JPH079707B2 - Objective lens drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device used in an optical disc device, and more particularly to a two-dimensional objective lens driving device that is small and has excellent responsiveness.

[Background of the Invention]

As an objective lens driving device, for example, as shown in Japanese Patent Laid-Open No. 60-43232, an objective lens is provided on a rotating arm so as to be separated from a support shaft, and the rotating arm is provided with a drive (focusing) means in a support shaft direction. Rotation direction drive (tracking)
It is known that the means are arranged. In this device, a large driving torque in the rotation direction is obtained by applying a driving force to the end of the rotation arm, and the rotation direction drive means can be downsized. However, in this device, the force in the direction of the driving force applied to the end portion of the rotating arm is not balanced with respect to the support shaft, so the rotating arm is driven by the above-mentioned slight clearance between the support shaft and the cylindrical portion of the rotating arm. Move straight in the direction of force. for that reason,
The displacement of the objective lens is the sum of rotation and rectilinear movement. When a driving force having a frequency matching the resonance frequency of the support shaft is applied to the tip of the rotating arm, the cylindrical portion of the rotating arm collides with the support shaft at that frequency, and the support shaft resonates. Therefore, the amplitude of the rectilinear movement of the rotating arm increases and the phase changes. As a result, the amplitude and phase of the displacement of the objective lens in the tracking direction are only rotated, and there are cases where normal control cannot be performed, which is different from the case where the objective lens is displaced in the tracking direction.

[Object of the Invention]

An object of the present invention is to provide an objective lens driving device which also serves as a balancer for the objective lens and which is provided with a rotation direction driving means that does not apply a force to the support shaft.

[Outline of Invention]

A feature of the present invention is that a support shaft is provided on a base plate, an objective lens holder is slidably and rotatably provided on the support shaft, and an objective lens is provided at one end of the objective lens holder. In the objective lens driving device, the holding body is provided with a rotation direction driving coil for rotating the holding body about the support shaft and an axial direction driving coil for moving the support body in the axial direction of the support shaft. The axial direction driving coil is provided on the objective lens holding body so as to be positioned around the support shaft, and the rotation direction driving coil is provided on the other side of the objective lens holding body. The yoke is provided on the base plate so as to face the side portions of the rotation direction driving coil and the magnet is provided inside the yoke.

With this configuration, the rotation direction drive coils are provided on the side portions of the other end of the objective lens holder,
Since the structure of the other end side of the objective lens holder can be made lighter and the rotating direction drive coils can generate forces of opposite directions and of equal magnitude, high speed responsiveness can be realized and positioning accuracy can be improved. Can be improved.

Example of Invention

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

1 is an exploded perspective view and FIG. 2 is a front view. In FIG. 1 and FIG. 2, the objective lens 1 is inserted and fixed to one end of the objective lens holder 2. The objective lens holder 2 is made of a lightweight and highly rigid non-magnetic material such as aluminum.
A bearing 3 is fixed to the objective lens holder 2. The bearing 3 forms a sliding portion with a support shaft 11 which will be described later, and is formed by processing a lightweight and highly rigid non-magnetic material. The axial driving coil 6 is fixed to the objective lens holding body 2 after being fixed to the coil holders 4 and 5 with the bearing 3 as the winding center. The rotation direction drive coils 7 and 8 are provided on the side opposite to the objective lens 1 with respect to the bearing 3 and at positions spaced apart from each other around the objective lens holder in the tracking direction, and have high rigidity such as polycarbonate at the center of the winding. After fixing the coil cores 9 and 10 formed of a non-magnetic material having the above-mentioned structure, the coil cores 9 and 10 are fixedly formed on the objective lens holder 2.

A support shaft 11 is vertically press-fitted and fixed to a base plate 17 made of a magnetic material such as iron. The support shaft 11 is formed by processing the same material as the bearing 3 described above, and is coated with a resin having a low friction coefficient on the sliding surface. Further, on the base plate 17, the yokes 12 and 13 forming the axial direction driving magnetic gear cups and the yoke forming the rotation direction driving magnetic gear cups.
14 is fixed.

Further, the yokes 15 and 16 which are commonly used for the axial drive and the rotational drive are formed by bending both sides of the base plate 17. Magnets 18 and 19 are fixed to the upper portions of these yokes 15 and 16, respectively. The yokes 15 and 16 described above may not be integrally formed with the base plate 17, but may be fixed to the base plate 17 later as separate parts.

The above-mentioned yoke 15 of the magnet 18 and the yoke 16 of the magnet 19 form magnetic gears 30 and 31, respectively, and the rotational direction drive coils 7 and 8 are respectively inserted into the magnetic gears 30 and 31. To be done.

The rotation direction driving coils 7 and 8 also serve as counterweights for the objective lens 1, and thus are provided on the opposite side of the objective lens 1 with respect to the bearing 3. Further, the rotation direction driving coils 7 and 8 are provided on a line perpendicular to the line connecting the objective lens 1 and the bearing 3. Next, the principle of driving in the rotation direction in the embodiment shown in FIGS. 1 and 2 will be described.
The electromagnetic force F1 generated in the rotation direction driving coils 7 and 8 and
Rotational direction driving coils 7 and 8 so that F2 is in the opposite direction
When a current is passed through, the electromagnetic forces F1 and F2 become a couple, and the objective lens 1 is rotated in the direction T. Since the electromagnetic forces F1 and F2 have the same magnitude and opposite directions, no force in the straight traveling direction is generated, and if the center of gravity of the movable portion is made to coincide with the center of the bearing 3, the movable portion will not move. It rotates around the center of the shaft and no force is generated between the bearing 3 and the support shaft 11. The rotation direction driving coils 7 and 8 do not need to be provided with a counterweight for the objective lens 1 separately, the weight of the movable portion is reduced, and the acceleration per unit current is increased in both the axial direction and the rotation direction.
In addition, since the dimension in the direction connecting the center of the objective lens 1 and the bearing 3 is also reduced, the rigidity is increased, and the directions generated by the alternating currents of the axial drive coil 6 and the rotational drive coils 7 and 8 are respectively generated. It is possible to reduce the amplitude of the high frequency vibration of. Therefore, the positioning control can be performed up to a high frequency, and the positioning accuracy in the focusing direction and the tracking direction is improved.

In this embodiment, the yokes 15 and 16 and the magnets 18 and 19 are integrated for driving in the axial direction and for driving in the rotating direction, which has the effect of improving the efficiency of the magnetic circuit and reducing the assembly and processing costs.

Further, in this embodiment, the direction of the force applied to the rotation direction driving coils 7 and 8 is perpendicular to the moving direction of the objective lens 1. Even if the forces generated in the rotation direction drive coils 7 and 8 are unbalanced, the force in the rectilinear direction acting on the movable portion is perpendicular to the tracking direction of the objective lens 1, and therefore the position of the objective lens 1 in the tracking direction is set. It has the effect of not affecting control.

〔The invention's effect〕

As described above, according to the present invention, it is possible to reduce the weight of the structure on the other end side of the objective lens holder, and to generate forces in opposite directions in the rotation direction driving coils that have the same magnitude. Therefore, high-speed response to tracking can be realized, and the positioning accuracy can be improved.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an embodiment of the objective lens driving device of the present invention, and FIG. 2 is a front view. 1 ... Objective lens, 2 ... Objective lens holder, 3 ... Bearing, 6 ... Axial drive coil, 7, 8 ... Rotation direction coil, 11 ... Spindle, 12, 13, 14, 15 , 16 …… York, 17 ……
Base plate, 18,19 ... Magnet.

Claims (1)

[Claims] 1. A support shaft is provided on a base plate, an objective lens holder is slidably and rotatably provided on the support shaft, and an objective lens is provided at one end of the objective lens holder. In an objective lens driving device, a body is provided with a rotation direction driving coil for rotating the body about the support shaft, and an axial direction driving coil for moving the support shaft in the axial direction of the support shaft, The axial direction driving coil is provided on the objective lens holder so as to be positioned around the support shaft, and the rotation direction driving coil is partially parallel to the axis line of the support shaft and To the center of the objective lens so as to be symmetrical with respect to a line connecting the center of the objective lens and the other end of the objective lens holding body, and forming a magnetic circuit, the yoke is provided with the axial drive coil and the rotation direction. One of the driving coils Side provided on the respective so as to face the base plate and, on one surface one of said yoke,
Through the yoke and the base plate, a magnetic flux is applied to a part of the axial drive coil to generate an electromagnetic force in the support shaft direction, and a magnetic force is applied to a part of the rotation direction drive coil. An objective lens driving device, characterized in that a magnet is provided to generate an electromagnetic force in the opposite direction.