JP3401774B2 - Two-axis actuator - Google Patents

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 disk, for example, a so-called compact disk (CD) or a magneto-optical disk. 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 is 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 orthogonal to the optical axis of the objective lens is adjusted so that the position of the spot of the light beam emitted from the semiconductor laser on the optical disc follows the eccentricity of the optical disc and the meandering of the track formed on the optical disc. To be 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 the objective lens is attached, a plurality of elastic supporting members, and a drive 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. In FIG.
The biaxial actuator 1 includes a lens holder 2 having an objective lens 2a attached to a tip thereof, and the lens holder 2
To the coil bobbin 3 attached by adhesion or the like
It has and.

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.

Further, the coil bobbin 3 is wound with a focusing coil and a tracking coil (not shown). By energizing each coil, the magnetic flux generated in each coil interacts with the magnetic flux generated by the yoke 6 attached to the fixed portion 4 and the magnet 7 attached thereto.

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, the driving voltage is supplied to each coil from the outside, so that the magnetic flux generated in each coil 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 support 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.

[0011]

However, in the biaxial actuator 1 having such a structure, the coil bobbin 3 is attached to the lens holder 2 only.
Is inserted into the opening of the lens holder 2 and the coil bobbin 3 is adhered inside the opening of the lens holder 2 with an adhesive. Therefore, it is difficult to position the coil bobbin 3 within the opening of the lens holder 2, and there is a problem that assembly workability is poor. Further, the lens holder 2 of the coil bobbin 3
The adhesive may squeeze out when adhering to the. Therefore, there is a problem that the accuracy of attachment of the coil bobbin 3 to the lens holder 2 is deteriorated due to the protruding adhesive.

Further, when the lens holder is divided into an upper part and a lower part, and the upper part and the lower part are integrally formed by adhering the upper part and the lower part together with an adhesive, the upper part and the lower part of the lens holder are mutually separated. After being bonded and formed integrally with an adhesive, a coil bobbin is inserted into the opening of the lens holder and bonded with the adhesive. Therefore, also in this case, as in the case of the integrally formed lens holder, there are problems that the assembling workability is poor and the mounting accuracy is reduced.

In view of the above points, an object of the present invention is to provide a biaxial actuator in which the coil bobbin can be easily and accurately attached to the lens holder.

[0014]

According to the present invention, the above object is to provide a lens holder which is divided into an upper portion and a lower portion and which is adhered integrally, and which supports an objective lens, and the lens holder with respect to a fixing portion. An elastic supporting member that elastically supports, and a coil bobbin fixed to the lens holder and around which a focusing coil and a tracking coil are wound, the coil bobbin is integrally formed when the upper and lower portions of the lens holder are bonded. This is accomplished by a biaxial actuator configured to be glued.

The lens holder of the biaxial actuator according to the present invention is preferably formed with an opening for inserting and fixing the coil bobbin, and either the upper part or the lower part of the lens holder is formed. Adjacent to the bonding surface, a notch is provided that penetrates into the opening from the outside.

Further, preferably, the cutout portion is provided on a side surface of the lens holder.

[0017]

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.

Since the coil bobbin is integrally bonded to the lens holder at the same time when the upper and lower divided lens holders are bonded to each other with an adhesive, the coil bobbin can be positioned with respect to the lens holder. It will be done accurately.

When a cutout is provided adjacent to either the upper surface or the lower adhesion surface of the lens holder, the adhesive between the upper and lower portions of the lens holder and the coil bobbin is the adhesive in the cutout. By injecting, the adhesive contacts the upper and lower parts of the lens holder and the coil bobbin, so that the upper and lower parts of the lens holder and the coil bobbin are integrally bonded. In this case, since the adhesive is in the cutout, it does not stick out from the cutout during bonding.

When the notch is provided on the side surface of the lens holder, the adhesive can be easily injected into the notch, and the workability of assembling the coil bobbin and the lens holder is improved. It will be.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to FIGS. It should be noted that the examples described below are suitable specific examples of the present invention, and therefore, various technically preferable limitations are given, but the scope of the present invention particularly limits the present invention in the following description. Unless otherwise stated, the present invention is not limited to these modes.

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
It includes b, 13c, 13d, a fixed portion 14, and a yoke 31. 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 and 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 side surface of the inner yoke 31a is inserted, and a focusing coil 12b. And a tracking coil 12c. Focusing coils 12b is wound in a coil bobbin 12 along the axis parallel to the optical axis of the 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 support 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. Furthermore, the elastic support members 13a,
A viscous body 16 acting as a damper is applied and hardened to the end regions 15 of 13b, 13c and 13d. The fixing portion 14 is attached to the adjusting plate 30 in a state where the lens holder 11 and the fixing portion 14 are connected by the four elastic supporting members 13a, 13b, 13c, 13d. The adjusting plate 30 is for adjusting the fixing position of the fixing portion 14 when the biaxial actuator is assembled. Then, the adjusting plate 30 is fixed to the base 31 formed integrally with the yoke by soldering or the like.

The fixing portion 14 is attached to the adjusting plate 30 by inserting a boss provided in the fixing portion 14 into the hole 30a shown in the adjusting plate 30 and fixing it with an adhesive or the like. Here, the base 31 has a pair of yokes 31a and 31b forming the magnetic circuit.
It is provided by bending the ends of the first objective lens side closer to each other. That is, the inner yoke 3 is attached to the base 31.
1a and the opposing yoke 31b are integrally formed by press working or the like, and the magnet 32 is attached to the inner side surface of the inner yoke 31a. As a result, the pair of yokes 31a and 31b and the magnet 32 form a magnetic circuit. Then, as described above, the fixing portion 14
When the coil bobbin 1 is attached to the yoke 31, the coil bobbin 1 is inserted into the gap between the magnet 32 and the opposing yoke 31b.
The focusing coil 12b and the tracking coil 12c, which are attached to No. 2, are inserted. At the same time, the inner yoke 31 a and the magnet 32 cause the coil bobbin 12 to move.
Will be inserted into the opening 12a.

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 made 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.

Biaxial actuator 10 according to this 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 cured,
A desired damping characteristic will be obtained. As a result, vibrations of the elastic support members 13a, 13b, 13c, 13d are damped during focusing or tracking.

Here, the upper part 11U of the lens holder 11
When assembling the lower surface of the lens holder 11 and the upper surface of the lower portion 11L so as to face each other, the upper portion 11U and the lower portion 11L of the lens holder 11 are first aligned to be positioned, and the coil bobbin 12 is inserted into the opening 11a of the lens holder 11. And position it. After that, the cutout portions 11d provided on both sides of the upper portion 11U of the lens holder 11
The adhesive 17 is injected into the inside. Thereby, the cutout portion 11d
The adhesive inside is on the side wall and the upper wall of the cutout 11d,
The upper part 11U of the lens holder 11 is contacted, the lower part 11L of the lens holder 11 is contacted below the cutout part 11d, and the inner opening of the cutout part 11d is inserted into the opening part 11a of the lens holder 11. It contacts the side wall of the inserted coil bobbin. As a result, the upper part 11U and the lower part 1 of the lens holder 11 are cured by curing the adhesive.
1L and the coil bobbin 12 are integrally bonded and fixed. Thus, the assembling work of the coil bobbin 12 to the lens holder 11 can be performed easily and with high accuracy.

As described above, in the above embodiment, when the upper and lower divided lens holders are bonded to each other by the adhesive, they are simultaneously bonded to the lens holder at the same time. The positioning will be accurate. Therefore, the mounting accuracy of the coil bobbin is improved. If a cutout is provided adjacent to either the upper or lower bonding surface of the lens holder, the adhesive is injected into the cutout to integrate the upper and lower parts of the lens holder with the coil bobbin. Glued to. Therefore, the workability of assembling the coil bobbin and the lens holder is improved. Furthermore, since the adhesive is in the cutout, it does not stick out from the cutout during bonding.
Assembling accuracy will be improved.

In the above-described embodiment, the elastic supporting members 13a, 13b, 13c, 13d are described as being simply fixed to the lens holder 11 and the fixing portion 14, respectively. Fixed part 1
It is obvious that the 4 may be integrally formed by insert molding or the like.

[0034]

As described above, according to the present invention, there is provided a biaxial actuator in which the coil bobbin can be easily and accurately attached to the lens holder.

[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 side view showing a state before assembly of a coil bobbin and a lens holder divided into upper and lower parts in the biaxial actuator of FIG. 1. FIG.

5 is a schematic side view showing a state after the coil bobbin and the lens holder divided into upper and lower parts in the biaxial actuator of FIG. 1 are assembled.

FIG. 6 is a schematic perspective view showing an entire configuration of an example of a conventional biaxial actuator for an optical pickup.

[Explanation of symbols]

10 biaxial actuator 11 lens holder 11a opening 11b recess 11c Objective lens 11d notch 12 coil bobbins 12a opening 12b Focusing coil 12c Tracking coil 12d connection pin 13a, 13b, 13c, 13d Elastic support member 14 Fixed part 15 Edge area 16 Viscous body 17 Adhesive

─────────────────────────────────────────────────── ─── Continuation of front page (72) Keiichi Shibata 6-7-35 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corp. (56) References JP-A-4-328336 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B ^7/ 09-7/22

Claims (2)

(57) [Claims] 1. A lens holder which is divided into an upper portion and a lower portion and which is integrally bonded and which supports an objective lens, an elastic supporting member which elastically supports the lens holder with respect to a fixing portion, and the lens holder. And a coil bobbin around which a focusing coil and a tracking coil are fixed, and the coil bobbin is inserted into the lens holder.
There is an opening for fixing the
Next to the adhesive surface on either the top or bottom of the holder
A notch is provided that is in contact with and penetrates into the opening from the outside.
A two-axis actuator characterized by being used . 2. The biaxial actuator according to claim 1, wherein the cutout portion is provided on a side surface of the lens holder.