JP3315950B2 - Objective lens actuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a structure of an objective lens actuator used for an optical disk device or the like.

[0002]

2. Description of the Related Art Conventionally, as a structure of an objective lens actuator, as shown in FIGS. 3 (a) and 3 (b),
A movable part 11 in which an objective lens 12 and drive coils 14 and 15 for driving the objective lens 12 in the focusing direction and the tracking direction are bonded to a resin holding member 16 with an adhesive; Some have a plurality of elastic support members 17 for fixing to the drive coil 18 and a magnetic circuit 19 including a permanent magnet and a yoke for generating a magnetic flux acting on the drive coils 14 and 15 described above. The movable section 11 is driven in a focusing direction and a tracking direction by selectively energizing the drive coils 14 and 15.

[0003]

Since the driving force and the driving direction of the movable portion 11 are generated by magnetic fluxes traversing the drive coils 14 and 15, the center of the driving force and the center of gravity of the movable portion 11 are different from each other. Is important to prevent generation of an unnecessary moment, enhance tilt characteristics, and suppress unnecessary resonance of a spring-mass system during dynamic driving to enhance frequency characteristics. In particular, with the recent increase in the density and capacity of optical disk devices, it is a major challenge to improve the tilt characteristics and frequency characteristics of objective lens actuators for reading and writing information.

However, as shown in FIG. 3A, the drive coils 14 and 15 are
The opening 16a is slightly wider than the outer shape of the drive coils 14 and 15,
It has a certain clearance S. Therefore, there is a possibility that an error occurs in the mounting position of the drive coils 14 and 15 by the clearance S. Actually, the size of the clearance is required to be at least about 100 μm in consideration of the variation in the outer shape of the driving coil and the ease of assembly, and therefore, the position of the driving force application point varies at most ± 100 μm. In the actual bonding step, the resin holding member and the drive coil are held and bonded using a positioning jig, so that the variation is reduced, but ± 50 μm.
Degrees can occur. When the drive coils 14 and 15 are shifted left and right from a position symmetrical with respect to the center of gravity O of the movable portion 11 when viewed from the focusing direction, the drive center in the focusing direction also moves with respect to the center of gravity O. As a result, a moment about the axis L passing through the center of gravity O is generated in the movable portion 11 during driving in the focusing direction, and the tilt characteristic of the optical axis of the objective lens 12 is deteriorated. At the same time, when the movable portion 11 is dynamically driven, unnecessary resonance of the spring-mass system is induced, which causes deterioration of frequency characteristics.

The present invention solves the above-mentioned problems of the prior art. A main object of the present invention is to position a driving coil of a movable portion of an objective lens actuator with high accuracy by using a simple structure and obtain the objective lens. An object of the present invention is to improve the tilt characteristics and frequency characteristics of the optical axis and thereby improve the performance of the objective lens actuator.

[0006]

According to the present invention, an objective lens, a driving coil for driving the objective lens in one or both of a focusing direction and a tracking direction, and the objective lens are provided. An objective lens actuator having a movable portion elastically supported by a fixed portion with an elastic support member and a magnetic circuit for generating a magnetic flux in the drive coil, the movable portion having a lens and a resin holding member for holding the drive coil; In the above , at least a part of the driving coil is heated to prevent its deformation.
This is achieved by providing an objective lens actuator characterized in that the objective lens actuator is covered with a curable resin and held by being insert-molded in the resin holding member. In particular , the entire drive coil is a thermosetting resin.
It is good to be covered with fat .

[0007]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

[0008] Figure 1 (a) is a plan view showing a configuration of a main part of an objective lens actuator for an optical disk apparatus, FIG. 1
(B) is a side view thereof. The objective lens actuator includes a movable section 1 and a fixed section 8. Movable part 1
Comprises a resin holding member 6 as a base, an objective lens 2 and a coil unit 3 including a drive coil 4 for driving the objective lens 2 in the focusing direction and a drive coil 5 for driving the objective lens 2 in the tracking direction. Hold on. Between the movable part 1 and the fixed part 8, four linear springs 7 as elastic support members are provided in parallel with each other.
The movable unit 1 is supported so as to be movable in the focusing direction and the tracking direction while urging the movable unit 1 to the neutral position.

Here, the resin holding member 6 is insert-molded by injection molding using the coil unit 3 composed of the drive coil 4 and the drive coil 5 as an insert material. Further, a wire spring 7 for elastically supporting the movable portion is also insert-molded in the resin holding member 6.

Generally, a resin injection molding die used for insert molding has extremely high dimensional accuracy. Therefore, by positioning each coil with the high-precision die and performing resin molding, both of them are formed. Does not occur. Thereby, the displacement of the coil unit 3 with respect to the resin holding member 6 becomes, for example, 20 μm or less, and the positioning accuracy is greatly improved. Further, by simultaneously inserting the wire spring 7 into the resin holding member 6, the accuracy of the spring mounting position can be improved, and the bonding work in the subsequent process is reduced, and the process is simplified.

On the other hand, the fixed part 8 is provided with a magnetic circuit 9 comprising a permanent magnet 9a and a yoke 9b so as to generate a magnetic flux acting on the drive coils 4 and 5 described above. are doing. The movable section 1 is driven in the focusing direction and the tracking direction by selectively energizing the drive coils 4 and 5.

[0012] FIG. 2 (a) Figure 1 shows the implementation form of the present invention
FIG. 2B is a view similar to FIG. 1A, and FIG. 2B is a view similar to FIG. 1B, and like parts are denoted by like reference numerals, and detailed description thereof is omitted. In the present configuration, the drive coils 4, 5,
The coil unit 3 is covered with a thermosetting resin 10 before being insert-molded on the resin holding member 6.

At present, a thin bobbin or an air-core coil without a bobbin is used as a drive coil in order to reduce the size and weight and to avoid an extra magnetic circuit gap to suppress a decrease in effective magnetic flux density. Often do. Such a coil has a low rigidity, and in some cases, may be deformed by insert (injection) molding having a high injection temperature or injection pressure. Therefore, the coil unit 3
Is coated in advance with a thermosetting resin 10 having high rigidity and heat resistance and reinforced, so that the coil unit 3 is attached to the resin holding member 6 by injection molding having a high injection temperature and injection pressure.
The shape can be maintained even by insert molding. Here, since the thermosetting resin can be injection-molded at a low pressure of about several tens of atmospheres, there is no fear that the drive coil is deformed during the molding.

[0014]

As is apparent from the above description, according to the objective lens actuator of the present invention, the movable part for holding the objective lens and the drive coil on the resin holding member, and the movable part for holding the movable part with respect to the fixed part In an objective lens actuator including an elastic support member for elastically supporting and a magnetic circuit for generating a magnetic flux in the drive coil, the drive coil is insert-molded into a resin holding member, and compared with a case where both are bonded. The holding position accuracy is significantly improved,
The tilt characteristics of the optical axis of the objective lens and the frequency characteristics of the movable part are improved, and the performance of the objective lens actuator is improved. In addition, the rigidity for maintaining the shape of the drive coil can be improved by coating and protecting and strengthening a part or the whole of the drive coil with another material such as a thermosetting resin before insert-molding the resin holding member. Even if it is low, there is no risk of deformation due to molding.

[Brief description of the drawings]

1 (a) is a plan view showing a configuration of a main portion of the optical disc apparatus the objective lens actuator for, (b) is a side view.

2 (a) is 1 similar plan view (a) and showing an implementation form of the present invention, (b) the same side view as FIG. 1 (b).

FIG. 3A is a plan view showing a configuration of a main part of a conventional objective lens actuator for an optical disk device, and FIG. 3B is a side view thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Movable part 2 Objective lens 3 Coil unit 4 Focusing drive coil 5 Tracking drive coil 6 Resin holding member 6a Opening 7 Wire spring 8 Fixed part 9 Magnetic circuit 9a Permanent magnet 9b Yoke 10 Thermosetting resin 11 Movable part 12 Objective lens 14 , 15 drive coil 16 resin holding member 16a opening 17 elastic support member 18 fixing part 19 magnetic circuit

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-31007 (JP, A) JP-A-8-203101 (JP, A) JP-A-10-143889 (JP, A) JP-A 8- 339918 (JP, A) JP-A-6-314611 (JP, A) JP-A-2000-11409 (JP, A) JP-A-2000-339723 (JP, A) JP-A-11-307382 (JP, A) Hei 10-243595 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B ^7/ 09-7/10 G02B ⁷ /02-7/16

Claims (2)

(57) [Claims] An objective lens, a drive coil for driving the objective lens in one or both of a focusing direction and a tracking direction, and a resin holding member for holding the objective lens and the drive coil a movable portion which is elastically supported with a resilient support member relative to the fixed portion and having, in the objective lens actuator comprising a magnetic circuit for generating magnetic flux to said drive coils, said drive coils, so as to prevent its deformation at least
An objective lens actuator, wherein a part of the objective lens actuator is covered with a thermosetting resin, and held by being insert-molded in the resin holding member. 2. A thermosetting resin as claimed in claim 2, wherein said drive coil comprises a thermosetting resin.
The objective lens actuator according to claim 1, wherein the objective lens actuator is coated with a fat .