JP2006277853A - Objective lens driving device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-priced objective lens driving device capable of reducing the number of manufacturing steps by suppressing the tilting of a yoke and a permanent magnet and the distortion of an objective lens caused by heating of a coil. <P>SOLUTION: A yoke is made of a single plate member, and divided from the center to be cut up on both sides. The four corners of the tip and the base of the yoke are notched to form a cross shape. More preferably, the tip of the yoke is bent in a direction opposed to the side of arranging a permanent magnet. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an objective lens driving device used in an optical disc apparatus for reproducing information recorded on a recording surface of an optical disc or recording information.

  An optical disc device is a device that records information on a disc-shaped information recording medium or reproduces recorded information. This optical disc apparatus has a relatively large amount of information that can be recorded on an information recording medium, and is easy to handle the information recording medium, so that it is widely used as an external storage device of a computer and a video / audio recording device.

  In such an optical disc device, an objective lens driving device is a device that drives the objective lens in the focusing direction and the tracking direction in order to accurately record or reproduce information following the rotation of the optical disc.

  A general objective lens driving device includes a magnetic circuit composed of a yoke and a permanent magnet, a movable part to which an objective lens is attached, a fixed part that holds the movable part, and elastically supports the movable part with respect to the fixed part. It is comprised from a supporting member. A focusing coil and a tracking coil are wound around the yoke, and when a current is passed through the focusing coil, the movable part is driven in the focusing direction by electromagnetic force generated by the action of magnetic flux from a permanent magnet attached to the movable part. . Similarly, when a current is passed through the tracking coil, the movable part is driven in the tracking direction by an electromagnetic force generated by the action of magnetic flux from a permanent magnet attached to the movable part.

  In such an objective lens driving device, if the objective lens is tilted, optical aberrations occur and the condensing spot widens, so that accurate information cannot be recorded on the disc or the reproduction signal is deteriorated. To do. In order to suppress the inclination of the objective lens, at the time of assembly, it is necessary to arrange the yoke around which the coil is wound and the permanent magnet attached to the movable portion so as to face each other.

  To solve the problem of the inclination of the yoke and the permanent magnet, the bobbin is formed by winding a coil, providing a positioning portion on a resin bobbin in which the yoke is insert-molded, and fitting it with a receiving portion provided on the base. An objective lens driving device fixed to the base is known (example shown in Patent Document 1 below). According to this, it is said that the bobbin inclination and positioning accuracy can be improved.

Japanese Patent Laid-Open No. 10-64111 (for example, FIG. 1)

  In the above prior art, fixing means such as welding or caulking is necessary to fix the bobbin to the base. At that time, there is a possibility that the bobbin is displaced or tilted due to the curing shrinkage of the solvent or the action of the load. In addition, the two bobbins must be individually adjusted and fixed to the base, resulting in an increase in the manufacturing process. In the above prior art, since the focusing coil is wound around the groove provided in the center of the bobbin, it is necessary to separate the bobbin and the base, wind the coil around the bobbin, and then fix the bobbin to the base. It was. In this case, the two bobbins must be individually adjusted and fixed to the base, and the bobbin may be misaligned or tilted due to errors in the measuring instrument used for adjustment or positioning errors in the holding jig. . Further, in order to fix the bobbin to the base, a fixing means such as welding or caulking is necessary. Even in this case, there is a possibility that the bobbin is displaced or tilted due to the curing shrinkage of the solvent or the action of the load.

  An object of the present invention is to provide a low-cost objective lens driving device that suppresses the inclination of a yoke and a permanent magnet and reduces the number of manufacturing steps.

The above-described object is achieved by forming the yoke by a single plate-like member, dividing the yoke into two parts from the central part thereof, and cutting and raising them on both sides.
Further, this is achieved by forming a cross shape in which the tip and the four corners of the yoke are cut out.
More preferably, the tip of the yoke is bent in the direction opposite to the side where the permanent magnet is disposed.

According to the present invention, the yoke is constituted by a single plate-like member, and the central portion thereof is cut and raised on both sides, so that the parallelism between the yoke and the magnet can be ensured. Thereby, the inclination of the objective lens can be suppressed. Further, since the yoke substrate exists as a magnetic body below the yoke, the magnetic flux emitted from the permanent magnet returns from the yoke through the yoke substrate to the permanent magnet again. Thereby, since the spread of magnetic flux can be suppressed, the efficiency of a magnetic circuit can be improved.
In addition, since the yoke is formed in a cross shape by cutting off the tip and the four corners of the yoke, it is possible to wind the focusing coil and the tracking coil around the yoke. Thereby, a manufacturing process can be reduced.

Furthermore, because the tip of the yoke is bent in the direction opposite to the side where the permanent magnet is arranged, it is caused by the rotation of the disk without transferring most of the heat generated when a current is passed through the coil to the objective lens. Heat can be dissipated into the surrounding air by airflow. This has the effect of preventing distortion of the objective lens due to the heat generated by the coil.
Therefore, it is possible to provide a low-cost objective lens driving device that suppresses the tilt of the objective lens due to the angular deviation between the yoke and the permanent magnet and the distortion of the objective lens due to the heat generation of the coil and reduces the number of manufacturing steps.

The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a perspective view of an objective lens driving apparatus 1 according to the present invention. In the figure, the x-axis direction indicates the tangential direction of the optical disk not shown, the y-axis direction indicates the tracking direction that is the radial direction of the optical disk, and the z-axis direction indicates the focusing direction that is the optical axis direction of the objective lens 2.

  The objective lens driving device 1 includes a movable part to which an objective lens is attached, a fixed part 8 that holds the movable part, a support member 9 that elastically supports the movable part with respect to the fixed part 8, yokes 51a and 51b, and permanent parts. The magnetic circuit is composed of a magnet 4.

The objective lens 2 is attached to the upper surface of the lens holder 3. A pair of permanent magnets 4 are mounted on the lens holder 3 in the x direction with the objective lens 2 interposed therebetween.
One end of the wire-like support member 9 is fixed to the vicinity of the end face of the fixing portion 8, and the other end is fixed to the lens holder 3. Here, the objective lens 2, the lens holder 3, and the permanent magnet 4 are movable parts. That is, this movable part moves with respect to the fixed part 8.

  The yokes 51a and 51b are formed from a plate-like member made of a single magnetic material. The manufacturing process of the yokes 51a and 51b will be described with reference to FIGS. First, as shown in FIG. 2, the outer shape (hatched portion) of the cut and raised portion at the center of the yoke substrate 50 is punched out. And the part produced | generated by stamping is bend | folded to both sides (the direction of the arrow of FIG. 3) by press work so that it may become perpendicular | vertical with respect to the surrounding surface of a board, and two yokes 51a and 51b are formed. To do. The yokes 51a and 51b thus formed have a cross shape in which the tip and the four corners of the base are cut off. As a result, in addition to the yokes 51a and 51b themselves projecting from the yoke substrate 50, projecting portions at both ends in the y direction are formed, so that the coil having the z direction as the central axis and the y direction as the center are formed. The coil as a shaft can be wound. That is, a set of two focusing coils 6a and 6b made of a single wire and a set of four tracking coils 7a, 7b and 7c made of a single wire on a set of two yokes 51a and 51b. 7d can be wound.

  The focusing coil 6 is wound along the z-direction central outline of the yokes 51a and 51b so that the central axis direction is in the z direction. The focusing coils 6a and 6b are wound so as to face each other in the x direction with the objective lens 2, the lens holder 3, and the permanent magnet 4 in between.

  On the other hand, the tracking coil 7 is wound around protrusions at both ends in the y direction of the yokes 51a and 51b so that the central axis direction is in the y direction. The tracking coils 7a and 7b are wound so as to face each other in the y direction. Similarly, the tracking coils 7c and 7d are wound so as to face each other in the y direction. The tracking coils 7a and 7b and 7c and 7d are wound so as to face each other in the x direction with the objective lens 2, the lens holder 3 and the permanent magnet 4 in between.

  Hereinafter, the winding procedure of the focusing coil 6 and the tracking coil 7 will be described with reference to FIGS. FIG. 4 is an explanatory diagram regarding the winding process of the focusing coil 6, and FIG. 5 is an explanatory diagram regarding the winding process of the tracking coil 7.

  First, the yokes 51a and 51b formed as described above are fixed to the winding machine. And it winds along the external shape of the center part of the z direction of one yoke 51a so that a center axis direction may turn into az direction (the direction of the arrow of FIG. 4). An intermediate line is drawn from the end of the focusing coil 6a to the other yoke 51b. Then, similarly to the focusing coil 6a, winding is performed along the outer shape of the yoke 51b at the center in the z direction so that the central axis direction is in the z direction. Further, the terminal line is drawn from the end of the focusing coil 6b to the yoke 51a again. The terminal line of the starting end of the focusing coil 6a and the terminal end of the focusing coil 6b is electrically connected to a flexible printed circuit board (not shown) by a conductive fusion material such as solder. Thereby, a set of two focusing coils 6a and 6b can be formed from a single wire.

  Next, the tracking coil 7 is wound in the following procedure. One yoke 51a is wound around one end of the projecting portions at both ends in the y direction so that the central axis direction is in the y direction (the direction of the arrow in FIG. 5). An intermediate line is drawn from the terminal end of the tracking coil 7a to the protruding portion at the other end, and wound around the protruding portion in the same manner as the tracking coil 7a. Next, an intermediate line is drawn from the end of the tracking coil 7b to the other yoke 51b, and thereafter wound similarly to the tracking coils 7a and 7b. Then, a terminal wire is drawn again from the end of the tracking coil 7d to the yoke 51a, and the starting end 7a of the tracking coil and the terminal wire at the end of the tracking coil 7d are electrically connected by a flexible printed circuit board (not shown) and a conductive fusion material such as solder. Connect. Thereby, a set of four tracking coils 7a, 7b, 7c, 7d can be constructed from a single wire.

  Here, the focusing coil 6a and the tracking coils 7a and 7b, and the focusing coil 6b and the tracking coils 7c and 7d are arranged so as to face each other with the objective lens 2, the lens holder 3 and the permanent magnet 4 in between. . In this embodiment, the yokes 51a and 51b for winding the coil and the yoke substrate 50 are formed from a single plate. Thereby, since the yokes 51a and 51b can be accurately formed perpendicularly to the yoke substrate 50, the yokes 51a and 51b and the permanent magnet 4 can be accurately arranged in parallel. Therefore, the inclination of the objective lens 2 can be suppressed. Further, since the yoke substrate 50 exists as a magnetic body, the magnetic flux emitted from the permanent magnet 4 passes through the yoke substrate 50 from the yoke 51 and returns to the permanent magnet 4 again. Thereby, since the spread of magnetic flux can be suppressed, the efficiency of a magnetic circuit can be improved.

Further, since the process of adjusting and fixing the yokes 51a and 51b for attaching the coil to the yoke substrate 50 can be eliminated, there is an effect of reducing the cost by reducing the number of parts and the manufacturing process.
In the above-described configuration, when a current is passed through the focusing coils 6a and 6b, the movable part is driven in the focusing direction by an electromagnetic force generated by the action of the magnetic flux from the permanent magnet 4 attached to the movable part. Similarly, when a current is passed through the tracking coils 7a, 7b, 7c, 7d, the movable part is driven in the tracking direction by an electromagnetic force generated by the action of magnetic flux from the permanent magnet 4 attached to the movable part.

FIG. 6 is a perspective view of the objective lens driving apparatus 1 showing a second embodiment of the present invention. In the second embodiment, not only the yokes 51a and 51b for winding the coil and the yoke substrate 50 are formed from a single plate, but also the objective lens 2 is disposed at the tips of the yokes 51a and 51b. The structure is bent in the opposite direction to the side. Since the other configuration of the second embodiment is the same as that of the first embodiment, detailed proof is omitted.

The bent portions 52a and 52b face the recording surface of the optical disk in parallel, and can radiate the heat generated by the coils 6 and 7 using convection due to the rotation of the optical disk. Further, since the coils 6 and 7 as the heat generating parts are directly wound around the yokes 51a and 51b themselves, the heat generated by the coils 6 and 7 can be efficiently transmitted to the yokes 51a and 51b. As a result, most of the heat generated by the coils 6 and 7 can be radiated from the bent portions 52a and 52b of the yokes 51a and 51b. There is an effect that can be suppressed.

  The present invention makes it possible to increase the speed and density of information recording on a disk in an objective lens driving apparatus and a disk apparatus using the same.

The perspective view of the objective lens drive device which shows one Example of this invention. BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing regarding the manufacturing process of a yoke which shows one Example of this invention. BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing regarding the manufacturing process of a yoke which shows one Example of this invention. Explanatory drawing regarding the winding process of a focusing coil which shows one Example of this invention. BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing regarding the winding process of a tracking coil which shows one Example of this invention. The perspective view of the objective lens drive device which shows one Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Objective lens drive device 2 Objective lens 3 Lens holder 4 Permanent magnet 50 Yoke board 51a Yoke 51b Yoke 52a Yoke bending part 52b Yoke bending part 6 Focusing coil 6a Focusing coil 6b Focusing coil 7 Tracking coil 7a Tracking coil 7c Tracking coil 7c Tracking Coil 7d Tracking coil
8 Fixing part 9 Support member

Claims (8)

A lens holder for holding an objective lens for condensing light on a recording surface of an optical disc; a permanent magnet attached to the lens holder; a yoke made of a magnetic material that forms a magnetic circuit with the permanent magnet; and In an objective lens driving device provided with a wound focusing coil and tracking coil,
2. The objective lens driving device according to claim 1, wherein the yoke is formed of a single plate-like member, and is formed by being cut and raised on both sides from the central portion. The objective lens driving device according to claim 1,
4. The objective lens driving device according to claim 1, wherein the yoke has four cross-sections in which the tip and four corners are cut out. The objective lens driving device according to claim 1 or 2,
2. The objective lens driving device according to claim 1, wherein a tip of the yoke is bent in a direction opposite to a side where the permanent magnet is disposed. An objective is characterized in that a yoke substrate is prepared, divided into two from the central portion thereof, cut and raised on both sides to form two yokes, and a lens holder for holding an objective lens is provided between the two yokes. A method for manufacturing a lens driving device. In the manufacturing method of the objective-lens drive device of Claim 4,
A method of manufacturing an objective lens driving device, wherein the yoke substrate is punched out so that portions of the yoke substrate serving as the two yokes are formed in a cross shape in which four ends and four corners are cut out. In the manufacturing method of the objective-lens drive device of Claim 4,
A method of manufacturing an objective lens driving device, wherein a focusing coil and a tracking coil are wound around the two yokes cut and raised. In the manufacturing method of the objective-lens drive device of Claim 5,
A method for manufacturing an objective lens driving device, wherein a tracking coil is wound around a notched protruding portion of the two yokes cut and raised. In the manufacturing method of the objective-lens drive device in any one of Claims 4 thru | or 7,
A method of manufacturing an objective lens driving device, wherein the tip ends of the two yokes are bent in a direction opposite to a side where the lens holder is disposed.

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