JPS6218631A - Objective lens driving device for optical disc device - Google Patents

Abstract

PURPOSE:To reduce the number of parts to make a device small-sized and light-weight by forming a yoke into a shape corresponding to outward shapes of a focusing-direction control coil and a tracking-direction control coil which the yoke faces. CONSTITUTION:An outside yoke 16 facing coils 6 and 7 has a part 161 facing a focusing-direction control coil 6 and a part 162 facing a tracking-direction control coil 7, and the part 162 is depressed by an extent by which the tracking- direction control coil 7 is projected from the focusing-direction control coil 6, namely, the thickness of the tracking-direction control coil 7. Thus, the gap between the outside yoke 16 and coils 6 and 7 is made smaller as the whole to reduce the magnetic resistance to the focusing-direction control coil 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an objective lens driving device for an optical disc device such as an optical disc playback device or a recording/playback device.

[Conventional technology]

FIG. 4 is a plan view showing the cover of a conventional objective lens drive device, FIG. 5 is a sectional view taken along the line V--V in FIG. 4, and FIG. 6 is the line ■-■ in FIG. FIG.

In the figure, (1) is the main body frame of the objective lens driving device, and (2) is the cover. (3) is the main body frame (1
), (4) is a disk (not shown)
(5) is an objective lens holding member that supports the objective lens (4) so that its optical axis is parallel to the support shaft (3) in the axial direction of the support shaft (3). It is mounted slidably and rotatably around the support shaft (3). (6) is a focal direction control coil wound around a coil bobbin (8) formed on the outer periphery of the objective lens holding member (5); (7) is a tracking direction control coil fixed thereon; 9) is the main body frame (1)
(10) is the inner yoke, (11) is the yoke (
9), (10) and a focal direction control permanent magnet forming a magnetic circuit through the focal direction control coil (6);
A gap (G) is provided between the outer yoke (9) and the inner yoke (10), and a coil bobbin (on which the focal direction control coil (6) is wound) is provided in this gap (G).
8) is inserted. (12) is a yoke placed opposite to the tracking direction control coil (7), which includes a tracking direction control permanent magnet (13).
are fixed, yoke (12), permanent magnet (13)
A magnetic circuit is formed through the tracking direction control coil (7).

Next, the operation will be explained. First, when a defocus of the optical spot is detected, a current corresponding to the amount of defocus flows through the focal direction control coil (6), which interacts with the magnetic field of the permanent magnet (11), and which in turn affects the objective lens holding member (5). The objective lens (4) is driven in the axial direction of the support shaft (3), and although not shown, the objective lens holding member (5) and the support shaft (3)
) or other fixed portions, the spring is braked and the focus of the objective lens (4) is controlled.

On the other hand, regarding tracking direction control, when a track deviation of the optical spot is detected, a current corresponding to the amount of deviation flows through the tracking direction control coil, interacts with the magnetic field of the tracking direction control permanent magnet (13), and The objective lens (4) is attached to the support shaft (3) together with the lens holding member (5).
), and tracking control is performed by applying spring damping with an elastic member in the same way as focus control.

[Problem that the invention seeks to solve]

The objective lens drive device of a conventional optical disk device is composed of two or more parts, and the permanent magnet and yoke are both separate parts for controlling the focal direction and controlling the tracking direction, reducing the number of parts. There was a problem that the size and weight were large.

The present invention has been made in order to solve the problems of the conventional ones, and it is an object of the present invention to provide an objective lens driving device which has a small number of parts, is small in size, and is light in weight.

[Means for solving problems]

The objective lens drive device according to the present invention uses a permanent magnet and a yoke in common for focal direction control and tracking direction control, and the yoke has a shape corresponding to the outer shape of the focal direction control coil and the tracking direction control coil that the yoke faces. This makes it possible to reduce the gap between the yoke and these coils.

[For production]

According to this invention, by integrating the permanent magnet and the yoke, the number of parts can be reduced, and the gap between the yoke and the coil can be reduced, so that the magnetic resistance can be reduced. [Embodiment of the Invention] An embodiment of the invention will be described below with reference to FIGS. 1 to 3. Fig. 1 is a plan view similar to Fig. 4, Fig. 2 is a sectional view taken along the line -H in Fig. 1, and Fig. 3 is a view of the objective lens holding member from the right or left in Fig. 2 is a side view of the present invention, and since parts (1) to (8) in the figure are the same as those of the prior art described above, their explanations will be omitted. In the figure, (
14) is a permanent magnet common to the focal direction control coil (6) and the tracking control coil (7); (15)
is an inner yoke common to both coils (6) and (7), and (16) is an outer yoke common to both coils (6) and (7). In this example, the outer yoke (1
6) faces the coils (6) and (7). The outer yoke (1°6) has a focal direction control coil (6) (two opposing parts (161)) and a tracking direction control coil (
7), and a portion (162) opposite to the portion (162).
) is recessed by the amount that the tracking direction control coil (7) protrudes from the focal direction control coil (6), that is, by the thickness of the tracking direction control coil (7), and thus the outer yoke (16) and the coil ( 6) and (7) can be made smaller as a whole, and the magnetic resistance to the focal direction control coil (6) can be made smaller.

Next, the operation will be explained. To control the position of the objective lens (4) in the focal direction, a magnetic circuit is formed that passes through the permanent magnet (14), the inner yoke (15), the focal direction control coil (6), and the outer yoke (16). A current corresponding to the amount of defocus is passed through the focus direction control coil (6), which interacts with the magnetic field of the permanent magnet (14) to move the objective lens holding member (5) and therefore the objective lens (4) towards the support shaft ( 3) to eliminate defocus by driving in the axial direction. Regarding the tracking direction, a magnetic circuit is formed that passes through the permanent magnet (14), the inner yoke (1), and the tracking direction control coil (force), and the outer yoke (16). The current flows through the control coil (7) and acts with the magnetic field from the permanent magnet (14) to rotate the objective lens (4) around the axis of the support shaft (3) to eliminate track misalignment.Spring braking is Proceed as before.

In addition, in the above embodiment, the tracking direction control coil (
7) is fixed above the focal direction control coil 6), but it may be provided below. In that case, the tracking direction control coil (force is not exposed to the outer yoke (16), but the focus direction control coil (6) swells in this part, and the outer yoke (16)
It is sufficient if the recessed portions (162) of the two are opposed to each other. Furthermore, the coils (6) and (7) may be provided on the inner peripheral surface of the objective lens holding member (5), in which case the inner yoke (15)
Tracking direction control coil (the part facing the force can be recessed. Alternatively, one of the coils (6) and (7) can be installed on the outer periphery of the objective lens holding member (5), and the other on the inner periphery. Furthermore, the permanent magnet (14) does not have to be located at the bottom of the inner yoke (15), but may be provided at the bottom of the outer yoke (16), for example, at any suitable location forming a magnetic circuit. Just place it.

〔Effect of the invention〕

As described above, according to the present invention, the permanent magnet and yoke are made common to the focal direction control coil and tracking direction control coil, respectively, so the number of parts is reduced and the device can be made smaller and lighter. Become. Moreover, since the yoke is recessed at the portion facing the tracking direction control coil so that the yoke as a whole can be placed close to the coil, the magnetic resistance is small and a large driving force can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a cover of an embodiment of the present invention, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, and FIG.
The figure is a side view of the objective lens holding member in the embodiment shown in Fig. 1, Fig. 4 is a plan view similar to Fig. 1 of the conventional objective lens drive device, and Fig. 5 is along the line ■-■ in Fig. 4. A cross-sectional view along
FIG. 6 is a sectional view taken along line M-Vl in FIG. 4. In the figure, (1) is the main body frame, (3) is the support shaft,
(4) is an objective lens, (5) is an objective lens holding member, (
6) is a focal direction control coil, (7) is a tracking direction control coil, (14) is a permanent magnet, (16) is an outer yoke, and (162) is a recessed portion of the outer yoke (16). Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Patent Attorney Masuo Oiwa $1 Figure 2 Figure 3 Figure 4 Room

Claims (1)

[Claims] (1) An objective lens that forms a light spot on the disk;
A support shaft fixed to the main body frame is provided to be slidable in the axial direction of the support shaft and rotatable around the support shaft, and the objective lens is arranged so that its optical axis is parallel to the support shaft. an objective lens holding member supported by the objective lens holding member; a focal direction control coil and a tracking direction control coil provided on the objective lens holding member; A yoke and a permanent magnet are arranged to face these coils so as to form a circuit, and a current corresponding to the focal deviation of the optical spot is passed through the focal direction control coil, and a current corresponding to the deviation in the tracking direction is passed through the coil. In the objective lens drive device for an optical disk device, the permanent magnet and the yoke are connected to the focusing direction control coil and the tracking direction control coil in order to control the position of the objective lens in the focal direction and the tracking direction. The yoke is formed to be common to the tracking direction control coil, and the yoke is recessed only in the portion facing the tracking direction control coil, so that the overall gap between the two coils can be reduced. An objective lens drive device for an optical disc device, characterized in that: