JP2006351068A - Optical pickup actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup actuator that its lens holder can smoothly slide on the support shaft. <P>SOLUTION: The actuator is composed of a base 1 and a lens holder 2. A support shaft 3 and a pair of permanent magnets 4, 4 with the support shaft 3 in between are erected on the base 1. The lens holder 2 retains the objective lens 5 and is supported free to slide axially and around the support shaft 3 between the permanent magnets 4, 4. A focusing coil 6 is fixed axially around the support shaft 3 with an adhesive of epoxy resin. The lens holder 2 has a cylinder 22 and a frame 23 concentrically surrounding it. The focusing coil 6 is fitted outside the frame 23, and the support shaft 3 is inserted free to slide into the inner hole of the cylinder 22. Cutouts 23c are formed on a pair of the short sides 23a composing the frame 23. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an optical pickup actuator mounted on an optical pickup device for reproducing and recording information on an optical disc such as a CD or a DVD as an information recording medium.

In the optical pickup device, it is required to focus the laser light emitted from the semiconductor laser on the recording surface of the optical disc with high accuracy through the objective lens. Therefore, an optical pickup actuator (hereinafter simply referred to as “ "Actuator" may be required).

As an actuator, there is a so-called shaft sliding type in which a lens holder holding an objective lens is supported so as to be slidable in an axial direction and a circumferential direction with respect to a support shaft fixed to a base. In this type of actuator, in general, a focus coil and a tracking coil fixed to the lens holder and both sides of the lens holder so that the lens holder is driven by electromagnetic action to perform focus adjustment and tracking adjustment with respect to the objective lens. And a pair of permanent magnets fixed to the base. By applying current to the focusing coil, the lens holder moves while sliding along the support shaft to adjust the focus. On the other hand, by applying current to the tracking coil, the lens is centered on the support shaft. The tracking adjustment is performed by rotating the holder while sliding.

For a conventional specific configuration of such an actuator (see, for example, Patent Document 1),
This will be described with reference to FIGS. FIG. 5 is a top view showing the appearance of a conventional actuator,
6 is a longitudinal sectional view showing the BB cross section of the actuator, FIG. 7 is a bottom view of the lens holder in the actuator, and FIG. 8 is an exploded perspective view of the lens holder as seen from the bottom side. As shown in these drawings, the conventional actuator is mainly composed of a base 1 and a lens holder 2.

The base 1 is fixed to a movable member (not shown) on which a semiconductor laser, an optical system, a photodetector, and the like in the optical pickup device are mounted, and is formed by sheet metal from a metal plate such as stainless steel. On the base 1, a cylindrical support shaft 3 is erected substantially at the center, and a pair of permanent magnets 4, 4 facing each other at a predetermined interval so as to be parallel to the support shaft 3 and sandwiching the support shaft 3. It is erected. Each of the permanent magnets 4, 4 has a protruding piece (the outer surface of which is bent from the base 1 (
It is integrated with the base 1 by being magnetically attached to (not shown). In addition, 1a in FIG. 6 is a through hole through which the laser beam passes.

Subsequently, the lens holder 2 is formed from a resin such as LCP (liquid crystal polymer), and the objective lens 5 is held at one end portion 21 (the right portion in FIGS. 5 to 7). Further, in the center of the lower surface of the lens holder 2, the support shaft 3 on the base 1 is parallel to the optical axis direction of the objective lens 5 (the direction perpendicular to the paper surface in FIGS. 5 and 7 and the vertical direction in FIG. 6). A cylindrical portion 22 having an inner diameter substantially the same as that of the cylindrical portion 22 is formed, and an inner hole of the cylindrical portion 22 passes through the lens holder 2 itself. The support shaft 3 of the base 1 is inserted into the inner hole of the cylindrical portion 22.

In addition, the four protrusions 25 protrude symmetrically from the outer periphery of the cylindrical portion 22 toward the four sides of the lens holder 2. A focusing coil 6 is externally attached to the four protrusions 25 so as to surround these four corners. A gap formed by the inner periphery of the focusing coil 6, the outer periphery of the cylindrical portion 22, and the protrusions 25 is filled with a thermosetting resin, for example, an epoxy resin adhesive, and the adhesive is cured. Thus, the focusing coil 6 is fixed to the lens holder 2. Thus, the focusing coil 6 is coaxial with the cylindrical portion 22.

Further, on both sides of the lens holder 2 outside the focusing coil 6 (upper and lower edge portions extending in the left-right direction in FIGS. 5 and 7), adjacent to the outer periphery of the focusing coil 6, tracking is performed. The coils 7 and 7 are fixed with a thermosetting resin adhesive.

As shown in FIG. 6, at the lower end of the focusing coil 6, a flat plate-like magnetic piece 8 having a substantially rectangular through hole at the center is positioned at the four corners of the through hole by the projections 25. Extrapolated in state. The magnetic piece 8 is also fixed to the lens holder 2 together with the focusing coil 6 by a thermosetting resin adhesive.

With such a configuration, the lens holder 2 has an inner hole of the cylindrical portion 22 inserted into the support shaft 3 of the base 1, and the axial direction with respect to the support shaft 3 between the permanent magnets 4, 4. And it comes to be slidably supported in the circumferential direction. At the same time, the tracking coils 7 and 7 are opposed to the permanent magnets 4 and 4 while the lens holder 2 is kept floating by the action of the magnetic attraction between the magnetic piece 8 and the permanent magnets 4 and 4. Is done. Moreover, in that state, the magnetic piece 8 is made up of the permanent magnets 4, 4.
The magnetic flux from the lens is effectively drawn and a high-density magnetic flux is applied to the focusing coil 6 and the tracking coils 7 and 7 disposed between them, thereby increasing the driving efficiency of the lens holder 2.
Japanese Patent Laid-Open No. 2001-23208

However, in the conventional actuator described above, since the adhesive for fixing the focusing coil 6 is widely present around the cylindrical portion 22, the cylindrical portion 22 is caused to contract by the shrinkage accompanying the hardening of the adhesive. The contraction force was received directly. For this reason, the cylindrical portion 22 may be deformed, which may affect the dimensional accuracy of the inner hole of the cylindrical portion 22. When the dimensional accuracy of the inner hole of the cylindrical portion 22 is deteriorated, smooth sliding with the support shaft 3 is hindered. As a result, the focus adjustment and tracking adjustment are hindered.

Accordingly, the present invention has been made in view of the above problems, and an object thereof is to provide an optical pickup actuator in which a lens holder can smoothly slide with respect to a support shaft.

In order to achieve the above object, an optical pickup actuator according to the present invention includes a base on which a support shaft and a pair of permanent magnets opposed to each other with the support shaft interposed therebetween, and an objective lens, and holds the permanent lens. The focus coil is fixed to the support shaft so as to be slidable in the axial direction and the circumferential direction between the magnets, and is coaxially fixed to the support shaft by an epoxy resin adhesive. A lens holder in which a pair of tracking coils facing each of the permanent magnets is fixed by an epoxy resin adhesive, and the lens holder is disposed in an inner hole. A cylindrical portion into which the support shaft is slidably inserted, and protrudes from the outer periphery of the cylindrical portion toward each of the four directions. There an optical pickup actuator having four projections extrapolated, and the following features. The lens holder surrounds the cylindrical portion coaxially instead of the protrusion, and has a rectangular frame portion into which the focusing coil is extrapolated, and the frame portion faces each permanent magnet. It consists of a pair of short sides and a pair of long sides perpendicular to each short side. Each short side portion is formed with one notch that allows deformation due to curing shrinkage of the adhesive in parallel with the support shaft.

With such a configuration, when the adhesive for fixing the focusing coil contracts as it hardens, the frame part directly receives the contracting force and deforms. At that time, the deformation of the frame portion is allowed flexibly by the cut. If it does so, the contraction force accompanying hardening of an adhesive agent will not be transmitted to a cylindrical part at all, but the dimensional accuracy of the inner hole of the cylindrical part which slides with a spindle will be secured stably.

In addition, an optical pickup actuator according to the present invention for achieving the above object includes a support shaft, a base on which a pair of permanent magnets facing each other with the support shaft interposed therebetween, and an objective lens are held. Between the permanent magnets, the support shaft is supported so as to be slidable in the axial direction and the circumferential direction, and the focusing coil is fixed to the support shaft coaxially by a thermosetting resin adhesive. An optical pickup actuator provided with a lens holder is characterized by the following points. The lens holder includes a cylindrical portion in which the support shaft is slidably inserted into an inner hole, and a rectangular frame portion that surrounds the cylindrical portion coaxially and into which the focusing coil is extrapolated. The frame portion is formed with notches that allow deformation due to curing shrinkage of the adhesive.

With such a configuration, when the adhesive for fixing the focusing coil contracts as it hardens, the frame part directly receives the contracting force and deforms. At that time, the deformation of the frame portion is allowed flexibly by the cut. If it does so, the contraction force accompanying hardening of an adhesive agent will not be transmitted to a cylindrical part at all, but the dimensional accuracy of the inner hole of the cylindrical part which slides with a spindle will be secured stably.

Here, based on practicality, the frame portion is composed of a pair of short side portions respectively opposed to the permanent magnets, and a pair of long side portions perpendicular to the short side portions, and the notch is It is preferable that the short sides are formed in parallel with the support shaft.

Further, it is preferable that a pair of tracking coils facing the respective permanent magnets outside the focusing coil is fixed to the lens holder with an adhesive of a thermosetting resin. The adhesive is preferably an epoxy resin adhesive.

According to the optical pickup actuator of the present invention, since the dimensional accuracy of the inner hole of the cylindrical portion is stably ensured, the inner hole of the cylindrical portion of the lens holder and the support shaft of the base can slide smoothly. As a result, focus adjustment and tracking adjustment can be performed stably.

Hereinafter, an embodiment of an optical pickup actuator of the present invention will be described in detail with reference to the drawings. FIG. 1 is a top view showing an appearance of an actuator according to an embodiment of the present invention, and FIG.
FIG. 3 is a longitudinal sectional view showing the AA cross section of the actuator, FIG. 3 is a bottom view of the lens holder in the actuator, and FIG. 4 is an exploded perspective view of the lens holder as viewed from the bottom surface side. In these drawings, portions having the same names and performing the same functions as those in FIGS. 5 to 8 are denoted by the same reference numerals, and repeated description is appropriately omitted.

In the actuator of the present embodiment, the configuration of the base 1 is the same as that of the conventional actuator, but the configuration of the lens holder 2 is greatly different in the following points.

In the lens holder 2 of the present embodiment, a rectangular frame portion 23 is formed coaxially with the cylindrical portion 22 so as to surround the cylindrical portion 22 instead of the protrusion 25 in the conventional lens holder 2. The outer periphery of the frame portion 23 has substantially the same contour shape as the inner periphery of the focusing coil 6, and a pair of short sides along both sides of the lens holder 2 (in the left-right direction in FIGS. 1 to 3). It has a portion 23a and a pair of long side portions 23b perpendicular to the portion 23a (the vertical direction in FIGS. 1 and 3 and the direction perpendicular to the paper surface in FIG. 2). Here, each short side portion 23a is formed with one cut 23c in parallel with the cylindrical portion 22 (support shaft 3), that is, in the vertical direction.

A focusing coil 6 is extrapolated to the frame portion 23 so as to surround it. The focusing coil 6 is fixed to the frame portion 23, that is, the lens holder 2 by curing the adhesive of a thermosetting resin, for example, an epoxy resin, previously applied to the outer periphery of the frame portion 23. Thus, the focusing coil 6 is coaxial with the cylindrical portion 22.

In such a configuration, when the adhesive for fixing the focusing coil 6 contracts as it hardens, the frame part 23 receives the contracting force directly and deforms. At that time, the deformation of the frame portion 23 is allowed flexibly by the notches 23c. Then, no shrinkage force accompanying the hardening of the adhesive is transmitted to the inner cylindrical portion 22 of the frame portion 23, and the dimensional accuracy of the inner hole of the cylindrical portion 22 that slides with the support shaft 3 is stably secured. The Therefore, the inner hole of the cylindrical portion 22 in the lens holder 2 and the support shaft 3 in the base 1 can slide smoothly, and as a result, focus adjustment and tracking adjustment can be performed stably.

As shown in FIG. 2, at the lower end of the focusing coil 6, there is a flat magnetic piece 8 having a rectangular through hole in the center with the same outline shape as the outer periphery of the frame portion 23. The four corners are extrapolated in a state where they are positioned by the squares of the frame portion 23. The magnetic piece 8 is also fixed to the lens holder 2 together with the focusing coil 6 by a thermosetting resin adhesive.

In addition, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, as long as the deformation of the frame portion 23 due to curing shrinkage of the adhesive can be flexibly allowed, a plurality of cuts 23c may be formed in each short side portion 23a, or may be formed in the long side portion 23b.

The present invention is useful for an optical pickup actuator mounted on an optical pickup device.

It is a top view which shows the external appearance of the actuator of one Embodiment of this invention. It is a longitudinal cross-sectional view which shows the AA cross section of the actuator of FIG. It is a bottom view of the lens holder in the actuator of FIG. It is the disassembled perspective view which looked at the lens holder of FIG. 1 from the lower surface side. It is a top view which shows the external appearance of the conventional actuator. It is a longitudinal cross-sectional view which shows the BB cross section of the actuator of FIG. It is a bottom view of the lens holder in the actuator of FIG. It is the disassembled perspective view which looked at the lens holder of FIG. 5 from the lower surface side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base 2 Lens holder 3 Support shaft 4 Permanent magnet 5 Objective lens 6 Focusing coil 7 Tracking coil 8 Magnetic piece 22 Cylindrical part 23 Frame part 23a Short side part 23b Long side part 23c Notch

Claims (5)

A base on which a support shaft and a pair of permanent magnets facing each other across the support shaft are installed;
The objective lens is held and supported between the permanent magnets so as to be slidable in the axial direction and the circumferential direction between the permanent magnets, and a focusing coil is coaxially bonded to the supporting shaft with an epoxy resin. A pair of tracking coils fixed by an agent and facing each of the permanent magnets outside the focusing coil, and a lens holder fixed by an epoxy resin adhesive, and an optical pickup actuator comprising:
The lens holder is
A cylindrical portion in which the support shaft is slidably inserted into the inner hole;
In the optical pickup actuator having four protrusions protruding from the outer periphery of the cylindrical portion toward each of the four sides, and each of the four corners being extrapolated as the four corners,
The lens holder, instead of the protrusion,
Surrounding the cylindrical portion coaxially, and having a rectangular frame portion into which the focusing coil is extrapolated,
The frame portion is composed of a pair of short side portions respectively facing the permanent magnets, and a pair of long side portions perpendicular to the short side portions,
The optical pick-up actuator, wherein each short side portion is formed with one notch that is parallel to the support shaft to allow deformation due to curing shrinkage of the adhesive. A base on which a support shaft and a pair of permanent magnets facing each other across the support shaft are installed;
An objective lens is held and supported between the permanent magnets so as to be slidable in the axial direction and the circumferential direction between the permanent magnets, and a focusing coil is coaxially formed with respect to the supporting shaft. In an optical pickup actuator provided with a lens holder fixed by an adhesive of
The lens holder is
A cylindrical portion in which the support shaft is slidably inserted into the inner hole;
Surrounding this cylindrical portion coaxially, a rectangular frame portion into which the focusing coil is extrapolated,
Have
The optical pickup actuator, wherein the frame portion is formed with a notch that allows deformation due to curing shrinkage of the adhesive. The frame portion is composed of a pair of short side portions respectively facing the permanent magnets, and a pair of long side portions perpendicular to the short side portions,
The optical pick-up actuator according to claim 2, wherein the cut is formed in each short side portion in parallel with the support shaft. The pair of tracking coils facing the respective permanent magnets outside the focusing coil are fixed to the lens holder by an adhesive of a thermosetting resin. The optical pickup actuator described. The optical pickup actuator according to claim 2, wherein the adhesive is an epoxy resin adhesive.

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