a disk rotary table 54 rotated by a spindle motor 53, an optical head 55, a bias magnetic field generation device 56, The loading mechanism 57 is incorporated. When the cartridge 52 accommodating the disk 51 is inserted into the magneto-optical disk drive device 50, FIG.
As shown in FIG. 5, the loading mechanism 57 sets the cartridge 52 on the disk turntable 54, and the bias magnetic field generator 56 that has been retracted upward is lowered.
The disk 51 is sandwiched and moved to a position facing the optical head 55. Then, while rotating the disk 51, a magnetic field is applied by the bias magnetic field generator 56, and the optical head 55 moves in the direction A to irradiate the laser beam, so that the disk 5
Information is recorded on and erased from the data. When reproducing information, laser light may be irradiated without applying a magnetic field. In addition,
In the figure, k ₁ is the escape space for the bias magnetic field generator 56,
K is the height of the magneto-optical disk drive device 50. An example of a bias magnetic field generator for generating a magnetic field necessary for recording or erasing information in such a magneto-optical disk drive device will be described with reference to FIG. In FIG. 15, a bias magnetic field generator 40 includes a main magnetic pole 41 and a yoke portion 42.
And a coil winding 43, and the main magnetic pole 41 is formed of a recording medium facing portion 41a and coil winding portions 41b and 41c. The coil winding 43 is wound around the coil winding portions 41b and 41c to form the coils 43a and 43b. In the bias magnetic field generator 40 configured as described above, currents are simultaneously applied to the coils 43a and 43b to generate a magnetic field. Further, as another example of the bias magnetic field generator, the one shown in FIG. 16 will be described. In FIG. 16, a bias magnetic field generator 45 includes a coil 48 a having an electric wire 48 wound around a bobbin 49, and a center yoke (main magnetic pole) 46.
, A side yoke 47, and a component (not shown) for positioning and fixing these members. A center yoke 46 is fitted in the center of the bobbin 49, and both ends 47a of the side yoke 47 are wrapped under the bobbin 49 to surround the coil 48a. Then, a current is passed through the coil 48a to generate a magnetic field. By the way, in the magneto-optical disk drive device 50 shown in FIGS. 13 and 14, the larger the thickness of the bias magnetic field generation device 56, the larger the upward escape space k ₁ , and the height K of the magneto-optical disk drive device 50 becomes. It gets bigger.

As described above,
In order to make the magneto-optical disk drive device thinner,
It is necessary to make the magnetic field generator thinner. However, in the conventional example of the bias magnetic field generator shown in FIG. 15, since the main magnetic pole 41 is composed of the coil winding portions 41b and 41c and the recording medium facing portion 41a, the bias magnetic field generator 4
The thickness t ₁ of 0 becomes large. Further, in the other conventional example shown in FIG. 16, the number of parts forming the bias magnetic field generator 45 is large and the cost is high. Also,
The bias magnetic field generator 45 is provided by the amount of the collar 49a of the bobbin 49 and the bent portion 47a of the side yoke 47.
The thickness t ₂ of the sheet becomes large. An object of the present invention is to solve a problem that a bias magnetic field generating device of a magneto-optical disk drive device has a problem that the thickness of the bias magnetic field generating device is large and that the number of parts is large and the cost is high.

According to the present invention, one of the two U-shaped sheet metal members has a bent portion adjacent to each other, and the bent portion constitutes a center yoke. It is solved by configuring the side yoke with. In addition, the present invention, in order to solve the above problems,
It is proposed that at least one convex portion and a concave portion for positioning be provided on one of the bent portions of each of the two U-shaped sheet metal members, and the convex portion and the concave portion be fitted to be adjacent to each other. Furthermore, the present invention proposes to press-fit a magnetic mold member into the center yoke in order to solve the above problems. Furthermore, in order to solve the above problems, the present invention provides
It is proposed that the magnetic mold member has a cap shape that covers the center yoke and that a taper portion is provided at the tip thereof.

In the bias magnetic field generator of the magneto-optical disk drive device, one bent portion of each of the two U-shaped sheet metal members is adjacent to each other, and the bent portion constitutes a center yoke, and each of the other bent portions forms a side portion. By constructing the yoke, the coil winding part of the main pole (center yoke) and the medium facing part can be eliminated, and the bobbin collar and side yoke of the coil around which the coil is wound can be eliminated. The generator can be thinned. Also, at least one positioning convex portion and one concave portion are provided on each of the bent portions of each of the two U-shaped sheet metal members, and the adjacent bent portions may be displaced by fitting and adjoining them. Since there is no step, a step is not generated in the center yoke, and a stable magnetic field can be obtained. Furthermore, by pressing the magnetic mold member into the center yoke,
The thickness of the center yoke can be increased, a required magnetic field can be obtained with a small amount of current, and heat generation can be reduced. Further, by forming the magnetic mold member into a cap shape that covers the center yoke and providing a taper portion at its tip, the gradient of the generated magnetic field becomes steep, and the perpendicular magnetic field necessary for reversing the magnetization of the disk can be efficiently generated. it can.

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, two U-shaped sheet metal members 10, 1
The first bent portions 10a and 11a are fixed by spot welding. The adjacent bent portions 10a and 11a form a center yoke 1a, and the other bent portions 10b and 11b form side yokes. A notch 2a is provided at the center of the insulating sheet 2 and can be inserted into the center yoke 1a. Lead wires 4a and 4b are soldered to both ends of the winding coil 3, and a connector 5 is further attached. As shown in FIG. 2, the insulating sheet 2 and the winding coil 3 are inserted into the center yoke 1a and bonded and fixed to form the bias magnetic field generator 1. In addition,
The two U-shaped sheet metal members 10 and 11 are not fixed by spot welding, but the winding coil 3 may be directly wound around the center yoke 1a and fixed by an adhesive. Unlike the conventional example shown in FIG. 15, the bias magnetic field generating device 1 of the present embodiment does not have a coil winding part and a medium facing part in the main magnetic pole, so the thickness T of the bias magnetic field generating device 1 is reduced. be able to.
Further, unlike the other conventional example shown in FIG. 16, since the bobbin and the positioning member are unnecessary, the number of parts can be reduced, and since the bobbin collar and the side yoke are not bent, the bias magnetic field generator 1 The thickness T can be reduced. 3, 4 and 5 are diagrams for explaining another embodiment of the present invention. In the magnetic field generator 35 shown in FIG. 3, a pair of positioning convex portions 21, 31 and concave portions 22, 32 are provided on each of the bent portions 20 a and 30 a of the U-shaped sheet metal members 20 and 30, respectively. And the concave portion 32, and the convex portion 31 and the concave portion 22 are fitted to each other so that the bent portions 20a and 30a are adjacent to each other to form a center yoke 35a, and the other bent portions 20b and 30b form side yokes. . The configuration of the other parts is exactly the same as that of the embodiment shown in FIG. As shown in FIG. 4, the U-shaped sheet metal member 20 has a pair of positioning projections 21 on one bent portion 20a.
And a recess 22 are provided. Convex portion 21 and concave portion 22
In the position where is provided, the distances f and f ′ from the long side 20c of the bent portion 20a to the centers of the convex portion 21 and the concave portion 22 are equal, and from the short sides d and e of the bent portion 20a to the convex portion 21 and the concave portion. Distances g to the center of 22 are equal to g '. Then, as shown in FIG. 5, a U-shaped sheet metal member 30 having the same shape as the U-shaped sheet metal member 20 is adjacent to the U-shaped sheet metal member 20 in a direction rotated by 180 degrees. As described above, the bent portions 20a and 30a are provided with the positioning convex portions 21 and 31 and the concave portions 22 and 32, respectively, and the convex portion 21 and the concave portion 32, and the convex portion 31 and the concave portion 22, respectively. Mated. By welding and fixing the two U-shaped sheet metal members 20 and 30 in this manner, the two U-shaped sheet metal members 20 and 30 are not displaced. Also,
Since the two U-shaped sheet metal members 20 and 30 have exactly the same shape, common parts can be achieved. The bias magnetic field generator 39 shown in FIG. 6 includes two U-shaped sheet metal members 3
7, 38 are adjacent to each other with a shift, and a step is formed in the center yoke 39a. The magnetic field distribution of the magnetic field generated by the bias magnetic field generator 39 in the disk radial direction has a peak at a position deviated from the center as shown in the graph of FIG. 7, which hinders the magnetization reversal of the disk. There is a risk of damage. However, according to the magnetic field generator 35 of this embodiment shown in FIGS. 3, 4 and 5, the two U-shaped sheet metal members 20 and 30 are not displaced and a stable magnetic field can be obtained. 8 and 9 are views showing still another embodiment of the present invention. In FIG. 8, two U-shaped sheet metal members 10 and 11, the insulating sheet 2, the winding coil 3, the lead wires 4a and 4b, and the connector 5 are the same as those in the embodiment shown in FIG. One of the two U-shaped sheet metal members 10 and 11 is provided with the bent portions 10a and 11a adjacent to each other, and the center yoke 6 is provided.
0a. The magnetic mold member 12 that can be press-fitted into the center yoke 60a is formed by mixing iron powder or the like when forming the member. As shown in FIG.
The insulating sheet 2 is inserted into the center yoke 60a, and the magnetic mold member 12 is further press-fitted. And winding coil 3
Is inserted and fixed by adhesion to form a bias magnetic field generator 60. In the bias magnetic field generator 60 of this embodiment, the center yoke 60a can be fixed by the magnetic mold member 12 and the thickness of the center yoke 60a is increased. Therefore, as shown in the graph of FIG. In comparison with a bias magnetic field generator that does not press in, a stronger magnetic field can be obtained even if the same current is applied, and in order to obtain the magnetic field necessary for reversing the magnetization of the disk, a smaller current can be applied and less heat is generated. . Note that FIG.
The graph of 0 represents the magnetic field j ₁ by the bias magnetic field generator 60 of this embodiment and the magnetic field j ₀ by the bias magnetic field generator in which the magnetic mold member 12 is not press-fitted, and the vertical axis H represents the magnetic field strength. FIG. 11 is a diagram showing still another embodiment of the present invention. Bias magnetic field generator 7 shown in FIG.
Reference numeral 0 denotes a center yoke 70a formed by the bent portions 10a and 11a of two U-shaped sheet metal members 10 and 11 which are adjacent to each other, and the cap-shaped magnetic mold member 13 shown in FIG. 12 is press-fitted into the center yoke 70a. Is. The cap-shaped magnetic mold member 13 is provided with a tapered portion 22 at its end. The structure of the other parts is exactly the same as that of the embodiment shown in FIGS. In the bias magnetic field generator 70 of the present embodiment, the center yoke 70a can be fixed by the cap-shaped magnetic mold member 13 and the tapered portion 22 is provided at the tip end thereof, so that the gradient of the generated magnetic field becomes steep. The perpendicular magnetic field required for reversing the magnetization of the disk can be obtained more efficiently.

As described above, in the bias magnetic field generator of the present invention, the center yoke and the side yoke can be constituted by two U-shaped sheet metal members, and a thin bias magnetic field generator can be manufactured with a small number of parts. be able to.
Further, since components such as an insulating sheet and a winding coil can be incorporated from the lower surface of the device, it is easy to assemble.
In addition, in each of the bent portions of the two U-shaped sheet metal members,
By providing the positioning projections and recesses one by one and fitting them together, the center yoke can be prevented from shifting and a stable magnetic field can be obtained. Furthermore, by press-fitting the magnetic mold member into the center yoke, the center yoke can be fixed and the thickness of the center yoke can be increased, and a stronger magnetic field can be generated.
In addition, by pressing the cap-shaped magnetic mold member with the tapered portion at the tip into the center yoke, the center yoke is fixed and the gradient of the generated magnetic field becomes steeper, and the perpendicular magnetic field necessary for reversing the magnetization of the disk is further improved. It can be obtained efficiently.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a bias magnetic field generator configured according to the present invention.

FIG. 2 is a front view of a bias magnetic field generator configured according to the present invention.

FIG. 3 is a sectional view of another embodiment of the present invention.

FIG. 4 is a perspective view of a U-shaped sheet metal member of the embodiment shown in FIG.

FIG. 5 is a bottom view of the U-shaped sheet metal member of the embodiment shown in FIG.

FIG. 6 is a cross-sectional view of a bias magnetic field generator having a step on the center yoke.

7 is a graph showing a magnetic field distribution of the bias magnetic field generator shown in FIG.

FIG. 8 is an exploded perspective view of still another embodiment of the present invention.

9 is a cross-sectional view of the embodiment shown in FIG.

10 is a graph showing a magnetic field distribution of the embodiment shown in FIG.

FIG. 11 is a sectional view of still another embodiment of the present invention.

FIG. 12 is a perspective view of a cap-type magnetic mold member.

FIG. 13 is a diagram illustrating a schematic configuration of a magneto-optical disk drive device.

FIG. 14 is a diagram for explaining the operation of the magneto-optical disk drive device shown in FIG.

FIG. 15 is a perspective view of a conventional bias magnetic field generator.

FIG. 16 is a cross-sectional view of another conventional bias magnetic field generator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bias magnetic field generator 1a Center yoke 2 Insulating sheet 3 Winding coil 10, 11 U-shaped sheet metal member 10b, 11b Side yoke 12 Magnetic mold member 13 Cap type magnetic mold member 21, 31 Positioning convex part 22, 32 Positioning Recess

Claims (4)

[Claims] 1. A bias magnetic field generator for a magneto-optical disk drive device, wherein one bent portion of each of the two U-shaped sheet metal members is adjacent to each other, and the bent portion constitutes a center yoke, and each of the bent portions of the other one. A bias magnetic field generator characterized in that a side yoke is formed of the. 2. A positioning convex portion and a concave portion are provided at one bent portion of each of the two U-shaped sheet metal members, and the convex portion and the concave portion are fitted to be adjacent to each other. The bias magnetic field generator according to claim 1. 3. The bias magnetic field generator according to claim 1, wherein a magnetic mold member is press-fitted into the center yoke. 4. The bias magnetic field generator according to claim 3, wherein the magnetic mold member has a cap shape that covers the center yoke, and a taper portion is provided at a tip thereof.