JPH06103596A - Device for driving objective lens - Google Patents

Abstract

PURPOSE:To stabilize a frequency and to improve performance by suppressing vibration in a U-shaped yoke and relieving useless mechanical vibration. CONSTITUTION:The U-shaped yoke 8 is provided fixedly on a casing 6 for holding a device having larger mass than that of other constitution parts. A cover 11 having proper rigidity is attached to the casing 6 for pressing the free ends of both side walls 8a, 8b of the of the U-shaped yoke 8. The vibration of both side walls 8a, 8b of the U-shaped, yoke 8 is suppressed by the cover 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device for optically reading information recorded on a recording medium, and more particularly to an objective lens driving device thereof.

[0002]

2. Description of the Related Art An example of a conventional objective lens driving device is shown in FIG. In FIG. 5, reference numeral 1 is a bobbin having a substantially H-shaped plane and holding the objective lens 2, and 3 is a bobbin 1.
A focus coil wound around the outer circumference of the focus coil, a radial coil 4 attached to an appropriate place on the focus coil 3 and a reference numeral 5 on a device holding housing (optical pickup device body) 6 of the objective lens driving device which also serves as a support base. Is a support block fixed to 7, a plurality of leaf springs 7 elastically supporting the bobbin 1 with respect to the support block 5 in a swingable manner, for example, four leaf springs, and 8 is a substantially U-shape fixed on the device holding housing 6. Is a U-shaped yoke, and 9 is a magnet attached to one of the opposite side walls 8a, 8b of the U-shaped yoke 8. The U-shaped yoke 8 and the magnet 9 form a magnetic circuit and Two sets of circuits are provided, and the focus coil 3 and the radial coil 4 of the bobbin 1 are arranged between the magnetic gaps of the respective magnetic circuits (between the side wall 8a and the magnet 9 opposed thereto). It is a structure.

The control of the current flowing through the focus coil 3 controls the movement of the bobbin 1 in the focusing direction, that is, the direction perpendicular to the recording surface of the disk 10, and the control of the current flowing through the radial coil 4 controls the bobbin 1. Is controlled in the radial direction, that is, in the radial direction of the disk 10.

[0004]

By the way, in the objective lens driving device of this type, it is necessary to cause the objective lens 2 to follow the disc 10 rotating at a high speed at a high speed. Therefore, stable frequency characteristics are required, Eliminating unnecessary mechanical vibration has been a major issue in improving performance.

There are several sources of such unnecessary vibrations, one of which is the U-shaped yoke, and since both side walls of the U-shaped yoke are cantilevered, electromagnetic waves generated during operation are generated. When the reaction force of the force or the high minute vibration of several kilometers HZ transmitted from the bobbin, the leaf spring, etc., the free end side of the side wall is swung in the directions of arrows A, B, C, D in FIG. It was something that

The present invention aims to improve the performance by suppressing the vibration of the U-shaped yoke as much as possible.

[0007]

An objective lens driving device according to a first aspect of the present invention is provided with a magnetic circuit using a U-shaped yoke having a substantially U shape, and a magnetic circuit is provided in a magnetic gap in the magnetic circuit.
A coil for a bobbin elastically supported by elastic supporting means is arranged, and the bobbin is driven in the focus direction or the radial direction by controlling the current flowing through the coil. In this case, the U-shaped yoke of the magnetic circuit is used as a device holding housing. A fixed cover is attached to the device holding housing so as to cover the magnetic circuit and the bobbin and to press the free end of the U-shaped yoke.

Further, in the objective lens driving device according to the second aspect, a plurality of magnetic circuits using a U-shaped yoke having a substantially U shape are provided, and the elastic gap is provided by elastic supporting means in the magnetic gaps of the magnetic circuits. Place the coil of the supported bobbin,
In the one in which the bobbin is driven in the focus direction or the radial direction by controlling the current flowing in the coil, the free end of the U-shaped yoke of each magnetic circuit is
It is to be fixed to a common plate material having appropriate rigidity.

Further, in an objective lens driving device according to a third aspect, in the second aspect, the plate member is connected and fixed to the device holding housing side by an elastic member.

Further, in the objective lens driving device according to the fourth aspect, a magnetic circuit using a U-shaped yoke having a substantially U shape is provided, and elastically supported by elastic supporting means in a magnetic gap in the magnetic circuit. A coil of a bobbin is arranged, and a current flowing through the coil is controlled to drive the bobbin in the focusing direction or the radial direction. An elastic member is bridged between the free ends of the U-shaped yoke.

[0011]

In the objective lens driving device according to claim 1, the U-shaped yoke is fixed to the device holding housing having a mass larger than that of other driving device parts, and the free end of the yoke is appropriately rigid. It is possible to suppress vibration at the free end of the yoke by pressing with the cover having the.

Further, in the objective lens driving device according to the second aspect of the present invention, by fixing the free ends of the U-shaped yokes to a common plate member, both side walls of the U-shaped yokes vibrate in opposite directions to each other and each U-shaped yoke is shaken. The yoke exerts an effect of suppressing vibrations in which the yokes swing in opposite directions. If a magnetic material is used for the plate material, it can also serve as a measure against magnetic flux leakage. or,
The objective lens driving device according to claim 3, wherein
In addition to the effect obtained by the objective lens driving device described above, the vibration energy of the plate material can be absorbed by the elastic member to attenuate the vibration, and the vibration can be suppressed more effectively.

Further, in the objective lens driving device according to the fourth aspect, the vibration energy of the both side walls of the U-shaped yoke is absorbed by the elastic member bridged therebetween, and the vibration is damped.

[0014]

Embodiments of the present invention shown in FIGS. 1 to 4 will be described in detail below. 1 to 4, parts common to those in FIG. 5 are designated by common reference numerals. First Embodiment FIG. 1 shows an objective lens driving device according to a first embodiment of the present invention, (a) is a plan view and (b) is a partial cross-sectional side view.

In this embodiment, the device holding housing 6 of the objective lens driving device is used as a support base.
The support block 5 and the U-shaped yoke 8 are fixedly provided on the upper side, and a cover 11 for protecting the objective lens driving device is attached with a screw 17, and by this cover 11, free ends of both side walls 8a and 8b of the U-shaped yoke 8 are attached. The cover 11 is made of a material having a rigidity enough to overcome the vibration transmitted to the U-shaped yoke 8. 1
Reference numeral 1a is a passage hole provided in the cover 11, through which the light beam focused on the recording surface of the disk 10 passes.

In this embodiment, the U-shaped yoke is fixed to the device holding housing 6 having a mass much larger than that of each component of the objective lens driving device, and both side walls 8a and 8b thereof are fixed. It is possible to suppress the vibration of the U-shaped yoke 8 and to stabilize the frequency characteristic by pressing down the free end of the cover 11 with the cover 11 having an appropriate rigidity.
In the above embodiment, the free end of the U-shaped yoke 8 may be pressed by the cover 11 via hard rubber or the like.

Second Embodiment FIG. 2 shows an objective lens driving device according to a second embodiment of the present invention, (a) is a plan view with a protective cover removed, and (b) is one. It is a partial cross section side view. In this embodiment, a support base 12 is provided separately from the device holding housing 6,
The support block 5 and the U-shaped yoke 8 are fixedly provided on the support base 12, and the support base 12 is supported by the device holding housing 6 via a conventionally known position adjusting means (not shown) to obtain an objective lens. In the objective lens driving device in which the position of the driving device can be adjusted with respect to the optical components such as the semiconductor laser and the light receiving element in the pickup device main body, the free ends of the U-shaped yokes 8 are fixed to the common plate member 13, respectively. ,
The plate member 13 is formed of a metal plate having a rigidity sufficient to overcome the vibration of the U-shaped yoke 8. In FIG. 3, reference numeral 13a indicates a passage hole formed in the plate member 13 for passing the light beam. Incidentally, the protective cover 14 does not need the rigidity as in the previous embodiment, and any material may be used.

In this embodiment, the free ends of the U-shaped yokes 8 are fixed to the plate member 13 having a proper rigidity, so that the side walls 8a, 8 of the U-shaped yoke 8 are fixed.
With respect to the vibrations in which b shakes in the opposite directions and the vibrations in which the U-shaped yokes 8 shake in the opposite directions, a suppressing effect is exerted, unnecessary mechanical vibrations are reduced, and frequency characteristics are stabilized. If a magnetic material is used for the plate material 13, the magnet 9
The magnetic flux leaking from the disk to the disk 10 side can be absorbed, and the countermeasure against the magnetic flux leakage can be effectively taken. Third Embodiment FIG. 3 shows an objective lens driving device according to a third embodiment of the present invention, (a) is a plan view, and (b) is a partial sectional side view. In the plan view shown in FIG. 3A, hatching indicates an elastic member described later, and does not represent a cross section.
This embodiment is a step ahead of the second embodiment, in which a relatively large rectangular opening 15a is formed in the protective cover 15, and the elastic member 1 is formed at the edge of the opening 15a.
The plate material 13 is connected and fixed via 6 and the plate material 1
The energy transmitted to 3 is absorbed by the elastic member 16 and is attenuated, so that the vibration is more effective than the second embodiment.

Fourth Embodiment FIG. 4 shows an objective lens driving device according to a fourth embodiment of the present invention, (a) is a plan view showing a state where a cover is removed, and (b) is a partial sectional view. It is a side view. In this embodiment, elastic members 18 are bridged between the free ends of both side walls 8a and 8b of each U-shaped yoke 8.
As the material, a damping material obtained by applying a special adhesive to butyl rubber or thin aluminum foil is used. According to this configuration, the vibration of both side walls 8a and 8b of the U-shaped yoke 8 is absorbed by the elastic member 18 and attenuated. Therefore, unnecessary mechanical vibration is reduced and the frequency characteristics can be stabilized.

[0020]

As described above, in the objective lens driving device of the present invention, U is one of the sources of unnecessary mechanical vibration.
By suppressing or absorbing / damping the vibration of the mold yoke, unnecessary mechanical vibration can be reduced, frequency characteristics can be stabilized, and high performance can be achieved, and a practically excellent product can be provided.

[Brief description of drawings]

1A and 1B show an objective lens driving device according to a first embodiment of the present invention, in which FIG. 1A is a plan view and FIG. 1B is a partial sectional side view.

2A and 2B show an objective lens driving device according to a second embodiment of the present invention, FIG. 2A is a plan view with a protective cover removed, and FIG.

3A and 3B show an objective lens driving device according to a third embodiment of the present invention, in which FIG. 3A is a plan view and FIG. 3B is a partial sectional side view.

4A and 4B show an objective lens driving device according to a fourth embodiment of the present invention, FIG. 4A is a plan view showing a state in which a cover is removed, and FIG.

FIG. 5 shows a conventional objective lens driving device,
(A) is a plan view, (b) is a side view, (c) is a front view

[Explanation of symbols]

 1 Bobbin 2 Objective Lens 3 Focus Coil 4 Radial Coil 6 Device Holding Housing 7 Leaf Spring 8 U-type Yoke 8a, 8b U-type Yoke Side Wall 9 Magnet 10 Disc 11, 14, 15 Cover 13 Plate Material 16, 18 Elastic Member

Claims (4)

[Claims] 1. A magnetic circuit using a U-shaped yoke having a substantially U-shape is provided, and a coil of a bobbin elastically supported by elastic supporting means is arranged in a magnetic gap in the magnetic circuit, and flows through this coil. In an objective lens driving device for driving the bobbin in a focus direction or a radial direction by controlling an electric current, a U-shaped yoke of the magnetic circuit is fixedly provided to the device holding housing, and the device holding housing is An objective lens driving device, characterized in that a cover having an appropriate rigidity is attached so as to cover the magnetic circuit and the bobbin and press the free end of the U-shaped yoke. 2. A plurality of magnetic circuits using a U-shaped yoke having a substantially U shape are provided, and a bobbin coil elastically supported by elastic supporting means is arranged in a magnetic gap in each of the magnetic circuits. In the objective lens driving device for driving the bobbin in the focus direction or the radial direction by controlling the current flowing in the, the free ends of the U-shaped yokes of the magnetic circuits are fixed to a common plate material having appropriate rigidity. An objective lens driving device characterized by: 3. The apparatus according to claim 2, wherein the plate member is connected and fixed to the device holding housing side with an elastic member.
The described objective lens drive device. 4. A magnetic circuit using a U-shaped yoke having a substantially U-shape is provided, and a coil of a bobbin elastically supported by elastic supporting means is arranged in a magnetic gap in this magnetic circuit, and flows through this coil. An objective lens driving device for driving the bobbin in a focusing direction or a radial direction by controlling an electric current, wherein an elastic member is bridged between free ends of the U-shaped yoke.