JP2000163771A - Objective lens driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an objective lens driving device that the leakage magnetic flux of an actuator to magnetic heads is reduced without reducing the moving amount in the vertical direction of an objective lens driving device or without enlarging the size of the objective lens driving device. SOLUTION: The width of a magnetic shielding plate 13 at the positional part being roughly upper side of the magnet 10b arranged at a side nearer to an objective lens between one pair of magnets 10a, 10b is made wider than that of the magnet 10b and the width of the magnetic shielding plate 13 at the positional part being roughly upper side of electric wiring parts 12 electrically connecting a focusing coil 6 or a tracking coil 7 to the main body of a device is made narrower than that of the electric wiring parts 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving apparatus, for example, an objective lens driving apparatus in an optical disk apparatus for irradiating a disk-shaped recording medium with a light spot and writing data magneto-optically in cooperation with a magnetic head. About.

[0002]

2. Description of the Related Art Conventionally, a CD (Compact Di) is used.
SC), MD (Mini Disc), and the like, there is a problem of improving the recording density along with the miniaturization of the device, and recently, the DVD (Digital Vi
Deo Disc or Digital Versat
High-capacity discs, such as an electronic disc (ile disc), are receiving attention. Above all, MD is attracting attention as a small, large-capacity, highly portable data storage medium. In particular, for high-density recording, a beam spot is miniaturized as an apparatus, and recording is performed as a medium. Developments are underway, such as the use of high-density magnetic film technology for the thin film constituting the layer. The data recorded on the MD can be not only music, but also image data or text data of documents, and can freely record and reproduce still images and moving images. Applications are expanding as equipment.

Under these circumstances, the MD is characterized by its high sound quality and high-speed access, and its market is expanding in a wide range of applications from portable use to in-vehicle use, and thinner and smaller devices are required. However, in order to reduce the size, it is essential to reduce the size of the objective lens driving device used in such MDs and the like. Hereinafter, a conventional objective lens driving device will be described with reference to the drawings.

FIGS. 3A and 3B are a plan view and a side sectional view of a conventional objective lens driving device. In the figure, an objective lens driving device 1 serving as an actuator is provided with a lens holder 3 for holding an objective lens 2, and on both sides thereof, the lens holder 3 for supporting the lens holder 3 movably in two directions with respect to a fixed part 4. A pair of wire-like elastic bodies 5 are attached to the upper and lower sides, respectively. A focusing coil 6 and a tracking coil 7 are provided in a central hole of the lens holder 3.
Is fixed.

A part of the tracking coil 7 and a part of the focusing coil 6 are inserted and arranged in a magnetic gap 9 of a magnetic circuit 8 fixed to the fixing part 4. This magnetic circuit 8
Is composed of a first magnet 10a, a second magnet 10b, and a U-shaped yoke 11 in which they are attached. The yoke 11 has a pair of yoke legs 11a and 11b. The focusing coil 6 is wound so as to surround the first magnet 10a remote from the objective lens 2 and the yoke legs 11a outside the first magnet 10a with a space therebetween.
An unnecessary portion 6a for generating a driving force is a magnetic gap 9
It is located outside.

The elastic body 5 is provided with an electric wiring section 12 for supplying power to the focusing coil 6 and the tracking coil 7 from the apparatus main body via the elastic body 5. The electric wiring section 12 is attached by solder or the like to electrically connect the winding ends of the elastic body 5, the focusing coil 6 and the tracking coil 7 to the apparatus main body, and has a convex shape. Further, a magnetic shielding plate 13 is provided so as to bridge the yoke legs 11a and 11b in order to reduce the leakage magnetic flux from the magnetic circuit 8.

With such a configuration, the focusing coil 6 moves the lens holder 3 in the direction of the arrow F (vertical direction) with respect to the fixing portion 4, and the tracking coil 7 moves the lens holder 3 in the direction of the arrow T with respect to the fixing portion 4. In this manner, the objective lens 2 is moved and moved (in the horizontal direction) to perform tracking and focusing.

[0008]

However, in such a configuration, the lens and the magnetic circuit are often used close to each other in order to reduce the size of the device. When applied to a magneto-optical disk that writes data magneto-optically on a recording medium in cooperation, the leakage flux of the magnetic circuit affects the magnetic flux generated from the magnetic head, making it impossible to record or to record incorrect information. There was a problem of doing it.

In order to reduce the leakage magnetic flux, it is conceivable to increase the width or increase the thickness of the magnetic shielding plate. However, if the width is increased, when the objective lens driving device moves in the vertical direction, The magnetic shield plate and the convex portion of the electric wiring portion come into contact with each other, so that the amount of movement of the objective lens driving device in the vertical direction is reduced. Also, if the thickness is increased, the objective lens driving device cannot be made thinner. There were various problems, such as a problem.

The present invention solves the above-mentioned conventional problems, and does not reduce the amount of vertical movement of the objective lens driving device or increase the size of the objective lens driving device without reducing the size of the objective lens driving device. An object of the present invention is to provide an objective lens driving device in which a leakage magnetic flux of an actuator is reduced.

[0011]

SUMMARY OF THE INVENTION An objective lens driving device according to the present invention includes an objective lens of a device for writing or reading information magneto-optically in cooperation with a magnetic head on a disk-shaped recording medium; A lens holder for holding
A focusing coil configured to be integrated with the lens holder, for displacing the lens holder in a focusing direction perpendicular to a recording medium surface of the disc-shaped recording medium, and configured integrally with the lens holder; A tracking coil for displacing in a tracking direction that is parallel and radial to the recording medium surface,
An electric wiring unit that electrically couples the focusing coil and the tracking coil to the apparatus main body; and a magnetic circuit unit that provides a magnetic flux to the focusing coil or the tracking coil and includes a pair of magnets arranged so that different poles face each other. An objective lens driving device fixedly disposed so as to cover an upper portion of the magnetic circuit unit and including a magnetic shielding plate for reducing leakage magnetic flux from the magnetic circuit unit,
Of the pair of magnets, the width of the magnetic shield plate, which is disposed on the side closer to the objective lens and substantially above the magnet, is larger than the width of the magnet, and the upper part of the electric wiring portion is substantially the same. Is smaller than the width of the wiring portion.

According to the present invention, it is possible to reduce the leakage magnetic flux of the actuator to the magnetic head without reducing the amount of vertical movement of the objective lens driving device or without increasing the size of the objective lens driving device. It becomes possible.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. In each of the embodiments, the same reference numerals are used for the same parts as those of the related art.

(Embodiment 1) FIGS. 1 (a) and 1 (b) are a plan view and a side sectional view showing the configuration of an embodiment of an objective lens driving device according to the present invention. In the figure, an objective lens driving device 1 serving as an actuator is provided with a lens holder 3 for holding an objective lens 2, and on both sides thereof, the lens holder 3 for supporting the lens holder 3 movably in two directions with respect to a fixed part 4. A pair of wire-like elastic bodies 5 are mounted on the upper and lower sides, respectively, and a focusing coil 6 for obtaining a vertical driving force is provided in a hole at the center of the lens holder 3.
A tracking coil 7 for obtaining a driving force in the horizontal direction is fixed.

A part of the tracking coil 7 and a part of the focusing coil 6 are inserted and arranged in a magnetic gap 9 of a magnetic circuit 8 fixed to the fixing part 4. This magnetic circuit 8
Is composed of a first magnet 10a, a second magnet 10b, and a U-shaped yoke 11 in which they are attached. The yoke 11 has a pair of yoke legs 11a and 11b. The focusing coil 6 is wound so as to surround the first magnet 10a remote from the objective lens 2 and the yoke legs 11a outside the first magnet 10a with a space therebetween.
An unnecessary portion 6a for generating a driving force is a magnetic gap 9
It is located outside.

The elastic body 5 is provided with an electric wiring section 12 for supplying power to the focusing coil 6 and the tracking coil 7 via the elastic body 5. The electric wiring section 12 includes an elastic body 5 and a focusing coil 6.
In order to electrically connect the winding end of the tracking coil 7 to the apparatus main body, the tracking coil 7 is attached with solder or the like, and has a convex shape. Further, in order to reduce the leakage magnetic flux from the magnetic circuit 8, a magnetic shield plate 13 is provided so as to bridge the yoke legs 11a and the yoke legs 11b. The width of each upper position portion is wider than the width of the second magnet 10b,
Focusing coil 6 or tracking coil 7
The width of a substantially upper position portion of the electric wiring portion 12 for electrically coupling the electric wiring portions is smaller than the interval between the electric wiring portions 12.

Next, the operation will be described. First, due to the change in the magnetic field generated by the magnetic head and the intensity of the light focused on the magneto-optical recording layer by the objective lens 2, when information is written optically, the leakage magnetic flux from the magnetic circuit 8 causes If the magnetic flux density exceeds a predetermined value at the position of the contacting magneto-optical recording layer, information recorded on the magneto-optical recording layer will be lost or erroneous information will be recorded. However, the width of the portion of the magnetic shield plate 13 substantially above the second magnet 10b is set to the second magnet 10b.
By making the width larger than the width b, the magnetic flux leakage from the second magnet 10b closer to the magnetic head can be reduced. For example, when a conventional magnetic shielding plate is used, the leakage magnetic flux at the position of the magnetic head, which was 0.002 T, can be reduced to 0.0015 T by the magnetic shielding plate. Therefore, information recorded on the magneto-optical recording layer is not lost or erroneous information is not recorded. Furthermore, the width of the substantially upper position portion of the electric wiring portion 12 for electrically coupling the focusing coil 6 or the tracking coil 7 of the magnetic shielding plate 13 to the apparatus main body is made smaller than the interval between the wiring portions. When the objective lens driving device 1 moves to the recording medium side in the vertical direction, the electric wiring portion 12
3, the amount of movement of the objective lens driving device 1 in the vertical direction is not limited even if countermeasures against leakage magnetic flux such as increasing the width of the magnetic shielding plate 13 are taken.

As described above, according to the present embodiment, the width of the substantially upper portion of the second magnet of the magnetic shielding plate is made larger than the width of the second magnet, and the electric wiring of the magnetic shielding plate is further increased. By configuring the width of the upper part of the portion to be smaller than the interval of the electric wiring portion, it is possible to reduce the magnetic flux leakage from the magnetic circuit to the magnetic head, so that the The recorded information will not be lost or erroneous information will not be recorded, and the vertical movement amount of the objective lens driving device will not increase even if countermeasures against magnetic flux leakage such as increasing the width of the magnetic shielding plate are taken. There is no restriction.

(Embodiment 2) FIGS. 2 (a) and 2 (b) are a plan view and a side sectional view showing a configuration of an objective lens driving apparatus according to Embodiment 2 of the present invention. In this embodiment, since many parts are the same as those in the first embodiment, FIG.
The same parts as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

In the present embodiment, of the pair of magnets,
Second magnet 10 arranged on the side close to the objective lens
The thickness of the magnetic shielding plate 13 in the upper portion of the b is larger than the thickness of the upper portion of the electric wiring portion 12 for electrically coupling the focusing coil 6 or the tracking coil 7 to the apparatus main body. The other parts are the same as in the first embodiment.

Next, the operation will be described. Due to the change in the magnetic field generated by the magnetic head and the intensity of the light focused on the magneto-optical recording layer by the objective lens 2, when information is written optically, the leakage magnetic flux from the magnetic circuit 8 comes into contact with the magnetic head. As described above, when the magnetic flux density exceeds a predetermined value at the position of the magneto-optical recording layer, information recorded on the magneto-optical recording layer is lost or erroneous information is recorded. In the embodiment, the thickness of the magnetic shield plate 13 at a position substantially above the second magnet 10b disposed closer to the objective lens among the pair of magnets is determined by electrically connecting the focusing coil 6 or the tracking coil 7 to the second magnet 10b. Since the thickness is substantially larger than the thickness of the upper portion of the electric wiring portion 12 to be coupled, the leakage magnetic flux from the second magnet 10b closer to the magnetic head is reduced. It can be. For example, when the thickness of the conventional magnetic shielding plate is 0.4 mm, the leakage magnetic flux is 0.0
What was 023T, the magnet 10
a is 0.4 mm, and the thickness of the magnet 10 b is 0.4 mm.
By setting the length to 7 mm, the leakage magnetic flux can be reduced to 0.0017 T, so that information recorded on the magneto-optical recording layer is not lost or erroneous information is not recorded. Further, the thickness of the magnetic shielding plate 13 at the upper portion of the electric wiring portion 12 is configured to be thin, so that when the objective lens driving device 1 moves in the vertical direction toward the recording medium, the magnetic shielding plate 13 Can be moved without contacting the electric wiring section 12 by the reduced thickness, so that the amount of movement of the objective lens driving device 1 in the vertical direction is reduced.

As described above, according to the present embodiment, the thickness of the magnetic shield plate at the substantially upper position of the second magnet disposed on the side closer to the objective lens is adjusted to the substantially upper position of the electric wiring portion. Since the magnetic flux leakage from the magnetic circuit to the magnetic head can be reduced by configuring to be larger than the thickness of the magnetic head, information recorded on the magneto-optical recording layer may be lost or erroneous information may be lost. Recording is not performed, and the restriction on the amount of vertical movement of the objective lens driving device is reduced.

[0023]

As described above, according to the present invention, of the pair of magnets, the width or the thickness of the magnetic shield plate at the position substantially above the magnet arranged closer to the objective lens is increased. In addition, by reducing the width or thickness of the magnetic shield plate substantially at the upper portion of the electric wiring portion for electrically coupling the focusing coil or the tracking coil, the amount of movement of the objective lens driving device in the vertical direction is reduced. Therefore, the advantageous effect that the leakage magnetic flux from the magnetic circuit portion can be reduced can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view and a sectional side view showing a configuration of an embodiment of an objective lens driving device according to the present invention.

FIG. 2 is a plan view and a side sectional view showing a configuration of an objective lens driving device according to a second embodiment of the present invention.

FIG. 3 is a plan view and a side sectional view of a conventional objective lens driving device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Objective lens drive device 2 Objective lens 3 Lens holder 4 Fixing part 5 Elastic body 6 Focusing coil 7 Tracking coil 8 Magnetic circuit 9 Magnetic gap 10a First magnet 10b Second magnet 11 Yoke 12 Electric wiring part 13 Magnetic shielding plate

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Hideki Aiko 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F term (reference) 5D118 AA11 BA01 BB01 BB06 BB07 DC03 ED02

Claims (2)

[Claims] 1. An objective lens of a device for writing or reading information magneto-optically in cooperation with a magnetic head on a disk-shaped recording medium, a lens holder for holding the objective lens, and an integral part of the lens holder. A focusing coil for displacing the lens holder in a focusing direction perpendicular to the recording medium surface of the disc-shaped recording medium, and integrally formed with the lens holder, with respect to the recording medium surface. A tracking coil for displacing in the tracking direction which is parallel and radial, an electric wiring portion for electrically coupling the focusing coil and the tracking coil to an apparatus main body, and applying a magnetic flux to the focusing coil or the tracking coil; Magnetism consisting of a pair of magnets arranged with opposite poles facing each other A circuit portion, and an objective lens driving device fixedly disposed so as to cover an upper portion of the magnetic circuit portion and including a magnetic shielding plate for reducing leakage magnetic flux from the magnetic circuit portion, wherein, among the pair of magnets, The width of the magnetic shield plate, which is disposed on the side closer to the objective lens and substantially above the magnet, is larger than the width of the magnet, and the width of the substantially upper part of the electric wiring section is the width of the wiring section. An objective lens driving device characterized by being smaller than the above. 2. An objective lens of a device for writing or reading information magneto-optically in cooperation with a magnetic head on a disk-shaped recording medium, a lens holder for holding the objective lens, and an integral part of the lens holder. A focusing coil for displacing the lens holder in a focusing direction perpendicular to the recording medium surface of the disc-shaped recording medium, and integrally formed with the lens holder, with respect to the recording medium surface. A tracking coil for displacing in the tracking direction which is parallel and radial, an electric wiring portion for electrically coupling the focusing coil and the tracking coil to an apparatus main body, and applying a magnetic flux to the focusing coil or the tracking coil; Magnetism consisting of a pair of magnets arranged with opposite poles facing each other A circuit portion, and an objective lens driving device fixedly disposed so as to cover an upper portion of the magnetic circuit portion and including a magnetic shielding plate for reducing leakage magnetic flux from the magnetic circuit portion, wherein, among the pair of magnets, An objective lens driving device, wherein the thickness of the magnetic shielding plate at a substantially upper position of the magnet disposed closer to the objective lens is larger than the thickness of the substantially upper position of the electric wiring portion. .