JPS58125240A - Pickup for optical disk - Google Patents

Abstract

PURPOSE:To execute position control of a lens barrel easily and exactly, by supporting the lens barrel provided with a lens, by a thrust magnetic bearing by electromagnetic force and a radial magnetic bearing. CONSTITUTION:A lens barrel 13 holding a lens 12 by a cylindrical outside frame 11 is held by a thrust magnetic bearing 14 and a radial magnetic bearing 15. As for the thrust bearing 14, a ringlike magnetic member 16 is stuck to the inside wall of the outside frame 11, and on one end face of this member 16, a collar cylindrical magnetic member 18 is provided through a permanent magnet 17, a winding 19 wound around a thrust shaft part 13a is placed in a gap part of the magnetic members 16, 18, and as for the radial magnetic bearing 15, 4 pieces of the first magnetic members 20, and the second magnetic member 21 are provided through a permanent magnet 22. On the magnetic members 16, 21, windings 19, 23 wound around bobbins are provided, and a prescribed current is made to flow to these windings 19, 23 so that outward force is operated, by which the lens barrel 13 is held at the normal position in the outside frame 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an electromagnetically supported optical disc pickup suitable for reproducing, for example, an audio optical digital recording disc.

[Prior art]

2. Description of the Related Art Conventionally, there has been an optical desk pickup shown in FIGS. 1a and 1b as a device for reproducing signals recorded on an optical disk.

1Δl As shown in Iζ, this optical disk pickup is stationary I! It consists of a movable lens barrel 2, and a lens 3 and the like are attached to the 'a barrel 2. This lens barrel 2.

The movable pedestal 4 is supported by a pair of parallel leaf springs 545b so that it can move only in one direction (the horizontal direction in the figure), and the movable pedestal 4 can only move in the direction of the axis of the lens barrel 2 (in the vertical direction in the figure). It is supported by a pair of parallel leaf springs 5g and 5b arranged above and below to obtain the same effect.

The stationary part 1 includes a magnetic circuit 7 made of a magnetic material.

In this magnetic circuit 7, an annular magnetic gap y' force s is formed. The movable frame 4 # has winding 8 to drive it.
is provided, the winding 8 being arranged within the magnetic gap 7'. The movable pedestal 4 generates a magnetic circuit 7 in the same way as in a normal loudspeaker by passing a current through this winding 8.
The drive is controlled by the electromagnetic force i received from.

In addition, in order to drive the lens barrel 2, there is one on both sides of the tip of the lens barrel 2.
A pair of attracting iron pieces 9m and 9b are provided, and a pair of electromagnets 10a and 10b are provided facing each other.

Therefore, by energizing these electromagnets 10m and 10b, the lens barrel 2 is driven and controlled by the magnetic attraction force with the attracting iron pieces 9a and 9b.

In this way, the lens barrel 2 can be driven relative to the stationary part 1 in two dimensions in the direction of the optical axis and in the direction perpendicular to the optical axis.

[Problems with conventional technology]

For such a structure,! The main things that determine the motion performance of the I cylinder 2 are the leaf springs 5a, 5b, M and 6m, 6b.
In particular, in the case of an optical disk pickup, it is necessary to control the characteristics of motion up to several fG (z), so the quality control of the material and the shape control must be strictly performed. First, it also had drawbacks such as requiring countermeasures against resonance in the high frequency range.

[Purpose of the invention]

An object of the present invention is to provide an optical disk pickup that can be easily and accurately controlled, and can significantly simplify quality control of raw materials, shape W, and resonance countermeasures.

[Summary of the invention]

This invention supports a lens barrel equipped with a lens using a thrust magnetic bearing and a radial magnetic bearing, which are generated by an electromagnetic force between a magnetic path formed by a magnetic member provided on the fixed side and a winding provided on the lens barrel side. Configure.

It is possible to perform two-dimensional control of the direction of the optical axis of the lens barrel and control in the direction perpendicular to the optical axis.

〔Effect of the invention〕

According to this invention, the lens barrel is supported in a non-contact manner by thrust magnetic bearings and radial magnetic bearings, so that material quality control, shape control, and resonance countermeasures are better than when conventional leaf springs are used. can be simplified. Furthermore, since the position of the lens barrel is controlled by applying currents to the respective windings of the thrust magnetic bearing and the radial magnetic bearing, the control can be easily and accurately performed.

[Embodiments of the invention]

An example of the lifetime right of this invention will be explained below with reference to one drawing.

In FIG. 2 (al, ib), reference numeral 11 denotes a cylindrical outer frame, and a lens barrel 13 holding a lens 12 is held on this outer frame 11 by a thrust magnetic bearing 14 and a radial magnetism 15.

The thrust bearing 14 has a one-shaped magnetic member 16 fixed to the inner wall of the lower part of the outer frame 11, and a magnetic member 18 in the form of a flanged cylinder is attached to one end surface of the magnetic member 16 via a magnetic source, for example, a permanent magnet 17. to be placed. Also.

As shown in the figure, a winding 19 is interposed between the thrust shaft portion 13a of the lens barrel 13 and the gap between the magnetic members 16 and 18.

On the other hand, the shear high air bearing 15 has at least three first magnetic members 20 forming an external magnetic path with a U-shaped cross section on the upper inner wall surface of the outer frame 11. 4@ are arranged at equal intervals along the

Then, from an intermediate position of the first magnetic member 20, the second magnetic member 21 forming an internal magnetic path as shown in FIG.
A magnetic member 20 is provided protrudingly. and.

At least one of the opposing surfaces of the first magnetic member 20 and the second magnetic member 21 is made to protrude by a predetermined area to form a magnet @212 that focuses magnetic flux. In the illustrated example, the end surface of the second magnetic member 21 is made to protrude from the plane of the magnet 22, and the end pole 21J! was formed.

As a result, the first magnetic member 20 and the second magnetic member 21
The gap dimension DI with the magnetic pole 218 surface of the first magnetic member 20
Dimension D between and magnet 22! It can be set smaller than . A winding 423 is interposed in the gap between the magnetic pole 211 surface of the second magnetic member 22 and the opposing first magnetic member 20. This winding 23 is connected to a bobbin 24 formed in a cylindrical shape.
and are arranged at equal intervals along the curve of the radial shaft portion 13b of the lens barrel 13 corresponding to the first magnetic member 20. At the time of nickel, the inside of % @ 23 wound on bobbin 24 (
@lI! i tube g! 4) Make sure that nA is always located in the magnetic path on the magnetic pole 21g surface of the second magnetic member 21, and the outer fill (outer frame III) end of the winding 23 is always located on the magnetic pole of the magnetic member 21 of ji2. The length and position of the winding portion are set so that it is located outside the magnetic path on the surface of 21a.

Next, this invention will be explained in detail. Now, when a predetermined current is passed through each winding 23 so that a force acts outward, the outer frame 1
The first magnetic member 20 fixed to 1 and the magnetic member 21 of @2
The lens barrel 13 is held at a normal position within the outer frame 11 by the electromagnetic force received from the magnetic path consisting of (b) and (b). When an external force is applied to the mirror 13 in this state of deafness and the optical axis of the lens barrel 13 is eccentric in the horizontal direction, the winding 23 in the direction of the core moves toward the corresponding magnetic member 21 of s2, so the winding that crosses the lines of magnetic force #23
effective area decreases and the suction force weakens.

On the other hand, since the winding 23 on the opposite side is attracted toward the center, the effective area of the winding 23 that crosses the lines of magnetic force increases, and the attractive force becomes stronger by this increase. That is, the magnetic force acting on the windings 23 in the direction in which the lens barrel 13 is eccentric is weakened, and conversely, the magnetic force acting on the windings 1!23 on the opposite side increases accordingly, so that the lens barrels 13 face each other. This difference in magnetic force acting on the winding @23 generates a restoring force corresponding to the inertia of the lens barrel 13, allowing the lens barrel 13 to return to its normal position.

Also, depending on one's physical strength, the optical axis of the lens barrel 13 is directed diagonally, for example to the right.
When the winding 23 on the right side is tilted by l#, the winding 23 on the upper right side moves outward, so the effective cross-sectional area crossing the lines of magnetic force decreases, and the magnetic force acting on the winding 23 on the right top part weakens. Conversely, since the winding 23 at the lower right side moves toward the center, the effective cross-sectional area crossing the lines of magnetic force increases, and the magnetic force acting on the winding 23 at the lower right side increases.

On the other hand, since the winding 23 on the upper left side moves toward the center,
As mentioned above, the effective cross-sectional area crossing the magnetic field lines increases, and the left @L
The magnetic force acting on the winding 23 of the section increases. Also the lower left volume? Since @23 moves outward, the effective cross-sectional area crossing the lines of magnetic force decreases, and the magnetic force acting on the lower left winding 23 weakens, as described above. Due to this, rotational torque is generated in the direction opposite to the rotation of the 1w1 cylinder 13, and 'a cylinder 1
3 can be returned to its normal position and looked after.

Note that when moving the lens barrel 13 in a direction perpendicular to the optical axis, increasing the current in the winding 23 in the desired direction increases the magnetic force acting on the winding 23 and moves the lens barrel 13 in the desired direction. be able to. At this time, if the current in the winding 23 on the opposite side is decreased, the driving force of the boundary portion 13 is doubled.

On the other hand, if it is necessary to move the iI cylinder 13 in the optical axis direction, the magnetic members 16 and 18 can be moved by adjusting the current flowing through the winding 19 wound around the thrust shaft portion 13m of the lens barrel 13, as in the conventional example. The drive can be controlled in the optical axis direction by the electromagnetic force I received from the magnetic circuit.

Therefore, the thrust shaft portion X3a of the lens barrel 13 is supported by the thrust magnetic bearing 14, and at least three windings 23 are arranged radially on the radial shaft portion 13b of the lens barrel 13, and these windings @23 are attached to the outer frame. By supporting the radial shaft 13b of the lens barrel 13 with the radial magnetic bearing 15 interposed in the direction orthogonal to the magnetic path of the fixed magnetic circuit, the lens barrel 13 can be held within the outer frame 11 by magnetic force. , it is possible to eliminate all the leaf springs required to hold the lens barrel 13 in the conventional example. Accordingly, various problems caused by the leaf spring can be solved, and quality control of the material, shape control 8, and countermeasures against resonance in a high frequency range can be easily performed. Also.

The magnetic force increases or decreases in accordance with the deflection of the lens barrel 13, and a restoring force acts on the lens barrel 13, so that the lens barrel can always be held in a normal position. Furthermore, by increasing the current flowing through the winding 23 in a desired direction, the magnetic force can be freely changed, so that @@13 can be driven and controlled in a direction perpendicular to its tip axis.

Next, another embodiment of the present invention will be explained with reference to FIGS. 3 to 5.

FIG. 3 is a perspective view showing a radial magnetic bearing, which is a main part of a second embodiment of the invention. In the figure, reference numeral 31 denotes a magnetic member f41 formed in the shape of a rectangular cylinder with a bottom, and a second magnetic member 32 forming an internal magnetic path is interposed inside the first magnetic member 31. Then, this second magnetic member 32 is fixed to the bottomed portion of the first magnetic member 31 via a magnet (not shown).

At this time, a gap of a predetermined size is provided between the first magnetic member 31 and the second magnetic member 32. This gap + C rectangle S
A winding 34 wound around a shaped coil bobbin 33 is interposed. At this time, the inner end of the first winding 34 is always connected to the second magnetic member 3.
so that the outer end of the winding 34 always lies within the magnetic path above the magnetic pole 32a ii of the second magnetic member 32.
The length and position of the winding part are set so that it is located outside the magnetic path on the 28th plane.

Therefore, with this configuration, the same effects as described above can be achieved, and by surrounding the first winding 34 with the first magnetic member 31, the current in the first winding can be effectively utilized.

FIG. 14 is a sectional view showing a radial bearing which is a main part of the third embodiment of the present invention. In fig.

41 is a magnetic member f41 formed into a U-shape in cross section.

The tip of this first magnetic member 41 is made to protrude to form a magnetic pole 41.
form 1. Then, a second magnetic member 43 is fixed to the bottomed portion of the first magnetic member 41 via a magnet 42 .

At this time, nAIfi of the second magnetic member 43 is
The magnetic pole 43m is formed by protruding from the plane of the magnetic pole 43m. This second
The magnetic member 43 and the magnet 4 have a gap size of @l between the magnetic member 143a of the magnetic member 43 and the magnetic pole 41a of the first magnetic member 41.
The gap size l is set to be smaller than that between the two. A winding 45 wound around a bottomed cylindrical coil bobbin 44 is interposed in the gap between the magnetic pole 41 and 43a. In this case, a relative relationship is created between the winding 45 and the magnetic path as described above.

Therefore, with such a configuration, it is possible to achieve the same effects as the above arrangement.

By providing the I11 surfaces of the first magnetic member 41 and the second magnetic member 43 in a protruding manner, the magnetic flux can be focused, the electromagnetic force can be increased, and the #control characteristics can be improved.

FIG. 5 is a vertical sectional view showing the configuration of a fourth practical example of the present invention. In FIG. 5, the same parts as in FIG. 21 are designated by the same reference numerals, and their explanation will be omitted. In the diagram, 51 is outside @
This is a magnetic member in which a first magnetic part 51a with a U-shaped cross section forming a magnetic path and a second magnetic part 51b forming an internal part are integrally formed in an E-shape. tlI of this magnetic member 51
Permanent magnets 52, 1.52b 8 and 52c are placed on each opposing surface of the Cl magnetic fi 51a and the second magnetic part 51b, respectively.
, 52d are provided facing each other.

and permanent magnets 52a, 52b and 52c, 52
A coil 23 wound around a coil bobbin 241 is interposed between the coil bobbin 241 and l in the same manner as in FIG.

Therefore, with such a configuration, it is possible to achieve the same effects as in the practical example described above. In addition, the first magnetic part 51
A permanent magnet 52M on the opposing surface of a and the second magnetic part 51b,
By arranging 52b or 52C, 52d,
Magnetic flux is made uniform, electromagnetic force and restoring force can be efficiently generated, and control characteristics can be significantly improved.

Note that the present invention is not limited to the above-mentioned embodiments, and can be implemented with various modifications without changing the gist.

For example, in the above embodiment, a permanent magnet was used as the magnetic generation source, but the present invention is not limited to a magnet, and an electromagnet may be used instead.

Furthermore, in each of the above embodiments, the individual windings of the thrust magnetic bearing and the radial magnetic bearing are wound in the same direction. When current flows in the same direction, it is also possible to wind in opposite directions so that the action is reversed, thereby strengthening the restoring force when the lens barrel is eccentric and stably holding it.

An example of the case where this is applied to the third embodiment shown in FIG. 4 is ζζ as shown in FIG. 6. In other words, if currents flow in opposite directions between the winding in the area B and the winding in the region B, the effects described for each of the above embodiments will be produced at both ends of the opposing surfaces of the magnetic poles 41m and 431. It turns out.

[Brief explanation of the drawing]

Figure 1 (a) g and (bl) show an example of a conventional optical disk pick, where (a) is a plan view and (b) is a vertical sectional view taken along the optical axis I of the lens barrel. , FIG. 2 (hot) and FIG. 2(b) show an embodiment of the present invention, in which (1) is a plan view and (bl is a vertical sectional view taken along the optical axis of the lens barrel. ls3 to 3). 4 is a diagram showing the main parts of the second and third embodiments of the present invention, FIG. 3 is a perspective view, FIG. 4 is a vertical sectional view, and FIG. 4, in which (a) is a plan view, (b) is a longitudinal sectional view taken along the optical axis of the lens barrel, and FIG. 6 is a sectional view showing a modification of the t43 embodiment. 1... Stationary part 2... Lens barrel 3... Lens 4... Movable frame 5m, 5b... Leaf spring 6m, 6b... Leaf spring 7... Magnetic circuit
7...Magnetic gap 8...Winding 9m, 9
b... Attraction iron piece toa, tab -... Electromagnet 11... Outer frame 12... Lens 13...
Lens barrel 1: 13g...Thrust shaft portion 13b
... Radial shaft portion 14 ... Thrust magnetic bearing 15
...Radial magnetic bearing 16...Magnetic member 17.
... Permanent magnet 18 ... Magnetic member 19 ... Winding wire 20 ... First magnetic member 21 ... Second magnetic member 211 ... Magnetic pole 22 ... Magnet
23... Winding 24... Bobbin 31... First magnetic member 32... Magnetic member of f42 32a... Magnetic pole 33
... Coil pobbin 34 ... Winding 41 ... First magnetic member 41a ... Magnetic pole 42 ... Magnet
43...Second magnetic member 43m-...Magnetic pole
44... Coil pobbin 45... Winding 51... Magnetic member 511... First magnetic part 5
1b--Second magnetic part 521-524--Permanent magnet 91E1 Figure (a) b (b) Figure 2 (a) Figure 3 Figure 4 Figure 5 (a) (b) 206- Figure 6

Claims (1)

[Claims] (1) A cylindrical outer frame, a lens barrel that holds a lens, and
A thrust magnetic bearing that holds the thrust shaft portion of the cylinder relative to the outer frame, and at least three stones of the same number on the inner circumference of the outer frame are provided at equal intervals and form an outer magnetic path having a U-shaped cross section. 1
a magnetic member, a second magnetic member protruding from a substantially intermediate portion of the first magnetic member and forming an internal magnetic path, and opposing surfaces of the second magnetic member and the magnetic member @1. A magnetic pole formed by protruding at least one side by a predetermined area, a magnetic generation source provided on at least one of the first magnetic member 2 and the second magnetic member, and a magnetic generation source provided on the radial shaft portion of the boundary portion. At the same time, the magnetic poles of the first magnetic member and the magnetic member of t42! ! 1. A pickup for an optical disk, characterized in that it is equipped with a winding inserted so as to intersect with the magnetic flux. 12)! 1. The optical disk drive according to claim 1, wherein the magnetic generation source is constituted by a permanent magnet. (3) The magnetic source is composed of an electromagnet! The scope of the patent claims herein is a pickup for an optical disk. (4) The optical disk pickup according to claim 1, wherein magnetic poles are formed by protruding permanent gravel from opposing surfaces of the first magnetic member and the second magnetic member, respectively. (5) The optical disc pickup according to claim 1, wherein the first magnetic member is cut into a cylindrical shape with a bottom. (6) The winding is divided into two at the center so that the magnetic forces generated in the magnetic circuit constituted by the twelfth and second magnetic members are opposite to each other. pickup for optical discs.