JP2698098B2 - Actuator for optical head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an optical head actuator for driving an objective lens in an optical head in both focusing and tracking directions.

<Prior Art> Various actuators for driving an objective lens of an optical head used in an optical disk drive or the like have been proposed. For example, Japanese Patent Application Laid-Open No. 61-271632 discloses an actuator in which an objective lens is provided with respect to a guide shaft. Holder supported at the free end,
A focusing drive coil wound around the outer periphery of a cylindrical coil bobbin that is fitted so as to be rotatable around the axis and slidable in the axial direction, and is integral with the holding body, and a tracking coil attached to the coil. A shaft-sliding actuator that drives a holding body in both focusing and tracking directions by magnetic action between a drive coil and a fixed magnetic unit such as a permanent magnet corresponding to both drive coils is disclosed.

According to the above structure, four rectangular driving coils for tracking are arranged symmetrically with respect to the axis, and a pair of fixed magnetic units including a yoke and a magnet sandwich the guide shaft. And one side of each coil is arranged in the magnetic gap of each fixed magnetic unit. In such an actuator, when a current flows through the coil, a current flows through one side of the coil located in the magnetic gap, thereby generating a driving force due to a magnetic action, thereby causing the guide shaft to rotate around the guide shaft. Then, the holder rotates, and the objective lens supported by the free end can be driven in the tracking direction.

However, since the driving force due to the magnetic action is generated only on one side of the coil, the driving efficiency is poor.
If a plurality of coils are provided in order to obtain a large driving force, there is a problem that positioning must be performed with high accuracy to balance the respective coils, and that wiring becomes complicated and assembly workability becomes complicated.

<Problems to be Solved by the Invention> In view of such problems of the related art, a main object of the present invention is to provide an optical head actuator capable of improving drive efficiency by a drive coil and improving assembly workability. To provide.

[Constitution of the Invention] <Means for Solving the Problems> According to the present invention, an objective lens in an optical head is supported at a free end, and an axial direction and a rotation are provided by a guide shaft. A first magnetic means provided on the holder to generate a driving force in the rotating direction; and a first magnetic means provided on the holder to generate the driving force in the axial direction. Optical head actuator having a second magnetic means, a first fixed magnetic unit for supplying a magnetic flux to the first magnetic means, and a second fixed magnetic unit for supplying a magnetic flux to the second magnetic means Wherein the first magnetic means comprises one annular coil provided on an outer peripheral surface of the holding body, and the first magnetic means is provided between the first magnetic means of the holding body and a rotation center in the axial direction. A through hole is formed through the A pair of permanent magnets disposed adjacent to each other so as to generate magnetic fluxes in directions opposite to each other corresponding to the two sections of the first magnetic means opposed to each other, and A yoke opposed to the permanent magnet so as to sandwich the first magnetic means, wherein the permanent magnet and the yoke of the first fixed magnetic unit are arranged so that the first magnet extends over the entire movable range of the holder.
The present invention is attained by providing an actuator for an optical head, wherein the magnetic means extends so as to sandwich the two opposed sections.

<Operation> With this configuration, the two sections of the annular coil always cross the magnetic fluxes in different directions generated by the pair of permanent magnets and the yoke over the entire movable range of the holding body, so that the two sections are mutually separated. When the currents flow in opposite directions, the holding member can be efficiently driven in the rotation direction with the same driving force generated by the magnetic action in the two sections.

Embodiments Hereinafter, the present invention will be described in detail with reference to the accompanying drawings with reference to specific embodiments.

FIG. 1 shows a configuration of an optical head actuator according to the present invention. A guide shaft 2 that functions as a part of a yoke 3 described later is provided upright at a central portion on the base member 1 having a substantially plate shape. A U-shaped yoke 3 is provided at the lower end of the guide shaft 2 so as to extend to the right and left sides and then to the upper side. A pair of permanent magnets 4 and 5 constituting the fixed magnetic unit are fixed. A yoke 6 having a fan shape centering on the guide shaft 2 is provided at one end of the base member 1 in the longitudinal direction. As shown in FIG. 3, the yoke 6 has an arc-shaped groove 7 extending substantially in the left-right direction, so that the yoke 6 has a U-shaped side surface. A pair of permanent magnets 8 and 9 having a shape substantially complementary to the groove 7 to form a first fixed magnetic unit together with the yoke 6 are provided on the inner surface of the groove 7 facing the guide shaft 2 side. Adjacently fixed.

A mirror member 10 having a mirror surface 10a inclined outward at an angle of about 45 degrees is fixed to an end of the base member 1 opposite to the yoke 6 about the guide shaft 2.

On the left and right sides of the base member 1, four band-shaped spring bodies 11 made of silicone rubber are provided so as to engage with protruding pieces 12a provided on the side surface of the holding body 12 described later.

The guide shaft 2 is inserted into a bearing hole 14 formed in the center of the holder 12 so as to penetrate the holder in the vertical direction.
12 is supported rotatably around the axis of the guide shaft 2 and slidably in the axial direction. A cylindrical portion 13 coaxial with the bearing hole 14 is provided at the lower center portion of the holding member 12 so as to protrude downward, and a second magnetic means wound annularly on the lower end surface of the cylindrical portion 13. Drive coil for focusing
15 is superposed so as to surround the guide shaft 2. A predetermined gap is formed between the inner peripheral surface of the focusing drive coil 15 and the guide shaft 2.

The yoke 6 of the holding member 12 formed so as to form an arc surface concentric with the bearing hole 14 is provided on the side end surface, that is, the right end surface (outer peripheral surface) in FIG. One tracking drive coil 18 as the first magnetic means wound around is attached. A bearing hole 14 is provided between the tracking drive coil 18 of the holder 12 and the bearing hole 14.
Through hole 20 which is parallel to the axis of
Are formed. The through hole 20 has a front portion of the yoke 6.
6a penetrates.

The tracking drive coil 18 formed of a substantially rectangular annular coil is provided such that a pair of sections 18a and 18b facing each other are orthogonal to the rotation direction. On the other hand, the permanent magnets 8 and 9 for tracking use
As shown in FIG. 3, the magnetic flux penetrates the opposing sections 18a and 18b of the drive coil 18 in opposite directions so as to generate magnetic fluxes in mutually opposite directions. ing. Here, as shown in FIG. 3, the permanent magnets 8 and 9 and the front portion 6a of the yoke 6 always form a pair of sections 18a and 18b of the tracking drive coil 18 throughout the movable range of the holder 12. It extends so as to sandwich it.

At the other end of the holder 12 in the longitudinal direction, that is, at the end on the side of the mirror member 10, a cylindrical supporting portion 17 for supporting the objective lens 16 is provided.
Is provided. Incidentally, the objective lens 16 is a convex lens,
It may be integrally molded with a transparent synthetic resin together with a cylindrical frame portion.

 The operation of the present embodiment will be described below.

As shown in FIG. 1, a magnetic flux formed in a magnetic gap between the guide shaft 2 as a core and the focusing permanent magnets 4 and 5 forms a focusing drive coil 15.
Through the holding member 12 by appropriately adjusting the direction and intensity of the current supplied to the drive coil.
Can be controlled in the axial direction of the guide shaft 2 (focusing direction).

On the other hand, the two sections 18 of the tracking drive coil 18
As described above, since the magnetic fluxes in the opposite directions always penetrate through the permanent magnets 8 and 9 for tracking and the front portion 6a of the yoke 6 as described above, it is necessary to supply the current to the drive coil 18. Accordingly, when currents in opposite directions flow through the sections 18a and 18b, a driving force in the same direction is generated in both sections 18a and 18b by magnetic action. Therefore,
In the case where a driving force generated only in one section of the coil is used, not only a single driving coil 18 can provide a sufficient driving force, but also the tracking force can be constantly obtained over the entire movable range of the holder 12. A pair of sections 18 of the drive coil 18
a, 18b, so that the holding body 12 extends
For example, a driving force can be efficiently generated at any position, for example, when moving in the axial direction or when already rotating. As described above, by appropriately adjusting the direction and intensity of the current supplied to the drive coil 18, the drive of the holder 12 can be controlled around the axis (tracking direction).

In this embodiment, one of the tracking drive coils 18 is used.
Since only one coil is used, there is no difference in the balance due to the individual difference of the coil when a plurality of coils are used. Also, since only one mounting space for the coil is required, the actuator can be reduced in size and weight.
In addition, since the manufacturing cost can be reduced and the rigidity can be increased by simplifying the shape, the natural frequency can be increased, and the drive sensitivity can be improved.

[Effects of the Invention] According to the present invention, as described above, the two opposing sections of the annular coil provided on the holder generate magnetic fluxes in different directions generated by the pair of permanent magnets and the yoke depending on the position of the holder. Since current always flows efficiently in opposite directions in the two opposing sections, the holding body can be efficiently driven in the turning direction with the same driving force generated in the two opposing sections. Therefore, the useless portion of the annular coil can be reduced as much as possible, the driving efficiency can be improved, and a constant driving force can be always obtained over the entire movable range of the holder, and the control thereof can be facilitated.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a configuration of an optical head actuator according to the present invention. FIG. 2 is a side sectional view of FIG. FIG. 3 is a plan view showing a main part of FIG. 1 Base member 2 Guide shaft 3 Yoke 4.5 Permanent magnet 6 Yoke 6a Front part 8.9 Permanent magnet 10 Mirror member 10a Mirror surface 11 Spring Member 12 Holder 12a Protruding piece 13 Cylindrical part 14 Bearing hole 15 Focusing drive coil 16 Objective lens 17 Lens holder 18 Tracking drive coil 18a / 18b … Section 20… Through hole

Claims (1)

(57) [Claims] An objective lens in an optical head is supported at a free end and supported by a guide shaft in an axial direction and a rotating direction, and a holder for generating a driving force in the rotating direction. A first magnetic unit provided on the holder, a second magnetic unit provided on the holder for generating a driving force in the axial direction, and a second magnetic unit for supplying a magnetic flux to the first magnetic unit. An optical head actuator comprising: a first fixed magnetic unit; and a second fixed magnetic unit that supplies a magnetic flux to the second magnetic means, wherein the first magnetic means is provided on an outer peripheral surface of the holder. A through-hole is formed between the first magnetic means and the rotation center of the holding body, the through-hole penetrating in the axial direction, and the first fixed magnetic unit comprises Two magnetic means facing each other A pair of permanent magnets arranged adjacent to each other so as to generate magnetic fluxes in directions opposite to each other corresponding to the section, and a yoke facing the permanent magnet so as to penetrate the through hole and sandwich the first magnetic means. Wherein the permanent magnet and the yoke of the first fixed magnetic unit extend so as to sandwich the two opposed sections of the first magnetic means over the entire movable range of the holder. An optical head actuator characterized by the above-mentioned.