JPS62173641A - Objective lens driving mechanism in optical disk device - Google Patents

Abstract

PURPOSE:To drive an objective lens smoothly and surely by connecting the bearing part of a holding frame and a driving mechanism substrate through a suspender and forming the middle part of the suspender so that the thickness in the axial direction of a driving supporting shaft of the holding frame is thinner than that in the direction of turning around the driving supporting shaft. CONSTITUTION:A suspender 20 consists of a suspender base part 20A inserted to a bearing part 3a of a holding frame 3 and a suspension part 20B which is extended in the direction orthogonal to the axial direction of a driving supporting shaft 2 and has an annular plane shape. A detaining hole 20h is formed in the suspension part 20B, and a supporting pin 1p projected on a suspension base 1S formed on a driving mechanism substrate 1 is inserted through the detaining hole 20h, and a retaining ring 21 is fitted to the front end of the supporting pin 1p. In two boundary positions 20k1 and 20k2 between the suspension part 20B and the suspender base part 20A of the suspender 20, the thickness of the suspension part 20B in the axial direction of the driving supporting shaft 2, namely, the focusing direction (arrow F) is made thinner than that in the direction of turning around the axial line of the driving supporting shaft 2, namely, the tracking direction (arrow T).

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION This invention relates to an improvement of an objective lens drive mechanism in an optical disc device such as an optical video disc player.

Needless to say, in this type of optical disc device,
In order to extract the information recorded on the disk, an objective lens is placed at a position facing the disk, and the objective lens focuses a light beam with high precision on the track position, which is a recording area formed at high density. It is composed of Therefore, the objective lens must be held by a drive mechanism whose position can be controlled so that the light beam can always accurately scan the track position.

As this type of objective lens drive mechanism, one shown in FIGS. 3 and 4, for example, is known. In the figure, reference numeral 1 indicates a drive mechanism board, and this drive mechanism board 1
A drive spindle 2 is attached to approximately the center of the drive spindle 2, and a holding frame 3 having a substantially E-shaped cross section and a horizontally long plate-like upper surface is attached to the drive spindle 2 along the axis of the drive spindle 2. It is attached via a bearing portion 3a that has the same direction (X-X direction) and the center line direction of the shaft hole. In addition, the holding frame 3 holds an objective lens 4 at a position apart from the drive spindle 2, while the holding frame 3 has a balancer at a position facing the objective lens 4 across the drive spindle 2. 5 is fixed.

Further, around the periphery of the holding frame 3, there is a focus direction drive coil 6 for making the holding frame 3 movable in the direction along the axis of the drive shaft 2, that is, in the focusing direction (direction of arrow F in FIG. 3). Further, a holding frame 3 is attached to a drive shaft 2 on the outer periphery of the focus direction drive coil 6.
The direction along the axis of , that is, the tracking direction (
A pair of track-direction drive coils 7.7 are wound around the track-direction drive coils 7.7 for movability in the direction of arrow T in FIG.

Note that reference numeral 8 is a through hole for guiding the light beam to the objective lens 4.

Here, an electromagnetic force in the focusing direction acts on the focus direction drive coil 6 constituting the first electromagnetic drive means based on electromagnetic interaction generated between the pair of focus direction drive magnets 9.9. Each of the focus direction drive magnets 9 is fixed to a pair of focus direction magnet holders 10 and 10 vertically disposed on the drive mechanism substrate 1, respectively. On the other hand, the track direction drive coil 7 constituting the second electromagnetic drive means exerts an electromagnetic force in the tracking direction based on the electromagnetic interaction generated between the pair of track direction drive magnets 11. The track direction drive magnet 11 is a pair of track direction magnet holders 12.1 vertically disposed on the drive mechanism board 1 at a position orthogonal to the above-mentioned focus direction magnet holder 10.
2 are fixed respectively.

On the other hand, the end of the balancer 5 and the suspension base 1a formed on the drive mechanism board 1 are connected to a suspender 13 made of a viscoelastic member having an abbreviated cross-sectional shape.
The function of the suspenders 13 allows the holding frame 3 to maintain a so-called neutral position when the track direction drive coil 7 is not subjected to electromagnetic force by the track direction drive magnet 11.

Problems to be Solved by the Invention However, according to the configuration of such a conventional objective lens drive mechanism, the center of the mounting position of the suspender 13 is located at a position opposite to the objective lens 4 with the drive support shaft 2 interposed therebetween. Moreover, since this suspender 13 is fixed at a position apart from the drive spindle 2, when the holding frame 3 is driven along the axial direction of the drive spindle 2, that is, when the objective lens 4
Due to the expansion and contraction phenomenon of the suspenders 13 that occurs when driving the objective lens 4 in the focusing direction, the holding frame 3 tends to tilt with respect to the axial direction of the drive shaft 2, resulting in a so-called sticking phenomenon, which causes the focus drive of the objective lens 4 to become difficult. The problem was that it had a negative impact on the

Means for Solving the Problems The present invention has been made to solve the problems of the prior art, and includes a drive shaft mounted approximately at the center of the drive mechanism board, and a bearing section connected to the drive shaft. installed,
A holding frame that is movable along the axial direction of the drive shaft and a direction around the axis and that holds the objective lens at a position spaced apart from the drive shaft; In an objective lens drive mechanism in an optical disk device, the objective lens drive mechanism is provided with first and second electromagnetic drive means provided to be movable in a direction along a direction and a direction along a plane orthogonal to the front axis, respectively. The substrate is connected to the substrate via suspenders made of a viscoelastic material and extending in a direction perpendicular to the axis of the drive support shaft, and the thickness of the support frame in the axial direction of the drive support shaft corresponds to the middle part of the suspenders. It is characterized by being formed to be thinner than in the rotational direction of the drive support shaft.

When the holding frame that holds the objective lens is driven along the axial direction of the drive shaft attached to the drive mechanism board, the suspenders made of a viscoelastic material extend between the bearing part of the holding frame and the drive mechanism board. The holding frame is extremely easy to move in the direction along the axial direction of the drive spindle because the axial direction of the drive spindle is thinner in the middle than in the direction perpendicular to the axial direction of the drive spindle. In addition, the center of gravity of the holding frame on the drive shaft is not displaced. Furthermore, when the holding frame rotates around the axis of the drive support shaft, the suspenders extend in the direction in which they extend.

The restoring force generated by this extension acts exclusively to return the holding frame around the drive shaft, so the center of gravity of the holding frame hardly shifts in this case as well.
In addition, in the middle part of the suspender, the direction around the axis of the drive shaft is thicker than the direction of the axis, so
There is no adverse effect on the rotation of the holding frame.

EXAMPLES The present invention will be explained below based on the drawings. Incidentally, members that are the same or equivalent to those shown in the prior art are given the same reference numerals and redundant explanations will be omitted.

In FIGS. 1 and 2, reference numeral 20 denotes suspenders made of a viscoelastic member, and this suspender 20 has a suspender base 20 that is inserted into the bearing portion 3a of the holding frame 3.
A and a suspension portion 20B integrally connected to the suspender base portion 20A, extending in a direction orthogonal to the axial direction of the drive support shaft 2, and having a substantially annular planar shape. This suspension portion 20B has a locking hole 2.
0h is formed, and a support pin 1ρ protruding from the suspension base IS formed on the drive mechanism board 1 is inserted into this locking hole 20h. A ring 21 is fitted into the ring 21.

Further, the suspension part 20B of the suspender 20 is located at two boundary parts 20 with the suspender base 20A, □, 20.
2, the thickness in the direction along the axis of the drive support shaft 2, that is, in the focusing direction (direction of arrow F) is thinner than in the direction around the axis of drive support shaft 2, that is, in the tracking direction (direction of arrow T). It is formed.

As a precaution, the suspenders 20 are connected to the drive mechanism board 1.
Since the balancer 5 is fixed in a symmetrical position to the objective lens 4 with the drive shaft 2 interposed between the holding frame 3, the connection with the suspenders 20 is released.

With this configuration, when a drive current flows through the focus direction drive coil 6, the holding frame 3 moves in the axial direction of the drive spindle 2, based on the electromagnetic interaction that occurs between it and the focus direction drive magnet 9. In other words, it is driven in the focusing direction F. in this case.

As described above, the suspender 20 has its suspender base 20a fixed to the bearing part 3a of the holding frame 3, and the suspension part 20b fixed to the drive mechanism board 1.
Even when the holding frame 3 moves along the drive shaft 2, the point of application of the force acting on the suspender 20 approximately coincides with the center of gravity of the holding frame 3, and furthermore, in the middle, the axis of the drive shaft Since the holding frame 3 is thinner than the direction perpendicular to the holding frame 3, it is extremely easy to move the holding frame 3 in the axial direction of the drive shaft 2. Therefore, the position of the center of gravity of the holding frame 3 on the drive support 11i1112 does not change. That is, almost no force acting on the holding frame 3 causes it to tilt with respect to the axial direction of the drive support shaft 2.

On the other hand, when a drive current flows through the track direction drive coil 7, the holding frame 3 is moved by the electromagnetic force acting on the track direction drive coil 7 based on the electromagnetic interaction generated between it and the track direction drive magnet 12. It rotates around the axis, that is, in the tracking direction T. In this case, the bearing portion 3a integral with the holding frame 3 also rotates, and the suspender base 20A of the suspender 20 rotates. However, since the end of the suspension part 20B is fixed to the drive mechanism board 1, the suspender 20 is deformed, and a compressive force is applied to one end of the suspender part 20B, and a tensile force is applied to the other end of the suspender part 20B. A restoring force acts on the frame 3 to return it to its original position, that is, the neutral position.

In this case, since the boundary portion 20 of the suspenders 20 has a predetermined thickness of 1.20 to 2 in the tracking direction, it does not have any adverse effect on the elastic properties such as the restoring force of the suspenders 20.

As described above, according to the present invention, the viscoelastic member is provided between the bearing portion of the holding frame and the drive mechanism substrate and extends in a direction perpendicular to the axial direction of the drive support shaft. Since the structure is equipped with suspenders, it is possible to avoid the so-called sticking phenomenon that occurs between the bearing part of the holding frame and the drive spindle, ensuring smooth and reliable driving of the holding frame and, in turn, the objective lens. This can greatly contribute to improving the mechanical reliability of the system.

[Brief explanation of drawings]

Fig. 1 is an exploded perspective view of essential parts showing an embodiment of the present invention, Fig. 2 is a cross-sectional view illustrating how the components shown in Fig. 1 are assembled into the device, and Fig. 3 is a conventional objective. FIG. 4 is a cross-sectional view illustrating the configuration of the lens drive mechanism, and a plan view thereof. DESCRIPTION OF SYMBOLS 1... Drive mechanism board, 2... Drive support shaft, 3... Holding frame, 3a... Bearing part. 4...Objective lens, 6...Focus direction drive coil. 7...Track direction drive coil, 20,...Suspender, 20A...Suspender base. 20B... Suspension part, 20, 20, 2... Boundary part (midway part). Figure 1 Figure 2 Figure 3 Figures 1 and 4

Claims (1)

[Scope of Claims] A drive support shaft attached to approximately the center of a drive mechanism board; A drive support shaft attached to the drive support shaft via a bearing portion and movable along the axial direction of the drive support shaft and the direction around the axis. a holding frame that is flexible and holds the objective lens at a position separated from the drive shaft; and the holding frame is movable in the direction of the optical axis of the objective lens and in the direction along a plane perpendicular to the optical axis. In the objective lens drive mechanism in an optical disk device, the objective lens drive mechanism is provided with first and second electromagnetic drive means provided to The suspension is connected through suspenders made of a viscoelastic member extending in the direction, and the middle part of the suspenders is connected so that the thickness in the axial direction of the drive support shaft of the holding frame is thinner than in the circumferential direction of the drive support shaft. An objective lens drive mechanism in an optical disk device, characterized in that the objective lens drive mechanism is formed as follows.