JPH08147735A - Biaxial actuator - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a biaxial actuator with improved impact resistance in the focusing direction. [Structure] Lens holder 11 for supporting an objective lens
And elastic supporting members 13a, 13b, 13c and 13d for elastically supporting the lens holder with respect to the fixing portion 14 and supplying current from the fixing portion side, and the coil bobbin 12 provided in the lens holder. In the biaxial actuator 10, the focusing coil 12b wound around the coil bobbin and the tracking coil 12c wound around the coil bobbin are included in the coil bobbin and the objective. Two pairs of stoppers 17a, 17b, 18a, 18b vertically protruding from the lens holder are provided so as to sandwich the center of gravity G of the lens holder on which the lens is attached in the X direction perpendicular to the focusing direction and the tracking direction. , A biaxial actuator 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxial actuator for an optical pickup used for recording / reproducing signals of an information recording medium for CD, MD, etc. and data storage.

[0002]

2. Description of the Related Art Conventionally, an optical pickup is used to reproduce or record an information signal on an information recording medium such as an optical disc, for example, a so-called compact disc (CD) or a magneto-optical disc. This optical pickup includes a semiconductor laser as a light source, an objective lens, an optical system, and a photodetector.

In an optical pickup, a light beam emitted from a semiconductor laser is focused on a recording surface of an optical disc by an objective lens via an optical system. The return light beam from the optical disc is separated from the light beam emitted from the semiconductor laser by the optical system and guided to the photodetector. The light beam emitted from the semiconductor laser follows the displacement of the optical disc in the direction orthogonal to the surface direction of the optical disc caused by the warp of the optical disc, etc., and is focused on the recording surface of the optical disc. The position of the objective lens in the optical axis direction is adjusted. At the same time, the position in the direction perpendicular to the optical axis of the objective lens is adjusted so that the position of the spot on the optical disk of the light beam emitted from the semiconductor laser follows the eccentricity of the optical disk or the meandering of the track formed on the optical disk. Is done.

The focus position of the light beam emitted from the semiconductor laser and the spot position on the recording surface of the optical disc are adjusted by adjusting the objective lens in the optical axis direction of the objective lens and in the direction orthogonal to the optical axis. It is done by adjusting. An electromagnetically driven actuator is used to adjust the position of the objective lens. This actuator is called an objective lens actuator or a biaxial actuator, and includes a bobbin to which an objective lens is attached, a plurality of elastic support members, and a driving unit that generates a driving force.
The bobbin is supported by a plurality of elastic supporting members with respect to the fixed portion such that the position in the optical axis direction of the objective lens, that is, the focus position and the position in the direction orthogonal to the optical axis of the objective lens, that is, the tracking position, are adjustable. ing. An example of this biaxial actuator will be described below with reference to FIG.

Such a biaxial actuator is constructed, for example, as shown in FIG. That is, in FIG. 5, the biaxial actuator 1 has a lens holder 2 to which the objective lens 2a is attached at the tip, and a coil bobbin 3 attached to the lens holder 2 by adhesion or the like.

The lens holder 2 has two ends perpendicular to the fixed portion 4 by two pairs of elastic supporting members 5 having one end on both sides of the lens holder 2 and the other end fixed to the fixed portion 4. Direction, that is, the tracking direction indicated by the reference symbol Trk and the focusing direction indicated by the reference symbol Fcs are movably supported.

The coil bobbin 3 is constructed as shown in FIG. That is, the coil bobbin 3 is provided with the opening 3a penetrating in the vertical direction, and the focusing coil winding portion 3b formed so as to surround the opening 3a and the focusing coil winding portion 3b. On the front side (objective lens side), tracking coil winding portions 3c are provided at two places on the left and right. A focusing coil 3d and a tracking coil 3e are wound around the focusing coil winding portion 3b and the tracking coil winding portion 3c, respectively.

By energizing each coil 3d, 3e, the magnetic flux generated in each coil 3d, 3e is
As shown in FIG. 5, the yoke 6 integrally attached to the fixed portion 4 and the magnetic flux of the magnet 7 attached thereto interact with each other. In this case, in each of the coils 3d and 3e, the magnetic flux generated in the coil portion located in the effective magnetic field between the inner yoke 6a and the opposing yoke 6b of the yoke 6 generates a driving force in the focusing direction or the tracking direction. It is like this.

That is, in the focusing coil 3d, the current F1 flowing through the portion facing the tracking coil 3e causes the lens holder 3 to move in the focusing direction Fcs based on Fleming's left-hand rule.
(See FIG. 7) is generated. In addition, in the tracking coil 3e, a force F2 that causes the current flowing in each of the vertically extending portions to move the lens holder 3 in the tracking direction Trk based on Fleming's left-hand rule.
(A force in a direction perpendicular to the paper surface in FIG. 7) is generated.

Further, the elastic support member 5 is formed of an elastic body and is fixed between the lens holder 2 and the fixing portion 4 so as to be parallel to each other. Here, the end region 5a of the elastic support member 5 on the side of the fixed portion 4 is formed in a rectangular shape as a whole. The end region 5a is different from the elongated body portion extending in the front-rear direction of the elastic support member 5 with respect to
It has slits provided on both sides thereof. In the end region 5a thus configured, the viscous body 8 is formed on the end region 5a so as to straddle the main body portion through the slit.
Is applied and cured. The viscous body 8 is, for example, an ultraviolet curable viscous body and is adapted to be cured by irradiating with ultraviolet rays after coating. This allows
The hardened viscous body 8 acts as a damper to suppress the vibration of the elastic support member 5.

According to the biaxial actuator 1 having the above-described structure, when a driving current is supplied to each coil from the outside, the magnetic flux generated in each coil mutually interacts with the magnetic flux generated by the yoke 6 and the magnet 7. This causes the coil bobbin 3 to move in the tracking direction Trk and the focusing direction Fcs. Thus, the objective lens 2a attached to the lens holder 2 is appropriately moved in the focusing direction and the tracking direction.

When the lens holder 2 is thus moved in the focusing direction and the tracking direction, the lens holder 2 tries to vibrate in the moving direction, but is provided near the rear end of the elastic supporting member 5. Vibration is suppressed by the damping action of the viscous body 8. As a result, the lens holder 2 is stopped in a stable state at the predetermined position.

By the way, in the biaxial actuator 1 having such a structure, the lens holder 2 and the objective lens 2 are provided.
a, the so-called movable part assembly consisting of the coil bobbin 3 around which the coils 3d and 3e are wound has its center of gravity so as not to cause a phase delay with respect to movement by the driving forces F1 and F2 during focusing and tracking. The driving force F1 and the driving force F2 are configured so as to substantially coincide with the applied position. Further, the movable portion assembly is provided with stoppers above and below the movable portion assembly so as to regulate the movement in the focusing direction.

[0014]

However, in the biaxial actuator 1 having such a structure, for example, as shown in FIG. 8, the biaxial actuator 1 drops upside down, and an impact in the focusing direction is applied. May be In this case, the stopper 2b provided on the upper edge of the lens holder 2 of the movable part assembly is the edge 9 of the chassis 9 or the like to which the biaxial actuator 1 is attached.
Contact a. Here, since the stopper 2b is provided near the center of the coil bobbin in the X direction (see FIG. 5) that is perpendicular to the normal focusing direction and the tracking direction, it is located behind the position where the driving forces F1 and F2 are applied. positioned. Therefore, when the impact is strong, the center of gravity G of the movable portion assembly tends to move further downward even after the stopper 2b contacts the edge portion 9a of the chassis 9 or the like. Therefore, in the movable part assembly, the moment M is generated so that the center of gravity moves downward around the stopper 2b. As a result, an excessive stress is applied to the elastic support member 5, and if a stress exceeding the allowable stress is applied, the elastic support member 5 will be deformed.

In view of the above points, it is an object of the present invention to provide a biaxial actuator having improved impact resistance in the focusing direction.

[0016]

According to the present invention, the above object is to provide a lens holder for supporting an objective lens, an elastic support for the lens holder with respect to a fixed portion, and a current flow from the fixed portion side. An elastic support member for supplying, a coil bobbin provided in the lens holder,
A focusing coil wound around this coil bobbin and a tracking coil wound around this coil bobbin are provided, and the center of gravity of the lens holder on which the coil bobbin and the objective lens are mounted is set to the focusing direction. This is achieved by a biaxial actuator having a plurality of stoppers protruding in opposite directions from the lens holder at positions sandwiching in a direction perpendicular to the tracking direction.

The plurality of stoppers of the biaxial actuator of the present invention may be formed on the coil bobbin.

The plurality of stoppers of the biaxial actuator of the present invention may be formed on the lens holder.

Of the plurality of stoppers of the biaxial actuator of the present invention, some of the stoppers may be formed on the coil bobbin and the other stoppers may be formed on the lens holder.

Further, the biaxial actuator of the present invention is
When a shock is applied in the focusing direction, the plurality of stoppers may simultaneously contact the receiving portion formed integrally with the fixed portion.

[0021]

According to the above construction, since the lens holder for holding the objective lens is supported by the elastic supporting member, the focusing coil or the tracking coil is energized to resist the tension of the elastic supporting member. Then, the lens holder is moved along the focusing direction or the tracking direction, and the objective lens is focused or tracked.

When a shock is applied to the biaxial actuator in the focusing direction, the center of gravity of the movable part assembly including the objective lens, the coil bobbin, and the lens holder is sandwiched in the front-back direction (direction orthogonal to the tracking direction and the focusing direction). The pair of stoppers provided above or below the lens holder abut on a receiving portion such as a chassis integrated with the fixing portion. At this time, one of the stoppers is in front of the center of gravity and the other stopper is behind the center of gravity, and abuts the receiving portion such as the chassis, so that the movable portion assembly is prevented from moving in the focusing direction by both stoppers. To be done. Therefore, the movable portion assembly does not generate a moment even when it receives an impact in the focusing direction.

When the above two stoppers are formed on either the coil bobbin or the lens holder,
Since the stopper is formed at the same time when the coil bobbin or the lens holder is molded, the cost can be kept low.

When an impact is applied in the focusing direction,
When the two stoppers are configured to simultaneously contact the receiving portion integrally formed with the fixed portion,
Moment does not occur instantly in the movable part assembly.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to FIGS. In addition, since the Examples described below are preferred specific examples of the present invention, various technically preferable limitations are given. However, the scope of the present invention particularly limits the present invention in the following description. The embodiment is not limited to these embodiments unless otherwise stated.

1 to 3 show an embodiment of a biaxial actuator according to the present invention. 1 to 3, the biaxial actuator 10 includes a lens holder 11,
Coil bobbin 12, a plurality of elastic support members 13a, 13
b, 13c, 13d, the fixing portion 14, and the yoke 31 are included. The lens holder 11 is, as shown in FIG.
Horizontal division line allows upper 11U and lower 11L
It is divided into two parts and is adhered to each other by an adhesive. Further, as shown in FIG. 3, the lens holder 11 is formed with an opening 11a to which a coil bobbin is attached and a recess 11b to which an objective lens is attached. A hole through which the light beam emitted from the semiconductor laser or the return light beam from the recording surface of the optical disk passes is formed on the bottom surface of the recess 11b. The objective lens 11c is attached to the recess 11b of the lens holder 11 by adhesion or the like.

Further, the lens holder 11 is supported by elastic supporting members 13a, 13b, 13c, 13d so as to be movable in the focusing direction Fcs and the tracking direction Trk.

The coil bobbin 12 is formed with an opening 12a into which a magnetic circuit composed of a yoke 31 integral with the base and a magnet 32 attached to the inner surface of the inner yoke 31a is inserted, and a focusing coil 12b. And a tracking coil 12c. The focusing coil 12b is wound along an axis parallel to the optical axis of the coil bobbin 12 objective lens 11c. The tracking coil 12c is formed by winding the coil into an elliptical shape or a rectangular shape, and is attached to one side surface of the focusing coil 12b. The upper surface of the coil bobbin 12 is covered with the yoke bridge 36. The yoke bridge 36 forms a closed magnetic circuit together with the yoke 31 of the magnetic circuit, thereby increasing the sensitivity of the magnetic circuit and preventing leakage magnetic flux. Further, the yoke bridge 36 functions as a stopper for the lens holder 11. The coil bobbin 12 is attached to the opening formed in the lens holder 11 with the focusing coil 12b and the tracking coil 12c attached.

The elastic supporting members 13a, 13b, 13
It is preferable that c and 13d have electrical conductivity and spring properties, and materials such as phosphor bronze, beryllium copper, titanium copper, tin-nickel alloy, and stainless are used. Due to these, in the present embodiment, for example, a leaf spring suspension is formed by thin sheet metal, and is fixed between the lens holder 11 and the fixing portion 14 so as to be parallel to each other. Thereby, the elastic support member 13
The a, 13b, 13c, and 13d may supply a drive current from the fixed portion side to the focusing coil 12b and the tracking coil 12c of the coil bobbin 12 via an external current supply means (not shown). Further, the viscous body 16 acting as a damper is provided in the end region 15 of the elastic support members 13a, 13b, 13c, 13d.
Has been applied and cured. The lens holder 11 and the fixing portion 14 have four elastic supporting members 13a, 13b, 13
adjustment plate 30 in a state of being connected by c and 13d.
On the other hand, the fixing portion 14 is attached. The adjusting plate 30 is used for fixing the fixed portion 1 when the biaxial actuator is assembled.
It is for adjusting the fixed position of No. 4. The adjusting plate 30 is formed on the base 3 formed integrally with the yoke.
1 is fixed by soldering or the like.

The fixing portion 14 is attached to the adjusting plate by inserting the boss provided in the fixing portion 14 into the hole shown in the adjusting plate 30 and fixing it with an adhesive or the like. Here, the base 31 is provided with a pair of yokes 31a and 31b forming the magnetic circuit by bending the ends of the base 31 on the objective lens side upward. That is, the inner yoke 31a and the opposing yoke 31b are integrally formed on the base 31 by press working or the like, and the magnet 32 is attached to the inner side surface of the inner yoke 31a. Thereby, the pair of yokes 31
A magnetic circuit is constituted by a and 17b and the magnet 32. Then, as described above, when the fixing portion 14 is attached to the yoke 31, the focusing coil 12b and the tracking coil 12c attached to the coil bobbin 12 are inserted into the gap between the magnet 32 and the opposing yoke 31b. It At the same time, the inner yoke 3
1a and the magnet 32 will be inserted in the opening 12a of the coil bobbin 12.

Further, the fixed portion 14 is the lens holder 11
Similarly, as shown in FIG. 3, it is divided into an upper portion 14U and a lower portion 14L by a horizontal dividing line, and they are adhered to each other by an adhesive.

Further, in the biaxial actuator 10, the upper portion 11U of the lens holder 11 is lower than the lower portion 11U thereof.
Notches 11d are provided on both sides of the lower surface facing L. This notch 11d is the upper part 1 of the lens holder 11.
1U is penetrated in the lateral direction, that is, in the direction parallel to the tracking direction Trk, and is opened to the outside and the opening 11a.

Further, in the biaxial actuator 10, the coil bobbin 12 is constructed as shown in FIG. In FIG. 4, the coil bobbin includes a focusing coil 12b wound so as to laterally surround an opening 12a penetrating up and down, and a tracking coil formed on a front side surface of the focusing coil 12b in the X direction. And a coil 12c.

Here, the coil bobbin 12 includes a focusing coil 12b and a tracking coil 12c.
The center of gravity G of the movable part assembly including the coil bobbin 12 around which the coil is wound, the objective lens 11c, and the lens holder 11 is located between the focusing coil 12b and the tracking coil 12c on the front side. Further, the coil bobbin 12 has a pair of stoppers 17a and 17b projecting upward from the upper surface of the coil bobbin 12 at positions sandwiching the center of gravity G from the front and the rear in the X direction (direction orthogonal to the tracking direction and the focusing direction). . The coil bobbin 12 has a pair of stoppers 18a and 18b protruding downward from the lower surface thereof. These stoppers 17a, 17b, 18a, 18b can be formed, for example, by integrally molding the resin main body of the coil bobbin 12 in the illustrated shape.

Biaxial actuator 10 according to the present embodiment
Is configured as described above, and currents based on the focus servo signal and the tracking servo signal are supplied to the focusing coil 12b and the tracking coil 12c wound around the coil bobbin 12, respectively. Thereby, the DC magnetic field of the magnetic circuit, the focusing coil 12b, and the tracking coil 12c.
The lens holder 11 or the objective lens 11c is driven in the focus direction Fcs and the tracking direction Trk by the alternating magnetic field generated by

Further, as a damper, the elastic support member 13 is used.
Since the viscous body 16 is applied to the end regions 15 of the a, 13b, 13c, and 13d on the side of the fixed portion 14 and hardened, desired damping characteristics can be obtained. As a result, vibrations of the elastic support members 13a, 13b, 13c, 13d are damped during focusing or tracking.

Here, as shown in FIG. 4, when the impact A in the focusing direction is applied to the biaxial actuator 10, the focusing coils 12b,
The center of gravity of the movable part assembly including the coil bobbin 12 around which the tracking coil 12c is wound, the objective lens 11c, and the lens holder 11 moves downward in the focusing direction. And the coil bobbin 1
A pair of stoppers 18a, 1 protruding downward from the lower surface of 2
8b contacts a receiving portion 19 such as a chassis. This prevents the movable part assembly from moving in the focusing direction. At this time, the abutting positions of the stoppers 18a and 18b on the receiving portion 19 such as the chassis are located in front of and behind the center of gravity G of the movable portion assembly in the X direction perpendicular to the focusing direction which is the direction of the impact A. ing.

Therefore, after the stoppers 18a and 18b are brought into contact with the receiving portion 19 such as the chassis, no moment is generated in the movable portion assembly, and the movement of the movable portion assembly in the focusing direction is surely performed. Will be blocked. In this case, the stoppers 17a, 17
b or 18a, 18b are brought into contact with the receiving portion 19 such as the chassis at the same time, the stoppers 17a, 17b
When the heights of b, 18a, 18b and the position of the receiving portion 19 are selected, the movement of the movable portion assembly is reliably prevented, and the generation of the moment is reliably eliminated.
When the impact A acts, the stoppers 17a and 17b come into contact with the pickup cover or the like located at a position opposite to the receiving portion 19, that is, an upper position in the figure.

As described above, in the above-described embodiment, when a shock is applied to the biaxial actuator in the focusing direction, the pair of stoppers above or below the lens holder are attached to the receiving portion such as a chassis integral with the fixing portion. Abut. At this time, one of the stoppers is in front of the center of gravity and the other stopper is behind the center of gravity in contact with the receiving portion such as the chassis. Therefore, even if an impact is applied in the focusing direction, a moment is not generated. Absent. Therefore, the impact resistance in the focusing direction is improved.

Although the stoppers 17a, 17b, 18a, 18b are formed on the upper surface or the lower surface of the coil bobbin 12 in the above-described embodiment, the present invention is not limited to this, and the center of gravity G of the movable part assembly in the X direction is not limited thereto. It may be formed on the upper surface or the lower surface of the lens holder 11 as long as it is positioned in front of and behind. Therefore, it is obvious that one of the front or rear stoppers 17a, 18a or 17b, 18b may be formed on the coil bobbin, and the other stopper 17b, 18b or 17a, 18a may be formed on the lens holder 11. . In addition, these stoppers are used for the lens holder 11
It is necessary to form a plurality so as to be located above and below, but it is not necessary that each pair be provided, and a greater number may be provided, and the shape thereof is not limited to that shown in the figure.

Further, the elastic support members 13a, 13b, 13
Although it has been described that the c and 13d are simply fixed to the lens holder 11 and the fixed portion 14, respectively, they may be integrally formed with the lens holder 11 and the fixed portion 14 by insert formation or the like. it is obvious. Further, the lens holder 11 is divided into an upper portion 11U and a lower portion 11L, but it is obvious that they may be integrally formed.

[0042]

As described above, according to the present invention, the impact resistance in the focusing direction is improved.
A biaxial actuator can be provided.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing the overall configuration of an embodiment of a biaxial actuator for an optical pickup according to the present invention as seen from the front.

FIG. 2 is a schematic perspective view showing the biaxial actuator of FIG. 1 as viewed from the rear.

FIG. 3 is an exploded perspective view of the biaxial actuator of FIG.

4 is a schematic sectional view of a coil bobbin in the biaxial actuator of FIG.

FIG. 5 is a schematic perspective view showing an overall configuration of an example of a conventional biaxial actuator for an optical pickup.

6 is a schematic perspective view of a coil bobbin in the biaxial actuator of FIG.

7 is a schematic side view showing driving force in each of the focusing direction and the tracking direction by each coil in the biaxial actuator of FIG.

8 is a schematic side view showing a state in which an impact force in a focusing direction acts on the biaxial actuator of FIG.

[Explanation of symbols]

 10 Biaxial Actuator 11 Lens Holder 11a Opening 11b Recess 11c Objective Lens 12 Coil Bobbin 12a Opening 12b Focusing Coil 12c Tracking Coil 12f Side Wall 13a, 13b, 13c, 13d Elastic Support Member 14 Fixing Part 14a Adhesive Surface 15 End Area 16 Viscous materials 17a, 17b, 18a, 18b Stopper 19 Receiving part for chassis, etc.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiichi Shibata 6-735 Kitashinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation

Claims (5)

[Claims] 1. A lens holder that supports an objective lens, an elastic support member that elastically supports the lens holder with respect to a fixed portion, a coil bobbin provided in the lens holder, and a coil bobbin wound around the coil bobbin. And a tracking coil wound around the coil bobbin, and the center of gravity of the lens holder on which the coil bobbin and the objective lens are mounted is set in a direction perpendicular to the focusing direction and the tracking direction. A biaxial actuator comprising a plurality of stoppers projecting in mutually opposite directions from the lens holder at a position sandwiched between the two axis actuators. 2. The biaxial actuator according to claim 1, wherein the plurality of stoppers are formed on a coil bobbin. 3. The biaxial actuator according to claim 1, wherein the plurality of stoppers are formed on a lens holder. 4. The biaxial according to claim 1, wherein some of the plurality of stoppers are formed on the coil bobbin and the other stoppers are formed on the lens holder. Actuator. 5. The structure according to any one of claims 1 to 4, characterized in that, when an impact in the focusing direction is received, the plurality of stoppers simultaneously come into contact with a receiving portion formed integrally with the fixed portion. The biaxial actuator according to claim 1.