JPH0736236B2 - Objective lens drive - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device, and more particularly to an objective lens driving device suitable for being incorporated in an optical disc record reproducing device.

[0002]

2. Description of the Related Art In recent years, in the field of audio equipment, a digital recording / reproducing system utilizing a PCM (pulse code modulation) technique has become popular. As we all know, PCM
The digital recording / reproducing method has advantages that the audio characteristics are not influenced by the characteristics of the recording medium, and that it is extremely resistant to noise. When a recording medium intended for a disk is used, its reproducing system is already known such as an optical system, an electrostatic system and a mechanical system.
Regardless of which of these reproduction methods is adopted, the reproduction apparatus is required to have a high level of function and performance not found in the conventional analog method.

For example, a CD is one of the optical reproduction systems.
In the optical disc record reproducing apparatus of the (compact disc) type, it is necessary to accurately read the information recorded finely on the disc with a track pitch of 1.6 μm. For this reason, the reading system must have sophisticated functions and performance.

However, the optical disc record reproducing apparatus generally adopts a method of reading information recorded on the disc through an objective lens. In this case, in order to realize good reproduction, the objective lens is always focused on the group or pit where the information of the disk is recorded, and the track of the objective lens is adjusted so that the track does not deviate from the track where the information is recorded. The position needs to be finely controlled. Therefore, in general, the objective lens is held by the objective lens driving device, and the driving device is controlled by the servo system using the read information signal, thereby performing focusing control and tracking control. .

By the way, the main part of the objective lens driving device for performing focusing control and tracking control as described above is usually constructed as shown in FIGS.

That is, the shaft 2 is planted in the central portion of the upper surface of the base 1 made of a magnetic material, and the shaft 2 is fitted with the shaft 2 through the bearing tube 3 which constitutes a slide bearing mechanism. A holding cylinder 4 formed in a bottomed cylindrical shape is mounted so as to be slidable in the axial direction and rotatable about the axis. A focusing coil for supporting the objective lens 5 by the so-called bottom wall 4a of the holding barrel 4 and utilizing the tubular portion 4b of the holding barrel 4 as a coil bobbin to control the axial position on the outer circumference of the tubular portion 4b. 6 and a tracking coil 7 for controlling the position around the axis are fixed. Further, the two inner yokes 8a and 8b are symmetrically fitted around the shaft 2 in such a manner that the two inner yokes 8a and 8b are fitted in a non-contact manner in the cylindrical portion 4b at a position facing the inner surface of the bottom wall 4a of the holding cylinder 4 on the upper surface of the base 1. The inner yokes 8a, 8a on the outside of the tubular portion 4b.
The outer yokes 9a, 9a, 9b
b is arranged, and the permanent magnet 10 magnetized in the axial direction is interposed between the outer yokes 9a and 9b and the upper surface of the base 1. 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 is formed between the small shaft 11 and the bearing cylinder 3 with, for example, rubber or the like. Damper member 12 for setting the neutral position in the tracking direction
Is intervening. Reference numeral 13 in FIG. 6 denotes a light transmission hole provided in the base 1 for guiding light to and from the objective lens 5.

In the objective lens driving device constructed as described above, the position of the holding cylinder 4 is changed in the Y-axis direction in FIG. 5 by the electromagnetic force accompanying the energization control of the focusing coil 6, whereby the focusing is performed. In addition to the control, the position of the holding cylinder 4 is rotated in the X-axis direction in FIG. 5 by the electromagnetic force associated with the energization control of the tracking coil 7, whereby the tracking control is performed. The energization control is performed by a servo system (not shown).

[0008]

However, the conventional objective lens driving device constructed as described above has the following problems. That is, the damper member 12 that determines the neutral position of the holding cylinder 4 is fixed at a position on the opposite side of the objective lens 5 with the axis 2 as a boundary. As described above, since the damper member 12 is fixed to the stationary portion at a portion distant from the center of the holding cylinder 4 to one side, when a displacement in the focus direction is given, a moment about the orthogonal axis is generated in the holding cylinder 4. . Therefore, a reaction force proportional to the moment is generated in the slide bearing mechanism that restricts rotation around the orthogonal axis. Since the sliding friction of the sliding bearing mechanism is almost proportional to the normal force, the larger the displacement in the focus direction, the larger the frictional force works. Therefore, the relationship between the quasi-static displacement in the focus direction and the force has a hysteresis characteristic as shown in FIG.

As described above, since the quasi-static displacement has a large hysteresis, there is a problem that it becomes difficult to pull in the servo. So, in order to solve such a problem, conventionally, it has been dealt with by increasing the surface accuracy of the bearing mechanism, but there is a limit to increasing the surface accuracy, and the actual solution has not been reached. Is.

Therefore, an object of the present invention is to suppress the hysteresis characteristic in the relationship between the quasi-static displacement in the focus direction and the force, to facilitate the pull-in in servo control, and to always obtain a stable control characteristic. An object is to provide an objective lens driving device.

[0011]

In order to achieve the above object, in the present invention, a movable body supporting an objective lens and a slide bearing permitting the movable body to slide in the axial direction and to rotate about the axis. Mechanism, a coil bobbin that is a part of the movable body and is provided around the axis of the slide bearing mechanism, and allows passage of magnetic flux, and at least the movable body supported by the coil bobbin is driven in the axial direction. In an objective lens driving device having a coil for
A ring-shaped positioning damper member having a curved portion is provided on the outer periphery of the coil bobbin so as to go around the axial center line in an axially symmetrical relationship about the axial center line of the plain bearing mechanism. The objective lens driving device is configured to connect the movable portion including the movable body and the coil bobbin to the stationary portion via the ring portion of the damper member.

[0012]

According to the objective lens driving device having the above-described structure, since the positioning ring-shaped damper members are symmetrically arranged about the axis, even if displacement in the focus direction is given, Since the damper members facing each other with the axial center line therebetween generate and balance moments about the opposite orthogonal axes, the vertical reaction force applied to the slide bearing mechanism does not increase.
Therefore, the hysteresis characteristic is suppressed, and the pull-in during servo control can be facilitated.

Further, since the damper member is arranged on the outer periphery of the coil bobbin, the assembly is extremely easy as compared with the case where it is arranged on the inner periphery of the coil bobbin (that is, the damper member is arranged inside the coil bobbin). Become.

Further, since the damper member is ring-shaped, when the movable body rotates about its axis, for example, the damper member is deformed to be convex toward the outer periphery. At this time, if the damper member is arranged outside the coil bobbin, the two are less likely to come into contact with each other, and it is possible to avoid the situation where the servo control of the movable body becomes unstable.

[0015]

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

FIG. 1 is a plan view of an objective lens driving device according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line CC in FIG. 1, and FIG. 3 is a partially cutaway view of the device. It is a perspective view.

In these drawings, reference numeral 21 denotes a magnetic material, for example, a disk-shaped base. Base 2
1 is provided with a hole 22 substantially in the center thereof, and the base 2
Inner yokes 23a, 23b are symmetrically provided on the upper surface of the plate 1 so as to project upward with respect to the hole 22. A shaft 24 is arranged between the inner yokes 23a and 23b, and the lower end side of the shaft 24 is inserted into the hole 22 and fixed by screws or other appropriate means.

The movable plate 25, on which the movable plate 25 made of, for example, a non-magnetic material and formed flat, is mounted on the shaft 24, is formed in a symmetrical shape with respect to the center position. A bearing tube 26 which is fitted to the shaft 24 and constitutes a slide bearing mechanism is provided at substantially the center thereof. The movable plate 25 is mounted so as to be free to slide in the axial direction and rotatable about the axis by fitting the bearing tube 26 and the shaft 24 together.

As shown in FIG.
As shown in FIG. 3, a hole 27 is provided, and the objective lens 28 is fixed to the movable plate 25 by using the hole 27 with its optical axis parallel to the axis 24. At the other end in the longitudinal direction of the movable plate 25, at a position symmetrical with respect to the mounting position of the objective lens 28 about the shaft 24, a movable portion including a coil and a coil bobbin, which will be described later, as shown in FIG. A counterweight 29 for fixing the overall center of gravity to the axis of the shaft 24 is fixed.

Therefore, on the surface of the movable plate 25 facing the base 21, the inner yokes 23a, 2 having the above-mentioned inner diameters are formed.
A cylindrical coil bobbin 30 is concentrically fixed to the shaft 24 and has a diameter larger than the distance between the outer surfaces 3b and smaller than twice the distance between the axis of the shaft 24 and the objective lens 28. . The coil bobbin 30 can be formed integrally with the movable plate 25 when the movable plate 25 is formed. A focusing coil 31 is wound around the outer peripheral surface of the coil bobbin 30, and two pairs of tracking coils 32 are fixed at symmetrical positions on the outer peripheral surface.

On the other hand, at the position outside the coil bobbin 30, the inner yokes 23a, 23 are arranged with the coil bobbin 30 interposed therebetween.
The outer yokes 33a and 33b are in a relationship to face b.
Is disposed between the outer yokes 33a and 33b and the base 21. The permanent magnet 34 is magnetized in the axial direction.
a and 34b are respectively interposed. The outer yoke 33a and the permanent magnet 34a are made of the non-magnetic material bolt 3
5, and the outer yoke 33b and the permanent magnet 34b are connected to the base 21 by bolts 36 made of a non-magnetic material.
It is fixed to. This fixing can also be fixed using an adhesive.

On the lower surfaces of both ends of the movable plate 25 in the longitudinal direction, thin support plates 37 having the same shape are formed.
a and 37b are fixed symmetrically around the axis 24. Then, at the same positions on the lower surfaces of the support plates 37a and 37b, two positions which are different by 180 degrees in the circumferential direction of the damper member 38 which is formed in a ring around the axis are fixed via an adhesive or the like. .

The damper member 38 is formed by punching or molding a thin silicon rubber plate, and is fixed on the line connecting the center of the objective lens 28 and the axis of the shaft 24 in the fixed state as described above. It is configured so that a plane-symmetrical shape is formed with respect to a plane located on the axis.

The damper member 38 is fixed to the outer yokes 33a and 33b via fixing mechanisms 39a and 39b at the circumferential center position between the support plates 37a and 37b. The fixing mechanisms 39a and 39b are applied to the upper end surfaces of the outer yokes 33a and 33b, respectively, and the spacer 40 having a groove P into which a part of the damper member 38 is fitted, and the upper surface of the spacer 40 are applied. The contact plate 41 and the screw 42 for integrally fixing the contact plate 41, the spacer 40 and the damper member 38 to the respective outer yokes 33a and 33b in a state where a part of the damper member 38 is fitted in the groove P are formed. It is configured.

Further, as is clear from FIGS. 1 to 3, the damper member 38 is arranged on the outer periphery of the coil bobbin 30.

With such a structure, the movable plate 25 is moved in the Y-axis direction in FIG. 3 by the electromagnetic force associated with the energization control of the focusing coil 31, whereby focusing control is performed and tracking is performed. Although the movable plate 25 is rotated in the X-axis direction in FIG. 3 by the electromagnetic force accompanying the energization control to the king coil 32, and the tracking control is performed by this, there is the following advantage.

That is, since the positioning damper member 38 is arranged symmetrically with respect to the axis, the damper member 38 substantially faces the shaft 24 even if the movable plate 25 is displaced in the focus direction. The damper parts generate opposite moments about the orthogonal axis and cancel each other out.
The moment about the orthogonal axis becomes zero. Therefore, the bearing tube 2
Since 6 is not inclined and pressed against the shaft 24, the hysteresis characteristic between the force applied in the focus direction and the quasi-static displacement can be sufficiently controlled. As a result, it is possible to facilitate pulling in the servo control.

Further, the damper member 38 is the coil bobbin 30.
Since it is arranged on the outer periphery of the coil bobbin, the assembly becomes extremely easy as compared with the case of being arranged on the inner periphery of the coil bobbin (that is, the case where the damper member is arranged inside the coil bobbin).

Further, since the damper member 38 has a ring shape, for example, when the movable plate 25 rotates about the axis, the damper member 38 is deformed so as to be convex toward the outer periphery. At this time, if the damper member 38 is arranged outside the coil bobbin 30, it is less likely that they will come into contact with each other, and it is possible to avoid a situation where the servo control of the movable plate 25 becomes unstable.

Further, since the positioning damper member 38 is provided symmetrically with respect to the line connecting the center of the objective lens 28 and the axis and the plane located on the axis, the movable plate 2 is also provided.
When 5 is displaced in the focus direction, it is possible to balance the component forces in the tracking direction of the damper members 38 that face each other across the symmetry plane. Therefore, crosstalk in the focusing direction and the tracking direction can be reduced, and more stable servo control in two directions can be realized.

Furthermore, when the symmetrical damper structure is formed by two or more damper members, if the damper member is made of rubber such as silicone,
Hardness changes greatly depending on molding conditions such as temperature and humidity during molding, resulting in variations in rigidity of each damper member, which causes the momentum of opposing damper members and component forces in the tracking direction to be out of balance, There is more hysteresis between the force and the quasi-static displacement, and more crosstalk in the focus and tracking directions. However, in this embodiment, since the one ring-shaped damper member 38 is used to provide the symmetry, the above problem can be solved, and the objective lens driving device in which the hysteresis characteristic is significantly suppressed is provided. Obtainable.

The present invention is not limited to the above embodiment. That is, it goes without saying that the present invention can also be applied to the holding cylinder type shown in FIG.
Further, the mounting position of the damper member on the movable side may be mounted on any position of the movable portion as long as the above-mentioned conditions are satisfied. Further, the shaft may be provided on the movable side and the bearing tube may be provided on the stationary side.

[0033]

As described above, according to the objective lens driving device of the present invention, since the positioning ring-shaped damper members are symmetrically arranged about the axis, the displacement in the focus direction is given. However, since the damper members facing each other with the axial center line therebetween generate and balance moments about opposite orthogonal axes, the vertical reaction force applied to the slide bearing mechanism does not increase. Therefore, the hysteresis characteristic is suppressed, and the pull-in during servo control can be facilitated.

Further, since the damper member is arranged on the outer circumference of the coil bobbin, the assembly is extremely easy as compared with the case where it is arranged on the inner circumference of the coil bobbin (that is, the damper member is arranged inside the coil bobbin). Become.

Further, since the damper member is ring-shaped, when the movable body rotates about its axis, for example, the damper member is deformed to be convex toward the outer periphery. At this time, if the damper member is arranged outside the coil bobbin, both are less likely to come into contact with each other, and it is possible to avoid the situation where the servo control of the movable body becomes unstable.

[Brief description of drawings]

FIG. 1 is a plan view showing a main part of an objective lens driving device according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line CC in FIG.

FIG. 3 is a perspective view showing the device by locally cutting it out.

FIG. 4 is a hysteresis characteristic diagram showing the characteristics of the present invention.

FIG. 5 is a perspective view of a main part of a conventional objective lens driving device.

6 is a sectional view taken along line AA in FIG.

7 is a sectional view taken along the line BB in FIG.

[Explanation of symbols]

 21 ... Base 23a, 23b ... Inner yoke 24 ... Shaft 25 ... Movable plate 26 ... Bearing tube 28 ... Objective lens 29 ... Counterweight 30 ... Coil bobbin 31 ... Focusing coil 32 ... Tracking coil 33a, 33b ... Outer yoke 34a, 34b ... Permanent magnets 37a, 37b ... Support plate 38 ... Damper members 39a, 39b ... Fixing mechanism

Claims (4)

[Claims] 1. A movable body that supports an objective lens, a slide bearing mechanism that allows the movable body to slide in the axial direction and rotate around the axis, and a shaft of the slide bearing mechanism that is a part of the movable body. In the objective lens drive device, which comprises a coil bobbin provided around the core wire and allowing passage of a magnetic flux, and a coil supported by the coil bobbin for driving at least the movable body in an axial direction, the slide bearing A ring-shaped positioning damper member having a curved portion is provided on the outer periphery of the coil bobbin so as to go around the axial center line in an axially symmetric relationship about the axial center line of the mechanism. An objective lens driving device, characterized in that a movable part including the movable body and the coil bobbin is connected to a stationary part via a ring part. 2. The positioning damper member according to claim 1, wherein the positioning damper member is formed in plane symmetry with respect to a plane located on a line connecting axially symmetrical positions and on a shaft center line. Objective lens driving device. 3. The objective lens driving device according to claim 1, wherein the outer diameter of the coil bobbin is formed to be smaller than twice the distance from the axis to the objective lens. 4. The objective lens driving device according to claim 1, wherein the damper member is arranged on the outer periphery of the objective lens.