KR100252121B1 - Objective lens actuator for optical pick-up - Google Patents

Abstract

PURPOSE: An objective lens drive unit of an optical pickup is provided to prevent interference between vertical and horizontal movements of a bobbin as well as rolling by improving the structure. CONSTITUTION: A bobbin(10) is set on a base(100), and four take-up portions(10a-10d) are attached to the bobbin with focusing/tracking coils(21,22,31,32). Focusing/tracking magnets(41,42,61,62) and focusing/tracking yokes(51,52,71,72) are mounted in accordance with the focusing/tracking coils. A magnetic field is formed perpendicular to an electric current flowing through each coil by the magnets and yokes. Thereby, an electromagnetic force is formed according to Fleming's left-hand law to drive the bobbin in an X or Y direction. A magnetic fluid is injected between each magnet and coil and between each coil and yoke. The magnetic fluid is a liquid magnetized by a magnetic field and is arranged in the magnetic field depending on magnetic flux distribution. The bobbin is floated from the base(100) by the magnetic fluid. Therefore, rolling and interference between vertical and horizontal movement are inhibited.

Description

Objective lens driving device for optical pickup

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving apparatus for optical pickup, and more particularly, to an objective lens driving apparatus for optical pickup configured to support a bobbin on which an objective lens is mounted by using a magnetic fluid.

In general, an optical pickup apparatus using an optical disk such as a digital video disk player (DVDP) or a compact disk player (CDP) is provided with an optical pickup that scans a light beam to a disk surface through an objective lens and detects a light beam reflected from the disk. It is. In order to reproduce high quality information with such an optical pickup, the optical beam must be precisely focused on the optical disc, and the scanned optical beam must accurately track the track formed on the optical disc. In general, driving the objective lens to adjust the focal length is called focusing, and driving the objective lens to accurately scan the light beam on the track is called tracking. Accordingly, an optical lens driving apparatus for performing the above focusing and tracking operations while driving the objective lens is employed in the optical pickup.

Referring to FIG. 1, which shows a conventional objective lens driving apparatus for an optical pickup, a bobbin 1 mounted with an objective lens 2 has a suspender 5 having elasticity in a holder 3 fixed to a base 4. Is supported by. The bobbin (1) is provided with a focusing coil (6) and a tracking coil (7), the magnetic field formed by the magnet (8) and the inner and outer yokes (9a) (9b) fixed to the base (4) and By interaction, the bobbin 1 is moved up and down (Y-axis direction) or left and right (X-axis direction).

By the way, in the optical pick-up actuator of the above structure, since the bobbin 1 is moved up and down or left and right in a state supported by the suspender 5 which has elastic force, this bobbin 1 is exactly up and down and left and right. Rather than being moved, the suspender 5 is moved as if it is rotated slightly with the holder 3 fixed. Therefore, as the focusing and tracking operation proceeds rapidly, mutual interference between vertical movement and vertical movement occurs so that the bobbin 1 tilts in the θ direction about an axis (z-axis direction) parallel to the suspender 5 ( rolling or r-skew) When this rolling phenomenon occurs, the result is that the axis of the light beam emitted through the objective lens 2 is caused to flow, so that information cannot be read from the correct position of the optical disc.

Accordingly, there is a demand for a new support method that can replace the above-described bobbin support structure by the suspender, and solve the problems of the rolling and the interference of the vertical and horizontal motions as described above.

SUMMARY OF THE INVENTION The present invention has been made in view of the above point, and an object thereof is to provide an optical pickup objective lens driving device having a structural improvement capable of solving problems of rolling and interference of up and down and left and right movements during bobbin movement.

1 is a perspective view showing a conventional objective lens driving device for an optical pickup;

2 is an exploded perspective view showing an objective lens driving device for an optical pickup according to the present invention;

3 is a combined perspective view of the objective lens driving device for the optical pickup shown in FIG.

4 is a cross-sectional view taken along line IV-IV of FIG. 3;

5 is a cross-sectional view taken along the line VV of FIG. 3.

<Description of Symbols for Major Parts of Drawings>

10 ... bobbin 11 ... objective lens

21, 22 ... focusing coil 31, 32 ... tracking coil

41,42,61,62 ... Magnets 51,52,71,72 ... York

80 ... magnetic fluid 100 ... base

The objective lens drive device for optical pickup of the present invention for achieving the above object, the base; A nonmagnetic bobbin mounted with an objective lens and mounted on the base; A focusing coil installed on one side of the bobbin to form an energization path for current for focusing; A tracking coil installed on the other side of the bobbin and forming an energization path for current for tracking; A focusing magnet and a focusing yoke installed on the base to face each other with the focusing coil interposed therebetween to form a magnetic field in a direction perpendicular to the energization direction of the focusing current; A tracking magnet and a tracking yoke installed on the base to face each other with the tracking coil interposed therebetween to form a magnetic field in a direction perpendicular to the energization direction of the tracking current; As a liquid magnetizable by a magnetic field, between the focusing magnet and the focusing coil, between the focusing coil and the focusing yoke, between the tracking magnet and the tracking coil, and between the tracking coil and the tracking yoke, respectively. Injected by the magnetic field, the magnetic field is moved to the strong side to form a deviation of the fluid pressure distribution, by moving the non-magnetic bobbin to a low fluid pressure portion to float and support from the base; magnetic fluid; includes Characterized in that.

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

2 to 5 show an objective lens driving apparatus for an optical pickup according to the present invention.

First, referring to FIG. 2, a bobbin 10 mounted with an objective lens 11 is mounted on a base 100, and a pair of focusing coils 21 and 22 and a tracking coil ( Four winding parts 10a, 10b, 10c, and 10d each of which 31 and 32 are wound are attached. Here, the focusing coils 21 and 22 and the tracking coils 31 and 32 are wound around 90 °, which means that the energization directions for focusing and tracking the bobbin 10 are perpendicular to each other. This is because the progress is made. In addition, the base 100 has four magnets 41, 42, 61, 62 and yoke (corresponding to the pair of focusing coils 21, 22 and tracking coils 31, 32, respectively). 51, 52, 71, and 72 are installed, and each of the magnets 41, 42, 61, 62, and the yoke 51, 52, 71, 72 is each coil 21 22, 31, 32 are installed so as to face each other in pairs. That is, the yoke 51, 52, 71, 72 is the outer yoke 51b, 52b, 71b, 72b positioned outside the bobbin 10, and the coils 21, 22. The inner yoke (51a) (52a) (71a) (72a) is fitted to the space portion in the center (31) (32) is wound, the magnets (41) (42) (61) (62) The inner yoke 51a, 52a, 71a, 72a is provided on the outer yoke 51b, 52b, 71b, 72b. Hereinafter, the magnets 41 and 42 and the yokes 51 and 52 corresponding to the focusing coils 21 and 22 are used as focusing magnets and focusing yokes and the tracking coils 31 and 32. The magnets 61 and 62 and the yokes 71 and 72 corresponding to the tracking magnets will be referred to as tracking magnets and tracking yoke. Each of these coils is formed by the focusing magnets 41 and 42, the focusing yokes 51 and 52, the tracking magnets 61 and 62, and the tracking yokes 71 and 72. The magnetic field is formed in a direction perpendicular to the current flowing through the current flowing through the 21, 22, 31, and 32, thereby generating an electromagnetic force according to Fleming's left-hand law, which causes the bobbin 10 to move in the X or Y direction of the drawing. Driven. In addition, the bobbin 10 is movably supported on the base 100, between the focusing magnets 41 and 42 and the focusing coils 21 and 22, and the focusing coils 21 and 22. Between the focusing yokes 51 and 52, between the tracking magnets 61 and 62 and the tracking coils 31 and 32, and the tracking coils 31 and 32 and the tracking yoke Magnetic fluids 80 (see FIG. 3) are respectively provided between the 51 and 52. The magnetic fluid 80 is a liquid magnetized by a magnetic field, and is arranged in the magnetic field according to the magnetic flux density distribution. That is, the liquid is concentrated toward a higher density, whereby the fluid pressure increases at a higher magnetic flux density. Therefore, when a nonmagnetic object is placed in the magnetized magnetic fluid 80, the object tends to move to a lower pressure of the fluid. Therefore, the wound portions 10a, 10b, 10c in the magnetic field generated by the magnets 41, 42, 61, 62 and the yokes 51, 52, 71, 72 as in the present invention. After placing the coils 21, 22, 31, 32 wound around the coil 10d, and injecting the magnetic fluid 80 in the above-described position, the fluid pressure is increased by the magnets 41, 42, 61. The windings 10a, 10b and 10c are minimized on the line connecting the centers of the 62 and the yoke 51, 52, 71 and 72 to the minimum. The bobbin 10 is moved so that the center of 10d) is located. Therefore, as shown in FIG. 3, after the respective members including the bobbin 10 are installed in the base 100, the magnetic fluid 80 is transferred to the focusing magnets 41 and 42 and the focusing coils 21 and 22. ), Between the focusing coils 21 and 22 and the focusing yokes 51 and 52, between the tracking magnets 61 and 62 and the tracking coils 31 and 32, and the tracking. When injected between the coils 31 and 32 and the tracking yoke 51 and 52, respectively, the wound portions 10a, 10b, 10c and 10d are applied to the fluid pressure of the magnetic fluid 80. The bobbin 10 is moved to be located at the minimum point, and is lifted from the base 100 as shown in FIGS. 4 and 5. In this state, even if the bobbin 10 is moved to either side, it returns to the point where the fluid pressure is minimum, that is, the position where it was initially located. Reference numeral F in FIG. 3 denotes a power supply for supplying current to the focusing coils 21 and 22, and reference numeral T denotes a power supply for supplying current to the tracking coils 31 and 32. FIG.

In the above configuration, due to the interaction of the electric current supplied to the focusing coils 21 and 22 and the magnetic field formed by the focusing magnets 41 and 42 and the focusing yokes 51 and 52, When the bobbin 10 is driven, the bobbin 10 is moved in the Y direction while being supported by the magnetic fluid 80. At this time, since the bobbin 10 is not supported by the member fixed to the holder 3 (see FIG. 1) like the suspender 5 (see FIG. 1), the bobbin 10 is moved in an injured state on the base 100 so that it is precisely vertical. It can move in the direction. When the electromagnetic force for moving the bobbin 10 is removed as described above, the bobbin 10 is returned to where it was initially located.

In addition, the bobbin 10 may be formed by the interaction between the current passing through the tracking coils 31 and 32 and the magnetic field formed by the tracking magnets 61 and 62 and the tracking yoke 71 and 72. When driven, the bobbin 10 is moved in the X direction while being supported by the magnetic fluid 80. At this time, since the bobbin 10 is moved in the injured state on the base 100, it is possible to accurately move in the horizontal direction.

As described above, in the objective lens driving apparatus of the present invention, since the bobbin 10 does not move like a conventional rotation, but moves exactly in the vertical and horizontal directions, the rolling phenomenon of tilting with respect to the Z axis in the drawing is suppressed. . In addition, since the bobbin 10 is moved in a state supported by the magnetic fluid 80, rather than the suspender 5 having a predetermined elastic restoring force (see FIG. 1), when the vertical and horizontal movements occur simultaneously, Since the interference of the movement is small, the position of the objective lens 11 can be accurately moved.

As described above, the objective lens driving apparatus for the optical pickup of the present invention uses a magnetic fluid to lift the bobbin from the base to support it, thereby suppressing a rolling phenomenon that may occur when the bobbin is driven, and also up, down, left and right. It can reduce the interference of the movement. In addition, since the magnetic fluid also has a damping effect, a separate damping material such as a silicon-based damper bond is not required.

It is to be understood that the invention is not limited to that described above and illustrated in the drawings, and that more modifications and variations are possible within the scope of the following claims.

Claims (1)

A base; A nonmagnetic bobbin mounted with an objective lens and mounted on the base; A focusing coil installed on one side of the bobbin to form an energization path for current for focusing; A tracking coil installed on the other side of the bobbin and forming an energization path for current for tracking; A focusing magnet and a focusing yoke installed on the base to face each other with the focusing coil interposed therebetween to form a magnetic field in a direction perpendicular to the energization direction of the focusing current; A tracking magnet and a tracking yoke installed on the base to face each other with the tracking coil interposed therebetween to form a magnetic field in a direction perpendicular to the energization direction of the tracking current; As a liquid magnetizable by a magnetic field, between the focusing magnet and the focusing coil, between the focusing coil and the focusing yoke, between the tracking magnet and the tracking coil, and between the tracking coil and the tracking yoke, respectively. Injected by the magnetic field, the magnetic field is moved to the strong side to form a deviation of the fluid pressure distribution, by moving the non-magnetic bobbin to a low fluid pressure portion to float and support from the base; magnetic fluid; includes The objective lens drive device for optical pickup, characterized in that.

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