JPH09106558A - Objective actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a resonance point and improve a disk rotating speed and a head speed by embedding a reinforcing member made of metal in a movable member supported on a base member by springs so that its vertical through hole is nearly surrounded. SOLUTION: An optical head has an objective 1, a movable member 2 which supports the objective 1 by one end support part 2b, the base member 3 which jogs by a driving device, mutually parallel leaf springs 4a and 4b, and 4c and 4d as a spring means which supports the movable member 2 on the base member 3 by the spring at a neutral position so that it can move in a focusing direction and a tracking direction. The vertical through hole 2c is formed in the intermediate part of the main body part 2a of the movable member 2, a focusing coil 5 is stuck closely to the opposite side from the support side of the objective 1, and a couple of right and left tracking coils 6 are stuck on the front end surface of this coil 5. On the base member 3, on the other hand, magnet units 7 and 8 formed of yokes and magnets are stood and while the magnet unit 7 intrudes into the focusing coil 5, the magnet unit 8 intrudes into the front part of the vertical hole 2c where the focusing coil 5 is absent, thereby facing the tracking coil 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens actuator used for an optical disk device, a magneto-optical disk device, and the like.

[0002]

2. Description of the Related Art Conventionally, for example, in an optical disk device or a magneto-optical disk device, an objective lens has been used to accurately condense light on each track of a disk or condense reflected light on a light receiving element. The movable member provided is spring-supported at a neutral position so as to be movable in a focusing direction and a tracking direction with respect to a base member by four leaf springs, and a magnetic actuator including a focusing coil, a tracking coil, and a magnet is provided. An optical head for driving and controlling the movable member is known, but an unnecessary vibration mode in a spring system for holding the movable member,
The problem is the inclination of the objective lens with respect to the optical axis in the low frequency range. Generally, these can be reduced by making the action point position of the inertia force of the movable portion coincide with the action point position of the coil driving force and the restoring force of the spring as much as possible.
As disclosed in Japanese Patent No. 437, a structure in which the shape of the movable member and the coil mounting position are symmetrical with respect to the optical axis of the objective lens is known.

However, in this structure, since it is difficult to reduce the size and weight, it is necessary to have a structure in which the movable member shape and the coil mounting position are asymmetric with respect to the optical axis of the objective lens.

A movable member for supporting an objective lens in such an optical head is disclosed in, for example, JP-A-6-3253.
As disclosed in Japanese Patent Application Publication No. 87-87, a main body portion provided with relatively large vertical through holes for loosely inserting a core erected on a base member, and a main body portion extending from the main body portion in a direction orthogonal to a focusing direction. There is a type that includes a projecting support piece of an objective lens and holds a focusing coil and a tracking coil in vertical holes of the main body.

On the other hand, in recent years, it has been desired to improve the disk rotation speed and the head speed of the above-mentioned optical disk device and magneto-optical disk device to increase the access speed. At that time, since vibration of the floating-supported movable member poses a problem, in order to improve the rigidity of the movable member and shift the resonance point to a high frequency band, conventionally, about 30% of glass fiber was contained. The resin-made movable member made of fiber-reinforced resin is used by injection molding.

[0006]

However, since the movable member of the optical head of the above-mentioned type is not symmetrical with respect to the supporting portion to the base member and a relatively large through hole is formed, the movable member of the movable member is not formed. It is difficult to secure the rigidity and set the point of inertial force application to a desired position, and the resonance point is, for example, 10 kHz to 20 k only by fiber-reinforced resin.
Since the focusing coil and the tracking coil are fixed to each other and to the movable member with an adhesive, the desired frequency band (about 30 kHz) is low.
However, it was difficult to further increase the disk rotation speed and the head speed to speed up the apparatus.

The present invention has been made in view of the above problems of the prior art, and its main purpose is to improve the rigidity of the movable member supporting the objective lens, that is, to increase the resonance point of the disk. The rotation speed and the head speed can be improved, and at the same time, the center of gravity of the movable member is set to a desired position,
Therefore, it is an object of the present invention to provide an objective lens actuator capable of increasing the speed of an optical disk device, a magneto-optical disk device, etc. and supporting a high recording density.

[0008]

According to the present invention, there is provided a base member which is spring-supported at a neutral position so as to be movable in a focusing direction and a tracking direction.
A main body having a vertical through hole for loosely inserting the core erected on the base member, a focusing coil and a tracking coil provided in the vertical through hole, and a direction orthogonal to the focusing direction from the main body. An objective lens actuator having a movable member formed of a supporting piece of the objective lens protrudingly provided in the movable member, wherein a reinforcing member made of metal is embedded in the movable member so as to substantially surround the upper and lower through holes. It is achieved by providing an objective lens actuator characterized by: In particular, a light and highly rigid metal (alloy) such as an aluminum alloy is preferably used as the metal used for the reinforcing member.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view of a main part of an optical head used in an optical disk device or a magneto-optical disk device to which the present invention is applied, and FIG. 2 is a plan view thereof. This optical head includes an objective lens 1 and a support 2 for supporting the objective lens 1 at one end.
The movable member 2 supported by b, the base member 3 that is roughly moved by a drive device (not shown) provided on the apparatus body side, and the movable member 2 can be moved to the base member 3 in the focusing direction and the tracking direction. As described above, it has four leaf springs 4a, 4b, 4c and 4d which are parallel to each other as spring means for supporting the spring in the neutral position. In addition, a vertical through hole 2c is formed in the middle of the main body 2a of the movable member 2.
The focusing coil 5 is attached to the side opposite to the side where the objective lens 1 is supported, and a pair of left and right tracking coils 6 are attached to the front end surface of the focusing coil 5. On the other hand, magnet units 7 and 8 composed of a yoke and a magnet are erected on the base member 3, and one magnet unit 7 protrudes into the focusing coil 5,
The other magnet unit 8 projects into the front portion of the upper and lower through holes 2c where the focusing coil 5 is absent, and faces the tracking coil 6.

Here, as also shown in FIG. 2, the movable member 2 formed by injection molding of glass fiber reinforced resin is reinforced with an irregular cross section made of an aluminum alloy so as to surround the upper and lower through holes 2c. The member 9 is embedded in the lower part by insert molding. The reinforcing member 9 has C-shaped reinforcing pieces facing each other so as to surround the upper and lower through holes 2c. By embedding this reinforcing member, the weight of only 4.6% is increased and the resonance point is 10 kHz conventionally.
In the case of this example, f was in the range of
1 = 28.0 kHz, f2 = 32.2 kHz, f3 = 3
The frequency could be increased to 4.0 kHz and f4 = 35.6 kHz, and the center of gravity of the movable member could be set at a desired position. In practice, an annular reinforcing member may be used, and as the material thereof, a known metal or ceramic material having high rigidity and lightweight can be arbitrarily selected and used. Further, in order to improve the rigidity of the movable member 2, the reinforcing member 9 can be formed into a split bobbin shape shown in FIG. 3, and a coil wound around the reinforcing member 9 can be inserted into the movable member in the insert mode. Further, the reinforcing member 9 may be assembled with an adhesive or the like after the molding, instead of the insert molding.

Of the four leaf springs 4a, 4b, 4c, 4d, one end of the lower leaf spring 4a, 4b is bonded to a pair of flanges 2d projecting in the tracking direction below the movable member 2, One end of each of the upper leaf springs 4c and 4d has a movable member 2
Is adhered to the upper end surface. Each leaf spring 4a, 4b, 4
The other ends of c and 4d are adhered by grooves 3c and 3d of a back plate 3a which is erected on the base member 3, and these grooves 3c and 3d are attached.
A known damper agent is filled and cured in d. still,
Each leaf spring 4a, 4b, 4c, 4d also serves as a wiring for electrically connecting the focusing coil 5 and the tracking coil 6 to a power source via an external control device (not shown).

When viewed from above in the focusing direction, the lower leaf springs 4a and 4b are offset outward so as not to overlap each other with respect to the upper leaf springs 4c and 4d. Thereby, each leaf spring 4a, 4b, 4c,
4d can be attached so as not to interfere with each other from the upper side in the focusing direction, and the adhesive can be simultaneously cured by irradiating ultraviolet rays from one direction.

[0014]

As is apparent from the above description, according to the objective lens actuator of the present invention, the reinforcing member made of metal is provided on the movable member supported by the spring on the base member so as to substantially surround the upper and lower through holes. By embedding, the center of gravity of the movable member that supports the objective lens can be set to a desired position, and at the same time, rigidity can be improved, that is, the resonance point can be increased to improve the disk rotation speed and the head speed,
It is possible to increase the speed of an optical disk device, a magneto-optical disk device, or the like, and when a bobbin-shaped reinforcing member wound with a coil is insert-molded on a movable member, the effect is more remarkable.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of an optical head used in an optical disk device, a magneto-optical disk device, or the like to which the present invention is applied.

FIG. 2 is a plan view of FIG. 1;

FIG. 3A is a perspective view showing an application example of a reinforcing member used in the present invention, and FIG. 3B is a plan view of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Objective lens 2 Movable member 2a Body part 2b Support part 2c Vertical through hole 2d Flange 3 Base member 3a Back plate 3c, 3d groove 4a, 4b, 4c, 4d Leaf spring 5 Focusing coil 6 Tracking coil 7, 8 Magnet unit 9 Reinforcement Element

Claims (4)

[Claims] 1. A vertical through hole for spring-supporting a base member in a neutral position so as to be movable in a focusing direction and a tracking direction, and a core vertically installed in the base member, and an inside of the vertical through hole. A main body having a focusing coil and a tracking coil provided in
An objective lens actuator having a movable member composed of a support piece of the objective lens projecting from the main body in a direction orthogonal to the focusing direction, the reinforcing member being made of metal so as to substantially surround the vertical through hole. Is embedded in the movable member, the objective lens actuator. 2. The objective lens actuator according to claim 1, wherein the reinforcing member has an irregular cross section. 3. The objective lens actuator according to claim 1, wherein the reinforcing member also serves as a bobbin for a coil. 4. The objective lens actuator according to claim 1, wherein a center of gravity of the objective lens actuator is set at a desired position by adjusting a weight of the reinforcing member.