JPS6325835A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To save a space and to simplify a control and detection and to improve the driving precision and the detection precision by laminating a driving coil and a speed detecting coil, which detects the displacement speed of the driving coil, in layers. CONSTITUTION:In an objective lens driving device used in a magneto-optic disk driving device, a driving coil 21 which generates a driving force by the magnetic action and is displaced in a magnetic gap and a speed detecting coil 22 which detects the displacement speed of the driving coil 21 are formed in layers. When the driving coil 21 is displaced by the current conducted to the driving coil 21, the displacement speed is detected by the speed detecting coil 22 which is joined with the driving coil 21 integrally and is formed in layers. The speed feedback or the like is controlled based on the detecting speed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an objective lens drive device used in a magneto-optical disk drive device.

Conventional technology Conventionally, for example, a 1i magnetic coil, in which a permanent magnet and a coil are arranged facing each other, and the driving force acting on the coil is changed by adjusting the strength and frequency of the current flowing through the coil, is used.
It is used in many fields.

When performing position control using such electromagnetic induction starting force, it is known that if so-called velocity feedback is performed, in which the velocity is detected and returned, the rigidity of the servo system against external vibrations etc. increases. In order to perform speed feedback, it is necessary to provide a speed sensor that detects the relative speed of the movable part of the electromagnetic coil with respect to the fixed part.

As such a speed sensor, there is a known one that appropriately detects and feeds back a reverse starting force (proportional to the relative speed) that is generated at both ends of the coil in the magnetic field due to the displacement of the movable part. ing.

The same applies to the objective lens drive device in the magneto-optical disk drive device, and the present invention aims to improve the control performance by feeding back the moving speed of the objective lens to the control system.

Problems with the Prior Art In a speed detection device that uses electromagnetic action in such a coil, if you try to use the coil for driving and the coil for speed detection, it is impossible to use the coil for driving during speed detection. Since this is difficult, it is necessary to create a structure that allows independent currents to flow in a time-sharing manner.

Therefore, the above-mentioned type in which the drive coil and the speed detection coil are combined has a problem that the structure is complicated and expensive.

Further, other problems of the prior art will be explained by taking as an example a coil used in an objective lens driving device for a magneto-optical disk shown in FIGS. 7 and 8.

FIG. 7 is a schematic diagram of a magneto-optical disk device, in which an optical disk 6 is rotationally driven by a motor 9, and a laser beam 4 emitted from a laser light source 3 is reflected by a mirror 5 and then transmitted through an objective lens 2. It converges on the surface of the disk recording medium 61 built into the magneto-optical disk 6, and is used to reproduce, erase, and erase information.
1 is an objective lens driving device for driving the objective lens 2 vertically and horizontally to control the convergence position of the lens light to follow the recording trunk of the disk recording medium 61, and 7 is the optical system described above. This is an optical head that houses the

The objective lens driving device 1 moves the objective lens 2 to a recording medium 6 such as a magneto-optical disk 6. The disk recording medium 6. is moved perpendicularly to the surface of the disk recording medium 6. This is to displace the objective lens 2 in accordance with the surface fluctuation of the disk and the eccentric rotation of the disk, and to constantly and accurately focus the laser beam onto the information trunk.The conventional general structure is shown in Fig. 8. .

That is, the objective lens driving device 1 is the 81st! As shown in FIG. 1, an objective lens barrel 11 that accommodates and supports the objective lens 2 is provided so as to be movable in the optical axis direction of the objective lens 2. It is attached to the intermediate support 13 by a parallel spring 12.12 movable in the tracking direction. Therefore, the objective lens 2 is supported so as to be swingable in the radial direction of the disk recording medium 610.

A rubber-like elastic body 14 is bonded to the inside of the parallel spring 12 movable in the tracking direction to absorb vibrations of the spring. Reference numeral 15 denotes a tubular counterbalance weight fitted around the lower portion of the outer periphery of the objective lens barrel 11.

On the other hand, the fixed support 17 forming the outer frame t1 of the objective lens drive device 1 is formed in a hollow cylindrical shape, and the tracking magnetic circuit 16 fixed inside thereof is composed of a tracking yoke 18 and a tracking magnet 19. is,
A tracking magnetic gap 20 is formed between the two. A tracking drive coil 21 whose one end is fixed to the objective lens barrel 11 is inserted into the tracking magnetic gap 20 so as to cross the gap 20 .

The above-described tracking magnetic circuit 16 and tracking drive coil 21 are provided as a set symmetrically with the optical axis of the objective lens 2 interposed therebetween.

Therefore, when the input current to the tracking drive coil 21 is changed, an external force acts on the tracking drive coil 21 due to electromagnetic action, displacing the objective lens i, ImM11, and the objective lens 2 supported therein in the trunking direction. let

In the figure, 27 is a focusing magnet, and 26 is a focusing yoke, which constitute a focusing magnetic circuit 25, which is fixed to the lower end of the intermediate support 13, and one end of which is inserted into the focusing magnetic gap 29 of the magnetic circuit 25. The focus drive coil 30 constitutes a drive means in the focus direction. In addition, 23.23 is a focus direction movable parallel spring that supports the intermediate support body 13 so as to be able to reciprocate only in the focus direction, and in this case has an annular flat plate shape, 24 is a rubber-like elastic body, and 28 is a focusing spring. This is a member for holding down the magnet 27.

In order to control the driving force in the tracking direction in such an objective lens driving device, when a velocity feedback coil is provided, the left and right trunking driving coils 2
1.21 may be used for driving, the other for tracking speed feedback, and the output of the tracking speed feedback coil is fed back to the tracking drive coil through the necessary circuits, but in this case, two Since the coil protrudes from the objective lens barrel 11 to the left and right, the overall size of the apparatus becomes large, which becomes an obstacle to making it more compact.

OBJECTS OF THE INVENTION Therefore, an object of the present invention is to simultaneously generate a driving force by electromagnetic action and detect its displacement speed in a device for driving the objective lens of the magneto-optical disk in the tracking direction or the focusing direction. can be done,
Another object of the present invention is to provide an objective lens driving device having an electromagnetic coil structure that can be miniaturized.

Structure of the Invention In order to achieve the above object, the main means employed by the present invention is to provide a driving coil that generates a driving force by magnetic action and is displaced in a magnetic gap, and a This is an objective lens driving device in which a speed detection coil for detecting a displacement speed is formed in a product N-coupled manner.

When the drive coil is displaced by the current flowing through the drive coil, the displacement speed is detected by a speed detection coil that is integrated with the drive coil and formed in a laminated manner.

Based on this, for example, speed feedback and other controls become possible.

Embodiment Next, an embodiment of the present invention shown in FIGS. 1 to 4 will be explained to provide an understanding of the present invention. Here, FIG. 1 is a side sectional view of an example of an objective lens driving device according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line A-A in FIG. 1, and FIG. 3 is used in the above embodiment. A perspective view of a tracking drive coil and a tracking magnetic circuit that can be used, Figure 4 +
a+ and ('b) are respectively plan views showing an example of the tracking drive coil, and FIG. 5 is a focus drive coil that can be used in the objective lens drive device;
An exploded perspective view of the focus magnetic circuit, and FIGS. 6(a) and 6(b) are a perspective view and a developed view of an example of the focus drive coil.

In addition, common elements with the conventional components shown in Fig. 8 include:
The same reference numerals will be used in the explanation. In addition, the following examples:
This is only one specific example of the present invention, and is not intended to limit the technical scope of the present invention.

As shown in FIG. 2, when the electromagnetic coil structure according to this embodiment is used, the tracking drive coil 21 and the tracking velocity feedback coil 22 are arranged in a stacked state, so that it can be used like a conventional tracking drive device. There is no need to provide a set of tracking coils on both sides of the optical axis of the objective lens 2, as shown in FIGS. 1 and 2.
The structure on the side opposite to the side where the tracking drive coil 21 and the tracking speed feedback coil 22 are provided is extremely simplified, and the motor 9 shown in FIG. 7 can be placed close to this simplified part. Therefore, it is possible to reduce the space required and increase the storage capacity of the disk. The tracking speed feedback coil 22 as described above is used for tracking drive during normal recording/reproduction (at this time, there are two tracking drive coils 21 and 22),
It can be used for speed feedback during access when the objective lens moves at high speed.

In the case of the structure shown in FIG. 1, the focus direction movable parallel spring 23 has a cantilevered leaf spring shape, but by providing a pair of parallel springs vertically as shown in the figure, the focus direction movable parallel spring 23 can be Inclination of the optical axis of the objective lens 2 is prevented.

Next, the electromagnetic coil 21 to be used as a fiI layer as described above.
The structure of No. 22 will be explained. Such a coil can also be formed by winding the conducting wire into a thin sheet, but this is disadvantageous in terms of the labor involved in winding the coil. In addition, for example, in the case of -layer winding, the adhesive force between the wires is weak (becomes 1
There is also a problem with workability when layering 11 layers.

In this regard, if a thin sheet-like coil is constructed from a flexible printed circuit, the conductor pattern can be processed by etching, so it can be easily manufactured, there is less variation, and workability during lamination is improved.

As mentioned above, a part of the Mi-layered sheet-like coil is used for tracking drive, and the rest can be used for tracking speed detection, and if necessary, speed feedback is performed to eliminate disturbance vibration. The rigidity of the servo system can be increased.

FIG. 3 shows a tracking drive coil 30 constructed by forming a sheet-like coil using the above-described flexible printed circuit and bonding the laminated sheet to the α-angled surface of the objective lens barrel 11. ' However, when using a flexible printed circuit like this where coils are stacked in multiple layers and these coils are used for partially different purposes, both ends of the coil must be pulled out and connected for each purpose. There is a need to.

The coil shown in FIG. 4 fat is a coil pattern in which a tracking drive coil 21 is printed on one side of a single flexible printed board. In this case, for example, both ends of the tracking drive coil 21 are A thin conducting wire 32 with low elasticity can be soldered and connected to the portion 34.34. Further, such a coil pattern also applies to a coil for tracking speed detection.

In the simple conductor drawing structure shown in Fig. 4(a) above, the conductors may interfere with each other and it may become impossible to identify the conductors for each purpose.
As shown in Figure 2, it is desirable to slightly change the pattern of the conductor lead-out portion depending on the application.

For example, in the example shown in FIG. 4('b), the tracking drive coil (I11 end 34 and the tracking speed detection coil end 33) are formed at slightly different parts when viewed in the thickness direction of the coil, and each The conductive wires connected to the ends are separated by purpose and can be easily identified.

What has been described above is an example in which the present invention is applied to drive the objective lens 2 in the tracking direction and detect the speed. It is also possible to use it as a speed detection coil for feedback.

FIG. 5 shows such a focus drive coil 30, a focus speed feedback coil 31 superimposed on the focus drive coil 30 in a laminated manner, and a focus magnetic gap into which the laminated coils 30 and 31 are inserted as shown in FIG. 29 is a perspective view showing the focus magnetic circuit 25 in an exploded state, and the focus drive coil 30 and the focus speed feedback coil 31 are formed in a cylindrical shape.

The structure of such a focusing coil is similar to that of the tracking coil, and may be formed by winding a conducting wire into a thin sheet, but it may also be formed from a thin sheet-like flexible printed circuit. Particularly when configuring a flexible printed circuit, it is disadvantageous to form it into an endless cylindrical shape, so for example, as shown in FIG. 6(a)
As shown in the perspective view, the cylinder 30a is partially cut out.
(31a) structure is convenient because it can be manufactured in the unfolded state as shown in FIG. 6(b).

The method of drawing out the lead spring from the focusing coil J is the same as that already described for the tracking coil, so the explanation will be omitted.

Finally, I will briefly explain velocity feedback. In FIG. 1, trunking coils 21, 22° objective lens barrel 11. Objective lens 2. When the mass of the tracking movable part consisting of the counterbalance quay 15 etc. is m, and the damping constant and spring constant of the movable parallel spring 12 in the luffing direction and the rubber-like elastic body 14 are respectively d and k, the quality N
The equation of motion when no external force is applied to m is expressed in Laplace transformed form: (ms2+ds+k)x2 = (ds+k)X.

(1) However, xl and x2 are displacements in the tracking direction of the tracking movable portion and the intermediate support body 13 that supports the tracking movable portion via the tracking direction movable parallel spring 12, respectively (the Laplace transform thereof).

The problem with servo systems is the disturbance vibration of XI.

does not follow and a relative displacement (XI-X2) occurs. Therefore, if equation (1) is expressed as a transfer function of (XI-X2) with respect to X, (XI-X2)/x, = ms2/ ( ms' + d s + k) = s' /
(3' + 2 ζ ω. S + ω. 2 )
... great) f and ω. ' −ni/m, ζ
= d/<2 J]i-7>, and the damping number ζ is determined by d and m and is constant.

On the other hand, detecting the time derivative of relative displacement (i.e. relative velocity),
The equation of motion when amplifying this and applying it to the drive coil is (ms+(d+a)) where the gain of the velocity feedback system is a.
s + kl X2 = ((d + a) s + kl
2/ (S'+2ζ'ω.S+ω.2)...(4)
However, ω. −7m ζ' = (d+a)/(2[T), and the damping number ζ is determined by the gain a of the velocity feedback system.
′ can be changed. In particular, if ζ′≧1 (
The denominator of equation 4) indicates non-vibration, which means that the tracking movable part does not resonate due to disturbance vibration, and the rigidity of the servo system increases.

Furthermore, free vibration of the movable part during access can also be suppressed.

In the above embodiments, the present invention was explained only in the case where the present invention was applied to a coil used for driving the objective lens in the tracking direction and/or focus direction of the objective lens driving device, but the present invention generates a driving force by electromagnetic action and It goes without saying that it is adaptable to any electromagnetic coil structure in which a drive coil to be displaced within and a speed detection coil for detecting the displacement speed of the drive coil are required.

Effects of the Invention As described above, the present invention has a structure in which a driving coil that generates a driving force by magnetic action and is displaced in a magnetic gap, and a speed detection coil that detects the displacement speed of the driving coil are laminated. Since this objective lens drive device is characterized by being formed in a Since the speed detecting coil and the speed detecting coil are not used together, the control and detection of each becomes simple, contributing to improvement in drive accuracy and detection accuracy, and furthermore, to a reduction in cost.

Furthermore, when flexible printed circuit coils with different patterns are used in a stacked manner, the ease of assembly and wiring work is improved.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of an example of an objective lens driving device according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line A-A in FIG. 1, and FIG. 3 is a sectional view taken along the line A-A in FIG. A perspective view of a tracking drive coil and a tracking magnetic circuit, FIGS. 4A and 4B are plan views each showing an example of the tracking drive coil, and FIG. 5 is a perspective view of a tracking drive coil that can be used in the objective lens drive device. Exploded perspective view of focus drive coil and focus magnetic circuit, Figure 6<
a> and (b) are a perspective view and a developed view of an example of the focus drive coil, FIG. 7 is a schematic diagram of the structure of a conventional magneto-optical disk device, and FIG. 8 is a diagram of a conventional magneto-optical disk device. FIG. 2 is a side sectional view showing a conventional objective lens driving device that can be used. (Explanation of symbols) 1...Objective lens drive device 2...Objective lens 3...Laser light source 4...
・Laser light 6...Magneto-optical disk 9...
Fixed support body 11...Objective lens barrel 12...
-Tracking direction movable parallel spring 13...Intermediate support 16...Tracking magnetic circuit 18...Tracking coil 19...Tracking magnet 21...Tracking drive coil 25...Focus magnetic circuit 29... Focus magnetic gap 30'... Tracking drive coil 30... Focus drive coil 30a (31a)... Notch 31... Focus speed feedback coil.

Claims (1)

[Claims] (1) A driving coil that generates a driving force by magnetic action and is displaced in a magnetic gap, and a speed detection coil that detects the displacement speed of the driving coil are formed in a laminated manner. Objective lens drive device.