JP3515790B2 - Optical head driving device in information recording / reproducing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head driving device in an information recording / reproducing apparatus for recording / reproducing information on / from an optical disk.

[0002]

2. Description of the Related Art In recent years, an optical disk memory has been in the limelight as a high-density and large-capacity memory, and research and development of a small-sized information recording / reproducing apparatus having a high-speed access function using it as an information recording medium has been actively conducted. . In the related art example, for example, in Japanese Patent Laid-Open No. 2-187932, a front yoke (a yoke inserted into an electromagnetic drive coil), a back yoke (a yoke to which a permanent magnet is attached), which constitutes a magnetic circuit, and a side yoke. A technique is disclosed in which (a yoke connecting a front yoke and a back yoke) is fastened with a screw, and a hole through which the screw penetrates is provided in a side yoke in a direction in which a magnetic flux flows.

On the other hand, Japanese Patent Laid-Open No. 2-249145 discloses a technique in which a concave portion is formed in a permanent magnet forming a magnetic circuit to expand a magnetic flux density range to be used.

[0004]

However, in the case of using the former technique, the side yoke is a portion where all the magnetic flux in the magnetic circuit is concentrated and it is necessary to secure a sufficient cross-sectional area. Since it is opened, there is a problem that the side yoke has to be thicker in the moving direction of the optical head (optical pickup). Further, the front yoke is formed longer than the back yoke in the moving direction of the optical head to form the mounting portion, and the mounting portion is fastened to the base member of the device by screws, so that the entire magnetic circuit is moved in the moving direction of the optical head. There is a problem of upsizing. Further, since eight screws are used per device for assembling and fixing the magnetic circuit, there is a problem that assembling workability is poor. On the other hand, when the latter technique is used, the permanent magnet generally has a very poor workability, and there is a problem that a shape having irregularities is difficult to manufacture and the cost is significantly increased.

Therefore, in order to solve the above problems, it is an object of the present invention to provide an optical head driving device in an information recording / reproducing device which can be reduced in size and thickness, access time can be shortened, and cost can be reduced. To do.

[0006]

The invention according to claim 1 is
In order to achieve the above-mentioned object, an optical head for recording and reproducing information, a means for supporting the optical head and guiding it in the moving direction of the optical head, and being fixed to the optical head and The drive coil has a winding center axis arranged parallel to the moving direction, and a magnetic circuit for applying a magnetic field to the driving coil in a direction perpendicular to the moving direction. Of the permanent magnet, which has a constant air gap with respect to the outer side surface or the inner side surface of the permanent magnet and is arranged in parallel to the moving direction, a first yoke to which one magnetic pole of the permanent magnet is fixed, and the other of the permanent magnets. And a second yoke connected to the first yoke at both ends in the moving direction of the first yoke while forming a magnetic gap that faces the magnetic pole of the drive coil. In the optical head driving device of the recording / reproducing apparatus, the second yoke passes through the driving coil, and the first yoke and the second yoke are provided on both sides of the optical head. Base members are arranged at line-symmetrical positions with respect to the moving direction, the first yoke and the second yoke are each formed of a sheet metal material, and a base member having a hole is provided at a position adjacent to the first yoke. The permanent magnet is fixed to a surface of the first yoke that is orthogonal to the thickness direction of the sheet metal material, so that the thickness direction of the sheet metal material of the first yoke is parallel to the magnetic field direction of the magnetic gap. Is formed in the thickness direction of the sheet metal material within the permanent magnet fixing range of the first yoke on the fixing side of the permanent magnet.
A fastening hole is formed at a position that does not obstruct the magnetic path, and the first yoke is fastened and fixed to the base member via the fastening hole and the hole by fastening means.

According to a second aspect of the invention, in order to achieve the above-mentioned object, in the optical head driving device of the information recording / reproducing apparatus according to the first aspect, the first yoke is fastened and fixed to the base member. A plurality of convex portions are provided on the surface to be formed, a concave portion that fits the convex portion is provided in the base member, and the fastening hole is provided in the vicinity of the central portion of the first yoke in the moving direction, The first yoke is fastened and fixed to the base member in a state where the convex portion and the concave portion are fitted to each other.

According to a third aspect of the present invention, in order to achieve the above-mentioned object, in the optical head driving device of the information recording / reproducing apparatus according to the first or second aspect, the first yoke has a plurality of the sheet metal members. It is configured by overlapping.

According to a fourth aspect of the present invention, in order to achieve the above object, in the optical head driving device of the information recording / reproducing apparatus according to the first or third aspect, the movement of the permanent magnet of the first yoke is performed. A cavity is formed on a surface in contact with the central portion in the direction, and a plurality of the fastening holes are formed at symmetrical positions with respect to the central portion, and the first yoke on the side fastened and fixed to the base member. An insertion hole is provided at a position corresponding to the fastening hole, the first yoke is fastened and fixed to the base member through the fastening hole, the insertion hole, and the hole by the fastening means, and the void recess and the The portions of the permanent magnet corresponding to the fastening holes are not in contact with the first yoke.

According to a fifth aspect of the present invention, in order to achieve the above object, in the optical head driving device of the information recording / reproducing apparatus according to the second aspect, the first yoke is
A plurality of the sheet metal materials are overlapped with each other, and the plurality of convex portions are formed by half blanking at positions symmetrical with respect to the center of the permanent magnet in the moving direction and are fastened and fixed to the base member. Insertion hole is provided at a position corresponding to the fastening hole of the first yoke on the side where the first yoke is stacked, and the fitting concave portion and the convex portion formed by the half blanking when a plurality of the first yokes are stacked. The first yoke is fastened and fixed to the base member by the fastening means through the fastening hole, the insertion hole and the hole, and
Portions of the permanent magnet corresponding to the fastening hole and the fitting recess are not in contact with the first yoke.

[0011]

According to the invention described in claim 1, the direction and the magnetic gap of the fastening hole of the first yoke are constituted by the above-mentioned constitution and means.
Of the optical head with respect to the direction of the magnetic field of the loop and the drive coil.
The attachment direction is the same.

According to the second aspect of the present invention, with the above-mentioned structure and means, the positioning / fixing means of the magnetic circuit can be processed at a low cost without saturating the magnetic flux and can be constructed with a simple shape. Workability is also improved.

According to the third aspect of the present invention, with the above-described structure and means, the positioning / fixing means for an arbitrary magnetic circuit shape can be manufactured at low cost and with a simple shape.

According to the fourth aspect of the present invention, when the void concave portion is formed on the surface of the first yoke which is in contact with the central portion in the moving direction of the permanent magnet, the magnetic circuit cross-sectional area is reduced. , The magnetic resistance increases. As a result, the influence of the magnetic flux generated by the drive coil due to the drive current,
That is, it is possible to reduce the deterioration of the response due to the increase of the inductance and the deterioration of the control characteristics due to the fluctuation of the driving thrust. In addition, the fastening hole formed symmetrically with respect to the central portion in the moving direction of the first yoke fixing the permanent magnet and the above-mentioned void recess form a portion where the permanent magnet is not in contact with the first yoke. Therefore, it is possible to expand the moving range of the optical head by controlling the distribution of the magnetic flux density in the magnetic gap in the moving direction.

According to the fifth aspect of the present invention, by the above-described structure and means, when it is necessary to form the first yoke on the permanent magnet fixed side thick in the magnetic gap direction due to, for example, the performance of the magnetic circuit, a plurality of first yokes are provided. By forming the sheet metal materials of the above in superposition, the thickness per sheet metal material forming the first yoke can be reduced, and as a positioning / fixing means of the magnetic circuit, for example, the lower hole of the fastening hole can be made small in diameter. It is possible to perform half blanking at low cost. Also,
A portion where the permanent magnet is not in contact with the first yoke is formed by the fitting concave portion and the fastening hole formed at positions symmetrical with respect to the center of the first yoke that fixes the permanent magnet in the moving direction. Therefore, it is possible to expand the moving range of the optical head by controlling the distribution of the magnetic flux density in the magnetic gap in the moving direction.

[0016]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Regarding the orientation of objects in the drawings, the vertical and horizontal directions thereof are used as they are unless otherwise specified.

First, referring to FIG. 1 and FIG.
A configuration of an optical head driving device as an embodiment corresponding to the described invention will be described. In FIG. 1, reference numeral 1 indicates a known optical head for recording, reproducing or erasing information. The optical head 1 has a housing structure and is guided and supported by two guide rails 2 so as to be movable in the moving direction x of the optical head 1. Two drive coils 3 are fixed to the left and right of the optical head 1, and a front yoke 4 long in the moving direction x is inserted into each of the drive coils 3. Convex fitting portions 4a are formed at both ends of the front yoke 4.

Reference numeral 5 indicates a back yoke. The back yoke 5 has a U-shape, and is arranged so that the U-shapes face each other with the optical head 1 interposed therebetween. The back yoke 5 is formed integrally with the side yoke 5S portion by bending one sheet metal material. A square bar-shaped permanent magnet 6 which is long in the moving direction x is fixed inside the U-shape of the back yoke 5. At both ends of the side yoke 5S of the back yoke 5,
The concave fitting portion 5a is formed. The front yoke 4 and the back yoke 5 are connected by fitting the convex fitting portions 4a and the concave fitting portions 5a formed at both ends thereof, respectively.

1 to 3, reference numeral 9 indicates a base member. The base member 9 has a U-shaped cross section with the opening facing upward, is integrally formed with the base of the optical head driving device, and is provided at a position adjacent to the outer surface of the back yoke 5. The base member 9 is formed with two holes 10 penetrating in the thickness direction thereof.

In the above structure, the front yoke 4,
A magnetic circuit 7 is formed by the back yoke 5 and the permanent magnet 6, and the drive coil 3 is provided in the magnetic gap of the magnetic circuit 7.
The optical head 1 is driven along the guide rail 2 in the moving direction x by supplying an arbitrary current to the drive coil 3. As shown in FIG. 2, in the back yoke 5, two tap holes 8 are formed in the plate thickness direction of the sheet metal material at the portion of the back yoke 5 to which the permanent magnet 6 is fixed. Then, the back yoke 5 is fastened and fixed to the base member 9 by inserting two screws 15 into the holes 10 of the base member 9 and screwing them into the tap holes 8 of the back yoke 5.

Here, it is more cost-effective to form the lower hole of the tap hole 8 by punching at the same time when the outer shape of the sheet metal material is formed, rather than forming it with a drilling machine or the like, but in this case,
Unless the diameter of the pilot hole of the tap hole 8 is equal to or larger than the thickness of the sheet metal material, its processing becomes difficult. Therefore, when the thickness of the back yoke 5 is large, it is necessary to increase the diameter of the pilot hole of the tap hole 8, and the magnetic path cross-sectional area of the portion of the back yoke 5 where the tap hole 8 is formed becomes small, and the magnetic flux thereof is reduced. Is saturated.

As a method for solving the above problem, a second embodiment corresponding to the invention of claim 2 is shown in FIGS. In both figures, one tap hole 8 is formed near the central portion of the back yoke 5A where the permanent magnet 6 is fixed in the moving direction x of the optical head 1. Further, on the surface of the back yoke 5A fixed to the base member 9A, two convex portions 11 are formed by half blanking of the sheet metal material. On the other hand, as shown in FIG. 5, the base member 9A has two recesses 12 penetrating in the thickness direction thereof.
Is formed at a predetermined position corresponding to the convex portion 11, and a hole 10 is formed at a predetermined position corresponding to the tap hole 8 of the back yoke 5A. And the back yoke 5A
Is positioned by fitting the protrusions 11 into the two recesses 12 of the base member 9A, and in this position, one screw 15 is inserted into the hole 10 of the base member 9A and the tap hole 8 of the back yoke 5A. It is fastened and fixed by inserting and screwing.

Here, the tap hole 8 is formed in the vicinity of the central portion in the moving direction x of the optical head 1 on the surface on which the permanent magnet 6 is fixed, and this portion is a portion where the magnetic flux density of the magnetic circuit is very small. Therefore, there is no problem that the magnetic flux is saturated. Further, since the half-extracted part of the sheet metal material on which the two convex portions 11 are formed is not a part where the total magnetic flux is concentrated, there is no problem that the magnetic flux is saturated if the half-extracted amount is reduced to some extent. Further, in the present embodiment, the number of screws for fixing the back yoke 5A is halved, so that there is an advantage that the workability is improved.

By the way, as a means for speeding up the access time, a method of improving the gap magnetic flux density of the magnetic circuit in the optical head driving device is effective, but in this case, the thickness of the yoke is increased to prevent the saturation of the magnetic flux. There is a need to. Further, it is necessary to reduce the thickness of the magnetic circuit in response to the reduction in thickness of the information recording / reproducing apparatus. For these reasons, the yoke becomes thinner in the height direction and becomes thicker in the thickness direction.
Further, it becomes difficult to form the tap hole 8 and the convex portion 11 by half blanking in the second embodiment.

As a method for solving the above-mentioned problem, claim 3
A third embodiment corresponding to the described invention is shown in FIGS. FIGS. 6 and 7 correspond to the first embodiment, and FIGS. 8 and 9 correspond to the second embodiment, respectively. The back yokes 5 and 5A correspond to the configurations shown in FIGS. 1 to 5. Is formed by stacking two sheet metal materials in the thickness direction.

The embodiment shown in FIGS. 6 and 7 is different from that of the first embodiment described above, and the embodiment shown in FIGS. 8 and 9 is different from that of the second embodiment described above in that the inner surface thereof has a permanent magnet. 6, a back yoke 5B for fixing 6 is provided, and the back yoke 5B is fixed to the back yoke 5 or the back yoke 5A by being overlapped and fixed in the thickness direction thereof, and the front yoke 4B connected to the back yoke 5B. They are different only in that they are fixed to the front yoke 4 by being superposed on each other in the thickness direction and connected to the back yoke 5B. Back yoke 5B and back yoke 5, Back yoke 5B and back yoke 5A
Alternatively, for example, a well-known adhesive is used to fix the front yoke 4 and the front yoke 4B.

In this embodiment, the back yokes 5, 5 are
B or back yoke 5A, 5B and front yoke 4,
4B is formed of two sheet metal materials, respectively, but the number is not limited to this, and the number of sheets that gives the most advantageous workability and cost may be selected depending on the shape of the magnetic circuit.

When the back yokes 5 and 5B or the back yokes 5A and 5B are overlapped and the thickness thereof becomes thicker, the side yoke portions at both end portions also become thicker, and the magnetic circuit as a whole has the same structure as the optical head 1. There is a problem that the size increases in the moving direction x. As means for reducing the size of the magnetic circuit in the moving direction x of the optical head 1, the permanent magnet 6 is expanded by expanding the usable range of the magnetic flux density by a technical means disclosed in Japanese Patent Laid-Open No. 2-249145. It is effective to reduce the size in the moving direction x.
However, the technical means disclosed in the above-mentioned Japanese Patent Laid-Open No. 2-249145 has a problem that the cost is significantly increased.
As a solution to the above problems, a fourth embodiment corresponding to the invention of claim 4 is shown in FIGS. 10 and 11, and a fifth embodiment corresponding to the invention of claim 5 is shown in FIGS. Each is shown in FIG.

The fourth embodiment differs from the first and third embodiments shown in FIGS. 1 to 3 and FIGS. 6 and 7 only in the structure of the two back yokes 5C and 5D. In FIG. 10, 1 is provided in the vicinity of the central portion of the back yoke 5C where the permanent magnet 6 is fixed in the moving direction x of the optical head 1 in FIG.
The void recess 13 which is an individual through hole is formed. Further, two tap holes 8 are formed at left and right symmetrical positions with the void recess 13 of the back yoke 5C as the center.
On the surface of the back yoke 5D fixed to the base member 9, tap holes 8 are provided at positions corresponding to the two tap holes 8 when the two back yokes 5C and 5D are superposed.
Insertion hole 10A and tap hole 8 for positioning having substantially the same diameter as
The insertion holes 10B each having a long hole that is longer in the left-right direction than the other are formed. Then, as shown in FIG. 11, in the back yoke 5D and the back yoke 5C, the two screws 15 are respectively inserted into the holes 10 of the base member 9 and the insertion holes 10A and 10B of the back yoke 5D, and the back yoke 5D is inserted. It is fastened and fixed to the base member 9 by being screwed into the two tap holes 8 of the yoke 5C, respectively.

The fifth embodiment differs from the second and third embodiments shown in FIGS. 4, 5, 8 and 9 only in the construction of the two back yokes 5E, 5F. In FIG. 12, the back yoke 5E on the side where the permanent magnet 6 is fixed is formed in a shape smaller than the back yoke 5A shown in FIGS. 8 and 9 by the thickness thereof. The back yoke 5F on the side fixed to the base member 9 has a tap hole 8 formed in the center of the back yoke 5A.
Instead, an insertion hole 10C slightly larger than the tap hole 8 is formed. On the surfaces of the back yokes 5E, 5F opposite to the two convex portions 11 formed by the half blanking process, recessed fitting concave portions 14 are formed in the traces of the half blanking.

When the back yoke 5F and the back yoke 5E are superposed, the convex portion 11 and the fitting concave portion 1 are formed.
4 and the recesses 12 of the base member 9 and the projections 11 of the back yoke 5F at the two positions are fitted to each other, thereby positioning them. The back yoke 5F and the back yoke 5E have one screw 1
5 is inserted into the hole 10 of the base member 9A and the insertion hole 10C of the back yoke 5F, and screwed into the tap hole 8 of the back yoke 5E to be fastened and fixed to the base member 9A.
Here, the convex portion 11 formed by the half blanking process and the fitting concave portion 14 left by the half blanking are the back yokes 5E and 5F.
It is designed to be fitted also as half-blank caulking for connecting the two. The connection structure of the base member 9A, the back yoke 5F, and the back yoke 5E is not limited to the one described above, and the recess 12 of the base member 9 and the protrusion 11 (fitting recess 14) of the back yoke 5F and the back yoke 5E are fitted together. It goes without saying that the size of the combined diameter may be set in consideration of the processing accuracy of each component.

[0032]

As described above, according to the first aspect of the invention, the first yoke has the above-described structure and operation.
Direction of the fastening hole, the direction of the magnetic field of the magnetic gap, and the drive coil.
The mounting direction of the optical head to the
To make the optical head drive device thinner in the height direction.
As a result, the size of the device can be reduced.

According to the invention described in claim 2, the positioning and fixing means of the magnetic circuit can be processed inexpensively without saturating the magnetic flux and can be constructed with a simple shape by the above-mentioned constitution and operation. The cost can be significantly reduced without increasing the size of the driving device, and the assembling workability is also improved.

According to the third aspect of the present invention, due to the above-described structure and action, when it is necessary to form the first yoke on the permanent magnet fixed side thick in the magnetic gap direction, for example, due to the need for magnetic circuit performance, a plurality of first yokes are provided. By forming the sheet metal materials of the above in superposition, the thickness per sheet metal material forming the first yoke can be reduced, and as a positioning / fixing means of the magnetic circuit, for example, the lower hole of the fastening hole can be made small in diameter. It can be processed at low cost.

According to the fourth aspect of the present invention, with the above-described structure and operation, when the void concave portion is formed on the surface of the first yoke which is in contact with the central portion in the moving direction of the permanent magnet, the magnetic circuit cross-sectional area is reduced. , Due to the increase in magnetic resistance, the influence of the magnetic flux generated by the drive coil due to the drive current,
That is, it is possible to reduce the deterioration of the responsiveness due to the increase of the inductance and the deterioration of the control characteristic due to the fluctuation of the driving thrust force. Further, the first yoke fixing the permanent magnet is formed symmetrically with respect to the central portion in the moving direction. Since the portion where the permanent magnet is not in contact with the first yoke is formed by the fastening hole and the void concave portion, the distribution of the magnetic flux density in the magnetic gap in the moving direction is controlled to expand the moving range of the optical head. Therefore, the performance of the magnetic circuit can be improved, and the size of the optical head driving device in the moving direction of the optical head can be reduced without increasing the cost.

According to the fifth aspect of the present invention, due to the above-described structure and action, when it is necessary to form the first yoke on the permanent magnet fixed side thick in the magnetic gap direction due to, for example, the performance of the magnetic circuit, a plurality of first yokes are required. By forming the sheet metal materials of the above in superposition, the thickness per sheet metal material forming the first yoke can be reduced, and as a positioning / fixing means of the magnetic circuit, for example, the lower hole of the fastening hole can be made small in diameter. It is possible to perform half blanking at low cost. Also,
A portion where the permanent magnet is not in contact with the first yoke is formed by the fitting concave portion and the fastening hole formed at positions symmetrical with respect to the center of the first yoke that fixes the permanent magnet in the moving direction. Therefore, the distribution of the magnetic flux density in the magnetic gap in the moving direction can be controlled to expand the moving range of the optical head, so that the performance of the magnetic circuit can be improved without increasing the cost. It is possible to reduce the size of the optical head driving device in the moving direction of the optical head.

[Brief description of drawings]

FIG. 1 is a perspective view of an essential part showing an embodiment of the invention described in claim 1. FIG.

2 (a) is a plan view of a main part of the configuration of the magnetic circuit of FIG. 1, and FIG. 2 (b) is a side view of the same part.

FIG. 3 is a cross-sectional view of a main part taken along line AA when the magnetic circuit of FIG. 2 is fastened and fixed to a base member.

FIG. 4 (a) is a plan view of relevant parts of a magnetic circuit according to an embodiment of the present invention, and FIG. 4 (b) is a side view of the essential parts.

5 is a cross-sectional view of a main part taken along line BB when the magnetic circuit of FIG. 4 is fastened and fixed to a base member.

FIG. 6 (a) is a plan view of relevant parts of a magnetic circuit according to an embodiment of the present invention, and FIG. 6 (b) is a side view of the essential parts.

7 is a cross-sectional view of the principal part taken along the line CC when the magnetic circuit of FIG. 6 is fastened and fixed to a base member.

FIG. 8A is a plan view of a main part of the configuration of a magnetic circuit according to another embodiment of the invention as set forth in claim 3;
(B) is a side view of the same main part.

9 is a cross-sectional view of the principal part taken along the line D-D when the magnetic circuit of FIG. 8 is fastened and fixed to a base member.

FIG. 10 (a) is a plan view of a main part of the configuration of a magnetic circuit according to an embodiment of the invention as set forth in claim 4;
(B) is a side view of the same main part.

11 is a cross-sectional view of the principal part taken along the line EE when the magnetic circuit of FIG. 10 is fastened and fixed to the base member.

12 (a) is a plan view of a main part of the configuration of a magnetic circuit according to an embodiment of the invention as set forth in claim 5;
(B) is a side view of the same main part.

13 is a cross-sectional view of a main part taken along line FF when the magnetic circuit of FIG. 12 is fastened and fixed to a base member.

[Explanation of symbols]

1 Optical Head 2 Shaft Rail 3 Drive Coil 4, 4B Front Yoke 5,5A, 5B, 5C, 5D, 5E, 5F as Second Yoke 6 Back Yoke as First Yoke 6 Permanent Magnet 7 Magnetic Circuit 8 Fastening Hole Hole 9 as base member 10 hole 10A, 10B, 10C insertion hole 11 convex portion 12 concave portion 13 void concave portion 14 fitting concave portion 15 screw as fastening means

   ─────────────────────────────────────────────────── ─── Continued front page       (56) Reference JP-A-2-249145 (JP, A)                 JP-A-3-122874 (JP, A)                 JP 63-58891 (JP, A)                 JP 62-210854 (JP, A)                 JP-A-2-146952 (JP, A)                 JP 64-55051 (JP, A)                 Actual Development Sho 61-114980 (JP, U)                 Actual Development Sho 60-114581 (JP, U)

Claims (5)

(57) [Claims] 1. An optical head for recording and reproducing information, a means for supporting the optical head and guiding it in the moving direction of the optical head, and a winding center axis fixed to the optical head and in the moving direction. A drive coil arranged in parallel to the
A magnetic circuit for applying a magnetic field to the drive coil in a direction perpendicular to the moving direction, the magnetic circuit having a constant air gap on an outer side surface or an inner side surface of the driving coil, and A permanent magnet arranged in parallel, a first yoke to which one magnetic pole of the permanent magnet is fixed, a magnetic gap facing the other magnetic pole of the permanent magnet and applying a magnetic field to the drive coil, and An optical head driving device in an information recording / reproducing apparatus, comprising: a second yoke connected to the first yoke at both ends in the moving direction of the first yoke; A coil is inserted, and the first yoke and the second yoke are arranged on both sides of the optical head in line symmetric positions with respect to the moving direction of the optical head. And the second yoke are each formed of a sheet metal material, and a base member having a hole is provided at a position adjacent to the first yoke, and is orthogonal to the thickness direction of the sheet metal material in the first yoke. The permanent magnet is fixed to a surface, whereby the thickness direction of the sheet metal material in the first yoke is formed parallel to the direction of the magnetic field of the magnetic gap, and the first side of the fixed side of the permanent magnet is fixed. Forming a fastening hole at a position that does not interfere with the magnetic path in the thickness direction of the sheet metal material in the permanent magnet fixing range of the yoke,
An optical head driving device in an information recording / reproducing apparatus, wherein the first yoke is fastened and fixed to the base member through the fastening hole and the hole by fastening means. 2. A plurality of convex portions are provided on a surface of the first yoke which is fastened and fixed to the base member, and a concave portion which is fitted to the convex portion is provided on the base member, and the fastening is performed. A hole is provided in the vicinity of a central portion of the first yoke in the moving direction, and the first yoke is fastened and fixed to the base member in a state where the convex portion and the concave portion are fitted to each other. The optical head driving device in the information recording / reproducing apparatus according to claim 1. 3. The optical head driving device in an information recording / reproducing apparatus according to claim 1, wherein the first yoke is formed by stacking a plurality of the sheet metal materials. 4. A void recess is formed on a surface of the first yoke which is in contact with a central portion of the permanent magnet in the moving direction, and a plurality of the fastening holes are formed at symmetrical positions with respect to the central portion. An insertion hole is provided at a position corresponding to the fastening hole of the first yoke that is fastened and fixed to the base member, and the first yoke connects the fastening hole, the insertion hole, and the hole by the fastening means. The portion of the permanent magnet that is fastened and fixed to the base member via and that corresponds to the void concave portion and the fastening hole, respectively, is not in contact with the first yoke. Head driving device in the information recording / reproducing apparatus of. 5. The first yoke is formed by stacking a plurality of sheet metal materials, and the plurality of protrusions are formed by half blanking at positions symmetrical with respect to the center of the permanent magnet in the moving direction. In addition, an insertion hole is provided at a position corresponding to the fastening hole of the first yoke on the side that is fastened and fixed to the base member, and the half blanking is performed when a plurality of the first yokes are stacked. The first yoke is fastened and fixed to the base member by the fastening means through the fastening hole, the insertion hole, and the hole in a state in which the fitting concave portion formed in 1 and the convex portion are fitted to each other. 3. The optical head drive in an information recording / reproducing apparatus according to claim 2, wherein the portions of the permanent magnet that respectively correspond to the fastening hole and the fitting recess are not in contact with the first yoke. apparatus.