JPH067451Y2 - Optical pickup - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an optical pickup for reproducing or recording an optical disc, and more particularly to a structure of a permanent magnet mounting portion in assembly of a magnet circuit of an actuator portion.

[Conventional technology]

A perspective view of a conventional objective lens actuator base to which a permanent magnet is attached is shown in FIG. 2a, and a sectional view of a magnetic circuit portion is shown in FIG. 2b.

The base 1 of the actuator is composed of a member made of sintered metal or magnetic metal. A pair of a front yoke 2 and a back yoke 3 for forming a magnetic circuit are integrated with the base 1 so as to stand at a right angle to the base 1. A permanent magnet 4 is bonded and fixed to the back yoke 3 on the surface facing the front yoke 2 with a gap 5 between the permanent magnet 4 and the base 1.

The permanent magnet 4 has an S pole on a plane to be bonded and fixed, and a support shaft 8
It has an N pole on an arcuate surface formed by a part of the outer circumference of a circle centered at. The front yoke 2 is also formed of a part of the outer circumference of a circle centered on the support shaft 8 and has a parallel arcuate gap with the permanent magnet 4 to form a parallel magnetic field. The gap 5 provided between the permanent magnet 4 and the base 1 has a function of reducing leakage of magnetic flux from the N pole of the permanent magnet 4 to the base 1 and increasing the magnetic flux density of the parallel magnetic field. A movable portion equipped with an objective lens (not shown) and a coil (not shown) is arranged in the parallel magnetic field, and is movable by a control current supplied to the coil.

By the way, since the permanent magnet 4 must effectively interlink the magnetic flux with the moving coil arranged in the parallel magnetic field,
The fixed position requires accuracy. Therefore, the structure shown in FIGS. 3a and 3b or 4a and 4b is considered as a means for improving the accuracy of the fixed position of the permanent magnet 4.

In the magnetic circuit of the objective lens actuator shown in FIGS. 3A and 3B, a base 6 for positioning the permanent magnet 4 is provided on the base 1 to form a guide for determining the fixed position of the permanent magnet 4.

Further, in the magnetic circuit shown in FIGS. 4A and 4B, in order to make the gap between the permanent magnet 4 and the base 1 constant, the permanent magnet 4 and the base 1 are fixed via a spacer 7 made of a non-magnetic material.

[Problems to be solved by the invention]

However, the above-mentioned magnetic circuit has a problem relating to the attachment of the permanent magnet. In the magnetic circuit described with reference to FIGS. 2A and 2B of the conventional example, since the fixed position of the permanent magnet is not constant, the position of the parallel magnetic field changes and the amount of magnetic flux interlinking with the moving coil changes. Furthermore, a change in the distance of the gap 5 causes a change in the leaked magnetic flux, which changes the magnetic flux density of the parallel magnetic field. Therefore, a large variation occurs in driving the actuator of the objective lens.

In the magnetic circuit of FIGS. 3A and 3B, since the base 6 of the permanent magnet 4 provided on the base 1 is the same magnetic material as the base 1, the N pole and the S pole of the permanent magnet 4 are close to each other and the leakage magnetic flux is increased. However, the magnetic flux density of the parallel magnetic field is reduced.

Further, in the magnetic circuit shown in FIGS. 4A and 4B, the spacer 7 is required although the performance of the magnetic circuit is not deteriorated.
The number of members and the number of man-hours increase, resulting in an increase in cost.

[Means for solving problems]

Therefore, in the present invention, in an optical pickup including a main body and an objective lens actuator having a permanent magnet,
The main body is provided with a convex portion, the actuator base is provided with a hole, the convex portion is penetrated through the hole to project from the actuator base, and the permanent magnet is placed on the top of the projected convex portion. It is characterized by.

[Action]

Therefore, the axial positioning of the support shaft of the permanent magnet can be determined by the height of the protrusion protruding from the hole of the base of the actuator. Further, the main body is often made of a member such as aluminum or plastic for reducing the weight. Since these members are non-magnetic materials, the convex portion formed of the same member does not affect the magnetic circuit.

Therefore, even if a permanent magnet is installed on the convex portion, it can be easily installed at a predetermined position without degrading the performance of the magnetic circuit.
Also, when fastening the actuator base and body,
Since the protrusion is fitted in the hole provided in the base of the actuator, the mounting accuracy is improved and the deviation of the optical axis of the optical system can be prevented.

〔Example〕

 An embodiment according to the present invention will be described below with reference to the drawings.

The same parts as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted.

FIG. 1a is a perspective view showing the structure of an actuator and a main body according to the present invention. Further, FIG. 1b shows a sectional view of a magnetic circuit portion in which the actuator and the main body are fastened, and FIG. 1c shows a front view showing the magnetic circuit configuration of the actuator.

In the figure, two holes 13 are provided in each of the permanent magnets 4 that are adhesively fixed to the pair of back yokes 3 and the base 11 of the actuator that faces each other. The size of this hole 13 is smaller than the thickness of the permanent magnet 4. The distance between the two holes 13 is such that the maximum distance obtained on the outer circumference of the two holes 13 is narrower than the width of the permanent magnet 4.

The main body 12 is made of an aluminum material, and a convex portion 14 corresponding to the hole 13 formed in the actuator base 11 is provided on the surface to be fastened to the actuator base 11. The height of this convex portion 14 is the same as the base 1 of the actuator.
The length is such that it penetrates the hole 13 of No. 1 and serves as a guide for fixing the magnet 4 to a predetermined place by adhesion. Further, the thickness of the convex portion 14 is slightly thinner than the hole 13 of the base 11 of the actuator, and is a thickness that fits with almost no play.

In the optical pickup having these configurations, the convex portion 14 and the hole 13 provided in the base 11 of the actuator are fitted to each other,
The base 11 of the actuator is fixed to the main body 12 using a fastener (not shown).

Next, an adhesive is applied to the back yoke 3, and the magnetized permanent magnet 4 is attracted and fixed to the back yoke 3 by using the convex portion 14 protruding from the hole 13 as a positioning guide.

[Effect of device]

Since the parts are small in size and the attraction force of the permanent magnet is strong, the sticking operation of the permanent magnet takes time to mount the permanent magnet at a predetermined position without being provided with a guide for positioning the permanent magnet, and variations are likely to occur. However, according to the present invention, the position of the permanent magnet that is adhesively fixed to the back yoke of the actuator can be easily and surely set by the above-mentioned positioning guide. Therefore, variations are reduced and workability is improved, so that the quality is stable.

Further, the convex portion used as a guide for installing the permanent magnet is composed of the same member as the main body, and since they are non-magnetic materials, they do not increase the leakage magnetic flux of the magnetic circuit.

Therefore, the drive system can be configured without degrading the performance of the magnetic circuit.

Further, when mounting the actuator on the main body, the projection is fitted in the hole provided in the base of the actuator, so that the mounting accuracy is improved and the deviation of the optical axis of the optical system can be prevented.

[Brief description of drawings]

1a is a perspective view showing an embodiment of the present invention, FIG. 1b is a sectional view of FIG. 1a, FIG. 1c is a front view of FIG.
FIG. A is a perspective view showing a conventional example, FIG. 2b is a sectional view of FIG. 2a, and FIGS. 3a, b, 4a, and b are sectional views and front views showing application examples of the conventional example. Show. 1, 11 Actuator base 2 Front yoke 3 Back yoke 4 Permanent magnet

Claims (1)

[Scope of utility model registration request] 1. A main body made of a non-magnetic material, a plurality of convex portions arranged on an upper surface of the main body, an actuator base having holes through which the convex portions are inserted and fixedly mounted on the upper surface of the main body. An optical pickup comprising: a yoke standing upright from the actuator base; a permanent magnet fixed to a side surface of the yoke; and an objective lens actuator that forms a magnetic circuit with the permanent magnet to obtain a driving force. The part is inserted into the fitting hole provided on the fixed side of the permanent magnet of the yoke and protrudes by a predetermined length, and the permanent magnet is mounted on the end part of the part to position the main body, the actuator and the permanent magnet. An optical pickup characterized by that.