JPH11232667A - Magnetic driving apparatus and optical disk apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To move an objective lens in a track and a focus directions without inclining an optical axis of the lens in an objective lens-driving apparatus used in an optical disk apparatus, etc. SOLUTION: A coil 3 is set at the side of a movable part loading an objective lens. An SC face of the coil 3 is made smaller than an SM face of a magnet 1 opposed to the coil 3. The coil 3 is moved within a range opposed to the magnet 1 to make a position where a driving force acts to the coil 3 agree with the center of gravity of the movable part (corresponding to a position of the center of gravity of a moving body).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic driving device utilizing a driving force generated by using a magnet and a coil, and more particularly, to a magnetic driving device using this magnetic driving device as an objective lens driving device. Recording information on an information recording medium,
The present invention relates to an optical disk device that performs reproduction.

[0002]

2. Description of the Related Art In an optical disk device, a laser beam is focused on a rotating recording medium by an objective lens to record or reproduce data. In order to irradiate a predetermined track with this laser light, a carriage on which an objective lens is mounted is moved to a predetermined track by a DC motor or a voice coil motor. However, the track position fluctuates slightly due to surface runout or eccentricity of the recording medium. Therefore, it is necessary to move the laser beam in a focus direction and a track direction, which will be described later, following the fluctuation. An objective lens driving device for moving the lens in the two directions is used.

FIG. 13 is a diagram showing a main part of an optical disk device, and a drive unit (not shown) rotates a disk 200 as a recording medium. A carriage 202 is movably arranged in a base 201 arranged below the disk 200, and the carriage 202 is moved to a vicinity of a predetermined track position in a radial direction of the disk 200, that is, a voice coil (not shown) in the track direction. It is moved by a motor or a DC motor.

[0004] An objective lens driving device 205 is mounted on the carriage 202 and emits laser light from a light source such as a laser diode built in the optical head 203.
The light is focused on the surface of the disk 200. In addition to the conventional example shown in FIG. 13, there is a type in which the optical head 203 is mounted on the carriage 202.

The objective lens driving device 205 has a mechanism for finely moving the objective lens 204 in a track direction and a direction perpendicular to the surface of the disk 200, that is, a focus direction. The irradiation position of the laser beam is moved in the two directions according to the change in the track position due to the eccentricity.

Next, FIG. 10 shows an example of a conventional objective lens driving device. In FIG. 10, the objective lens 100 is mounted on an objective lens holding member 101. The coil holding member 103 is attached to the objective lens holding member 101 (or the objective lens holding member 101 and the coil holding member 1).
The focus coil 104 is attached to the coil holding member 103, and two track coils 1 are provided at both ends of the focus coil 104.
05 are each attached.

On the other hand, the objective lens holding member 101 is connected to the actuator base 108 via four elastic members 106.
Are elastically supported by two fixing members 107 fixed to the fixing member 107.

[0008] A U-shaped yoke 110 is attached to the actuator base 108.
The magnet 109 is arranged on one of the pieces 10 facing each other, the focus coil 104 is arranged on the other piece, and the track coil 105 and the magnet 109 are arranged to face each other.

By controlling the current flowing through the focus coil 104 and the track coil 105,
A driving force determined by Fleming's left-hand rule is generated in the focus coil 104 and the track coil 105, and the driving force moves the objective lens holding member 101 connected to the coil holding member 103, and moves the objective lens 100 in the focus direction and the track direction. Go to

However, the conventional objective lens driving device shown in FIG. 10 has a problem with respect to the fluctuation of the inclination of the optical axis of the objective lens. This will be described in detail with reference to FIG.

FIG. 11A is a perspective view of a driving section composed of a magnet and a coil, and FIGS. 11B and 11C are views seen from the direction a in the perspective view. FIG. 11 (B)
FIG. 11C shows a positional relationship between the respective members when a current is not flowing through the track coil 105. FIG. 11C shows a state when a current is passed through the track coil 105 and the focus coil 104 and the track coil 105 move in the track direction. The positional relationship of each member is shown.

As shown in FIG. 11B, when a current is not flowing through the track coil 105, the position of a point where the driving force generated by the current flowing through the focus coil 104 and the magnetic field from the magnet 109 acts equivalently. The center of gravity of the movable part (consisting of the objective lens 100, the objective lens holding member 101, the coil holding member 103, the focus coil 104, and the track coil 105) of the objective lens system supported by the elastic member 106 matches. However, as shown in FIG. 11C, when the focus coil 104 and the track coil 105 move in the track direction, the center of gravity moves, but the point on which the driving force acts does not move. Will be shifted.

The reason why the optical axis of the objective lens is tilted due to the difference between the center of gravity and the point where the driving force acts will be described with reference to FIG. FIG. 12 is a view taken in the direction of the arrows cc in FIG. 11C, and the magnets 109 are indicated by dotted lines. When a current is applied to the focus coil 104, a portion of the focus coil 104 where a driving force is generated is a magnet 1
The portion existing in the magnetic field from 09 is indicated by a hatched portion that is described as “a portion where the magnet is projected onto the focus coil”.

As shown in FIG. 12, the driving force F is applied to a point A which is the center of the hatched portion (the focus coil 1).
04 is formed by winding conductors at a uniform pitch), but the center of gravity of the movable part is at the center of the focus coil 104 because it does not fluctuate due to movement.
When the focus coil 104 moves after moving in the track direction as shown in FIG. 12, the movable portion rotates around the center of gravity after the movement. As shown in FIG.
When the driving force is in the direction shown in the figure, the objective lens optical axis mm
Has a problem that it tilts in the direction B shown in the figure.

[0015]

As the recording capacity of the recording medium increases, the pitch between tracks becomes narrower, and the allowable value of the deviation between the track position and the spot position of the laser beam also becomes smaller. Is coming.

One of the causes of the deviation of the spot position between the track position and the laser light is a change in the inclination of the optical axis of the objective lens when the objective lens is moved. Accordingly, it has become increasingly necessary to suppress this fluctuation.

However, as described above, in the conventional objective lens driving device, when the movable portion moves, the point on which the driving force acts is shifted from the center of gravity, so that the objective lens optical axis is tilted. However, there was a problem that the data recording / reproducing performance deteriorated.

The present invention relates to a magnetic drive device utilizing a generated driving force by using a magnet and a coil, wherein the position of the center of gravity on the movable portion side and the position of a point where the drive force acts on the movable portion are provided. It is an object of the present invention to provide a drive device whose positional relationship with does not fluctuate even when the movable part moves, and more specifically,
An object of the present invention is to provide an objective lens driving device in which the optical axis of the objective lens does not tilt even when the movable section moves.

[0019]

In order to achieve the above-mentioned object, the present invention provides a method according to the present invention, wherein a point where a driving force applied to a movable portion holding an objective lens acts is within a movable range of the movable portion. It can be configured to be always near the center of gravity of the movable part, and preferably at the same position, and therefore, the inclination of the optical axis of the objective lens is suppressed.

That is, according to the first aspect of the present invention, there is provided a magnet and a coil which are arranged to face each other, one of the magnet and the coil is fixed, and the magnet and the coil are generated by a magnetic field from the magnet and a current flowing through the coil. The other is configured to move by the driving force, the other has a smaller area than the one, and the surface projected to the one opposing surface within the range in which the other moves is the opposing surface The gist of the present invention is a magnetic drive device characterized by being included in the inside.

According to a second aspect of the present invention, in the magnetic drive device according to the first aspect, the coil includes a plurality of coils wound around a magnetic member and having different winding axis directions. Abstract.

According to the third aspect of the present invention, the other moving member is fixed to a lens system for condensing a light beam for recording or reproducing information on a recording medium. The gist of the present invention is an optical disk device including a magnetic drive device.

The gist of the present invention will be described in detail with reference to FIG. 1 showing the principle of the present invention, taking an example in which the present invention is applied to an objective lens driving device of an optical disk device. (A) of FIG.
Is a magnet 1 magnetized in the illustrated direction, having a width L and a height H.
Moving body 4 having magnetic member 2 and coil 3
It is a perspective view which shows the arrangement relationship of. FIG. 1B is a diagram when the moving body 4 moves in the C direction by Δ in parallel with the magnet 1 as viewed from the B direction.

In FIG. 1, the dimensions d and W of the coil 3 are smaller than the dimensions L and H of the magnet 1, respectively. FIG.
Then, in order to explain the principle of the present invention in an easy-to-understand manner, the case where the moving body 4 is installed on the movable part (that is, the magnet 1 is fixed and the moving body 4 moves) is described. And the coil is only one type of the coil 3.

Next, the terms used in the claims of the present invention will be explained. In the invention of claim 1, the "opposing surface" described as "the other has an opposing surface smaller than the one" is the same as that in FIG.
D for forming the coil 3 described as SC of the coil 3 of FIG.
× W. Also, "the other opposing surface projected onto the one opposing surface is within a range in which the other moves"
"The one opposing surface" is the S1 of the magnet 1 in FIG.
M is a plane, and the “projected other facing surface”
Is the d × W portion of the coil 3 in FIG.
The "winding axis" described in the second aspect of the present invention corresponds to an axis around which a conductor of a coil is wound when the conductor of the coil is wound, and an example is described as a winding axis in FIG. .

Next, the principle will be specifically described. FIG.
As shown in (B), even after the moving body 4 moves the distance Δ, the moving body 4 is located within the outer shape range of the magnet 1 indicated by the dotted line, that is, within the range in which the magnetic field intensity generated from the magnet 1 is substantially uniform. Therefore, the driving force F generated when the coil 3 is energized is
It acts equivalently on the center point of the coil 3 shown in FIG. If the moving range of the moving body 4 is within the dotted line shown in FIG. 1B, that is, if the magnetic field strength is within a substantially uniform range, the point at which the driving force F acts is located at the center of the coil 3. It is constant in points.

Therefore, if the moving body 4 is configured so that the center point on which the driving force F acts and the center of gravity of the moving body 4 coincide, the driving force acting on the coil 3 when the coil 3 is energized. No rotational moment is generated by F.

In FIG. 1, only the moving body 4 is shown and described. However, a moving section holding an objective lens is provided in connection with the moving body 4, and the center of gravity of the whole of the moving body 4 and the moving section and the drive are provided. If the point at which the force F acts is brought closer to, and more preferably, coincides with, the rotational moment does not occur as described above, so that there is an effect of suppressing the tilt of the optical axis of the objective lens. It is possible to provide an objective lens driving device corresponding to a higher density of the capacity.

Further, although the magnetic member 2 is not necessarily used, it is preferable to use the magnetic member 2 so that the magnetic field distribution does not fluctuate greatly with the movement of the moving body 4. 2, the magnet 3 returns to the magnet 1, and has the effect of reducing the effect of this magnetic field on the coil conductor on the side not facing the magnet 1, so that the coil 3 can be reduced in size, and therefore the objective lens There is an effect that the driving device can be downsized.

[0030]

Embodiments of the present invention will be described below.
FIG. 2 shows a first embodiment of the present invention, in which an objective lens 10 is provided.
Is fixed to the objective lens holding member 11, and the objective lens holding member 11 is connected to the coil holding member 15. The coil holding member 15 is formed by winding two types of coils around the magnetic member 12, a track coil 13 whose winding axis direction is the track direction and a focus coil 14 whose winding axis direction is the focus direction. It is fixed.

Further, the coil holding member 15 is fixed to the fixing member 17 via an elastic member 16 (two in this embodiment, two in the front and two behind the objective lens holding member 11).
The fixing member 17 is connected to the actuator base 18.
It is fixed to.

Here, the functions of the objective lens holding member 11 and the coil holding member 15 may be combined into one member to reduce the number of parts. On the other hand, the magnet 19 having the illustrated magnetization direction is fixed to the yoke 20, and this yoke 20
Are fixed to the actuator base 18.

The reason why the coils 13 and 14 and the magnet 19 are arranged in a direction orthogonal to the track direction and the focus direction is that each coil 1
This is because the gap between the magnets 3 and 14 and the magnet 19 is not changed.

In this embodiment, the movable part is the objective lens 10,
Objective lens holding member 11, coil holding member 15, track coil 13, focus coil 14, and magnetic member 1
2 and the like.

In this embodiment, in order to operate the track coil 13 and the focus coil 14 in a uniform magnetic field without disturbing the magnetic field from the magnet 19, the yoke 20 and the magnetic member 12 are made of a magnetic material. The objective lens holding member 11, the coil holding member 15, and the actuator base 18 are made of a non-magnetic material such as aluminum or a resin material. Further, the magnetic member 12 may be a mixture of a magnetic material and a non-magnetic material. Further, as a material of the elastic member 16, spring steel, brass, nickel silver, phosphor bronze, piano wire, steel wire, or the like is preferable, and the track coil 13 and the focus coil 14 are electrically connected to a circuit (not shown). Also use. The shape of the elastic member 16 is usually a plate shape, but may be a linear shape, or may be a composite material of a metal material and a non-metal material.
It is not necessary to limit to four as in the embodiment.

In the present embodiment, the shape and weight of the coil holding member 15 are devised so that the entire center of gravity of the movable portion, the magnetic member 12, the track coil 13 and the focus coil 14 and the like can be adjusted by the magnets 19 of the coils 13 and 14. It is configured so as to be located at the center of the surface opposite to.

The operation of the coil and the magnet of this embodiment will be described with reference to FIG. FIG. 3A shows the coil and the magnet portion extracted from FIG. 2 and FIG. 3B shows the coil and the magnet when the movable part is moved by ΔT in the track direction and ΔF in the focus direction. It is the figure which looked at the positional relationship of a magnet from the a direction of (A).

As shown in FIG. 3B, the surfaces of the track coil 13 and the focus coil 14 facing the magnet 19 provided on the movable portion side have dimensions of LT and LF in the track direction and the focus direction, respectively. It is configured to fit within a WT, WF smaller than a certain magnet 19. Therefore, the magnet 19 which faces the track coil 13 and the focus coil 14 after the movement shown by the solid line in FIG.
As described above, the driving force acts on the center of gravity, and no rotational moment that tilts the optical axis of the objective lens is generated. Here, the WT and WF will be described in further detail. If the objective lens 10 is moved within the range of ± ΔT and ± ΔF in the track direction and the focus direction, respectively, WT is L
T-2ΔT or less, and WF may be LF-2ΔF or less (however, the track coil 1 facing before moving)
3, when the centers of the focus coil 14 and the magnet 19 coincide when viewed from the direction a).

Further, in the first embodiment, the magnetic member 1
The positional relationship between the magnet 2 and the magnet 19 is such that a tensile stress is generated in the elastic member 16 and, therefore, the elastic member 16 does not bend. The coil 13 and the focus coil 14 can be located in a stable magnetic field.

The arrangement of the track coil 13 and the focus coil 14 between the objective lens 10 and the magnet 19 has the effect of reducing the size of the entire objective lens driving device.

In the above description, as described above, the case where the coil is provided on the movable portion side has been described. However, the coil need not always be provided, and a magnet may be provided on the movable portion side. The case where a magnet is provided on the movable portion side will be described with reference to FIG.

In FIG. 4, a magnet 43 having the illustrated magnetization direction is provided on the movable portion side, and a magnetic member 40 having a first coil 41 and a second coil 42 is provided at the position of the magnet 19 in FIG. FIG. 4A shows the positional relationship of the magnet 43 and the like at this time, and FIG. 4B shows the positional relationship as viewed from the direction a.

Here, the surfaces of the coil and the magnet facing each other are WT × LF for the first coil, WF × LT for the second coil, and the movable part facing these surfaces. The surface of the magnet 43 provided on the side is reduced.

That is, the first coil 41 and the second coil 4
The surface of the magnet 43 is smaller than the size of the crossing portion of No. 2. As can be seen from FIG. 4B, which shows this state as viewed from the direction a, the size WT of the crossing portion is maintained even after the magnet 43 moves.
If the size of the facing surface of the magnet 43 is determined to be within the size of × WF, the point at which the driving force acts on the magnet 43 as long as the magnet 43 moves within the range of WT × WF. Can be regarded as the center point of the magnet 43. Therefore, if the point is configured to be the center of gravity of the movable portion, no rotational moment is generated by the driving force, and the problem that the optical axis is inclined with the movement of the objective lens does not occur.

As described above, another advantage when the magnet is used on the movable portion side is that the electrical connection can be made without passing through the movable portion, so that reliable electrical connection can be made, and the weight of the coil is not necessarily reduced. Since it is not necessary to use a thick conductor, a large current can flow even if the number of turns of the coil is reduced, and a desired driving force can be generated. This has the effect of improving the responsiveness of the movement control.

Next, FIG. 5 shows a second embodiment of the present invention. In FIG. 5, components having the same functions as those of the members and the like described in the first embodiment are denoted by the same reference numerals. This second
In the second embodiment, as in the first embodiment, the track coil 13 and the focus coil 14 are provided on the movable portion side, and the magnets 19 are provided at positions facing each other. It is similar to the example.

The feature of the second embodiment is that the magnet 19 is arranged between the objective lens 10, the track coil 13 and the focus coil 14 as shown in FIG. In addition to the effects of the example, the objective lens holding member 11 and the coil holding member 15 have an effect of easily setting the center of gravity of the movable portion.

Next, FIG. 6 shows a third embodiment of the present invention. Also in FIG. 6, the same reference numerals are used for those having the same functions as the first embodiment. In the third embodiment,
On both sides of the objective lens holding member 11, a coil group of the track coil 13 and the focus coil 14 and two magnets 19 are arranged symmetrically about the objective lens 10. In the third embodiment, as in the first embodiment, the track coil 13 and the focus coil 1
4 are provided, and magnets 19 are provided at positions facing each other, and the relationship between the facing surfaces is the same as in the first embodiment.

The feature of this embodiment is that the respective members are arranged symmetrically with respect to the optical axis of the objective lens 10, so that there is an effect that the balance can be easily obtained. Next, FIG. 7 shows a fourth embodiment of the present invention. This embodiment relates to a magnetic member for winding a coil, and FIG.
FIG. 7B shows a state in which the track coil 13 and the focus coil 14 are wound around the magnetic member itself provided with the magnetic material protrusion member 30 made of a magnetic material at a corner. The action of the magnetic projection member 30 allows the winding range of the track coil 13 and the focus coil 14 to be easily set, and has an effect of facilitating coil production.

Further, as shown in FIG. 7 (C), the same effect and lighter weight can be obtained by providing a groove 32 in the area where the coil is wound around the magnetic member 31, as shown in FIG. It becomes possible.

Next, FIG. 8 shows a fifth embodiment of the present invention. In the first to fourth embodiments, the winding axis direction of the track coil and the focus coil is set to the track direction and the focus direction. However, in the fifth embodiment, the coil winding is performed. The axis is wound in a winding axis direction different from the track direction and the focus direction.

FIG. 8A shows two types of coils 34, magnets 19, and a yoke 20 supporting the magnets 19, in which the direction of the winding axis of the coils is ± 45 ° different from the focus direction on the magnetic member 33.
FIG. FIG. 8B is a view of the magnetic member 33 and the coil 34 as viewed from the magnet 19 side. In the coil of the fifth embodiment, since the coil winding direction is not made coincident with the track direction and the focus direction, the coil current is controlled so that the vector sum of the driving force generated in each coil becomes a desired force. There is a need. The feature of the fifth embodiment is that the winding width CW of the coil shown in FIG.
Although depending on the like, the widths WT and WF of the coil 34 in the track direction and the focus direction can be reduced, and accordingly, the corresponding magnet shape can be reduced, and the entire objective lens driving device can be downsized.

Next, FIG. 9 shows a sixth embodiment of the present invention. In the sixth embodiment, a gap is provided between the magnetic member 12 and a coil surface of the track coil 13 and the focus coil 14 wound around the magnetic member 12 that do not face the magnet. 9) shows a perspective view, and FIG. 9 (B) shows a view from the a direction described in the perspective view. Most of the magnetic lines of force from the magnet pass through the magnetic member 12 and return to the magnet, so that no driving force is generated in the coil on the surface that does not face the magnet, but by providing this gap, the effect of the magnetic field can be further reduced. The magnetic member 12, the track coil 13 and the focus coil 14 of this embodiment can be
By using this embodiment, the point where the driving force acts and the position of the center of gravity can be brought closer to each other and further matched.

In the above description, the optical paths of the laser light and the like have not been described in detail in the first to third embodiments, but it is easy to guide the laser light and the like to the objective lens by a known technique. Therefore, the description is omitted.

In the above description, the coils are installed on the movable section in the second and third embodiments. However, as described in detail in the first embodiment, the coils may be installed on the movable section. good. Also,
Although a specific embodiment in which the fourth, fifth, and sixth embodiments are mounted on an objective lens driving device is not shown, it is easily possible to mount them.

In the first to third embodiments described above, examples in which the magnetic driving device of the present invention is applied to the objective lens driving device have been described. In addition to the driving device, the present invention can be applied to any configuration in which the center of gravity of the movable portion and the point at which the driving force acts on the movable portion need to coincide.

[0057]

According to the first aspect of the present invention, it is possible to provide a magnetic drive device in which the position of the point where the driving force acts on the movable portion does not change even if the movable portion is moved to a desired position. If the position of the driving point and the position of the center of gravity of the movable part are brought close to each other, and preferably coincide with each other, there is an effect that the movable part can be moved without generating a rotational moment. Furthermore, in this magnetic drive device, the elastic support is configured to generate tensile stress, so that the gap between the coil and the magnet can be kept constant and the movable part can be moved, so that the magnetic field applied to the coil can be reduced. Since there is no fluctuation, the driving force can be controlled by the magnitude of the current flowing through the coil, and there is an effect that the movement control of the movable portion becomes easy.

Further, according to the invention of claim 2, claim 1
In addition to the effects of the invention, it is possible to apply a magnetic field only to a desired portion of the coil, and to reduce the size of the coil,
Therefore, since the movable portion can be configured to be small and lightweight, there is an effect that the movable portion of the magnetic drive device can be moved at high speed.

Further, according to the invention of claim 3, claim 1
In addition to the effects of the invention, the objective lens driving device having the objective lens mounted on the movable portion side does not tilt the optical axis of the objective lens due to the movement of the movable portion, and therefore, has a high density recording capacity in the optical disc device. There is an effect that information can be recorded or reproduced on the optical information recording medium. In addition, the objective lens driving device is configured to generate a tensile stress on the elastic support, so that the gap between the coil and the magnet can be kept constant and the objective lens can be moved, so that the magnetic field applied to the coil can be reduced. Since there is no variation, it is possible to control the driving force to the objective lens holding unit by the magnitude of the current supplied to the coil, and there is an effect that an optical disk apparatus in which the movement control of the objective lens is easy can be realized.

Further, a magnetic field can be applied only to a desired portion of the coil, and the coil shape can be reduced in size. Therefore, the movable portion can be made smaller and lighter, so that the objective lens driving device can be moved at a high speed. Therefore, there is an effect that an optical disc device capable of performing an operation such as recording or reproduction of information at a high speed can be realized.

[Brief description of the drawings]

FIG. 1 illustrates the principle of the present invention.

FIG. 2 is a diagram showing a first embodiment.

FIG. 3 is a diagram illustrating the operation of a coil and a magnet (when the coil moves).

FIG. 4 is a diagram for explaining the operation of a coil and a magnet (when the magnet moves).

FIG. 5 is a diagram showing a second embodiment.

FIG. 6 is a diagram showing a third embodiment.

FIG. 7 shows a fourth embodiment.

FIG. 8 shows a fifth embodiment.

FIG. 9 is a diagram showing a sixth embodiment;

FIG. 10 shows a conventional example.

FIG. 11 is a diagram showing the operation of a conventional moving body.

FIG. 12 is a diagram for explaining occurrence of inclination of an optical axis of an objective lens.

FIG. 13 is a diagram illustrating an arrangement of an objective lens driving device.

[Explanation of symbols]

 Reference Signs List 10 Objective lens 12 Magnetic member 13 Track coil 14 Focus coil 19 Magnet

Claims (3)

[Claims] 1. A device comprising a magnet and a coil arranged opposite to each other,
One of the magnet or the coil is fixed, and the other is moved by a driving force generated by a magnetic field from the magnet and a current flowing through the coil, and the other is configured to have a facing surface smaller than the one. And the other opposing surface projected onto the one opposing surface is included in the one opposing surface within a range in which the other moves. 2. The magnetic drive device according to claim 1, wherein the coil is wound around a magnetic member and includes a plurality of coils having different winding axis directions. 3. The magnetic drive device according to claim 1, wherein the other moving member is fixed to a lens system for condensing a light beam for recording or reproducing information on a recording medium. An optical disc device characterized by the above-mentioned.