JPH01273234A - Object lens drive device - Google Patents

Abstract

PURPOSE:To reduce the size and weight of an object lens drive device and to improve the reliability of the device by positioning an elastic supporting member inside a focus coil in the radial direction and, in addition, inside a bobbin in the focusing direction and stretching the member in the radial direction of the bobbin and supporting the bobbin in a state where the bobbin can be moved in the focusing and tracking directions by means of a linear pressure change. CONSTITUTION:An elastic supporting member 24 is provided inside a focus coil 16 in the radial direction and, in addition, inside a bobbin 15 in the focusing direction and stretched in the radial direction so as to prevent the movement of the bobbin 15 in the upward and downward directions and in the radial direction of the coil 16 beyond the coil 16. Moreover, the member 24 supports the bobbin 15 which guides the revolution and sliding of a shaft 18 by means of a bearing 19 in such a state where the bobbin 15 can be moved in the focusing and tracking directions. Since the supporting member 24 is provided inside the coil 16 and can easily support the movable centroid of the coil 16, furthermore, the contacting area and pressing force between the shaft 18 and bearing 19 can be maintained an almost fixed states and wear of the shaft and bearing is reduced. Thus an object lens drive device which is miniaturized and improved in reliability while the movable ranges in both focusing and tracking directions are maintained in the same levels is obtained.

Description

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

2. Description of the Related Art The structure of a conventional objective lens driving device will be described with reference to FIGS. 6 and 7.

In each figure, 1 is a bobbin, and an objective lens 2 is provided at a position eccentric to the rotation center axis, and an elastic support member 1 is provided.
3, it is supported rotatably and movably in the axial direction. The support shaft 3 is vertically erected on the yoke base 4,
It fits into a bearing 6 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 peace spot, and when it is irradiated onto the recording surface, it is reflected from the recording surface, but it is not possible to make good recordings.
In order to obtain reproduction characteristics, the objective lens 2 rotates around the support shaft 3 to perform a slacking operation, and slides in the direction of the support shaft to perform a focusing operation.

Next, a driving mechanism for performing focusing and tracking operations will be explained. A tracking drive yoke e, a focus drive magnet 7, and a focus drive inner yoke 8 are provided on the yoke base 4, one pair each, and a tracking drive magnet 9 is provided on the tracking drive yoke θ. The focus drive magnet 7 has a focus drive outer yoke 10.
is installed. The bobbin 1 and the focus coils 2 and 11 are located between the focus drive inner yoke 8 and the focus drive outer yoke 1o so as to be rotatable and slidable. Further, a tracking coil 12 is provided on the focus: I/l/11, and a bearing part 6 is inserted and supported by the support shaft 3 so that the tracking drive magnet 9 and a part of the tracking coil/l/12 face each other. .

Problems to be Solved by the Invention However, the above configuration has the following problems. For example, when the objective lens driving device is made smaller and thinner by making the entire recording/reproducing apparatus smaller and thinner, it is necessary to make the movable part thinner by making the bobbin thinner and smaller in diameter and by making the focus coil multilayered. In addition, in order to improve the reliability of the drive system, which is subject to significant wear on the support shaft due to rotation and sliding, and changes in wear on the support shaft due to differences in the drive system's posture, bearings that support the center of gravity of the movable part are It is necessary to reduce local wear of However, the conventional elastic support member is either located above or below the bobbin 1 (below in the conventional example shown), or is mounted radially outward of the focus coil.
By attaching the bobbin, the reaction force must be made to vary linearly within the movable range of the bobbin in the rotational and sliding directions, making it difficult to make it smaller and thinner and to increase reliability by supporting the center of gravity. was.

In view of the above problems, the present invention makes it possible to make an objective lens drive device smaller and thinner and more reliable without reducing the movable range of the bobbin in the focus direction and tracking direction than before. The object of the present invention is to provide an objective lens driving device.

Means for Solving the Problems In order to achieve the above object, 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 that supports the bobbin movably, 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 orthogonal to the focus direction, and these coils. In order to operate the focus coil, the bobbin support member is provided with an inner circumferential yoke of the focus coil and a magnet attached to these yokes, and the bobbin support member is located inside the bobbin in the focus direction, and further inside the focus coil in the radial direction. The present invention is characterized by comprising an elastic support member positioned so as to support the vicinity of the center of gravity of the movable portion including the bobbin and the coil.

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

By positioning the elastic support member radially inside the focus coil and inside the bobbin in the focus direction, and stretching it in the radial direction of the bobbin, this elastic support member is prevented from overhanging above or below the bobbin. In addition, it is possible to avoid overlapping the focusing coil in the radial direction.

In addition, the elastic support member moves the bobbin, which is guided by a shaft through a bearing to rotate around this shaft and slide in the axial direction, in the focusing direction or tracking direction by a rectangular reaction force change. can be supported.

In addition, by positioning the elastic support member on the inner circumferential side of the focus coil, it becomes easier to support the movable center of gravity.
The contact area and pressing force between the shaft and the bearing can be kept approximately constant, thereby slowing down the progress of wear.

As a result, the elastic support member can be provided while maintaining the movable range of the pobbin in the focusing direction and the tracking direction without interfering with making the entire device smaller and thinner and improving the reliability of the drive device.

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 an external view of an objective lens driving device in an embodiment of the present invention, and FIG. 2 is an exploded perspective view thereof.

In FIGS. 1 and 2, 14 is an objective lens, 15 is a pobin, 18 is a focusing coil, 17 is a tracking coil, 18 is a support shaft, 19 is a bearing, 2° is an outer yoke, and 21
is a magnet, and 22 is an inner yoke. The pobbin 16 supports the objective lens 14 and also supports the focus coil/L/16 on a part of its outer periphery. Four tracking coils/V17 having a curvature approximately equal to the outer diameter of the focus coil are bonded to the outer periphery of the focus coil 16.

A bearing 19 provided at the center of the pobbin 16 is fitted into a support shaft 18 vertically erected on the base 23. Further, the portion of the focus car/L/16 that is not in contact with the pobbin 16 is located in the magnetic circuit between the outer ring 2° and the magnet 21. focus carp/l/
By passing a current through 18, a driving force in the direction of the rotation center axis acts on the focus coil/L/16. Focusing is performed by controlling the movement of the objective lens 14 in the rotation center axis direction by changing the magnitude and direction of this current in accordance with the signal output obtained by detecting the focal shift of the laser beam with respect to the recording section.

The tracking coil L/17 is wound concentrically or in a rectangular shape close to a square, and as shown in FIG. It can be roughly divided into parts 17G and 17d through which current flows in the circumferential direction. A part of the tracking carp/L'17 is attached to the magnet 21.
It is arranged to face the tracking carp/
When a current is applied to L/17, in the portion 17C117d where the current flows in the local direction of the rotational center axis, currents in opposite directions flow and receive driving forces in opposite directions from the magnet 21, and those forces cancel each other out.

Only one of the parts 17a and 17b through which current flows in the direction of the rotation center axis of the tracking coil/v17 faces the magnet 21, and rotational driving force is applied only to this facing part. Generally, four tracking coils 17 are installed at substantially symmetrical positions, and the direction of the current is taken into consideration so that each coil receives a force in the same rotational direction. Then, a drive current corresponding to the signal output obtained by detecting the deviation of the laser beam from a predetermined recording track is applied to the tracking coil A/17, and by rotationally displacing the objective lens 14, the recording track of the laser beam is to ensure tracking.

Reference numeral 24 denotes an elastic support member, which is fixedly supported by the inner yoke 22 having a notch and a notch 28 provided at the center of the pobbin 16.

In order to make the objective lens drive device thinner, it is necessary to reduce the dimensions of the outer yoke 20° magnet 21 and inner yoke 22 in the focus direction, and to make the movable part thinner. On the other hand, for miniaturization, it is necessary to position the magnet 21 and the elastic support member 24 near the support shaft 18 to reduce the overall diameter. In this embodiment, in order to simultaneously realize thinness and size reduction, the elastic support member 24 is positioned between the pobbin 16 and the inner yoke 22, and the elastic support member 24 is positioned inside the focus coil bobbin 15 in the focusing direction. To,
A notch is made in the side surface of the pobbin 16, one end of the elastic support member 24 is fixed within the notch, and the other end is further fixed within the notch 26 of the inner yoke 22.

This notch 2θ prevents a part of the elastic support member 24 from contacting the inner peripheral surface of the inner yoke 22 when the pobbin 16 rotates or slides, and also prevents the elastic support member 24 from contacting the inner peripheral surface of the inner yoke 22 when the pobbin 16 rotates or slides. be located at approximately the same height. Thereby, the center of gravity of the movable part can be supported by the pair of elastic support members 24.

The inner yoke 22 that supports the magnet 21 is the magnet 2
It is not necessary to support the entire surface of 1, and the yoke pace 23
The magnetic flux density of the inner yoke 22 decreases as it moves away from the surface, and the influence on the driving force by the inner yoke 22 at a portion that is a certain distance from the yoke base is small. FIG. 3 shows the influence of the difference between the height of the inner yoke 22 and the height of the magnet on the magnetic flux density of the coil portion. Even in a state where the height of the inner yoke is lower than that of the magnet, and the upper end 2n of a magnet with a height of 6ff is exposed, the magnetic flux density is still 90% or more of that when supported on the entire surface, and no significant decrease in magnetic flux density is observed. I can't.

Still, the relationship between the displacement of the elastic support member 24 and the reaction force is shown in FIG. As a result, it has been confirmed that the claw-shaped elastic support member 24 whose both ends are fixed to the bobbin 16 and the inner yoke 22 near the support shaft 18 can sufficiently satisfy linearity and vibration characteristics.

As described above, according to this embodiment, the elastic support member 24 is located inside the bobbin 16 in the focus direction, and is further attached in a horizontal position inside the focus coil/l/16 in the radial direction, and both ends of the elastic support member 24 are attached to the inside of the bobbin 16 in the radial direction. By fixedly supporting it on the yoke 22, it is possible to reduce the size and thickness and improve reliability.

In this embodiment, the inner yoke 22 supports the magnet 21, but the outer yoke 2o may support the magnet 21, or a notch 26 may be provided in the inner yoke 22 to expose the upper end of the magnet 21. However, it goes without saying that the inner yoke 22 may be provided with a projection or a hole and the elastic support member 24 may be fixed therein.

Effects of the Invention As described above, according to the present invention, the elastic support member can protrude vertically in the focusing direction and protrude outward in the radial direction of the focusing coil without deteriorating the performance of the objective lens driving device. This can be avoided, the center of gravity of the movable part can be supported, and the objective lens drive device can be made smaller and lighter and more reliable at the same time.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of an objective lens drive device in an embodiment of the present invention, Fig. 2 is an exploded perspective view of Fig. 1, and Fig. 3 shows the inner yoke height and focus coil when the height of the magnet is constant. Graph 1 shows the relationship between the applied driving force, FIG. 4 is a graph showing the relationship between the displacement of the elastic support member and the reaction force used in this example, and FIG. 6 is a perspective view of the tracking coil.
FIG. 6 is an external view of a conventional objective lens driving device, and FIG. 7 is a sectional view of FIG. 6. 14... Objective lens, 16... Group/bobbin, 1
6... Focus coil, 17... Group tracking coil, 20... Outer yoke, 21...
... Magnet, 22 ... Inner yoke, 24.
...Elastic support member. Name of agent: Patent attorney Toshio Nakao and 1 other person A4
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+7--racking coil 18--support shaft f9-shaft side a 20-m-outer 3J) 2t--magnet 22--inner cork 2nd figure masu-volatile deaf hemorrhoids & 3rd Figure 5 - Rinomoza fmm 1 Figure 4

Claims (3)

[Claims] (1) A bobbin to which an objective lens for illuminating a light spot on a recording medium is attached; a bobbin support member for movably supporting the bobbin in the focusing direction and the tracking direction; A focusing coil that drives the bobbin in a focusing direction parallel to the focusing direction, a tracking coil that drives the bobbin in a tracking direction perpendicular to the focusing direction, an inner yoke of the focusing coil for operating these coils, and a yoke attached to these yokes. The bobbin support member is stretched in the radial direction of the bobbin to support the bobbin so as to be movable in the focus direction and the tracking direction, and is located inside the bobbin in the focus direction, and further includes a magnet that supports the focus coil. An objective lens drive device comprising an elastic support member positioned radially inside of the movable portion and supporting the vicinity of the center of gravity of the movable portion including the bobbin and the coil. (2) The objective lens driving device according to claim 1, wherein both ends of the elastic support member are fixed to the bobbin and the inner yoke. (3) The objective lens driving device according to claim 1, wherein the inner yoke supports the magnet only on a part of the surface facing the focus coil.