JP3260792B2 - Bias magnetic field supply device - Google Patents

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 supply device for generating a bias magnetic field for recording or erasing information in a magneto-optical disk drive using an electromagnet.

[0002]

2. Description of the Related Art A magneto-optical disk, which is a magnetic recording medium used in a magneto-optical disk device, has a medium surface (disk surface).
The magnetic film has a magnetic anisotropy in a direction perpendicular to the film surface. When a light beam is applied to a magneto-optical disk that has been magnetized in one direction in a direction perpendicular to the medium surface while applying a bias magnetic field in the opposite direction, the magnetization direction is reversed. By utilizing this, information can be recorded by reversing the direction of magnetization according to the information. Then, by irradiating a light beam while applying a bias magnetic field in the opposite direction (that is, a magnetic field in the first magnetization direction) to the medium surface of the magneto-optical disk on which information is recorded, the recorded information can be erased.

On the other hand, when reproducing recorded information,
A light beam is applied to the magneto-optical disk. Then, the reflected light or the transmitted light from the magneto-optical disk undergoes the Kerr effect or the filady effect, and rotates when the polarization plane of the light enters the recording medium. Therefore, information can be reproduced by detecting the rotation direction.

FIG. 11 shows an outline of a magneto-optical disk device that performs these operations. In this magneto-optical disk device, a disk-shaped magneto-optical disk (magnetic recording medium) 51 rotated by a spindle motor 50 is opposed to an optical head 52 that moves in a radial direction, that is, a direction indicated by an arrow A in FIG. The bias magnetic field supply device 53 is disposed with the magneto-optical disk 51 interposed therebetween. Such a device can perform both recording and reproduction. However, in order to perform the recording, a magnetic field supply device for applying a bias magnetic field to the medium surface of the magneto-optical disk 51 is required as described above.

Conventionally, as a bias magnetic field supply device for generating a bias magnetic field using an electromagnet for such a purpose, a center yoke (main magnetic pole) is used as described in, for example, JP-A-2-50302. The coil winding portion is composed of a magnetic recording medium facing portion, and the coil winding portion has a length in the radial direction of the magneto-optical disk shorter than the recording width of the disk, and the magnetic recording medium facing portion is a magneto-optical disk. Are made longer than the recording width of the disk in order to save power and make the magnetic field distribution uniform over the entire recording width.

[0006]

However, in such a bias magnetic field supply device, a coil is wound around a coil winding portion of a main magnetic pole by a predetermined number of turns by an automatic winding machine or the like, and the winding end side is provided. If it is cut as it is, the coil wound around it will loosen (break apart). for that reason,
Conventionally, a special wire rod with a heat-fusible member attached in advance to the outside of the insulating coating covering the coil is used, and after the coil is wound, heat is applied to it to attach it to the outside of the insulating coating. By melting the heat-fusible member and adhering adjacent coils to each other to prevent loosening of the coil, the cost is increased by the use of the special wire and the coil is After heating or melting the heat-fusible member, it must be cooled until it solidifies, which is troublesome and poor in workability.

In a normal case, an insulating tape is wrapped around the coil after the winding for insulation and to prevent the coil from being damaged, so that the number of parts increases and the assembling is troublesome. There was a problem that it would take. Further, in the magneto-optical disk drive, the center of the center yoke serving as the main magnetic pole and the center of the objective lens need to be arranged on a straight line in order to reduce the variation in the bias magnetic field. To this end, it is necessary to minimize the deviation between the center of the center yoke and the center of the drive device for driving the magneto-optical disk, so that it is necessary to increase the processing accuracy of the side yoke and the center yoke, which increases the cost. It was one of the factors.

[0008] The present invention has been made in view of the above problems, and is a coil wound on a bobbin without using a special wire having a heat-fusible member attached to the outside of an insulating coating. The purpose is not to loosen. In addition, the insulation of the coil can be maintained without wrapping the insulation coil around the coil wound around the bobbin to prevent the coil from being damaged, and the coil can be maintained due to contact with external parts. It is also an object to prevent scratching.

It is another object of the present invention to make the center of the center yoke coincide with the center of the bias magnetic field supply device and to reduce the variation of the bias magnetic field intensity without increasing the processing accuracy of the side yoke and the center yoke. . It is another object of the present invention to prevent the starting wire of the coil from interfering with the winding of the coil.

[0010]

In order to achieve the above object, the present invention provides a bias magnetic field supply apparatus as described above, wherein a center yoke and a center hole are formed in the center yoke.
Bobbin fitted to the bobbin and the side attached to the bobbin
A yoke, a coil wound around the bobbin, and a terminal attachable to the bobbin and connecting both ends of the coil or at least a winding end and a power supply cable. The terminal, the bobbin and the coil are connected to the side yoke and the center. It is surrounded by a resin holder that holds the yoke.

In the above-mentioned bias magnetic field supply device, a positioning portion for accurately positioning the center yoke is provided in the resin holder, the center yoke is positioned and held by the resin holder, and the center yoke and the coil are wound. It is effective to fix the mounted bobbin and the side yoke integrally at a predetermined position of the magneto-optical disk device.

Further, a center yoke, a bobbin having the center yoke fitted in a center hole, and a bobbin mounted on the bobbin.
Side yoke, and a coil wound on the bobbin, the bobbin is formed with a conductive pattern serving as a terminal for connecting both ends of the coil or at least a winding end end and a power supply cable, and the bobbin and It is preferable that the bias magnetic field supply device be configured by surrounding the coil with a resin holder that holds the side yoke and the center yoke.

In the bias magnetic field supply device, it is effective to form a conductive pattern on the surface of the bobbin on which the coil is wound. Further, in any of the above bias magnetic field supply devices, the winding start end of the coil is drawn out through a through hole formed in a position near the center hole of the bobbin and a through hole formed in the side yoke corresponding to the through hole, and It is good to connect with the cable of.

[0014]

According to the bias magnetic field supply device configured as described above, at least the winding end of the coil wound on the bobbin by a predetermined number of turns is connected to the terminal before the coil is mounted on the bobbin with a predetermined tension applied. If the terminal is attached to the bobbin by winding or soldering to the bobbin, the terminal can be wound around the bobbin without using a special wire rod with a heat-fusible member attached to the outside of the insulating coating. The loosened coil can be prevented.

Since the bobbin around which the coil is wound and the terminal is mounted is surrounded by the side yoke and the resin holder, external parts do not come into contact with the wound portion of the coil. Therefore, the insulation of the coil can be maintained without winding the insulating tape around the coil, and the coil can be prevented from being damaged. Further, a positioning portion for accurately positioning the center yoke is provided in the resin holder, the center yoke is positioned and held by the resin holder, and the center yoke, the bobbin around which the coil is wound, and the side yoke are integrally formed. If it is fixed at a predetermined position of the magneto-optical disk device, the center of the center yoke and the center of the bias magnetic field supply device can be matched without increasing the processing accuracy of the side yoke and the center yoke. Variation can be reduced.

In addition, a conductive pattern is formed on the bobbin as a terminal for connecting both ends of the coil or at least a winding end and a power cable, and the bobbin and the coil are made of a resin holding a side yoke and a center yoke. Even when the coil is surrounded by the holder, the coil can be attached to the conductive pattern by soldering or the like without causing the coil to be loosened in a state where a predetermined tension is applied to the end of the coil. In addition, since the coil wound on the bobbin is prevented from contacting external components by the side yoke and the resin holder, the coil can be kept insulated without wrapping an insulating tape around it, and the coil is damaged. Can be prevented.

If the conductive pattern is formed on the surface of the bobbin on which the coil is wound, the end of the coil can be prevented from protruding outside the bobbin, so that the insulation is improved. Further, if the winding start end of the coil is drawn through a through hole provided in a position close to the center hole of the bobbin and a through hole formed in the side yoke corresponding to the through hole and connected to a power supply cable, Since the wire at the beginning of winding of the coil does not cross the winding portion of the coil, it is possible to perform clean winding of the coil.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is an exploded perspective view of a bias magnetic field supply device showing one embodiment of the present invention, FIG. 2 is a longitudinal sectional view of the bias magnetic field supply device in an assembled state, and FIG. 3 is also attached to the bias magnetic field supply device. FIG. 3 is a plan view showing a resin holder.

This bias magnetic field supply device is for generating a bias magnetic field for recording or erasing information in a magneto-optical disk device. As shown in FIG. 1, a center yoke 1 is fitted to the center yoke 1. Center hole 2
, A coil 4 wound around the bobbin 3, and ends 4a, 4b on both sides of the coil 4 which can be attached to the bobbin 3 and power supply cables 5a, 5b connected by terminals 12, 13, respectively. And a terminal 6 that
The terminal 6, the bobbin 3 and the coil 4 are surrounded by a resin yoke 8 (see also FIG. 3) for holding the side yoke 7 and the center yoke 1 in an assembled state as shown in FIG.

The bobbin 3 is a resin excellent in heat resistance and moldability, for example, polyphenylene sulfide (PPS)
As shown in FIG. 1, flange portions 3a and 3b having the same size are formed in the upper and lower directions, and the outer peripheral shape of a winding core portion 3c serving as a coil winding portion therebetween is made elliptical, and the central portion thereof is formed. And a rectangular center hole 2 for fitting a center yoke 1 to the center hole.

FIG. 1 shows the inner surfaces of the upper and lower flange portions 3a and 3b.
The engagement grooves 11a, 1 are provided at a predetermined depth near the right end.
1b, 11c are respectively formed, and the engagement grooves 11a, 1c are formed.
1b, engaging projections 6a,
The engagement protrusions 6c are formed on the lower surface of the terminal 6 so as to correspond to the engagement grooves 11c. , So that the position is not easily shifted.

Then, at the fixed position where the terminal 6 is inserted as far as it will go, with the side yoke 7 shown in FIG. The length of the side yoke 7 is set so as not to contact the inner surface. The terminal 6 is formed of a resin having excellent heat resistance and moldability similarly to the bobbin 3, and has a predetermined shape so that the pin-shaped terminals 12 and 13 do not come into contact with each other as shown in FIG. Plant at intervals.

The terminals 12 and 13 of the terminal 6 include
The other ends of the cables 5a and 5b, one ends of which are connected to the connector 9, are fixed by soldering. The center yoke 1 is made of, for example, martensitic or ferritic iron, and has a crimping projection 1a, 1b formed on the upper surface and a vertically long main magnetic pole 1c formed integrally below.

Then, the side yoke 7 is mounted on the bobbin 3 to which the coil 4 is wound around the core portion 3c and the terminals 6 having both ends connected to the terminals 12 and 13 are inserted and fixed at predetermined positions. It is inserted from the direction of arrow B in FIG. The center yoke 1 is inserted into the center hole 2 of the bobbin 3 from below.
Is inserted from the side of the caulking protrusions 1a and 1b, and the protrusion 1
a and 1b are inserted into a square hole 7a formed in the center of the upper surface of the side yoke 7, and the caulking projections 1a and 1b are caulked as shown in FIGS. 7 is fixed.

Further, a resin holder 8 is mounted from below the side yoke 7 so that the bobbin 3 and the coil 4 (both inside and not visible) are not exposed to the outside as shown in FIG. The cables 5a and 5b are pulled out through grooves 8e (see also FIGS. 1 and 3) formed in the resin holder 8. At the center of the bottom of the resin holder 8, there is provided a magnetic pole restricting groove 15 serving as a positioning portion shown in FIG. 3 for accurately positioning the center yoke 1 in the state shown in FIG. By fitting the main pole 1c of the center yoke 1 without play, the center yoke 1 is positioned and held so as not to move in the left-right direction in FIG.

In this state, the center yoke 1 and the coil 4
The screws 29, 29 are inserted into the mounting grooves 8a, 8b formed on both sides of the resin holder 8 as shown in FIG.
It is screwed into a screw hole (not shown) on the magneto-optical disk device side to fix them at predetermined positions. In addition, as the material used for the side yoke 7, martensitic or ferritic iron is used similarly to the center yoke 1. The resin holder 8 is manufactured by molding using, for example, polyphenylene sulfide (PPS) which is a resin having good heat resistance and moldability.

According to the bias magnetic field supply device of this embodiment, the end 4b on the winding end side of the coil 4 wound around the bobbin 3 by a predetermined number of turns is given a predetermined tension as shown in FIG. At the position where the coil 4 is not loosened, the terminal 13 of the terminal 6 (held by a jig or the like at a position close to the bobbin 3) before being attached to the bobbin 3 and the end 4a on the winding start side are connected to the terminal 12 And the terminal 6 is attached to the engaging projection 6a by soldering or the like.
6c is engaged with the engaging grooves 11a to 11c, respectively, and inserted into the bobbin 3 without using a special wire rod in which a heat-fusible member is previously attached to the outside of the insulating coating. In addition, loosening of the coil wound around the bobbin 3 can be prevented. Further, since the bobbin 3 and the terminal 6 are used, the coil can be easily wound mechanically, so that the assembling property is improved.

The bobbin 3 on which the coil 4 is wound and the terminal 6 is mounted is surrounded by the side yoke 7 and the resin holder 8 as shown in FIG. Does not come into contact with external parts, so that the insulation of the coil can be maintained without wrapping an insulating tape around the coil 4 and the coil can be prevented from interfering with other parts. Scratches can be prevented.

Further, both ends 4a, 4b of the coil 4
If the connection between the coil and the cables 5a and 5b is soldered in the air without holding them by a jig or the like, the ends of the coils in the free state move, resulting in poor workability. Even if the connection can be made, if the connection portion is repeatedly subjected to stress by loading or the like, the stress may come off. According to this embodiment, the ends 4a and 4b of the coil 4 and the cables 5a and 5b are connected.
Since such a connecting portion is firmly fixed to the terminal 6 and has a high cable mounting strength, such a problem does not occur.

Generally, the distribution of the magnetic field in the direction of rotation of the magneto-optical disk on the lower surface of the center yoke (magnetic head) is as shown in FIG. That is, the magnetic field decreases rapidly as it deviates from the center of the center yoke. Therefore, in order to improve the recording characteristics, it is necessary to accurately position the center yoke with respect to the driving device for driving the magneto-optical disk, that is, to position the center of the center yoke and the center of the objective lens on a straight line.

However, in the case of a configuration as seen in a conventional bias magnetic field supply device, the position of the center yoke must be adjusted unless the dimensional tolerances (including bending tolerances such as deformation) and assembling tolerances of the components are strict. Could not be determined at the correct position with respect to the drive device for driving the magneto-optical disk, which increased the cost.

However, in this bias magnetic field supply device, the dimension L of the magnetic pole regulating groove 15 shown in FIGS. 2 and 3 is tightly fitted to the main magnetic pole 1c of the center yoke 1, and the magnetic pole regulating groove 15 is formed. As shown in FIG. 2, a gap S1 is formed between the bottoms 8c and 8d of the resin holder 8 and the edges on both sides of the opening formed on the lower surface of the side yoke 7.
, S2, respectively, and even if the mounting position of the center yoke 1 is shifted in the left-right direction in the figure, the bottoms 8c, 8d of the resin holder 8 are separated by the gaps S1, S2.
The center lines of the mounting grooves 8a and 8b formed for fixing the resin holder 8 to the magneto-optical disk drive and the magnetic pole regulating grooves 15 of the resin holder 8 as shown in FIG. Since the center line is aligned with the center line, the center yoke 1 can be accurately positioned with respect to the driving device while being manufactured at low cost.

That is, according to this embodiment, even if the assembly of the center yoke 1 is inclined as shown in FIG. 6 or shifted laterally as shown in FIG. An accurate position can be determined with respect to the drive device for driving the disk. Moreover, the groove width (dimension L) of the magnetic pole regulating groove 15 of the resin holder 8 made of a molded product.
The center yoke 1 can be accurately positioned only by tightening the tolerance of the center yoke, so that the cost can be reduced as much as there is no need to increase the processing accuracy of the side yoke and the center yoke.

FIG. 8 is a perspective view showing an embodiment in which a conductive pattern is formed on a bobbin instead of a terminal, and portions corresponding to FIG. 1 are denoted by the same reference numerals.
Bias magnetic field supplying device according to this embodiment, the medium of Example similar center yoke 1 of FIG. 1, the center yoke 1
A bobbin 23 which is fitted into Kokoroana 2, instrumentation on the bobbin 23
And a coil 4 wound around the bobbin 23, and the bobbin 23 is provided with end portions 4 on both sides of the coil 4.
a, 4b and the power supply cables 5a, 5b are formed with conductive patterns 26a, 26b respectively serving as terminals, and the bobbin 23 and the coil 4 are made of a resin holder 8 (which holds the side yoke 7 and the center yoke 1). It surrounds as with the embodiment of FIG. 4 by reference to FIGS. 1 to 3).

The conductive patterns 26a and 26b are arranged in parallel at intervals so that they do not conduct with each other, and the inner surface of the bobbin 23 around which the coil 4 is wound,
That is, in this embodiment, it is formed at the end on the upper surface side of the flange portion 23b. The conductive pattern may be formed by insert-molding a conductive pattern on the bobbin 23 or by forming a conductive pattern 26a, 26b on a substrate in advance using a double-sided tape or an adhesive.
(It may be the lower surface of the upper flange portion 23a.) Then, the end portions 4a, 4b on both sides of the coil 4 are attached to the conductive patterns 26a, 26b.
Are soldered, and the cables 5a and 5b connected to the power supply are soldered there.

Also in this case, the end 4b of the coil 4 at the winding end side can be attached to the conductive pattern 26b without causing the coil 4 to be loosened while applying a predetermined tension thereto. it can. Therefore, coil 4
Does not protrude outside the bobbin 23, so that the bobbin 2
Even if the insulating tape is not wound around the coil 4 wound around the coil 3, the coil 4 does not contact the inner surface of the inserted side yoke 7 (see FIG. 4). In this state, contact of the external component with the coil 4 can be prevented by the side yoke 7 and the resin holder 8, so that the insulation of the coil can be maintained and the coil can be prevented from being damaged.

In this embodiment, the conductive pattern 26
a and 26b are formed on the inner surface (upper surface of the flange portion 23b) of the bobbin 23 around which the coil 4 is wound.
The connection between the ends 4a, 4b and the cables 5a, 5b is covered by the side yoke 7.
At a position where it does not contact the inner surface of the connector), and there is no danger that the connection portion will come into contact with other components. Further, FIG.
The engagement grooves 11a to 11 for terminal attachment as shown in FIG.
Since there is no need to form 1c, bobbin processing becomes easier.

FIG. 9 is a perspective view showing the vicinity of an essential part of an embodiment of a bias magnetic field supply device capable of aligning and winding a coil on a bobbin. FIG. 10 is a diagram showing a winding when a coil is wound on a bobbin in a normal winding manner. FIG. 9 is a perspective view for explaining a state where aligned winding cannot be performed due to a first coil end. As shown in FIG. 10, the coil 4 wound on the bobbin generally has to be pulled out to the outside of the coil 4 on which the winding start end 4a is wound, so that the coil 4 is wound around the bobbin by the end 4a of the coil 4. The coil 4 is not arranged and wound.

Therefore, in order to enable the winding of the coil, for example, when the winding end end of the coil ends on the lower side, the winding start side of the coil is placed on the inner surface (upper side) of the lower flange portion of the bobbin. It is necessary to form an escape groove with a depth that allows the end of the coil to pass through without contacting the wound coil, in a direction transverse to the wound coil, and to pull out the end of the coil through the groove to the outside of the coil .

However, the bobbin 23 'shown in FIG.
However, since the upper and lower flanges 23a and 23b are desired to be thinned (0.3 to 0.5 mm) to the limit due to the miniaturization of components, there is no room for forming a clearance groove for passing the winding start side of such a coil. In this embodiment, as shown in FIG. 9, the end 4a on the winding start side of the coil 4 is provided at a position close to the center hole 2 of the bobbin 23 'and communicates with the outer peripheral surface of the core 23c.
And is drawn out through a through hole 7b formed in the side yoke 7 corresponding to the through hole 25 and is connected to one of the cables 5a of the power supply, so that the flange portions 23a and 23b of the bobbin 23 'are made as thin as possible. However, the coil 4 can be wound around the bobbin 23 '.

The end 4b on the winding end side of the coil 4
Is connected to the cable 5b by soldering via the conductive pattern 26b. Although not shown in FIG. 9, the coil 4 is wound in this embodiment, and the side yoke 7 is inserted into a bobbin 23 'having its coil end connected to the cables 5a and 5b. After the center yoke 1 (see FIG. 1) is inserted into the center hole 2 of 23 'and caulked, a resin holder 8 made of a molded product is attached to the center yoke 1 in the same manner as in the embodiment of FIG. Prevent leakage of current to the part.

[0042]

As described above, according to the present invention, a coil wound on a bobbin without using a special wire having a heat-fusible member attached to the outside of the insulating coating of the coil. Can be prevented, so that the cost can be reduced. In addition, the insulation of the coil can be maintained without winding an insulating tape around the coil to prevent insulation or damage to the coil, and the coil can be prevented from being damaged due to contact with external components.

Further, a positioning portion for accurately positioning the center yoke is provided in the resin holder, thereby positioning and holding the center yoke. The center yoke, the bobbin and the side yoke are integrally formed in the magneto-optical disk drive. If fixed at a predetermined position, the center of the center yoke and the center of the bias magnetic field supply device can be matched without increasing the processing accuracy of the side yoke and the center yoke, so that the variation in the bias magnetic field intensity can be reduced. .

Further, if a conductive pattern is formed on the bobbin as a terminal for connecting both ends of the coil or at least the end of the winding and the power supply cable, the terminal becomes unnecessary, so that the number of parts is reduced and the terminal is connected to the bobbin. Since there is no need to provide a groove or the like for mounting the slab, processing becomes easy. If the conductive pattern is formed on the surface of the bobbin on which the coil is wound, the end of the coil does not protrude outside the bobbin, so that the insulation is improved.

Further, if the winding start end of the coil is drawn out through a through hole provided at a position close to the center hole of the bobbin and a through hole formed in the side yoke corresponding to the through hole, the winding of the coil can be started. Does not cross the winding portion of the coil, so that a clean coil can be aligned and wound.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a bias magnetic field supply device according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of the bias magnetic field supply device in an assembled state.

FIG. 3 is a plan view of a resin holder attached to the bias magnetic field supply device.

FIG. 4 is a perspective view of the bias magnetic field supply device in an assembled state.

FIG. 5 is a diagram showing a distribution of a magnetic field in a rotation direction of a magneto-optical disk on a lower surface of a general center yoke.

FIG. 6 is a longitudinal sectional view showing a state in which the center yoke 1 is inclined and assembled in the bias magnetic field supply device of FIG. 2;

FIG. 7 is a longitudinal sectional view showing a state in which the center yoke 1 is mounted in the bias magnetic field supply device so as to be shifted in the horizontal direction.

FIG. 8 is a perspective view showing an embodiment in which a conductive pattern is formed on a bobbin instead of a terminal.

FIG. 9 is a perspective view showing the vicinity of a main part of an embodiment of a bias magnetic field supply device which enables aligned winding of a coil on a bobbin.

FIG. 10 is a perspective view for explaining a state in which when a coil is wound around a bobbin in a normal winding manner, aligned winding cannot be performed due to a coil end at the beginning of winding.

FIG. 11 is a schematic diagram for explaining an outline of a conventional magneto-optical disk device.

[Description of sign]

DESCRIPTION OF SYMBOLS 1 Center yoke 1c Main pole 2 Center hole 3, 23, 2
3 'bobbin 4 coil 4a, 4b end 5a, 5b cable 6 terminal 7 side yoke 7b through hole 8 resin holder 15 magnetic pole regulating groove (positioning portion) 25 through hole 26a, 26b
Conductive pattern

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-128613 (JP, A) JP-A-62-46450 (JP, A) JP-A-5-40903 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G11B 11/105 G11B 5/03

Claims (5)

(57) [Claims] 1. A bias magnetic field supply device for generating a bias magnetic field for recording or erasing information in a magneto-optical disk device, comprising: a center yoke; a bobbin having the center yoke fitted in a center hole ; A side yoke attached to the bobbin,
A coil wound around the bobbin, and a terminal for connecting the both ends or at least the winding end and the power cable can be the coils attached to the bobbin, the terminal and the bobbin and coil and the side yoke the A bias magnetic field supply device surrounded by a resin holder that holds a center yoke. 2. The bias magnetic field supply device according to claim 1, wherein a positioning portion for accurately positioning the center yoke is provided on the resin holder, and the center yoke is positioned and held by the resin holder. A bias magnetic field supply device, wherein the center yoke, the bobbin around which the coil is wound, and the side yoke are integrally fixed at a predetermined position of a magneto-optical disk device. 3. A bias magnetic field supply device for generating a bias magnetic field for recording or erasing information in a magneto-optical disk device, comprising: a center yoke; a bobbin having the center yoke fitted in a center hole ; A side yoke attached to the bobbin,
And a coil wound around the bobbin, the forming a conductive pattern serving as terminals for connecting the two ends or at least the winding finish end and the power supply cables of said coil bobbin, the side yokes of the bobbin and coil bias magnetic field supply apparatus characterized by the enclosed by a resin holder for holding the center yoke. 4. The bias magnetic field supply device according to claim 3, wherein the conductive pattern is formed on a surface of the bobbin on which the coil is wound. 5. The bias magnetic field supply device according to claim 1, wherein a winding start end of the coil is provided at a position close to the center hole of the bobbin, and the through-hole is provided at the through-hole. A bias magnetic field supply device, wherein the bias magnetic field supply device is drawn out through a through-hole formed in the side yoke and connected to the power supply cable.