JPS63255837A - Light pick-up device - Google Patents

Abstract

PURPOSE:To cheaply form a miscellaneous shape focusing magnetic circuit by forming an outer circumferential yoke and an inner circumferential yoke by applying the sintering method to a magnetic material, and manufacturing a permanent magnet by molding a resin including a magnetic material. CONSTITUTION:An outer circumferential yoke 2a and an inner circumferential yoke 2b are formed to the miscellaneous shape to notch a part of the cylindrical shape by the method to sinter an iron type powder material so as not to block off the light. Because of a metallic mold, the variance of the dimensional accuracy is also little and a constant focusing magnetic circuit can be constituted. A permanent magnet 1 molds a resin including a magnetic material to a prescribed shape and cheaply obtained by magnetizing the molded substance. After the permanent magnet, outer circumferential yoke an inner circumferential yoke are separately manufactured, these are combined. Thus, while performance is secured, the miscellaneous shape focusing magnetic circuit can be made small in size and cheap in cost.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an optical pickup device, particularly a reproducing device or recording device that performs focusing and tracking of a light spot focused on an information recording surface of an optical disc. /
The present invention relates to an optical pickup device for a playback device.

[Prior Art] FIG. 1 is a partially cutaway perspective view of a drive unit of a conventional optical pickup device, and in the figure, (1)
(2a) is a cylindrical permanent magnet for focus control made by sintering and magnetizing a magnetic material, (2a) is an outer circumferential yoke that constitutes a focus magnetic circuit, and (2b) is a magnetic circuit that is continuous with the outer circumferential yoke (2a). The inner circumferential yoke is connected to the permanent magnet (
1) is attached to the inner surface of the outer yoke (2a). The outer circumferential yoke (2a) and the inner circumferential yoke (2b) are manufactured by cutting an iron-based base material, and then subjected to anti-rust plating.

(3) is the focusing coil, (4) is the inner yoke (
2b) with good perpendicular precision, and a lens holder (5) is fitted onto this support shaft (4) so that it can slide in the direction of arrow A and freely rotate in the direction of arrow B. An objective lens (6) and a balancer (7) are fixed to this lens holder (5) at left and right positions spaced a certain distance from the support shaft (4), and the lower cylindrical part of this lens holder (5) is provided with the focusing lens. A coil (3) is attached.

Next, the operation will be explained. Focusing coil (3
) by applying a servo current to the lens holder (5).
slides in the direction indicated by the arrow depending on the polarity of the servo current, changing the distance between the objective lens (6) and the optical disk (not shown) to perform focusing servo. By this focusing servo, the position of the light beam incident on the objective lens (6) from the Z direction is controlled and focused onto the optical disk.

[Problems to be Solved by the Invention] Since the conventional optical pickup device is configured as described above, when downsizing by reducing the distance between the objective lens (6) and the support shaft (4), the Z The cylindrical focus control permanent magnet (1) and the outer peripheral yoke (2a) must have an irregular shape with a part cut out so that the light rays from the direction are not blocked.

In addition, in order to press-fit the support shaft (4) into the inner circumferential yoke (2b) with good perpendicular precision and without counterboring the support shaft, it was necessary to tighten the precision of the press-fit hole.

However, in order to downsize the optical pickup device and ensure the required accuracy, the outer yoke (2a) and the inner yoke (2b)
) cannot change the shape and dimensional accuracy of the ferrous base material, so creating the outer and inner yokes by cutting the iron base material has the problem that the cost of the focusing magnetic circuit becomes extremely high. .

This invention was made to solve the above-mentioned problems, and aims to reduce the size and cost of an optical pickup device.

Means for Solving Problem E] The optical pickup device according to the present invention includes an outer circumferential yoke and an inner circumferential yoke made by sintering an iron-based powder material, a permanent magnet made by resin molding containing a magnetic material, and then , a focusing magnetic circuit is constructed by combining the two.

[Function] The focusing magnetic circuit of the present invention is constructed by manufacturing the outer yoke and the inner yoke by sintering an iron-based powder material, the permanent magnet by molding a resin containing a magnetic material, and then combining the two. As a result, it is possible to obtain a focusing magnetic circuit having an irregular shape in a small size and at low cost while maintaining the performance of the conventional device.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. This invention is mainly based on changes in the material and manufacturing method of the components of the focusing magnetic circuit, and the external shape is exactly the same as the conventional device shown in FIG.

The outer circumferential yoke (2a) and the inner circumferential yoke (2b) are manufactured by a sintering method using an iron-based powder material to have an irregular shape in which a part of a cylindrical shape is cut out so as not to block the light rays. In this case, the accuracy of the press-fit hole of the support shaft (4) of the inner yoke (2b) is as follows:
Because this inner yoke (2b) is manufactured using a sintering method using iron-based powder materials, the base material is soft, so with the same pressing force as conventional equipment, the accuracy is higher than when cutting iron-based base materials. can be made looser. Furthermore, since it is molded, there is little variation in dimensional accuracy and a consistent focusing magnetic circuit can be constructed.

Further, the permanent magnet (1) can be obtained at low cost by molding a resin containing a magnetic material into a predetermined shape and magnetizing this molded product.

In the above example, the permanent magnet, the outer yoke, and the inner yoke were manufactured separately and then used in combination, but the permanent magnet, outer yoke, and inner yoke were made of the same resin material containing the magnetic material It is also possible to use a material that is formed by molding and magnetized after molding.

[Effects of the Invention] As described above, according to the present invention, the outer circumferential yoke and the inner circumferential yoke are manufactured by sintering a magnetic material, and the permanent magnet is manufactured by molding a resin containing a magnetic material. So,
This has the effect that focusing magnetic circuits with irregular shapes that accompany the miniaturization of optical pickup devices can be manufactured at low cost while maintaining the performance of conventional devices.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of a driving device portion of an optical pickup device. In the figure, (1) is a permanent magnet, (2a) is a magnetic yoke (outer yoke), and (2b) is a magnetic yoke (inner yoke).
, (3) is a focusing coil, (5) is a lens holder, and (6) is an objective lens. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent Patent attorney Masuo Oiwa (and 2 others) 1st ward 1: Permanent magnet 20: Outer yoke 2b: Inner yoke

Claims (1)

[Claims] An optical pickup device including a lens holder that holds an objective lens, and a drive device that drives the lens holder to focus and track a light spot focused on a disk via the objective lens,
A magnetic yoke is made by sintering iron-based powder material and has a structure in which the optical path part is freed, and a magnetic yoke is made by molding a resin containing a magnetic material and then magnetized and has a structure in which the optical path part is free. and a coil fixed to the lens holder so as to be inserted into a magnetic gap formed by the magnetic yoke and the permanent magnet.