JPS6398847A - Objective lens driver - Google Patents

Abstract

PURPOSE:To widen the operating range in which a prescribed force functions on a lens support member and the operating range of tracking by providing a circular-arc shaped notch corresponding to a circular-arc shaped magnet on a part close to the circular-arc shaped magnet of an iron core of an electro magnet. CONSTITUTION:The circular-arc shaped notch 14 is formed to a part 13 closest to the circular-arc magnet 4 in the assembled state. Then a tracking coil 8 is provided on the iron core 12 and a spacer 15 and a focusing coil 7 is provided so as to be orthogonal to the tracking coil 8 to constitute an electromagnet 16. Thus, in the assembled state, the in the iron core 12 of the electromagnet 16, the forming face of the circular-arc shaped notch 4 is opposed to the circular-arc magnet 4 via a spacer 15, and the magnetic field by the tracking coil 8 is generated along the operating locus of the circular-arc magnet 4 and a force exerted to the magnet 4 is made nearly constant even when the lens support 3 is turned around the rotary shaft 2.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an objective lens drive Sm of an optical pickup used in an optical disc player or the like.

Conventional technology> Conventionally, a generally used objective lens driving device uses a bobbin as a lens support member, and winds a single force sing coil and a tracking coil 7 around this bobbin, and this is fixed to a frame using a pair of magnets. M placed between
Many of them are C-type, but this structure requires wiring to supply electricity to the moving coil, which complicates the structure and makes assembly work more complicated.

Therefore, an MM type as shown in FIG. 3 has been proposed. That is, the rotating shaft 2 is provided inside the frame 1,
A lens support member 3 made of a non-magnetic material is rotatably attached to this, and a pair of arc-shaped magnets 4 and an objective lens 6 fixed to the tip of an arm 5 are attached to this, and focusing coils are arranged perpendicularly to each other. A pair of electromagnets 10 in which a tracking coil 8 and a tracking coil 8 are wound around a substantially rectangular parallelepiped iron core 9 are respectively arranged on the outer periphery of the lens support member 3 in correspondence with the arcuate magnets 4.

The axis of the focusing coil 7 is parallel to the rotational axis 2, and the axis of the tracking coil 8 is parallel to the tangent line touching the outer periphery of the arcuate magnet 4. With the above structure, by energizing the tracking coil 8, the lens support member 3 rotates around the rotational axis 2, and by energizing the focusing coil 7, the lens support member 3 is parallel to the rotational axis 2. Move to.

By these operations, the beam of laser light passing through the objective lens 6 is accurately positioned on the track so that the signal on the recording medium can be accurately read, and focusing is performed.

<Problems to be Solved by the Invention> In the structure shown in FIG.
The part that creates the strongest magnetic field is a flat surface. On the other hand, since the magnet 4 has an arc shape and rotates along the arc, the distance between the magnet 4 and the iron core 9 changes, causing a difference in the strength of the force acting between them. There was a point where the tracking operating range had to be narrowed.

This invention focuses on such a gap and aims to keep the distance between the magnet and the iron core substantially constant and to make the applied force constant.

<Means for solving the problem of confusion> In order to achieve the above-mentioned object, this invention uses the method shown in FIG.
In the objective lens drive J device having this structure, an arc-shaped notch corresponding to the arc-shaped magnet is provided in a portion of the iron core of the electromagnet that is close to the arc-shaped magnet.

Effect> Since the iron core of the electromagnet is provided with an arcuate notch corresponding to the arcuate magnet, the distance between the magnet and the iron core remains almost constant even if the lens support member rotates. For this reason,
A nearly constant force now acts between the magnet and the iron core, creating a tracking feature! I! It becomes possible to widen the IfL range.

<Example> Next, an example shown in Fig. PpJ1 and Fig. 2 will be described. Note that the same parts as in FIG. 3 are designated by the same reference numerals.

In the figure, reference numeral 12 denotes an iron core, and an arcuate notch 14 is formed in a portion that will be the portion 13 closest to the arcuate magnet 4 in the assembled state. This notch 14 is approximately concentric with the arc of the arc-shaped magnet 4,
A spacer 15 made of a non-magnetic material such as plastic and having the same shape as the cutout 14 is glued to this part, so that the overall shape of the core 12 is the same as the original rectangular parallelepiped before the cutout 14 is formed. It is as it should be. On top of this iron core 12 and spacer 15, a portion close to the magnet 4 is placed on the pongee 2.
A tracking coil 8 is provided as shown in FIG. 2(b), /), and a focusing coil 7 is provided perpendicular to this tracking coil 8, as shown in FIG. An electromagnet 16 as shown in (c) is configured.

Therefore, in the assembled state as shown in FIG.
The iron core 12 has a circular arc notch through the spacer 15.
The formed surface of the curved portion 14 is in a state opposite to the arc-shaped magnet 4, a magnetic field by the tracking coil 8 is generated along the operating locus of the arc-shaped magnet 4, and the lens support member 3 rotates around the rotating cylindrical member 2. Even if the magnet 4 moves, the force acting on the magnet 4 remains almost constant. *In addition, a spacer 15 of the same shape made of a non-magnetic material is adhered to the arc-shaped notch 14, and the overall shape of the iron core 12 is a rectangular parallelepiped, so the work of winding the coil is similar to that of the conventional rectangular parallelepiped iron core 9. This can be done in exactly the same manner as in the case, and the provision of the arc-shaped notch 14 does not interfere with the wire winding work.

<Effects of the Invention> As is clear from the above-mentioned embodiments, an arc-shaped notch corresponding to the arc-shaped magnet is provided in the core of the electromagnet, and even when the lens support member rotates, the magnet and the core are not connected to each other. The distance is kept almost constant.

Therefore, when the lens support member rotates, the range in which a constant force acts on the lens support member becomes wider than in the conventional example, making it possible to obtain an objective lens drive device with a wide tracking operation range and good performance. Yes, and the iron core is Rf
There is also the advantage that the entire pickup can be made lighter by adopting an i version. In addition, if a spacer is provided in the arc-shaped notch of the iron core as in the embodiment, it is possible to work on the 8-parallel wire of the coil with the same workability as in the past.

[Brief explanation of the drawing]

Figure Ii is a bottom view of one embodiment of this invention, Figure 2 (,)
FIGS. 2(c) to 2(c) are perspective views of essential parts of the same, respectively, and FIG. 3 is a plan view of the conventional example. 2... Rotating shaft, 3... Lens support member 4
...Arc-shaped magnet, 6...Objective lens 7...
Focusing coil, 8... Tracking coil, 12... Iron core 13
...The part 14 closest to the arcuate magnet...
Arc-shaped notch, 15... Spacer 16... Electromagnet

Claims (1)

[Claims] 1. A lens supporting member including an arc-shaped magnet centered on a rotation axis and an objective lens fixed to the tip of an arm is rotatably supported, and a focusing coil and a tracking coil are connected to the lens supporting member. In the objective lens driving device, a substantially upright electromagnet is disposed on the outer periphery of the lens support member in correspondence with the arc-shaped magnet, and the arc-shaped magnet is arranged in a portion of the iron core of the electromagnet near the arc-shaped magnet. An objective lens driving device characterized by having a corresponding arcuate notch. 2. Claim 1, in which a non-magnetic member is arranged in the arc-shaped notch of the iron core so as to have the original upright shape, and a focusing coil and a tracking coil are provided thereon.
The objective lens driving device described in .