JP2005004884A - Optical pickup - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resonance prevention mechanism for an inner yoke of an optical pickup actuator. <P>SOLUTION: The optical pickup 10 is miniaturized by reducing the spacing between legs 16a and 16b of the inner yoke 16 as much as possible. When the spacing between the legs 16a and 16b is reduced, the resonance of the inner yoke 16 is induced by the vibration of an objective lens holding section which arises at the time of the tracking operation and focusing operation of the objective lens holding section and the accuracy of a servo mechanism for correcting a tracking error and focusing error is deteriorated. The resonance of the inner yoke is thereupon forcibly obstructed by drilling mortises 50 to a cover 45 to be fixed to a frame 14 and press-fitting tenons 46 formed at free ends 17a and 17b of the legs 16a and 16b into the mortises. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical pickup used for recording / reproduction of a CD (compact disc) or a DVD (digital video disc), and more particularly to an actuator yoke for correcting errors in a tracking direction and a focusing direction.
[0002]
[Prior art]
In general, an optical pickup has a base portion 100 configured as shown in FIG. 4 when a movable member of an actuator is removed. A support shaft 101 is erected at the center, and a movable portion (not shown) is slid along the support shaft 101. Supports movement and rotation. A support member of the objective lens on which a drive coil controlled by a drive current of a servo control circuit is mounted on the movable portion is supported and guided by the support shaft 101 and rotates and slides. When a tracking error or a focusing error occurs in an objective lens held by an objective lens holder (not shown), a drive signal is supplied to the corresponding drive coil to drive the objective lens holder by electromagnetic induction, and around the support shaft 101 Then, the objective lens holder is rotated or slid in the axial direction, and the objective lens is displaced in the tracking direction or the focusing direction to correct the tracking error or the focusing error.
[0003]
The correction operation of the objective lens holder includes a signal current flowing through the drive coil fixed to the objective lens holder, and the drive magnets 104a to 104d and the inner yoke fixed to the outer yoke 102 disposed opposite to both sides of the drive coil. It is controlled by an electromagnetic drive circuit configured by interaction with the magnetic field formed by 106a and 106b. Usually, the inner yokes 106a and 106b are U-shaped tuning forks connected by the base 106, and when the lens holder is driven, the inner yokes 106a and 106b resonate in response to vibrations generated when the lens holder is driven. There is a tendency, the servo control characteristics at the time of focusing and tracking deteriorate, the responsiveness of the objective lens holder deteriorates, and high-accuracy servo control cannot be performed.
[0004]
Accordingly, the inner yokes 106a and 106b forming part of the magnetic circuit are firmly fixed to the base portion 108 integral with the outer yoke 102 in order to obtain strength and rigidity that do not resonate (Japanese Patent Laid-Open No. 2003-59072). However, in order to meet the demands for downsizing and thinning as well as lowering the price of optical pickups associated with the portable use of personal computer CD players and the like, it is necessary to first close the intervals between the inner yokes 106a and 106b. . However, if the interval between the inner yokes 106a and 106b is reduced, the mounting bottom area of the base 106 that provides the mounting surface is reduced, and resonance is easily induced in the inner yokes 106a and 106b. For this reason, the performance of the actuator is lowered, and the error correction servo function is hindered, so that the reduction in size and weight of the apparatus has been prevented.
[0005]
[Problems to be solved by the invention]
However, the demand for the performance of optical pickups is increasing year by year, and effective means to increase the drive sensitivity of the actuator is to reduce the weight of the movable part, but if it is not possible to reduce the weight, it is necessary to strengthen the magnetic circuit In this case, the cost increases. Optical pickups are also required to reduce costs, so at present, high performance and low price cannot be achieved at the same time. If weight reduction of moving parts is not solved by downsizing of moving parts, we will respond to customer requests. I can't. For this purpose, it is essential to reduce the distance between the inner yokes 106a and 106b.
[0006]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to overcome the above-mentioned problems and to reduce the size of an optical pickup with improved performance without increasing the cost by a structure that prevents the resonance of the yoke accompanying the downsizing.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an optical pickup according to the present invention includes a lens holder that holds an objective lens and is movable in a tracking direction and a focusing direction, a drive coil fixed to the lens holder, and the drive coil. In an optical pickup device comprising an objective lens actuator comprising a drive magnet disposed opposite to an inner yoke and an inner yoke disposed opposite to the drive magnet across the drive coil, the inner yoke is opened. A restraining member for locking the end was provided. Furthermore, a cover that is normally provided in the actuator is used as the restraining member.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an optical pickup according to the present invention will be described below with reference to the drawings. 1A and 1B are schematic external views of an actuator 10 in an optical pickup according to the present invention. FIG. 1A is a plan view, and FIG. 1B is a side view taken along line bb in FIG. In FIG. 1, the actuator 10 includes a frame 14 including an outer yoke 12, an inner yoke 16, a support shaft 18, and an objective lens holding portion 22 on which an objective lens 20 is mounted.
[0009]
The actuator 10 is attached to a conveyance table (not shown) for scanning a recording disk in the radial direction together with optical system devices such as a light receiving / emitting element, a half mirror, and a prism mirror of an optical pickup. A screw hole 26 is threaded into the mounting tab 24 extending to the front. The frame 14 is screw-coupled by a screw hole 26 with an elastic body interposed between the frame and the carriage, and the screwing amount of the screw (not shown) to be coupled is adjusted to adjust the alignment of the optical system device to the optical axis. Is done.
[0010]
A pair of outer yokes 12 extend perpendicularly to the base 28 from opposite side edge portions of the frame 14, and magnets 30 are fixed to the inner surfaces of the pair of opposing outer yokes 12 with an adhesive, respectively. Yes. Further, the support shaft 18 is press-fitted and fixed in a fitting hole 32 formed in the center portion of the base 28 of the frame 14 and is erected vertically with respect to the base 28. Further, the inner yoke 16 is fixed to the frame 14, and a magnetic field is formed by the magnet 30 fixed to the outer yoke 12.
[0011]
The objective lens 20 is fixed to the objective lens holding frame 34 that is extended to one end side of the objective lens holding portion 22. In addition, tracking coils 36 to 39 are paired and fixed at appropriate positions on opposite side surfaces, and a focusing coil 40 is fixed to the lower part. The support shaft 18 is fitted into the bearing portion 42 of the objective lens holding portion 22 assembled in this way, and the objective lens holding portion 22 is slidable in the axial direction (focusing direction: arrow Fo) with respect to the support shaft 18. In addition, it is supported and guided so as to be rotatable around the axis (tracking direction: arrow Tr). In this embodiment, the tracking coils 36 to 39 and the focusing coil 40 are disposed between the magnet 30 and the inner yoke 16, and the objective lens 20 fixed to the holding frame 34 of the objective lens holding unit 22 has an optical axis. Be aligned.
[0012]
An optical pickup configured using this actuator 10 condenses laser light emitted from a light emitting element provided on a carrier with an objective lens 20 via a half mirror or a prism mirror, and applies the light to a recording track on the disk. Focus as a spot. Further, the reflected light passes through the objective lens 20 again and returns to the light receiving element via the prism mirror and the half mirror. In other words, the optical pickup converts the optical information obtained by the optical path configured in this way into an electrical signal by the light receiving element, and reproduces the recording on the disc.
[0013]
In the actuator 10, the tracking coils 36 to 39 and the focusing coil 40 are respectively interposed between the inner yoke 16 and the magnet 30 on both sides to constitute an electromagnetic drive circuit. In the optical pickup, the magnetic flux generated by energizing the focusing coil 40 interacts with the magnetic flux of the magnet 30 to generate thrust, and the objective lens holding portion 22 is slid in the axial direction of the support shaft 18. The focusing direction (arrow Fo) is controlled. On the other hand, the thrust generated by the interaction between the magnetic flux generated by the energization of the tracking coils 36 to 39 and the magnetic flux of the magnet 30 rotates the objective lens holding portion 22 around the support shaft 18 to control the tracking direction (arrow Tr). (See FIG. 1).
[0014]
As a result, when a tracking error occurs in the objective lens 20, a drive current is selectively supplied to the tracking coils 36 to 39, and the objective lens holding unit 22 rotates around the support shaft 18, thereby generating a tracking error. The objective lens 20 is pivotally displaced in the correction direction. When a focusing error occurs in the objective lens 20, a driving current is supplied to the focusing coil 40 to move the objective lens holding unit 22 up and down along the axial direction of the support shaft 18 to correct the focusing error. The objective lens is linearly displaced.
[0015]
During the drive for performing the above correction operation, the objective lens holding unit 22 is vibrated. At this time, a phenomenon that resonates with the vibration of the objective lens holding portion 22 occurs in the inner yoke 16, and the servo control characteristics in the focusing correction operation and the tracking correction operation deteriorate, and the correction accuracy decreases.
[0016]
In order to reduce the size of the actuator 10, the distance d (see FIG. 2 (b)) between both vertically opposing legs 16a and 16b of the inner yoke 16 is reduced to reduce the plate thickness. The 16 free ends 17 a and 17 b are more easily affected by the vibration of the objective lens holding portion 22. Therefore, the free ends 17a and 17b of the opposing leg portions 16a and 16b of the inner yoke 16 where the amplitude is maximized by the vibration are restrained by the restraining member 44 so that the objective lens holding portion 22 does not resonate even when the objective lens holding portion 22 vibrates. Forcibly, the movement of the inner yoke 16 is stopped.
[0017]
FIG. 2 is a partial view of the actuator 10 excluding the objective lens holding portion 22, the tracking coils 36 to 39, the focusing coil 40, and the support shaft 18 in order to make the configuration of the inner yoke 16 clearer. (B) is sectional drawing along the bb line of (a), (c) is a fragmentary sectional view along the cc line of (a). Members common to those in FIG. 1 are denoted by the same reference numerals.
[0018]
FIG. 3 is an exploded perspective view of FIG. 2 for clarifying the relationship between the inner yoke 16 and the vibration restraining member 44 which is the gist of the present invention. (A) is the restraining member 44, (b) is the inner yoke 16, (c) is a partially enlarged view of the free end of the inner yoke 16, (d) is the frame 14, the support shaft 18, the base 28, the mounting tab 24 and The outer yoke 12 and the like are included. The same reference numerals are used for members common to FIG.
[0019]
The inner yoke 16 that is generally U-shaped and shaped like a tuning fork is composed of a pair of opposing leg portions 16a and 16b. The free end 17a and 17b on the open end side and the connecting portion 15 that joins both the leg portions 16a and 16b at the base. Is provided. If the distance d between the legs 16a and 16b is reduced for miniaturization, the connecting portion 15 sandwiched between the legs 16a and 16b becomes narrow, and a strong coupling to the base 28 of the frame 14 cannot be expected, and the inner yoke 16 resonates. It becomes easy. Therefore, the connecting portion 15 is expanded laterally to extend the mounting seat portion 15a, and through holes 15b for caulking coupling are punched out at two locations.
[0020]
The caulking projection 48 corresponding to the through hole 15b is ejected from the base 28 of the frame 14 to fit the through hole 15b, and the caulking projection 48 is caulked to fix the inner yoke 16 integrally with the frame 14 with high fixing strength. The free ends 17a and 17b of the leg portions 16a and 16b are notched so that both ends of the width form a receiving seat 47 leaving a square horn 46 at the center of the end face, and are formed in the horn hole 50 of the restraining member 44. Come on.
[0021]
In this embodiment, a cover 45 that normally protects the actuator 10 from dust is used as the restraining member 44. The cover 45 is a flat plate formed substantially the same shape as the outer shape of the frame 14, and is provided with outward locking claws 52 that are engaged with the frame 14 at three locations. Since the latching claw 52 requires elasticity for slight deformation and restoration upon engagement, transparency is not a necessary condition, but an engineering plastic having appropriate elasticity is selected.
[0022]
Each of the locking claws 52 has an upper surface 52 a parallel to the surface of the cover 45, and a notch groove 56 is formed in a square shape at a position corresponding to a portion of the frame 14 that extends laterally from the outer yoke 12. The cover 45 is hooked on the frame 14 with the upper surface 52a abutting against the ceiling surface 56a. The cover 45 is fixed in such a manner that a part of the outer yoke 12 is sandwiched from above and below by the peripheral edge 45a of the cover 45 that is in contact with the upper end surface 12a of the outer yoke 12 and the upper surface 52a of the locking claw 52.
[0023]
The lower surface 52b opposite to the upper surface 52a of the locking claw 52 is a slope that descends from the outside to the inside, and is pushed into the frame 14 while sliding the locking claw 52 along the inner surface of the outer yoke 12 (arrow). P) Easy operation (see FIG. 2B). When pushed forward to a position where the peripheral edge 45a of the cover 45 and the upper end surface 12a of the outer yoke are pressed against each other, the locking claw 52 is fitted into the notch groove 56 of the outer yoke by the elastic snap action of the neck portion 52c to achieve engagement.
[0024]
The cover 45 has a large window 54 for passing the optical axis of the objective lens 20 at a position corresponding to the objective lens 20. Further, the cover 45 is provided with a hole 50 for inserting a flange 46 formed at the center of the end surface of the free ends 17a and 17b of the leg portions 16a and 16b at a position corresponding to the inner yoke 16. The hoso hole 50 defines a concave shape that protrudes the crimping seat 50a on the inside, and presses the opposing surface of the hoso 46 with the convex surface of the crimping seat 50a to restrain and fix the leg free ends 17a and 17b of the inner yoke 16. . Since both sides of the crimping seat 50a are notched, the crimping seat 50a has a degree of freedom of being able to be slightly elastically displaced in the surface direction, thereby facilitating the insertion of the hoses 46.
[0025]
The cover 45 is lowered in parallel toward the outer yoke 12 from the opening side of the frame 14 (upper side in the drawing) by aligning the position of the locking claw 52 corresponding to the position of the notch groove 56 of the outer yoke 12 (arrow P). ), The engagement of the locking claw 52 with the notch groove 56 and the insertion of the tenon 46 into the tenon hole 50 are forcibly performed simultaneously (see FIG. 2B). Engagement of the locking claw 52 and the notch groove 56 is ensured, and after both wings of the hoso hole 50 have settled on the receiving seats 47 on both sides of the hoso 46, they are moved upward into the crimping seats 50a of the hoso hole 50 by pushing operation. When the curved deformation is recognized, it is forcibly pushed into the hole 50 and aligned so as to be flush with the upper surface of the cover 45, and the restraint of the lever 46 is further strengthened.
[0026]
The operation of the restraining member 44 in the optical pickup according to the present invention will be described below. The free ends 17a and 17b of both the leg portions 16a and 16b of the inner yoke 16 are forcibly press-fitted into a relief hole 50 provided in a cover 45 in which the relief 46 is used as the restraining member 44, and the movement is prevented. As a result, the enlargement / reduction displacement of the distance d between the free ends 17a and 17b, where the displacement is most severe due to vibration in the inner yoke 16, is constrained, so that the inner yoke 16 does not have any vibration regardless of its own vibration. Can not resonate. Further, by engaging the cover 45 as the restraining member 44 with the inner yoke 16, vibration or resonance of the cover 45 is prevented.
[0027]
With the above configuration, the downsizing of the inner yoke 16 does not have any adverse effect on the focusing and tracking correction operations of the actuator, and the book including the actuator 10 thus reduced in size and weight. The optical pickup according to the invention can always maintain the servo control characteristics at the time of focusing and tracking with high accuracy.
[0028]
Although the embodiments have been described above, the present invention is not limited to the illustrated embodiments, and the shape and configuration thereof are changed or modified without departing from the configuration requirements of the present invention. Obtainable. For example, in the above-described embodiment, the objective lens holding portion 22 is configured to be supported by the support shaft 18. However, when the optical pickup is configured in a wire suspension system, a plurality of objective lens holding portions are known as is well known. It may be modified to be supported by a wire of books. In addition, the size can be reduced even if a dedicated part (metal plate or the like) other than the cover is used to lock the open end of the inner yoke to prevent vibration.
[0029]
【The invention's effect】
As is apparent from the above description, according to the optical pickup according to the present invention, the restraining member for locking the open end of the inner yoke is provided. By fixing the open end of this, vibration can be prevented, and the yoke mounting area can be reduced or the yoke can be made thin without affecting the servo function. For this reason, the actuator can be reduced in size and weight, which can contribute to lowering the price. Moreover, even if the actuator is reduced in size and weight, even if the driving force is the same, the driving sensitivity is improved, so that high performance can be desired without increasing the cost.
[0030]
Further, according to the optical pickup according to the present invention, the cover provided on the actuator is used as a restraining member for locking the open end of the inner yoke, so that the number of parts and the number of assembling steps are increased. There is nothing, and the cost can be reduced.
[Brief description of the drawings]
1A is a plan view of an optical pickup according to an embodiment of the present invention, and FIG. 1B is a side view taken along line bb of FIG.
2 is a partial view of the embodiment of FIG. 1, in which (a) is a plan view, (b) is a cross-sectional view taken along line bb of (a), and (c) is cc of (a). It is a fragmentary sectional view in alignment with a line.
3 is an exploded perspective view of the embodiment of FIG. 2, in which (a) is a cover, (b) is an inner yoke, (c) is a partially enlarged view of (b), and (d) is a frame including a support shaft. is there.
4A is a plan view and FIG. 4B is a cross-sectional view taken along line bb in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Actuator 12 Outer yoke 14 Frame 16 Inner yoke 17a, 17b Free end 18 Support axis 20 Objective lens 22 Objective lens holding part 30 Magnet 36-39 Tracking coil 40 Focusing coil 45 Cover 46 Hozo 50 Hozo hole 52 Locking claw 56 Notch groove

Claims (2)

A lens holder that holds the objective lens and is movable in the tracking direction and the focusing direction, a drive coil fixed to the lens holder, a drive magnet disposed opposite to the drive coil, and the drive coil An optical pickup device comprising an objective lens actuator comprising an inner yoke disposed opposite to the opposite side of the drive magnet, and provided with a restraining member for locking the open end of the inner yoke. . The optical pickup according to claim 1, wherein a cover provided on the actuator is used as a restraining member that locks the open end of the inner yoke.

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