JP3495392B2 - Objective lens drive - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device, and more particularly to an objective lens driving device suitable for use in an optical disk device, a magneto-optical disk device and the like.

[0002]

2. Description of the Related Art As a conventional technique relating to this type of objective lens driving device, for example, a technique disclosed in Japanese Patent Laid-Open No. Sho 62-208437 is known.

In this prior art, the objective lens is arranged on the rotating arm so as to be separated from the supporting shaft, and the supporting shaft axis direction driving means (focusing) and the rotating direction driving means (tracking) are arranged on the rotating arm. It is a thing.

FIG. 5 is a perspective view showing the structure of an objective lens driving device according to the prior art. The prior art will be described below with reference to this drawing. In FIG. 5, 1 is an objective lens, 2 is a rotating arm, 3 is a bearing, 4 is an axial drive coil, 5
Reference numerals a and 5b are rotational direction driving coils, 7a to 7d are yokes, and 8a to 8d are magnets.

In the prior art shown in the drawing, as shown in FIG. 5, a rotary arm 2 is provided with a plurality of rotary direction driving coils 5a, 5b having an objective lens 1 and a symmetric surface opposed to a spindle 9. The movable portion, which is disposed and in which the axial drive coil 4 is disposed, is configured by magnets 8a to 8d, yokes 7a to 7d, and the like, and is coupled to a fixed portion that forms a magnetic circuit. The movable portion composed of the objective lens 1, the axial driving coil 4, the rotational driving coil 5, the bearing 3 and the like is symmetrically supported by the elastic member with respect to the support shaft 9 of the fixed portion. ing. As a result, a magnetic circuit having a magnetic field distribution substantially in the opposite direction is formed by the magnets 8b and 8d with respect to the symmetry planes of the plurality of rotation direction driving coils 5a and 5b.

In the prior art configured as described above, since only a turning moment around the support shaft can be generated, a translational force is not applied to the support shaft, and the bearing 3 and the support shaft 9 are separated from each other. It is possible to reduce friction generated between them and vibrations of the support shaft 9 and other components transmitted to the bearing 3.

[0007]

However, in the above-mentioned conventional technique, the rotational direction driving coils 5a and 5 having the symmetry planes are used.
Since a magnetic field in the opposite direction to b is given to the symmetry plane, a total of four magnets are used, including the one also used as the axial drive coil 4, which makes it difficult to reduce the size and cost. I have a problem.

Further, in the above-mentioned prior art, the rotational axis driving coils 5a and 5b having symmetrical surfaces have a substantially linear projection surface shape in the axial direction of the spindle, which is for driving in the rotational direction from the spindle. There is a problem in that the distance to the coil leading end is long, and therefore the moment of inertia is large, and in order to increase the rotational acceleration, the magnets 8a to 8d and the rotational direction driving coil 5 must be large. ing.

As described above, the prior art does not consider downsizing and cost reduction, and the friction generated between the bearing and the support shaft and the support shaft and other vibrations transmitted to the bearing are not considered. In order to reduce and obtain a predetermined rotational acceleration characteristic, there is a problem that the device becomes large.

Such a problem is that even-numbered driving coils are arranged in each magnetic circuit so as to be point-symmetric with respect to the support shaft, and balance is provided as counter balance of the objective lens. The weight is placed on the opposite side of the spindle from the objective lens, and the magnet is placed parallel to the straight line connecting the objective lens and the spindle so that the distribution of the magnetic flux due to this is symmetric with respect to the spindle. It can be solved by doing.

However, in the above-mentioned structure, the movable portion is made heavy and the balance weight which deteriorates the dynamic characteristics is provided, and the rotation direction driving coil arranged on the objective lens side is
Since it may block the laser light that enters the objective lens,
It is necessary to make the rotation direction driving coil small, which causes a problem such as a decrease in rotation acceleration.

Further, in the above-mentioned structure, a translational force in the tracking direction is generated by the driving current flowing in the horizontal portion of the rotation direction driving coil and the vertical leakage flux of the magnet acting on this portion, and the translational force in the tracking direction is generated. The bearing is in strong contact with the shaft, which causes a problem that it becomes impossible to reduce friction generated between the bearing and the support shaft and vibration from the support shaft transmitted to the bearing.

The object of the present invention is to solve the above-mentioned problems of the prior art and to reduce the friction between the bearing and the support shaft and the vibration of the support shaft and other vibrations transmitted to the bearing, as in the case of the prior art. An object of the present invention is to provide an objective lens driving device that can obtain a predetermined rotational acceleration characteristic and can be further downsized and reduced in cost.

[0014]

According to the present invention, the above object is to provide an objective lens, a coil for driving a support shaft in an axial direction, and
A plurality of rotation direction driving coils are separated from the spindle.
Rotatably mounted on a support shaft
The axial drive coil and the rotational drive
A plurality of magnetic circuits that generate magnetic flux that intersects with the coil
Equipped with rotation around the spindle and sliding of the spindle in the axial direction
In the objective lens driving device capable of
The distance between the parts facing each other connects the objective lens and the support shaft.
In front of multiple magnetic circuits that differ at both ends in the direction of the
The shape projected in the axial direction of the spindle is
Symmetrical to the straight line connecting the support shaft, and passing through the support shaft,
Arranged so as to be asymmetric with respect to a straight line orthogonal to the straight line.
And the rotation direction drive coil is connected to the objective lens.
A straight line connecting to the support shaft and a line perpendicular to the support shaft
Is provided apart from the straight line in the direction of
The shape projected in the line direction is approximately
It is achieved by curving in a V shape in the direction of decreasing distance .

Further, the above-mentioned object is to reduce the influence of the translational force in the tracking direction generated by the drive current flowing in the horizontal portion of the rotating direction drive coil and the vertical leakage flux from the magnet acting on this portion. As described above, a force having substantially the same magnitude as the translational force and in the opposite direction is generated in the rotation direction drive coil, and the rotation arm, the axial direction drive coil, the rotation direction drive coil, and the bearing. This is achieved by supporting a movable portion composed of an objective lens and the like with a plurality of elastic members that generate forces and moments that are substantially symmetrical with respect to the support shaft.

[0016]

[0017]

The magnetic flux radiated from the magnet intersects with the coil for driving the rotation direction, and an electromagnetic force is generated by supplying a driving current to the coil. This electromagnetic force serves as a rotational moment that rotates the objective lens about the support shaft, and it is desirable to generate only the electromagnetic force that originally provides the rotational moment. However, in reality, a translational force in the tracking direction is generated in addition to the rotation moment due to the action of the leakage magnetic flux in the vertical direction from the magnet and the current flowing in the horizontal portion of the rotation direction driving coil.

It is desirable that this translational force is originally small in order to increase the frictional force between the bearing and the support shaft and to adversely affect the device such that the vibration of the support shaft is easily transmitted to the bearing.

The present invention, a magnet shaped Ha or, placed by shifting the rotational direction drive coil relative to the magnet
By be Rukoto, since the arranged asymmetrically the rotational direction drive coil from the magnetic flux center of the magnetic circuit, will be the magnetic flux emanating from the magnet is交鎖oblique to the rotational direction drive coil, The electromagnetic force generated by this is also generated in an oblique direction.

This electromagnetic force can be considered separately as an electromagnetic force for generating a rotation moment for rotating the objective lens and an electromagnetic force orthogonal to the electromagnetic force. Of these electromagnetic forces, the electromagnetic force that is orthogonal to the electromagnetic force that generates the rotation moment is a translational force, but it is different from the rotation moment due to the action of the leakage flux and the current flowing through the horizontal portion of the rotation direction drive coil. The direction is opposite to the translational force due to the electromagnetic force generated in the direction.

Therefore, according to the present invention, the unnecessary translational force in the tracking direction can be totally eliminated, so that the frictional force between the bearing and the support shaft becomes large, and the support shaft and Other problems, such as easy transmission of vibration to the bearing, do not occur. Further, in the present invention, since the tip of the rotation direction driving coil 5 is bent in a dogleg shape,
Since the distance from the support shaft is small, the moment of inertia can be reduced, and the rotational acceleration characteristics can be improved.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an objective lens driving device according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a top view showing the structure of an embodiment of the present invention, FIG. 2 is a sectional view showing the structure of an embodiment of the present invention, and FIG.
Is a perspective view for explaining the operation of the embodiment of the present invention, and FIG. 4 is a top view for explaining the operation of the embodiment of the present invention. Figure 1
In FIG. 4, 4a and 4b are axial driving coils, and 6
a to 6d are suspensions, 10 is a base plate, and other reference numerals are the same as those in FIG.

In FIG. 1 showing the structure of an embodiment of the present invention, an objective lens 1 is inserted and fixed to one end of a rotary arm 2 made of a lightweight and highly rigid non-magnetic material such as a PPS material. The bearing 3 provided on the rotating arm 2 constitutes a sliding portion with respect to the support shaft 9 of the fixed portion, and is formed by machining from a lightweight and highly rigid non-magnetic material, or is injection-molded from a PPS material or the like. ing.

The spindle axis (focus) direction driving coils 4a and 4b are fixed to a bobbin formed on the rotary arm 2 substantially symmetrically with respect to the spindle 9. In addition, the rotational direction driving coils 5a and 5b are used for the objective lens 1
Is also provided on the side opposite to the objective lens 1 with respect to the bearing 3. Further, the rotational direction driving coils 5a and 5b are separated in the direction (tracking direction) orthogonal to the straight line connecting the objective lens 1 and the support shaft 9, so that only a part of the coil exists in the magnetic circuit . It is provided in a position and is fixed to the bobbin. The rotation direction driving coils 5a and 5b are bent in a dogleg shape in a direction in which the distance from the support shaft is shortened near the center thereof.

As shown in FIG. 2, a support shaft 9 is press-fitted and fixed substantially vertically to a base plate 10 of a fixed portion made of a magnetic material such as iron. The support shaft 9 is made of a highly rigid material, and its sliding surface is coated with a resin having a low friction coefficient.

Further, the base plate 10 has yokes 7a, 7b, 7c, 7 forming magnetic gaps 11a, 11b.
d is formed on the yokes 7a and 7c, and the support shaft axis direction driving coils 4a and 4b and the rotation direction driving coils 5a and 5c are formed on the yokes 7a and 7c.
magnets 8a, 8b that generate a magnetic field that also serves as both b and
Is attached. Magnets 8a and 8b of the yokes 7a and 7c
The surface to which is attached is inclined with respect to the inner yokes 7b and 7d so as to have a V shape when viewed from a distance from the support shaft axial direction, and the magnets 8a and 8b are fixed to the surfaces, respectively. As a result, magnetic gaps 11a and 11b are formed with different distances between the magnets 8a and 8b and the inner yokes 7b and 7d in the direction connecting the objective lens 1 and the support shaft 9.

Further, the magnets 8a of the outer yokes 7a and 7c,
The surface opposite to the surface to which 8b is attached is substantially parallel to the inner yokes 7b and 7d as shown in FIG.
Therefore, the plate thickness of the outer yokes 7a and 7c is the same as that of the objective lens 1
Is not uniform with respect to the direction connecting the shaft 9 and the support shaft 9, and is thicker on the objective lens 1 side. The rotation direction driving coils 5a and 5b have the magnetic gaps 11a and 1b in which the intervals of the portions corresponding to about half of these are different depending on the location.
It is located within 1b. The polarities of the magnets 8a and 8b are arranged such that the supporting shaft sides are S poles as shown in the figure.

Objective lens 1, axial drive coil 4,
The movable portion composed of the rotation direction driving coil 5, the bearing 3, the rotation arm 2, and the like includes a magnet 8, a yoke 7, a coil-shaped suspension 6a, 6b, 6c, and 6d extending in the tracking direction. It is connected to a fixed portion composed of the base plate 10 and the like. Coiled suspension 6a
6d are arranged substantially parallel to each other, and the four axial positions of the spindles are arranged at substantially the same height, that is, on a plane perpendicular to the spindles.

The suspensions 6a and 6b are wound in a symmetric manner with respect to the support shaft 9. In the embodiment shown in FIG. 1, coils 6a and 6d and 6b and 6c are wound in the same direction. It is a suspension 6. This coil-shaped suspension 6 can also serve as a lead wire for each of the drive coils 4a, 4b, 5a, 5b by being made of a conductor.

Next, the operation of the embodiment of the present invention configured as described above will be described with reference to FIGS. In addition, the operation in the axial direction of the support shaft requires two axial drive coils.
Although individual pieces are provided, they are the same as in the case of the conventional technique, and therefore the description thereof will be omitted, and only the operation in the rotating direction will be described here.

Now, it is assumed that no drive current is flowing through the rotation direction drive coils 5a and 5b. In this case, since the rotational direction driving coils 5a and 5b and the objective lens 1 are in a balanced state and elastically supported by the suspensions 6a to 6d, a large space is provided between the support shaft 9 and the bearing 3. Power does not work.

The rotating direction driving coils 5a, 5b
When the drive currents i ₂ and i ₁ flow through the coil, the rotational direction drive coils 5a and 5b generate magnetic fluxes j ₂ and j ₁ as shown in FIG. 3, and the magnetic fluxes f ₂ and f ₁ are generated by the action of the magnetic fluxes. ₁ occurs.
Since the electromagnetic forces f ₂ and f ₁ are couples having substantially the same magnitude and opposite directions, a rotational torque that rotates the objective lens 1 around the support shaft 9 is generated. Therefore, the objective lens 1 rotates around the support shaft 9 and operates in the tracking direction.

However, in the above description, since the leakage magnetic fluxes j _{3 to} j ₆ are radiated from the magnets 8b and 8a, the action of this magnetic flux and the current flowing through the horizontal portions of the rotational direction drive coils 5a and 5b. The rotation direction driving coils 5b, 5
a generates an electromagnetic force f ₃ ~f ₆ except electromagnetic force f _1, f _2.

In one embodiment of the present invention constructed as shown in FIGS. 1 and 2, the magnets 8a and 8b are arranged in a V shape,
Since one rotation direction driving coil 5a, 5b on one side is arranged asymmetrically with respect to the center of the magnetic flux of the magnetic circuit, FIG.
As shown in, the magnetic fluxes j ₂ and j ₁ from the magnets 8a and 8b are
The coils are inclined and crossed with respect to the rotational direction driving coils 5a and 5b. Therefore, the electromagnetic forces f ₈ and f ₇ are generated with an inclination with respect to the straight line connecting the objective lens 1 and the support shaft 9 as shown in the figure. The components f ₂ and f ₁ of the electromagnetic forces f ₈ and f _{7 in} the direction orthogonal to the tracking direction are the same as the electromagnetic forces f ₂ and f ₁ shown in FIG. To rotate,
Operate in the tracking direction.

On the other hand, the tracking direction components f _{10 of} the electromagnetic forces f ₈ and f ₇ generated by the rotation direction driving coils 5a and 5b,
f ₉ is a translational force which moves the movable portion in the tracking direction, the electromagnetic force f ₃ generated by the leakage magnetic flux j ₃ to j ₆ in the vertical direction emitted from the magnet 8b, 8a of the aforementioned
It acts to cancel ~ f ₆ .

In one embodiment of the present invention, by appropriately setting the tilt angles of the magnets 8a and 8b and the magnetic force, these unnecessary translational forces can be almost eliminated, and the objective lens 1 can be supported by the spindle. Couple forces f ₂ and f ₁ for rotating with respect to 9
Only a pair of magnets 8a and 8b can provide good rotation characteristics, and a device that is smaller and less expensive than the prior art has characteristics equivalent to those of the prior art. Can be obtained.

Further, in the embodiment of the present invention, as described above, the rotating direction driving coils 5a and 5b are bent in a dogleg shape, and the coil is supported by the supporting shaft of the portion which does not generate the rotating direction driving force. Since the distance from 9 is short and therefore the moment of inertia is arranged to be as small as possible, the acceleration characteristic in the rotation direction can be improved more efficiently.

In the embodiment of the present invention, as shown in FIGS. 1 and 2, a part of the surface of the outer yokes 7a and 7c opposite to the mounting surface of the magnets 8a and 8b is referred to as inner yokes 7b and 7d. Since they are formed so as to be substantially parallel to each other, a flat surface can be secured even when a flexible substrate or the like is attached to the outer circumference of the objective lens driving device, and these operations are not hindered.

The suspensions 6a to 6d have a coil shape extending in the tracking direction, as shown in FIG.
Since the four shafts are arranged symmetrically with respect to the support shaft 9 so as to be substantially parallel to each other, and the positions of the four support shafts in the axial direction are arranged at substantially the same height, the movable portion is movable in the axial direction and the rotation direction. Even if it moves in the moving direction, it does not generate an unnecessary force for rotating or translating the entire movable part around the support shaft 9. Further, since the coiled suspension has a good linearity of displacement with respect to a load, it is possible to set a wide adjustment range of rigidity in the axial direction and the direction perpendicular thereto by selecting the coil winding diameter, the wire diameter and the number of windings.

[0041]

[0042]

As described above, according to the present invention, it is possible to reduce the friction between the support shaft and the bearing and the vibration of the support shaft and other vibrations transmitted to the bearing, as well as in the case of the prior art, and at the same time It is possible to obtain the rotational acceleration characteristics described above, further reduce the size and cost, and configure the objective lens driving device with a small number of parts.

[Brief description of drawings]

FIG. 1 is a top view showing the configuration of an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the configuration of an embodiment of the present invention.

FIG. 3 is a perspective view illustrating the operation of the embodiment of the present invention.

FIG. 4 is a top view illustrating the operation of the embodiment of the present invention.

FIG. 5 is a perspective view showing a configuration of an objective lens driving device according to a conventional technique.

[Explanation of symbols]

1 Objective lens 2 rotating arm 3 bearings 4, 4a, 4b Axial drive coil 5a, 5b Rotation direction driving coil 6a-6d suspension 7a-7d yoke 8a-8d magnet 9 spindles 10 base plate

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 62-33343 (JP, A) JP 62-202335 (JP, A) JP 7-14200 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G11B 7/09 G11B 7/095

Claims (4)

(57) [Claims] 1. An objective lens, a coil for driving an axial direction of a support shaft, and a plurality of coils for driving a rotation direction, each of which is rotatably provided on a support shaft provided separately from the support shaft. A moving arm, and a plurality of magnetic circuits that generate magnetic fluxes that intersect the axial direction driving coil and the rotation direction driving coil, and rotate about a spindle and move in the axial direction of the spindle. In the slidable objective lens driving device, the distance between the parts facing each other is such that
The ends that are different from each other in the direction of the line that connects the
A shape obtained by projecting a magnetic circuit in the direction of the spindle axis is symmetric with respect to a straight line connecting the objective lens and the spindle, and is asymmetric with respect to a straight line passing through the spindle and orthogonal to the straight line.
Is arranged so that, before Kikaido direction drive coil, in the direction perpendicular respectively to the lines and the support shaft connecting the said and the objective lens support shaft, provided apart from the straight line, the support shaft An objective lens driving device characterized in that the shape projected in the axial direction is curved in a V shape in the direction in which the distance from the support shaft is shortened at approximately the center thereof. Wherein said rotation direction drive coil, the objective lens driving device according to claim 1, characterized in that the presence of only a part of its inside the magnetic circuit. 3. A rotating arm rotatably provided on the support shaft is supported by being connected to a fixed portion provided with the magnetic circuit by a plurality of coil-shaped suspensions. The suspension is arranged substantially parallel to each other on a plane perpendicular to the support shaft, and the winding direction of the coiled suspension is symmetrical with respect to the support shaft. Objective lens driving device. 4. The objective lens driving device according to claim 3, wherein the coiled suspension is formed of a conductor and also serves as a drive conductor for the axial drive coil and the rotational drive coil. .