JPH09190637A - Objective lens actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance driving sensitivity and to reduce a self-inductance component of a coil in an objective lens actuator used for an optical disk device. SOLUTION: This actuator is composed of a yoke 12 arranged opposite to a magnet 3 and coils 6a and 6b wound around the yoke 12 in the biaxial direction, and the center 12a of the yoke 12 in its thickness direction is positioned on the magnet 3 side by more than at least the thickness of the yoke 12 against the winding center 6c of the coils respectively. Consequently, the driving sensitivity is enhanced, and self-inductance is reduced while a phase lag angle is made small to prevent the coils from heating up due to electric noise of a driving current, and hence the focus control and tracking control can stably be performed following variations of a wobble and an eccentricity, etc., of a disk.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens actuator of an optical disk device for optically recording or reproducing information by projecting a light spot on a disk-shaped recording medium.

[0002]

2. Description of the Related Art In recent years, a device for recording and reproducing information (hereinafter, referred to as an optical disk device) using a disk-shaped optical recording / reproducing medium (hereinafter, referred to as a disk) has advantages of large capacity and high speed. Recognized and widely used for voice, image and data recording. Among the components incorporated in the optical disk device, the objective lens actuator is positioned as an important mechanical component that affects recording / reproducing performance.

A conventional objective lens actuator will be described below with reference to the drawings. 2 is a sectional view of a coil of a conventional example, FIG. 3 is an external perspective view of an objective lens actuator of a conventional example, and FIG. 4 is an exploded perspective view of the objective lens actuator.

In FIGS. 2, 3 and 4, a lens holder 2 which is a lens holding member made of synthetic resin has an objective lens 1 adhered and fixed on the upper surface and an optical plate 4 on the lower surface of the drawing, and both side surfaces are fixed. The tip of the suspension wire 8, which is a linear spring member, is molded and fixed to the protrusion 2a by molding. Two magnets 3 which are magnetized in the NS direction as shown in the figure are fixed to the protruding portion 2a and the other both side surfaces at positions of 90 degrees by adhesion or molding.
The suspension wire 8 is provided on one side wall 10a of the frame-shaped housing 10 which is a fixing member made of synthetic resin.
The other end is molded and fixed at four points of fixing points 8a to 8d by molding. And mounting hole 1
1 is provided as appropriate.

The coil frame 13 made of synthetic resin has
A winding portion 13a is provided at the center, and a protrusion 1 is provided at one end at both upper ends thereof.
The covering portion 13b having 3c is further provided with two wire winding processing grooves 13e and 13f on both outer sides thereof, and further, the positioning fixing pins 10b protruding at the four corners of the housing 10 are firmly fitted and fixed. There are positioning fixed holes 13g on both lower surfaces. The electromagnetic coil 15 has a winding 15 around the winding Y13-Y2 on the winding 13a.
A winding 15b having an arrow X1-X2 as an axis is stacked and wound on a. A yoke 14 is molded and formed on the central winding portion 13a of the coil frame 13. York 14
The coil windings 15a and 15b are wound around the yoke center 14a as an axis because they are sandwiched by the resin 13h having a uniform thickness on both sides of. As an example of FIG. 2, the yoke 14 has a thickness of 0.8 mm and the resin 13h has a thickness of 0.25 mm.
The coil winding 15a is wound so that the width of the winding portion 13a is 1.3 mm.

The winding start and winding end of each winding are wound around the wire processing grooves 13e and 13f several times, and soldered to the outer edge portions of each wound wire to be fixed. For example, a flexible printed circuit board is brought into contact with this portion and soldered to give a signal current to the electromagnetic coil 15.

The operation of the conventional objective lens actuator constructed as described above will be described below. Both ends of the suspension wire 8 are fixed, the lens holder 2 is cantilevered with respect to the support holder 10,
Move the lens holder 2 to the arrow X1-X2 and the arrow Y1-Y2.
It is possible to move parallel to the direction. The electromagnetic coil 15 having an arrow X1-X2 as an axis and an arrow Y1-
When a current is applied to the two types of windings with Y2 as the axis and two types of windings, the electromagnetic force generated between the winding 3 and the magnet 3 magnetized in the NS direction facing each other causes the arrow X1- X
The driving force in the Y2 and Y1-Y2 directions is generated and the lens holder 2
And therefore the objective lens 1 fixed on it by the arrow X
Drive in the 1-X2, Y1-Y2 directions.

As a result, the focus position of the laser beam focused on the disc (not shown) above the objective lens through the objective lens 1 can be moved, and the surface deflection of the disc surface in the plane direction and the eccentricity in the radial direction, etc. The recording or reproducing operation of the information signal is performed following the.

The driving force is determined by the magnetic flux between the yoke and the magnet and the coil arranged between the yoke and the magnet. Considering the direction of current flow, current flows in opposite directions in the coil disposed between the yoke and the magnet and the coil on the side opposite to the magnet side of the yoke, resulting in loss of driving force.

In driving the objective lens actuator, negative feedback is applied to the electromagnetic coil 15 including an electric circuit and a mechanical system (not shown), so that control is performed so as to follow the surface wobbling and eccentricity of the disk. If the frequency of the current is f, the self-inductance is L, and the resistance of the coil is R, the phase delay angle ψ of the objective lens actuator is given by ψ = tan ⁻¹ (2 · π · f · L / R) (1) To be done. As a conventional example, the self-inductance La of the electromagnetic coil 15a is 420 [μH / 1 kHz], the resistance Ra is 14.7 [Ω], the self-inductance Lb of the electromagnetic coil 15b is 188 [μH / 1 kHz], and the resistance Rb is 11.9. Since it is [Ω], the phase delay angle of the objective lens actuator of the conventional example is φa = −10.2 [deg / 1 kHz] φb = −5.7 [deg / 1 kHz]. The larger the self-inductance of the coil, the larger the phase delay angle. If the phase delay angle is large, stable control cannot be performed, so the smaller the phase delay angle, the better.
In other words, in order to perform stable control, it is necessary to increase the frequency of the drive current to advance the phase to increase the control gain, but if the frequency of the drive current is set to the high range, disturbance (electrical noise) is likely to occur. .

[0011]

As described above, in the configuration of the above-mentioned conventional example, the coil disposed between the yoke and the magnet and the coil on the side opposite to the magnet side of the yoke are supplied with current in opposite directions. Since it flows, there is a problem that a loss occurs as a driving force.

Further, since the phase delay angle is large, the frequency of the drive current must be set to a high frequency in order to perform stable control, which causes electrical noise and causes a current containing noise to flow in the coil. There was a problem that the coil generated heat.

In view of the above problems, the present invention provides an objective lens actuator which improves the driving sensitivity and reduces the self-inductance component of the coil.

[0014]

In order to solve the above problems, an objective lens actuator according to the present invention comprises an objective lens, a magnet, a holding member for holding the objective lens and the magnet, a support frame, and a holding member. And a support frame, a linear spring member, a yoke arranged so as to face the magnet, and a coil wound around the yoke in two axial directions. On the other hand, the center of the yoke in the thickness direction is located on the magnet side by at least the yoke thickness.

The objective lens actuator of the present invention having the above-mentioned structure reduces the self-inductance component of the coil to reduce the phase delay angle and the braking gain without changing the shapes of the magnet, the objective lens holding member, the support frame and the suspension wire. To increase the stability of the disc so that it can stably follow the unwanted movement of the disc.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention described in claim 1 of the present invention is, in an objective lens actuator, an objective lens, a magnet, a holding member for holding the objective lens and the magnet, a support frame, and a holding member. It is composed of a linear spring member that connects the support frame, a yoke that is arranged so as to face the magnet, and a coil that is wound around the yoke in two axial directions, with respect to the winding center of each coil. The center of the yoke thickness direction is located on the magnet side by at least the yoke thickness or more, and the center of the coil winding and the center of the yoke thickness direction are adjusted without changing the shape of the magnet, the objective lens holding member, or the like. By not matching, the drive sensitivity can be improved, the self-inductance can be reduced, the phase delay angle can be reduced, and stable control can be performed.

According to a second aspect of the present invention, in the objective lens actuator according to the first aspect, the yoke is molded on the coil frame, and the thickness of the molding material surrounding the yoke in the thickness direction of the yoke is at least twice the thickness of the yoke. The present invention is configured so that there is a difference as described above, and shows the most effective configuration range in which the action of claim 1 is obtained.

FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 is a coil sectional view of an objective lens actuator according to an embodiment of the present invention.
A yoke 12 is molded and formed on the central winding portion 5a of the coil frame 5. In the winding portion 5a, the electromagnetic coil 6 has an arrow X1-X2 on the winding 6a centered on the arrow Y1-Y2.
A winding wire 6b having an axis of is stacked and wound. York 1
The resin 5a is formed on the end surface of the magnet 2 on the magnet side, and the resin 5b is formed on the opposite end surface of the yoke 12. Since the difference between the thickness of the resin 5a and the thickness of the resin 5b is twice or more the yoke thickness. The center 12a of the yoke in the thickness direction does not coincide with the center 6c of the coil winding and is located in the direction of the magnet 3.

Next, a specific example of the present invention will be described. In FIG. 1, the yoke 12 has a thickness of 0.3 mm, and the resin 5a molded on the end surface of the yoke 12 on the magnet side has a thickness of 0.15.
mm, the thickness of the resin 5b molded on the end surface of the yoke 12 opposite to the magnet side is 0.85 mm. The operation will be described. When a current flows in the electromagnetic coil 6, a driving force in the directions of arrows X1-X2 and Y1-Y2 is generated in the magnet 3 by the electromagnetic force, and the lens holder 2 is fixed, that is, the objective lens 1 fixed thereto. Through arrows X1-X2, Y1-Y
Although it is driven in two directions, the magnetic flux is dense due to the narrow gap between the yoke and the magnet, and conversely, the influence of the magnetic flux on the coil on the side opposite to the magnet side of the yoke is reduced, thus reducing the loss of driving force. Driving sensitivity is improved. In this example, the displacement between the center of the yoke in the thickness direction and the center of the coil winding is 0.35 mm,
As a result, the driving sensitivity could be improved by 10 to 30%.

Although the self-inductance is reduced by increasing the distance between the coil and the yoke, if the yoke thickness is reduced to 0.8 mm from the conventional value of 0.8 mm to further increase the distance between the coil and the yoke as in the actual example. The self-inductance is 265 when the winding 6a is 420 [μH / 1 kHz].
[ΜH / 1 kHz], winding 6b is 188 [μH / 1 kHz]
z] was 138 [μH / 1 kHz], and the phase delay angle could be reduced by 20 to 45%.

As described above, according to this embodiment, the coil frame-winding is improved, that is, the coil winding center and the yoke thickness direction, without changing the shapes of the magnet, the objective lens holding member, the support frame, the suspension wire and the like. The drive sensitivity can be improved by not matching the center of, the self-inductance can be reduced, the phase delay angle can be reduced, and stable control can be performed.

In the embodiment, the thickness of the resin is made different so that the center of the coil winding and the center of the yoke in the thickness direction are made different. You can put it on.

Further, the above embodiment has a basic configuration,
Changes may be made in the details within the scope of the rights of the present invention, and techniques known in the art may be added.

[0024]

As described above, according to the objective lens actuator of the present invention, the driving sensitivity is improved by positioning the center of the coil winding direction in the yoke thickness direction on the magnet side by at least the yoke thickness. By reducing the inductance and reducing the phase delay angle, it is not necessary to set the high frequency of the drive current to a high level, and it is possible to prevent heat generation in the coil due to electrical noise due to disturbance.
It is possible to perform stable focus control and tracking control by following fluctuations in the surface deflection and eccentricity of the disk.

[Brief description of the drawings]

FIG. 1 is a sectional view of a coil according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a conventional coil

FIG. 3 is an external perspective view of a conventional objective lens actuator.

FIG. 4 is an exploded perspective view of a conventional objective lens actuator.

[Explanation of symbols]

 1 Objective Lens 2 Lens Holder 3 Magnet 5 Coil Frame 5a Winding Part Resin 5b Winding Part Resin 6a Winding Coil 6b Winding Coil 6c Coil Winding Center 8 Suspension Wire 10 Housing 12 Yoke 12a Yoke Center

Claims (2)

[Claims] 1. An objective lens, a magnet, a holding member that holds the objective lens and the magnet, a support frame, a linear spring member that connects the holding member and the support frame, and a magnet facing the magnet. It is composed of a arranged yoke and a coil wound around the yoke in two axial directions, and a center in the yoke thickness direction with respect to the winding center of each coil is located on the magnet side at least more than the yoke thickness. Objective lens actuator. 2. The objective lens actuator according to claim 1, wherein the yoke is molded on the coil frame, and the thickness of the molding material surrounding the yoke in the thickness direction of the yoke differs by at least twice the thickness of the yoke.