JP2001243644A - Lens actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress parastic revolving motion, to improve assembling precision and to perform a stable operation by suitably setting compliance in respective directions, in a structure wherein a movable part holding an objective lens is supported to a fixed block by plural number of supporting springs so as to be elastically movable. SOLUTION: A holder 4 holding the objective lens 3 is supported to the fixed block 9 by four wire springs 7 respectively and symmetrically set up. The fixed position side of the fixed block 9 is made wider than the fixed position side of the holder 4 with respect to the interval in the tracking direction in the free linear part between the holder 4 and the fixed block 9 in respective wire springs 7, and moreover respective wire springs 7 are bent in the fixed part of the fixed block 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens actuator used for an optical disk recording / reproducing apparatus.

[0002]

2. Description of the Related Art In an actuator used for active control, it is necessary to employ a movable mechanism for minimizing a loss operation due to nonlinearity or the like.
For this reason, a spring support structure is often used as a support structure for a lens actuator used in an optical disk recording / reproducing apparatus requiring high precision control.
As described in Japanese Patent No. 6176, a structure in which an optical pickup is supported by four support springs (linear elastic members) can be exemplified.

On the other hand, with the necessity of mounting a high NA objective lens with the increase in recording density, it is necessary to reduce the optical axis tilt due to the parasitic rotational motion during translational driving of focusing and tracking. However, Patent No. 2856176
In the structure as described in Japanese Patent Publication No.
Since the compliance (elastic coefficient) in both directions of the support spring needs to be set low and the external dimensions are restricted due to the reduction in size and weight, the arrangement size of the support spring is limited. However, there is a problem that the torsional rigidity in the radial direction is reduced.

[0004] For this reason, an assembling error, a parasitic moment of the driving thrust at the time of focusing and tracking translation shift, or a slight asymmetry due to an assembling error of the support spring causes a parasitic rotational motion in the radial direction at the time of translation driving. In addition to the problem described above, the production yield or cost is often burdened.

Here, a qualitative model of compliance in a support structure using four parallel wire springs will be described.

The longitudinal elastic modulus of a wire spring material is expressed as E (N /
m ² ), the transverse elastic modulus is G, the wire spring has a circular cross section, the secondary moment of area is Ib (m ⁴ ), the secondary moment of the same pole is Ip (m ⁴ ), and the mounting position of the wire spring in the tracking direction is When z (m), the mounting position in the same focus direction is y (m), and the effective length of the wire spring is 1 (m), the compliance in the focus direction, the tracking direction, and the radial rotation direction are respectively ks (f). ,
ks (t) and kr (r),

[0007]

Ks (f) = ks (t) = 12 × E × Ib / l
³ {N / m} kr (r) = 4 × G × Ip / l + ks (f) × z ² + k
s (t) × y ² {N · m / rad}.

Here, in order to obtain desired characteristics corresponding to the active control, low compliance is desired in order to increase the sensitivity in the focus direction and the tracking direction. In this case, as shown in the above (Equation 1), , Kr
Since the first term in the equation (r) is smaller than the second and third terms, it depends on ks (f) and ks (t) after all. kr (r) is the passive direction,
We would like to have high compliance to prevent the above-mentioned parasitic rotational motion.
There are dimensional restrictions in the focusing and tracking directions for weight reduction, and the above-mentioned ks (f), ks
Since there is a demand for lower compliance in (t),
Simply cannot be solved.

Also, as described in US Pat. No. 4,991,161, a method of improving compliance in the radial rotation direction by arranging wire springs in a C shape is known. However, US Pat.
Only the content described in the specification of JP-A No. 1 considerably increases the compliance in the tracking direction. In addition, in the case of this structure, a large thrust is required to generate a desired displacement, so that the amount of the generated parasitic moment is also increased, thereby canceling the high compliance effect in the radial rotation direction. Will be. Further, in the case of this structure, it is difficult to take measures against a so-called yawing vibration mode, which is another parasitic rotational motion. Furthermore, in the case of the above-mentioned structure, if it is adopted in a structure called a lens offset arrangement which requires thinning, it is difficult to align the center of focus and tracking thrust with the center of mass. This is particularly problematic because the center lens position is far away.

In the structure described in Japanese Patent No. 2856176, it is possible to reduce the vibration mode by increasing the damping effect. No epoch-making compliance improvement in the radial rotation direction can be expected. In addition, with this structure, since a force is applied to the range used as the effective length of the wire spring and the wire spring is deformed, asymmetry due to a so-called processing error easily occurs, and conversely, variation in compliance or due to asymmetry. This is clearly disadvantageous in terms of characteristic fluctuation.

[0011]

As a problem common to both of the above-mentioned prior art examples, since the shape of the movable portion that determines the length of the wire spring and the shape of the fixed portion on the fixed block are not taken into account, both parts are actually manufactured. Due to a slight rotational displacement at the time of positioning, the length of the wire spring becomes asymmetric twice as much as the amount of subtraction. This is particularly noticeable when wire springs arranged in a C shape are employed. Since the compliance of each wire spring is inversely proportional to the cube of the effective length, as in the above-mentioned ks (f) formula, this asymmetry appears as a large compliance difference in each of the wire springs on both sides, resulting in a pure translation. Even when thrust is applied, a displacement difference occurs on both sides.

For this reason, in both of the conventional examples, it can be said that, although it is possible to improve the mode countermeasure and the compliance in the radial rotation direction, respectively, it is difficult to prevent parasitic rotation as a result. In addition, as another problem that the compliance of the wire springs on the left and right sides affects the asymmetry, there is a problem of the shape of the through hole in the wire spring fixing portion on the fixing block.

That is, as a method of fixing the wire spring, a method of soldering a metal wire spring to a printed circuit board fixed on a fixed block in order to also serve as a power supply line is generally used. However, since the through-hole for penetrating the wire spring in the fixed block is formed by a simple round hole, increasing the hole diameter increases the size of the fixed block and deteriorates the workability of soldering. is there. On the other hand, when the hole diameter is reduced, the gap between the wire spring and the inner wall of the through hole is compressed, so that the flux contained in the solder liquefies at the time of soldering, and the flux flows into the gap between the hole inner wall and the wire spring. The free length of the wire spring is changed to penetrate and solidify as in a capillary phenomenon, and as a result, compliance or its symmetry is deteriorated. This phenomenon is particularly likely to occur when the wire spring described in Japanese Patent No. 2856176 is bent when the wire spring is fixed.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, and to provide a structure in which a movable portion for holding an objective lens is elastically displaceably supported on a fixed block by a plurality of support springs so that compliance in each direction is properly adjusted. Accordingly, it is an object of the present invention to provide a lens actuator which suppresses parasitic rotational movement, improves assembly accuracy, and enables stable operation.

[0015]

According to one aspect of the present invention, there is provided a lens actuator for driving an objective lens with respect to an optical recording medium for focusing and tracking control. There is a fixed magnetic circuit consisting of a magnet and a back yoke, a magnetic flux generation source, a support structure that can be elastically displaced according to the amount of thrust generated, a holder to which the objective lens is fixed, and focusing and tracking thrust according to the respective current values. And a movable portion having a solenoid coil capable of generating a force, wherein the elastically displaceable support structure is formed by using four or more support springs between the movable portion and the fixed block. And a distance in the tracking direction in a free linear portion between the support springs is set to the movable portion. The fixed position side with respect to the fixed block is widened with respect to the fixed position side, and the support spring is curved near the fixed portion of the fixed block. With this structure, compliance in the tracking direction is kept low. Since the compliance in the radial rotation direction can be improved as it is, parasitic rotation can be prevented, and a yawing vibration mode due to a damping effect can be dealt with.

According to a second aspect of the present invention, in the lens actuator according to the first aspect, the curved shape of the support spring is an outer bent shape.

According to a third aspect of the present invention, in the lens actuator according to the first aspect, the curved shape of the support spring is an inwardly bent shape.

According to a fourth aspect of the present invention, in the lens actuator according to the first or second aspect, a tangent at a curved portion of each support spring intersects with an optical axis of the objective lens. With this structure, it is possible to prevent the optical axis of the objective lens from being shifted after the support spring is assembled.

According to a fifth aspect of the present invention, in the lens actuator according to the first aspect, the shape of the support spring fixing position in the fixing block is a cylinder having a surface substantially orthogonal to a tangent to a curved portion of the support spring. Characterized by a surface or a spherical surface or an inclined surface approximating them,
With this structure, the shape of the fixed block is such that the free length of the support spring is unlikely to change even if a rotational displacement occurs during the positioning and fixing of each part. It is possible to suppress such a parasitic rotational motion during translational driving.

According to a sixth aspect of the present invention, in the lens actuator of the first aspect, the shape of the supporting spring fixing position in the fixing block is a cylindrical surface or a spherical surface centered on the supporting spring fixing position in the movable portion, or a cylindrical surface or a spherical surface thereof. The structure is such that the free length of the support spring is hard to change even if a rotation error occurs when positioning and fixing each part. Can be prevented from occurring, and it is possible to suppress the parasitic rotational motion at the time of translational driving as in the related art.

According to a seventh aspect of the present invention, in the lens actuator according to the first aspect, the shape of the support spring fixing position in the fixing block is a cylindrical surface or a spherical surface centered on an intersection of the extension axis of the support spring or a spherical surface or the like. The structure is such that the free length of the support spring is hard to change even if a rotation error occurs when positioning and fixing each part. Can be prevented from occurring, and it is possible to suppress the parasitic rotational motion at the time of translational driving as in the related art.

The present invention as set forth in claim 8 is directed to claim 1,
The lens actuator according to 5, 6, or 7, wherein
The fixing hole provided in the fixing block, into which the support spring is inserted and fixed, is characterized in that the hole shape is a long hole or an elliptical hole that is long in the bending direction of the support spring. Alternatively, the bending process can be facilitated, and the occurrence of a defect caused by the penetration of the flux used for fixing the support spring by soldering into the hole can be prevented. Asymmetrical movements and parasitic rotational movement caused by these asymmetries can be prevented.

The present invention described in claim 9 is the fifth invention.
The lens actuator according to 6, 7, or 8, wherein
The positioning reference axis for fixing the fixed block to the support member is matched with the center on the cylindrical surface,
With this structure, the reference shaft and the support spring fixing portion can be made coaxial, and it is possible to prevent asymmetric compliance.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing a front side of a lens actuator for explaining a first embodiment of the present invention. FIG. 2 is a perspective view showing a rear side of the lens actuator of FIG. Numeral 2 is a magnet installed on the base 1 facing the other, 3 is an objective lens, 4 is a holder for holding the objective lens 3, 5 is a focusing coil, 6 is a tracking coil, and 7 is four in this example (at least A wire spring, which is a holder supporting spring, and a printed circuit board 8 for fixing the wire spring and supplying power to the coil, which is fixed to both sides of the holder 4, and 9 for fixing the end of the wire spring 7. It is a fixed block.

The movable part comprises the objective lens 3 fixed and held by the holder 4, the focusing coil 5, the tracking coil 6, and the printed circuit board 8. Further, the fixing portion is composed of a base 1 also serving as a magnetic circuit back yoke, a magnet 2, and a fixing block 9 fixed on the base 1.

A fixed magnetic circuit is formed by the magnet 2 serving as a magnetic flux generating source and the base 1 serving as a back yoke, and the holder 4 is formed by four wire springs 7 installed in a symmetrical relationship with each other. The objective lens 3 supported by the fixed block 9 so as to be elastically displaceable in accordance with the amount of thrust generated and held and fixed by the holder 4
Is configured such that focusing and tracking thrust can be generated in accordance with the current value flowing through the focusing coil 5 and the tracking coil 6.

The other end of the wire spring 7, one end of which is fixed to the printed circuit board 8 of the holder 4, passes through a pair of recesses 10 for filling a damper material at a distance from the inner wall of the fixed block 9, and FIG. As shown in FIG. 1, a flexible printed circuit board (not shown) provided through an elongated hole 11 formed in communication with a recess 10 of a fixed block 9 and provided on an arcuate surface portion 9a formed on a rear wall of the fixed block 9. It is fixed to the pattern by soldering.

However, the fixing pattern of the wire spring 7 may be a pattern formed on a printed circuit board, or another example is a metal pattern directly formed on a fixing block 9 made of molded resin by a plating method. There may be.
Further, as the damper material filled in the depression 10, for example, a silicone-based gel material is used.

Further, a positioning slot 12 is formed on the fixed block 9. A positioning reference shaft 13 is inserted into the positioning long hole 12, and Y shown in FIG.
Positioning of the fixed block 9 in the rotation direction around the axis is performed. The positioning reference shaft 13 may be formed on the base 1 or may be provided on an assembling workbench where the position of the base 1 is fixed with respect to the reference. After the positioning, a fixing operation is performed. As a fixing method, a method such as bonding or screwing between the base 1 and the fixing block 9 can be adopted.

In this embodiment, a metal wire spring is used as the wire spring 7, and an example of using soldering for power supply connection is used as a fixing method. An appropriate material may be selected and used according to design conditions, or a support spring having elasticity such as a leaf spring may be used. Depending on the material and structure of the support spring,
It is conceivable that an adhesive or an insert molding method is appropriately selected and adopted as the fixing method.

FIG. 3 is a plan view of the lens actuator according to the first embodiment. The holder 4 is supported by four wire springs 7 with respect to the fixed block 9. Free linear part 7a between
, The distance in the tracking direction is increased such that the fixed position of the fixed block 9 is wider than the fixed position of the holder 4.
Each of the wire springs 7 is bent outward in the vicinity of the fixed portion of the fixed block 9.

FIG. 4 is a plan view of the lens actuator of the second embodiment. The difference from the configuration of the first embodiment is the curved shape of the wire spring 7, and the other configuration is basically the same as that of the first embodiment. Therefore, the corresponding members are denoted by the same reference numerals, and detailed description is omitted. That is, in the second embodiment, the distance in the tracking direction of the free linear portion 7a between the holder 4 and the fixed block 9 in each wire spring 7 is set to be closer to the fixed position side of the fixed block 9 than to the fixed position side of the holder 4. Is similar to that of the first embodiment except that each wire spring 7 is bent inwardly in the vicinity of the fixed portion of the fixed block 9.

In the second embodiment, since the angle of the free straight line of the wire spring 7 is set to be large and the curve is bent inward, the compliance in the radial rotation direction (roll rotation direction) is reduced while increasing the compliance in the tracking direction. It has a great effect for enhancement.

In the first embodiment, the angle of the free straight line of the wire spring 7 is smaller than that of the second embodiment, and the curve is outward bending. In the case of this configuration, the effect of enhancing the compliance in the roll rotation direction is smaller than in the case of the second embodiment, but the dimension in the tracking direction (Z-axis) shown in FIG. By doing so, a similar effect can be obtained.

In the first embodiment, as shown in FIG. 3, the tangent line A at the curved portion on both sides of the linear spring 7 in the tracking direction in the fixed block 9 is connected to the optical axis O of the objective lens 3.
It is configured to intersect at the top or near the optical axis O. Further, as shown in FIG. 3, the shape of the arc-shaped surface portion 9a formed on the back wall of the fixed block 9 to which the other end of the wire spring 7 is fixed is
The curved portion of the wire spring 7 is a cylindrical surface or a spherical surface that is substantially perpendicular to the tangent line A, or an inclined surface similar thereto, and the optical axis O of the objective lens 3 coincides with the arc center of the arc surface portion 9a. (Fig. 3
And the stabilization of the length of the wire spring 7,
Even if the fixed block 9 is displaced after the wire spring 7 is assembled, the displacement can be made about the optical axis O of the objective lens 3.
Can be prevented and suppressed. Moreover, while suppressing the increase in compliance in the tracking direction, which was previously impossible at the same time, the epoch-making enhancement of the compliance in the roll rotation direction and the effective damping ability of yawing and pitching mode resonance at the same time. Will be able to meet.

In the first and second embodiments, FIG.
As shown in FIG. 1, the shape of the arc-shaped surface portion 9a formed on the back wall of the fixed block 9 to which the other end of the wire spring 7 is fixed,
A cylindrical surface having a center P at the position where the wire spring 7 is fixed in the holder 4, a spherical surface, or an inclined surface similar thereto, or the other end of the wire spring 7 is fixed as illustrated in FIG. The shape of the arcuate surface portion 9a formed on the rear wall of the fixed block 9 is changed to the intersection X of the extension axis L of the wire spring 7.
It is also conceivable to use a cylindrical surface around the center, or a spherical surface, or an inclined surface approximating them,
As described above, by appropriately combining with the configuration described in the second embodiment, the compliance in the roll rotation direction can be reduced while suppressing the increase in the compliance in the tracking direction, which cannot be simultaneously solved conventionally. , And the ability to effectively attenuate yawing and pitching mode resonance.

Further, as shown in FIG. 7, the wire spring 7 is fixed at the center of the positioning reference shaft 13 installed when the fixed block 9 is fixed to the base 1 and at the back wall of the fixed block 9. Arc surface part 9 formed near the part
By making the center of the arc a coincide with the center of the arc, in addition to the above-described effects, it is possible to prevent the occurrence of misalignment during positioning.

As shown in FIG. 2, the shape of the long hole 11 formed in the fixing block 9 at the portion where the wire spring 7 is inserted and fixed is changed to a long hole or a long hole in the bending direction of the wire spring 7. By providing the elliptical hole, the wire spring 7 can be provided with a margin for assembling and arrangement, and the wire spring 7 can have a margin in the accuracy of the bending process. As a result, it is possible to prevent the occurrence of inconvenience caused by intrusion into the hole as described above, and thus it is possible to prevent the conventional dispersion of compliance or the asymmetry of the support due to the entry of the flux and the parasitic rotational movement caused by these. .

As described above, according to the configuration of the present embodiment,
A structure in which the movable portion including the holder 4 and the fixed block 9 are connected by four or more wire springs 7 and the free linear portion 7a of the wire spring 7 is fixed to the fixed position side of the movable portion with respect to the fixed position side of the movable portion. The width on the position side is widened in the tracking direction, and the wire spring 7
Is curved at or near the fixed portion of the fixed block 9 to form the arcuate surface portion 9a, so that the compliance in the radial rotation direction can be dramatically improved while keeping the compliance in the tracking direction low. In addition, yawing and pitching vibrations can be effectively attenuated. The compliance in the tracking direction can be kept fairly low, and the vibration damping effect is high as compared with the case where no curvature is provided.

In addition, since the shape of the long hole 11 formed in the fixing block 9 at the portion where the wire spring 7 is inserted and fixed is a long hole or an elliptical hole long in the bending direction of the wire spring 7, The shape can be bent inward or outward as required, and a stable curved shape can be given to the wire spring after inserting the wire spring at the free straight part and positioning the parts. It is also effective in preventing flux from entering by the capillary effect of soldering,
Further, the torsional rigidity in the radial rotation direction is much higher than when a parallel wire spring is bent through a round hole formed in a fixed block as in the related art.

Further, the shape of the fixed block 9 at the wire spring fixing position after the bending is such that the effective length of the wire spring is hard to change even if a rotational deviation occurs in the positioning of the parts, so that the variation in compliance in each direction can be achieved. Alternatively, the occurrence of asymmetry can be suppressed or prevented.

Further, by combining the configurations of the above embodiments as appropriate, more effective effects as a lens actuator can be obtained.

[0044]

As described above, according to the lens actuator of the present invention, it is possible to increase the compliance in the radial rotation direction while keeping the compliance in the tracking direction low, so that the parasitic rotation can be prevented. Thus, it is possible to cope with the yawing vibration mode due to the damping effect, and it is also possible to prevent the occurrence of variations or asymmetry in assembling of the respective parts and the occurrence of problems such as optical axis deviation resulting therefrom.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a front side of a lens actuator for describing a first embodiment of the present invention.

FIG. 2 is a perspective view showing a rear side of the lens actuator according to the first embodiment of the present invention.

FIG. 3 is a plan view of the lens actuator according to the first embodiment of the present invention.

FIG. 4 is a plan view of a lens actuator for describing a second embodiment of the present invention.

FIG. 5 is an explanatory diagram for explaining a modification applied to the embodiment of the present invention;

FIG. 6 is an explanatory diagram for explaining another modification applied to the embodiment of the present invention;

FIG. 7 is an explanatory diagram for explaining another modification applied to the embodiment of the present invention;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base 2 Magnet 3 Objective lens 4 Holder 5 Focusing coil 6 Tracking coil 7 Wire spring 8 Printed circuit board for fixing and coil feeding 9 Fixed block 9a Arc surface part of fixed block 11 Slot 12 Slot 12 for positioning 13 Positioning reference axis

Claims (9)

[Claims] 1. A lens actuator for driving an objective lens with respect to an optical recording medium for focusing and tracking control, comprising: a fixed magnetic circuit comprising a magnet as a magnetic flux generating source and a back yoke; A lens comprising a support structure capable of elastic displacement according to the amount, and a movable part including a holder to which the objective lens is fixed and a solenoid coil capable of generating focusing and tracking thrust according to the respective current values. In the actuator, the elastically displaceable support structure has a structure in which the movable portion and the fixed block are connected to each other using four or more support springs. Expand the fixed position side with respect to the fixed block with respect to the fixed position side with respect to the movable part. And a lens actuator, characterized in that said support spring is curved at a fixed portion near the fixed block. 2. The lens actuator according to claim 1, wherein a curved shape of the support spring is an outer bent shape. 3. The lens actuator according to claim 1, wherein the curved shape of the support spring is an inwardly bent shape. 4. The lens actuator according to claim 1, wherein a tangent at a curved portion of each of the support springs is configured to intersect with an optical axis of the objective lens. 5. The shape of the support spring fixing position in the fixing block is a cylindrical surface or a spherical surface that is substantially perpendicular to a tangent to a curved portion of the support spring, or a slope approximating them. The lens actuator according to claim 1, wherein 6. The support spring fixing position of the fixed block is a cylindrical surface or a spherical surface centered on the support spring fixing position of the movable portion, or an inclined surface similar thereto. A lens actuator as described. 7. A shape of a support spring fixing position in the fixing block is a cylindrical surface or a spherical surface centered on an intersection of an extension axis of the support spring, or an inclined surface similar thereto. A lens actuator as described. 8. The fixing hole provided in the fixing block, into which the support spring is inserted and fixed, is formed as an elongated hole or an elliptical hole that is long in the bending direction of the support spring. The lens actuator according to claim 1, 5, 6, or 7. 9. The center of a positioning reference axis set when fixing the fixing block to a base is made coincident with the center of the cylindrical surface.
9. The lens actuator according to 6, 7, or 8.