JPS60138741A - Objective lens driver - Google Patents

Abstract

PURPOSE:To arrange a lens without giving any effect on a disc drive motor by mounting a coil bobbin with a small outer diameter having a prescribed size to a moving plate of oval form so as to part the objective lens from an axial center. CONSTITUTION:The oval shape of the moving plate 25 is supported by a slide bearing mechanism comprising a shaft 24 and a bearing cylinder 26, and the objective lens 28 is fitted to lengthwise end. Moreover, the coil bobbin 30 having the outer diameter smaller than twice the distance from the slide bearing mechanism to the objective lens 28 is fitted to the moving plate 25. Thus, the outer diameter of the coil bobbin 30 is made small and the position of the objective lens 28 is parted from the axial center, then the lens device is arranged without giving effect such as small sized disc drive motor or prolonged shaft.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an objective lens driving device, and particularly to an objective lens driving device suitable for being incorporated into an optical disc record playback device.

[Background Art of the Invention and Problems Therewith] In recent years, in the field of audio equipment, digital recording and reproducing methods using PCM (pulse code modulation) technology are becoming popular. As is well known, the PCM digital recording and reproducing system has the advantage that the audio characteristics are not affected by the characteristics of the recording medium and that it is very resistant to noise. As a recording medium, optical, electrostatic, mechanical, etc. are already known as playback methods for disks. No matter which of these reproduction methods is adopted, the reproduction Ml is required to have advanced functions and performance not found in conventional analog methods.

For example, in an optical disc record playback device that uses the CD (compact disc) system, which is an optical playback system, it is necessary to accurately read information that is precisely recorded on the disc at a track pitch of 1.6 μm. , the reading system must have advanced functions and performance.

However, optical disc record playback devices generally employ a method of reading information recorded on a disc through an objective lens. In this case, in order to achieve good playback, the objective lens must always be focused on the group or pit where information is recorded on the disc, and the objective lens must be focused so that the track does not deviate from the track where information is recorded. It is necessary to precisely control the position. For this reason, generally, the objective lens is held by an objective lens drive device, and the drive device is controlled by a servo system using read information signals, thereby performing focusing control and tracking control. There is.

By the way, the main parts of the objective lens drive device that performs the above-mentioned focusing control and tracking control are as follows:
Usually, the configuration is as shown in FIGS. 1 to 3.

That is, a shaft 2 is implanted in the center of the upper surface of a base 1 made of a magnetic material, and a bearing sleeve 3 is fitted onto the shaft 2 to form a sliding bearing mechanism with the shaft 2. A holding cylinder 4 formed in the shape of a cylinder with a bottom is attached so as to be slidable in the axial direction and rotatable around the axis. The objective lens 5 is supported by the so-called bottom wall 4a of the holding tube 4, and the cylindrical portion 4b of the holding tube 4 is used as a coil bobbin, and a focusing coil 6 is provided on the outer periphery of the cylindrical portion 4b for controlling the position in the axial direction. and a tracking coil 7 for controlling the position around the axis. Further, two inner yokes 8a are disposed on the upper surface of the base 1 at positions facing the inner surface of the bottom wall 4a of the holding cylinder 4, and are fitted into the cylinder portion 4b without contact.

8b projecting symmetrically about the axis 2, and outer yokes 9a and 9b are arranged on the outside of the cylindrical portion 4b to face the outer surfaces of the inner yokes 8a and 8b, respectively. , 9b and the upper surface of the base 1, a permanent magnet 10 magnetized in the axial direction is interposed. Further, a small shaft 11 is provided upright on the upper surface of the base 1 and at a position facing the inner surface of the bottom wall 4a of the holding cylinder 4, and between this small shaft 11 and the bearing cylinder 3 there is provided a small shaft 11 formed of, for example, rubber. A damper member 12 for setting the neutral position M in the tracking direction is interposed. In addition, 13 in FIG. 2 indicates a light transmission hole provided in the base 1 and guiding light to and from the objective lens 5.

The objective lens drive device configured in this way moves the holding cylinder 4 by electromagnetic force accompanying the control of energization to the focusing coil 6.
The position of the holding cylinder 4 is changed in the X-axis direction in FIG. 1, thereby performing focusing control, and the position of the holding cylinder 4 is changed in the X-axis direction in FIG. It is rotated to perform tracking control. These energization controls are performed by a servo system (not shown).

However, the conventional objective lens drive device configured as described above has the following problems. That is, since the objective lens 5 is supported by the bottom wall 4a of the holding tube 4 and the cylindrical portion 4b of the holding tube 4 is used as a coil bobbin, the diameter of the holding tube 4 is equal to the radius of the sliding bearing mechanism. cannot be less than twice the sum of the values. For this reason, the distance from the center of the objective lens 5 to the end surface in the tracking direction, that is, the distance indicated by 1 in FIG. 3, cannot be made sufficiently small. Since 1 is large in this way, as shown in FIG.
When attempting to read information on the innermost circumference of the disk drive motor M, in order to avoid interference with the disk drive motor M, a small-diameter disk drive motor M must be used, or the motor shirt l- as shown in FIG. It was necessary to lengthen S and arrange the motors M at different levels.

However, in the case shown in Fig. 4, the reliability of the motor M deteriorates, and in the case shown in Fig. 5, the vibration characteristics deteriorate due to the vibration of the shaft S, so that a stable disk There is a problem in that not only is it difficult to obtain this rotation, but it is also difficult to downsize the entire reproduction system.

[Object of the Invention] The present invention was made in view of the above circumstances, and its purpose is to reduce the distance from the center of the objective lens to the end surface in the tracking direction, thereby reducing the distance from the center of the objective lens to the end surface in the tracking direction. An object of the present invention is to provide an objective lens driving device that can alleviate the influence of.

[Summary of the Invention] The objective lens drive device according to the present invention uses a flat movable plate as a member that supports the objective lens.

The movable plate is supported by a sliding bearing 6111, and an objective lens is supported at one longitudinal end of the movable plate. Further, a coil bobbin having an outer diameter smaller than twice the distance from the slide bearing 111111 to the objective lens is supported by the movable plate in alignment with the axis of the slide bearing mechanism.

[Effects of the Invention] With the above configuration, the objective lens is located outside the coil bobbin. Therefore, the ability to reduce the outer diameter of the coil bobbin and the ability to move the center of the objective lens away from the center of the coil bobbin combine to reduce the distance from the end surface that contacts the disk drive motor to the center of the objective lens. As a result, even when a normal disk drive motor is used, interference with the motor can be suppressed, and it is possible to provide something that contributes to realizing a stable system. At the same time, it can also contribute to miniaturization of the entire system.

[Embodiments of the invention] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 6 is a plan view of an objective lens driving device according to an embodiment of the present invention, and FIG. 7 is a plan view of the objective lens driving device according to an embodiment of the present invention. FIG. 8 is a partially cutaway perspective view of the same device.

In these figures, reference numeral 21 indicates a base made of magnetic material and formed, for example, in the shape of a disk. A hole 22 is provided approximately in the center of the base 1, and inner yokes 23a, 23 are provided symmetrically on the upper surface of the base 1 with the hole 22 as the center.
b protrudes upward. A shaft 24 is disposed between the inner yokes 23a and 23b, and one end of the shaft 24 is inserted into the hole 22 and fixed by screws or other appropriate means.

A flat movable plate 25 made of, for example, a non-magnetic material is attached to the shaft 24. The movable plate 25 is formed in a symmetrical shape with respect to the center position, and has a bearing tube 26 approximately in the center thereof that fits with the shaft 24 to form a sliding bearing. The movable plate 25 is mounted so that it can freely slide in the axial direction and rotate freely around the axis by fitting the bearing tube 26 and the shaft 24 together. A hole 27 is provided at one longitudinal end of the movable plate 25, as shown in FIG.
8 is fixed to the movable plate 25 with its front axis parallel to the shaft 24. Further, at the other end of the movable plate 25 in the longitudinal direction, at a position symmetrical to the mounting position of the objective lens 28 with respect to the axis 24, as shown in FIG. A counterweight 29 is fixed for aligning the center of gravity of the entire portion with the axis of the shaft 24.

The surface of the movable plate 25 facing the base 21 has an inner yoke 23a having the inner diameter described above.

A coil bobbin 30 formed in a cylindrical shape and having an outer diameter larger than the distance between the outer surfaces of the shaft 23b and smaller than twice the distance between the axial center line of the shaft 24 and the objective lens 28 is fixed concentrically to the shaft 26. . This coil bobbin 30 can also be formed integrally with the movable plate 25 when the movable plate 25 is formed. A forcing coil 31 is wound around the outer peripheral surface of the coil bobbin 30, and two sets of tracking coils 32 are fixed at symmetrical positions on the outer peripheral surface.

On the other hand, outer yokes 33a and 33b are arranged outside the coil bobbin 30 so as to face the inner yokes 23a and 23b, respectively, via the coil bobbin 30, and between these outer yokes 33a and 33b and the base 21. Permanent magnets 34a and 34b magnetized in the axial direction are inserted, respectively.

The outer yoke 33a and the permanent magnet 34a are fixed to the base 21 by a pole 35 made of a non-magnetic material, and the outer yoke 33b and the permanent magnet 34b are fixed to the base 21 by bolts 36 made of a non-magnetic material. This fixing can also be done with adhesive. Further, the counterweight 29 and the outer yoke 33a.

33b, there is a damper member 3 for setting the neutral position of the movable plate 25 in the tracking direction, as shown in FIG.
7 is provided. This damper member 37 is formed, for example, by punching out a thin rubber material, and is approximately M-shaped as shown in FIG. The hole 38 formed in the center is fixed to the counterweight 29 itself by a member constituting the counterweight 29, and both ends are fixed to studs 41 erected on the upper surface of the base 31 by, for example, adhesive. has been done.

With such a configuration, the movable plate 25 is moved in the X-axis direction in FIG. 8 by the electromagnetic force accompanying the control of energization to the focusing coil 31, thereby performing focusing control and also controlling the tracking coil 32. Although the movable plate 25 is rotated in the X-axis direction in FIG. 8 by the electromagnetic force accompanying the energization control, and tracking control is thereby performed.
It has the following advantages:

That is, since the objective lens 28 is located outside the coil bobbin 30, the diameter of the coil bobbin 30 can be made smaller than that of the conventional one, and as a result, the distance IJ from the center of the objective lens 28 to the end surface in the tracking direction can be reduced.
l can be made small. Therefore, it is possible to arrange this objective lens drive device without placing an undue burden on the disk drive motor and the entire set, contributing to the realization of a compact and stable disk drive system, and ultimately, as mentioned above. You will get the same effect.

In addition, in the case of the embodiment, since the movable parts are balanced by the counterweight 29, abnormal vibrations caused by play between the shaft 24 and the bearing tube 26 are less likely to occur, and the objective lens The vibration characteristics of the drive device can be improved. Furthermore, a sufficiently large rotational moment can be generated in the fixed portion of the damper member 37 by the coil bobbin 30h. Therefore, the rigidity of the damper member 37 can be smaller than when it is fixed inside the coil bobbin, and if the shape of the damper member is the same, the influence on the focus direction can be reduced, so that the above-mentioned effect can be further exerted. At the same time, the damper member 37 can be easily fixed. Furthermore, since the counterweight 29 is also used as a damper fixing fitting, the number of parts can be reduced and assembly can be made easier. Furthermore, since the mounting position of the counterweight 29 is symmetrical to the mounting position of the objective lens, the resonance of the movable plate 25 can generate 10kHz.
The vibration mode near z can be set so that the bearing section becomes the antinode of vibration. Therefore, the friction between the shaft 24 and the bearing sleeve 26 works well, the Q value of resonance can be reduced, and the servo band can be expanded to higher frequencies.

Note that the present invention is not limited to the embodiments described above. That is, in the embodiments described above, the movable plates are symmetrical in shape with respect to the center, but the movable plates do not necessarily have to be symmetrical in shape. The point is that the center of gravity of the movable part can be set at the center of the bearing.

Further, either the tracking coil or the focusing coil may be placed inside. Alternatively, the shaft may be provided on the movable plate side and the bearing sleeve may be provided on the base side.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the main parts of a conventional objective lens drive device, FIG. 2 is a view taken along the line AA in FIG. 1, and FIG. 3 is a view taken along the line BB in FIG. 1. , FIG. 4 and FIG. 5 are diagrams for explaining the problems of the conventional device, and FIG.
The figure is a plan view of the main part of an objective lens drive device according to an embodiment of the present invention, FIG. 7 is a view taken along the line C--C in FIG. 6, and FIG. Perspective view shown, No. 9
The figure is a perspective view showing a damper member incorporated in the device. 21... Base, 23a, 23b... Inner yoke, 24... Shaft, 25... Movable plate, 26... Bearing tube, 28... Objective lens, 29... Counter weight, 30 ...Coil bobbin, 31...Focusing coil, 32...Tracking coil, 33a, 3
3b...Outer yoke, 34a, 34b...Permanent magnet. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 9 Figure 7

Claims (1)

[Scope of Claims] (1) A base, a flat movable plate, and a movable plate provided between the movable plate and the base, which allows the movable plate to slide only in the axial direction and rotate about the axis. a sliding bearing mechanism supported on a base; an objective lens supported at one longitudinal end of the movable plate; a coil bobbin supported by the movable plate so as to align with the axis of the sliding bearing mechanism, and an electromagnetic drive element including a coil attached to the coil bobbin and applying an axial force and an axial force to the coil bobbin. An objective lens driving device comprising: (21) The movable plate includes a counterweight that aligns the center of gravity of the movable portion with the center of the slide bearing 1llIl at a portion located on the opposite side to the side on which the objective lens is supported with respect to the slide bearing mechanism. The objective lens driving device according to claim 1, characterized in that: (3) the counterweight is a support member that supports one end side of the damper member for setting the neutral position of the movable plate; The objective lens driving device according to claim 2, characterized in that the objective lens driving device also serves as an objective lens driving device.