JP4853458B2 - Objective lens unit - Google Patents

Description

The present invention relates to an objective lens unit used for an optical pickup such as a DVD player or a DVD recorder, and in particular, allows a lens holder to be accurately and smoothly focused.

Conventionally, there are the objective lens units shown in FIGS. 7 to 11. FIG. 7 is a longitudinal sectional view, FIG. 8 is a plan view, FIG. 9 is an exploded perspective view of the main part, and FIG. Is an exploded longitudinal sectional view of the main part, FIG. 10B is an assembly view of the main part, and FIG.

As shown in FIGS. 7 to 10, the lower portion of the guide shaft 3 is press-fitted into the shaft hole 2 penetrating the base body 1a of the metal plate act base 1, and the upright plate 1b from both front and rear edges of the base body 1a. , 1c are erected, and the upper surface of each of the upright plates 1b, 1c is a cover mounting surface 4, and the upper surface 3a of the guide shaft 3 is flush with the cover mounting surface 4 at the same horizontal level S. Magnets 5 are fixed to side plates 1d and 1e that are formed and erected from both side edges of base body 1a.

A slide base 6 in which the act base 1 is slidable along the radial direction of the disk D
The act base 1 is placed on the slide base 6 by the adjusting screws 7 and the springs 8 that are mounted on the slide base 6 and connect the three support plates 1f to 1h extending from the act base 1 to the side. It is fixed in an adjusted state.

As shown in FIGS. 7 and 8, a guide hole 11 penetrating in the center of the lens holder 10 with the objective lens OL is movably fitted to the guide shaft 3, and a focus coil 12 and a tracking coil 13 are fitted in the lens holder 10. And are fixed.

As shown in FIGS. 7 to 9, a synthetic resin act cover 15 is placed on each cover placement surface 4, and a plurality of (four in this example) projecting from both front and rear edges of the act cover 15. Hook 1
By engaging 5a with the recessed step portion 16 of each upright plate 1b, 1c, the act cover 15 is provided.
Is locked to the act base 1, and through holes 1 i and 15 b are formed through the act base 1 and the act cover 15 so as to face the objective lens OL. In FIG. 7, reference numeral 17 denotes a printed circuit board fixed to the upright plate 1c, and is connected to the focus coil 12 and the tracking coil 13 through lead wires 17a. Reference numeral 18 denotes a collimator lens.

The operation principle will be described. The lens holder 10 is focused in the focus directions a and b along the guide shaft 3 by energizing and exciting the focus coil 12, and the lens holder is energized by energizing the tracking coil 13. By tracking 10 in the tracking directions c and d around the guide shaft 3, the laser light P is projected from the laser diode to the disk D through the collimator lens 18 and the objective lens OL, and recorded on the disk D based on the reflected light. Read information.

According to the above configuration, since the act cover 15 is formed of a synthetic resin, FIG.
As shown in phantom lines, the act cover 15 may be warped and deformed into an upward arc shape. When the act cover 15 is attached to the act base 1, as shown in FIG. The act cover 15 is separated from the upper surface 3a of the guide shaft 3, and a gap α is generated between them.

As described above, when the optical pickup is driven with the act cover 15 warped attached to the act base 1, as shown in FIG. 11, the rear part of the lens holder 10 that has risen most along the focus directions a and b is acted. By hitting the cover 15, the front portion of the lens holder 10 is lifted in the direction of the arrow e, and the lens holder 10 is tilted. Therefore, the focusing of the lens holder 10 becomes unstable and a reading error may occur. .

As shown in another operational view of FIG. 12, even if the act cover 15 does not warp, the guide shaft 3 is over-fitted into the shaft hole 2 so that the upper surface 3a of the guide shaft 3 is covered with the cover mounting surface 4. When the gap α is generated between the act cover 15 and the upper surface 3a of the guide shaft 3, the same problem as described above occurs.

As one of related techniques, there is one described in Patent Document 1, which means that the upper surface 3a of the guide shaft 3 is separated from the cover mounting surface 4 by a predetermined distance k as shown in the longitudinal sectional view of FIG. The cross-shaped stopper 20 having the same height as the interval k is integrally protruded at the position facing the guide shaft on the lower surface of the act cover 15, and the lens holder 10 that has risen most along the focus directions a and b is the stopper 20. It is trying to hit.
JP 2007-58933 A

In the technique described in Patent Document 1, as shown in FIG. 13B, the act cover 15 is warped and deformed in an upward arc shape, whereby a gap α is formed between the stopper 20 and the upper surface 3 a of the guide shaft 3. Even if the act cover 15 does not warp as shown in FIG. 13C, the guide shaft 3 is over-fitted into the shaft hole 2 and the upper surface 3a of the guide shaft 3 is placed on the cover. There is a case where a clearance α is formed between the stopper 20 and the upper surface 3a of the guide shaft 3 below the surface 4, and in this case, focusing of the lens holder 10 is performed as in the conventional example shown in FIGS. There is a possibility that reading error may occur due to instability.

An object of the present invention is to provide an objective lens unit in which focusing of a lens holder can be performed precisely and smoothly in view of the above-described conventional drawbacks.

In order to achieve the above object, according to the first aspect of the present invention, the lower portion of the guide shaft is press-fitted into a shaft hole penetrating the base body of the metal plate act base, and the upright plate is extended from both front and rear edges of the base body. The upper surface of each upright plate is used as a cover mounting surface, and the upper surface of the guide shaft is flush with the cover mounting surface at the same horizontal level, and the guide shaft is provided with an objective lens. A lens holder is movably fitted, a synthetic resin act cover placed on each cover placement surface is locked to an act base, and excites a focus coil and a tracking coil provided on the lens holder. The lens holder is focused along the guide shaft, and the lens holder is tracked around the guide shaft. In object lens unit, the upper surface of the guide shaft
A stopper with a larger diameter than the guide shaft and a predetermined height is placed on the lower surface of the act cover.
The actuating mechanism is provided by contacting the stopper with the upper surface of the guide shaft.
The bar is elastically displaced in an upward arc shape .

According to the first aspect of the present invention, since the large-diameter stopper is pressed against the upper surface of the guide shaft by the urging force generated by elastically displacing the act cover, the optical pickup is driven to move the lens holder in the focus direction. Even when the lens holder is raised to the maximum, the center portion of the lens holder hits the stopper and is prevented from further rising, and the lens holder is not tilted as in the prior art, and the lens holder is precisely and smoothly focused. Thus, no reading error can occur.

Moreover, since the stopper is integrally projected on the act cover and the number of parts is not increased, it is economical.

1 to 6 show an objective lens unit according to an embodiment of the present invention.
2 is the same plan view, FIG. 2 is the same plan view, FIG. 3 is the same exploded perspective view, FIG. 4A is an exploded vertical sectional view of the same main part, FIG. 4B is an assembly drawing of the same main part, FIG. 5 is the same operation diagram.

As shown in FIGS. 1 to 4, the guide shaft 3 faces the upper surface 3 a of the guide shaft 3.
A plan view circular shape (or a polygon such as a quadrangle) having an outer diameter h2 larger than the outer diameter h1 and a predetermined height t.
The stopper 21 is integrally projected on the lower surface of the act cover 15. The configuration other than the above is shown in FIG.
Since it is almost the same as the configuration shown in FIG. 10, the same reference numerals are given to the same parts, and the description thereof is omitted.

The assembly procedure will be described. As shown in FIG. 4 (b), the stopper 21 is brought into concentric contact with the upper surface 3a of the guide shaft 3, and the hooks 15a are engaged with the concave steps 16 of the upright plates 1b and 1c. As a result, the act cover 15 is elastically displaced in an upward arc shape, and the act cover 15 is locked to the act base 1.

As an example of specific dimensions, the outer diameter h1 of the guide shaft 3 is 2 mm, the outer diameter h2 of the stopper 21 is 3 mm, the height t of the stopper 21 is 0.2 mm, and the height t of the stopper 21 is
The act cover 15 is warped by an amount corresponding to (0.2 mm) and elastically displaced upward in an arc shape. For the sake of easy understanding on the drawings, the elastic displacement state of the act cover 15 is exaggerated.

According to the above configuration, the large-diameter stopper 21 is pressed against the upper surface 3a of the guide shaft 3 by the urging force F generated by elastically displacing the act cover 15 (see FIG. 4B). Even when the lens holder 10 is driven and raised to the maximum along the focus directions a and b, as shown in FIG. 5, the central portion of the lens holder 10 hits the stopper 21 and is prevented from rising further, as in the conventional case. The lens holder 10 does not tilt (see FIG. 11)
The lens holder 10 can be focused precisely and smoothly so that no reading error occurs.

Moreover, since the stopper 21 is integrally projected on the act cover 15 and the number of parts is not increased, it is economical.

As shown in another operational view of FIG. 6, the guide shaft 3 is over-fitted into the shaft hole 2,
Even if a gap α (for example, 0.1 mm) is generated between the upper surface 3 a of the guide shaft 3 and the cover mounting surface 4, a large-diameter stopper is provided by the urging force F generated by elastically displacing the act cover 15. Since 21 is pressed against the upper surface 3a of the guide shaft 3, the same effects as those shown in FIGS. 1 to 5 can be obtained.

It is a longitudinal cross-sectional view which shows the objective lens unit which is one Embodiment of this invention. It is the same top view. It is a disassembled perspective view of the principal part. (A) is an exploded longitudinal sectional view of the main part, and (b) is an assembly view of the main part. FIG. FIG. It is a longitudinal cross-sectional view which shows a prior art example. It is the same top view. It is a disassembled perspective view of the principal part. (A) is an exploded longitudinal sectional view of the main part, and (b) is an assembly view of the main part. FIG. FIG. (A) is a longitudinal cross-sectional view of another conventional example, (b) is an operation diagram of the main part, and (c) is another operation diagram of the main part.

1 Act base 1a Act base base body 1b, 1c Standing plate 2 Shaft hole 3 Guide shaft 3a Top surface of guide shaft 4 Cover mounting surface 10 Lens holder 12 Focus coil 13 Tracking coil 15 Act cover 21 Stopper D Disk S Horizontal level OL Objective lens h1 Guide shaft outer diameter h2 Stopper outer diameter t Stopper height

Claims (1)

The lower part of the guide shaft is press-fitted into a shaft hole penetrating the base body of the metal plate act base, the upright plates are erected from both front and rear edges of the base body, and the upper surface of each upright plate is connected to the cover mounting surface. The upper surface of the guide shaft is formed flush with each cover mounting surface at the same horizontal level, and a lens holder with an objective lens is movably fitted to the guide shaft,
A synthetic resin act cover placed on each cover placement surface is locked to the act base, and the lens holder is moved along the guide shaft by exciting the focus coil and tracking coil provided on the lens holder. In the objective lens unit in which the lens holder is tracked around the guide shaft , the diameter is larger than the guide shaft and has a predetermined height.
A stopper is integrally projected on the lower surface of the act cover.
An objective lens unit, wherein the act cover is elastically displaced in an upward arc shape by contacting the surface .

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