JPH054097Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an actuator for an optical pickup device, and more particularly, to an improvement of an actuator for an optical pickup device that performs focusing and tracking using one fixed shaft.

[Conventional technology]

Conventionally, various devices have been proposed as actuators for focusing and tracking in optical pickup devices, but they can be broadly classified into two types. One is to move the focusing lens of the optical system up and down with one drive system to perform focusing, and tracking is to rotate a mirror provided in front of the focusing lens using another drive system to adjust the optical axis of incidence to the focusing lens. It is a tilting method.

The other one is focusing and tracking.
It is called a two-axis actuator that rotates around two fixed axes and slides up and down.

Compared to the former actuator method mentioned above, the latter method allows the optical path of the optical system to be made smaller and is widely used.

By the way, the present applicant has previously proposed an improvement to this two-axis actuator type optical pickup device.
A previously proposed optical pickup device (unknown prior to the filing of the present application) will be described below with reference to FIGS. 5 and 6. FIG. 5 is a plan view showing the actuator of this optical pickup device, and FIG. 6 is a perspective view of the magnet and yoke used in FIG.

In FIG. 5, a shaft 3 is placed on a substantially square substrate 1.
A magnet 2 is fixed on both sides. On the other hand, the movable means 7 includes an optical system such as a focusing lens 4, a first coil 5 for focusing (hereinafter referred to as a focus coil), and a second coil 6 for tracking (hereinafter referred to as a tracking coil). provided. A shaft 3 fixed to a substrate 1 is inserted through a bearing 9 provided approximately at the center of a movable means 7, so that the movable means 7 can freely rotate and slide with respect to the shaft 3.

For example, two magnets 2 are arranged between the focus coil 5 and the tracking coil 6, the inner surface of which is magnetized as a N pole, and the outer surface of which is magnetized as an S pole. Because of this structure, both the focus coil 5 and the tracking coil 6 are sufficiently close to the magnet 2, and one magnet 2 can drive the tracking coil 6 and the focus coil 5, and the magnet 2 The magnetic flux from can be used effectively. In this case, magnet 2
Considering the magnetic flux of , if the width W of the magnet shown in FIG. If the width W is wide, the magnetic flux from the magnet 2 will not diverge and will be in a parallel state, so the magnetic flux density will be stronger in the return path portion (the side closer to the axis 3) of the winding of the tracking coil 6, and the forward path portion will become stronger. (the side closer to magnet 2) approaches a value equal to the magnetic flux density. Since current flows in opposite directions in the winding of the tracking coil 6 in the forward and return directions, the driving forces are subtracted from each other. As a result, there was a problem in that the driving force in the tracking coil 6 was reduced, and the driving force for performing the tracking servo was reduced.

Therefore, in order to solve this problem, one of the two substantially U-shaped yokes 8, 8 connected by a coupling yoke 10 as shown in FIGS. 5 and 6, The inner wall of the leg was attached to the surface of the magnet 2 on the tracking coil 6 side, and the other leg was placed outside the focus coil 5.

By providing such U-shaped yokes 8, 8 on the magnet 2, the yoke 8 is in contact with one N pole of the magnet 2.
Since the magnetic flux generated in one leg can be guided to the other leg, the magnetic flux diverges toward the focus coil 5 side, and the magnet width on the tracking coil 6 side increases.
W ₁ becomes effectively narrower and tracking coil 6
The amount of cancellation of the driving force can be reduced.

[Problem that the invention attempts to solve]

As mentioned above, the magnet width W on the tracking coil 6 side
By making W as narrow as W ₁ , the tracking driving force can be increased. This magnet width W ₁ is W ₁ if the winding width of the tracking coil 6 is W ₂
By making it close to the tracking coil width like = W ₂ , the tracking signal output is maximized and efficiency is improved. However, if W ₁ is brought close to W ₂ as described above, the tracking coil 6 and the corner 12 of one leg of the yokes 8 will come into contact when the movable means 7 is rotated about the shaft 3. There were flaws.

The present invention was developed in view of the above-mentioned drawbacks, and its purpose is to create an optical pickup that focuses magnetic flux on one winding side of the tracking coil 6 and allows the tracking coil to rotate freely. To provide the actuator of the device.

[Means for solving problems]

The actuator of the optical pickup device according to the present invention includes a movable means 7 having an optical system 4 fitted so as to be rotatable around a fixed shaft 3 and slidable up and down, and a movable means 7 on a circumference coaxial with the fixed shaft 3. a first coil 5 wound around a fixed shaft 3; Both are arranged at a fixed part between one second coil 6 and the first and second coils 5 and 6, and an S pole is placed between the first and second coils 5 and 6 on the first coil side. Or, it is equipped with a magnet 2 with an N pole or an S pole arranged on the second coil side, and depressions 11, 11 are provided on both sides of the part of the magnet 2 that faces the second coil 6. .

[Effect]

By providing the recess 11 in the magnet 2, the effective magnet width _W1 of the magnet placed on the tracking coil 5 side can be made approximately the width _W2 of the tracking coil 6, and the tracking driving force can be maximized. Therefore, an actuator for an optical pickup device that does not affect the focus driving force can be obtained.

〔Example〕

Hereinafter, one embodiment of the actuator of the optical pickup device according to the present invention will be described in detail with reference to FIGS. 1 to 4.

Fig. 1 is an exploded perspective view of one embodiment of the present invention, Fig. 2 is a plan view of the embodiment, Fig. 3 is a cross-sectional view taken along line A-A' in Fig. 2, and Fig. 4 is a It shows a perspective view of a magnet and a yoke part. 1 to 3, a coupling yoke 10 and a coupling yoke 10 similar to that described in FIG.
The magnet 2 is fixed via two U-shaped yokes 8,8. The magnet 2 has a substantially semi-cylindrical cross section as shown in FIG.
are arranged to face a tracking coil 6 fixed to a movable means 7, which will be described later, and the arched surface 2a faces the focus coil 5. Further, along the height direction of the magnet 2, two recesses 11, 11 each having a semicircular cross section are provided on both sides of the portion facing the tracking coil 6 on the flat surface 2b side. The width W 3 of the flat surface 2b of the magnet 2 facing the tracking coil 6 is the winding width W ₂ of the tracking coil ₆ .
It is possible to select approximately the same width as (see Figure 2).
Furthermore, the width W ₄ of one leg of the yoke 8 is such that when the movable means 7 rotates around the shaft 3, the tracking coil 6 attached to the movable means 7
Select a width that does not touch the corner 12 of one of the legs.

The movable means 7 is a bridge portion 7a made of synthetic resin.
A bearing 9 is provided by making a through hole in the center of the bridging part, and a notch part 7 is formed in a direction perpendicular to the extending direction of the bridging part 7a passing through the bearing 9.
c, 7d are formed. For example, air-core tracking coils 6, 6 wound around an axis perpendicular to a plane including the shaft 3 fitted into the bearing 9 are fitted here. The focusing lens 4 is placed eccentrically from the center of the bearing 9, and the winding frame 7b is formed in a cylindrical shape coaxially with the center of the bearing 9. A coil 5 is wound.
When the bearing 9 of the movable means 7 is inserted into the shaft 3 set on the substrate 1 as shown by the arrow, the bridge portion 7a of the movable means 7 is formed.
The magnet 2 and one leg of the yoke are inserted into the hollow parts 7e and 7f between the winding frame part 7b, and the other leg is inserted into the hollow parts 7e and 7f between the winding frame part 7b.
The movable means 7 is disposed outside of the shaft 3 and assembled as shown in FIGS. 2 and 3, and is pivotally connected to the shaft 3 so as to be rotatable and slidable in the extending direction of the shaft 3.

In the configuration described above, the magnet 2 has a semicircular shape with a width W of 10 mm, a height of 8 mm, and a thickness of 2.5 mm, and one leg of the U-shaped yoke 8 is opposed to the flat surface 2b of this magnet. Let them come into contact with you. The width of this leg W ₄ = 2.5mm is magnet 2
The winding width W 2 _of the tracking coil 6 is 2 mm, and the magnet width W ₁ of the opposing effectively narrowed surface is 5 mm, and the magnet width is 3 mm.
Two recesses 11, 11 each having a depth of 0.6 mm and a semicircular cross section were provided along the height direction of the magnet 2, and the width of the magnet on the surface facing the tracking coil 6 was set to W ₃ =2.5 mm. The tracking driving force increased by 2.8 dB and the focus driving force decreased by 0.5 dB or less when compared with the one without the depression 11.

As described above, according to the present invention, the width of the magnet on the tracking coil side, which has been effectively reduced by the yoke, can be further reduced.

In the above embodiment, the recess 11 formed in the magnet 2 has a semicircular cross section, but the recess 11 may have a rectangular or triangular cross section as appropriate. Furthermore, although the case has been described in which the yokes 8 and 8 are provided on the magnet 2 and the recesses 11 are arranged side by side, it is clear that the yokes 11 may not be provided and only the recesses 11 and 11 may be formed, and the shape of the yoke 11 may also be changed. Of course, the present invention is not limited to the embodiments described above.

[Effect of idea]

Since the present invention is constructed as described above, it is possible to increase the tracking driving force without reducing the focusing driving force, and the construction is simple and has great practical effects.

[Brief explanation of drawings]

Fig. 1 is an exploded perspective view of one embodiment of the present invention;
Figure 3 is a plan view showing one embodiment of the invention, Figure 3 is a sectional view taken along line A-A' in Figure 2, Figure 4 is a perspective view showing a magnet and yoke used in an embodiment of the present invention, and Figure 5 The figure is a plan view of the conventional example, and FIG. 6 is a perspective view of the magnet and yoke used in FIG. 5. 1 is the substrate, 2 is the magnet, 3 is the shaft, 4 is the lens, 5
is a focus coil, 6 is a tracking coil,
7 is a movable means, 8 is a yoke, 9 is a bearing, and 11 is a recess.

Claims (1)

[Claims for Utility Model Registration] A movable means having an optical system fitted therein so as to be rotatable and slidable up and down around a fixed shaft; at least one second coil wound around an axis perpendicular to a plane including the fixed shaft between the first coils of the fixed shaft and disposed on the movable means; It is arranged in a fixed part between the first and second coils, and has an S pole (N pole) on the first coil side and an N pole (S pole) on the second coil side between the first and second coils. )
1. An actuator for an optical pickup device, comprising: a magnet having a magnet arranged thereon, wherein a recess is provided on both sides of a portion of the magnet that faces the second coil.