JP3283203B2 - 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 used for an optical pickup device such as a CD and a DVD. In particular, the present invention relates to an objective lens driving device provided with a magnetic spring mechanism for holding the objective lens at a neutral position.

[0002]

2. Description of the Related Art As an objective lens driving device that can be used in an optical pickup device such as a CD or a DVD, an objective lens driving device of a shaft sliding type is known. Fig. 4 (A)
As shown in FIG.
A lens holder 20 for holding the objective lens 2, a sliding shaft 28 for supporting the holder 20 so as to be movable in the axial direction and about the center axis, and a lens holder 20.
And an outer yoke plate 29 provided to surround the outer periphery of the outer yoke. On the inner peripheral surface of the outer yoke plate 29, focusing magnets 33 and 34 and tracking drive magnets 43 and 44 are alternately fixed in the circumferential direction, and the outer wall (inside) of the lens holder 20 is opposed to these magnets. Drive coil 3 for focusing on yoke plate)
1, 32 and tracking drive coils 41, 44 are attached. Accordingly, when the focusing drive coils 31 and 33 are energized, the focusing drive coils 31 and 32 and the focusing magnets 33 and 33 are turned on.
Since the magnetic force is generated during the period 4, the lens holder 20 moves along the axis of the slide shaft 28 to perform the focusing operation. On the other hand, when the tracking drive coils 41 and 42 are energized, a magnetic force is generated between the tracking drive coils 41 and 42 and the tracking magnets 43 and 44, so that the lens holder 20 rotates around the axis of the sliding shaft 28. Then, a tracking operation is performed.

As shown in FIG . 4B in an enlarged manner, in the objective lens driving device 100, magnetic pieces 51 and 52 are attached to the outer wall of the lens holder 20 at positions facing the magnets 33 and 34. The lens holder 20 is held at a predetermined neutral position by using a magnetic force acting on the magnetic pieces 51 and 52. That is, the lens holder 20 is held at the neutral position by the magnetic spring mechanism. Then, focusing servo and tracking servo are performed using the neutral position as an initial position.

[0004]

As shown in FIG . 4C , the magnetic pieces 51, 52 are formed by driving coils 31, 32, respectively.
May be smaller than the hollow part. In this case, the magnetic piece 5
The magnets 33, 3 as indicated by arrow A
Since the magnetic force attracted to the side of the lens holder 4 acts, the magnetic force may cause the magnetic pieces 51 and 52 to fall off the outer wall of the lens holder 20 or cause a positional shift. In the conventional objective lens driving device 100, attention is not paid to this point, and no attempt is made to prevent the magnetic pieces 51, 52 from dropping or displacing due to the magnetic attraction of the magnets 33, 34.

Accordingly, an object of the present invention is to prevent a magnetic piece, which is a component of a magnetic spring function for holding a lens holder (objective lens) at a neutral position, from falling off or being displaced by magnetic attraction by a magnet. It is an object of the present invention to propose an objective lens driving device which can prevent the occurrence of a problem.

[0006]

According to the present invention, there is provided a lens holder for holding an objective lens, a holder supporting member for supporting the lens holder so as to be displaceable in a focusing direction and a tracking direction.
A focusing magnetic drive circuit for displacing the lens holder in the focusing direction, a tracking magnetic drive circuit for displacing the lens holder in the tracking direction, and at least one of the focusing magnetic drive circuit and the tracking magnetic drive circuit And a magnetic piece disposed in one of the magnetic drive circuits,
In an objective lens driving device configured to hold the lens holder at a predetermined neutral position by a magnetic force acting on the magnetic piece, a magnetic drive circuit in which the magnetic piece is disposed includes a lens drive circuit for the lens holder and the holder support member. A drive coil fixed to the coil mounting portion configured on one side, and a magnet fixed to the other of the lens holder and the holder support member in a state facing the drive coil, wherein the magnetic piece is , Mounting the coil
The drive coil of the coil mounting part is fixed with the part sandwiched
Fixed on the back side opposite to the front side
It is characterized by.

In the objective lens driving device having this configuration, the magnetic attraction force acting on the magnetic piece does not act in the direction in which the magnetic piece is dropped, but acts in the direction in which the magnetic piece is pressed against the back side of the coil mounting portion. Therefore, also in the objective lens driving device of the present invention, it is possible to prevent the magnetic piece from dropping off or to be displaced, and to always hold the lens holder at an appropriate neutral position.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An objective lens driving device to which the present invention is applied will be described below with reference to the drawings.

FIG. 1 is a schematic plan view of an objective lens driving device according to an embodiment of the present invention, and FIG. 2 is a side view thereof. As shown in these figures, an objective lens driving device 10 is a shaft sliding type objective lens driving device, and a lens holder 20 holding two lenses, an objective lens 2 for CD and an objective lens 3 for DVD. And a sliding shaft 28 for supporting the lens holder 20.
Numeral 0 is movable in the direction of the axis F (focusing direction) and supported rotatably about the axis F (tracking direction). The objective lens driving device 10 according to the present embodiment includes a bottom plate portion to which the lower end of the sliding shaft 28 is fixed, and an outer yoke plate that rises from the bottom plate portion in the direction of the axis F and surrounds the outer periphery of the lens holder 20. 29, and the lens holder 20 is moved between the outer yoke plate 29 and the lens holder 20 in the focusing direction F.
And a tracking magnetic drive circuit 40 for displacing the lens holder 20 in the tracking direction T. Further, the objective lens driving device 10 of the present embodiment includes magnetic pieces 51 and 52 disposed in the magnetic driving circuit of the tracking magnetic driving circuit 40. The lens is driven by the magnetic force acting on these magnetic pieces 51 and 52. The holder 20 is configured to be held at a predetermined neutral position.

The lens holder 20 includes a substantially cylindrical bearing 21 and an inner yoke plate 2 which concentrically surrounds the bearing 21.
2, a plurality of rib groups 23 connecting the bearing 21 and the inner yoke plate 22; and lens holders 24, 2 formed on the upper surface of the inner yoke plate 22 at intervals of approximately 90 degrees around the bearing 21.
5 is provided. A sliding shaft 28 is inserted into a shaft hole of the bearing portion 21. The objective lens 2 for CD is fixed to the lens holder 24 so that its optical axis is parallel to the axial direction of the sliding shaft 28, while the lens holder 25 has D
The VD objective lens 3 is fixed so that its optical axis is parallel to the axial direction of the slide shaft 28.

The tracking magnetic drive circuit 40 is provided on the sliding shaft 28 of the arc-shaped outer peripheral surface 221 of the inner yoke plate 22.
And two tracking drive coils 41 and 42, which are arranged opposite to each other with the interposition therebetween, and tracking magnets 43 and 44 fixed to the outer yoke plate 29 so as to face the coils 41 and 42. The tracking drive coils 41 and 42 are flat-type air-core coils, and the outer peripheral surface 2 of the inner yoke plate 22 is formed by a method such as bonding.
21. Tracking magnet 4
The poles 3 and 44 are polarized such that the N and S poles are arranged in the circumferential direction, and are polarized so that the respective poles have opposite polarities in the tracking direction T. For this reason,
When a drive current is supplied to the tracking drive coils 41 and 42, the outer yoke, the tracking magnet 43,
The tracking drive coils 41 and 42 and the inner yoke plate 22 constitute a substantially closed tracking magnetic drive circuit 40. A thrust in the tracking direction T is generated in the lens holder 20 by the tracking magnetic drive circuit 40, and the lens holder 20 is moved along the axis L.
Rotates around the circumference of. That is, a tracking operation is performed.

On the other hand, the focusing driving circuit 30
Focusing drive coils 31 and 32 formed at two locations facing each other across the lens sliding shaft 28 in the arc-shaped outer peripheral surface 221 of the inner yoke plate 22, and these coils 3.
Focusing magnets 33 and 34 are fixed to the outer yoke plate 29 so as to face the first and second magnets 32.
The focusing drive coils 31 and 32 are flat type air core coils, and are attached to the outer peripheral surface of the inner yoke plate 22 by a method such as bonding.
2 and the tracking drive coils 41 and 42 are fixed alternately. Focusing magnet 3
Reference numerals 3 and 34 denote magnets that are polarized and magnetized so that the N and S poles are arranged in the direction of the axis L of the sliding shaft 28. The focusing magnets 33 and 34 are arranged such that the respective poles are oppositely magnetized in the focusing direction.

In the objective lens driving device 10 of this embodiment, the lens holder 20 is held at a predetermined neutral position.
The rectangular magnetic pieces 51 and 52 for performing
2, that is, a focusing drive
Inner circumference on the opposite side to the outer circumference surface on which the files 31 and 32 are attached
It is fixedly arranged on the surface by a method such as bonding. Therefore, when a drive current is supplied to the focusing drive coils 31 and 32, the outer yoke, the focusing magnets 33 and 34, the focusing drive coils 31, 3
2. The magnetic drive circuit 3 for focusing which is substantially closed by the magnetic pieces 51 and 52 and the inner yoke plate 22
0 is configured. This focusing magnetic drive circuit 3
By 0, a thrust of the focusing method F is generated in the lens holder 20, and the lens holder 20 moves along the axis L. That is, a focusing operation is performed.

Further, a focusing driving coil 31,
In a state in which the tracking drive coils 41 and 42 are not excited (a state in which a drive current is not supplied), a magnetic attraction force by the focusing magnets 33 and 34 acts on the magnetic pieces 51 and 52. Due to this magnetic attraction, the lens holder 20 is held at a predetermined position in the circumferential direction around the sliding shaft 28 and at a predetermined height in the axial direction of the sliding shaft 28.

Here, as shown in FIG. 3 in an enlarged manner, the magnetic pieces 51 and 52 are connected to the inner peripheral surface 223 of the inner yoke plate 22 by the slider.
That is, the driving coils 31 and 32 for focusing are attached.
The inner peripheral surface opposite to the outer peripheral surface
Is fixed. For this reason, the magnets 33 and 34
Magnetic attraction force causes the magnetic pieces 51 and 52 to move the inner yoke plate 2
2 acts in the direction of pressing against the inner peripheral surface 223. Accordingly, it is possible to prevent the magnetic pieces 51 and 52 from dropping from the inner yoke plate 22 or being displaced. This allows
The lens holder 20 holding the objective lenses 2 and 3 can always be held at a proper neutral position. Generally, in an objective lens driving device configured to hold the lens holder 20 at a neutral position, the neutral position is used as an initial position for focusing servo and tracking servo. Therefore, according to the objective lens driving device 10 to which the present invention is applied, focusing and tracking control can always be performed with high accuracy.

The magnetic pieces 51 and 52 are not fixed to the inner peripheral surface 223 of the inner yoke plate 22 as they are, but are not fixed to the inner peripheral surface 223 of the inner yoke plate 22. Of course, it is also possible to form a mounting portion and fix the magnetic piece there. Further, a magnetic piece may be arranged in the tracking magnetic drive circuit 40, or a magnetic piece may be arranged in both the focusing magnetic drive circuit 30 and the tracking magnetic drive circuit 40.

Although the embodiment has been described with respect to an example in which each drive coil is fixed to the lens holder 20 side, the present invention is also applicable to an objective lens driving device in which each magnet is arranged on the lens holder 20 side. The present invention can be applied. For example, in an objective lens driving device in which a drive coil is fixed to an outer yoke plate, a magnetic piece may be fixed to the outer peripheral surface of the outer yoke plate.

[0018]

As described above, in the objective lens driving device of the present invention, the lens holder is held at the neutral position.
Coil for attaching a magnetic piece to drive coil
On the back side opposite to the front side where the
ing. In this case, even if the magnetic attraction force of the magnet acts on the magnetic piece, it is possible to prevent the magnetic piece from falling off or being displaced. Thus, it is possible to always hold the lens holder at an appropriate neutral position, and always perform focusing control and tracking control for reproducing or recording on the optical disc with high accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic plan configuration diagram of an objective lens driving device to which the present invention is applied.

FIG. 2 is a side view of the objective lens driving device shown in FIG.

FIG. 3 is an enlarged sectional view taken along line BB of FIG . 1 ;

FIG. 4 is a schematic configuration diagram of a conventional objective lens driving device.
You.

DESCRIPTION OF SYMBOLS 10 Objective lens driving device 2, 3 Objective lens 20 Lens holder 22 Inner yoke plate 221 Outer peripheral surface 223 Inner peripheral surface 28 Sliding shaft 29 Outer yoke plate 30 Focusing magnetic drive circuit 31, 32 Focusing drive coil 33 , 34 Focusing magnet 40 Tracking magnetic drive circuit 31, 32 Tracking drive coil 33, 34 Tracking magnet 51, 52 Magnetic piece

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-10-162389 (JP, A) JP-A-9-237427 (JP, A) JP-A-62-54837 (JP, A) JP-A-1- 312743 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G11B ^7/ 09-7/135

Claims (1)

(57) [Claims] A lens holder holding an objective lens;
A holder supporting member that supports the lens holder so as to be displaceable in a focusing direction and a tracking direction, a focusing magnetic drive circuit that displaces the lens holder in the focusing direction, and a tracking magnet that displaces the lens holder in the tracking direction. A drive circuit and at least one of the focusing magnetic drive circuit and the tracking magnetic drive circuit, and a magnetic piece disposed in one of the magnetic drive circuits, and the lens holder is moved by the magnetic force acting on the magnetic piece. In the objective lens driving device configured to hold the magnetic piece at a predetermined neutral position, the magnetic driving circuit on which the magnetic piece is disposed is fixed to a coil mounting portion formed on one of the lens holder and the holder supporting member. Drive coil and the lens A magnet fixed to the other of the holder and the holder support member so as to face the drive coil, wherein the magnetic piece sandwiches the coil mounting portion;
The mounting part is opposite to the surface on which the drive coil is fixed.
An objective lens fixed to the opposite back surface
Drive.