JPH0279227A - Objective lens driving device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to various types of optical discs and optical cards, such as optical video disc players, compact digital audio disc players, optical data memory devices, etc.
The present invention relates to an objective lens drive device used in a reproduction pickup.

2. Description of the Related Art The structure of a conventional objective lens driving device will be described with reference to FIGS. 5, 6, and 7. In each figure, 1 is a bobbin, and an objective lens 2 is provided at a position eccentric from the central axis of rotation, and is supported by an elastic support member 13 so as to be rotatable and movable in the axial direction. The support shaft 3 is vertically erected on the yoke base 4 and is fitted into a bearing 5 provided at the center of the bobbin 1. The laser beam emitted from the semiconductor laser is focused by the objective lens 2 to form a beam spot, and when it is irradiated onto the recording surface, it is reflected from the recording surface, but in order to obtain good recording and reproduction characteristics, the objective lens 2 is 3 to perform the tracking operation A, and sliding in the direction of the support shaft to perform the focusing operation.

Next, a drive mechanism for performing a focusing operation and a tracking operation will be explained. A pair of tracking and focus driving yokes 6 and a pair of magnets 7 are provided on the yoke base 4, and a focus coil 8 and a tracking coil 9 located on the outer peripheral surface of the focus coil 8 can be rotated and slidably displaced. It is located on the inner peripheral side of the yoke 6 so that The tracking coil 9 is adhesively supported on the outer surface of the focus coil 8, and the focus coil 8, the portion of the bobbin 1 that supports the objective lens, and the elastic support member 13 are located in a layered manner and are not on the same plane.

Problems to be Solved by the Invention However, the above configuration has the following problems. For example, when the objective lens drive device is made smaller and thinner due to the overall smaller and thinner recording/reproducing device, tracking coils and focus coils are made smaller and thinner, and in order to suppress the decrease in the driving force applied to these coils, high-performance Using a magnet, reducing the coil wire diameter, or increasing the coil current will increase the problem of cost and heat generation (and is not realistic. Also, it will cause wear and tear on the spindle due to rotation and sliding). In order to improve the reliability of the drive system, bearings that support the center of gravity of the movable part must reduce local wear. , the conventional elastic support member is positioned above or below the bobbin 1 (in the conventional example shown above), or is fixedly supported outside the focus coil in the radial direction, thereby controlling the rotation direction and sliding of the bobbin. Because the reaction force of the elastic support member changes linearly within the range of movement in the direction, it is possible to reduce the size and thickness.
It has been difficult to simultaneously achieve high reliability through center-of-gravity support. In view of the above problems, the first aspect of the present invention is to reduce the size and thickness of the objective lens drive device and improve its reliability without reducing the driving force applied to the tracking coil and the focus coil. It is an object of the present invention to provide an objective lens driving device that can be realized at low cost while improving the vibration characteristics of a movable part. Also,
A second aspect of the present invention is to provide an objective lens drive device that can be easily made smaller and thinner without causing heat generation due to a tracking coil or reduction in magnetic efficiency. That is.

Means for Solving the Problems In order to solve the above-mentioned problems, the objective lens driving device of the present invention includes a bobbin to which an objective lens for irradiating a light spot onto a recording medium is attached, and a bobbin that moves the bobbin in a focusing direction and a tracking direction. a bobbin support member movably supporting the bobbin; a focus coil that drives the bobbin in a focus direction parallel to the optical axis direction of the objective lens; a tracking coil that drives the bobbin in a tracking direction perpendicular to the focus direction; a yoke located on the outer peripheral side of the focus coil to operate the coil;
In the objective lens driving device including a magnet attached to the yoke, a gap is provided on a side surface of the focus coil for fixing and supporting the bobbin support member, and the bobbin support member drives the objective lens through the gap. It is characterized by being configured to support the center of gravity of the movable part of the lens drive device. Further, a second invention of the present invention is characterized in that, in addition to the main components of the first invention, a tracking coil is located on the inner peripheral side of the focus coil and is wound around a bobbin for the focus coil.

For production The operation of the first aspect of the present invention is as follows.

When making the objective lens drive device thinner, it is possible to achieve a significant reduction in thickness by providing a focus coil and a tracking coil on the outermost periphery of the bobbin that supports the objective lens. Elastic support members had to be stretched on the sides of the coil. However, by providing a gap on the side of the focus coil to fix the elastic support to the bobbin,
It can be supported by the center of gravity of the movable part, and the contact area and pressing force between the shaft and bearing can be kept almost constant.
Reliability can be improved by slowing down the progress of bearing wear. In addition, as the objective lens drive device becomes smaller and thinner, there is almost no dimensional margin above and below the objective lens drive device, and by attaching the elastic support member to the side surface where dimensional restrictions are relatively small, the movable range of the movable part can be expanded. It is also possible to improve the performance of the elastic support member. The second aspect of the present invention has the following effects:
By providing a tracking coil on the inner circumferential side of the focus coil and using a part of the focus coil bobbin as the tracking coil bobbin, the tracking coil acts as a part of the focus coil bobbin, and the number of turns of the tracking coil can be adjusted by changing the wire diameter. The size of the tracking coil can be increased. Only one of the parts of the tracking coil where current flows in the direction of the spindle faces the magnet. However, this is no longer the case with the tracking coil.Furthermore, even if the number of turns of the tracking coil increases, magnetic efficiency can be easily increased simply by making the arc of the opposing magnet thicker. It is possible to increase it.

EXAMPLE Hereinafter, an objective lens driving device according to an example of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of an objective lens driving device in an embodiment of the first invention and the second invention of the present invention, FIG. 2 is an exploded perspective view of the same, and FIG. 3 is a plan view. 1, 2, and 3, 14 is an objective lens, 15 is a bobbin, 16 is a focusing coil, 17 is a tracking coil, 18 is a support shaft, 19 is a bearing, 20 is a yoke, 21 is a magnet, 22 is a balancer, and 23 is an elastic support member. The bobbin 15 supports the objective lens 14, supports the tracking coil 17 at its four corners, and supports the focus coil 16 at its outermost circumference including the tracking coil. The focus coil 16 is connected to the shaft 18
It has a convex shape on the line connecting the objective lens 14 and the objective lens 14, and has a concave shape in the direction perpendicular thereto. A gap 16a is provided on the side surface of the focus coil 16 so that the elastic support member 23 can be fixed in this concave portion, and the elastic support member 23 passes through the focus coil 16 via a pin 23a and attaches to the bobbin 15. is fixed. That is,
The bottle 23a is fitted into a hole provided in the bobbin 15a and fixed with adhesive or the like. A bearing 19 provided at the center of the bobbin 15 is fitted into a support shaft 18 vertically erected on the base 24. Further, the focus coil 1
The convex portion 6 and the portion of the tracking coil 17 through which current flows in the direction of the spindle are located so as to face the magnet 21 . By passing a current through the focus coil 16, a driving force in the direction of the rotation center axis is applied to the focus coil 16 (the magnitude and direction of this current are determined by the signal output obtained by detecting the focal shift of the laser beam with respect to the recording surface) Focusing is performed by controlling the movement of the objective lens 14 in the direction of the rotational center axis by changing it accordingly. - Generally, four tracking coils 17 are installed at almost symmetrical positions, and each coil applies a force in the same rotational direction. The direction of the current is taken into consideration so that the

Then, a drive current corresponding to the signal output obtained by detecting the deviation of the laser beam with respect to a predetermined recording track is applied to the tracking coil 17, and by rotationally displacing the objective lens 14, the tracking of the laser beam with respect to the recording track is ensured. do. First, the effects of this embodiment will be explained. In order to make the objective lens drive device smaller and thinner, it is required to have a configuration in which the focus coil 16, tracking coil 17, and bobbin 15 are all housed on the same plane. In order to prevent such forces from acting and reduce wear on the bearing, it is necessary to provide support at the center of gravity of the movable part with an elastic support member. In this embodiment, the bobbin 15, the focus coil 16, and the tracking coil 17 have the same dimensions in the spindle direction, and the dimensions are the same even when they are combined. By winding the focus coil around the bobbin 16, the thin wall part that existed in conventional focus coil bobbins is eliminated, and the frequency characteristics of the movable part are also improved.

Conventionally, the elastic support member was located above or below the movable part and did not support the center of gravity. A gap 16a is provided between the two sides of the objective lens drive device.This allows the local pressing force on the shaft by the bearing to be lower than before even when the objective lens is tilted, and by reducing wear on the bearing, the objective lens driving device can be The reliability can be improved.Next, the operation related to the second invention of this embodiment will be described.Tracking coil 1
7 is wound in a nearly rectangular shape and generates a driving force in the tracking direction when the coil portion through which current flows in the same direction as the axis is located in a magnetic field. One tracking coil has two parts where current flows in the same direction as the support shaft, and the directions are opposite to each other. The bobbin 15 is made such that one part faces the magnet 21 and the other part is located far away from the magnet 21. This allows for a wide range of movement in the tracking direction. In addition, since the coils are arranged in a substantially straight line in the part where the tracking coil 17 faces the magnet 21, it is easy to position the coil in the part of the magnet 21 with the highest magnetic efficiency, and the magnetic efficiency is also lower than that of the conventional one. This is higher than when the magnetic circuit is wound in a concentric circle.For this reason, even if the magnetic circuit is an open magnetic field type, the magnetic efficiency can be almost the same as when using a conventional closed loop type magnetic circuit. In addition, the tracking coil 17 is located on the inner circumferential side of the focus coil 16 where the bobbin 15 was conventionally located, and the tracking coil 17 itself acts as a bobbin for the focus coil 16. Therefore, the vibration characteristics of the movable part do not deteriorate.As described above, according to this embodiment, the elastic support member 2 is attached to the side surface of the focus coil 16.
By providing a gap 16a for fixedly supporting 3 on the bobbin 15, the center of gravity of the movable part can be supported by the elastic support member 23, and the bearing can drive the objective lens by reducing the local pressing force of the part. The reliability of the device can be improved. In addition, by locating the tracking coil 17 inside the focus coil 16 and winding it around the end of the bobbin 15, it is possible to improve the magnetic efficiency of the tracking coil 17 and make the objective lens drive device smaller and thinner. It is possible to increase the number of turns and improve the vibration characteristics of the movable part.

In this embodiment, the focus coil 16 has a concave portion, but it may also have a circular or elliptical shape. In addition, although the number of tracking coils 17 is four,
Needless to say, it is possible to use a configuration other than the number of pieces, or a configuration in which two pieces are used instead of four pieces, which also serve as tracking coils facing the magnet on the opposite side. Furthermore, as shown in FIG. 4(a), the focus coil 16 was provided with a gap for inserting a pin 23a for attaching the elastic support member 23 to the bobbin 15, but as shown in FIG. 4(b), Alternatively, the upper and lower surfaces of the bobbin 15 only in the vicinity of the bins may be shaved, and the focus coil may be positioned thinly (spread out) on the upper and lower surfaces of the bobbin 15.

Effects of the Invention As described above, according to the present invention, by providing a gap on the side surface of the focus coil for fixing and supporting the elastic support member to the bobbin, the center of gravity of the movable part can be supported by the elastic support member. The reliability of the objective lens driving device can be improved by reducing the local pressing force of the bearing. In addition, by locating the tracking coil inside the focus coil and winding it around the end of the bobbin, we are able to improve the magnetic efficiency of the tracking coil and make the objective lens drive device smaller and thinner, while also increasing the number of turns of the tracking coil. It is possible to improve the vibration characteristics of the movable part.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an objective lens objective drive device according to an embodiment of the present invention, FIG. 2 is an exploded perspective view of the same embodiment, FIG. 3 is a plan view of the same, and FIGS. An explanatory diagram showing the shape of a focus coil in an embodiment, FIG. 5 is an exploded perspective view of a conventional objective lens drive device, FIG. 6 is a sectional view of FIG. 5, and FIG. 7 is a perspective view of the movable part of FIG. 5. It is. 14... Objective lens, 15... Bobbin, 16... Focus coil, 17...
・Tracking coil, 20... Yoke, 21
. . . Magnet, 22 . . . Balancer, 23 . . . Elastic support member. Name of agent: Patent attorney Shigetaka Awano and one other person Figure 3 Figure 5 Figure 6

Claims (1)

[Claims] (1) A bobbin to which an objective lens for irradiating a light spot onto a recording medium is attached; a bobbin support member that supports the bobbin movably in the focusing direction and the tracking direction; and a bobbin supporting member that supports the bobbin in a direction along the optical axis of the objective lens. A focus coil that drives the bobbin in a focus direction that is parallel to the focus direction, a tracking coil that drives the bobbin in a tracking direction that is orthogonal to the focus direction, and a yoke that is located on the outer peripheral side of the focus coil to operate these coils. and a magnet attached to the yoke, a gap is provided on a side surface of the focus coil for fixedly supporting the bobbin support member on the bobbin, and the An objective lens drive device in which a bobbin is supported by a bobbin support member. 2. The objective lens driving device according to claim 1, wherein the focus coil is provided with a pair of concave portions, and the bobbin support member is fixedly supported in the concave portions on the same plane as the focus coil. 3. The objective lens driving device according to claim 1, wherein the tracking coil is located on the inner peripheral side of the focus coil and is wound around a bobbin around which the focus coil is wound.